The paper presents the results of numerical solution of the evolution law for the constrained mean-curvature flow. This law originates in the theory of phase transitions for crystalline materials and describes the evolution of closed embedded curves with constant enclosed area. It is reformulated by means of the direct method into the system of degenerate parabolic partial differential equations for the curve parametrization. This system is solved numerically and several computational studies are presented as well.
The paper presents the results of numerical solution of the Allen-Cahn equation with a non-local term. This equation originally mentioned by Rubinstein and Sternberg in 1992 is related to the mean-curvature flow with the constraint of constant volume enclosed by the evolving curve. We study this motion approximately by the mentioned PDE, generalize the problem by including anisotropy and discuss the computational results obtained.
We deal with numerical computation of the nonlinear partial differential equations (PDEs) of Black-Scholes type which incorporate the effect of transaction costs. Our proposed technique surmounts the difficulty of infinite domains and unbounded values of the solutions. Numerical implementation shows the validity of our scheme.
The article introduces a new technique for nonlinear system modeling. This approach, in comparison to its alternatives, is straight and computationally undemanding. The article employs the fact that once a nonlinear problem is modeled by a piecewise-linear model, it can be solved by many efficient techniques. Thus, the result of introduced technique provides a set of linear equations. Each of the equations is valid in some region of state space and together, they approximate the whole nonlinear problem. The technique is comprehensively described and its advantages are demonstrated on an example.
A simple, vector-based graphics editor, designed for experimental data presentation, schematics, large structured chemical formulae etc. in a modest IBM PC, MS DOS environment is described. Its applications in semiautomatic image analysis, especially ¡n the implementation of design-based stereological methods for estimating global geometrical characteristics of studied samples and in 3D volume reconstruction from serial sections are discussed.
Experimentally based models of cardiac cells have been developed since 1960.The early models were based on extension of the Hodgkin-Huxley nerve impulse equations. Including only a few membrane currents they were able to successfully reconstruct the depolarization and repolarization of cellular membrane. Since that time, the models have underwent extensive modifications and reached a high degree of physiological detail. This short review is aimed to outline the history of their development and show the importance of computer modelling for the research in cardiac cell electrophysiology. and Obsahuje seznam literatury
The paper investigates ways to model the response of vibro-isolation mounts that utilise viscoelastic materials. Simple models based on linear and nonlinear static stiffness are developed. Dynamic response is approximated through appropriate scaling of the viscoelastic Young's modululs and use of the measured material loss factor. The approach is validated using cylindrical mounts made of polyurethane. The response of a 68 kg mass supported by two mounts and subjected to two different high-amplitude shock loads is predicted. Measured and predicted behaviour correlate closely for the nonlinear model while the linear model gives a reasonable representation. It is noted that the sensitivity of such mounts to temperature is high: the change in response associated with a temperature excursion of 10 °C is significantly greater than the inaccuracy involved with using the linear model. and Obsahuje seznam literatury
This work presents a numerical solution for the process of mixing gaseous fuels with air in the combustion chamber of an engine. The combustion parameters are influenced to a considerable degree by the characteristics of the mixture before its ignition. These characteristics can be influenced by the process of formation of the fuel and air mixture. Under certain simplified circumstances this process can be reproduced by means of commercially available software, and the results generated can be used
for the optimisation of the engine performance. and Obsahuje seznam literatury
The aim of this contribution was to review the possibilities of presentation of orthogonal ECG signals and to evaluate the progress in computerized electrocardiography achieved in Czechoslovakia. The information about the cardiac electric field in orthogonal electrocardiography is defined and consequently displayed as a fixed single dipole (vector). The spatial trajectory of vector end-point (spatial vectorcardiographic loop) can be presented in different ways — as orthogonal electrocardiogram, polarcardiogram, planar vectorcardiogram and decartogram, respectively. The advantages of particular methods of presentation, as well as their limitations are discussed. Computer-assisted electrocardiography was introduced in Czechoslovakia in 1974. The original AVA program has been further developed in the Research Institute of Medical Informatics (formerly Research Institute of Medical Bionics). The currently developed system CardioSys allows the utilization of all the possibilities of orthogonal ECG and vectorcardiographic presentation for clinical and epidemiological cardiology as well as for the research.