bluuebunny/crossref_metadata_2025 huggingface dataset:
Educación sentimental, humorismo y nuevos modelos femeninos: Plaerdemavida («Tirant»), Triola («Platir») y otras doncellas confidentes en libros de caballerías
Authors: Zoppi Federica
Published: December 2020

En el presente artículo se analiza un estereotipo femenino de los libros de caballerías, el de las doncellas confidentes,desde la perspectiva de la función didáctica que desempeñan en el ámbito sentimental y erótico respecto a sus amigas. Enfocando algunas figuras concretas, como Plaerdemavida en Tirant lo Blanc y Triola en Platir, se considera elvalor del humorismo en la asunción de un papel educativo que posibilita el establecimiento, por parte de estas mujeres,de un juego con el concepto de amor y de sexualidad. Dicho juego participa en la creación de un paradigma deconducta femenina que se escapa de las normas convencionales para abrazar también costumbres potencialmentetransgresivas desde el punto de vista social.
Tres poemas amadisianos de Pere Gimferrer, José Manuel Lucía Megías y Luis Alberto de Cuenca
Authors: Mérida Jiménez Rafael
Published: December 2020

Análisis literario de las representaciones de Urganda la Desconocida en textos poéticos de Luis Alberto de Cuenca,Pere Gimferrer y José Manuel Lucía Megías, publicados a partir de 1985. La Desconocida es uno de los seres sobrenaturales más originales de las letras hispánicas. El sincretismo que revelan sus orígenes sufrió una profunda revisióna a largo del Amadís de Gaula, de Garci Rodríguez de Montalvo, factor que redundó en su importancia en el imaginario literario del siglo XVI. De la mano de tres de los poetas que mejor conocen la tradición literaria del Medioevo,se valorarán las significaciones éticas y estéticas de esta insólita resurrección poética, muy diferente en cada uno delos autores.
Per l’identificazione del «Gaufredo» citato dal Marqués de Santillana
Authors: Cherchi Paolo
Published: December 2020

Nella Defunsión de Don Enrique de Villena, testo del Marqués de Santillana, appare citato un certo «Gaufredo» chenon si è potuto identificare chiaramente finora. Le proposte d’idenficazione sono scarsamente credibili semplicementeperché i nomi ricordati non ebbero mai una risonanza che autorizzasse la loro presenza in un canone. Si proponeGaufredo di Viterbo, autore del Pantheon, opera legata alla cultura spagnola. I lettori del Marqués avrebberoriconosciuto immediatamente questo scrittore.
Key physics mechanism of the research reactor based slow positron source
Authors: Wang Guan-Bo  , Li Run-Dong  , Yang Xin  , Cao Chao  , Zhang Zhi-Hua  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In the world there have been built five reactor based slow positron sources producing very intense beams, of which, the NEPOMUC source generates the highest intensity about 3109 e+/s after updated. The beam intensity depends on the power of the core, the converter material, and the moderator geometry. It is important to have good knowledge of the influencing factors and relevant processes for building a positron source in China Mianyang Research Reactor (CMRR). In this paper, the basic mechanism and several pivotal processes are studied and modeled, including the high energy ray induced fast positron generated in target, the moderation of fast positron to slow positron, the emission of slow positron from surface, the extraction of slow positron from surface to external grid, and finally the focusing and transport by beam optic system. The beam intensity at the end of the solenoid can be deduced as I = Emth 12, where 1 is the slow positron extraction efficiency from moderators, 2 is the efficiency of lens extraction and solenoid transportation, and Emth is the slow positron emission rate from surface. The value of Emth can be expressed as Emth= AP 2L+e+pbmod, where A is the effective surface area of the moderator, P is the generating rate of the fast positron in unit volume, L+ is the slow positron diffusion length, e+ is the branching ratio of surface positron ( 0.25), i.e. the ratio of positrons reaching the surface to that emitted freely, pbmod ( 0.4) is the probability of the emitted moderated positron. Therefore, attention should be paid to the values of P, L+, 2 and A to enhance the beam intensity. P is in proportion to the neutron absorption rate by cadmium, which requires higher neutron flux of incidence. L+ is sensitive to the moderator material and its annealing condition. For the well annealed single crystal tungsten, the value of L+ is about 100 nm, while for that annealed at 1600 ℃, it decreases to only 40 nm. The value of 1 is related to the moderator depth/width ratio, the extraction voltage, and the moderator back layout. Although deeper ring can enlarge the moderator area A, the average extraction efficiency 1 decreases obviously. Considering the product of 1 and A, the recommended depth/width ratio is 3 : 1. Validations are performed by employing two types of experimental results, including several isotope slow positron sources and the PULSTAR reactor based source. The calculated efficiencies of isotope sources match well with the experimental measured results, which verifies our basic model and parameters. With these parameters and models, the intensity of PULSTAR reactor based positron source at system exit is calculated to be 5.8108e+/s, which matches well with the reported measured value of (0.5-1.1)109e+/s. Some suggestions are made and will be considered in our future design of positron source.
Fast production of 87Rb Bose-Einstein condensates
Authors: Chen Liang-Chao  , Meng Zeng-Ming  , Wang Peng-Jun  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China;,   Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: December 2020

A rapid atomic beam of rubidium (87Rb) is produced by two-dimensional magneto-optical trap (2D MOT), and then trapped by three-dimensional magneto-optical trap (3D MOT) with high vacuum for further cooling. After a process of optical molasses cooling, atoms are reloaded into a magnetic trap, where radio frequency (RF) evaporation cooling is implemented. The precooled atoms in the magnetic trap are then transferred into a far detuning optical dipole trap, where Bose-Einstein condensate (BEC) appears by further evaporation cooling. The 3D MOT is loaded to its maximum within 25 s and then BEC is prepared in 16 s. Due to the linear intensity of magnetic trap, the frequency can be scanned fast in the RF evaporation cooling process. In our experiment, the frequency scans from 39 MHz to 15 MHz in 6 s and then scans to 2 MHz in 5 s. The number of atoms in 3D MOT is about 11010, and there are 5105 atoms in the BEC after a succession of cooling processes. To optimize the performances of 2D MOT, a special light path is constructed. And prisms with high reflectivity are used to reduce the imbalance between opposite propagating cooling +beams. Furthermore, quarter-wave plates are used to keep the polarization state of the cooling beam when reflected by prisms or mirrors. The atoms are cooled to a temperature about 15 K in the magnetic trap by RF evaporation. In such a low temperature, the loss of magnetic trap (Majorana loss) will prevent the atoms from reaching a high density, and the atoms cannot be cooled further. To reduce the loss rate of the magnetic trap, the far blue detuning light (532 nm, 18 W) is added to plug the zero point of the magnetic trap. In the optically plugged magnetic trap, atoms with high density are cooled down enough, which gives a good start for the loading of optical dipole trap.
Research on diffusiophoresis of self-propulsion Janus particles based on lattice Boltzmann method
Authors: Zhou Guang-Yu  , Chen Li  , Zhang Hong-Yan  , Cui Hai-Hang  ,   School of Environment and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Published: December 2020

Studies of the driving force of the self-propulsion Janus particles are very important in the fields of micro-power and nano-motor. In this paper, we choose the micron Pt-SiO2-type Janus particle as a research object, which is propelled by self-generated concentration gradient in the dilute solution of H2O2, focusing on the self-propulsion of the single particle. According to the force analysis of the Janus particle, the surface force can be decomposed into the viscous resistance of the fluid, the Brownian force derived from the molecular thermal fluctuation, and the diffusiophoresis caused by the diffusion of the solute component. The main aim of this paper is to find the way to accurately simulate the diffusiophoresis generated by the huge concentration gradient on a microscale. The lattice Boltzmann method (LBM) is a modern mesoscopic method based on the microscopic particle characteristics of the fluid, which makes it more intuitive to deal with the interaction between the fluid and solid. It is more advantageous than the traditional numerical method in the description of this micro-interface dynamic problem, i.e., the self-propulsion of Janus particle. On a certain time scale, when the Janus particle shows the directional motion, the influence of the Brownian force can be ignored. Thus, the analytical process can be simplified. Based on the momentum theorem, the method of calculating the diffusiophoresis produced by concentration diffusion is proposed. We introduce the momentum exchange in the half-way bounce-back scheme of LBM into the model of the multicomponent diffusion and reaction. Through counting the surface force we can obtain the diffusiophoresis acting on the Janus particle. Moreover, this diffusiophoresis model is modified by comparing the experimental fluid resistance with simulated one. This comparision verifies the validity of the diffusiophoresis model. Then, the analysis of the variation of diffusiophoresis proves that the value of diffusiophoresis is independent of the fluid velocity. Through the further application of this model, the different shapes of Janus particles with the same volume are compared in simulations. The results show that the self-diffusiophoresis is mainly determined by the axial projection area. In addition, the reaction area of the particle also affects the value of the diffusiophoresis.
Lorentz force filtering and fast steering mirror optical compensation in optical axis stability control for photoelectric mast
Authors: Liu Zong-Kai  , Bo Yu-Ming  , Wang Jun  , Cui Ke  ,   Advanced Launch Collaborative Innovation Center, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

The photoelectric mast equipped on the underwater vehicle is the key equipment for photoelectric tracking. While the vehicle moves under water, especially, at high speed, more complex vortexes are generated at the surface, which will give rise to great disturbance to the stability of optical axis. In this paper, firstly, based on the basic control equations of electromagnetic field and fluid mechanics, the effects of the Lorentz force on flow field structure and vortex induced vibration are numerical simulated with using the finite volume method with hierarchy grids. Secondly, the structural characteristics, transfer functions and PID control strategies of fast steering mirror (FSM) are analyzed. Finally, combining the transfer function of FSM and the force characteristics, the effect of the composite control on the stability of submarine photoelectric tracking system is discussed by MATLAB. The results show that the Lorentz force can adjust the boundary layer and suppress vortex induced vibration, based on which the FSM can be used to further improve the accuracy of the optical tracking system. This research offers a new exploration in the field of electromagnetic fluid control, as well as a novel development of the traditional research direction of fluid mechanics. Therefore it appears to have a certain scientific significance and practical value.
Study on ultrafast dynamics of low-temperature grown GaAs by optical pump and terahertz probe spectroscopy
Authors: Fan Zheng-Fu  , Tan Zhi-Yong  , Wan Wen-Jian  , Xing Xiao  , Lin Xian  , Jin Zuan-Ming  , Cao Jun-Cheng  , Ma Guo-Hong  ,   Department of Physics, Shanghai University, Shanghai 200444, China;,   Key Laboratory of Terahertz Solid State Technology, Shanghai Institute Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

Low-temperature-grown GaAs (LT-GaAs) possesses high carrier mobility, fast charge trapping, high dark resistance, and large threshold breakdown voltage, which make LT-GaAs a fundamental material for fabricating the ultrafast photoconductive switch, high efficient terahertz emitter, and high sensitive terahertz detector. Although lots of researches have been done on the optical and optoelectrical properties of LT-GaAs, the ultrafast dynamics of the photoexcitation and the relaxation mechanism are still unclear at present, especially when the photocarrier density is close to or higher than the defect density in the LT-GaAs, the dispersion of photocarriers shows a complicated pump fluence dependence. With the development of THz science and technology, the terahertz spectroscopy has become a powerful spectroscopic method, and the advantages of this method are contact-free, highly sensitive to free carriers, and sub-picosecond time resolved. In this article, by employing optical pump and terahertz probe spectroscopy, we investigate the ultrafast carrier dynamics of photogenerated carriers in LT-GaAs. The results reveal that the LT-GaAs has an ultrafast carrier capture process in contrast with that in GaAs wafer. The photoconductivity in LT-GaAs increases linearly with pump fluence at low power, and the saturation can be reached when the pump fluence is higher than 54 J/cm2. It is also found that the fast process shows a typical relaxation time of a few ps contributed by the capture of defects in the LT-GaAs, which is strongly dependent on pump fluence: higher pump fluence shows longer relaxation time and larger carrier mobility. By employing Cole-Cole Drude model, we can reproduce the photoconductivity well. Our results reveal that photocarrier relaxation time is dominated by the carrier-carrier Coulomb interaction: under low carrier density, the carrier-carrier Coulomb interaction is too small to screen the impurity-carrier scattering, and impurity-carrier scattering plays an important role in the photocarrier relaxation process. On the other hand, under high pump fluence excitation, the carrier-carrier Coulomb interaction screens partially the impurity-carrier scattering, which leads to the reduction of impurity-carrier scattering rate. As a result, the photocarrier lifetime and mobility increase with increasing pump fluence. The experimental findings provide fundamental information for developing and designing an efficient THz emitter and detector.
Analytical channel potential model of amorphous InGaZnO thin-film transistors with synchronized symmetric dual-gate
Authors: Qin Ting  , Huang Sheng-Xiang  , Liao Cong-Wei  , Yu Tian-Bao  , Deng Lian-Wen  ,   School of Physics and Electronics, Central South University, Changsha 410083, China
Published: December 2020

Oxide indium gallium zinc thin film transistor (IGZO TFT) is a promising candidate for mass production of next-generation flat panel display technology with high performance. This is due to many merits of IGZO TFTs, such as high mobility, excellent uniformity over large area, and low cost. In recent years, IGZO TFTs with dual gate structure have attracted enormous attention. Compared with the conventional single gate IGZO TFTs, the dual gate IGZO TFTs have many advantages including increased driving ability, reduced leakage current, and improved reliability for both negative biasing stressing and positive biasing stressing. Although the measurement results of fabricated circuit samples have proven that dual gate IGZO TFTs are beneficial for the integration of digital circuit and active matrix light emitting display with in-array or external compensation schematics, there has been no proper analytic model for dual gate IGZO TFTs to date. As the analytic model is crucial to circuit simulations, there are great difficulties in circuit designs by using dual gate IGZO TFTs. Although there are some similarities between the operating principal of the dual gate IGZO TFTs and that of the dual gate silicon-on-insulator devices, the complexity of conducting mechanism of IGZO TFTs is increased due to the existence of sub-gap density of states (DOS) in the IGZO thin film. In this paper, an analytical channel potential model for IGZO TFT with synchronized symmetric dual gate structure is proposed. Gaussian method and Lambert function are used for solving the Poisson equation. The DOS of IGZO thin film is included in the proposed model. Analytical expressions for the surface potential (S) and central potential (0) of the IGZO film are derived in detail. And the proposed channel potential model is valid for both sub-threshold and above-threshold region of IGZO TFTs. The influences of geometry of dual-gate IGZO TFT, including thickness values of gate oxide layer and IGZO layer, on the device performance are thoroughly discussed. It is found that in the case of small gate-to-source voltage (VGS), as the conducting of IGZO layer is weak, both S and 0 increase linearly with the increase of VGS due to the increase of voltage division between the oxide and IGZO layer. However, the increase of S and 0 starts to saturate once VGS is larger than threshold voltage due to the shielding of electrical field by the induced electron layer of IGZO surface. With the evolution of VGS, the calculated results of S and 0 by using the proposed dual gate IGZO TFT model are in good agreement with the numerical results by technology computer aided design simulation method. Therefore, the proposed model is promising for new IGZO TFT electronics design automation tool development.
Meso-scale transport characteristics and budget diagnoses of water vapor in binary typhoons
Authors: Li Qi-Hua  , Lu Han-Cheng  , Zhong Wei  , Wang Wei-Chao  , Guo Xing-Liang  , Yuan Meng  ,   Institutes of Aeronautical Meteorology, Air Force Academy of Equipment, Beijing 100085, China;,   Institutes of Meteorology and Oceanography, PLA National University of Defense Technology, Nanjing 211101, China;,   The 94855 Troop of PLA, Quzhou 324001, China
Published: December 2020

In this paper, we simulate a process of binary typhoon and the budget diagnoses of water vapor in this process to analyze the transportation characteristics of water vapor and their influences on the variation of typhoon intensity. The results show that the interactions between typhoon Fitow and surrounding systems, including subtropical high, mid-latitude trough, west of the continent high and Southeast trailing typhoon Danas, change the background wind fields of Fitow, and then adjust the transport channels of moisture. Those surrounding systems, especially the trailing typhoon Danas which can be called the collection-transfer station of water vapor, have important effects on the intensity maintenance and the northern strong precipitation in the offshore and landing period of Fitow. The distribution and evolution of water vapor flux convergence band are consistent with those of strong convection band, revealing that the water vapor transport has important influences on the structure and intensity of the inner-core convection band in typhoon. The budget results show that the time series of total water vapor flux and typhoon intensity change synchronously. And the eastern boundary is the main source of water vapor transport, and the southern and northern boundary are also important, while the western boundary makes a negative contribution. The inflow transport channel is mainly located at the bottom of the troposphere, while the outflow transport area of water vapor is located at middle- and low-level troposphere of western boundary. The vertical transportation of water vapor plays an important role in redistributing the internal moisture of typhoon. The duration of sever convection band in typhoon is accompanied by the strong vertical transport of water vapor, which indicates that the vertical transport of water vapor is important for developing the strong convection in U and V type typhoon.
Thermal transport and microscopic dynamics in filled skutterudite YbFe4Sb12 studied by ab initio molecular dynamics simulation
Authors: Wang Yan-Cheng  , Qiu Wu-Jie  , Yang Hong-Liang  , Xi Li-Li  , Yang Jiong  , Zhang Wen-Qing  ,   State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;,   University of Chinese Academy of Science, 19 Yuquan Road, Beijing 100049, China;,   Materials Genome Institute, Shanghai University, Shanghai 200444, China
Published: December 2020

Filled skutterudite is a typical thermoelectric material with high thermoelectric figure of merit at intermediate temperatures. One of the important features is the low lattice thermal conductivity (L) caused by the low frequency vibrations of filler atoms in the oversized void cages. In the past decades, it has been still under debate whether the underlying phonon scattering mechanism should be considered to be resonant scattering or enhanced three-phonon process. To clarify the role played by the filler atoms in reducing the lattice thermal conductivity, we study the microscopic dynamical process of filler and related interactions by means of ab initio molecular dynamics (AIMD) and temperature dependent effective potential (TDEP) technique. Firstly, we simulate the dynamical trajectories of fully filled skutterudite YbFe4Sb12 at different temperatures through AIMD. In this approach, the nonlinear guest-host interactions at finite temperatures are taken into consideration naturally from dynamical trajectories. Then, we extract the effective temperature-dependent harmonic and anharmonic interatomic force constants (IFCs) by TDEP method through the statistical analyses of both trajectories and forces. The atomic participation ratios and lifetimes of phonon modes are calculated based on the effective IFCs. The results demonstrate that the local vibration modes of Yb couple with acoustic branches and reduce the lifetimes of the lattice phonons significantly. However, the calculated L, which is on the assumption that the filler interacts with lattice phonons through three-phonon collision, still deviates from the experimental result. In order to rationalize the discrepancy, we analyze the correlation properties between different Yb atoms by velocity coherence in atomic dynamical motions. The localized and independent vibration characteristic of Yb is found in this analysis. This implies that the motions of Yb atoms deviate from the periodic and collective vibration excitation paradigm of phonon. Therefore, the mechanism for how filler atoms scatter lattice phonon and enhance thermal resistance is beyond three-phonon scattering process. We thus introduce resonant scattering into the lifetimes of Yb-dominant localized vibration modes, and so-calculated L is in a good agreement with the experimental data. Overall, we come to a conclusion that both the phonon-phonon interaction and the resonant scattering due to the localized oscillators cause the low lattice thermal conductivity of YbFe4Sb12.
Phase modulation analysis for optical fiber strain caused by raindrop collision
Authors: Zhu Hui  , Sun Xiao-Han  ,   National Research Center for Optical Sensing/Communications Integrated Networking, Southeast University, Nanjing 210096, China
Published: December 2020

Optical fiber vibration sensing technology is based on the phase modulation of the transmitted light caused by the external vibration to achieve vibration measurement. A lot of researches have reported a variety of schemes for optical fiber vibration sensing and set up several application systems, achieving the functions of oil field safety monitoring, perimeter security, pipeline safety monitoring, etc. The phase modulation caused by raindrops is mixed with the sensing signal, however, when the sensing fiber cable is exposed to the atmospheric environment and the rainfall directly acts on the sensing cable. It is difficult to distinguish the valid signal which can cause the false alarms, which thereby seriously affects the normal operation of the sensing system. To our knowledge, to date, there has been no report on the phase modulation of the transmitted light in the optical fiber caused by raindrops.
Based on the theory of cloud dynamics, the transformations of refractive index and shape in the core of optical fiber and the phase modulation of light caused by raindrop collision with optical fiber cable are analyzed. The model of optical phase modulation caused by raindrop collision with optical fiber cable is established, and the relationship between phase modulation and rainfall intensity is obtained. With the increase of rainfall intensity, the phase modulation increases. When the length of the optical fiber cable is fixed, the larger the cable diameter, the larger the phase modulation is. The larger the length of the cable, the greater the phase modulation is, with the cable diameter fixed. The phase modulation caused by raindrops has a positive correlation with the cable diameter and the cable length, which is related to the rainfall intensity received on the cable surface, and increases monotonically with the rainfall intensity. A laboratory verification system for phase modulation caused by raindrop collision with optical fiber cable is established, and the relationship between the phase modulation caused by raindrops and the output signal is obtained. The experimental results are compared with the simulation results at the rainfall intensities of 3, 5, 7, 10, 15, 18, 22, and 30 mm/h. The experimental and simulated results are consistent with each other under different rainfall intensities and the error is less than 9%. The results show that the model can be used to simulate the phase modulation caused by rainfall under different rainfall intensities. It provides a theoretical basis for studying the effect of rainfall on the vibration sensing system, based on which the application system can be optimized and the feasible rainfall compensation scheme can be found.
Development of a 4 T (46 K) 100 mm high-temperature superconducting coil made of homemade MOCVD-YBCO coated conductors
Authors: Ding Fa-Zhu  , Zhang Jing-Ye  , Tan Yun-Fei  , Chen Zhi-You  , Dong Ze-Bin  , Zhang Hui-Liang  , Shang Hong-Jing  , Xu Wen-Juan  , Zhang He  , Qu Fei  , Gao Zhao-Shun  , Zhou Wei-Wei  , Gu Hong-Wei  ,   Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;,   Key Laboratory of Applied Superconductivity, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The second-generation high-temperature superconductor (2G HTS) is a good candidate for high field magnet due to its high critical temperature Tc,high critical current density Jc,and high irreversibility field Hirr.This paper presents the design and development of a 4.08 T (46 K) coil made of homemade 2G HTS.In order to meet the design requirement of HTS coil,the electromagnetic finite element modeling and optimization are carried out on the basis of the research of the properties of YBa2Cu3O7-x(YBCO) tapes.And the design scheme of HTS coil is completed.Then the HTS coil with an inner diameter of 100 mm is successfully constructed according to the scheme.It consists of a stack of 10 double-pancakes with the same outer diameter wound with YBCO tapes.The diameter and height of the HTS coil are 236 and 359 mm,respectively.A total of 1600 meters of YBCO tape are used to wind this HTS coil.We measure the I-V curves of superconducting coil at different cryogenic temperatures.First,liquid nitrogen is used to cool the HTS coil to 77 K,and then the temperature is reduced to 65 K by the decompression cooling method.The cooling coil containing liquid helium is used to exchange heat and cool the solid nitrogen to obtain much lower cryogenic temperature.The maximum operating currents of the HTS magnet at 77,65,and 55 K are 65,147,and 257 A,respectively,corresponding to the center magnetic field of 0.78,1.77,and 3.1 T.At 46 K,the HTS coil with an inner diameter of 100 mm generates a 4.08 T field at the center.And the magnetic field of superconducting coil is basically uniform in the medium plane.The results demonstrate a strong potential of home-made YBCO magnet for direct current high-field applications.
A time-varying Doppler spectrum model of radar sea clutter based on different scattering mechanisms
Authors: Zhang Jin-Peng  , Zhang Yu-Shi  , Li Qing-Liang  , Wu Jia-Ji  ,   National Key Laboratory of Electromagnetic Environment, China Research Institute of Radiowave Propagation, Qingdao 266107, China;,   School of Electronic Engineering, Xidian University, Xi'an 710071, China
Published: December 2020

The Doppler spectrum modeling of the sea clutter is of great significance for using the Doppler radar to suppress the sea clutter and detect the target on sea surface. Taking into account the characteristics of the Doppler spectrum components corresponding to three scattering mechanisms, the Bragg, whitecap, and breaking-wave, we propose a time-varying Doppler spectrum model of radar sea clutter in this paper. The Doppler spectrum shifts and bandwidths of the three scattering mechanisms are considered respectively, and a Doppler shift of an added wave speed is introduced into this model. Because the spectrum intensity is defined as a random variable being a function of the measuring time of the sea clutter series, the model has the ability to model both the long-time averaged Doppler spectra and the short-time Doppler spectra. By modeling the short-time Doppler spectra and the long-time averaged Doppler spectra of the shore-based radar sea clutter measured in the China Yellow Sea at P and S bands, it is indicated that the proposed model has a higher precision than the conventional model, and especially, the modeling errors decrease significantly in the cases of the short-time Doppler spectra with long measuring time and the long-time averaged Doppler spectra with complex shapes.
Successive lag synchronization on dynamical networks with non-uniform communication delays
Authors: Zhang Di  , Zhang Yin-Xing  , Qiu Xiao-Fen  , Zhu Guang-Hu  , Li Ke-Zan  ,   School of Mathematics and Computing Science, Guangxi Key Laboratory of Cryptography and Information Security, Guilin University of Electronic Technology, Guilin 541004, China
Published: December 2020

In dynamical networks, usually there are time delays among nodes during their communication. Different pairs of nodes generally have different time delays (i.e., having non-uniform communication delays). It has more practical significance to study the successive lag synchronization on dynamical networks with non-uniform communication delays. So, in this paper we construct a dynamical network model with non-uniform communication delay. Then, by designing linear feedback control and adaptive feedback control, and by using the Lyapunov function method, we obtain sufficient conditions for guaranteeing the stability of successive lag synchronization. Finally, in the numerical simulation, we choose the Chua's circuit as the local nonlinear dynamic and two kinds of topological structures for dynamical network to verify the effectiveness and correctness of obtained results.
Mach-Zehnder interferometer based on fiber taper and fiber core mismatch for humidity sensing
Authors: Cheng Jun-Ni  ,   School of Energy Engineering, Yulin University, Yulin 719000, China
Published: December 2020

A simple and high sensitivity optical fiber relative humidity (RH) sensor based on Mach-Zehnder interferometer (MZI) is proposed and demonstrated in this paper. A single-mode fiber and a graded-index multimode fiber are connected by a fiber taper to form a section. Then an uncoated dispersion compensation fiber is sandwiched between two short sections of the graded-index multimode fiber.Therefore, a sensing structure is set up as a single-mode fiber-taper fiber-graded-index multimode fiber-dispersion compensation fiber-graded-index multimode fiber-taper laser-single-mode fiber. The taper fiber is used to augment the energy of the cladding mode. The two nodes of the graded-index multimode fiber can be looked as a mode coupler. Thus an MZI is constructed. Since the external RH change can make the transmission spectrum energy changed, we can obtain the RH by detecting the peak energy variation of the interference pattern induced by the evanescent-field interaction. The experimental results show that the peak energy changes linearly with surrounding relative humidity. Under the condition of 35%Rh-85%RH, the sensitivity of the sensor with a 20 mm dispersion compensation fiber is -0.0668 dB/%RH and the linearity is 0.995. Moreover, temperature response characteristics are investigated. Experimental results suggest that the transmission spectrum energy of the sensor is insensitive to temperature. With temperature increasing, the transmission spectrum presents obviously a red-shift, yet the peak energy of the monitoring point barely moves, which demonstrates its potential for measuring simultaneously RH and temperature. The proposed sensor has a small size and simple manufacturing process, which can make it widely used to measure RH.
High resolution electron bombareded complementary metal oxide semiconductor sensor for ultraviolet detection
Authors: Liu Hu-Lin  , Wang Xing  , Tian Jin-Shou  , Sai Xiao-Feng  , Wei Yong-Lin  , Wen Wen-Long  , Wang Jun-Feng  , Xu Xiang-Yan  , Wang Chao  , Lu Yu  , He Kai  , Chen Ping  , Xin Li-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
Published: December 2020

High resolution and high sensitive low light level imaging sensors are crucial in many applications such as astronomical observation, high energy physics, night vision and remote sensing. The electron bombarded complementary metal oxide semiconductor (EBCMOS) sensor is a novel imager in which very high gain can be produced by hitting the semiconductor with high voltage without any noise generation. In addition, it can process high-definition image with kHz frame rate. These advatages make the EBCMOS an ideal device for ultrafast single-photon imgaing. In this article, we present an EBCMOS sensor working in the ultraviolet range by combing the technology of vacuum photocathode and back illuminated CMOS together. This EBCMOS sensor can realize very high resolution in 40 mlx light illumination environment. The achieved spatial resolution is 25 lp/mm (line paris per millimeter) when the electric field intensity is 5000 V/mm. The liner relation between electric field intensity and the resolution indicates that much better perofromance can be achieved if the electric field intensity increases to a much higher value. The EBCMOS sensor developed in this paper can be directly applied to UV weak light detection, moreover it will provide a good reference for further developing the visible and near infrared sensitive EBCMOS sensors.
Photon-excited carriers and emission of graphene in terahertz radiation fields
Authors: Tao Ze-Hua  , Dong Hai-Ming  , Duan Yi-Feng  ,   School of Physical Science and Technology, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

Graphene exhibits excellent electronic and optical properties, which has been proposed as an advanced material for new generation of electronic and optical devices. We develop a detailed theoretical mode to investigate the optical properties of graphene-wafer systems. The photon-excited carriers and emission are obtained based on the mass-balance equation and the charge number conservation equation, which are derived from Boltzmann equation. The analytical results of photon excited carrier density and photon emission coefficient are achieved self-consistently in terahertz radiation fields. It is found that the photon excited carrier density increases with doped electron density or temperature decreasing. The higher the doped electron density and the lower the temperature, the larger the photon emission coefficient is. The optical emission increases with doped electron density increasing, and the optical emission increases with temperature decreasing. It shows that photon-excited carriers and emission of graphene can be effectively tuned by gate voltage. These theoretical results can be used to understand the relevant experimental findings. This theoretical study can benefit the applications in advanced optoelectronic devices based on graphene, especially terahertz devices.
Enhanced photonic spin Hall effect due to controllable permittivity of alloy film
Authors: Wan Ting  , Luo Zhao-Ming  , Min Li  , Chen Min  , Xiao Lei  ,   School of Information and Communication Engineering, Hunan Institute of Science and Technology, Yueyang 414006, China;,   School of Physics and Electronic, Hunan Institute of Science and Technology, Yueyang 414006, China
Published: December 2020

Photonic spin Hall effect (SHE) is an interesting transport phenomenon, and has attracted growing attention. The spin-dependent splitting of photonic SHE as a weak effect is just tens of nanometers so that it can usually be detected indirectly with the weak measurement techniques. To detect it directly and use it properly, many efforts have been devoted to enhancing the photonic SHE. Recently, the surface plasmon resonance (SPR) excited by a pure nanometal structure is used to enhance the photonic SHE. However, the pure metal permittivities are limited, therefore the regulation of the photonic SHE is also restricted. It is worth mentioning that the alloy made from the pure metal with different composition proportions can achieve the artificial control of permittivity. More importantly, the alloy can also be used to manipulate the SPR. In this paper, we systematically investigate the photonic SHE in a nanoalloy structure composed of BK7 glass, alloy film and air in order to realize the enhancement of photonic SHE. First of all, the resonant angle of SPR varying with the permittivity of alloy is studied by using the angular spectrum theory of beam. It is found that the resonant angle of the SPR is mainly influenced by the real part of the permittivity of alloy, while the imaginary part has little influence on it. The resonant angle of SPR will increase with the increase of the real part of the permittivity. Secondly, the spin-dependent splitting is studied by changing the alloy permittivity when the incident angle is set to be a resonant angle. We find that the distribution of the larger spin-dependent splitting at the resonant angle is zonal. The optimal permittivity of alloy film is ε2=-2.8 + 1.6i, and the alloy can be composed of Ag and Ni according to the Bruggerman theory. Under the condition of the optimal permittivity, the spin-dependent splitting reaches about 1.2×105 nm at a resonant angle of 51.5°, which is about 40 times larger than the previous result in a pure nanometal structure. Finally, when the incident angle is fixed at 44.1°, it is revealed that the spin-dependent splitting varying with the permittivity is axially symmetric and spherical radiation is centered at a maximum value. The farther away from the center, the smaller the corresponding beam shift is. The alloy permittivity in the spherical radiation center is ε2=-10.6 + 1.2i, which can be composed of Au and Ag. The value of spin-dependent splitting reaches about 8000 nm, which is greatly improved when compared with the previous maximum value 3000 nm in a pure nanometal structure. These findings can effectively enhance the photonic SHE and provide theoretical basis for the research and development of nanophotonic devices such as the SPR-based sensor.
Coherent anti-Stokes Raman scattering spectrum of vibrational properties of liquid nitromethane molecules
Authors: Peng Ya-Jing  , Sun Shuang  , Song Yun-Fei  , Yang Yan-Qiang  ,   Department of Physics, Bohai University, Jinzhou 121013, China;,   Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The initial decomposition micro-mechanism of energetic materials has attracted much attention because it is a critical factor for the safe use of energetic materials. The thermally triggered chemical reactions are usually related to the vibrational properties of molecules. A time-resolved coherent anti-Stokes Raman scattering (CARS) spectrum system is constructed to study the molecular coherent vibrational dynamics of nitromethane at a microscopic level for clarifying the relation of molecular vibration to initial chemical reaction. In this experiment, the ultra-continuous white light is used as Stokes light, and the CARS spectra of different vibrational modes can be obtained by adjusting the time delay of the Stokes light. The vibrational dephasing time of different chemical bonds in nitromethane is provided by fitting the vibrational relaxation curves. The dephasing time of the CH stretching vibration located at 3000 cm-1 is shown to be 0.18 ps, which is far less than the dephasing time 6.2 ps of the CN stretching vibration located at 917 cm-1. The vibrational dephasing time is closely related to thermal collision for liquid nitromethane system without intermolecular hydrogen bond, that is, the scattering of thermal phonons causes the dephasing of coherent vibration. Therefore, the stretching vibration of the CH bond is more easily affected by the thermal phonon than the stretching vibration of the CN bond. The CH bond of nitromethane molecule is expected to be excited first, causing an initial chemical reaction under thermal loading.
Continuous-wave intracavity YVO4/BaWO4 Raman laser pumped by a wavelength-locked 878.9 nm laser diode
Authors: Zhang Yun-Chuan  , Fan Li  , Wei Chen-Fei  , Gu Xiao-Min  , Ren Si-Xian  ,   Institute of Applied Photonic Technology, College of Physics Science and Technology, Yangzhou University, Yangzhou 225002, China;,   National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
Published: December 2020

In this paper, the composite Nd:YVO4 laser crystal is in-band pumped by a wavelength-locked laser diode at 878.9 nm, with the purpose of reducing thermal effects and improving pump absorption simultaneously. By using the YVO4 and BaWO4 crystals as Raman media, the influences of crystal properties, resonator structure and stability on the performance of continuous-wave intracavity Raman laser are investigated experimentally and theoretically. The results show that the resonator stability greatly affects laser performance due to the long cavity length of intracavity Raman laser. By choosing the Raman medium with high Raman gain, we can not only obtain higher Raman conversion efficiency, but also reduce the thermal effect to a certain extent. Furthermore, the smaller the curvature radius of the output mirror in the plano-concave cavity structure, the greater the power density of the fundamental laser in the Raman crystal is and the wider the dynamic stability region of the resonator, and hence the higher output power of the Raman laser can be achieved. Finally, by using 30-mm BaWO4 crystal as Raman medium, a highest Raman output of 3.02 W is obtained at a pump power of 25.1 W, corresponding to a diode-to-Stokes optical conversion efficiency of 12%.
Influence of Zr doping on solubility of Xe in UO2: A first-principle study
Authors: Zhang Zhong  , Wang Huan  , Wang Kai-Yuan  , An Huan  , Liu Biao  , Wu Jian-Chun  , Zou Yu  ,   Key Laboratory of Radiation Physics and Technology, Ministry of Education;Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

As a major fuel of the light-water reactors, UO2 has excellent properties such as high melting point, good radiation resistance, corrosion resistance, compatibility with cladding materials, and strong ability to tolerate fission gas. The Zr atoms are inevitably introduced into UO2 lattice during the operation of a nuclear reactor, which can affect the solubility of Xe in the UO2. In this paper, we calculate the formation energy of vacancy defect and the binding energy of Xe in vacancy of Zr doped UO2.
The calculations presented here are based on density functional first-principle and projector augmented-wave method. A plane-wave basis set with a cutoff energy of 400 eV is used. The generalized gradient approximation refined by Perdew, Burke and Ernxerhof is employed for determining the exchange and correlation energy. Hubbard U term is used for considering the f-electron localization. Brillouin zone is set to be within 555 k point mesh generated by the Monkhorst-Pack scheme. The self-consistent convergence of total energy is 110-4 eV/atom. The calculations are performed in a 222 supercell.
In order to verify the calculating process, the formation energies of U and O point defects are compared with those in the literature. Then the influence of Zr doping in the UO2 on the solubility of Xe in the UO2 is studied. The results show that the ability to form the vacancy defects is different in the U-rich and O-rich environment of UO2. The vacancy defects in UO2 are more likely to form in O-rich UO2. The Zr doping will lead to the increasing of the formation energies of defects in both cases.
The Zr doping will also change the binding energy of Xe in void. For all the systems studied, only the binding energy of Xe adsorbed to the void consisting of four point defects increases, while the rest decrease. The solution energy, equaling the sum of the binding energy of Xe and the vacancy formation energy, will increase after doping Zr, because the decrement in binding energy is generally less than the increment in vacancy formation energy.
In summary, the presence of Zr will weaken the solubility of Xe in UO2, which is mainly due to the hindering of vacancy defects from forming. This result has a certain value in studying the dissolution of fission product Xe after a small amount of Zr has entered into the UO2 fuel in nuclear reactor.