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CN 11-5639/O4
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HighLights More»   
  • Photonic generation of RF and microwave signal with relative frequency instability of 10-15

    Lu-Lu Yan(闫露露), Wen-Yu Zhao(赵文宇), Yan-Yan Zhang(张颜艳), Zhao-Yang Tai(邰朝阳), Pan Zhang(张攀), Bing-Jie Rao(饶冰洁), Kai Ning(宁凯), Xiao-Fei Zhang(张晓斐), Wen-Ge Guo(郭文阁), Shou-Gang Zhang(张首刚), Hai-Feng Jiang(姜海峰)
    Chin. Phys. B 2018, 27 (3): 030601
    We demonstrate the ultra-stable frequency sources aiming to improve the short-time instability of primary frequency standards. These sources are realized by using photonic generation approach, and composed of ultra-stable lasers, optical-frequency-combs, optical signal detecting parts, and synthesiz...

  • 4.3 THz quantum-well photodetectors with high detection sensitivity

    Zhenzhen Zhang(张真真), Zhanglong Fu(符张龙), Xuguang Guo(郭旭光), Juncheng Cao(曹俊诚)
    Chin. Phys. B 2018, 27 (3): 030701
    We demonstrate a high performance GaAs/AlGaAs-based quantum-well photodetector (QWP) device with a peak response frequency of 4.3 THz. The negative differential resistance (NDR) phenomenon is found in the dark current-voltage (I-V) curve in the current sweeping measurement mode, from which the break...

  • Phase diagram, correlations, and quantum critical point in the periodic Anderson model

    Jian-Wei Yang(杨建伟), Qiao-Ni Chen(陈巧妮)
    Chin. Phys. B 2018, 27 (3): 037101
    Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matrix embedding theory, we study the ground state properties of the periodic Anderson model on a two-dimensional square lattice. We systemati...

  • NMR evidence of charge fluctuations in multiferroic CuBr2

    Rui-Qi Wang(王瑞琦), Jia-Cheng Zheng(郑家成), Tao Chen(陈涛), Peng-Shuai Wang(王朋帅), Jin-Shan Zhang(张金珊), Yi Cui(崔祎), Chong Wang(王冲), Yuan Li(李源), Sheng Xu(徐胜), Feng Yuan(袁峰), Wei-Qiang Yu(于伟强)
    Chin. Phys. B 2018, 27 (3): 037502
    We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance (NQR), and zero-field nuclear magnetic resonance (NMR) measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectr...

  • Formation of unusual Cr5+ charge state in CaCr0.5Fe0.5O3 perovskite

    Jian-Hong Dai(戴建洪), Qing Zhao(赵庆), Qian Sun(孙倩), Shuo Zhang(张硕), Xiao Wang(王潇), Xu-Dong Shen(申旭东), Zhe-Hong Liu(刘哲宏), Xi Shen(沈希), Ri-Cheng Yu(禹日成), Ting-Shan Chan(詹丁山), Lun-Xiong Li(李论雄), Guang-Hui Zhou(周光辉), Yi-feng Yang(杨义峰), Chang-Qing Jin(靳常青), You-Wen Long(龙有文)
    Chin. Phys. B 2018, 27 (3): 037503
    A new oxide CaCr0.5Fe0.5O3 was prepared under high pressure and temperature conditions. It crystallizes in a B-site disordered Pbnm perovskite structure. The charge combination is determined to be Cr5+/Fe3+ with the presence of unusual Cr5+ state in octahedral coordination, although Cr4+ and Fe4+ oc...

Chin. Phys. B  
  Chin. Phys. B--2018, Vol.27, No.3
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TOPICAL REVIEW—Thermal and thermoelectric properties of nano materials

General theories and features of interfacial thermal transport

Hangbo Zhou(周杭波), Gang Zhang(张刚)
Chin. Phys. B, 2018, 27 (3): 034401 doi: 10.1088/1674-1056/27/3/034401
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A clear understanding and proper control of interfacial thermal transport is important in nanoscale devices. In this review, we first discuss the theoretical methods to handle the interfacial thermal transport problem, such as the macroscopic model, molecular dynamics, lattice dynamics, and quantum transport theories. Then we discuss various effects that can significantly affect the interfacial thermal transport, such as the formation of chemical bonds at interface, defects, interface roughness, strain, substrates, atomic species, mass ratios, and structural orientations. Then importantly, we analyze the role of inelastic scattering at the interface, and discuss its application in thermal rectifications. Finally, the challenges and promising directions are discussed.

Thermal properties of transition-metal dichalcogenide

Xiangjun Liu(刘向军), Yong-Wei Zhang(张永伟)
Chin. Phys. B, 2018, 27 (3): 034402 doi: 10.1088/1674-1056/27/3/034402
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Beyond graphene, the layered transition metal dichalcogenides (TMDs) have gained considerable attention due to their unique properties. Herein, we review the lattice dynamic and thermal properties of monolayer TMDs, including their phonon dispersion, relaxation time, mean free path (MFP), and thermal conductivities. In particular, the experimental and theoretical studies reveal that the TMDs have relatively low thermal conductivities due to the short phonon group velocity and MFP, which poses a significant challenge for efficient thermal management of TMDs-based devices. Importantly, recent studies have shown that this issue could be largely addressed by connecting TMDs and other materials (such as metal electrode and graphene) with chemical bonds, and a relatively high interfacial thermal conductance (ITC) could be achieved at the covalent bonded interface. The ITC of MoS2/Au interface with chemical edge contact is more than 10 times higher than that with physical side contact. In this article, we review recent advances in the study of TMD-related ITC. The effects of temperature, interfacial vacancy, contact orientation, and phonon modes on the edge-contacted interface are briefly discussed.

Thermal conductivity of nanowires

Zhongwei Zhang(张忠卫), Jie Chen(陈杰)
Chin. Phys. B, 2018, 27 (3): 035101 doi: 10.1088/1674-1056/27/3/035101
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Thermal conductivity of nanowires (NWs) is a crucial criterion to assess the operating performance of NWs-based device applications, such as in the field of heat dissipation, thermal management, and thermoelectrics. Therefore, numerous research interests have been focused on controlling and manipulating thermal conductivity of one-dimensional materials in the past decade. In this review, we summarize the state-of-the-art research status on thermal conductivity of NWs from both experimental and theoretical studies. Various NWs are included, such as Si, Ge, Bi, Ti, Cu, Ag, Bi2Te3, ZnO, AgTe, and their hybrids. First, several important size effects on thermal conductivity of NWs are discussed, such as the length, diameter, orientation, and cross-section. Then, we introduce diverse nanostructuring pathways to control the phonons and thermal transport in NWs, such as alloy, superlattices, core-shell structure, porous structure, resonant structure, and kinked structure. Distinct thermal transport behaviors and the associated underlying physical mechanisms are presented. Finally, we outline the important potential applications of NWs in the fields of thermoelectrics and thermal management, and provide an outlook.

Review of thermal transport and electronic properties of borophene

Dengfeng Li(李登峰), Ying Chen(陈颖), Jia He(何佳), Qiqi Tang(汤琪琪), Chengyong Zhong(钟承勇), Guangqian Ding(丁光前)
Chin. Phys. B, 2018, 27 (3): 036303 doi: 10.1088/1674-1056/27/3/036303
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In recent years, two-dimensional boron sheets (borophene) have been experimentally synthesized and theoretically proposed as a promising conductor or transistor with novel thermal and electronic properties. We first give a general survey of some notable electronic properties of borophene, including the superconductivity and topological characters. We then mainly review the basic approaches, thermal transport, as well as the mechanical properties of borophene with different configurations. This review gives a general understanding of some of the crucial thermal transport and electronic properties of borophene, and also calls for further experimental investigations and applications on certain scientific community.

Nanoscale thermal transport: Theoretical method and application

Yu-Jia Zeng(曾育佳), Yue-Yang Liu(刘岳阳), Wu-Xing Zhou(周五星), Ke-Qiu Chen(陈克求)
Chin. Phys. B, 2018, 27 (3): 036304 doi: 10.1088/1674-1056/27/3/036304
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With the size reduction of nanoscale electronic devices, the heat generated by the unit area in integrated circuits will be increasing exponentially, and consequently the thermal management in these devices is a very important issue. In addition, the heat generated by the electronic devices mostly diffuses to the air in the form of waste heat, which makes the thermoelectric energy conversion also an important issue for nowadays. In recent years, the thermal transport properties in nanoscale systems have attracted increasing attention in both experiments and theoretical calculations. In this review, we will discuss various theoretical simulation methods for investigating thermal transport properties and take a glance at several interesting thermal transport phenomena in nanoscale systems. Our emphasizes will lie on the advantage and limitation of calculational method, and the application of nanoscale thermal transport and thermoelectric property.

Thermal transport in phosphorene and phosphorene-based materials: A review on numerical studies

Yang Hong(洪扬), Jingchao Zhang(张景超), Xiao Cheng Zeng(曾晓成)
Chin. Phys. B, 2018, 27 (3): 036501 doi: 10.1088/1674-1056/27/3/036501
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The recently discovered two-dimensional (2D) layered material phosphorene has attracted considerable interest as a promising p-type semiconducting material. In this article, we review the recent advances in numerical studies of the thermal properties of monolayer phosphorene and phosphorene-based heterostructures. We first briefly review the commonly used first-principles and molecular dynamics (MD) approaches to evaluate the thermal conductivity and interfacial thermal resistance of 2D phosphorene. Principles of different steady-state and transient MD techniques have been elaborated on in detail. Next, we discuss the anisotropic thermal transport of phosphorene in zigzag and armchair chiral directions. Subsequently, the in-plane and cross-plane thermal transport in phosphorene-based heterostructures such as phosphorene/silicon and phosphorene/graphene is summarized. Finally, the numerical research in the field of thermal transport in 2D phosphorene is highlighted along with our perspective of potentials and opportunities of 2D phosphorenes in electronic applications such as photodetectors, field-effect transistors, lithium ion batteries, sodium ion batteries, and thermoelectric devices.

Surface effects on the thermal conductivity of silicon nanowires

Hai-Peng Li(李海鹏), Rui-Qin Zhang(张瑞勤)
Chin. Phys. B, 2018, 27 (3): 036801 doi: 10.1088/1674-1056/27/3/036801
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Thermal transport in silicon nanowires (SiNWs) has recently attracted considerable attention due to their potential applications in energy harvesting and generation and thermal management. The adjustment of the thermal conductivity of SiNWs through surface effects is a topic worthy of focus. In this paper, we briefly review the recent progress made in this field through theoretical calculations and experiments. We come to the conclusion that surface engineering methods are feasible and effective methods for adjusting nanoscale thermal transport and may foster further advancements in this field.

Raman spectroscopy characterization of two-dimensional materials

Fang Liang(梁芳), Hejun Xu(徐何军), Xing Wu(吴幸), Chaolun Wang(王超伦), Chen Luo(骆晨), Jian Zhang(张健)
Chin. Phys. B, 2018, 27 (3): 037802 doi: 10.1088/1674-1056/27/3/037802
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Two-dimensional (2D) materials have become a hot study topic in recent years due to their outstanding electronic, optical, and thermal properties. The unique band structures of strong in-plane chemical bonds and weak out-of-plane van der Waals (vdW) interactions make 2D materials promising for nanodevices and various other applications. Raman spectroscopy is a powerful and non-destructive characterization tool to study the properties of 2D materials. In this work, we review the research on the characterization of 2D materials with Raman spectroscopy. In addition, we discuss the application of the Raman spectroscopy technique to semiconductors, superconductivity, photoelectricity, and thermoelectricity.

Thermal conduction of one-dimensional carbon nanomaterials and nanoarchitectures

Haifei Zhan(占海飞), Yuantong Gu(顾元通)
Chin. Phys. B, 2018, 27 (3): 038103 doi: 10.1088/1674-1056/27/3/038103
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This review summarizes the current studies of the thermal transport properties of one-dimensional (1D) carbon nanomaterials and nanoarchitectures. Considering different hybridization states of carbon, emphases are laid on a variety of 1D carbon nanomaterials, such as diamond nanothreads, penta-graphene nanotubes, supernanotubes, and carbyne. Based on experimental measurements and simulation/calculation results, we discuss the dependence of the thermal conductivity of these 1D carbon nanomaterials on a wide range of factors, including the size effect, temperature influence, strain effect, and others. This review provides an overall understanding of the thermal transport properties of 1D carbon nanomaterials and nanoarchitectures, which paves the way for effective thermal management at nanoscale.

Solitary wave for a nonintegrable discrete nonlinear Schrödinger equation in nonlinear optical waveguide arrays

Li-Yuan Ma(马立媛), Jia-Liang Ji(季佳梁), Zong-Wei Xu(徐宗玮), Zuo-Nong Zhu(朱佐农)
Chin. Phys. B, 2018, 27 (3): 030201 doi: 10.1088/1674-1056/27/3/030201
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We study a nonintegrable discrete nonlinear Schrödinger (dNLS) equation with the term of nonlinear nearest-neighbor interaction occurred in nonlinear optical waveguide arrays. By using discrete Fourier transformation, we obtain numerical approximations of stationary and travelling solitary wave solutions of the nonintegrable dNLS equation. The analysis of stability of stationary solitary waves is performed. It is shown that the nonlinear nearest-neighbor interaction term has great influence on the form of solitary wave. The shape of solitary wave is important in the electric field propagating. If we neglect the nonlinear nearest-neighbor interaction term, much important information in the electric field propagating may be missed. Our numerical simulation also demonstrates the difference of chaos phenomenon between the nonintegrable dNLS equation with nonlinear nearest-neighbor interaction and another nonintegrable dNLS equation without the term.

On fairness, full cooperation, and quantum game with incomplete information

Zhen-Zhou Lei(雷振州), Bo-Yang Liu(刘博阳), Ying Yi(易英), Hong-Yi Dai(戴宏毅), Ming Zhang(张明)
Chin. Phys. B, 2018, 27 (3): 030202 doi: 10.1088/1674-1056/27/3/030202
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Quantum entanglement has emerged as a new resource to enhance cooperation and remove dilemmas. This paper aims to explore conditions under which full cooperation is achievable even when the information of payoff is incomplete. Based on the quantum version of the extended classical cash in a hat game, we demonstrate that quantum entanglement may be used for achieving full cooperation or avoiding moral hazards with the reasonable profit distribution policies even when the profit is uncertain to a certain degree. This research further suggests that the fairness of profit distribution should play an important role in promoting full cooperation. It is hopeful that quantum entanglement and fairness will promote full cooperation among distant people from various interest groups when quantum networks and quantum entanglement are accessible to the public.

Analytical model of tilted driver-pickup coils for eddy current nondestructive evaluation

Bing-Hua Cao(曹丙花), Chao Li(李超), Meng-Bao Fan(范孟豹), Bo Ye(叶波), Gui-Yun Tian(田贵云)
Chin. Phys. B, 2018, 27 (3): 030301 doi: 10.1088/1674-1056/27/3/030301
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A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil. It is frequently observed in an eddy current (EC) array probe. In this work, a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evaluation. Basically, the core of the formulation is to obtain the projection of magnetic vector potential (MVP) from the driver coil onto the vector along the tilted pickup coil, which is divided into two key steps. The first step is to make a projection of MVP along the pickup coil onto a horizontal plane, and the second one is to build the relationship between the projected MVP and the MVP along the driver coil. Afterwards, an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields. The calculated values from the resulting model indicate good agreement with those from the finite element model (FEM) and experiments, which validates the developed analytical model.

Separability criteria based on Heisenberg-Weyl representation of density matrices

Jingmei Chang(常景美), Meiyu Cui(崔美钰), Tinggui Zhang(张廷桂), Shao-Ming Fei(费少明)
Chin. Phys. B, 2018, 27 (3): 030302 doi: 10.1088/1674-1056/27/3/030302
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Separability is an important problem in theory of quantum entanglement. By using the Bloch representation of quantum states in terms of the Heisenberg-Weyl observable basis, we present a new separability criterion for bipartite quantum systems. It is shown that this criterion can be better than the previous ones in detecting entanglement. The results are generalized to multipartite quantum states.

Effect of Raman-pulse duration related to the magnetic field gradient in high-precision atom gravimeters

Yuan Cheng(程源), Yu-Jie Tan(谈玉杰), Min-Kang Zhou(周敏康), Xiao-Chun Duan(段小春), Cheng-Gang Shao(邵成刚), Zhong-Kun Hu(胡忠坤)
Chin. Phys. B, 2018, 27 (3): 030303 doi: 10.1088/1674-1056/27/3/030303
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The effect of the Raman-pulse duration related to the magnetic field gradient, as a systematic error, is playing an important role on evaluating the performance of high-precision atomic gravimeters. We study this effect with a simplified theoretical model of the time-propagation operator. According to the typical parameters, we find that this effect should be taken into account when the gravimeter reaches an accuracy of 10-10g, and the larger the pulse duration is, the more obvious the systematic effect will be. Finally, we make a simple discussion on the possibility of testing this effect.

The global monopole spacetime and its topological charge

Hongwei Tan(谭鸿威), Jinbo Yang(杨锦波), Jingyi Zhang(张靖仪), Tangmei He(何唐梅)
Chin. Phys. B, 2018, 27 (3): 030401 doi: 10.1088/1674-1056/27/3/030401
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We show that the global monopole spacetime is one of the exact solutions of the Einstein equations by treating the matter field as a non-linear sigma model, without the weak field approximation applied in the original derivation by Barriola and Vilenkin. Furthermore, we find the physical origin of the topological charge in the global monopole spacetime. Finally, we generalize the proposal which generates spacetime from thermodynamical laws to the case of spacetime with global monopole charge.

Effects of intrinsic and extrinsic noises on transposons kinetics

Alssadig A M Yousif, Lulu Lu(鹿露露), Mengyan Ge(葛梦炎), Ying Xu(徐莹), Ya Jia(贾亚)
Chin. Phys. B, 2018, 27 (3): 030501 doi: 10.1088/1674-1056/27/3/030501
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The absolute concentration robustness (ACR) steady state of a biochemical system can protect against changing a large concentration of the system's components. In this paper, a minimal model of autonomous-nonautonomous transposons driven by intrinsic and extrinsic noises is investigated. The effects of intrinsic and extrinsic noises on ACR steady state of the transposons kinetics are studied by numerical simulations. It is found that the predator-prey-like oscillations around the ACR steady state are induced by the intrinsic or extrinsic noises. Comparing with the case of intrinsic noises, the extrinsic noises can inhibit the amplitude of oscillations of transposon kinetics. To characterize the predator-prey-like oscillations, we calculate the probability distributions and the normalized correlation functions of a system in the stability domain. With the increasing of noise intensity, the peak of the probability distribution is shifted from the ACR steady state to the trivial steady state. The normalized autocorrelation and cross-correlation functions indicate that the state of the predator-prey oscillator is transmitted to 50 successive generations at least.

Image encryption technique based on new two-dimensional fractional-order discrete chaotic map and Menezes-Vanstone elliptic curve cryptosystem

Zeyu Liu(刘泽宇), Tiecheng Xia(夏铁成), Jinbo Wang(王金波)
Chin. Phys. B, 2018, 27 (3): 030502 doi: 10.1088/1674-1056/27/3/030502
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We propose a new fractional two-dimensional triangle function combination discrete chaotic map (2D-TFCDM) with the discrete fractional difference. Moreover, the chaos behaviors of the proposed map are observed and the bifurcation diagrams, the largest Lyapunov exponent plot, and the phase portraits are derived, respectively. Finally, with the secret keys generated by Menezes-Vanstone elliptic curve cryptosystem, we apply the discrete fractional map into color image encryption. After that, the image encryption algorithm is analyzed in four aspects and the result indicates that the proposed algorithm is more superior than the other algorithms.

Reconstruction of dynamic structures of experimental setups based on measurable experimental data only

Tian-Yu Chen(陈天宇), Yang Chen(陈阳), Hu-Jiang Yang(杨胡江), Jing-Hua Xiao(肖井华), Gang Hu(胡岗)
Chin. Phys. B, 2018, 27 (3): 030503 doi: 10.1088/1674-1056/27/3/030503
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Nowadays, massive amounts of data have been accumulated in various and wide fields, it has become today one of the central issues in interdisciplinary fields to analyze existing data and extract as much useful information as possible from data. It is often that the output data of systems are measurable while dynamic structures producing these data are hidden, and thus studies to reveal system structures by analyzing available data, i.e., reconstructions of systems become one of the most important tasks of information extractions. In the past, most of the works in this respect were based on theoretical analyses and numerical verifications. Direct analyses of experimental data are very rare. In physical science, most of the analyses of experimental setups were based on the first principles of physics laws, i.e., so-called top-down analyses. In this paper, we conducted an experiment of “Boer resonant instrument for forced vibration” (BRIFV) and inferred the dynamic structure of the experimental set purely from the analysis of the measurable experimental data, i.e., by applying the bottom-up strategy. Dynamics of the experimental set is strongly nonlinear and chaotic, and it's subjects to inevitable noises. We proposed to use high-order correlation computations to treat nonlinear dynamics; use two-time correlations to treat noise effects. By applying these approaches, we have successfully reconstructed the structure of the experimental setup, and the dynamic system reconstructed with the measured data reproduces good experimental results in a wide range of parameters.

Soliton structures in the (1+1)-dimensional Ginzburg-Landau equation with a parity-time-symmetric potential in ultrafast optics

Wenyi Li(李文义), Guoli Ma(马国利), Weitian Yu(于维天), Yujia Zhang(张玉佳), Mengli Liu(刘孟丽), Chunyu Yang(杨春玉), Wenjun Liu(刘文军)
Chin. Phys. B, 2018, 27 (3): 030504 doi: 10.1088/1674-1056/27/3/030504
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In this paper, the (1+1)-dimensional variable-coefficient complex Ginzburg-Landau (CGL) equation with a parity-time (PT) symmetric potential U(x) is investigated. Although the CGL equations with a PT-symmetric potential are less reported analytically, the analytic solutions for the CGL equation are obtained with the bilinear method in this paper. Via the derived solutions, some soliton structures are presented with corresponding parameters, and the influences of them are analyzed and studied. The single-soliton structure is numerically verified, and its stability is analyzed against additive and multiplicative noises. In particular, we study the soliton dynamics under the impact of the PT-symmetric potential. Results show that the PT-symmetric potential plays an important role for obtaining soliton structures in ultrafast optics, and we can design fiber lasers and all-optical switches depending on the different amplitudes of soliton-like structures.

Hydrophobic nanochannel self-assembled by amphipathic Janus particles confined in aqueous nano-space

Gang Fang(方钢), Nan Sheng(盛楠), Tan Jin(金坦), Yousheng Xu(许友生), Hai Sun(孙海), Jun Yao(姚军), Wei Zhuang(庄巍), Haiping Fang(方海平)
Chin. Phys. B, 2018, 27 (3): 030505 doi: 10.1088/1674-1056/27/3/030505
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Hydrophobic nanochannel plays a significant role in many physical, biological, and geological phenomena and exhibits impressive applications due to both its ubiquitous distribution and great ability to transport hydrophobic molecules, including various oils and gases. Based on theoretical modeling, we herein reveal that the amphipathic Janus nanoparticles have a large probability to self-assemble into uninterrupted hydrophobic nanochannels inside the aqueous nano-space, although there are large portions of the Janus nanoparticles to be hydrophilic. The key to this observation is the attractions between the hydrophobic regimes on neighboring amphipathic Janus particles through hydrophobic interaction in aqueous nano-space. More surprisingly, the permeation efficiency of hydrophobic molecules through the uninterrupted hydrophobic channel in Janus particles aggregate is even higher than that in the aggregate of hydrophobic particles. We note that the proposed amphipathic Janus particles can be transported to the appropriate positions by the water since the hydrophilic regimes still remain a strong particle-water interaction. We also note that most natural subsurface rocks are not completely hydrophobic or hydrophilic but have complex surfaces with inhomogeneous wetting property. Our work therefore provides a detailed molecular level understanding of the formation of underground strata as well as the new insight for constructing the artificial hydrophobic channels for various applications, such as the design of proppants to enhance the recovery of the unconventional oil/gas.

Photonic generation of RF and microwave signal with relative frequency instability of 10-15 Hot!

Lu-Lu Yan(闫露露), Wen-Yu Zhao(赵文宇), Yan-Yan Zhang(张颜艳), Zhao-Yang Tai(邰朝阳), Pan Zhang(张攀), Bing-Jie Rao(饶冰洁), Kai Ning(宁凯), Xiao-Fei Zhang(张晓斐), Wen-Ge Guo(郭文阁), Shou-Gang Zhang(张首刚), Hai-Feng Jiang(姜海峰)
Chin. Phys. B, 2018, 27 (3): 030601 doi: 10.1088/1674-1056/27/3/030601
Full Text: [PDF 961 KB] (Downloads:417) RICH HTML
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We demonstrate the ultra-stable frequency sources aiming to improve the short-time instability of primary frequency standards. These sources are realized by using photonic generation approach, and composed of ultra-stable lasers, optical-frequency-combs, optical signal detecting parts, and synthesizers. Preliminary evaluation shows that the sources produce fixed-frequency at 9.54(/9.63) GHz, 10 MHz, and tunable-frequency around 9.192 GHz with relative frequency instability of 10-15 for short terms.

4.3 THz quantum-well photodetectors with high detection sensitivity Hot!

Zhenzhen Zhang(张真真), Zhanglong Fu(符张龙), Xuguang Guo(郭旭光), Juncheng Cao(曹俊诚)
Chin. Phys. B, 2018, 27 (3): 030701 doi: 10.1088/1674-1056/27/3/030701
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We demonstrate a high performance GaAs/AlGaAs-based quantum-well photodetector (QWP) device with a peak response frequency of 4.3 THz. The negative differential resistance (NDR) phenomenon is found in the dark current-voltage (I-V) curve in the current sweeping measurement mode, from which the breakdown voltage is determined. The photocurrent spectra and blackbody current responsivities at different voltages are measured. Based on the experimental data, the peak responsivity of 0.3 A/W (at 0.15 V, 8 K) is derived, and the detection sensitivity is higher than 1011 Jones, which is in the similar level as that of the commercialized liquid-helium-cooled silicon bolometers. We attribute the high detection performance of the device to the small ohmic contact resistance of ~2Ω and the big breakdown bias.

Weak wide-band signal detection method based on small-scale periodic state of Duffing oscillator

Jian Hou(侯健), Xiao-peng Yan(闫晓鹏), Ping Li(栗苹), Xin-hong Hao(郝新红)
Chin. Phys. B, 2018, 27 (3): 030702 doi: 10.1088/1674-1056/27/3/030702
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The conventional Duffing oscillator weak signal detection method, which is based on a strong reference signal, has inherent deficiencies. To address these issues, the characteristics of the Duffing oscillator's phase trajectory in a small-scale periodic state are analyzed by introducing the theory of stopping oscillation system. Based on this approach, a novel Duffing oscillator weak wide-band signal detection method is proposed. In this novel method, the reference signal is discarded, and the to-be-detected signal is directly used as a driving force. By calculating the cosine function of a phase space angle, a single Duffing oscillator can be used for weak wide-band signal detection instead of an array of uncoupled Duffing oscillators. Simulation results indicate that, compared with the conventional Duffing oscillator detection method, this approach performs better in frequency detection intervals, and reduces the signal-to-noise ratio detection threshold, while improving the real-time performance of the system.

Demonstration of multi-Watt all-fiber superfluorescent source operating near 980 nm

Yankun Ren(任彦锟), Jianqiu Cao(曹涧秋), Hanyuan Ying(应汉辕), Heng Chen(陈恒), Zhiyong Pan(潘志勇), Shaojun Du(杜少军), Jinbao Chen(陈金宝)
Chin. Phys. B, 2018, 27 (3): 030703 doi: 10.1088/1674-1056/27/3/030703
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The superfluorescent Yb-doped fiber source operating near 980 nm is studied. The design requirement is theoretically discussed aiming to suppress the amplified spontaneous emission around 1030 nm in the 980-nm superfluorescent fiber source. Based on the theoretical study, a multi-Watt, all-fiber, bi-directional, pumped, superfluorescent source operating near 980 nm is designed and experimentally demonstrated for the first time, to the best of our knowledge. The recorded 8.38-W combined output power is obtained with a 3-dB bandwidth about 3.5 nm. The power scaling of the 980-nm superfluorescent fiber source is limited by the parasitic laser oscillation.

Vapor cell geometry effect on Rydberg atom-based microwave electric field measurement

Linjie Zhang(张临杰), Jiasheng Liu(刘家晟), Yue Jia(贾玥), Hao Zhang(张好), Zhenfei Song(宋振飞), Suotang Jia(贾锁堂)
Chin. Phys. B, 2018, 27 (3): 033201 doi: 10.1088/1674-1056/27/3/033201
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The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cell, high-resolution spatial distribution of the microwave electric field strength is achieved for both a cubic cell and a cylinder cell. The spatial distribution of the microwave field strength in two dimensions is measured with sub-wavelength resolution. The experimental results show that the shape of a vapor cell has a significant influence on the abnormal spatial distribution because of the Fabry-Pérot effect inside a vapor cell. A theoretical simulation is obtained for different vapor cell wall thicknesses and shows that a restricted wall thickness results in a measurement fluctuation smaller than 3% at the center of the vapor cell.


Ab-initio calculations of structural, electronic, and optical properties of Zn3(VO4)2

Nisar Ahmed, S Mukhtar, Wei Gao, Syed Zafar Ilyas
Chin. Phys. B, 2018, 27 (3): 033101 doi: 10.1088/1674-1056/27/3/033101
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The structural, electronic, and optical properties of Zn3(VO4)2 are investigated using full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). Various approaches are adopted to treat the exchange and correlation potential energy such as generalized gradient approximation (GGA), GGA+U, and the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The calculated band gap of 3.424 eV by TB-mBJ is found to be close to the experimental result (3.3 eV). The optical anisotropy is analyzed through optical constants, such as dielectric function and absorption coefficient along parallel and perpendicular crystal orientations. The absorption coefficient reveals high absorption (1.5×106 cm-1) of photons in the ultraviolet region.

Exploration of strong-field double ionization of C3H6 with the structures of propene and cyclopropane in intense laser fields

Qing-Yun Xu(徐清芸), Yan-Rong Tian(田艳荣), Hui-Zhong Lu(卢惠中), Jun Zhang(张军), Tong-Tong Xu(徐彤彤), Hong-Dan Zhang(张宏丹), Xue-Shen Liu(刘学深), Jing Guo(郭静)
Chin. Phys. B, 2018, 27 (3): 033202 doi: 10.1088/1674-1056/27/3/033202
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By using classical ensemble method, we investigate the double ionization of C3H6 molecule with different structures (propene and cyclopropane) in intense laser fields. The numerical results show that the non-sequential double ionization occurs in propene molecule rather than cyclopropane molecule in 1200 nm laser field. To further explain this interesting phenomenon, the momentum distribution of double ionized electrons is presented and the result presents the “finger-like” structure at about 30 TW/cm2 of propene molecule, and this structure is more obvious than that in cyclopropane molecule. The above phenomena are also demonstrated by analysing the energy distributions of double-ionized electrons versus time. Moreover, we also investigated the angular distribution at the end of pulse, which is different between propene and cyclopropane.

Influence factor analysis of field-free molecular orientation

Jing-Song Liu(刘劲松), Qi-Yuan Cheng(程起元), Da-Guang Yue(岳大光), Xu-Cong Zhou(周旭聪), Qing-Tian Meng(孟庆田)
Chin. Phys. B, 2018, 27 (3): 033301 doi: 10.1088/1674-1056/27/3/033301
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The effects of the characteristics of molecules and external fields on field-free molecular orientation are investigated through the comparison of HBr with LiH driven by the combination of a two-color laser pulse and a time-delayed THz laser pulse. It is shown that the dipole interaction has greater influence on field-free orientation than the hyperpolarizability interaction. In addition to the temperature dependence of orientation degree, the effects of the amplitudes of the two-color laser pulse and THz laser pulse, rising time, and THz laser frequency on molecular orientation are also discussed.

Solvent effects and potential of mean force study of the SN2 reaction of CH3F+CN- in water

Chen Li(李琛), Peng Liu(刘鹏), Yongfang Li(李永方), Dunyou Wang(王敦友)
Chin. Phys. B, 2018, 27 (3): 033401 doi: 10.1088/1674-1056/27/3/033401
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We used a combined quantum mechanics and molecular mechanics (QM/MM) method to investigate the solvent effects and potential of mean force of the CH3F+CN- reaction in water. Comparing to gas phase, the water solution substantially affects the structures of the stationary points along the reaction path. We quantitatively obtained the solvent effects' contributions to the reaction:1.7 kcal/mol to the activation barrier and -26.0 kcal/mol to the reaction free energy. The potential mean of force calculated with the density functional theory/MM theory has a barrier height at 19.7 kcal/mol, consistent with the experimental result at 23.0 kcal/mol; the calculated reaction free energy at -43.5 kcal/mol is also consistent with the one estimated based on the gas-phase data at -39.7 kcal/mol.


Further analysis of scintillation index for a laser beam propagating through moderate-to-strong non-Kolmogorov turbulence based on generalized effective atmospheric spectral model

Jing Ma(马晶), Yu-Long Fu(付玉龙), Si-Yuan Yu(于思源), Xiao-Long Xie(谢小龙), Li-Ying Tan(谭立英)
Chin. Phys. B, 2018, 27 (3): 034201 doi: 10.1088/1674-1056/27/3/034201
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A new expression of the scintillation index (SI) for a Gaussian-beam wave propagating through moderate-to-strong non-Kolmogorov turbulence is derived, using a generalized effective atmospheric spectrum and the extended Rytov approximation theory. Finite inner and outer scale parameters and high wave number “bump” are considered in the spectrum with a generalized spectral power law in the range of 3-4, instead of the fixed classical Kolmogorov power law of 11/3. The obtained SI expression is then used to analyze the effects of the spectral power law and the inner scale and outer scale on SI under various non-Kolmogorov fluctuation conditions. These results will be useful in future investigations of optical wave propagation through atmospheric turbulence.

Optical encryption of multiple three-dimensional objects based on multiple interferences and single-pixel digital holography

Ying Wang(王莹), Qi Liu(刘琦), Jun Wang(王君), Qiong-Hua Wang(王琼华)
Chin. Phys. B, 2018, 27 (3): 034202 doi: 10.1088/1674-1056/27/3/034202
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We present an optical encryption method of multiple three-dimensional objects based on multiple interferences and single-pixel digital holography. By modifying the Mach-Zehnder interferometer, the interference of the multiple objects beams and the one reference beam is used to simultaneously encrypt multiple objects into a ciphertext. During decryption, each three-dimensional object can be decrypted independently without having to decrypt other objects. Since the single-pixel digital holography based on compressive sensing theory is introduced, the encrypted data of this method is effectively reduced. In addition, recording fewer encrypted data can greatly reduce the bandwidth of network transmission. Moreover, the compressive sensing essentially serves as a secret key that makes an intruder attack invalid, which means that the system is more secure than the conventional encryption method. Simulation results demonstrate the feasibility of the proposed method and show that the system has good security performance.

Implication of two-coupled tri-stable stochastic resonance in weak signal detection

Quan-Quan Li(李泉泉), Xue-Mei Xu(许雪梅), Lin-Zi Yin(尹林子), Yi-Peng Ding(丁一鹏), Jia-Feng Ding(丁家峰), Ke-Hui Sun(孙克辉)
Chin. Phys. B, 2018, 27 (3): 034203 doi: 10.1088/1674-1056/27/3/034203
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Stochastic resonance (SR) has been proved to be an effective approach to extract weak signals overwhelmed in noise. However, the detection effect of current SR models is still unsatisfactory. Here, a coupled tri-stable stochastic resonance (CTSSR) model is proposed to further increase the output signal-to-noise ratio (SNR) and improve the detection effect of SR. The effects of parameters a, b, c, and r in the proposed resonance system on the SNR are studied, by which we determine a set of parameters that is relatively optimal to implement a comparison with other classical SR models. Numerical experiment results indicate that this proposed model performs better in weak signal detection applications than the classical ones with merits of higher output SNR and better anti-noise capability.

Multi-window transparency and fast-slow light switching in a quadratically coupled optomechanical system assisted with three-level atoms

Wan-Ying Wei(魏晚迎), Ya-Fei Yu(於亚飞), Zhi-Ming Zhang(张智明)
Chin. Phys. B, 2018, 27 (3): 034204 doi: 10.1088/1674-1056/27/3/034204
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We study theoretically the features of the output field of a quadratically coupled optomechanical system assisted with three-level atoms. In this system, the atoms interact with the cavity field and are driven by a classical field, and the cavity is driven by a strong coupling field and a weak signal field. We find that there exists a multi-window transparency phenomenon. The width of the transparent windows can be adjusted by controlling the system parameters, including the number of the atoms, the powers of the lasers driving the atoms and driving the cavity, and the environment temperature. We also find that a tunable switch from fast light to slow light can be realized in this system.

Optomechanically induced transparency with Bose–Einstein condensate in double-cavity optomechanical system

Li-Wei Liu(刘利伟), Duo-Jie Gengzang(更藏多杰), Xiu-Jia An(安秀加), Pei-Yu Wang(王培煜)
Chin. Phys. B, 2018, 27 (3): 034205 doi: 10.1088/1674-1056/27/3/034205
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We propose a novel technique of generating multiple optomechanically induced transparency (OMIT) of a weak probe field in hybrid optomechanical system. This system consists of a cigar-shaped Bose-Einstein condensate (BEC), trapped inside each high finesse Fabry-Pérot cavity. In the resolved sideband regime, the analytic solutions of the absorption and the dispersion spectrum are given. The tunneling strength of the two resonators and the coupling parameters of the each BEC in combination with the cavity field have the appearance of three distinct OMIT windows in the absorption spectrum. Furthermore, whether there is BEC in each cavity is a key factor in the number of OMIT windows determination. The technique presented may have potential applications in quantum engineering and quantum information networks.

Effect of multiple rescattering processes on harmonic emission in spatially inhomogeneous field

Cai-Ping Zhang(张彩萍), Chang-Long Xia(夏昌龙), Xiang-Fu Jia(贾祥富), Xiang-Yang Miao(苗向阳)
Chin. Phys. B, 2018, 27 (3): 034206 doi: 10.1088/1674-1056/27/3/034206
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The effect of multiple rescattering processes on the harmonic emission from He atom in a spatially inhomogeneous field is discussed by solving the one-dimensional time-dependent Schrödinger equation and the classical equation of motion. By establishing the physical model of the harmonic emission in the inhomogeneous field, we discuss the related characters of the multiple rescatterings process in the harmonic generation process. It shows that the second rescattering rather than the first rescattering tends to determine the harmonic cutoff energy when the inhomogeneous parameter is larger than 0.0055. Additionally, with the classical simulation, the underlying physical mechanism of the continuum-continuum harmonics is also revealed. Moreover, this work may provide new physical insight into the harmonic generation in an inhomogeneous field, and is beneficial to further extract the harmonic emission from molecular systems.

Enhanced second harmonic generation in a two-dimensional optical micro-cavity

Jian-Jun Zhang(张建军), Hui-Fang Wang(王慧芳), Jun-Hua Hou(候俊华)
Chin. Phys. B, 2018, 27 (3): 034207 doi: 10.1088/1674-1056/27/3/034207
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We introduce a two-dimensional Bose-Einstein condensation model consisting of massive photon and photon-pair. Based on the new nonlinear model, the traditional process of second harmonics generation is reinvestigated. In order to describe the process, a new quantum phase, the harmonic phase, is introduced. The order parameter of the new physical phase is also given in this paper.

Random phase screen influence of the inhomogeneous tissue layer on the generation of acoustic vortices

Zhiyao Ma(马致遥), Jun Ma(马骏), Dong Zhang(章东), Juan Tu(屠娟)
Chin. Phys. B, 2018, 27 (3): 034301 doi: 10.1088/1674-1056/27/3/034301
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The influence of the inhomogeneous tissue layer on the generation of acoustic vortices (AV) is studied theoretically and experimentally based on the phase screen model. By considering the time-shift of a random phase screen, the formula of acoustic pressure for the AV beam generated by a circular array of eight planar piston sources is derived. With the actual correlation length of the abdominal wall, numerical simulations before and after the insertion of the inhomogeneous tissue layer are conducted, and also demonstrated by experimental measurements. It is proved that, when the thickness variation of the phase screen is less than one wavelength, no significant influence on the generation of AVs can be produced. The variations of vortex nodes and antinodes in terms of the location, shape, and size of AVs are not obvious. Although the circular pressure distribution might be deformed by the phase interference with a larger thickness variation, AVs can still be generated around the center axis with perfect phase spirals in a reduced effective radius. The favorable results provide the feasibility of AV generation inside the human body and suggest the application potential of AVs in object manipulation for biomedical engineering.

Acoustic radiation force on a multilayered sphere in a Gaussian standing field

Haibin Wang(汪海宾), Xiaozhou Liu(刘晓宙), Sha Gao(高莎), Jun Cui(崔骏), Jiehui Liu(刘杰惠), Aijun He(何爱军), Gutian Zhang(张古田)
Chin. Phys. B, 2018, 27 (3): 034302 doi: 10.1088/1674-1056/27/3/034302
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We develop a model for calculating the radiation force on spherically symmetric multilayered particles based on the acoustic scattering approach. An expression is derived for the radiation force on a multilayered sphere centered on the axis of a Gaussian standing wave propagating in an ideal fluid. The effects of the sound absorption of the materials and sound wave on acoustic radiation force of a multilayered sphere immersed in water are analyzed, with particular emphasis on the shell thickness of every layer, and the width of the Gaussian beam. The results reveal that the existence of particle trapping behavior depends on the choice of the non-dimensional frequency ka, as well as the shell thickness of each layer. This study provides a theoretical basis for the development of acoustical tweezers in a Gaussian standing wave, which may benefit the improvement and development of acoustic control technology, such as trapping, sorting, and assembling a cell, and drug delivery applications.

Numerical analysis of plasma arc physical characteristics under additional constraint of keyhole

Bin Xu(徐斌), Fan Jiang(蒋凡), Shujun Chen(陈树君), Manabu Tanaka(田中学), Shinichi Tashiro(田代真一), Nguyen Van Anh
Chin. Phys. B, 2018, 27 (3): 034701 doi: 10.1088/1674-1056/27/3/034701
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The physical characteristics of a plasma arc affect the stability of the keyhole and weld pool directly during keyhole plasma arc welding (KPAW). There will be significant change for these characteristics because of the interaction between the keyhole weld pool and plasma arc after penetration. Therefore, in order to obtain the temperature field, flow field, and arc pressure of a plasma arc under the reaction of the keyhole, the physical model of a plasma arc with a pre-set keyhole was established. In addition, the tungsten and base metal were established into the calculated domain, which can reflect the effect of plasma arc to weld pool further. Based on magneto hydrodynamics and Maxwell equations, a two-dimensional steady state mathematical model was established. Considering the heat production of anode and cathode, the distribution of temperature field, flow field, welding current density, and plasma arc pressure were solved out by the finite difference method. From the calculated results, it is found that the plasma arc was compressed a second time by the keyhole. This additional constraint results in an obvious rise of the plasma arc pressure and flow velocity at the minimum diameter place of the keyhole, while the temperature field is impacted slightly. Finally, the observational and metallographic experiments are conducted, and the shapes of plasma arc and fusion line agree with the simulated results generally.

Laser-driven relativistic electron dynamics in a cylindrical plasma channel

Pan-Fei Geng(耿盼飞), Wen-Juan Lv(吕文娟), Xiao-Liang Li(李晓亮), Rong-An Tang(唐荣安), Ju-Kui Xue(薛具奎)
Chin. Phys. B, 2018, 27 (3): 035201 doi: 10.1088/1674-1056/27/3/035201
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The energy and trajectory of the electron, which is irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge and a uniform negative current, have been analyzed in terms of a single-electron model of direct laser acceleration. We find that the energy and trajectory of the electron strongly depend on the positive charge density, the negative current density, and the intensity of the laser pulse. The electron can be accelerated significantly only when the positive charge density, the negative current density, and the intensity of the laser pulse are in suitable ranges due to the dephasing rate between the wave and electron motion. Particularly, when their values satisfy a critical condition, the electron can stay in phase with the laser and gain the largest energy from the laser. With the enhancement of the electron energy, strong modulations of the relativistic factor cause a considerable enhancement of the electron transverse oscillations across the channel, which makes the electron trajectory become essentially three-dimensional, even if it is flat at the early stage of the acceleration.

Areal density and spatial resolution of high energy electron radiography

Jiahao Xiao(肖家浩), Zimin Zhang(张子民), Shuchun Cao(曹树春), Ping Yuan(袁平), Xiaokang Shen(申晓康), Rui Cheng(程锐), Quantang Zhao(赵全堂), Yang Zong(宗阳), Ming Liu(刘铭), Xianming Zhou(周贤明), Zhongping Li(李中平), Yongtao Zhao(赵永涛), Chuanxiang Tang(唐传祥), Wenhui Huang(黄文会), Yingchao Du(杜应超), Wei Gai(盖炜)
Chin. Phys. B, 2018, 27 (3): 035202 doi: 10.1088/1674-1056/27/3/035202
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Ultrafast imaging tools are of great importance for determining the dynamic density distribution in high energy density (HED) matter. In this work, we designed a high energy electron radiography (HEER) system based on a linear electron accelerator to evaluate its capability for imaging HED matter. 40 MeV electron beams were used to image an aluminum target to study the density resolution and spatial resolution of HEER. The results demonstrate a spatial resolution of tens of micrometers. The interaction of the beams with the target and the beam transport of the transmitted electrons are further simulated with EGS5 and PARMELA codes, with the results showing good agreement with the experimental resolution. Furthermore, the experiment can be improved by adding an aperture at the Fourier plane.

Experimental investigation on electrical characteristics and ignition performance of multichannel plasma igniter

Sheng-Fang Huang(黄胜方), Hui-Min Song(宋慧敏), Yun Wu(吴云), Min Jia(贾敏), Di Jin(金迪), Zhi-Bo Zhang(张志波), Bing-Xuan Lin(林冰轩)
Chin. Phys. B, 2018, 27 (3): 035203 doi: 10.1088/1674-1056/27/3/035203
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Relighting of jet engines at high altitudes is very difficult because of the high velocity, low pressure, and low temperature of the inlet airflow. Successful ignition needs sufficient ignition energy to generate a spark kernel to induce a so-called critical flame initiation radius. However, at high altitudes with high-speed inlet airflow, the critical flame initiation radius becomes larger; therefore, traditional ignition technologies such as a semiconductor igniter (SI) become infeasible for use in high-altitude relighting of jet engines. In this study, to generate a large spark kernel to achieve successful ignition with high-speed inlet airflow, a new type of multichannel plasma igniter (MCPI) is proposed. Experiments on the electrical characteristics of the MCPI and SI were conducted under normal and sub-atmospheric pressures (P=10-100 kPa). Ignition experiments for the MCPI and SI with a kerosene/air mixture in a triple-swirler combustor under different velocities of inlet airflow (60-110 m/s), with a temperature of 473 K at standard atmospheric pressure, were investigated. Results show that the MCPI generates much more arc discharge energy than the SI under a constant pressure; for example, the MCPI generated 6.93% and 16.05% more arc discharge energy than that of the SI at 30 kPa and 50 kPa, respectively. Compared to the SI, the MCPI generates a larger area and height of plasma heating zone, and induces a much larger initial spark kernel. Furthermore, the lean ignition limit of the MCPI and SI decreases with an increase in the velocity of the inlet airflow, and the maximum velocity of inlet airflow where the SI and MCPI can achieve successful and reliable ignition is 88.7 m/s and 102.2 m/s, respectively. Therefore, the MCPI has the advantage of achieving successful ignition with high-speed inlet airflow and extends the average ignition speed boundary of the kerosene/air mixture by 15.2%.


Structural phase transition, strength, and texture in vanadium at high pressure under nonhydrostatic compression

Lun Xiong(熊伦), Jing Liu(刘景)
Chin. Phys. B, 2018, 27 (3): 036101 doi: 10.1088/1674-1056/27/3/036101
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The structural phase transition, strength, and texture of vanadium have been studied under nonhydrostatic compression up to 70 GPa using an angle-dispersive radial x-ray diffraction technique in a 2-fold paranomic diamond anvil cell and up to 38 GPa using an angle-dispersive x-ray diffraction technique in a modified Mao-Bell diamond anvil cell at room temperature. We have confirmed a phase transition from body-centered cubic structure to rhombohedral structure at 27-32 GPa under nonhydrostatic compression. The radial x-ray diffraction data yields a bulk modulus K0=141(5) GPa and its pressure derivative K'0=5.4(7) for the bcc phase and K0=154(13) GPa with K'0=3.8(3) for the rhombohedral phase at ψ=54.7°. The nonhydrostatic x-ray diffraction data of both bcc and rhombohedral phases yields a bulk modulus K0=188(5) GPa with K'0=2.1(3). Combined with the independent constraints on the high-pressure shear modulus, it is found that the vanadium sample can support a differential stress of ~1.6 GPa when it starts to yield with plastic deformation at ~36 GPa. A maximum differential stress as high as ~1.7 GPa can be supported by vanadium at the pressure of ~47 GPa. In addition, we have investigated the texture up to 70 GPa using the software package MAUD. It is convinced that the body-centered cubic to rhombohedral phase transition and plastic deformation due to stress under high pressures are responsible for the development of texture.

Estimation of enhanced low dose rate sensitivity mechanisms using temperature switching irradiation on gate-controlled lateral PNP transistor

Xiao-Long Li(李小龙), Wu Lu(陆妩), Xin Wang(王信), Xin Yu(于新), Qi Guo(郭旗), Jing Sun(孙静), Mo-Han Liu(刘默寒), Shuai Yao(姚帅), Xin-Yu Wei(魏昕宇), Cheng-Fa He(何承发)
Chin. Phys. B, 2018, 27 (3): 036102 doi: 10.1088/1674-1056/27/3/036102
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The mechanisms occurring when the switched temperature technique is applied, as an accelerated enhanced low dose rate sensitivity (ELDRS) test technique, are investigated in terms of a specially designed gate-controlled lateral PNP transistor (GLPNP) that used to extract the interface traps (Nit) and oxide trapped charges (Not). Electrical characteristics in GLPNP transistors induced by 60Co gamma irradiation are measured in situ as a function of total dose, showing that generation of Nit in the oxide is the primary cause of base current variations for the GLPNP. Based on the analysis of the variations of Nit and Not, with switching the temperature, the properties of accelerated protons release and suppressed protons loss play critical roles in determining the increased Nit formation leading to the base current degradation with dose accumulation. Simultaneously the hydrogen cracking mechanisms responsible for additional protons release are related to the neutralization of Not extending enhanced Nit buildup. In this study the switched temperature irradiation has been employed to conservatively estimate the ELDRS of GLPNP, which provides us with a new insight into the test technique for ELDRS.

First principles study of ceramic materials (IVB group carbides) under ultrafast laser irradiation

Nan-Lin He(何南燐), Xin-Lu Cheng(程新路), Hong Zhang(张红), Gai-Qin Yan(闫改琴), Jia Zhang(张佳)
Chin. Phys. B, 2018, 27 (3): 036301 doi: 10.1088/1674-1056/27/3/036301
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Group IVB carbides have been applied in extreme aerospace environments as hard ceramic coatings; ZrC is being considered as a replacement for SiC in nuclear reactors. Therefore, a thorough understanding of the laser irradiation response of group IVB carbides is of clear significance. However, the existing knowledge on the fundamental properties of IVB group carbides is limited and insufficient with regard to both irradiated and non-irradiated characteristics. We investigate the effect of ultrafast laser irradiation on the lattice stability of ceramic materials (IVB group carbides) using the density functional perturbation theory (DFPT). The calculated phonon frequencies of TiC and ZrC at the ground state are in good agreement with previous calculations and experimental values. The phonon frequencies of IVB group carbides are positive, even though the electronic temperature reached 5 eV. Thus, IVB group carbides are more stable under ultrafast laser irradiation, which has greater benefits in nuclear and aeronautical applications compared to metals (W, Na), semimetals (Bi), and semiconductors (Si, SiC). The thermodynamic properties of ZrC are calculated as functions of their lattice temperature at different electronic temperatures. The elastic shear constants of IVB group carbides satisfy the Born stability criteria at Te=5 eV. In addition, a comparison of the predicted melting temperatures of IVB group carbides, reveal that HfC is better suited for extreme high-temperature environments.

Power flow analysis in a hybrid phononic crystal structure

Hanbei Guo(郭寒贝), Qiang Li(李强), Liubin Zhou(周刘彬), Lei Qiang(强磊)
Chin. Phys. B, 2018, 27 (3): 036302 doi: 10.1088/1674-1056/27/3/036302
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To reveal the energy transmission through a hybrid phononic crystal structure, power flow analysis is carried out in this paper. Hysteretic damping having significant relationship with power flow is added and corresponding theoretical formulas of the dispersion relation are derived. Besides, the power flow in the hybrid structure is calculated by using the finite element method. The results show that as the damping increases, the boundaries of the band gaps become smoother and dimmer, i.e., broader width. With the increase of damping, the power flow is lowered at the resonance frequencies, while slightly increases near the resonance frequencies. The power flow maps manifest energy distribution in the hybrid structure within and out of the band gaps, which can be exploited in the optimization of the structure design.

Phase diagram, correlations, and quantum critical point in the periodic Anderson model Hot!

Jian-Wei Yang(杨建伟), Qiao-Ni Chen(陈巧妮)
Chin. Phys. B, 2018, 27 (3): 037101 doi: 10.1088/1674-1056/27/3/037101
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Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matrix embedding theory, we study the ground state properties of the periodic Anderson model on a two-dimensional square lattice. We systematically investigate the phase diagram away from half filling. We find three different phases in this region, which are distinguished by the local moment and the spin-spin correlation functions. The phase transition between the two antiferromagnetic phases is of first order. It is the so-called Lifshitz transition accompanied by a reconstruction of the Fermi surface. As the filling is close to half filling, there is no difference between the two antiferromagnetic phases. From the results of the spin-spin correlation, we find that the Kondo singlet is formed even in the antiferromagnetic phase.

First-principles investigations of proton generation in α-quartz

Yunliang Yue(乐云亮), Yu Song(宋宇), Xu Zuo(左旭)
Chin. Phys. B, 2018, 27 (3): 037102 doi: 10.1088/1674-1056/27/3/037102
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Proton plays a key role in the interface-trap formation that is one of the primary reliability concerns, thus learning how it behaves is key to understand the radiation response of microelectronic devices. The first-principles calculations have been applied to explore the defects and their reactions associated with the proton release in α -quartz, the well-known crystalline isomer of amorphous silica. When a high concentration of molecular hydrogen (H2) is present, the proton generation can be enhanced by cracking the H2 molecules at the positively charged oxygen vacancies in dimer configuration. If the concentration of molecular hydrogen is low, the proton generation mainly depends on the proton dissociation of the doubly-hydrogenated defects. In particular, a fully passivated E'2 center can dissociate to release a proton barrierlessly by structure relaxation once trapping a hole. This research provides a microscopic insight into the proton release in silicon dioxide, the critical step associated with the interface-trap formation under radiation in microelectronic devices.

Magnetism, optical, and thermoelectric response of CdFe2O4 by using DFT scheme

Q Mahmood, M Yaseen, K C Bhamu, Asif Mahmood, Y Javed, Shahid M Ramay
Chin. Phys. B, 2018, 27 (3): 037103 doi: 10.1088/1674-1056/27/3/037103
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Comparative analysis of electronic, magnetic, optical, and thermoelectric properties of CdFe2O4, calculated by employing PBEsol+mBJ has been done. The PBEsol reveals metallic nature, while TB-mBJ illustrates ferromagnetic semiconducting behavior. The reasons behind the origin of ferromagnetism are explored by observing the exchange, crystal field, and John-Teller energies. The optical nature is investigated by analyzing dielectric constants, refraction, absorption coefficient, reflectivity, and optical conductivity. Finally, thermoelectric properties are elaborated by describing the electrical and thermal conductivities, Seebeck coefficient, and power factor. The strong absorption for the visible energy and high power factor suggest CdFe2O4 as the potential candidate for renewable energy applications.

Structural, electronic, elastic, and thermal properties of CaNiH3 perovskite obtained from first-principles calculations

S Benlamari, H Bendjeddou, R Boulechfar, S Amara Korba, H Meradji, R Ahmed, S Ghemid, R Khenata, S Bin Omran
Chin. Phys. B, 2018, 27 (3): 037104 doi: 10.1088/1674-1056/27/3/037104
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A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carried out via first-principles full potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) method designed within the density functional theory (DFT). To treat the exchange-correlation energy/potential for the total energy calculations, the local density approximation (LDA) of Perdew-Wang (PW) and the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) are used. The three independent elastic constants (C11, C12, and C44) are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant (a0), bulk modulus (B0), and its pressure derivative (B'0) are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.

Effect of P impurity on mechanical properties of NiAlΣ5 grain boundary: From perspectives of stress and energy

Xue-Lan Hu(胡雪兰), Ruo-Xi Zhao(赵若汐), Jiang-Ge Deng(邓江革), Yan-Min Hu(胡艳敏), Qing-Gong Song(宋庆功)
Chin. Phys. B, 2018, 27 (3): 037105 doi: 10.1088/1674-1056/27/3/037105
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In this paper, we employ the first-principle total energy method to investigate the effect of P impurity on mechanical properties of NiAl grain boundary (GB). According to “energy”, the segregation of P atom in NiAlΣ5 GB reduces the cleavage energy and embrittlement potential, demonstrating that P impurity embrittles NiAlΣ5 GB. The first-principle computational tensile test is conducted to determine the theoretical tensile strength of NiAlΣ5 GB. It is demonstrated that the maximum ideal tensile strength of NiAlΣ5 GB with P atom segregation is 144.5 GPa, which is lower than that of the pure NiAlΣ5 GB (164.7 GPa). It is indicated that the segregation of P weakens the theoretical strength of NiAlΣ5 GB. The analysis of atomic configuration shows that the GB fracture is caused by the interfacial bond breaking. Moreover, P is identified to weaken the interactions between Al-Al bonds and enhance Ni-Ni bonds.

Spin flip in single quantum ring with Rashba spin-orbit interation

Duan-Yang Liu(刘端阳), Jian-Bai Xia(夏建白)
Chin. Phys. B, 2018, 27 (3): 037201 doi: 10.1088/1674-1056/27/3/037201
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We theoretically investigate spin transport in the elliptical ring and the circular ring with Rashba spin-orbit interaction. It is shown that when Rashba spin-orbit interaction is relatively weak, a single circular ring can not realize spin flip, however an elliptical ring may work as a spin-inverter at this time, and the influence of the defect of the geometry is not obvious. Howerver if a giant Rashba spin-orbit interaction strength has been obtained, a circular ring can work as a spin-inverter with a high stability.

Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

Runrun Hao(郝润润), Hai Zhong(钟海), Yun Kang(康韵), Yufei Tian(田雨霏), Shishen Yan(颜世申), Guolei Liu(刘国磊), Guangbing Han(韩广兵), Shuyun Yu(于淑云), Liangmo Mei(梅良模), Shishou Kang(康仕寿)
Chin. Phys. B, 2018, 27 (3): 037202 doi: 10.1088/1674-1056/27/3/037202
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The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in Pt/YIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents (σsc), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electrochemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements.

Electro-statically controllable graphene local heater

Hui-Shan Wang(王慧山), Lian-Wen Deng(邓联文), Lei Li(李蕾), Qiu-Juan Sun(孙秋娟), Hong Xie(谢红), Hao-Min Wang(王浩敏)
Chin. Phys. B, 2018, 27 (3): 037203 doi: 10.1088/1674-1056/27/3/037203
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We report on current-induced thermal power investigation of graphene nanostructure for potential local-heating applications. It is found that the efficiency of heating can be greatly improved if graphene is patterned into structures with narrow width and long channel. In a narrow graphene-ribbon, the Joule heating power exhibits an obvious dependence on the back-gate voltage. By monitoring Raman spectra, the temperature of graphene-ribbon can be determined. The temperature of graphene-ribbon is modulated by the electric field effect when the sample is sourced with a relatively high current.

Distinct edge states and optical conductivities in the zigzag and armchair silicene nanoribbons under exchange and electric fields

Jianfei Zou(邹剑飞), Jing Kang(康静)
Chin. Phys. B, 2018, 27 (3): 037301 doi: 10.1088/1674-1056/27/3/037301
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Based on the tight binding model, we investigate the low energy bandstructures, edge states, and optical absorptions for the silicene nanoribbons (SiNRs) with different terminations under an in-plane exchange field and/or a perpendicular electric field. We find that the zigzag SiNRs are gapped by the exchange field, but they could reenter the metallic state after the application of the electric field. Contrarily, a certain kind of armchair SiNRs remain gapless even if a weak exchange field is present. Furthermore, the combination of the exchange and electric fields could effectively modulate the penetration length and the components of the edge states in the SiNRs. The corresponding optical conductivities for the SiNRs are also calculated, which show remarkable dependence on the edge types of the SiNRs and the two external fields.

Distinctive distribution of defects in CdZnTe: In ingots and their effects on the photoelectric properties

Xu Fu(符旭), Fang-Bao Wang(王方宝), Xi-Ran Zuo(左希然), Ze-Jian Wang(王泽剑), Qian-Ru Wang(王倩茹), Ke-Qin Wang(王柯钦), Ling-Yan Xu(徐凌燕), Ya-Dong Xu(徐亚东), Rong-Rong Guo(郭榕榕), Hui Yu(于晖), Wan-Qi Jie(介万奇)
Chin. Phys. B, 2018, 27 (3): 037302 doi: 10.1088/1674-1056/27/3/037302
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Photoelectric properties of CdZnTe:In samples with distinctive defect distributions are investigated using various techniques. Samples cut from the head (T04) and tail (W02) regions of a crystal ingot show distinct differences in Te inclusion distribution. Obvious difference is not observed in Fourier transform infrared (FTIR) spectra, UV-Vis-NIR transmittance spectra, and I-V measurements. However, carrier mobility of the tip sample is higher than that of the tail according to the laser beam induced current (LBIC) measurements. Low temperature photoluminescence (PL) measurement presents sharp emission peaks of D0X and A0X, and relatively large peak of D0X (or A0X)/Dcomplex for T04, indicating a better crystalline quality. Thermally stimulated current (TSC) spectrum shows higher density of shallow point defects, i.e., Cd vacancies, InCd+, etc., in W02 sample, which could be responsible for the deterioration of electron mobility.

Strong coupling between localized 5f moments and itinerant quasiparticles in the ferromagnetic superconductor UGe2

Wen Zhang(张文), Yi Liu(刘毅), Xiaoying Wang(王小英), Yun Zhang(张云), Donghua Xie(谢东华)
Chin. Phys. B, 2018, 27 (3): 037501 doi: 10.1088/1674-1056/27/3/037501
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The heavy fermion physics arises from the complex interplay of nearly localized 4f/5f electrons and itinerant band-like ones, yielding heavy quasiparticles with an effective mass about 100 times (or more) of the bare electrons. Recently, experimental and theoretical investigations point out a localized and delocalized dual nature in actinide compounds, where itinerant quasiparticles account for the unconventional superconductivity in the vicinity of a magnetic instability. Here we report the strong coupling between localized 5f moments and itinerant quasiparticles in the ferromagnetic superconductor UGe2. The coupling is nearly antiferromagnetic. As embedded in the ferromagnetic matrix of localized 5f moments below TC ≈ 52 K, this coupling leads to short-range dynamic correlations of heavy quasiparticles, characterized by fluctuations of magnetic clusters. Those cluster-like spins of itinerant quasiparticles show a broad hump of magnetization at TX ≈ 28 K, which is typical for the spin-glass freezing. Thus, our results present the direct observation of itinerant quasiparticles coexisting with localized 5f moments by conventional magnetic measurements, providing a new route into the coexistence between ferromagnetism and superconductivity in heavy fermion systems.

NMR evidence of charge fluctuations in multiferroic CuBr2 Hot!

Rui-Qi Wang(王瑞琦), Jia-Cheng Zheng(郑家成), Tao Chen(陈涛), Peng-Shuai Wang(王朋帅), Jin-Shan Zhang(张金珊), Yi Cui(崔祎), Chong Wang(王冲), Yuan Li(李源), Sheng Xu(徐胜), Feng Yuan(袁峰), Wei-Qiang Yu(于伟强)
Chin. Phys. B, 2018, 27 (3): 037502 doi: 10.1088/1674-1056/27/3/037502
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We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance (NQR), and zero-field nuclear magnetic resonance (NMR) measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at TN=TC≈ 74 K. The zero-field 79Br and 81Br NMR are resolved below TN. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K. Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system.

Formation of unusual Cr5+ charge state in CaCr0.5Fe0.5O3 perovskite Hot!

Jian-Hong Dai(戴建洪), Qing Zhao(赵庆), Qian Sun(孙倩), Shuo Zhang(张硕), Xiao Wang(王潇), Xu-Dong Shen(申旭东), Zhe-Hong Liu(刘哲宏), Xi Shen(沈希), Ri-Cheng Yu(禹日成), Ting-Shan Chan(詹丁山), Lun-Xiong Li(李论雄), Guang-Hui Zhou(周光辉), Yi-feng Yang(杨义峰), Chang-Qing Jin(靳常青), You-Wen Long(龙有文)
Chin. Phys. B, 2018, 27 (3): 037503 doi: 10.1088/1674-1056/27/3/037503
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A new oxide CaCr0.5Fe0.5O3 was prepared under high pressure and temperature conditions. It crystallizes in a B-site disordered Pbnm perovskite structure. The charge combination is determined to be Cr5+/Fe3+ with the presence of unusual Cr5+ state in octahedral coordination, although Cr4+ and Fe4+ occur in the related perovskites CaCrO3 and CaFeO3. The randomly distributed Cr5+ and Fe3+ spins lead to short-range ferromagnetic coupling, whereas an antiferromagnetic phase transition takes place near 50 K due to the Fe3+-O-Fe3+ interaction. In spite of the B-site Cr5+/Fe3+ disorder, the compound exhibits electrical insulating behavior. First-principles calculations further demonstrate the formation of CaCr0.55+Fe0.53+O3 charge combination, and the electron correlation effect of Fe3+ plays an important role for the insulting ground state. CaCr0.5Fe0.5O3 provides the first Cr5+ perovskite system with octahedral coordination, opening a new avenue to explore novel transition-metal oxides with exotic charge states.

Magnetostructural transformation and magnetocaloric effect in Mn48-xVxNi42Sn10 ferromagnetic shape memory alloys

Najam ul Hassan, Ishfaq Ahmad Shah, Tahira Khan, Jun Liu(刘俊), Yuanyuan Gong(龚元元), Xuefei Miao(缪雪飞), Feng Xu(徐锋)
Chin. Phys. B, 2018, 27 (3): 037504 doi: 10.1088/1674-1056/27/3/037504
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In this work, we tuned the magnetostructural transformation and the coupled magnetocaloric properties of Mn48-xVxNi42Sn10 (x=0, 1, 2, and 3) ferromagnetic shape memory alloys prepared by means of partial replacement of Mn by V. It is observed that the martensitic transformation temperatures decrease with the increase of V content. The shift of the transition temperatures to lower temperatures driven by the applied field, the metamagnetic behavior, and the thermal hysteresis indicates the first-order nature for the magnetostructural transformation. The entropy changes with a magnetic field variation of 0-5 T are 15.2, 18.8, and 24.3 J·kg-1·K-1 for the x=0, 1, and 2 samples, respectively. The tunable martensitic transformation temperature, enhanced field driving capacity, and large entropy change suggest that Mn48-xVxNi42Sn10 alloys have a potential for applications in magnetic cooling refrigeration.

Calculation of electric field-temperature (E, T) phase diagram of a ferroelectric liquid crystal near the SmA-SmCα* transition

F Trabelsi, H Dhaouadi, O Riahi, T Othman
Chin. Phys. B, 2018, 27 (3): 037701 doi: 10.1088/1674-1056/27/3/037701
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In this work we perform a theoretical calculation in order to reconstitute the (E-T) phase diagram of a chiral smectic liquid crystal in the vicinity of the SmA-SmCα* transition. This reconstruction is carried out on the basis of a thermodynamic calculation of the slope of the curve joining the SmCα* domain and the unwound SmC*. An empiric correction of the mean field term of Landau De-Gennes development is necessary to accomplish this reconstruction. Thereafter, an experimental validation is performed to verify our calculations.

Particle swarm optimization and its application to the design of a compact tunable guided-mode resonant filter

Dan-Yan Wang(王丹燕), Qing-Kang Wang(王庆康)
Chin. Phys. B, 2018, 27 (3): 037801 doi: 10.1088/1674-1056/27/3/037801
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A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wavelength is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement (in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm (140 nm) is obtained by horizontal movement of 168 nm (vertical movement of 435 nm) combined with an about 11° variation of incident angle.

Influence of fluorescence time characteristics on the spatial resolution of CW-stimulated emission depletion microscopy

Haiyun Qin(秦海芸), Wei Zhao(赵伟), Chen Zhang(张琛), Yong Liu(刘勇), Guiren Wang(王归仁), Kaige Wang(王凯歌)
Chin. Phys. B, 2018, 27 (3): 037803 doi: 10.1088/1674-1056/27/3/037803
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As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous-wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.

High mobility ultrathin ZnO p-n homojunction modulated by Zn0.85Mg0.15O quantum barriers

Jing-Jing Yang(杨景景), Qing-Qing Fang(方庆清), Wen-Han Du(杜文汉), Ke-Ke Zhang, Da-Shun Dong(董大舜)
Chin. Phys. B, 2018, 27 (3): 037804 doi: 10.1088/1674-1056/27/3/037804
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The adding of ZnMgO asymmetric double barriers (ADB) in p-ZnO:(Li, N)/n-ZnO homojunction affects the p-n junction device performance prominently. Two different homojunctions are fabricated on Si (100) substrates by pulsed laser deposition; one is the traditional p-ZnO:(Li, N)/n-ZnO homojunction with different thicknesses named as S1 (250 nm) and S2 (500 nm), the other is the one with ADB embedded in the n-layer named as Q (265 nm). From the photoluminescence spectra, defect luminescence present in the S-series devices is effectively limited in the Q device. The current-voltage curve of the Q device shows Zener-diode rectification property because the two-dimensional electron gas tunnels through the narrow ZnMgO barrier under a reverse bias, thus decreasing the working p-n homojunction thickness from 500 nm to 265 nm. The ADB-modified homojunction shows higher carrier mobility in the Q device. The electroluminescence of the ZnO homojunction is improved in Q compared to S2, because the holes in p-type ZnO (Li, N) can cross the wide ZnMgO barrier under a forward bias voltage into the ZnO quantum well. Therefore, electron-hole recombination occurs in the narrow bandgap of n-type ZnO, creating an ultraviolet light-emitting diode using the ZnO homojunction.

Thermomechanical response of aluminum alloys under the combined action of tensile loading and laser irradiations

Mohsan Jelani, Zewen Li(李泽文), Zhonghua Shen(沈中华), Maryam Sardar
Chin. Phys. B, 2018, 27 (3): 037901 doi: 10.1088/1674-1056/27/3/037901
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This study reports the investigation of the thermomechanical behavior of aluminum alloys (Al-1060, Al-6061, and Al-7075) under the combined action of tensile loading and laser irradiations. The continuous wave ytterbium fiber laser (wavelength 1080 nm) was employed as the irradiation source, while tensile loading was provided by the tensile testing machine. The effects of various pre-loading and laser power densities on the failure time, temperature distribution, and the deformation behavior of aluminum alloys are analyzed. The experimental results represent the significant reduction in failure time for higher laser power densities and for high preloading values, which implies that preloading may contribute a significant role in the failure of the material at elevated temperature. Fracture on a microscopic scale was predominantly ductile comprising micro-void nucleation, growth, and coalescence. The Al-1060 specimens behaved plastically to some extent, while Al-6061 and Al-7075 specimens experienced catastrophic failure. The reason and characterization of material failure by tensile and laser loading are explored in detail. A comparative behavior of under-tested materials is also investigated. This work suggests that studies considering only combined loading are not enough to fully understand the mechanical behavior of under-tested materials. For complete characterization, one should consider the effect of heating as well as loading rate and the corresponding involved processes with the help of thermomechanical coupling and the thermal elastic-plastic theory.

Synthesis of strong SiV photoluminescent diamond particles on silica optical fiber by chemical vapor deposition

Zongchun Yang(仰宗春), Yingshuang Mei(梅盈爽), Chengke Chen(陈成克), Yinlan Ruan(阮银兰), Xiaojun Hu(胡晓君)
Chin. Phys. B, 2018, 27 (3): 038101 doi: 10.1088/1674-1056/27/3/038101
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The separated silicon-vacancy (SiV) photoluminescent diamond particles were synthesized on a silica optical fiber by hot filament chemical vapor deposition (HFCVD). The effects of the pre-treated method and chamber pressure on the microstructure and photoluminescence of the diamond particles were investigated. The results show that the diamond particles are homogeneously distributed on the surface of the optical fiber. With the chamber pressure increasing from 1.6 kPa to 3.5 kPa, the shape of the particles transforms from flake to circle, while the diamond particles cannot be deposited on the fiber with the pressure further increased to 4.5 kPa. The samples synthesized under 2.5 kPa chamber pressure are composed of diamond particles with size around 200-400 nm, exhibiting stronger SiV photoluminescence with the width of around 6 nm.

Quantitative deformation measurements and analysis of the ferrite-austenite banded structure in a 2205 duplex stainless steel at 250℃

Ji-Hua Liu(刘计划)
Chin. Phys. B, 2018, 27 (3): 038102 doi: 10.1088/1674-1056/27/3/038102
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The deformation process of the microstructure in 2205 duplex stainless steel (DSS) under thermo-mechanical coupling at 250℃ was investigated using digital image correlation (DIC). A thermal tension test of duplex stainless steel (2205DSS) with a banded structure was carried out to observe the initial deformation of the microstructure. It was found that inhomogeneous strain fields occurred primarily in austenite. The maximum normal strain in austenite was almost positive, while that in ferrite was almost negative. In addition, a thermal cyclic-loading test was conducted, and the strain field was characterized by e11. Strain heterogeneities were induced after 400 cycles, which spread within the austenite and at the phase boundaries with the load increasing. The high tensile-strain regions were always located adjacent to regions of intense compressive strain. Based on the strain matrix sum vs. cycle number, we found that hardening occurred in the early cycles followed by softening.

Enhanced ionic conductivity in LAGP/LATP composite electrolyte

Shi-Gang Ling(凌仕刚), Jia-Yue Peng(彭佳悦), Qi Yang(杨琪), Ji-Liang Qiu(邱纪亮), Jia-Ze Lu(卢嘉泽), Hong Li(李泓)
Chin. Phys. B, 2018, 27 (3): 038201 doi: 10.1088/1674-1056/27/3/038201
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Nasicon materials (sodium superionic conductors) such as Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and Li1.4Al0.4Ti1.6(PO4)3 (LATP) have been considered as important solid electrolytes due to their high ionic conductivity and chemical stability. Compared to LAGP, LATP has higher bulk conductivity around 10-3 S/cm at room temperature; however, the apparent grain boundary conductivity is almost two orders of magnitude lower than the bulk, while LAGP has similar bulk and grain boundary conductivity around the order of 10-4 S/cm. To make full use of the advantages of the two electrolytes, pure phase Li1.5Al0.5Ge1.5(PO4)3 and Li1.4Al0.4Ti1.6(PO4)3 were synthesized through solid state reaction, a series of composite electrolytes consisting of LAGP and LATP with different weight ratios were designed. XRD and variable temperature AC impedance spectra were carried out to clarify the crystal structure and the ion transport properties of the composite electrolytes. The results indicate that the composite electrolyte with the LATP/LAGP weight ratio of 80:20 achieved the highest bulk conductivity which shall be due to the formation of solid solution phase Li1.42Al0.42Ge0.3Ti1.28(PO4)3, while the highest grain boundary conductivity appeared at the LATP/LAGP weight ratio of 20:80 which may be due to the excellent interfacial phase between Li1+xAlxGeyTi2-x-y(PO4)3/LATP. All the composite electrolytes demonstrated higher total conductivity than the pure LAGP and LATP, which highlights the importance of heterogeneous interface on regulating the ion transport properties.

An improved secondary electrons energy spectrum model and its application in multipactor discharge

Wan-Zhao Cui(崔万照), Heng Zhang(张恒), Yun Li(李韵), Yun He(何鋆), Qi Wang(王琪), Hong-Tai Zhang(张洪太), Hong-Guang Wang(王洪广), Jing Yang(杨晶)
Chin. Phys. B, 2018, 27 (3): 038401 doi: 10.1088/1674-1056/27/3/038401
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Secondary electron emission (SEE) of metal and dielectric materials plays a key role in multipactor discharge, which is a bottle neck problem for high-power satelliate components. Measurements of both the secondary electron yield (SEY) and the secondary electron energy spectrum (SES) are performed on metal samples for an accurate description of the real SEE phenomenon. In order to simplify the fitting process and improve the simulation efficiency, an improved model is proposed for the description of secondary electrons (SE) emitted from the material surface, including true, elastic, and inelastic SE. Embedding the novel SES model into the electromagnetic particle-in-cell method, the electronic resonant multipactor in microwave components is simulated successfully and hence the discharge threshold is predicted. Simulation results of the SES variation in the improved model demonstrate that the multipactor threshold is strongly dependent on SES. In addition, the mutipactor simulation results agree quite well with the experiment for the practical microwave component, while the numerical model of SEY and SES fits well with the sample data taken from the microwave component.

Factors influencing the performance of paintable carbon-based perovskite solar cells fabricated in ambient air

Wei-Kang Xu(许伟康), Feng-Xiang Chen(陈凤翔), Gong-Hui Cao(曹功辉), Jia-Qi Wang(王嘉绮), Li-Sheng Wang(汪礼胜)
Chin. Phys. B, 2018, 27 (3): 038402 doi: 10.1088/1674-1056/27/3/038402
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To date, many efforts have been made to improve the performance of paintable carbon-based (PC-based) perovskite solar cells (PSCs). Though great progress has been achieved, their power conversion efficiencies are still relatively low compared with hole-transport-materials-based PSCs. General research on influencing factors of performance in PC-based PSCs is still insufficient. In this work, PC-based PSCs were fabricated in ambient air and four groups of controlled experiments were performed in which the PbI2 layers were prepared with or without antisolvent extraction treatment. These four groups of experiments were designed to find out the effect of different influencing factors on PC-based PSCs performance, for example, PbI2 residual, the surface morphology of the perovskite film, the surface roughness of the perovskite film, and the contact status of the perovskite/carbon electrode interface. With a systematic analysis, we demonstrated that the contact status of the perovskite/carbon electrode interface played a vital role in PC-based PSCs, and a flat, smooth perovskite surface could help to improve this contact status significantly. Besides, on the precondition of a poor contact interface, no PbI2 residual and a good surface morphology only brought limited benefits to the performances of PC-based PSCs.

Analysis of multiple cell upset sensitivity in bulk CMOS SRAM after neutron irradiation

Xiaoyu Pan(潘霄宇), Hongxia Guo(郭红霞), Yinhong Luo(罗尹虹), Fengqi Zhang(张凤祁), Lili Ding(丁李利)
Chin. Phys. B, 2018, 27 (3): 038501 doi: 10.1088/1674-1056/27/3/038501
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In our previous studies, we have proved that neutron irradiation can decrease the single event latch-up (SEL) sensitivity of CMOS SRAM. And one of the key contributions to the multiple cell upset (MCU) is the parasitic bipolar amplification, it bring us to study the impact of neutron irradiation on the SRAM's MCU sensitivity. After the neutron experiment, we test the devices' function and electrical parameters. Then, we use the heavy ion fluence to examine the changes on the devices' MCU sensitivity pre-and post-neutron-irradiation. Unfortunately, neutron irradiation makes the MCU phenomenon worse. Finally, we use the electric static discharge (ESD) testing technology to deduce the experimental results and find that the changes on the WPM region take the lead rather than the changes on the parasitic bipolar amplification for the 90 nm process.

Simulation and experimental study of a novel bifacial structure of silicon heterojunction solar cell for high efficiency and low cost

Haibin Huang(黄海宾), Gangyu Tian(田罡煜), Lang Zhou(周浪), Jiren Yuan(袁吉仁), Wolfgang R. Fahrner, Wenbin Zhang(张闻斌), Xingbing Li(李杏兵), Wenhao Chen(陈文浩), Renzhong Liu(刘仁中)
Chin. Phys. B, 2018, 27 (3): 038502 doi: 10.1088/1674-1056/27/3/038502
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A novel structure of Ag grid/SiNx/n+-c-Si/n-c-Si/i-a-Si:H/p+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifacial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current (Jsc), while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover, real cells composed of the novel structure with dimensions of 75 mm×75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the Jsc of 41.7 mA/cm2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm2. We conclude that the configuration of the Ag grid/SiNx/n+-c-Si/n-c-Si/i-a-Si:H/p+-a-Si:H/TCO/Ag grid is a promising structure for high efficiency and low cost.

A novel knowledge-based potential for RNA 3D structure evaluation

Yi Yang(杨毅), Qi Gu(辜琦), Ben-Gong Zhang(张本龚), Ya-Zhou Shi(时亚洲), Zhi-Gang Shao(邵志刚)
Chin. Phys. B, 2018, 27 (3): 038701 doi: 10.1088/1674-1056/27/3/038701
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Ribonucleic acids (RNAs) play a vital role in biology, and knowledge of their three-dimensional (3D) structure is required to understand their biological functions. Recently structural prediction methods have been developed to address this issue, but a series of RNA 3D structures are generally predicted by most existing methods. Therefore, the evaluation of the predicted structures is generally indispensable. Although several methods have been proposed to assess RNA 3D structures, the existing methods are not precise enough. In this work, a new all-atom knowledge-based potential is developed for more accurately evaluating RNA 3D structures. The potential not only includes local and nonlocal interactions but also fully considers the specificity of each RNA by introducing a retraining mechanism. Based on extensive test sets generated from independent methods, the proposed potential correctly distinguished the native state and ranked near-native conformations to effectively select the best. Furthermore, the proposed potential precisely captured RNA structural features such as base-stacking and base-pairing. Comparisons with existing potential methods show that the proposed potential is very reliable and accurate in RNA 3D structure evaluation.

A computational study of the chemokine receptor CXCR1 bound with interleukin-8

Yang Wang(王洋), Cecylia Severin Lupala, Ting Wang(王亭), Xuanxuan Li(李选选), Ji-Hye Yun, Jae-hyun Park, Zeyu Jin(金泽宇), Weontae Lee, Leihan Tan(汤雷翰), Haiguang Liu(刘海广)
Chin. Phys. B, 2018, 27 (3): 038702 doi: 10.1088/1674-1056/27/3/038702
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CXCR1 is a G-protein coupled receptor, transducing signals from chemokines, in particular the interleukin-8 (IL8) molecules. This study combines homology modeling and molecular dynamics simulation methods to study the structure of CXCR1-IL8 complex. By using CXCR4-vMIP-Ⅱ crystallography structure as the homologous template, CXCR1-IL8 complex structure was constructed, and then refined using all-atom molecular dynamics simulations. Through extensive simulations, CXCR1-IL8 binding poses were investigated in detail. Furthermore, the role of the N-terminal of CXCR1 receptor was studied by comparing four complex models differing in the N-terminal sequences. The results indicate that the receptor N-terminal affects the binding of IL8 significantly. With a shorter N-terminal domain, the binding of IL8 to CXCR1 becomes unstable. The homology modeling and simulations also reveal the key receptor-ligand residues involved in the electrostatic interactions known to be vital for complex formation.

Molecular dynamics simulations of membrane deformation induced by amphiphilic helices of Epsin, Sar1p, and Arf1

Zhen-Lu Li(李振鲁)
Chin. Phys. B, 2018, 27 (3): 038703 doi: 10.1088/1674-1056/27/3/038703
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The N-terminal amphiphilic helices of proteins Epsin,Sar1p,and Arf1 play a critical role in initiating membrane deformation.The interactions of these amphiphilic helices with the lipid membranes are investigated in this study by combining the all-atom and coarse-grained simulations.In the all-atom simulations,the amphiphilic helices of Epsin and Sar1p are found to have a shallower insertion depth into the membrane than the amphiphilic helix of Arf1,but remarkably, the amphiphilic helices of Epsin and Sar1p induce higher asymmetry in the lipid packing between the two monolayers of the membrane.The insertion depth of amphiphilic helix into the membrane is determined not only by the overall hydrophobicity but also by the specific distributions of polar and non-polar residues along the helix.To directly compare their ability to deform the membrane,the coarse-grained simulations are performed to investigate the membrane deformation under the insertion of multiple helices.

First integrals of the axisymmetric shape equation of lipid membranes

Yi-Heng Zhang(张一恒), Zachary McDargh, Zhan-Chun Tu(涂展春)
Chin. Phys. B, 2018, 27 (3): 038704 doi: 10.1088/1674-1056/27/3/038704
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The shape equation of lipid membranes is a fourth-order partial differential equation. Under the axisymmetric condition, this equation was transformed into a second-order ordinary differential equation (ODE) by Zheng and Liu (Phys. Rev. E 48 2856 (1993)). Here we try to further reduce this second-order ODE to a first-order ODE. First, we invert the usual process of variational calculus, that is, we construct a Lagrangian for which the ODE is the corresponding Euler-Lagrange equation. Then, we seek symmetries of this Lagrangian according to the Noether theorem. Under a certain restriction on Lie groups of the shape equation, we find that the first integral only exists when the shape equation is identical to the Willmore equation, in which case the symmetry leading to the first integral is scale invariance. We also obtain the mechanical interpretation of the first integral by using the membrane stress tensor.

Spatial memory enhances the evacuation efficiency of virtual pedestrians under poor visibility condition

Yi Ma(马毅), Eric Wai Ming Lee(李伟民), Meng Shi(施朦), Richard Kwok Kit Yuen(袁国杰)
Chin. Phys. B, 2018, 27 (3): 038901 doi: 10.1088/1674-1056/27/3/038901
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Spatial memory is a critical navigation support tool for disoriented evacuees during evacuation under adverse environmental conditions such as dark or smoky conditions. Owing to the complexity of memory, it is challenging to understand the effect of spatial memory on pedestrian evacuation quantitatively. In this study, we propose a simple method to quantitatively represent the evacuee's spatial memory about the emergency exit, model the evacuation of pedestrians under the guidance of the spatial memory, and investigate the effect of the evacuee's spatial memory on the evacuation from theoretical and physical perspectives. The result shows that (i) a good memory can significantly assist the evacuation of pedestrians under poor visibility conditions, and the evacuation can always succeed when the degree of the memory exceeds a threshold (φ>0.5); (ii) the effect of memory is superior to that of “follow-the-crowd” under the same environmental conditions; (iii) in the case of multiple exits, the difference in the degree of the memory between evacuees has a significant effect (the greater the difference, the faster the evacuation) for the evacuation under poor visibility conditions. Our study provides a new quantitative insight into the effect of spatial memory on crowd evacuation under poor visibility conditions.

Flowrate behavior and clustering of self-driven robots in a channel

Bo Tian(田波), Wang-Ping Sun(孙王平), Ming Li(李明), Rui Jiang(姜锐), Mao-Bin Hu(胡茂彬)
Chin. Phys. B, 2018, 27 (3): 038902 doi: 10.1088/1674-1056/27/3/038902
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In this paper, the collective motion of self-driven robots is studied experimentally and theoretically. In the channel, the flowrate of robots increases with the density linearly, even if the density of the robots tends to 1.0. There is no abrupt drop in the flowrate, similar to the collective motion of ants. We find that the robots will adjust their velocities by a serial of tiny collisions. The speed-adjustment will affect both robots involved in the collision, and will help to maintain a nearly uniform velocity for the robots. As a result, the flowrate drop will disappear. In the motion, the robots neither gather together nor scatter completely. Instead, they form some clusters to move together. These clusters are not stable during the moving process, but their sizes follow a power-law-alike distribution. We propose a theoretical model to simulate this collective motion process, which can reproduce these behaviors well. Analytic results about the flowrate behavior are also consistent with experiments.
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