精确提取InSAR时间去相关分量的方法

提出了一种干涉合成孔径雷达(InSAR,Synthetic Aperture Radar Interferometry)回波信号时间去相关分析的新方法,该方法主要包括三个步骤:采用自适应区域增长算法(IDAN,Intensity-Driven Adaptive Neighborhood)估计所有干涉子集的相干性;利用迭代最小二乘去除估计量偏差;采用相干性分解技术对无偏样本相干性进行分离,获得精确的时间去相关分量.以美国南加州洛杉矶地区的ENVISAT ASAR数据集为例,对新方法和现有方法进行了比较研究.结果表明,新的融合算法能够获得更加可靠、精度更高的时间去相关分量,并具有非阈值和近乎完全的自适应性.本文的研究将有利于改善与时间相干性有关的地球物理参数反演,也有利于地表变化周期性和随时间变化的气候环境实时监测等.     

基于EOOPN的作战单元任务成功性评估仿真模型

师旅级作战单元是世界各国目前乃至将来应付一般的中小规模冲突的主要作战单位,建立其任务成功性评估模型,计算给定维修保障方案下师旅级作战单元任务成功概率,可以评价现有维修保障方案的保障效果,从而为师旅级作战单元执行任务前维修保障方案的制定和优化提供决策依据。在分析师旅级作战单元任务和构成特点的基础上,本文给出了一种扩展的面向对象Petri网(EOOPN)模型的定义和建模步骤,并利用它建立了师旅级作战单元任务成功性评估模型,最后将该模型应用于某防空旅某次任务想定,从而说明该模型的有效性和实用性。     

Locality constraints within multiscale model for non‐linear material behaviour

This paper presents a two‐scale approach for the mechanical and numerical modelling of materials with microstructure‐like concrete or fibre‐reinforced concrete in the non‐linear regime. It addresses applications, where the assumption of scale separation as the basis for classical homogenization methods does not hold. This occurs when the resolution of micro and macro scale does not differ ab initio or when evolving fluctuations in the macro‐fields are in the order of the micro scale during the loading progress. Typical examples are localization phenomena. The objective of the present study is to develop an efficient solution method exploiting the physically existing multiscale character of the problem. The proposed method belongs to the superposition‐based methods with local enrichment of the large‐scale solution ū by a small‐scale part u ′. The main focus of the present formulation is to allow for locality of the small‐scale solution within the large‐scale elements to achieve an efficient solution strategy. At the same time the small‐scale information exchange over the large‐scale element boundaries is facilitated while maintaining the accuracy of a refined complete solution. Thus, the emphasis lies on finding appropriate locality constraints for u ′. To illustrate the method the formulation is applied to a damage mechanics based material model for concrete‐like materials. Copyright © 2006 John Wiley & Sons, Ltd.     

景洪水电站右冲沙底孔坝段在爆破震动效应下的安全评价

利用ANSYS软件对景洪水电站右冲沙底孔坝段在爆破开挖条件下进行动、静分析,并将时程法引入到承载能力极限状态设计分析方法中,进行稳定验算.结果表明爆破地震效应对右冲沙底孔坝段的抗滑稳定有较大的影响,但不会危及坝段的整体稳定,并根据计算结果确定各个爆破开挖阶段控制点的安全控制振速.     

Rapid Prototyping with Constraints-based Scheduling for Multimedia Applications

With the increased demand in multimedia applications, the need to provide better system support is greater than ever. Multimedia applications have an added dimension of time in their execution which results in stringent timing requirements. Existing systems incorporate such stringent timing requirements either at the system-level or the application-level. System-level supports are typically operating-system-dependent whereas application-level supports are achieved by building timing controls into the application itself. This lengthens the application development time and fails to take full advantage of operating system's capabilities. In this paper, we propose a framework that resides between the system-level and application-level support. The framework consists of two layers: an interface layer that incorporates high-level end-to-end timing constraints, and a system layer that implements a host-end scheduling mechanism to support high-level end-to-end timing specifications. Two applications have been developed using this framework. The results indicate that the framework is able to support rapid-prototyping of multimedia applications with stringent timing requirements.     

Expressing and Enforcing Timing Constraints in a Dynamic Real-Time CORBA System

Distributed real-time applications have presented the need to extend the Object Management Group's Common Object Request Broker Architecture (CORBA) standard to support real-time. This paper describes a Dynamic Real-Time CORBA system, which supports the expression and enforcement of end-to-end timing constraints as an extension to a commercial CORBA system. The paper also describes performance tests that demonstrate the system's ability to enforce expressed timing constraints.     

A Smooth Path Tracking Algorithm for Wheeled Mobile Robots with Dynamic Constraints

In order to avoid wheel slippage or mechanical damage during the mobile robot navigation, it is necessary tosmoothly change driving velocity or direction of the mobile robot. This means that dynamic constraints of the mobile robotshould be considered in the design of path tracking algorithm. In the study, a path tracking problem is formulated asfollowing a virtual target vehicle which is assumed to move exactly along the path with specified velocity. The drivingvelocity control law is designed basing on bang-bang control considering the acceleration bounds of driving wheels. Thesteering control law is designed by combining the bang-bang control with an intermediate path called the landing curve whichguides the robot to smoothly land on the virtual target's tangential line. The curvature and convergence analyses providesufficient stability conditions for the proposed path tracking controller. A series of path tracking simulations and experimentsconducted for a two-wheel driven mobile robot show the validity of the proposed algorithm.     

On an assignment problem with side constraints

We describe a branch and bound algorithm for an assignment problem subject to a special set of side constraints. The problem has application in the design of tool carousels for certain flexible manufacturing systems. The resulting model represents a special case of the restricted facilities layout problem in which it is forbidden to locate any facility in certain zones. The bounds for the algorithm are generated by relaxing the side constraints and using the Hungarian method to solve the resulting assignment problem. Partitioning in a manner similar to subtour elimination for the travelling salesman problem leads to encouraging computational results.     

多媒体系统中的媒体时态关系表示

首先介绍已有的时态关系表示方法,并比较各时间模型的特点,在此基础上,结合多媒体开发实例提出媒体时态关系表示在多媒体应用程序制作过程中的应用。