• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.3
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• pp.303-312
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• 2009

In this study, a waveguide system for focusing the electric field is presented to emit the microwave-driven plasma visible light. This system consists of a magnetron for the microwave power supply, the waveguide section for power propagation, and the mesh-type cavity reactor. The quartz bulb containing a dose of sulfur powder and buffer gas Ar is located in the reactor, and forced by the strongly concentrated electric field for generating and exciting the sulfur plasma. That is, the conductor tips are loaded on each inner wall of the waveguide and the reactor, and then the plasma bulb is positioned between the tips, hence focusing the strong electric field on the bulb. Furthermore the waveguide section is designed for minimizing the degradations of matching characteristics according to the variations of the electrical conductivities of plasma at the transitory phase for plasma generation, hence providing the stable operation. Finally, the 2.45 GHz aluminum waveguide system is constructed, and then experiments for emitting the visible light are performed by using 400 W-class magnetron, showing the validity of designed system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.496-502
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• 2007

In this paper, a slotted waveguide feeder for the electric field uniformity in multi-mode cavity is designed and fabricated. In case of the conventional feeder, a mode stirrer or a turntable is used for improving electric field uniformity in the multi-mode cavity. The proposed feeder has four slots, which have uniform radiation characteristic, on broad wall and shorted terminations at both ends. The electric field uniformity is simulated by CST's MWS(Microwave Studio) for the conventional and proposed feeders, respectively. The fabricated feeder shows the return loss of less than -20 dB at 2.45 GHz. To verify the validity of our proposal, the temperature distribution of the water samples in the multi- mode cavity is observed after a few minutes' heating. The proposed feeder is confirmed to have much better field uniformity in the multi-mode cavity than the conventional feeder.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.75-82
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• 1999

TE$_{01\;{\delta}}$ mode Cavity Resonators with a low loss dielectric rod and YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) endplates were prepared and their microwave properties were studied at temperatures above 30 K. Both sapphire and rutile were used as the dielectrics. The TE$_{01\;{\delta}}$ mode Q$_0$ of the resonator, designed to work as a tunable resonator with variations in the gap distance (s) between the dielectric rod and the top YBCO, was more than 1000000 at s = 0 mm and at 30 K and .the resonant frequency of 19.56GHz when a sapphire rod was used for the dielectric. The TE$_2Cu_3O_{7-{\delta}}$ mode resonant frequency (f$_0$) appeared to decrease as the temperature is raised. Meanwhile, the temperature dependence of the TE$_2Cu_3O_{7-{\delta}}$ mode f$_0$ of the rutile-loaded resonator appeared different with f$_0$ increasing according to the temperature and Q$_0$ more than 300000 at 30 K and f$_0$ = 8.56 CHz. Comparisons were made between the microwave properties of the sapphire-loaded and the rutile-loaded resonators. Also, applications of the TE$_2Cu_3O_{7-{\delta}}$ mode cavity resonator for a tunable resonator with a very high Q$_0$ as · well as a characterization tool for surface resistance measurements of HTS films are described.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1196-1202
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• 1999

This work was to determine the microbial and physico-chemical changes of HTST-pasteurized soymilk using microwave energy. Soymilk was HTST pasteurized$(at\;90^{\circ}C\;for\;20\;sec)$ by three methods: by heating in a stainless steel tube immersed in a hot water bath(MP0), by heating in a microwave cavity to a defiled temperature and then holding in a hot water bath(MP1), and by both heating and holding in a microwave cavity(MP2). The microbial quality based on the total plate count was in the order of MP0, MP2 and MP1. The three samples pasteurized by different methods showed the similar microbial quality with respect to the coliform count, psychrotrophic bacterial count and phosphatase activity. The destruction of trypsin inhibitor was in the order of MP0, MP1 and MP2. There were no significant differences in pH, titratable acidity, viscosity and vitamin $B_2$ content before and after pasteurization and among the different pasteurization methods. The similar or higher quality retention of the MP1 or MP2 supports the possibility of using microwave energy for the HTST pasteurization of soymilk and other fluid food products.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1753-1755
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• 1996

This paper presents an analysis of the 3D microwave oven considering its forming. The results were compared with experimental data. Finite Element Method(FEM) using edge clement is employed for the analysis. For solving the large sparse system matrix equation was solved using the parallelized QMR method. Analysis of the 3d cavity has troublesome difficulties such as spurious solutions, too many memory and long computation time. We overcome this difficulties by using edge clement for spurious solutions and the parallelized QMR method by the aid of Paralle Virtual Machine(PVM) for the memory and computation time.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1741-1743
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• 1996

This paper presents simulations of the pancake in the simplified 3D microwave oven. The results were compared with experimental data. For the comparison we used infrared photography of the heated pancake and electric field distribution obtained by simulation. Finite Element Method (FEM) using edge element is employed for the simulation. For solving the large sparse system parallelled QMR method was used.

• Journal of Magnetics
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• v.18 no.2
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• pp.178-182
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• 2013

We have developed a new non-conventional electron paramagnetic resonance (EPR) spectrometer, in which no resonant cavity was used. We previously demonstrated a wide frequency range operation of an EPR spectrometer using two loop antennas, one for a microwave transmission and the other for signal detection [1]. In contrast to Ref. [1], the utilization of a microstrip antenna as a transmitter enhanced a capability of wide-band operation. The replacement of conventional capacitors with varactor diodes makes resonance condition easily reproducible without any mechanical action during tuning and matching procedure since the capacitance of the diodes is controlled electronically. The operation of the new EPR spectrometer was tested by measuring a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample in the frequency range of 0.8-2.5 GHz.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.293-295
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• 2004

PLS(Plasma Light System) is one of the electrodeless lamp discharged by micro wave. In this new lamp has high efficacy and CRI(Color Rendering Index). It is mainly composed of microwave part and optical part. Microwave parts consist of magnetron, wave-guide and cavity-mesh, while optical parts consist of bulb, mirror and reflector. In this paper, we studied experimentally the heat-resistance and temperature distribution characteristics of bulb in PLS.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.339-343
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• 2016

Background: Evaluation of deoxyribonucleic acid (DNA)-strand break is important to elucidate the biological effect of ionizing radiations. The conventional methods for DNA-strand break evaluation have been achieved by Agarose gel electrophoresis and others using an electrical property of DNAs. Such kinds of DNA-strand break evaluation systems can estimate DNA-strand break, according to a molecular weight of DNAs. However, the conventional method needs pretreatment of the sample and a relatively long period for analysis. They do not have enough sensitivity to detect the strand break products in the low-dose region. Materials and Methods: The sample is water, methanol and plasmid DNA solution. The plasmid DNA pUC118 was multiplied by using Escherichia coli JM109 competent cells. The resonance frequency and Q-value were measured by means of microwave dielectric absorption spectroscopy. When a sample is located at a center of the electric field, resonance curve of the frequency that existed as a standing wave is disturbed. As a result, the perturbation effect to perform a resonance with different frequency is adopted. Results and Discussion: The resonance frequency shifted to higher frequency with an increase in a concentration of methanol as the model of the biological material, and the Q-value decreased. The absorption peak in microwave power spectrum of the double-strand break plasmid DNA shifted from the non-damaged plasmid DNA. Moreover, the sharpness of absorption peak changed resulting in change in Q-value. We confirmed that a resonance frequency shifted to higher frequency with an increase in concentration of the plasmid DNA. Conclusion: We developed a new technique for an evaluation of DNA damage. In this paper, we report the evaluation method of DNA damage using microwave dielectric absorption spectroscopy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.636-639
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• 2000

Effects of sintering temperature and time on relative permittivity $\varepsilon$$\_$r/, unloaded quality factor Q$.$f and temperature coefficient of resonant frequency $\tau$$\_$f/ of dielectric resonator materials produced from commercial ZST powder were investigated in some detail. Q$.$f values, as determined from cavity perturbation method at 1.6 GHz, gradually increased with sintering temperature reaching the maximum at 1420$^{\circ}C$. However, bulk density and relative permittivity values, which increased with temperature, started to decrease above 1380$^{\circ}C$. In addition, Q$.$f values slightly increased with sintering time at the sintering temperature of 1300$^{\circ}C$∼1380$^{\circ}C$, while bulk density and relative permittivity values were approximately constant. It was also found that $\tau$$\_$f/ values were not affected by sintering temperature and time within the experimental conditions used.