• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.387-390
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit Incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.5
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• pp.419-426
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• 2019

Mosapride accelerates gastric emptying by acting on 5-hydroxytryptamine type 4 ($5-HT_4$) receptor and is frequently used in the treatment of gastrointestinal (GI) disorders requiring gastroprokinetic efficacy. We tested the effect of mosapride on 5-hydroxytryptamine type 3 ($5-HT_3$) receptor currents because the $5-HT_3$ receptors are also known to be expressed in the GI system and have an important role in the regulation of GI functions. Using the whole-cell voltage clamp method, we compared the currents of the $5-HT_3$ receptors when 5-HT was applied alone or was co-applied with mosapride in cultured NCB-20 cells known to express $5-HT_3$ receptors. The $5-HT_3$ receptor current amplitudes were inhibited by mosapride in a concentration-dependent manner. Mosapride blocked the peak currents evoked by the application of 5-HT in a competitive manner because the $EC_{50}$ shifted to the right without changing the maximal effect. The rise slopes of $5-HT_3$ receptor currents were decreased by mosapride. Pre-application of mosapride before co-application, augmented the inhibitory effect of mosapride, which suggests a closed channel blocking mechanism. Mosapride also blocked the opened $5-HT_3$ receptor because it inhibited the $5-HT_3$ receptor current in the middle of the application of 5-HT. It accelerated desensitization of the $5-HT_3$ receptor but did not change the recovery process from the receptor desensitization. There were no voltage-, or use-dependency in its blocking effects. These results suggest that mosapride inhibited the $5-HT_3$ receptor through a competitive blocking mechanism probably by binding to the receptor in closed state, which could be involved in the pharmacological effects of mosapride to treat GI disorders.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.2
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• pp.87-94
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• 2005

It is not clear whether $Ca^{2+}-induced$ $Ca^{2+}$ release from the sarcoplasmic reticulum (SR) is involved in the regulation of atrial natriuretic peptide (ANP) release. Previously, we have shown that nifedipine increased ANP release, indicating that $Ca^{2+}$ entry via voltage-gated L-type $Ca^{2+}$ channel activation decreases ANP release. The purpose of the present study was two-fold: to define the role of SR $Ca^{2+}$ release in the regulation of ANP release and whether $Ca^{2+}$ entry via L-type $Ca^{2+}$ channel is prerequisite for the SR-related effect on ANP release. Experiments were performed in perfused beating rabbit atria. Ryanodine, an inhibitor of SR $Ca^{2+}$ release, increased atrial myocytic ANP release ($8.69{\pm}3.05$, $19.55{\pm}1.09$, $27.31{\pm}3.51$, and $18.91{\pm}4.76$% for 1, 2, 3, and $6{\mu}M$ ryanodine, respectively; all P<0.01) with concomitant decrease in atrial stroke volume and pulse pressure in a dose-dependent manner. In the presence of thapsigargin, an inhibitor of SR $Ca^{2+}$ pump, ryanodine-induced increase in ANP release was not observed. Thapsigargin attenuated ryanodine-induced decrease in atrial dynamic changes. Blockade of L-type $Ca^{2+}$ channel with nifedipine abolished ryanodine-induced increase in ANP release ($0.69{\pm}5.58$% vs. $27.31{\pm}3.51$%; P＜0.001). In the presence of thapsigargin and ryanodine, nifedipine increased ANP release and decreased atrial dynamics. These data suggest that $Ca^{2+}$-induced $Ca^{2+}$ release from the SR is inversely involved in the regulation of atrial myocytic ANP release.

• The Korean Journal of Physiology and Pharmacology
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• v.15 no.4
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• pp.195-201
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• 2011

The flavonoid quercetin is a low molecular weight compound generally found in apple, gingko, tomato, onion and other red-colored fruits and vegetables. Like other flavonoids, quercetin has diverse pharmacological actions. However, relatively little is known about the influence of quercetin effects in the regulation of ligand-gated ion channels. Previously, we reported that quercetin regulates subsets of nicotinic acetylcholine receptors such as ${\alpha}3{\beta}4$, ${\alpha}7$ and ${\alpha}9{\alpha}10$. Presently, we investigated the effects of quercetin on muscle-type of nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding human fetal or adult muscle-type of nicotinic acetylcholine receptor subunits. Acetylcholine treatment elicited an inward peak current ($I_{ACh}$) in oocytes expressing both muscle-type of nicotinic acetylcholine receptors and co-treatment of quercetin with acetylcholine inhibited $I_{ACh}$. Pre-treatment of quercetin further inhibited $I_{ACh}$ in oocytes expressing adult and fetal muscle-type nicotinic acetylcholine receptors. The inhibition of $I_{ACh}$ by quercetin was reversible and concentration-dependent. The $IC_{50}$ of quercetin was $18.9{\pm}1.2{\mu}M$ in oocytes expressing adult muscle-type nicotinic acetylcholine receptor. The inhibition of $I_{ACh}$ by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate human muscle-type nicotinic acetylcholine receptor channel activity and that quercetin-mediated regulation of muscle-type nicotinic acetylcholine receptor might be coupled to regulation of neuromuscular junction activity.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.249-251
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• 2013

본 논문은 LCL 필터를 가진 계통연계형 인버터 기반 마이크로그리드가 독립 운전 모드에서 동작할때의 인버터 출력 전압 제어 방식에 대해 다루고 있다. 분산 전원 기반의 마이크로그리드가 독립 운전 모드로 전환될 경우 마이크로그리드는 분산 전원만으로 전체 지역적 부하를 담당해야 하는 의무를 지니게 된다. 따라서 이때 마이크로그리는 전압원으로 가정되며 이를 위해 전압 제어가 수행되어져야 하며 담당하고 있는 부하가 불평형 또는 비선형 부하 일 경우 역상차, 영상차, 특정 차수의 고조파가 발생되기 때문에 기존의 전압 제어 방식을 사용할 경우 출력 전압에 높은 THD 가 발생하게 되며 이는 부하의 성능을 저해하는 요소로 작용한다. 따라서 본 논문에서는 기존의 PI 제어기 대신 특정 주파수에서 높은 제어 게인을 갖게하는 P+ 다중 공진제어기를 선정하였으며 이를 특정 고조파 별로 다중으로 제어함으로써 비선형-불평형 부하 연결에 의한 악영향에 대처하고자 하였다. P+ 다중 공진제어에 의한 출력 전압 THD 개선 효과는 PSIM Simulation 을 통해 검증되었으며 기존의 PI, Advanced PI 제어기와 그 성능이 비교 분석되었다.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.2
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• pp.159-165
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• 1999

Three-phase AC-DC flyback converter with high power factor correction and tight regulation is presented in this p paper. The advantage of the proposed converter does not require expensive high voltage and high cun‘ent devices that a are normally needed in popular boost type 3-phase converter. In this paper the detailed small signal analysis of the m modular 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included t to confirm the validity of the analysis.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.151-157
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• 1994

Intracellular free $Ca^{2+}$ contributes to regulation of various events occurring in vascular smooth muscle cells. One of these events is modulating the membrane iou currents. Single smooth muscle cells were isolated from rabbit mesenteric artery. Three kinds of $Ca^{2+}-activated\;current$ were studied with the patch clamp method. $Ca^{2+}-activated\;K^+\;current$ with a large oscillation was recorded in the depolarized potential range. The single channel conductance of this current was about 250 pS. It was abolished by replacing intracellular $K^+\;with\;Cs^+$. A $Ca^{2+}-activated$ nonselective cation current was observed in both the depolarized and hyperpolarized potential ranges. And it was blocked by replacement of extracellular $Na^+$ with N-methylglucamine (NMG) or extracellular application of $Cd^{2+}$. $Ca^{2+}-activated\;Cl^-\;current$ was revealed in the whole voltage range and was blocked by niflumic acid. These results indicate that at least three kinds of $Ca^{2+}-activated$ ionic currents exist in smooth muscle cells from rabbit superior mesenteric artery.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.129-131
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• 2006

This paper presents a new ZVS-PWM high frequency inverter. The ZVS operation is achieved in the whole load range by using a simple auxiliary reverse blocking switch in parallel with series resonant capacitor. The operating principle and the operating characteristics of the new high frequency circuit treated here are illustrated and evaluated on the basis of simulation results. It was examined that the complete soft switching operation can be achieved even for low power setting ranges by introducing the high frequency dual duty cycle control scheme. In the proposed high frequency inverter treated here, the dual mode pulse modulation control strategy of the asymmetrical PWM in the higher power setting ranges and the lower power setting ones, the output power of this high frequency inverter could introduce in order to extend soft switching operation ranges. Dual duty cycle is used to provide a wide range of output power regulation that is important in many high frequency inverter applications. It is more suitable for induction heating applications the operation and control principle of the proposed high frequency inverter are described and verified through simulated results.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1494-1503
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• 2016

Power quality promotion has received increasing attention because of the wide use of semiconductor devices in recent decades. Reactive power regulation is crucial to ensuring the stable operation of power systems. In this study, a continuous reactive power controller, which is referred to as a parallel-connected magnetic energy recovery switch (MERS), is developed to regulate voltage or power factor in power grids. First, the operating principle is introduced, and a mathematical model is built. Second, a new control method for restraining current harmonics and the peak voltages of capacitors is presented. Using the proposed method, the MERS shows a wide range in terms of reactive power compensation. Finally, the performance of the proposed controller is demonstrated through computer simulations and experiments. Unlike STATCOMs, the proposed controller entails low losses, adopts a small dc capacitor, and offers ease of use.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.837-841
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• 2009

언제, 어디서나 컴퓨터 사용과 통신이 가능한 유비쿼터스 환경의 구축과 개발은 부존자원이 부족한우리나라의 산업 전략에 부합하며 현재 우리나라가 보유한 정보통신 관련기술의 우위를 바탕으로 성장할 가능성이 큰 분야로써 정부가 미래의 10대 성장 동력으로 선정한 분야의 한가지 이다. 배전시스템에서의 이 분야 기술 개발의 핵심내용은 유비쿼터스 기술을 활용한 고 신뢰도의 배전계통 운용 및 높은 수준의 전기품질 관리체제 구축 그리고 이를 통한 관련 산업 즉, 전력거래, 전력시장 유지 및 운영을 위한 핵심 세부 콘텐츠와 부가서비스의 창출을 위한 기반 인프라의 개발 및 구축에 있는데, 이 기반기술의 중심에 배전시스템이 있으므로 이를 고 신뢰, 고품질 기반의 시스템으로 지능화하는 것이 필요하다. 따라서 본 논문에서는 태양광, 풍력 등의 분산전원이 계통에 연계되는 장래의 스마트배전시스템에 대하여, 기존의 배전계통의 전압조정방안과 비교, 분석하여 기술적인 적합여부를 종합적으로 평가하고자 한다.