• 한국강구조학회 논문집
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• 제13권5호
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• pp.557-566
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• 2001

데크플레이트를 사용한 합성슬래브가 합성거동을 발휘하기 위해서는 데크플레이트와 콘크리트의 부착강도가 확보되어야한다. 합성슬래브에서 전단부착강도는 콘크리트와 데크플레이트의 화학적 부착력, 마찰저항 기계적 상호작용에 의해 발생한다. 또 기계적 상호작용은 길이 방향 전단력 전달 장치인 엠보싱 및 쉬어코넥터, 데크플레이트 형상 등에 의해서 확보되어 진다. 그리고 기계적 상호작용의 효과는 상호 접착부의 수직박리를 구속할 수 있는 데크의 형상과 쉬어코넥터 설치에 따른 단부정착 여부에 따라 크게 달라진다. 그러므로, 본 연구에서는 폐쇄형 데크플레이트에 대하여 기계적 전달장치인 엠보싱과 쉬어 코넥터로 사용되는 스터드 볼트에 대한 전단 보강장치의 부착효과를 Push-off 실험을 통하여 규명하였으며 이들 인자들에 대하여 제안식을 제시하였다. 이는 합성슬래브 설계방법의 기초자료로 이용될 수 있을 것으로 사료된다.

• 대한기계학회논문집B
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• 제41권4호
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• pp.277-283
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• 2017

본 연구에서는 높이에 따른 점프 전략 변화를 이해하기 위해 반동을 이용한 수직 점프 시 상변화 시점에서의 지면반력 벡터가 높이에 따라 어떻게 변하는지 분석하였다; 반동과 추진 구간에서 유사한 힘 작용선을 갖는 수직 점프의 경우, 상변화 시점에서 반동의 이득을 나타내는 합력 벡터의 크기와 방향이 일정한 경향성을 가지고 높이에 따라 변화할 것이라 가정하였다. 9명의 청년군 모두는 정해진 5 종류의 높이를 총 5세트에 걸쳐 랜덤 방식으로 점프하였으며, 해당 높이를 유도하기 위해 지면으로부터 191 cm에서 221 cm 사이에 일정한 간격을 두고 마커를 배치하였다. 점프 높이가 증가함에 따라 반동 시 무게중심을 낮추고, 수평, 수직 방향의 힘을 증가시키는 것이 관찰되었는데, 이는 추진일을 증가시키기 위해 관절의 가용범위를 넓히고 초기 힘(또는 가속도) 이득을 늘리기 때문으로 생각된다.

• 한국방재학회 논문집
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• 제10권3호
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• pp.31-38
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• 2010

본 연구에서는 교량 구조물-궤도 종방향 상호작용, 교량 구조물-차량 상호작용을 고려한 신뢰성 최적설계 방법을 제안하고, 알고리즘의 개발을 통하여 본 연구에서 제안한 방법의 효율성을 검증하였다. 구조해석 프로그램은 ABAQUS를 사용하였으며, 최적화 방법은 Automated Design Synthesis(ADS)에서 신뢰성면에서 우수한 ALM-BFGS방법을 사용하였다. 일반적으로 ALM-BFGS방법은 최적해 방향을 탐색하는데 있어 1방향 탐색을 하지 않으며 Push-Off Factor 값이 보통 0.1~0.2에서 대부분 수렴하나 본 연구에서는 'Heuristic Decision Method' 의하여 결정된 Push-Off Factor 값이 90일 때 1방향 탐색인 Golden Section Method의 적용이 필요하였으며, 알고리즘이 잘 수렴함을 확인하였다. 구조물-궤도 종방향 상호작용, 구조물-차량의 상호작용에 의한 응답을 제약조건으로 설정하여 단면 설계시 반영될 수 있도록 하였다. 본 연구는 구조물-궤도 종방향 상호작용 및 구조물-차량 상호작용을 고려한 설계기법에 대한 효율성 및 경제성을 증명하기 위하여 5${\times}$(1@50m) 2주형 강합성 거더교에 대한 최적설계를 수행하였으며, 본 연구에서 제안하는 상호작용을 고려하는 설계기법이 기존의 상호작용을 고려하지 않은 설계방법보다 경제적이며 효율적임을 확인하였다.

• Journal of Power Electronics
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• 제12권2호
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• pp.242-248
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• 2012

Self oscillating current fed push pull resonant inverters can be controlled without using special drivers. Dc current flows through the choke coil and the power switches, although the driving signals of the power switches are sinusoidal. When the base current is near zero, the transistors cannot be operated in switching mode. Hence higher switching power losses and instantaneous peak power during off transitions are observed. In this study, an alternative design has been proposed to overcome this problem. A prototype circuit has been built which provides dc bias current to the base of the transistors. Experimental results are compared with theoretical calculations to demonstrate the validity of the design. The proposed design decreases the peak and average power losses by about 8 times, when compared to conventional designs.

• 전력전자학회논문지
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• 제18권3호
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• pp.247-255
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• 2013

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1324-1326
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• 2000

This paper proposes a Current-Fed Push Pull type DC-DC converter using LCCC Resonant circuit and Zero Voltage Switching function to reduce turn on and off loss at the switching instants. This paper have the advantage which is able to operating safely in load short, because of DC reactor is connected with resonance reactor in order to supply a fixed current with low ripple from DC Power supply. The capacitor ($C_1$, $C_2$) connected in switch are common using as resonance capacitor and ZVS capacitor. The analysis of the proposed Current-Fed Push Pull type DC-DC converter is generally described by using normalized parameter, and we have evaluated characteristic values which is needed to design a circuit. We confirm a rightfulness theoretical analysis by comparing a theoretical values and experimental values obtained from experiment using MOSFET as switching devices.

• Computers and Concrete
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• 제26권2호
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• pp.151-159
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• 2020

This paper presents an evaluation of shear transfer across cracks in reinforced concrete through finite element modelling (FEM) and analytical predictions. The aggregate interlock is one of the mechanisms responsible for the shear transfer between two slip surfaces of a crack; the others are the dowel action, when the reinforcement contributes resisting a parcel of shear displacement (reinforcement), and the uncracked concrete comprised by the shear resistance until the development of the first crack. The aim of this study deals with the development of a 3D numerical model, which describes the behavior of Z-type push-off specimen, in order to determine the properties of interface subjected to direct shear in terms cohesion and friction angle. The numerical model was validated based on experimental data and a parametric study was performed with the variation of the concrete strength. The numerical results were compared with analytical predictions and a new equation was proposed to predict the maximum shear stress in cracked concrete.

• 한국동물학회지
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• 제32권4호
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• pp.329-338
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• 1989

Present study examined the effect of intermittent versus continuous infusion of progesterone(P) on LHRH release in uiuo from the mediobasal hvpothalamus of ovariectomiEed, estradiol-primed adult rats bearing push-pull cannulae. Three experimental groups were studied: 1) control (perfusion medium only),2) intermittent perfusion of P (10-min on,20-min off, and 3) continuous perfusion of p. p (10 ng/mll was directly infused into the MBH following a 3 hr basal collection. Perfusates were collected at 10 min intents린s on ice and LHRH release was measured by LHRH radioimmunoassav. Cycle detector analysis revealed that the spontaneous HRH output in the control group was pulsatile over a 7 hr push-pull perfusion period. The mean basal LHRH release, pulse amplitude and pl서se period were 0.68 $\pm$ 0.03 ps110 min, 1.15 $\pm$0.08 pg and 60 $\pm$ 9 min, respectivelv. Intermi구eat perfusion of P clearly stimulated the mean LHRH release (pre-P vs post-P: 1.14 $\pm$ 0.18 vs 1.99 $\pm$ 0.53 pg) without changes in LHRH pulse frequency. In contrast to intermittent infusion of p, continuous administration of P faithed to modify LHRH release, since the mean LHRH release and pulse amplitude between pre-P and post-P perfusion urere similar. The in vitro study clearly showed that intermittent, but not continuous administration of P is effective in stimulating LHRH release. Therefore, it appears that rhythmic secretion of P mal be the erective signal for activating the neural LHRH apparatus.

• 한국멀티미디어학회논문지
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• 제4권3호
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• pp.205-214
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• 2001

As the real time multimedia data service has become available due to the rapid progress of computer and Internet technology, the users can enjoy the newly developed service, which is called Video On-Dem-and(VOD). However, most of service providers have not paid their attention much on the software for various service modes on VOD, but they are only concentrating un the hardware to provide with the high resolution video display. Therefore, the service providers are recently to pay more attention on the software to cope with the various demands of users than hardware. So this paper has designed and implemented the VOD service system for those demands. Since the VOD service system suggested by this paper enable off-line search functions through E-mail, the users can possibly get the necessary information from off-line Search without connecting to the server while the current VOD service can prominently help users to save the time and effort to sea고 and select the Video contents by using periodical current awareness service supported by PUSH technology and user oriented information booking and feedback service supported by SDI service.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.8-10
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• 2019

In this paper, a bidirectional three-phase push pull converter is analyzed for the high power, wide voltage range applications. From comparison analysis of two switching methods: PWM plus phase-shift (PPS) and dual-asymmetric PWM (DAPWM) with the effect of dead-time, the proposed hybrid control is aimed to reduce the circulating current under wide voltage range operation. Value of leakage inductance effect to the peak current value, current stress and conduction loss in facing the load variation. Trade-off between power range and slew rate of transformer current was analyzed for properly selecting value of the transformer leakage inductance. Experimental results from a 22-kW prototype are provided to validate the proposed concept.