bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetically correlated I-V nonlinearity and electrical transport property of the double-layered perovskite La1.8Ca1.2Mn2O7 compound
Authors: Deng Heng  , Yang Chang-Ping  , Huang Chang  , Xu Ling-Fang  ,   (1)The Faculty of Physics and Electronic Technology and Key Laboratory of Ferroelectric and Piezoelectric Materials and Devices of Hubei Province, Hubei University, Wuhan 430062, China; (2)The Faculty of Physics and Electronic Technology and Key Laboratory of Ferroelectric and Piezoelectric Materials and Devices of Hubei Province, Hubei University, Wuhan 430062, China, State Key Laboratory of Metastable Materials Science and Technology, Yan
Published: December 2020

The double-layered perovskite La1.8Ca1.2Mn2O7 ceramic was synthesized by traditional solid-state reaction after heat treatment for two times at high temperature. Its structure, magnetic and electrical properties were characterized by x ray diffraction (XRD), scanning electron microscopy (SEM), HL5500PC and physical properties measurement system (PPMS). It has a double-layered Sr3Ti2O7 tetragonal structure with lattice constants a, b=3.901 (1 =0.1 nm) and c=19.369 , and unit cell volume V=295.21 3. The Curie temperature TC is 177 K. The I-V characteristic shows a nonlinearity increasing with decreasing temperature at low temperatures below the magnetic critical point of TC and the nonlinear coefficient α goes up to a maximum of 68.6 when the temperature goes down to the lowest of 14 K in this experiment. However, the nonlinearity disappears when temperature goes above the magnetic transition point of TC. It indicates that a magnetically correlated Schottky barrier between grain boundaries is responsible for the I-V nonlinearity when temperature is below the Curie temperature. A maximum value of 0.18 eV was obtained for the magnetic Schottky barrier at 14 K after using a back to back pn junction model to describe such a potential barrier between grain boundaries.
A knotted polymer chain passing through a pore
Authors: Wen Xiao-Hui  , Zhang Lin-Xi  ,   (1)Department of Physics, Wenzhou University, Wenzhou 325027, China; (2)Department of Physics, Zhejiang University, Hangzhou 310027, China
Published: December 2020

A knotted polymer chain passing through a pore is investigated by molecule dynamics method. In this paper, we take 31 knot as an example. It is found that, during the process of translocation, the size of the knot fluctuates until the knot is unknotted. In addition, the effect of the knot on the translocation velocity of the knotted chain is also discussed. For the given external force, the average translocation time τ satisfies the scaling relation:τ～N α, and the scaling exponent α increases with the external force f. For short knotted polymer chains, the average translocation time τ decreases when the external force f increases. However, for very long knotted polymer chains, the average translocation time τ increases when the external force f increases. In the meantime, the position of knot in a knotted polymer chain also affects the average translocation time τ strongly. The closer the knot approaches the first translocated monomer, the longer the average translocation time. This investigation can provide some insights into the translocation of knotted polymer chains (especially knotted DNA) through the nanopore, and help us understand the translocation behavior of biomacromolecules.
Directional growth of monotectic alloy with and without shear flow
Authors: Wang Jian-Yuan  , Chen Chang-Le  , Zhai Wei  , Jin Ke-Xin  ,   School of Science, Northwestern Polytechnical University, Xi'an 710129, China
Published: December 2020

The directional growth process of para-dichlorobenzene and succinonitrile (DCB-SCN) monotectic alloy is realized under static condition and in presence of shear flow. The experimental results show that, with the increase of pulling rate, the DCB phase exhibits faceted growth while the monotectic structure undergoes a transition in which "separated liquid and solid phases-aligned fibrous composite structure-droplet dispersion in solid matrix" take place. When shear flow is applied, perturbation and fluctuation appear at each growing crystal plane. In the meantime, the fibrous spacing is larger compared with those under the same pulling rate without flow. However, the spacing and pulling rate also follow the relationship λV0.5=C. In the formation process of droplet dispersion structure, shear flow enhances the nucleation rate of second liquid drops and hinder the growth and interaction of second liquid droplets at the solid-liquid interface, leading to the refinement of the final droplet dispersion structure.
Effect of low diffusion coefficient on glass phase formation in Pd77Cu6Si17 alloy
Authors: Wang Zhen-Zhong  , Wang Nan  , Yao Wen-Jing  ,   Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The microstructure evolution of laser rapidly solidified Pd77Cu6Si17 alloy was investigated. The experimental results showed that with increasing growth velocity, a phase transition series of Pd3Si dendrite+eutectic-ξ dendrite+eutectic-eutectic grain-regular eutectic-amorphous phase occurred. The critical velocity of amorphous transition was determined to be about 6 mm/s and the smallest lamellar spacing was 35 nm. Compared with those of Al-25 wt% Sm and Al-32.7 wt% Cu alloys, it was proposed that low diffusion coefficient is the main reason for the good glass formation ability of Pd77Cu6Si17 alloy.
Performance of SnO2:F/SnO2 composite film as front-electrode for CdTe solar cells
Authors: Zeng Guang-Gen  , Li Bing  , Zheng Jia-Gui  , Wu Li-Li  , Zhang Jing-Quan  , Lei Zhi  , Li Wei  , Feng Liang-Huan  ,   Department of Materials Science, Sichuan University, Chengdu 610064, China
Published: December 2020

Decreasing CdS thickness is one of the effective ways to improve the conversion efficiency of CdS/CdTe solar cells. In order to eliminate the adverse effects of the decrease in CdS thickness on the performances of the devices, it is necessary to introduce a buffer layer between CdS and front electrode layer. The un-doped SnO2thin films, as a buffer layer, were deposited on SnO2:F thin film by magnetic reactive sputtering. Then the composite film was annealed at 550 ℃ in N2/O2=4 ∶1 ambience for 30 minutes. The morphology, structure and optical properties of the composite film before and after annealing were studied by AFM, XRD, UV-Vis and the electrical properties were analyzed, respectively. As a result, the crystal lattice parameters of un-doped SnO2 films matched those of the substrate, so the un-doped SnO2 films, which had an obvious preferred orientation along (110) plan, had the same structure as the substrate materials. This implied that there was no lattice mismatch. After annealing, the surface topography and electricity uniformity were improved, higher than 80% transparency was obtained, and resistance increased to meet the requirements of the buffer layers. Finally, continuous and homogeneous SnO2:F/ SnO2 composite thin films have been obtained, which were very suitable for CdS/CdTe cells.
Base pairs composition, on-site energies of electrode and DNA-metal coupling effects on current-voltage characteristic of DNA molecule
Authors: Ma Song-Shan  , Zhu Jia  , Xu Hui  , Guo Rui  ,   College of Physical Science and Technology, Central South University, Changsha 410083, China
Published: December 2020

Based on a tight-binding approximation and transfer matrix method, we investigated the effects of the composition of nucleotide base pairs, on-site energies of the electrode and DNA-metal coupling strength on the current-voltage characteristic. The results indicate that the saturation current of DNA molecule which is composed of one single kind of nucleotide base pair is much higher than that composed of two kinds of nucleotide base pair. Meanwhile, the DNA molecule which is rich in G-C base pairs has higher electronic transport ability. When the bias is low, the on-site energies of the electrode have the effect of impeding charge injection. On the other hand, when the bias is high, the on-site energies of the electrode have the effect of enhancing charge injection. In addition, we can find that a stronger DNA-metal coupling does not always result in a larger saturation current. When tdm=td, there is a resonance injection, which is optimized for electron transport. When tdm departs from td, the resonance injection is reduced, which lead to the stronger of DNA-metal coupling at the range of tdm>td and the lower of saturation current of DNA.
Phantom study of the classification of liver fibrosis based on nuclear magnetic resonance elasto-graphy
Authors: Xu Ling-Feng  , Yu Jie  , Huang Qing-Ming  , Huang Yong  , Wang Xiao-Yan  , Lu Lun  , Wang Hong-Zhi  , Zhang Xue-Long  , Cheng Hong-Yan  , Li Geng-Ying  , Wang He  ,   Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200438, China;,   GE Healthcare (China), Shanghai 201203, China;,   Institute of Medical Imaging Technology, University of Shanghai Science and Technology, Shanghai 200093, China;,   Institute of Medical Imaging Technology, University of Shanghai Science and Technology, Shanghai 200093, China, Shanghai Medical Instrumentation College, Shanghai 200093, China;,   Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai 200062, China;,   Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai 200062, China, Institute of Medical Imaging Technology, University of Shanghai Science and Technology, Shanghai 200093, China, Shanghai Medical In
Published: December 2020

Accurate detection of liver fibrosis stage and fibrosis procession is crucial for assessing prognosis and candidacy for treatment of patients with chronic hepatic disease. A significant need exists for developing a noninvasive technique for quantitative detection of liver fibrosis stage. Magnetic resonance elasto-graphy (MRE) is one of the most repidly advancing technologies for classifying the liver fibrosis. This study establishes a platform for liver fibrosis classification, and discusses some details in developing stimulator and displacement-phase imaging pulse. At last, the preliminary result and analysis of phantom experiment are given, which would form a basis for subsequent research on phantom MRE and its clinic application.
Distribution of most probable temperature of daily average temperature records in China and the slowing down of warming trend
Authors: Qian Zhong-Hua  , Feng Guo-Lin  , Gong Zhi-Qiang  ,   (1)Department of Atmospheric and Science, Lanzhou University, Lanzhou 730000, China; (2)Department of Atmospheric and Science, Lanzhou University, Lanzhou 730000, China, Key Laboratoy of Regional Climate-Environment Research for Temperature East Asia (RCE-TEA), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, Ch
Published: December 2020

Most probable temperature (MPT) is defined according to the skewed function by using daily average temperature records of the National Meteorological Information Center from 1961 to 2008 in China, it can represent every stations background temperature explicitly. MPT interannual variations show that MPT in summer was relativelly low-temperature-major before the mid-1990s and from then on was warming with fluctuation, but since 2005 the trend slowed down, and that MPT in winter was relatively low-temperature-major in 1961—1986, and from 1987 to the beginning of the 21st century was warming up obviously, but since 2000 the warming trend slowed down. The warming amplitude in winter was stronger than that in summer and the time of beginning of warming in winter was earlier than that in summer by about 5—10 years. Studying three climate states of MPT changes of 1961—1990, 1971—2000 and 1981—2008, we found that in summer MPT got warmer obviously in the third climate state, while in winter in the second state. MPT warming trend was slowing down in the third state. Its worthy of note that in Sichuan, Guangdong and Guangxi MPT even began to decline in the last few years. Whether it means climatic transformation or not needs further research.
Modeling of infrared characteristics of deep space target
Authors: Sun Cheng-Ming  , Yuan Yan  , Zhang Xiu-Bao  ,   Key Laboratory of Precision Opto-mechatronics Technology, Ministry of Education, Beijing Universityof Aeronautics and Astronautics, Beijing 100191, China
Published: December 2020

An accurate modeling method is proposed for the infrared characteristics of space target. Fully considering the heat conduction among the surfaces and the effect of inner heat source, the heat balance equation is presented for space target in the background radiation environment, and on the basis of structural and material properties of the target, the temperature distribution of target surface is calculated by node network method. According to the optical radiation and scattering theory, the mathematical model on infrared characteristics of space target is established and the general calculation method for infrared characteristics of space target is derived. Finally, the temperature field and irradiation distribution of ZY-1 and FY-3 satellite are computed using the given parameters. The computation results illustrate the validity of the theoretical analysis.
Epidemic-spreading model for networks with different anti-attack abilities of nodes and nonuniform transmission of edges
Authors: Song Yu-Rong  , Jiang Guo-Ping  ,   College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

With considering different anti-attack abilities of nodes and nonuniform transmission of edges in real networks, an SIR model is proposed to investigate the threshold behaviors of epidemic in scale-free networks based on the mean-field theory. In the proposed model, a vulnerability function related to node degree is introduced to describe the diversity of nodes’ anti-attack abilities, and a transmission function related to node degree is also introduced to describe the nonlinear infectivity of nodes. Theoretical analyse and numerical simulations show that the diversity of node anti-attack ability and the nonuniform transmission of diseases on edges can yield a positive epidemic threshold,meaning that the risk of epidemic prevalence is reduced.
Left-hand and right-hand inverse operators of quantum operators and its mathematical property
Authors: Xu Shi-Min  , Zhang Yun-Hai  , Xu Xing-Lei  , Li Hong-Qi  ,   Department of Physics Heze University, Heze 274015, China
Published: December 2020

The right-hand inverse operator of the annihilation operators and the left-hand inverse operator of the creation operator are given by using the contour integration. Furthermore, the corresponding relation between the right-hand inverse or left-hand inverse operator derived and the column elementary transformation or row transformation of a matrix is investigated.
Direct Bell state measurement for optical beams with correlated amplitude quadratures and anticorrelated phase quadratures
Authors: Wang Dong  ,   School of Mathematics and Physics, Anhui University of Technology, Maanshan 243002, China
Published: December 2020

A new method is produced of directly measuring EPR beams. This measurement scheme can be used for measuring the correlation degree of EPR beams with correlated amplitude quadratures and anticorrelated phase quadratures without using local oscillators. Then a new scheme for quantum dense coding is proposed based on this measurement scheme.
Study on the energy consumption of cellular automaton FI model for mixed traffic flow
Authors: Xue Yu  , Wen Jian  , Tian Huan-Huan  , Kan San-Jun  ,   (1)Department of Physics and Information Science, Yulin Normal University, Yulin 537000, China; (2)Institute of Physical Science and Engineering, Guangxi University, Nanning 53004, China; (3)Institute of Physical Science and Engineering, Guangxi University, Nanning 53004, China;Department of Physics and Information Science,  Yulin Normal University, Yulin 537000, China
Published: December 2020

Based on the Fukui-Ishibashi model (FI model), the energy consumption in the mixed traffic flow is investigated via considering three factors: maximum velocity, length of vehicle, and the ratio of the mixed traffic flow. Simulations and analyses indicate that the energy consumption of the mixed traffic flow with the same length and different maximum velocities is related to the slow maximum velocity and its ratio. The slower the maximum velocity and its ratiare, the more energy will be consumed. Moreover, for the mixed traffic flow with the same maximum velocity and different lengths of vehicle, the energy consumption is related to the ratio of mixed vehicles. Longer vehicles induce more energy consumption. For a mixed traffic flow with the different maximum velocities and lengths of vehicle, its energy consumption is determined by the ratio of the mixed vehicles and delay probability p. The energy consumption of FI model drops off suddenly and trends to zero at the maximum flow rate, where there exits a maximum peak, which is significantly different from the result from the NaSch model.
Control of thermal diffusion fractal growth of thin plate under environmental disturbance
Authors: Zhang Li  , Liu Shu-Tang  ,   School of Control Science and Engineering, Shandong University, Jinan 250061, China
Published: December 2020

The control of thermal diffusion fractal growth of thin plate in reality under the environmental disturbance is introduced. The quantitative relationship between growth probability and environmental disturbance is obtained. According to the relationship, we predict that the growth surface will aggregate in the region of the environmental disturbance and be controlled by restricting the disturbance. The simulations show that the environmental disturbance, which is composed of a trigonometric function as a nonlinear term and a source term having a round region, controls the growth variation effectively. In addition, the change in fractal dimension of surface growth illustrates that the complexity of the growth increases as the environmental disturbance increases.
The statistical fractal characteristic of aerosol scattering pulse signal group
Authors: Yang Juan  , Bian Bao-Min  , Peng Gang  , Yan Zhen-Gang  , Li Zhen-Hua  ,   Department of Information Physics and Engineer, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

The amplitude statistical distribution funetion p(l) of the aerosol scattering pulse signals is measured with high resolution through combining the high-speed data acquisition card PCI-9812 and the photoelectric sensor of laser airborne particle counter. The experimental results show that the distribution founction p(l) of the whole signal group and the different pulse width subsets all fit the lognormal distribution with very high precision in the range of amplitude definition (V0,VM) under the condition of big samples, which indicates that the random signal group has a statistical fractal (self-similarity) characteristic. According to the further theoretical results, it is analyzed that function p(l) has a nonlinear scale invariance. Besides, this function shows a geometrical similarity to the power law l-(1-ε) when statistical parameter , where ε<<1.
Synchronizability of mobile Ad Hoc networks
Authors: Dai Cun-Li  , Zhao Yan-Yan  , Wu Wei  , Zeng Lun-Wu  ,   College of Engineering, Nanjing Agricultural University, Nanjing 210031, China
Published: December 2020

The synchronizability of mobile Ad Hoc networks is investigated in this paper. The synchronizability is measured by eigenratio R. A smaller value of eigenratio R leads to a better synchronizability. The results indicate that with the increase of clustering coefficient C, eigenratio R increases in interval, but with the process going on, eigenratio R decreases. The eigenratio varies with clustering coefficient reither in direct proportion nor in inverse proportion, but rises first and reduces later,so there aooears a clear maximum value in between.
Experimental investigation of displacement measurement with homodyne detection
Authors: Li Rui  , Zhai Ze-Hui  , Zhao Shu-Jin  , Gao Jiang-Rui  ,   (1)College of physics and electronic eigeneering, Shanxi University, Taiyuan 030006, China; (2)College of physics and electronic eigeneering, Shanxi University, Taiyuan 030006, China;State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China
Published: December 2020

We report one-dimensional small displacement measurement of TEM00 mode with balanced homodyne detection. The smallest measurable displacement in our experimental setup is 0.3 nm. The conjugate properties of displacement and tilt are tested. Finally we analyze the effect of the deviation of local oscillator beam from TEM10 mode on the displacement measurement result. Experimental results are consistent well with the theoretical analyses.
Theoretical study on the structure, spectra and thermodynamic property of 5-(2-aryloxy-methylbenzimidazole-1-carbadehyde)-1,3,4-oxadiazole-2-thione
Authors: Li Xue-Mei  , Zhang Jian-Ping  ,   Department of Physics and Electronic Engineering, Leshan Normal University, Leshan 614000, China
Published: December 2020

The geometry structure optimization and frequency calculation of the title compound molecule have been studied using density functional theory B3LYP method, and infrared spectrum, Raman spectrum and thermodynamic properties at different temperatures have been obtained. The electronic absorption spectrum in gas and different solvent have been calculated and simulated. The results showed that the formation of intra-molecular hydrogen bond was helpful to stability of the title compound molecule, which was in good agreement with experimental crystal structure. The peak of maximal absorption located at 236 nm in gas, belonging to near UV, and solvent effect made the maximal absorption wavelength blue-shifted about 20 nm, and independent of solvent polarity.
The excited states structure for chloroethylene under the external electric field
Authors: Cai Shao-Hong  , Zhou Ye-Hong  ,   (1)School of Science, Guizhou University, Guiyang 550025, China; (2)The Key Laboratory of Economic System Simulation, Guizhou College of Finance and Economics, Guiyang 550004 China
Published: December 2020

The ground states parameters, dipole moment, charge distribution of chloroethylene under different intense electric fields ranging from 0 to 0.05 a. u. are optimized using density functional theory (DFT)B3P86 at 6-311G basis set level. Without external electric fields, the excitation energy, wavelength, oscillator strengths from ground state to the first nine different excited states are calculated by employing the revised hybrid CIS-DFT method (CIS-B3P86) and the excited states under different electric fields are also investigated. The results show that with increasing the electric field the molecular geometry is strongly dependent on the field strength. The whole energy are proved firstly increasing, then decreasing and the dipole moment firstly decreasing then increasing. The excitation energies of the first nine excited states of chloroethylene decrease with the increase of the applied electric field, indicating that the molecule is easy to be excited and dissociated under the electric field.
Effect of external electric field excitation on titanium monoxide
Authors: Xu Guo-Liang  , Xia Yao-Zheng  , Liu Xue-Feng  , Zhang Xian-Zhou  , Liu Yu-Fang  ,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The present paper is devoted to the calculating of transition wavelengths, oscillator strength, Einstein An0 and B0ncoefficients of titanium monoxide molecule from ground state to the first six different excited states by employing the density function theory BLYP and the single substitute configuration interaction approach with basis set 6-311 + + G **. The excited states of titanium monoxide molecule under different external electric fields are also investigated. It is shown that the α HOMO-LUMO gaps become smaller and the electrons of the occupied orbital tend to the virtual orbital as the external electric field intensity increases, and the β HOMO-LOMO gaps become bigger, while the variation in excitation wavelength of high-excited states turns more complicated than that of low-excited states, and the coupling strengths of excited states increase with external electric field increasing.
Three-dimensional classical micro-canonical simulation of nonsequential double ionization with a few-cycle laser pulse
Authors: Tang Qing-Bin  , Zhang Dong-Ling  , Yu Ben-Hai  , Chen Dong  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000 China
Published: December 2020

A three-dimensional classical micro-canonical model is used to investigate the ion momentum distributions of Ar atom in nonsequential double ionization with a few-cycle laser pulse. It is found that the momentum distribution has a strong dependence on the carrier-envelope phase of the few-cycle pulse. The centre of gravity of the asymmetry distribution shifts from negative to positive ion momenta with carrier-envelope phase increasing and it is reversed when the carrier-envelope phase changes by π. The momentum distributions of the Ar2+ ion show excellent agreement with the experimental results when we take into account the change in Coulomb potential between the nucleus and electron in the recollision process.
Using two methods to study non-sequential double ionization
Authors: Wei Ya-Na  , Yang Shi-Ping  ,   Department of Physics, Hebei Normal University, Shijiazhuang 050016, China
Published: December 2020

The semiclassical rescattering model and the quantum-mechanical S matrix model are used to study the non-sequential double ionization of atoms and molecules in strong laser fields.Based on these two models, we can calculate ionization rate with different laser intensities, recoil ions momentum distribution and two-electron energy distribution. The numerical simulation results show that the semiclassical rescattering model coincides with the quantum-mechanical S matrix model when non-sequential double ionization of atoms and molecules is researched in strong laser fields.
The first-principle calculations and analysis on density of states of silion plane (111) formed by nitrogen film
Authors: Lü Quan  , Huang Wei-Qi  , Wang Xiao-Yun  , Meng Xiang-Xiang  ,   Institute of Nanophotonic Physics, Guizhou University, Guiyang 550025, China
Published: December 2020

Nitrogen and silicon atoms have the smallest mismatch of bonding in the Si surface (111), and different percentages of nitrogen atoms are adopted to passivate silicon surface dangling bonds in the Si (111) orientation. The first-principle calculations showed that the band gap is broadened and the localized trap states are generated when the nitrogen atom content is 75%—100% in the Si surface (111). Then the corresponding local electronic-state model is proposed, and the physical mechanism of the previous experimental results of the visible PL emission on SiN films is clarified.
Influence of quartz tube on the nanosecond pulsed discharge in a cone-to-plane air gap
Authors: Lü Xiao-Gui  , Ren Chun-Sheng  , Ma Teng-Cai  , Zhu Hai-Long  , Qian Mu-Yang  , Wang De-Zhen  ,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

This letter reports on the experimental investigation of the influence of a quartz tube on the nanosecond pulsed discharge in a cone-to-plane air gap, with the quartz tube inserted between the electrodes in the direction parallel to the electric field. While the tube is moved along the axies of the electric field, four different phenomena appear, of which the possible mechanism is discussed. The characteristics of the discharges are diagnosed by optical methods. For five conditions, the rotational temperatures are all 295 K, and the vibration temperatures are all 2200 K, the results mentioned above demonstrate that the plasmas generated in different conditions are in a nonequilibrium state each. Furthermore, a way to produce raise to a uniform glow-like discharge mode is proposed.
Application of a collisinal-radiative model for the analysis of K-shell line spectra emitted by Z-pinch plasma
Authors: Li Jing  , Xie Wei-Ping  , Huang Xian-Bin  , Yang Li-Bing  , Cai Hong-Chun  , Pu Yi-Kang  ,   (1)Department of Engineering Physics, Tsinghua University, Beijing 100084, China; (2)Institute of Fluid Physics, Chinese Academy of Enginoering Physics, Mianyang 621900, China; (3)Institute of Fluid Physics, Chinese Academy of Enginoering Physics, Mianyang 621900, China;Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

In this paper, the principle of the collisional-radiative model for the estimation of plasma parameters from the ratios of K-shell spectral lines was introduced. The structure of a computer program, ZSPEC, developed for the analysis of K-shell line spectra emitted by Z-pinch plasma based on the collisioanl-radiative model was described in detail. The calculation for neon plasma were presented, including the number fractions of major ionization stages at different electron temperature and the contours of K-shell line ratios in the plane defined by electron density and electron temperature. ZSPEC had been used to analyze the measured results of neon gas-puff Z-pinch experiment performed on Yang accelerator. By comparing the K-shell line ratios of neon plasma obtained by an elliptical crystal spectrometer with the results calculated by ZSPEC, the time and space averaged electron temperature and electron density of the K-shell plasma for the shot with 540 kA peaking current were determined to be 240 eV and 1.0×1019 cm-3, respectively.
Effect of orientation on integrity of single crystal during laser melted single crystal
Authors: Wang Nan  , Yao Wen-Jing  , Tang Lin-Feng  , Guan Qiang  ,   (1)Department of Applied Physics, and Northwestern Polytechnical University, Xi’an 710072, China; (2)Xi’an Aero-Engine Group Corporation, Ltd, Xi’an 710000, China
Published: December 2020

The geometrical model is used to investigae the orientation of dendrite growth in a laser weld single crystal and the variation of the distribution of orientation zones when angle ξ between the laser scanning direction and the [100] orientation in (001) surface changes. With the increase of ξ, the 0] zone increases whereas the [010] zone shrinks. Meanwhile, the growth velocities of dendrite are different in different orientation zones inside the weld pool. The undercooling region is then constructed on the basis of the calculation results. It is found that the undercoolings are larger at the boundaries than in the grains for all orientation zones, which makes the boundaries vulnerable to the CET transition and production of the new grains. Moreover, with the increase of ξ, the abilities to form the new grains are different on the two sides of the weld pool. For comparison, the DD3 single crystals are laser welded and the experimental results are in good agree meent with theoretical ones.
Effect of Ga on optical properties of novel Te-based far infrared transmitting chalcogenide glasses
Authors: Nie Qiu-Hua  , Wang Guo-Xiang  , Wang Xun-Si  , Xu Tie-Feng  , Dai Shi-Xun  , Shen Xiang  ,   College of Information Science and Engineering, Ningbo University, Ningbo 315211, China
Published: December 2020

A series of (100-x)(GeTe4)-xGa (x=0, 5, 10 mol%) far infrared transmitting chalcogenide glasses is prepared by the traditional melt-quenching method. In this paper, the differential thermal analysis (DTA), visible/near-infrared absorption spectroscopy, infrared transmission spectra are adopted to analyze composition, structure and performance of the GeTe4 glass system with the addition of Ga. The results show that the Te-Ga bond is formed, which can reduce Te metallic character. When the content of Ga is 10 mol%, the glass is of the best thermal stability. With the addition of Ga, the transmission percentage is improved and infrared cut-off wavelength of the glasses extends beyond 20 μm. Based on the metallization criterion and average bond energy, the relationship between optical band gap and composition is investigated.
Interface structure effects on optical property of undoped ZnSe/BeTe type-Ⅱ quantum wells
Authors: Zheng Yu-Jun  , Xu Xian-Gang  , Ji Zi-Wu  , Lu Yun  ,   (1)Graduate School and faculty of Engineering, Chiba University, Chiba 263-8522, Japan; (2)School of Physics, Shandong University, Jinan 250100, China; (3)State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
Published: December 2020

The results are reported of the spatially indirect photoluminescence (PL) spectrum measurements performed on undoped ZnSe/BeTe type-Ⅱ quantum wells with special interface structures at low temperatures (5—10 K). The PL spectra have two main peaks that show a weak PL intensity and a low linear polarization degree and that their linear polarizations are contrary to each other, And the PL spectra are strikingly dependent on an applied external electric field perpendicular to the layers. The results show that the special interface structures reduce spatially indirect radiative recombination efficiency and linear polarization degree, and that a weak built-in electric field exists in the heterostructure. With the increase of excitation intensity, the PL peak on high energy side shows a rapid increase. This is explained by the formation of high charge density on both sides of the high energy side interface.
Simulation of frost formation process on cold plate based on fractal theory combined with phase change dynamics
Authors: Liu Yao-Min  , Liu Zhong-Liang  , Huang Ling-Yan  ,   The Education Ministry Key Laboratory of Enhanced Heat Transfer and Energy Conservation, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

Simulation of frost formation process on cold surface is carried out based on fractal theory combined with phase change dynamics. Before frosting, the phenomena of vapor condensation, droplet growth and frozen on cold plate are successfully simulated based on phase change dynamics and then a fractal simulation of the frost formation and growth process over the frozen droplets is carried out based on diffusion limited aggregation (DLA) model. The simulation results accord well with the experimental results. The time when the condensation droplets are present and frozen on the surface during simulation process is nearly the same as the experimental result. Before the droplets are frozen, the trend that the surface contact radius of the droplet varies with condensation time is similar to actual one. The simulation results also show that the thickness of frost layer is nearly equal to the measured value. By that means, the feasibility of this method of simulating the frost formation is verified and the new attempt made to foster the combination between fractal theory and phase change dynamics is of great significance. This study also provids a foundational theory work for a more reasonable and accurate frosting process model.
Effect of hydrogen on ferroelectric properties of Bi4Ti3O12 during forming gas annealing
Authors: Zhao Qing-Xun  , Ma Ji-Kui  , Geng Bo  , Wei Da-Yong  , Guan Li  , Liu Bao-Ting  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

Degradation of Bi4Ti3O12 ferroelectricity during forming gas annealing is investigated by the first-principles method based on the density functional theory(DFT) the generalized gradient approximation(GGA). We calculate the variations of total energy with the displacement of Ti along the c axis, electron density and total density of states in hydrogen-free and hydrogenated models. The results show that the electron densities of Ti-O and Bi-O exhibit significant changes between the Bi4Ti3O12 ferroelectric phases for the hydrogenated and hydrogen-free cases, and the strong hybridization between H and O is favorable to the formation of a convalent bond. The total energy of ferroelectric phase for the hydrogenated case is bigger than that of paraelectric phase because hydrogen incorporation into the lattice has a direct effect on polarization pinning by possibly forming a hydroxyl bond. This demonstrates that hydrogen introduction during forming gas annealing hinders the phase transition of the Bi4Ti3O12 from tetragonal paraelectricity to orthogonal ferroelectricity, and electrical conductivity of Bi4Ti3O12 is increased. This may be an important factor causing severe degradation of Bi4Ti3O12 ferroelectricity.
Abnormal photoabsorption in high resistance GaN epilayer
Authors: Liu Wen-Bao  , Zhao De-Gang  , Jiang De-Sheng  , Liu Zong-Shun  , Zhu Jian-Jun  , Zhang Shu-Ming  , Yang Hui  ,   State Key Laboratory on Integrated Optoelectronics,Institute of Semiconductors,Chinese Academy of Sciences,Beijing 100083,China
Published: December 2020

Unintentionally doped GaN epilayers are grown by the metalorganic chemical vapor deposition (MOCVD). Photovoltaic (PV) spectroscopy shows that there appears an abnormal photoabsorption in some undoped GaN films with high resistance. The peak energy of the absorption spectrum is smaller than the intrinsic energy band gap of GaN. This phenomenon may be related to exciton absorption. Then metal-semiconductor-metal (MSM) Schottky photodetectors are fabricated on these high resistance epilayers. The photo spectrum responses are different when the light individually irradiates each of the two electrodes with the photodetector which are differently biased. When the excitation light irradiates around the reverse biased Schottky junction,the responsivity is almost one order of magnitude larger than that around the forward biased junction. Furthermore,when the excitation light irradiates the reverse biased Schottky junction,the peak energy of the spectrum has a prominent red-shift compared with the peak energy of the spectrum measured with the excitation light irradiating the forward biased Schottky junction. The shift value is about 28 meV, and it is found to be insensitive to temperature. According to the analyses of the distribution of the electric field within the MSM device and the different dependences of the response on the electric field intensity between the free carriers and excitons,a reliable explanation for the different response among various areas is proposed.
AlGaInP LED with surface structure of two-dimensional photonic crystal
Authors: Chen Yi-Xin  , Zheng Wan-Hua  , Chen Wei  , Chen Liang-Hui  , Tang Yi-Dan  , Shen Guang-Di  ,   (1)Beijing University of Technology and Opto-Electronic Technology Laboratory,Beijing 100124,China; (2)Institute of Semiconductor,Chinese Academy of Sciences,Beijing 100083,China
Published: December 2020

Some progress in the research of GaN based LED with photonic crystal structure has been made recently. Based on the photonic crystals photonic band gap effect and photon grating diffraction principle,the extraction efficiency of LED with photonic crystal can be improved. In this paper,the restriction on AlGaInP LEDs extraction efficiency is analyzed,and the photonic crystal is introduced in to the AlGaInP LED to improve the extraction efficiency. The theoretical analyses and the experiment results show that the output luminous intensity of LED with photonic crystal is improved by 16%,which results from some effect of the GaN based LED with photonic crystal.
Transport and rectification properties of Pr0.5Ca0.5MnO3/Si heterojunction
Authors: Wan Ji-Yu  , Jin Ke-Xin  , Tan Xing-Yi  , Chen Chang-Le  ,   Department of Applied Physics,Northwestern Polytechnical University,Xi'an 710072,China
Published: December 2020

Pr0.5Ca0.5MnO3(PCMO) is been prepared by a solid-state reaction technique, and the thin film of PCMO is deposited on an n-type silicon substrate by a pulsed laser deposition method. Experimental results indicate the transport character of the film may be consistent with the variable range hopping model in a temperature range of 80—300 K, but it changes from one-dimension to two-dimensional and then turns three-dimensional with temperature increasing. It may be attributed to the effect of orbit order on the transport characteristics. The PCMO/Si heterojunction possesses good rectifieation property under a magnetic field,and at a positive voltage the heterojunction shows its magnetoresistance to have a remarkable transition from positive to negative.
Effect of precursor composition on superconductivity properties of YBCO film prepared by TFA-MOD method
Authors: Ding Fa-Zhu  , Gu Hong-Wei  ,   Key Laboratory of Applied Superconductivity,Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China
Published: December 2020

The YBCO films were prepared on LAO single crystal by TFA-MOD process. The structure and properties of YBCO films were investigated through changing the Y123 stoichiometry. It is found that higher JC values in self-filed of YBCO films are achieved by using the starting solution with the Ba ∶Y ratio of 1.5 ∶1. X- ray diffraction analysis revealed that Y2Cu2O5 phases are formed in the final YBCO films,which may lead to very effective vortex pinning and then enhance the JC of YBCO films.
Effect of external electric field on phase transitions of ferroelectric thin films
Authors: Liang Xiao-Lin  , Gong Yue-Qiu  , Liu Zhi-Zhuang  , Lü Ye-Gang  , Zheng Xue-Jun  ,   (1)Faculty of Material and Photoelectronic Physics,Xiangtan University,Xiangtan 411105,China; (2)Hunan University of Science and Engineering,Yongzhou 425100,China; (3)Hunan University of Science and Engineering,Yongzhou 425100,China;Faculty of Material and Photoelectronic Physics,Xiangtan University,Xiangtan 411105,China
Published: December 2020

A nonlinear thermodynamic theory is used to investigate the effect of external electric field on the phase transitions of Pb(Zr0.3Ti0.7)O3(PZT) thin films epitaxially grown on dissimilar cubic substrates. The "misfit strain-external electric filed" phase diagram and the relationship between electirc filed and polarization are constructed for PZT thin films. The external electric field can transform the monoclinic r phase into the c phase,when its value reaches 186 kV/cm for PZT thin film grown on the SrTiO3 substrate. On the other hand,the domain switching of PZT thin film is investigated experimentally by scanning probe microscopy(SPM) via varying the applied polarizing electric field. The piezo-phase images reveal that most ferroelectric domains are clearly detectable. In the r phase,the domains can be reversed into the direction of polarization of the c phase,when the applied electric field increases to 200 kV/cm,which is close to the theoretical value (186 kV/cm).
High efficiency amorphous/microcrystalline silicon tandem solar cells deposited in a single chamber system
Authors: Zhang Xiao-Dan  , Zheng Xin-Xia  , Wang Guang-Hong  , Xu Sheng-Zhi  , Yue Qiang  , Lin Quan  , Wei Chang-Chun  , Sun Jian  , Zhang De-Kun  , Xiong Shao-Zhen  , Geng Xin-Hua  , Zhao Ying  ,   Institute of Photo-electronic Thin Film Devices and Technology of Nankai University, Key Laboratory of Photo-Electronic Thin Film Devices and Technology of Tianjin, Tianjin 300071, China
Published: December 2020

Based on the previous research on the deposition of amorphous/microcrystalline (micromorph) silicon tandem solar cells, silane concentration for the deposition of microcrystalline bottom cell is selected to further optimize the performance for micromorph tandem solar cells by using very high frequency technique. Finally, micromorph silicon tandem solar cell with 11.02% (Area=1.0cm2) initial conversion efficiency is fabricated at a certain silane concentration, and it has a structure suitable for trapping light. Furthermore, 100cm2 micromorph module with 9.04% initial conversion efficiency is also successfully obtained.
Effect of pinhole diameter on correction accuracy of closed-loop adaptive optics system using self-referencing interferometer wavefront sensor
Authors: Bai Fu-Zhong  , Rao Chang-Hui  ,   (1)Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China; Key Laboratory on Adaptive Optics of the Chinese Academy of Sciences, Chengdu 610209, China; (2)Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China; Key Laboratory on Adaptive Optics of the Chinese Academy of Sciences, Chengdu 610209, China;School of Mechanical Engineering, Inner Mongolia University of Technology,
Published: December 2020

When the self-referencing interferometer wavefront sensor (SRIWFS) is applied to the absolute measurement of wavefront phase, the pinhole diameter should be less than half the Airy-disk diameter (dA) produced by an unaberrated optic so as to obtain a good approximation to a reference plane wave. In this way, however, the intensity transmission is also greatly reduced. To increase the intensity transmission as much as possible and improve the fringe contrast especially in the beginning of closed-loop correction, the maximal pinhole diameter allowed in the closed-loop correction with using SRIWFS is studied. Computer simulation and experiment demonstrate that a pinhole with not greater than 1.5dA can obtain a satisfied correction result and the Strehl ratio after correction is greater than 80%. Additionally, for a plane wavefront the intensity transmission will be increased from 63% to 90% as the pinhole diameter increases from 0.5dA to 1.5dA.
Disturbance effects of some representative chemical releases in ionosphere
Authors: Hu Yao-Gai  , Zhao Zheng-Yu  , Zhang Yuan-Nong  ,   College of Electronic Information, Wuhan University, Wuhan 430079, China
Published: December 2020

In this paper, a 3-D chemical release dynamics model including neutral gas diffusion, chemical reaction and ambipolar diffusion of plasma, is proposed first. And then the software frame is developed for the study of chemical releases in the ionosphere. The computer simulation on some representative chemical releases including H2O, CO2, H2 and SF6 is carried out finally. The temporal-spatial effects of the local turbulence introduced by these chemical releases are discussed.
Stiefel manifold particle filtering
Authors: Zhu Zhi-Yu  , Yang Guan-Xiao  ,   School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Published: December 2020

In order to solve the problems of particle degeneration and lackness of diversity of particle filter, a new particle filter based on Stiefel manifold (SMPF) is proposed in this paper. In the SMPF the system model is based on Stiefel manifold, Langevin distribution is used as a prior density, the matrix normal distribution serves a as likelihood function, and particle is sampled on the manifold distribution. First, manifold is embedded in Euclidean space, then the mean of particles is calculated in Euclidean space and its result is projected back to embedded manifold. So the influence on variance of particle weight caused by statistic characteristics of noise is removed, and a kind of universal selecting scheme of important probability density function is acquired which is hardly restrained to system state model. The simulation results based on univariate nonstationary growth model nonlinear system indicate that the SMPF works much better than scentless particle filter in real-time performance, robustness, filtering precision and filtering efficiency.