doc. Ing. Vítězslav Pankrác, CSc.

Hyperthermia is already well established in cancer treatment as a sensitizer to radiotherapy and chemotherapy. It is based on heating of tumor area to temperatures between 41 and 45◦C. Usually it is induced by electromagnetic or ultrasound waves. In both cases selective heating of the treated area is accomplished by superposition of fields and is due to physical and technical limitations a challenging task. A very promising concept for preferential heating of the tumor area is based on accumulation of magnetic nanoparticles in the tumor and heating them with time-harmonic magnetic fields. In this work we use 1 ml sample of four different magnetic nanoparticles with different cores and coatings dispersed in PBS and deionized water. The individual samples were exposed to a time-harmonic magnetic field and the sample temperature was monitored throughout the exposure. The concentration of nanoparticles in the samples was chosen to correspond to realistic values that may be present in biological tissues without being toxic. For this purpose, we designed and manufactured an exposure system operating at 200 kHz. The exposure time was set to 5 minutes and the amplitude of the applied magnetic field intensity was up to 5 kA ·m− 1. The temperature was monitored by an optical thermometer. Temperature measurements indicated the possibility to exert effective increase of temperature during the time period indicated in samples with nanoparticles dispersed in deionized water. In this paper we will introduce the exposure system as well as some results.

The analysis of magnetic field of a thin-wall air induction coil with a shape of finite cylinder of arbitrary cross section is described. The result of the analysis is a method for finding the scalar magnetic potential of the coil with the help of mutual inductance of the coil and the elementary loop. The magnetic flux density of the coil is found as the gradient of the scalar magnetic potential. The proposed analysis is verified using two examples, which are thin-wall air coils with a shape of finite cylinder of circular and rectangular cross sections. The magnetic flux density calculated by the presented method is compared with other approaches for both examples with excellent agreement.

Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections.WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.

This paper describes the method by which it is possible to construct simple algorithms for the calculation of the axial and transverse components of the intensity of the magnetic field of current loops and thin-wall air coils (solenoids). These are planar loops and tightly wound coils with a cross-section of an arbitrary shape and parallel walls in an axial direction. Computational algorithms show the same formal structure for every shape of coil; the shape of the coils is defined by the special shape function. The method is based on the superposition of the magnetic field of the equivalent magnetic dipoles. Utilization of this method can be observed, for example, in the calculation of the magnetic field of a cylindrical current loop and a thin cylindrical coil, for which the resulting relations are compared with a familiar method of calculation, on which solving equations for the vector potential is based. The method of calculation described can also be equally effectively used for coils of a non-circular shape. In this study, for the purpose of illustration, simple algorithms are created for the calculation of the magnetic field of a rectangular coil and the calculated values of the magnetic field are compared with the actual measurements.

The general method of calculation described in this paper is applicable to the calculation of the self and mutual inductance of thin-walled solenoids of general shape with parallel axes in both coaxial and non-coaxial relative positions. The method is based on the solution of integral equation, the validity of which is defined in the text and additionally the physical interpretation of each section of the equation is documented. The manner of utilization of the method is demonstrated for the cases known in systems with a circular solenoid and subsequently applied to the case of two solenoids of rectangular shape in a general relative position. In these cases a similarly detailed algorithm is compiled and the measurements are then compared with the calculation results.

The commonly known mathematical formulas for calculating the mutual inductance of thin coaxial cylindrical coils (thin wall solenoids) in air can be modified and generalized so that they are also applicable for the relatively simple and versatile calculation of the mutual inductance of thin non-coaxial coils with parallel axes. This is a geometric arrangement whereby one coil is circular cylindrical and the other can be of any requisite shape (e.g. square, rectangular). This manner of calculation is demonstrated in this article using as an example two thin wall solenoids and also for a situation in which one coil is circular cylindrical and the second is rectangular. Detailed algorithms have been developed for both these situations, which can serve for the creation of a computer programme.

Článek popisuje základní často používané aplikace tlumivek v silnoproudé elektrotechnice podle jejich rozčlenění v ĆSN EN 60289 -Tlumivky

This paper focuses on the calculation of the deformation forces when short-circuit occurs in chokes. The aim was to describe the mechanism generating deformation forces and determine the possible resistance of the equipment. The computer program for rapid and accurate calculation of this problem was presented.

V článku je měřením na modelech charakteristických tvarů ověřena správnost prezentované metody pro výpočet vlastních a vzájemných indukčností koaxiálních válcových vzduchových cívek..

Článek popisuje ověřenou metodu pro přesný výpočet vlastních a vzájemných indukčností koaxiálních válcových vzduchových cívek libovolných rozměrů v obecné vzájemné poloze a předkládá vytvořený počítačový program pro řešení této úlohy.

Článek obsahuje porovnání základních druhů konstrukčního uspořádání tlumivek s ohledem na tvar magnetického obvodu a vinutí s přihlédnutím k výběru tlumivek pro různé aplikace.

This paper report on a modeling of three Phase AC Reactors by means of an Inductance-Substitution Circuit. This model is helpful in analyzing of the behavior of real reactors in distribution system and applications. Short-circuit current and short-circuit forces between the three adjacent coils of reactor in case of a line-to-ground and line-to-line fault was computed and presented. The model of the reactor is based on the system of differential equations and makes a computation of transient currents and forces possible. The method of virtual work to determine short-circuit forces was used.

V článku je popsáno použití nástrojů CAD/CAM pro výuku na katedře elektromagnetického pole FEL ČVUT v Praze. Katedra disponuje několika softwarovými produkty, které jsou v současné době považovány za nejvyspělejší a jsou schopny simulovat komplexně elektromagnetické problémy. Nejdůležitější simulátory jsou zde popsány současně s jejich pedagogickým využitím.

Paper presents several results of the study and experimental verification of a shielding effectiveness of relatively small metallic enclosures, which operate above the first resonance. There is no standard for measurement and therefore different aspects of measurement and methodology are discussed. Relative size, volume, quality factor of the enclosure, position, radiator type, reciprocity etc. are discussed.

The paper describes a novel kind of miniature fractal microstrip patch antenna based on the Inverted koch Square fractal. Tuning possibilities were extended by using the J-probe with more degrees of freedom compared to a conventional L-probe. A parametric study was performed using a full-wave simulator IE3D.

Normalized site attenuation testing (NSA) is the process to evaluate the quality of test site for EMC testing. The standard EMC measurement uses the NSA in the frequency range 30 MHz - 1 GHz. It is supposed the use of higher frequencies for EMC measurement in a near future, where the measurement of wall reflections is usually recommended for site testing. Experiences based on the measurement of NSA, the antennas and its calibration (antenna factor), polarization and geometry of measurement and parasitic influence of floor reflections are mentioned in the paper. Problems of EMC test sites are also discussed with pedagogical aspects from point of view Electromagnetic Field Theory and its simulation tools.

The article describes an application and the results of new site-qualificatioin technique suitable for frequencies above 1 GHz.

V příspěvku je diskutována současná úloha výuky elektromagnetismu na elektrotechnických fakultách. Je zmíněno použití elektromagnetických simulátorů ve výuce a popsán praktický struktorovaný příklad výuky na popisu vyzařování liniového zářiče.

This paper present several results of the study and experimental verification of a shielding effectiveness of relatively small metallic enclosures, which operates above the first resonance. Different aspects of measurement and methodology are discussed - including relative size, volume, quality factor of the enclosure, position and radiator type, reciprocity measurement etc.

V článku je popsáno zařízení pro automatizované měření velikosti a prostorového rozložení stejnosměrných a nízkofrekvenčních magnetických polí. Měřící systém je určen pro měření v prostoru o rozměrech 300x300x600 mm, jeho hlavní součástí je motorový pohon s třemi krokovými motory. Pohon je řízen jednotkou napojenou přes rozhraní RS 232 na počítač PC. Motorový pohon posouvá ramenem, na kterém je umístěna třídimenzionální Hallova sonda. V článku je také popsán modul pro sběr naměřených hodnot, který obsahuje tříkanálový přístrojový zesilovač s AD převodníkem. Je zde popsána i konstrukce 3D Hallovy sondy pro stejnosměrná a nízkofrekvenční měření.

This paper summarizes particular results achieved while working on Interactive Course in Electromagnetic Field Theory on the Internet project, which received funding for 2003 from the "Fond rozvoje vysokých škol" under grant no. FRV2449/2003. The aim of the project is to create and to present on the faculty server an interactive course in electromagnetic field theory. Students can gain practical experience and improve their knowledge of the subject. The final aim is to improve students' ability to solve general problems in electromagnetic field theory, which forms the basis of all branches of electrical engineering.