R. Martavicius

SIE Method of Analysing Microwave Fields of a 3D Heart Model

The Singular Integral Equations Method (SIE) used in this article allowed us to solve Maxwells Equations for a Three-Dimensional (3D) asymmetric heart model when a microwave catheter (MC) was placed inside the model and radiated microwaves. Here we explain the main idea of our SIE method. We first separated the solution of equations from satisfying the boundary conditions. For this purpose, we found the solution of the differential equations having a point source. This fundamental solution is used in our integral representation of a problem. The integral representation automatically satisfied the differential equations but has an unknown density function which must be found from the boundary conditions. The solution of the differential equations, obtained by our SIE method, was rigorous, that is it satisfied the differential equations and all boundary conditions. The false roots did not occur when applying our SIE method.All surfaces of the heart model were defined as a triangular mesh covering the 3Dheart surfaces. The heart model consisted of cardiac muscle and the right and left atriums with ventricles which were filled with blood. In this article we presented our calculations of the microwave electric field inside of a heart model. We have seen that our SIE method enabled one to optimal the size and shape of a MC when used to remove abnormal tissue in a heart model. We discovered that the electric field distribution most suitable for microwave ablation was a curved microwave catheter pressed against the lateral surface of heart atrium.

Analyses of the gyroelectric plasma rod waveguide

Semiconductor rod waveguides are widely used in the large variety of devices [1]. Scientists and engineers have been investigating circular cylindrical waveguides for many years due to their excellent electrodynamical characteristics (e.g. a large broadbandwidth) and the wide possibilities for their implementation in microwave and optoelectronic devices as well as solid-state electronics. Here we present an electrodynamical analysis of the n-InSb semiconductor rod waveguide. The waveguide radius is r = 1.5 mm and the electron concentration of the semiconductor n-InSb is N = 1019 m−3 [2, 3]. We have admitted that electrophysical parameters of n-InSb are the following: the relative permittivity of lattice εL = 17.8, an effective mass m* = 0.014 mel, the mobility of the electrons µel = 60 m2/(V·s). The magnetic induction B0 of the external constant magnetic field is equal to 0.9T. We present here the dispersion characteristics and the electric field distributions of modes propagating in the n-InSb waveguide.

Influence Coefficients of Constructive Parameters of Meander Slow-Wave System with Additional Shields

Abstract Constructions of meander slow-wave systems with additional shields grounded at different positions are presented. The construction of meander slow-wave systems with additional shields grounded at both edges is investigated in detail. The influence of the main constructive parameters on the electrical characteristics of meander slow-wave systems with additional shields grounded at both edges is evaluated. The main constructive parameters of the investigated system are: the length of the conductor, the width of meander conductor, the width of additional shield, and the width of the gap between adjacent meander conductors. Sonnet® software package, which is based on the method of moments, has been used during the investigation. The results of the influence of constructive parameters to the phase delay time, input impedance, and the width of pass-band of the system are discussed.

An Electrodynamical Analysis of a Model Heart

Presents a numerical analysis of an electrodynamical problem. The problem was solved by using our Singular Integral Equations’ Method. We formulated the problem in this way. A metal microwave catheter (antenna) was placed inside of a three dimensional asymmetric model heart. The catheter radiated a microwave with a frequency of 10 GHz. The model heart was limited by a noncoordinate shape surface. The model heart consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood and the walls of the heart consisted of myocardium tissue. In this article we analysed four model electrodynamical problems that could be used in medical microwave ablation. Several different dependences of electric field distributions were investigated at different locations and shapes of microwave catheters at two cross-sections of the heart. Our calculations showed that the electric field distribution was best suited for the ablation when we used a curved catheter that touched the inner wall of the heart. Ill. 6, bibl. 11 (in Lithuanian; summaries in Lithuanian, English, Russian).

Analysis of the compression ratio and quality in aerial images

Abstract In modern photomap systems, images are stored in centralized storage. Choosing a proper compression format for the storage of an aerial image is an important problem. This paper analyses aerial image compression in popular compression formats. For the comparison of compression formats, an image quality evaluation algorithm based on the calculation of the mean exponent error value is proposed. An image quality evaluation experiment is presented. The distribution of errors in aerial images and explanation of the causes for worse than usual compression effect are analysed. An integrated solution for the aerial image compression problem is proposed and the compression format most suitable for aerial images is specified.

Electric field distributions in the cross-sections of the SiC hollow-core waveguides

The SiC material can be used in wide area of applications. Silicon is the material that dominates in the electronics industry today. A change of technology from silicon to silicon carbide is going to revolutionize the power electronics. So the SiC power devices are beginning to be commercialized nowadays [1]. Hollow-core (HC) waveguides have excellent properties. For instance, HC waveguides can be used for high power lasers, no end reflections and small beam divergence [2]. We have investigated a hollow-core cylindrical SiC waveguide. The investigations were made at different temperatures. The permittivity of the SiC material depends on the temperature. The values of temperatures were taken from [3]. We have calculated the dispersion characteristics and the electric field distributions of the hollow-core SiC waveguide with radius r = 1 mm. It should be accented that all our calculations were made taking into account waveguide material losses.

Image Wavelet Transform for PCB Soldering's Quality Evaluation

An integration degree of modern printed circuit boards (PCB) is continually increasing. One of the important stages in the manufacturing of electronic devices is component soldering onto PCB pads. The soldering process is affected by many factors, which may lead to the formation of undesirable soldering defects. Some kinds of defects including bridge defects are detected visually. In the current article the possibility of bridge defect detection in a multi-pin surface mount component PCB images using wavelet transform is analyzed.