Journal:Informatica
Volume 8, Issue 3 (1997), pp. 401–424
Abstract
This paper deals with the design problem of generalized linear controllers for linear systems with after-effect so that the resulting closed-loop system is globally uniformly asymptotically stable in the Lyapunov's sense. The controllers are universal in the sense that they include the usual delays (namely, point, distributed and mixed point-distributed delays) which can be finite, infinite or even time-varying. In Part I of the paper, some preliminary concepts and results on stabilizability are given.
Journal:Informatica
Volume 8, Issue 3 (1997), pp. 377–400
Abstract
In this paper we define a class of edge-weighted graphs having nonnegatively valued bisections. We show experimentally that complete such graphs with more than three vertices and also some special graphs with only positive edges can be applied to improve the existing lower bounds for a version of the quadratic assignment problem, namely with a matrix composed of rectilinear distances between points in the Euclidean space.
Journal:Informatica
Volume 8, Issue 3 (1997), pp. 367–376
Abstract
Queueing systems with a single device are well developed (see, for example, Borovkov, 1972; 1980). But there are only several works in the theory of multiphase queueing systems in heavy traffic (see Iglehart, Whitt, 1970b) and no proof of laws of the iterated logarithm for the probabilistic characteristics of multiphase queuing systems in heavy traffic. The law of the iterated logarithm for the waiting time of a customer is proved in the first part of the paper (see Minkevičius, 1995). In this work, theorems on laws of the iterated logarithm for the other main characteristics of multiphase queuing systems in heavy traffic (a summary queue length of customers, a queue length of customers, a waiting time of a customer) are proved.
Journal:Informatica
Volume 8, Issue 3 (1997), pp. 345–366
Abstract
Statistical properties are examined for a class of pipelined-block linear time-varying (LTV) and linear time-invariant (LTI) discrete-time systems. Pipelined-block equations are derived, using the general solution of LTV discrete-time system in state space. Afterwards, we analysed the state covariance and output covariance matrices of pipelined-block LTV and LTI discrete-time systems in state space. For this class of pipelined-block realizations expressions are found for calculation of characteristics of the roundoff noise. Finally, scaling in the pipelined LTV discrete-time systems in state space is considered.
Journal:Informatica
Volume 8, Issue 3 (1997), pp. 331–343
Abstract
Efficiency of one automatic estimation and c1usterization procedure of one-dimensional Gaussian mixture which combines EM algorithm with non-parametric estimation is considered. The paper is based on mathematical methods of statistical estimation of a mixture of Gaussian distributions presented by R. Rudzkis and M. Radavičius (1995). The main result of the implementation of the mathematical methods is completely automatic procedure which can start from no information about unknown parameters and finish with final mixture model (tested for adequacy).
Journal:Informatica
Volume 8, Issue 3 (1997), pp. 317–330
Abstract
Most efforts in business process reengineering to date are motivated by potential improvement in performance measures such as costs, quality of products or services, and cycle time for their delivery. While obviously important, these factors do not necessarily reflect any intrinsic improvement in how work is organized. This paper presents an approach to the structural analysis of business processes. The goal is to capture an inherent degree of synchronization of the various interdependent activities involved. This way, the process before and after reengineering, or alternative designs, can be compared without arbitrary scaling effects introduced by nonstructural variables. Our methodology for modeling and analysis incorporates established techniques in fuzzy logic and systems. Its application to a well-known example is used as illustration.
Journal:Informatica
Volume 8, Issue 2 (1997), pp. 289–309
Abstract
This paper addresses the application of convergence rules of gradient-type discrete algorithms to discrete adaptive control algorithms for linear time-invariant systems, which are based on Lyapunov's – like functions, in order to improve the transient performances based on fast adaptation. In particular, the adaptation covergence is increased as a generalized or filtered error increases through the application of Armijo rule for regulating the decrease of each Lyapunov's-like function on which the particular adaptation algorithm is based. The proposed scheme can be implemented with minor modifications in systems subject to unmodelled dynamics if some weak knowledge on such a dynamics is available consisting of upper-bounds of the dimension and norm of the unmodelled parameter vector.
Journal:Informatica
Volume 8, Issue 2 (1997), pp. 273–288
Abstract
In this paper, the following questions for computing coefficients of Fourier series are discussed: n-order Filon quadrature formula and its partial cases, some features of applying the Filon method in computing coefficients when the adaptive integration strategy is employed, the program implementation of 3-order and 5-order Filon quadrature formulas, using the adaptive integration strategy, and the experimental results of applying them in computing coefficients of Fourier series.
Journal:Informatica
Volume 8, Issue 2 (1997), pp. 265–272
Abstract
The paper discusses the peculiarities of the mono-channel normalized queueing system model with the nonstationary arrival rate of customers. To stabilize the output flow rate at the desirable level – the on-line control system of the service intensity has to be organized. This problem can be solved by means of the automatic control theory approach.