Informatica

We present an analysis of the separation of concerns in multi-language design and multi-language specifications. The basis for our analysis is the paradigm of the multi-dimensional separation of concerns, which claims that multiple dimensions of concerns in a design should be implemented independently. Multi-language specifications are specifications where different concerns of a design are implemented using separate languages as follows. (1) Target language(s) implement domain functionality. (2) External (or scripting, meta-) language(s) implement generalisation of the repetitive design features, introduce variations, and integrate components into a design. We present case studies and experimental results for the application of the multi-language specifications in hardware design.

In the paper, we analyze the software that realizes the self-organizing maps: SOM-PAK, SOM-TOOLBOX, Viscovery SOMine, Nenet, and two academic systems. Most of the software may be found in the Internet. These are freeware, shareware or demo. The self-organizing maps assist in data clustering and analyzing data similarities. The software differs one from another in the realization and visualization capabilities. The data on coastal dunes and their vegetation in Finland are used for the experimental comparison of the graphical result presentation of the software. Similarities of the systems and their differences, advantages and imperfections are exposed.

This paper analyses the control of nonlinear plant with the changing dynamics. Adaptive controllers, based on fuzzy logics, are synthesized for the control of air pressure and water level. Their satisfactory efficiency is experimentally demonstrated under different working conditions. Fuzzy controllers are compared to conventional PI and PID controllers.

In this paper we consider non-deterministic finite Rabin–Scott's automata. We obtain some properties for the basis automaton, which is, like automaton of canonical form, an invariant of a given regular language. We obtain also a new algorithm of constructing the basis automaton for a given regular language.

Real life scheduling problems are solved by heuristics with parameters defined by experts, as usual. In this paper a new approach is proposed where the parameters of various heuristics and their random mixtures are optimized to reduce the average deviations from the global optimum.

In the paper two methods for data structure analysis and visualisation are presented: the simultaneous nonlinear mapping (Sammon, 1969) and the sequential one (Montvilas, 1995). These two methods were compared according ability to map the data on the plane, mapping accuracy and a mapping time. It was showed that the sequential nonlinear mapping has some bigger total mapping error but needs considerable less calculation time than that of the simultaneous one. Examples are given.

An adaptive control scheme for mechanical manipulators is proposed. The control loop essentially consists of a network for learning the robot's inverse dynamics and on-line generating the control signal. Some simulation results are provided to evaluate the design. A supervisor is used to improve the performances of the system during the adaptation transients. The supervisor exerts two supervisory actions. The first one consists basically of updating the free-design adaptive controller parameters so that the value of a quadratic loss function is maintained sufficiently small. Such a function involves past tracking errors and their predictions both on appropriate time horizons of low performances during the adaptation transients. The supervisor exerts two supervisory actions. The second supervisory action consists basically of a on-line adjustment of the sampling period within an interval centered in a nominal value of the sampling period. The sampling period is selected so that the transient of the tracking error is improved according to the simple intuitive rule of using a sampling rate faster as the tracking error changes faster.

Recently, Park and Lim (1998) proposed two key distribution systems for secure VSAT satellite communications. One provides indirect authentication, and another scheme enables that two parties can directly authenticate each other. However, this article will show that the proposed schemes are insecure enough by presenting two impersonation attacks on them. Besides, an improved scheme will be proposed, which is secure against the impersonation attack and provides direct mutual authentication between two parties.