Vol. 62, No. 23 (2013)
2013, 62 (23): 230401. doi: 10.7498/aps.62.230401
This paper mainly deals with the effects of eccentricity on the gravitational waveforms emitted by the non-conservative post-Newtonian (PN) Hamiltonian formulations of the spinning compact binaries. The numerical results show that the change of eccentricity has a slight influence on the time-domain gravitational waveforms from the conservative spinning compact binaries, but the frequency bands of gravitational waveforms is broadened with increasing eccentricity. Owing to the effects of dissipation from the gravitational radiation reaction, the separation and the eccentricity decrease gradually with time, and the gravitational waveforms emitted from the non-conservative PN spinning compact binaries are modulated by the eccentricity, meanwhile the amplitude of the waveforms enhances with the increase of eccentricity; the duration of the waveforms decreases.
Theoretical and experimental study of a novel double-well optical dipole trap for two-species of cold atoms or molecules
2013, 62 (23): 233701. doi: 10.7498/aps.62.233701
A novel scheme based on light diffraction to generate a double-well optical trap for trapping and controlling two-species samples of cold atoms or molecules is proposed. Specialized phase modulation similar to the binary phase-grating is implemented in a diffraction device of liquid crystal spatial light modulator (LC-SLM). A continuous and reversible evolution between single-well trap and double-well trap is investigated. Corresponding experiments are performed and the results are in agreement with theories. Our results show that the proposed scheme has a controllability advantage, which is beneficial to the loading and controlling two-species samples in cold atoms or molecules experiments.
2013, 62 (23): 237803. doi: 10.7498/aps.62.237803
Transformation from Lu-based nanocrystals in hexagonal and cubic mixed phases to pure cubic phase was observed through adjusting the doping concentration of Mn2+. The mechanism for the phase transformation was discussed in detail. Studies on the time and frequency domain spectra indicated that the semi-pure red emissions in cubic Na5Lu9F32: 40% Mn2+, 20% Yb3+, 2% Ln3+ (Ln=Er3+, Ho3+) nanocrystals were caused by a two-step energy transfer between Mn2+ and Ln3+ ions. After incorporating of Mn2+ ions into the host lattices, the local symmetry around the luminescent ion was reduced, which induced the increase of radiative rates for transitions that were mainly contributed by electric dipole radiations. Considerable enhancements in upconversion and downconversion luminescence were accompanied. The result of the current study has great application potential in bioimaging and solar cells.
2013, 62 (23): 230201. doi: 10.7498/aps.62.230201
We have applied the Lie group analysis method to the time fractional Boussinesq equation. This equation can be reduced to an equation which is related to the Erdelyi-Kober fractional derivative by Lie method as a result. It is shown that the approach introduced here is effective and easy to implement.
The traveling wave approximate solution for a class of atmospheric wading wave system by generalized variational iteration
2013, 62 (23): 230202. doi: 10.7498/aps.62.230202
In this paper, a class of wading wave system is considered. Firstly, the corresponding functional is constructed; secondly, its Lagrange operators are selected. Then, using the modified generalized variational iteration method, the corresponding traveling wave approximate analytic solutions are obtained.
2013, 62 (23): 230301. doi: 10.7498/aps.62.230301
The two-layer Q-ball solutions in the complex scalar field model are studied in this paper, and the Q-ball charge and energy are calculated in an analytical form. Meantime, the energy stability is analyzed, and the perturbative expression of Q-ball is obtained by means of Klein-Gordon equation. Moreover, the physical effect of Q-ball dark matter is also discussed.
2013, 62 (23): 230302. doi: 10.7498/aps.62.230302
In this paper we present a new scheme for quantum state sharing of an arbitrary unknown two-qubit state by using a non-maximally five-qubit cluster state as quantum channel. In this scheme, the non-maximally five-qubit cluster state is shared by a sender (Alice), a controller (Charlie), and a receiver (Bob), who does not need to introduce an auxiliary particle but only operates an appropriate unitary transformation. The sender introduces an auxiliary particle and makes orthogonal complete bases measurement, and the controller makes a single-particle projective measurement on his particle, then the quantum state sharing can be probabilistically realized.
2013, 62 (23): 230303. doi: 10.7498/aps.62.230303
Quantum signaling states have decoherence because of the environment during the transmission. It causes signaling damage and thus will have impact on building high survivability quantum entanglement signaling network. In order to study the influence deeply, Poisson damage model of quantum signaling network is established. First, disaster magnitude is defined base on signaling fidelity. Second, average damage signaling quantum bits and survival function of quantum signaling network is put forward by basic quantum theory. At last, research on the signaling damage repair strategy and simulation is analyzed. Simulation results show that increasing of disaster magnitude will greatly reduce the signaling network survivability. However, increasing the nodes and controlling signaling damage caps may improve survivability. The repair strategy which costs small number of cycles can rapidly increase the signaling fidelity from 0.6 to 0.9 and the survival function of the signaling network from 0.4 to 0.9.
2013, 62 (23): 230501. doi: 10.7498/aps.62.230501
Because of the special structure and intracellular functions of myosin Ⅵ molecular motor, its dynamic principle has become a research focus. Starting from its structure and experimental phenomenon, the elastic-diffusion model of myosin Ⅵ in a periodic potential field is established, and the stochastic dynamics of the molecular motors, which conform to the Langevin equation, is analyzed by Monte Carlo simulations. By means of the environmental noise, myosin Ⅵ molecular motors could take stable stepping motion and effective transport according to its elastic potential energy and periodic potential of track, and a load can weaken the transportation power of the molecular motor system. For a given elastic coefficient, the longer the elastic chain of myosin Ⅵ, the lower the average velocity of it. By selecting a reasonable size of elasticity coefficient, the average velocity can be the maximum for a given elastic chain. In addition, the load can increase exponentially the mean dwelling time of myosin Ⅵ at the connection site.
Design and simulation of chaotic circuit for flux-controlled memristor and charge-controlled memristor
2013, 62 (23): 230502. doi: 10.7498/aps.62.230502
In this work,we design a fifth-order chaotic circuit with HP memristors, which consists of a flux-controlled memristor and a charge-controlled memristor. By changing the control parameters, the circuit evolves into different orbits, such as periodic orbits, double-scroll, of single-scroll. In order to ensure the occurrence of chaotic behaviors in the circuit, simulators of the charge-controlled memristor and the flux-controlled memristor are designed with conventional electronic devices, and Pspice simulation is conducted on the resulting circuit. Pspice simulation results verify the correctness of the theorectical analysis.
The spectra of chaotic maps are much wider than those of chaotic flows, and their overlapped regions with Gaussian white noise are much larger, thus the denoising method for chaotic flows is unsuitable for chaotic maps. Within a semi-blind analysing framework, the parameter estimating problem for chaotic systems can be boiled down to a least square evaluating procedure. In this paper we start with estimating the evolution parameters of chaotic maps by using a least square fitting method. After that, phase space reconstruction and projection operation are employed to get noise suppression for the observed data. The simulation results indicate that the proposed algorithm surpasses the extended Kalman filter (EKF) and the unscented Kalman filter (UKF) in denoising, as well as maintaining the characteristic quantities of chaotic maps.
2013, 62 (23): 230504. doi: 10.7498/aps.62.230504
We present a “master-slave-response” synchronization system of chaotic multiple-quantum-well lasers. And we study the applications of chaotic parallel synchronization for optical logic gates. An injection multiple-quantum-well laser drives two responding systems of multiple-quantum-well lasers to obtain chaotic synchronization while the injection multiple-quantum-well laser can synchronize the responding systems. We present theoretically the constructions of the fundamental all-optical gates based on the parallel synchronization of responding systems and define their computational principle. By modulating the driving light into the responding systems, all-optical logic gates characterizing logic function are realized by synchronizing or unsynchronizing appropriately the two chaotic states of responding systems. We present all-optical XNOR, NOR, NOT logic gates and their logic computational methods. Numerical simulation result validates the feasibility of the system.
2013, 62 (23): 230505. doi: 10.7498/aps.62.230505
A new numerical method is presented to solve optimal control problem of a chaotic system based on Gauss pseudospectral method (GPM). Firstly, the Lagrange interpolation polynomials are constructed on Legendre-Gauss nodes and used to parameterize the state and control the trajectories in optimal control of the chaotic system. Then, the chaotic optimal control problem in the continuous space is transformed into a nonlinear programming (NLP) problem through GPM. Furthermore, the NLP problem is solved by the sequential quadratic programming algorithm. Finally, the proposed method is applied to the optimal control of the typical Lorenz, Chen, and Liu chaotic systems respectively. The simulation processes indicate that the GPM is effective, fast and feasible for solving optimal control problems of chaotic systems.
2013, 62 (23): 230506. doi: 10.7498/aps.62.230506
Firstly, a new fractional-order chaotic system is proposed. When the linear term x in the second formula of the system was replaced by its absolute value, the range of its unique parameter k that makes the wing of the original system doubled is explored in detail. Furthermore, the numerical simulation and the circuit simulation of the original system and its double-wing system are achieved via Matlab and Multisim software respectively. Finally, based on sliding mode control theory and stability theory in fractional calculus, a new sliding mode controller is designed to realize the synchronization of the new system and its double-wing system respectively. Simulation results are provided to illustrate the effectiveness of the proposed scheme.
2013, 62 (23): 230507. doi: 10.7498/aps.62.230507
A new nonlinear synchronization control strategy for a parameter mismatch system based on exact linearization via feedback is presented. First, a nonlinear affine model of parameter mismatch system is established, and the precondition of exact linearization is verified based on the differential geometry theory. Through the nonlinear coordinate transformation, the linear decoupling system is obtained, so the state feedback control law can be determined by the linear optimal control theory. It is found by simulation results that the proposed synchronization method based on exact linearization via feedback can ensure the successful control of the parameter mismatch system.
2013, 62 (23): 230701. doi: 10.7498/aps.62.230701
We propose an optimization design method for actively shielded whole-body open high-field superconducting MRI magnet which accordingly has been simplified to contain only four pairs of superconducting coils. The new design method of open structure superconducting MRI magnet integrates the linear programming algorithm and the genetic algorithm optimization. Through several times of linear programming, and by taking into account the magnetic field, inhomogeneity in DSV, the scope of 5-Gauss fringe field, maximum hoop stress and maximum magnetic field, we can, with the least consumption of lines, get the coils’ initial position and shape, the number of layers of each coil and the number of turns of each layer. And the genetic algorithm was then employed to improve the magnetic field inhomogeneity in DSV to meet the requirements of high-quality imaging. This integrated optimization design method is flexible and effective for designing both open MRI magnet and traditional cylindrical MRI magnet. This paper also illustrates the method for a 1.2 T open MRI magnet optimization design.
Method of imaging performance deterioration anlysis and its experiment simulated high heating sapphire MW infrared window during near-hypersonic flight
2013, 62 (23): 230702. doi: 10.7498/aps.62.230702
During supersonic flight, the heat radiation of aero-craft optical window has negative effect on infrared imaging performance. A computational model of radiance transmit route and radiation intensity was built in the paper. And the paper also gave the radiation emission model and infrared imaging model. The problem of heat radiance imaging was transform to the problem of optical computation. The simulation results showed that method proposed by the paper was effective to analysis the heat window radiation problem. An heating sapphire window experiment is designed to validate the simulation result. By subtraction between the deduced image based on model and experiment image, it is found that average error for each pixel is about 0.45. By analysis of experiment results, the infrared image contrast degree and Signal-to-Noise was reduced to about one third of the original ones. And the NETD of infrared system with heating window rose from 52 mK to 954 mK. The heating window radiation analysis model presented by the paper can effectively estimate aero-thermal effects on mid-wave infrared imaging system. The designed experiment developed a effective way to verify imaging system performance. And it is also much meaningful for optimal infrared spectral band selection, imaging parameter adjustment and the hot dome radiation suppression to reduce the image degradation.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
2013, 62 (23): 231101. doi: 10.7498/aps.62.231101
Conformal invariance and conserved quantity for a variable mass holonomic system in relative motion have been studied. The definition and the determining equations of conformal invariance for a variable mass holonomic system in relative motion are given. The necessary and sufficient conditions that the system’s conformal invariance be of Lie symmetry are deduced. With the aid of a structure equation which the gauge function should satisfy, the system’s corresponding conserved quantity is obtained. Finally, an illustrative example is given to verify the results.
ATOMIC AND MOLECULAR PHYSICS
The lattice parameters, band structure, density of states, effective mass, carrier concentration and electrical resistivity of 3C-SiC in different doped forms (undoped, B-doped, Al-doped and B-Al co-doped) are calculated using the plane wave ultrasoft pseudopotential based on density functional theory. Calculations indicate that as the B or Al replaces Si atoms, both the conduction band and valence band shift to higher energy level. The top of valence band shifts quicker, resulting in the decrease of the band gap. B-Al co-doped 3C-SiC shows the narrowest bandgap while the pure one has the widest. Effective mass of B-doped 3C-SiC decreases but that of Al-doped 3C-SiC increases; while B-Al co-doped 3C-SiC effective mass, whose value approaches to the undoped, can be understood in terms of different compensation. As the acceptor impurities, B and Al will greatly increase the carrier density of valence band top, and the carrier density of the co-doped is three times as Large as the B-doped or Al-doped 3C-SiC. In addition, B-Al co-doping has the lowest resistivity among the four doping forms displaying its significant advantages in electrical property.
2013, 62 (23): 233102. doi: 10.7498/aps.62.233102
We present a theoretical study on the ionization and excitation dynamics of CO in various linear-polarized laser fields with in the frame work of the time-dependent density functional theory (TDDFT), applied to valence electrons, coupled non-adiabatically with molecular dynamics of the ions. It is found that the stronger the laser intensity, the more the energies are absorbed by CO and the earlier the ionization takes place with more electrons emitted. Moreover, the bond length of CO is stretched associated with more violent contraction vibration. The dipole moment along the laser polarization is enlarged when the laser intensity is enhanced. This study on the influence of the polarization of laser pulse on the excitation of CO indicates that the ionization of CO is maximized and the contraction vibration becomes most violent when the laser is polarized along the molecular axis. Ionization is restrained when the polarization angle is increased and the dipole vibration shows a strong dependence on the laser polarization. Furthermore, it is found that the electron density surrounding the carbon atom is distributed along the molecular axis particularly when the dispersion of the electrons around the oxygen atom is greatly influenced by the laser polarization.
2013, 62 (23): 233301. doi: 10.7498/aps.62.233301
Vanadium nitride is an important metallurgical additive and a good electrode material. Studying its interior microstructure is necessary for fully understanding its intrinsic nature and for better applications. Two groups of known experimental transition data of low-lying rotational quantum states and the analytical formula derived by Sun group in their previous works are used in this work to predict the high-lying accurate R-branch emission spectra of the (0, 0) band in the f1Φ–a1Δ and d1∑+–X3Δ1 systems of the VN molecule. Theoretical results not only reproduce all known experimental spectral lines accurately, but also generate correct values of the unknown spectral lines up to J=80 that are not available experimentally. This study defines a contribution degree C to measure the contributions of known experimental spectral lines to the predicted line. The contribution degree C makes it easier for one to understand the relationships and influences among the transition lines (rotational states) of the given system.
Multi-reference calculations on the potential energy curves and spectroscopic properties of the low-lying excited states of BS+
2013, 62 (23): 233302. doi: 10.7498/aps.62.233302
The high-level quantum chemistry ab initio multi-reference configuration interaction method (MRCI) with reasonable aug-cc-p VQZ basis sets is used to calculate the potential energy curves of 5 -S states of BS+ radical related to the dissociation limit B+(1Sg)+S(3Pg) and B+(1Sg)+S(1D), where the ground state of X3 is determined. The spin-orbit interaction is firstly considered, which makes the calculated 5 -S states split in to 9 states. Calculated results show that avoided crossing rule exists between the states of the same symmetry. Analysis of electronic structures of -S states shows that the -S electronic states are multi-configuration in nature. Then the spectroscopic constants of the bound -S and states are obtained by solving the radial Schrdinger equation. All of these data will provide accurate information of the electron structure for further research on BS+ in theory and experiment.
Theoretical study on angular distribution and polarization characteristics of X-ray emission following dielectronic recombination of lithium-like ions
2013, 62 (23): 233401. doi: 10.7498/aps.62.233401
Based on the multiconfiguration Dirac-Fock method and the theory of density matrix, we have calculated the magnetic sublevel captured cross section of intermediate doubly-excited state 1s2s22p3/2J = 1 formed by dielectronic recombination of lithium-like ions (26 Z 92). Then, we obtain the angular distribution and linear polarization of X-rays of electric-dipole radiation 1s2s22p3/2J = 11s22s2J = 0. In this study, emphasis is placed on the effects of the Breit interaction on the relevant physical quantities. We find that the influences of the Breit interaction on the alignment for the capture to the doubly-excited state 1s2s22p3/2J = 1 are dramatic, resulting in the remarkable change in the angular distribution and polarization properties of the X-ray emission.
2013, 62 (23): 233601. doi: 10.7498/aps.62.233601
We have changed the resonance energy of the graphene oxide molecular clusters by using the external electric field. From the graphene oxide resonance fluorescence we could study the polarization dynamics of graphene oxide under the electric field. It is found that the electric field makes the FWHM of fluorescence resonance peak tend to be saturated, and the temporal change of fluorescence resonance of the graphene oxide molecular clusters reflects the directional polarization and the deformation polarization generated in the graphene oxide due to the electric field.
ELECTROMAGENTISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2013, 62 (23): 234201. doi: 10.7498/aps.62.234201
In practical applications of transient electromagnetic methods, irregularity of the transmitting loop or current waveform makes the source an extended one. Since neglect of the effect of the extended source will cause some errors in both forward modeling and data interpretation, it makes great sense to calculate the responses that take this effect into account. For a spatially extended source over layered medium, step response is firstly calculated and taken as the basic response, then principle of reciprocity and the integral of the second kind are used to propose a new method that can compute the response based on the coordinates of the loop. For an extended source in time, an improved step-function summation method is proposed to deal with the contradiction between the precision of result and consuming of time. Comparisons with the published work have proved the validity and accuracy of our methods. The effect of the traditional approximations of the extended source is also investigated and some analysis for the numerical results is presented for advanced usage.
2013, 62 (23): 234202. doi: 10.7498/aps.62.234202
Multilayer dielectric grating (MDG) is one of the key optical elements of high-power laser systems. To meet the need of MDGs for high-power laser systems, experimental investigation on MDG with a top layer of HfO2 has been carried out using Kaufman-type ion beam etcher. The optimal ion source conditions have been obtained by etching of HfO2 in pure Ar and Ar/CHF3 mixture plasmas. Compared with pure Ar plasma etching, better selectivity was achieved with Ar/CHF3. The redeposition of sidewalls effects are quite obvious during etching, which results in the increase in duty cycle of etched grating. As there is a distribution of etch rate along the direction normal to the scan movement, a special-shaped mask was made to be used as a substrate holder, which increases uniformity of the etched profile. In order to process repeatability, the ion source should be cleaned up, the cathode and neutralizer filament should be changed after etching process to full completion. Based on the above techniques, a number of MDGs have been achieved, each of which has a mean diffraction efficiency greater than 95%, a line density 1480 lines/mm, and on aperture up to 80 mm×150 mm. Experimental results agree fairly well with the designed, which provides a good reference for the large aperture MDGs ion beam etching.
2013, 62 (23): 234203. doi: 10.7498/aps.62.234203
In order to study the effect of micro-cracks on the damage growth, the different field enhancements of the Hertzian micro crack are investigated by varying its angle, width, and depth. Simulation results show that the most harmful cracks are those with inclination angles from 20.9° to 45°, and the cracks with an angle less than 45° and larger than 48.2° are also harmful, but the cracks with inclination angle of 45° are the least harmful. Increasing the depth of the Hertzian cracks will lead to their field enhancement factors increasing with a quadratic relationship. However, increasing the width does not make it essential to the increase of its field enhancement ability. The development of micro-cracks can be approximated by increase its depth and width, so the development of cracks will lead to the increase of its light field modulation capability, and also to its damage growth rate to accelerate, following an exponential law.
Study on the temperature modified method for monitoring gas concentrations with tunable diode laser absorption spectroscopy
2013, 62 (23): 234204. doi: 10.7498/aps.62.234204
Tunable diode laser absorption spectroscopy (TDLAS) is often used to detect gas concentrations in many fields. But because of the variation of ambient temperature, the measured harmonic signal amplitudes are affected and may lead to the monitoring errors. The impact of temperature on the measurement as well as the temperature compensation method is emphasized. So in order to modify the inversion results and adapt industrial measurement, combustion diagnostics, the numerical fitting empirical modified equation and theoretical modified equation from HITRAN database are discussed and compared in this paper. In experiment, the 21% oxygen as the safety monitoring gas and absorption wavelength at 760.77 nm are employed. Meanwhile, the first harmonic signals are also used to decrease the laser intensity fluctuations. We thus obtained the unmodified and modified results with the tube furnace in the temperature range 300–900 K (interval 50 K). Experimental results show that these two modified methods have some effective influence on the temperature changes and can be applied to gas monitoring correction to improve the accuracy and feasibility of the TDLAS technology. In addition, the methods also provide evidence for the real-time gas monitoring in the application of combustion diagnosis.
Study on surface waves formed at the interface between linear dielectric and centrosymmetric photorefractive crystals
2013, 62 (23): 234205. doi: 10.7498/aps.62.234205
We report localized surface waves at the interface between linear dielectric and centrosymmetric photorefractive (CP) crystals. Adjusting the values of the guiding parameter δ and the propagation constant b, we can easily get three types of surface waves: delocalized surface waves, shock surface waves, and localized surface waves. When the difference between b and δ exceeds a certain threshold value, the localized surface waves can form at the interface between linear dielectric and CP crystals. For positive δ values, the part of the energy of localized surface waves concentrated in the nonlinear CP crystals is always higher than that in the linear dielectric, and increases monotonically with b. The stability properties of the localized surface waves are investigated numerically and it is shown that they can be stable. In a given system, the orders and waveforms of localized surface waves are controlled by adjusting the variable parameters which determine the strength of nonlinear effects.
2013, 62 (23): 234206. doi: 10.7498/aps.62.234206
The 850-nm vertical-cavity surface-emitting laser (VCSEL) with liquid crystal overlay is presented utilizing the birefringence of nematic liquid crystal. Threshold current, peak of optical power and I-P characteristics at different temperatures were studied. At 293 K, the current between the first polarization hop and the second one has an increase of 2.2 mA after overlaying the liquid crystal. At 313 K and 3 mA, the optical power difference between the two orthogonally polarized lights increases from 133.6 to 248.8 μW. The experimental results show that the nematic liquid crystal enlarges the stable range and the discrete of optical power of orthogonally polarized state. Our research could provide insight into the design and fabrication of VCSEL with stable polarization at high temperatures.
Generalized linear reconstructing algorithm based on homomorphic signal processed in digital holographic microscopy
2013, 62 (23): 234207. doi: 10.7498/aps.62.234207
In order to improve the accuracy and the speed of reconstructing an image, the digital holographic generalized linear reconstructing algorithm based on homomorphic signal processing is proposed. By using the pre-magnification digital holographic imaging system and the principle of homomorphic signal processing, the proposed algorithm is analyzed theoretically. The achieving condition for and reconstructing process of the proposed algorithm is presented. Then the theoretical results are demonstrated by simulations and experimental data. Results show that the zero-order term of digital hologram frequency spectrum can be eliminated effectively by the proposed algorithm so as to realize the high-precision reconstruction of the digital hologram. Because a whole quadrant is chosen as the filtered area, the manual frequency filtering operation needed in common linear reconstructing algorithm is avoided and then the reconstructing speed is improved greatly. Meanwhile, the high-frequency component of the reconstructed original image can be reserved up to the hilt so that the high resolution image can be achieved.
PN-based single carrier block transmission with iterative frequency domain equalization over underwater acoustic channels
2013, 62 (23): 234301. doi: 10.7498/aps.62.234301
Single carrier modulation with time-domain equalization (SC-TDE) in underwater acoustic channel is sensitive to receiver parameters and its computational complexity is very high. Orthogonal frequency division multiplexing (OFDM) signal has high peak-to-average power ratio (PAPR) and is sensitive to Doppler shift. Aiming at these problems, this paper proposes the pseudo-noise (PN)-based single carrier block transmissions through underwater acoustic channels and corresponding receiver algorithms. The receiver employs PN signals for residual Doppler shift estimation, and channel estimation. A low complexity T/4 fractional iterative frequency domain equalizer is introduced to improve the system performance. One underwater acoustic communication system has been designed and tested in a lake in November 2011. At a distance of 1.8 km under a complex channel condition, the useful data rates of around 1500 and 3000 bps are achieved with un-coded bit error rates 10-2–10-4 in the lake experiment.
2013, 62 (23): 234401. doi: 10.7498/aps.62.234401
It is an important approach to solve energy problem by improving performance of heat transfer process. The macro physical meaning of new physical quantity for heat transfer process optimization “entransy” is analyzed by comparing it with interrelated concepts in mechanics. From three aspects: the connection of entransy and the external heat transfer ability, efficiency of heat transfer process defined by entransy, and the relation of heat transfer driving force with entransy, the macro physical meaning of entransy is derived, which is the potential energy of heat in the temperature field. Moreover, the application of entransy theory in engineering is introduced through entransy theory optimization in convective heat transfer.
2013, 62 (23): 234402. doi: 10.7498/aps.62.234402
The heat dissipation capability of the slow-wave structure (SWS) of the traveling-wave tube (TWT) is an important influencing factor that restricts the increase of the output power, the stability, and the reliability. Due to several unique and fascinating characteristics, the diamond material has been employed in the SWS manufacture to enhance the thermal conduction to a certain extent. The influences of the supporting rods deposited with diamond film, the helix deposited with diamond film, and the diamond supporting rods on the heat dissipation capability have been studied using theoretical, simulation, and experimental methods. This method is closely associated with the computer simulation in experimental test and increases the simulation accuracy. Valuable conclusions have been obtained.
2013, 62 (23): 234501. doi: 10.7498/aps.62.234501
The dynamic equation of relative rotation nonlinear dynamic system with Mathieu-Duffing oscillator is investigated. Firstly, the bifurcation response align of the relative rotation system under primary resonance-basic parameters condition is deduced using the method of multiple scales, and a singularity analysis is employed to obtain the transition set of steady motion. Secondly, a global bifurcation of the system, some probable routes leading to chaos and multiple times leading to chaos with parametric and external excitation amplitude changes have been discussed by using Melnikov method, and the necessary condition for chaotic motion of the system is presented. Finally, a numerical method is employed to further prove the effectiveness of the theoretical research.
2013, 62 (23): 234502. doi: 10.7498/aps.62.234502
The Noether symmetries and the conserved quantities of dynamics for non-conservative systems with time delay are proposed and studied. Firstly, the Hamilton principle for non-conservative systems with time delay is established, and the Lagrange equations with time delay are obtained. Secondly, based upon the invariance of the Hamilton action with time delay under a group of infinitesimal transformations which depends on the generalized velocities, the generalized coordinates and the time, the Noether symmetric transformations and the Noether quasi-symmetric transformations of the system are defined and the criteria of the Noether symmetries are established. Finally, the relationship between the symmetries and the conserved quantities are studied, and the Noether theory of non-conservative systems with time delay is established At the end of the paper, some examples are given to illustrate the application of the results.
2013, 62 (23): 234701. doi: 10.7498/aps.62.234701
Spray dust mechanism is to use spray to wet and reduce the coal mine dust. Based on lattice Boltzmann method, the dynamic behaviors of droplet spreading on solid surface are simulated numerically in consideration of the molecules reaction between fluid and solid. Results show that the spreading diameter and dynamic contact angle change exponentially with time. The relationship between droplet surface tension and maximum spreading diameter is determined; it is shown that the wettability of solid surface has a great influence on the maximum spreading velocity. All the above numerical results are in good agreement with the experimental and theoretical results reported in the literature. Moreover, the solid surface with high hydrophobicity is further investigated. It is found that the spreading contact angle can be less than 90° if the droplet surface tension is small enough, which agrees well with the theoretical formula. The simulation also shows that there occurs oscillations in the spreading process and retraction when the droplet spreads to its maximum.
2013, 62 (23): 234702. doi: 10.7498/aps.62.234702
Considering the process of insoluble-surfactant-laden film dewetting on a solid substrate, we have established the base state and disturbance evolution equations for the film thickness and interfacial surfactant concentrations based on the lubrication approximation. Transient growth analysis (TGA) was carried out to investigate the stability characteristics of evolution process, and the effects of intermolecular forces were discussed. Results indicate that the introduction of disturbance wave for k=1 is conducive to enhance the stability of film evolution, and the disturbance energy gradually decays; however, the effect changes unexpectedly with the increment of wave number: when k ≥ 2, the stability of dewetting process is deteriorated while disturbance energy grows by degrees and the film flow shows unstable characteristics. Thickening the initial film thickness can effectively improve the stability of film dewetting. Van der Waals force enlarges the disturbance on the film surface and leads to the decline of stability. Conversely, Born force and electrostatic force are propitious for the film evolving stably.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2013, 62 (23): 236101. doi: 10.7498/aps.62.236101
A theoretical study on 13 oligopeptides of glycine and alanine by density function theory (DFT) is given in this paper. Geometric structures, vibration frequency, average binding energies, dipole moment are studied, and IR spectra of the oligopeptides are examined. Results show that with increasing number of residues the average binding energies tend to a regular pattern, IR frequencies of typical functional groups start to shift, but stretching and bending vibrations of the groups show the opposite trend of red shift and blue shift. It is revealed that the physical and chemical properties of the silk fibroin peptide chain show size effect and anisotropic in the growth process. This phenomenon may come from the coupling effect of the similar groups, and the different effects of intramolecular hydrogen bond on the stretching and bending vibration.
2013, 62 (23): 236102. doi: 10.7498/aps.62.236102
By using the first-principles method and the density-functional theory, the electronic properties of graphene nanoribbons(GNRs) with periodic nanoholes passivated by oxygen are studied. It is shown that for the zigzag graphene nanoribbon (ZGNR) in nonmagnetic state(NM), the metallic properties not only still remain but also are obviously enhanced after the holes are punched. But for the antiferromagnetic-state (AFM) ZGNR, after punching holes, it would be changed from semiconductor to metal. While for the ferromagnetic-state (FM) ZGNR, it can be transformed from metal to semiconductor or semimetal after punching holes. Besides, for the punched armchair graphene nanoribbon (AGNR), its band gap will be significantly widened. The in-depth analysis shows that these results are due to the effects of oxygen atoms on electronic properties of GNRs, and also due to the different quantum confinement effects from the neck subprime nanoribbon (NSNR) and edge subprime nanoribbon (ESNR) with different width and edge shape(zigzag or armchair). These findings are important for developing nano electronic devices.
Damage and structural defects in the surface lager of pure molybdenum induced by high-current pulsed electron beam
2013, 62 (23): 236103. doi: 10.7498/aps.62.236103
High-current pulsed electron beam (HCPEB) technique was applied to induce the surface irradiation of pure molybdenum. Microstructures and damaging effect of the irradiated surface were investigated in detail by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After 1 pulse of HCPEB irradiation, a high level of residual stress is amassed in the irradiated surface layer, while after several pulses of irradiation, a large number of adiabatic shear bands are formed on the unmelted regions of the surface, and local cracking occurs in these regions. Microstructure observations show that scattered dislocations and large amounts of vacancy clusters are formed on the irradiated surface. The adiabatic shear bands are composed of fine recrystallized grains with an average size about 1 μm. The partial softening of the irradiated surface induced by adiabatic shear bands, and the segregation of interstitial atoms in grain boundaries are primarily responsible for the surface cracking of the material. Further, nanocrystallines (20 nm) are also formed in some melted regions of the surface.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Effect of concentration of heavy oxygen vacancy in rutile and anatase (TiO2) on electric conductivity performance studied by simulation and calculation
2013, 62 (23): 237101. doi: 10.7498/aps.62.237101
The pure and heavy oxygen vacancy for both rutile and anatase supercell models of TiO1.9375 were structured by using first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory, the geometry optimizations, band structures, and density of states of these models were calculated. Results show that the volumes become greater for both heavy oxygen vacancy rutile and anatase, meanwhile, all of the stability, mobility, and conductivity of anatase supercell model of TiO1.9375 ore greater than the rutile supercell model, which are in agreement with the experimental results.
Simulation and calculation of the Mott phase transition and magnetroelectric performance of Magnli phase titanium suboxides
2013, 62 (23): 237102. doi: 10.7498/aps.62.237102
The pure and Magnli phase titanium suboxides for both rutile and anatase supercell models of TiO1.9375 were structured by using first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory; the geometry optimizations, the band structures, and density of states of these models were calculated. Results show that the volumes become greater for Magnli phase titanium suboxides in both rutile and anatase; meanwhile, the stability may reduce slightly, leading to a Mott transition. The nonmagnetic property of anatase titanium suboxides, and the magnetic property of rutile titanium suboxides, as wall as the conductive property of anatase titanium suboxides are higher than rutile titanium suboxides, in agreement with the experimental results.
2013, 62 (23): 237103. doi: 10.7498/aps.62.237103
Based on the structure of strained Si/SiGe NMOSFET, a unified drain current model is presented in this paper. The model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a smoothing function, and guarantees the continuities of the drain current and its derivatives.Furthermore, the model accuracy is enhanced by including carrier velocity saturation and channel length modulation effects. Comparisons between the model and the measured data show that the drain current model can describe the device characteristics well. The proposed model is useful for the design and simulation of digital and analogy circuits made of strained Si.
2013, 62 (23): 237104. doi: 10.7498/aps.62.237104
Exciton binding energies in InGaAsP/InP quantum well with different contents of In are calculated through variational method in the effective mass approximation. The variation of exciton binding energy as a function of well width, In content, and applied external electric field is studied. It is shown that the exciton binding energy is a non-monotonic function of well width. It increases first until reaching a maximum, and then decreases as the well width increases farther. In addition, with the increase of In content, the well width should increase to reach the maximum value of exciton binding energy. It is also found that the external electric field has little effect on binding energy, but when the electric field is large enough, it will destroy the excitonic effect. These results may provide some theoretical basis for the design and control of InGaAsP/InP optical devices.
2013, 62 (23): 237301. doi: 10.7498/aps.62.237301
A high-k dielectric conduction enhancement SOI LDMOS is proposed and investigated by simulation. The high-k dielectric pillars are located at sidewalls of the drift region. The high-k dielectric assists the self-adapted depletion in the drift region, reshapes the electric field distribution, and makes the three-dimensional RESURF effect realized in a high-voltage blocking state. Dependences of the breakdown voltage (VB) and the specific on-resistance (Ron,sp) on device parameters are exhibited using three-dimensional simulation. Simulation results show that the proposed structure increases VB by 16%–18% and decreases Ron.sp by 13%–20%, compared with the conventional super-junction SOI LDMOS. Furthermore, the charge-imbalance caused by the substrate-assisted depletion effect is alleviated.
2013, 62 (23): 237302. doi: 10.7498/aps.62.237302
In order to meet the multi-band and integration requirements of the communication apparatus, the coupling and resonance mechanism can be exploited to design a frequency selective surface (FSS), with two pass-bands at Ku-band and Ka-band, which is composed of three metallic layers and fabricated on a flat substrate equivalent to a solid wall radome or an A-sandwiched radome. According to the physical structure of the FSS, an equivalent circuit model is established to analyze the filtering mechanism, and the transmission characteristics of the radomes with FSS are obtained by using a full-wave analysis software. The first pass-band at Ku-band with miniaturization property can be achieved by coupling the electric and magnetic field of the three surfaces, while the second pass-band at Ka-band can be achieved by the resonance of the square loop slots embedded in the capacitive surfaces. The transmissions of the solid wall radome and A-sandwiched radome with FSS are 89% and 94.7% at Ku-band, and 88.2% and 93.7% at Ka-band, respectively. When the incident angle is varied from normal to 60°, the frequency response characteristics of the two pass-bands are stable. Finally, the experimental results of the prototype with a solid substrate measured in free-space environment are in good agreement with the simulated values. The proposed radome structure with FSS, which is based on the coupling and resonance mechanism, can achieve two stable pass-bands at Ku-/Ka-band. This may provide some theoretical and experimental assistance for the study of the multi-band and wide band spacing FSS.
2013, 62 (23): 237303. doi: 10.7498/aps.62.237303
By considering the effect of molecular vibrational states, a system of dye semi-conductor coupled with metal nano-particle linear absorption spectra and its electron transfer dynamics are studied in dipole-dipole approximation. As the results of the coupling of metal nano-particle, a wider absorption spectrum and the enhancement of electron transfer have been achieved. Effects of nano-metal surface plasmons on the ultrafast heterogeneous electron transfer are discussed in detail.
High-temperature piezoelectirc thin films of 0.20BiInO3-0.80PbTiO3 deposited by pulsed laser deposition（Retracted Article)
2013, 62 (23): 237701. doi: 10.7498/aps.62.237701
High-temperature piezoelectric thin films of 0.20BiInO3-0.80PbTiO3 (20BI-PT) were prepared via pulsed laser deposition and investigated by comparison with 0.15BiInO3-0.85PbTiO3(15BI-PT). XRD patterns show that (100) peak of 20BI-PT has been split, indicating a higher tetragnality than in 15BI-PT. FESEM images reveal some triangular grains corresponding to -oriented grains in 20BI-PT. The remanent polarization (Pr) and coercive field (Ec) of 20BI-PT are ～ 28 C/cm2 and ～120 kV/cm, respectively. It is shown that the transverse piezoelectric coefficient e31, f keeps almost the same in 20BI-PT and 15BI-PT. The temperature dependence of dielectric permittivity in 20BI-PT reveals a higher Curie temperature (590 ℃) than that in 15BI-PT and no apparent frequency dependence is detected. Rayleigh analyses are performed to identify the extrinsic contributions to dielectric nonlinearity for different x. It is seen that x=0.15 exhibits greater extrinsic contributions to dielectric nonlinearity than the other compositions.
2013, 62 (23): 237702. doi: 10.7498/aps.62.237702
BaxSr1-xTiO3 (0.40≤x≤0.70) ceramics have been prepared by the conventional solid-state reaction method. The changes of vibration modes in the pure BaxSr1-xTiO3 system have been investigated for an in-situ electric field by Raman spectra, and the transition from the cubic phase to tetragonal phases were obviously observed near the Curie temperature (Tc). Detailed results indicate that the A1(TO3) and E(TO4) modes correspond to the vibrations of O-Ti-O bond along a-axis in the ab plane, which are strongly related to the lattice structure of ABO3. With increasing electric field, the intensity of A1(TO3)/E(TO4) ratio is increased, suggesting that more and more paraelectric states are transformed into ferroelectric states, thus leading to the deformation of lattice, which results in the decrease of dielectric constant and the increase of tunability. The electric-induced-structure phase transitions responsible for the nonlinear dielectric properties are also discussed.
A polarization-independent and ultra-broadband terahertz metamaterial absorber studied based on circular-truncated cone structure
2013, 62 (23): 237801. doi: 10.7498/aps.62.237801
In this paper, we present an ultra-broadband polarization-independent terahertz (THz) metamaterial absorber (MA) made of circular truncated cone metamaterial. Absorptivity higher than 92.3% at normal incidence is obtained in a wide range of frequencies from 2 to 10 THz. We employ an isotropic metamaterial cell which consists of alternating layers of Au metal and SiO2 dielectric spacer. The absorption spectra of the THz MA are calculated using the finite-difference time domain (FDTD) method within the CST Microwave Studio 2009 in the frequency range of 0–10 THz. Our broadband absorber can be regarded as a group of micro-absorbers perpendicularly stacked and their absorption peaks coupling to each other to form an ultra broadband absorption. This THz MA has the advantages of broadband, polarization-independent and fabrication facility, and thus can be widely applied in THz wave harvesting, detection, spectrum imaging and stealthy technology.
2013, 62 (23): 237802. doi: 10.7498/aps.62.237802
Polarized Raman spectra of single crystal Bi2ZnOB2O6 have been recorded in the spectral range 101600 cm-1 at room temperature. Factor group analysis was used to obtain the normal modes of vibration of the crystal. The Raman peaks under 300 cm-1 are assigned to external modes, which are related to the rotational and transitional movement of the [BiO6], [ZnO4], [BO4] and [BO3] groups. Compared with the vibrational spectra of the compounds referred, the satisfactory assignment of most of the high-energy modes to vibrations of Bi-O, B-O and Zn-O bonds can be achieved. In particular, the Raman high-frequency peak located at 1407 cm-1 is attributed to the B-O vibration in the [BO3] triangle.
2013, 62 (23): 237804. doi: 10.7498/aps.62.237804
In this paper, we present a detailed theoretical study of nonlinear terahertz optical properties of graphene in the presence of electric field and terahertz radiation field. The optical current is computed and investigated on the basis of quantum theory and semi-classical Boltzmann equations. It shows a large nonlinear terahertz response and the nonlinearity becomes larger with increasing electric field or decreasing terahertz frequencies. Moreover, it is found that the optical nonlinearity can be modified and controlled by electric fields.
Simulation and experimental research of phase transmission features based on evanescent field coupled graphene waveguide
2013, 62 (23): 237805. doi: 10.7498/aps.62.237805
The applications of graphene-based optical waveguide devices have been demonstrated to be one of the important directions of development for a new generation of photonic devices, and the research of graphene-based optical fiber and integrated photonic devices has attracted a great deal of attention at home and abroad. In this paper, a graphene planar optical waveguide is proposed which could transmit light by the evanescent field coupling with a microfiber. Finite element method is adopted to simulate the optical field intensity distribution and phase features of light propagating along graphene planar optical waveguide, and an experiment is performed to verify these features. Experimental results show that the transmission distribution and phases of the evanescent field are modulated by graphene obviously, it could effectively gather and transmit the high-order modes, exhibiting denser equal-phase faces on unit propagating length. In this work, we propose a new method in which the microfiber is adopted to investigate the transmission phase feature of graphene by evanescent wave coupling, which could be used as references for the design and application of graphene-based optical devices, such as modulator, filter, laser and sensor.
2013, 62 (23): 237806. doi: 10.7498/aps.62.237806
In this work, we first investigate the optical properties of nanorod arrays with normal inter-rod spacing (>100 nm) and realize the tuning of nanorod localized surface plasma resonance (LSPR) by changing array parameters (e.g., periodicity). Then we filter our individual colors in the visible range using nanorod arrays with ultrasmall inter-rod spacing and ultrahigh density fabricated by electron beam lithography (EBL) and ion etching. The functional nanorod arrays developed in this work are compatible with current digital light processing technique, enabling screen with ultrasmall pixels which can find extensive applications in display and imaging.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2013, 62 (23): 238101. doi: 10.7498/aps.62.238101
A study to shed light on the existence of silicon-graphdiyne as well as their stability, structural and other properties, has been carried out using an efficient semi-empirical Hamiltonian scheme based on quantum mechanics. Its most stable structure is a single planar structure with a lattice constant of 12.251 Å. The system occurs structural phase transition at 1520 K. When the temperature is above 1520 K, the basic structure will be destroyed, While the temperature is below 1520 K, the system can restore its initial structure. It is found that sp hybridization exists between Si and C atoms in this conjugated structure. The study of pair distribution function shows that sp bond length is about 1.58 Å. The sp hybridization would gradually transform into other forms of hybridization at high temperatures. Our calculation indicates that delocalized π-bonds exist in this system and all the lengths of Si-C bonds tend to be more uniform. The energy gap is 1.416 eV. LUMO and HOMO energy levels are 0.386 eV and –1.03 eV respectively. It is found that the silicon-graphdiyne should be n-type material.
2013, 62 (23): 238102. doi: 10.7498/aps.62.238102
In this paper, the strain effect on the morphological instability of the circular island is studied in terms of the BCF (Burton, Cabera, Frank) model. We introduce strains into the BCF model under the Gibbs-Thomson condition and investigate the instability of the island due to the combined effect of the misfit strain, applied strain, deposition flux, line tension, and the far-field flux. Thus, we obtain the perturbation growth rate and the critical deposition flux. Results indicate that the misfit strain and the far-field flux tend to destabilize the growth of the island, and the line tension has a stabilizing effect. In addition, the larger island is more stable during the growth of the island. Up to the critical radius, as the misfit strain increases, the critical flux increases. When taking into account the applied strain, the negatively applied strain stabilizes the growth of the island and decreases the critical flux. These results are almost opposite to the case of the positive strain. This could potentially provide on important theoretical basis for controlling the growth and stability of the films.
2013, 62 (23): 238401. doi: 10.7498/aps.62.238401
In this paper, a high-efficiency Denisov-type launcher, a hardcore of quasi-optical mode converters in high-power gyrotron oscillators, is investigated. Based on integral expression of Bessel functions and geometric optics, the propagation of EM wave in circular waveguides, the syntheses of amplitude and phase of nine modes are analyzed in detail. A generalized method for designing the launcher with a dimpled waveguide wall operating in different modes is demonstrated. This method shows how to select a set of appropriate coupled modes to synthesize the Gaussian-like distribution on the inner wall of the launcher. A program is developed and its accuracy is confirmed by a high-power gyrotron at 140 GHz, in TE28,8 mode theoretically. Numerical calculations show a good agreement with reported results.
2013, 62 (23): 238402. doi: 10.7498/aps.62.238402
By considering the correlations between cross-polarized sub-channels, the traditional multi-input multi-output (MIMO) channel models are proved to be unable to reflect the effect of antenna polarization on correlation coefficients. To solve the problem, a new modeling theory is proposed to amend the traditional model. Furthermore, the method of calculating correlation coefficients of the MIMO system with hybrid-diversity antennas in traditional channel models is proved to be an inaccurate approximation, and a new method of modeling with statistical data of MIMO systems with hybrid-diversity antennas is presented. The new model is able to replicate the correlation coefficients accurately and meet the high-precision requirements.
2013, 62 (23): 238403. doi: 10.7498/aps.62.238403
In this paper, based on the theory of mode-matching and the coupled wave theory, A W-band TE62 mode generator by using waveguide mode transformation is presented. Because of the eigen-mode selection of coaxial waveguide, a TE1 mode in standard rectangular waveguide is coupled into a coaxial waveguide to excite a TE61 mode by an aperture. A transition follows on it to change the coaxial waveguide into a circular one. Finally, TE61–TE62 mode converter is achieved by using a periodic radius perturbation in circular waveguide. Calculation and analysis of the relationship between the mode conversion efficiency and structure parameters of waveguide also are finished. The validity of this study is confirmed by using electromagnetic simulation software. The conversion efficiency of TE62 mode reaches 94.5% at the center frequency 95 GHz, and the mode purity reaches 98.16% The bandwidth of the efficiency above 85% reaches 1 GHz, which can meet the demand of the high–frequency cold test of gyrotrons.
Comparison between memory characteristics of MONOS memory with LaON/SiO2 or HfON/SiO2 as dual-tunnel layer
2013, 62 (23): 238501. doi: 10.7498/aps.62.238501
Memory characteristics of MONOS memory with LaON/SiO2 or HfON/SiO2 as dual-tunnel layer were comparatively investigated. Experimental results show that the MONOS memory with LaON/SiO2 as dual-tunnel layer exhibits large memory window, high program/erase (P/E) speed, good endurance and retention properties. The basic mechanism lies in the large dielectric constant of LaON which increases the injection efficiency of carriers during programming/erasing, the smaller Oxygen diffusion coefficient in LaON which leads to the reduction of interface traps and thus the leakage of stored charges through trap-assisted tunneling during retention. Moreover, strong La-N, Hf-N and O-N bonds are formed at/near the interface due to Nitrogen incorporation, which effectively decreases the damages of the P/E cycle stress to the interface, and thus achieves excellent endurance. In addition, impacts of annealing temperatures on characteristics of MONOS memory were investigated. It is demonstrated that the memory annealed at 800 ℃ has better memory properties than that annealed at 700 ℃, which is attributed to the fact that the 800 ℃ NO annealing can incorporate more N into LaON (HfON), and well release strains, thus reducing defects in these dielectrics.
Coupling analysis of electrocardiogram and electroencephalogram based on improved symbolic transfer entropy
2013, 62 (23): 238701. doi: 10.7498/aps.62.238701
Exploration of the coupling relationship in dynamical system has always been a hot topic of many scholars at home and abroad, the traditional symbolic dynamics analysis method may lead to the results from the serious effect of non-stationary time series. This paper employs coarse graining extraction based on research of original transfer entropy. Through theoretical and experimental analysis, we find that the results of transfer entropy have different distribution trend under different extraction conditions in the coupling analysis of electroencephalogram and electrocardiogram. We choose the best effect of signal data extraction method and apply it to the later application analysis. Furthermore, this paper proposes improvement on the method of time series symbolization, using dynamic adaptive segmentation method. The experimental results show that the whether waking period or sleeping stage, coupling between electroencephalogram and electrocardiogram is more significant when using improved symbolic transfer entropy algorithm. It is also better to capture the dynamic information of the signal and the change of complexity of system dynamics, which is more conductive to clinical testing in practical application and has a better effect on the analysis of non-stationary time series.
2013, 62 (23): 238801. doi: 10.7498/aps.62.238801
In this paper, the electrodeposited Cu-In-Ga metallic precursors have been sulpho-selenized by using H2S gas as the sulfur source and Se vapor as selenium source. Through the comparative experiments of selenization, sulfization and sulpho-selenization of the Cu-In-Ga metallic precursor, it has been found that the formations of CuInS2 phase and CuIn(S,Se)2 phase have priority over and restrain the formation of CuInSe2, so that the InSe phase diffuses into the film and weakens the phenomenon of separation into two phases in the film. Then the process of first selenization and sulfization next was made to optimize the preparation of Cu(In,Ga)(S,Se)2 film. At 250 ℃, the pre-selenization temperature, the solar cells with 570 mV open circuit voltage are prepared, while at a higher pre-selenization temperature, the solar cells with a large short-circuit current are prepared. Finally the optimized solar cell with 10.4% efficiency is obtained.
2013, 62 (23): 238901. doi: 10.7498/aps.62.238901
Based on the NaSh model, the rules of straight movement and lane change are defined while considering the change of driving behavior under the guidance of traffic signs at ramp; besides, a traffic model with sensitive lane change under the cellular automation is proposed. Furthermore, computer numerical simulation result indicates that the procedure of sensitive lane change can effectively reduce the lane change ratio of the straight moving vehicles, thus obviously it has an inhibitory effect on unnecessary lane change; what is more, the longer the sensitive lane change zone, the more effective the inhibitory function is. However, the traffic signs at ramp cannot be set as far as possible. Lower the lane change ratio is, shorter the sensitive lane change zone needed is. The traffic signs at ramp are set with proper distance according to the lane change ratio can effectively increase systematic traffic flow as well as the critical entrance probability.
2013, 62 (23): 238902. doi: 10.7498/aps.62.238902
The development of research on social network makes a great contribution to the study of network evolution though much of the work focuses on a macroscopic evolutionary mechanism. In this paper, based on public goods games, an optimized evolutionary dynamic multi-community network model generated by the co-evolution process of evolutionary games and network topology is put forward (dMCPGG). Edges are revised according to the difference between expected payoff and effective payoff through time. Considering the heterogeneous topology, a new preferential rule based on the topological potential is introduced to quantify the nodes’ importance when choosing and updating the payoff of individuals in the public goods games. Finally, the results of simulations demonstrate that the dMCPGG model can reproduce the random world and scale-free world features, such as the nodes’ degree, clustering coefficient and average path length. Finally, we apply our model to United State Congress voting data and verify its rationality.