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Three-Dimensional Multi-mesh Material Point Method for Solving Collision Problems

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Communications in Theoretical Physics 2008年第5期49卷 1129-1138页

作者： PAN Xiao-fei XU Ai-Guo ZHANG Guang-cai ZHANG Ping ZHU jian-Shi MA Shang ZHANG Xiong Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P.O. Box 8009-26 Beijing 100088 China School of Aerospace Tsinghua University Beijing 100084 China

A new multi-mesh contact algorithm for three-dimensional material point method is presented. The contact algorithm faithfully recovers the opposite acting forces between colliding bodies. Collision procedures between regular bodies and/or rigid bodies are treated within the same framework. Multi-value of momentum and mass are defined on every node to describe the contact/sliding/separation procedure. Both normal and tangential velocities of each particle at the contact surface are calculated in respective individual mesh. A Coulomb friction is applied to describe the sliding or slipping between the contacting bodies. The efficiency of the contact algorithm is linearly related to the number of the contacting bodies because the overlapped nodes are labeled by sweeping the material particles of all bodies when the nodal momentum and mass are formed at every time step. Numerical simulation shows that our contact algorithm possesses high accuracy and low numerical energy dissipation, which is very important for solving collision problems.

关键词： material-point method (MPM) energy conservation contact algorithm multi-mesh

Distortion Theorem for Bloch Mappings on the Unit Ball ■~n

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Acta Mathematica Sinica,English Series 2009年第10期25卷 1583-1590页

作者： jian fei WANG Tai Shun LIU College of Mathematics and Physics Information Engineering Zhejiang Normal University Jinhua 321004 P. R. China Department of Mathematics Huzhou Teachers College Huzhou 313000 P. R. China

In this paper, we obtain a version of subordination lemma for hyperbolic disk relative to hyperbolic geometry on the unit disk D. This subordination lemma yields the distortion theorem for Bloch mappings f ∈ H（B^n） satisfying ｜｜f｜｜0 = 1 and det f＇（0） = α ∈ （0, 1], where｜｜f｜｜0 = sup{（1 - ｜z｜^2 ）n＋1/2n det（f＇（z））[1/n ： z ∈ B^n}. Here we establish the distortion theorem from a unified perspective and generalize some known results. This distortion theorem enables us to obtain a lower bound for the radius of the largest univalent ball in the image of f centered at f（0）. When a = 1, the lower bound reduces to that of Bloch constant found by Liu. When n = 1, our distortion theorem coincides with that of Bonk, Minda and Yanagihara.

关键词： mapping distortion theorem Bloch mapping univalent ball hyperbolic distance holomorphic

Tracking people through partial occlusions

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The Journal of China Universities of Posts and Telecommunications 2009年第2期16卷 117-121页

作者： LU jian-guo cai An-hi School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

This article presents a novel people-tracking approach to cope with partial occlusions caused by scene objects. Instead of predicting when and where the occlusions will occur, a part-based model is used to model the pixel distribution of the target body under occlusion. The subdivided patches corresponding to a template image will be tracked independently using Markov chain Monte Carlo （MCMC） method. A set of voting-based rules is established for the patch-tracking result to verify if the target is indeed located at the estimated position. Experiments show the effectiveness of the proposed method.

关键词： partial occlusion part-based model MCMC voting-based rules

Foundation Treatment in Urban Underground Engineering Using Big Data Analysis for Smart City Applications

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Computer Modeling in Engineering & Sciences 2022年第7期132卷 153-172页

作者： fei Liu Yunkai Zhang jian Zhang School of Civil and Transportation Engineering Beijing University of Civil Engineering and ArchitectureBeijing102616China Beijing Advanced Innovation Center for Future Urban Design Beijing102616China School of Science Beijing University of Civil Engineering and ArchitectureBeijing102616China

A core element of the sustainable approach to global living quality improvement can now become the intensive and organized usage of underground *** is a growing interest in underground building and growth *** reduced consumption of electricity,effective preservation of green land,sustainable wastewater and sewage treatment,efficient reverse degradation of the urban environment,and reliable critical infrastructure management can improve the quality of *** the same time,technological innovations such as artificial intelligence(AI),cloud computing(CC),the internet of things(IoT),and big data analytics(BDA)play a significant role in improved quality of ***,this study aims to integrate the technological innovations in urban underground engineering to ensure a high quality of ***,this study uses big data analytics to carry out the status quo of foundation treatment and proposes a conceptual framework named the BDA with IoT on urban underground engineering(BI0T-UUE).This framework connects hidden features with various high-level sensing sources and practical predictive model characterization to lower building costs,productive infrastructure management,preparedness for disasters,and modern community smart *** IoT integration gives an optimum opportunity to work towards the functionality of‘‘digital doubles’’of secret infrastructure,both economical and scalable,with the increasing sophistication and tooling of the *** simulation analysis ensures the highest efficiency and cost-effectiveness of the underground engineering with a value of 96.54%and 97.46%.

关键词： Underground engineering internet of things big data analytics status quo economic and social smart city

HYDRAULIC CHARACTERISTICS OF SLIT-TYPE ENERGY DISSIPA-TERS

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Journal of Hydrodynamics 2012年第6期24卷 883-887页

作者： WU jian-hua MA fei YAO Li College of Water Conservancy and Hydropower Engineering Hohai University

Slit-Type Energy Dissipater （STED） has been a kind of important devices for energy dissipation. The flow through the STED is longitudinally extended and the velocity is decreased by means of the cross-section increase of the flow, which is closely related to geometric and hydraulic parameters of the STED. Therefore, it is necessary to investigate and control the hydraulic condi- tions through the STED, including the nappe section form, the conversion condition, and the effect of energy dissipation with the geometric and hydraulic parameters. In the present work, ＂I-type＂ and ＂T-type＂ nappe forms were experimentally classified, the con- version conditions of the nappe forms were empirically provided, and the effects of geometric parameters of the STED on energy dissipation were roughly analyzed. It is concluded that the contraction angle of the STED is a key factor influencing the hydraulic characteristics of the STED.

关键词： contraction angle energy dissipation fin nappe form shock wave Slit-Type Energy Dissipater (STED)

Designing planar cubic B-spline curves with monotonic curvature for curve interpolation

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Computational Visual Media 2020年第3期6卷 349-354页

作者： Aizeng Wang Chuan He fei Hou Zhanchuan cai Gang Zhao School of Mechanical Engineering&Automation Beihang UniversityBeijing 100191China State Key Laboratory of Virtual Reality Technology&Systems Beihang UniversityBeijing 100191China State Key Laboratory of Computer Science Institute of SoftwareChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Faculty of Information Technology Macao University of Science and TechnologyMacao 999078China

Monotonic curvature plays an important role in industrial design and styling of curves with aesthetic shapes,e.g.,in automobile and aircraft design[1].Used in conventional parametric CAD/CAM systems,general B-splines are not adequate for aesthetic *** for the straight line and circle,monotonic curvature distribution,associated with pleasing shape,is very difficult to achieve.

关键词： curvature monotonic curves

Deployment simulation of cable-strut structures considering cable sliding

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Science China(Technological Sciences) 2012年第12期55卷 3263-3269页

作者： cai jianGuo FENG jian WANG Kai Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast UniversityNanjing 210096China National Engineering Research Center for Prestress Southeast UniversityNanjing 210096China

The influence of cable sliding on the deployment of foldable cable-strut structures was studied in this paper. In order to develop an effective program for the cable sliding program, two-node cable element based on the analytical solution of elastic cate- nary was studied. Then the cable sliding stiffness was defined as the ratio of the variation of the cable force to the variation of the cable length. To validate the proposed numerical method, analyses of two examples given in references were carried out. The results show that the method given in this paper is accurate and effective, which can be used to model the cable sliding in cable structures. Finally, the deployment process of a foldable cable-strut structure, which is composed of four-bar linkages and cables, was discussed. It can be found that the effect of cable sliding on the behavior of cable-strut structures is significant. The length changes of active cables are smaller when the cable sliding is considered. Moreover, the nodal coordinate changes also become faster when the numerical model is with cable sliding.

关键词： deployment elastic catenary cable-strut structures cable sliding nonlinear analysis

Effect of Na^+ on xonotlite crystals in hydrothermal synthesis

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International Journal of Minerals,Metallurgy and Materials 2013年第1期20卷 88-93页

作者： fei Liu Xiao-dan Wang jian-xin Cao School of Chemistry and Chemical Engineering Guizhou University

The effect of Na＋ ion concentration on the crystalline phase composition and morphology of xonotlite crystals pre- pared in a CaO-SiO2-H20 system via hydrothermal synthesis was analyzed. X-ray diffraction （XRD） and scanning electron mi- croscopy （SEM） results indicate that Na＋ ion concentration has a significant impact on the composition and morphology of crystalline phases in the products under the initial conditions of a molar ratio of CaO/SiO2 of 1.0 and a reactant concentration of 0.05 mol.L-1 at 225℃ for 15 h. The main crystalline phase in the products has a phase transition from xonotlite to pectolite, and the morphology changes from fibrous to broomlike shape with the Na＋ ion concentration increasing. Therefore, the content of Na^O in the raw material should be less than 5wt% for preparing pure xonotlite crystals via hydrothermal synthesis in a CaO-SiO2-H20 system.

关键词： crystals xonotlite pectolite hydrothermal synthesis morphology

Anti-interference self-alignment algorithm by attitude optimization estimation for SINS on a rocking base

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Journal of Systems Engineering and Electronics 2023年第5期34卷 1333-1342页

作者： XUE Haijian WANG Tao cai Xinghui WANG Jintao LIU fei High-Tech Institute of Xi’an Xi’an 710025China Military Representative Office of Rocket Army Equipment Department Qingdao 266071China

The performance of a strapdown inertial navigation system(SINS)largely depends on the accuracy and rapidness of the initial alignment.A novel anti-interference self-alignment algorithm by attitude optimization estimation for SINS on a rocking base is presented in this *** algorithm transforms the initial alignment into the initial attitude determination problem by using infinite vector observations to remove the angular motions,the SINS alignment is heuristically established as an optimiza-tion problem of finding the minimum *** order to further improve the alignment precision,an adaptive recursive weighted least squares(ARWLS)curve fitting algorithm is used to fit the translational motion interference-contaminated reference vectors according to their time domain *** studies and experimental results favorably demonstrate its rapidness,accuracy and robustness.

关键词： strapdown inertial navigation system(SINS) initial alignment anti-interference rocking base adaptive recursive weighted least squares(ARWLS)