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Poisson-Arago spot for gravitational waves

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Science China(Physics,Mechanics & Astronomy) 2021年第12期64卷 2-7页

作者： HongSheng Zhang XiLong fan School of Physics and Technology University of JinanJinan 250022China School of Physics and Technology Wuhan UniversityWuhan 430072China

For the observer at infinity, a Schwarzschild black hole serves as an attractive opaque disk with a radius of 3√3 M that will produce the diffraction pattern of gravitational waves(GWs). In this study, we demonstrate that a bright spot, which is a diffraction effect analogous to the Poisson-Arago spot in optics, will appear when an ingoing(quasi-)plane GW is diffracted by a Schwarzschild black hole. Here, we propose the diffraction effect of the GWs described by the exact diffraction solution of the GWs using the Heun function. For the first time, the Fresnel half-wave zone method is proposed to calculate the angular part of the GW scattering stripes for the observer at infinity. The prospect of observing the diffraction bright spot is discussed with an eikonal approximation. For normal incidence(quasi)-plane waves with 100 Hz(0.1 Hz) frequency diffracted by the central black hole of the Milky Way, the time delay between the Earth bathed in a bright spot and the minimum of the first dark stripe is 3.86(3860) d. We will witness the second bright fringe(40% amplitude of the central bright spot) after 6.2(6200) d. This new diffraction pattern involving the early phase of inspirals and pulsars as continuous gravitational wave sources is a potential scientific target for future space-and ground-based gravitational wave detectors, respectively.

关键词： gravitational waves diffraction black hole

Square Distance Symmetric Co-occurrence Matrix Thresholding Method Based on Relative Homogeneity

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Chinese Journal of Electronics 2020年第4期29卷 686-692页

作者： ZHANG Hong fan Jiulun Xi'an University of Posts and Telecommunications Automatic Sorting Technology Research Center State Post Bureau of the People's Republic of China

We studied a novel image thresholding method using symmetric co-occurrence matrix probability information, in which, the relative homogeneity characteristics of the segmented object and background is explored, square distance co-occurrence matrix thresholding criterion is reformed, and the relative criterion of square distance symmetric co-occurrence matrix is *** new thresholding method applies the spatial information of image and takes the relative information between classes into *** experimental results show that,comparing with the existing correlation methods, the proposed method can extract the object more integrity,and reserve the edge more clearly.

关键词： Image thresholding Symmetric Cooccurrence Matrix Square distance Relative homogeneity

A flexible technique to select objects via convolutional neural network in VR space

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Science China(Information Sciences) 2020年第1期63卷 57-76页

作者： Huiyu LI Linwei fan School of Computer Science and Technology Shandong University Shandong Province Key Lab of Digital Media Technology Shandong University of Finance and Economics Shandong Co-Innovation Center of Future Intelligent Computing Shandong Technology and Business University

Most studies on the selection techniques of projection-based VR systems are dependent on users wearing complex or expensive input devices, however there are lack of more convenient selection *** this paper, we propose a flexible 3 D selection technique in a large display projection-based virtual environment. Herein, we present a body tracking method using convolutional neural network(CNN) to estimate3 D skeletons of multi-users, and propose a region-based selection method to effectively select virtual objects using only the tracked fingertips of multi-users. Additionally, a multi-user merge method is introduced to enable users’ actions and perception to realign when multiple users observe a single stereoscopic *** comparing with state-of-the-art CNN-based pose estimation methods, the proposed CNN-based body tracking method enables considerable estimation accuracy with the guarantee of real-time performance. In addition, we evaluate our selection technique against three prevalent selection techniques and test the performance of our selection technique in a multi-user scenario. The results show that our selection technique significantly increases the efficiency and effectiveness, and is of comparable stability to support multi-user interaction.

关键词： convolutional neural network interaction techniques pose estimation virtual reality 3D selection

Optimal Quinary Cyclic Codes with Minimum Distance Four

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Chinese Journal of Electronics 2020年第3期29卷 515-524页

作者： fan Jinmei ZHANG Yanhai College of Science Guilin University of Technology

The necessary and sufficient condition for the quinary cyclic codes with generator polynomial（x+1）mα（x）mαe（x） to have parameters [5m-1, 5m-2m-2, 4]is provided by analyzing solutions of certain equations over the finite field F5m. And thus several classes of new optimal quinary cyclic codes with the same parameters and generator polynomial are constructed based on analyzing irreducible factors of certain polynomials with low degrees over finite fields.

关键词： Finite field Cyclic code Irreducible polynomial Monomial

Closed-loop flow control of an ultra-compact serpentine inlet based on nondimensional model

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Chinese Journal of Aeronautics 2020年第10期33卷 2555-2562页

作者： Xingya DA Jianchao fan High Speed Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000China

Ultra-compact serpentine inlet faces serve inlet-engine compatibility issues due to flow *** ensure inlet-engine compatibility over a wide range of Mach number,novel active flow control techniques with the ability of being opened or adjusted as needed draw many attentions in recent *** this paper,a feedback control system was developed based on the method of microjet *** proposed system includes a pressure adjusting valve to adjust the control effort,a dynamic pressure sensor to sense the inlet distortion intensity,a signal processing instrument to calculate the Root-Mean-Squared(RMS)pressure,and a controller to implement feedback *** achieve high quality closed-loop controls at dynamic conditions,a novel nondimensional feedback method was *** advantage of this nondimensional method was validated at both off-design and arbitrarily changing Mach number *** a sectional PI control law,the RMS control error reduced more than 56%at arbitrary changing *** in this paper also showed that the dynamics of this nondimensional system can be simplified as a stable second-order overdamped system.

关键词： Closed-loop flow control Flow distortion Nondimensional feedback PI control Serpentine inlet

Electric potential and energy band in ZnO nanofiber tuned by local mechanical loading

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Applied Mathematics and Mechanics(English Edition) 2021年第6期42卷 787-804页

作者： Shuaiqi fan Ziguang CHEN School of Aerospace Engineering Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment Wuhan 430074China

Recent success in strain engineering has triggered tremendous interest in its study and potential applications in nanodevice design. In this paper, we establish a coupled piezoelectric/semiconducting model for a wurtzite structure ZnO nanofiber under the local mechanical loading. The energy band structure tuned by the local mechanical loading and local length is calculated via an eight-band k·p method, which includes the coupling of valance and conduction bands. Poisson's effect on the distribution of electric potential inversely depends on the local mechanical loading. Numerical results reveal that both the applied local mechanical loading and the local length exhibit obvious tuning effects on the electric potential and energy band. The band gap at band edges varies linearly with the applied loading. Changing the local length shifts the energy band which is far away from the band edges. This study will be useful in the electronic and optical enhancement of semiconductor devices.

关键词： piezoelectric semiconductor(PS) local mechanical loading strain engineering energy band

Double-loop robust tracking control for micro machine tools

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Science China(Technological Sciences) 2011年第11期54卷 3054-3063页

作者： fan ShiXun NAGAMUNE Ryozo fan DaPeng College of Mechatronic Engineering and Automation National University of Defense Technology Changsha 410073 China Department of Mechanical Engineering the University of British Columbia Vancouver BC V6TIZ4 Canada

This paper addresses double-loop robust tracking controller design of the miniaturized linear motor drive precision stage with mass and damping ratio uncertainties. As an inner-loop, a disturbance observer （DOB） is employed to suppress exogenous low frequency disturbances such as friction and cutting force. To further eliminate the residual disturbance and to guarantee the robust tracking to the reference input, μ-synthesis outer-loop controller is designed. For eliminating the steady state error, a technique is proposed to design the μ-synthesis outer-loop controller with an integrator. A guideline to select the bandwidth of the Q-filter in the DOB is provided. Simulations using a model of a prototype micro-milling machine indicate that the proposed outer-loop synthesis scheme is superior to the H∞ suboptimal control in disturbance rejection performance and steady state tracking performance. Furthermore, it is shown experimentally that the proposed double-loop robust tracking controller improves the tracking performance of the stage by 29.6% over PID control with a DOB inner-loop.

关键词： micro machine tools robust tracking μ-synthesis disturbance observer

Growth kinetics of interfacial reaction layer products between cubic boron nitride and Cu-Sn-Ti active filler metal

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Journal of Materials Science & Technology 2021年第33期92卷 69-74页

作者： Yonggang fan Cong Wang School of Metallurgy Northeastern UniversityShenyang110819China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou730000China

In the present investigation,the growth kinetics of interfacial reaction layer products between cubic boron nitride(CBN) and Cu-Sn-Ti filler metal has been thoroughly *** morphological and compositional features of respective compounds have been demonstrated for a wide brazing temperature ranging from 1153 K to 1223 *** is found that within 30 minutes brazing holding time,the reaction layer growth is largely determined by the population of Ti N via effective Ti diffusion with an activation energy of 223.51 k J/mol,leading to parabolic growth *** is further revealed that TiN grows both in axial and length dimensions,which eventually extends to the forefront and covers the reaction layer.

关键词： Cubic boron nitride Cu-Sn-Ti Interfacial reaction layer Activation energy

Semi-analytical Solutions for Wellbores with Graded Skin Zones in Poroelastic Media

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Acta Mechanica Solida Sinica 2024年第3期37卷 385-395页

作者： Zhiqiang fan Zhihe Jin School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China Department of Mechanical Engineering University of MaineOronoME04469USA

In analyzing the complex interaction between the wellbore and the reservoir formation,the hydromechanical properties of the region proximal to the wellbore,referred to as the“wellbore skin zone”,play a pivotal role in determining flow dynamics and the resulting formation *** models of the wellbore skin zone generally assume a constant permeability throughout,resulting in a sharp permeability discontinuity at the skin-reservoir *** paper introduces a model for a wellbore with a continuously graded skin zone of finite thickness within a poroelastic *** solutions are derived using the Laplace transform method,addressing both positive and negative skin *** results are presented to illustrate the effects of graded permeability/skin zone thickness on pore pressures and stresses around a *** results highlight a distinct divergence in stress and pore pressure fields when comparing wellbores with negative skin zones to those with positive skin zones or no skin at all.

关键词： Poroelastic Graded permeability Analytical solution Wellbore Skin zone