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HighLights More»   
Effect of annealing temperature on structure and stress properties of Ta2O5/SiO2 multilayer reflective coatings
Liu Bao-Jian, Duan Wei-Bo, Li Da-Qi, Yu De-Ming, Chen Gang, Wang Tian-Hong, Liu Ding-Quan
Acta Physica Sinica, 2019, 68 (11): 114208
Collaborative quantum computation with redundant graph state
Tian Yu-Ling, Feng Tian-Feng, Zhou Xiao-Qi
Acta Physica Sinica, 2019, 68 (11): 110302
Controllable growth of InAs quantum dots on patterned GaAs (001) substrate
Wang Hai-Ling, Wang Ting, Zhang Jian-Jun
Acta Physica Sinica, 2019, 68 (11): 117301
Current Issue Accepts In Press Earlier Issues Top Downloaded SCI Top Cited
  Acta Physica Sinica--2019, 68 (11)   Published: 05 June 2019
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INVITED REVIEW

Recent progress of near-field studies of two-dimensional polaritonics

Duan Jia-Hua, Chen Jia-Ning
Acta Physica Sinica. 2019, 68 (11): 110701 doi: 10.7498/aps.68.20190341
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Due to the capability of nanoscale manipulation of photons and tunability of light-matter interaction, polaritonics has attracted much attention in the modern physics. Compared with traditional noble metals, two-dimensional van der Waals materials provide an ideal platform for polaritons with high confinement and tunability. Recently, the development of scanning near-field optical microscopy has revealed various polaritons, thereby paving the way for further studying the quantum physics and nano-photonics. In this review paper, we summarize the new developments in two-dimensional polaritonics by near-field optical approach. According to the introduction of near-field optics and its basic principle, we show several important directions in near-field developments of two-dimensional polaritonics, including plasmon polaritons, phonon polaritons, exciton polaritons, hybridized polaritons, etc. In the final part, we give the perspectives in development of near-field optics.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

High-pressure neutron diffraction techniques based on Paris-Edingburgh press

Shi Yu, Chen Xi-Ping, Xie Lei, Sun Guang-Ai, Fang Lei-Ming
Acta Physica Sinica. 2019, 68 (11): 116101 doi: 10.7498/aps.68.20190179
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Since the 1990s, with the benefit of available large-volumed samples, wide detector windows, and portability, Paris-Edinburgh press has been widely used in neutron facilities to study the structures and physical properties of condensed matter under high-pressure extreme conditions. In the present study, We perform high-pressure neutron diffraction experiments in neutron source of China using the Paris-Edinburgh press. The experiments are carried out on a high-pressure neutron diffraction spectrometer (Fenghuang) at China Mianyang Research Reactor (CMRR). Fenghuang is a high-intensity and moderate-resolution diffractometer which has been upgraded from a neutron powder diffractometer and can be used under ambient and extreme conditions. A single cylinder pump with a max load of 200 MPa provides a loading pressure for Paris-Edinburgh press, and a precise mobile platform is used to hang and to locate the Paris-Edinburgh press. Using the tungsten-carbide (WC) toroidal anvils with TiZr gasket, we obtain the neutron diffraction spectra of Fe samples at different pressures successfully. We also obtain the neutron diffraction spectra respectively at pressures of 9.7 GPa and 10.7 GPa by using a WC single-toroidal anvil and a WC double-toroidal anvil under load 100 MPa. The TiZr gasket blows out before the load reaches 100 MPa in the WC single-toroidal anvil assembly, while it remains good in the WC double-toroidal anvil assembly under the same load. The WC single-toroidal anvil assembly becomes unstable under load about 80 MPa, and the WC double-toroidal anvil assembly is still stable under load 100 MPa. Thus, the stability of the double-toroidal anvil assembly is much higher than that of the single-toroidal anvil assembly. It is found that the thickness of the gasket edge is very important for the stability of the assembly during loading. The thicker the edge of the gasket, the more stable the assembly is. The main reason is that the groove of the double concave anvil can enhance the lateral support ability of the gasket, thereby making the double concave surface assembly more stable than the single concave surface assembly.

Terahertz wave absorption for alkylcyclohexyl-isothiocyanatobenzene liquid crystal materials

Yan Hao-Lan, Cheng Ya-Qing, Wang Kai-Li, Wang Ya-Xin, Chen Yang-Wei, Yuan Qiu-Lin, Ma Heng
Acta Physica Sinica. 2019, 68 (11): 116102 doi: 10.7498/aps.68.20190209
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According to density functional theory, in this paper we report a simulation result obtained by using the Gaussian09 package. Adopted in the calculation are an optimized Opt Freq and a base group of B3LYP/6-311g to simulate the absorption of 16 kinds of liquid crystal (LC) molecules of 4-(trans-4-n-alkylcyclohexyl) isothiocyanatobenzenes (CHBT) in a 0.1-5.0 terahertz band (THz). The results show that in the low terahertz band, the absorption is caused mainly by the vibration and rotation of the molecules. So for convenience, we present an novel analytical method of studying the influence of molecular moment of inertia and mass center of gravity shift on absorption. An important result is found that the length of the molecular alkyl chain can lead to different molecular mass, mass center of gravity and moment of inertia, which causes the rotation and vibration of the molecule to be different. These factors lead to the difference in terahertz wave absorption. In the 0.1-5.0 terahertz band, the molecules with 3-7 alkyl chain carbon atoms show a strong absorption. As a reference, reducing and increasing the carbon atoms in the alkyl chain will cause the molecules to reduce the absorption of terahertz waves. In the end, the calculated results are compared with the experimental results obtained from 10 molecules according to the reference data in a frequency range of 0.3-3.0 terahertz. It is found that in the low frequency band there exist some differences between the calculation results and the experimental measurements, in which the difference in the position of the absorption peak may originate from a hydrogen bond. Comparing the relative magnitudes of the absorption intensities, it is found that the experimental measurements are consistent with the calculated results, indicating that the absorption intensity comes from the absorption of dipole vibration and rotation, which demonstrates the positive significance of computational simulation. We look forward to the experimental measurements in the future, and correct the calculation methods and keywords as well as the parameters such as temperature calculation that is to be done in future work. As a theoretical basis, the calculation results can better reflect the absorption of molecular materials, and it is expected to provide useful suggestions for designing and synthesizing the liquid crystal molecules.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Integer quantum Hall effect in a spin-orbital coupling system

Liang Tao, Li Ming
Acta Physica Sinica. 2019, 68 (11): 117101 doi: 10.7498/aps.68.20190037
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Electron transport mechanism of a two-dimensional infinite slab subjected to Rashba spin-orbital coupling is studied in this paper. We calculate the Hall conductance and the longitudinal resistance of the integer quantum Hall effect (IQHE). In a strong magnetic field, the Landau levels of electrons increase rapidly at large wave vectors due to the constraint of the two edges of the sample while they remain flat at small wave vectors. Although the Zeeman effect can split the energy levels of spin degeneracy under a strong magnetic field, the spacing between the Landau levels is exactly equal to the spin splitting, thus the spin degeneracies have not been fully resolved. The spin-orbital coupling fully resolves the spin degeneracies of the energy levels. This is the key to reproducing the IQHE. Electrons with rapid increasing energies are localized at the two edges of the sample and transport along the edges to form separated currents with opposite directions. In this case, back scattering of electrons is prohibited due to the localization of these two branches. Since the electrons on the upper and lower edges originate respectively from the left and right electrode, they also have the chemical potentials of the electrons in those electrodes, respectively. The computation result shows that the Hall conductance appears as plateaus at integer times of e2/h. Temperature influences the accuracy of the Hall plateaus. As an international resistance standard, exceeding a critical temperature can produce significant errors to the Hall plateaus. Below the critical temperature, the accuracy can reach 10-9. Finally the mechanism of the longitudinal resistance of the IQHE is discussed and computed numerically. It is shown that only the wave-functions with opposite and small wave vectors have a significant overlap in the bulk of the sample and thus contribute to the longitudinal resistance. Due to the separation of currents in different directions in space, the longitudinal resistance does vanish at the Hall plateaus but it appears when the Hall conductance jumps from one plateau to another one.

Comparative study of thermoelectric properties of Mg2Si0.3Sn0.7 doped by Ag or Li

Yuan Guo-Cai, Chen Xi, Huang Yu-Yang, Mao Jun-Xi, Yu Jin-Qiu, Lei Xiao-Bo, Zhang Qin-Yong
Acta Physica Sinica. 2019, 68 (11): 117201 doi: 10.7498/aps.68.20190247
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In recent decades, Mg2(Si, Sn) solid solutions have long been considered as one of the most important classes of eco-friendly thermoelectric materials. The thermoelectric performance of Mg2(Si, Sn) solid solutions with outstanding characteristics of low-price, non-toxicity, earth-abundant and low-density has been widely studied. The n-type Mg2(Si, Sn) solid solutions have achieved the dimensionless thermoelectric figure of merit ZT~1.4 through Bi/Sb doping and convergence of conduction bands. However, the thermoelectric performances for p-type Mg2(Si, Sn) solid solutions are mainly improved by optimizing the carrier concentration. In this work, the thermoelectric properties for p-type Mg2Si0.3Sn0.7 are investigated and compared with those for different p-type dopant Ag or Li. The homogeneous Mg2Si0.3Sn0.7 with Ag or Li doping is synthesized by two-step solid-state reaction method at temperatures of 873 K and 973 K for 24 h, respectively. The transport parameters and the thermoelectric properties are measured at temperatures ranging from room temperature to 773 K for Mg2(1-x)Ag2xSi0.3Sn0.7 (x=0, 0.01, 0.02, 0.03, 0.04, 0.05) and Mg2(1-y)Li2ySi0.3Sn0.7 (y=0, 0.02, 0.04, 0.06, 0.08) samples. The influences of different dopants on solid solubility, microstructure, carrier concentration, electrical properties and thermal transport are also investigated. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show that the solid solubility for Ag and for Li are x=0.03 and y=0.06, respectively. Based on the assumption of single parabolic band model, the value of effective mass~1.2m0 of p-type Mg2(1-x)Ag2xSi0.3Sn0.7 and Mg2(1-y)Li2ySi0.3Sn0.7 are similar to that reported in the literature. The comparative results demonstrate that the maximum carrier concentration for Ag doping and for Li doping are 4.64×1019 cm-3 for x=0.01 and 15.1×1019 cm-3 for y=0.08 at room temperature, respectively; the Li element has higher solid solubility in Mg2(Si, Sn), which leads to higher carrier concentration and power factor PF~1.62×10-3 W·m-1·K-2 in Li doped samples; the higher carrier concentration of Li doped samples effectively suppresses the bipolar effect; the maximum of ZT~0.54 for Mg1.92Li0.08Si0.3Sn0.7 is 58% higher than that of Mg1.9Ag0.1Si0.3Sn0.7 samples. The lattice thermal conductivity of Li or Ag doped sample decreases obviously due to the stronger mass and strain field fluctuations in phonon transport.

Controllable growth of InAs quantum dots on patterned GaAs (001) substrate Hot!

Wang Hai-Ling, Wang Ting, Zhang Jian-Jun
Acta Physica Sinica. 2019, 68 (11): 117301 doi: 10.7498/aps.68.20190317
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InAs/GaAs quantum dot (QD) is one of the promising material systems for the quantum information processing due to their atomic-like optical and electrical properties. There are many previous researches reporting the InAs QDs which can be implemented as solid-state single-photon sources for quantum information and quantum computing. However, the site-controlled growth of QDs is the prerequisite for addressability and integration. There are very few researches focusing on the systematic study of preferential nucleation of InAs QDs on a patterned GaAs (001) substrate. In this work, we study the preferential nucleation sites of InAs QDs on a patterned GaAs (001) substrate with different trench sidewall inclinations. With small inclination angle of the trench sidewalls, the InAs QDs nucleate preferentially inside the trenches, while with large inclination angle, the edges of the trenches appear to be the preferential nucleation sites. By utilizing the established method, a pair of InAs dots can be uniformly achieved in the patterned pits through tuning the inclination angle of the pits. The site-controlled single InAs QD and InAs QD molecules on the patterned substrates could have potential applications in quantum information processing and quantum computing.

Ultra-wideband linear polarization converter based on square split ring

Xu Jin, Li Rong-Qiang, Jiang Xiao-Ping, Wang Shen-Yun, Han Tian-Cheng
Acta Physica Sinica. 2019, 68 (11): 117801 doi: 10.7498/aps.68.20190267
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Polarization state of electromagnetic wave has important applications in satellite communication, radar detection, and stereoscopic display imaging. Therefore, the control of polarization state of electromagnetic wave is an important direction in scientific research. The traditional method of manipulating the polarization state is mainly realized based on Faraday effect and birefringent crystal, which has a certain requirement for the material thickness (leading to large volume), and does not have broadband characteristics (leading to narrow band). Recently, metamaterial with subwavelength meta-atoms, has achieved many exotic phenomena and functionalities that cannot be found in nature. As an important branch of metamaterial-based devices, polarization converter has attracted great attention and achieved significant progress. However, most of them cannot realize ultra-broadband, high-efficiency, wide-angle, and simple geometry simultaneously.
In this paper, a linear polarization converter based on a square split ring metasurface is proposed. Due to the anisotropic structure, the amplitudes of the reflected electric field along the two diagonal lines are equal, and their phase difference is 180°. As a result, the polarization direction of the incident wave can be rotated 90°. The simulation results show that the polarization conversion ratio (PCR) is higher than 90% in a frequency range from 7.12 to 18.82 GHz, which means that the relative bandwidth reaches 90%. The significant bandwidth expansion is attributed to the four electromagnetic resonances generated in a square-split-ring unit. We investigate the influence of geometric parameters on PCR in detail. We also examine the performance of the proposed structure under oblique incidence. It has little effect on the co-polarization and cross-polarization reflection coefficients when the incident angle is changed from 0° to 45°. Even if the incident angle reaches 45°, the mean PCR remains above 80%. The PCRs of the four electromagnetic resonant points are all close to 100%. Finally, we fabricate and measure the proposed polarization converter that contains 30×30 unit cells. The experimental results are in good agreement with the simulation results, and thus validating the design.
In conclusion, we propose both theoretically and experimentally a linear polarization converter that possesses ultra-broadband, high-efficiency, wide-angle, and simple geometry simultaneously. The proposed scheme can be extended to terahertz and even optical frequencies.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

Thermal analysis on crystal phase synthesis of iron nitride film and its magnetic properties

Lu Qi-Hai, Tang Xiao-Li, Song Yu-Zhe, Zuo Xian-Wei, Han Gen-Liang, Yan Peng-Xun, Liu Wei-Min
Acta Physica Sinica. 2019, 68 (11): 118101 doi: 10.7498/aps.68.20182195
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The phase transition law of Fe-N system is very important for efficiently synthesizing single-phase γ'-Fe4N thin films. The γ"-FeN thin films are deposited on silicon wafers via DC reactive magnetron sputtering; some of them are stripped from the silicon wafers and measured by using the synchronous thermal analysis (TG-DSC) for studying the phase transition law of Fe-N system. The results of TG-DSC show that at a heating rate of 10℃/min, the Fe-N system has five phase transitions in a temperature range between room temperature (RT) and 800℃, i.e. I (330-415℃):γ''-FeN→ξ-Fe2N with an endothermic value of 133.8 J/g; Ⅱ (415-490℃):ξ-Fe2N→ε-Fe3N with no obvious latent heat of phase change; Ⅲ (510-562℃):ε-Fe3N→γ'-Fe4N with an exotherm value of 29.3 J/g; IV (590-636℃):γ'-Fe4N→γ-Fe with an exotherm value of 42.6 J/g; V (636-690℃):γ-Fe→α-Fe with an endothermic value of 14.4 J/g. According to the phase transition law of Fe-N system, the crystal phase of iron nitride thin film is effectively regulated by vacuum annealing. The x-ray diffraction pattern (XRD) results show that the iron nitride thin film obtained by direct-sputtering in pure N2 is a single-phase γ"-FeN film, and it becomes a single-phase ξ-Fe2N film after being annealed at 350℃ for 2 h, a single-phase ε-Fe3N film after being annealed at 380℃ for 2 h, and a single-phase γ'-Fe4N film after being annealed at 430℃ for 7 h. The annealing temperature for the phase transition of Fe-N thin film is generally lower than that predicted by the TG-DSC experimental results, because it is affected by the annealing time too, that is, prolonging the annealing time at a lower temperature is also effective for regulating the crystal phase of Fe-N thin film. The magnetic properties of the Fe-N thin film are also studied via vibrating sample magnetometer (VSM) at room temperature. The γ'-Fe4N polycrystalline thin film shows an easy-magnetized hysteresis loop for the isotropic in-plane one, but a hard-magnetized hysteresis loop with a large demagnetizing field for the out-of-plane one, which belongs to the typical magnetic shape anisotropy. However, their saturation magnetizations are really the same (about 950 emu/cm3) both in the plane and out of the plane.

Adsorption of NO2 by hydrazine hydrate-reduced graphene oxide

Li Chuang, Cai Li, Li Wei-Wei, Xie Dan, Liu Bao-Jun, Xiang Lan, Yang Xiao-Kuo, Dong Dan-Na, Liu Jia-Hao, Li Cheng, Wei Bo
Acta Physica Sinica. 2019, 68 (11): 118102 doi: 10.7498/aps.68.20182242
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Reduced graphene oxide, as a candidate for gas detection due to its unique atomic structure, is arousing the wide interest of researchers. In this paper, hydrazine hydrate is used to reduce graphene oxide prepared by the modified Hummers method. A chemical resistance gas sensor is fabricated. The prepared reduced graphene oxide is used as a gas sensitive layer of Au planar interdigital electrode. The gas sensing characteristics such as responsivity, recovery and repeatability of NO2 gas are studied. The results show that the graphene oxide reduced by hydrazine hydrate can detect the NO2 gas at a concentration of 1-40 ppm under room temperature. It has good responsivity and repeatability. The recovery rate can reach more than 71%. However, the sensitivity is only 0.00201 ppm-1, and there is much room for improvement. In addition, the response time and recovery time for NO2 at 5 ppm concentration are 319 s and 776 s, respectively. The sensing mechanism of the hydrazine hydrate-reduced graphene oxide gas sensor can be attributed to charge transfer between the NO2 molecule and the sensing material. The outstanding electrical properties of the reduced graphene oxide promote the electron transfer process. This allows the sensor to exhibit excellent gas sensing performance at room temperature. The reduced graphene oxide appears as a typical p-type semiconductor and the oxidizing gas NO2 acts as an electron acceptor. Therefore, the adsorption of NO2 gas leads to the enhancement of the hole density and conductivity of the reduced graphene oxide. Another reason is the presence of defects and oxygen-containing functional groups on graphene sheets. Some oxygen-containing groups remain on the graphene surface after an incomplete reduction reaction. Compared with pure graphene, the reduced graphene oxide has hydroxyl groups and epoxy groups remaining on the surface. These functional groups will functionalize the material and promote the adsorption of gases. At the same time, the reduction reaction will further produce vacancies and structural defects. This will provide more reaction sites and thus conduce to the material further adsorbing the gas. In summary, the experimental research in this paper is of significance for studying the mechanism and characteristics of the reduced graphene oxide by using hydrazine hydrate as a reducing agent, and it can provide reference and lay a foundation for the applications of future graphene sensors.

A method of determining microwave dissipation of Josephson junctions with non-linear frequency response

Chen Heng-Jie, Xue Hang, Li Shao-Xiong, Wang Zhen
Acta Physica Sinica. 2019, 68 (11): 118501 doi: 10.7498/aps.68.20190167
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Based on Josephson junction (JJ), superconducting quantum bit (qubit) is operated at frequencies of several GHz. Dissipation of JJs in this frequency range can cause energy relaxation in qubits, and limit coherence time, therefore it is highly concerned and needs to be determined quantitatively. The dissipation of JJs can be quantified by microwave quality factor. It is usually done at very low temperature (~mK) to determine whether a JJ is suitable for qubit devices by measuring the quality factor. In this paper, a method based on nonlinear frequency response of JJs is proposed to determine the quality factor. This method can be used in thermal activation regime, which may bring great conveniences to experiments. To analyze high frequency properties of JJs, the dynamic equation of a current-biased JJ, which describes high frequency oscillation of the JJ, is introduced. A fourth-order potential approximation is used to obtain the analytical equation of non-linear response. The dependence on quality factor, as well as on amplitude, of difference between JJ's plasma frequency and resonant frequency, is derived from the equation. The approximate treatment is quantitatively validated by our numerical simulations with practical JJ parameters including different environment influences. Thus, based on nonlinear frequency response of JJs, a reliable and simple method to determine quality factor of JJ is proposed, which is desirable for exploring JJ based microwave devices such as parametric amplifier, superconducting qubit. Being driven well into the nonlinear microwave response regime, due to frequency-amplitude interaction, the resonant frequency of a current bias JJ deviates from the JJ's plasma frequency. The deviation is directly related to the microwave quality factor. Hence, the quality factor can be deducted from the experimental measurement of the resonant frequency deviation, with different microwave power values applied. In comparison with linear resonance experiment, the nonlinear resonance used by the proposed method produces stronger signal. Therefore it is more robust against external noise. When being conducted at high temperature, the proposed method is more reliable. The accuracy of the measured quality factor primarily depends on those of the JJ's parameters such as critical current and capacitance, while those parameters can be experimentally determined with high precision.

Analysis and simultion for Compton camera's imaging resolution

Song Zhang-Yong, Yu De-Yang, Cai Xiao-Hong
Acta Physica Sinica. 2019, 68 (11): 118701 doi: 10.7498/aps.68.20182245
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Compared with traditional gamma-ray imaging equipment, the Compton camera is a very promising imaging device in nuclear medicine and molecular imaging, and has a strong potential application in monitoring beams in heavy-ion-therapy because of its high efficiency feature. A demonstration device for heavy ion cancer treatment with complete intellectual property right has been built at Institute of Modern Physics, Chinese Academy of Sciences in Wuwei city of Gansu Province. At present the device is being up-graded, and the heavy ion cancer treatment is being generalized in national wide. In view of the broad prospects of heavy ion cancer treatment, the imaging resolution of Compton camera is analyzed theoretically, and three errors effecting the imaging resolution, which are energy resolution, position resolution of detector and the Doppler effect, are determined. Then the three errors are simulated by using the Geant 4 packages. The physical process in simulation is selected as the G4EMPenelopePhysics model, which makes the atomic shell cross section data for low energy physical process used directly. The Compton camera geometry consists of two layers of detectors. The layer close to γ source is called detector and the other one is called absorption detector. The material of scatter detector is selected as low-Z silicon and carbon, and the absorb detector is high-Z germanium. The thickness value of scatter detector and absorb detector are both 20 mm. The spacing between the two layers is 100 mm. The simulation results by Geant 4 are used to reconstruct the image of point-like γ source through using the back-projection algorithm. The simulation results and the re-constructed images indicate that the difference between the image full width at half maximum induced by 2 mm position resolution and that induced by 5.0% relative energy resolution of scatter detector is about 10%, and amount to that by the Doppler effect of Silicon. For the γ ray with energies of several hundred keV, the energy resolution of Si detectors is easily better than 1.0% in practice. Therefore, the detector's position resolution dominates the image quality of the Compton camera. Considering the Doppler effect, manufacturing techniques and imaging efficiency, 2.0 mm-sized crystal unit and 1.0% energy resolution power is suggested for practically manufacturing the Compton camera.

Correlation between the electrical transport performance and the communicability sequence entropy in complex networks

Chen Dan, Shi Dan-Dan, Pan Gui-Jun
Acta Physica Sinica. 2019, 68 (11): 118901 doi: 10.7498/aps.68.20190230
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Optimization of the network's electrical transport properties not only conduces to understanding the relationship between structure and network function, but also can improve the electrical engineering technology. The effective way to solve this problem is to treat the network from the information viewpoint and seek the information structure measure which affects crucially the network electrical transport performance. Recent studies have shown that the communicability sequence entropy of complex networks can effectively quantify the global structural information of networks. Based on this measure, the difference between networks can be quantified effectively, and the connotation of communicability sequence entropy is explained. In this paper, we predict that the electrical transport performance of complex networks has a strong correlation with the communicability sequence entropy. For this reason, we mainly study the correlation characteristics of the electrical transport performance and communicability sequence entropy of small-world networks, scale-free networks, degree-correlated scale-free networks, community networks, and IEEE57 and other electrical node networks. The results show that the electrical transport performances of these networks are all a monotonically increasing function of communicability sequence entropy, namely, the communicability sequence entropy, and the electrical transport properties have a positive correlation. Specifically, in the process evolving from a regular network to a small-world network, the communicability sequence entropy and electrical transport performance of the network increase gradually. For scale-free networks, in the process of increasing degree distribution exponent, communicability sequence entropy and electrical transport performance of the network increase gradually. For degree-correlated scale-free networks, during the evolution from assortative to disassortative topology, communicability sequence entropy and electrical transport performance both decrease gradually. For networks with community structure, the communicability sequence entropy and electrical transport performance decrease with the increase of the number of communities. Finally, the correlation between communicability sequence entropy and electrical transport performance of two classical node power supply networks and corresponding randomization network models are also studied. The results show that as the order of d increases, both communicability sequence entropy and electrical transport performance decrease. And both are getting closer to the original network's communicability sequence entropy and electrical transport performance. The rule is beneficial to providing an effective strategy for designing a high transmission efficiency of the power network, that is, we can optimize the electrical transport performance by improving the network communicability sequence entropy.

Opinion formation model with co-evolution of individual behavior and social environment

Liu Xiao-Hang, Wang Yi-Ning, Qu Zi-Min, Di Zeng-Ru
Acta Physica Sinica. 2019, 68 (11): 118902 doi: 10.7498/aps.68.20182254
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Entering the information era, the formation of public opinion is largely associated with the complex system constructed by the Internet, thereby possessing new characteristics. The formation of public opinion is the result of the interaction of individual behavior with social environment. In reality, the environmental factor and the individual behavior are usually related to each other and co-evolve with time. Based on the Ising model, in this paper established is an opinion formation model that includes the process of the accumulation and digestion of the social tension. In the model, a parameter named effective dissolving factor c is designed to represent the extent of the interaction between the system and the social environment. A two-dimensional dynamical system is involved in the model to describe the dynamics of individual behavior and social tension. The co-evolution behavior of the system is studied. Based on the Landau mean field theory, the stationary states of the dynamical system under different parameter values, i.e. the value of effective dissolving factor c, their stability and bifurcation of the system, are analyzed. Finally, the computer simulation method is used to verify the results. The research shows that with the co-evolution mechanism of the system, our model exhibits certain self-organization characteristics. When the effective dissolving factor c is smaller than the threshold value, the system will reach final consensus opinion, resulting in a macroscopically ordered state. Otherwise, when the dissolving factor c exceeds a threshold value, the system is stable in the disordered state. It is interesting to find that there is such a critical value of the parameter that it leads the system to be self-organized into a critical state from any initial state. The future detailed investigation on the criticality of the co-evolving system is also suggested, such as testing whether the system has evolved into the critical state according to the finite-sized scaling theory and calculating the critical exponent of the system. In addition, in this paper provided is a new perspective to tackle practical problems in public opinion. Based on the mechanism of the formation of public opinion revealed by our model, researchers are encouraged to conduct studies on how to monitor the state of public opinion more precisely and to predict the tipping point of the system evolution.

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

An adaptive quantum state-hopping communication strategy based on kangaroo entanglement hopping model

Nie Min, Wei Rong-Yu, Yang Guang, Zhang Mei-Ling, Sun Ai-Jing, Pei Chang-Xing
Acta Physica Sinica. 2019, 68 (11): 110301 doi: 10.7498/aps.68.20190163
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Quantum communication in free space will be disturbed by natural environment such as fog and dust. However, to build a global quantum satellite wide area communication network, we must solve the problem of 24-h all-weather communication between satellite and earth. With the evolution of time, the degree of interference becomes deeper. In order to improve the performance of quantum communication under such an interference, in this paper we analyze the change of single quantum state channel over time under the background interference, and propose an quantum state-hopping communication strategy based on the kangaroo entanglement hopping model (KEHM), and simulate the performance and parameters of the strategy. Kangaroos are social animals. When they are frightened, they will jump synchronously in the same way with the same step length, height and frequency. According to this model, we make the two communicating parties realize synchronous quantum state jump according to the prearranged pattern. The simulations show that when the ratio between the average power of background quantum noise and the average power of quantum signal is 5, the quantum bit error rate decreases from 0.4524 to 0.1116 with the quantum state hopping frequency increasing from 1 to 15. When the single quantum state transmission success rate is 0.95 and the quantum bit rate is greater than 200 qubit/s, the probabilities of successful transmission of quantum bits at different state hopping frequencies are greater than 0.97. When the quantum reception efficiency of the receiver is 0.8, the quantum state pass rate increases from 0.3667 to 0.9986 with the average quantum number of the source increasing from 1 to 10. When the average quantum number of the source is 6, the passing rate of quantum state increases from 0.6262 to 0.9855 with the quantum receiving efficiency of the receiver increasing from 0.2 to 0.99. However, if the average quantum number of the transmitter is large enough and the receiving efficiency of the receiver is close to 1, the passing rate of the quantum state is also close to 1. The adaptive control strategy of quantum state hopping is based on real-time quantum channel state detection. Its core idea is to remove the quantum states which are seriously disturbed from the quantum state hopping set, and to realize the synchronous hopping of communication parties on the quantum states with low interference. Adopting the strategy of quantum state hopping adaptive control can further reduce the quantum bit error rate of the system. The error rate gain of adaptive control system increases with the increase of the success probability of processing the disturbed quantum state. When the probability of processing the disturbed quantum state is 0.95, the system error rate gain can reach 1.301. The performance of quantum state hopping system is improved obviously. To sum up, the adaptive quantum state-hopping communication strategy based on the kangaroo entanglement hopping model proposed in this paper greatly enhances the comprehensive immunity of the system and ensures the security of quantum information network, and provides an important reference for the healthy development of wide-area quantum satellite communication network in the future.

Collaborative quantum computation with redundant graph state Hot!

Tian Yu-Ling, Feng Tian-Feng, Zhou Xiao-Qi
Acta Physica Sinica. 2019, 68 (11): 110302 doi: 10.7498/aps.68.20190142
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Quantum computation is a computing model based on quantum theory, which can outperform the classical computation in solving certain problems. With the increase of the complexity of quantum computing tasks, it becomes important to distribute quantum computing resources to multi-parties to cooperatively fulfill the complex tasks. Here in this paper a scheme based on the one-way quantum computing model is proposed to realize collaborative quantum computation. The standard one-way quantum computing model is based on graph states. With graph states used as resources, one can realize a universal quantum computer through using single-qubit measurements and feed-forward. In contrast to the standard one-way computation, the main resource for collaborative quantum computation is a redundant graph state (also a multi-particle highly entangled state). Unlike in the traditional graph state where each particle corresponds to a specific node, in a redundant graph state, several particles correspond to a single node, which means that each node of the graph has several redundant copies. With the help of a redundant graph state, several parties can share a graph state flexibly at will. A redundant graph state is prepared and then distributed to several parties where each of them obtains a full copy of all nodes. By communicating with each other and measuring the particles in different ways, a standard graph state is prepared and distributed among these parties. The collaborative computation then finishes through the common one-way quantum computing operations. Besides the general scheme, a concrete optical implementation of a two-party cooperative single-qubit quantum state preparation based on a six-photon redundant graph state is also put forward. Such a redundant graph state is proposed to be prepared by using the spontaneous parametric down-conversion entangled source and quantum interference. With this redundant graph state, a standard three-node graph state can be shared with the two parties in an arbitrary way. This scheme does not only make the collaborative quantum computation across several parties possible and flexible, but also guarantee the privacy of each party's operations. This feature would be particularly useful in the case where the computing resource is obtained from an outside provider. This scheme paves the way for realizing quantum computation in more general and complicated applications.

Flat chaos generated by optical feedback multi-mode laser with filter

Li Kun-Ying, Li Pu, Guo Xiao-Min, Guo Yan-Qiang, Zhang Jian-Guo, Liu Yi-Ming, Xu Bing-Jie, Wang Yun-Cai
Acta Physica Sinica. 2019, 68 (11): 110501 doi: 10.7498/aps.68.20190171
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Optical chaos has a wide range of applications in communications, such as secure communication, high-resolution lidar ranging, optical time domain reflectometer, and high-rate physical random bit generator.In recent years, external-cavity feedback semiconductor lasers (ECLs) are the most common chaotic laser generation systems due to their characteristics of wide bandwidth, large amplitude, and simple structure, and the dynamic characteristics of chaotic signals have attracted much attention. However, limited by the relaxation oscillation of the laser, the energy of the chaotic signal directly generated by ECL is mainly concentrated at high relaxation oscillation frequency. Thus, the low-frequency component encounters the problem of energy loss.In practical applications, the signal detection/acquisition device usually responds to a 3-dB low-pass filtering characteristic. Therefore, the available effective bandwidth of the chaotic signal should actually be 3-dB bandwidth. The lack of low-frequency components will limit the energy utilization rate of chaotic signals and restrict the relevant performances of chaotic applications (such as reliability and transmission of chaotic secure communication, randomness and generation rate of physical random bits, measurement accuracy and range of lidar ranging or optical time-domain reflectometer).In the paper, we propose a broadband chaos generation scheme with simple structure and losing no low-frequency components. Specifically, we experimentally analyze the radio frequency (RF) spectra of the single-mode and the multi-mode output from an optical feedback Fabry-Perot (FP) semiconductor laser after and before filtering. The experimental results show that comparing with the multi-mode chaotic signal, the low-frequency energy of the single-mode chaotic spectrum is enhanced by 25 dB, and the 3-dB bandwidth of the single-mode chaotic signal can reach 6 GHz. Further theoretical analysis demonstrates that the enhancement of low-frequency component in the single-mode chaotic signal is caused by the mode-competing in multi-mode laser. It is concluded that this method can well solve the problem of low-frequency energy loss in conventional optical feedback chaotic systems, and is beneficial to improving the energy utilization rate of chaotic signals, which is of great significance for improving the performance of chaotic secure communication, random bit generation, lidar ranging, optical time domain reflectometer, and other relevant applications.

Color image encryption method based on computer generated hologram and θ modulation

Xi Si-Xing, Yu Na-Na, Wang Xiao-Lei, Zhu Qiao-Fen, Dong Zhao, Wang Wei, Liu Xiu-Hong, Wang Hua-Ying
Acta Physica Sinica. 2019, 68 (11): 110502 doi: 10.7498/aps.68.20182264
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In this paper, a new method of encrypting a color image based on θ modulation is proposed by using the tricolor principle and computer-generated hologram (CGH) technology. The encryption process includes the θ-modulated three primary color components and the coding of computer-generated hologram, which is implemented in a Fresnel diffraction and spatial filtering system. Firstly, the color image modulated by the first random phase key is divided into three encryption channels by red laser, green laser, blue laser, and tricolor filters. Each channel is introduced by a transmissive amplitude-type sinusoidal grating with different directions, which is used to separate the three primary color components in the spatial spectrum plane. Secondly, the modulation results of tricolor components are superimposed together to form a compound image, and the phase truncation of the superposition result is performed to achieve the asymmetric encryption. Finally, the amplitude of the compound image is modulated by the second random phase key and is encoded into a binary real-value gray-color CGH by Roman-type coding method. Therefore, the gray-color information of the original image is completely hidden in the encrypted CGH, which is more general and deceptive in the storage and transmission process. Decryption is an inverse process of the encryption. Firstly, the encrypted CGH is placed on the input plane of the spatial filtering and Fresnel diffraction system. Secondly, the demodulation of CGH phase key and the spatial filtering based on optical filter are performed. Finally, the color plaintext image is obtained by using the correct Fresnel diffraction. The simulation results show the validity and feasibility of the proposed method. In addition, the anti-noise attack and anti-shearing attack performance of this color image encryption method are investigated. Compared with results from the three presented methods reported in the literature, our investigated results demonstrate that this method has good robustness to noise attack and shearing attack, and has obvious advantages when the attack noise density is larger. Due to the characteristics of high security and anti-noise, we believe that this color image encryption method promises to have important applications in the information transmission and multi-user authentication.

Entropy measurement of ordered patterns in neuronal network with repulsive coupling

Huang Zhi-Jing, Li Qian-Yun, Bai Jing, Tang Guo-Ning
Acta Physica Sinica. 2019, 68 (11): 110503 doi: 10.7498/aps.68.20190231
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Traveling waves, standing waves, and spiral waves occur spontaneously in the brain neural network in some brain states. The occurrence of these ordered spatiotemporal patterns is often related to some neurological diseases. However, the mechanisms behind the generation of the ordered pattern are not fully understood. How to quantitatively describe the nature of these spatiotemporal patterns still needs further exploring. In order to solve these problems, the Hindmarsh-Rose neuron model is used to study the dynamic behavior of the two-dimensional (2D) neuronal network with double-coupling layer, which is composed of nearest-neighbor excitatory coupling and long-range repulsive coupling layers and evolves from an initial state with a random phase distribution. An improved cluster entropy is proposed to describe the spatiotemporal pattern of the neuronal network. The numerical simulation results show that the repulsive coupling can either promote the formation of ordered patterns or suppress the formation of ordered patterns. When the repulsive coupling strength and excitatory coupling strength are appropriately selected, the chaotic network can spontaneously generate single spiral wave, multiple spiral wave, traveling wave, the coexistence of spiral wave and others wave state, the coexistence of target wave and others wave state, the coexistence of traveling wave and standing wave, etc. The probability with which spiral wave and traveling wave occur reach 0.4555 and 0.1667 respectively. The probability with which target wave and other states co-occur, and the probability with which the traveling wave and the standing wave co-occur, are 0.0389 and 0.1056, respectively. These ordered wave patterns and chaotic states can be distinguished by using the proposed cluster entropy. When the repulsive coupling strength is large enough, the neuronal network is generally in chaotic state. It is found by calculating cluster entropy that a large cluster can appear in the neuronal network when the excitatory coupling strength and repulsive coupling strength are both weak. These results can conduce to understanding the self-organization phenomena occurring in the experiments and also to treating various neurological diseases.

Measurement of ultrashort laser pulses with rapid-scanning frequency-resolved optical gating device

Wen Jin-Hui, Hu Ting, Wu Qin-Fei
Acta Physica Sinica. 2019, 68 (11): 110601 doi: 10.7498/aps.68.20190034
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Frequency-resolved optical gating (FROG) is now one of the main methods of characterizing the ultrashort laser pulses. There are mainly three SHG-FROG methods, i.e. the standard FROG, the single-shot FROG and GRENOUILLE, each of which has its own features and application areas. Although the standard SHG-FROG has balanced advantages in sensitivity, accuracy and applicability for various test pulses, its speed is much slower than the others':it often takes a few seconds or even minutes to record the FROG trace, which is dependent on the size of FROG image. Nowadays continuous development of the technique of digital imaging brings to high resolution CCD/CMOS image cameras with tens of millions pixels and fast refreshing rate. Unfortunately the standard FROG cannot make use of these image cameras for the real-time measurement of ultrashort pulses. To solve this problem, in this paper a rapid-scanning FROG device based on the standard SHG-FROG is demonstrated, where sinusoidal waves from a signal generator synchronously drive a voice coil actuator and a galvo-scanner, so that the spectra of the autocorrelation at different delays are successively reflected onto an area camera. As long as the camera is triggered to shoot continuously, the entire FROG trace can be recorded quickly within 1 s. Furthermore, several guidelines for good performance with this device are provided, including the settings of the amplitude and frequency of the driving sinusoidal waves, the selections of the focuses of the collimating lens F1 and the focusing lens F2, and the method of delay calibration. This device is suitable for the real-time measurement of ultrashort pulses with large chirps or complex structures where large-size FROG images need to be captured. In order to show the capability of this device, femtosecond pulses delivered directly from a home-made Kerr-lens mode-locked Ti:sapphire laser as well as the chirp pulses dispersed by a 200 mm-thick BK7 slab are measured. Two scan ranges are selected in order to achieve enough effective data points in the FROG traces of these two test pulses. Using standard procedure of pulse retrieval of FROG, the two pulses are reconstructed with pulse widths 58 fs and 492 fs, respectively. From the retrieved spectral phases of these test pulses, the GDD value of the BK7 slab can be deduced to be 8740 fs2, which is in good agreement with the theoretical value of 8815 fs2. Thus the experimental results confirm the accuracy and applicability of this FROG device.

ATOMIC AND MOLECULAR PHYSICS

First principles study of effect of vaiable component Al on HfO2 resistance

Dai Guang-Zhen, Jiang Yong-Zhao, Ni Tian-Ming, Liu Xin, Lu Lin, Liu Qi
Acta Physica Sinica. 2019, 68 (11): 113101 doi: 10.7498/aps.68.20181995
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In order to improve the resistance properties of HfO2 and increase the consistency and uniformity of conductive filaments formed by oxygen vacancies (VO), the first-principles calculation method based on density functional theory is used to study the micro-properties of Al-doped HfO2 resistive materials. The results show that the interval Al (Int-Al) is more suitable for being incorporated into HfO2, and the closer to the relative position of VO the Int-Al, the faster the convergence rate of the resistive material tends to be stable, and the smaller the formation energy. The effects of different Int-Al concentrations on the formation of HfO2 supercells with VO defects show that when the concentration of doped Int-Al is 4.04%, the fractional charge state density map can form relatively good charge channels. The maximum and critical equipotential surface values are highest, which is conducive to improving the consistency and uniformity of the formation of conductive filaments in HfO2 resistive materials. The calculation of energy formation shows that the change is slow when the concentration of Int-Al is lower than 4.04%. When the concentration of Int-Al is higher than 4.04%, the abnormal increase occurs, which indicates that the defect system becomes more and more difficult to form with the increase of the concentration of Int-Al.

 

The introduction of the impurity and the VO defect destroy the original complete crystal structure, which causes the position of the atoms around the impurity to shift, and the valence electron orbit and the energy level of the crystal are changed, and the distribution of the internal charges of the HfO2 defect system is affected. In order to study the effect of the change of the lattice structure on the formation of the VO conductive filament, the VASP software package is used to calculate the relative ratio of the atoms in the lattice structure of the HfO2 defect system as the reference and the relative ratio of the HfO2 defect system after the optimizing the lattice structure. Further study of the change of lattice structure, when the concentration of doped Int-Al is 4.04%, shows that the defect formation energy decreases significantly, which is conducive to the formation of perfect conductive channel. The conductive channel has a certain reference significance for improving the performance of HfO2 based resistive variable memory materials.

All-electron calculation of ground state vibration-rotation energy levels of 7Li2(0, ±1) molecular systems

Wang Qiao-Xia, Wang Yu-Min, Ma Ri, Yan Bing
Acta Physica Sinica. 2019, 68 (11): 113102 doi: 10.7498/aps.68.20190359
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The investigation of spectroscopic information is important for understanding the mechanisms of molecular photochemical and photophysical reactions. As a prototype to study the electronic structures and spectra of diatomic molecular systems, the vibration-rotational spectra of alkali dimer and its ions have aroused considerable research interest in the last two decades. Single-reference and multi-reference coupled cluster theory in combination with correlation consistent Gaussian basis set are adopted to study the ground-state potential energy curves of 7Li2(0,±1) molecular systems. The correlation effect and relativistic effect of all the electrons are taken into account in the calculation. And the spectroscopic constants, including the equilibrium internuclear distance Re, the harmonic vibrational frequency ωe, the anharmonic constant ωexe, the equilibrium rotational constant Be, and the dissociation energy De of the molecular system and vibration-rotational energy level information of the ground states are obtained by solving the radial Schrödinger equations. The calculated spectroscopic constants of the neutral and positive ion system accord well with the experimental values; however for the negative ion system, the calculation of equilibrium internuclear distance needs further improving, and other spectroscopic constants are consistent well with the experimental values. The present computational results indicate that the ground state wave functions of neutral and positive ion systems have obvious single reference configuration characteristics, while the ground state of negative ion molecule system should be described with multireference configuration wave functions. The vibration-rotational energy levels of ground state with different theoretical methods are in good agreement with the experimental values. The vibrational-rotational energy levels and spectroscopic constants of neutral and positive ion systems are well reproduced, and some experimental information about spectrum is still lacking. Although the difference among the equilibrium internuclear distances for the ground state of the negative ion, obtained from different theoretical methods are still existent, the results of the vibrational level interval accord well with each other. This study provides useful information about spectrum for accurately investigating the electronic structures and spectra of the ground state of Li2 molecular system and its two isotopic molecules, especially for the negative ion system with little information about spectrum.

First-principles study of five isomers of two-dimensional GeSe under in-plane strain

Zuo Bo-Min, Yuan Jian-Mei, Feng Zhi, Mao Yu-Liang
Acta Physica Sinica. 2019, 68 (11): 113103 doi: 10.7498/aps.68.20182266
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Using first-principles calculations, we investigate the stability and electronic properties of five isomers of two-dimensional (2D) GeSe monolayer under in-plane strain. Our calculated results show that the five isomers of GeSe monolayer are all stable. It is found that the α-GeSe has a direct band gap, while each of the β-GeSe, γ-GeSe, δ-GeSe and ε-GeSe possesses an indirect band gap. By applying compressive or tensile uniaxial and biaxial strain to the five GeSe isomers, the indirect-to-direct transition in band gap is found. In the α-GeSe, the changes from indirect-to-direct and semiconducting-to-metallic are both found under an applied strain. In the 2D β-GeSe and γ-GeSe, an adjustable range of indirect band gap under strain is found. Moreover, a direct band gap in the δ-GeSe is found separately under the biaxial compression strain of σxy=-2% and σxy=-4%. By applying a tensile strain of 10% along the armchair direction in ε-GeSe, a transition from an indirect to direct band gap occurs. When the tensile strain is continuously increased to 20%, the band structure of ε-GeSe maintains direct character. This direct band gap can be tuned from 1.21 eV to 1.44 eV. When 10% tensile strain is applied along the biaxial direction, the transition in band gap from indirect-to-direct also occurs. Our results indicate that the direct band gap can be tuned from 0.61 eV to 1.19 eV when the tensile strain is increased from 10% to 19% in ε-GeSe.

Investigation of the two-color polarization spectroscopy between the excited states based on cesium atoms

Zhang Jin-Fang, Ren Ya-Na, Wang Jun-Min, Yang Bao-Dong
Acta Physica Sinica. 2019, 68 (11): 113201 doi: 10.7498/aps.68.20181872
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Two-color polarization spectroscopy (TCPS) of cesium 6S1/2-6P3/2-8S1/2 (852.3 nm + 794.6 nm) ladder-type system in a room-temperature vapor cell are investigated. The frequency of 852.3 nm laser used as a pump beam is locked on one of the hyperfine transitions between the ground state 6S1/2 and excited state 6P3/2 by the saturated absorption spectroscopy technique, which can populate some atoms on the 6P3/2 excited state and induce anisotropy in the atomic medium. The frequency of 794.6 nm laser serving as a probe beam is scanned across the whole 6P3/2→8S1/2 transition to ascertain this anisotropy, and thus the TCPS is obtained. In experiment, we measure and analyse the influence of frequency detuning of 852.3 nm pump laser on TCPS, and especially reveal that some of hyperfine energy levels of intermediate excited state 6P3/2, which has no direct interaction with the 852.3 nm pump laser, are also populated by a small fraction of atoms with a specific speed in the direction of pump laser beam due to Doppler effect, so they also have contribution to the TCPS when the 794.6 nm probe laser is scanned to the resonance transition line between the 6P3/2 and 8S1/2 states after the Doppler frequency shift has been considered. In addition, we prove that the atomic coherence like electromagnetically induced transparency effect obviously results in a narrower line width of TCPS in the case of counter-propagating experimental configuration than that in the case of pump beam co-propagating with the probe beam in the Cs vapor cell. Finally, we apply the TCPS with dispersive shaped feature to frequency stabilization with no modulation, and the frequency fluctuations of 794.6 nm laser are~0.5 MHz and~9.2 MHz for the frequency-locking and free running in~225 s, respectively. The above research work is expected to play a role in precisely measuring the atomic energy level structure and its related hyperfine structure constant (magnetic dipole and electric quadrupole coupling constants), and also in stabilizing the laser frequency to the excited state transition especially for the optical fiber communication, two-color laser cooling/trapping neutral atoms, optical filter, etc.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

Magnetic monopole array model for modeling ship magnetic signatures

Guo Cheng-Bao, Yin Qi-Qi
Acta Physica Sinica. 2019, 68 (11): 114101 doi: 10.7498/aps.68.20190201
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Aiming at the problems of low accuracy and low adaptability of the existing ship magnetic field inversion modeling methods with equivalent sources, a new method of inversion modeling of magnetic monopole array of ship magnetic fields is proposed. Three-dimensional ship magnetic monopole array is arranged according to the ship ferromagnetic structure, and the inversion prediction model of ship magnetic fields is established by regularization technology. Three typical forms of magnetic monopole arrays are established:rectangular magnetic monopole array on the horizontal surface of the draft line, cuboid magnetic monopole array enclosing the ship hull, three-dimensional ship magnetic monopole array distributed according to the ship's ferromagnetic structure. The theoretical analysis shows that the three-dimensional ship magnetic monopole array reduces the blindness of the equivalent magnetic source setting, and the obtained equivalent magnetic source is highly consistent with the real magnetic source, which can reproduce the complete magnetic field information of the ship to a greater extent. The magnetic field of a typical virtual ship is applied to the validation test. The results show that the proposed three-dimensional ship magnetic monopole array has higher precision and adaptability than the rectangular or cuboid magnetic monopole array. In particular, the proposed three-dimensional ship magnetic monopole array can realize the mutual conversion between the near and far magnetic fields, and between the magnetic fields above and below the ship. The proposed three-dimensional ship magnetic monopole array model has the unique advantages of small complexity, simple modeling and flexible layout, and it provides an alternative method for the high-precision data processing and explanation to the inversion modeling of ship magnetic fields, ship magnetic field positioning, et al.

A method of designing asymmetric double-sided off-axis aspheric mirror detection compensation zoom light path

Feng Shuai, Chang Jun, Niu Ya-Jun, Mu Yu, Liu Xin
Acta Physica Sinica. 2019, 68 (11): 114201 doi: 10.7498/aps.68.20182253
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With the development of multispectral common-aperture high-precision detection technology, the asymmetric double-sided off-axis aspheric mirror is playing an increasingly important role in characterizing the correcting phase difference, increasing the relative caliber of system, expanding the view angle of field, simplifying system structure, and reducing weight and volume. But high-precision detection is a key step restricting the applications of these mirrors. At present, the compensation method of the interference test is the most effective mean of off-axis aspheric surface detection which has a simple structure, large compensation range, small number of components and is easy to control. However for the detection of asymmetric double-sided off-axis aspheric mirrors, two sets of alone compensators are still used, in which the efficiency is low and the switching compensator will reduce the accuracy of detection. Aiming at this problem, in this paper we propose a zoom null compensation method which is based on the Offner refracting compensation method. In this method, the off-axis aperture stop causes the light to be off-axis and split, the common lens group is moved to zoom, and the mirror folds the light path. There are two off-axis apertures are provided for off-axis and splitting, four lenses which form three lens groups are used to move positions for zooming, two mirrors are used to fold light. An optical design software is used to simulate the experiment, and implements the design for the high-precision detection of optical path for the asymmetric double-sided off-axis aspherical mirror by using this set of null compensation method. The simulation result shows that the theoretical residual wave aberration increases up to 0.0003λ root-mean-square (RMS) and 0.0001λ RMS with the designed system compensation, which meet the requirement for detection. At the same time, the tolerance analysis is carried out according to the design result, the actual residual wave aberrations within the existing tolerance range are 0.0326λ RMS and 0.0316λ RMS, which meet the requirements for manufacturing and assembly. The present work provides a new idea for the high-precision detection of asymmetric double-sided off-axis aspheric mirror. At the same time, the quality of the detected beam in this paper is achieved under ideal conditions, and the quality of beam will be considered in the next research work.

Multi-section images parallel encryption based on optical scanning holographic cryptography technology

Wang Ren-De, Zhang Ya-Ping, Zhu Xu-Feng, Wang Fan, Li Chong-Guang, Zhang Yong-An, Xu Wei
Acta Physica Sinica. 2019, 68 (11): 114202 doi: 10.7498/aps.68.20190162
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In this paper, the function of parallel encrypting multiple images and reproducing arbitrary layers of images is realized by improving the double pupil function in optical scanning holography. In an optical scanning holography (OSH) system, a dual-pupil heterodyne incoherent image processing technique is used to record holographic images. By adjusting the two pupil functions in the optical system, the interference fringes can be modified to achieve different imaging effects. In this paper, the ring pupil and random phase plate are used to act as two pupil functions to interfere to form a ring random phase plate, and thus realizing the fast scanning of multi-layer images. Then the multi-layer images can be quickly encrypted by one imaging technique. The scanned signals are quickly collected by photoelectric detectors, and they synthesize encrypted holograms by computer. By using the digital holography to decrypt the holograms, the precise reproduction of any layer image can be achieved. The OSH system with random phase pupil is strongly dependent on the longitudinal position of the system in digital reconstruction. The defocusing noise can be converted into random noise and the effect of defocusing layer on imaging can be effectively suppressed. However, in practice, it is necessary to average multiple images to achieve better imaging effect, and the accuracy of random phase plate is required. In this paper, most of the random noise can be filtered with the aid of ring pupil, and all the information about multi-layer graphics can be recorded and reconstructed by one scan. In the process of reconstruction, the influence of defocusing image can be effectively eliminated, and the decryption of any layer image can be realized. This method collects encrypted image by photoelectric detector, and does not need complex algorithm reconstruction nor phase iteration, which greatly reduces the time expended in the encryption process. In the process of encryption, the key space of the system is increased, and the encrypted image obtained has high security. In this paper, correlation coefficient is used to evaluate the encryption effect of this method, and the effectiveness and security of this method are verified by simulation experiments. For cutting resistance, when 75% of the information is lost, the correlation coefficient can still reach more than 0.5. For the sensitivity of information, the integrity of decrypted image will be seriously damaged when the wavelength and distance shift very little. For the anti-noise ability, under the influence of Gauss noise and salt and pepper noise, the correlation coefficient and image recognition degree are high. This method is very time-saving, and the result of encryption has high security, high sensitivity, strong ability to resist clipping and noise.

Phonon blockade induced by a non-Hermitian Hamiltonian in a nanomechanical resonator coupled with a qubit

Liao Qing-Hong, Deng Wei-Can, Wen Jian, Zhou Nan-Run, Liu Nian-Hua
Acta Physica Sinica. 2019, 68 (11): 114203 doi: 10.7498/aps.68.20182263
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Nanomechanical resonator has important applications in the field of high-precision detection because it has a high-Q factor, high vibration frequency, small size, and other excellent characteristics. Superconducting qubit has very large magnetic dipole moments, so it can be easily combined with nanomechanical resonator. Furthermore, the system parameters including frequency and coupling strength can be designed according to requirements beforehand, which makes a superconducting qubit an ideal artificial atom. Compared with natural atom, superconducting qubit has abundant energy levels. For these reasons, nanomechanical system has aroused wide interest in the engineering, electron, physical and other fields of science and technology. According to the recent research, a new approach to the zero eigenvalues of non-Hermitian Hamiltonian is applied to the optomechanical system. It was found that the scheme is superior to conventional photon blockade (CPB) and unconventional photon blockade (UPB) in the cavity quantum electrodynamics (QED) system. So we propose a scheme to induce phonon blockade in order to explore a new avenue to the research about phonon blockades in the quantum open system. We study the phonon blockade in an optomechanical system that a qubit is coupled with nanomechanical resonator (NAMR) driven by two external weakly driving fields respectively in this way. In this paper, the Hamiltonian of such a system can be treated by the non-Hermitian Hamiltonian and it can be described in the form of matrix. Then the phenomenon of phonon blockade occurs when all the eigenvalues in the form of matrix are equal to zero. It is found that strong phonon antibunching can be triggered in both strong and weak nonlinearity when we use the method which has been already used in a gain optical cavity system. The distinct result reflects the advantage of our approach which possesses some outstanding characters between the ordinary methods (conventional phonon blockade and unconventional phonon blockade). In addition, the effect of our avenue on phonon blockade is analyzed and also the distinction between the conventional phonon blockade (CPNB) and unconventional phonon blockade (UPNB) is compared with each other in detail. By analytical calculation, the optimal conditions are given and the underlying physical mechanism is explained. In the comparison between CPNB and UPNB, we show the superiority of our scheme through some graphs. Finally, we describe briefly the measurements of phonon blockade in the NAMR-qubit system via a superconducting cavity. The proposal may provide a theoretical way to guide the manufacture of phonon devices in the future. The results obtained here may have a great significance and application in the field of quantum information processing and precision measurement.

Dual-wavelength external-cavity surface-emitting laser

Qiu Xiao-Lang, Wang Shuang-Shuang, Zhang Xiao-Jian, Zhu Ren-Jiang, Zhang Peng, Guo-Yu He-Yang, Song Yan-Rong
Acta Physica Sinica. 2019, 68 (11): 114204 doi: 10.7498/aps.68.20182261
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Dual-wavelength laser sources have important applications in the interferometry and the nonlinear-frequency-conversion generated mid-infrared or terahertz-band coherent radiation. Vertical-external-cavity surface-emitting lasers own outstanding advantages such as high output power, good beam quality and flexible emission wavelength, which make them very suitable for dual-wavelength running. In this paper, we employ a collinear Y-type cavity to produce a dual-wavelength laser. There are two semiconductor gain chips in the resonant cavity, one has an active region of In0.185Ga0.815As/GaAs strained multiple quantum wells and a designed wavelength of 960 nm, and the other has an active region of In0.26Ga0.74As/GaAsP0.02 strained multiple quantum wells and a target wavelength of 1080 nm. The peak wavelength of the photoluminescence of chip 1 is 950 nm, which is 10 nm shorter than the designed wavelength under weak pump, and the peak wavelength of the photoluminescence of chip 2 is 1094 nm, which is 14 nm longer than the target wavelength under low pump. When the pump power is increased, the peak wavelengths of the photoluminescence of two gain chips are both red-shifted. The oscillating laser wavelengths are centered at 953 nm and 1100 nm, the corresponding full width at half maximum (FWHM) values of the laser spectra are 1.1 nm and 2.7 nm, respectively. The wavelength spacing of the dual-wavelength is 147 nm, and the related mid-infrared coherent radiation is about 7.1 μm on the assumption that the dual-wavelength laser is used for difference frequency generation. When the absorbed pump power of each gain chip is 5.8 W, the total output power of the dual-wavelength laser reaches 293 mW at room temperature.

Fiber gratings matching and output characteristics of fiber laser

Liu Jia-Xing, Liu Xia, Zhong Shou-Dong, Wang Jian-Qiang, Zhang Da-Peng, Wang Xing-Long
Acta Physica Sinica. 2019, 68 (11): 114205 doi: 10.7498/aps.68.20190178
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In order to improve the output power and processing quality in industrial applications, it is important to optimize the output characteristics of the high-power fiber lasers. The slope efficiency, backward leaking power and stimulated Raman scattering are key issues in high-power fiber laser design. The parameters matching the fiber gratings, which are the critical components, have a direct influence on the whole fiber laser system. In this paper, the parameters matching the fiber gratings in fiber lasers are investigated. Firstly, the origin of slope efficiency, backward leaking power and stimulated Raman scattering are analyzed in theory. Then the influences on output characteristics of fiber lasers comprised of the output coupler gratings, which have different bandwidths and reflectivities, are experimentally studied. Finally, the optimized parameters and matching principle of fiber gratings in high-power fiber laser are obtained, thus providing an alternative method to improve the output characteristics of high-power continuous wave fiber laser.

Experimental study on influence of fiber numerical aperture on mode instability threshold of ytterbium fiber oscillator

Chen Yi-Sha, Liao Lei, Li Jin-Yan
Acta Physica Sinica. 2019, 68 (11): 114206 doi: 10.7498/aps.68.20182257
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The phenomenon mode instability is the most limiting factor for further scaling the output power and beam quality in high power fiber lasers. Thus, it is meaningful and necessary to study the influencing factor of mode instability and finally find the approaches to mitigating its influence. Theoretical calculations reveal that the fiber V-parameter has a negative effect on fiber amplifier mode instability threshold. Nevertheless, the influence of fiber core numerical aperture (NA) on fiber oscillator mode instability threshold has rarely been investigated compared with that on the fiber amplifier. In this paper, we build a high-power all-fiber laser oscillator pumped by 976nm laser diodes and measure its laser efficiency and mode instability threshold of 20/400 step-index ytterbium doped fiber with different fiber core NA. Experimental result reveals that at the same 976 nm pump power, the fiber with relatively low core NA (~0.059) has a higher mode instability threshold power than that with relatively high core NA (~0.064), and that even a higher core NA (~0.064) fiber has a higher laser efficiency than lower core NA (~0.059) fiber. The fact shows that the fiber core NA has a significant influence on mode instability threshold, and a relatively high core NA results in a lower mode instability threshold. Also, numerical simulations explain the reason why the fiber core NA has a negative effect on mode instability threshold in fiber oscillator. First of all, the higher fiber core NA will support more propagating modes in fiber, and the lower fiber core NA will result in higher order mode (HOM) content leaking into fiber cladding and the overlap of HOM content and gain area is reduced, thus the gain of HOM is relatively reduced. Also, the bending loss of HOM is very sensitive to fiber core NA variation, and the increase of fiber core NA will reduce the bending loss of HOM dramatically. In conclusion, the fiber core NA has a significant negative effect on fiber oscillator mode instability threshold, and numerical simulationscan explain the physical origin of the negative effect of fiber core NA on laser oscillator mode instability threshold. Thus, for the mode instability mitigation in high power laser oscillator, optimizing the NA of active fiber conduces to the increase of mode instability threshold, which is helpful and necessary for further scaling the output power and beam quality.

Analytical method for four wave mixing in space-frequency multiplexing optical fibers

Wan Feng, Wu Bao-Jian, Cao Ya-Min, Wang Yu-Hao, Wen Feng, Qiu Kun
Acta Physica Sinica. 2019, 68 (11): 114207 doi: 10.7498/aps.68.20182129
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In recent years, the transmission capacity of wavelength division multiplexing (WDM) communication systems has gradually approached to the nonlinear Shannon limit. To meet the increasing demand for communication capacity, space division multiplexing (SDM) has become one of the most concerned technologies. In this paper, the four-wave mixing process (FWM) in fibers is considered from the frequency domain to the mode division multiplexing (MDM) spatial domain under pump depletion and the exact analytical solution to the FWM coupled-mode equations in the space-frequency domain is in detail deduced. The analytical method is verified by numerically calculating the amplitude and phase evolution of the idler wave in non-degenerate four-wave mixing. We discuss three new applications of the analytical solution as follows. 1) Using the phase matching condition we select the terms in the multi-wave coupling equation, and only retain the coupling term that plays a major role. According to the analytical solution in this paper, the phase matching percentage parameter is introduced to determine the FWM coupling terms necessary for multi-wave coupling equations, thus simplifying the multi-wave coupling problem in the study. 2) Combining the analytical solution with the numerical calculation results, we find the initial phase relationship between the output idler and the input guided wave for phase-insensitive FWM, and we provide the analytical expression for a theoretical basis to efficiently design the FWM-based phase arithmetic devices in parallel operating at WDM and MDM systems. 3) We propose a nonlinear compensation algorithm based on analytical solution, which can be used in the few-mode transmission system. The algorithm can fast evaluate or compensate for the fiber nonlinearity by taking into account the pump depletion of the FWM effect. Compared with the traditional digital back propagation (DBP) algorithm, our algorithm has the advantage of lower complexity.

Effect of annealing temperature on structure and stress properties of Ta2O5/SiO2 multilayer reflective coatings Hot!

Liu Bao-Jian, Duan Wei-Bo, Li Da-Qi, Yu De-Ming, Chen Gang, Wang Tian-Hong, Liu Ding-Quan
Acta Physica Sinica. 2019, 68 (11): 114208 doi: 10.7498/aps.68.20182247
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In the optical system of spaceborne laser altimeter, dielectric mirror is an indispensable optical film element. Its surface shape quality directly affects the resolution and accuracy of distance measurement of the detection system. It is pressing and necessary to carry out research on the surface shape control technology of dielectric mirror to eliminate or reduce the effect of film stress on surface shape. The Ta2O5/SiO2 multilayer reflective coatings are deposited on quartz substrates by using the ion beam assisted electron beam evaporation (IBE), and then annealed in air in a temperature range from 200 to 600℃. The effect of annealing temperature on the structure, optical and stress properties of Ta2O5/SiO2 multilayer reflective coatings are systemically investigated by using x-ray diffraction, atomic force microscope, spectrophotometer and laser interferometer. The results show that all the Ta2O5/SiO2 multilayer reflective coatings, after being annealed, are amorphous in structure. The annealing temperature has a great influence on the surface roughness of reflective coating. With the increase of annealing temperature, the surface roughness of reflective coating first decreases and then gradually increases, but is still smaller than that of as-deposited sample. After being annealed, the reflectance spectrum of reflective coating shifts slightly toward the long-wave direction, and the reflectivity increases a little. When being annealed at 500-600℃, the compressive stress of reflective coating could be transformed into tensile stress, and the surface is changed from convex to concave shape. It can be concluded that annealing at an appropriate temperature can effectively release residual stress of Ta2O5/SiO2 multilayer reflective coating and eliminate the deformation of substrate caused by film stress, and thus improving the surface shape quality of dielectric mirror., After being annealed, the reflective coating still possesses the stable structure and spectral properties, so that dielectric mirror can meet the application requirements of spaceborne laser altimeter. In this paper, the experimental results are of great significance for applying the annealing technology to the surface shape control technology of dielectric mirrors.

Transmission characteristics of vortex beams in a sixfold photonic quasi-crystal fiber

Wei Wei, Zhang Zhi-Ming, Tang Li-Qin, Ding Lei, Fan Wan-De, Li Yi-Gang
Acta Physica Sinica. 2019, 68 (11): 114209 doi: 10.7498/aps.68.20190381
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In an optical fiber communication system, vortex beams have aroused great interest in the last several decades. Vortex beams possess many intriguing properties. For example, they have the ability to carry orbital angular momentum (OAM) which is mutually orthogonal. The OAM is a fundamental physical quantity of light which can be used as information carriers for transmission channel of optical fiber. Combined with the existing multiplexing techniques such as wavelength division multiplexing technique, advanced multilevel amplitude modulation formats, etc., the vortex beams provide an alternative to the increase of the transmission capacity and spectral efficiency of the optical fiber transmission system. Recently, long-length transmission of vortex-beam in optical fiber has been realized and there have also occurred some new designs of optical fiber on vortex beams, such as air-core ring shaped fiber, graded index vortex fiber, multi-ring fiber, and supermode fiber. Photonic crystal fiber (PCF) is flexible in design. Therefore, it is easy to regulate the transmission performance of PCF by adjusting the radius and the pitch of the air holes and so on. In this paper, we propose a newly designed sixfold photonic quasi-crystal fiber (SPQCF) to transmit vortex beams stably. Transmission characteristics of this newly designed fiber are simulated and calculated by using COMSOL multiphysics software. When the wavelength of the incident light is 1550 nm, the effective index difference between the vortex modes in a group is more than 10-4 which is large enough to preclude the LP modes from being formed, and to transmit 7 vector modes (10 OAM modes). Changing the radius and pitch of the air holes, we can regulate the dispersion characteristic and confinement loss of the SPQCF flexibly. At 1550 nm, the confinement loss of the SPQCF maintains 10-8-10-7 which is low enough to confine the vortex beams in the fiber core. When the incident light wavelength of HE21 ranges from 1500 nm to 1800 nm (r0=1.9 μm), the dispersion coefficient of the SPQCF is between 63.51-65.42 ps·nm-1·km-1 which tends to be flat. By changing r0, the flat trend is adjusted to different wavelength range. This dispersion characteristic possesses great potential for the transmission of optical solitons. The effective mode area (HE21) is about 40 μm2 and the nonlinear coefficient (HE21) is maintained on the order of 10-3 between 1500-1600 nm. These features suppress the generation of nonlinear effect in the fiber and benefit the transmission of vortex beams. The stable transmission distance is longer than 1 km. In summary, we design a new type of PCF featuring quasi-crystal structure which has a ring shaped fiber core and supports the transmission of vortex beams stably.

Evolution of non-frequency shift components of pulse tail in normal dispersion region of highly nonlinear fiber

Sun Jian, Li Tang-Jun, Wang Mu-Guang, Jia Nan, Shi Yan-Chao, Wang Chun-Can, Feng Su-Chun
Acta Physica Sinica. 2019, 68 (11): 114210 doi: 10.7498/aps.68.20190111
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Supercontinuum generated in normal dispersion region of highly nonlinear fiber (HNLF) is widely used in signal processing and communication benefiting from its good flatness and high coherence. Because of the normal dispersion, optical wave breaking (OWB) occurs when non-frequency shift components and frequency shift components caused by self-phase modulation (SPM) overlap in time domain, and ends when non-frequency shift components disappear. The evolution of non-frequency shift components at the front and rear edge of optical pulse play an essential role in the supercontinuum generation process. In this paper, the evolution of non-frequency shift components in normal dispersion region is numerically calculated and analyzed based on generalized nonlinear Schrödinger equation. The results demonstrate that non-frequency shift components shrink gradually as the pulse propagates in the normal dispersion region. Cross-phase modulation (XPM) and stimulated Raman scattering (SRS) play a major role in this process, while the third-order dispersion imposes little effect on it. Because of XPM, non-frequency shift components at the front and rear edge shrink gradually, and keep red shifting and blue-shifting respectively. The influence of XPM on the non-frequency shift components at both edges is symmetrical. However, the influence of SRS on the evolution of non-frequency-shift components at both edges is asymmetric. At the front edge, SRS transfers the energy from non-frequency shift component to frequency shift component, which is opposite to that at the rear edge. At the front edge, SRS accelerates the shrinking process of the non-frequency shift component, while it slows down the shrinking process at the rear edge. And this asymmetric effect is more obvious when the peak power of the pulse is higher and SRS is more efficient. The evolution of the non-frequency shift components of chirped pulses propagating in the normal dispersion region is studied. Comparing with the unchirped pulse, the non-frequency shift components at the front and rear edge of the chirped pulse have different wavelengths. For the negative chirped pulse, the wavelength spacing between the overlapped frequency-shift components and non-frequency shift components is larger, which is easier to satisfy the SRS gain range. Therefore, the evolution of non-frequency-shift components at the front and rear edge of the negative chirped pulse are more asymmetric due to the higher SRS efficiency. For positive chirped pulses, the wavelength spacing between the overlapped components is difficult to satisfy the SRS gain range. The evolution of non-frequency-shift components in the positive chirped pulses is more symmetrical due to the lower SRS efficiency.

Shaping self-accelerating Bessel-like optical beams along arbitrary trajectories by magnetic fluid deformable mirror

Wei Xiang, Wu Zhi-Zheng, Cao Zhan, Wang Yuan-Yuan, Dziki Mbemba
Acta Physica Sinica. 2019, 68 (11): 114701 doi: 10.7498/aps.68.20190063
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With the development of laser technology, the application scope of nondiffracting beams, such as Bessel beams, Mathieu beams, cosine beams, and parabolic beams, which remain invariant along their propagation, continues to expand. During its propagation, the main lobes of these beams tend to bend towards off-axis position, which is called self-accelerating (or self-bending) property. A Bessel-like beam with self-acceleration can realize the propagation of the main lobe along a curved trajectory while maintaining the non-diffraction. Because of the above property, Bessel-like beams have been utilized in various areas such as guiding particles along arbitrarily curved trajectories, self-accelerating beams in nonlinear medium, plasma guidance, and laser-assisted guiding of electric discharges around objects.
In this paper, we propose a method of bending the trajectory of Bessel-like beams by using a magnetic fluid deformable mirror (MFDM) instead of traditional spatial light modulator (SLM) and Pancharatnam-Berry (PB) phase manipulation. The MFDM provides a method without pixelation, where all parameters can be rapidly modified for fine-tuning. Furthermore, compared with the conventional deformable mirror, the MFDM has the advantages of a continuous and smooth mirror surface, large shape deformation, low manufacture cost, easy extension, and large inter-actuator stroke. Therefore, it is easy for the MFDM to generate the ideal shape of an axicon. Firstly, according to geometric analysis, the asymmetrical mirror profile to produce a self-accelerating Bessel-like optical beam is proposed. The proposed mirror profile can be used to compensate for the difference in optical path length for each annular slice of the axicon. If a collimated Gaussian beam is incident on the mirror combining the axicon and the asymmetrical mirror profiles, which can obtain Bessel-like beams with arbitrarily curved trajectories. Secondly, the resultant of the self-accelerating Bessel-like beams along parabolic trajectories is validated by the simulation in MATLAB. Finally, a prototype of MFDM consisting of the dual-layer arrays of miniature electromagnetic coils, a Maxwell coil and the magnetic fluid filled in a circular container is fabricated for the experiment. The experimental results show that the Bessel-like beams propagate along the parabolic trajectories, with the MFDM used, and the accuracy of the curved trajectories is verified. The proposed method in this paper opens a new experimental way to the study of Bessel-like beam; the theoretical approach can also be generalized mathematically for other non-paraxial beam propagation.

Acta Physica Sinica
Accepts
Note: The papers published below will continue to be available from this page until they are assigned to an issue. To see an article, click its [PDF] link. To review many abstracts, check the boxes to the left of the titles you want, and click the 'Selected articles' button. To see one abstract at a time, click its [Abstract] link.
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The Effect of Collision Parameter on a Magnetized Electronegative Plasma Sheath Structure

Accept: 2016-10-11
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The structure of an electronegative plasma sheath in an oblique magnetic field is investigated. More over, the collisions between positive ions and neutral particles are taken into account. It is assumed that the system consists of hot electrons, hot negative ions and cold positive ions. Also the negative ions and the electrons are assumed to be described by the Boltzmann distributions of their own temperatures, and the accelerated positive ions are treated by means of the continuity and momentum balance equations through the sheath region. In addition, the assumption that the collision cross section has a power law dependence on the positive velocity is introduced. After theoretical derivation, an exact of sheath criterion is obtained. The numerical simulation results include the distributions of the positive ions density for different invariable ion Mach number satisfying Bohm criterion, the comparison of net space charge distributions for variable and invariable ion Mach number. Furthermore, three species of charged particles density, the net space charge and the spatial electric potential in the sheath are studied numerically for different collision parameters under the condition of the fixed ion Mach number. The results show that the ion Mach number has not only the lower limit but also the upper limit. The ion Mach number affects the sheath structure by influencing the distribution of the positive ion density, and different conclusions can be obtained because ion Mach number is adopted as variable or invariable value while discussing the effects of the other variables which can result in the variety of the ion Mach number on the sheath formation. The reason is the actual sheath structure modification brought on by the variation of a parameter can be resolved into two parts. One is the sheath formation change caused directly by the variation of the parameter, the other is the sheath formation change caused by the Bohm criterion modification which the variation of the parameter results in. Therefore, an identical ion Mach number should be adopted when researching the direct effects of a parameter variety on plasma sheath structure. In addition, it is concluded that the collisions between positive ions and neutral particles make positive ions density curve higher and electrons’ lower than the case without collisions. Negative ions density does not alter significantly whether there exists collision or not. Besides there is a peak in the profile of the net space charge while in the presence of ion-neutral collision and the net space charge peak moves toward the sheath edge. The spatial potential increases and the sheath thickness decreases on account of the presence of the collisions between ions and neutral particles.
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Calculation of Hamilton energy function of dynamical systems by using Helmholtz theorem

null
Accept: 2016-10-11
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The Helmholtz theorem confirmed that any vector field could be decomposed of gradient and rotational field. The supply and transmission of energy occur during the propagation of electromagnetic wave accompanied by variation of electromagnetic field, thus the dynamical oscillators and neurons can absorb and release energy in presence of complex electromagnetic condition. Indeed, the energy in nonlinear circuit is often time-varying when the capacitor is in charged or discharged, and occurrence of electromagnetic induction is available. Those nonlinear oscillating circuits can be mapped into dynamical systems by using scale transformation. Based on mean field theory, the energy exchange and transmission between electronic field and magnetic field could be estimated by appropriate nonlinear dynamical equations for oscillating circuits. In this paper, it investigates the calculation of Hamilton energy for a class of dimensionless dynamical systems based on Helmholtz’s theorem. Furthermore, scale transformation could be used to develop dynamical equations from the realistic nonlinear oscillating circuit, so the Hamilton energy function could be approached effectively. These results could be much useful for self-adaptive control of dynamical systems.
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Ballistic thermal rectification in the three-terminal graphene nanojunction with asymmetric connection angles

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Accept: 2016-10-11
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By using the nonequilibrium Green’s function method, the ballistic thermal rectification in the three-terminal graphene nanojunction is studied. The dynamics of atoms are described by the interatomic fourth-nearest neighbor force-constant model. The nanojunction has a Y-shaped structure, created by a combination of a straight graphene nanoribbon and a leaning branch as the control terminal holding a fixed temperature. No heat flux flows through the control terminal. There exists a temperature bias between the two ends of the graphene nanoribbon served as the left and right terminals, respectively. The primary goal of this paper is to demonstrate that the ballistic thermal rectification can be introduced by the asymmetric structure with different connection angles between terminals. The control terminal has a smaller connection angle with respect to the left terminal than to the right terminal. The forward direction is defined as being from the left terminal to the right terminal. The results demonstrate that, given the same control temperature and absolute temperature bias, the heat flux in the graphene nanoribbon tends to run preferentially along the forward direction. When the difference between the connection angles increases, the rectification ratio rises. Compared to the zigzag graphene nanoribbon, the rectification ratio of the armchair nanoribbon is more sensitive to the direction the control terminal. However, the greatest rectification ratio is found in the zigzag graphene nanoribbon which has a connection angle of 30 degrees with respect to the armchair branch. In addition, the direction of the control terminal can be adjusted to raise more than 50% of the rectification ratio of the graphene thermal recti?er based on the width discrepancy between the left and right terminals. The mechanism of the ballistic thermal recti?cation is also discussed. In the three-terminal graphene nanojunction, a smaller connection angle with respect to the control terminal leads to more phonon scattering. The confirmation of this conclusion comes from a comparison of phonon transmission between different couples of terminals, which shows that, in most of the frequency spectrum, the phonon transmission between the control terminal and the left terminal is smaller than that between the control terminal and the right terminal. Given the same control terminal temperature and temperature bias, the asymmetric connection angles therefore will introduce a higher average temperature of the left and right terminals, and a larger heat flux in the forward process. Moreover, the average temperature difference between in the forward process and in the reverse process is found to be proportional to the temperature bias, and the proportionality coefficient will get bigger if the asymmetry is strengthened.
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The Propagation Properties of Vortex Beams in a Ring Photonic Crystal Fiber

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Accept: 2016-10-11
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In the last decade, the vortex beams have received lots of attention for their orbital angular momentum. When they are applied to optical fiber communication field, the data channels will increase and information propagation speed will be effectively improved. Recently, researchers have shown the capability of long length stably propagation, nonlinear frequency conversion and mode division multiplexing of vortex modes in a ring fiber. Due to the photonic crystal fiber (PCF) has very flexible design degrees of freedom, it will enable a wide range of propagation properties. In this paper, A SiO2 air-holes ring PCF is proposed for separation and propagation of optical vortex modes. By using COMSOL Multiphysics software, the vortex modes(TE01, HE_21^± and TM01) are simulated and calculated. The differences of the effective refractive index between them are 4.59×〖10〗^(-4) and 3.62×〖10〗^(-4) respectively. One can analyze the propagation properties of vortex beams in the ring PCF by changing the size of first layer air holes’ radius and air hole pitch. When the incident light wavelength of TE01 mode ranges from 1650 nm to 1950 nm, this ring PCF can achieve a total dispersion variation between 44.18 to 45.83 ps?nm^(-1)?km^(-1), which is tend to be flat. When incident light wavelength is 1550 nm, the nonlinear coefficient of TE01 mode vortex light is 1.37 W^(-1)?km^(-1); Due to the long wavelength light is easier to leakage through the cladding than the short wavelength light, the confinement loss increases with the wavelength. When incident light wavelength is 2000 nm, there is still an eight-orders-of-magnitude of the low confinement loss. Theoretically, flat dispersion and low loss vortex beams in this fiber can be beneficial to propagate stably, and the vortex modes lay the foundation for long distance propagation in the optical fiber. In the future, this ring PCF will be used in optical fiber communication field and application in aspects such as continuous spectrum research, which can make it have immense advantage to traditional fibers.
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Penta-decomposition of instantaneous field in spanwise-rotating turbulent plane Couette flow

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Accept: 2016-10-11
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Spanwise-rotating turbulent plane Couette flow (RPCF) is one of the fundamental prototypes for wall-bounded turbulent flows in the rotating reference frames. In this turbulent problem, there are large-scale roll cells, which are widely studied. In this paper, a penta-decomposition method is proposed to separate the instantaneous velocity and the total kinetic energy into five parts, including a mean part, a streamwise part and a cross-flow part of the secondary flow, and a streamwise part and a cross-flow part of the residual field, aimed to explore the energy balance and transfer among different shares of the turbulent kinetic energy in RPCF at Reynolds number Rew=Uwh/ν=1300 (here, Uw is the half the wall velocity difference, and h is half channel-height) and rotation number Ro=2Ωzh/Uw (Ωz is the constant angular velocity in the spanwise direction) in the range of 0≤Ro≤0.9. The results show that the energy is transferred between streamwise part (cross-flow part) of secondary flows and residual field through the correlation between the vorticity of secondary flows and shear stress of residual field. The rotation term acts as a bridge to transfer the energy between streamwise part and cross-flow part of secondary flows (residual field). Moreover, pressure-strain redistribution term also plays an important role in the energy transfer between streamwise part and cross-flow part in residual field. For the streamwise part of residual field, in certain rotate rates, the energy obtained from the streamwise part of secondary flows is larger than that got from mean flow, implying that the streamwise motions of secondary flows have a significant impact on the streamwise motions of residual field.
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A fast particle simulation method for calculating the multipactor threshold based on the frequency domain solutions in microwave devices

null
Accept: 2016-10-11
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In order to compute the multipactor thresholds of microwave devices with high ef?ciency and precision, a novel fast particle-in-cell (PIC) method is proposed, which takes advantages of the frequency-domain (FD) electromagnetic field solver of CST Microwave Studio (MWS). At the initial stage of multipactor (when there are not many electrons in the devices), the self-consistent field generated by the electrons is much smaller than the applied electromagnetic field. Therefore it can be ignored in calculating the multipactor threshold and this will significantly reduce the computation burden. During simulations of multipactor processes, the FD fields pre-calculated by CST MWS are converted into time-domain (TD) scaling with the square root of the input power. Then the electrons are advanced by Boris algorithm. When the electrons hit the boundaries of the simulation region, where triangular facets from CST are used for discretization, the secondary electrons would be emitted. After series of simulations with variable input powers, the multipactor threshold is determined according to time evolutions of the electron number. As verifications, the multipactor thresholds in a parallel plate and a coaxial transmission line are investigated. Compared with the results of CST Particle Studio (PS), the fast method obtains almost the same thresholds, while the computational efficiency is improved more than 1 order of magnitude. Since the self-consistent field generated by the electrons is ignored in the fast method and it is considered in CST PS, the results validate that the self-consistent field can be ignored in calculating the multipactor threshold. Finally, taking a parallel plate transmission line and a stepped impedance transformer as examples, we studied the effects of the number of initial macro-particles on the calculation precision. When the initial particles are so few that it can hardly reflect the randomness of the multipactor process, it results in a higher calculated value. With the increase of the number of initial macro-particles, the calculated multipactor threshold is lower and more accurate. It is convergent when the number reaches about 2000 for the parallel plate transmission line and 4000 for the stepped impedance transformer, respectively. Taking into account other microwave devices with more complex electromagnetic field distribution, in order to ensure precision, it is recommended to select the number of initial macro-particles 8000. In addition, although CST MWS was used to obtain the electromagnetic fields and boundary information in this paper, of course, other electromagnetic software (such as HFSS) can also be adopted as an alternation.
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The effect of linear bubble vibration on wave propagation in unsaturated porous media containing air bubbles

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Accept: 2016-10-11
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Biot model is widely applied in geophysics, petroleum engineering, civil engineering and ocean engineering since it has been presented. This leads to a considerable development of the research on the wave propagation in saturated porous medium. However, fully saturated porous medium is rarely found in nature, almost all the rocks or soils contain two kinds of fluid, such as gas and petroleum. So many researches has been done on the wave propagation in unsaturated porous medium by domestic and abroad scholars. It is well known that the presence of a small volume of gas bubbles in a liquid can greatly alter the velocity and attenuation of acoustic waves in the liquid. Evidence is beginning to accumulate that the velocity and attenuation of acoustic waves in a saturated marine sediment can be affected by the presence of gas bubbles in the saturating liquid. To investigate the sound propagation in porous media when the pore water contains a small amount of air bubbles, this paper integrates the volume vibration of bubbles in pore water into the continuity equation of pore-fluid filtration in porous media based on Biot theory, so as to obtain the continuity equation of pore-fluid filtration with bubble volume vibration. On this basis, according to the relationship between the instantaneous radius of bubbles and the background pressure of the medium under the linear vibration of bubbles, as well as the equations of motion of the fluid medium and porous medium, a new displacement vector wave equation of porous media under the influence of bubbles is derived, which establishes the model for the sound velocity dispersion and attenuation prediction under the unsaturated porous media. The presence of air bubbles increases the compressibility of pore fluid, which leads to the decrease in the sound velocity of the bubbly saturated porous media. When the wave frequency equals to the resonance frequency of the bubbles, the bubbles in pore water will produce resonance; the medium will present to be highly dispersive and the velocity can greatly exceed the gas-free velocity, but these have not been measured in field data; and the absorption cross section of the air bubble can reach the maximum, which leads to the maximum attenuation of the porous media. It should be noted that the attenuation coefficient calculated with this model is related to the damping of bubble motion(radiation, thermal and internal friction) and the dissipation of the relative motion between the pore water and porous solid frame. The obtained numerical analysis is consistent with the above conclusions, which indicates that the volume concentration, the bubble size and the excitation frequency of sound field are important parameters affecting the sound wave propagation in the saturated porous media containing few bubbles.
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Ferroelectric phase transition of perovskite SnTiO3 based on first principles

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Accept: 2016-10-11
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Due to their spontaneous polarization, ferroelectric materials have excellent dielectric, piezoelectric, pyroelectric and other properties, which enable them to be used in many applications, such as capacitors, filters, sensors, detectors, and transducers, among others. In this paper, we employ a first-principles-based effective Hamiltonian method to investigate perovskite SnTiO$_3$, obtaining essential coefficients for the effective Hamiltonian via ab initio computations, which are used in subsequent Monte-Carlo simulations to predict the phase transition temperature of SnTiO$_3$, and different structural phases involved in such phase transition.
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Nonlocal Symmetries and Interaction Solutions of the (2+1)-dimensional Higher Order Broer-Kaup System

xiangpeng xin Hanze Liu Xi-qiang LIU
Accept: 2016-10-11
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The (2+1)-dimensional higher-order Broer-Kaup (HBK) system is studied by nonlocal symmetry method and consistent tanh expansion (CTE) method. In this paper, via the localization of the residual symmetries, the nonlocal symmetries are localized to Lie point symmetries and symmetry groups are also obtained. Many types of soliton solutions and interaction solutions among different nonlinear excitations such as solitons, periodic waves etc. are constructed. In order to study their dynamic behaviors, corresponding images are explicitly given.
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Development of a intranuclear-cascade code CBIM applicable to the nuclear reaction with incident particle energy above 45MeV

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Accept: 2016-10-11
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The Monte Carlo intra-nuclear cascade program CBIM has been developed for describing nuclear reactions involving protons, neutrons and pions on complex nuclei. In order to describe cascade process, several simplifications have been made in the following: firstly, neither reaction, reflection, refraction, nor ionization will be taken into account before the incident particle enters the target nucleus; secondly, target nucleus is regarded as spherical and the atom number should be greater than 2; thirdly, the knocked nucleon is determined by cross section sampling; last, in the center-of-mass frame, the scattering angle is sampled based on differential cross section distribution.. The basis physics model bases on the above assumptions and Bertini intra-nuclear cascade model; meanwhile, nucleon-nucleon angle differential distributions of INCL in the center-of-mass frame have been introduced to overcome the shortage of Bertini model. The interactions between nucleon and nucleon or between nucleon and pion, for example, elastic scattering, pion production and charge exchange, are simulated in the code. In the particles collision, the nucleon density changes with the target nucleus radius; and the interaction cross sections refer to 22 kinds of experimental cross sections in Bertini model. The intra-nuclear cascades induced by 45MeV~3500MeV neutron, proton or pion below 2500MeV can be simulated by this code. Finally, comparisons with experiment on reaction cross section over the energy range 60~378MeV, and some simulation results by MCNPX, GEANT4 and PHITS over the energy range 65~3000MeV, the CBIM results are in reasonable agreement with them over the broad energy range considered.
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Omnidirectional photonic bandgap of the one-dimensional plasma photonic crystal based on a novel Fibonacci quasiperiodic structure

Accept: 2016-10-11
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Take the binary one-dimensional plasma photonic crystal based on Fibonacci quasiperiodic structure as an object, on the basis of the photonic bandgap characteristics of the structure with different initial sequence and number of period, a novel structure of one-dimensional plasma photonic crystal is proposed in this paper to enlarge the omnidirectional photonic bandgap (OPBG). Compared with previously reported structures in literatures, this structure is simpler in configuration with fewer layers and materials, and its OPBG width is wider. The influence of the parameters of the plasma material, such as the thickness, plasma frequency and collision frequency, on the OPBG characteristics of this structure is systematically discussed and compared with that of the structure in literatures. The research results can provide important theoretical guidance for the design of novel omnidirectional reflectors.
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Quantum secure direct communication protocol based on the mixture of Bell state particles and single photons

Zheng-Wen CAO
Accept: 2016-10-11
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By studying the properties of the mixture of Bell state particles and single photons, the paper designs a quantum code scheme with high coding capacity, and proposes a novel quantum secure direct communication protocol with high transmission efficiency. Alice prepares Bell state particles and single photons, and divides Bell state particles into two sequences $S_A$ and $S_B$. $S_B$ is sent to Bob for the first security check using quantum correlation properties of particles. When the check result shows that the quantum channel is safe, using designed quantum code scheme, Alice encodes her classical message on the mixed quantum state sequence of Bell sequence $S_A$ and single photon sequence $S_S$. Then, some single photons that are used for security check are re-inserted randomly into the encoded sequence, and the order of particles is rearranged to ensure to check Eve's attack. Alice sends the new sequence to Bob. Bob delays and receives it. And then, the quantum channel is conducted security check for the second time. The transmission error rate is calculated, if the error rate is lower than the tolerance threshold, the channel is safe. Bob decodes and reads Alice's message. The first security check is to determine whether quantum channel is safe. The second security check could test whether there are eavesdroppers during information transmission. Safety analysis is done by using quantum information theory to the proposed protocol. The error rate introduced by Eve and the amount of information by Eve are calculated. It is showed that this protocol can effectively resist measurement-resend attack, intercept-resend attack, auxiliary particle attack, denial of service attack and Trojan attack. Among them, auxiliary particle attack is analyzed in details. The transmission efficiency and coding capacity are also analyzed. The transmission efficiency is 2, the quantum bit rate is 1, and the coding capacity is that a quantum state can encode three bits of classical messages. We also compare the proposed protocol to many existing popular protocols in terms of efficiency, e.g., Ping-Pong protocol, Deng,F.G. et al.'s Two-step and One-pad-time quantum secure direct communication protocol, Wang,J. et al.'s quantum secure direct communication protocol based on entanglement swapping and Quan,D.X. et al.'s one-way quantum secure direct communication protocol based on single photon. It is proved that this proposed protocol has higher transmission efficiency. In addition, complex U operation and entanglement swapping are not used, and implementation process is simplified. However, this protocol is devoted to theoretical research of quantum secure direct communication. There are still some difficulties in the practical application. For example, the storage technology of quantum states is not mature at present. It is not easy to prepare and measure Bell state particles and combine them with single photons, and so on. The implementation of this protocol depends on the development of quantum technology in the future.
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The Relationship between Dielectric Properties and Nanoparticle Dispersion of Nano- SiO2/Epoxy Composites

null
Accept: 2016-10-11
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Nano-SiO2 was modified by silane coupling agent and modified nano-SiO2 powder and nano-SiO2 dispersing liquid was obtained. Unmodified and modified nano-SiO2/Epoxy composites made by “mechanical mixing method”, and modified namo-Silica/Epoxy composites made by “bubble mixing method” were prepared, respectively. The content of nano-SiO2 in the composite is 2wt%, 3wt%, 4wt%, 5wt% and 6wt%. Breakdown strength and corona-resistance characteristics of the composites were tested. The results show that, with the increase of nano-SiO2 loading, the breakdown strength and corona-resistance of nano-SiO2/Epoxy composites increase. The maximum breakdown strength of namo-Silica/Epoxy composites was appeared when the nano-Silica content is 5wt%. The SEM images of 5wt% nano-Silica loading composites were analyzed by Software Image J, and the Morisita’s Index method was used to evaluate the dispersion of nano-Silica particles in the matrix quantitatively. The best dispersion was found in the composites made by “bubble mixing method”. The relationship between dielectric properties and nano-particle dispersions of nano-Silica/Epoxy composites was discussed.
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Combined noise source identification method based on spherical microphone array with random unifrom distribution of elements

null
Accept: 2016-10-11
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As the developing of techlology, noise controlling is paied wide attention in recent years. Noise source identification is the key step for noise controlling. Spherical microphone array, which can located the noise source of arbitrary direction in three dimensional space, is widely used for noise source identification in recent years. Conventional methods for noise source localization include spherical near field acoustic holography and spherical focused beamforming. The acoustic quantities are reconstructed by using spherical near field acoustic holography method to realize the noise source identification, while the noise source can also be located by using focused beamforming based on spherical harmonic wave decomposition. However, both these methods have their own limitations while being used in noise source identification. Spherical near field acoustic holography has low resolution in high frequency with far distance from noise source to measurement array for noise source identification, whereas the spherical focused beamforming has low localization resolution in low frequency. Noise source identification is discussed here and a 64-element microphone spherical array with randomly uniform distribution of elements is designed. The combination methods of noise source identification by using spherical near field acoustic holography and mode decomposition focused beamforming are researched. The performance of the proposed combination methods is simulated, and an experiment of noise source identification is carried out based on the designed spherical microphone array to test the validity of proposed method. The dividing frequency point is when selecting noise source identification methods between near field acoustic holography of spherical wave decomposition by using the spherical array designed in this paper. Research results show that high resolution of noise source identification can be obtained by using near field acoustic holography when reconstruction frequency is with a distance from noise source to the center of spherical array, while high resolution of noise source localization can be achieved by using spherical wave decomposition beamforming when signal’s frequency is with a distance from noise source to the center of spherical array. Spherical array with random uniform distribution of elements maintains stable identification ability in all bearing. Spherical near field acoustic holography has high resolution distinguish ability in near field and low frequency, while focused beamforming method has high resolution distinguish ability in far field and high frequency. Therefore the noise source can be efficiently identified by using the proposed combined method of near field holography and focused beamforming with less elements and small aperture spherical microphone array.
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Optimization design of a Gamma-to-Electron spectrometer for high energy gammas induced by fusion

null
Accept: 2016-10-11
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Apart from neutrons, the fusion core produces gamma rays during one fusion reaction. The spectrum of gamma ray can provide very important information for fusion diagnosis. However, due to the gamma energy and yield in one fusion pulse, the gamma spectrometer used should have high detection efficiency and energy resolution. The concept of a Gamma-to-Electron magnetic spectrometer GEMS provides the idea to build up such a spectrometer to meet this requirement. Based on this concept design, four important parts of this facility are investigated. The first part is the gamma-electron converter. The main physics processes include Compton scattering of gamma ray with converter material generating electron, the electron Multiple Coulomb scattering (MCS) inside the converter and the electron attenuation. Affected by the thickness of convector, these processes gives a complex influence on the detection efficiency and angular-energy distribution of the electrons which are emitted from the downstream face of the convector. The Monte Carlo code Geant4 is employed to investigated the functions of Compton scattering, MCS and converter thick on the angular-energy distribution. The second one is the collimation. The collimation is used to select the forward direction election, the performance of cutoff angle of the collimator on the detection efficiency and resolutions, as well as the correlation between electron transportation direction and energy, are also studied using Geant4 code. The third part is the dipole magnetic field. There are several parameters of geometric and magnetic, therefore, a multi-thread parallelized Genetic algorithm is developed to get the best result. Both the irregular geometry (shape) and dipole magnetic field strength are optimized to achieve the best energy resolution and detection efficiency. The obtained magnetic field has intensity less than 100 Gauss, and its performance on gathering elections is also verified by Geant4 code. The last one is the location of electron detectors. The study shows that all the electron detectors should be located according to not a straight line but a quadratic curve. Then the optimized spectrometer is simulated by Geant4 to get the responses of gamma rays with various energies. For the gammas provided by fusion reaction, the simulation shows that when the neutron yield is about 2.5×1015 and 1.2×1016, the energy resolution reaches 0.5 MeV and 0.25 MeV, respectively, provided that different thick Be converters are employed. All in all, this optimized GEMS can be employed to measure the spectrum of gamma rays generated by the fusion reaction.
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Influnence of Nonspherical Effects on the Secondary Bjerknes Force in a Strong Acoustic Field

null
Accept: 2016-10-11
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The secondary Bjerknes force between bubbles in an acoustic field is a well-known acoustic phenomenon. The major theoretically researches of the secondary Bjerknes force were owing to two spherical bubbles. The secondary Bjerknes force between two spherical bubbles which is calculated based on the linear equations is very small and negligible, therefore these theoretically researches did not give a well explanation for the phenomenon, such as “streamer formation” and Multi-bubble sonoluminescence (MBSL). Experiments of sonoluminescence (SL) show that bubbles in a sound field are not entirely spherical bubbles. Nonspherical effects have an important influence on the secondary Bjerknes force when two bubbles come close to each other in a strong acoustic field (>1.0×〖10〗^5 Pa). How does the shape distortion of a nonspherical bubble cause the change of the secondary Bjerknes force between two bubbles, and the secondary Bjerknes force how to affect the oscillation and movement of bubbles are major problems which we wish to solve. The of the secondary Bjerknes force between a nonspherical bubble and a spherical bubble is obtained by considering the shape oscillation of a nonspherical bubble. We numerical simulate the secondary Bjerknes force between a nonspherical bubble and a spherical bubble based on the nonlinear oscillation equations of two bubbles, and compare the secondary Bjerknes force between a nonspherical bubble and a spherical bubble to the secondary Bjerknes force between two spherical bubbles in the same condition. We discuss the influence of nonspherical effects on the secondary Bjerknes force between two bubbles. The results show that when the amplitude of driving pressure is greater than the Blake threshold of a nonspherical bubble and makes the bubble oscillate stably, the secondary Bjerknes force between this nonspherical bubble and a spherical bubble is different to the secondary Bjerknes force between two spherical bubbles in direction and magnitude. The secondary Bjerknes force between a nonspherical bubble and a spherical bubble is much bigger than that of two spherical bubbles. The interactional distance of the secondary Bjerknes force between a nonspherical bubble and a spherical bubble is further than that of two spherical bubbles. The secondary Bjerknes force between a spherical bubble and a nonspherical bubble depends on the radii of two bubbles, distance between two bubbles, shape mode of the nonspherical bubble and the amplitude of driving pressure. Our research is more close to the actual bubbles in liquid. We also prove that big mutual interaction between bubbles is mainly cause for the formation of a stable structure between bubbles. For bubbles, big mutual interaction causes the cavitation become easier. These results are important to explain the phenomenon in an acoustic field, such as “streamer formation” and Multi-bubble sonoluminescence (MBSL).
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The Principle and Application of Diagonal Reducing Method in the Complex Noise Fields

null
Accept: 2016-10-11
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Acoustic environment has low signal-to-noise ratio (SNR); hence, array signal processing is always used for noise reduction and signal enhancement. Because the delay-and-sum beamforming method performs robust, so it is almost widely used, but the array gain is limited by the array aperture. The actual underwater ambient noise is complex, which includes uncorrelated noise and correlated noise. The noise power of each array element is unequal. The noise covariance matrix is not a scaled identity matrix. Consequently, the performance of array signal processing method decreases obviously. Aiming at these two problems, the diagonal reducing method of the covariance matrix in the complex noise fields is proposed. Firstly, a reducing matrix, which is defined as a diagonal matrix with unequal diagonal elements, is subtracted from the covariance matrix so as to reduce the noise, and a new matrix is obtained. Secondly, the delay-and-sum beamforming is done by using the new matrix to obtain the beaming output. The analytic solution and approximate solution of reducing matrix are obtained under the constraint condition that the output SNR attains its maximum. Thirdly, the estimation of the reducing matrix is determined by minimizing the function that is defined as the error between the covariance matrix and the estimated covariance matrix. This minimization problem is accomplished in an iterative method. Fourthly, if the noise is uniform white noise or the nonuniform white noise, this proposed method performs well. While, under the complex noise field the performance of the proposed method may be deteriorated. So the effects of the correlation of the noise field and the input SNR on the estimated error is analyzed. In fact, the weaker the correlation is, or the smaller the input SNR is, the smaller the estimated error is. Lastly, the simulation experiment and the lake trial are implemented. The simulation results show that the diagonal reducing method of the covariance matrix reduces some ambient noise, the noise output power is decreased, the output SNR is increased, and the proposed method improves performance of array signal processing. The experimental results show that the output SNR of the target using the proposed method is increased by about 14 dB. The diagonal reducing method of covariance matrix has definite value to engineering application, and is computationally attractive.
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Moving target compressive imaging based on improved row scanning measurement matrices

null
Accept: 2016-10-11
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Abstract: Moving target imaging (MTI) plays an important role in practical applications. How to capture dynamic images of the targets with high quality is a front-burner issue in the field of MTI. In order to improve the reconstruction quality, a new MTI model based on compressed sensing (CS) is proposed here, applying a sampling protocol of the row-scanning together with a motion measurement matrix constructed by our own. It is proved by the simulation and the experimental results that a relatively higher quality can be achieved through this approach. Furthermore, an evaluation criterion of reconstructed images is introduced to analyze the relationship between the imaging quality and the moving speed of the target. By contrast, the performance of our algorithm is much better than that of traditional CS algorithms under the same moving speed condition. As a result, it suggests that our imaging method may have a great application prospect in the earth observation of unmanned aerial vehicles, video monitoring in the product line and other fields.
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Spatial Correlation of Underwater Bubble clouds Based on Acoustic Scattering

null
Accept: 2016-10-11
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Using effective medium theory to describe acoustic scattering from bubble clouds, one of the underlying assumptions shows that the probability of an individual bubble being located at some position in space is independent of the locations of other bubbles. However, bubbles within naturally occurring clouds are usually influenced by the motion of the fluids which makes they become preferentially concentrated or clustered. According to Weber’s method, it is a useful way to importing spatial correlation function to describe this phenomenon in bubble clouds. The spatial correlation function is contained in acoustic scattering and it is important to notice that the spatial correlation should be dependent of the position and radius of each bubble due to the ‘‘hole correction’’ or the effect of the dynamics of the fluids. Because of these reasons, it is hard to invert the spatial distribution of bubble clouds using spatial correlation function in acoustic scattering. A method is described here in which bubble clouds are separated into many small subareas and the conception called effective spatial correlation function which is the statistic of spatial correlation function used to describe the correlation between each subarea of bubble clouds. Since the effective spatial correlation function is independent of bubbles’ radius and positions, the bubble clouds’ distribution and the trend of clustering can be inverted by using this function. The result of simulation indicates that the effective spatial correlation function can precisely track the position of the clustering center, even the clustering center covered by other bubble clouds can be detected. Using multi-bean sonar measuring the bubbly ship wake generated by a small trial vessel, the method is used to invert the spatial distribution and clustering centers of bubble field in the ship wake. The results show that effective spatial correlation function accurately inverts the distribution and clustering centers of bubbles in ship wake. Furthermore, the method presented in this paper could distinguish the bubble clouds caused by different reasons and detect upper ocean bubble clouds covered by other bubbles generated by wave breaking.
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Uncertainty Quantification in the Calculation of keff Using Sensitity and Stochastic Sampling method

null
Accept: 2016-10-11
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In the neutronics simulation of nuclear reactor, the uncertainties associated to the integral parameters due to the uncertainties in nuclear data are usually quantified using the sensitivity and uncertainty (S/U) analysis method based on the perturbation theory. S/U analysis method is only applicable to the linear model, moreover neutronics code generally can not be directly used in sensitivity analysis. Sampling approach, which evaluating the uncertainties by performing a set of stochastic simulations, is easy to implement and the uncertainties quantified is close to exact. The function of uncertainty quantification based on sampling approach have been added to uncertainty analysis code SURE. Before applying the sampling method to the uncertainty quantification in the simulation of complex problems, it is necessary to carry out a careful verification. The uncertainties of the calculated effective neutron multiplication factor keff for two selected simple critical benchmark experimental model are quantified using SU method and sampling method respectively. The keff uncertainties due to all nuclides and reaction types nuclear data quantified by two methods are in good agreement, and the correctness of the sampling function of SURE code is verified. The keffs distributions from sampling method obey normal distribution, which embodies a linear relation between input nuclear data and output keff in the range of the uncertainty range of nuclear data, and sensitivity analysis method is adaptable to quantify uncertainty of calculated keff.
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A super-resolution infrared microscopy based on a doughnut pump beam

null
Accept: 2016-10-11
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This paper presents an approach to break through the diffraction limitation in infrared microscopies. In this method, instead of Gaussian pump beam, an intensive vortex beam is firstly focused on the sample, leading to saturation absorption of the peripheral molecules in the point spread function (PSF). The vortex beam is followed by a Gaussian beam with the same wavelength, which can only be absorbed by the molecules near the center, resulting in shrunken PSF which means higher resolution. Furthermore, the PSF of a system based on this approach is numerically simulated. With an 100 nJ pulse energy vortex beam and a 0.1 nJ pulse energy probe beam, the theoretical resolution (full width at half maximum, FWHM) is measured to be about 236 nm which is 14 times better than that of the traditional infrared microscopy.
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Fast Bayesian Blind Restoration for Single Defocus Image with Iterative Joint Bilateral Filters

null
Accept: 2016-10-11
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It is significant to realize effective defocus image restoration for acquiring clear image in military and geological examination field. Most of existing algorithms have the problems of large computational cost, ringing and noise sensitivity, hence a novel approach by iterative joint bilateral filtering under Bayesian framework is proposed. Firstly, it utilizes defocus image depth estimation to compute the point spread function in the Bayesian framework. Then a minimum optimization problem is built to represent the blind restoration problem. After inferring the solution procedure of the minimum optimization problem, we find that the joint bilateral filters can be used to search the optimal solution, which not only simplify the searching procedure but also reduce the computational cost. Finally, an iterative joint bilateral filtering was designed to realize the image restoration. That means the original restored image obtained from the bilateral filtering is used to design the guide image for the joint bilateral filters, and the guide image will serve as the input of the optimization problem for acquiring the better optimal result. This procedure was repeated until convergence. The experiment results indicate that this method can yield the ringing, reduce the computational cost and remove the noise. Generally speaking, the average pixel error of 85% images is under 0.03, which has improved 19% comparing with the same error rang of existing algorithms. And 78% shorter than those of compared algorithms. It can be used in the engineering practice of blind restoration for single defocus image.
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First-principles study on the thermodynamic stabilities and electronic structures of long-period stacking ordered phases in the Mg-Y-Cu alloys

null
Accept: 2016-10-11
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A first-principles method based on density functional theory has been used to investigate thermodynamic stability and electronic characteristics of long-period stacking ordered (LPSO) phases 14H and 18R (18R(m),18R(t)) in Mg–Y–Cu alloys. The present calculations are performed using Vienna Ab-initio Simulation Package (VASP) with projector augmented plane wave pseudopotential, and generalized gradient approximation is used to treat with and describe the exchange-correlation interaction. The plane wave cutoff energy is set to 360 eV, the forces on all the atoms is less than 0.02 eV/?. The calculated negative enthalpies of formation show that both 14H and 18R can exist in Mg–Y–Cu system, 14H and 18R are stable with respect to the Mg, Cu and Y elements, the reaction energies indicate that 14H is more stable than 18R. The density of states (DOS) of these phases reveals that the main bonding peaks of 14H is located at energy range between -6.82 eV and 2.09 eV, those of 18R(m) at energy range between -6.82 eV and 2.02 eV, and 18R(t) at energy range between -6.82 eV and 1.98 eV. The Cu 3d orbits, Y 4d orbits, Mg 3s and Mg 2p orbits are broadly distributed in the entire region, while Cu 4s orbits, Y 4s and Y 4p orbits are very weak in whole region. For 14H,18R(m) and 18R(t) phases, the bonding originates mainly from the valence electrons of Mg 3s, Mg2p, Cu 3d and Y 4d orbits. The presence of pseudogap indicates that the bonds in 14H and 18R phases are noticeable covalent. In addition, the charge density on (0 0 0 1) plane of 14H and 18R phases are analyzed, and the results indicate that the Cu-Y bonds exhibits covalent feature in 14H and 18R, the covalent bonding of 14H phase is stronger than that of 18R phase.
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A broadband low-frequency sound insulation structure based on two-dimensionally inbuilt Helmholtz resonators

null
Accept: 2016-10-11
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A man-made acoustic structure with broadband low-frequency sound insulation property is designed based on circularly inbuilt Helmholtz resonators. Beyond this structure, a two-dimensional quiet zone can be created. Being the same as the simulating model, an experimental structure is fabricated. Experiments are carried out to study its sound insulation properties. The experimental results are very coincident with the simulating one, which show that this structure has an excellent sound insulation effect in the frequency band of 680-1050Hz, and the maximum insulation sound pressure level can reach 41dB. Meanwhile, the distribution of the two-dimensional sound field above this structure is measured. The results point out that the range of the insulation area can be changed with the change of the incident frequency. In addition, the sound insulation effect is sensitive to the resonant state of the Helmholtz resonators. This work will be of help for designing new sound protection devices.
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Total Dose Dependence of Hot Carrier Injection Effect in the NMOS Devices

null
Accept: 2016-10-11
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The equipments and devices which were long-time running in space were affected by space radiation effects and hot carrier injection effects at the same time which would reduce their optional times. Normally, the single mechanism test simulation method was used on the ground simulation test but the multi-mechanism effects was affected the space equipments and devices, included total irradiation dose effect, hot carrier injection effect, and so on. The total dose dependence of hot carrier injection (HCI) effect in the 0.35μm NMOS Devices was studied in this paper. Three samples were test with different conditions (sample 1# with TID and HCI test, sample 2# with TID, annealing and HCI test, sample 3# only with HCI test). The results shows that threshold voltage of NMOS devices with 5000s HCI test after 100krad (Si) total dose radiation shift negatively then positively during total dose irradiation test and HCI test,and it was more than the devices without radiation test. But the threshold voltage shift of NMOS devices with 5000s HCI test and 200hours annealing test after TID test was more than the devices without radiation test and lower than the devices without annealing test. That was, the parameters of NMOS device varied faster with the association effects (included total dose irradiation effect and HCI effect) than with single mechanism effect. It was indicated that the hot electrons were trapped by the oxide trap charges induced by irradiation effect and then became recombination centre. And then the oxide trap charges induced by irradiation effect reduced and became to negative electronic. The interface trap charges induced by irradiation effect were reduced and then increased and it was because that the electrons of hole-electron pairs in the Si-SiO2 interface were recombined by oxide traps in the oxide during the forepart of HCI test but then the electrons were trapped by interface traps in the Si-SiO2 interface because the electrons from source area were injected to interface during the HCI test. So the threshold voltage shift was positively due to the negative oxide trap charges and interface trap charges. The association effect was attributed to the reduction of oxide traps induced by recombination with hot electrons and the increase of the interface traps induced by irradiating trapped with hot electrons.
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Optoelectronic properties of N/B doped graphene

null
Accept: 2016-10-11
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Since its discovery in 2004, graphene has attracted great attention because of its unique chemical bonding structure, which has excellent chemical, thermal, mechanical, electrical and optical properties. Due to the zero band gap material, graphene has limited its development in the field of Nano Electronics. Only expanding the band gap of the graphene can promote the application of graphene in Nano Electronics. In this paper, we constructed three models of intrinsic graphene, N-doped graphene and B-doped graphene. The energy band structures, electronic density of states and optical properties of N/B doped graphene with intrinsic graphene and different doping concentrations were studied. The absorption spectra, the reflection spectra, the refractive index, the conductivity and the dielectric function were studied. The study shows that the electronic states near the Fermi level of N/B doped graphene are mainly composed of C-2p and N-2p/B-2p orbitals, and N/B doping can induce the change of the Fermi level and the photoelectric properties of graphene. The conclusion of this paper can provide a theoretical basis for the application of graphene in optoelectronic devices.
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The study of the dynamic of the slow electrons transmitted through straight glass capillary and tapered glass capillary

null
Accept: 2016-08-18
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It was found that the transmission rate of the electrons through insulating capillaries as a function of the time/incident charge is not the same as that for the ions. The question arouse that, by using the electrons, if the negative charge patches can be formed to facilitate the transmission of the followed electrons, substantiating that the so-called guiding effect works also for electrons. This study aims to observe the time evolution of the transmission of electrons through a straight glass tube and a tapered glass capillary. This would reveal the details that how and/or if the negative charge patches can be formed when the electron are being transported through them. In this work, a set of MCP/phosphor two-dimensional detection system based on Labview platform was developed to obtain the time evolution of the angular distribution of the transmitted electrons. The pulsed electron beams through a small hole with the diameter of 0.5 mm was obtained to test our detection system. The time evolution of the angular profile of 1.5 keV electrons transmitted through the glass tube/capillary was observed. The transmitted electrons are observed on the detector for a very short time and disappear for a time and then back again for both the glass tube and tapered glass capillary, leading to an oscillation. The positive charge patches are formed in the insulating glass tube and tapered glass capillary since the secondary electron emission coefficient for the incident energy is larger than 1. It is due to the fast discharge of the deposited charge, leading to an increase of the transmission rate, while the fast blocking of the incident electrons due to the deposited positive charge, leads to a decrease of the transmission rate. The geometrical configuration of the taper glass capillary tends to make the secondary electrons deposited at the exit part to form the negative patches that facilitate transmission of electrons, similar to the guiding of positive charged ions. This suggests that if the stable transmission needs to be reached for the production of the electron micro-beam by using tapered glass capillaries, the steps has to be taken to have the proper grounding and shielding of the glass capillaries and tubes. Our results show a difference for electrons in transmission through the insulating capillary from that of highly charged ions.
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null
Accept: 2016-08-18
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internuclear-distance-dependent ionization of H$_2^+$ in strong laser fields in a classical perspective

null
Accept: 2016-08-18
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The enhanced ionization of H$_2^+$ in strong laser fields is studied by numerically simulating the classical Hamiltonian equation with the fix-nuclei approximation. The classical trajectory of the electron shows the electron gains energy from the laser field by circulating one electron, then passes through the interatomic barrier and move around the other nucleus before ionization. The ionization probability is maximum when the energy difference between the ground state and the the higher value of the interatomic barrier and outatomic Coulomb barrier is minimum. The classical calculation offers a perspective to inspect the intriguing phenomena in quantum systems.
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Partition and growth of convection patterns in Poiseuille-Rayleigh-Benard flow

null
Accept: 2016-08-18
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In this paper, the Simple algorithm is used to numerically simulate the two-dimensional fully hydrodynamic equations. Partition of convection pattern , growth and the effect of horizontal flow on the characteristical parameters of different patterns in Poiseuille-Rayleigh-Benard flow are studied. The result indicated that flow zone is divided into three zones by the upper and lower critical Reynolds numbers , such as traveling wave zone, localized traveling wave zone, horizontal flow zone.and increase with reduced Rayleigh number. In the growth stage of the convection pattern, the growth process of three kinds of patterns with time is different, but the convection rolls grow all from downstream; Variation of characteristic parameters with time is also different, maximum vertical velocity and Nusselt number of traveling wave and localized traveling wave enter into the stable stage of the cycle variation after the exponential growth stage;and of horizontal flow pattern down to a stable constant after slow growth. and of three types of patterns decrease with increasing Reynold number, there are different rules in the different pattern areas. In this paper, formulas on variation ofandwith and formulas on variation ofandwithin different convection patterns are suggested.
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Acta Physica Sinica
2019
2019 Vol.68 No.12  2019-05-21
Acta Physica Sinica
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     No.19      No.20      No.21      No.22      No.23      No.24
2016 Vol.65      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13      No.14      No.15      No.16      No.17      No.18
     No.19      No.20      No.21      No.22      No.23      No.24
2015 Vol.64      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13      No.14      No.15      No.16      No.17      No.18
     No.19      No.20      No.21      No.22      No.23      No.24
2014 Vol.63      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13      No.14      No.15      No.16      No.17      No.18
     No.19      No.20      No.21      No.22      No.23      No.24
2013 Vol.62      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13      No.14      No.15      No.16      No.17      No.18
     No.19      No.20      No.21      No.22      No.23      No.24
2012 Vol.61      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13      No.14      No.15      No.16      No.17      No.18
     No.19      No.20      No.21      No.22      No.23      No.24
2011 Vol.60      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2010 Vol.59      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2009 Vol.58      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13
2008 Vol.57      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2007 Vol.56      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2006 Vol.55      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2005 Vol.54      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2004 Vol.53      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2003 Vol.52      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2002 Vol.51      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2001 Vol.50      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
2000 Vol.49      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1999 Vol.48      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
     No.13
1998 Vol.47      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1997 Vol.46      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1996 Vol.45      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1995 Vol.44      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1994 Vol.43      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1993 Vol.42      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1992 Vol.41      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1991 Vol.40      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1990 Vol.39      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1989 Vol.38      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1988 Vol.37      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1987 Vol.36      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1986 Vol.35      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1985 Vol.34      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1984 Vol.33      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1983 Vol.32      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1982 Vol.31      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1981 Vol.30      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1980 Vol.29      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1979 Vol.28      No.1      No.2      No.3      No.4      No.5      No.6
1978 Vol.27      No.1      No.2      No.3      No.4      No.5      No.6
1977 Vol.26      No.1      No.2      No.3      No.4      No.5      No.6
1976 Vol.25      No.1      No.2      No.3      No.4      No.5      No.6
1975 Vol.24      No.1      No.2      No.3      No.4      No.5      No.6
1974 Vol.23      No.1      No.2      No.3      No.4      No.5      No.6
1973
1972
1971
1970
1969
1968
1967
1966 Vol.22      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9
1965 Vol.21      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1964 Vol.20      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1963 Vol.19      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1962 Vol.18      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1961 Vol.17      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1960 Vol.16      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8
1959 Vol.15      No.1      No.2      No.3      No.4      No.5      No.6
     No.7      No.8      No.9      No.10      No.11      No.12
1958 Vol.14      No.1      No.2      No.3      No.4      No.5      No.6
1957 Vol.13      No.1      No.2      No.3      No.4      No.5      No.6
1956 Vol.12      No.1      No.2      No.3      No.4      No.5      No.6
1955 Vol.11      No.1      No.2      No.3      No.4      No.5      No.6
1954 Vol.10      No.1      No.2      No.3      No.4
1953 Vol.9      No.1      No.2      No.3      No.4
1952
1951 Vol.8      No.1      No.2      No.3
1950 Vol.7      No.5      No.6
1949 Vol.7      No.4
1948 Vol.7      No.3
1947 Vol.7      No.1      No.2
1946 Vol.6      No.2
1945 Vol.6      No.1
1944 Vol.5      No.1      No.2
1943
1942
1941
1940 Vol.4      No.1
1939 Vol.3      No.2
1938
1937 Vol.3      No.1
1936 Vol.2      No.1      No.2
1935 Vol.1      No.3
1934 Vol.1      No.2
1933 Vol.1      No.1
物理学报
· Numerical simulation of soliton trapping of the supercontinuum in photonic crystal fiber [2012, No.12:124203-124203] (38648)
· Large-eddy simulation and experimental study of deflecting oscillation of planar opposed jets [2013, No.8:84704-084704] (38155)
· Effect of concentration of heavy oxygen vacancy in rutile and anatase (TiO2) on electric conductivity performance studied by simulation and calculation [2013, No.23:237101-237101] (30726)
· Quasiparticle band structure calculation for SiC using self-consistent GW method [2012, No.13:137103-137103] (29043)
· Proximity-effect-induced superconductivity by granular Pb film on the surface of Bi2Te3 topological insulator [2013, No.16:167401-167401] (27091)
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