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A new optimization algorithm applied in electromagnetics——Maxwell's equations derived optimization (MEDO)

Science China(Information Sciences) 2020年第10期63卷 19-41页

作者： Donglin SU Lilin LI Shunchuan YANG Bing LI Guangzhi CHEN Hui XU School of Electronics and Information Engineering Beihang University Research Institute for Frontier Science Beihang University MIIT Key Laboratory of E3 for Smart System and Equipment Beihang University EMC Technology Institute Beihang University shenyuan honors Colledge Beihang University

In this paper, a novel global optimization algorithm, named as Maxwell’s equations derived optimization(MEDO), is proposed. Using the Maxwell’s equations to analyse the behaviors of the timevarying current, the Ampere force is obtained from Fleming’s left hand rule. MEDO introduces an ‘Ampere force’ term, which is derived from Maxwell’s equations and is rigorous in physics, to drive the variables to the global optimal solution in the search space. In addition, introducing ‘gravity’ to MEDO can increase the stability of the optimizations. 11 classical benchmarks are tested, and results show that MEDO can always converge to numerical optimal solutions. To evaluate the proposed MEDO in solving the electromagnetic problems, four practical engineering applications are considered including the linear antenna array synthesis,frequency selected surface optimization, numerical dispersion reduction for finite-difference method, and parameters extraction of typical waveform. These examples are significant in electromagnetics, but tough to be solved because of their high dimensionality and strong nonlinearity. Numerical results show that MEDO can outperform several classic optimization methods, like wind driven optimization(WDO) and particle swarm optimization(PSO). Therefore, the electromagnetics-inspired MEDO is robust and of great potential in solving the electromagnetic optimization problems.

关键词： electromagnetic theory heuristic optimization high-dimensionality Maxwell's equations multi-modal

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A Comprehensive Method to Reject Detection Outliers by Combining Template Descriptor with Sparse 3D Point Clouds

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Journal of Shanghai Jiaotong university(Science) 2017年第2期22卷 188-192页

作者：郭立 honors college Northwestern Polytechnical UniversityXi’an 710072China

We are using a template descriptor on the image in order to try and find the object. However, we have a sparse 3D point clouds of the world that is not used at all when looking for the object in the images. Considering there are many false alarms during the detection, we are interested in exploring how to combine the detections on the image with the 3D point clouds in order to reject some detection outliers. In this experiment we use semi-direct-monocular visual odometry (SVO) to provide 3D points coordinates and camera poses to project 3D points to 2D image coordinates. By un-projecting points in the tracking on the selection tree (TST) detection box back to 3D space, we can use 3D Gaussian ellipsoid fitting to determine object scales. By ruling out different scales of detected objects, we can reject most of the detection outliers of the object. © 2017, Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg.

关键词： semi-direct-monocular visual odometry(SVO) tracking on the selection tree(TST)-recognizer 3D point-clouds Gaussian ellipsoid fitting

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A real-time abnormal operation pattern detection method for building energy systems based on association rule bases

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Building Simulation 2022年第1期15卷 69-81页

作者： Chaobo Zhang Yang Zhao Yangze Zhou Xuejun Zhang Tingting Li Institute of Refrigeration and Cryogenics Zhejiang UniversityHangzhouChina Chu Kochen honors college Zhejiang UniversityHangzhouChina

Expert systems are effective for anomaly detection in building energy ***,it is usually inefficient to establish comprehensive rule bases manually for complex building energy *** rule mining is available to accelerate the establishment of the rule bases due to its powerful capability of discovering rules from numerous *** paper proposes a real-time abnormal operation pattern detection method towards building energy *** can benefit from both expert systems and association rule *** rules are utilized to establish association rule bases of abnormal and normal operation *** established rule bases are then utilized to develop an expert system for real-time detection of abnormal operation *** proposed method is applied to an actual chiller plant for evaluating its *** show that 15 types of known abnormal operation patterns and 11 types of unknown abnormal operation patterns are detected successfully by the proposed method.

关键词： building energy systems building energy conservation expert systems association rule mining anomaly detection

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Lie Symmetry Analysis and Conservation Laws of a Generalized Time Fractional Foam Drainage Equation

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Communications in Theoretical Physics 2016年第7期65卷 35-40页

作者：王丽田守富赵振涛宋晓秋 Department of Mathematics China University of Mining and Technology Sun Yueqi honors college China University of Mining and Technology

In this paper, a generalized time fractional nonlinear foam drainage equation is investigated by means of the Lie group analysis method. Based on the Riemann–Liouville derivative, the Lie point symmetries and symmetry reductions of the equation are derived, respectively. Furthermore, conservation laws with two kinds of independent variables of the equation are performed by making use of the nonlinear self-adjointness method.

关键词： a generalized time fractional nonlinear foam drainage equation Riemann–Liouville derivative Lie point symmetry symmetry reduction conservation law

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Multiple off-axis acoustic vortices generated by dual coaxial vortex beams

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Chinese Physics B 2018年第2期27卷 393-400页

作者：李雯戴思捷马青玉郭各朴丁鹤平 Key Laboratory of Optoelectronics of Jiangsu Province School of Physics and TechnologyNanjing Normal University honors college Nanjing Normal University

As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.

关键词： dual coaxial acoustic vortex(AV) beams multiple off-axis AVs on-axis center-AV topological charge phase-coded approach

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An untethered cable-driven ankle exoskeleton with plantarflexion-dorsiflexion bidirectional movement assistance

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Frontiers of Information Technology & Electronic Engineering 2020年第5期21卷 723-739页

作者： Tian-miao WANG Xuan PEI Tao-gang HOU Yu-bo FAN Xuan YANG Hugh MHERR Xing-bang YANG School of Mechanical Engineering and Automation Beihang UniversityBeijing 100083China shenyuan honors college Beihang UniversityBeijing 100083China School of Biological Science and Medical Engineering Beihang UniversityBeijing 100083China MIT Media Lab Massachusetts Institute of TechnologyCambridgeMA 02139-4307USA Beijing Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijing 100083China

Lower-limb assisted exoskeletons are widely researched for movement assistance or rehabilitation *** to advantages of compliance with human body and lightweight,some cable-driven prototypes have been developed,but most of these can assist only unidirectional *** this paper we present an untethered cable-driven ankle exoskeleton that can achieve plantarflexion-dorsiflexion bidirectional motion bilaterally using a pair of single *** main weights of the exoskeleton,i.e.,the motors,power supplement units,and control units,were placed close to the proximity of the human body,i.e.,the waist,to reduce the redundant rotation inertia which would apply on the wearer’s leg.A cable force transmission system based on gear-pulley assemblies was designed to transfer the power from the motor to the end-effector effectively.A cable self-tension device on the power output unit was designed to tension the cable during *** gait detection system based on a foot pressure sensor and an inertial measurement unit(IMU)could identify the gait cycle and gait states *** validate the power output performance of the exoskeleton,a torque tracking experiment was *** the subject was wearing the exoskeleton with power on,the muscle activity of the soleus was reduced by 5.2%compared to the state without wearing the *** preliminarily verifies the positive assistance effect of our *** study in this paper demonstrates the promising application of a lightweight cable-driven exoskeleton on human motion augmentation or rehabilitation.

关键词： Ankle exoskeleton Plantarflexion-dorsiflexion bidirectional assistance Biological gait torque Cable-driven Gait detection

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Study on Airflow Characteristics in the Semi-Closed Irregular Narrow Flow channel

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Journal of Thermal Science 2016年第2期25卷 123-129页

作者： JIN Yuzhen HU Xiaodong ZHU Linhang HU Xudong JIN Yingzi Zhejiang Provincial Key Lab of Modern Textile Machinery & Technology Zhejiang Sci-Tech University 1201 Chu Kochen honors college Zhejiang University

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关键词： air-jet loom profiled dents numerical simulation airflow characteristics semi-closed channel

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Three-dimensional Numerical Simulation of the Movement of the Flexible Body under Different Constraints

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Journal of Thermal Science 2014年第6期23卷 593-599页

作者： JIN Yuzhen LI Jun ZHU Linhang DU Jiayou JIN Yingzi LIN Peifeng Zhejiang Provincial Key Lab of Modern Textile Machinery & Technology Zhejiang Sci-Tech University 1201 Chu Kochen honors college Zhejiang University

For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough *** this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1:*** Reynolds number of the airflow is 513,belonging to the area of low Reynolds *** control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible *** numerical results show that it is possible to simulate the characteristics of the flexible body's movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is *** flexible body would turn over forward along the airflow's diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible *** preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.

关键词： fluid-structure interaction numerical simulation flexible body adaptive grid control method

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An Improved Higher-Order Time Integration Algorithm for Structural Dynamics

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Computer Modeling in Engineering & Sciences 2021年第2期126卷 549-575页

作者： Yi Ji Yufeng Xing Institute of Solid Mechanics Beihang UniversityBeijing100083China Shen Yuan honors college Beihang UniversityBeijing100083China

Based on the weighted residual method,a single-step time integration algorithm with higher-order accuracy and unconditional stability has been proposed,which is superior to the second-order accurate algorithms in tracking long-term *** improving such a higher-order accurate algorithm,this paper proposes a two sub-step higher-order algorithm with unconditional stability and controllable *** the proposed algorithm,a time step interval[t_(k),t_(k)+h]where h stands for the size of a time step is divided into two sub-steps[t_(k),t_(k)+γh]and[t_(k)+γh,t_(k)+h].A non-dissipative fourth-order algorithm is used in the rst sub-step to ensure low-frequency accuracy and a dissipative third-order algorithm is employed in the second sub-step to lter out the contribution of high-frequency ***,two approaches are used to design the algorithm parameterγ.The rst approach determinesγby maximizing low-frequency accuracy and the other determinesγfor quickly damping out highfrequency *** present algorithm usesρ_(∞)to exactly control the degree of numerical dissipation,and it is third-order accurate when 0≤ρ_(∞)<1 and fourth-order accurate whenρ_(∞)=***,the proposed algorithm is self-starting and easy to *** illustrative linear and nonlinear examples are solved to check the performances of the proposed two sub-step higher-order algorithm.

关键词： Time integration algorithm two-sub-step higher-order accuracy controllable dissipation unconditional stability

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Characteristics and Applications of Current-Driven Magnetic Skyrmion Strings

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Chinese Physics Letters 2022年第10期39卷 66-70页

作者： Zhaonian Jin Minhang Song Henan Fang Lin Chen Jiangwei Chen Zhikuo Tao Bell honors School Nanjing University of Posts and TelecommunicationsNanjing 210003China college of Electronic and Optical Engineering&college of Microelectronics Nanjing University of Posts and TelecommunicationsNanjing 210003China

We investigate the current-driven characteristics and applications of magnetic skyrmion strings by micromagnetic *** the spin-polarized driving current,the skyrmion string presents different moving trajectories in different layers due to the skyrmion Hall ***,a series of skyrmion bobbers can be generated with a notch defect placed in the surface and the skyrmion bobbers will follow the skyrmion *** varying the current density,the bobbers'characteristics such as number and velocity can be manipulated,which inspires us to propose a skyrmion string-based *** addition,an AND logic gate and an OR logic gate in the identical scheme based on the skyrmion string are *** logic and OR logic behaviors can be realized by varying the driving current *** findings will contribute to further research of magnetic skyrmion strings for data storage,processing,and energy-efficient computing.

关键词： effect identical polarized

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