Papers by Keyword: Electromagnetic Field (EMF)

Abstract: Microwave heating was discovered more than 60 years ago. And nowadays, it became popular for the use as domestic ovens. Microwave has also been utilized for the industrial processes, such as drying and roasting. On the other hand, there have been many applications of microwave, being investigated for materials' processing and environmental technologies. They are attempted to take advantage of some specific characteristics in microwave heating, which differs from that of the conventional one. Rapid heating, internal heating, selective heating are the features to be taken into consideration. Moreover, so-called "non-thermal effect" is the additional feature in which researchers are particularly interested. In this article, it is intended to describe fundamental aspects in microwave heating and introduce some selected topics of research projects performed in our research group. They include researches on fabrication of some functional materials and on handling industrial wastes etc. In this article, it is also intended to interpret the phenomena observed in these applications from the fundamental view points of electromagnetic wave interaction with materials.

Abstract: The issues of structural changes produced in ceramic materials on the basis of Al₂O₃ and ZrO₂(Y₂O₃) during thermomagnetic processing (B=0.02–1 T) are considered. The contribution of the electromagnetic field to the linear shrinkage of processed ceramic samples has been estimated to be 1–6%. The possibility of using the thermomagnetic processing method for obtaining the disperse and homogeneous structure has been shown. The technological modes of processing under the electromagnetic field are suggested, facilitating self-cleaning and perfecting the crystalline structures of Al₂O₃ and ZrO₂(Y₂O₃), including annealing in the temperature range of 800–1200 °C within 8–12 hours.

Abstract: Because of the fast development of high buildings and large mansions and the increasing applications of electronic information technology, all kinds of advanced electronic equipments are installed in buildings. These equipments have qualities of low insulation, weak endurance of overvoltage and overcurrent and sensitivity for EMC disturb. Then more and more serious hazards and indirect economic losses are arising from lightning disturbance. Therefore, in order to cut down such big losses it is really necessary to conduct the research of stroke-incidence rules and take effective measures to protect buildings against lightning. Theories and practice show that the lightning protection is a systematic engineering. The exterior protection and interior protection should be constituted as an integer. This paper mainly studies the telecommunication equipments in the building disturbed and harmed by the lightning electromagnetic field. To protect this injure effectively we must find out the distributions of the lightning electromagnetic field in the building. Three cases of the lightning electromagnetic field distributions in the building have been discussed in the paper.

Abstract: Aluminum is the richest metallic element in the earth, the ingots cast by DC casting process are usually extruded into aluminum bars. When the final products do not require high strength, this process appears to be low efficiency and high cost. We try to design a new technology to cast aluminum bar by horizontal direct chill (HDC) casting process directly. An electromagnetic field is applied during the horizontal continuous casting of 6061 aluminium bar with a diameter of 30mm. The experimental results show the asymmetry of the sump can be overcome by electromagnetic field. Ingot with good upper and lower surface quality is obtained. The structure of ingot is refined and the angle between growth direction and horizontal direction becomes small with increasing casting speed.

Abstract: The characteristics of a chiral negative refraction parallel-plate waveguide under PMC boundary are studied theoretically, and the corresponding dispersion relations, cut-off frequencies, propagating guided modes are obtained. Some novel features are found, such as fundamental mode will be not exist only if the chirality parameter κ>1, in addition, the cutoff frequency is no longer the conventionally defined frequency when propagation constant is zero, but the least frequency that guided mode can still propagate. According to the relations between propagation constant β and wavenumbers k₊,k_-, the dispersion curves are divided into three regions , and the electromagnetic field components in the regions are analyzed in detail.

Abstract: Based on the FE software ANSYS, the coupling temperature fields of pin-disc friction pair were simulated and analyzed in pin-disc friction rig. The results show that the temperatures of pin-disc friction pair with magnetic field are higher than that without magnetic field, under the same relative displacement, speed and normal pressure. The maximum coupling temperature increase slowly and then increase quickly with the increasing of normal pressure, under the constant magnetic field intensity and speed. The maximum coupling temperature decreases with the increase of relative speed, when the relative sliding distance and magnetic field intensity are constant.

Abstract: This research aims to develop instruction model using cognitive learning theories on electromagnetic field and wave for undergraduate of electrical engineering program. The new instruction model called FATAC model was developed. It consists of 5 steps as; 1) Find 2) Adjust 3) Teach 4) Actions and 5) Conclusion. The content of dissertation has 3 Units; 1) Maxwell equations and electromagnetic wave are direct variation with time 2) Microwave planar and 3) Poynting vector and wave propagation. Thirty students of level 3 in technical education, rajamangala university of technology isan, khonkaen campus were a sampling group. Tools of dissertation included lesson plans, learning media as powerpoint presentation, electromagnetic wave propagation simulation program, wave propagation demonstration set, and filed strength meter. The research results consisted of; 1) The opinion on the FATAC model was high level (=4.21,S.D.=0.48). 2) The learning effectiveness of the instructional model was 76.15/76.73 (higher than 75/75 of the hypothesis). 3) The quality of instruction package by experts was high level (=4.27 ,S.D=0.62) and 4) The mean of satisfaction of the sampling group was high level (=4.23 ,S.D=0.57). Therefore, in conclusion, instruction model using cognitive learning theories on electromagnetic wave and propagation for undergraduate of electrical engineering program can be applied for electromagnetic theory subject and high efficiency.

Abstract: For considering the magnetic fields produced by the UHVDC transmission in our country which may have influence on human and communication equipment. This paper use ANSYS finite element software to modeling to analysis the regularity of distribution and order of magnitude of the magnetic fields produced by the UHVDC transmission. By comparing with the limitation of the correspond criteria. We can infer that the electromagnetic fields produced by the UHVDC transmission whether have influence on our environment and harmful to human.

Abstract: Pico Satellite Telecommunication with Ground Station (GS) is Characterized by a Limitedline of Sight that Affects Transmission Delay and Data. in this Paper, a New Fuzzy Logic Control Systemmodel is Proposed to Ensure a Long Lasting Ground Station (G.S) Visibility to Pico Satellite Duringorbiting in Leo. Developed System is Helpful to Control Wave Propagation for Transmission. Presentedmethod Describes a Fuzzy Switching Control System for both Side Microstrip Antennas Array Systemmodel that Guarantee a Maximum Transmission Time and Achieves Small Satellite Communicationcontrol Performance with Simplified Control Scheme. the Method Includes Switched Systemmodeling, Fuzzy Control System Design, and Optimized Fuzzy Modeling Algorithm; in Addition Petri Netmodeling is Developed to Predict System Behavior. Added Algorithms were Simulated and Tested.Proposed System and Integrated Algorithms Performance were Demonstrated in the Reportedsimulations and Tests Results.

Abstract: A finite element technique and computer code for the numerical analysis of 3D transient electromagnetic fields and temperature distribution due to negative sequence currents in large synchronous turbogenerator rotors are developed. Electromagnetic-thermal phenomena in a 300 MVA class turbogenerator rotor during a line-to-line short circuit on two phases of the machine are numerically investigated. Effect of the various conditions of the rotor cooling on its thermal state is studied. Numerical results obtained can be used for the computer simulation of the thermo-mechanical behaviour of the rotor.