Invariance of the aperiodic property for polynomials with perturbedcoefficients

A procedure for obtaining the maximal intervals of the coefficients for a perturbed polynomial to be still strictly aperiodic is presented. Lemmas, theorems, and proofs are given. An illustrative example is presented     

Strict Hurwitz property of polynomials under coefficientperturbation

A simple procedure for computing the allowable interval coefficient perturbations of a strictly stable polynomial is presented. The amount of computations involved is very little, while the procedure is able to handle the case where the relative uncertainty of the polynomial coefficients are not known. It can also handle the case of linearly dependent parameter uncertainties. The procedure can also be modified to treat the case of simple nonlinear dependent parameter uncertainties. The details of the modified procedure will depend on the nature of the nonlinearity     

Aperiodic property of interval polynomials

An examination is made of the aperiodic property of interval polynomials. The authors also characterize the zero locations of aperiodic interval polynomials. Examples are given that clarify the points made     

Invariance of the strict Hurwitz property for polynomials with perturbed coefficients

Given a strictly Hurwitz polynomialf(lambda) = lambda^{n} + a_{n-1} lambda^{n-1} + a_{n-2}lambda^{n-2}+...+ a_{1}lambda + a_{0}, it is of interest to know how much the coefficients aican be perturbed while simultaneously preserving the strict Hurwitz property. For systems withn leq 4, maximal intervals of the aiare given in a recent paper by Guiver and Bose [1]. In this note, a theorem of Kharitonov is exploited to obtain a general result for polynomials of any degree.     

Convergence property of interval matrices and interval polynomials

In association with robust control-system design and analysis, the Hurwitz property of interval matrices and interval polynomials has recently been actively investigated. However, its discrete counterpart, the convergence property, has seemingly not been much discussed. In this paper, this property is studied in comparison with the Hurwitz counterpart. Some conditions under which interval matrices or interval polynomials are convergent are derived.     

Invariance of a strict Hurwitz property for uncertain polynomials with dependent coefficients

This note is concerned with the invariance of strict Hurwitz property for uncertain polynomials having dependent coefficients. A feasible test criterion is provided which reduces the conservatism of the Kharitonov theorem.     

Stability analysis of systems with aperiodic sample-and-hold devices

Motivated by the widespread use of networked and embedded control systems, improved stability conditions are derived for sampled-data feedback control systems with uncertainly time-varying sampling intervals. The results are derived by exploiting the passivity-type property of the operator arising in the input-delay approach to the system in addition to the gain of the operator, and are hence less conservative than existing ones.     

Sparse hierarchical regression with polynomials

Machine Learning - We present a novel method for sparse polynomial regression. We are interested in that degree r polynomial which depends on at most k inputs, counting at most $$\ell$$ monomial...     

Stability of polynomials with conic uncertainty

In this paper we describe a conic approach to the stability theory of uncertain polynomials. We present necessary and sufficient conditions for a conic setp ₀+K of polynomials to be Hurwitz stable (K is a convex cone of polynomials of degree n and degp ₀=n). As analytical tools we derive an edge theorem and Rantzer-type conditions for marginal stability (semistability). The results are applied to prove an extremal-ray result for conic sets whose cone of directions is given by an interval polynomial.The second author would like to thank the Deutsche Forschungsgemeinschaft (DFG) for its support during the writing of this paper.     

严格服务等级约定的区分Web服务技术研究

随着Internet的普及和Web应用的发展,满足客户不同业务需求成为人们关注的问题．该文基于业务类的访问资源需求和服务等级给出了一种资源划分策略,用来确定业务类在访问率波动较小条件下达到服务级别所需的资源;提出一种资源效用控制机制,用来适应访问的突发性和保证业务类服务等级要求．通过按周期进行资源划分,同时利用资源控制机制来适应周期内的访问突发,得到了严格服务等级约定的区分Web服务(简称SLADS)．文章通过建立原型与其它方法进行了实验比较,结果表明SLADS方法能够有效支持业务类的严格服务等级和提高资源利用率．     

严肃遇到傻瓜

导语“我是一个艺术家,既绘画,也玩黏土、玩偶、雕塑,甚至包装设计也做。虽分属不同领域,但它们都有一个关键点——包装。相信我,包装在当代的重要性已不亚于产品本身,甚至凌驾于它之上。香水就是个好例子,它只是有味道的液态水罢了,现代人之所以买它,很重要的一个原因是为其精美的包装或附送的礼品所诱惑。如今,甚至更有用黄金王冠作包装的香水……而我的工作,就是不用黄金,也能吸引你去购买。”     

Slack-based multiprocessor scheduling of aperiodic real-time tasks

We provide a constant time schedulability test and priority assignment algorithm for an on-line multiprocessor server handling aperiodic tasks. The so called Dhall’s effect is avoided by dividing tasks in two priority classes based on their utilization: heavy and light. The improvement in this paper is due to assigning priority of light tasks based on slack—not on deadlines. We prove that if the load on the multiprocessor stays below \((3 - \sqrt{5} )/2 \approx 38.197\%\), the server can accept an incoming aperiodic task and guarantee that the deadlines of all accepted tasks will be met. This is better than the current state-of-the-art algorithm where the priorities of light tasks are based on deadlines (the corresponding bound is in that case 35.425%).The bound \((3 - \sqrt{5} )/2\) can be improved if the number of processors m is known. There is a formula for the sharp bound \(U_{\mathit{threshold}}(m) = \frac{3m - 2 - \sqrt{5m^{2} - 8m + 4}}{2(m - 1)}\), which converges to \((3 - \sqrt{5} )/2\) from above as m→∞. For m≥3, the bound is higher (i.e., better) than the corresponding sharp bound for the state-of-the-art algorithm where the priorities of light tasks are based on deadlines.A simulation study also indicates that when m>3 the best effort behavior of the priority assignment scheme suggested here is better than that of the traditional scheme where priorities are based on deadlines.     

Supervisory control for fault-tolerant scheduling of real-time multiprocessor systems with aperiodic tasks

Supervisory control theory is a well-established theoretical framework for feedback control of discrete event systems whose behaviours are described by automata and formal languages. In this article, we propose a formal constructive method for optimal fault-tolerant scheduling of real-time multiprocessor systems based on supervisory control theory. In particular, we consider a fault-tolerant and schedulable language which is an achievable set of event sequences meeting given deadlines of accepted aperiodic tasks in the presence of processor faults. Such a language eventually provides information on whether a scheduler (i.e., supervisor) should accept or reject a newly arrived aperiodic task. Moreover, we present a systematic way of computing a largest fault-tolerant and schedulable language which is optimal in that it contains all achievable deadline-meeting sequences.     

Damping margins of polynomials with perturbed coefficients

Considers the polynomial P(s)=t₀ Sⁿ+t₁ S^n-1 +···+t_n where 0<a _j⩽t_j⩽b_j. Recently, V.L. Kharitonov (1978) derived a necessary and sufficient condition for this polynomial to have only zeros in the open left-half plane. Two lemmas are derived to investigate the existence of theorems similar to the theorem of Kharitonov. Using these lemmas, the theorem of Kharitonov is generalized for P(s) to have only zeros within a sector in the complex plane. The aperiodic case is also considered     

Computations with quasiseparable polynomials and matrices

In this paper, we survey several recent results that highlight an interplay between a relatively new class of quasiseparable matrices and univariate polynomials. Quasiseparable matrices generalize two classical matrix classes, Jacobi (tridiagonal) matrices and unitary Hessenberg matrices that are known to correspond to real orthogonal polynomials and Szegö polynomials, respectively. The latter two polynomial families arise in a wide variety of applications, and their short recurrence relations are the basis for a number of efficient algorithms. For historical reasons, algorithm development is more advanced for real orthogonal polynomials. Recent variations of these algorithms tend to be valid only for the Szegö polynomials; they are analogues and not generalizations of the original algorithms.     

Damping ratio of polynomials with perturbed coefficients

Let a family of polynomials be P(s)=t ₀Sⁿ+t₁s ^n-1 . . .+t_n where O<α _j⩽t_j⩽β. Recently, C.B. Soh and C.S. Berger have shown that a necessary and sufficient condition for this equation to have a damping ratio of φ is that the 2ⁿ⁺¹ polynomials in it which have t_k=α_k or t_k=β_k have a damping ratio of φ. The authors derive a more powerful result requiring only eight polynomials to be Hurwitz for the equation to have a damping ratio of φ using Kharitonov's theorem for complex polynomials     

Scheduling aperiodic tasks in dynamic priority systems

In this paper we present five new on-line algorithms for servicing soft aperiodic requests in realtime systems, where a set of hard periodic tasks is scheduled using the Earliest Deadline First (EDF) algorithm. All the proposed solutions can achieve full processor utilization and enhance aperiodic responsiveness, still guaranteeing the execution of the periodic tasks. Operation of the algorithms, performance, schedulability analysis, and implementation complexity are discussed and compared with classical alternative solutions, such as background and polling service. Extensive simulations show that algorithms with contained run-time overhead present nearly optimal responsiveness.A valuable contribution of this work is to provide the real-time system designer with a wide range of practical solutions which allow to balance efficiency against implementation complexity.     

Strict completion of Logic Programs

The paper presents a new approach to the problem of completeness of the SLDNF-resolution. We propose a different reference theory that we call strict completion. This new concept of completion (comp^*(P)) is based on a program transformation that given any program transforms it into a strict one (with the same computational behaviour) and the usual notion of program completion. We consider it a reasonable reference theory to discuss program semantics and completeness results. The standard 2-valued logic is used. The new comp^*(P) is always consistent and the completeness of all allowed programs and goals w.r.t. comp^*(P) is proved.     

CAN总线中非周期信息的随机动态优先级调度

针对CAN总线中非周期信息传输的“死锁”现象,利用动态优先级提升机制中消息在发送队列的位置随等待时间动态改变的思想,对非周期性信息的传输采用基于随机数的动态优先级调度策略,以解决CAN总线中非周期信息传输的“死锁”问题。