• 동의생리병리학회지
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• 제17권6호
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• pp.1463-1467
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• 2003

In the present study, the effects of Ginseng radix and Ophiopogonis tuber on field potentials in rat hippocampal slices and cardiac muscle slices were investigated by multi-channel extracellular recording using MED64 system. The field potentials in the brain slices represent synaptic transmission and nerve excitability, and the field potentials in heart muscles represent muscle contractility. The present results show that the aqueous extract of Ginseng radix enhanced field potentials in the both hippocampal slices and cardiac muscle slices. In contrast, the aqueous extract Ophiopogonis tuber exerted no significant effect on the field potentials in the hippocampal slices and cardiac muscle slices. These results suggest the possibility that Yin-Yang theory could be studied in relation with excitability in neurons and muscles.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.302-304
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• 1998

Self magnetic field in a Bus bar usually degrades the critical current in it. Actually the total critical current of a Bus bar is not the same as the sum of total critical current of each stacked HTS tape. This is due to the self field effects in a bus bar. To reduce the degradations of critical current in a bus bar, we need to analyze the self field distributions in a bus bar. Conceptually, by rearranging the each stacked tapes, the self field effects can be minimized. In this paper, we calculate the self magnetic field distributions across a bus bar analytically, with the variations of the relative angle of the two conductors in a go-and-return pair. As a result, we suggest that the optimum relative angle exist which minimize the self field effect in a bus bar.

• 대한물리의학회지
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• 제7권3호
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• pp.349-356
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• 2012

Purpose : This study was designed to investigate the effects of pulsed electromagnetic field on functional recovery and expression of GAP-43 after incomplete spinal cord injury (SCI) in rats. Methods : To confirm the damage of SCI and effects of pulsed electromagnetic field, 20 Sprague-Dawley male rats were used and divided randomly 2groups (SCI, PEMF). Incomplete SCI was induced by using modified NYU drop model. After operation, functional recovery test, immunohistochemistry and western blot analysis were measured at 1, 2, 3 weeks. Pulsed electromagnetic field were apply three weeks (one times a day, five days a week and twenty minutes a session). Results : In the this study, applications of pulsed electromagnetic field after incomplete SCI induced the significant improvement in functional recovery and expression of neurotrophic factor. The results were as follows; Foot print test, PEMF were significantly decreased than the SCI (p<.05). Expression of GAP-43, PEMF were significantly increased than the SCI at 2 and 3 weeks (p<.05). Conclusion : In conclusion, pulsed electromagnetic field were positive effect in functional recovery and expression of GAP-43 after incomplete SCI in rats.

• Earthquakes and Structures
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• 제17권6호
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• pp.533-543
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• 2019

This paper presents a study on the behavior of an RC bridge under near-field and far-field ground motions. For this purpose, a dynamic nonlinear finite element time history analysis has been conducted. The near-field and far-field records are chosen pairwise from the same events which are fits to the seismic design of the bridge. In order to perform an accurate seismic evaluation, the model has been analyzed under two vertical and horizontal components of ground motions. Parameters of relative displacement, residual displacement, and maximum plastic strain have been considered and compared in terms of near-field and far-field ground motions. In the following, in order to decrease the undesirable effects of near-field ground motions, a viscous damper is suggested and its effects have been studied. In this case, the results show that the near-field ground motions increase maximum relative and residual displacement respectively up to three and twice times. Significant seismic improvements were achieved by using viscous dampers on the bridge model. Somehow under the considered near-field ground motion, parameters of residual and relative displacement decrease dramatically even less than the model without damper under the far-field record of the same ground motion.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.991-996
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• 2014

Power frequency magnetic field is still a critical problem for new construction of overhead power transmission lines in Korea because most people have been concerned about possibly carcinogenic effects of it. Although reference level of power frequency(60Hz) magnetic field has been set to 200uT in ICNIRP guidelines published in 2010, Korean government has no intention of adjusting 83.3uT specified by law in 2006 to this new reference level in consideration of people's concerns for the time being. Regardless of the current regulated magnetic field value, electric utility company has been trying to reduce magnetic field in the residential area in the vicinity of overhead power transmission lines to take into account of public concerns on the long-term effect of magnetic fields. In an effort to reduce magnetic field, engineering side has made considerable efforts to develop passive loop based, cost-effective mitigation technique of power frequency magnetic field more than ten years. In order to verify developed power frequency magnetic field mitigation technique based on passive loop, a horizontal type of passive loop was designed and installed for commercially operating 154kV overhead power transmission line for the first time in Korea. The measurement results before and after the installation of passive loop showed that magnetic field could be reduced to about 20%. The electrical environmental effects such as AN, RI and TVI were assessed before and after the installation of passive loop and these values were complied with the requirements specified by electric utility. It has been confirmed from the field test results that passive loop could be commercially and cost-effectively utilized to mitigate power frequency magnetic field.

• 천문학회지
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• 제29권spc1호
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• pp.397-398
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• 1996

Large field spectrographs are severely influenced by atmospheric refraction. LAMOST is a large field multi-object spectroscopy telescope with $5^{\circ}$ field of view, f/5 focus ratio and 20m focal length. There will be 4000 fibers simultaneous on it's $\phi$1.75m focal plane. Here we discuss the atmospheric refraction effects on LAMOST in two hands. One is the effect of differential refraction across the field, another is the effect of atmospheric dispersion. According to the calculation, we find that: 1. The largest deviation from center within the field is 4.;32" during a 1.5-hour integration at $80^{\circ}$ declination. 2. The directions of deviation are complex, so the deviations can't be decreased by rotating the field. We also give out the atmospheric dispersions.

• Wind and Structures
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• 제20권2호
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• pp.169-189
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• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.

• 한국결정성장학회지
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• 제6권1호
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• pp.1-10
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• 1996

초크랄스키법에 의한 8언치 실리콘 단결정 성장시 커스프자장의 영향에 관한 수치 해석적 연구를 행하였다. 액상실리콘의 유동에 대한 모렐은 저레이놀즈수 모렐을 사용하였다. 대칭커스프자장은 유션의 강도를 감쇄하였고, 특히 도가니 벽면 근처에서의 유동의 감쇄효과가 현저하였다. 결정으로 혼업되는 산소의 농도는 인가되는 커스프자장의 증가에 따라 감소하였다. 그리고, 결정으로 혼업되는 산소농도의 균일성은 향상되었다. 비대칭커스프 자장은 결정으로 혼 입되는 산소의 농도를 중가시켰지만, 반경방향의 산소농도의 분포는 일정하게 유지되었다. 대칭 과 비대청 커스프자장의 적절한 조합을 행하면 축방향으로 일정한 산소의 분포를 갖는 적절한 조업조건이 도출될 것으로 예상된다.

• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.267-271
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• 2008

The RF shimming technique has been used to improve the transmit RF field homogeneity in highfield MRI. In the RF shimming technique, the amplitude and phase of the driving currents in each coil element are optimized to get homogenous flip angle or uniform image intensity. The inductive and capacitive coupling between the coil elements may degrade the RF field homogeneity if not taken into account in the optimization procedure. In this paper, we have analyzed the coupling effects on the RF shimming using a sixteen-element TEM RF coil model operating at 300 MHz. We have found that the coupling effects on the RF shimming can be reduced by putting high dielectric material between the active rung and the shield.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1637-1640
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• 2005

This paper presents a technique for electromagnetic field analysis on surge response due to Mid-span back-flashovers effects in lightning protection system of 500 kV EHV single circuit transmission tower by the neural networks method. These analyses are based on modeling lightning return stroke as well as on coupling the electromagnetic fields of the stroke channel to the line. The ground conductivity influences both the electric field as well as the coupling mechanism and hence the magnitude and wave shape of the induced voltage. The technique can be used to analyzed the corona voltage effect, the effective of stroke to the span tower, the surge impedance of transmission lines. The maximum voltage from flashovers effects in the lines. The model is compatible with general electromagnetic transients programs such as the ATP-EMTP. The simulation results show that this study analyses for time-domain with those produced by a cascade multi-section model, the surge impedance of a full-sized tower hit directly by a lightning stroke is discussed.