• 전기전자학회논문지
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• 제11권4호
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• pp.331-339
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• 2007

The problem of architecting a reliable transport system across an overlay network using split TCP connections as the transport primitive is mainly considered. The considered overlay network uses the application-level switch in each intermediate host. We first argue that natural designs based on store-and-forward principles that are maintained by split TCP connections of hop-by-hop approaches. These approaches in overlay networks do not concern end-to-end TCP semantics. Then, a new transport protocol-Overlay Transport Protocol (OTP)-that manages the end-to-end connection and is responsible for the congestion/flow control between source host and destination host is proposed. The proposed network model for the congestion and flow control mechanisms uses a new window size-Ownd-and a new timer in the source host and destination host. We validate our analytical findings and evaluate the performance of our OTP using a prototype implementation via simulation.

• Journal of Power Electronics
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• 제8권4호
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• pp.363-370
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• 2008

In this paper, three kinds of PWM strategies for a three-phase current-fed dc/dc converter are proposed and compared in terms of losses and voltage transfer ratio. Each PWM strategy is described graphically and their switching losses are analyzed. With the proposed PWM C strategy, one turn-off switching of each bridge switch is eliminated to reduce switching losses under the same switching frequency. In addition, RMS current through the bridge switches is lowered by using parallel connection between two bridge switches and thus, conduction losses of the switches are reduced. Further, copper losses of the transformer are decreased due to the reduced RMS current of each transformer's winding. Therefore, total losses are minimized and the efficiency of the converter is improved by using the proposed PWM C strategy. Digital signal processor (DSP: TI320LF2407) and a field-programmable gate array (FPGA: EPM7128) board are used to generate PWM patterns for three-phase bridge and clamp MOSFETs. A 500W prototype converter is built and its experimental results verify the validity of the proposed PWM strategies.

• 제어로봇시스템학회논문지
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• 제14권6호
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• pp.535-542
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• 2008

This paper presents a high efficiency half-bridge DC-DC converter for an LED backlight drive system of LCD module inspection equipment. The proposed converter improves the converter efficiency using characteristics of the asymmetrical half-bridge converter and the self-driven synchronous rectifier, and thus improves the total efficiency of the LED backlight drive system. The synchronous rectifier applied to the proposed converter is the new topological synchronous rectifier, which changes slightly the transformer structure and the synchronous switch connection in the asymmetrical half-bridge converter with a conventional self-driven synchronous rectifier. Since the proposed converter utilizes the transformer leakage inductor as its resonant inductor, its structure is simplified. The proposed converter well operates under the universal DC input voltage ($250{\sim}380V$). The operational principle and a design example for a 100W prototype are discussed in detail, respectively. Experimental results are shown for the designed prototype converter under universal DC input voltage.

• 한국안전학회지
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• 제29권3호
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• pp.20-27
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• 2014

Cooling equipment is the frequent occurrence of fire despite the absence of the heating element. National fire statistics in 2013 show that a total of 263 fires occurred in the cooling equipment and the number of electric fan has 145 fire cases. This is accounted for 55.1% of the whole. Electric fan is the electrical appliance that the heat is generated on the winding wire and the iron core. If such characteristic is not controled properly, fire would break out at the electric fan. also there is a gap filled with an insulator between connection terminals of the capacitor in the electric fan. But in case that the gap on the capacitor is covered with some conductive material such as dust, there would be a fire as well caused by electrical heating locally. Although many studies related with those have been conducted, electric fan fire is continuously occurred. In this study, thermal characteristics and current signal in various conditions such as the heat generation of windings including iron cores of the motor and the dielectric breakdown of terminals on the capacitor connected to the motor were detected. In order to measure the maximum temperature, "third level" wind velocity button was pushed and the time selection switch to "continuation" was set. Analyzed data would be available for the fire safety of the electric fan.

• 대한산업공학회지
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• 제36권3호
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• pp.203-211
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• 2010

This study examines a cointegrated vector autoregressive (VAR) model where parameters are subject to switch across the regimes in the term structure of interest rates. To employ the regime switching framework, the Markov-switching vector error correction model (MS-VECM) is allowed to the regime shifts in the vector of intercept terms, the variance-covariance terms, the error correction terms, and the autoregressive coefficient parts. The corresponding approaches are illustrated using the term structure of interest rates in the US Treasury bonds over the period of 1958 to 2009. Throughout the modeling procedure, we find that the MS-VECM can form a statistically adequate representation of the term structure of interest rate in the US Treasury bonds. Moreover, the regime switching effects are analyzed in connection with the historical government monetary policy and with the recent global financial crisis. Finally, the results from the comparisons both in information criteria and in forecasting exercises with and without the regime switching lead us to conclude that the models in the presence of regime dependence are superior to the linear VECM model.

• 한국통신학회논문지
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• 제28권1A호
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• pp.7-16
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• 2003

무선 ATM 망은 광대역 멀티미디어 서비스 제공을 위해 셀의 크기가 작은 마이크로/피코 셀 구조를 채택하므로 단말의 이동성 지원을 위한 핸드오버 기능은 매우 중요하다. 본 논문에서는 무선 ATM 망에서 이동교환기간 핸드오버를 신속하게 처리하기 위한 동적 경로 예약 핸드오버 기법을 제안한다 제안한 기법은 이동교환기간 핸드오버를 위해 최대근접공통노드로부터 인접 이동교환기까지 가상 채널을 미리 설정하므로 실제 핸드오버 시에 연결의 재라우팅에 소요되는 시간을 단축할 수 있다 특히 일정 주기마다 예측 알고리즘을 수행하여 다음 주기에 발생할 핸드오버 호의 수를 예측하여 가상 채널을 예약함으로써 기존 DVCT 기법에 비하여 예약 채널 수, 예약 채널 이용률 및 시그널링 복잡성을 개선하였다.

• Journal of Communications and Networks
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• 제6권1호
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• pp.38-45
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• 2004

The ABR point-to-multipoint connection is now playing a more important role than before. Many consolidation algorithms have been proposed to solve the consolidation noise problem and the slow transient response problem. But few timeout algorithms are proposed to handle the non-responsive branches for the multicast connections. Chen’s algorithm needs exchanging control messages between switches [9]. Besides, it may mistake a responsive branch as a non-responsive branch because of fast changes in source rates, which causes wrong information in BRM cells and may lead to network congestion and data losses in the responsive branch. We propose a simple timeout algorithm which can handle the non-responsive branches without exchanging message between switches. The timeout value for each switch is computed locally. Simulation results show that the proposed timeout algorithm can efficiently handle the non-responsive branches and utilize the available bandwidth within a small period of time. In addition, our algorithm could handle the situation when the source rates change quickly.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.97-101
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• 2008

Voice over IP is a telephone service which sends and receives the voices through the Internet. Because the infrastructure of wireless and mobile communication networks such as 3G, Wi-Fi and WiMAX has expanded, the study about Mobile VoIP, which provides the voice service from wireless network, has been actively in progress. Since Rei 6 HSPA in 3GPP and Rev A lxEVDO in 3GPP2, VoIP through the data channel is more efficient than circuit switch. It is predicted that VoIP over 4G will be more effective and 4G mobile VoIP business will be vitalized in the future. In addition, there are businesses which offer VoWLAN by using software such as Skype and Fring. They provide services which cheapen the price of international calls and long distance calls. This paper will present the Korean and other countries' mobile VoIP trends, its classification along the network connection, the study on techniques, and conditions of mobile VoIP. It also will be described a view of terminal convergence and service convergence.

• Journal of Power Electronics
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• 제10권6호
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• pp.611-620
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• 2010

This paper presents a new architecture, called "Power Electronics Remote Wiring and Measurement Laboratory (PermLAB)", that translates a common gateway interface (CGI) string from a remote web user to a web server connected to a 3-dimension switching matrix board, can be used to switch on and off, and to control a cluster of instruments and components. PermLAB addresses real-time connection, switching, and data acquisition over the Internet instead of using simulated data. A software procedure uses a signature system to identify each instrument and component in a complex system. The Web-server application is developed in HTML, JavaScript and Java, and in C language for the CGI interface, which resides in a controller portion of LabVIEW. The LabVIEW software fully integrates the Web sever, LabVIEW data acquisition boards and controllers, and the 3-dimensional switching matrix board. The paper will analyze a half-wave rectifier (AC - DC converter) circuit connected over the Internet using the PermLAB. PermLAB allows students to obtain real data by real-time wiring of real circuits in the laboratory using a "virtual breadboard" on the Web. The software for the Web-based 3-dimensional system is flexible, portable, can be integrated into many laboratory applications or expanded, and easily accessible worldwide.

• Journal of Chest Surgery
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• 제32권7호
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• pp.621-627
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• 1999

배경: 본 연구에서는 교정형 대혈관전위증으로 양심실교정이 가능하여 개심술을 시행받은 65례의 환아를 대 상으로 질환의 해부학적 특성, 수술방법 및 결과를 분석하였다. 대상 및 방법: 1984년부터 1998년 9월까지의 교정형 대혈관전위증으로 양심실교정을 받은 65례의 환자들을 대상으로 하였으며 주로 환자의 의무기록을 참조하여 후향적으로 동반기형에 따른 수술법의 차이 및 각각의 수술법에 따른 합병증등 단기 및 중장기 성 적을 분석하였다. 결과 평균 연령은 5.4$\pm$4.8세(2개월~18세)이었으며 남:녀비는 39:26이었다. 형태로는 {S,L,L}이 53례{I,D,D}가 12례였다. 폐동맥 협착이나 폐쇄가 동반되지 않았던 경우가 13례(20%)였으며 심실 혹은 심방중격결손증과 폐동맥 협착증이 동반된 경우가 26례(40%)였고 심실중격결손증과 폐동맥 폐쇄증이 동반된 례가 26례(40%)였다. 술전 경도이상의 삼첨판막 폐쇄부전을 보인 환자는 38.5%(26/65)였다. 완전교정 술전 단락술은 22명의 환자에서 24차례 시행하였다. 교정술의 방법으로 폐동맥심실유출로 협착이 없던 13례 에서는 7례에서 심실 혹은 심방 중격결손증만을 폐쇄하였고, 3례에서 삼첨판막치환술을, 3례에서 좌심실을 체순환으로 사용하는 중복치환술(Senning+Rastelli, Senning+REV, Senning+ASO)을 시행하였다. 심실,혹은 심방 중격결손증과 폐동맥 협착이 있던 26명의 환자에서는 24례에서 우심실을 체순환으로 사용하는 기존의 방법 (Rastelli술식 9례, 심실중격결손증 폐쇄후 폐동맥판막절개술 7례, REV형 술식 4례, 중격결손 폐쇄후 폐동맥 판막하 근육절제가 3례, 삼첨판막치환술이 1례)으로 수술하였으며 2례에서 중복치환술(Senning+Rastelli, Mustard+REV)을 시행하였다. 심실중격결손증과 폐동맥폐쇄증이 있었던 26명의 환자에서는 18명에서 심실중 격결손증을 폐쇄하고 Rastelli술식을 시행하였고, 7례에서 중복치환술(Senning+Rastelli)을 시행하였으며, 1례는 심실중격결손증을 폐쇄하고 REV형 술식을 시행하였다. 술후 추적 기간동안 우심실을 체순환으로 사용한 환 자들에서의 삼첨판막폐쇄부전은 술전 평균 1.3$\pm$1.4도에서 2.2$\pm$1.0도로 통계적으로 의미있게 증가하였다 (p<0.05). 그러나 중복치환술을 시행받은 환자들은 술후 삼첨판막의 폐쇄부전의 증가가 없었다. 술전 완전 방 실차단을 보인 환자는 2례(3.1%)있었으며 술후 새롭게 발생한 완전방실차단은 7례(10.8%)있었다. 술후 기타 장,단기 합병증으로는 폐동맥심실유출로도관(conduit) 재협착이 10례, 혈전증(판막: 2례, 인조혈관: 1례, 폐동 맥: 1례)이 4례, 2주 이상의 지속적 흉관배액이 4례, 유미흉이 3례, 출혈에 의한 재수술이 3례, 기타 급성 신 부전, 종격동염, 횡경막신경 마비가 각각 2례씩 있었으며, 중복치환술을 받은 환자들과 전통적 술식으로 수 술받은 환자에서 술후 합병증의 차이는 없었다. 65명의 환자를 평균 54$\pm$49개월(0~177개월)간 추적관찰하였 으며, 수술 초기에 사망한 환자는 13명으로 20.0%(13/65)의 수술사망율을 보였으며 3명의 환자가 추적기간중 사망하여 24.6%(16/65)의 전체사망율을 보였다. 중복치환술을 받은 환자의 수술사망율은 33.3%(4/12)였다. 술 후 1년, 5년, 10년 누적생존율은 각각 75.0$\pm$5.6%, 75.0$\pm$5.6%, 69.2$\pm$7.6%였다. 가장 흔한 사망원인으로는 술 후 저심박출증후군으로 8례였으며 삼첨판막 폐쇄부전이 심해져 심부전으로 사망한 경우도 5례로 사망의 중 요 원인이었다. 결론 저자들은 본 연구를 통하여 기존의 형태학적 우심실을 체순환으로 사용하는 방법과 형태학적 좌심실을 체순환으로 사용하는 해부학적 교정법인 중복치환술중 어느 것이 우월하다고 결론지을 수는 없었으나 해부학적 교정술이 삼첨판막의 폐쇄부전의 진행을 막을수 있다는 면에서 이점이 있으리라 사 료되며 보다 세분화된 적응증의 결정과 아울러 장기적인 추적관찰 및 비교가 필요하리라 생각된다