bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of the 3-inch photomultiplier tube for the neutrino detection
Authors: Guo Le-Hui  , Tian Jin-Shou  , Lu Yu  , Li Hong-Wei  ,   Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   Hainan Zhanchuang Photonics Technology Co. Ltd, Hainan 571924, China;,   Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: December 2020

Photomultiplier tubes (PMTs) widely used in neutrino detectors are critical to reconstructing the direction of the neutrino accurately. Large photocathode coverage, compact design and good time properties for single-photoelectron light are essential performances to meet the requirements for the next generation detectors. Therefore, a novel digital optical module housing 31 3-inch. diameter PMTs is developed. In order to maximize the effective photocathode area and improve the time performance, a modified PMT with a larger photocathode area and 10 dynodes is optimized with the aid of the CST Particle Studio in this paper. Based on the Monte Carlo method and finite integration theory, the main characteristics of the modified PMT, such as uniformity, collection efficiency, gain and transit-time spread, are investigated. As the earlier stages of the PMT contribute the greatest weight to the total transit time spread, the transit time spread of single-photoelectron from photocathode to the first dynode (TTSCD1) is discussed mainly in this paper. The influences of the dynodes position on collection efficiency and TTSCD1 are analyzed. The voltage ratio scheme is also optimized slightly to obtain better collection efficiency and minimum TTSCD1. By tracing the trajectories of secondary electrons from the first to the second dynode stage, dynodes are optimized for improving timing performance and secondary electrons collection efficiency. Direct collection efficiency of secondary electrons from the first dynode to the second is improved from 56.38% to 61.01%. The effective photocathode diameter of the modified PMT is increased from traditional 72 mm to 77.5 mm and the effective area of photocathode is increased by 30.87% compared with the traditional one. What is more, the length of the new PMT is reduced to 103 mm so that the available space of the multi-PMT digital optical module is increased by 63.09% compared with the traditional one containing the high-voltage power supplies, front-end and readout electronics, refrigerating equipment, etc. The simulation results show that the mean collection efficiency of the modified PMT is ~96.40% with the supply voltage of 1000 V and it changes little by changing the supply voltage from 900 V to 1300 V. The mean transit time spread from photocathode to the first dynode is ~1 ns which is better than the transit time spread of the traditional model. And the gain can reach above 106 with a supply voltage of above 1100 V.
Analyses of characetristics of air passenger group mobility behaviors
Authors: Huang Fei-Hu  , Peng Jian  , You Ming-Yang  ,   College of Computer Science, Sichuan University, Chengdu 610065, China
Published: December 2020

In this paper, we use the civil aviation passenger reservation record data to analyze the characteristics of air passenger group mobility behaviors. We find that the airline network has restriction on passengers traveling, which causes the group travel length distribution to be more consistent with the stretched exponential distribution and to have no scale-free property. The passenger travel interval time satisfies a truncated power law distribution rather than the power law distribution. Meanwhile, holidays have a great influence on passengers traveling. In particular, during the Spring Festival, the summer vacation, and National Day, the number of traveling passengers is far more than at any other time. And passengers who will travel during the holidays prefer to book tickets in advance. By analyzing the throughput, we find that it has a periodicity and is easy to be affected by festival and holidays. Moreover, the throughput of the airport is greatly related to the number of cities which are navigable to each other.
Chaotic dynamics of the fractional Willis aneurysm system and its control
Authors: Gao Fei  , Li Teng  , Tong Heng-Qing  , Ou Zhuo-Ling  ,   School of Science, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

The Willis aneurysm system has some limitations in the description of the complex hemodynamic mechanism of blood with viscoelasticity. The fractional calculus has been used to depict some complex and disordered processes in organisms. Thus, we propose a fractional Willis aneurysm system (FWAS) byusing the Caputo fractional differential and its theory in the present article. Firstly, the existence and uniqueness of solution for FWAS are investigated theoretically. Then, we prove that the FWAS has a chaotic characteristic by analyzing the phase portraits and Poincar section, and it is a rational extension of its integer order form. We investigate the influences of pulse pressure and fractional order on the FWAS by means of bifurcation diagram and period doubling bifurcation. The results show that small changes of pulse pressure and fractional order canlead to a remarkable effect on the motion state of the FWAS. As the chaotic FWAS indicates that the brain blood flow is unstable, and the cerebral aneurysms are more likely to rupture in a very chaotic velocity field. Therefore we use two methods to control the chaotic FWAS. One is to design a suitable controller based on the stability theorem of fractional nonlinear non-autonomous system, and the other is to use a pulse control by taking the inspirit function of drug as impulse function. The numerical simulations show that the proposed two methods can control the blood flow velocity and speed up the periodic fluctuation within a small range, which shows that the cerebral aneurysm is not easy to rupture. The results obtained in this paper display that the fractional differential is a feasible method to characterize the Willis aneurysm system. The theoretical results in our article can provide some theoretical guidance for controlling and utilizing the actual FWAS system.
Development of an intranuclear-cascade code CBIM applicable to the nuclear reaction with incident particle energy above 45 MeV
Authors: Hu Zhi-Liang  , Zhou Bin  , Zeng Zhi-Rong  , Liang Tian-Jiao  ,   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China;Dongguan Institute of Neutron Science, Dongguan 523808, China
Published: December 2020

The Monte Carlo intra-nuclear cascade program CBIM has been developed for describing spallation reactions involving protons, neutrons and pions on complex nuclei.
In order to describe cascade process, several simplifications and assumptions are made in the following:firstly, neither reaction, nor reflection, nor refraction, nor ionization will be taken into account before the incident particle enters into the target nucleus; secondly, target nucleus is regarded as being spherical and the atom number should be greater than 2; thirdly, the knocked nucleon is determined by cross section sampling; finally, in the center-of-mass frame, the scattering angle is sampled based on differential cross section distribution.
The basis physics model is based on the above assumptions and Bertini intra-nuclear cascade model; meanwhile, nucleon-nucleon angle differential distributions of INCL in the center-of-mass frame are introduced to overcome the shortage of Bertini model. The interactions between nucleon and nucleon or between nucleon and pion, such as elastic scattering, pion production and charge exchange, are included in the code. In the particles collision, the nucleon density changes with the target nucleus radius; and the interaction cross sections refer to 22 kinds of experimental cross sections in Bertini model. The intra-nuclear cascades induced by 45-3500 MeV neutron, proton or pion below 2500 MeV can be simulated by this code.
Finally, comparisons between experimental reaction cross section over the energy range 60-378 MeV, and some simulation results by MCNPX, GEANT4 and PHITS over the energy range 65-3000 MeV show that they are in reasonable agreement with the CBIM results over the broad energy range considered.
The extended “ladder” transition controlled by two harmonic pulses
Authors: Niu Ying-Yu  , Wang Rong  , Qiu Ming-Hui  , Xiu Jun-Ling  ,   School of Science, Dalian Jiaotong University, Dalian 116028, China
Published: December 2020

The extended “ladder” transition controlled by two harmonic pulses is investigated by using a time-dependent quantum wave packet method. The molecular population transfers from the state|0, 0> angle to the states|5, 0> angle and|5, 2> angle induced by the fundamental and second-harmonic pulses, and to the states|5, 3> angle and |6, 2> angle induced by the fundamental and third-harmonic pulses. The calculated results show that the two harmonic pulses can induce a nearly 100% of population to transfer to the target state. The relative phase of two pulses can affect the population distribution. The variation of population has a period of π for the fundamental and second-harmonic pulses, and a period of 2π for the fundamental and third-harmonic pulses.
Progress in far-field focusing and imaging with super-oscillation
Authors: Jiang Zhong-Jun  , Liu Jian-Jun  ,   Laboratory for Micro-/Nano-Optoelectronic Devices of the Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China;,   Institute for Lasers, Photonics and Biophotonics, State University of New York at Buffalo, Buffalo, New York 14260, USA
Published: December 2020

Superoscillation is known as a counter-intuitive property of a band-limited function that oscillates faster than its highest Fourier component in a prescribed interval. Based on superoscillation, micro/nano optical devices, breaking through the diffraction limit in the far-field independent of evanescent waves, have potential applications, including super-resolution, nano-photolithography, high-density optical storage, etc. In this paper, superoscillation is introduced simply, and several optical superoscillatory designs with focusing and imaging abilities are summarized primarily, and some defects and future research emphases in these designs are pointed out.
Effect of linear bubble vibration on wave propagation in unsaturated porous medium containing air bubbles
Authors: Zheng Guang-Ying  , Huang Yi-Wang  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Biot model has widely been used in geophysics, petroleum engineering, civil engineering, and ocean engineering since it was presented, and thus the research on the wave propagation in saturated porous medium has made much progress. However, fully saturated porous medium is rarely found in nature. Almost all the rocks or soils contain two kinds of fluids, such as gas and petroleum. Many researches have been done on the wave propagation in unsaturated porous medium. As is well known, a small volume of gas bubbles existing in a liquid can greatly change the velocity and attenuation of acoustic wave in the liquid. Evidences are beginning to be accumulated that the velocity and attenuation of acoustic wave in a saturated marine sediment can be affected by the gas bubbles existing in the saturated liquid. To investigate the sound propagation in a porous medium when the pore water contains a small number of air bubbles, in this paper we integrate the volume vibrations of bubbles in pore water into the continuity equation of pore-fluid filtration in porous medium based on Biot theory, so as to obtain the continuity equation of pore-fluid filtration with bubble volume vibration. On this basis, according to the relationship between the instantaneous radius of bubble and the background pressure of the medium under the linear vibration of bubble, as well as the equations of motion of the fluid medium and porous medium, a new displacement vector wave equation of porous medium under the influence of bubble is derived, which establishes the model for the sound velocity dispersion and attenuation prediction under the unsaturated porous medium. The presence of air bubbles increases the compressibility of pore fluid, which leads to the decrease in the sound velocity of the bubbly saturated porous medium. When the wave frequency equals the resonance frequency of the bubbles, the bubbles in pore water will produce resonance; the medium will present high dispersion and the velocity can greatly exceed the gas-free velocity. However, these have not been measured in field data. The absorption cross section of the air bubble can reach a maximum value, which leads to the maximum attenuation of the porous medium. It should be noted that the attenuation coefficient calculated with this model is related to the damping of the bubble motion due to radiation, thermal and internal friction, and the dissipation of the relative motion between the pore water and porous solid frame. The obtained numerical analysis is consistent with the above conclusion, which indicates that the volume concentration, the bubble size and the excitation frequency of the sound field are important parameters affecting the sound wave propagation in the saturated porous medium containing few bubbles.
Complete equation of state based on specific heat
Authors: Fan Xiao-Bing  , Chen Jun-Xiang  , Xiang Shi-Kai  ,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621999, China
Published: December 2020

In thermodynamics, the complete equation of state (EOS) for closed system is a functional relation defined by two independent state variables, and all other thermodynamic relations can be deduced by it. For example, Helmholtz free energy F as a function of specific volume v and temperature T of the system is a complete EOS. Unfortunately, the concrete expressions of these complete EOSs are unavailable. Here we establish a practical form of the complete EOS based on the pressure function pT(v) and constant-volume specific heat function Cv(v，T) This complete EOS is mathematically equivalent to the Helmholtz free energy F. Here pT(v) is determined by the measurement and Cv(v，T) can be expressed by two parts. One part is the lattice contribution based on the Debye model and the other part is electronic contribution obtained from the free electron model. Using this complete EOS we calculate the isothermal equation for six metals from the Hugoniot data. Good agreement between the isothermal equation and the experimental data verifies the reliability of the complete EOS. Through this complete EOS we can derive the concrete expression of physical parameters, and these physical parameters including the volume expansion coefficient, the volume speed of sound, the adiabatic modulus, and W-J coefficient are calculated by using the experimental data of Cu. Analyzing their variation trends we can timely adjust parameter in the calculation of the EOS. This kind of complete EOS is useful in the field of high temperature and high pressure physics.
Ferroelectric phase transition of perovskite SnTiO3 based on the first principles
Authors: Ye Hong-Jun  , Wang Da-Wei  , Jiang Zhi-Jun  , Cheng Sheng  , Wei Xiao-Yong  ,   Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China;,   College of Science, Air Force Engineering University, Xi'an 710043, China;,   State Key Laboratory for Mechanical Behavior of Materials, School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Due to their spontaneous polarizations, ferroelectric materials have excellent dielectric, piezoelectric, pyroelectric properties, which enable them to be employed in many applications, such as capacitors, filters, sensors, detectors, and transducers, etc. In this paper, we use a first-principles-based effective Hamiltonian method to investigate perovskite SnTiO3, obtain essential coefficients for the effective Hamiltonian via ab initio computations, which are used in subsequent Monte-Carlo simulations to predict the phase transition temperature of SnTiO3, and different structural phases involved in such phase transition.
Magnetization dynamics in ferromagnetic coupling interconnect wire using multiferroic logic scheme
Authors: Yang Xiao-Kuo  , Zhang Bin  , Cui Huan-Qing  , Li Wei-Wei  , Wang Sen  ,   Science College, Air Force Engineering University, Xi'an 710051, China
Published: December 2020

Nowadays, the intense research effort is focused on exploring alternative emerging device to perform binary logical function. A promising device technology is multiferroic nanomagnet logic. The main reason for the interest in this nanomagnetic switch is its nonvolatility and comparatively low power consumption in combination with the ability to perform logic and storage in one single element. The basic element of multiferroic nanomagnet logic is a sub-100 nm size single domain magnet. Usually, the x-y direction defines the in-plane dimension, while the z axis direction depicts the thickness of nanomagnet. The in-plane magnetizations along easy axis are used to encode binary logic states 1 and 0, respectively; while along the hard axis they denote null logic. The logic operation and data transmission in magnetic logic are realized by the dipole-coupled magnetostatic interactions. In multiferroic nanomagnet logic, the interconnect wire is a very important component since it forms data transmission channel of any nanomagnetic logic circuit. There are two kinds of interconnected wires in this technology, namely antiferromagnetic coupling interconnected wire and ferromagnetic coupling interconnected wire. In this paper, the switching dynamics of a multiferroically and nanomagnetically interconnected wire employing ferromagnetic coupling is simulated by solving the Landau-Lifshitz-Gilbert equation with neglecting the thermal fluctuation effects. The wires are implemented with dipole-coupled two-phase (magnetostrictive/piezoelectric) multiferroic elements that are clocked with electrostatic potentials of 100 mV applied to the piezoelectric layer generating 20 MPa stress in the magnetostrictive layers for switching. Specifically, the ferromagnetic coupling effect model for multiferroic nanomagnet interconnected wire is established, and its magnetization dynamics is simulated by using different stress clocking. It is found that moderate strain (19.7-20.1 MPa) can ensure~180 magnetization reversal, and the logic state is successfully transferred in the ferromagnetic coupling interconnected wire. It is also found that the strong ferromagnetic coupling between multiferroic nanomagnets blocks effective magnetization reversal. This may arise from small spacing-induced out-of-plane magnetization, which does not favor the in-plane magnetization. These findings can provide some guidance for multiferroic logic circuit design.
Ballistic thermal rectification in the three-terminal graphene nanojunction with asymmetric connection angles
Authors: Gu Yun-Feng  , Wu Xiao-Li  , Wu Hong-Zhang  ,   College of Electronic and Mechanical Engineering, Nanjing Forestry University, Nanjing 210037, China
Published: December 2020

By using the nonequilibrium Green's function method, the ballistic thermal rectification in the three-terminal graphene nanojunction is studied. The dynamics of atoms is described by the interatomic fourth-nearest neighbor force-constant model. The nanojunction has a Y-shaped structure, created by a combination of a straight graphene nanoribbon and a leaning branch as the control terminal holding a fixed temperature. No heat flux flows through the control terminal. There exists a temperature bias between the two ends of the graphene nanoribbon serving as the left and right terminals, respectively. The primary goal of this paper is to demonstrate that the ballistic thermal rectification can be introduced by the asymmetric structure with different connection angles between terminals. The control terminal has a smaller connection angle with respect to the left terminal than to the right terminal. The forward direction is defined as being from the left terminal to the right terminal. The results demonstrate that, given the same control temperature and absolute temperature bias, the heat flux in the graphene nanoribbon tends to run preferentially along the forward direction. When the difference between the connection angles increases, the rectification ratio rises. Compared with that of the zigzag graphene nanoribbon, the rectification ratio of the armchair nanoribbon is much sensitive to the direction the control terminal. However, the greatest rectification ratio is found in the zigzag graphene nanoribbon which has a connection angle of 30 degrees with respect to the armchair branch. In addition, the direction of the control terminal can be adjusted to raise more than 50% of the rectification ratio of the graphene thermal rectifier based on the width discrepancy between the left and right terminals. The mechanism of the ballistic thermal rectification is also discussed. In the three-terminal graphene nanojunction, a smaller connection angle with respect to the control terminal leads to more phonon scatterings. The confirmation of this conclusion comes from a comparison of phonon transmission between different couples of terminals, which shows that in most of the frequency spectrum, the phonon transmission between the control terminal and the left terminal is smaller than between the control terminal and the right terminal. Given the same control terminal temperature and temperature bias, the asymmetric connection angles therefore will introduce a higher average temperature of the left and right terminals, and a larger heat flux in the forward process. Moreover, the average temperature difference between in the forward process and in the reverse process is found to be proportional to the temperature bias, and the proportionality coefficient will become bigger if the asymmetry is strengthened.
Vibrational resonance in a periodic potential system with stable noise
Authors: Jiao Shang-Bin  , Sun Di  , Liu Ding  , Xie Guo  , Wu Ya-Li  , Zhang Qing  ,   Faculty of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China;,   Shaanxi Key Laboratory of Complex System Control and Intelligent Information Processing, Xi'an 710048, China
Published: December 2020

A periodic potential system excited by multi-low frequency weak signals, the high frequency signal and additive stable noise is constructed. Based on this model, the vibrational resonance phenomenon under stable noise is investigated by taking the mean signal-noise-ratio gain (MSNRI) of output as a performance index. Then the influences of stability index (0 2), the skewness parameter (-1 1) of stable noise, the amplification factor D and the high frequency signal amplitude B, and frequency on the resonant output effect are explored. The results show that under the different distributions of stable noise, the multi-low frequency weak signals detection can be realized by adjusting the high frequency signal parameter B or to induce vibrational resonance within a certain range. When (or ) is given different values, the curve of MSNRI-B has multiple peaks with the increase of B for a certain frequency , and the values of MSNRI corresponding to peaks of the curve of MSNRI-B are equal. So the intervals of B which can induce vibrational resonances are multiple, and the multiple resonance phenomenon turns periodic with the increase of B. Similarly, the curve of MSNRI- also has multiple peaks with the increase of for a certain amplitude B, so the intervals of which can induce vibrational resonances are also multiple. The difference is that the multiple resonance phenomenon becomes irregular with the increase of . Besides, the resonance intervals of B and do not change with nor . Under the different values of amplitude factor D, the resonance intervals of B (or ) do not change with the increase of D, indicating that only the energy of the high frequency signal transfers toward the signals to be measured, and the energy of stable noise does not transfer toward the signals to be measured. Besides, when B and are fixed, it can still be realized to detect the weak signal with the increase of D, which shows that the weak signal detection method based on vibrational resonance can overcome the shortcoming that noise intensity in industrial sites cannot be regulated and controlled. The results provide a new method of detecting the weak signal, and have potential application value in signal processing.
Full field of view polarization effect measurement and error analysis of non-polarized channels of spaceborne directional polarimetric camera
Authors: Qian Hong-Hu  , Meng Bing-Huan  , Yuan Yin-Lin  , Hong Jin  , Zhang Miao-Miao  , Li Shuang  , Qiu Zhen-Wei  ,   Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;,   University of Science and Technology of China, Hefei 230026, China;,   Key Laboratory of Optical Calibration and Characterization, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The optical system of spaceborne directional polarimetric camera that employs an ultra wide-angle lens for its multiangle, a filter wheel for its multispectral and also its multipolarization capability, a CCD itself for its imaging has a certain polarization effect, which can affect the radiometric accuracy of the non-polarized channels of the instrument. The transmittance of the oblique light rays that are incident on the optical element surfaces is sensitive to the orientation of the electric field, contributing to the linear polarization effect of optical system. The precise polarization measurement and calibration of the passive imaging polarimetry are in urgent need to eliminate the instrumental polarization effect and to improve its radiometric accuracy for observation scenes. The non-polarized channel radiometric model considering the linear polarization effect is deduced in detail by analyzing the instrumental principle and optical structures. Moreover, the reasonably simplified model is established based on the actual lens characteristics. A calibration method in which completely linearly polarized light with different kinds of polarization angles irradiates sparsely the instrument within full field of view and subsequently fits the response in the least square sense, is proposed and simulated. In addition, the measured relative errors of the intensity of incident light with different kinds of polarization states caused by the calibration deviations of instrumental principal physical parameters are analyzed and calculated, such as the azimuthal angle of single pixels, explicit optic polarization rate and low frequency spatial relative transmittance. The actual instrumental parameter values and their calibration deviation amounts are acquired by carrying out the laboratory calibration experiment for instrument and combining the least square fitting. Furthermore, the maximum radiometric calibration relative error caused by the deviation of the physical parameter called explicit optic polarization rate is calculated to be 0.4%, fulfilling completely the requirement of radiometric relative accuracy 5% and retaining abundant tolerance. The study provides a theoretical basis and an experimental guidance in high accurately measuring radiation, calibrating and processing data for the instrumental non-polarized channels with full field of view.
Ab initio calculation of the potential curve of B3u- state of O2
Authors: Li Chen-Xi  , Guo Ying-Chun  , Wang Bing-Bing  ,   School of Physics and Materials Science, East China Normal University, Shanghai 200241, China;,   Laboratory of Optical Physics, Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The B3u- state of O2 molecule is an upper state of the most strongly allowed triplet-triplet (B3u-X3g-) absorption, the Schumann-Runge (SR) transition, which plays a crucial role in protecting the earth from suffering UV radiation. Photo-dissociation of O2 molecule in the SR transition is the major source of odd oxygen (O and O3) in the stratosphere. Comprehensive knowledge of the electronic states, especially their potential energy curves (PECs), is necessary to understand those phenomena. In this paper, we calculate the PEC of B3u- state of O2 by using the internally contracted multi-reference configuration interaction including Davison correction method, which is denoted by icMRCI+Q, and utilize the complete active space self-consistent field (CASSCF) function as a reference function. The calculation is implemented in the MOLPRO suite of codes. Firstly, we carry out the state-averaged (SA) calculation on the four lowest states, A'3u, B3u-, 23u and 23u- states, which are in the same irreducible representation of symmetric group. The active space of CASSCF consists of full valence space. The augmented correlation-consistent aug-cc-pV5Z basis set is used. The results show that the PEC of B3u- state does not displays double well structure, which is contradictory to Liu's result (Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014 124 216). By analyzing the PEC structure, we find that the double well of Liu's result comes from the root flipping, that is, the PEC interchange from B3u- state into 23u state. In our case the root flipping is avoided by the SA calculation. Secondly, in order to ensure that the most important configurations are included in the reference function, we calculate the PEC of B3u- state of O2 molecule at CASSCF/aug-cc-pVTZ level by changing the active space. We find that the bound well of the PEC will not appear unless the active space includes 2u orbital which is beyond the full valence space. That means that the Rydberg configurations including 2u orbital play a crucial role in forming the bound well. And the result is further improved by adding into the active space another two orbitals 4g and 4g whose orbital energies are both less than 2u. Finally, we add the Rydberg configurations into the multi-reference configuration function by putting 2u, 4g, 4u into the active space and then carry out the calculation at an icMRCI+Q/aug-cc-pVTZ level. The obtained B3u- state PEC and its spectroscopic constants are in good agreement with the experimental data compared with previous results. Moreover, the process we determine the reference configurations is useful for making accurate calculation at an MRCI level on other species.
Finite element analysis and experimental study on electrical damage of silicon photodiode induced by millisecond pulse laser
Authors: Zhao Hong-Yu  , Wang Di  , Wei Zhi  , Jin Guang-Yong  ,   Key Laboratory of Solid Laser Technology and Applications of Jilin Province, School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, based on the thermal elasto-plastic constitutive theory and the equivalent specific heat method, the electrical damage in the silicon-based positive-intrinsic-negative (PIN) photodiode irradiated by millisecond (ms)-pulsed laser is investigated. On condition that the internal material of the photodiode is isotropic and threelayer structure of the P-I-N satisfying temperature continuity and heat flow balance, a two-dimensional (2D) simulation axisymmetric model for silicon-based PIN photodiode irradiated by ms-pulsed laser is built. The thermal and stress field distribution are simulated in the silicon-based PIN photodiode irradiated by the Nd:YAG ms-pulsed laser at 1064 nm through using the finite element simulation software. At the same time, electrical parameters before and after the experiment of the silicon-based PIN photodiode irradiated by pulsed laser are measured. The experimental results show that the surface is melted and ablated gradually with the increase of temperature in the high energy pulsed laser, and there is a gradient change for the temperature in spatial distribution. With the increase of laser energy density, photoelectric detector shows the temperature rise phenomenon and damage effect is more obvious. When the tensile stress or compressive stress is greater than 1.7 GPa, the photosensitive surface and the silicon lattice are damaged with the changes of thermal and stress fields. Bond cleavage can change the photogenerated carrier transport channel, and the transport time can be longer. In this process, the photogenerated electron-hole pairs are readily recombined, carrier lifetime decrease and carrier concentration increase, which leads to the increase of the dark current and the decrease of the responsivity. Eventually the performance of photodetector detection is reduced. Through comprehensive comparison between experiment and simulation, one can confirm that this theoretical model has a considerable level of reliability. The conclusion we can draw is that the threshold of electrical damage is 1.7 GPa. So the control of annealing temperature is extremely important for the process of making PIN photodiode. Preventing the lattice damage of the material can improve the product yield rate. In addition, from the point of view of the use of products, the stability of the working environment can extend the service life of products, and the detection accuracy is guaranteed. Conclusively, the results in this paper establish the foundation to investigate the electrical damage mechanism in the silicon-based PIN photodiode irradiated by ms-pulsed laser.
Measurement of absorption spectrum around 1.572 μm
Authors: Shao Jun-Yi  , Lin Zhao-Xiang  , Liu Lin-Mei  , Gong Wei  ,   College of Electronics and Information Engineering, South-Central University for Nationalities, Wuhan 430074, China;,   State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
Published: December 2020

Differential absorption lidar (DIAL) is widely accepted as a most promising remote sensing technique for measuring the atmospheric CO2, and has been built in many countries to study the global climate change and carbon cycle. However, the imperfect information about CO2 spectrum leads to evident errors in estimating some parameters (such as the absorption cross sections, the broadening coefficients, the optical depth, etc.) which are the critical parameters in retrieving processes of a DIAL, and will eventually result in unacceptable errors of XCO2 retrievals. Coping with that problem, a self-built constant temperature differential absorption spectroscopy system has been set up which can be used to accurately measure the absorption spectrum of carbon dioxide in the band of 1.57 μm.#br#On that basis, the absorption spectra of the pure carbon dioxide are measured respectively at the temperatures from 230 K to 320 K and the pressures from 20 kPa to 100 kPa by the highprecision oscilloscope and wavelength meter. A series of optical depths at absorption peak is respectively calculated at different temperatures and the results show that the optical depth linearly and monotonically changes while the temperature increases from 230 K to 320 K. At the same time, the relations between the corresponding absorption cross sections and temperature are analyzed, showing that the absorption cross sections first increases and then decreases with temperature increasing. The self-broadening coefficients are inferred from the spectral data at the same temperature and different pressures, and the temperature-dependent exponent is calculated. Furthermore, the air-broadening coefficients are calculated by carbon dioxide absorption spectrum data from different mixing ratios and its temperature-dependent exponent is obtained. The temperature-dependent exponent of self-broadening coefficient is 0.644 and the temperature-dependent exponent of air-broadening coefficient is 0.764, which are almost the same as the data in the high-resolution transmission molecular absorption database (HITRAN). The numerical calculation formulae of optical depth and absorption cross section are verified through these results.#br#Those parameters supplement the widely-used HITRAN database. Moreover, quantitative analysis is conducted to explore the influences of temperature and pressure on CO2 spectrum, thereby establishing a function for modeling the differential absorption optical depth and the absorption cross-section. The above results have already been used in China's CO2-DIAL and lay a foundation of accurate retrieval. It is believed that other similar CO2-DIAL of which operating wavelength is around 1.572 μm would also benefit from those newly measured parameters.
Fluorescence radiation characteristics based on evanescent wave pumping in a microfluidic chip
Authors: Chu Yu-Fei  , Zhang Yuan-Xian  , Liu Chun  , Pu Xiao-Yun  ,   Depatment of Physics, Yunnan University, Kunming 650091, China
Published: December 2020

A bare quartz optical fiber is implanted in a microfluidic channel of polydimethylsiloxane (PDMS) substrate. Pumping the microfluid by a continuous wave laser with a wavelength of 532 nm along the fiber axis, the fluorescent spectra from the channel filled with lower refractive index (RI) dye solution are obtained. Due to the fact that the evanescent field of the pump beam is homogeneous around fiber, the fluorescent emission from the rim of fiber is uniform. It is found experimentally that the fluorescent emission intensity decreases with the axial distance of fiber, and the intensity is very sensitive to the RI of the dye solution and the dye concentration. For the dye solution with a large RI, the emitted fluorescent intensity attenuates along the fiber axis more obviously than that of the dye solution with a small RI. For the high dye concentration solution, the emitted fluorescent intensity attenuates along the fiber axis also more significantly than that of the low dye concentration solution. Therefore, it is possible to obtain a uniform fluorescence radiation along the fiber axis by selecting a suitably smaller RI and a lower dye concentration solution. The observed experimental phenomena are well explained based on the mechanism of evanescent wave pumping fluorescent radiation. Based on the features of fluorescent emission in the microfluidic chip, a PDMS chip with three micro-channels is designed and fabricated. After injecting ethanol solutions of rhodamine 640, rhodamine B and rhodamine 6 G separately into the three channels and pumpingthese solutions by evanescent wave along the optical fiber axis, three fluorescence emissions with different wavelength ranges are successfully observed in a single PDMS chip.
Design and research of three-dimensional thermal cloak with arbitrary shape based on the transformation thermodynamics
Authors: Xia Ge  , Yang Li  , Kou Wei  , Du Yong-Cheng  ,   College of Power Engineering, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

Based on the form-invariance of the thermal conduction equation different from wave equation, transformation thermodynamics has opened up a new area for the arbitrarily manipulating of heat fluxes at discretion by using thermal metamaterials. Moreover, it can help researchers to design different kinds of thermal devices with many unique properties that cannot be simply realized by natural materials, such as thermal cloaking, thermal concentrating, thermal rotating and thermal illusion. Among these devices, the conventional thermal cloak enabling heat fluxes to travel around the inner region, has attracted the most significant attention so far. At the present time, the studies of the thermal cloak mainly focus on two-dimensional space with arbitrary shape and three-dimensional space with regular shape, which appear to be far from enough to meet the engineering requirements. In this paper, we derive the general expression of the thermal conductivity for three-dimensional thermal cloak with arbitrary shape according to the transformation thermodynamics. In this paper, the thermal conductivity in the polar coordinate system is transformed into that in the Cartesian coordinate system by means of coordinate transformation. On the basis of the expression of the thermal conductivity, we adopt full-wave simulation by using the software COMSOL Multiphysics to analyze the cloaking performances of five designed thermal cloaks, i.e., spherical thermal cloak, ellipsoidal thermal cloak, three-dimensional conformal thermal cloak with arbitrary shapes, non-conformal thermal cloak with the sphere outside the ellipsoid, and three-dimensional non-conformal thermal cloak with arbitrary shapes. The results show that the heat fluxes travel around the protection area, and eventually return to their original paths. The temperature profile inside the thermal cloak keeps unchanged, and the temperature field outside the thermal cloak is not distorted, which proves that the cloak has a perfect thermal invisible effect. Both the conformal and non-conformal thermal cloak have perfect thermal protection and invisible function. In this paper, the transformation thermodynamics is extended from two-dimensional thermal cloak to three-dimensional thermal cloak with better universality. At the same time, this technology provides more flexibility in controlling heat flow and target temperature field, which will have potential applications in designing microchip, motor protection and target thermal stealth. It is believed that the method presented here can be applied to other branches of physics, such as acoustics, matter waves and elastic waves.
Janssen ratio in granular solid measured by photoelastic method
Authors: Zong Jin  , Zhou Zhi-Gang  , Wang Wen-Guang  , Zhang Sheng  , Lin Ping  , Shi Yu-Ren  , Hou Mei-Ying  ,   Northwest Normal University, Lanzhou 730070, China;,   Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condense Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;,   College of Physics, University of Chinese Academic of Sciences, Beijing 100049, China;,   Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730070, China;,   College of Physics and Hydropower Engineering, Gansu Normal University For Nationalities, Hezuo 747000, China
Published: December 2020

In this work Janssen ratio is measured in a dense granular pack. The pressure on the side walls as a function of the depth of the pack with top load under gravity is measured by photoelastic method. The samples are prepared by point source method with and without tapping. A non-monotonic distribution of the side pressure along the depth is found. Numerical simulation is performed and shows qualitative consistency with the experimental finding. The apparent weight of the sample is measured for different filling heights and for different top loads. Comparing with the normal stresses on the silo wall for different heights, we obtain the Janssen ratio J =xx/zz as a function of height. We find that although uJ = 0.11 is a constant as is expected, the Janssen Ratio is height dependent. It becomes height independent only when the top load is large enough.
Rapid solidification mechanism of Fe-Al-Nb alloy droplet and its influence on microhardness under microgravity condition
Authors: Gu Qian-Qian  , Ruan Ying  , Dai Fu-Ping  ,   Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

High temperature Fe-Al-Nb alloys will be prospectively applied to the industrial field, i.e., aviation, gas turbine, etc. In this paper, rapid solidification of Fe67.5Al22.8Nb9.7 ternary alloy under microgravity condition is realized by using drop tube containerless processing technique. Our purpose is to investigate the microstructural transition pattern and relevant micromechanical properties, and then to reveal the influence of rapid eutectic growth on application performance. The sample of 2 g is placed in a quartz tube with an orifice at the bottom, and the quartz tube is then placed at the top of 3 m drop tube. The sample is inductively melted and further superheated to a certain temperature with the protecting mixture gas composed of argon and helium. The alloy melt is ejected through the orifice by an argon gas flow and dispersed into fine droplets. The droplets are undercooled and finally rapidly solidified during their free fall in the drop tube. The alloy droplets with the diameter sizes ranging from 40 to 1000 m are achieved. The liquidus temperature of the alloy is 1663 K. The microstructure of the alloy consists of Nb(Fe, Al)2 and (Fe) phases. In the master alloy prepared by arc melting, the segregation along the gravity direction takes place because of the difference in cooling rate inside the master alloy. By comparison, the microstructures of the alloy droplets are homogeneous. The variations of thermodynamical parameters with droplet size are analyzed. As droplet diameter decreases, its Nusselt and Reynolds numbers rise from 3 to 8 and from 5 to 137, respectively, its undercooling and cooling rate increase from 50 to 216 K and from 1.23103 to 5.53105 K s-1 respectively. This causes the corresponding microstructural transition. A small amount of primary Nb(Fe, Al)2 phase transforms from dendrite to equiaxed grain, the lamellar eutectic is replaced by the fragmented eutectic. The relationship between eutectic interlamellar spacing and undercooling satisfies an exponential equation, indicating that the eutectic is refined by three times. Consequently, mainly owing to the eutectic refinement, the microhardness of the alloy increases by 10% with the increase of undercooling according to the Hall-Petch behavior in terms of both eutectic grain size and interlamellar spacing. Compared with the microstructure of the alloy undercooled to the same level under electromagnetic levitation in our recent work, the microstructure in drop tube is more refined due to the larger cooling rate, contributing to the microhardness of the alloy increasing by 2%-6%.