bluuebunny/crossref_metadata_2025 huggingface dataset:
Applications and progress of slow positron beam technique in the study of metal/alloy microdefects
Authors: Hu Yuan-Chao  , Cao Xing-Zhong  , Li Yu-Xiao  , Zhang Peng  , Jin Shuo-Xue  , Lu Er-Yang  , Yu Run-Sheng  , Wei Long  , Wang Bao-Yi  ,   College of Physical Engineering, Zhengzhou University, Zhengzhou 450001, China;,   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In recent decades, the positron annihilation spectroscopy technique has been used to characterize the microdefects of materials due to its advantages of non-destruction and high sensitivity on an atomic level. Positron annihilation spectroscopy technique is widely used in the microstructure study of thin film material surface and interface due to the rapid development of the slow positron beam technology. The slow positron beam technique can provide depth distribution information about material surface microstructure. Therefore, it is widely used to study the distributed defect concentrations in crystalline materials and the properties of thin films, surfaces and interfaces of layered materials. This article summarizes the slow positron beam technique applications and progress in the study of metal alloy materials. Firstly, this article introduces the slow positron beam technology development and application research achievement in detail. Secondly, it provides how to acquire the slow positron beam, introduces some kinds of and the principles of experimental measurements, and the major methods include Doppler bradening spectroscopy, coincidence Doppler broadening and PL. Thirdly, according to the defects induced by different ways, the latest experimental results about the material internal microdefect formation mechanism, evolution mechanism, defect feature research, such as microstructure, chemical environment, electron density and momentum distribution are introduced. The methods of inducing defects mainly include irradiation, physical deformation and chemical corrosion. Particles irradiation can be classified as four parts according to the different types of particles. In addition, monolayer and multilayer thin films have also been summarized. Finally, the new technique of thermal desorption spectroscopy and experimental measurements of age-momentum correlation are proposed. We can know that positron annihilation spectroscopy technology is a very special and effective nuclear spectroscopy analysis method in material microstructure study, and the slow positron beam technique makes it possible to study the depth distribution information about the thin film material surface microstructure. There is no doubt that this technique will play a huge role in the progress of material science and the creation of industrial material.
Numerical simulation of light absorption enhancement in microcrystalline silicon solar cells with Al nanoparticle arrays
Authors: Ding Dong  , Yang Shi-E  , Chen Yong-Sheng  , Gao Xiao-Yong  , Gu Jin-Hua  , Lu Jing-Xiao  ,   Key Laboratory of Materials Physics of Ministry of Education, School of Physical Engineering, Zhengzhou University, Zhengzhou 450052, China
Published: December 2020

Metal nanoparticles with low cost and high performance have good potential applications in light-trapping of solar cells. In this paper, a three-dimensional model is proposed to simulate the light absorption of microcrystalline silicon (μc-Si:H) thin film solar cells. The effects of spherical and hemispherical Al nanoparticle arrays located on the front surfaces of solar cells are investigated, and the particle radius and array period are optimized by the finite element method. The results show that the optimal Al nanoparticle arrays can enhance broadband absorption in thin film solar cells. For spherical particle arrays, the key parameter that influences light absorption in solar cells is period/radius ratio (P/R) or particle surface coverage. When P/R=4-5, the optimum integrated absorption enhancement (Eabs) is over 20% under AM1.5 illumination compared with the solar cell without nanoparticles. The value of Eabs is small and decreases with the increase of P/R when P/R>5, and Eabs is less than zero when P/RP=500 nm and R=120 nm, the spectral absorption rate as a function of wavelength shows broadband absorption including four distinct peaks, which are attributed to quadrupole plasmon resonance mode, dipole resonance mode and waveguide mode respectively according to the electric field distribution in the solar cell. For hemispherical particle arrays, the maximum value of Eabs is 24.5%, which is higher than that of the solar cell with optimized spherical particle arrays. This is due to the high coupling efficiencies of the particles, so that most of the scattered light is directly coupled into the substrate. However, the value of Eabs is very sensitive to the hemispherical particle radius. As the radius decreases, the scattering cross-section and scattering efficiency of the particle decrease dramatically. As the radius increases, the dipole plasmon resonance wavelength rapidly shifts towards longer wavelength (red shift). Both of these are detrimental to absorption enhancement of solar cells. Thus we conclude that spherical Al particle arrays are more preferable in actually fabricating the light-trapping of solar cells.
Stress analysis of a cylindrical composition-gradient electrode of lithium-ion battery in generalized plane strain condition
Authors: Peng Ying-Zha  , Zhang Kai  , Zheng Bai-Lin  , Li Yong  ,   School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
Published: December 2020

A novel cylindrical composition-gradient electrode is considered to be one of most potential structures in lithium-ion battery. To investigate the mechanism of a cylindrical composition-gradient electrode under potentiostatic operation, we take Li1.2(Mn0.62Ni0.38)0.8O2 for example. The effects of the three main factors, i.e., diffusion coefficient, Youngs modulus, partial molar volume of solute, on the stress field in the cylindrical electrode are discussed. Each of the three material parameters is assumed to be a linear function of the distance from the center to surface. The small deformation theory and thermodynamic theory are employed to establish the mathematical model of composition-gradient cylindrical electrode. The mechanics equations and diffusion equation of cylindrical electrode are derived for an inhomogeneous material in plane strain condition. By comparing with single-phase electrode, it is found that Youngs modulus increasing from the center to the surface greatly reduces the max tensile radial stress and tensile hoop stress and changes the location of max radial stress since the radial displacement of the center is restricted. The time for the lithium-ions to reach the center is longer and the tensile stress near the center decreases at dimensionless time =0.0574 when diffusion coefficient decreases along the radial direction. Owing to the smaller diffusion coefficient at the surface, there is a reduction in the number of lithium-ions through the unit area in unit time when their corresponding concentration gradients are the same. The variation of partial molar volume means that the volume expansion caused by the intercalation of lithium-ions decreases along the radial direction. Therefore the partial molar volume decreasing along the radial direction considerably reduces the radial stress and the distribution of tangential stress becomes flat. The center point is picked, showing the development of hoop stress. The results show that the hoop stress increases and reaches a maximal value close to the dimensionless time =0.0574. Maximal tensile hoop stress at the center is reduced in an inhomogeneous material. The tensile hoop stress turns into compressive stress over time when elastic modulus and partial molar volume are denoted with E(r) and (r) respectively. The results indicate that the cylindrical composition-gradient electrode with core enriched Ni and edge enriched Mn reduces the max tensile radial stress and tensile hoop stress. It is an efficient way to avoid mechanical fracture in electrode since evidence has accumulated that tensile stress is the lead cause of crack in electrode. The result also provides useful guidance for mitigating the stresses in a cylindrical electrode.
Relationship between modulation frequency and range accuracy in the double polarization modulation range finding system
Authors: Xiao Yang  , Yu Jin-Long  , Wang Ju  , Wang Wen-Rui  , Wang Zi-Xiong  , Xie Tian-Yuan  , Yu Yang  , Xue Ji-Qiang  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Accurate measurement of absolute distance is crucial for developing the progressive military, aerospace, manufacturing large scientific instruments and other fields. Instead of the traditional phase discrimination scheme in general phase-shift distance measurement, the double polarization modulation range-finding system can simplify the simulation phase circuit, reduce the phase shift noise and improve the accuracy by using interference phase demodulation. The in-depth discussion of theoretical derivation and experimental verification are proposed based on the double polarization modulation range-finding system. The detailed theoretical analysis of optical structure is proposed, and the factors affecting the range accuracy are analyzed based on the theoretical formula of ranging result. Finally, the theoretical formula of range accuracy is obtained, and experimental validation is carried out. In this experiment, the wavelength of laser source is 735 nm, and the phase modulator is 4431 model from the Newport company. The ranging experiment is conducted in the modulation frequency ranges of 0.75-0.85 GHz, 2.7-2.8 GHz, 4.3-4.4 GHz, 6.1-6.2 GHz, and 7.8-7.9 GHz. Experimental results indicate that the measurement accuracy of phase-shift range-finding technology is improved with the increase of modulation frequency. Moreover, the accuracy is proportional to the parameter f/N, in which f is the modulation frequency uncertainty and N is an integer in our algorithm. With the appropriate modulation frequency, the range accuracy of the double polarization modulation range-finding system can reach up to 10-7.
First-principle study of the optical absorption spectra of chalcogen on D-A and D--A copolymers
Authors: Li Jin  , Wang Hai-Yan  , Li You  , Zhang Qiu-Yue  , Jia Yu  ,   International Laboratory for Quantum Functional Materials of Henan, School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China;,   Advanced Analysis and Computation Center, Zhengzhou University, Zhengzhou 450052, China
Published: December 2020

D-A type copolymer as an organic polymer solar cell electronic material in recent years has attracted wide attention. In order to improve the efficiency of energy conversion, many active layer materials, especially the donor materials, have been designed and synthesized. By inducing the different donor and acceptor units, the absorption spectrum can better match with the solar spectrum and the carrier mobility can increase. In this paper, by using the density functional theory method, we investigate the electronic structures and optical absorption spectra of D-A and D--A copolymers. Benzodithiophene (BDT) as the electron donor unit, and dibenzothiophene (BT) as the electron acceptor unit are used to simulate D-A (PBDT-BX, X = O, S, Se, Te) copolymer systems; and D--A (PBDT-DTBX, X = O, S, Se, Te) structures are constructed with thiophene ring as a bridge between D and A. Firstly, our calculation results indicate that when X is replaced separately by elements O, S, Se and Te in D-A copolymers, the LUMO levels move close to the Fermi level, while the changes of the HOMO energy levels are relatively small, resulting in the band gap decreasing gradually. Then, the analysis of the density of states (DOS) shows that the contribution of LUMO comes from the BT unit and HOMO from the BDT unit. Also the difference in charge density shows that the thiophene ring enhances the charge transfer between BT and BDT. Besides, the studies of the optical absorption spectrum reveal that there appear two strong absorption peaks with the increase of atomic number of X, of which one is at about 4.0 eV and has no obvious change, and the other increases intensively and is red-shifted. Moreover, compared with the D-A structure, the D--A structure has the band gap that will decrease obviously and has a lowest value when X is Te. The optical absorption peak also increases significantly as the atomic number of oxygen group elements increases and peak position is red-shifted. The range of optical absorption peak is mainly from 703.9 to 519.4 nm. According to the absorption spectrum and DOS the optical absorption peak at about 4.0 eV is mainly contributed by the BDT unit. Overall, our findings provide a good understanding of mechanism about the red-shift of optical absorption spectra of copolymers and can serve as guidance for organic polymer design in photovoltaic cell experimentally.
Compression of extreme ultraviolet pulse for atom with resonant structure exposed to an infrared laser field
Authors: Tang Rong  , Wang Guo-Li  , Li Xiao-Yong  , Zhou Xiao-Xin  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   Experimental Center, Northwest University for Nationalities, Lanzhou 730030, China
Published: December 2020

The short attosecond (as) pulse is a basic tool for probing the ultra-fast electronic dynamics in matter. High-order harmonic generation (HHG) of atoms exposed to intense laser field is the most promising method of producing the short attosecond pulses. Therefore, the generation of ultra-short attosecond pulses through HHG has been of great interest. How to obtain the ultra-short pulse from HHG has been a hot research subject in recent years. In the present paper, we investigate the characteristic of HHG from atoms with both resonant and non-resonant structure (for short, the general atom) by using numerically solving a one-dimensional time-dependent Schrodinger equation of atom driven by two-color field (infrared (IR) laser + extreme ultraviolet (XUV)). We find that the HHG spectra from resonant atom are obviously different from those of the general atom. For a resonant atom, besides the great increase of the intensity of HHG at some energy (resonant energy + ionized energy), the intensity of HHG at the central frequency of XUV pulse is sensitive to the intensity of XUV pulse. Even the intensity of XUV pulse is weak, the enhancement of HHG spectra from resonant atom is still significant, while the general atom does not has this feature. Only the strength of the XUV pulse is much stronger than that in the case of resonant atom, the spectra of HHG near the center frequency of XUV from atom with non-resonant structure can significantly be enhanced. More importantly, adjusting the time delay of two-color laser pulse makes the width of input XUV pulse compressed obviously in the case of the resonant atom. By performing the time-frequency analysis of Morlet transform, we explain the compression of the attosecond pulse. The reason is that the relation of the input XUV pulse frequency to the resonant frequency of HHG for resonant atom makes the bandwidth of HHG in the region of the center frequency of XUV wider than that of the input attosecond pulse during the emission. Thus, we can obtain shorter pulse by superposing several orders HHG among the enhanced regions. Finally, we propose a way to compress the width of the input XUV pulse by using filter-multi-feedback method. Based on our scheme, the width of the input XUV pulse can be compressed from 200 as to 120 as, thereby offering a new method of obtaining shorter attosecond pulse in experiment.
Characteristics of quartz crystal energy storage
Authors: Cai Jia-Huan  , Li Ping  , Wen Yu-Mei  , Bao Yi-Zhuang  , Liu Shuang-Jian  ,   Research Center of Sensors and Instruments, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China
Published: December 2020

As the weak ambient energy is hard to be stored directly and rapidly and unable to drive the electronic load into working properly, a high-efficiency energy storage circuit, with quartz crystal serving as a storage element, is presented. When an alternating electric field is applied to it, the quartz crystal will generate mechanical oscillations of a certain frequency. Since the quartz crystal possesses a high quality factor, in the piezoelectric crystal plate there appears a severe mechanical resonance with a small excitation voltage. In the resonant condition, the external weak electrical energy can be converted into mechanical energy stored in the quartz crystal. The principles of quartz crystal energy storage and instantaneous energy discharge are theoretically analyzed. The relationships between the output voltage and the time and between the maximum instantaneous output power and the load in the processes of quartz crystal charging and discharging are deduced, respectively. The storage characteristics of the quartz crystal are investigated experimentally. The experimental results show a good accordance with the theoretical analysis. A quartz crystal of 1 MHz resonant frequency is adopted in this research. When the input voltage amplitude of the energy storage circuit is 100 mV, the optimal matching load is 820 and the maximum instantaneous output power of quartz crystal discharging circuit is 150 W. The storage efficiency and the release efficiency of the quartz crystal can reach up to 77% and 71.4% respectively. These results provide evidence for quartz crystal energy storage in the condition of weak ambient energy.
Passive impulsive source range estimation based on warping operator in shallow water
Authors: Wang Dong  , Guo Liang-Hao  , Liu Jian-Jun  , Qi Yu-Bo  ,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

An approach to passive impulsive source range estimation in shallow water is proposed. The approach is based on warping transformation of the energy density function of the received signal. Because of the influence of the sea bottom, it is difficult to find a warping operator adapted to the dispersion characteristics of modes in shallow water. Even though the modes can be separated from each other by using the warping operator adapted to the ideal waveguide, it is impossible to obtain the analytic solutions of the characteristic frequencies, while the energy density function of the received signal is not affected by the sea bottom. Like the received signal and the autocorrelation function of the signal, the frequency spectrum of the warped energy density function of the received signal also owns invariable frequency features. These characteristic frequencies equal the difference in the cut-off frequency between two modes in ideal waveguide, which are easy to calculate with the knowledge of the depth and the average sound speed of the water. What is more, the warping operator transforms mode pairs in energy density function with the same mode number difference into one monotone, which means one characteristic frequency is not unique for one mode pair. In shallow water, the acoustic field is typically composed of a group of modes with close mode numbers. Therefore, the smaller the mode number difference, the more the mode pairs, and the higher the spectral peak of the corresponding monotone is. When the source range is unknown, the approximate relation formula between the extracted characteristic frequency in a supposed source range and the real characteristic frequency is derived, based on which a fast passive source range estimation method is proposed. The proposed method successfully avoids using the guide source and the calculation of replica field, which is necessary in existing passive range estimation algorithms. And applying warping operator to the energy density function of the received signal makes it easy to obtain the analytic solutions of the characteristic frequencies, which is impossible in previous researches. The method is successfully applied to the Yellow Sea impulsive signal data collected by a single hydrophone in November 2011. The mean relative error of range estimation is less than 8%.
Influence of grain size on the thermal conduction of nanocrystalline copper
Authors: Liu Ying-Guang  , Zhang Shi-Bing  , Han Zhong-He  , Zhao Yu-Jin  ,   Shool of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, China
Published: December 2020

Naocrystalline (nc) material shows lower thermal conductivity than its coarse grain counterpart, which restricts its engineering applications. In order to study the effects of grain size and grain boundary on the thermal conductivity of nc material, nc copper is prepared by the high pressure sintering method. The pure nc Cu powder is used as the starting material, and the high pressure sintering experiment is carried out under a DS614 MN cubic press. Prior to the high pressure sintering experiment, the Cu powders are first pre-compressed into cylinders, then they are compressed under 5 GPa at temperatures ranging from 700 to 900 ℃ for 30 min. The grain size and micro-structural characteristics are investigated by the scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that the sintered Cu bulk material can achieve nearly full densification with a relative density of 99.98% and the grain growth of the Cu particles is effectively inhibited. The thermal conductivity measurement is performed by NETZSCH LFA-427 at 300 K and 45% RH. The test results show that the thermal conductivity of nc copper is lower than that of its coarse grain counterpart, and the thermal conductivity increases with grain size increasing. For example, as the grain size increases from 390 to 715 nm, the corresponding thermal conductivity increases from 200.63 to 233.37 Wm-1K-1, which are 53.4% and 60.6% of the thermal conductivity of the coarse grain copper, respectively. For a better understanding of the effects of grain boundary and size on the thermal conductivity of nc material, a simple modified model, with special emphasis on the contributions of electron and phonon conduction, is presented by incorporating the concept of the Kapitza resistance into an effective medium approach. The theoretical calculations are in good agreement with our experimental results. The combination of experimental results and theoretical calculations concludes that the thermal conductivity of nc material is weakened mainly by two factors: the grain boundary-electron (phonon) scattering on the grain boundary and the electron (phonon)-electron (phonon) scattering in the grain interior. That is to say, the thermal resistance of nc material can be divided into two parts: one is the intragranular thermal resistance from the grain, the other is the intergranular thermal resistance from the grain boundaries. As is well known, when the grain size decreases to a nano-range, the volume fraction of the grain boundary presents a sharp increase, and the intergranular thermal resistance from the grain boundaries becomes more important.
Buffer capacity of granular materials and its influencing factors based on discrete element method
Authors: Ji Shun-Ying  , Fan Li-Fang  , Liang Shao-Min  ,   State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116023, China
Published: December 2020

As a typical energy dissipation system, granular material acts as a buffer under the action of impact load, with absorbing and dissipating energy effectively through the sliding friction and viscous contacts between particles. In this paper we study the buffer capacity of granular material under impact load, by the discrete element method (DEM). The spherical elements are filled randomly into a rigid cylinder under the action of gravity. A spherical projectile with a certain initial velocity drops into the granular bed from a given height. The impact loads on the projectile and the rigid bottom plate of cylinder are both obtained with DEM simulations. The simulated impact loads on the bottom plate are compared well with the physical experiment data. The influences of granular thickness, sliding friction and initial concentration on buffer capacity are investigated under the impact of spherical projectile. The DEM results show that granular thickness H is a key factor for buffer capacity. In the DEM simulations, the impact load on bottom plate presents unique characteristics under various granular thickness values. With granular thickness increasing from zero, a transition from one peak to two peaks takes place, then the two peaks return to one peak in the time curve of impact load. The evolution of impact load peak with its temporal interval is discussed. A critical thickness Hc is obtained. The impact force decreases with the increase of granular thickness when H Hc, but is independent of the granular thickness when H Hc. Moreover, the impact forces are simulated under various sliding friction coefficients and initial concentrations. It is found that the smooth and loose granular material has more effective buffer capacity. Finally, the spatial structures of force chains and the distribution of impact forces on bottom plate are discussed to reveal the mechanism of buffer properties of granular material on a micro scale.
Uncertain parameters of Jones-Wilkin-Lee equation of state for detonation products of explosive
Authors: Wang Yan-Jin  , Zhang Shu-Dao  , Li Hua  , Zhou Hai-Bing  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

Equation of state of detonation products possesses various types of mathematical expressions which describe the relation between pressure and volume. Jones-Wilkin-Lee (JWL) equation of state is a widely used equation of state of detonation products because of its simplicity in hydrodynamic calculations. The JWL equation of state may accurately describe the process of expansion drive of detonation products. The JWL equation of state contains parameters, and describe the relation among the volume, energy and pressure of detonation products. These parameters may be determined by detonation experimental data and numerical method. Traditional numerical method is adjusting parameters based on experimental data and numerical experience. Obviously, artificial ingredient may affect the calibrating result in traditional method. This paper uses the Bayesian method to determine the unknown (uncertain) parameter of JWL equation of state for detonation products. The method can calibrate the uncertain parameters based on the known parameter information, the experimental and simulating data. The results of the paper are consistent with those in the reference papers. By theoretical analysis the calibration result accords with the physical signification of the parameters of JWL equation of state. The epistemic uncertainty is slightly reduced. The calibration result collects all the parameter information in the prior parameter information, experimental data and numerical results. The experimental data are totally included in a 90% confidence interval of simulation. The numerical result shows that this method can be used to study the uncertain parameter of JWL equation of state for some sample explosives. Especially, the method reduces the artificial ingredient in the parameter calibration.
Effects of fine structure of absorption spectrum and spin-singlet on zero-field-splitting parameters for BaCrSi4O10 and AgGaSe2:Cr2+
Authors: Tan Xiao-Ming  , Zhao Gang  , Zhang Di  ,   School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China;,   School of Jiaotong, Ludong University, Yantai 264025, China
Published: December 2020

The compounds doped with or containing Cr2+ ions are extensively used as optoelectronic and nonlinear optical materials, because they have special optical, magnetic and electric properties. These properties are very closely related to the absorption spectra and zero-field-splitting. The studies of the absorption spectra and zero-field-splitting are very important for realizing the doped microscopic mechanism and understanding the interaction between impurity ions and host crystals, and they may be useful to material designers. The concept of the standard basis adapted to the double group chain is adopted in the strong-field scheme by the crystal field theory. This concept emphasizes the standardization of the basis of the whole 3d4 configuration space including all spin states. Thus, the basis functions can be constructed according to each irreducible representation of the double group and each basis function has a certain expression. Each standard basis adapted to the double group chain can be built from the former by a linear transformation, which forms a basis chain. Thus, the complete energy matrix including spin singlet is constructed for Cr2+ ion in tetragonal symmetry environment in the strong-field-representation by the crystal field theory. The fine structures of absorption spectra and the spin-singlet contributions to zero-field-splitting parameters for BaCrSi4O10 and AgGaSe2:Cr2+ are studied by diagonalizing the complete energy matrix. The fine structures for the two systems and the zero-field-splitting parameters for BaCrSi4O10 are given theoretically for the first time. The fine structures are assigned by the irreducible representation of the group. The results show that the spin-singlet contribution to D is negligible, but the contributions to a and F are important. The contributions arise from the interaction of the spin quintuplets with both spin triplets and spin singlets via spin-orbit coupling. However, the selection rule of spin-orbit coupling shows that the spin singlets do not affect the quintuplets directly but indirectly via the spin triplets. Thus, all spin states should be considered to obtain more accurate zero-field-splitting values.
Controlling interactions between bright solitons in Bose-Einstein condensate
Authors: He Zhang-Ming  , Zhang Zhi-Qiang  ,   College of Science, Hunan University of Technology, Zhuzhou 412007, China;,   Department of Basic Course, Zhengzhou College of Science and Technology, Zhengzhou 450064, China
Published: December 2020

Considering the periodically driving linear potential, we study the interactions between two solitons in Bose-Einstein condensate (BEC). By using Darboux transformation, the double bright soliton solution of Gross-Pitaevskii equation is obtained. Then we numerically calculate the properties of interaction between the two bright solitons in BEC, and obtain a critical value of the S-wave scattering length (SL). It is shown that, when the SL is more than the critical value, the attractive interaction and the atom transfer between two bright solitons can be observed. While the SL is less than the critical value, two bright solitons can keep stable and localized. Furthermore, the stable periodic oscillations of two solitons can be observed by slowly changing the potential. These results will be conducive to the BEC soliton experiments.
Physical hardware trojan failure analysis and detection method
Authors: Luo Yang  , Wang Ya-Nan  ,   China Information Security Evaluation Center, Beijing 100871, China
Published: December 2020

The semiconductor industry is rapidly developing in the global market, and chip design companies usually purchase the third-party EDA tools in order to shorten the design cycle of IC and reduce manufacturing cost. Therefore, in the IC chip production procedure there exist a lot of insecurity factors, and the hardware security of IC chips becomes the most important issue of the national security defense. Physical hardware trojan will modify the value of register, leak sensitive data and cause device degradation failure. Furthermore, the physical hardware trojans only modify the physical properties of the circuit chip rather than injects the malicious functional circuit. They are hidden more deeply than logical hardware trojans. Therefore, it is far-reaching significance issues for the hardware trojan detection methods and national security to study logic circuit transmission characteristics and the chip degradation failure physical mechanism which are caused by injection physical hardware trojans. In this paper, a metal-oxide-semiconductor field-effect transistor (MOSFET) device with injection dopant hardware trojan is realized by using ATHENA process simulation system to achieve the ion implantation process. The ATLAS simulation devices are tested using hot carrier injection degradation (hot carrier degradation is denoted by HCD) stress model for the degradation failure process which is caused by injecting the hot carrier injection hardware trojan (HCHT) into the MOSFET device. Another normal MOSFET combines with dopant hardware trojan MOSFET or hot carrier injection hardware trojan MOSFET to comprise the same inverter logic circuit by using the ATLAS two-dimensional (2D) device simulation system with SmartSpice instructions mode. The effect on logic circuit output characteristics caused by physical hardware trojan is studied by using Spice simulation to output the DC and AC transient time characteristics. It is also studied how the W/L value of a hardware trojan transistor influences the output characteristics of the logic circuit. We design an experiment to study transient characteristics of the same inverter logic module which consists of different W/L values of a transistor at different temperatures. The experiment is realized by Spice circuit simulation. In this paper, the effects of the variations of the HCD stress intensity and temperature on output characteristic are analyzed for hot carrier injection hardware trojan. The results indicate that the negative effect of hardware trojan on logic circuit DC current output characteristic is more obvious than AC transient time characteristic. Thus, we propose an effective method and a convenient procedure to detect the injection physical hardware trojan in packaged chips. Furthermore, the test process is a feasible operation method of detecting physical hardware trojan.
Analysis and calibration of precision for point source transmittance system
Authors: Li Zhao-Hui  , Zhao Jian-Ke  , Xu Liang  , Liu Feng  , Guo Yi  , Liu Kai  , Zhao Qing  ,   Xi'an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, Xi'an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Owing to space optical system working for a long time outside the field of view, where there is strong background radiation, and the fact that the point source transmittance (PST) is an important evaluation indicator for stray light suppression of this optical system, the development of stray light equipment for testing PST has received more and more attention. Though the development of PST testing system has been extensively studied, none of them elaborate on the calibration of the PST testing system. Besides, most of the PST testing systems are at a laboratory research stage, and the calibration of neither testing stability nor accuracy is recognized. Therefore, on the basis of the PST testing system established, one calibration lens is designed to calibrate the PST testing system. By comparing the measured PST values of the calibration lens with the analyzed values, the PST testing system can be evaluated. The calibration lens model is built to analyze PST values at different off-axis angles by using the ray tracing software Tracepro. We consider the accuracy of modeling, and on the basis of simplifying the structure design, we measure bidirectional reflectance distribution function (BRDF) values of the painted surface of the calibration lens, and then estimate values of lens surface from Harvey-Shack model and PSD theory by taking these property data into the model of simulation. Ultimately PST analyzed values of calibration lens can be obtained. Finally, by comparing the measured values of calibration lens, which are tested by using PST testing system, with the analyzed values, the calibration of the PST testing system is completed. In the PST testing process of calibration lens, by analyzing the data at different off-axis angles, the accuracy of repeated measurements and threshold of PST testing system can be obtained. At the same time, testing errors caused by the stability of light source, detector linearity, air scattering and structure of double cylindrical chamber are analyzed through the testing data. The data show that when double cylindrical chamber clean class is ISO7, the PST threshold of this equipment is 10-8, and the accuracy of repeated measurements is 7.9%. Taking into account the detection capability, the PST threshold of this equipment is 10-10 when environmental condition is better than ISO6.
Loss-induced localized field enhancement and optical bistable state in heterostructure containing single-negative materials
Authors: Dong Li-Juan  , Xue Chun-Hua  , Sun Yong  , Deng Fu-Sheng  , Shi Yun-Long  ,   Institute of Solid State Physics, Shanxi Datong University, Datong 037009, China;,   Department of Computer Engineering, Guangxi University of Science and Technology, Liuzhou 545006, China;,   Pohl Institute of Solid State Physics, Tongji University, Shanghai 200092, China;,   Shanxi Province Key Laboratory of MicrostrutureElectromagnetic Functional Materials, Shanxi Datong University, Datong 037009, China;,   Key Laboratory of New Microstructure Function Materials(Shanxi Datong University) in Shanxi Province, Datong 037009, China
Published: December 2020

Permittivity depends on the electric field intensity in a nonlinear material, and it changes with the incident intensity of the electromagnetic wave. This phenomenon leads to the occurrence of optical bistability. The optical bistable threshold value depends on the localized degree of electromagnetic field in the nonlinear material, and the stronger the localized field, the lower the threshold value is. However, the loss of material is one of the important factors influencing the strength of the local field. It is commonly believed that the loss is not conducible to reducing the threshold value because increased loss can weaken the localized degree of fields. For the lossy single-negative metamaterial, the transmission is nonmonotonic as the loss varies. That is to say, the transmission first decreases and then increases in the lossy single-negative metamaterial. Therefore, the nonlinear transmission in the lossy single-negative metamaterial may lead to novel physical phenomena. Permeability-negative material and permittivity-negative material are two kinds of different single-negative metamaterials. In this paper, the optical bistable phenomena in the heterostructure of permeability-negative material and permittivity-negative material are studied by using the transfer matrix method. Here, the permittivity-negative material is nonlinear material. The results show that the optical bistable threshold value first increases and then falls down as the loss increases. The variance of the localized electromagnetic field at the interface between the permeability-negative layer and the permittivity-negative layer at the discussed frequency is discussed in the present paper to understand the nonmonotonic phenomenon. Further studies indicate that the nonmonotonic localized electromagnetic field is also presented at the interface between the permeability-negative layer and permittivity-negative layer. That is to say, the enhancement of the localized field can be obtained when the loss is increased, which results in the nonmonotonic optical bistable threshold value in the heterosturcture composed of the single-negative metamaterials. In the final analysis, the abnormal phenomenon is induced by the loss in the single-negative metamaterial, which is the special property of single-negative metamaterial.
Time delay estimation method of X-ray pulsar observed profile based on the optimal frequency band
Authors: Fang Hai-Yan  , Liu Bing  , Li Xiao-Ping  , Sun Hai-Feng  , Xue Meng-Fan  , Shen Li-Rong  , Zhu Jin-Peng  ,   School of Aerospace Science and Technology, Xidian University, Xi'an 710126, China
Published: December 2020

In order to improve the time delay estimation accuracy of the observed profile in the X-ray pulsar based navigation, the spectral characteristics of the observed profile of X-ray pulsar and the drawback of the classical Taylor fast Fourier transform (FFT) time delay estimation method are analyzed. It is found that when estimating the time delay, we can abandon the higher frequency components that are always affected by noise seriously, but only utilize the information about the low frequency part. Based on this idea, by modifying the weigh function of the classical Taylor FFT time delay estimation method, a new time delay estimation algorithm based on the optimal frequency band is proposed, in which the optimal frequency band is determined by establishing the relationship between the selected frequency band and the time delay estimation accuracy under different signal-to-noise ratios (SNRs). Then by using the real data obtained with the proportional counter array, the low-energy (2-60 keV) detection instrument boarded on the Rossi X-ray Timing Explorer satellite, the optimal frequency as a function the SNR of observed profile is given for the PSR B0531+21 (namely the Crab pulsar) through the Monte-Carlo technique. Since the parameters of different pulsars are known, in practical navigation, the optimal frequency in an observation time for a certain pulsar can be estimated in advance by using the simulation data or the obtained real data of the pulsar, which can remarkably alleviate the onboard computational burden. Finally, a series of numerical simulations and experiments using real data of Crab pulsar are designed to evaluate the performance of the proposed time delay estimation algorithm. The main results can be summarized as follows: the proposed estimator outperforms the normally used fast approximate maximum-likelihood (FAML), cross correlation (CC), nonlinear least square (NLS) and weighted nonlinear least-square (WNLS) estimators when the observation time is short or the source flux is small; when the observation time is long or the source flux is large, its estimation accuracy is almost the same as those of CC and NLS estimators and lower than those of the FAML and WNLS estimators, but its computational complexity is smaller than those of NLS, FAML and WNLS estimators. The above results indicate the high estimation accuracy and high computational efficiency of the proposed time delay estimation method, which can be used in the case that the observation time is restricted to be short or the source flux of the usable pulsar is small in X-ray pulsar based navigation.
Steady state characteristics in FHN neural system driven by correlated non-Gaussian noise and Gaussian noise
Authors: Shen Ya-Jun  , Guo Yong-Feng  , Xi Bei  ,   School of Science, Tianjin Polytechnic University, Tianjin 300387, China
Published: December 2020

Recently, the dynamics problems of nonlinear systems driven by noises have attracted considerable attention. The researches indicate that the noise plays a determinative role in system evolution. This irregular random interference does not always play a negative role in the macro order. Sometimes it can play a positive role. The various effects of noise are found in physics, biology, chemistry and other fields, such as noise-induced non-equilibrium phase transition, noise-enhanced system stability, stochastic resonance, etc. Especially, in the field of biology, the effects of noise on life process are significant. At present, a large number of researchers have studied the kinetic properties of the neuron system subjected to noises. However, these studies focus on the Gaussian noise, while the researches about non-Gaussian noise are less. In fact, it is found that all the noise sources among neuronal systems, physical systems and biological systems tend to non-Gaussian distribution. So it is reasonable to consider the effects of the non-Gaussian noise on systems, and it is closer to the actual process. Therefore, it has some practical significance to study the FHN system driven by the non-Gaussian noise and analyze the kinetic properties of this system. In this work, we study the stationary probability distribution (SPD) in FitzHugh-Nagumo (FHN) neural system driven by correlated multiplicative non-Gaussian noise and additive Gaussian white noise. Using the path integral approach and the unified colored approximation, the analytical expression of the stationary probability distribution is first derived, and then the change regulations of the SPD with the strength and relevance between multiplicative noise and additive noise are analyzed. After that, the simulation results show that the intensity of multiplicative noise, the intensity of additive noise, the correlation time of the non-Gaussian noise and the cross-correlation strength between noises can induce non-equilibrium phase transition. This means that the effect of the non-Gaussian noise intensity on SPD is the same as that of the Gaussian noise intensity. However, the non-Gaussian noise deviation parameter cannot induce non-equilibrium phase transition. Moreover, we also find that the increases of the multiplicative noise intensity and the cross-correlation strength between noises are conducive to the conversion of the exciting state into the resting state. And with the additive noise intensity and the correlation time increasing, the conversion of the resting state into the exciting state becomes obvious. Meanwhile, the increase of non-Gaussian noise deviation parameter increases the probability of staying in the resting state.