• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.22-24
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• 2003

In this work, in order to investigate the effect of multiple lightning impulse currents on zinc oxide arrester blocks. We have been designed and fabricated a multi-impulse generator which can produce quintuple voltages with $1.2/50{\mu}s$ to 100kV and quintuple currents with $8/20{\mu}s$ to 12kA and we have evaluated the characteristics of zinc oxide arrester block using several electrical and physical methods after the multi-impulse test. It was found that the multi-impulse failures of ZnO arrester blocks were mainly caused by surface flashover and the multi-impulse currents test would be more suitable than single impulse current test in evaluation of the characteristics of zinc oxide arrester blocks corresponding to actual situations.

• 상하수도학회지
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• 제27권3호
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• pp.383-394
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• 2013

A sedimentation basin is used to remove suspended sediments which can cause abrasive and erosive wear on hydraulic turbines of hydropower plants. This sediment erosion not only decreases efficiency of the turbine but also increases maintenance costs. In this study, the three-dimensional numerical simulations were carried out on the overseas hydropower project. The simulations of flow and suspended sediment concentration were obtained using FLOW-3D computational fluid dynamics code. The simulations provide removal efficiency of a sedimentation basin based on particle sizes. The influence of baffles on the flow field and the removal efficiency of suspended sediments in the sedimentation basin has been investigated. This paper also provides the numerical simulations for sediment-induced density currents that may occur in the sedimentation basin. The simulation results indicate that the formation of density currents decreases the removal efficiency. When a baffle is installed in the sedimentation basin, the baffle provides intensive settling zones resulting in increasing the sediments settling. Thus the enhanced removal efficiency can be achieved by installing the baffle inside the sedimentation basin.

• The Korean Journal of Physiology and Pharmacology
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• 제4권5호
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• pp.403-408
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• 2000

The outward currents elicited in hamster eggs by depolarizing pulses were studied. The currents appeared to comprise at least two components, a transient outward component $(I_{to})$ and a steady-state outward component $(I_{\infty}).\;I_{to}$ was transiently followed by the cessation of inward $Ca^{2+}$ current $(I_{Ca}),$ and its current-voltage (I-V) relation was a mirror image of that of $(I_{Ca}).$ Either blockade of $(I_{Ca})$ by $Co^{2+}$ or replacement of $Ca^{2+}$ with $Sr^{2+}$ abolished $I_{to}$ without change in $I_{\infty}.$ Intracellular EGTA (10 mM) inhibited $I_{to}$ but not $I_{\infty}.$ suggesting strongly that generation of $I_{to}$ requires intracellular $Ca^{2+}.$ Apamin (1 nM) abolished selectively $I_{to},$ indicatingthat $I_{to}$ is $Ca^{2+}-dependent\;K^+$ current. On the other hand, $I_{\infty}$ was $Ca^{2+}-independent.$ Both $I_{to}$ and $I_{\infty}$ were completely inhibited by internal $Cs^+$ and external TEA. The estimated reversal potential of $I_{to}$ was close to the theoretical $E_K.$ Taken together, both outward currents were carried by $K^+$ channels. From these results, $I_{to}$ is likely to be a current responsible for the hyperpolarizing responses seen in hamster eggs at fertilization.

• The Korean Journal of Physiology and Pharmacology
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• 제7권1호
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• pp.25-28
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• 2003

Ion channel inhibitors are widely used for pharmacological discrimination between the different channel types as well as for determination of their functional role. In the present study, we tested the hypothesis that 4-aminopyridine (4-AP) could affect the large conductance $Ca^{2+}$-activated $K^+$ channel ($BK_{Ca}$) currents using perforated-patch or cell-attached configuration of patch-clamp technique in the rabbit pulmonary arterial smooth muscle. Application of 4-AP reversibly inhibited the spontaneous transient outward currents (STOCs). The reversal potential and the sensitivity to charybdotoxin indicated that the STOCs were due to the activation of $BK_{Ca}$. The $BK_{Ca}$ currents were recorded in single channel resolution under the cell-attached mode of patch-clamp technique for minimal perturbation of intracellular environment. Application of 4-AP also inhibited the single $BK_{Ca}$ currents reversibly and dose-dependently. The membrane potential of rabbit pulmonary arterial smooth muscle cells showed spontaneous transient hyperpolarizations (STHPs), presumably due to the STOC activities, which was also inhibited by 4-AP. These results suggest that 4-AP can inhibit $BK_{Ca}$ currentsin the intact rabbit vascular smooth muscle. The use of 4-AP as a selective voltage-dependent $K^+$ (KV) channel blocker in vascular smooth muscle, therefore, must be reevaluated.

• Journal of Ginseng Research
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• 제23권4호
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• pp.230-234
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• 1999

혈관의 평활근 세포막에 존재하는 포타슘채널은 근세포의 막전압을 조절하여 근수축 및 이완을 조절한다. 네가지 유형의 포타슘채널이 근세포막에 존재하며 이중 전도도가 큰 칼슘의존성-포타슘채널$(BK_{Ca})$은 평활근 막전압 조절에 중요한 기능을 담당하는 채널로 알려져 있다. 현재 홍삼 복합사포닌이 혈관 평활근의 이완을 증진시켜 혈압강하를 촉진시킨다고는 알려져 있으나 어떤 분자적 기전이나 전기생리학 기전으로 작용하는지 정확히 알려져 있지 않다. 본 연구는 홍삼 복합사포닌 및 사포닌 $Rg_3$ 성분이 토끼 관상동맥 평활근 세포의 $BK_{Ca}$채널의 활성을 증진시켜 막전압을 과분극시키고 곧 평활근 이완을 촉진한다는 가설을 테스트하였다. 관상동맥 평활근세포의 $BK_{Ca}$채널은 막전압 의존성, 외향정류(outward rectification) 특성을 보였고 단일채널의 전도도는 200pS으로 측정되었으며 charybdotoxin 및 tetraethylammonium에 억제되는 약리학적 특성을 보였다 Whole-cell $BK_{Ca}$활성은 홍삼 복합사포닌에 의해서 농도 의존적으로 증가되었으나 막전압 의존성은 변화되지 않았으며, 단일채널이 열리는 시간은 증가되었다. 홍삼 사포닌 $Rg_3$성분도 막전압 의존성에는 영향을 주지 않으면서$BK_{Ca}$의 활성을 증가시켰으며 단일채널이 열리는 시간도 증가시켰다. 따라서 홍삼 복합사포닌 및 사포닌 $Rg_3$성분은 $BK_{Ca}$의 활성을 증가시켜 막전압을 과분극시켜 평활관의 이완을 촉진한다고 여겨진다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.145-150
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• 2004

Using the DGPS of high precision take in a bouy, the wave-induced currents were observed by Lagrange method at Bonggile beach of the East Sea. At June, the northward wave-induced currents were dominated by the SSW waves. And the southward flaws were appeared at September and November. When 0.2-0.4m wave heights attacked the beach, the mean speed of the wave-induced currents was 0.15-0.3m/s at June and September, when the 1.0-1.6m wave heights incidented at November, that was about 0.3-0.6m/s. On the other hand, the observed results were compared with the simulated results which were solved by the 2-D model, WICU-DIVAST. It was showed the reasonable agreements.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1610-1613
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• 2016

An analytical method for harmonic estimation of magnetization currents has been developed. The method is based on the results of the waveforms qualitative analysis. The calculation and the experimental results are compared. A good matching is observed.

• 해양환경안전학회지
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• 제24권2호
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• pp.179-187
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• 2018

수치모델실험을 사용하여 한국 서남해 압해도 주변 해역의 조류 및 조석잔차류 분포를 파악하였다. 조류는 대체로 반 일주조가 탁월하며, 조류 주방향은 압해도 주변 다도해역이 좁은 협수로인 관계로 대부분 수로를 따라 형성되었다. 조류타원 형태는 주변수심 및 인근에 산재한 섬 주위 해저지형의 영향으로 대부분 직선에 가까운 왕복성이었으나, 매화도~증도 사이 기점도, 화도, 당사도 주위에 약한 회전성 조류타원 형태였다. 창조류는 화원반도 서쪽 연안을 따라 팔금도~암태도, 암태도~증도 수로에서 북동류한 조류와 함께 압해도 북서쪽 다도해로 빠지고, 낙조류는 반대로 북서 다도해의 협수로를 따라 암태도~증도, 암태도~팔금도를 통과하고 암태도~증도에서의 조류는 팔금도~화원반도 서쪽 연안을 따라 남류했다. 압해도 연안은 창조시 북류한 흐름이 해안에서 동서로 분류되어 압해도 서쪽과 동쪽을 따라 흐르고 낙조시는 조간대 만곡부에서 남류한 흐름과 섬 서쪽과 동쪽에서 남~남동류한 흐름이 팔금도~화원반도 사이로 흘렀다. 조류유속이 강한 곳은 암태도~압해도 사이 합류역이었다. 조석잔차류는 다도해 협수로의 빠른 유속으로 섬 주변 흐름 하류역에 후류와 또는 지형성와류가 형성되었다. 압해도 서쪽에 약한 반시계방향 와류와 압해도 북서 만곡부에 시계방향 환류가 존재했다. 북쪽 협수로를 제외한 압해도 연안은 조간대가 발달되어 조석잔차류 유속이 미약하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제1권6호
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• pp.613-624
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• 1997

Dorsal root ganglion (DRG) is composed of neuronal cell bodies of primary afferents with diverse functions. Various types of ion channels present on DRG neurons may reflect those functions. In the present study, voltage-gated potassium currents in DRG neurons of neonatal rats were characterized by whole-cell voltage clamp method. Two types of delayed rectifier and three types of transient potassium currents were identified according to their electrophysiological properties. The delayed rectifier currents were named $I_{Ke}$ (early inactivating) and $I_{K1}$ (late inactivating). Steady state inactivation of $I_{Ke}$ began from -100 mV lasting until -20 mV. $I_{K1}$ could be distinguished from $I_{Ke}$ by its inactivation voltage range, from -70 mV to +10 mV. Three transient currents were named $I_{Af}$ (fast inactivation), $I_{Ai}$ (intermediate inactivation kinetics), and $I_{As}$ (slow inactivation). $I_{Af}$ showed fast inactivation with time constant of $10.6{\pm}2.0$ msec, $I_{Ai}$ of $36.9{\pm}13.9$ msec, and $I_{As}$ of $60.6{\pm}2.9$ msec at +30 mV, respectively. They also had distinct steady state inactivation range of each. Each cell expressed diverse combination of potassium currents. The cells most frequently observed were those which expressed both $I_{K1}$ and $I_{Af}$, and they had large diameters. The cells expressing $I_{Ke}$ and expressing $I_{Ke}$, $I_{Ai}$, and $I_{As}$ usually had small diameters. Judging from cell diameter, capsaicin sensitivity or action potential duration, candidates for nociceptor were the cells expressing $I_{Ke}$, expressing $I_{Ke}$ and $I_{Ai}$, and expressing $I_{Ke}$ and $I_{As}$. The types and distribution of potassium currents in neonatal rat DRG were similar to those of adult rat DRG (Gold et al, 1996b).

• 대한토목학회논문집
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• 제28권6B호
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• pp.643-651
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• 2008

본 연구에서는 횡방향 언덕-저면의 하상형상을 갖는 개수로 흐름을 수치모의 하였다. 곡선좌표계에 대한 지배방정식을 유도하고, 난류폐합을 위해 Speziale(1987)가 제안한 비선형 $k-{\varepsilon}$ 모형을 이용하였다. 개발된 모형의 개수로 흐름에 대한 적용성 및 모형 상수의 민감도를 분석하기 위해 직사각형 개수로 흐름을 수치모의 하였다. 그 결과 모형상수 $C_D$와 $C_E$는 각각 이차흐름 강도 및 난류의 비등방성에 영향을 미치는 것으로 확인되었다. 또한 비선형 $k-{\varepsilon}$ 모형이 자유수면에서 발생되는 난류의 비등방성을 정확히 모의할 수 없는 것으로 나타났으나, 전반적인 이차흐름 분포는 비교적 잘 예측하는 것으로 확인되었다. 한편 개발된 모형을 이용하여 횡방향 하상형상을 갖는 개수로 흐름을 수치모의하고 기존의 실험 결과와 비교하였다. 그 결과 비선형 $k-{\varepsilon}$ 모형이 하상형상의 언덕과 저면에서 발생되는 상향류 및 하향류를 비교적 정확히 예측하는 것으로 나타났으며, 계산된 주흐름방향 평균유속 및 난류구조 역시 기존의 실험 결과와 잘 일치하였다. 그러나 비선형 $k-{\varepsilon}$ 모형은 하상형상의 저면을 향하는 하향류를 과소 산정하는 것으로 확인되었다.