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Prediction of added resistance of a ship in waves at low speed

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Journal of Hydrodynamics 2019年第6期31卷 1231-1239页

作者： Feng Diao Ji-kang Chen Wen-yang duan Wei-xin Zhou jingpu Chen Jin-fang Wei China Ship Scientific Research Center Wuxi 214082China College of Shipbuilding Engineering Harbin Engineering UniversityHarbin 150001China

This paper presents predictions of the added resistance of a ship in waves at a low speed according to the IMO minimum propulsion power requirement by a hybrid Taylor expansion boundary element method(TEBEM).The flow domain is divided into two parts:the inner domain and the outer domain.The first-order TEBEM with a simple Green function is used for the solution in the inner domain and the zero order TEBEM with a transient free surface Green function is used for the solution in the outer domain.The TEBEM is applied in the numerical prediction of the motions and the added resistance in waves for three new designed commercial ships.The numerical results are compared with those obtained from the seakeeping model tests.It is shown that the prediction of the ship motions and the added resistance in waves are in good agreement with the experimental results.The comparison also indicates that the accuracy of the motion estimation is crucial for the prediction of the wave added resistance.In general,the TEBEM enjoys a satisfactory accuracy and efficiency to predict the added resistance in waves at a low speed according to the IMO minimum propulsion power requirement.

关键词： Taylor expansion boundary element method(TEBEM) added resistance in waves low speed minimum propulsion power

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蜂窝移动网络拥塞控制机制研究综述

高技术通讯 2022年第10期32卷 1036-1048页

作者：李莉莉周建二李清段经璞王志强南方科技大学未来网络研究院深圳518055 鹏城实验室深圳518055 清华大学深圳研究生院深圳518057

网络拥塞控制是保证提供可靠公平的网络服务的基础。5G网络在组网架构、网络性能和业务需求等方面的升级,给网络拥塞控制提出了新的挑战。针对5G网络特征,研究人员提出了多种具有针对性的网络拥塞算法。本文首先从5G网络整体框架、5G网... 详细信息

网络拥塞控制是保证提供可靠公平的网络服务的基础。5G网络在组网架构、网络性能和业务需求等方面的升级,给网络拥塞控制提出了新的挑战。针对5G网络特征,研究人员提出了多种具有针对性的网络拥塞算法。本文首先从5G网络整体框架、5G网络关键技术、蜂窝网络常用模型和部署情况等方面,分析5G网络的特征。然后介绍传统拥塞控制算法,分析传统拥塞算法在5G蜂窝网络中的局限性。根据5G网络特征,分类分析针对蜂窝移动网络的拥塞控制算法。最后分析针对5G网络,拥塞控制算法可能的新的优化方向。

关键词：蜂窝网络 5G拥塞控制网络特征算法分类

Nanomaterials for lubricating oil application:A review

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Friction 2023年第5期11卷 647-684页

作者： Linlin duan Jian LI Haitao duan State Key Laboratory of Special Surface Protection Materials and Application Technology Wuhan Research Institute of Materials ProtectionWuhan 430030China

Friction and wear are ubiquitous,from nano-electro-mechanical systems in biomedicine to large-scale integrated electric propulsion in aircraft carriers.Applications of nanomaterials as lubricating oil additives have achieved great advances,which are of great significance to control friction and wear.This review focuses on the applications of nanomaterials in lubricating oil and comprehensively compares their tribological characteristics as lubricating oil additives.Statistical analysis of tribology data is provided and discussed accordingly;moreover,the interaction between nanomaterials and sliding surface,lubricating oil,other additives,and synergistic lubrication in nanocomposites are systematically elaborated.Finally,suggestions for future research on nanomaterials as lubricating oil additives are proposed.Hence,this review will promote a better fundamental understanding of nanomaterials for lubricating oil application and help to achieve the superior design of nanoadditives with outstanding tribological performances.

关键词： nanomaterial additive friction modifier lubrication wear

Fully actuated system approaches for continuous-time delay systems: part 1. Systems with state delays only

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Science China(Information Sciences) 2023年第2期66卷 158-187页

作者： Guangren duan Center for Control Science and Technology Southern University of Science and Technology Center for Control Theory and Guidance Technology Harbin Institute of Technology

In this paper, the fully actuated system(FAS) approaches for continuous-time systems with time-varying state delays are proposed. Two types of continuous-time high-order FAS models with time delays: single-order time-delay FAS models and multi-order time-delay FASs, are proposed. Particularly, the type of sub-FASs that do not completely but partially satisfy the full actuation is investigated, and the sets of feasible points are defined. When the system states are constrained to the feasible set, a controller can be easily constructed for the sub-FAS such that the closed-loop system is a constant linear system with an arbitrarily assignable eigenstructure. In addition, it is demonstrated that the feasibility constraint can be transformed into a constraint on the initial values of the system, which vanishes when the system is a(global)FAS. Based on the unique control characteristic of the type of FAS models, the concepts of controllability and stabilizability of general dynamical time-delay systems are also proposed. The effect of the proposed theories is illustrated with examples.

关键词： time-delay systems fully actuated systems controller designs controllability stabilizability

Reliability-based selective maintenance for redundant systems with dependent performance characteristics of components

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Journal of Systems Engineering and Electronics 2023年第3期34卷 804-814页

作者： CAO Hui duan Fuhai duan Yu’nan School of Mechanical Engineering Dalian University of TechnologyDalian 116024China

The reliability-based selective maintenance(RSM)decision problem of systems with components that have multiple dependent performance characteristics(PCs)reflecting degradation states is addressed in this paper.A vine-Copulabased reliability evaluation method is proposed to estimate the reliability of system components with multiple PCs.Specifically,the marginal degradation reliability of each PC is built by using the Wiener stochastic process based on the PC’s degradation mechanism.The joint degradation reliability of the component with multiple PCs is established by connecting the marginal reliability of PCs using D-vine.In addition,two RSM decision models are developed to ensure the system accomplishes the next mission.The genetic algorithm(GA)is used to solve the constraint optimization problem of the models.A numerical example illustrates the application of the proposed RSM method.

关键词： D-vine genetic algorithm(GA) reliability-based selective maintenance(RSM) redundant system Wiener stochastic process

Brockett's Second Example:A FAS Approach Treatment

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系统科学与复杂性学报:英文版 2023年第5期36卷 1789-1808页

作者： duan Guang-Ren Shenzhen Key Laboratory of Control Theory and Intelligent Systems Southern University of Science and TechnologyShenzhen 518055China Center for Control Theory and Guidance Technology Harbin Institute of TechnologyHarbin 150001China

In this paper,several equivalent forms of the well-known Brockett's second example system are firstly presented.The stabilization of the system is then treated in the fully actuated system approach.A simple continuous time-invariant sub-stabilizing controller is designed,and the corresponding region of attraction is characterized.As a result,all trajectories of the system starting from the characterized region of attraction are driven exponentially to the origin.Since the region of attraction is very large,the designed sub-stabilizing controller can be directly useful in many practical situations.In cases where the initial values are indeed needed to be chosen out of the region of attraction,extremely simple pre-controllers can be designed,which drive the system trajectories into the designed region of attraction.A simulation of the designed control system is carried out to show the effect of the proposed approach.

关键词： Brockett integrator continuous time-invariant controllers fully actuated system approach region of attraction sub-stabilization

Discrete-time delay systems: part 1. Global fully actuated case

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Science China(Information Sciences) 2022年第8期65卷 87-104页

作者： Guangren duan Center for Control Science and Technology Southern University of Science and Technology Center for Control Theory and Guidance Technology Harbin Institute of Technology

A basic introduction to the fully actuated system(FAS) approaches for discrete-time systems with delays is given. Firstly, general dynamical discrete-time FAS models with time-varying state delays and constant input delays are proposed. The FAS models are classified into affine ones and non-affine ones,and also ones with and without interconnections. Secondly, controllers for such FASs are designed, which result in constant linear closed-loop systems with arbitrarily assignable eigenstructure. Different from the case of FAS with state delays only, the controller for a discrete-time FAS with an input delay involves a prediction scheme which is constructed based on the open-loop system. The contribution of this paper has laid a fundamental basis for FAS approaches to discrete-time delay systems, and further specific analysis and design problems can be established similar to the continuous-time system case.

关键词： discrete-time systems time-delay systems time-varying delays fully actuated systems control designs

Stabilization via Fully Actuated System Approach:A Case Study

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Journal of Systems Science & Complexity 2022年第3期35卷 731-747页

作者： duan Guang-Ren Center for Control Science and Technology Southern University of Science and TechnologyShenzhen 518055China Center for Control Theory and Guidance Technology Harbin Institute of TechnologyHarbin 150001China

In this note,a benchmark example system which is not stabilizable by a smooth state feedback controller is considered with the fully actuated system(FAS)approach.It is shown that a smooth controller exists which drives the trajectories starting from a large domain in the initial value space to the origin exponentially.Such a result brings about a generalization of Lyapunov asymptotical stability,which is termed as global exponential sub-stability.The region of attraction is allowed to be an unbounded open set of the initial values with closure containing the origin.This sub-stability result may be viewed to be superior to some local stability results in the Lyapunov sense because the region of attraction is much larger than any finite ball containing the origin and meanwhile the feasible trajectories are always driven to the origin exponentially.Based on this sub-stabilization result,globally asymptotically stabilizing controllers for the system can be provided in two general ways,one is through combination with existing globally stabilizing controllers,and the other is by using a pre-controller to first move an initial point which is not within the region of attraction into the region of attraction.

关键词： Feedback stabilization fully actuated system approach nonlinear systems region of attraction singularity sets

Brockett’s First Example: An FAS Approach Treatment

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Journal of Systems Science & Complexity 2022年第2期35卷 441-456页

In this note,the well-known Brockett’s first example system is treated with the fully actuated system(FAS)approach.Firstly,it is shown that the system can be exponentially substabilized by a smooth controller in the sense that,except those starting from initial values on the z0-axis of the initial value space,all trajectories of the designed system as well as the control signals decay to zero exponentially.Secondly,global stabilization is realized through a way of enabling the trajectories starting from initial values on the z0-axis also to go to the origin.The idea is to firstly move an initial point on the z0-axis away from the axis using a pre-controller,and then to take over by the designed exponentially sub-stabilizing controller.

关键词： Exponential sub-stabilization feedback stabilization fully actuated system approach region of attraction singularity sets