bluuebunny/crossref_metadata_2025 huggingface dataset:
Sense of Coherence and Driver Stress in Ridesharing Drivers as Moderated by Community Affiliation
Authors: Grasiaswaty Novika , Sadida Nuri , Aliviary Alexandra
Published: December 2020

The present research aimed to test whether community involvement moderates the relationship between sense of coherence (SOC) and driver stress among online ridesharing drivers. The study used a quantitative design to collect data via questionnaires. All 112 participants were male and chose online ridesharing as their primary occupation. Participants were assessed using the Work Sense of Coherence Scale and Driver Stress Scale, a subscale of Driving Behavior Inventory. Community involvement was measured with a close-ended question in the demographic section of the questionnaire, with dichotomous options provided (1 = community participation; 0 = no community participation). Collected data were analyzed using JASP to examine the moderating effect. The results of this study showed that community involvement moderates the relationship between SOC and driver stress in online ridesharing drivers.
Effects of Internship Satisfaction, Subjective Norms, and Self-Efficacy on Student Intern’s Job Application Intention
Authors: Putra Ibnu Handono , Purba Debora Eflina
Published: December 2020

Internship programs can serve as recruitment and selection strategies that facilitate data collection on the abilities of potential employees to manage their daily work duties. This study aims to examine factors that may influence a student intern’s intentions to apply to convert the internship into a permanent employee position at the same company after graduating from university. The study is grounded in the theory of planned behavior to probe whether internship satisfaction, subjective norms, and self-efficacy are predictors of the intentions of student interns to apply for jobs at companies that offer internship programs. Data collected from 261 Indonesian university students demonstrated that internship satisfaction and subjective norms positively and significantly predicted the intentions of student interns to apply to convert their internships into permanent jobs at the same company. However, self-efficacy did not predict such conversion intentions. Finally, the practical implications of these outcomes are discussed, and directions for prospective research are suggested.
Special scattering in photorefractive crystal LiNbO3:Fe
Authors: Zhang Yan  , Zhao Yue-Feng  , Zhao Li-Na  , Zheng Li-Ren  , Gao Yuan-Mei  ,   College of Physics and Electronics, Shandong Normal University, Ji'nan 250014, China;,   College of Physics and Electronic Engineering, Taishan University, Tai'an 271021, China
Published: December 2020

We observe special scattering light by using a simple experimental device and record the dynamic behavior with a camera. A laser beam from an Nd:YAG laser, which is expanded by the spatial filter (SF) and collimated by the lens L1 (f1=300 mm), is focused into a line light through a pair of cylindrical lenses L2, L3 (f2=f3=200 mm) and irradiates the LiNbO3:Fe crystal. On condition that the directions of line beam (f) and c-axis of the crystal are both parallel to the horizontal direction, we observe experimentally that the scattering light spreads gradually in the horizontal direction in the far field as irradiation time goes on. Then the scattering light reaches a steady state after 10 min. The scattering light beam is composed of vertical filaments. When the line beam is horizontal and the c-axis is vertical, the scattering light composed of horizontal filaments firstly appears in the vertical direction. About 30 min later, the scattering light appears and spreads along the horizontal direction to the far field as irradiation time goes on. At this time, the scattering light is also composed of vertical filaments. That is to say, we observe the scattering light whose direction is inconsistent with the c axis of the crystal. We also give the corresponding theoretical explanation to the phenomenon. We suppose that the line beam consists of many close-set thread-like sub-beams, which are vertical to the direction of the line beam. When the line beam irradiates the photorefractive crystal, the sub-beams record the gratings in the crystal according to photorefractive nonlinear effect. The gratings diffract the input beam. The scattering light and the incident beam interfere with each other, thereby recording the new grating. At the same time, the new gratings also diffract the incident beam. It goes full circle. So energy transfers from incident beam to the scattering light beam. The direction of the scattering light beam spreads along the direction of the line beam.
Detection and estimation of weak pulse signal in chaotic background noise
Authors: Su Li-Yun  , Sun Huan-Huan  , Wang Jie  , Yang Li-Ming  ,   School of Science, Chongqing University of Technology, Chongqing 400054, China
Published: December 2020

As is well known, people has been suffering noise interference for a long time, and more and more researches show that a lot of weak signals such as pulse signal are embedded in the strong chaotic noise. The purpose of weak signal detection and recovery is to retrieve useful signal from strong noise. It is very difficult to detect and estimate the weak pulse signal which is mixed in the chaotic background interference. Therefore, the detection and recovery of weak signal are significant and have application value in signal processing area, especially for the weak pulse signal detection and recovery. By studying various methods of detecting and estimating the weak pulse signal in strong chaotic background noise, in this paper, we propose an efficient hybrid processing technique. First, based on the short-term predictability and sensitivity to the tiny disturbance, a new method is proposed, which can be used for detecting and estimating the weak pulse signals in chaotic background that the nonlinear mapping is unknown. We reconstruct a phase space according to Takens delay embedding theorem; then we establish the local linear autoregressive model to predict the short-term chaotic signal and obtain the fitting error, and judge whether there are weak pulse signals. Second, we establish a single-jump model for pulse signals, and combine the local linear autoregressive model with it to build a double local linear (DLL) model for estimating the weak pulse signal. DLL model contains two parameters, and the two parameters affect each other. We use the back-fitting algorithm to estimate model parameters and ultimately recover the weak pulse signals. Detecting and estimating the pulse signals in chaotic background turns into estimating the parameters of DLL model. The minimum fitting error criterion is used as the objective function to estimate the parameters of the DLL model. To make the estimation more exact, we can use the formula of mean square error. The new algorithm presented here in this paper does not need to know the prior knowledge of the chaotic background nor weak pulse signal, and this algorithm is also simple and effective. Finally, the simulation results show that the method is effective for detecting and estimating the weak pulse signals based on the chaotic background noise. Specifically, the weak pulse signal can be extracted well with low SNR and the minimum mean square error or the minimum normalized mean squared error is very low.
Force analysis and pressure quantitative measurement for the high pressure cubic cell
Authors: Wang Hai-Kuo  , Ren Ying  , He Duan-Wei  , Xu Chao  ,   Institute of Materials Pressure Treatment, School of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450001, China;,   Laboratory of High Pressure Science and Technology, Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;,   College of Sciences, Wuhan University of Science and Technology, Wuhan 430065, China
Published: December 2020

Large volume cubic press is one of the most popular high pressure devices which can produce pressures up to about 7 GPa. It is well known experimentally that the enhancing of the maximum pressure generated in the large volume cubic press has attracted wide attention among scientists and engineers because the higher pressure is capable of synthesizing some materials with interesting properties. In the large volume cubic press, pyrophyllite is typically used as a pressure-transmitting medium. A specimen immersed in such a solid experiences a generalized stress state. The pressure distribution in pyrophyllite is an important parameter for characterizing the sample environment and designing the experiments at high pressure. There is a need for the quantitative measurement of pressure gradients in the pyrophyllite pressure medium, so that the accurate experimental data under high pressure can be obtained. In the large volume cubic apparatus (68 MN), we put a circuit into the high pressure cubic cell, so that the pressures at various positions can be measured by using the phase transitions in Bi, Tl and Ba. In the present work, the relationship between the total press load and the press load allocated to the anvil face, and the relationship between the total press load and the press load allocated to gaskets are established at room temperature. The results show that with the increase of the total press load, the load allocated to the gaskets is increased sharply, while the curve of load allocated to the anvil face versus total press load reaches a plateau, which results in the cell pressure reaching upper limit when the cell pressure reaches up to about 5 GPa. According to the experimental results, the stress state of the cubic cell under high pressure is analyzed and the reason why the pressure generated in the large volume cubic chamber is difficult to exceed 7 GPa is explained. Based on the geometrical structure of the cubic cell, the scheme to increase the upper pressure limit for cubic cell by using the material with high bulk modulus as the pressure transmitting medium and the material with low bulk modulus as the gasket, is proposed. Additionally, the method of calculating the pressure values at different positions along the axis of symmetry in the cubic cell is given through the quantitative calibration of the pressure gradient in the axial direction of the cubic cell. This method can provide more accurate pressure data for high pressure experiments.
Local adaptive heterogeneous synchronization for interdependent networks with delayed coupling
Authors: Wang Yu-Juan  , Tu Li-Lan  , Song Shuai  , Li Kuan-Yang  ,   College of Science, Wuhan University of Science and Technology, Wuhan 430065, China
Published: December 2020

With the development of the networks, the coupling between networks has become increasingly significant. Here, the networks can be described as interdependent networks. An interdependent network can have two different kinds of links, a connectivity link and a dependency link, which are fundamental properties of interdependent networks. During the past several years, interdependent complex network science has attracted a great deal of attention. This is mainly because the rapid increase in computing power has led to an information and communication revolution. Investigating and improving our understanding of interdependent networks will enable us to make the networks (such as infrastructures) we use in daily life more efficient and robust. As a significant collective behavior, synchronization phenomena and processes are common in nature and play a vital role in the interaction between dynamic units. At the same time, the time delay problem is an important issue to be investigated, especially in biological and physical networks. As a matter of fact, time delays exist commonly in the real networks. A signal or influence traveling through a network is often associated with time delay. In this paper, the local adaptive heterogeneous synchronization is investigated for interdependent networks with delayed coupling consisting of two sub-networks, which are one-by-one inter-coupled. The delays exist both in the intra-coupling and in the inter-coupling between two sub-networks, the intra-coupling and inter-coupling relations of the networks satisfy the requirements for nonlinearity and smoothness, and the nodes between two sub-networks have different dynamical systems, namely heterogeneous systems. Based on the Lyapunov stability theory, linear matrix inequality, and adaptive control technique, with proper controllers and adaptive laws for the networks, the sufficient conditions are proposed to synchronize the sub-networks of the interdependent networks into heterogeneous isolated systems, respectively. In order to illustrate the main results of the theoretical analysis clearly, some numerical simulations for an interdependent network with NW small world sub-network and BA sub-network are presented, in which each sub-network has 100 nodes and the heterogeneous systems are Lorenz and Rössler systems. The numerical simulations show that using the controllers and adaptive laws proposed, the network obtains the local heterogeneous synchronization quickly, that is, the nodes of two sub-networks are synchronized into Lorenz and Rössler systems separately. Thus, they verify the feasibility and correctness of the proposed techniques. It is worth noting that the presented results are delay-independent. In the future, our research will be directed to the further investigation of the delay-dependent synchronization of interdependent networks by using the current results as a basis.
Total ionizing dose effects of γ and X-rays on 55 nm silicon-oxide-nitride-oxide-silicon single flash memory cell
Authors: Cao Yang , Xi Kai , Xu Yan-Nan , Li Mei , Li Bo , Bi Jin-Shun , Liu Ming ,   University of Chinese Academy of Sciences, Beijing 100049, China,   Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

The total ionizing dose (TID) effects on 55 nm SONOS flash cell, caused by 60Co-γ ray and 10 keV X-ray radiation source, are systematically investigated in this paper. The degradation of electrical characteristics is discussed while the underlying physical mechanism is analyzed. The drift of I-V characteristic curve, the degradation of memory window, and the increase of stand-by current are observed after TID irradiation separately by the two radiation sources. The data retention capability is also affected by the TID irradiation. The I-Vg curve of the programmed single flash cell significantly drifts towards the negative direction after TID irradiation, while the negative drift of erased state is much slower. Referring to the erased state, the drift directions of Id-Vg curves for γ- and X-ray radiation source are obviously different. The physical mechanism of irradiation damage in a 55 nm SONOS single flash cell is discussed in detail by the energy band theory and TCAD simulations. The storage charge loss in silicon nitride layer, the charge accumulation, and the generation of interface states all together lead to the degradation of threshold voltage and stand-by current after TID irradiation. Another cause for the increase of stand-by current is the positive trapped charges in the isolated oxide induced by irradiation, which leads to the generation of leakage paths. Significant dose enhancement effect of X-ray irradiation is observed in this paper. Device model of memory transistor c is established while the dose enhancement effect of X-rays is investigated by Geant 4 tool. The high-Z materials above the poly-silicon gate lead to the dose enhancement effect of X-rays’ irradiation, which results in the higher degradation. The density of electron-hole pairs produced by irradiation in W layer is much higher than in Cu layer. In particular, W layer is a critical factor regardless of the thickness, which can be obviously observed in the simulation.
Fast single-pixel imaging based on optimized reordering Hadamard basis
Authors: Li Ming-Fei , Yan Lu , Yang Ran , Liu Yuan-Xing ,   Quantum Engineering Research Center, China Aerospace Science and Technology Corporation, Beijing 100094, China,   Beijing Institute of Aerospace Control Devices, Beijing 100039, China
Published: December 2020

Single-pixel imaging is a computational imaging scheme that offers novel solutions for multi-spectral imaging, feature-based imaging, polarimetric imaging, three-dimensional imaging, holographic imaging, and optical encryption. The single-pixel imaging scheme can be used for imaging in wave band such as infrared and micro wave imaging, or will be useful in the case where the array detector technique is difficult to meet the requirement such as the sensitivity or the volume. The main limitation for its application comes from a trade-off between spatial resolution and acquisition time, in other words, from relatively high measurement and reconstruction time. Although compressive sensing technique can be used to improve the acquisition time by reducing the number of samplings, the computational time to reconstruct an image is not fast enough to satisfy the real-time video. In this paper, we propose to reduce the required signal acquisition time by using a novel sampling scheme based on optimized ordering of the Hadamard basis, and improve the image reconstruction efficiency by using fast Walsh-Hadamard transform. In our method, the Hadamard basis is rearranged in the ascendant order of the values of its " sparsity” coefficients which are obtained through " Daubechies wavelets 1 (Haar wavelets)”, " Daubechies wavelets 2” wavelet transform and discrete cosine transform, and then compute each total sum of the transformed coefficients’ absolute value, respectively. The measurement order of the Hadamard basis is then rearranged directly according to Walsh order and random permutation order. The peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of the retrieved images are computed and compared to test all the five reordering schemes above both in our numerical simulation and outdoor experiments. We find that the reordering method based on Haar wavelet transform is the best PSNR and SSIM and it can reconstruct image under a sampling ratio of 25% which corresponds to the recovering time in which 300 frame per second @64 × 64 pixels single-pixel imaging can be achieved. The optimized measurement order of Hadamard basis greatly simplifies post processing, resulting in significantly faster image reconstruction, which steps further toward high frame rate single-pixel imaging’s applications. Moreover, we propose a novel method to optimize measurement basis in single-pixel imaging, which may be useful in other basis optimizing, such as optimized random speckles, etc.
Percolation of interdependent networks with conditional dependency clusters
Authors: Han Wei-tao , Yi Peng ,   National Digital Switching System Engineering and Technological R&D Center, Zhengzhou 450000, China
Published: December 2020

Modern systems are always coupled. Previous studies indicate that coupled systems are more fragile than single systems. In a single system, when a fraction of 1-p nodes are removed, the percolation process is often of the second order. In a coupled system, due to the lack of resilience, the phase transition is always of the first order when removing a fraction of nodes. Most of previous studies on coupled systems focus on one-to-one dependency relation. This kind of relationship is called a no-feedback condition. Existing studies suppose that coupled systems are much more fragile without a no-feedback condition. That is to say, if a node depends on more than one node, the coupled system will breakdown even when a small fraction of nodes are removed from the coupled system. By observing the real world system, real nodes are often dependent on a dependency cluster, which consists of more than one other node. For example, in an industry chain, an electronic equipment factory may need several raw material factories to supply production components. Despite part of the raw material factories being bankrupt, the electronic equipment factory can carry out productionnormally because the remaining raw material factories still supply the necessary production components. But theoretical analysis shows that the robustness of such a coupled system is worse than that of one-to-one dependency system. Actually, the coupled system in real world does not usually disintegrate into pieces after some nodes have become invalid. To explain this phenomenon, we model a coupled system as interdependent networks and study, both analytically and numerically, the percolation in interdependent networks with conditional dependency clusters. A node in our model survives until the number of failed nodes in its dependency cluster is greater than a threshold. Our exact solutions of giant component size are in good agreement with the simulation results. Though our model does not have second order phase transition, we still find ways to improve the robustness of interdependent networks. One way is to increase the dependency cluster failure threshold. A higher threshold means that more nodes in the dependency cluster can be removed without breaking down the node depending on the cluster. Other way is to increase the size of dependency clusters, the more the nodes in the dependency cluster, the more the failure combinations are, which increases the survival probability of the node depending on cluster. Our model offers a useful strategy to enhance the robustness of coupled system and makes a good contribution to the study of interdependent networks with dependency clusters.
Extreme ultraviolet polarization vortex beam based on high harmonic generation
Authors: Fan Xin , Liang Hong-Jing , Shan Li-Yu , Yan Bo , Gao Qing-Hua , Ma Ri , Ding Da-Jun ,   Institution of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
Published: December 2020

Polarization is a property of vector beam that is widely used in many areas of science and technology. And vector beam is also called polarization vortex beam. Radially polarized beam and azimuthally polarized beam are the paradigm of vector beam. Extreme ultraviolet (EUV) vector beam could be applied in many fields such as diffractive imaging, Extreme Ultraviolet Lithography (EUVL), or ultrafast control of magnetic properties. In our experiments, a home-made EUV spectrometer was used to generate a tunable ultrafast EUV coherent light source based on high-order harmonic generation (HHG) by intense femtosecond laser. The apparatus features by using the plane grating in conical diffraction. The radially polarized vector beam and Gaussian beam with 800 nm, 35 fs laser pulses were applied to interact with Argon atoms, respectively. The high harmonic spectrums with a polarization singularity and a Gaussian distribution were observed. The experimental results demonstrate that the EUV vector beam could be transfered from near-infrared driven laser during the highly nonlinear interaction. The short-wavelength radiation with a polarization singularity can reach a photon flux of 108 per second. And the harmonic orders produced by Gaussian beam are significantly higher than that of vector field. The mechanism of macroscopic phase matching was discussed. It indicates that the phase matching for vector harmonic yields is similar with that driven by a Gaussian beam. In this case, EUV vector beam through HHG has been obtained, which provides one important method for attosecond vector pulses and opens new possibilities for exploring and manipulating the time-dependent evolution of quantum states in atom and molecule.
Quantitative relations between fundamental nonlinear waves and modulation instability
Authors: Duan Liang , Liu Chong , Zhao Li-Chen , Yang Zhan-Ying ,   School of Physics, Northwest University, Xi’an 710127, China,   Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi’an 710069, China
Published: December 2020

Nonlinear waves are ubiquitous in various physical systems, and they have become one of the research hotspots in nonlinear physics. For the experimental realization, observation and application of nonlinear waves, it is very important to understand the generation mechanism, and determine the essential excitation conditions of various nonlinear waves. In this paper, we first briefly review the experimental and theoretical research progress of nonlinear waves in recent years. Based on the exact nonlinear wave solutions and linear stability analysis results, we systemically discuss how to establish the quantitative relations between fundamental nonlinear waves and modulation instability. These relations would deepen our understanding on the mechanism of nonlinear waves. To solve the excitation conditions degenerations problem for some nonlinear waves, we further introduce the perturbation energy and relative phase to determine the excitation conditions of nonlinear waves. Finally, we present a set of complete parameters that can determine the excitation conditions of nonlinear waves, and give the excitation conditions and phase diagrams of the fundamental nonlinear waves. These results can be used to realize controllable excitation of nonlinear waves, and could be extended to many other nonlinear systems.
Flexible nitrogen dioxide gas sensor based on reduced graphene oxide sensing material using silver nanowire electrode
Authors: Li Chuang , Li Wei-Wei , Cai Li , Xie Dan , Liu Bao-Jun , Xiang Lan , Yang Xiao-Kuo , Dong Dan-Na , Liu Jia-Hao , Chen Ya-Bo ,   Department of Basic Science, Air Force Engineering University, Xi’an 710051, China,   Tsinghua National Laboratory for Information Science and Technology, Institute of Microelectronics, Tsinghua University, Beijing 100084, China,   The First Aeronautic Institute, Air Force Engineering University, Xinyang 464000, China,   Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

In recent years, flexible gas sensors have aroused wide interest of researchers due to their enormous potential applications in wearable electronic devices. In this paper, a flexible gas sensor is prepared. We use silver nanowires as flexible interdigital electrodes for gas sensors and reduced graphene oxide as gas-sensing materials. We also study its gas sensitivity and flexibility properties such as responsiveness, recovery, and repeatability to nitrogen dioxide. The experimental results show that the silver nanowire flexible electrode and the reduced graphene oxide gas sensor prepared can detect the NO2 gas with a concentration of 5—50 ppm at room temperature. The response (Ra/Rg) of the sensor to 50 ppm NO2 is 1.19. It demonstrates high response ability and repeatability. The recovery rate can be kept above 76%. The sensitivity of the sensor is 0.00281 ppm-1. The response time and recovery time of the prepared AgNWs IDE-rGO sensor for 5 ppm NO2 gas are 990 s and 1566 s, respectively. At the same time, the sensor still exhibits excellent gas sensing performance at a bending angle in range from 0° to 45°. The device has relatively stable conductivity and good bending tolerance. The sensing mechanism of the sensor can be attributed to the direct charge transfer between the reduced graphene oxide material and NO2 gas molecules. In addition, the high catalytic activity and excellent conductivity of Ag that is a common catalyst material, may also play an important role in improving the gas sensitivity of reduced graphene oxide materials. Silver nanowires, as a material for interdigital electrodes, provide excellent conductivity for device as well as support for the flexibility of device. It provides the fabricated sensor for good mechanical flexibility. And the gas-sensing performance of the AgNWs IDE-rGO sensor is mainly achieved by the use of reduced oxidized graphene material reduced by hydrazine hydrate. In summary, the silver nanowire flexible electrode and the graphene gas sensor prepared in this work are helpful in realizing the flexibility of the gas sensor. It lays a foundation for the further application of flexible gas sensors and has great application prospects in wearable electronic equipments.
Dense light field reconstruction algorithm based on dictionary learning
Authors: Xia Zheng-De , Song Na , Liu Bin , Pan Jin-Xiao , Yan Wen-Min , Shao Zi-Hui ,   Shanxi Key Laboratory of Signal Capturing & Processing, School of Science, North University of China, Taiyuan 030051, China,   Shanxi Key Laboratory of Signal Capturing & Processing, School of Information and Communication Engineering, North University of China, Taiyuan 030051, China,   Science and Technology on Transient Impact Laboratory, Beijing 102202, China,   Unit 32178, Beijing 100220, China
Published: December 2020

The camera array is an important tool to obtain the light field of target in space. The method of obtaining high angular resolution light field by a large-scaled dense camera array increases the difficulty of sampling and the equipment cost. At the same time, the demand for synchronization and transmission of a large number of data also limits the sampling rate of light field. In order to complete the dense reconstruction of sparse sampling of light field, we analyze the correlation and redundancy of multi-view images in the same scene based on sparse light field data, then establish an effective mathematical model of light field dictionary learning and sparse coding. The trained light field atoms can sparsely express the local spatial-angular consistency of light field, and the four-dimensional (4D) light field patches can be reconstructed from a two-dimensional (2D) local image patch centered around each pixel in the sensor. The global and local constraints of the four-dimensional light field are mapped into the low-dimensional space by the dictionary. These constraints are shown as the sparsity of each vector in the sparse representation domain, the constraints between the positions of non-zero elements and their values. According to the constraints among sparse encoding elements, we establish the sparse encoding recovering model of virtual angular image, and propose the sparse encoding recovering method in the transform domain. The atoms of light field in dictionary are screened and the patches of light field are represented linearly by the sparse representation matrix of the virtual angular image. In the end, the virtual angular images are constructed by image fusion after sparse inverse transform. According to multi-scene dense reconstruction experiments, the effectiveness of the proposed method is verified. The experimental results show that the proposed method can recover the occlusion, shadow and complex illumination in satisfying quality. That is to say, it can be used for dense reconstruction of sparse light field in complex scene. In our study, the dense reconstruction of linear sparse light field is achieved. In the future, the dense reconstruction of nonlinear sparse light field will be studied to promote the practical application of light field imaging.
Review of pedestrian tracking: Algorithms and applications
Authors: Cao Zi-Qiang , Sai Bin , Lu Xin ,   College of Systems Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Pedestrian tracking is a hotspot and a difficult topic in computer vision research. Through the tracking of pedestrians in video materials, trajectories can be extracted to support the analysis of individual or collected behavior dynamics. In this review, we first discuss the difference between pedestrian tracking and pedestrian detection. Then we summarize the development of traditional tracking algorithms and deep learning-based tracking algorithms, and introduce classic pedestrian dynamic models. In the end, typical applications, including intelligent monitoring, congestion analysis, and anomaly detection are introduced systematically. With the rising use of big data and deep learning techniques in the area of computer vision, the research on pedestrian tracking has made a leap forward, which can support more accurate, timely extraction of behavior patterns and then to facilitate large-scale dynamic analysis of individual or crowd behavior.
Theoretical studies on bidirectional interfacial shear stress transfer of graphene/flexible substrate composite structure
Authors: Bai Jia-Hao , Guo Jian-Gang ,   Tianjin Key Laboratory of Modern Experimental Mechanics, Department of Mechanics, Tianjin University, Tianjin 300354, China
Published: December 2020

Interfacial mechanical properties have a great influence on the overall mechanical performance of graphene/flexible substrate composite structure. Therefore, it is necessary to study interfacial shear stress transfer between graphene and flexible substrate. In this paper, a two-dimensional nonlinear shear-lag model (2D model) is presented. Taking the effects of Poisson’s ratio of the graphene and substrate into consideration, the bidirectional interfacial shear stress transfer between graphene and flexible substrate subjected to uniaxial tension is investigated by the 2D model when the Poisson’s ratio of substrate is larger than that of graphene. In the elastic bonding stage, the semi-analytical solutions of the bidirectional normal strains of the graphene and bidirectional interfacial shear stresses are derived, respectively, and their distributions at different positions are illustrated. The critical strain for interfacial sliding is derived by the 2D model, and the results show that the critical strain has a micron-scaled characteristic width. The width size of graphene has a significant influence on the critical strain when it is less than the characteristic width, but the size effect can be ignored when the width of graphene is larger than the characteristic width. In addition, the Poisson’s ratio of substrate can also affect the critical strain. Based on the 2D model, the finite element simulations are made to investigate the distribution of graphene's normal strains and interfacial shear stresses in the interfacial sliding stage. Furthermore, compared with the results obtained via one-dimensional nonlinear shear-lag model (1D model), the distributions of graphene’s normal strains and interfacial shear stresses calculated by 2D model show obvious bidimensional effects both in the elastic bonding stage and in the interfacial sliding stage when the width of graphene is large. There exists a compression strain in the graphene and a transverse (perpendicular to the tensile direction) shear stress in the interface, which are neglected in the 1D model. And the distributions of graphene’s tensile strain and longitudinal (along the tensile direction) interfacial shear stress are not uniform along the width, which are also significantly different from the results of 1D model. Moreover, the critical strain for interfacial sliding derived by the 2D model is lower than that obtained by the 1D model. However, when the width of graphene is small enough, the 2D model can be approximately replaced by the 1D model. Finally, by fitting the Raman experimental results, the reliability of the 2D model is verified, and the interfacial stiffness (100 TPa/m) and shear strength (0.295 MPa) between graphene and polyethylene terephthalate (PET) substrate are calculated.
Study of defects in potassium-doped tungsten alloy by positron annihilation technique
Authors: Zhang Pei-Yuan , Deng Ai-Hong , Tian Xue-Fen , Tang Jun ,   College of Physics, Sichuan University, Chengdu 610064, China,   Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

Tungsten alloy is known as a promising plasma-facing material (PFM) in IETR because of high strength, high-temperature stability, low sputtering erosion, low tritium retention, etc. However, tungsten has some disadvantages, such as high ductile-brittle transition temperature, low temperature brittleness, and radiation embrittlement. For the severe environment of PFM, various techniques have been adopted to improve W-based materials, among which the potassium doping is an effective bubble strengthening method, it can bring in nano-sized K bubbles, and enhance the toughness and strength, thermal shock performance, irradiation resistance of the materials. The K bubbles, which can pin grain boundaries (GBs) and dislocations, are the most characteristic defects in W-K alloy and have been widely reported. However, little attention is paid to other defects such as vacancies, GBs and dislocations. In fact, high-density dislocations exist in W-K alloy and vacancies play a considerable role in forming the K bubbles. Thus, positron annihilation technique (including the positron annihilation lifetime spectrum and slow positron beam Doppler broadening spectrum), which is a useful technique for detecting defects in solids, can be used to study these defects in W-K alloy samples. The positron lifetime of potassium bulk is about 376 ps and the positron lifetime of tungsten bulk is about 110 ps. But by simulating positron lifetime of defects in tungsten, it is found that potassium atoms in tungsten lattice do not exhibit the characteristic positron lifetime. Therefore, potassium is not considered in analyzing positron annihilation lifetime spectra of W-K alloy samples with different potassium content (46, 82, 122, 144 ppm). Three-state capture model is established in this paper, the dislocation density and vacancy cluster concentration of these samples are obtained. From the results, the dislocation densities in all samples are very high, but vacancy cluster concentrations are relatively low, and the vacancy cluster concentration in the sample with 82 ppm potassium content is the lowest in all samples. The behavior of potassium atoms in the sintering process is also discussed. Then the slow positron beam Doppler broadening spectra of W-K alloy samples and pure tungsten samples are measured and the obtained data are fitted by VEPFIT. It is noted that the defects in W-K alloy samples are much more than those in pure tungsten sample, and are distributed homogeneously with depth. The positron diffusion length information simultaneously obtained is compared with these values computed by dislocation density and vacancy cluster concentration, confirming the positrons trapped by potassium bubbles and grain boundaries are existent.
Control of spiral waves in excitable media under polarized electric fields
Authors: Pan Jun-Ting , He Yin-Jie , Xia Yuan-Xun , Zhang Hong ,   Ocean College, Zhejiang University, Zhoushan 316021, China,   Zhejiang Institute of Modern Physics, Department of Physics, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Spiral waves are ubiquitous in diverse physical, chemical, and biological systems. Periodic external fields, such as polarized electric fields, especially circularly polarized electric fields which possess rotation symmetry may have significant effects on spiral wave dynamics. In this paper, control of spiral waves in excitable media under polarized electric fields is reviewed, including resonant drift, synchronization, chiral symmetry breaking, stabilization of multiarmed spiral waves, spiral waves in subexcitable media, control of scroll wave turbulence, unpinning of spiral waves in cardiac tissues, control of spiral wave turbulence in cardiac tissues, etc.
Influence of secondary electron emission characteristic of dielectric materials on microwave breakdown
Authors: Weng Ming , Xie Shao-Yi , Yin Ming , Cao Meng ,   Key laboratory of Physical Electronics and Devices, Ministry of Education, School of Electronic and Informtion Engineering, Xi’an Jiaotong University, Xi’an 710049, China,   Northwest Institute of Nuclear Technology, Xi’an 710613, China
Published: December 2020

For a microwave device filled with dielectrics, the secondary electron (SE) emission has a very important influence on the mechanism of microwave breakdown including low pressure discharge and multipactor. In this work, the SE yields (SEYs) and the SE energy spectra of seven kinds of dielectric materials are first measured and then used to examine their effects. In the positive charging process under electron irradiation, the surface potential of the dielectric layer trends to be steady with the SEY being one. Based on the measurement data, the steady surface potential is calculated under the charging stability condition. The steady surface potential is bigger for a bigger SEY. For a given SEY, the steady surface potential is found to be proportional to the peak energy Epeak of the SE energy spectrum. Furthermore, the effect of steady surface potential on low pressure discharge and multipactor are respectively studied for a parallel plate system filled with a dielectric layer. A static electric field related to the positive charging is introduced. The electron diffusion model in low pressure discharge process is modified by considering the static electric field. The electrons drift in a fixed direction under the action of static electric field, and the electron diffusion length decreases. Consequently, the effective electrons for low discharge decreases and the threshold microwave power increases. Therefore, a dielectric material with higher SEY and bigger Epeak is helpful in suspending the inhibition of low pressure discharge. Furthermore, the effect of steady electric field on multipactor is also explored. Two effects related to dielectric material and metal are analyzed in detail. The SE emission from dielectric material is held back by the steady electric field and some low energy electrons return back to the dielectric materials. The effective SEY thus decreases. On the other hand, the electric field reduces the landing electron energy on the metal, and the corresponding SEY also decreases. The electron oscillation condition with considering both microwave field and stead electric field is derived and the threshold values for microwave power of multipactor are calculated. The susceptibility curves corresponding to different materials are plotted. Our result may be used to choose the filling dielectric materials for a microwave device.
Autophagy in T cells from aged donors is maintained by spermidine and correlates with function and vaccine responses
Authors: Alsaleh Ghada , Panse Isabel , Swadling Leo , Zhang Hanlin , Richter Felix Clemens , Meyer Alain , Lord Janet , Barnes Eleanor , Klenerman Paul , Green Christopher , Simon Anna Katharina
Published: December 2020

Vaccines are powerful tools to develop immune memory to infectious diseases and prevent excess mortality. In older adults, however vaccines are generally less efficacious and the molecular mechanisms that underpin this remain largely unknown. Autophagy, a process known to prevent aging, is critical for the maintenance of immune memory in mice. Here, we show that autophagy is specifically induced in vaccine-induced antigen-specific CD8+ T cells in healthy human volunteers. In addition, reduced IFNγ secretion by RSV-induced T cells in older vaccinees correlates with low autophagy levels. We demonstrate that levels of the endogenous autophagy-inducing metabolite spermidine fall in human T cells with age. Spermidine supplementation in T cells from old donors recovers their autophagy level and function, similar to young donors’ cells, in which spermidine biosynthesis has been inhibited. Finally, our data show that endogenous spermidine maintains autophagy via the translation factor eIF5A and transcription factor TFEB. In summary, we have provided evidence for the importance of autophagy in vaccine immunogenicity in older humans and uncovered two novel drug targets that may increase vaccination efficiency in the aging context.
Computer code comprehension shares neural resources with formal logical inference in the fronto-parietal network
Authors: Liu Yun-Fei , Kim Judy , Wilson Colin , Bedny Marina
Published: December 2020

Despite the importance of programming to modern society, the cognitive and neural bases of code comprehension are largely unknown. Programming languages might ‘recycle’ neurocognitive mechanisms originally developed for natural languages. Alternatively, comprehension of code could depend on fronto-parietal networks shared with other culturally-invented symbol systems, such as formal logic and symbolic math such as algebra. Expert programmers (average 11 years of programming experience) performed code comprehension and memory control tasks while undergoing fMRI. The same participants also performed formal logic, symbolic math, executive control, and language localizer tasks. A left-lateralized fronto-parietal network was recruited for code comprehension. Patterns of activity within this network distinguish between ‘for’ loops and ‘if’ conditional code functions. In terms of the underlying neural basis, code comprehension overlapped extensively with formal logic and to a lesser degree math. Overlap with executive processes and language was low, but laterality of language and code covaried across individuals. Cultural symbol systems, including code, depend on a distinctive fronto-parietal cortical network.
A prefrontal-bed nucleus of the stria terminalis circuit limits fear to uncertain threat
Authors: Glover Lucas R , McFadden Kerry M , Bjorni Max , Smith Sawyer R , Rovero Natalie G , Oreizi-Esfahani Sarvar , Yoshida Takayuki , Postle Abagail F , Nonaka Mio , Halladay Lindsay R , Holmes Andrew
Published: December 2020

In many cases of trauma, the same environmental stimuli that become associated with aversive events are experienced on other occasions without adverse consequence. We examined neural circuits underlying partially reinforced fear (PRF), whereby mice received tone-shock pairings on half of conditioning trials. Tone-elicited freezing was lower after PRF conditioning than fully reinforced fear (FRF) conditioning, despite an equivalent number of tone-shock pairings. PRF preferentially activated medial prefrontal cortex (mPFC) and bed nucleus of the stria terminalis (BNST). Chemogenetic inhibition of BNST-projecting mPFC neurons increased PRF, not FRF, freezing. Multiplexing chemogenetics with in vivo neuronal recordings showed elevated infralimbic cortex (IL) neuronal activity during CS onset and freezing cessation; these neural correlates were abolished by chemogenetic mPFC→BNST inhibition. These data suggest that mPFC→BNST neurons limit fear to threats with a history of partial association with an aversive stimulus, with potential implications for understanding the neural basis of trauma-related disorders.
Reduction of elevated proton leak rejuvenates mitochondria in the aged cardiomyocyte
Authors: Zhang Huiliang , Alder Nathan N , Wang Wang , Szeto Hazel , Marcinek David J , Rabinovitch Peter S
Published: December 2020

Aging-associated diseases, including cardiac dysfunction, are increasingly common in the population. However, the mechanisms of physiologic aging in general, and cardiac aging in particular, remain poorly understood. Age-related heart impairment is lacking a clinically effective treatment. Using the model of naturally aging mice and rats, we show direct evidence of increased proton leak in the aged heart mitochondria. Moreover, our data suggested ANT1 as the most likely site of mediating increased mitochondrial proton permeability in old cardiomyocytes. Most importantly, the tetra-peptide SS-31 prevents age-related excess proton entry, decreases the mitochondrial flash activity and mitochondrial permeability transition pore opening, rejuvenates mitochondrial function by direct association with ANT1 and the mitochondrial ATP synthasome, and leads to substantial reversal of diastolic dysfunction. Our results uncover the excessive proton leak as a novel mechanism of age-related cardiac dysfunction and elucidate how SS-31 can reverse this clinically important complication of cardiac aging.