Sliding mode control for two-time scale systems: stability issues

The paper presents some results on global exponential stability of linear time invariant systems with different time scales. The full system is decomposed in two reduced ones by means of singular perturbations and a smooth approximation of a Variable Structure Control is synthesized for each of them using Reaching Law approach. The global closed loop stability is then proved for the whole system using Lyapunov methods and a particular state space decomposition. Moreover a literal form for ε∗ (a parameter which measures the minimum separation between time scales) is derived.     

A flight control system for aerial robots: algorithms and experiments

This paper presents a hierarchical flight control system for unmanned aerial vehicles. The proposed system executes high-level mission objectives by progressively substantiating them into machine-level commands. The acquired information from various sensors is propagated back to the higher layers for reactive decision making. Each vehicle is connected via standardized wireless communication protocol for scalable multi-agent coordination. The proposed system has been successfully implemented on a number of small helicopters and validated in various applications. Results from waypoint navigation, a probabilistic pursuit-evasion game and vision-based target tracking demonstrate the potential of the proposed approach toward intelligent flying robots.     

Stochastic stabilization of differential systems with general decay rate

Some sufficient conditions concerning stability of solutions of stochastic differential evolution equations with general decay rate are first proved. Then, these results are interpreted as suitable stabilization ones for deterministic and stochastic systems. Also, they permit us to construct appropriate linear stabilizers in some particular situations.     

ISO 9000 versus CMM: Standardization and certification of IS development

A growing number of software developers use standards as a basis for their quality systems. Some of them go one step further and have their quality systems certified. In this paper, two well-known quality standards, ISO 9000 and the CMM, are compared. It is concluded that both standards are useful but there is a growing need for more specific standards.     

Modeling users through an expert system and a neural network

With the number of Internet and Web users increasing rapidly, electronic service providers are competing to satisfy and better serve customers looking for information or channels of advertisement. A wide variety of browses, specialized sites, custom made software, etc. are being offered on a regular basis. However, the user has to filter through a large number of files before finding what he/she is really looking for. This paper presents a user modeling expert system, SIGMA, based on neural networks for encapsulating Internet and Web users' habits and preferences. SIGMA is an artificial intelligence application designed to answer an Internet client needs and preferences. It analyses the user supplied demographic data and the monitored transactions then generate a tailored profile that is ultimately used to filter what information is being passed on to him/her in an effort to reduce and hopefully eliminate the time and energy expended in sifting through raw and often unwanted data.     

A modular algorithm for resource allocation

This paper concerns resource allocation in distributed message passing systems, i.e., the scheduling of accesses to exclusive system resources shared among concurrent processes. An efficient modular resource allocation algorithm is presented that uses any arbitrary resource allocation algorithm as a subroutine. It improves the performance of the subroutine by letting each process wait only for its currently conflicting processes, and therefore, allows more concurrency. For appropriate choices of the subroutine, we obtain resource allocation algorithms with the minimum worst case response times. Simulation studies were conducted which also indicate that on average, the obtained algorithms perform faster and require a smaller number of messages than other previously known algorithms, especially when resource contention among processes is high and the average time that a process remains in the critical region is large. Received: May 1997 / Accepted: May 1998     

复杂电力系统灾变防治的综合集成方法论

电网的大规模互联成为世界范围内电力系统发展的必然趋势。现代电力系统的强非线性和高维等复杂特性,使得传统的理论分析方法已不能较好地分析复杂电网的动态行为及由电网连锁反应故障造成的大面积停电事故的成因。作为科学的方法论,综合集成方法论综合了计算机网络技术、数据融合技术、知识与信息及专家群体智能的各方面优势,其应用在研究方式和工作方式上都突破了传统还原论思想的束缚。从复杂性科学的角度,介绍了复杂电力系统的特征,并着重论述了应用研究复杂系统的方法论——从定性到定量综合集成方法进行电力系统灾变防治研究的方法。     

A contribution to the development of strategic control and planning instruments: An acquisition case study

The present paper is part of the efforts made by the authors in recent years to develop strategic control and planning instruments in corporations using OR‐techniques like system dynamics, control theory, and group multicriteria decision aid. A more general framework called ‘adaptive control methodology’ (ACM) combines all these techniques. It has been presented in several papers. The objective of the present analysis is to calibrate this instrument and to tune it to the corporate needs by analysing real‐world applications. More specifically, several case studies have been investigated in large multinational organisations in the food sector. An acquisition case has been used for the calibration purpose. It is analysed in the paper from the ACM perspective to provide additional material for revisiting and improving the methodology.     

谈现代小说中人力车夫形象

通过《一件小事》、《薄奠》和《骆驼祥子》三部作品中的比较分析,从“人力车夫”这一都市劳动人民的主人公形象,我们可以看到其工人阶级的友爱精神和高尚品质,同时,要清醒认识到在旧制度下劳动者的悲剧命运是无法避免的。