bluuebunny/crossref_metadata_2025 huggingface dataset:
Amorphous/crystalline blend effects on the performance of polymer-based photovoltaic cells
Authors: Peng Rui-Xiang  , Chen Chong  , Shen Wei  , Wang Ming-Tai  , Guo Ying  , Geng Hong-Wei  ,   (1)中国科学院等离子体物理研究所，合肥  230031; (2)中国科学院等离子体物理研究所，合肥  230031；中国科学院新型薄膜太阳电池重点实验室，合肥  230031；安徽建筑工业学院材料科学与工程系，合肥  230022
Published: December 2020

Bilayer TiO2/polymer photovoltaic cells are prepared by using regioregular poly（3-hexylthiophene） （P3HT） and branched poly（ethyleneimine） （BPEI） as an additive to P3HT. Influences of BPEI, an amorphous polymer, on the performance of bilayer TiO2/P3HT cells are investigated by means of steady-state current-voltage measurements and dynamic intensity-modulated photovoltage spectroscopy, in combination with differential thermal analysis, UV-vis absorption and photoluminescence spectroscopy. Due to the high crystallinity of P3HT, bilayer TiO2/P3HT cell exhibits a poor performance. As P3HT is blended with BPEI in the weight ratio of WBPEI/P3HT=1％—5％, the performance of the devices is greatly improved; in particular, as WBPEI/P3HT= 1%, the cell exhibits an open-circuit voltage of 0.8V and a short-circuit current of 20μA/cm2. Results show that the influence of BPEI on the cell performance originates from the changed interfacial contact at TiO2/P3HT interface rather than the varied optical properties of P3HT in P3HT-BPEI blend. BPEI imposes two competitive effects on interfacial contact between TiO2 and P3HT, depending on the compositional structure of the blend. On one hand, BPEI improves the interfacial contact by reducing the crystallinity of P3HT and enhancing the interaction between P3HT and TiO2. On the other hand, the interfacial contact will become worse with more BPEI chains accumulating on TiO2 surface. A good contact at TiO2/P3HT interface facilitates the access to a high exciton dissociation efficiency, a long lifetime of photogenerated electrons and further a high device efficiency. The results presented in this paper are expected to provide new insights and a novel strategy for improving the performance of polymer-based photovoltaic cells.
Study of vibro-acoustography with high spatial resolution based on sector array transducers
Authors: Zhao Gui-Min  , Lu Ming-Zhu  , Wan Ming-Xi  , Fang Li  ,   西安交通大学生物医学信息工程教育部重点实验室，西安  710049
Published: December 2020

This study investigates the vibro-acoustography of sector array transducers. Based on the vibro-acoustography and basic sector-array field theory, a modified and accurate velocity potential function is obtained. We further calculated and simulated the point spread function （PSF） of the system, designed the phantom of tissue, and simulated the phantom imaging. In the end, the influencing factors on spatial resolution with sector array transducers are analyzed on the basis of the simulation results. The results reveal that high resolution and contrast can be achieved, and this imaging method is of great value in detecting thermal lesion after high intensity ultrasound surgery and so on. The resolution will be improved by increasing central frequency, reducing geometric focal distance, and using transducers with larger aperture size.
The synthesis of polyacrylic acid lead as radiation-protection composite materials and its radiation shielding properties
Authors: Zhang Yu  , Dai Yao-Dong  , Chang Shu-Quan  , Kang Bin  ,   南京航空航天大学材料科学与技术学院，南京  210016
Published: December 2020

Polyacrylic acid （PAA） lead was successfully prepared as radiation-protection materials via graft copolymerization route. The product was characterized and analyzed with Fourier transform infrared spectroscopy （FT-IR） and scanning electron microscopy （SEM）. Gamma energy-spectrum measurement was carried out to evaluate its radiation-shielding properties. EGSnrc user code was also employed to theoretically simulate its above properties based on Monte Carlo method and analyze the influences of this material on the fluence and dose in the detecting area. The results revealed that this composite material has excellent radiation-shielding ability and this ability decreased with the increase of γ-ray energy. According to our theoretical simulation, in pure air, the change of fluence is discontinnous and looks like a ladder whose step width beomes narrower grdually and the dose increased slowly whith depth. When the sample was put into the air, in the air medium area, the changes of fluence and dose were no longer related with ray energy but with the sample thickness, while in the sample medium area, the changes of fluence and dose were not rectilinear and the rate of changes makes an obviously turn at the boundary between the sample and air.
The long range correlation of East Asia’s atmosphere
Authors: Wang Qi-Guang  , Hou Wei  , Zheng Zhi-Hai  , Gao Rong  ,   (1)国家气候中心，中国气象局气候研究开放实验室，北京  100081; (2)扬州大学物理科学与技术学院，扬州  225002；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)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

The paper investigates the height and temperature fields reanalysis data of NCEP/NCAR by means of detrended fluctuation analysis method, and gives their scaling exponent distribution of East Asia region. The empirical investigation indicates that both of height field and temperature filed have the property of long range correlation, which matches with the features of space distribution as a whole. As for the grid data of the same layer, the long range correlation varies obviously when the latitude changes. The low-latitude areas near the equator have a bigger scaling exponent and a better long range correlation, whereas the mid-latitude and high latitude areas have a smaller scaling exponent and a worse long range correlation. The average scaling exponent increases with the layer growth of height field data, and the scaling exponent varies obviously when the latitude changes. The scaling exponent of Qinghai-Tibet Plateau is obviously greater than other areas at the same latitude. For the data of temperature, the average scaling exponent first decreases with the layer growth then increases, and the average scaling exponent has a definite latitude trait. All in all, the scaling exponent of height field’s long range correlation is greater than that of temperature field. The investigation for different seasons displays that the long range correlation exists in height field and temperature field as well. And we find that the scaling exponent of winter time is greater than that of other seasons. This may provide a theory for the summer flood season forecast which is based on the winter information.
Lie symmetries and Noether conserved quantities of generalized nonholonomic mechanical systems
Authors: Dong Wen-Shan  , Huang Bao-Xin  ,   潍坊学院物理与电子科学系，潍坊 261061
Published: December 2020

In this paper we study the Lie symmetries and Noether conserved quantities of generalized nonholonomic mechanical systems， and establish the determining equations， the restriction equations and the additional restriction equations. The structure equation and the form of Noether conserved quantities are obtained. The inverse problems of Lie symmetries are discussed and an example to illustrate the application of the result is given.
Experimental study on smoothing by spectral dispersion using linear frequency-modulated pulse
Authors: Zhang Rui  , Wang Jian-Jun  , Su Jing-Qin  , Liu Lan-Qin  , Deng Qing-Hua  ,   中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

Precise physical experiments place strict requirements on target illumination uniformity in inertial confinement fusion research. Currently, the main stream of beam smoothing technology adopted in solid-state laser driver combines smoothing by spectral dispersion （SSD）, phase plate and beam overlapping. A new smoothing method aimed at indirect-drive laser fusion is studied here, which uses linearly modulated light and angular spectral dispersion. After using this technique, high frequency modulations on the far field could be smoothed. In the meantime, near field after the dispersion grating could be smoothed too. Experimental results show that the measured spectrum is similar to the simulated one. Phase modulator is not necessary in this method, while it is a crucial element in traditional SSD method.
Geometric representation of Noether symmetry for dynamical systems
Authors: Liu Chang  , Zhao Yong-Hong  , Chen Xiang-Wei  ,   (1)北京理工大学应用力学系，北京  100081; (2)商丘师范学院教务处，商丘  476000; (3)商丘师范学院物理与信息工程系，商丘  476000
Published: December 2020

In this article Noether symmetry of Lagrange systems, Hamilton systems and Birkhoff systems are discussed by geometric methods. And the corresponding Noether conserved quantities are deduced.
Molecular structure and electronic spectrum of CaS under electric fields
Authors: He Jian-Yong  , Long Zheng-Wen  , Long Chao-Yun  , Cai Shao-Hong  ,   贵州省光电子技术与应用重点实验室，贵阳 550025；贵州大学物理系，贵阳 550025
Published: December 2020

The method B3LYP of the density functional theory （DFT） at 6-311++G（d, p） level has been used to obtain equilibrium structure of the ground state of CaS molecule, optimized parameters, dipole moment, charge distribution, HOMO energy level, LUMO energy level, energy gaps, infrared spectrum and harmonic frequency under different external electric fields ranging from -0.03 a.u. to 0.045 a.u. The results shows that with increasing the external electric field, the molecular geometry becomes strongly dependent on the field strength and behaves asymmetrically to the direction of the applied electric field. At the same time, the bond length and dipole moment μ of the ground state are changed from decreasing to increasing. At F=0.02 a.u., the minimum of bond length and dipole moment are 0.2289 nm and 1.5969 D. HOMO energy level and LUMO energy level are changed from increasing to decreasing. A decrease of the total energy gaps are found in the process of increasing the external electric field, which tells that the molecule is excited easily under a specific electric field. Excitation energies and oscillator strengths are affected by the external electric field. These results are useful for the study on the electroluminescence of CaS molecule.
Mutual coupling suppressing based on a new type electric resonant SRRs in microstrip array
Authors: Tang Ming-Chun  , Xiao Shao-Qiu  , Gao Shan-Shan  , Guan Jian  , Wang Bing-Zhong  ,   电子科技大学应用物理研究所，成都 610054
Published: December 2020

Based on electric resonance principle and image theory, a new type of periodical grounded edge-coupled split ring resonator （SRR） structure is designed in this paper. Then the proposed metamaterial structure is used to suppress the mutual coupling between elements in microstrip array. Compared with the traditional structures for suppressing mutual coupling, the proposed metamaterial structure has not only small size （to be specific, a small thickness of 0005 operation wavelength）, but also the ability to suppress the mutual coupling with excellent performance （-168 dB）. The obtained results indicate that the metamaterial has an enormous potential in designing compact and high-performance microstrip arrays.
Investigation on a long pulse relativistic extended interaction cavity oscillator
Authors: Huang Hua  , Luo Xiong  , Lei Lu-Rong  , Luo Guang-Yao  , Zhang Bei-Zhen  , Jin Xiao  , Tan Jie  ,   中国工程物理研究院应用电子学研究所，绵阳  621900
Published: December 2020

The mechanism of modulation and rf extraction of an S-band on an injection locked, long pulse, relativistic extended interaction cavity oscillator （REICO） is studied in this paper by experiment, theory, and simulation. The origin of pulse shortening and mode competition of the REICO driven by the long pulse intense relativistic electron beams （IREBs） is explored. The modified structure of REICO with coupler is proposed for the first time, which suppresses the pulse shortening and mode competition remarkably. The pulse width of the modulated IREB is increased from 60 ns to 140 ns, and the magnitude of the modulated IREB is increased from 2 kA to 5 kA. The microwave radiation power and efficiency are promoted obviously after adjusting the parameters of the IREB and the leading magnetic field. Using a 580 kV, 48 kA, 210 ns electron beam with 11 T leading magnetic field, more than 400MW radiated power was extracted in 160 ns FWHM pulses at 289 GHz. The power efficiency is 27%, and the energy efficiency is 23%. The radiated power is 400 MW and the FWHM pulse is 184 ns when pulse repetition frequency of IREBs is 20 Hz. The experimental results are well consistent with the simulations. The injection locked REICO generates high power microwave of power 400 MW with pulse width 100 ns.
An atomistic simulation of structure and thermal stability of［110］Au nanowire during continuous heating
Authors: Tian Hui-Chen  , Liu Li  , Wen Yu-Hua  ,   (1)呼伦贝尔学院物理与电子信息学院，呼伦贝尔  021008; (2)呼伦贝尔学院物理与电子信息学院，呼伦贝尔  021008；厦门大学物理系，厦门大学理论物理与天体物理研究所，厦门  361005; (3)厦门大学物理系，厦门大学理论物理与天体物理研究所，厦门  361005
Published: December 2020

We have used molecular dynamics method with quantum corrected Sutton-Chen type many-body potentials to study the structure and thermal stability of［110］ Au nanowires, and investigate its melting mechanism and shape evolution by introducing the Lindemann index and the minimum radius. The results show that the transformation from fcc to hcp structure occurs in local regions of nanowire before premelting. The melting starts from surface and evolves into interior region, resulting in the overall melting of the nanowire. Subsequently, the neck occurs and induces the final breaking of nanowire into a spherical cluster.
First-principles study of electronic transport properties of C20F20 molecule
Authors: An Yi-Peng  , Yang Chuan-Lu  , Wang Mei-Shan  , Ma Xiao-Guang  , Wang De-Hua  ,   鲁东大学物理与电子工程学院,烟台  264025
Published: December 2020

Using first-principles density functional theory and non-equilibrium Green’s function method, we investigated the electronic transport properties of C20F20 molecule. The calculation shows that the zero bias equilibrium conductance of C20F20 molecule is 0.385 G0. The I-V curve presents good linear characteristic. Under finite bias voltage the molecule displays stable conductance characteristic, and could be made as one steadying resistance molecular device.
The study on the electronic structure and optical properties of OsSi2
Authors: Li Xu-Zhen  , Xie Quan  , Chen Qian  , Zhao Feng-Juan  , Cui Dong-Meng  ,   贵州大学理学院，贵州大学新型光电子材料与技术研究所，贵阳  550025
Published: December 2020

Electronic structure, densities of states and optical properties of orthorhombic OsSi2 was calculated by the first-principle density function theory pseudopotential method. The calculated results show that OsSi2 is an indirect semiconductor with the band gap of 0.813 eV, the valence bands of OsSi2 are mainly composed of Os 5d and Si 3p, the conduction bands are mainly composed of Si 3p, 3s as well as Os 5d . The stastic dielectric function ε1（0） is 15.43, the reflectivity n0 is 3.93. Furthermore, the dielectric functions, refractivity index, reflectivity, absorption, conductivity and loss function of OsSi2 are analyzed in terms of the calculated band structure and densities of states. The results offer theoretical data for the design and application of OsSi2.
Effect of pressure on the Fermi resonance of benzene
Authors: Zhou Mi  , Zhang Peng  , Liu Tie-Cheng  , Xu Da-Peng  , Jiang Yong-Heng  , Gao Shu-Qin  , Li Zuo-Wei  ,   超硬国家重点实验室，吉林大学物理学院，长春  130023
Published: December 2020

Raman spectra of benzene have been obtained at pressure of 13 GPa. The results shows that with the increase of pressure，all the Raman bands blue shift，accompanied with the splitting and change of relative intensity of some spectral bands. For the vibrational Fermi resonance bands ν1+ν6—ν8，according to the Betran theory，the unperturbed peak separation Δ0 increases with pressure，which is due to the ratio of frequency-pressure of the combined ν1+ν6 bands is larger than that of fundamental ν8. As a consequence，the coupling coefficient ω and the intensity ratio Rf/a decrease. The Fermi resonance phenomenon disappears when the pressure is up to 11 Gpa，which can be explaned by high-pressure phase transition method. This report enriches the studies of environmental effect on the Fermi resonance，and provides positive reference value for the spectral certification and assignment.
Effect of casting process of polymer active layer on performances of polymer solar cells
Authors: Xu Miao  , Peng Jun-Biao  ,   华南理工大学高分子光电材料与器件研究所，特种功能材料教育部重点实验室，广州  510640
Published: December 2020

Hole mobility of poly［2-methoxy-5-（2′-ethylhexyloxy）-1，4- phenylenevinylene］ （MEH-PPV） film fabricated by spin-casting and drop-casting has been measured by time-of-flight （TOF） technique. The non-dispersive hole transport current waveform is obtained. The results exhibit that the hole mobility of MEH-PPV prepared by drop-casting is higher than that of the film prepared by spin-casting. The solar cells based on MEH-PPV and fullerene derivative blend films prepared by spin-casting and drop-casting，respectively，were fabricated. The power-conversion efficiency （PCE） of the drop-casting device has a great improvement of over 35%，compared with that of spin-casting one. The improvement is attributed to the stronger absorption and better balance of electron and hole transport in MEH-PPV polymer films.
Retrieval and validation of ionospheric measurements from COSMIC radio occultation
Authors: Xu Xian-Sheng  , Hong Zhen-Jie  , Guo Peng  , Liu Rong-Jian  ,   (1)上海大学上海市应用数学和力学研究所，上海  200030；温州大学数学与信息科学学院，温州  325000; (2)温州大学数学与信息科学学院，温州  325000; (3)中国科学院上海天文台，上海  200030
Published: December 2020

The relative total electron content （TEC） is obtained through the combination of COSMIC radio occultation ionospheric measurements L1 and L2 phase. The TEC data are then calibrated by non-occultation observation data on the auxiliary side to remove portion of TEC above the LEO orbit altitude. The electron density profile can be retrieved from TEC by Abel integral transformation，with a spherically symmetric assumption of electron density and an approximation of signal straight-line propagation. The computation standard deviation of F2-layer critical frequency f0F2 is about 059 MHz，and the standard deviation of F2-layer peak altitude hmF2 is about 3308 km，as through comparing 4903 COSMIC ionospheric occultation profiles with those from ionosonde stations，of which the longtitude deviations are less than 10°，the latitude deviations are less than 2°.
Multipartite entanglement in the Heisenberg XX chain with impurity
Authors: Qin Meng  ,   中国人民解放军理工大学理学院,南京 211101
Published: December 2020

We studied the entanglements of the Heisenberg XX chain with impurity in the presence of a uniform magnetic field along the z axes by means of negativity. Through analyzing NL-A and N1-A, we show that the critical temperatures for nonzero negativities depend on the impurity parameter J1 and the magnetic field B. It is also shown that as qubit L increases, the entanglements increase when L is odd but decrease when L is even. And the entanglements of the even-qubit chains are larger than those of the odd-qubit chains. The condition is similar with L=3 for NL-A when qubit L is odd, but the entanglements increase with the increase of even qubit L.
Guiding of 60 keV O+ ions through Al2O3 nanocapillaries with two different diameters
Authors: Chen Yi-Feng  , Chen Xi-Meng  , Lou Feng-Jun  , Xu Jin-Zhang  , Shao Jian-Xiong  , Sun Guang-Zhi  , Wang Jun  , Xi Fa-Yuan  , Yin Yong-Zhi  , Wang Xing-An  , Xu Jun-Kui  , Cui Ying  , Ding Bao-Wei  ,   (1)兰州大学核科学与技术学院，兰州  730000; (2)兰州大学核科学与技术学院，兰州  730000；兰州物理研究所真空低温技术与物理国防科技重点实验室，兰州  730000
Published: December 2020

The transmission of 60 keV O+ ions through Al2O3 nanocapillaries at a series of different tilt angles is measured. The capillaries with diameters of 50 nm and 30 nm respectively and 10 μm in length are used. The angular distribution and the transmission yields of transported ions are investigated. Our results indicate both the existence of guiding effect when ions pass through the capillary and a significant dependence on the tilt angle. The results also show that the transmission yield increases as the diameter of capillary decreases，and the theoretical model used in our work explains it well.
The influence of the defects without diffusion function on dynamics of spiral wave
Authors: Tang Dong-Ni  , Tang Guo-Ning  ,   广西师范大学物理科学与技术学院,桂林 541004
Published: December 2020

The Br model is considered. The influence of the defect, defined by failure of the diffusion effect, on dynamics of spiral wave is investigated by introducing in to the system some defects. These defects are uniformly distributed. It was found numerically that these defects can lead to the reduction of the excitability of medium and the wave speed. When the number of defects is large enough, these defects can induce the meandering or the breakage of an originally stable spiral wave. On the other hands, the defects can yet cause an unstable spiral wave to become a rigidly rotating or meandering spiral wave. The phenomenon that Doppler effect causes unstable spiral wave to break up into co-existing states of spatiotemporal chaos and small spiral waves is observed for the first time. The physical mechanism of these phenomena are briefly discussed.
Bursting phenomenon and the bifurcation mechanism in generalized Chua’s circuit
Authors: Chen Zhang-Yao  , Zhang Xiao-Fang  , Bi Qin-Sheng  ,   江苏大学理学院,镇江  212013
Published: December 2020

By introducing the electrical controlling circuit composed of inductance and capacitance, a fourth order model of generalized Chuas circuit with fast-slow effect has been established for certain parameter conditions. The conditions for fold bifurcation as well as Hopf bifurcation of the fast subsystem are investigated with the variation of the slow variable. Furthermore, the dynamical evolution of the entire system is explored, in which the fast-slow effect existing in the system is focused. Two types of bursting phenomenon, namely, the symmetric fold/fold and fold/Hopf periodic bursters, as well as their mechanism, are presented, which discloses the difference between the two burstings from the view point of bifurcation.
Density functional theory study of hydrogen adsorption on C@Al12 cluster
Authors: Lu Qi-Liang  , Luo Qi-Quan  , Chen Li-Li  ,   安徽大学物理与材料科学学院，合肥  230039
Published: December 2020

Density functional theory has been employed to investigate the structure and stability of C@Al12Hn (1≤n≤7) clusters. Hydrogenated C@Al12 clusters exhibit pronounced stability for even numbers of H atoms. Large HOMO-LUMO gaps，large binding energy and increased ionization potentials imply that these clusters should be physically and chemically stable. The analysis of the charge density of the HOMO plot illustrates that a pair of hydrogen atoms prefer to occupy opposing on-top sites for clusters with an even n number. Studies of deformation charge density plots demonstrate that the bonding characteristic between the H atoms and the C@Al12 moiety is mainly covalent. The total magnetic moment is 1μB for C@Al12Hn with an odd number for n.
Emission spectra of terahertz quantum-cascade lasers based on the terahertz quantum-well photodetectors
Authors: Tan Zhi-Yong  , Guo Xu-Guang  , Cao Jun-Cheng  , Li Hua  , Han Ying-Jun  ,   中国科学院上海微系统与信息技术研究所,信息功能材料国家重点实验室,上海  200050
Published: December 2020

The emission of a 41 THz quantum cascade laser (THz QCL) has been measured by a spectrally-matching terahertz quantum-well photodetector (THz QWP). The measured emission spectra have been analyzed with respect to the spectral shape and peak position. The relative light power of the laser under different drive currents have been estimated from the emission spectra and then the lasing domain and threshold current density of the laser has been determined. The temperature-dependent response of THz QWP to the laser has also been investigated. The analyzed results indicate that the THz QWPs could be a good detector for characterizing the emission properties of the THz QCLs and may be the receivers in the terahertz communications.
Nonclassical properties of atomic radiation field in a nonlinear photonic crystal
Authors: Yan Yan  , Wei Qiao  , Li Gao-Xiang  ,   (1)华中师范大学物理科学与技术学院，武汉  430079; (2)华中师范大学物理科学与技术学院，武汉  430079；长江大学物理科学与技术学院，荆州  434023
Published: December 2020

We study spectral properties and photon statistical characteristics of a strongly driven two-level atom produced within a nonlinear photonic crystal. This study reveals that when a large discontinuity in the local photon density of states and the cavity field mode is resonant with the central component of the Mollow spectrum of atomic resonance fluorescence, there is squeezing of the cavity field below the quantum shot noise limit and the peak of the cavity field spectrum that is achieved in the nonlinear photonic crystal is higher than that in the linear photonic crystal. Furthermore, we can see the statistics of the photons emitted by the atom into the microcavity is sub-Poissonian and close to Poissonian when the frequency of the driving field is high.
Methods for determining and detuning the length of nonlinear crystal in optical pulse chirped amplifier
Authors: Deng Qing-Hua  , Ding Lei  , He Shao-Bo  , Tang Jun  , Xie Xu-Dong  , Lu Zhen-Hua  , Dong Yi-Fang  ,   中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

Three kinds of simulating models for optical pulse chirped amplifier (OPCPA) are introduced at first. Then the three-step way to determine the length of the nonlinear crystal for most stable output is put forward. In this method, all the there models are used. As the more complex models are used, the ranging length for simulation becomes shorter. So it is efficient and accurate to useing this method to determine the optimized nonlinear crystal length. Then the way is also studied to introduce some phase mismatching in OPCPA to detune the nonlinear crystal length for most stable output. Simulating results show that as the mismatching angles increases, the nonlinear crystal length for most stable output becomes longer. So it is suggested that the nonlinear crystal be manufactured longer than designed. Most stable output can be obtained by introducing some phase mismatching in the experiments.
Modified finite-difference frequency-domain method for two-dimensional metallic photonic crystal analysis
Authors: Li Yan-Lin  , Xue Qian-Zhong  , Du Chao-Hai  , Hao Bao-Liang  ,   (1)中国科学院电子学研究所，中国科学院高功率微波源与技术重点实验室，北京  100190; (2)中国科学院电子学研究所，中国科学院高功率微波源与技术重点实验室，北京  100190；中国科学院研究生院,北京  100190
Published: December 2020

In contrast to dielectric photonic crystals, the propagation characteristics of metallic photonic crystals are of great importance in millimeter wave and submillimeter wave applications. It is convenient and reliable to get the band diagrams and field distributions of photonic crystals after solutions of the eigenmode equations, which is derived from the Yee-mesh-based finite-difference frequency-domain method. However, this method cannot be used for the analysis of metallic photonic crystals because of the essential distinctions between metal and dielectric. Based on this method, we derive eigenmode equations for two-dimensional metallic photonic crystals by introducing the metal surface boundary conditions. And then, after some numerical calculations, the transverse electric mode and the transverse magnetic mode global band gaps of different lattice structures are obtained, including both square lattice and triangular lattice. Finally, we discuss the advantages of metallic periodic structures in mode selection and device integration by the comparison between metallic photonic band gap and dielectric photonic band gap.
Numerical simulation of particle segregation behavior in different vibration modes
Authors: Zhao La-La  , Liu Chu-Sheng  , Yan Jun-Xia  , Jiang Xiao-Wei  , Zhu Yan  ,   中国矿业大学机电工程学院，徐州  221116
Published: December 2020

Particle segregation processes in different vibration modes are simulated based on 3D discrete element method (DEM). The phenomena of wave motion of large particles in upper layer that appears in the segregation processes of linear vibration mode, accumulation and circulation that appear in circular and elliptical vibration mode are analyzed. And the influences of vibration intensity on the segregation pattern of the circular and elliptical mode were also discussed. The results show that the segregation behaviors in different modes can be well explained by a combination of three mechanisms: void filling, sidewall-driven transport of particles and nonequipartition of energy, and the distribution of particle velocity vectors. The vibration intensity has a great effect on the segregation pattern of circular and elliptical mode. For each vibration mode, fine particle segregation effect and stable particle moving state is obtained when the value of vibration intensity is about 3.
Generation of helical beams with pre-determined energy distribution based on phase modulation gratings
Authors: Qi Xiao-Qing  , Gao Chun-Qing  , Liu Yi-Dong  ,   (1)北京理工大学光电学院，北京  100081; (2)电子科技大学物理电子学院，成都  610054
Published: December 2020

The generation of helical beams with different pre-determined orbital angular momentum states based on computer-generated holograms is studied. The phase-type diffraction gratings are designed by using the Gerchberg-Saxton iterative method，and realized by using the spatial light modulator (SLM). In the experiments diffraction fields with different helical beams distribution are obtained by using the gratings. The theoretical simulation agrees with the experimental results. This method is meaningful for the information transmission based on the orbital angular momentum.
The effect of laser irradiation on ZnO thin films
Authors: Zhao Yan  , Jiang Yi-Jian  ,   北京工业大学激光工程研究院，北京  100124
Published: December 2020

The effect of KrF pulsed excimer laser irradiation on intrinsic defects，ultra-violet (UV) emission and surface morphology of ZnO thin films was investigated，and also the origin of room temperature UV emission was discussed in detail. It was found that，the KrF laser can break the Zn—O bonds; therefore，the concentration of VO (or Zni) defects increases，leading to the decrease of resistivity and increase of carrier concentration. By adjusting the laser energy densities，the donor defect concentration can be controlled in a wide range. Simultaneously，under the heat of laser，the melting grains connect with each other，resulting in the great decrease of surface roughness. Room temperature UV emission of ZnO film is composed of contribution from free-exciton (FX) recombination and its longitudinal-optical phonon replica (FX-LO), the defect density determines the relative strengths of FX to FX-LO emission intensities，which strongly affect the peak position and intensity of UV emission of ZnO film. This investigation indicates that the laser irradiation is an effective technique to modulate the exciton emission by controlling the defect density，which is important for the application of high performance of UV emitting optoelectronic devices.
A classification method for nonlinear fluorescent spectra based on edges matching
Authors: Chen Yang  , Jia Li-Ping  , Zhang Tai-Ning  , Guo Peng  , Wang Xiang-Hui  , Chang Sheng-Jiang  ,   (1)南开大学现代光学研究所，天津  300071; (2)石家庄经济学院，石家庄  050031
Published: December 2020

A pre-process of feature extraction and classification approach based on spectrum edges matching is proposed to analyze the complicated nonlinear fluorescence spectra emitted by the interaction between femto-second (fs) laser and the impurities in air. The spectra data is denoised and compressed from 3979 points to 664 points using wavelet (WT) transform. By similarity analysis we create the characteristic spectra of 3 kinds of gases and the weights for classification. A new method of classification is proposed based on the edges matching and the comparison with characteristic spectra. Compared with existing methods，our method can not only get 100% classification accuracy，but also gives the characteristic position and the matching degree. The analysis of the matching degree shows that our method works well at low concentrations and has a potential application of identifying gases of lower concentration.
Persistent spin current properties in a special structure of quantum ring with multiple arms
Authors: Du Jian  , Wang Su-Xin  , Yuan Ai-Guo  ,   承德民族师范高等专科学校物理系,承德 067000
Published: December 2020

A new model of quantum ring with multiple arms whose middle arm is curved was proposed in this article.This is an unequal arm quantum ring with a shortest upper arm and a longest lower arm.The results indicate that the persistent spin current shows nonperiodic vibration with the size of the semiconductor ring increasing when the total magnetic flux is zero.And it is related to the electrodes’ magnetic moment direction as well as the tunneling electrons’ spin orientation. The average persistent spin current in the lower arm is minimum on account of its longest length. When the AB magnetic flux strengthens, the persistent spin current in each arm generates periodic oscillation and shows mutual restriction.The difference in each arm is related to the arm length and the magnetic flux distribution. Furthermore,the Rashba spin-orbit interaction affects the phase and the phase difference of the persistent spin current. Our results also imply that the persistent spin currents which the two kind of wave functions correspond to are separated under definite conditions.
Spin-glass behavior and valence states of transition-metal ions of SrMn0.5Fe0.5O3
Authors: Mei Ye  , Chen Liang  , Cao Yong-Zhen  , Liu Bao-Qin  , He Jun-Hui  , Zhu Zeng-Wei  , Xu Zhu-An  ,   (1)扬州大学物理科学与技术学院，扬州 225002; (2)浙江大学物理系，杭州 310027
Published: December 2020

Polycrystalline perovskite SrMn0.5Fe0.5O3 has been synthesized by solid state reaction method. The crystal structure, magnetic properties and valence states of Mn and Fe ions have been investigated. X ray diffraction (XRD) and subsequent Rietveld refinement confirmed that SrMn0.5Fe0.5O3 is found to be a primitive cubic crystal structure，Mn and Fe atoms randomly occupy the center of oxygen octahedron. Also with the measure of XPS which indicates that Mn ions show trivalent and tetravalent state, while Fe ions are in trivalent state. Paramagnetic phase was observed in high temperature (>230 K), the spin-glass behavior at low temperature (3+ ions located in the octahedral sites.
The inverse magnetostrictive effect in Tb0.3Dy0.7Fe2
Authors: Zhang Hui  , Zeng De-Chang  ,   华南理工大学材料科学与工程学院，广州  510640
Published: December 2020

The inverse magnetostrictive effect, also called magnetomechanical effect, in Terfenol-D material, has been investigated in this paper. Based on Stoner-Wohlfarth (SW) model, taking into account magnetocrystalline and stress-induced anisotropy energy, and following the free energy minimization procedure, direction cosines of magnetization in Terfenol-D single crystal in demagnetized state have been obtained as a function of the compressive stress. The nonlinear equations for equilibrium have been solved numerically. The results indicated that under compressive stress, magnetic anisotropy in Terfenol-D is determined by a competition between magnetocrystalline and stress-induced anisotropy energy, and changes from cubic symmetry to uniaxial. A comparison between experimental and numerical results showed that there is a maximum magnetostriction in Terfenol-D at a certain stress. According to our numerical results, experimental observations that compressive stress makes Terfenol-D hard to be magnetized and leads to the maximum magnetostriction can be explained. The computation in this paper presents a more accurate approach to similar investigations, and its numerical results would be helpful for a better understanding of magnetization process of similar materials.
Preparation and near-infrared luminescence properties of Bi-doped BaF2 crystal
Authors: Zhou Peng  , Su Liang-Bi  , Li Hong-Jun  , Yu Jun  , Zheng Li-He  , Yang Qiu-Hong  , Xu Jun  ,   (1)上海大学材料科学与工程学院电子信息材料系，上海  200072; (2)上海大学材料科学与工程学院电子信息材料系，上海  200072；中国科学院上海硅酸盐研究所透明与光功能无机材料重点实验室，上海  201800; (3)中国科学院上海硅酸盐研究所透明与光功能无机材料重点实验室，上海  201800; (4)中国科学院上海硅酸盐研究所透明与光功能无机材料重点实验室，上海  201800；宁波大学信息科学与工程学院光电子功能材料研究所，宁波  315211
Published: December 2020

Bi2O3:BaF2 and BiF3:BaF2 crystals were prepared by TGT (temperature gradient method). Near-infrared broadband luminescence was observed in as-grown Bi2O3:BaF2 crystal. The emission band peaks at 961 nm in the range of 850—1250 nm，with FWHM about 202 nm. The luminescence of Bi2+ and Bi3+ ions in the visible region was observed in BiF3:BaF2 crystal, but there was no near-infrared emission. Then the BiF3: BaF2 crystal was exposed to γ-rays in order to reduce valence states of Bi ions. Near-infrared broadband luminescence was observed in γ-irradiated BiF3:BaF2 crystal. The emission band peaks at 1135 nm in the range of 850—1500 nm，with FWHM about 192 nm. The mechanisms of near-infrared luminescence in Bi2O3:BaF2 crystals and γ-irradiated BiF3:BaF2 crystals were discussed.
Effect of the electric field on the decay of excited states in poly-phenylenevinylene
Authors: Cheng Ping  , Gao Feng  , Chen Xiang-Dong  , Yang Ji-Ping  ,   合肥工业大学电子科学与应用物理学院,合肥  230009
Published: December 2020

To gain an insight into the effect of electric field on the electro-luminescence of organic light emission diode, the ultrafast pump-probe spectroscopy is used to investigate the transient phenomena of the excitons induced by the electric field. Under the excitation density of 230 μJ/cm2, the decay of the singlet excitons shows a fast and a slow component. The amplitude factor and the relaxation time of fast component are field-dependent. Compared with the zero biascase, the relaxation time of the fast component becomes faster at a bias of 6.4×105 V/cm, its amplitude factor is increased from 22% to 72%, about 50% initial excitons are dissociated by the electric field. The slow component is field-independent, its relaxation time-constant is about 890 ps. The longitudinal acoustic phonons with sound velocity of 17 /ps generated by excitation pulse are observed.
Quantum efficiency decay mechanism for reflection-mode negative electron affinity GaN photocathode
Authors: Qiao Jian-Liang  , Chang Ben-Kang  , Du Xiao-Qing  , Niu Jun  , Zou Ji-Jun  ,   (1)南京理工大学电子工程与光电技术学院，南京  210094; (2)南京理工大学电子工程与光电技术学院，南京  210094；南阳理工学院电子与电气工程系，南阳  473004; (3)重庆大学光电工程学院，重庆  400030
Published: December 2020

Aimming at the decay tendency of reflection-mode negative electron affinity (NEA) GaN photocathode and the different decay speeds of quantum efficiency corresponding to the different wave bands, and referring to the decay tendency of quantum efficiency curve provided by foreign authors for reflection-mode NEA GaN photocathode, the quantum efficiency decay mechanism for reflection-mode NEA GaN photocathode was studied. The surface model ［GaN (Mg) : Cs］: O-Cs for GaN photocathode after being activated with cesium and oxygen was used. And the change of surface barrier in the decay course of quantum efficiency was considered. The reduction of the effective dipole quantity is the basic reason causing quantum efficiency reduction. And it is the change of surface I, II barrier shape that causes the difference of dropping speeds of quantum efficiencies corresponding to different wave bands.
Frequency coupling in bistable system and the mechanism of stochastic resonance
Authors: Lin Min  , Meng Ying  ,   中国计量学院计量测试工程学院，杭州 310018
Published: December 2020

We study the motion of a particle in a bistable potential in the presence of single frequency signal and dual-frequency signal, and give the approximate analytical relationship between response peak-to-peak value and driven peak-to-peak value of the bistable system under the control of dual-frequency signal. The paper also reveals a peculiar phenomenon of the non-linear system, that is frequency coupling of different frequencies and the energy infiltration from the frequency of input to the other. The analysis is carried out from the view point of dynamics mechanism and the frequency spectrum distribution. It deepens the understanding of the mechanism of stochastic resonance in the bistable system. The results of numerical simulation prove the validity of theoretical analysis.
Hojman method for construction of Birkhoffian representation and the Birkhoff symmetry
Authors: Ding Guang-Tao  ,   安徽师范大学物理与电子信息学院，芜湖  241000
Published: December 2020

The Hojman method for construction of the Birkhoffian representation is discussed. By using Hojman method, the Birkhoff symmetry is restudied. A new idea of this symmetry is presented. A new proof of the Birkhoff conserved quantity is given. It is shown that the Birkhoff symmetry depends only on the Birkhoff tensors. An example is given to show the application of the result.
Study of tunable Fabry-Perot filter based on piezoelectric polymer film
Authors: Zhou Ke-Yu  , Ye Hui  , Zhen Hong-Yu  , Yin Yi  , Shen Wei-Dong  ,   浙江大学现代光学仪器国家重点实验室，杭州  310027
Published: December 2020

Tunable Fabry-Perot filter (FPF) has high practical value in optic communications. Piezoelectric copolymer P(VDF-TrFE) can be used as spacer material in FPF to obtain large tunability in wide range because of its great electrostrictive effect. The filter has been fabricated with the structure of DBR/electrode/spacer/electrode/DBR. The copolymer is partly etched at where the light traverses. The transmittance spectra have been studied. The resonant wavelengths have been modulated by applied voltage. The optical length is measured to be 804 μm, which shrinks under the electric field. The filter exhibits a total optical path-length change of -0757% under an electric field of 140 V. The results indicate that the electrostrictive effect plays a major role.
Characterization of chirped pulses with modified-zero-additional-phase spectral phase interferometry for direct electric-field reconstruction
Authors: Wen Jin-Hui  , Liu Jun  , Zhang Hui  , Chen Jia-Long  , Huang Zi-Zhu  , Jiao Zhong-Xing  , Lai Tian-Shu  ,   中山大学物理科学与工程技术学院，光电材料与技术国家重点实验室，广州  510275
Published: December 2020

At present, pulse measurement systems based on spectral phase interferometry for direct electric-field reconstruction (SPIDER) may have problems in chirped pulse characterization. In this paper we propose and demostrate a Modified-ZAP SPIDER system to solve this problem. Femtosecond pulses from a KLM Ti:sapphire laser and the chirped pulses obtained by broadening by a 80 mm BK7 glass block are respectively measured. The experimental results show that the novel MZAP-SPIDER system performs well in chirped pulse measurement.
Control and analysis of a third-order nonautonomous ferroresonance chaotic circuit with a transformer
Authors: Liu Chong-Xin  , Zhai Du-Qing  , Dong Zi-Han  , Liu Yao  ,   西安交通大学电气工程学院,电力设备电气绝缘国家重点实验室，西安 710049
Published: December 2020

In this paper, the chaos dynamics behavior of a third-order nonautonomous ferroresonance chaotic circuit with single phase transformer has been analyzed and simulated. We drew the conclusion that there is only a nonlinear flux-controlled inductance in this circuit, which has been investigated and simulated by using a fourth-order autonomy improved system. We confirm that the chaotic behavior exists in this circuit by computer simulation and circuit experiment. A simple method of controlling chaos is proposed by varying the linear capacitance parameters.
Bandwidth enhancement of a chaotic semiconductor laser transmitter by cross-phase modulation
Authors: Yan Sen-Lin  ,   南京晓庄学院物理与电子工程系，南京 210017
Published: December 2020

A novel method of bandwidth enhancement of a chaotic carrier from a semiconductor laser transmitter is studied by cross-phase modulation (XPM). And a physical model of laser dynamics is presented under the condition of XPM effect of optical fiber path. A frequency detuning formula with optical dual-feedback and XPM effect is deduced. The nonlinear phase shift arisen from XPM effect impacts on the gain and bandwidth enhancement factor of the laser. The second order nonlinear effect of the fiber enriches the varieties in the amplitude and the phase of the laser while the nonlinear phase shift produces a lot of new frequencies, which spread the bandwidth. Numerical results reveal that, with XPM effect, the new bandwidth is the quadruple of the bandwidth without XPM effect, and the relaxation oscillation frequency of the chaotic laser is increased to 285 times that of the laser without XPM effect. It is found that the enhancement of the chaotic bandwidth depends evidently on the optical fiber length, the power input into the optical fiber, the mirror reflectance and the second order nonlinear coefficient.
Thermoelectric refrigerator of a double-barrier InAs/InP nanowire heterostructure
Authors: He Bing-Xiang  , He Ji-Zhou  ,   南昌大学物理系，南昌 330031
Published: December 2020

In this paper, the electron transport through a double-barrier InAs /InP nanowire heterostructure between two reservoirs at different temperatures and chemical potentials is studied. The transport probability of electron is obtained by using transfer matrix method, and the heat flow carried by the electrons transfer is derived. The performance characteristic curves of the refrigerator are plotted by numerical calculation. The influence of the barrier width and well width on the operation performance of the refrigerator is analyzed. It is found that when the well width is fixed, the position of resonance energy level increases while the width of resonance energy level decreases as the barrier width increases, and for the same bias the larger the barrier width, the smaller the cooling rate, while the larger the relative coefficient of performance. When the barrier width is fixed, for the same bias, the relative coefficient of performance will decrease as the well width increases. The curve obtained when both the well width and barrier width vary, is similar to the curve obtained when the well width varies and barrier width is fixed. Thus we can see that cooling rate and the relative cooling factor are mainly affected by the well width.
A model of human behavior dynamics and exact results
Authors: Guo Jin-Li  ,   上海理工大学管理学院,上海  200093
Published: December 2020

Baraba′si has proposed a queue model of the human behavior. In this paper we compare the Baraba′si results and Va′zquez results.　We proposed a model of human behavior dynamics by taking into consideration the service-time distribution. We obtained exact results for the model by calculating the waiting time distribution and sojourn time distribution of active tasks. The results show that the waiting time distribution of the model is a power-law distribution with exponent 2 for the highest priority first selection protocol. This exponent approximates to degree exponent 2.1 observed in Hsue-Shen Tsien correspondence pattern.
Study on the high-power, high-repetition-rate and multi-wavelength femtosecond laser system
Authors: Liu Hua-Gang  , Hu Ming-Lie  , Liu Bo-Wen  , Song You-Jian  , Chai Lu  , Wang Qing-Yue  ,   天津大学精密仪器与光电子工程学院，光电信息技术科学教育部重点实验室,天津  300072
Published: December 2020

High-power and high-repetition-rate multi-wavelength femtosecond pulses are obtained by the nonlinear frequency up-conversion of large mode area photonic crystal fiber femtosecond system. Effects of focal length on the transverse mode of second harmonic are theoretically analyzed and experimentally demonstrated, showing that the longer the focal length, the better the mode quality. Under the condition of fundamental average power of 218 W, pulse duration of 110 fs and repetition rate of 50 MHz, generation of the second, third and fourth harmonics are achieved at the wavelengths of 520, 347, and 261 nm, with the maximum average power of 105, 47, and 214 W, respectively. The conversion efficiencies of frequency doubling and frequency tripling are 482% and 216%, and the conversion efficiency of frequency quadrupling from the second harmonic is 204%. Pulse duration of the fourth harmonic pulse is 408 fs, as measured by the cross-correlation technique.