bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial-temporal characteristics of record-breaking temperature events over China in recent 46 years
Authors: Xiong Kai-Guo  , Feng Guo-Lin  , Wang Qi-Guang  , Hu Jing-Guo  ,   (1)扬州大学物理科学与技术学院，扬州  225009; (2)扬州大学物理科学与技术学院，扬州  225009；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029; (3)扬州大学物理科学与技术学院，扬州  225009；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029；国家气候中心，中国气象局气候研究开放实验室，北京  100081
Published: December 2020

Based on the theory of probability distribution of record-breaking events and daily high/low observational temperature data in China form 1960 to 2005, the spatial-temporal characteristics of record-breaking temperature are investigated. We found that the annual mean frequency of record-breaking high temperature is about 2.5 times greater than normal in 1976—2005, while for record-breaking low temperature is 4.5 times less. Record-breaking high temperature is obviously more than normal in Northwest, North China, Northeast and Tibet, while the record-breaking low temperature is obviously less than normal there. As to the relative trend of record-breaking temperature events, the record-breaking high temperature somewhat increases in most parts of China, but the record-breaking low temperature become less and less all over China. For the development trend of strength, the record-breaking high temperature events, have somet enhancement in high latitude areas of China, but the record-breaking low temperature events have no change or only eventually become weakening in this area and also in XinJiang and Tibet. It should to be payed attention that the strength of record-breaking low temperature events becomes obviously enhanced in south China. In studying the relationship of annual frequency of record-breaking high/low temperature events and pacific warm pool index, we found that there are significant correlations between them for most parts of China.
Soliton-like homotopic approximate analytic solution for a class of disturbed nonlinear evolution equation
Authors: Shi Lan-Fang  , Mo Jia-Qi  ,   (1)安徽师范大学数学系,芜湖  241000; (2)南京信息工程大学数理学院,南京  210044
Published: December 2020

The approximate solution for a class of disturbed nonlinear evolution equation is considered taking a simple and valid technique. We first introduce approximate solution of a corresponding typical differential equation. And then the approximate solution for a original disturbed nonlinear evolution equation is obtained using the homotopic mapping method.
Propagation property of ultra-short laser pulses in multi-level quantum system
Authors: Lu Jian-Qing  , Zhang Xiang-Yun  , Zhang Shi-An  , Jia Tian-Qing  , Sun Zhen-Rong  , Wang Zu-Geng  ,   (1)华东师范大学数学系，应用数学和交叉学科研究中心，上海  200062; (2)华东师范大学物理系，精密光谱科学与技术国家重点实验室，上海  200062
Published: December 2020

The propagation property of an ultrashort pulse in multi-level quantum system has been investigated with numerical method. A strong absorption is observed and its degree depends on the characteristic time of quantum system. For rather weak laser field, the self-induced transparency can still be observed with proper pulse area of the input ultrashort laser. When the ultrashort laser pulse becomes stronger, it will be split, and its basic split unit （i.e. the minimum area of a stably propagating laser pulse） A0 is not the same as that of two-level quantum system, which depends on the number of the excited states and their dipoles. Furthermore, after a rather long propagating distance, there only remains a shorter but more intense sub-pulse with an area of A0.
Theoretical study on molecular reaction dynamics of the SiH2 system
Authors: Feng Xing  , Zhu Zheng-He  , Liu Xiao-Ya  , Yang Xiang-Dong  , Huang Wei  ,   (1)四川大学原子与分子物理研究所,成都  610065; (2)四川大学原子与分子物理研究所,成都  610065；四川农业大学生命科学与理学院,雅安  625014; (3)中国工程物理研究院，绵阳  621900
Published: December 2020

The atomic and molecular reaction dynamics for Si（1Dg）+H2（0，0）and H（2Sg）+SiH（0,0） have been studied on the potential energy function SiH2（X1A1） by Monte-Carlo quasi-classical trajectory approach.It is shown that the reaction Si（1Dg）+H2（0，0）has no threshold energy，and the principal product of this reaction is SiH2（X1A1）.However, the reaction H（2Sg）+SiH （0,0） gives a great number of products of the interchange reaction of H（2Sg）+SiH （0,0）→Si（1Dg）+H2（0，0），and it has also no energy threshold.
Super-resolution characteristics of time-reversed electromagnetic wave
Authors: Ge Guang-Ding  , Wang Bing-Zhong  , Huang Hai-Yan  , Zheng Gang  ,   电子科技大学应用物理研究所，成都  610054
Published: December 2020

Time-reversed electromagnetic wave has the property of super-resolution in some special far-field circumstances. A model with the property of super-resolution was constructed and simulated by time-reversal technique. By analyzing the simulation results, we can find the main reason for realization of property of super-resolution. The research provides support for the design of compact multi-antenna wireless communication system.
Divergent characteristic of the second order moment of nonparaxial vector beams
Authors: Deng Xiao-Jiu  , Wang Guo-An  , Liu Cai-Xia  , Lai Chuan-Wei  ,   合肥工业大学物理系，合肥  230009
Published: December 2020

Based on the accurate expression of light intensity of nonparaxial vector beams at the transverse plane and the vectorial second order moment theory of light beam propagation，by applying rigorous vectorial diffraction theory of the angular spectrum representation，the nonparaxial propagation of any vectorial diffraction beam has been systemically investigated，the integral expressions of beam width，transversal divergence angle have been presented，and the divergent characteristic of the second order moment of nonparaxial vector beams has been demonstrated. The definitions of beam width，transversal divergence angle of non-paraxial vector beams and some related problems have been discussed.
Wigner functions of multiple-photon excited coherent states
Authors: Lan Hai-Jiang  , Pang Hua-Feng  , Wei Lian-Fu  ,   (1)柳州师范高等专科学校物理与信息科学系，柳州  545003；西南交通大学量子光电信息实验室，成都  610031; (2)西南交通大学量子光电信息实验室，成都  610031
Published: December 2020

Wigner functions in phase space are reconstructed for the excited coherent states，which are generated by applying the inverse of k-Boson operators repeatedly to the coherent states. The non-classicality of these states is discussed by calculating their Wigner functions in Fock-state space. Numerical results show that these excited coherent states always reveal non-classical characteristics，no matter whether the excited number k is even or odd，and also the corresponding non-classicality is more obvious with the number k increasing.
Sound field separation technique based on single surface measurement using pressure-velocity transducers
Authors: Zhang Yong-Bin  , Xu Liang  , Bi Chuan-Xing  , Chen Xin-Zhao  ,   合肥工业大学噪声振动工程研究所,合肥  230009
Published: December 2020

The sound field separation technique based on single surface measurement is investigated in this paper. A modified separation formula based on the spatial Fourier transform is presented to overcome the inherent singularity of the current single surface separation technique. However due to the wraparound error associated with fast Fourier transform （FFT）, the accuracy of separation technique based on FFT is not satisfactory and a novel separation method based on the statistically optimized nearfield acoustic holography is proposed to improve the separation. The simulations as well as experiments carried out with the p-u intensity probe produced by Microflown demonstrate the validity of the proposed modified formula and the effectiveness of the new separation method.
Cyclic shift keying spread spectrum underwater acoustic communication
Authors: He Cheng-Bing  , Huang Jian-Guo  , Han Jing  , Zhang Qun-Fei  ,   西北工业大学航海学院,西安  710072
Published: December 2020

Aimed at solving the problem of low data rate of direct sequence spread spectrum underwater acoustic communication and that of complexity of the receivers of M-ary spread spectrum underwater acoustic communication, cyclic shift keying spread spectrum underwater acoustic communication is proposed based on the good characteristic of spread sequences. At the transmitter, base waveform is cyclically shifted according to the input information. At the receiver, only one correlator is used to estimate the time delay and decode. Multi-code spread spectrum based on cyclic shift is presented. Lake experiments at both middle and long range were conducted for the proposed methods. Single and two code cyclic shift keying underwater acoustic communication were realized in the range of 15 km and the bandwidth of 2 kHz. The data rate was 438 bit/s with bit error ratio around 10-2—10-5. The result demonstrated the bandwidth efficiency and low complexity of the proposed methods and the applicability for long range underwater acoustic communication and multi-user underwater acoustic communication network.
Influence of bubble content on laser-induced cavitation bubble oscillation in glycerol-water mixture
Authors: Zhao Rui  , Xu Rong-Qing  , Liang Zhong-Cheng  , Lu Jian  , Ni Xiao-Wu  ,   (1)南京理工大学应用物理系，南京  210094; (2)南京邮电大学光电工程学院，南京  210003
Published: December 2020

The effect of viscosity and bubble content on cavitation bubble oscillation is investigated by the fiber-optical sensor based on the beam deflection in combination with theoretical analysis. The maximum bubble radius at each oscillating cycle in different viscous fluid is determined by experiment. It is observed that the maximum bubble radius at each oscillating cycle does not decrease but increases. A reasonable explanation based on experimental results and numerical calculation is given to this anomaly. The results indicate that both the bubble content and the viscosity have obvious influence on the bubble oscillation and it does increase during the bubble oscillating cycle.
Breakdown parameter in hybrid method
Authors: Lan Xu-Dong  ,   北京应用物理与计算数学研究所，北京  100094
Published: December 2020

The multiscale flow is a hot topic recently. The hybrid method by coupling different methods is the main approach to investigate multiscale flows.The two processes involved in hybrid method are determining interface position and transferring information through the interface. The paper discusses the existing breakdown parameters and proposes a unified form of the breakdwon parameter.
Plasma screening effect on the differential cross sections of collision ionization of H by He2+
Authors: Ding Ding  , He Bin  , Liu Ling  , Zhang Cheng-Hua  , Wang Jian-Guo  ,   (1)北京应用物理与计算数学研究所，北京  100088; (2)北京应用物理与计算数学研究所，北京  100088；辽宁大学物理学院，沈阳  110036; (3)辽宁大学物理学院，沈阳  110036
Published: December 2020

A classical trajectory Monte Carlo method is used to investigate the collision ionization of H by He2+ in Debye plasma, and the total and differential cross sections are obtained for collision energies of 5—400 keV/u in a large plasma parameter range. The interaction between charged particles is described by the Debye-Hückel model. Plasma screening changes the ionization energy and classical microcanonical distribution of bound electrons and the interaction between electron and the projectile, which result in the modification of ionization cross sections. It is found that both the total and differential cross sections increase with the increasing of screening interaction, and especially for energies below 10 keV/u, the cross sections are one to two magnitudes larger than those in the unscreened case. The emitted electron moves to the higher energy range, and the binary-encounter ionization mechanism becomes more important and a new hump appears due to the screening effect. Our unscreened cross section is in a good agreement with the experimental measurement for collision energies beyond 70 keV/u.
Spatial distributions of the intensity of luminescence and the vibrational temperature of single micro-discharge channel in air dielectric barrier discharge
Authors: Dong Li-Fang  , Yang Li  , Li Yong-Hui  , Zhang Yan-Zhao  , Yue Han  ,   河北大学物理科学与技术学院，保定  071002
Published: December 2020

A stable micro-discharge channel（filament）in air discharge is obtained by discharge cleaning method in a dielectric barrier discharge system with two water electrodes. The distributions of intensity of luminescence and the vibrational temperature of a single micro-discharge filament are measured from instantaneous anode to instantaneous cathode. It is found that the emission intensity of discharge filament presents a distribution like a goblet with base locating at instantaneous cathode in each half period of the applied voltage. The vibrational temperature reaches the maximum at the middle of gap of the two parallel electrodes and is the minimum at the instantaneous anode.
Synthesis and electric, magnetic properties of single crystalline and twin-crystalline Co-doped ZnO thin films
Authors: Lu Zhong-Lin  , Zou Wen-Qin  , Xu Ming-Xiang  , Zhang Feng-Ming  ,   (1)东南大学物理系,南京  210096; (2)东南大学物理系,南京  210096；成功大学物理系,台南  701；南京大学物理系,南京  210093; (3)南京大学物理系,南京  210093
Published: December 2020

c-oriented Co-doped ZnO （Zn0.96Co0.04O） thin films have been grown on the a-plane and c-plane sapphire substrates using molecular-beam epitaxy, respectively. In contrast to single crystalline Zn0.96Co0.04O film grown on a-plane sapphire, the film grown on c-plane sapphire were found to be twin-crystalline; some domains have a 30° rotation to reduce the large mismatch. The presence of these rotation domains in the twin-crystalline ZnO thin film causes much more carrier scattering at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers, as compared with those of the single crystalline one. X-ray absorption fine structure studies revealed that most Co ions were in divalent state and actually substituted into ZnO lattice without formation of any detectable secondary phase. As compared with just a small saturation moment in the single crystalline Zn0.96Co0.04O thin film, the much stronger ferromagnetism in the twin-crystalline one indicates that the ferromagnetic origin should be highly correlated with structural defects in the twin-crystalline film. The possible magnetic mechanisms were discussed.
Using conductive atomic force microscope on carbon nanotube networks
Authors: Zhao Hua-Bo  , Li Zhen  , Li Rui  , Zhang Zhao-Hui  , Zhang Yan  , Liu Yu  , Li Yan  ,   (1)北京大学化学与分子工程学院 物理与化学重点实验室，北京  100871; (2)北京大学物理学院，人工微结构与介观物理国家重点实验室，北京  100871
Published: December 2020

Conductive atom force microscopy observations have been performed on carbon nanotube networks. The results indicate that within an imaging range of several tens of micrometers the resistance of a carbon nanotube is much smaller than the contact resistance between two crossed carbon nanotubes and so the potential difference hardly appears along a carbon nanotube if the carbon nanotube network is electrically biased. Besides, if several semiconducting carbon nanotubes wind into a bundle, they tend to appear like metallic carbon nanotubes.
Band structure of phononic crystal constructed by Fibonacci super-cell on square lattice
Authors: Hao Guo-Jun  , Fu Xiu-Jun  , Hou Zhi-Lin  ,   华南理工大学物理系,广州  510640
Published: December 2020

Using the plane-wave expansion method, we study the band structure of a phononic crystal with water rods embedded in mercury to form a super-cell according to the two-dimensional Fibonacci array. It is found that each band splits into three sub-bands with the change of quasilattice constants and there exist intermediate states, which reflect the peculiar properties of quasiperiodic systems.
Electrical properties of the deformed carbon nanotube field-effect transistors
Authors: Liu Hong  , Yin Hai-Jian  , Xia Shu-Ning  ,   南京师范大学物理科学与技术学院，南京  210046
Published: December 2020

On the basis of the tight-binding theory, we derive the band structure formula of the deformed carbon nanotube. The results show that the band gap varies with increasing deformation, which shows that the deformation can change the nature of the conductivity of carbon between the metal-type and semiconductor-type. Especially for zigzag nanotubes，there are three different rules goveoning this translation, which is dependent on the remainder of n divided by 3. Furthermore, by using Natori theory on the field-effect transistor we study the current-voltage characteristics of deformed carbon nanotube field-effect transistors. For strain deformation, the conductivity of zigzag nanotube presents different characteristics with the remainder of n by 3. For armchair nanotubes, the conductivity does not change with the strain parameter. However, for torsion deformation, the conductivity rapidly increases, specially for the armchair tube. It has many obviously different conductivity behaviors between zigzag tubes and armchair tubes. At some special torsion angles, the conductivity of zigzag tube and armchair tube has obvious changes, which reveals the translation between metal-type and semiconductor-type conductivities.
Morphology and defect of a-GaN grown by metal orgamic chemical vapor deposition
Authors: Cui Ying-Chao  , Xie Zi-Li  , Zhao Hong  , Mei Qin  , Li Yi  , Liu Bin  , Song Li-Hong  , Zhang Rong  , Zheng You-Dou  ,   南京大学物理系，微结构国家实验室，江苏省光电信息功能材料重点实验室，南京  210093
Published: December 2020

On the substrate of r-sapphires a-GaN films grown by metal orgamic chemical vapor deposition was etched in molten KOH-NaOH for 1.0,1.5 and 2.0 min. Scanning electron microscope, atomic force microscope, X-ray diffraction and cathodoluminescence was used to study its morphology and defect. We find that etching for 1.5 min at the temperature of 400 ℃ is appropriate for a-GaN on sapphires substrate. Different from c-GaN which show hexagonal pits, a-GaN shows parallelogram strips. In the direction of c axis it is easier to be etched. That is because the polarity of a-GaN films is anisotropic which leads to different absorption capacities of OH ions in different directions. We also find hexagonal protuberance on the surface which is associated with threading dislocations.
Current phase relation in the superconducting tunnel junction
Authors: Wu Yi-Hua  , Wang Zhen-Yan  , Shen Rui  ,   南京大学物理系，固体微结构物理国家重点实验室，南京  210093
Published: December 2020

The dc Josephson current in the equal spin pairing superconducting tunnel junction is calculated in this paper. It is shown that the current phase relation is I∝sin 4φ when the orbital pairing symmetries of the two superconductors fall into the irreducible representations A and 2E of the magnetic point group D4, respectively.
Multi-scale modeling of radiation damage in FeCr alloy
Authors: He Xin-Fu  , Yang Wen  , Fan Sheng  ,   中国原子能科学研究院，北京  102413
Published: December 2020

Since irradiation experiments of ferritic/martensitic （F/M） FeCr alloys show that F/M steels undergo much less swelling than austenitic steels during neutron or charged particle irradiation，in addition, it is well-known that high chromium content of F/M alloys provide good resistance against corrosion, they are considered as one of the most attractive candidate materials for future nuclear facilities, such as Fusion Reactor, ADS and generation Ⅳ reactors. Although irradiation experiments can not be replaced by modeling, a purely experimental approach to understanding the effects of irradiation is also not practicable, so in recent years substantial progress has been made in the field of multi-scale modeling of radiation damage in F/M FeCr alloys. The present paper is a review of methods used and results achieved within the last couple of years, and some suggestions are put forward for the further improvements.
New infinite sequence exact solutions to the general lattice
Authors: Taogetusang  ,   The College of Mathematical Science, Inner Mongolia Normal University, Huhhot 010022, China
Published: December 2020

To seek infinite sequence exact solutions to nonlinear difference-differential equations, a kind of auxiliary equation of hyperbolic function type is intruduced, and the Bä,cklund transformation of the solutions to the equation and the formula of nonlinear supperposition of solutions are presented. Based on these and combing auxiliary equation with function transformation, the general lattice equation is chosen as example for which the infinite sequence exact solutionsto the equation are obtained.
Propagating solitons and chaotic behaviour of (2+1)-dimensional Korteweg-de Vries system
Authors: Wu Hong-Yu  , Ma Song-Hua  , Fang Jian-Ping  ,   Department of Physics,Zhejiang Lishui College,Lishui 323000,China
Published: December 2020

With a projective equation and a linear variable separation method, new exact solutions of the (2+1)-dimensional Korteweg-de Vries system(KdV) is derived. Based on the derived solitary wave excitation, we obtain the propagating solitons and study the chaotic behaviours with a new chaotic system.
Spreading of epidemics in complex networks with infective medium and spreading delay
Authors: Wang Ya-Qi  , Jiang Guo-Ping  ,   (1)Center for Control and Intelligence Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China; (2)Center for Control and Intelligence Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China, College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

In this paper, we propose a new susceptible-infected-susceptible (SIS) model with infective medium and spreading delay (MD-SIS) to study epidemic spreading in networks based on the mean-field theory. Theoretical analysis and simulation results show that the existence of infective medium and spreading delay can significantly enhance the risk of outbreak of epidemics and accelerate the epidemic spreading in the networks. For a given propagation rate, we found that the epidemic prevalence on the homogeneous network varies logarithmically with infection probability of infective medium and spreading delay respectively, and the epidemic prevalence on the scale-free network has a power-law relation with infection probability of infective medium, but a linear relation with spreading delay.
Image encryption based on arithmetic coding with order-1 Markov model
Authors: Duan Li-Li  , Liao Xiao-Feng  , Xiang Tao  ,   Department of Computer Science , Chongqing University,Chongqing 400044, China
Published: December 2020

Encryption based on compression can provide compression and encryption in a single step, in which redundancy is removed by compression and security is guaranteed by encryption. A novel secure arithmetic coding scheme based on order-1 Markov model is proposed in this paper, and it is applied to image encryption where images can be transmitted securely on the Internet and the proposed algorithm significantly improve the compression efficiency of coding. Experimental results and security analyses indicate that, the algorithm can not only resist existing attacks based on arithmetic coding, but also be immune to other cryptanalysis.
Stability analysis of a relative rotation time-delay nonlinear dynamic system
Authors: Liu Hao-Ran  , Zhu Zhan-Long  , Shi Pei-Ming  ,   (1)Institute of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China; (2)Institute of Information Technology and Engineering, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The dynamic equation of a relative rotation time-delay nonlinear dynamic system is established, which contains time-varying stiffness, nonlinear damping and harmonic excitation. The bifurcation equation of time-delay dynamic system is deduced by the method of multiple scales. The structure stability of the system is studied by singularity theory, the transfer concourse of primary resonance equation and topological structure of bifurcation function are obtained. The dynamic stability of the system is discussed by the Hopf bifurcation theory and the condition for the limit cycle occurrance is given. Moreover, it is indicated by numerical method that parameters of time delay affect the limit cycle amplitude.
Drag reduction in turbulent channel flow by spanwise oscillating Lorentz force
Authors: Mei Dong-Jie  , Fan Bao-Chun  , Huang Le-Ping  , Dong Gang  ,   Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Direct numerical simulation (DNS) of a turbulent channel flow is carried out to investigate the effect and mechanism of using spanwise oscillating Lorentz force to reduce boundary layer friction.We discussed the influence of Lorentz force intensity St and oscillating frequency T+ on the drag reduction effect and turbulent burst events. The results suggest the varying tendencies with St or T+ of the frequency of the turbulent bursts events are opposite to the intensity of the turbulent bursts events,and there exists an optimal parameter to achieve the largest amount of drag reduction.The composite effect of St and T+ can be well described by the equivalent spanwise wall velocity W+.
Generalized Stenfan-Boltzmann law of the Dirac field of Barriola-Vilenkin black hole
Authors: Meng Qing-Miao  , Li Zhong-Rang  , Li Yu-Shan  ,   Department of Physics, Heze University, Heze 274015, China
Published: December 2020

Using the thin film model of black hole, the thermal radiation laws of the Barriola-Vilenkin black hole are studied. We obtained the result that the thermal radiation of the black hole always satisfies the generalized Stenfan-Boltzmann law. The derived generalized Stenfan-Boltzmann coefficient is no longer a constant. When the cut-off distance and the thin film thickness are both fixed, it is a proportional coefficient related to the space-time metric near the event horizon and the average radial effusion velocity of the radiation particles in the thin film. The radiation energy flux of the Dirac field of the Barriola-Vilenkin black hole is proportional to the average radial effusion velocity of the radiation particles in the thin film, and inversely proportional to the square of the black hole mass.
First-principles calculation of elastic and thermodynamic properties of copper nitride
Authors: Li Shi-Na  , Liu Yong  ,   College of Science, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

A first-principles full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory is applied to the study of the static equilibrium lattice structure as well as the elastic constants of the cubic anti-ReO3 structural copper nitride(Cu3N). The quasi-harmonic Debye model, in which the phononic effects are considered, is used to investigate the thermodynamic properties of Cu3N. The pressure and temperature dependences of lattice constant, heat capacity and thermal expansion coefficient are successfully obtained . The bulk modulus and Debye temperature are also calculated at different pressures and temperatures.
Photoacoustic signal saturation characteristics of concentrated gases
Authors: Li Zhi-Hui  , Yuan Chang-Ying  , Meng Gui  , Yan Zheng-Xin  , Shang Li-Ping  ,   (1)National School of Defense Technology, Southwest University of Science and Technology, Mianyang 621010,China; (2)School of Energy Engineering, Xi’an University of Science and Technology, Xi’an 710054, China; (3)School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010,China
Published: December 2020

The photoacoustic (PA) spectrum of methane in the concentration range of 5%—100% has been experimentally investigated by coustant direct current drive coupling mechanical chopper technology. The results indicated that abnormal signal saturation occurred at high gas concentrations. The main reasons and its correlated factors of the photoacoustic signal has been quantitatively analyzed based on signal absorption and photoacoustic principles. It is found that the change in coupling coefficient of sound source and optical cavity modes caused by the intensity of incident light absorbed by gas sample is the major reason, and a criterion was put forward for signal saturation depth estimation.
Gas concentration and temperature reconstruction by genetic simulated annealing algorithm based on multi-wavelengths diode laser absorption spectroscopy
Authors: Li Ning  , Weng Chun-Sheng  ,   National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Gas concentration and temperature distribution reconstruction is realized based on tunable diode laser absorption spectroscopy. A measurement system using wavelength multiplexing technology with four absorption transitions is designed to reduce the number of projections and enrich the gas absorption measurement data. According to the nonlinear system established, a hybrid algorithm based on genetic algorithm and simulated annealing algorithm is introduced to obtain the global optimization and improve the search efficiency. A model for H2O concentration and temperature distribution in combustion is assumed, and numerical simulation is utilized to reconstruct the images with the transitions within 1.3—1.5 μm range. Both concentration and temperature distribution reconstruction results are in agreement with the model. The influence of random errors in projections on reconstruction is also analyzed. The increased error in projection would lead to larger mean square error of temperature reconstruction results, but little affect the concentration reconstruction results.
Time-domain inverse scattering problem for two-dimensional frequency-dispersive lossy media
Authors: Liu Guang-Dong  , Zhang Ye-Rong  ,   College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

A time-domain inverse scattering method for reconstruction of dispersive dielectric properties of two-dimensional (2D) lossy media based on the Debye model by using functional analysis and variational methods is developed. Firstly, the approach formulates a cost functional to turn the inverse problem into a constrained minimization problem according to least squares criterion, then the resulting constrained minimization problem is transformed into an unconstrained minimization problem by using a penalty function technique, and then the closed Fréchet derivatives of the Lagrange function with respect to the properties are derived based on the calculus of variations. Finally, one can solve the resulting problem by using any gradient-based algorithm and the finite-difference time-domain (FDTD) method. Also, the first-order Tikhonov’s regularization is adopted to cope with noise and the ill-posedness of the problem. In numerical example, the presented algorithm is applied to a 2D breast model with the help of the Polak-Ribière-Polyak (PRP) conjugate gradient (CG) method, and the results demonstrate its feasibility.
Electromagnetically induced absorption and transparency in a closed lambda-shaped four-level system
Authors: Li Xiao-Li  , Zhang Lian-Shui  , Yang Bao-Zhu  , Yang Li-Jun  ,   College of Physical Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

A quasi-lambda four-level system shows both electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT). In addition to an optical coupling field and a probing field, there is a radio field which interacts with two excited state hyperfine levels of the quasi-lambda four-level system consisting of two excited state hyperfine levels and two ground state hyperfine levels. If a driving field which interacts with two ground state hyperfine levels is introduced, the quasi-lambda four-level system is modified to a closed-lambda four-level system. The behaviors of the driving field and radio field are studied in this paper and it is seen that the occurence of EIA or EIT and the whole probing properties are controlled by the Rabi frequencies of both driving field and radio field.
Evolution of silicon surface microstructure induced by Nd:YAG nanosecond laser
Authors: Yuan Chun-Hua  , Li Xiao-Hong  , Tang Duo-Chang  , Yang Hong-Dao  , Li Guo-Qiang  ,   College of Science, Southwest University of Science and Technology, Laboratory of Matter Characteristic Research Under Extreme Condition, Laser and Plotoelectron Laboratory, Mianyang 621010, China
Published: December 2020

We investigate the evolution of surface microstructure created on single crystal silicon wafer by irradiation of cumulative Nd:YAG nanosecond laser pulses (wavelength 532 or 355 nm) in vacuum. The wavy structures are formed on silicon surface by 532 or 355 nm laser on early stage of laser pulse irradiation, and nearly concentric but slightly disordered semi-circular rings are formed under 355 nm laser pulse irradiation. With the number of laser pulses increasing, the structures gradually evolved into the concave-convex structures which are similar to the beads. And finally quasi-ordered arrays of conical spikes are formed. The growth of these microstructures depends on the capillary waves and self-organization of structures. We find that the cross-ring structures are caused by the superposition of some wavy structures created by capillary waves in the process of 355 nm laser pulses irradiation.
Enhancement of contrast ratio in chirped pulse amplified laser system by cross-polarized wave generation
Authors: Liu Cheng  , Wang Zhao-Hua  , Li Wei-Chang  , Liu Feng  , Wei Zhi-Yi  ,   (1)Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China;(2)Department of Applied Physics, National University of Defense Technology, Changsha 410073, China
Published: December 2020

This paper reports our experimental research on the laser contrast ratio enhancement in the XL-Ⅲ (eXtreme Light Ⅲ) facility with the technology of cross-polarized wave (XPW) generation. Based on the theoretical analysis of the relerant principles, we introduced an XPW filter in the facility, which was upgraded with a double chirped pulse amplification (DCPA) scheme. Under optimized system design and alignment, we measured the conversion efficiency from fundamental wave to cross-polarized wave to be higher than 10%. The pre-pulses in nanosecond scale were deeply suppressed and the contrast ratio in picosecond scale was enhanced from 10-5 to 10-7. Our results show the XPW generation provides an effective technique to improve the contrast ratio of a Chirped-pulse amplification laser system, which is a key issue in ultrahigh intensity laser-matter researches.
Propagation of femtosecond chirped Gaussian pulse in dense three-level Λ-type atomic medium
Authors: Wang Zhen-Dong  , Liang Bian  , Liu Zhong-Bo  , Fan Xi-Jun  ,   (1)College of Physics and Electronics, Shandong Normal University, Jinan 250014, China; (2) College of Physics and Electronics, Taishan University, Taian 271021, China
Published: December 2020

We investigate propagation of femtosecond chirped Gaussian laser pulse in a dense three-level Λ-type atomic medium by using the numerical solution of the full Maxwell-Bloch equations without the slowly varying envelope and the rotating-wave approximations, and the solution is obtained by PC-FDTD method. It is shown that, variation of the sign and size of the chirp coefficient has considerable effect on pulse propagation property, and the effect is closely relative to size of the pulse area. When the area of chirped pulse is smaller than 4π, splitting doesn’t occur and the chirped pulse evolves gradually to an approximate normal Gaussian pulse (C=0), and this characteristic doesn’t vary with the chirp coefficient varying. However, variation of the chirp coefficient will changed the amplitude and group velocity of the pulse. For the positive chirp(C>0), amplitude and group velocity of the pulse decrease with chirp coefficient increasing, for the negative chirp(CC increasing. Both the chirped pulses with area equal to larger than 4π will split into sub-pulses of different numbers and shapes, the time and number of the pulse splitting will be determined by the sign and size of the chirp coefficient. But in the two cases, the pulse splitting patterns are much different, and the effects of the coefficient are also different. When the pulse area equals 4π, larger chirp coefficient will lead to increased sub-pulse number, but when the pulse area is larger than 4π, larger chirp coefficient will lead to decreased sub-pulse number. In addition, regardless of pulse area being larger or smaller, changing sign and size of the chirp coefficient always produces obvious effect on the atomic population.
Reflectivity uncertainty analysis of planar mirror calibration in BSRF
Authors: Chen Bo-Lun  , Yang Zheng-Hua  , Cao Zhu-Rong  , Dong Jian-Jun  , Hou Li-Fei  , Cui Yan-Li  , Jiang Shao-En  , Yi Rong-Qing  , Li San-Wei  , Liu Shen-Ye  , Yang Jia-Min  ,   State Key Laboratory of Laser Fusion, Laser Fusion Research Center, China Academy of Engineeing Physics, Mianyang 621900, China
Published: December 2020

A key diagnostic for absolute radiation flux and radiation temperature in hohlraum experiments is the Dante soft x-ray spectrometer in which grazing incidence x-ray mirrors are used to diminish the high energy response of the filters. The reflectivities of planar mirrors made of different materials were calibrated in BSRF in 2009.Considering both the influence of the source such as the spectra resolution,harmonic and the attenuation of the source intensity and the influence of the coherence of two detectors responses,we give the corrected mirror reflectivities and the uncertainty, including the statistical uncertainty of the expermental data.
Properties of photon counting imaging system with Si thin films
Authors: Zhao Fei-Fei  , Liu Yong-An  , Hu Hui-Jun  , Zhao Bao-Sheng  ,   (1)State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119, China; (2)State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119, China, Graduate School of Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

The Si thin films on ceramic substrates,which were fabricated by electron beam evaporation,were applied as charge induction layers in photon counting imaging system with induction readout. The structures and micrograph of Si thin films were studied. The X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) images indicate that the thin film has amorphous structure and is coarse due to the lattice boundary of ceramic substrate. The experimental setup was established and the detector resolution,counting rate,pulse height distribution curves etc., with different Si film thickness were compared. The results suggest that the film thickness influences on spatial resolution less than on the counting rate. Moreover,the properties of the system with Si and Ge thin films of the same resistance were compared,which shows that the properties such as distortion,counting rate and dark count rate are better with the Si films.
Hamilton’s principle based on thermomass theory
Authors: Song Bai  , Wu Jing  , Guo Zeng-Yuan  ,   (1)College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; (2)Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, School of Aerospace, Tsinghua University, Beijing 100084, China
Published: December 2020

Based on thermomass theory, the Hamilton's principle as well as the Lagrangian equations governing the motion of thermomass were established by methods analogous to those of classical mechanics. With the kinetic energy of thermomass taken into consideration, the Hamiltons principle for thermomass is expected to be capable of dealing with non-Fourier phenomena. When the kinetic energy is small enough to be ignored, the principle gets back to Fourier transfer. The application of Lagrangian equations was illustrated by the approximate solution of a 1D transient heat conduction problem with heat source. The unification of thermal and mechanical theories was demonstrated from the perspective of analytical mechanics, the drawbacks of existing theory are discussed, a new way to the approximate solution of heat transfer problem was suggested, and in the meantime the concepts of thermomass and energy of thermomass were to some extent justified.
A symmetric product of two optimal third-order force gradient symplectic algorithms
Authors: Li Rong  , Wu Xin  ,   School of Science, Nanchang University, Nanchang 330031, China
Published: December 2020

This paper provides two new fourth-order force gradient symplectic intrgrators,each of which is obtained from a symmetric product of two identied optimal third-order force gradient symplectic algorithms reported in the literature. They are both greatly superior to the fourth-order non-gradient symplectic method of Forest and Ruth in the accuracy of either energy on chaotic perturbed Kepler problems or the energy eigenvalues for one-dimensional Schrö,dinger equations. So are they to the known optimalfourth-order force gradient symplectic scheme.
Plasma convergence time of radiation hohlraum with single-end drive on SG-III prototype laser facility
Authors: Cao Zhu-Rong  , Li San-Wei  , Jiang Shao-En  , Ding Yong-Kun  , Liu Shen-Ye  , Yang Jia-Min  , Zhang Hai-Ying  , Yang Zheng-Hua  , Li Hang  , Yi Rong-Qing  , He Xiao-An  ,   Research Center of Laser Fusion, Chinese Academy of Engineering Physics, Mianyang 621900,China
Published: December 2020

Plasma convergence time of half-hohlraum target with single-end drive by 8 bundled lasers are researched on SG-III prototype laser facility. Four radiation sources were established by changing the structure of target bottom. The relation between plasma radial convergence time obtained by x-ray framing camera and radiation temperature from soft x-ray spectrometer have been investigated. The results showed that plasma radial convergence time is directly proportional to radiation temperatures on different structures of target bottom, which lengthens as radiation temperature increases.
Impact of injecting positions on penetration and deposition of supersonic molecular beam on Tokamak
Authors: Jiao Yi-Ming  , Yao Liang-Hua  , Feng Bei-Bin  , Chen Cheng-Yuan  , Zhou Yan  , Shi Zhong-Bing  , Dong Jia-Qi  , Duan Xu-Ru  ,   Southwestern Institute of Physics, Chengdu 610041, China
Published: December 2020

Fuelling and particle control are important topics for ITER physics. Because of the low efficiency of gas puffing and the high cost of pellet injection, other methods were explored in the last decades. A new method for plasma gas fueling, the pulsed supersonic molecular beam injection (SMBI) was successfully developed at Southwestern Institute of Physics in China and applied on HL-1M and HL-2A devices in recent years. SMBI possesses a great advantage over conventional gas puffing, mainly due to the higher instantaneous fueling intensity and speed, smaller spread of velocity and angular distribution of the particles than the latter. In this paper, we report the experiment results of the SMB injected from LFS and HFS in HL-2A device, the effect of  Δ B on SMB penetration is considered. During SMB injection in Tokamak, there is a rapid movement of the ablation beam substance towards the outward major radius R direction. The favorable injection from the high field side in order to promote deeper fuel penetration can be obtained. The motion has been attributed to a vertical curvature and  Δ B drift current induced inside the ionized ablated SMB particles by the 1/R toroidal field variation. The uncompensated vertical drift current inside the weakly diamagnetic ablation particles will cause charge separation at the plasma edge. The resulting electrostatic field induces the  E×B  drift to the large R side of the torus.
Preionization of buffer chamber in ATON Hall thruster
Authors: Liu Hui  , Wu Bo-Ying  , E Peng  , Duan Ping  ,   (1)Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150001, China; (2)Department of Mathematics, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

ATON is a new type of Hall thruster proposed in the 1990s, while the buffer chamber is a new structure used in it. In this paper, the main functions of buffer chamber are analyzed, and the method by adopting additional electric source is proposed to increase the preionization rate. Then the particle in cell method is used to simulate the plasma behavior in it. The numerical results show that additional electric power source can increase preionization rate effectively.
Application of wavelet transform in the dynamic frequency spectrum analysis of magnetohydrodynamics oscillations on HT-7 Tokamak
Authors: Ma Tian-Peng  , Hu Li-Qun  , Chen Kai-Yun  ,   (1)Department of Basic Sciences, Beifang Ethnic University, Yinchuan 750021, China; (2)Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Gaussian complex wavelet transform was used in the dynamic frequency spectrum analysis of HT-7 MHD (magneto-hydrodynamic) oscillations. It is shown that this method can provide good temporal resolution and spatial resolution, which is suitable to analyze the dynamic frequency spectrum of MHD oscillations. Typical discharges with sawtooth and MHD instabilities are analyzed with this method. The results show that the oscillation frequency is associated with the plasma pressure gradient.
Molecular dynamics simulation of temperature effects on CF+3 etching of Si surface
Authors: Qin You-Min  , Zhao Cheng-Li  , He Ping-Ni  , Gou Fu-Jun  , Ning Jian-Ping  , Lü Xiao-Dan  , Bogaerts A.  ,   (1)Institute of Plasma Surface Interactions, Guizhou University, Guiyang 550025, China; (2)Institute of Plasma Surface Interactions, Guizhou University, Guiyang 550025, China, Material and Metallurgy, College of Guizhou University, Guiyang 550003, China; (3)Key Laboretory of Radiation Physics and Technology Ministry of Education, Chengdu 610064, China, Foundation of Material Institute for Plasma Physics, 3439 MN Nieuwegein, Netherlands; (4)Research Group PLASMANT, University of Antwerp, B-2610
Published: December 2020

Molecular dynamics method was employed to investigate the effects of the reaction layer formed near the surface region on CF+3 etching of Si at different temperatures. The simulation results show that the coverages of F and C are sensitive to the surface temperature. With increasing temperature, the physical etching is enhanced, while the chemical etching is weakened. It is found that with increasing surface temperature, the etching rate of Si increases. As to the etching products, the yields of SiF and SiF2 increase with temperature, whereas the yield of SiF3 is not sensitive to the surface temperature. And the increase of the etching yield is mainly due to the increased desorption of SiF and SiF2. The comparison shows that the reactive layer plays an important part in the subsequeat impacting, which enhances the etching rate of Si and weakens the chemical etching intensity.