Self-Bounded Controlled Invariant Subspaces in Model Following by Output Feedback: Minimal-Order Solution for Nonminimum-Phase Systems

Self-bounded controlled invariant subspaces are shown to play a crucial role in the synthesis of minimal-order dynamic regulators achieving model following by output feedback with stability. The approach, completely embedded in the geometric context, provides insight into the internal eigenstructure of the minimal self-bounded invariant subspace, thus leading to an effective treatment of nonminimum-phase systems.     

An O(n 3 L) adaptive path following algorithm for a linear complementarity problem

In this paper we propose an O(n ³ L) algorithm which is a modification of the path following algorithm [8] for a linear complementarity problem. The path following algorithm has to take a short step size in each iteration in order to bound the number of overall arithmetic operations by O(n ³ L). In practical computation, we can determine the step size adaptively. Mizuno, Yoshise, and Kikuchi [11] reported that such an adaptive algorithm required about O(L) iterations for some test problems. Here we show that we can use a rank one update technique in the adaptive algorithm so that the number of overall arithmetic operations is theoretically bounded by O(n ³ L).Research supported in part by the U.S. Army Research Office through the Mathematical Sciences Institute of Cornell University.Research supported in part by NSF grants ECS-8602534 and DMS-8904406 and ONR contract N-00014-87-K0212.     

基于阈值分割的并行压缩鬼成像方法

为了提高鬼成像的速度,提出了基于阈值分割的并行压缩差分鬼成像方法。首先通过设置合理的阈值筛选出涨落较为明显的数据进行采样;然后再通过并行分块降低图像维度,提高整体运算速度;最后通过压缩感知重构算法重构图像。通过对图"BUAA"的半物理仿真以及透射物体"光"的实验结果表明,与普通的二阶赝热光关联成像相比,该方法能以更少的采样次数和运行时间重构图像,可提升成像信噪比。     

基于协同爬猴群算法的传感器优化布置方法研究

基于协同进化的思想,提出了一种用于传感器优化布置的协同爬猴群算法。采用双重编码的方式,克服了原猴群算法只能解决连续变量优化问题的缺陷。在爬过程中引入采用猴群的整体行为来影响猴子搜索方向的聚群行为,以及利用全局最优猴子的位置来影响猴子搜索方向的追尾行为,通过对两种行为进行合理选择,有效提高了爬过程的搜索效率与速度。最后以大连国贸大厦为例,进行了参数敏感性分析以及传感器优化布置方案的选择,结果表明协同爬猴群算法的搜索效率较原猴群算法有大幅提高,能较好地解决传感器优化布置问题。     

Leader-following consensus control for networked multi-teleoperator systems with interval time-varying communication delays

We study the leader-following consensus stability and stabilization of networked multi-teleoperator systems with interval time-varying communication delays. With the construction of a suitable Lyapunov-Krasovskii functional and the utilization of the reciprocally convex approach, novel delay-dependent consensus stability and stabilization conditions for the systems are established in terms of linear matrix inequalities, which can easily be solved by various effective optimization algorithms. One illustrative example is given to illustrate the effectiveness of the proposed methods.     

Efficient implementation of x-ray ghost imaging based on a modified compressive sensing algorithm

Towards efficient implementation of x-ray ghost imaging (XGI), efficient data acquisition and fast image reconstruction together with high image quality are preferred. In view of radiation dose resulted from the incident x-rays, fewer measurements with sufficient signal-to-noise ratio (SNR) are always anticipated. Available methods based on linear and compressive sensing algorithms cannot meet all the requirements simultaneously. In this paper, a method based on a modified compressive sensing algorithm with conjugate gradient descent method (CGDGI) is developed to solve the problems encountered in available XGI methods. Simulation and experiments demonstrate the practicability of CGDGI-based method for the efficient implementation of XGI. The image reconstruction time of sub-second implicates that the proposed method has the potential for real-time XGI.     

基于交互式并行驾驶模拟实验的跟驰状态汽车驾驶倾向性动态辨识模型验证方法

驾驶倾向性的实时识别是实现汽车辅助驾驶尤其是主动安全预警系统智能化的关键理论和技术.通过交互式并行模拟驾驶实验获取跟驰状态下各倾向性类型的行车数据对建立的驾驶员倾向性的动态辨识模型进行验证,并将验证结果与心理问卷测试的结果相对比.结果表明所建辨识模型可行,能够实现对跟驰状态下驾驶员倾向性类型的实时识别,为个性化汽车主动安全系统的实现提供理论基础.     

实验研究探测器大小与散焦长度对无透镜鬼衍射的影响

无透镜鬼衍射是一种特殊的非局域关联成像技术,通过对包含物体信息的测试光路和不含物体信息的参考光路的光场强度涨落关联进行测量,在参考光路上可得到物体的衍射图样。利用赝热光源实验研究了探测器尺寸大小和光路散焦长度对无透镜鬼衍射质量的影响。实验以四缝物体为例,定量研究了探测器大小和散焦是如何改变无透镜鬼衍射的成像结果,并和理论模拟进行了比较,获得了比较一致的结果。利用图像相关度定量分析了实验结果与理想无透镜鬼衍射图像的差别,发现这两者都会使无透镜鬼衍射的质量变差。     

Modified Ghost Fluid Method as Applied to Fluid-Plate Interaction

The modified ghost fluid method (MGFM) provides a robust and efficient interface treatment for various multi-medium flow simulations and some particular fluid-structure interaction (FSI) simulations. However, this methodology for one specific class of FSI problems, where the structure is plate, remains to be developed. This work is devoted to extending the MGFM to treat compressible fluid coupled with a thin elastic plate. In order to take into account the influence of simultaneous interaction at the interface, a fluid-plate coupling system is constructed at each time step and solved approximately to predict the interfacial states. Then, ghost fluid states and plate load can be defined by utilizing the obtained interfacial states. A type of acceleration strategy in the coupling process is presented to pursue higher efficiency. Several one-dimensional examples are used to highlight the utility of this method over loosely-coupled method and validate the acceleration techniques. Especially, this method is applied to compute the underwater explosions (UNDEX) near thin elastic plates. Evolution of strong shock impacting on the thin elastic plate and dynamic response of the plate are investigated. Numerical results disclose that this methodology for treatment of the fluid-plate coupling indeed works conveniently and accurately for different structural flexibilities and is capable of efficiently simulating the processes of UNDEX with the employment of the acceleration strategy.     

虚拟流体方法的显隐算法

基于算子分裂,把欧拉方程分裂成对流项和非对流项两部分,建立一种基于原始变量的二阶显隐算法.由通常的虚拟流体方法显式地预估流场,用隐式的压力修正对预估解进行修正.计算结果表明,这样可以有效增大时间步长,提高计算效率.