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CRACK TIP PLASTICITY OF A THERMALLY LOADED PENNY-SHAPED CRACK IN AN INFINITE SPACE OF 1D QC

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Acta Mechanica Solida Sinica 2015年第5期28卷 471-483页

作者： xiangyu li Peidong li Guozheng Kang School of mechanics and engineering Southwest Jiaotong University Key Laboratory of Advanced Technologies of Materials Ministry of Education of China

The present work is concerned with a penny-shaped Dugdale crack embedded in an infinite space of one-dimensional （1D） hexagonal quasicrystals and subjected to two identical axisymmetric temperature loadings on the upper and lower crack surfaces. Applying Dugdale hypothesis to thermo-elastic results, the extent of the plastic zone at the crack tip is determined. The normal stress outside the plastic zone and crack surface displacement are derived in terms of special functions. For a uniform loading case, the corresponding results are presented by simpli- fying the preceding results. Numerical calculations are carried out to show the influence of some parameters.

关键词： penny-shaped Dugdale crack plastic zone 1D hexagonal quasicrystals thermalloadings

GMAT:A Graph Modeling Method for Group Preference Prediction

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Journal of Systems Science and Systems Engineering 2024年第4期33卷 475-493页

作者： xiangyu li Xunhua Guo Guoqing Chen International Business School Jinan UniversityZhuhai519070China School of Economics and Management Tsinghua UniversityBeijing100084China

Preference prediction is the building block of personalized services,and its implementation at the group level helps enterprises identify their target customers *** methods for preference prediction mainly focus on behavioral interactions to extract the associations between groups and products,ignoring the importance of other auxiliary records(e.g.,online reviews and social tags)in association *** paper proposes a novel method named GMAT for group preference prediction,aiming to collectively detect the sophisticated association patterns from user generated content(UGC)and behavioral *** doing so,we construct a tripartite graph to collaborate these two types of data,and design a deep-learning algorithm with mutual attention module for generating the contextualized representations of groups and *** experiments on two real-world datasets show that GMAT is superior to other baselines in terms of group preference ***,GMAT is able to improve prediction accuracy compared with its different variants,further verifying the proposed method’s effectiveness on association pattern detection.

关键词： Group preference UGC tripartite graph deep learning

Statics of FGM circular plate with magneto-electro-elastic coupling:axisymmetric solutions and their relations with those for corresponding rectangular beam

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Applied Mathematics and Mechanics(English Edition) 2015年第5期36卷 581-598页

作者： Yanzheng WANG Weiqiu CHEN xiangyu li Department of Engineering Mechanics Zhejiang University State Key Laboratory of CAD & CG Zhejiang University School of Mechanics and Engineering Southwest Jiaotong University

This paper investigates the static behavior of a functionally graded circular plate made of magneto-electro-elastic（MEE） materials under tension and *** analysis is directly based on the three-dimensional governing equations for magnetoelectro-elasticity, with the boundary conditions on the upper and lower surfaces satisfied exactly and those on the cylindrical surface satisfied approximately（in the Saint Venant sense）. The analytical solutions, derived with a direct displacement method, are valid for any functionally graded material（FGM） with its properties varying independently in a continuous manner along the thickness direction. For homogeneous materials, these solutions are degenerated to the ones available in the literature. Interesting relations are also found between the solutions for a functionally graded magneto-electro-elastic（FGMEE） circular plate and those for an FGMEE rectangular beam, and even those for a functionally graded elastic beam when only the elastic displacements are considered. The beam solutions are also derived using a direct displacement method. Numerical examples are presented to verify the present analytical solutions, show the effects of material heterogeneity and multi-field coupling, and indicate the correspondence between the plate solutions and beam solutions.

关键词： functionally graded circular rectangular magneto correspondence elasticity heterogeneity exactly piezoelectric

Review of chiplet-based design: system architecture and interconnection

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Science China(Information Sciences) 2024年第10期67卷 5-24页

作者： Yafei liU xiangyu li Shouyi YIN School of Integrated Circuits Tsinghua University Laboratory of Integrated Circuits and Intelligence Systems Research Institute of Tsinghua University in Shenzhen

Chiplet-based design, which breaks a system into multiple smaller dice(or “chiplets”) and reassembles them into a new system chip through advanced packaging, has received extensive attention in the post Moore's law era due to its advantages in terms of cost, performance, and agility. However, significant challenges arise in this implementation approach, including the mapping of functional components onto chiplets, co-optimization of package and architecture, handling the increased latency of communication across functions in different dies, the uncertainty problems of fragment communication subsystems, such as maintaining deadlock-free when independently designed chiplets are combined. Despite various design approaches that attempt to address these challenges, surveying these approaches one-after-another is not the most helpful way to offer a comparative viewpoint. Accordingly, in this paper, we present a more comprehensive and systematic strategy to survey the various approaches. First, we divide them into chiplet-based system architecture design and interconnection design, and further classify them based on different architectures and building blocks of interconnection. Then, we analyze and cross-compare each classification separately, and in addition, we present a topical discussion on the evolution of memory architectures, design automation, and other relevant topics in chiplet-based designs. Finally, some discussions on important topics are presented,emphasizing future needs and challenges in this rapidly evolving field.

关键词： chiplet-based design package architecture interconnection silicon interposer

Efficient optimization method for variable-specific-impulse low-thrust trajectories with shutdown constraint

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Science China(Technological Sciences) 2022年第3期65卷 581-594页

作者： JIA FeiDa QIAO Dong HAN HongWei li xiangyu School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Key Laboratory of Autonomous Navigation and Control for Deep Space Exploration Ministry of Industry and Information TechnologyBeijing 100081China

This paper develops a sequential convex programming(SCP)-based method to solve the minimum-fuel variable-specific-impulse low-thrust transfer problem considering shutdown constraint,with emphasize on improving the computational *** variable parameter engine is more applicable for many low-thrust scenarios,therefore,both a continuously variable model and a ladder variable model are ***,the original problem is convexified by processing the constraint feasible domain,which is composed of the nonlinear dynamic equations and second-order equality constraint,into convex ***,the approximation is generated to close the optimal solution of the low-thrust problem by iteratively solving the convexified ***,the switching self-detection and adaptive node refinement methods are presented,which can improve the accuracy of the solution and accelerate the convergence during the approximation process and is especially necessary and effective in the scenarios with shutdown *** numerical simulations,the comparison with the homotopic approach shows that the proposed method only needs 4%computational time as that of the homotopic approach,and two variable-specificimpulse examples further demonstrate the effectiveness and efficiency of the proposed method.

关键词： low-thrust trajectory variable-specific-impulse shutdown constraint sequential convex programming switching self-detection and adaptive node refinement

Coverage in Cooperative LEO Satellite Networks

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Journal of Communications and Information Networks 2023年第4期8卷 329-340页

作者： Bodong Shang xiangyu li Caiguo li Zhuhang li Eastern Institute for Advanced Study Eastern Institute of TechnologyNingbo 315200China

Low-earth orbit(LEO)satellite networks ignite global wireless ***,signal outages and co-channel interference limit the coverage in traditional LEO satellite networks where a user is served by a single *** paper explores the possibility of satellite cooperation in the downlink *** tools from stochastic geometry,we model and analyze the downlink coverage of a typical user with satellite cooperation under Nakagami fading ***,we derive the joint distance distribution of cooperative LEO satellites to the typical *** model incorporates fading channels,cooperation among several satellites,satellites'density and altitude,and co-channel *** Monte Carlo simulations are performed to validate analytical *** and numerical results suggest that coverage with LEO satellites cooperation considerably exceeds coverage without ***,there are optimal satellite density and satellite altitude that maximize the coverage probability,which gives valuable network design insights.

关键词： Low-earth orbit satellite cooperative communications coverage probability satellite-terrestrial networks non-terrestrial networks

Analytical configuration uncertainty propagation of geocentric interferometric detection constellation

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Astrodynamics 2023年第3期7卷 271-284页

作者： Dong Qiao Xingyu Zhou xiangyu li School of Aerospace Engineering Beijing Institute of TechnologyBeijing100081China

Long-term configuration stability is essential for an interferometric detection constellation(IDC),which is closely related to initial ***,it is vital to evaluate the uncertainty and characterize the configuration *** this study,an analytical method was developed for the configuration uncertainty propagation of a geocentric triangular *** angular momentum and the argument latitude were found to be significantly affected by the initial uncertainty and were selected as the core *** averaging the perturbation in one revolution,an analytical solution was proposed for propagating the core orbital elements in one ***,the analytical solution of the orbit elements during the mission period is obtained by multiplying the solutions in iterative *** relationship between the selected orbital elements and the configuration stability parameters was established using an analytical *** effects of the initial uncertainty in different directions on the configuration and stable domains were *** show that the developed method is highly efficient and accurate in predicting the configuration *** relative error with respect to the Monte Carlo simulations was less than 3%with a time consumption of 0.1%.The proposed method can potentially be useful for constellation design and stability analysis.

关键词： geocentric interferometric detection constellation(IDC) configuration stability configuration uncertainty propagation stable parameters

Three-dimensional analytical solution for a transversely isotropic functionally graded piezoelectric circular plate subject to a uniform electric potential difference

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Science China(Physics,Mechanics & Astronomy) 2008年第8期51卷 1116-1125页

作者： li xiangyu DING HaoJiang CHEN WeiQiu Department of Civil Engineering Zhejiang UniversityHangzhou 310027China

This paper studies the problem of a functionally graded piezoelectric circular plate subjected to a uniform electric potential difference between the upper and lower surfaces. By assuming the generalized displacements in appropriate forms,five differential equations governing the generalized displacement functions are derived from the equilibrium equations. These displacement functions are then obtained in an explicit form,which still involve four undetermined integral constants,through a step-by-step integration which properly incorporates the boundary conditions at the upper and lower surfaces. The boundary conditions at the cylindrical surface are then used to determine the integral constants. Hence,three-dimen sional analytical solutions for electrically loaded functionally graded piezoelectric circular plates with free or simply-supported edge are completely determined. These solutions can account for an arbitrary material variation along the thickness,and thus can be readily degenerated into those for a homogenous plate. A numerical example is finally given to show the validity of the analysis,and the effect of material inhomogeneity on the elastic and electric fields is discussed.

关键词： functionally graded material piezoelectric material circular plates uniform electric potential direct displacement method

Effect of orbital shadow at an Earth-Moon Lagrange point on relay communication mission

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Science China(Information Sciences) 2017年第11期60卷 211-220页

作者： Yuhua TANG Weiren WU Dong QIAO xiangyu li School of Aerospace Engineering Beijing Institute of Technology

The shadow effect is an important constraint to be considered during the implementation of exploration missions. In this paper, for the Earth-Moon Lagrange point L2 relay communication mission, shadow effect issues on a periodic orbit about L2 are investigated. A systematic analysis based on the time domain and phase space is performed including the distribution, duration, and frequency of shadows. First, the lindstedtPoincare and second-order differential correction methods are used in conjunction with the DE421 planetary ephemeris to achieve a mission trajectory family in a high-precision ephemeris model. Next, on the basis of a conical shadow model, the influence of different orbital phases and amplitudes on the shadow is analyzed. The distribution of the shadow is investigated as well. Finally, the configuration of the shadow and its characteristics are studied. This study provides an important reference and basis for mission orbit design and shadow avoidance for relay satellites at an Earth-Moon Lagrange point.

关键词： Earth-Moon system equilibrium point relay orbit shadow effect motion control