Informatica

This paper presents the set of verification rules to detect faults in specification of model of computerized information system. Computerized information system model is specified using Enterprise modeling approach, which integrates static and dynamic dependencies. Typical communication action loop is a basic construct of Enterprise modeling approach. Actions, which process data resources of computerized information system, are analyzed.

In this paper our attention is focused on the study of the properties for some families of contextual languages with catenation (see Fortiş, 1999, also Păun, 1982; Păun, 1997). Also, we are defining and analyzing some new properties characteristic to these families of languages. Using these properties we are able to establish some necessary conditions, and some pumping properties for families of contextual languages with catenation.

Filtering of feature matches is heuristic method aimed to reduce the number of feasible matches and is widely employed in different image registration algorithms based on local features. In this paper we propose to interpret the filtering process as an optimal classification of the matches into the correct or incorrect match classes. The statistics, according to which the filtering is performed, uses differences of the geometrical invariants obtained from ordered sets of local features (composite features) of proper cardinality. Further, we examine some computationally efficient implementation schemes of the classification. Under the assumption of Gaussian measurement error, the conditional distribution densities of invariants can be approximated by well-known linearization approach. Experimental evidences obtained from fingerprint identification, which confirm viability of the proposed approach, are presented.

The article presents results of the national survey on teaching and studying informatics at Grades 11 and 12 in the Lithuanian secondary school. This study explores the influence of different factors on students' achievements in informatics. The purpose of this work is to study the interaction between various characteristics of student, teacher and school, and factors of studying and teaching informatics and their joint influence on students' achievements in informatics. In addition, the article explores and contrasts the casual influence structures on the students' knowledge of two different branches of informatics: computer application and programming. To explore these interrelations, PLSpath analytic procedure has been used.

The sequential nonlinear mapping is suitable for sequential detection of states of dynamic systems (Montvilas, 1999a). In addition, it can indicate the undesirable states and even the damages of dynamic systems. The last is complicated when the damage is caused by a small changing of respective parameter describing the state. In the paper the problem of nonlinear mapping to be sensitive for the small changing of parameters and the problem related with dimensionality of parameters are solved by using a special pre-processing of data. Examples are given.

The aim of the given paper is development of a joint input-output approach and its comparison with a direct one in the case of an additive correlated noise acting on the output of the system (Fig. 1), when the prediction error method is applied to solve the closed-loop identification problem by processing observations. In the case of the known regulator, the two-stage method, which belongs to the ordinary joint input-output approach, reduces to the one-stage method. In such a case, the open-loop system could be easily determined after some extended rational transfer function (25) is identified, including the transfer functions of the regulator and of the open-loop system, respectively, as additional terms. In the case of the unknown regulator, the estimate of the extended transfer function (27) is used to generate an auxiliary input. The form of an additive noise filter (36), that guarantees the minimal value of the mean square criterion (35), is determined. The results of numerical simulation and identification of the closed-loop system (Fig. 5) by computer, using the two-stage method and the direct approach are given (Figures 6–12, Table 1).

This paper describes a preliminary algorithm performing epilepsy prediction by means of visual perception tests and digital electroencephalograph data analysis. Special machine learning algorithm and signal processing method are used. The algorithm is tested on real data of epileptic and healthy persons that are treated in Kaunas Medical University Clinics, Lithuania. The detailed examination of results shows that computerized visual perception testing and automated data analysis could be used for brain damages diagnosing.

Peyravian and Zunic (2000) proposed a password transmission scheme and a password change scheme over an insecure network. Their proposed solutions do not require the use of any symmetric-key or public-key cryptosystems. However, this article points out that their schemes have several security flaws for practical applications. A slight improvement on their schemes is proposed in this paper to remove the security flaws.

One of speech synthesis main problems is synthesis of unvoiced fricatives. One of our previously stated conclusions is that consonant x is influenced by before and behind existing phonetic elements. The aim of experiments described in this paper is to evaluate influence of different x allophones for speech intelligibility and automatic speech recognition.