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Virtual source approach for maximizing resolution in high-penetration gamma-ray imaging

Matter and Radiation at Extremes 2024年第3期9卷 19-30页

作者： Yuchi Wu Shaoyi Wang Bin Zhu Yonghong Yan Minghai Yu Gang Li Xiaohui Zhang Yue Yang Fang Tan Feng Lu Bi Bi Xiaoqin Mao Zhonghai Wang Zongqing Zhao Jingqin Su Weimin Zhou Yuqiu Gu National Key Laboratory of Plasma Physics Laser Fusion Research CenterCAEPMianyangSichuan 621900China College of Physics Sichuan UniversityChengdu 610065China

High-energy gamma-ray radiography has exceptional penetration ability and has become an indispensable nondestructive testing(NDT)tool in various *** high-energy photons,point projection radiography is almost the only feasible imaging method,and its spatial resolution is primarily constrained by the size of the gamma-ray *** conventional industrial applications,gamma-ray sources are commonly based on electron beams driven by accelerators,utilizing the process of bremsstrahlung *** size of the gamma-ray source is dependent on the dimensional characteristics of the electron *** research has been conducted on various advanced accelerator technologies that have the potential to greatly improve spatial resolution in *** our investigation of laser-driven gamma-ray sources,a spatial resolution of about 90μm is achieved when the areal density of the penetrated object is 120 g/cm^(2).A virtual source approach is proposed to optimize the size of the gamma-ray source used for imaging,with the aim of maximizing spatial *** this virtual source approach,the gamma ray can be considered as being emitted from a virtual source within the convertor,where the equivalent gamma-ray source size in imaging is much smaller than the actual emission *** the basis of Monte Carlo simulations,we derive a set of evaluation formulas for virtual source scale and gamma-ray emission *** optimal conditions,the virtual source size can be as small as 15μm,which can significantly improve the spatial resolution of high-penetration imaging to less than 50μm.

关键词： resolution approach utilizing

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UNet Based onMulti-Object Segmentation and Convolution Neural Network for Object Recognition

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Computers, Materials & Continua 2024年第7期80卷 1563-1580页

作者： Nouf Abdullah Almujally Bisma Riaz Chughtai Naif Al Mudawi Abdulwahab Alazeb Asaad Algarni Hamdan A.Alzahrani Jeongmin Park Department of Information Systems College of Computer and Information SciencesPrincess Nourah bint Abdulrahman UniversityP.O.Box 84428Riyadh11671Saudi Arabia Department of Computer science Air UniversityIslamabad44000Pakistan Department of Computer science College of Computer Science and Information SystemNajran UniversityNajran55461Saudi Arabia Department of Computer sciences Faculty of Computing and Information TechnologyNorthern Border UniversityRafha91911Saudi Arabia Information Technology Department College of Computing and InformaticsSaudi Electronic UniversityRiyadh13316Saudi Arabia Department of Computer Engineering Korea Polytechnic UniversitySiheung-siGyeonggi-do237Republic of Korea

The recent advancements in vision technology have had a significant impact on our ability to identify multiple objects and understand complex *** technologies,such as augmented reality-driven scene integration,robotic navigation,autonomous driving,and guided tour systems,heavily rely on this type of scene *** paper presents a novel segmentation approach based on the UNet network model,aimed at recognizing multiple objects within an *** methodology begins with the acquisition and preprocessing of the image,followed by segmentation using the fine-tuned UNet ***,we use an annotation tool to accurately label the segmented *** labeling,significant features are extracted from these segmented objects,encompassing KAZE(Accelerated Segmentation and Extraction)features,energy-based edge detection,frequency-based,and blob *** the classification stage,a convolution neural network(CNN)is *** comprehensive methodology demonstrates a robust framework for achieving accurate and efficient recognition of multiple objects in *** experimental results,which include complex object datasets like MSRC-v2 and PASCAL-VOC12,have been *** analyzing the experimental results,it was found that the PASCAL-VOC12 dataset achieved an accuracy rate of 95%,while the MSRC-v2 dataset achieved an accuracy of 89%.The evaluation performed on these diverse datasets highlights a notably impressive level of performance.

关键词： UNet segmentation blob fourier transform convolution neural network

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A Compact Eulerian Interface-Capturing Algorithm for Compressible Multimaterial Elastic-Plastic Flows with Mie-Gr uneisen Equation of State

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Advances in Applied Mathematics and Mechanics 2023年第2期15卷 485-521页

作者： Xiang Li Dong-Jun Ma Nan-Sheng Liu Pei Wang Institute of Applied Physics and Computational Mathematics Beijing 100094China Department of Modern Mechanics University of Science and Technology of ChinaHefeiAnhui 230027China Center for Applied Physics and Technology Peking UniversityBeijing 100871China

This paper presents an Eulerian diffuse-interface method using a high-order compact difference scheme for simulating elastic-plastic flows with the Mie–Gruneisen(MG)equation of state(EoS).For simulations of multimaterial problems,numerical errors were generated in the material discontinuities owing to inconsistent treatment of the convective *** on the normal-stress-based mechanical equilibrium assumption for elastic-plastic solids,we introduce an improved form of the consistent localized artificial diffusivity(LAD)method to ensure an oscillation-free interface for velocity and normal *** proposed algorithm uses a hyperelastic model.A mixture type of the model system was formed by combining the conservation equations for the basic conserved variables,an equation of a unified deviatoric tensor describing solid deformation,and an additional set of equations for solving the material quantities in the MG *** one-and two-dimensional problems with various discontinuities,including the elastic-plastic Richtmyer–Meshkov instability,were considered for testing the proposed method.

关键词： Multimaterial elastic-plastic flow Eulerian solid-dynamics high-order accurate schemes compact finite difference localized artificial diffusivity

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Arbitrary Lagrangian‑Eulerian Discontinuous Galerkin Methods for KdV Type Equations

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Communications on Applied Mathematics and Computation 2022年第2期4卷 530-562页

作者： Xue Hong Yinhua Xia School of Mathematical sciences University of Science and Technology of ChinaHefei 230026AnhuiChina

In this paper,several arbitrary Lagrangian-Eulerian discontinuous Galerkin(ALE-DG)methods are presented for Korteweg-de Vries(KdV)type equations on moving *** on the L^(2) conservation law of KdV equations,we adopt the conservative and dissipative numerical fuxes for the nonlinear convection and linear dispersive terms,***,one conservative and three dissipative ALE-DG schemes are proposed for the *** invariant preserving property for the conservative scheme and the corresponding dissipative properties for the other three dissipative schemes are all presented and proved in this *** addition,the L^(2)-norm error estimates are also proved for two schemes,whose numerical fuxes for the linear dispersive term are both dissipative *** precisely,when choosing the approximation space with the piecewise kth degree polynomials,the error estimate provides the kth order of convergence rate in L^(2)-norm for the scheme with the conservative numerical fuxes applied for the nonlinear convection ***,the(k+1∕2)th order of accuracy can be proved for the ALE-DG scheme with dissipative numerical fuxes applied for the convection ***,a Hamiltonian conservative ALE-DG scheme is also presented based on the conservation of the Hamiltonian for KdV *** examples are shown to demonstrate the accuracy and capability of the moving mesh ALE-DG methods and compare with stationary DG methods.

关键词： Arbitrary Lagrangian-Eulerian discontinuous Galerkin methods KdV equations Conservative schemes Dissipative schemes Error estimates

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Radially Symmetrical Problems for Compressible Fluids with a High-Resolution Boundary Condition

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Advances in Applied Mathematics and Mechanics 2023年第2期15卷 428-449页

作者： Zijin Zhu Xiaoyan Hu Guoxi Ni Institute of Applied Physics and Computational Mathematics BeijingChina Graduate School of China Academy of Engineering Physics BeijingChina

Imposing appropriate numerical boundary conditions at the symmetrical center r=0 is vital when computing compressible fluids with radial *** and other traditional techniques are often employed,but spurious numerical oscillations or wall-heating phenomena can *** this paper,we emphasize that because of the conservation property,the updating formula of the boundary cell average can coincide with the one for interior cell *** achieve second-order accuracy both in time and space,we associate obtaining the inner boundary value at r=0 with the resolution of the corresponding one-sided generalized Riemann problem(GRP).Acoustic approximation is applied in this *** creates conditions to avoid the singularity of type 1/r and aids in obtaining the value of the singular quantity using L’Hospital’s *** challenging scenarios are tested to demonstrate the effectiveness and robustness of our approach.

关键词： Radially symmetrical high-resolution conservation singularity numerical boundary condition GRP acoustic approximation

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Sinc-Multistep Schemes for Forward Backward Stochastic Differential Equations

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Advances in Applied Mathematics and Mechanics 2023年第3期15卷 737-768页

作者： Xu Wang Weidong Zhao School of Mathematics&Institute of Finance Shandong UniversityJinanShandong 250100China

In this work,by combining the multistep discretization in time and the Sinc quadrature rule for approximating the conditional mathematical expectations,we will propose new fully discrete multistep schemes called“Sinc-multistep schemes”for forward backward stochastic differential equations(FBSDEs).The schemes avoid spatial interpolations and admit high order of *** stability and the K-th order error estimates in time for the K-step Sinc multistep schemes are theoretically proved(1≤K≤6).This seems to be the first time for analyzing fully time-space discrete multistep schemes for *** examples are also presented to demonstrate the effectiveness,stability,and high order of convergence of the proposed schemes.

关键词： Forward backward stochastic differential equations multistep schemes Sinc quadrature rule error estimates

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Structural parameter design method for a fast-steering mirror based on a closed-loop bandwidth

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Frontiers of Mechanical Engineering 2020年第1期15卷 55-65页

作者： Guozhen CHEN Pinkuan LIU Han DING School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

When a fast-steering mirror(FSM)system is designed,satisfying the performance requirements before fabrication and assembly is *** study proposes a structural parameter design approach for an FSM system based on the quantitative analysis of the required closed-loop ***,the open-loop transfer function of the FSM system is *** accordance with the transfer function,the notch filter and proportional-integral(PI)feedback controller are designed as a closed-loop *** gains of the PI controller are determined by maximizing the closed-loop bandwidth while ensuring the robustness of the ***,the two unknown variables of rotational radius and stiffness in the open-loop transfer function are optimized,considering the bandwidth as a constraint ***,the structural parameters of the stage are determined on the basis of the optimized results of rotational radius and *** are conducted to verify the theoretical analysis.A prototype of the FSM system is fabricated,and corresponding experimental tests are *** results indicate that the bandwidth of the proposed FSM system is 117.6 Hz,which satisfies the minimum bandwidth requirement of 100 Hz.

关键词： fast-steering mirror structural parameter PI controller bandwidth notch filter

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Simulation of proton–neutron collisions in inverse kinematics and its possible application

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Nuclear science and Techniques 2021年第4期32卷 60-69页

作者： Bi-Lu Li Gang-Lin Yu Shi-Fei Shen Department of Engineering Physics Tsinghua UniversityBeijing 100084China

Neutrons have played a vital role in many nuclear physics *** some cases,the inverse kinematics of neutrons colliding with other nuclei are also worth *** this study,the inverse kinematics of thermal neutrons colliding with high-energy protons is simulated by using the Monte Carlo *** neutrons are taken as target particles,whereas protons are incident *** simulation implies that,after collision,the energy of the output neutron at 0°equals the energy of the incident proton.A possible application of the result is proposed that might yield single-energy *** key parameters of the conceptual design were evaluated,demonstrating that the design may reach high-neutron-energy resolution.

关键词： Inverse kinematics Mono-energetic neutron Proton Monte Carlo

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Determination of polarization states in(K,Na)NbO3 lead-free piezoelectric crystal

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Journal of Advanced Ceramics 2020年第2期9卷 204-209页

作者： Mao-Hua ZHANG Chengpeng HU Zhen ZHOU Hao TIAN Hao-Cheng THONG Yi Xuan LIU Xing-Yu XU Xiao-Qing XI Jing-Feng LI Ke WANG State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Department of Physics Harbin Institute of TechnologyHarbin 150001China

Polarization switching in lead-free(K0.40Na0.60)NbO3(KNN)single crystals was studied by switching spectroscopy piezoresponse force microscopy(SS-PFM).Acquisition of multiple hysteresis loops on a closely spaced square grid enables polarization switching parameters to be mapped in real *** amplitude and phase hysteresis loops show collective symmetric/asymmetric characteristics,affording information regarding the switching behavior of different *** such,the out-of-plane polarization states of the domains,including amplitudes and phases can be *** results could contribute to a further understanding of the relationships between polarization switching and polarization vectors at the nanoscale,and provide a feasible method to correlate the polarization hysteresis loops in a domain under an electric field with the polarization vector states.

关键词： piezoelectrics lead-free (K0.40Na0.60)NbO3(KNN) switching spectroscopy piezoresponse force microscopy(SS-PFM) ferroelectric domain

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Length and stiffness effects of the attached flexible plate on the flow over a traveling wavy foil

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Acta Mechanica Sinica 2021年第9期37卷 1404-1415,I0002页

作者： Lin Tian Zhiye Zhao Wenjiang Wang Nansheng Liu Department of Modern Mechanics University of Science and Technology of ChinaHefei230026China

Flow over a traveling wavy foil attached with a flexible plate has been numerically investigated using the lattice Boltzmann method combined with the immersed boundary method. The influence of the flexibility and length of the caudal fin on the locomotion of swimming fish through this simplified model, whereas the fish body is modeled by the undulating foil and the caudal fin by the plate passively flapping as a consequence of fluid-structure interaction. It is found that the plate flexibility denoted by the bending stiffness, as well as the length ratio of tail and body, plays an important role in improving thrust generation and propulsive efficiency. It is also revealed that there exists a parameter region of the plate length and stiffness, in which positive propeller efficiency can be achieved. The effect of the passively flapping flexible plate on the pressure field and the vortex production on the wake is further discussed. It is found that when the length ratio of caudal fin and body is greater than 0.2, a reverse von Kármán vortex street occurs when the bending stiffness is about greater than 1.0, and a great thrust is generated as a result of a large pressure difference occurring across the flexible plate. This work provides physical insight into the role of the caudal fin in fish swimming and may inspire the design of robotic fish.

关键词： Flow-structure interactions Lattice Boltzmann method Immersed boundary method Fish-like swimming

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