Journal:Informatica
Volume 17, Issue 3 (2006), pp. 407–426
Abstract
Several best effort schemes (next-hop routing) are used to transport the data in the Internet. Some of them do not perform flexible route computations to cope up with the network dynamics. With the recent trends in programmable networks, mobile agent technology seems to support more flexible, adaptable and distributed mechanism for routing. In this paper, we propose a Mobile Agent based Routing (MAR) scheme with the objectives similar to Routing Information Protocol (RIP). A comparative study of both the schemes (MAR and RIP) in terms of communication overheads, convergence time, network bandwidth utilization and average session delays is presented. The results demonstrate that the MAR scheme performs better than RIP. MAR has comparatively less communication overheads and convergence time and also offers more flexibility and adaptability as compared to RIP. In addition, this paper also presents a MAR based network load balancing.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 393–406
Abstract
In this work labeling of planar graphs is taken up which involves labeling the p vertices, the q edges and the f internal faces such that the weights of the faces form an arithmetic progression with common difference d. If d=0, then the planar graph is said to have an Inner Magic labeling; and if d≠0, then it is Inner Antimagic labeling. Some new kinds of graphs have been developed which have been derived from Wheels by adding vertices in a certain way and it is proposed to give new names to these graphs namely Flower-1 and Flower-2. This paper presents the algorithms to obtain the Inner Magic and Inner Antimagic labeling for Wheels and the Inner Antimagic labeling for Flower-1 and Flower-2. The results thus found show much regularity in the labelings obtained.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 381–392
Abstract
This paper discusses the determination of the spare inventory level for a multiechelon repairable item inventory system, which has several bases and a central depot with emergency lateral transshipment capability. Previous research is extended by removing a restrictive assumption on the repair time distribution. A mathematical model that allows a general repair time distribution, as well as an algorithm to find a solution of the model, is developed. Thus, the main focus of this study is to improve the accuracy of previous models and to estimate the gain in accuracy from use of the current methodology. Computational experiments are performed to estimate the accuracy improvement and to determine the managerial implications of the results.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 363–380
Abstract
The Augmented Representation of Cultural Objects (ARCO) system provides software and interface tools to museum curators to develop virtual museum exhibitions, as well as a virtual environment for museum visitors over the World Wide Web or in informative kiosks. The main purpose of the system is to offer an enhanced educative and entertaining experience to virtual museum visitors. In order to assess the usability of the system, two approaches have been employed: a questionnaire based survey and a Cognitive Walkthrough session. Both approaches employed expert evaluators, such as domain experts and usability experts. The result of this study shows a fair performance of the followed approach, as regards the consumed time, financial and other resources, as a great deal of usability problems has been uncovered and many aspects of the system have been investigated. The knowledge gathered aims at creating a conceptual framework for diagnose usability problems in systems in the area of Virtual Cultural Heritage.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 347–362
Abstract
This paper introduces a new concept of convertible user designating confirmer partially blind signature, in which only the designated confirmer (designated by the user) and the user can verify and confirm the validity of given signatures and convert given signatures into publicly verifiable ones. We give a formal definition for it and propose a concrete provably secure scheme with a proof of security and a brief analysis of efficiency. Assuming the intractabilities of the Discrete Logarithm Problem and the ROS-Problem, the proposed scheme is unforgeable under adaptive chosen-message attack.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 325–346
Abstract
The paper proposes a methodology for evaluation of specification language functionality characteristics. It describes background of the proposed methodology, discusses the methodology in detail, and shortly describes experimental results obtained using the proposed methodology to evaluate the functionality of Z and UML languages.
Journal:Informatica
Volume 17, Issue 3 (2006), pp. 309–324
Abstract
Three parallel algorithms for solving the 3D problem with nonlocal boundary condition are considered. The forward and backward Euler finite-difference schemes, and LOD scheme are typical representatives of three general classes of parallel algorithms used to solve multidimensional parabolic initial-boundary value problems. All algorithms are modified to take into account additional nonlocal boundary condition. The algorithms are implemented using the parallel array object tool ParSol, then a parallel algorithm follows semi-automatically from the serial one. Results of computational experiments are presented and the accuracy and efficiency of the presented parallel algorithms are tested.
Journal:Informatica
Volume 17, Issue 2 (2006), pp. 297–304
Abstract
The paper addresses the problem of discrimination of homographs when a lengthy segment of an uttered word is missing. The considered discrimination procedure is done by recognizer that operates on cepstrum coefficients extracted from the speech signal. For restoration of the missing speech segment rather than use of the known speech signal, it has been proposed to calculate speech signal characteristics: the period of fundamental frequency and intensity. By experimentation it has been shown that the polynomial approximation of speech signal characteristics improves homograph discrimination results. An extra computational burden associated with the proposed method is not high because it involves recalculation of the already extracted Fourier coefficients.
Journal:Informatica
Volume 17, Issue 2 (2006), pp. 279–296
Abstract
Given a set of objects with profits (any, even negative, numbers) assigned not only to separate objects but also to pairs of them, the unconstrained binary quadratic optimization problem consists in finding a subset of objects for which the overall profit is maximized. In this paper, an iterated tabu search algorithm for solving this problem is proposed. Computational results for problem instances of size up to 7000 variables (objects) are reported and comparisons with other up-to-date heuristic methods are provided.
Journal:Informatica
Volume 17, Issue 2 (2006), pp. 259–278
Abstract
The objective is to investigate two emerging information technologies in graduate studies and scientific cooperation. Internet is the first technology. The open source is the second. They help each other in many ways. We investigate the joint influence of both.
Results of complexity theory show the limitations of exact analysis. That explains popularity of heuristic algorithms. It is well known that efficiency of heuristics depends on the parameters. Thus we need some automatic procedures for tuning the heuristics. That helps comparing results of different heuristics. This enhance their efficiency, too.
An initial presentation of the basic ideas is in (Mockus, 2000). Preliminary results of distance graduate studies are in (Mockus, 2006a). Examples of optimization of sequential statistical decisions are in (Mockus, 2006b).
In this paper the theory and applications of Bayesian Heuristic Approach are discussed. In the next paper examples of Bayesian Approach to automated tuning of heuristics will be regarded. The examples of traditional methods of optimization including applications of linear and dynamic programming will be investigated in the last paper. These papers represents three parts of the same work. However each part can be read independently.
All the algorithms are implemented as platform independent Java applets or servlets. Readers can easily verify and apply the results for studies and for real life optimization models.
The information is on the main web-site http://pilis.if.ktu.lt/∼jmockus and four mirrors.