• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.389-396
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• 2003

This paper describes a novel ac/dc power converter suitable for frequent output short-circuit faults. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there Is no overshoot of the dc voltage because the dc output fillet capacitors stay at a undischarged state. The proposed converter has the characteristics of a simplified structure, reduced cost, weight, and volume compared to the conventional power supplies for frequent output short-circuit. Analysis, simulations, and experiments are carried out to investigate the operation and usefulness of the proposed scheme.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.110.2-110.2
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• 2011

일본 Sanyo 사에 의해서 획기적으로 HIT 태양전지가 개발된 바 있다. 이러한 HIT 태양전지는 기존의 확산-접합 Si 태양전지에 비해서 저비용 고효율의 장점을 갖는다: 22% 이상의 변환효율, $200^{\circ}C$ 이하의 공정온도, 낮은 태양전지 온도 의존도, 높은 개방전압. 한편 Sanyo사의 HIT 태양전지는 n-형 Si 웨이퍼를 이용한 반면에, 최근 미국 National Renewable Energy Laboratory는 p-형 Si 웨이퍼를 이용해서 변환효율 19% 대의 HIT 태양전지를 개발한 바 있다. 그 동안 지속적으로 p-형 Si HIT 태양전지를 고효율화하기(< 22%) 위해서 많은 노력이 진행되어 왔지만 이와 같은 노력에도 불구하고 아직 p-형 HIT는 n-형 HIT 태양전지에 비해서 다소 성능면에서 떨어져 있다. 본 연구는 n- 및 p-형 실리콘 웨이퍼로 구성된 HIT 태양전지의 물리적인 차이점에 초점을 맞추고, 결정 및 비정질 실리콘 층의 역할에 대해서 연구하였다. 특히 태양전지 효율을 향상시키는 요소들로서 결정 실리콘의 불순물 준위(n- 및 p-형) 또는 비저항, 비정질 실리콘으로 구성된 emitter 층, intrinsic 층, 경계면이 고려되었다. 그리고 이러한 요소들이 HIT 태양전지에 미치는 영향을 조사하기 위해서 AMPS-1D 컴퓨터 프로그램을 사용하였고, 이를 통해서 HIT 태양전지의 결정 및 비정질 실리콘 층의 역할을 물리적 정량적으로 분석하였다. 본 연구에 적용되는 HIT는 ITO/a-Si:H(p+)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n+) 및 ITO/a-Si:H(n+)/a-Si:H(i)/c-Si(p)/a-Si:H(i)/a-Si:H(p+)의 구조로서 다음과 같은 태양전지 특성을 갖는다: n-형 HIT의 경우, fill factor ~ 0.78, 단락전류밀도 ~ 38.1 $mA/cm^2$, 개방전압 0.74 V, 변환효율 22.3 % (그리고 p-형 HIT의 경우, fill factor ~ 0.76, 단락전류밀도 ~ 36.5 $mA/cm^2$, 개방전압 0.69 V, 변환효율 19.4 %).

• The Korean Journal of Nuclear Medicine
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• v.33 no.4
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• pp.388-397
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• 1999

Purpose: Propranolol is known to decrease portal pressure by reducing blood flow of portal vein. Perrectal portal scintigraphy with Tc-99m pertechnetate has been introduced to evaluate the portal circulation and early diagnosis of liver cirrhosis. We evaluated the effects of propranolol on portal circulation by using per-rectal portal scintigraphy. Materials and Methods: We analyzed the portal hemodynamics by per-rectal portal scintigraphy in 51 patients with liver cirrhosis, 10 chronic hepatitis and 10 normal subjects. 38 patients with cirrhosis underwent per-rectal portal scintigraphy before and after propranolol medication. Perrectal portal scintigraphy was performed after per-rectal administration of 370 MBq of Tc-99m pertechnetate. The shunt index was calculated as the ratio, expressed as a percentage of heart radioactivity to the sum of heart and liver radioactivity during the first 30 seconds. Results: The shunt index in 40 patients with cirrhosis ($59.8{\pm}27.2%$) was significantly higher than that of normal control ($5.0{\pm}1.2%$. p<0.01) and chronic hepatitis ($11.4{\pm}3.5%$, p<0.01). Shunt index was significantly different according to Child's classification and the degree of esophageal varix (p<0.01). After propranolol medication, shunt index was significantly decreased from $59.9{\pm}27.3%$ to $51.3{\pm}15.3%$ (p<0.01) in 38 patients with liver cirrhosis. There was no significant difference of the amount of shunt index reduction after propranolol according to Childs' classification and the degree of esophgageal varix. Conclusion : The effect of propranolol on portal circulation was demonstrated as decreasing shunt index on per-rectal portal scintigraphy in patients with liver cirrhosis. Per-rectal portal scintigraphy may be useful to evaluate the portal circulation and to predict the effect of propranolol in patients with liver cirrhosis.

• Journal of Chest Surgery
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• v.29 no.5
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• pp.495-503
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• 1996

The bidirectional cavopulmonary shunt may be useful as an intermediate procedure before Fontal oper- ation in high-risk patients, because it provides adequate relief of cyanosis and relief of ventricular volume overload. But there are no established theory about the effects of bidirectional cavopulmonary shunt on pulmonary arterial development. The purpose of this article is a study of changes of pulmonary artery size after bidirectional cavopulmonary shunt. Ca diac catheterization and angiography procedures were done on 19 patients who underwent bidirectional cavopulmonary shunt from February 1992 to July 1994, their results were reviewed. Preoperative cardiac catheterization and angiography procedures were performed at a mean interval of ).8 $\pm$4.8($\pm$SEM) months before surgery and following catheterization at a mean postoperative interval of 19.6 $\pm$4.8 months. Pulmonary arterial sixte measurement were standardized for body surface area(Pulmon- arty artery index), and for diameter of descending thoracic aorta(McGoon ratio). Patient's age, body stir- face area, pulmonary angioplasty, preoperative McGoon ratio and follow-up intervals were considered as variables. Before bidirectional cavopulmonary shunt, patient's mean age, body surface area, arterial 02 saturation, diameter of right pulmonary artery, diameter of left pulmonary artery, pulmonary artery Index, McGoon ratio were 13.7$\pm$15.6 months, 0.40$\pm$0.12m2, 71.4$\pm$12.4m2, 7.1$\pm$1.7mm, 6.2$\pm$1 , 191.8$\pm$82.7mm21m2, 1.73 $\pm$0.49, respectively. After bidirectional cavopulmonary shunt, the values were changed to 39.9 $\pm$ 16.2 months, 0.58$\pm$0.07 m2, 83.0$\pm$3.8m2, 9.0$\pm$ 1.5 mm, 7.7$\pm$2.0, 197.3$\pm$57.1 mm2/m2, 1.76$\pm$0.32, respect- ively With patients'development (age, body surf'ace area), diameters of pulmonary arteries were increased, but pulmonary artery indices and McGoon ratios were not changed. And there were no effects of age, body surf'ace area, amount of increased 02 saturation, pulmonary angiography and follow-up duration on the increment of pulmonary ar- tery size. But when the McGoon ratio was as low as 1.2, there were significant increase in postoperative pulmonary artery sizes. There was a significant correlation between preoperative pulmonary artery index (PAI) and McGoon ratio (MGR) ; PAI : MGRxl18.0-12.4 In conclusion, bidirectional cavopulmonary shunt provides adequate increment of arterial 02 saturation and does not increase the pulmonary artery size. Further investi ation is mandatory to evaluate the effect of pulsatile bidirectional cavopulmonary shunt on pulmonary artery growth.

• Electric Engineers Magazine
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• v.226 no.6
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• pp.27-28
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• 2001

방향지락계전기는 비접지식 배전선과 저항접지식 송전선 등의 지락검출에 사용, 이는 유도권판형 또는 Transistor 방식이 채용되고 있으며 근래에 들어와 정지형 또는 Digital 방식으로 대처해 가는 과정에 있다.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.176-179
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• 1998

• 전기의세계
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• v.35 no.11
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• pp.710-715
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• 1986

직류송전은 선로의 건설비가 저렴하고 안정도의 문제가 없어 대전력 장거리송전이 가능하며, 비동기 연계를 할 수 있고, 조류제어가 신속.용이할 뿐만 아니라 단락용량을 증가시키지 않고도 계통의 연계강화가 가능한 점등의 잇점이 있으며, 특히 케이블 송전에 매우 유리한 송전방식이다. 그러나 선로의 건설비는 교류송전방식에 비해 저렴한 반면, 교직변환소의 건설비가 고가이므로 소용량 근거리 송전에는 경제성이 없으며, 고조파 및 고주파 장해대책이 필요하고, 전력계통 구성의 자유도가 떨어지는 점등의 문제가 있다. 본고에서는 직류송전의 역사적 배경과 설비의 현황, 운전실적 및 연구추진현황, 금후의 전망등에 관해서 기술하였다.

• The Korean Journal of Nuclear Medicine
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• v.33 no.1
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• pp.49-56
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• 1999

Purpose: Heart to liver ratio on T1-201 per rectal scintigraphy (shunt index) is known to be useful in the assessment of portal systemic shunt. We assessed T1-201 uptake pattern and early liver/heart uptake rate of T1-201 and correlated with shunt index in patients with chronic active hepatitis (CAH) and liver cirrhosis (LC). Materials and Methods: Fifty eight patients with biopsy-proven chronic liver disease (35 with CAH, 23 with LC) underwent T1-201 per rectum scintigraphy after instillation of 18.5 MBq of T1-201 into the upper rectum. We evaluated hepatic uptake (type 1 : homogeneous, 2: inhomogeneous segmental, 3: inhomogeneous nonsegmental) and extrahepatic uptake of spleen, heart and kidney (grade 0: no uptake, 1: less than liver, 2: equal to liver, 3: greater than liver). We measured the early liver/heart uptake rate (the slope of the liver to heart uptake ratio for 10 min) and shunt index (heart to liver uptake ratio). T1-201 uptake pattern and early liver/heart uptake rate of T1-201 was correlated with the pathologic diagnosis and shunt index. Results: Hepatic uptake patterns of type 1 and 2 were dominant in CAH (CAH: 27/35, LC. 8/23), and type 3 in LC (CAH: 8/35, LC: 15/23)(p<0.005). The grades of extrahepatic uptake were higher in LC than in CAH (spleen: p<0.001, other soft tissue: p<0.005). The early liver/heart uptake rate of CAH ($0.110{\pm}0.111$) was significantly higher than that of LC ($0.014{\pm}0.090$)(p<0.001). The sensitivity and specificity of the early liver/heart uptake rate were 77.7% and 67.7% in differentiating LC from CAH. There was negative correlation between early liver/heart uptake rate and shunt index (r=-0.3347, p<0.01). Conclusion: Hepatic and extrahepatic uptake pattern and early liver/heart uptake rate on T1-201 per rectum scintigraphy are useful in the assessment of portal systemic shunt in patients with chronic liver disease.

• The Korean Journal of Pharmacology
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• v.20 no.1 s.34
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• pp.23-32
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• 1984

The effects of morphine on the transmembrane potential and the short circuit current in the isolated frog skin were studied under different experimental conditions. The measurem ents of the transmembrane potential and the short circuit current were carried out according to Ussing and Zerahn's method. Experimental results were summerized as follows: 1) $5{\pm}10^{-3}$M of morphine markedly depressed the transmembrane potential and the short circuit current of the naive preparation. The peak of these inhibitory effects of morphine was observed about 1 hour after administration of the drug. 2) However $10^{-4}$M of naloxone did not affect these effects of morphine. 3) Decrease of $K^+$, increase of $K^+$ or $Ca^{2+}$ in the perfusate, markedly potentiated the inhibitory action of morphine on both transmembrane potential and short circuit current of the frog skin, and addition of $Mn^{2+}$ to the solution depressed the effect of morphine on the transmembrane potential, while the inhibitory effect of morphine on the short circuit current was diminished in the $Ca^{2+}$-free ringer solution, and increase of $Mg^{2+}$ concentration depressed those effect of morphine on both electrical parameters. 4) In the morphine treated preparations, transmembrane potential and short circuit current were decreased in the early phase of drug treatment ($1{\sim}2$ days), but gradually increased to the significantly high level from the control (48 days after treatment). In these preparations, the effects of morphine on both electrical parameters were also potentiated in the early phase, but markedly diminished in the late phase of treatment. From the above results, it is postulated that the pharmacological actions of morphine as well as development of the tolerance by morphine may be partially related to the changes of ion fluxes and/or permeabilities of skin by the drug.

• Electric Engineers Magazine
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• s.279
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• pp.30-35
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• 2005

전력계통 사고는 3상 단락에 비해 1선 지락사고가 대부분을 차지하고 있으며 적절한 접지를 통해 대지전압의 이상상승을 억제하고 보호 계전기에 의한 지락고장 검출 고장구간을 자동선택 차단하여 전력기기의 손상과 사고파급을 방지하여야 한다. 그러나 플랜트의 경우, 계통접지방식과 지락보호 시스템에 대한 이해부족으로 상기의 목적을 제대로 만족하지 못하는 사례와 정전으로 인한 2차적인 생산피해도 많이 발생하고 있다. 따라서 본론에서는 계통접지 방식 중에서 비접지 방식의 전반적인 이해를 돕고자 하며, 이를 토대로 비접지 계통의 지락보호 협조에 대하여 학습하고자 한다. 본 내용은 파워세븐엔지니어링을 검색하면 자료를 다운받을 수 있음.