Journal:Informatica
Volume 3, Issue 2 (1992), pp. 256–274
Abstract
The results of investigation of the resource management in radar search are presented in the paper. The time for search of manoeuvring targets is minimized by optimal distribution of radar power among the space directions and by optimization of search parameters.
The problem of the optimal control of radar search is extremely complicated in the general case and in real situations, therefore we have compared only some strategies (e.g., one stage cyclic strategy, various multistage strategies).
In some simple cases (e.g., motionless targets) optimal parameters of multistage strategies maybe found but in the general case the efficiency of strategies may be evaluated with the help of statistical simulation. The simulation time was essentially reduced by some simplifications of models, by the forecast of discrete coordinates of the targets and by the use of averaged values.
The usage of the proposed strategies enables us to reduce the time of search by 2–3 times. Those strategies may be executed in real time.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 247–255
Abstract
The problem we are dealing with is following. There exist certain number of nodes η, transmitting messages at random time moments. If time interval between messages transmitted by different nodes are less than some given value, a collision occurs. We can fix the collision, but we cannot determine the nodes engaged in the collision. The hierarchical decomposition of the nodes is used to resolve the collision. At every hierarchical level, a subset of nodes “suspected” as participating in the collision is divided in a certain number of groups. There is a time period given to every group, at which messages can be transmitted. This proceeds while no more collisions occurs. This paper covers the problems of selecting a number of groups, to minimize the longest collision resolution time, as well as average collision resolution time.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 241–246
Abstract
The Freudian psychoanalysis in its modern form assumes that activities of a patient depend on his physical and mental state (“energy”), and result in maintaining his life, in useless waste of his energy (“symptoms”), and in (“useful”) contribution to the society and to patient's energy level.
Another contribution to patient's energy level comes from the society. It comprises life amenities, medication, and “education”. Patient's mental state is characterized by two parameters, “symbolic” and “imaginary”. Both parameters affect the outcome of patient activities, and are affected by contributions to his “energy”.
A mathematical description of this model as a dynamical system is presented. Significance of obtained solutions for psychoanalysis is discussed.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 225–240
Abstract
In this paper, we present two heuristics for solving the unconstrained quadratic 0–1 programming problem. First heuristic realizes the steepest ascent from the centre of the hypercube, while the second constructs a series of solutions and chooses the best of them. In order to evaluate their worst-case behaviour We define the performance ratio K which uses the objective function value at the reference point x=1/2. We show for both heuristics that K is bounded by 1 from above and this bound is sharp. Finally, we report on the results of a computational study with proposed and local improvement heuristics.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 198–224
Abstract
A random walk dan be used to model various types of discrete random processes. It may be of interest at some point to find the peak of this function. A direct method of doing so involves evaluating the function at every point and recording the highest value. However, it may be desirable to find the peak without having, to evaluate the function at every point. A search technique was developed to find the peak of a random walk with a minimal number of function evaluations using probabilistic means to guess at where the peak will most likely occur given the parameters of a specific function. A computer program was written to implement the search strategy and a series-of random walk functions of varying lengths were generated to test its performance. Data was compiled and the results show that the search is capable of finding the peak with a significant reduction in the number of function evaluations needed for a point by point search, especially for functions of greater walk length.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 173–197
Abstract
Finite-difference algorithm for solving convection-diffusion equation with small coefficient at Laplace operator is developed. It is based on equivalent partial differential equation approach. Both linear and nonlinear equations are considered and appropriate finite-difference schemes are proposed. Some analysis of their properties is conducted. The computational efficiency of this algorithm is studied using various test problems. Some results on numerical simulation of capillary isotachophoresis is presented.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 159–172
Abstract
This paper is devoted to the investigation of difference schemes for the solution of an important free-surface problem: modelling of a liquid-metal contact. The existence of a solution and the convergence of proposed iterative processes are investigated in a weak sense, using the alternative form of the problem as a nonlinear constrained minimization problem.
Journal:Informatica
Volume 3, Issue 2 (1992), pp. 141–158
Abstract
Difference methods in velocity-pressure variables having a number of important properties are constructed and investigated in this paper for a two-dimensional Navier-Stokes equation. Power neutral approximations of convective members and pressure gradients ensure a conservativity and absolute stability of the proposed algorithms. Their stability and convergence are investigated. The existence and uniqueness of velocity components and pressure gradients is proved.