bluuebunny/crossref_metadata_2025 huggingface dataset:
Sectorial oscillation of acoustically levitated viscous drops
Authors: Shao Xue-Peng  , Xie Wen-Jun  ,   Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The sectorial oscillation of acoustically levitated viscous drops is investigated by applying a series of aqueous glycerol solutions (viscosity = 0.9475.65 mPas). It is found that there exists a critical viscosity c for a definite mode of sectorial oscillation, and that mode can be excited only when c. The critical viscosities for the l = 29th mode sectorial oscillation are experimentally determined with a modulation amplitude to the acoustic field reaching = 0.23. It is found that ln c decreases approximately linearly with l. Analysis based on the parametric resonance theory indicates that in order to excite the sectorial oscillation, the equatorial radius of the drop must be perturbed overs a threshold hc, which is proportional to the viscosity and increases with l. Therefore, the sectorial oscillations can hardly be excited to those drops with high viscosity and large oscillation modes. Both the amplitude and resonant modulating frequency width decrease with the enlargement of viscosity. No obvious effect of viscosity is found on the eigenfrequency of sectorial oscillation.
Effects of Ge profile in base region on thermal characteristics of SiGe HBTs
Authors: Zhao Xin  , Zhang Wan-Rong  , Jin Dong-Yue  , Fu Qiang  , Chen Liang  , Xie Hong-Yun  , Zhang Yu-Jie  ,   College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

As is well known, the base Ge composition can improve the DC characteristics, frequency characteristics and noise characteristics of SiGe HBTs. However, the reports about the effects of Ge profile on HBTs thermal characteristics are rare. In this paper, by use of SILVACO simulator, the effects of different Ge gradients on thermal and electrical characteristics of SiGe HBT are investigated. It is found that under the same total Ge amount condition, as Ge gradient increases, the fT of device increases significantly, the uniformity of temperature distribution becomes better, the influences of temperature on the and fT are weakened, but the gain becomes smaller. For the device with uniform Ge composition, the is high, but the influence of temperature on the is enormous, the uniformity of temperature distribution is poor. Based on these results, in order to make a tradeoff among thermal, gain and frequency characteristics, a novel Ge composition structure with the combination of the uniform and graded Ge composition is proposed. The results show that the novel Ge composition structure SiGe HBT has good performances lower peak temperature, better uniform temperature profile, smaller variabilities of and fT with temperature, sufficient high and fT compared with the uniform Ge composition device. These new results provide valuable reference for the device thermal design, and are supplemental to the research and application of SiGe HBTs.
Quasiparticle band structure calculation for SiC using self-consistent GW method
Authors: Gao Shang-Peng  , Zhu Tong  ,   Department of Materials Science, Fudan University, Shanghai 200433, China
Published: December 2020

Quasiparticle band structures of 3C-SiC and 2H-SiC were calculated using ab initio many body perturbation theory with GW approximation. Quasiparticle energies along high symmetry lines in the first Brillouin zone were evaluated using quasiparitcle self-consistent GW (QPscGW) method and the Maximally-localized Wannier Function interpolation. Both 3C-SiC and 2H-SiC have an indirect band gap with valence band maximum locating at point. The conduction band maximum of 3C-SiC is at X point. As a comparison, band gaps of 3C-SiC calculated by DFT-LDA, one-shot G0W0 and QPscGW are 1.30 eV, 2.23 eV and 2.88 eV respectively. The conduction band minimum of 2H-SiC locates at K point with a band gap of 2.12 eV, 3.12 eV and 3.75 eV predicted by DFT-LDA, one-shot G0W0 and QPscGW respectively. Lattice parameters calculated by DFT-LDA were used in this work. The QPscGW calculations are based on pseudopotential method, predicting slightly larger bandgaps for both 3C-SiC and 2H-SiC comparing with experiments.
Investigation of the nonlinear response mechanism of photovoltaic HgCdTe detector irradiated by CW band-in laser
Authors: Jiang Tian  , Cheng Xiang-Ai  , Zheng Xin  , Xu Zhong-Jie  , Jiang Hou-Man  , Lu Qi-Sheng  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   Science and Technology on Electro-Optical Information Security Control Laboratory, Sanhe 065201, China
Published: December 2020

The medium wave HgCdTe photovoltaic detector (band gap ～0.33 eV) is irradiated by a CW band-in laser. The experimental results are shown that the detector enter into nonlinear response state as the incidence laser power increase. When the detector entered into nonlinear response state, the open circle voltage (Voc) signal decreased with the laser power. The Voc signal rapidly decreased when the laser turned on and the Voc signal rapidly increased when the laser turned off. The effect of laser induced temperature field and temperature dependence built-in field of pn junction were considered. The laser power variation of laser turn on and turn off were aslo considered. The analytical model of photovoltaic detector irradiated by above-band gap CW laser was built up. The calculation results agree well with the experiment results. It is shown that the temperature dependence built-in field of pn junction is the main mechanism induced the nonlinear response. The magnitude of Voc signals with laser turn on and turn off is decided by light intensity and temperature.
Phonon softening and superconductivity of -pyrochlore oxide superconductors AOs2O6 (A=K, Rb)
Authors: Sun Jia-Fa  , Wang Wei  ,   Information College of Huaibei Normal University, Anhui 235000, China;,   School of Physics and Electronic Information, Huaibei Normal University, Anhui 235000, China
Published: December 2020

Using the first-principles calculational method based on the density functional theory, we study the structural instabilities, phonon softenings, and their relation to the superconductivities of two -pyrochlore oxide superconductors AOs2O6(A=K, Rb). It is found that there are structural instabilities of alkali ions along the 〈111〉 direction in the two -pyrochlore oxide superconductors AOs2O6(A=K, Rb), especially in KOs2O6. Meanwhile, a comparison of the phonon frequency at zone-center between KOs2O6 and RbOs2O6 shows that the frequency of KOs2O6 is lower in general than that of RbOs2O6, leading to the stronger electron-phonon coupling. We conclude that K atom located in a large oxygen cage has an unusual large atomic displacement parameter and strong activity, thereby resulting in strong phonon softening. This is the foundamental cause for stronger electron-phonon coupling and higher superconducting transition temperature of KOs2O6. These are of significance for explaining the superconductivities in -pyrochlore oxide superconductors AOs2O6(A=K, Rb).
Effect of adjustable bias voltage on magnetoelectric properties of magnetostrictive/piezoelectric laminated transducer structure
Authors: Li Ping  , Huang Xian  ,  Wen Yu Mei  ,   Research Center of Sensors and Instruments, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China
Published: December 2020

The magnetoelectric properties of PZT5/Terfenol-D/PZT8 laminated transducer structure are analyzed and detected for adjusting the bias voltage across PZT5. A control method of one-order resonant frequency for a magnetostrictive/piezoelectric laminated magnetoelectric transducer structure is proposed. The resonant frequency and the prestrain of the magnetoelectric laminated structure can be adjusted by changing the bias voltage across PZT5. The relationships between the control voltage, the strain, the Young's modulus, the resonant frequencies and the resonant magnetoelectric coefficient are analyzed. Theoretical analyses show that the resonant frequency of the laminated structure is almost a linear function of the applied dc bias voltage at a small strain. The magnetoelectric coefficient is hardly related to the control voltage. The experimental results verify the theoretical analyses. For a control voltage of 170 V to +170 V, the resonant frequency can be linearly adjusted. The adjusted maximum of the resonant frequency is 1 kHz. The ratio of the adjusted value to the bias control voltage is 2.94 Hz/V. For a bias magnetic field from 0 Oe to 225 Oe, the resonant frequency is almost unrelated to the bias magnetic field. The magnetoelectric voltage coefficient changes with the bias magnetic field. A maximum magnetoelectric voltage coefficient of 1.65 V/Oe is obtained at a bias magnetic field of 178 Oe.
Application of high-k dielectrics in novel semiconductor devices
Authors: Huang Li  , Huang An-Ping  , Zheng Xiao-Hu  , Xiao Zhi-Song  , Wang Mei  ,   Department of Electronic and Information Engineering, Beihang University, Beijing 100191, China;,   Department of Physics, Beihang University, Beijing 100191, China
Published: December 2020

As the feature size of MOSFET scales beyond 45 nm, SiO2 as gate dielectric fails to meet the performance requirement because of the high gate oxide leakage current. It is necessary to replace SiO2 with high-k materials. However, high-k materials as gate dielectric have some limitations and are not expectedly compatible with the conventional structure, inducing new challenges such as bad interfacial quality, increased threshold voltage, mobility degradation, etc. In this paper we review the problems encountered in the introduction of high-k gate dielectric into planar devices and the solutions in terms of material, device structure and process integration. Some novel applications of high-k materials in new devices and the future trend are also reviewed.
Improving the light-soaking stability of a-Si: H/μc-Si: H tandem solar cells
Authors: Hou Guo-Fu  , Lu Peng  , Han Xiao-Yan  , Li Gui-Jun  , Wei Chang-Chun  , Geng Xin-Hua  , Zhao Ying  ,   Institute of Photo-electronics Thin Film Devices and Technique of Nankai University, Key Laboratory of Photo-electronics Thin Film Devices and Technique of Tianjin, Key Laboratory of Photo-electronic Information Science and Technology of Ministry of Education (Nankai University), Tianjin 300071, China
Published: December 2020

Improving the light-soaking stability of silicon-based thin film solar cells is a very important issue for industrial production. In order to obtain high-efficiency a-Si:H/μc-Si:H tandem solar cells with good light-soaking stability, In this paper we first present the results about a-Si:H top solar cell with high light-soaking stability. Then we mainly investigate the influences of N/P tunnel junction and silane concentration (SC) profiling of μc-Si:H i-layer on the light-soaking stability of a-Si:H/μc-Si:H tandem solar cells. Up to now we have been able to obtain a-Si:H/μc-Si:H tandem solar cell with a light-soaking degradation ratio of only 7%.
Dynamical identification of a heavy sauna weather event in northern China in 2009
Authors: Yang Shuai  , Gao Shou-Ting  , Chen Bin  ,   Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorological Sciences, Beijing 100081, China
Published: December 2020

A sauna weather event in northern China in July 2009 is numerically simulated and diagnostically analyzed. The atmospheric circulation characteristics, the horizontal and vertical distributions of temperatures and moistures, and the distribution of potential vorticities are studied. It is found that anticyclone dominates the upper troposphere during the sauna weather event. In the horizontal chart, the relative humidity in the lower troposphere is large. From the vertical sections, descending airflow dominates the moist and warm sectors at the middle and lower levels. There are clear humidity gradient, evident vertical gradient of temperature, and slanting distribution of potential vorticity. The sauna weather event occurs in the generally high-temperature environment of summertime, so it is difficult to dynamically identify and diagnose the sauna weather depending on some single factor, e.g., temperature or moisture. According to the high-temperature, large-moisture, and strong-potential vorticity characteristics during the sauna weather in northern China, a moist thermal potential vorticity parameter MTPV, may be expressed as ▽ q (▽ ▽ Q), where q is the sum of water vapor and all hydrometeors including cloud water, rain water, cloud ice, snow and graupel; is potential temperature; Q is potential vorticity) which is appropriate for sauna weather, is introduced. Then it is used to dynamically diagnose sauna weather event. And it is simplified by calculation analysis in case study. It is found that the MTPV anomaly is accompanied by the sauna weather process. Although high temperature, large moisture and strong slanting potential vorticity development present in the sauna weather process in northern China in July 2009, their coverages for these single variables are larger than our target region of this sauna weather event. While for the MTPV and its simplified form combining these variables, their anomalies maintain in the lower troposphere around Beijing and its peripheral areas in northern China, viewing from either zonal or meridional section. Therefore, both MTPV and its simplified form can better dynamically identify this high-temperature and high-humidity sauna weather event.
Infinitesimal canonical transformation and integral for a generalized Birkhoff system
Authors: Ge Wei-Kuan  , Zhang Yi  , Lou Zhi-Mei  ,   Department of Physics, Huzhou Teachers College, Huzhou 313000, China;,   College of Civil Engineering, Suzhou University of Science and Technology, Suzhou 215011, China;,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

An infinitesimal canonical transformation and an integral for a generalized Birkhoff system are studied. The equations of the generalized Birkhoff system are established. The results of the infinitesimal canonical transformation and the integral for the Birkhoff system are generalized to the generalized Birkhoff system. An example is given to illustrate the application of the result.
An algebraic approach to the generalization of n-dimensional coupled harmonic oscillators system
Authors: Jin Ming-Jie  , Tan Lei  ,   Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, China;,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou 730000, China
Published: December 2020

Using the quadratic form theory, we achieve the decoupling of systematic Hamiltonian of generalization of n-dimensional coupled harmonic oscillators and derive the diagonalized Hamiltonian by three linear transformations with keeping the commutation relations unchanged. The energy eigenvalue and the eigenfunction of the system are also obtained.
Study on the phase transitions of ferroelectric systems by Weiss's molecular field theory with an external field
Authors: Zhang Jin-Lu  , Li Yu-Qiang  , Zhao Xing-Yu  , Huang Yi-Neng  ,   Scientific Research Department, Xinjiang Education Institute, Urumqi 830043, China;,   Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matter Physics, Physical College of Science and Technology, Yili Normal University, Yining 835000, China;,   National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

The descriptions of the paramagnetic-ferromagnetic and paraelectric-ferroelectric phase transitions (PTs) by Weiss's molecular field theory (WMFT) are quite successful, and the WMFT is also a theoretical basis of initial analysis of the PTs of structural disorder and complex compositional systems because of its mean-field characteristic. However, there is not any study on the PT behaviors of the WMFT with external field, and only the case of two orientational states of molecules for ferroelectric systems has been investigated by the WMFT. Although the descriptions of the above two kinds of PTs by the WMFT are quite similar, the exact ones and the corresponding results are different more or less due to the difference in microscopic unit between the magnetization and polarization In this work, the exact descriptions of the ferroelectric systems with arbitrary orientational states of molecules by the WMFT are provided, including the temperature dependences of the spontaneous polarization, the internal energy, the specific heat and the static polarizability, and then the evolutions of the PTs with an external field are studied. The obtained results are as follows. 1) Without the external field, the PTs of the systems are of the second order, and the transition temperatures and spontaneous polarizations decrease, which are different from those of the ferromagnetic systems, but the internal energy, the specific heat and the polarizability increase with the increase of the orientational states. 2) The external field drives the second order PT to a diffusive one, and diffusive temperature range becomes wider as the field is increases. The results mentioned above would benefit the deep studies of ferroelectric PT, especially the diffusive one.
Blind detection of M-ary quaternary phase shift keying signals by a complex Hopfield neural network with amplitude-phase-type hard-multistate-activation-function
Authors: Zhang Yun  , Zhang Zhi-Yong  , Yu Shu-Juan  ,   College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China;,   College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

Considering the disadvantage of the algorithms based on statistics, a novel algorithm based on complex Hopfield neural network with amplitude-phase-type hard-multistate-activation-function (CHNN-APHM) is proposed to detect M-ary quaternary phase shift keying (MPSK) signals blindly. An amplitude-phase-type hard-multistate-activation-function is constructed. The stabilities of the CHNN-APHM with asynchronous and synchronous operating mode are also analyzed separately. While the weighted matrix of CHNN-APHM is constructed by the complementary projection operator of received signals, the problem of quadratic optimization with integer constraints can be successfully solved with the CHNN-APHM, and the MPSK signals are blindly detected. Simulation results show that the algorithm reaches the real equilibrium points with shorter received signals and if is applicable for channel with common zeros.
Study on chromatic dispersion of beam splitter in spatially modulated Fourier transform spectrometer
Authors: Lü Jin-Guang  , Liang Jing-Qiu  , Liang Zhong-Zhu  ,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Due to the chromatic dispersion of beam splitter, the interferogram units from various wavelengths could shift by different offsets, leading to interferogram aliasing in transverse space. Simultaneously, the interferograms of different wavelengths have different offsets of optical path difference, which makes the interferogram aliasing in vertical space. According to geometric optics principles, the transverse aliasing of the interferogram reduces the area of the interferogram unit, and the vertical aliasing of the interferogram leads to a phase-frequency response which could reduce the spectral line intensity. The calculation and the analysis indicate that the transverse aliasing area is only 3.4% of the total area of the interferogram unit in our study, which could be removed in the data processing; and the phase delay from the vertical aliasing of the interferogram is proportional to the thickness difference between the beam splitter and the compensating plate. The maximal thickness difference is provided when the contrast reversion appears in the interference fringe. Finally, we correct the chromatic dispersion from the aliasing interferogram by solving linear equation set, and recover the ideal spectrum.
Incoherent broadband cavity enhanced absorption spectroscopy for measurements of HONO and NO2 with a LED optical source
Authors: Ling Liu-Yi  , Qin Min  , Xie Pin-Hua  , Hu Ren-Zhi  , Fang Wu  , Jiang Yu  , Liu Jian-Guo  , Liu Wen-Qing  ,   Anhui Institute of Optics and Fine Mechanics, Key Laboratory of Environmental Optics and Technology, Chinese Academy of Science, Hefei 230031, China;,   Institute of Electric and Information Technology, Anhui University of Science and Technology, Huainan 232001, China
Published: December 2020

An application of incoherent broadband cavity enhanced absorption spectroscopy with a near-ultraviolet LED (peak 372 nm and FWHM is 13 nm) to simultaneously detecting HONO and NO2 is described. The light emitted from the LED is collimated and then coupled into an 70 cm long high finesse cavity formed with two high reflectivity mirrors. The spectra are respectively recorded when the cell is filled with He and then N2, and the mirror reflectivity is determined from the change in transmitted intensity due to the difference in Rayleigh scattering cross-section between He and N2. The maximum of mirror reflectivity is 0.99962 at 390 nm in a spectral region of 360-390 nm, and corresponding maximum of light path length is about 1.71 km when NO2/HONO mixture is measured. The concentrations of HONO and NO2 are obtained using least-squares fit. Detection sensitivity (1) of 0.6 ppbv for HONO and 1.9 ppbv for NO2 are achieved using an acquisition time of 1000 s. The experimental results demonstrate the possible application of this technology to in situ monitoring the trace gases in the atmosphere.
Measurement of a gas using none dispersive infrared technique with two analysis channels
Authors: Sun You-Wen  , Liu Wen-Qing  , Wang Shi-Mei  , Huang Shu-Hua  , Zeng Yi  , Xie Pin-Hua  , Chen Jun  , Wang Ya-Ping  , Si Fu-Qi  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

In this paper, we propose a method of measuring a gas by using non-dispersive infrared (NDIR) technique with two analysis channels. The filter parameters of the two analysis channels are calculated by line-by-line integral of the selected absorption spectrum of SO2. The influences of temperature and air pressure on strengths and Lorentzian shape functions are considered accurately in the calculation. The absorption wavelengths at 7.32 μm and 4.0 μm are chosen to detect the SO2 whose concentrations are ≤qslant 280 ppm and > 280 ppm, respectively. The calibration curves of the two analysis channels are obtained by least-squares fitting two 3-order polynomials. The linearity, the sensitivity and the accuracy of the analysis system are analyzed. SO2 concentration with a large range from ～ 5 ppm to 10000 ppm can be retrieved with the measurement linearity > 0.99 and measurement error < 5%. The reasonable tradeoff is made to optimize both sensitivity and measurement range jointly. A fair balance between measurement sensitivity and large span range is obtained. Furthermore, sufficiently good measurement linearity makes cross-interference correction possible in the NDIR multi-gas analyzer.
A new technique for generating non-diffracting beam with long propagation distance using two axicons
Authors: Zheng Wei-Tao  , Wu Feng-Tie  , Zhang Qian-An  , Cheng Zhi-Ming  ,   College of Information Science and Engineering, Quanzhou 362021, China
Published: December 2020

A new technique for generating quasi non-diffracting beam with long propagation distance by using simple optical elements including the convergent lens and axicons is proposed. The theory of generating such a beam is studied with geometrical optics and diffraction theory. The formation process of the beam is simulated, and the transverse intensity distributions at various distances are obtained. The simulation results show that the transverse intensity distribution at long-distance accords with Bessel distribution. A comparison between the quasi non-diffracting beam, which is obtained by our experiment, and that in the literature (Belyi et al. 2010 Opt. Exp. 18 1966) shows that its propagation distance is more than 50 m longer, and the beam divergence angle is compressed by 22 times. In the experiment, the beam patterns are captured at different propagation positions, and the obtained results are in good agreement with the theoretical analyses.
Effective radius of curvature of spatially partially coherent beams propagating through non-Kolmogorov turbulence
Authors: Huang Yong-Ping  , Zhao Guang-Pu  , Xiao Xi  , Wang Fan-Hou  ,   Computational Physics Key Laboratory of Sichuan Province, Yibin 644007, China;,   School of Physics and Electronic Engineering, Yibin University, Yibin 644007,China
Published: December 2020

The laser beam propagation through atmospheric turbulence is of importance for both theoretical study and practical applications. Taking the Gaussian Schell-model (GSM) beam as a typical example of spatially partially coherent beams,based on the non-Kolmogorov spectrum and generalized Huygens-Fresnel principle, the analytical expression for the effective radius of curvature of GSM beams propagating through non-Kolmogorov turbulence is derived. The effects of turbulence parameters (including generalized exponent parameter, inner scale l0, and outer scale L0) and propagation distance z on the effective radius of curvature of GSM beams are stressed. It is shown that the effective radius of curvature of GSM beams increases with outer scale L0 decreasing for 3.6 4 and the inner scale l0 increasing, but dose not monotonically vary with the increases of exponent parameter and propagation distance z. The results are explained physically.
Research on the influence of impurity particles on the optical breakdown threshold value of stimulated Brillouin scattering medium
Authors: Hasi Wu-Li-Ji  , Wang Xue-Yang  , Guo Xiang-Yu  , Zhong Zhao-Ming  , Fan Rui-Qing  , Lin Dian-Yang  , He Wei-Ming  , Lü Zhi-Wei  ,   National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150080, China
Published: December 2020

In this paper, we establish the physical model of hot damage to the stimulated Brillouin scattering (SBS) medium, and with numerical simulation method the curve of the temperature of impurity particles versus the radius is investigated. The result indicates that impurity particle has a maximal thermal effect radius and when the sizes of particles contained in the medium are near the radius, the optical breakdown phenomenon is most likely to appear, and at this point the optical breakdown threshold is lowest. We use FC-3283, GF-180 and HFE-7100 as the SBS medium in Continuum Nd: YAG laser system. The SBS medium passes through the filter with different diameters. We study the optical breakdown thresholds and energy reflectivities before and after filtration. It is demonstrated that with the filter diameter decreasing, the optical breakdown threshold increases gradually and the energy reflectivity is significantly improved through filter. In addition, a method of using He-Ne laser transmission light spot size to judge whether optical breakdown phenomenon happens, is also developed. This method is convenient and accurate, and can effectively reduce the error caused by naked eye observation.
Modeling bi-direction pedestrian flow by cellular automata and complex network theories
Authors: Ren Gang  , Lu Li-Li  , Wang Wei  ,   Key Laboratory of Transportation Planning and Management of Jiangsu Province, School of Transportation, Southeast University, Nanjing 210096, China
Published: December 2020

In this paper the experiment to study the features of pedestrians' walking preference is designed. Then the cellular automata model which considering pedestrians' walking preference features is built, in which the forward-parameter, right-parameter, surpass-parameter and the correction-parameters are included to mend the probability of the pedestrian getting to each neighboring cell. Based on this model and k-nearest-neighbor interaction pattern, the complex network of pedestrians is modeled. The simulation results obtained from the model well illustrate the density-speed curve and density-volume curve. Meanwhile the self-organization phenomena of the bi-direction pedestrian flow can be observed from the model simulation. In the further analysis of the pedestrian flow's basic parameter and the main feature parameters of pedestrians' complex network, it is found out that the average speed and the average path length are changed with the state of the flow. Finally it can be concluded that there is a linear negative correlation between these two parameters by fitting the data; in other words, pedestrian flow with shorter average-path length has a higher average speed.
Modeling and simulation of weaving pedestrian flow in subway stations
Authors: Chen Ran  , Li Xiang  , Dong Li-Yun  ,   Shanghai Institute of Applied Mathematics and Mechanics, Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

There are differences in efficiency when pedestrian flows with various directions pass through the bottleneck of a subway in different manners, and the mechanisms of congestion at the bottleneck are distinct as well. The weaving motion of pedestrian flows with various directions in subways is simplified into two crowds with different ODs passing through the bottleneck which connects two parallel channels. The lattice gas model is improved by introducing the floor field so that it is suitable for the description of pedestrian flow under complex situations. It is shown by experiments that different ways lead to the difference in total time when the crowds pass through the field of interest. Then the total time of crowds passing through the field in different ways is investigated numerically, and the effect of bottleneck width is taken into account as well. Numerical simulations confirm the findings from experiments. It is found that the diagonal movement of a pedestrian should be included in the model in order to give a better description of real pedestrian traffic. And the mechanism of congestion near the bottleneck is discussed in detail.
The current status of surface wave plasma source development
Authors: Dong Tai-Yuan  , Ye Kun-Tao  , Liu Wei-Qing  ,   School of Science, Jiangxi University of Science and Technology, Ganzhou 341000, China
Published: December 2020

In this paper, a flat-type surface wave plasma (SWP) source generated by microwave discharg is introduced systematically. The principle of the surface wave plasma is analyzed and the energy absorption mechanism of the surface wave plasma discharge is explored. A novel wave-mode converter composed of the single-mode resonator array, sub-wavelength diffraction grating and a new type of slot antenna array is introduced. The research findings, such as the mechanism of the generation, the realization, the characteristics of plasma parameters and the numerical simulation of the new SWP sources are beneficial to industrial applications, will promote the effectiveness of the microelectronics industry and obtain a new breakthrough.
Enhancing photovoltaic effect of Co2-C98/Al2O3/Si heterostructures by Al2O3
Authors: Zhang Xin  , Zhang Xiao-Zhong  , Tan Xin-Yu  , Yu Yi  , Wan Cai-Hua  ,   Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;,   Beijing National Center of Electron Microscopy, Beijing 100084, China;,   China Battery Industry Association, Beijing 100740, China
Published: December 2020

As energy crisis is aggravated, solar cell, as a common form of the development and utilization of solar energy, has attracted more and more attention all over the world. With solar cells developing towards the direction of high efficiency, thin film, non-toxic and rich raw materials, the pure silicon solar cell could not meet these requirements, so the new material and process are imminently required. This paper deals with the photovoltaic effect of the carbon material based on the silicon heterostructure, and its possible application to solar cells. Co2-C98/Al2O3/Si heterostructure with a 4 nm-thick Al2O3 layer shows the best photovoltaic effect performance with a short-current density of 18.75 mA/cm2, an open-circuit voltage of 0.447 V and a power conversion efficiency of 3.27% with AM1.5 illumination, which is much better than Co2-C98/Si heterostructure without the Al2O3 layer. The effect of Al2O3 layer is attributed to the reduction of the interface defects, the suppression of the surface recombination and the enhancement of barrier height, which are proved by the capacitance-voltage and current-voltage measurements under dark condition. This work may shed light on the carbon/silicon based solar cells.
Study on the optical characteristic of black silicon antireflection coating prepared by plasma immersion ion implantation
Authors: Liu Jie  , Liu Bang-Wu  , Xia Yang  , Li Chao-Bo  , Liu Su  ,   Institute of Microelectronics, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China;,   Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

Surface texturing is an effective method to reduce surface reflectance and improve the efficiency of silicon solar cell. In this paper, the black silicon antireflection coating is fabricated by using plasma immersion ion implantation. The surface morphology and reflectance are investigated by atomic force microscope and UV-VIS-NIR spectrophotometer, respectively. Results show that mountain-like structure with a depth of 0550 nm is fabricated on black silicon surface. Both the fractional area occupied by silicon and refractive index decrease smoothly with the increase of depth across the antireflection coating. The weighted average reflectance of black silicon is as low as 6.0% in a wavelength range of 3001000 nm. The depression mechanism of the optical reflectance is analyzed by simulating the structure with the transfer matrix method, and the simulation result fits the measured spectrum well.
Effect of crystallographic orientation on instability behavior of planar interface in directional solidification
Authors: Wang Li-Lin  , Wang Xian-Bin  , Wang Hong-Yan  , Lin Xin  , Huang Wei-Dong  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The instability process of planar interface in directional solidification with respect to the crystallographic orientation is studied using a transparent model alloysuccinonitrile-acetone. Three typical crystal grains which have preferred dendrite, tilted dendrite and seaweed patterns at rapid pulling velocity respectively are chosen in our experiment. The experimental results show that the preferred dendrite grain has the shortest incubation time and the smallest initial perturbation wavelength of planar interface instability, the tilted dendrite grain has the largest ones and the seaweed grain has median ones. These results accord qualitatively with previous analytical results and phase-field simulation results. It is also found that the interfacial non-steady-state evolution behaviors of the preferred dendrite grain and the tilted dendrite grain are significantly different from that of the seaweed grain, suggesting that the non-steady-state evolution behavior of planar interface instability is closely related to the crystallographic orientation.
First-principles study of lattice dynamic of IrTi alloy
Authors: Zhang Wei  , Chen Wen-Zhou  , Jiang Zhen-Yi  ,   School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710121, China;,   Institute of Modern Physics, Northwest University, Xi'an 710069, China
Published: December 2020

The structural behaviors of IrTi are studied using first-principles density-functional theory with pseudopotentials and a plane-wave basis. Phonon calculations indicate that the tetragonal (L10) structure is dynamically unstable. We obtain the orthorhombic structure (Cmmm) which is shown to be a global energy minimum by the frozen phonon method. The resulting structure is mechanically and dynamically stable and its lattice constant is similar to the experimentally observed lattice constant of low-temperature structure, which demonstrates that the low-temperature phase of IrTi is the orthorhombic structure (Cmmm). Thus, we put an end to the experimental debate regarding the low-temperature phase: whether it is orthorhombic or monoclinic, and demonstrate theoretically that the IrTi alloys will undergo a cubic→tetragonal→orthorhombic transformation.
Estimating topology of complex networks based on sparse Bayesian learning
Authors: Hao Chong-Qing  , Wang Jiang  , Deng Bin  , Wei Xi-Le  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

We propose a method of estimating complex network topology with a noisy environment. Our method can estimate not only dynamical equation of the chaotic system and its parameters but also topology, the dynamical equation of each node, all the parameters, coupling direction and coupling strength of complex dynamical network composed of coupled unknown chaotic systems using only noisy time series. Estimating the system structure and parameter is regard as estimating the linear regression coefficients by reconstructing system with universal polynomial structure. Reconstruction algorithm of Bayesian compressive sensing is used for estimating the coefficients of regression polynomial. For the reconstruction from noisy time series we adopt relevance vector machine, namely we use sparse Bayesian learning to solve sparse undetermined linear equation to obtain the objects mentioned above. The Lorenz system and a scale free network composed of 200 Lorenz systems are provided to illustrate the efficiency. Simulation results show that our method improves the robust to noise compared with the compressive sensing and has fast convergence speed and tiny steady state error compared with the least square strategy.
Multi-resolution density modularity for finding community structure in complex networks
Authors: Zhang Cong  , Shen Hui-Zhang  , Li Feng  , Yang He-Qun  ,   Antai College of Economics and Management, Shanghai Jiaotong University, Shanghai 200052, China;,   Shanghai Center for Satellite Remote Sensing and Measurement Application, Shanghai 201199, China
Published: December 2020

In reality many complex networks present modules or community structures obviously. Modularity is a benefit function used in quantifying the quality of a division of a network into communities. And it usually can be used as a basis for optimization methods of detecting community structure in networks. But the most popular modularity which is proposed by M. E. J. Newman and M. Girvan has the resolution limit in community detection. Multi-resolution modularity cannot overcome the misclassifications caused by merging and splitting the communities either. In this paper, we propose a multi-resolution density modularity based on the network density. The proposed function is tested on the artificial networks. Computational results show that it can reduce the rate of misclassification considerably. And the systematicness of the community structures can be demonstrated by the multi-resolution density modularity.
The development of atmosphere-current-wave fully coupled model and its application during a typhoon process
Authors: Liu Lei  , Fei Jian-Fang  , Huang Xiao-Gang  , Cheng Xiao-Ping  ,   Institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

The shared memory and semaphores of inter-process communication in Linux system are used as the pipeline to couple the WRF, POM and WW3 models. The forcing from atmosphere to sea and wave, the changes in atmospheric underlying surface induced by ocean and the wave-induced mixing are all involved in the high-resolution fully coupled typhoon model. The typhoon ‘KAEMI’ is taken as a simulated example and the outcomes are compared with the available observation data to verify the good performance of the fully coupled model. The results show that after the spin-up, the coupled model could reproduce the typhoon, and the simulated surface lowest pressure, wind speed and track are all consistent with the observations. Meanwhile, the model can also have a good performance about the sea surface temperature cooling and the significant wave height. The simulated errors are related to the microphysical process parameterizations, the large initial fields, the construction of bogus typhoon and the physical process parameterization in upper ocean.
Rain effect on C-band scatterometer wind measurement and its correction
Authors: Zhou Xuan  , Yang Xiao-Feng  , Li Zi-Wei  , Yu Yang  , Ma Sheng  ,   Institute of Remote Sensing Applications, Chinese Academy of Sciences, Beijing 100101, China;,   741 Troops of PLA, Beijing 100095, China
Published: December 2020

It is viewed traditionally that the attenuation and scattering of rain have no effect on C-band scatterometer because its wavelength is greater than the diameter of raindrops, so rain effects on C-band scatterometer wind measurement are often ignored. According to the attenuation and the volume backscatter of the scatterometer signal by raindrops and the perturbation of the water surface by rain, in this paper, we derive the radar equation of the rainfall, collect the data from ASCAT backscatter, rain data from PR and wind field from the European Centre for Medium-Rang Weather Foremasts in 2010, and quantitatively analyze the influence of rainfall on the normalized radar backscattering cross section of the C-band scatterometer. Our results show that the attenuation increases as the rain rate and the incidence angle increase, the volume backscatter and the perturbation of the water surface increase with the increase of rain rate and decrease with the increase of incidence angle, and the influence of the perturbation on the wind measurement of the scattermeter is greater than the volume backscatter. In addition, we establish the C-band active microwave radiative transfer model for the rainfall by the radar equation and the collected data. The experimental results indicate that the new model can improve the C-band scatterometer wind measurement accuracy under rainfall conditions.
The research on the sensitivity of climate change in China in recent 50 years based on composite index
Authors: Wu Hao  , Hou Wei  , Qian Zhong-Hua  , Hu Jing-Guo  ,   College of Physical Science and Technology, Yangzhou University, Yangzhou 225002, China;,   National Climate Center, Beijing 100081, China;,   Department of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
Published: December 2020

Climate change index is one of advanced issues in climate change research. There exist many specific indices in climate change research in China and other countries, but comprehensive indexes are very rare. So in this paper, a comprehensive climate change index (CCI) is defined based on single factor of temperature and precipitation index to assess the sensitivity of climate change, and the comprehensive information about climate change is obtained. Because the index size represents the difference in frequency between before and after extreme climate events around abrupt climate change, reflecting the ability for one region to respond to climate change and the sensitivity to the climate change, the index indicates a variety of information about climate change and can provide a certain judgment basis to better deal with extreme climate events. According to the CCI, the climate change and its regional sensitivity in China in recent 50 years are discussed. The results show that Inner Mongolia, northeast central, northwest and central Yunnan have higher CCI indexes, which indicates that the extreme climate events in these regions happen more frequently after the abrupt climate change. The mean CCI is computed of all stations in each province in China, showing that South China and east part of Southwest China each have a minimal index, indicating that these areas are not sensitive to climate change; in the North and Northeast China extreme events happen frequently. Climate change is obvious in high latitude and tropical and subtropical regions, the North and Southwest China are more sensitive, while the South of the Yellow River is less sensitive. The coastal areas with relatively high CCI have strong sensitivities due to the heavy rainfall influence from monsoon and typhoon.
GPS occultation excess phase computed utilizing the updated single difference technique
Authors: Bi Yan-Meng  , Chen Jie  , Yang Guang-lin  , Liao mi  , Wu Rong-Hua  ,   National Satellite Meteorological Center, Beijing 100081, China
Published: December 2020

The parameters retrieved from GPS occultation data can be assimilated into numerical weather prediction model. The accuracy of excess phase is affected by the noise from ionosphere and L2 frequency, especially, when L2 signal is encrypted. In order to improve the accuracy of excess phase and remove the noise by the single Difference (SD) method from reference link into occulted link, we use the updated single difference (USD) method to compute atmospheric excess phase. The combined frequency LC data from the reference link are used and smoothed in an interval time window of 2 s. The antenna phase center correction and relativity correction are estimated. The USD method is validated by utilizing COSMIC data. The case analyses of representative rising and setting occultation events indicate that the excess phases from USD and COSMIC are in good agreement. The excess phase of globally distributed 440 occultation events is also computed. The results show that USD method can obviously improve the distribution of mean bias and standard deviation of bias, which demonstrates the reliability of our USD algorithm. The USD method can be applied to the data processing for FY-3 GNOS (GNss Occultation Sounder) occultation mission which uses semi-codeless technique to track L2 signal.
Numerical method of designing nuclear magnetic resonance logging device sensor
Authors: Hu Hai-Tao  , Xiao Li-Zhi  , Wu Xi-Ling  ,   State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China
Published: December 2020

Optimal design of nuclear magnetic resonance (NMR) logging device sensor can enhance its detection performance and improve signal-to-noise ratio, and the accuracy of results from numerical method is absolutely critical for optimal design. In this paper, an eccentric NMR logging device static field distribution and radio frequency field distribution are simulated by the electromagnetic finite element method, and the influences of model shape, model size and element shape on simulation results are analyzed. A comparison between the measurements and simulation data indicates that they are in good agreement with each other. In the design process of NMR logging device sensor, by choosing a circinal model which is similar to the shape of borehole, setting model size to be 10-15 times the sensor diameter, and adopting triangle element, the accuracy of numerical simulation can be improved and the reliability of optimization design can also be enhanced.