• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1867-1869
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• 1996

In this paper, in order to obtain the statistic information for parameters of electric and magnetic field waveforms associated with lightning discharges, the electric and magnetic fields produced by lightning discharges in the summer of 1995 were measured by a hemisphere-type electric field sensor and a loop-type magnetic field sensor, which were installed at the campus of Inha University in Inchon. The signals of the electric and magnetic fields were continuously recorded by a transient digitizer having a resolution of 12 bit and a memory capacity of 5000 point. Negative lightning discharges are produced very more than positive lightning discharges in the summer of Korea. The 10 to 90 % rise time of electric and magnetic fields was 2 $2\;{\sim}\;10\;{\mu}s$. And the zero-crossing time of electric field was $15\;{\sim}\;25\;{\mu}s$, whereas that of magnetic field was $20\;{\sim}\;30\;{\mu}s$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.307-308
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• 2007

This work shows the experimental results obtained from ageing at a temperature of 100 C for 48, 70 and 312 h, although the application of AC electrical tension in samples and the measuring of current leakage are presented. The measurements in samples were carried out with samples prepared from the deformulated commercial materials and respectively reformulated into thin films. The obtained results showed the mechanisms of conduction of samples in low and high electric fields. It was also identified an electric tension transition showing that in low fields it prevails the Ohm's law conduction, and in high electric fields it prevails the conduction of space charge limited current (SCLC). These results can support the natural rubber formulation process having as their main objective the reducing of the mechanisms that occur under high conduction current in high electric fields, which leads the material to a dielectric breakdown. Raw Natural rubber in Brazil is extracted from rubber trees (Hevea brasiliensis) in farms in So Paulo State by using some new plantation technology in smaller spaces, with trees placed a few meters from each other. In the Amazon rain forest the rubber trees are found naturally and their spacing may be of hundreds of meters or even kilometers between them. It is necessary to research this raw material from different internationally standard clones to characterize dielectric and electric properties for industrial applications. Moreover, this natural material has a low commercial price when compared to the synthetic ones.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.11
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• pp.585-590
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• 2002

In this paper, the 3 dimensional surface charge method is applied to calculate electric fields distribution inside a general and an optimal model of GIS with a metal impurity and a void respectively. We know the optimal model can reduce tangential electric fields at solid insulator surface to 70% of the general model and infulence fields distribution near a metal impurity. Meanwhile, we find the optimal model does not decrease field distribution inside a void in the insulator.

• Coupled systems mechanics
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• v.7 no.1
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• pp.5-25
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• 2018

A fully-coupled thermodynamic-based transient finite element formulation is proposed in this article for electric, magnetic, thermal and mechanic fields interactions limited to the linear case. The governing equations are obtained from conservation principles for both electric and magnetic flux, momentum and energy. A full-interaction among different fields is defined through Helmholtz free-energy potential, which provides that the constitutive equations for corresponding dual variables can be derived consistently. Although the behavior of the material is linear, the coupled interactions with the other fields are not considered limited to the linear case. The implementation is carried out in a research version of the research computer code FEAP by using 8-node isoparametric 3D solid elements. A range of numerical examples are run with the proposed element, from the relatively simple cases of piezoelectric, piezomagnetic, thermoelastic to more complicated combined coupled cases such as piezo-pyro-electric, or piezo-electro-magnetic. In this paper, some of those interactions are illustrated and discussed for a simple geometry.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.81-88
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• 2006

In this study, the electric and magnetic fields measuring system were designed and fabricated to investigate the electric characteristics of lightning discharges. Frequency bandwidth of electric field measuring system ranges from 40[Hz] to 2.6[MHz] and its response characteristic is 2.1[(V/m)/mV]. Frequency bandwidth of magnetic field measuring system ranges from 300[Hz] to 1[MHz] and its response characteristic is 2.8[nT/mV]. Electric and magnetic fields due to intracloud lightning discharges were observed and their waveform parameters were statistically analyzed. As a result, waveform parameters of electric and magnetic fields are nearly independent of polarity. The mean rise times and the zero-crossing times of electric and magnetic fields are approximately $5.5[{\mu}s]\;and\;21[{\mu}s]$, respectively.

• Journal of Magnetics
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• v.21 no.1
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• pp.102-109
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• 2016

In this paper, the theoretical and experimental characteristics of magnetic and electric fields in the vicinity of high voltage lines are investigated. To realize these measurements and calculations, we have developed some equations for two overhead power line configurations of 150 kV (single circuit, double circuit), based on Biot-savart law, image and Maxwell theories, in order to calculate the magnetic and electric fields. The measurements were done to a maximum distance from the tower of 50 m, at a height of 1m from the ground. These experiments take into consideration the real situations of the power lines and associated equipment. The experimental results obtained are near to that of the Biot-Savart theoretical results for a far distance from the tower; and for a distance close to the power line, the results from the image theory are in good agreement with the experimental results.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.185-188
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• 2015

An experimental study on downwardly and upwardly spreading flames over slanted electrical wire, which is insulated by Polyethylene(PE), was conducted with applied AC electric field. The result showed that downwardly and upwardly spreading flames with angle of inclination leaned toward burnt side and unburned side, respectively. With applied AC electric fields, size of downwardly spreading flame decreased slightly and that of upwardly spreading flame increased significantly. Flame spread rate showed various trends in terms of inclination, applied voltage and frequency.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.820-823
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• 2002

The asymptotic problem of a semi-infinite conducting crack parallel to the poling direction in ferroelectric ceramics subjected to electric fields is analyzed. The main mechanism for the conducting crack growth behavior is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. The shape and size of the switching zone is shown to depend strongly on the relative magnitude on the ratio of the coercive electric field to the yield electric field. It is shown that the crack growth can be either enhanced or retarded depending on the ratio of the coercive electric field to yield electric field.

• The Journal of Korean Physical Therapy
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• v.12 no.2
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• pp.69-82
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• 2000

Physical therapists are exposured to radio-and microwave-frequency electromagnetic radiation by operating electrotherapy units. So there is few protection system in physical therapy room. Clinical pathology room and so on where various kins of electromagnetic instruments is used in hospital while protection failities like protection wall or protection glass is being used only in radiological room to reduce the damage of radiation. Acoording to Larsen's survey on female physical therapist in denmark. it was said that the percentage of congenital malfornation was $3.6\%$ and cadiac malformation made up $0.7\%$. It is likely that effect of electromagnetic fields on the result cannot be ruled out. Rita ouellet-Hellstron and Walter F. Steward insisted that the danger of abortion increase in the case of pregnant femeal physical therapist exposured to microwave diathermy. The intention of our study is arousing the necessity of microwave protection in P.T room and finding the proper method for physical therapist safe. The results of this study were as follows: 1. Each electrotherapy units are occurrenced the electromagnetic fields, and specially amply occurrenced in H.P,I.C.T 2 unit operating, M.W.D unit head on parallel, S.W.D unit head on parallel. all electrotherapy units are operating. 2. There were electric fields mount are consideration to species of electrotherapy units(p<.05). 3. There were magnetic fields mount are consideration to species of electrotherapy units(p<.05). 4. There were electric fields mount are consideration to distance of electrotherapy units(p<.05). 7. There were magnetic fields mount are consideration nut to distance of electrotherapy units(p>.05). 8. Before and after protection on magnetic fields mount are consideration to all distance(0m, 0.3m, 1m, 3m, 5m)(p<.05) 9. Before and after protection on electric fields mount are consideration to 0m, 1m, 3m distance(p<.05), and consideration not to 0.3m, 5m distance(p>.05) 10. After protection fellow the each electrotherapy units. distance, intencity to electromagnetic fields are reduced(p<.05).

• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.134-141
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• 2015

The effect of a 60 Hz time-varying electric field was studied using a facing-electrode device (FED) and a coplanar-electrode device (CED) for further investigation of the genotoxicity of 60 Hz time-varying magnetic field (MF) from preceding research. Neither a single 30-minute exposure to the CED or to the FED had any obvious biological effects such as DNA double strand break (DSB) and apoptosis in cancerous SCC25, and HeLa cells, normal primary fibroblast IMR90 cells, while exposures of 60 Hz time-varying MF led to DNA damage with induced electric fields much smaller than those used in this experiment. Nor did repetitive exposures of three days or a continuous exposure of up to 144 hours with the CED induce any DNA damage or apoptosis in either HeLa or IMR90 cells. These results imply that the solitary electric field produced by time-varying MF is not a major cause of DSBs or apoptosis in cancer or normal cells.