WANG氏RC互连线模型平衡截断化简的分解算法

平衡截断（Balanced Truncation）是一种有效的模型简化（Model Reduction）方法,它的优点是简化模型有一个误差上限,使简化模型的性能得到保证.该文介绍一种平衡实现的分解算法,并应用Matlab对一4阶的Wang氏RC互连线模型的平衡实现及其模型截断简化进行编程仿真.单位阶跃响应和波特图显示原始模型与平衡模型曲线重合.给出了1阶、2阶、3阶平衡截断简化模型的阶跃响应和波特图,并对简化模型的理论误差上限与模型的实际最大误差进行了对比.方法可用于对IC互连线等模型的简化.     

无线传感器网络数据传输延时分配算法

为了提高箭载无线传感网络对火箭温度、冲击、热流等物理参数的处理能力,需对所采集的数据进行自适应延时分配,因此设计一种基于时隙窗口间隔均衡控制的无线传感器网络数据传输延时分配算法。构建火箭温度、振动、冲击等参数的数据采集模型,采用分布式网格均衡配置方法对无线传感器网络中的节点进行均衡部署;结合最短路径寻优方法使数据采集过程中的信道分配达到均衡,构建数据采集最短路径寻优控制模型,采用输出比特序列重组方法进行数据采集过程中的传输延迟配置;结合码元调节技术对数据传输进行自适应扩频调节,利用时隙窗口间隔均衡控制方法实现无线传感器网络数据传输延时分配。实验结果表明,采用该方法进行无线传感器网络数据传输延时分配的自适应性较好,输出稳定性较强、分配输出错误率低,有效性更强。     

A Dynamic Load Balancing Mechanism for Distributed Systems

It is desirable in a distributed system to have the system load balanced evenly among the nodes so that the mean job response time is minimized.In this paper,we present a dynamic load balancing mechanism(DLB).It adopts a cntralized approach and is network topology independent.The DLB mechanism employs a set of threscholds which are automatically adjusted as the system load changes.It also provides a simple mechanism for the system to switch between periodic and instantaneous load balancing policies with ease.The performance of the proposed algorithm is evaluated by intensive simulations for various parameters.Te simulation results show that the mean job response time in a system implementing DLB algorithm is significantly lower than the same system without load balancings.Furthermore,compared with a previously proposed algorithm,DLB algorithm demonstrates improved performance,especially when the system is heavily loaded and the load is unevenly distributed.     

Bayesian estimation of unrestricted and order-restricted association models for a two-way contingency table

In two-way contingency tables analysis, a popular class of models for describing the structure of the association between the two categorical variables are the so-called “association” models. Such models assign scores to the classification variables which can be either fixed and prespecified or unknown parameters to be estimated. Under the row-column (RC) association model, both row and column scores are unknown parameters without any restriction concerning their ordinality. It is natural to impose order restrictions on the scores when the classification variables are ordinal. The Bayesian approach for the RC (unrestricted and restricted) model is adopted. MCMC methods are facilitated in order the parameters to be estimated. Furthermore, an alternative parametrization of the association models is proposed. This new parametrization simplifies computation in the MCMC procedure and leads to a natural parameter space for the order constrained model. The proposed methodology is illustrated via a popular dataset.     

Tracking While Zooming Using Affine Transfer and Multifocal Tensors

This paper presents algorithms for tracking unknown objects in the presence of zoom. Since prior models are unavailable, point and line matches in affine views are used to characterize the structure and to transfer a fixation point into new images in a sequence. Because any affine projection matrix is permitted, the intrinsic camera parameters such as focal length may change freely. Also, since the techniques do not require long feature tracks, a further desirable property is insensitivity to partial occlusion caused, for instance, by part of the object falling off the image plane while zooming in. If only point matches are available, a previous method based on factorization is applied. When also incorporating lines, the affine trifocal and quadrifocal tensors are used for tracking in monocular and stereo systems respectively. Methods for computing the tensors, minimizing algebraic error, are developed. In comparison with their projective counterparts, the affine tensors offer significant advantages in terms of computation time and convenience of parameterization, and the relations between the different tensors are shown to be much simpler. Successful tracking is demonstrated on several real image sequences.     

考虑探测效能的空空导弹分布式协同中制导律

本文以多枚空空导弹逆轨拦截高速运动目标为背景,提出了一种以协同探测为终端约束的分布式协同中制导律.通过对误差源和误差传递链路进行分析,建立了中末交班概率计算模型,基于虚拟导引点研究了协同视场拼接方法.在视线法向,针对位置协同和角度协同等约束条件,设计了基于高斯伪谱法的最优制导律.在视线方向,基于二阶多智能体一致性理论,设计了分布式时间协同制导律,构造李雅普诺夫泛函证明了该方法可使系统在有限时间达到稳定,并推导出了一致性时间上界.仿真结果表明该制导律可使多弹以各自期望的视线角同时到达指定交班区域,实现视场拼接、协同探测的需求,有效提高了中末交班概率.     

On the balanced truncation of LTV systems

This note furthers results on the balanced truncation of stable linear time-varying discrete-time systems. The main result contributes better error bounds than the currently available ones in certain model reduction scenarios; this is demonstrated in an example of a four-mass translational system. Also, this note gives new finite error bounds for the balanced truncation of stable eventually periodic models.     

Average consensus of continuous‐time multi‐agent systems with quantized communication

This paper focuses on the average consensus problem of first‐order and second‐order continuous‐time multi‐agent systems with logarithmic quantized information transmission. The balanced and strongly connected digraphs are utilized to characterize the interaction topologies between agents. Based on the state estimation, distributed state updating mechanisms are introduced for every agent such that all agents’ states achieve average consensus asymptotically. By means of differential inclusion theory, we discuss the existence and convergence property of the Krasovskii solutions to the closed‐loop system models. By designing the proper control gain parameters and quantizer accuracy, two sufficient conditions are established to guarantee the achievement of average consensus. Finally, two numerical simulations are provided to illustrate the effectiveness of theoretical results. Copyright © 2013 John Wiley & Sons, Ltd.     

数据流Eager传输:一种分布式流体系结构中的性能优化技术

分布式流体系结构扩展了分布式环境下的流计算模型,可在互联网上为大数据计算应用提供高效低成本的运行环境。互联网中较长的通信开销制约了计算性能。提出了一种数据流Eager传输的性能优化技术,以挖掘计算与通信之间的并行性,隐藏通信延迟。在分布式流体系结构原型系统中实现了该技术。实验结果表明,应用程序采用该优化技术之后的平均时间开销减少了19.58%,表明该优化技术能够显著提高应用的性能,具有良好的应用前景。     

具有可调参数的模型降阶新方法

本文提出了一种具有可调参数的模型简化新方法.此法从系统动态特性上揭示了简化模 型与原系统之间"类等效"的对应关系.由对系统主要频率响应数据的拟合(或最优化方法)确 定参数.降阶模型不仅保持高阶系统的稳态特性(低频特性)和稳定性,还能按设计者需要有 选择地保持原系统的其它主要性能(例如带宽、相对稳定性等)、保持其它任意频段的特性.最 后,文章给出实例.     

Stable Adaptive Fuzzy Control with TSK Fuzzy Friction Estimation for Linear Drive Systems

This paper considers the control of a linear drive system with friction and disturbance compensation. A stable adaptive controller integrated with fuzzy model-based friction estimation and switching-based disturbance compensation is proposed via Lyapunov stability theory. A TSK fuzzy model with local linear friction models is suggested for real-time estimation of its consequent local parameters. The parameters update law is derived based on linear parameterization. In order to compensate for the effects resulting from estimation error and disturbance, a robust switching law is incorporated in the overall stable adaptive control system. Extensive computer simulation results show that the proposed stable adaptive fuzzy control system has very good performances, and is potential for precision positioning and trajectory tracking control of linear drive systems.     

限制失真的网格参数化方法

针对当前网格参数化效率较低、映射失真较严重的问题，提出一种限制失真的网格参数化方法。首先，预处理原始网格模型。输入原3D网格模型，采用Half-Edge数据结构来重新组织网格并切割网格模型产生相应的切缝；构建Tutte映射把3D网格映射到一个2D凸多边形域，即构建2D网格模型。然后，进行限制失真的网格参数化计算。将Tutte映射后的2D网格模型作为限制失真计算的初始数据，建立相对于原3D模型网格的失真度量函数；求得该度量函数的最小值点，即为映射后的网格坐标集合；将映射后的网格作为限制失真映射的输入网格，设定迭代终止条件，循环迭代直至迭代结束，得到收敛的最优网格坐标；在计算映射失真度时，针对等距映射失真采用Dirichlet能量函数度量，针对共形映射失真采用尽可能等距（MIPS）能量函数度量；在求解映射失真度量函数的最小值点时采用代理函数法结合组合牛顿法的最优解方法。最终，实现了该方法并开发了一个原型系统。在原型系统中，分别设计了限制等距失真和限制共形失真的网格参数化实验，对程序执行时间和失真能量下降情况进行了统计和对比，提供了相应的纹理映射效果展示。实验数据表明，所提出的方法执行效率高、映射失真能量下降快，最优值收敛质量稳定；纹理映射时纹理着色均匀、布局紧致、线条均匀，符合实际应用的标准。     

Real-time load balancing scheduling algorithm for periodic simulation models

A scheduling algorithm is crucial for real-time simulations because it guarantees that each model meets its deadline. Traditional online real-time scheduling algorithms such as Earliest Deadline First (EDF) introduce a high overhead when scheduling a large number of models. In this paper, a new algorithm called time-stepped load balancing (TLS) is proposed to address the real-time execution of a model set in a time-stepped simulation. A load balancing schedule table is generated before a simulation and rebalanced at runtime to dynamically schedule the changed model set. This table is organized by the execution periods of the models and balanced according to the load of each time step. Moreover, the slack time is distributed evenly among the steps to improve the real-time reliability. An extension to the algorithm for a multi-core environment is further studied to address those models with long execution times. Experimental results show that our scheduling algorithm outperforms the classical EDF approach. The highest performance improvement of TLS over EDF reaches 3–4% in terms of saving processor resources, and the jitter is about 4 times less when 90 entities are employed in a typical tank combat simulation scenario.     

一种可实现高精度时间同步的数据传输方法

KM2A探测器阵列是高海拔宇宙线观测站(LHAASO)的主体探测器阵列之一,近7000个探测器平均分布在1.3 km 2的实验范围内。针对大面积分布式布局的高能物理实验中读出电子学系统的时间同步和数据传输问题,提出一种可实现高精度时间同步的数据传输方法。借助TCP/IP协议栈和White Rabbit时钟同步技术融合时钟网络与数据网络,TCP/IP协议栈在仅保留PC通信协议的基础上,无需增加额外硬件,即可实现高效可靠的数据传输和高精度时钟同步。测试结果表明,该方法可以实现探测器阵列内LHAASO KM2A读出电子学插件间时间同步精度优于1 ns,同时保证了数据传输的可靠性。     

An Analysis of the Effect of Network Parameters on the Performance of Distributed Database Systems

Performance analysis studies of distributed database systems in the past have assumed that the message transmission time between any two nodes of a network is constant. They disregard the effect of communication network parameters such as network traffic, network topology, and capacity of transmission channels. In this paper, an analytical model is used to estimate the delays in transmission channels of the long haul network supporting the distributed database system. The analysis shows that the constant transmission time assumption cannot be justified in many cases, and that the response time is sensitive to the parameters mentioned above. Extensions and performance analysis in the context of interconnection networks are also discussed.     

电力光缆网分布式综合量测统一平台开发研究

电力光纤通信作为电力系统的重要组成部分,其本身的可靠运行对整个电力系统安全稳定的生产运行有着重大的意义。与公用通信网络网相比,电力通信网络的可靠性要求更高。电力光缆通常与输配电线路共用同一线廊,如OPGW和OPPC中的光缆直接反映出线路的温度,应力等。结合影响电力光缆网的各种关键因素,介绍了主要监测参量的坚持原理,结合不同场景分析不同的监测方式,以综合监测平台为主线,提供了分布式综合量测平台开发的工程建设和开发思路,对监测结果进行归一化处理,并开发系统原型,在南方电网试点成功应用。     

High-quality and interactive animations of 3D time-varying vector fields

In this paper, we present an interactive texture-based method for visualizing three-dimensional unsteady vector fields. The visualization method uses a sparse and global representation of the flow, such that it does not suffer from the same perceptual issues as is the case for visualizing dense representations. The animation is made by injecting a collection of particles evenly distributed throughout the physical domain. These particles are then tracked along their path lines. At each time step, these particles are used as seed points to generate field lines using any vector field such as the velocity field or vorticity field. In this way, the animation shows the advection of particles while each frame in the animation shows the instantaneous vector field. In order to maintain a coherent particle density and to avoid clustering as time passes, we have developed a novel particle advection strategy which produces approximately evenly-spaced field lines at each time step. To improve rendering performance, we decouple the rendering stage from the preceding stages of the visualization method. This allows interactive exploration of multiple fields simultaneously, which sets the stage for a more complete analysis of the flow field. The final display is rendered using texture-based direct volume rendering     

Quaternion‐based visual servo control in the presence of camera calibration error

Visual servo control systems use information from images along with knowledge of the optic parameters (i.e. camera calibration) to position the camera relative to some viewed object. If there are inaccuracies in the camera calibration, then performance degradation and potentially unpredictable response from the visual servo control system may occur. Motivated by the desire to incorporate robustness to the camera calibration, different control methods have been developed. Previous adaptive/robust controllers (especially for six degree‐of‐freedom camera motion) rely heavily on properties of the rotation parameterization to formulate state estimates and a measurable closed‐loop error system. All of these results are based on the singular axis–angle parameterization. Motivated by the desire to express the rotation by a non‐singular parameterization, efforts in this paper address the question: Can state estimates and a measurable closed‐loop error system be crafted in terms of the quaternion parameterization when the camera calibration parameters are unknown? To answer this question, a contribution of this paper is the development of a robust controller and closed‐loop error system based on a new quaternion‐based estimate of the rotation error. A Lyapunov‐based analysis is provided which indicates that the controller yields asymptotic regulation of the rotation and translation error signals given a sufficient approximate of the camera calibration parameters. Simulation results are provided that illustrate the performance of the controller for a range of calibration uncertainty. Copyright © 2009 John Wiley & Sons, Ltd.     

A frequency weighted model order reduction technique and error bounds

A new frequency weighted technique for balanced model reduction is proposed. The proposed technique not only provides stable reduced order models for the case when both input and output weightings are included but also yields frequency response error bounds. The method is illustrated using numerical examples and the results are compared with other frequency weighted model reduction techniques.     

Ordering of simultaneous events in distributed DEVS simulation

Simultaneous events are the events scheduled to occur at the same simulation time. This paper proposes a new event ordering mechanism for handling simultaneous events of DEVS models in distributed simulation. The DEVS formalism provides a formal framework for specifying discrete event models in a modular, hierarchical form. Thus, the formalism can ease the model verification and validation problems of distributed simulation. Also, the formalism separates models from underlying simulation algorithms. Hence, DEVS models can be simulated in both sequential and distributed environments without any modification. One important issue for such framework is to obtain the same results in both simulation environments. However, in distributed simulation of DEVS models, the processing order of simultaneous events may affect the simulation results. Thus, some ordering mechanism of events is required for well-defined simulation results. The proposed mechanism orders simultaneous events correctly with respect to their causal relationships in distributed DEVS simulation. Also, the mechanism guarantees the same ordering of simultaneous events in both sequential and distributed simulation environments.