The modelling of the heat conduction in electrical cables is a complex mathematical problem. To get a quantitative description of the thermo‐electrical characteristics in the electrical cables, one requires a mathematical model for it. It must involve the different physical phenomena occurring in the electrical cables, i.e. heat conduction, convection and radiation effects, description of heat sources due to current transitions. Since the space in mobile systems is limited and weight is always reduced, wire conductor sizes must be kept as small as possible. Thus the main aim is to determine optimal conductor cross‐sections for long standing loads. In this paper we develop and validate a set of mathematical models and numerical algorithms for the heat transfer simulation in cable bundles. The numerical algorithms are targeted to the two‐dimensional transient heat transfer mathematical models. Finally, a validation procedure for the coefficient validation of the differential equations is carried out. Results of numerical experiments are presented.
Investigation of the relationship between stroke area size and patient status implies evaluation of the stroke area location, volume and shape. Computed tomography (CT) examination became very popular in such type of investigations due to its moderate price and less discomfort for patient in comparison with other techniques. We propose an algorithm for segmented CT images post‐processing, which consists of several stages: filtering of CT slices, smoothing and extension of stroke region boundary, filling of stroke space, and computing of stroke volume via all slices. Post‐processing of several CT images using this technique showed that all accidental points can be filtered successfully and therefore the aim of ischémie stroke area determination can be reached. We are convinced that the quality of initial information (results of stroke area segmentation) plays a crucial role for later image processing.
We present the simple and fast symmetry plain detection algorithm, that recognizes Falx cerebri curve on each human brain computed thomogrpahy slice. Symmetry curves appear approximately on 30% images and using such images as reference it is possible to determine symmetry plane. We propose an algorithm based on hybrid methods, that allows detect symmetry plane with deviation angle until 25 0. The method is based on fuzzy logic that selects region of interest and symmetry curves. Direct pixels selection with evaluation of symmetry curve properties are used to calculate symmetry plane with high speed.
In this paper we propose new heuristic numerical algorithm for determination of the optimal wires diameters in electrical cables. Two multilevel parallel versions of the optimization algorithm are constructed. The first algorithm is based on master-slave technique and the second algorithm uses the data-parallel strategy. Multilevel structure of the algorithms gives a possibility to adapt them to parallel architecture, for example, cluster of multicore computers. Some results of numerical experiments are presented which agree well with theoretical analysis.
Darbe nagrinėjamas sunkiojo nespūdžiojo skysčio tekėjimo uždavinys, kai dalis paviršiaus yra laisva. Skaitiškai sprendžiant tokius uždavinius svarbiausios dviproblemos. Pirmoji—netiesinio Navjė-Stokso uždavinio diskrečioji aproksimacija srityje su fiksuotu paviršiumi, o antroji problema—judančių paviršių skaitinis aproksimavimas. Darbe suformuluoti trys algoritmai pagrindiniam uždaviniui spręsti. Pirmajame panaudota konstruktyvi Puchnačiovo diferencialinio uždavinio sprendinio egzistencijos įrodymo schema. Šiuo metodu iteracinio proceso metu netiesinis Navjė-Stokso uždavinys sprendžiamas fiksuotoje erdvės srityje ir tikslinamas laisvasis srities paviršius. Tai išskaido uždavinį į du paprastesnius uždavinius, kurių kiekvieno sprendimas yra pakankamai nuodugniai išnagrinėtas literatūroje. Tiriama Puchnačiovo metodo konvergavimo sritis. Antrasis algoritmas gaunamas sprendžiant linearizuotą nestacionarų Navjė-Stokso uždavinį, t.y. nereikalaujame, kad kiekvienoje išorinėje iteracijoje netiesinė diskrečioji Navjė-Stokso sistema būtu tiksliai išspredžiama. Šio algoritmo vienos iteracijos realizacija yra efektyvesnė, lyginant su pirmuoju algoritmu, tačiau iteracijų skaičius didesnis. Abiejų pirmųjų algoritmų konvergavimas gali būti naudojamas diferencialinio uždavinio sprendinio stabilumo tyrimui. Trečiajame algoritme realizuota Niutono metodo modifikacija. Šiame algoritme nėra atskiriamos NavjėStokso ir laisvojo paviršiaus lygtys. Gautoji netiesinių lygčių sistema sprendžiama Gauso-Zeidelio metodu. Svarbus skaičiavimo eksperimento uždavinys—palyginti visų trijų algoritmų konvergavimo sritis.
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