• 전기전자학회논문지
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• 제19권2호
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• pp.260-264
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• 2015

본 논문에서는 부하전류를 감지하여 스위칭 방식과 선형 방식의 레귤레이터를 동작하기 위한 mode selector를 제안한다. 제안된 mode selector는 선형 방식과 스위칭 방식으로의 모드 전환이 가능하며, 경부하 조건에서 낮은 효율을 갖는 스위칭 방식의 레귤레이터의 단점을 보완하고자 제안되었다. 경부하 조건에서는 선형 방식의 레귤레이터로 mode를 전환함으로써 경부하 상태에서도 높은 효율을 제공할 수 있다. 설계한 mode selector는 동부 하이텍의 $0.18{\mu}m$ CMOS 공정을 이용하였다.

• 한국생산제조학회지
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• 제25권6호
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• pp.462-470
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• 2016

The locking load of a conventional manhole depends on the weight of its cover. Locking-type manhole structures with a special locking mechanism were recently developed to prevent accidents such as stolen cover, away cover from a frame. The weight of the manhole structure can be reduced under structural safety because the locking force of a locking-type manhole is greater than the weight of the cover. A light-weight manhole cover is developed in this study by using a finite element stress analysis and the design of experiments. Static stress analysis and fracture experiments are also conducted to analyze the states of the initial product. The optimum light-weight manhole cover considering manufacturing molds is developed and tested. Consequently, the weight was found to reduce by 16%. In addition, the fracture load increased by 38%.

• 한국기계가공학회지
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• 제20권11호
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• pp.9-16
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• 2021

As the climate changes rapidly due to warming, it is becoming very important to ensure the stability of environmental structures. It is necessary to choose a material that withstands repeated external forces (wind loads) and satisfies members and joints that have energy absorbing power. Even if the strength of the traffic light attachment is sufficient, if the rigidity is insufficient, there is a limit to the displacement during strong winds. Excessive deformation may cause damage and fall, resulting in a safety accident. The author intends to study mechanical properties and resistance to external environment as a structural material capable of withstanding wind load (50m/sec) by fabricating a C/GFRP composite traffic light attachment using the pultrusion method (Pultrusion).

• 오토저널
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• 제12권5호
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• pp.97-106
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• 1990

A method of weight evaluation of the load-bearing structural elements of cars is presented and the weight ratio of the analysis model is investigated. Replacing the materials of floor elements of the car into the high-strength steel, a considerable weight-reduction of the model has been obtained. The 1500cc model is selected for the present study and the stick model analysis is employed for the structural analysis. The torsional stiffness of the weight-reduced model is also evaluated and it is shown it has a reasonable rigidity. The ratio of the weight of the load-bearing structural elements to the unladen vehicle weight of cars is about 0.12for the 1500cc model and the weight-reduction of this study can be obtained around 17% of the weight of the load-bearing structural elements.

• 대한전기학회논문지:전력기술부문A
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• 제48권6호
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• pp.704-711
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• 1999

This paper presents a design of fuzzy power system stabilizer (FPSS) using adaptive evolutionary computation (AEC). We have proposed an adaptive evolutionary algorithm which uses a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner in order to take merits of two different evolutionary computations. FPSS shows better control performances than conventional power system stabilizer (CPSS) in three-phase fault with heavy load which is used when tuning FPSS. To show the robustness of the proposed FPSS, it is appliedto damp the low frequency oscillations caused by disturbances such as three-phase fault with normal and light load, the angle deviation of generator with normal and light load and the angle deviation of generator with heavy load. Proposed FPSS shows better robustness than CPSS.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.430-435
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• 2008

Hyundai-Rotem Company has designed and manufactured Light Railway Vehicle (LRV) according to the Urban Rail Transit Code, which applies to urban railway vehicles in Korea. The Urban Rail Transit Code specifies the loads, for which vehicle bodies shall be capable of withstanding, identifies how material data shall be used and presents the principles to be used for design verification by analysis and test. The structural design of railway vehicle bodies depends on the loads they are subjected to and the characteristics of the materials they are manufactured from. Therefore Hyundai-Rotem Company has carried out Finite Element Analysis (FEA) and has performed load tests on the vehicle body according to the Urban Rail Transit Code. This research contains the results obtained by the analysis and the load tests. The analysis was carried out using I-DEAS Master Series 12 and load test were carried out using specially designed test jigs and equipment are used for the load tests.

• Journal of Power Electronics
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• 제18권4호
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• Journal of Power Electronics
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• 제16권6호
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• pp.2024-2034
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• 2016

This paper presents a DC-DC buck converter with a Phase-Locked Loop (PLL) that can compensates for power efficiency degradation over a wide input range. Its switching frequency is kept at 2 MHz and the delay difference between the High side driver and the Low side driver can be minimized with respect to Process, Voltage and Temperature (PVT) variations by adopting the PLL. The operation mode of the proposed DC-DC buck converter is automatically changed to Pulse Width Modulation (PWM) or PWM frequency modes according to the load condition (heavy load or light load) while supporting a maximum load current of up to 1.2 A. The PWM frequency mode is used to extend the CCM region under the light load condition for the PWM operation. As a result, high efficiency can be achieved under the light load condition by the PWM frequency mode and the delay compensation with the PLL. The proposed DC-DC buck converter is fabricated with a $0.18{\mu}m$ BCD process, and the die area is $3.96mm^2$. It is implemented to have over a 90 % efficiency at an output voltage of 5 V when the input range is between 8 V and 20 V. As a result, the variation in the power efficiency is less than 1 % and the maximum efficiency of the proposed DC-DC buck converter with the PLL is 95.4 %.

• 전자공학회논문지
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• 제50권8호
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• pp.151-161
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• 2013

본 논문에서는 입력전압을 감지하지 않는 전류연속/임계동작모드 active power factor correction(PFC) circuit을 제안하였다. 기존의 입력전압을 감지하지 않는 PFC circuit의 경우 출력전류가 낮은 경 부하 조건에서 DCM 동작을 수행하고, 이에 따라 PF가 감소하는 문제가 발생한다. 제안한 PFC circuit은 70KHz의 주파수로 CCM 동작을 수행하고, 경 부하 조건에서 최대 200KHz까지 스위칭 주파수가 가변되는 CRM 동작을 수행하도록 하였다. 이를 통해 경 부하 조건에서 PF가 감소하는 문제를 해결하였다. PFC controller IC는 $0.35{\mu}m$ BCDMOS 공정을 이용하여 제작하였으며, 240W급 PFC prototype을 제작하여 실험하였다. 제안한 PFC circuit은 기존의 PFC circcuit 대비 최대 10%의 역률이 향상되었고, IEC 61000-3-2 Class D 규격에 따른 경 부하 조건에서는 최대 4% 역률이 향상되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.109-116
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• 2007

본 논문의 목적은 경량기포모르터를 충전한 스틸스터드와 복합스터드 내력벽체의 내화성능을 KS규준에 따라 평가하는데 있다. 주거용과 상업용 건물의 최소 내화 요구시간은 2시간이다. 시험 결과로부터 스틸 스터드와 복합스터드에 경량기포 모르터를 충전한 두 시험체 모두 2시간 내화 성능을 만족하는 것으로 나타났다. 또한 복합스터드 패널 시험체의 경우 내화 성능면에서 스틸 스터드 패널 시험체 보다 우수하다는 것을 정량적 평가하였다.