Research status and application on the focusing properties of cylindrical vector beams
Cylindrical vector beams are spatially inhomogeneously polarized, whose intensity in the center is zero, and can produce special field components in the vicinity of focus when they are focused by an objective lens. In the case of optical system with high apodization factor, radial polarization can achieve tight focus by adapting pupil filtering and image restoration technology compared with linear and circular polarization. The properties of cylindrical vector beams are introduced. Based on electric dipole radiation model and vector diffraction theory, focal field properties for cylindrical vector beams focused by a high-NA objective lens are discussed. The method to achieve tight focus by cylindrical vector beams is presented. Furthermore, we consider it feasible for the super resolution laser polarized differential confocal microscopy by adapting the differential confocal microscopy, and put forward the prospective development.
Recent progress in preparation of material and device of two-dimensional MoS2
After several decade developments the critical dimension of an integrated circuit will reach its limit value in the next 10-15 years, and the substitute materials been to be researched. Graphene has beed considered the most likely candidate, however, pristine graphene does not have a bandgap, a property that is essential for many application, including transistors. The two-dimensional layer of molybdenum disulfide (MoS2) has recently attracted much attention due to its excellent semiconductor property and potential applications in nanoelectronics. The device preparation, two-dimensional material research and property analysis of MoS2 are summarized and the trend for future research on large sigle-layer MoS2 crystal is presented.
Investigation of effective EM parameter based on impedance simulation
Few-layer graphene membrane as an ultrafast mode-locker in erbium-doped fiber laser
Single-layer graphene film is fabricated on the copper foil by using chemical vapor deposition method, and the corresponding Raman spectrum is measured. The graphene membrane is transferred to the facet of zirconium oxide of a fiber jumper. The mode-lock Er-doped fiber laser with few-layer graphene membrane as saturable absorber is experimentally studied, which has a ring structure and uses a 10% portion of a fiber coupler as the laser output. The laser generates a pulse train at a 7.69 MHz repetition rate, with a full width at half maximum of 58.8 ps. The corresponding time-bandwidth product is 1.98, indicating that the pulses are chirped. The peak wavelength and 3 dB bandwidth of the laser are 1560.1 nm and 0.27 nm respectively. Through changing the air gap between two the fiber ends, 4 nm wavelength tuning is observed.
High energy dissipative soliton mode-locked fiber oscillator based on a multipass cell
To investigate the energy scaling level of large-mode-area photonic crystal fiber-based dissipative soliton mode-locked fiber oscillators under limited pump power, a multipass cell is inserted in the cavity to lower the repetition rate of the system, and thus higher single energy level can be mapped under the same average power level. High energy mode-locked fiber lasers based on two spectral filters with different bandwidths are demonstrated both working in the all-normal dispersion regime at a repetition rate of 15.58 MHz. Employment of filters with FWHMs of 6nm and 12 nm can achieve stable mode-locked pulses with average powers of 3.73 W and 4.9 W, corresponding to single pulse energies as high as 239 nJ and 314 nJ, respectively. The FWHM durations of the dechirped pulses by a transmission grating pair can reach 56 fs and 75 fs, which can generate pulses with peak powers exceeding 3MW in both cases.
Statistical features of aerodynamic effective roughness length over heterogeneous terrain
With a new scheme of effective roughness length for heterogeneous terrain, based on the atmospheric boundary layer Monin-Obukhov similarity theory as well as flux and mass conservation principles, the statistical features of effective roughness length and its sensitivity to atmospheric stratification stability and roughness step for three surface category case are investigated. The results show that the effective roughness length is greater than the area-weighted logarithmic average one and the effective drag coefficient is more than 10% greater than the average one in most cases. The effective roughness length is much more sensitive to the roughness step, though it is dependent on the atmospheric stratification stability, and the relative percentage of effective roughness length and the effective drag coefficient will be 4 times and 3 times, respectively, for the double roughness step case. Therefore, the area-weighted average roughness length should be replaced by the effective one when the surface heterogeneity is considered in numerical models, which can represent the integrated effect of heterogeneous terrain.
Theoretical analysis of polarization eigenstate and magnetic sensitivity in a ring laser gyro
Disturbance by ambient magnetic field is an important factor, which leads to measurement error of the laser gyro. In order to reduce the magnetic sensitivity, the polarization eigenstate in ring cavity is analyzed with matrix perturbation method, considering factors of small nonplanarity, mirror anisotropy and stress birefringence, gain and so on. The main factors affecting the magnetic sensitivity of the laser gyro are discussed. Ellipticities of eigen modes in clockwise and anti-clockwise direction caused by nonplanarity are identical and both are proportional to magnetic sensitivity. The influence of stress birefringence on ellipticity is related to mirror position, propagating direction of eigenmodes and main axis of stress. Nonplanarity is zero when ellipticities of eigen modes in clockwise and anti-clockwise direction are equal without stress birefringence in the passive cavity. A lower cavity loss is better to reduce the magnetic sensitivity of the laser gyro. The minimum magnetic sensitivity is not identical with peak gain for the laser gyro. Large phase and amplitude anisotropies of mirrors are useful to reduce magnetic sensitivity and ellipticity. These findings are significant for the reduction of magnetic sensitivity in ring laser gyros.
Intercomparison of slant column measurements of NO2 by ground-based MAX-DOAS
In September 2011, we used 3 ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) instruments of different designs and operation protocols to measure tropospheric NO2 for about 20 days, at the Station of Atmospheric Comprehensive Observatory, Institute of Atmospheric Physics, Chinese Academy of Sciences (Xianghe 117.0°N, 39.77°E). All instruments are oriented to an azimuth angle of 270° (north), in a common wavelength range and with a set of cross sections for the inversion of NO2 slant column in visible and UV wavelength range respectively. Intercomparison of NO2 slant columns among three MAX-DOAS is introduced. The results obtained from the different instruments are in good accordance with each other, and the correlation coefficients are all higher than 0.95, but systematical errors exist. Daily average errors of three MAX-DOAS instruments are almost below 6%, showing that the instruments work steadily and the data are cogent. The UV results are smaller than those in the visible range, especially on the overcast days, related to the wavelength dependence of Rayleigh and Mie scattering. After the correction of systematical errors, there is better consistency among different results, which indicates that the three MAX-DOAS instruments have a capability to validate the atmospheric component products of satellite.
Bright and dark solitons in metamaterials obtained by extended F-expansion method
The ultra-short pulse equation in a metamaterial is solved by the extended F-expansion method. The new phenomena and characteristics of solitons, caused by the anomalous self-steepening effect and the second-order nonlinear dispersion in metamaterials, are discussed. The results show that the second-order nonlinear dispersion in the positive-index region may take the place of the linear dispersion to form the bright and dark solitons. Due to the switchable sign of the anomalous self-steepening effect in the positive-index and negative-index regions, the bright and dark solitons separately exist in the anomalous and normal dispersion regions under some specific conditions. The moving directions of the centers of bright and dark solitons can be controlled by the sign of the anomalous self-steepening effect or by the combination of the anomalous self-steepening effect and third-order linear dispersion.
Optimized digital micro-holographic imaging system
Study of nonlinear acoustic field of high intensity focused ultrasound by the fractional wave
Bifurcation of a kind of nonlinear-relative rotational system with combined harmonic excitation
Drag-reduction of one-dimensional period and puasiperiod groove structures
Mosaic structure in epitaxial GaN filmvarying with thickness
Molecular dynamics simulation of the critical and subcritical nuclei during solidification of nickel melt
Rolling effects on electronic characteristics for graphene nanoribbons
Investigation on the fabrication of Ag-doped ZnO nanorods by hydrothermal method
First-principles study on electronic structures of Al, N Co-doped ZnO nanotubes
By using first principles calculation based on density functional theory, band structures, densities of states and electron density differences for an ideal (6, 0) ZnO nanotube (ZnONT), Al doped, N doped and Al, N co-doped nanotubes are investigated. The calculated results reveal that the doped nitrogen atom results in the formation of acceptor level in the band gap of the ZnONT, which indicates that the doped nanotube has the characteristic of a p-type semiconductor. While the high locality of the acceptor level leads to a lower solubility for the doped nitrogen atoms, the acceptor level is broadened and shows delocalizing characteristics in nanotube with Al, N co-doped. This co-doping may be an efficient method of preparing p-type ZnONTs.
Ab initio study of the bcc-to-hcp transition mechanism in Fe under pressure
We perform ab initio calculations on two different transition mechanisms of the bcc-to-hcp phase transition in Fe under pressure distinguished by the occurrence of the metastable fcc intermediate phase on the transition path, that is, the bcc-hcp and the bcc-fcc-hcp. The calculated results indicate that the occurrence of the fcc intermediate state during the transition is energetically unfavorable, which is consistent with the recent in situ XRD experiments. The enthalpy barrier of the fcc-hcp increases with pressure increasing, which indicates that the pressure tends to impede the transformation from fcc to hcp phase in Fe. The details of the structural and magnetic behaviors of the intermediate states during the transition are investigated, which indicates that there are complex magnetism transitions during the phase transition. The physical origins of the influence of magnetism on the phase transition are discussed. Moreover, the origin of the occurrence and evolution of the fcc metastable structure during the transition in the MD simulations are also discussed.
Molecular dynamics simulation of the thermophysical properties of phase change material
Growth mechanism and optoelectronic properties of vanadium oxide films prepared by Sol-Gel
Calculation of crystal-melt interfacial free energy of Cu by molecular dynamics simulation
Influnce of heat treatment on the structure and optical properties of glow discharge polymer films
The glow discharge polymer (GDP) films each with a thickness of about 5 μm are deposited by low-pressure plasma polymer apparatus. The GDP films are heat-treated at different tempertures of 280, 300, 320 and 340 ℃ in Ar atmosphere. The influence of heat treatment on the structure of GDP film is characterized by FT-IR. The optical transparency and optical band of GDP film are investigated by UV-VIS spectrum. The results show that with temperature increasing, the relative content of CH3 decreases, while the relative content values of CH2 and CH increase. The H content in GDP film decreases. The optical band gap decreases, and the transmittance in a range of more than 600nm decreases too.
Acoustic phonon transport and thermal conductance in quantum waveguide with abrupt quantum junctions modulated with double T-shapedquantum structure
Studies on electrical properties of graphene nanoribbons with pore defects
Gas-sensing properties at room temperature for the sensors based on tungsten oxide thin films sputtered on n-type ordered porous silicon
Research on the capacitance-voltage characteristic of strained-silicon NMOS accumulation capacitor
Accumulation MOS capacitor is more linear than inversion MOS capacitor and is almost independent of the operation frequency. In this paper, we present first the formation mechanism of the “plateau”, observed in the C-V characteristic of the strained-Si NMOS capacitor, and then a physical model for strained-Si NMOS capacitor in accumulation region. The results from the model show to be in excellent agreement with the experimental data. The proposed model can provide valuable reference for the strained-Si device design, and is has been implemented in the software for extracting the parameter of strained-Si MOSFET.
Effective response to external DC and AC electric field in nonlinear cylindrical coated composite
Investigation into the turn-off mechanism and time of IGBT based on voltage and current
Bonding-antibonding ground state transition in coupled quantum dots
The two lowest single-particle hole states in two vertically coupled quntum dots (CQDs) are investigated by using the six-band K·P model. A bonding-antibonding ground-state transition is observed with interdot distance increasing. This result is counterintuitive, for the antibonding molecular ground state has never been observed in natural diatomic molecules. By comparing the wavafunction component of hole, we verify that the reordering of bonding and antibonding orbitals with interdot distance increasing is caused by spin-orbit interaction of holes.
Electronic structure and spin-polarization of boron-nitride nanoflake
Boron-nitride graphene-like monolayer possesses a similar atomic arrangement to that of the famous graphene. However, due to the large difference in electronegetivity between boron and nitrogen atoms, the electronic properties of the two nanomaterials are different significantly. Here, we report on our theoretical investigation of the electronic structure and spin-polarization of zigzag-edged boron-nitride triangular nanoflake using a Hubbard model and the first-principles calculations within density-functional theory. Our numerical results indicate that in contrast to graphene nanoflake with spin-polarized ground state, the boron-nitride nanoflak has the zero-energy state that is either empty or fully occupied, and its ground state is thus spin-unpolarized which breaks the Lieb's law. However, the electron occupation and spin-polarization of the zero-energy state of boron-nitride nanoflake can be tuned by doping it with electrons or holes. These results are expected to offer the theoretical basis for the applications of boron-nitride nanomaterials in spintronics.
Numerical study of the superconductor-insulator transition in double-layer graphene driven by disorder
Effects of stress on the hysteresis loss and coercivity of ferromagnetic film
Micromagnetic simulation of magnetization reversal on the annular free layer with nick in magnetic random access memory
Dielectric property and relaxation mechanism of CaCu3Ti4O12 ceramic
In this paper, the dielectric property of CaCu3Ti4O12 ceramic is measured by Novocontrol wide band dielectric spectrometer in a temperature range of -100-100 ℃ and frequency range of 0.1 Hz-10 MHz, and the corresponding dielectric relaxation mechanism is discussed. Firstly, on the basis of quantitative analysis of macroscopic shell-core structure, the possibility of colossal dielectric constant (CDC) originating from the surface insulated layer effect is rejected. Secondly, after the analysis of the nature of classical Maxwell-Wagner sandwich polarization and its activation energy, classical Maxwell-Wagner mechanism is also abandoned. Finally, a new model of trapped electron relaxation at the boundary of Schottky barrier is proposed. The new mechanism correctly reflects the essential connection between intrinsic point defects, conductivity and dielectric constant of CaCu3Ti4O12material.
Measurement of refractive index of luminescent photoelastic coating
The refractive index of the coating is one of the essential parameters used for principal strain separation in luminescent photoelastic coating (LPC) method by oblique incidence technique. According to the theoretical analysis of the amplitude of the emitted light exciting the coating, which returns along the same path as the oblique incident excitation light, we propose a new online method of measuring the refractive index of the LPC based on optical Fresnel response of the coating. The refractive index of the coating containing Rhodamine B as luminescent dye, is measured under the excitation at a wavelength of 465 nm and an incident angle of 60°. The experimental result proves the feasibility of the new method, and the present method is also applicable to the refractive index measurement of other luminescent coating.
p-ZnO thin film/n-Si heterojunction light-emitting diode fabricated by chemical vapor deposition and its characterization
First principles study of structures, static polarizabilities and optical absorption spectra of Cun-1Au (n=2–10) clusters
Nanoring color filters based on Fabry-Pérot cavities
High-quality Ge1-xSnx alloys grown on Ge(001) substrates by molecular beam epitaxy
As a new group-IV semiconductor alloy, Ge1-xSnx is a very promising material for applications in photonic and microelectronic devices. In this work, high-quality germanium-tin (Ge1-xSnx) alloys are grown on Ge(001) substrates by molecular beam epitaxy, with x=1.5%, 2.4%, 2.8%, 5.3%, and 14%. The Ge1-xSnx alloys are characterized by high resolution X-ray diffraction (HR-XRD), Rutherford backscattering spectra (RBS), and transmission electron micrograph (TEM). For the samples with Sn composition x≤ 5.3%, the Ge1-xSnx alloys each exhibit a very high crystalline quality. The ratio of channel yield to random yield (χmin) in the RBS spectrum is only about 5%, and the full width at half maximum (FWHM) of the Ge1-xSnx peak in HR-XRD curve is 100''. For the sample with x=14%, the crystalline quality of the alloy is degraded and FWHM is 264.6''.
Hard X-ray measurement for indirect-driven imploding by chemical vapor deposited diamond detectors
Design of a low-frequency broadband circuit analog absorbers based on wire media
Influence of working pressure on the state of H2/C4H8 glowing discharge plasma
Influences of growth orientation on strain and strain relaxation of quantum dots
Different growth orientations influence the mechanical properties and behavior of quantum dots, due to the anisotropy of elasticity and surface energy of the material. In this paper, the relations of the strain energy, strain relaxation energy and free energy to growth orientation are analyzed for the self-assembled InAs/GaAs semiconductor quantum dots, based on finite element method of cubic elasticity theory. The results show that the strain relaxation of the (211) quantum dots is biggest, and that of the (100) quantum dots is smallest. These can provide the theoretical basis for the growth of quantum dots in a controlled fashion.
Spatiotemporal modulation induced coexistence of meandering spiral wave and travelling spiral wave
Spiral dynamics induced by spatiotemporal modulation is investigated in the generic excitable Barkley model. The coexistence of meandering spiral wave and travelling spiral wave in the same medium is discovered under proper spatiotemporal modulation. The underlying mechanism behind this coexistence phenomenon is analyzed. And the two necessary conditions which are needed to observe the coexistence of meandering spiral wave and travelling spiral wave in the excitable Barkley model are discussed.
Subwavelength antenna array based on far-field time reversal
Influences of the multiple electron overtaking on the bunching process of the wide-gap klystron amplifier under high power injection condition
Mechanical stress in superconducting coils during winding process
Electronic conductivity effective masses along arbitrary directional channel in uniaxial strained Si(001)
Radiation damage induced by various particles on CC4013 devices
During serving in orbit, spacecraft will be affected by the radiation environment of the space high-energy charged particles, leading to the performance degradation or even malfunctions of electronic components. The complementary metal oxide semiconductor (CMOS) devices are sensitive to ionization damage. Therefore, it is valuable to research the mechanism of radiation effects on CMOS devices, and is significant to engineering and theory. The CC4013 CMOS integrated circuits are irradiated with 60 MeV Br ions, 5 MeV protons and 1 MeV electrons. Based on the data calculated by Geant4 code, the ionizing absorbed dose induced by 60 MeV Br ions is greatest, and the ionizing absorbed dose induced by 1 MeV electrons is lowest. The degradation of CC4013 device during the irradiation test is in-situ measured with Keithley 4200-SCS semiconductor characteristic system. From the experimental results, the threshold voltage degradation in CC4013 under an exposure of 1 MeV electrons is greatest at the same dose, a little lower under 5 MeV protons, and lowest under 60 MeV Br ions.
Wireless energy transfer system based on metglas/PFC magnetoelectric laminated composites
Mechanism of target wave excited by current with diversity
The formation of target wave in the network of Hodgkin-Huxley neuron with four variables is investigated by inputing a distribuled current. A stimulus current (I1) is input in to a local square area, and another stimulus current (I2) is input into the nodes of the network thus the distributed current is depicted. The development of target wave is measured by changing the coupling intensity, the size (number of the controlled neurons) of the local area into which current I1 is input, the gradient current (ΔI =I1-I2). It is found that higher gradient current (ΔI) is necessary to induce target wave when local area into which current I1 is input is smaller in size and the coupling intensity is higher in value. Finally, the potential mechanisms of the stimulus current and target wave formation are discussed in brief. Eextensive numerical results confirm that the developed target wave is robust to a certain channel noise.
Photothermal response of extracellular solution to the near-infrared laser irradiation determined by its optical absorption properties
Study of the contact property between BZO and p-a-SiC in amorphous silicon solar cell
An efficient management strategy for enhancing traffic capacity in scale-free networks
Previous research has shown that the community structure of the network well significantly affect information transmission, and the obvious community structure will significantly reduce the network transmission performance. To address the problem, first we define the link importance to communities, which is based on the spectrum of network adjacency matrix. Then we propose a topological management strategy called community weaken control strategy (CWCS) to enhance traffic capacity, which weakens the community structures by logically closing or cutting some links with great link importance. We implement the scheme in both a global shortest-path routing strategy and local routing strategy, and compare it with the previous scheme HDF that removes the links among hub nodes. The simulation results show that the traffic capacity can be greatly enhanced and the average transport time is effectively reduced under the shortest path routing strategy. Under the local routing strategy, the traffic capacity can also be greatly enhanced when the tunable parameter α lies in a range from 0 and 2.
Chaotic signal denoising method based on independent component analysis and empirical mode decomposition
Application of extended Fourier amplitude sensitivity test (EFAST) method in land surface parameter sensitivity analysis
Study on weak signal detection method with Duffing oscillators
Effects of time-periodic modulation of cross-correlation intensity between noises on stochastic resonance of over-damped linear system
For an over-damped linear system subjected to correlated additive and multiplicative noise and a periodic signal, when the cross-correlation intensity between noises is a time-periodic function, the analytical expression of the output signal-to-noise ratio (SNR) is derived by means of the stochastic averaging method. It is found that this system has richer dynamic behaviors than the linear systems in which cross-correlation intensity between noises is constant, that the evolution of the output SNR with the cross-correlation modulation frequency presents periodic oscillation, and that the parameters of cross-correlation intensity between noises diversify the stochastic resonance phenomena.The time-periodic modulation of cross-correlation intensity between noises is conductive to enhancing the sensitivity to weak periodic signal detection and implementing the frequency estimation of weak periodic signal.
Improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter
An improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter is proposed in this paper. Based on state-space averaging in every switching cycle, the improved discrete-time model combines the advantages of the average model and the traditional discrete-time model, which can accurately analyze the digital control delay and sample-and-hold process inherently in digital controlled system. Consequently, under the accuracy premise, the improved discrete-time model can effectively simplify the traditional discrete-time modeling. As an example, an LC filter capacitor-voltage and inductor-current feed-back plus voltage-reference feed-forward control algorithm is analyzed based on the improved discrete-time model. The stability boundary and oscillation frequency are accurately predicted. Finally, theoretical results are verified by simulations and experiments.
Analysis of noisy chaotic time series prediction error
Chaotic time series prediction model of wind power based on ensemble empirical mode decomposition-approximate entropy and reservoir
According to the chaotic feature of wind power time series, a combined short-term wind power forecasting approach based on ensemble empirical mode decomposition (EEMD)-approximate entropy and echo state network (ESN) is proposed. Firstly, in order to reduce the calculation scale of partial analysis for wind power and improve the wind power prediction accuracy, the wind power time series is decomposed into a series of wind power subsequences with obvious differences in complex degree by using EEMD-approximate entropy. Then, the forecasting model of each subsequence is created with least squares support vector machine (LSSVM), ESN and EEMD-ESN improved with the regularized high frequency parts. Finally, the simulation is performed by using the real data collected from a certain wind farm, the results show that the EEMD-ESN model is better in the training speed and forecasting accuracy, than those obtained from the least square support vector machine (LSSVM) model, which provides a new useful reference for the short-term forecasting of wind power in online engineering application.
Simulation and experimental results of evacuation of pedestrian flow in a classroom with two exits
Phase-field-crystal modeling for two-dimensional transformation from hexagonal to square structure
The two-mode phase-field-crystal (PFC) method is used to calculate the phase diagram and to simulate the transformation of hexagonal to square structure in two dimensions. The nucleation, grain growth and dynamic feature of the phase structure transformation show that square phase prefers to be present at the juncture place of the three hexagonal grains, and swallows the hexagonal phase at grain boundary. The square grains grow and push the boundary of hexagonal grain toward the inside of hexagonal grain and then the square grains grow up and extend the area of square phase. The orientations of new square grains due to the structure transformation are nearly randomly distributed, and have no relation to those of hexagonal grains. The dynamic curve of area fraction of square phase shows the typical "S" shape with time increasing. The Avrami index curve shows that there are two stages in the transformation. The Avrami index n of second satge in simulation is in a range from 2.0 to 3.0, which is in good agreement with the value from the JMAK theory.
Adaptive synchronization and parameter identification for Lorenz chaotic system with stochastic perturbations
In this paper, Lorenz chaotic system with stochastic perturbation and unknown parameters is investigated, in which the stochastic perturbations is one-dimensional random process of the standard Wiener. Based on stochastic Lyapunov stability theory, Itô formula and adaptive control method combined with three adaptive control laws and two adaptive control laws respectively, two mean square Asymptotic adaptive synchronization standards are put forward theoretically. These new standards are in a simple form and easy to deal with. Moreover, with these standards, not only drive system with stochastic perturbations can be synchronized with the respond system, but also unknown parameters in the system can be identified. Finally, the Matlab numerical simulations confirm that the proposed results are correct and effective.
Structural, electronic and magnetic properties of ConAl (n= 1–8) clusters
Based on DFT-GGA calculations, we systematically investigate the structures, electronic and magnetic properties of ConAl (n= 1–8) clusters. The results indicate that the aluminum prefers to maximize the number of Co-Al bonds by selecting the site which increases the coordination of cobalt atoms with Al. The doped Al makes the stability of ConAl clusters weakened and the magnetism decreased as compared with that of Con+1 clusters. The reduction magnitude of magnetism of the doping Al accords well with recent Stern-Gerlach experimental result for larger ConAlM clusters. In all of the ConAl alloy clusters, the Al atom is found to be aligned antiferromagnetically with its neighbor Co atoms except for Co4Al. As compared with the magnetism of pure Co cluster, the magnetism of ConAl cluster is reduced, which is attributed mainly to nor-magnetism Al element embeding and the weakening of spin polarization of the Co atoms.
Theoretical study of structural stabilities of BiXO3 (X= Cr, Mn, Fe, Ni)
The stable chemical potential phases of BiXO3 (X= Cr, Mn, Fe, Ni) are studied by density functional theory with the consideration of thermodynamics equilibrium conditions. It is found that the BiFeO3 and BiCrO3 have stable chemical potential regions and are expected to be synthesized, under thermodynamic equilibrium conditions. On the contrary, no stable regions are found for BiMnO3 and BiNiO3, indicating that they are hard to synthesize. Therefore the approaches to their preparation under non-thermodynamic equilibrium conditions should be considered.
Hydrogen storage capacity of lithium decorated B6 cluster
The structures and the hydrogen storage capacities of the B6 clusters and the lithium decorated B6 clusters are investigated by using the density functional theory. The results show that the hydrogen is adsorbed in the atomic form by chemical bonds in the three possible structures of the B6 cluster. The lithium atoms do not cluster on the surface of decorated B6 cluster. Every lithium atom, as hydrogen molecules are adsorbed on the surface of lithium atoms decorated B6 clusters, can adsorb several intact hydrogen molecules. Of the lithium decorated B6 clusters the B6 cage cluster which is decorated by two lithium atoms can most adsorb the intact hydrogen molecules. The calculated gravimetric density and the average adsorption energy of hydrogen molecule are 20.38% and 1.683 kcal/mol, respectively, which are suitable for reversible hydrogen storage under the ambient condition of the normal temperature and pressure.
Photoionization of odd-parity bound excited states of Sm atom
The chiral asymmetry revealed by the Raman differential bond polarizability of (2R, 3R)-(-)- 2, 3-butanediol
The Raman optical activity (ROA) of (2R, 3R)-2, 3-butanediol is investigated through the intensities of Raman spectrum and ROA spectrum, bond polarizability and differential bond polarizability. In view of the two possible optimized structures, i.e., C1 and C2 group, we obtain the conclusion that ample information concerning the physical pictures of this chiral system does not depend on the two variant structures.Based on the analysis of bond polarizabilities, the charge moves from the periphery to the skeleton structure in the Raman relaxation process. The analysis of differential bond polarizabilities shows that the signs of differential bond polarizabilities on the both sides of the plane associated with the asymmetric C and H atoms are opposite. This means that the chiral asymmetry of this molecule is rather complete.Also, it is observed that bond polarizabilities for the symmetric modes are larger than for the antisymmetric modes, while for the differential bond polarizabilities, the situation is just reverse.
Dissociation of H2 on Al7- cluster studied by ab initio calculations
Experimental and theoretical study of Ar·CO cluster
The photoionization mass spectra and photoionization efficiency curves of Ar·CO clusters are obtained with synchrotron radiation mass spectrometry. By comparison with absolute photoabsorption spectra of CO, the photoionization efficiency curve of Ar·CO clusters in an energy region from 13.9 to 14.6 eV reflects mainly the properties of Rydberg series converging to the X2∑+ (v+= 1, 2 and 3) of CO+, and these of n= 3 vibration sequence of the series converging to the A2Π state of CO+. In the energy region from 14.6 to 15.75 eV, the curve reflects mainly the absorption property of CO, but its five strong peaks shift toward blue due to the interaction between Ar and CO. In an energy region from 15.75 to 15.80 eV, the curve reflects mainly the absorption properties of Ar and CO. At the same time, ionization energy of Ar·CO, and dissociation energies of Ar·CO and Ar·CO + are also calculated using the theory of quantum chemistry.
Density functional theory study of the adsorption of CO on Wn (n= 1–6) clusters
CO molecules adsorbed on the Wn clusters are systematically investigated by using density functional theory at the B3LYP/LANL2DZ level.The result indicates that the ground state structures of WnCO clusters are generated when CO molecules are adsorbed on Wn clusters or anionic cluster. We find that among the molecular adsorption states exists mainly the form of end-on type geometry, and that the bridge site adsorption type geometry plays a supplementary role. On the face, the adsorption is a non-dissociative adsorption. The CO bond length increases 0.120–0.123 nm in WnCO cluster (compared with 0.116 nm in free CO molecule), which demonstrates that the CO molecules are activated. The stability analysis shows that W3CO and W5CO clusters are more stable than other clusters; natural bond orbital (NBO) analysis indicate that the interaction between W atom and CO molecule is primarily contributed by hybridization of molecular orbits within CO and 6s, 5d, 6p and 6d orbits of W atoms.
High power microwave breakdown in gas using the fluid model with non-equilibrium electron energy distribution function
Auto-alignment in four-pass amplifier with wavefront correction system
Effect of wall secondary electron emission on the characteristics of double sheath near the dielectric wall in Hall thruster
Fractal characteristics research of lightning and its application to automatic recognition
The early warning signals of abrupt climate change in different regions of china
Influence of radiation electron energy on deep dielectric charging characteristics of low density polyethylene
The effect of the radiative pressure on the potential function in asynchronous rotational binary