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A framework for plasticity-based topology optimization of continuum structures

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2023年第7期124卷 1493-1509页

作者： Zhang, Xue Li, Xifan Zhang, Yujia Univ Liverpool Sch Engn Dept Civil Engn & Ind Design Liverpool England

In this paper, a framework is proposed for topology optimization of continuum structures considering plasticity. The method merges the rigid-plastic analysis and the density-based topology optimization. To obtain a clean black-and-white design, the density in the objective function is penalized using an exponential function. The solution of the final plasticity-based topology optimization problem exhibits as a sequence of second-order cone programming (SOCP) problems that can be resolved efficiently using the advanced primal-dual interior point method. Compared to the conventional stress-constrained topology optimization techniques, the developed method accounts for plasticity and the finite element analysis of structures does not need to be carried out separately. Furthermore, the proposed method requires no relaxation techniques for imposing local stress-constrain and possesses good computational efficiency for large-scale problems.

关键词： density-based method limit analysis second-order cone programming stress constraint topology optimization yield criterion

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Nonisothermal Failure Envelopes of Strip Shallow Foundations Resting on Partially Saturated Clay Subjected to Combined Inclined and Eccentric Loadings

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INTERNATIONAL JOURNAL OF GEOMECHANICS 2023年第1期23卷 p1-20页

作者： Chenari, Masoud Jamshidi Payan, Meghdad Ghasemi-Fare, Omid Univ Guilan Fac Engn Dept Civil Engn Rasht *** Iran Univ Louisville Dept Civil & Environm Engn 132 Eastern Pkwy Louisville KY 40292 USA

Shallow foundations are commonly resting on partially saturated soil and are very likely to be exposed to severe variations of temperature. The degree of saturation and matric suction will be changed at the elevated temperatures, thus resulting in different hydromechanical behavior and a considerable variation in the imposed suction stress. In this study, the effect of temperature increase on the ultimate bearing capacity of strip shallow foundations resting on partially saturated clay layer subjected to vertical (V)-horizontal (H)-moment (M) combined loading is examined through a set of finite-element limit analyses (FELA) adopting lower bound theorems and second-order cone programming (SOCP). The unified effective stress for partially saturated soils is first incorporated into the soil yield function, considering the significant effect of temperature variations on suction stress by means of the well-established previously developed nonisothermal soil-water retention curve (SWRC) model. The equilibrium equations corresponding to the combined loading are also incorporated into the FELA formulations to account for the effects of inclined and eccentric loadings. Accordingly, the failure loci of obliquely and eccentrically loaded shallow foundations are presented for a wide range of temperatures. It is shown that with an increase of the temperature in the underlying unsaturated clay, the suction stress within the soil medium significantly rises, and thus, the failure wedges as well as the failure loci for both eccentric and inclined loadings substantially expand at elevated temperatures, revealing the considerably greater bearing capacity of the strip footing. The contact pressure beneath the foundation in all loading scenarios increases with an increase in the temperature of the underlying clay. This trend is much less pronounced at higher angles of load inclination, while it is barely affected by the load eccentricity. In addition, with an increase in the induced tem

关键词： Combined loading Elevated temperature Lower bound finite-element limit analysis Nonisothermal second-order cone programming Shallow foundation Suction stress

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Time-optimal path following for non-redundant serial manipulators using an adaptive path-discretization

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ROBOTICA 2023年第6期41卷 1856-1871页

作者： Marauli, Tobias Gattringer, Hubert Mueller, Andreas Johannes Kepler Univ Linz Inst Robot Altenberger Str 69 A-4040 Linz Austria

The time-optimal path following (OPF) problem is to find a time evolution along a prescribed path in task space with shortest time duration. Numerical solution algorithms rely on an algorithm-specific (usually equidistant) sampling of the path parameter. This does not account for the dynamics in joint space, that is, the actual motion of the robot, however. Moreover, a well-known problem is that large joint velocities are obtained when approaching singularities, even for slow task space motions. This can be avoided by a sampling in joint space, where the path parameter is replaced by the arc length. Such discretization in task space leads to an adaptive refinement according to the nonlinear forward kinematics and guarantees bounded joint velocities. The adaptive refinement is also beneficial for the numerical solution of the problem. It is shown that this yields trajectories with improved continuity compared to an equidistant sampling. The OPF is reformulated as a second-order cone programming and solved numerically. The approach is demonstrated for a 6-DOF industrial robot following various paths in task space.

关键词： serial manipulators kinematics dynamics motion planning singularities optimization second-order cone programming

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Strain localization of Mohr-Coulomb soils with non-associated plasticity based on micropolar continuum theory

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3316-3327页

作者： Jianbin Tang Xi Chen Liusheng Cui Zongqi Liu Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing100044China

To address the problems of strain localization, the exact Mohr-Coulomb (MC) model is used based on second-order cone programming (mpcFEM-SOCP) in the framework of micropolar continuum finite element method. Using the uniaxial compression test, we focused on the earth pressure problem of rigid wall segment involving non-associated plasticity. The numerical results reveal that when mpcFEM-SOCP is applied, the problems of mesh dependency can be effectively addressed. For geotechnical strain localization analysis involving non-associated MC plasticity, mpcFEM-SOCP in conjunction with the pseudo-time discrete scheme can improve the numerical stability and avoid the unreasonable softening issue in the pressure-displacement curves, which may be encountered in the conventional FEM. It also shows that the pressure-displacement responses calculated by mpcFEM-SOCP with the pseudo-time discrete scheme are higher than those calculated by mpcFEM-SOCP with the Davis scheme. The inclination angle of shear band predicted by mpcFEM-SOCP with the pseudo-time discrete scheme agrees well with the theoretical solution of non-associated MC plasticity.

关键词： Strain localization Micropolar continuum Mohr-Coulomb(MC)model Non-associated plasticity second-order cone programming

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Coordinated optimization of source-storage-load in distribution network based on edge computation

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ENERGY REPORTS 2023年 9卷 492-498页

作者： Qi, Zhan Jian, Su Jiaying, Lin Shen, Guo China Elect Power Res Inst Beijing 100192 Peoples R China

A large number of distributed photovoltaics are linked to the distribution network, which may cause serious power quality problems. Based on edge computing, this article put forward a strategy that aggregates multiple distributed resources, such as distributed photovoltaics, energy storage, and controllable load to solve this problem, emphasizing the coordination and optimization between distributed resources. Firstly, an edge computing architecture that can be fully applicable to the coordination of source-storage-loads is constructed. Based on this architecture, the distributed photovoltaic, energy storage and interruptible loads are optimized with the minimum operating cost of edge computation nodes as the objective function. Combined with the operation requirements of the distribution system, lessen the system network loss and make sure the stable and safe operation of the net;Finally, the model is changed with a second-order cone model and verified in an improved IEEE 33 node example. The results show that this method can effectively reduce the loss cost of the system, and can effectively solve the problem of system voltage exceeding the limit, reduce the voltage fluctuation, and maintain the safe and stable operation of the system. (c) 2023 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： Edge computation Source-load-storage second-order cone programming Coordination optimization strategy

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Convergence of augmented Lagrangian methods in extensions beyond nonlinear programming

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MATHEMATICAL programming 2023年第1-2期199卷 375-420页

作者： Rockafellar, R. Tyrrell Univ Washington Dept Math Box 354350 Seattle WA 98195 USA

The augmented Lagrangian method (ALM) is extended to a broader-than-ever setting of generalized nonlinear programming in convex and nonconvex optimization that is capable of handling many common manifestations of nonsmoothness. With the help of a recently developed sufficient condition for local optimality, it is shown to be derivable from the proximal point algorithm through a kind of local duality corresponding to an optimal solution and accompanying multiplier vector that furnish a local saddle point of the augmented Lagrangian. This approach leads to surprising insights into stepsize choices and new results on linear convergence that draw on recent advances in convergence properties of the proximal point algorithm. Local linear convergence is shown to be assured for a class of model functions that covers more territory than before.

关键词： Generalized augmented Lagrangians Generalized nonlinear programming Multiplier methods ALM Localized proximal point algorithm Linear convergence criteria Sufficient conditions for local optimality Variational convexity Strong variational sufficiency second-order variational analysis Local duality Conic programing second-order cone programming Semidefinite programming Convex and nonconvex optimization Nonsmooth optimization

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Secure Optimal Precoding for User-Centric Cell-Free Massive MIMO System

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IEEE WIRELESS COMMUNICATIONS LETTERS 2023年第1期12卷 31-35页

作者： Gao, Xiang Li, Yong Cheng, Wei Dong, Limeng Liu, Penglu Northwestern Polytech Univ Sch Elect & Informat Xian 710072 Peoples R China

The security of user-centric cell-free massive multiple-input multiple-output (UC-CF mMIMO) system in the presence of multiple collusive eavesdroppers (Eves) is investigated in this letter. The access points (APs) share the estimated channel state informations (CSIs) of serving users to central processing unit (CPU). Utilizing the received partial CSIs, the CPU optimizes precoding via formulating a secrecy rate maximization problem under minimum rate requirements of users and power constraints of APs. The formulated problem is non-convex, and the optimum solution is acquired by iteratively solving a sequence of second-order cone programming problems. The numerical simulations present the comparison of secrecy performance achieved in different AP selection methods of UC-CF system, and CF system.

关键词： Precoding Signal to noise ratio Fading channels Channel estimation Symbols Interference Downlink User-centric cell-free massive MIMO optimal precoding secrecy rate second-order cone programming

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GLOBAL TOPOLOGY OPTIMIZATION OF FRAME STRUCTURES CONSIDERING THE DENSITY OF MEMBERS

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AIJ Journal of Technology and Design 2023年第72期29卷 713-718页

作者： Okuzono, Naoto Fujita, Shinnosuke Faculty of Environmental Engineering Univ. of Kitakyushu Japan

It is known that the topology optimization (TopOpt) problem of frame structures can be formulated as a mixed-integer second-order cone programming problem (MISOCP), when the compliance is minimized and the cross-section of each member is selected from a set of predetermined candidates. However, when considering the constructability of real-world building structures, it is insufficient to only minimize compliance. In this paper, in order to control the density of members, the constraints of the number of members connected to each node are additionally considered into TopOpt by MISOCP treated in the previous study. © 2023 Architectural Institute of Japan. All rights reserved.

关键词： second-order cone programming

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Multi-Objective Mixed-Integer Convex programming Method for the Siting and Sizing of UPFCs in a Large-Scale AC/DC Transmission System

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IEEE TRANSACTIONS ON POWER SYSTEMS 2023年第6期38卷 5671-5686页

作者： Liang, Weikun Lin, Shunjiang Liu, Jie Dong, Ping Liu, Mingbo South China Univ Technol Sch Elect Power Engn Guangzhou 510640 Peoples R China

To solve the problem of uneven distribution of power flow and limited transfer capability for the transmission section in a large-scale AC/DC transmission system, a multi-objective mixed-integer convex programming method for the siting and sizing of unified power flow controllers (UPFCs) in an AC/DC transmission system is proposed. Considering the four objectives of the annual equivalent investment and operation cost, bus voltage deviation, transfer capability of the transmission section, and renewable energy accommodation, a multi-objective optimization model is established. By using the convex relaxation method, the original mixed-integer nonlinear programming model is transformed into a mixed-integer second-order cone (SOC) programming model to improve the computational efficiency. Furthermore, a successive inscribed polygon method is proposed to tighten the relaxation gap for the SOC constraints in the optimization model and improve the calculation accuracy. In addition, a direct and fast method for solving the compromise optimal solution of the multi-objective optimization model is proposed. Finally, the effectiveness of the proposed method is demonstrated by an actual 8733-bus large-scale AC/DC transmission system and the modified IEEE-39 bus AC/DC system.

关键词： programming Power conversion Mathematical models Optimization Voltage Prediction algorithms Load flow UPFC AC/DC transmission system multi-objective optimization optimal siting and sizing second-order cone programming relaxation gap tightening

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A Novel SCA-Based Method for Beamforming Optimization in IRS/RIS-Assisted MU-MISO Downlink

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IEEE WIRELESS COMMUNICATIONS LETTERS 2023年第2期12卷 297-301页

作者： Kumar, Vaibhav Zhang, Rui Di Renzo, Marco Tran, Le-Nam Univ Coll Dublin Sch Elect & Elect Engn Dublin D04 V1W8 4 Ireland Chinese Univ Hong Kong Shenzhen Shenzhen Res Inst Big Data Shenzhen 518172 Peoples R China Natl Univ Singapore Dept Elect & Comp Engn Singapore 117583 Singapore Univ Paris Saclay CNRS CentraleSupelec Lab Signaux & Syst F-91192 Gif Sur Yvette France

this letter, we consider the fundamental problem of jointly designing the transmit beamformers and the phase shifts of the intelligent reflecting surface (IRS)/reconfigurable intelligent surface (RIS) to minimize the transmit power, subject to quality-of-service constraints at individual users in an IRS-assisted multiuser multiple-input single-output downlink communication system. In particular, we propose a new successive convex approximation based second-order cone programming approach in which all the optimization variables are simultaneously updated in each iteration. Our proposed scheme achieves superior performance compared to state-of-the-art benchmark solutions. In addition, the complexity of the proposed scheme is O(N-s (3.5 )), while that of state-of-the-art benchmark schemes is O(N-s(7)), where N-s denotes the number of reflecting elements at the IRS.

关键词： Intelligent reflecting surface reconfigurable intelligent surfaces MU-MISO second-order cone programming successive convex approximation

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