基于PolyTrans的IGES文件简化

CAD软件与基于多边形的3D软件之间数据转换需求不断增加,但是CAD模型复杂度和精细度却越来越高,数据转换的难度变大.为了解决这一难题,结合PolyTrans,分析如何解决一般3D软件难以导入大型的IGES(Initial Graphics Exchange Specifi-cation)文件的问题.从PolyTrans模型简化模块的理论依据着手,研究如何控制多边形的数量、降低文件的复杂性和减少文件的数量,使大型CAD装配模型能顺利地以单个实体形式导入Lightwave、3DS MAX以及Maya类的3D软件.并结合具体科研项目,给出了模型优化前后各指标参数对比情况.     

Robust Stabilization Over Communication Channels in the Presence of Unstructured Uncertainty

This technical note is concerned with the problem of controlling plants over communication channels, where the plant is subject to two types of unstructured uncertainty: additive uncertainty and stable coprime factor uncertainty. Necessary lower bounds on the rate of transmission (or channel capacity) C, for robust stabilization, are computed explicitly. In particular, it is shown that the lower bound in the additive uncertainty case corresponds to a fixed point of a particular function. In the stable coprime factor uncertainty case, the derivation relies on linear fractional transformation concepts. The results are important in determining the minimum channel capacity needed in order to stabilize plants subject to unstructured uncertainty over communication channels. For instance, the bounds obtained can be used to analyze the effect of uncertainty on the channel capacity. An illustrative example is provided.     

Applying eco-visualisations of different interface formats to evoke sustainable behaviours towards household water saving

The shortage of water resources is a global issue. This study attempts to utilise eco-visualisation interface design to affect users’ water-usage behaviour. Three interface proposals were designed in this study: numeric, water droplet (abstract symbol), and swimming fish (animated image). These three different interface formats range from abstract to figurative and from neutral to affective. A total of 93 subjects were divided into three groups and randomly performed designated dishwashing tasks twice. One of the tasks was completed without the assistance of any interface, whereas the other involved applying one of the three interface formats with eco-visualisations. In this study, the Self-Assessment Manikin scales, the System Usability Scale, and the Questionnaires for User Interaction Satisfaction were used to measure the emotional dimensions and perceived usability and to record the differences in water usage volume. The results indicated that the emotional valence evoked by the animated image interface was significantly higher than that by the numeric interface. The effect of the numeric interface formats on the subjects focused on emotional arousal, whereas other interfaces emphasised emotional valence. With the aid of the eco-visualisations of interface design, the evoked emotional response and enhanced usability could help improve sustainable behaviours towards water saving.     

Topology optimization based on level set for a flexible multibody system modeled via ANCF

A topology optimization methodology is proposed for the flexible multibody system undergoing both large overall motion and large deformation. The system of concern is modeled via the absolute nodal coordinate formulation. The equivalent static load method is employed to transform the topology optimization of the nonlinear dynamic response of the system into a static one, and evaluated to adapt to the absolute nodal coordinate formulation by splitting the elastic deformations of the flexible components from the overall motions of those components. During the static topology optimization, the material interface is implicitly described as the zero level set of a higher-dimensional scalar function. Then, the semi-implicit level set method with the additive operator splitting algorithm is employed to solve the corresponding Hamilton-Jacobi partial differential equation. In addition, the expert evaluation method of weights based on the grey theory is utilized to define the objective function, and a modified augmented Lagrange multiplier method is proposed to treat the inequality volume constraint so as to avoid the oscillation and drift of the volume. Finally, two numerical examples are provided to validate the proposed methodology.     

Multi-objective and multi-case reliability-based design optimization for tailor rolled blank (TRB) structures

Structural and Multidisciplinary Optimization - Light weight and crashworthiness signify two main challenges facing in vehicle industry, which often conflict with each other. In order to achieve...     

Reachability determination in acyclic Petri nets by cell enumeration approach

Reachability is one of the most important behavioral properties of Petri nets. We propose in this paper a novel approach for solving the fundamental equation in the reachability analysis of acyclic Petri nets, which has been known to be NP-complete. More specifically, by adopting a revised version of the cell enumeration method for an arrangement of hyperplanes in discrete geometry, we develop an efficient solution scheme to identify firing count vector solution(s) to the fundamental equation on a bounded integer set, with a complexity bound of O((nu)^n−m), where n is the number of transitions, m is the number of places and u is the upper bound of the number of firings for all individual transitions.     

Optimization for limited angle tomography in medical image processing

This paper aims to reduce the problems of incomplete data in computed tomography, which happens frequently in medical image process and analysis, e.g., when the high-density region of objects can only be penetrated by X-rays at a limited angular range. As the projection data are available only in an angular range, the incomplete data problem can be attributed to the limited angle problem, which is an ill-posed inverse problem. Image reconstruction based on total variation (TV) reduces the problem and gives better performance on edge-preserving reconstruction; however, the artificial parameter can only be determined through considerable experimentation. In this paper, an effective TV objective function is proposed to reduce the inverse problem in the limited angle tomography. This novel objective function provides a robust and effective reconstruction without any artificial parameter in the iterative processes, using the TV as a multiplicative constraint. The results demonstrate that this reconstruction strategy outperforms some previous ones.     

增强战斗力的有效途径:虚拟战争

在军事领域中,随着军事斗争的复杂性的不断增加,人们一直在寻求一种能在实验条件下“预先实践战争”的方法,来深入地研究未来战争的规律。现代科学技术的飞速发展,使得人们这一愿望得以实现。在虚拟现实技术基础上发展起来的“虚拟战争”方法,正是研究增强军队战斗力的有效途径。本文对这一课题作了概要的阐述。     

Control theoretic smoothing splines

Some of the relationships between optimal control and statistics are examined. We produce generalized, smoothing splines by solving an optimal control problem for linear control systems, minimizing the L²-norm of the control signal, while driving the scalar output of the control system close to given, prespecified interpolation points. We then prove a convergence result for the smoothing splines, using results from the theory of numerical quadrature. Finally, we show, in simulations, that our approach works in practice as well as in theory