bluuebunny/crossref_metadata_2025 huggingface dataset:
High temperature sample environment upgrade of ISIS engineering materials in-situ diffraction experiment
Authors: Zhan Xia , Joe Kelleher , Gao Jian-Bo , Ma Yan-Ling , Chu Ming-Qiang , Zhang Shu-Yan , Zhang Peng , Sanjooram Paddea , Gong Zhi-Feng , Hou Xiao-Dong ,   Centre of Excellence for Advanced Materials, Dongguan 523808, China,   ISIS Neutron and Muon Source, Harwell OX11 0QX, United Kingdom,   Songshan Lake Laboratory for Materials Science, Dongguan 523808, China,   Shanghai Aircraft Manufacturing Co.,Ltd, Shanghai 200436, China,   Materials Engineering Department, Open University, Milton Keynes MK7 6AA, United Kingdom,   Research Institute for Future Transport & Cities, Coventry University, Coventry CV1 5FB, United Kingdom
Published: December 2020

The ISIS Neutron Facility of Rutherford Appleton Laboratory (RAL) in the UK plays an important and world leading role in in-situ engineering materials testing, one of the most typical neutron diffractometers known as Engin-X, used to measure residual stress and phase transformation and to do micromechanics research, through using different sample environment equipment, such as mechanical fatigue loading frame, cryogenic temperature furnace of cooling the sample down to 1.5 K and particularly high temperature furnace of heating the sample up to 1100 ℃ under loading condition. The present maximum heating capability of the Engin-X high temperature furnace at ISIS can be increased to above 1100 ℃, that would allow more extremely challenging high temperature engineering problems around the world to be investigated. With this ambition in mind, in this paper we use TracePro software initially to optimize the geometry of the present Engin-X furnace reflectors and their configurations’ arrangement. One is to use ellipse-sphere combination and the other is to use ellipse-sphere-ellipse combination to replace the present Engin-X high temperature furnace’s half ellipse reflector geometry. The results show that the former plus further reflector surface coating and reasonable side shielding arrangement result in a total increase of 109% of energy absorption by the sample. The latter makes a further 6% of increase of energy absorption by the sample. Such results are further checked by subsequent ANSYS thermal analysis to investigate the temperature distributions within the centre portion of the sample. The ANSYS simulation results further reveal that both the ellipse-sphere and ellipse-sphere-ellipse configurations are able to increase the maximum capability of the Engin-X high temperature furnace at ISIS from the present 1100 ℃ to 1399 ℃ and 1423 ℃, respectively. In this paper, we present the details of the simulations and all the configurations of the Engin-X high temperature furnace.
Comparative study of squeezed vacuum states prepared by using 1064-nm solid-state and fiber-laser as pump source
Authors: Yang Wen-Hai , Diao Wen-Ting , Cai Chun-Xiao , Song Xue-Rui , Feng Fu-Pan , Zheng Yao-Hui , Duan Chong-Di ,   China Academy of Space Technology (Xi’an), Xi’an 710100, China,   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

Squeezed states, which have fewer fluctuations in one quadrature than vacuum noise at the expense of increasing fluctuations in the other quadrature, can be used to enhance measurement accuracy, increase detection sensitivity, and improve fault tolerance performance for quantum information and quantum computation. In this paper, the influences of relative intensity noise (RIN) of all-solid-state single-frequency laser and single-frequency fiber laser on the squeezing factor of squeezed vacuum states are experimentally and theoretically studied. Here, an all-solid-state single-frequency laser and a single-frequency fiber laser each are used as a light source of the system generating squeezed vacuum states. The homodyne detection is used to compare the RIN of all-solid-state single-frequency laser and that of single-frequency fiber laser at the analysis frequency of 1 MHz. The results show that the RIN of the all-solid-state single-frequency laser and single-frequency fiber laser are higher than those of the shot noise limitation 2.3 dB and 30 dB at the analysis frequency of 1 MHz, respectively. The RIN of all-solid-state single-frequency laser is far less than that of the single-frequency fiber laser. As a result, squeezed vacuum state with maximum quantum noise reduction of (13.2 ± 0.2) dB and (10 ± 0.2) dB are directly detected. Theoretical calculation shows that the influence of the RIN on the measurement accuracy is the major factor of degrading the squeezing factor with the fiber laser as the pump source. The measurement error of squeezed vacuum state caused by the RIN of single-frequency fiber laser is about 2.6 dB. The discrepancy of the pump power between the two lasers is another factor of affecting the squeezing factor, corresponding to 0.6 dB quantum noise difference. The theoretical calculations are consistent with the experimental results, which provides some guidance for developing the practical squeezed states with highly squeezing level.
The characteristics of multiple isothermal tempered Fe-based alloy ribbons
Authors: Xu Xiao-Jia , Fang Zheng , Lu Xuan-Ang , Ye Hui-Qun , Fan Xiao-Zhen , Zheng Jin-Ju , He Xing-Wei , Guo Chun-Yu , Li Wen-Zhong , Fang Yun-Zhang ,   College of Physics, Electronic and Information Engineering, Zhejiang Normal University, Jinhua 321004, China,   Key Laboratory of Solid State Optoelectronic Devices of Zhejiang Povince, Zhejiang Normal University, Jinhua 321004, China,   Tourism College of Zhejiang, Hangzhou 311231, China,   College of Science and Technology, Xinjiang University, Akesu 843100, China
Published: December 2020

The magnetic properties of Fe-based alloy ribbons are sensitive to stress, and it’s an interesting scientific question whether stress-induced magnetic anisotropy during annealing procedure can be eliminated by tempering. In this paper, the synchrotron radiation technique was used to observe the microstructure of Fe73.5Cu1Nb3Si13.5B9 amorphous ribbons annealed at 540 ℃ for 30 minutes under 394.7MPa stress and tempered several times at the same temperature. The macroscopic elongation of the samples during stress annealing and tempering was recorded by SupereyesB011 microcamera, and the magnetic anisotropy of the samples was measured by HP4294A impedance analyzer. After fitting the experimental data, it is found that: (a) The lattice anisotropy, macroscopic strain and magnetic anisotropy of the sample show negative exponential attenuation with the tempering times, and their final residual are 19.04%. 98.27% and 31.65%. (b) Multiple tempering can not completely eliminate lattice anisotropy, macroscopic strain and magnetic anisotropy induced by stress annealing. (c) The magnetic anisotropy of the sample has a linear relationship with the lattice anisotropy, but the intercept between the reverse extension line of the relation curve and the longitudinal coordinate is not zero. When the lattice anisotropy is zero, there is still 16.36% magnetic anisotropy. This is different from Ohnuma's conclusion that lattice anisotropy is the direct cause of magnetic anisotropy. (d) The structure anisotropy caused by the residual stress after stress annealing is the main cause of magnetic anisotropy, but it is not the only reason. The directional congregation of agglomerated nanocrystalline grains caused by creep of amorphous substrates during stress annealing is also an important cause of magnetic anisotropy induced by stress annealing. Moreover, the magnetic anisotropy induced by the directional congregation of agglomerated nanocrystalline grains due to the creep of amorphous substrates during stress annealing can not be completely eliminated by tempering.
Distributed temperature measurement with millimeter-level high spatial resolution based on chaotic laser
Authors: Zhang Qian , Wang Ya-Hui , Zhang Ming-Jiang , Zhang Jian-Zhong , Qiao Li-Jun , Wang Tao , Zhao Le ,   Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, Taiyuan 030024, China,   Institute of Optoelectronic Engineering, College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

The high-precision structural health monitoring of large civil structures and materials are increasingly demanded with widely using the distributed fiber sensors. A Brillouin optical correlation domain analysis for millimeter-levelhigh spatial resolution sensing using broadband chaotic laser is proposed and demonstrated. Through the analysis of the influence of polarization state and feedback strength on the chaotic laser, we experimentally achieve a broadband chaotic laser with a spectrum over 7.5 GHz in –3 dB which means that the theoretical spatial resolution is 3 mm, and we also successfully measure the distribution of fiber Brillouin gain spectrum with a temperature over 300 m measurement range with 7.05 mm spatial resolution, which is the first time that the sensor system based on chaotic laser has achieved the measurement with millimeter-level. However, there is still a difference in spatial resolution between the experimental and theoretical values. We can find that the chaotic laser has a time-delay feature; besides, with the broadening of chaotic laser, the threshold of stimulated Brillouin scattering in optical fibers increases while the Brillouin gain will weaken if the pump power is not enough here, and the cross-correlation peak of chaotic laser will narrow. All these problems cause the Brillouin gain signal to be easily submerged by noise, so the performance of the chaotic Brillouin optical correlation domain analysis system will decrease ultimately. Therefore, we also propose an optimization of Brillouin optical correlation domain analysis system by introducing the time-gated scheme into pump branch. It is obvious that the peak power of the pump wave is heightened by more than 9.5 dB after being amplitude-modulated by a square pulse with a pulse width of greater than acoustic phonon lifetime, and the signal-to-back ground noise ratio of the gain spectrum is improved effectively in theory; the cross correlation between chaotic pump wave and probe waveis locked within a pulse duration time, and the residual stimulated Brillouin scattering interactions existing outside the central correlation peak can be largely inhibited. In this optimized setup, the performance of the distributed temperature sensing is improved to 3.12 mm spatial resolution, which corresponds well to the theoretical value. The improved chaotic Brillouin optical correlation domain analysis technology will have a great potential application in high-precision structural health monitoring of large civil structures.
Average symbol error rate for integrated satellite-terrestrial cooperative transmission with interference
Authors: Liu Xiao-Yu , Lin Min , Wang Jin-Yuan , Ouyang Jian , Huang Qing-Quan ,   College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China,   The Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing 210003, China,   College of Communication Engineering, Army Engineering University of PLA, Nanjing 210007, China
Published: December 2020

As an indispensable method of constructing ubiquitous communication network, satellite communication technology has received significant attention in both industrial and academic areas recently. In this paper we investigate the performance of an integrated satellite-terrestrial cooperative network in the presence of co-channel interference, which consists of a satellite source having a single antenna, a terrestrial relay equipped with multiple antennas to assist satellite signal transmission, and a single-antenna user corrupted by multiple co-channel interference. On the assumption that the user receives the signals from direct link and relaying link with decode-and-forward protocol, the output signal-to-interference-plus-noise ratio of the user with the maximal ratio combining scheme is firstly obtained. Then, according to the Meijer-G function, we derive the moment generating function of the destination and the relay, where the satellite links are assumed to experience Shadowing-Rician fading while the terrestrial links undergo Rayleigh fading, and the analytical average symbol error rate expression for the considered system is obtained. Finally, the simulation results demonstrate the effectiveness of the theoretical analysis and reveal theinfluences of antenna number, interference number, and modulation schemes on the system performance. Therefore, our work provides useful guidelines for the engineers in designing the integrated satellite-terrestrial cooperative networks for future satellite mobile communication.
Recovering in-plane six-fold magnetic symmetry of epitaxial Fe films by N+ implantation
Authors: Jiang Xing-Dong , Guan Xing-Yin , Huang Juan-Juan , Fan Xiao-Long , Xue De-Sheng ,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China,   Northwest Institute of Nuclear Technology, Xi’an 710024, China
Published: December 2020

In order to study the effect of ion implantation on the in-plane magnetic anisotropy of epitaxial magnetic films, a 3-nm Al buffer layer is epitaxially grown on an Si (111) substrate with a miscut angle, and then 25-nm Fe is grown on the buffer layer. High-resolution X-ray diffraction reveals that the epitaxial Fe film has a (111)-oriented bcc structure. The epitaxial Fe films are implanted by 10 keV N+ ions with dose up to 5 × 1016 ions/cm2. The change and mechanism of the in-plane magnetic anisotropy of the epitaxial Fe film are studied systematically. It is found that the in-plane magnetic anisotropy of the epitaxial Fe film is gradually changed from two-fold to six-fold symmetry with the increase of N+ implantation dose. It is confirmed by transmission electron microscopy and etching experiments that ion implantation changes the surface and interface state of Fe film. This result is consistent with the result from the SRIM software simulation. The in-plane magnetic uniaxial anisotropy of epitaxial Fe film comes from atomic steps at the surface and the interface of the Fe film. These steps result from Si (111) substrate with a miscut angle. Ion implantation has effects on sputtering and atomic diffusion. The sputtering effect causes the step at the surface of the Fe film to be erased, and the diffusion of the atom leads the step at the interface of the Fe film to disappear. The in-plane uniaxial anisotropy induced by the atomic step is weakened, and the magnetocrystalline anisotropy induced by the Fe (111) plane is dominant. Therefore, the epitaxial Fe film exhibits Fe (111) plane induced six-fold magnetic symmetry after high-dose N+ implantation. This work indicates that the in-plane magnetic anisotropy of Fe films epitaxially grown on Si (111) substrate with miscut angle can be modified and precisely controlled by ion implantation. This work may be of practical significance for improving the density of in-plane magnetic recording material.
Simulation research on formation and compressive properties of aluminum nanowires inside carbon nanotubes and boron-nitride nanotubes
Authors: Yuan Jian-Hui , Lei Qin-Wen , Liu Qi-Cheng ,   Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering, School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China
Published: December 2020

To know the basic configuration and application characteristics of aluminum (Al) nanostructure, the structure performances of carbon nanotube (CNT) and boron-nitride NT (BNNT) filled with Al atoms are studied through molecular dynamics. Optimization results show that the Al atoms in the tube are arranged neatly into various shapes of nanowires. A bunch of one-dimensional (1D) Al nanowires (AlNWs) is formed in (5, 5) CNT and BNNT, and large beams of AlNWs are formed in (10, 10) NT, including 11 beams of 1D AlNWs with highly axial symmetry in (10, 10) CNT and 5 beams of spiral AlNWs in BNNT (10, 10). Further data analysis for radical distribution function (RDF) shows that AlNWs inside CNT have larger atomic distribution density, but those inside BNNT with larger diameter have better crystallinity than those with similar size inside the CNT. These results can provide a method of designing the nanowires with different structures and shapes in different micro-nano devices (such as nanospring, nanosolenoid, and others). Comparison of the axial compression behaviors of the composite NTs and their energy analysis reveal that the critical buckling strain of AlNW@CNT is significantly larger than that of AlNW@BNNT. For the same type of compound structure, the buckling strain decreases with NT diameter increasing. Therefore, smaller AlNW@CNT has stronger axial compressive resistance. The main reasons are as follows: 1) The AlNW in carbon NTs has a relatively large Al atomic distribution in the axial direction, which is conducive to the formation of σ bond to increase structural stability and mechanical performance. It also plays a decisive role in enhancing compressive performance. 2) The AlNW in the large-diameter boron nitride NTs is helical in shape, and more Al atoms are distributed in the direction of the cross section, thereby relatively reducing the number of axial pressure-bearing atoms. In addition, for the same type of nanotube, a tube with a small diameter results in closer hexagons to the tube wall and larger interaction. These conditions are more conducive to resisting the transverse subsidence under axial pressure. The energy analysis results indicate that the van der Waals force is one of the main causes for NT composite stability and increasing compressive strength. These results can provide a reference for selecting different Al nanowire-reinforced composite structures under different application conditions, such as high temperature, high pressure, oxidation resistance, and others.
Collaborative quantum computation with redundant graph state
Authors: Tian Yu-Ling , Feng Tian-Feng , Zhou Xiao-Qi ,   State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University,  Guangzhou 510000, China
Published: December 2020

Quantum computation is a computing model based on quantum theory, which can outperform the classical computation in solving certain problems. With the increase of the complexity of quantum computing tasks, it becomes important to distribute quantum computing resources to multi-parties to cooperatively fulfill the complex tasks. Here in this paper a scheme based on the one-way quantum computing model is proposed to realize collaborative quantum computation. The standard one-way quantum computing model is based on graph states. With graph states used as resources, one can realize a universal quantum computer through using single-qubit measurements and feed-forward. In contrast to the standard one-way computation, the main resource for collaborative quantum computation is a redundant graph state (also a multi-particle highly entangled state). Unlike in the traditional graph state where each particle corresponds to a specific node, in a redundant graph state, several particles correspond to a single node, which means that each node of the graph has several redundant copies. With the help of a redundant graph state, several parties can share a graph state flexibly at will. A redundant graph state is prepared and then distributed to several parties where each of them obtains a full copy of all nodes. By communicating with each other and measuring the particles in different ways, a standard graph state is prepared and distributed among these parties. The collaborative computation then finishes through the common one-way quantum computing operations. Besides the general scheme, a concrete optical implementation of a two-party cooperative single-qubit quantum state preparation based on a six-photon redundant graph state is also put forward. Such a redundant graph state is proposed to be prepared by using the spontaneous parametric down-conversion entangled source and quantum interference. With this redundant graph state, a standard three-node graph state can be shared with the two parties in an arbitrary way. This scheme does not only make the collaborative quantum computation across several parties possible and flexible, but also guarantee the privacy of each party’s operations. This feature would be particularly useful in the case where the computing resource is obtained from an outside provider. This scheme paves the way for realizing quantum computation in more general and complicated applications.
A method of determining microwave dissipation of Josephson junctions with non-linear frequency response
Authors: Chen Heng-Jie , Xue Hang , Li Shao-Xiong , Wang Zhen ,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China,   CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, China,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Based on Josephson junction (JJ), superconducting quantum bit (qubit) is operated at frequencies of several GHz. Dissipation of JJs in this frequency range can cause energy relaxation in qubits, and limit coherence time, therefore it is highly concerned and needs to be determined quantitatively. The dissipation of JJs can be quantified by microwave quality factor. It is usually done at very low temperature (~mK) to determine whether a JJ is suitable for qubit devices by measuring the quality factor. In this paper, a method based on nonlinear frequency response of JJs is proposed to determine the quality factor. This method can be used in thermal activation regime, which may bring great conveniences to experiments. To analyze high frequency properties of JJs, the dynamic equation of a current-biased JJ, which describes high frequency oscillation of the JJ, is introduced. A fourth-order potential approximation is used to obtain the analytical equation of non-linear response. The dependence on quality factor, as well as on amplitude, of difference between JJ’s plasma frequency and resonant frequency, is derived from the equation. The approximate treatment is quantitatively validated by our numerical simulations with practical JJ parameters including different environment influences. Thus, based on nonlinear frequency response of JJs, a reliable and simple method to determine quality factor of JJ is proposed, which is desirable for exploring JJ based microwave devices such as parametric amplifier, superconducting qubit. Being driven well into the nonlinear microwave response regime, due to frequency-amplitude interaction, the resonant frequency of a current bias JJ deviates from the JJ’s plasma frequency. The deviation is directly related to the microwave quality factor. Hence, the quality factor can be deducted from the experimental measurement of the resonant frequency deviation, with different microwave power values applied. In comparison with linear resonance experiment, the nonlinear resonance used by the proposed method produces stronger signal. Therefore it is more robust against external noise. When being conducted at high temperature, the proposed method is more reliable. The accuracy of the measured quality factor primarily depends on those of the JJ’s parameters such as critical current and capacitance, while those parameters can be experimentally determined with high precision.
High-pressure neutron diffraction techniques based on Paris-Edingburgh press
Authors: Shi Yu , Chen Xi-Ping , Xie Lei , Sun Guang-Ai , Fang Lei-Ming ,   Key Laboratory for Neutron Physics, Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, China
Published: December 2020

Since the 1990s, with the benefit of available large-volumed samples, wide detector windows, and portability, Paris-Edinburgh press has been widely used in neutron facilities to study the structures and physical properties of condensed matter under high-pressure extreme conditions. In the present study, We perform high-pressure neutron diffraction experiments in neutron source of China using the Paris-Edinburgh press. The experiments are carried out on a high-pressure neutron diffraction spectrometer (Fenghuang) at China Mianyang Research Reactor (CMRR). Fenghuang is a high-intensity and moderate-resolution diffractometer which has been upgraded from a neutron powder diffractometer and can be used under ambient and extreme conditions. A single cylinder pump with a max load of 200 MPa provides a loading pressure for Paris-Edinburgh press, and a precise mobile platform is used to hang and to locate the Paris-Edinburgh press. Using the tungsten-carbide (WC) toroidal anvils with TiZr gasket, we obtain the neutron diffraction spectra of Fe samples at different pressures successfully. We also obtain the neutron diffraction spectra respectively at pressures of 9.7 GPa and 10.7 GPa by using a WC single-toroidal anvil and a WC double-toroidal anvil under load 100 MPa. The TiZr gasket blows out before the load reaches 100 MPa in the WC single-toroidal anvil assembly, while it remains good in the WC double-toroidal anvil assembly under the same load. The WC single-toroidal anvil assembly becomes unstable under load about 80 MPa, and the WC double-toroidal anvil assembly is still stable under load 100 MPa. Thus, the stability of the double-toroidal anvil assembly is much higher than that of the single-toroidal anvil assembly. It is found that the thickness of the gasket edge is very important for the stability of the assembly during loading. The thicker the edge of the gasket, the more stable the assembly is. The main reason is that the groove of the double concave anvil can enhance the lateral support ability of the gasket, thereby making the double concave surface assembly more stable than the single concave surface assembly.
Magnetic monopole array model for modeling ship magnetic signatures
Authors: Guo Cheng-Bao , Yin Qi-Qi ,   School of Electrical Engineering, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

Aiming at the problems of low accuracy and low adaptability of the existing ship magnetic field inversion modeling methods with equivalent sources, a new method of inversion modeling of magnetic monopole array of ship magnetic fields is proposed. Three-dimensional ship magnetic monopole array is arranged according to the ship ferromagnetic structure, and the inversion prediction model of ship magnetic fields is established by regularization technology. Three typical forms of magnetic monopole arrays are established: rectangular magnetic monopole array on the horizontal surface of the draft line, cuboid magnetic monopole array enclosing the ship hull, three-dimensional ship magnetic monopole array distributed according to the ship’s ferromagnetic structure. The theoretical analysis shows that the three-dimensional ship magnetic monopole array reduces the blindness of the equivalent magnetic source setting, and the obtained equivalent magnetic source is highly consistent with the real magnetic source, which can reproduce the complete magnetic field information of the ship to a greater extent. The magnetic field of a typical virtual ship is applied to the validation test. The results show that the proposed three-dimensional ship magnetic monopole array has higher precision and adaptability than the rectangular or cuboid magnetic monopole array. In particular, the proposed three-dimensional ship magnetic monopole array can realize the mutual conversion between the near and far magnetic fields, and between the magnetic fields above and below the ship. The proposed three-dimensional ship magnetic monopole array model has the unique advantages of small complexity, simple modeling and flexible layout, and it provides an alternative method for the high-precision data processing and explanation to the inversion modeling of ship magnetic fields, ship magnetic field positioning, et al.
Chaotic laser parallel series synchronization and its repeater applications in secure communication
Authors: Yan Sen-Lin ,   Electronic Engineering School, Nanjing Xiaozhuang University, Nanjing 211171, China
Published: December 2020

In this paper, chaotic parallel synchronization and quasi-periodic parallel synchronization between two mutually coupled different semiconductor lasers and other lasers are studied, and the regeneration of chaotic laser and key technology of repeater are discussed. The complex dynamic system and network of laser parallel series are presented in mathematics and in physics, and the network topology diagram and optics path are specified. A mathematical-physical model is given to study how to obtain parallel synchronization via the coupled driving nonlinear equations. The operating principle of the repeater is put forward for chaotic secure communication, and the channel equation of repeater is established because the laser chaotic behavior is extremely sensitive to external influences and system parameter changes. The laser’s chaotically regenerating and transmitting is successfully realized via two sets of repeaters. The chaotic encoding communication with repeaters is successfully completed while the encoding information signal is accurately extracted from the chaotic carrier by a filter and calculating the synchronous difference. We adopt three sets of lasers as a research case to simulate and verify the theory of laser parallel series network we put forward to fit perfectly the obtained numerical results. We study the parameter mismatch problem of the system, where the synchronous difference is numerically calculated by varying some parameters of the lasers. In the case of smaller parameter mismatch, the system has a highly synchronous capability to a certain degree. This is a novel laser chaotic encoding network in chaotic secure communication and characterizes the core technical elements of the repeater. The laser transmitter has four nonlinear interaction variables, where the nonlinear interaction between the amplitude and phase of the two optical fields results in highly nonlinear dynamics. The system has the characteristics of high nonlinearity, multi-variable, high-dimension, and multi-key. So it is highly secure and not easy to crack. The results have an important reference value for the chaos applications in remote secure communication, optical network and laser technology.
Electronic structures and Li diffusion in cathode material Li2FeO2 of Li-ion batteries
Authors: Lin Chuan-Jin , Zheng Feng , Zhu Zi-Zhong ,   College of Physics and Information Engineering, Minnan Normal University, Zhangzhou 363000, China,   Jiujiang Research Institute, College of Physical Science and Technology, Xiamen University, Xiamen 361005, China
Published: December 2020

The electronic structures and lithium diffusion in the cathode material Immm-Li2FeO2 of lithium-ion batteries are calculated by the first-principles method based on the density functional theory. The calculated results show that Immm-Li2FeO2 is ferromagnetic, and the band structure indicates a semi-metal character. The d-electrons of Fe ions are in the low spin state, with a spin polarization of 8.01%. The spin-up and spin-down band structure are also analyzed by using the l-decomposed electronic density of states. Furthermore, the energy barriers for the lithium ion diffusion in different directions are calculated by the nudged elastic band method. For comparison, the potential barriers for the Li2MO2 (M = Co, Ni, Cu) are also calculated. The results suggest that it is easier for Li ion to diffuse in the c-axis directionof Li2FeO2, with an energy barrier of only 0.1 eV. The energy barrier is 0.21 eV for Li to diffuse in the ab-axis direction, while the diffusion barrier is 0.39 eV along the a-axis direction of Li2FeO2. All these values of energy barriers are lower than those in other Fe-based cathodes mentioned, indicating that the Li diffusion coefficient in Immm-Li2FeO2 should be larger than those of other materials, which also indicates that the Li2FeO2 is of great importance as cathode material.
Group velocity dispersion analysis of terahertz quantum cascade laser frequency comb
Authors: Zhou Kang , Li Hua , Wan Wen-Jian , Li Zi-Ping , Cao Jun-Cheng ,   Key Laboratory of Terahertz Solid State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China,   Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The frequency comb which is characterized by equally-spaced frequency lines with high mode coherence has received much attention since its first demonstration in near-infrared and optical frequency range. In the terahertz frequency range, the electrically-pumped terahertz quantum cascade laser (THz QCL) based on semiconductors is an ideal candidate for achieving frequency comb operation in a frequency range between 1 THz and 5 THz. The group velocity dispersion (GVD) is a key factor for the frequency comb. A higher GVD can pull the frequencies from their equidistant values and limit the comb bandwidth. Therefore the laser dispersion needs to be compensated for in order to make the total GVD sufficiently low and flat, such as using a Gires-Tournois interferometer (GTI) or the double chirped mirror (DCM). However, a successful design still depends on the knowledge of the total GVD in the laser. In this paper, we show how to calculate the GVD in metal-metal waveguide THz QCLs by taking into account the dispersions from the GaAs material, the waveguide, and the laser gain, which conduces to the understanding of the frequency comb behavior. The waveguide loss is modelled by the finite element method. The loss due to intersubband absorption is calculated by Fermi's gold rule. All the losses, i.e., waveguide loss, mirror loss, and intersubband absorption loss, are summed up to calculate the clamped gain. The material loss can be calculated by using the reststrahlen band model. Because of these losses and gain, the refractive index needs to be replaced by a complex refractive index. The real part of the complex refractive index is the refractive index, which can be calculated from the Kramers-Kronig relationship that connects the loss or gain with the refractive index. Then the GVD introduced by the material loss, waveguide loss, and clamped gain can be finally calculated. The results show that the total GVD of THz QCL is approximately –8 × 105~8 × 105 fs2/mm which is strongly determined by the clamped gain. Finally, the developed numerical model is employed to study the dispersion compensation effect of a GTI mirror which is coupled into a QCL gain cavity. The design of the THz QCL based on GTI structure is more flexible and feasible than that of the DCM. The result shows that by carefully designing the geometry of GTI, the dispersion of a THz QCL can be compensated for, thus achieving the broadband terahertz frequency combs.
Identification of interference normal mode pairs of low frequency sound in shallow water
Authors: Meng Rui-Jie , Zhou Shi-Hong , Li Feng-Hua , Qi Yu-Bo ,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The interference characteristics of normal modes in low-frequency broadband sound can be applied to source localization and environmental parameter inversion in shallow water. However, the identification ambiguity of interference normal mode pairs generally occurs in practical applications due to unknown source position, some weakly-excited normal modes, mismatched environmental model, etc. For the applications of a horizontal line array, a model-based processing approach is proposed to determine the orders of the interference normal mode pairs based on the intrinsic dispersion characteristics of interference normal mode pairs in the received signals and the range-independent properties of the array beam output angles. Firstly, the normal mode pair filtering is achieved by using the WARPING transform of the signal autocorrelation function in the element domain of the horizontal line array. Then, the arrival angles of the filtered interference normal mode pairs are estimated by using array beamforming. Finally, the estimated beam output angles are matched with the replica values computed by sound field model. The approach is verified by using the explosive pulse signals received by the seafloor-deployed 32-element horizontal line array at the North Yellow Sea in 2011. Furthermore, some simulations are involved to analyze the effects of environmental parameter mismatches including water sound speed profile, sea bottom parameters and water depth on the identification performance of interference normal mode pairs. The results show that the water depth is a major factor influencing the extracted values of the beam output angles of interference normal mode pairs. The approach might fail when the water depth mismatch exceeds 14% of the practical value. However, the effects of water sound speed profile mismatch and sea bottom parameters mismatch are negligible. The effect of signal-to-noise ratio in the element domain on a horizontal line array is also simulated in order to analyze the limitation of identification performance, which shows that the required signal-to-noise ratio in the element domain should be more than 2 dB.
Effects of q-nonextensive distribution of electrons on secondary electron emission in plasma sheath
Authors: Zhao Xiao-Yun , Zhang Bing-Kai , Wang Chun-Xiao , Tang Yi-Jia ,   School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236037, China
Published: December 2020

A one-dimensional fluid model is used to investigate the characteristics of secondary electron emitted by the interaction between electrons and the wall in plasma sheath with nonextensive electrons. The study focuses on the effects of electron nonextensive parameter on Bohm criterion, the wall potential, the critical emission coefficient of secondary electrons and the density of seconday electrons in plasma sheath through numerical simulation. Some conclusions are obtained. It is shown that secondary electron is significantly affected by electron nonextensive parameter. Whether the electron distribution is superextensive or subextensive, the critical Mach number at the sheath edge increases with the secondary electron emission coefficient increasing, but decreases with q-parameter increasing. The increase of q-parameter can cause the wall potential to increase and the critical emission coefficient of secondary electron at the wall to decrease. And for different types of plasmas, the effects of nonextensive parameter on the critical emission coefficient of secondary electron are different. The larger the mass number of ion in plasma, the smaller the influence of nonextensive parameter on the critical secondary electron emission coefficient will be. In addition, the increase of nonextensive parameter can result in the decrease of the sheath thickness and the increase of the number density of secondary electrons. It is found that the superextensive electron distribution has greater influence on the characteristics of secondary electron emission in plasma sheath than the subextensive electron distribution.
Plasmon resonance energy transfer and research progress in plasmon-enhanced photocatalysis
Authors: Zhou Li , Wang Qu-Quan ,   Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China,   The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta 30332, United States of America,   The Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
Published: December 2020

Plasmon resonance energy transfer refers to the coherent energy transfer via dipole-dipole coupling from surface plasmons to adjacent exciton nanosystems such as semiconductor quantum dots or dye molecules. The plasmon resonance energy transfer is a non-radiative plasmon decay pathway, which can also act as an available channel to extract the plasmon-harvested energy. In addition, hot electron relaxation (non-radiative channel) and scattering (radiative channel) are also the dissipation pathways of surface plasmon resonances. The plasmon-harvested energy can be effectively transferred to other nanosystems or converted into other energy forms through these correlated dissipation pathways. In this paper, the underlying mechanism and dynamics of the plasmon resonance energy transfer as well as the related energy and charge transfer processes (such as near field enhancement and coupling, far field scattering, plasmon-induced hot electron transfer) are introduced. The recent research progress of the plasmon-enhanced photocatalysis by energy and charge transfer is reviewed.
Omnidirectional cloaking based on spoof surface plasmonic structure
Authors: Quan Jia-Qi , Sheng Zong-Qiang , Wu Hong-Wei ,   School of Mechanics and Photoelectric Physics, Anhui University of Science and Technology, Huainan 232001, China,   National Key Laboratory of Solid Microstructure Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

Surface plasmons include surface plasmon polaritons and localized surface plasmons, which are electromagnetic wave confined at the interface of the metal and dielectric. Spoof surface plasmonic structure has many special optical properties, which is of great significance for designing new-generation optical elements. In order to transfer the features of the surface plasmon polaritons and localized surface plasmons to microwave-terahertz region, Pendry et al. (Pendry J B, Martin-Moreno L, Garcia-Vidal F J 2004 Science 305 847) have proposed the spoof surface plasmon polaritons based on a metal structure with grooved stripes. In this paper, a hollow textured perfect electric conductor cylinder with periodic cut-through slits structure is designed to suppress the light scattering of the object in any direction and achieve the effect of omnidirectional cloaking while the transverse magnetic polarization wave propagates along the x direction. And the locations of the electrical and magnetic modes can be freely modulated by tailoring the structural geometric construction. In order to find the physical mechanism behind the abnormal phenomenon, through theoretical analysis and numerical simulation, we find that the strong scattering suppression of this spoof surface plasmonic polariton structure is caused by the interference between the background wave and Mie scattering of the structural unit, and it can be equivalent to a ring metamaterial due to the special structural design, in order to achieve the omnidirectional cloaking. It implies that we can hide objects in metal strips due to the fact that the metal in the microwave-to-terahertz region is equivalent to a perfect electrical conductor. This opens up a new way to analyzing the physical cloaking and optical response of spoof surface plasmonic polaritons structure. In addition, we also analyze the influence of the structure on the movement law of the scattering spectrum under different structural parameters. This enables us to have an in-depth understanding of the influence of structural parameters on the structural scattering spectrum. Our results can be applied to the microwave-to-terahertz region and a variety of advanced optic devices such as radars, cloaking coatings, sensors and detectors.
Electronic structures and optical properties of Fe, Co, and Ni doped GaSb
Authors: Pan Feng-Chun , Lin Xue-Ling , Cao Zhi-Jie , Li Xiao-Fu ,   School of Physics and Electronic-Electrical Engineering, Ningxia University, Yinchuan 750021, China
Published: December 2020

The electronic structures and optical properties of transition metal (TM, TM refers to Fe, Co, and Ni, respectively) doped GaSb are studied by the LDA+U method of the first-principles calculation. The results indicate that these TMs can enhance the absorption amplitudes of GaSb semiconductors in the infrared region, and improve the photocatalytic performances of GaSbs effectively. For the doped systems, TMs tend to substitute for Ga and form TM@Ga defect. The charge layout and bond population of TMs imply that the electric dipole moment induced by lattice distortion separates photoelectrons from holes to some degree, and consequently enhancing the photocatalytic performance. The impurity levels induced by TMs are close to the Fermi level, which illustrates that the imaginary part of complex dielectric function has the capability of response when the energy of photon is zero. Meanwhile, the static dielectric constant of the doped system is also enhanced compared with that of the un-doped system. The doped TMs can improve the optical properties of GaSb systems for three dopants effectively, but the Ni dopant is the best for the photocatalysis properties of GaSb in the three dopants. The further analysis shows that the uniform Ni can hinder the recombination of electron-hole pairs, and the optical absorption range and absorption peak are both biggest when Ni molar concentration is 10.94%, which is favorable for photocatalytic performance. Our results will extend the applications of GaSb to the fields of infrared thermal photovoltaic cells, infrared light detector, and infrared semiconductor laser.