Recent Advances on Vibration Control of Structures Under Dynamic Loading

In this paper, a review of recent journal articles on passive, active, semi-active, and hybrid vibration control of structures subjected to dynamic loading is presented. Passive systems reviewed include tuned mass damper (TMD), tuned liquid column damper (TLCD), tuned liquid column ball damper (TLCBD), circular TLCD (CTLCD), and pendulum TLCD (PTLCD). Active control systems include active tuned mass dampers (ATMD) and piezoelectric actuators. Semi-active systems include magnetorheological (MR) damper, negative stiffness devices (NSD), magneto-rheological damper TMD (MR-TMD), variable stiffness semi-active TMD (VS-STMD), variable damper STMD (VD-STMD), and recentering variable friction device (RVFD). Hybrid systems include active base isolation system and semi-active MR dampers with nonlinear base isolators. The current frontier of research is semi-active control of structures as well hybridization of various control systems. The problem is complex requiring integration of several different hardware and software technologies with structural design such as smart materials, adaptive dampers, actuators, sensors, and control and signal processing algorithms. This complexity also makes it an exciting area of research and development.     

Numerical Treatment of Elliptic Problems Nonlinearly Coupled Through the Interface

This work is devoted to the study of the numerical treatment of linear elliptic problems in adjoined domains nonlinearly coupled at the interface. The problem arises in semi-discretization of mass diffusion problems typically when an osmotic effect is taken into account. Convergence of both the Conjugate Gradient and the Fixed Point method are considered and compared.     

Recent Advances on Topology Optimization of Multiscale Nonlinear Structures

Research on topology optimization mainly deals with the design of monoscale structures, which are usually made of homogeneous materials. Recent advances of multiscale structural modeling enables the consideration of microscale material heterogeneities and constituent nonlinearities when assessing the macroscale structural performance. However, due to the modeling complexity and the expensive computing requirement of multiscale modeling, there has been very limited research on topology optimization of multiscale nonlinear structures. This paper reviews firstly recent advances made by the authors on topology optimization of multiscale nonlinear structures, in particular techniques regarding to nonlinear topology optimization and computational homogenization (also known as FE²) are summarized. Then the conventional concurrent material and structure topology optimization design approaches are reviewed and compared with a recently proposed FE²-based design approach, which treats the microscale topology optimization process integrally as a generalized nonlinear constitutive behavior. In addition, discussions on the use of model reduction techniques is provided in regard to the prohibitive computational cost.     

A Survey of Cyber Attacks on Cyber Physical Systems: Recent Advances and Challenges

A cyber physical system (CPS) is a complex system that integrates sensing, computation, control and networking into physical processes and objects over Internet. It plays a key role in modern industry since it connects physical and cyber worlds. In order to meet ever-changing industrial requirements, its structures and functions are constantly improved. Meanwhile, new security issues have arisen. A ubiquitous problem is the fact that cyber attacks can cause significant damage to industrial systems, and thus has gained increasing attention from researchers and practitioners. This paper presents a survey of state-of-the-art results of cyber attacks on cyber physical systems. First, as typical system models are employed to study these systems, time-driven and event-driven systems are reviewed. Then, recent advances on three types of attacks, i.e., those on availability, integrity, and confidentiality are discussed. In particular, the detailed studies on availability and integrity attacks are introduced from the perspective of attackers and defenders. Namely, both attack and defense strategies are discussed based on different system models. Some challenges and open issues are indicated to guide future research and inspire the further exploration of this increasingly important area.      

Physical Safety and Cyber Security Analysis of Multi-Agent Systems: A Survey of Recent Advances

Multi-agent systems(MASs)are typically composed of multiple smart entities with independent sensing,communication,computing,and decision-making capabilities.Nowadays,MASs have a wide range of applications in smart grids,smart manufacturing,sensor networks,and intelligent transportation systems.Control of the MASs are often coordinated through information interaction among agents,which is one of the most important factors affecting coordination and cooperation performance.However,unexpected physical faults and cyber attacks on a single agent may spread to other agents via information interaction very quickly,and thus could lead to severe degradation of the whole system performance and even destruction of MASs.This paper is concerned with the safety/security analysis and synthesis of MASs arising from physical faults and cyber attacks,and our goal is to present a comprehensive survey on recent results on fault estimation,detection,diagnosis and fault-tolerant control of MASs,and cyber attack detection and secure control of MASs subject to two typical cyber attacks.Finally,the paper concludes with some potential future research topics on the security issues of MASs.     

UIDT:一种基于摄像头的用户界面模型

为了弥补WIMP界面模型对视觉交互描述的不足,提出一种基于视觉交互的用户界面模型．首先在分析和总结视觉交互过程的基础上,以活动理论为基础,提出一种以用户为中心、面向任务和基于事件驱动的用户界面模型;然后描述了该模型的组成结构及其相互关系;最后给出了一个基于此模型的视频手势交互系统实例．实验结果表明,该模型能够有效地支持视觉交互设计,使用户界面满足可用性要求．     

Reduced-Order GPIO Based Dynamic Event-Triggered Tracking Control of a Networked One-DOF Link Manipulator Without Velocity Measurement

In networked robot manipulators that deeply integrate control, communication and computation, the controller design needs to take into consideration the limited or costly system resources and the presence of disturbances/uncertainties. To cope with these requirements, this paper proposes a novel dynamic event-triggered robust tracking control method for a one-degree of freedom (DOF) link manipulator with external disturbance and system uncertainties via a reduced-order generalized proportional-integral observer (GPIO). By only using the sampled-data position signal, a new sampled-data robust output feedback tracking controller is proposed based on a reduced-order GPIO to attenuate the undesirable influence of the external disturbance and the system uncertainties. To save the communication resources, we propose a discrete-time dynamic event-triggering mechanism (DETM), where the estimates and the control signal are transmitted and computed only when the proposed discrete-time DETM is violated. It is shown that with the proposed control method, both tracking control properties and communication properties can be significantly improved. Finally, simulation results are shown to demonstrate the feasibility and efficacy of the proposed control approach.      

基于EASI模型的实物保护系统动态评估方法

为了提高实物保护系统的防护性能,提出一种基于EASI模型的实物保护系统动态脆弱性评估方法(Dynamic Assessment of Physical Protection System,DAPPS).考虑到极端气候环境对实物保护系统的防护性能的影响,根据各类环境传感器所探测到的外部环境情况实时动态计算最薄弱路径上的拦...     

IP追踪新进展

在信息化社会发展过程中,互联网的应用已成为人们最重要的通信手段.然而,在网络应用大规模发展的同时,网络安全的状况不容乐观,网络安全问题也日益突出.在众多网络安全问题当中,分布式拒绝服务攻击(DDoS)是最具威胁的问题之一.IP源追踪技术是监测和防御DDoS攻击的重要手段,能够实时隔离或阻断攻击,使得各项入侵响应措施更加准确有效,且在提供法律举证和威慑攻击者等方面具有积极作用,对于缔造一个安全可信的网络环境具有重要意义.本文介绍了近几年IP追踪算法的新进展,分析比较各种算法的优缺点,并指出IP追踪技术所面临的问题展望了其今后的发展趋势.     

A Dynamic Multilevel Model for the Simulation of the Small Structures in Homogeneous Isotropic Turbulence

In turbulence simulations, the small scales of motion, even if they carry only a very small percentage of the whole kinetic energy, must be taken into account in order to accurately reproduce the statistical properties of the flows. This induces strong computational restrictions. In an attempt to understand and model the nonlinear interaction between the small and large scales, a dynamic multilevel procedure is proposed and applied to homogeneous turbulence. As in large eddy simulation, filtering operators are used to separate the different scales of the velocity field. In classical models (Smagorinsky), only the large scale equation is resolved. A different approach is proposed here. Indeed, by analyzing the nonlinear interaction term in the large scale equation, we show that they locally have a very small contribution to the whole dynamic of the flow. We then propose to treat them less accurately. Specific treatments for these terms are achieved by a space and time adaptative procedure; the cut-off value (filter width) which defines the scale separation varies as time evolves. Simulations at Re in the range of 60 to 150 have been performed until statistical steady states are reached, i.e. over long time period. Comparisons with direct simulations (DNS) show that this numerical modeling provides an efficient resolution of the nonlinear interaction term. The multilevel algorithm is shown to be stable; the corresponding simulated flows reach a statistically steady state very close to the DNS ones. The shape of the energy spectrum functions as well as the characteristic statistical properties of the velocity and its derivatives are accurately recovered.     

Automated Testing of Physical Security: Red Teaming Through Machine Learning

Modern surveillance systems for practical applications with diverse and mobile sensors are large, complex, and expensive. It is known that unexpected behaviors can emerge from such systems, and when these behaviors correspond to weaknesses in a surveillance system, we call them emergent vulnerabilities. Given their cost and importance to security, it is essential to test these systems for such vulnerabilities prior to deployment. To that end, we automate the testing process with multiagent systems and machine learning. However, the conventional—and most intuitive–approach is to focus the machine learning on the subject system, which leads to a high‐dimensional problem that is intractable. Instead, we demonstrate in this paper that learning attacks on the system is tractable and provides a viable testing method. We demonstrate this with a series of studies in simulation and with a small‐scale model system featuring elements typically found in real physical surveillance systems. Our machine learning method finds successful attacks in simulation, which we can duplicate with the physical system. The method is scalable, with the implication that it could be used to test larger, real surveillance installations.     

智能控制工程研究的进展

结合智能控制研究的几个理论分支,着重从机器人控制,机械制造,电力电子学,工业过程和广义控制几个方面分析了当前智能控制的主要应用领域,指出其中的研究热点和重点,通过总结智能控制工程的现状,提出进一步开展智能控制应用研究的若干对策,包括从基础理论研究和应用系统评估上寻求更成熟的理论指导,明确智能控制研究的目标是建立智能系统模型并实现控制器的智能化,在选择应用对象和设计控制器对遵循“简单”与“复杂”的辨证关系,重视知识技术创新和加快新型智能控制软硬件研制的步伐等。     

自动控制在中国的某些近期发展

本文在给出一简短的历史回顾后,主要概述中国近20年改革开放期间,特别是近几年来,大陆学者在自动控制理论及应用方面取得的若干重要进展.     

Computational Logic in Multi-Agent Systems: Recent Advances and Future Directions

Starting from the early days of multi-agent systems research, considerable effort has been devoted to giving formal foundations to agent technologies. Work done in this direction, based on computational logic, is an attempt to bridge an existing gap, between theoretical frameworks and their practical implementations. In the last two editions of the workshop on Computational Logic in Multi-Agent Systems, CLIMA'01 and CLIMA'02, two discussion panels have been organized, aimed at bringing researchers together and exchanging ideas on a number of topics. In this article, we elaborate on the outcome of such panels, to draw some considerations about the recent advances and future directions of Computational Logic in Multi-Agent Systems.     

A Nondestructive Dynamic Characterization of a Microheater Through Digital Holographic Microscopy

This paper describes the possibility of employing a digital holographic microscope (DHM) to carry out a noncontact and nondestructive characterization of a microheater integrated on a silicon nitride membrane and subjected to a high thermal load. Microheaters can be affected by the presence of the residual stress due to the technological processes appearing in the form of undesired bowing of the membrane. Moreover, when the temperature of the microheater increases, a further warpage of the structure can be induced. A DHM allows for evaluation, with high accuracy, the deformations due to the residual stress and how these deformations are affected by the thermal loads due to the microheater operating mode. In particular, this dynamic analysis is made possible by measuring the unwanted longitudinal displacement induced by the thermal expansion of both the device and its mechanical support. Taking into account this displacement, it is possible to have a continuous monitoring of profile deformation induced by the working condition of the microheater.     

基于SOA的技术交易全程服务系统接口组件研究与设计

针对技术交易全程服务平台建设面临的多个参与主体、多个系统的集成的问题,支撑平台采用以服务总线为核心的平台体系结构,但Web服务的多样化及差异性,往往带来了其管理接口的多样化和差异性。文章在研究SOA和WebService基本概念和服务模型的基础上,提出了基于SOA的统一应用服务接口模型,以解决异构系统集成的问题。     

基于点的三维模型压缩技术研究进展

基于点的图形学是近年来的一个研究热点,但由于基于点的模型(点模型)数据往往非常庞大,为便于存储和网络传输,有效地对这些数据进行压缩非常重要.总结了点模型的压缩流程,并给出了点模型压缩算法的分类原则;然后以单分辨率算法和渐进算法为主线,详细介绍了点模型压缩的最新研究进展,分析比较了相应的关键技术;最后对该领域未来的发展提出了一些研究建议.     

DSCM:一个支持动态演化的服务组件架构模型

针对服务组件架构(Service Component Architecture,SCA)的动态管理和演化的不足,文章研究SCA的动态重构技术.在符合SCA模型规范基础上结合开放服务网关规范(Open Service Gateway Initiative,OSGi)技术,提出一个开放环境下的动态服务组建模型DSCM(Dynamic Service Component Model),它以Object Teams技术作为基础设施,从而提高应用系统的可理解性、重用性、扩展性、适配性和进化能力.DSCM支持分布式和异构平台的整合,支持简单老式java对象(Plain Old Java Object,POJO)增强和管理的机制,使得框架具有通用性和无入侵性.     

GSM:一种多服务器系统的动态负载均衡调度模型

设多服务器系统由 n个服务器结点和 1个中心任务调度结点组成 ,所有服务器具有同样的处理能力 ,任务的到达是一速率参数为 nλ的泊松流 ,任务的服务器处理时间服从参数为 1/μ的指数分布 (λ<μ) ,一次负载信息收集时间和任务调度时间在理想情况下可忽略不计 .基于这些假设 ,提出了多服务器系统的广义超级市场调度模型 (GeneralizedSuperm arket Model,GSM) ,详细分析并证明了该调度模型的解特性 .结论表明 :对于大规模多服务器系统 ,广义超级市场调度模型与随机选择服务调度策略相比 ,可指数级地提高平均任务消耗时间性能 ;与文献 [1,2 ,3]的结果相比 ,达到其极小化平均任务消耗时间     

State of the Art in Time-Dependent Flow Topology: Interpreting Physical Meaningfulness Through Mathematical Properties

We present a state-of-the-art report on time-dependent flow topology. We survey representative papers in visualization and provide a taxonomy of existing approaches that generalize flow topology from time-independent to time-dependent settings. The approaches are classified based upon four categories: tracking of steady topology, reference frame adaption, pathline classification or clustering, and generalization of critical points. Our unique contributions include introducing a set of desirable mathematical properties to interpret physical meaningfulness for time-dependent flow visualization, inferring mathematical properties associated with selective research papers, and utilizing such properties for classification. The five most important properties identified in the existing literature include coincidence with the steady case, induction of a partition within the domain, Lagrangian invariance, objectivity, and Galilean invariance.