Informatica

Despite the vast and rich panorama of hypertext research, to date there are still no clear definitions of what hypertext really is. Classical references describe the concept “hypertext” as a non-linear way of thinking, reading, and accessing the information which is best done on the computer screen. This paper shows the present situation where hypertext is seen as the interaction between the learner and an information source; it raises questions about how information should be organised so as to promote better learning. Due to the fact that the present empirical results still show no consensus among hypertext researchers about the different representations of educational hypertexts; this paper will bring together three perspectives, in particular traditional, pedagogical and psychological points of view, in order to obtain a coherent view of the current situation in hypertext research. The traditional perspective will outline two main problems that seem endemic to hypertext: problems of navigation and cognitive overload. The pedagogical perspective will summarise the main ideas of three possible theoretical justifications of existing educational hypertexts: the ideas of concept mapping, cognitive flexibility theory, and semantic networking. The psychological perspective will evaluate hypertext from the perspective of human factors (or ergonomics).

A multiple criteria decision support system has been developed and implemented on the personal computer. Three interactive methods of increasing complexity are realized. The main applications of the system were in the scope of decisions on the best energy development strategy for Lithuania.

A development of algorithms and writing of programs are considered as closely related but not identical parts of computer programming. Some differences between them are important for learning of computer programming, in particular, in distance learning. These differences are identified and discussed from the pedagogical point of view. The arguments for the selection of pedagogical based and cost-effective delivery modes in the case of distance learning are investigated. Practical examples supporting theoretical arguments are given on the activities of Lithuanian schools.

Stochastic programming problems with simple recourse belong to problems depending on a random element only through the corresponding probability measure. Consequently, this probability measure can be treated as a parameter of the problem.

The problem of the classification, description by the difference equations and possible models of quasihomogeneous autoregressive random fields, existing in one-dimensional space R¹, is considered. The properties of the quasihomogeneous areas as well as of the parameters changing by not the jumps areas of such fields are considered also. The quasihomogeneous areas determination algorithm is proposed.

The input–output relationship of the periodically time-varying (PTV) systems, impulse response of the PTV state–space system, and the transfer function of the PTV system are presented. A coefficient sensitivity is investigated by using a virtual PTV state-space system in which periodically time-varying coefficients are stochastically varied.

In the presented paper a method for treating a random signal bearing an information about the behaviour of a technological process is given. The main goal of the given method is to remove possible failures arising in analog sensors, which yield nonstationary behaviour of an observed signal. Then the smoothed signal is tested by a suitable test described in the paper for the regular or irregular behaviour of a technological process. One understands by the regular behaviour of a technological process that within prescribed bounds.

We consider here the average deviation as the most important objective when designing numerical techniques and algorithms. We call that a Bayesian approach.

We consider here the optimization problems of simple competitive model. There are two servers providing the some service. Each server fix the price and the rate of service. The rate of service defines the customer losses waiting in line for the service. The customer go to the server with lesser total service cost. The total cost includes the service price plus waiting losses. A customer goes away, if the total cost exceeds some critical level. The flow of customers and the service time both are stochastic. There is no known analytical solution for this model. We get the results by Monte Carlo simulation. We get the analytical solution of the simplyfied model.

An essentially new method for discrete sequential detection of abrupt or slow multiple changes in several unknown properties of random processes is considered. The method is based on a sequential nonlinear mapping into two-dimensional vectors of many-dimensional vectors of parameters which describe the properties of random process. The mapping error function is chosen and the expressions for sequential nonlinear mapping are presented along with some experimental results. Theoretical minimum amount of at the very beginning simultaneously mapped vectors is obtained.