• 한국자동차공학회논문집
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• 제22권1호
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• pp.52-58
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• 2014

To improve the performance of clutch actuator of clutch-by-wire system for commercial vehicles, it is necessary to understand the driving characteristics of the system. To explain and predict the effects of driving characteristics on clutch characteristics, AMESim software is used. The simulation model of clutch-by-wire system is developed in the AMESim environments under the geometrical dimensions and driving mechanisms of the clutch-by-wire system, such as the rotation speed of the DC motor, the gear ratio of the reducer, the design parameters of the release fork, the coefficient of the clutch diaphragm spring, and so on. The results show that the theoretical analysis of the clutch-by-wire system for commercial vehicles using the AMESim software find out the driving characteristics of the clutch actuator, and predict the performance characteristics of the clutch-by-wire system.

• Journal of Pharmaceutical Investigation
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• 제35권3호
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• pp.143-150
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• 2005

Solid lipid nanoparticles(SLNs) are particulate systems for parenteral drug administration and have good biocompatibility and stability. SLNs were prepared with lauric acid, as the lipid core. Tween 20 and tween 80 were used as surfactant. 5-fluorouracil and l-benzoyl-5-fluorouracil were used as model drugs. Drug-loaded SLNs were prepared by the hot homogenization technique in order to evaluate the physical stability, entrapment efficiency of drugs as well as release profile. The particle size of SLNs was $40{\sim}600$ nm. By increasing speed, the mean particle size of SLNs was decreased. And entrapment efficiency in the case of using 1-Benzoyl-5-fluorouracil was higher than using 5-Fluorouracil. The higher surfactant concentration, the faster release rate at the range of $1.5{\sim}2.5%$.

• 대한기계학회논문집
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• 제17권2호
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• 한국정밀공학회지
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• 제28권2호
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• pp.239-244
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• 2011

Nano Imprint Lithography(NIL) is technique for copying a pattern from stamp with nano size pattern in order to replicated the materials. It is very important to demold in order to make NIL process effectively. Self Assembled Monolayers(SAM) coater is manufactured by means of decreasing surface energy with the stamp surface treatment to improve release characteristics. Manufactured device contains tilting and rotation option for increasing process life time by coating on the sidewall of the pattern in stamp. The stamp coated with optimized tilting angle $30^{\circ}$ and rotation speed of 10rpm has more imprinting cycles than the stamping coated without tilting and rotation. Effective SAM coating on the sidewall of the pattern in stamp will improve by 50% of process life time.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.188-194
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• 2005

The direct injection diesel engine is one of the most efficient thermal engines. For this reason DI diesel engines are widely used for heavy-duty applications. But the world is faced with very serious problems related to the air pollution due to the exhaust emissions of diesel engine. So, that is air pollution related to exhaust gas resulted from explosive combustion should be improved. Exhaust Gas Recirculation(EGR) is a proven method to reduce NOx emissions. In this study, the experiments were performed at various engine loads while the EGR rates were set from $0\%$ to $30\%.$ The emissions trade-off and combustion of diesel engine are investigated. The brake specific fuel consumption rate is very slightly fluctuated with EGR in the range of experimental conditions. The ignition delay increased with increasing EGR rate. The maximum value of premixed combustion for the rate of heat release is increased with increasing EGR rate. NOx emissions are decreased with increasing EGR rate at high load and high speed. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke emissions.

• 한국통신학회논문지
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• 제34권2C호
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• pp.234-241
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• 2009

TETRA Enhanced Data Service (TEDS) 는 기존의 협대역 ETSI TETRA Release 1 표준안을 개선하여 주파수 선택적인 페이딩 채널에서 고속의 패킷 데이터 전송이 가능한 표준 규격이다. TEDS 표준에서 사용하는 M-QAM 변조방식의 성능은 채널 추정 성능에 크게 영향을 받는다. 본 논문에서는 Per-Survivor Processing (PSP) 기법을 사용하여 고속 채널 환경에 적합한 새로운 decision-directed 채널 추정 기법을 제안한다. 제안된 채널 추정기법은 이동 환경에서 기존 파일럿 신호 기반의 채널 추정 기법에 비해 TETRA 수신 성능을 향상시킬 수 있음을 전산 모의 실험을 통해 보인다.

• Journal of Communications and Networks
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• 제13권1호
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• pp.70-76
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• 2011

This paper presents the unified user equipment (UE) baseband modulation and demodulation (modem) hardware platform architecture to support multiple radio access technologies. In particular, this platform selectively supports two systems; one is HEDGE system, which is the combination of third generation partnership project (3GPP) Release 7 high speed packet access evolution (HSPA+) and global system for mobile communication (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE), while the other is LEDGE system, which is the combination of 3GPP Release 8 long term evolution (LTE) and GSM/GPRS/EDGE. This is done by applying the flexible pin multiplexing scheme to a hardwired pin mapping process. On the other hand, to provide stable connection, high portability, and high debugging ability, the stacking structure is employed. Here, a layered board architecture grouped by functional classifications is applied instead of the conventional one flatten board. Based on this proposed configuration, we provide a framework for the verification step in wireless cellular communications. Also, modem function/scenario test and inter-operability test with various base station equipments are verified by system requirements and scenarios.

• 한국자동차공학회논문집
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• 제2권6호
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.177-185
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• 2007

The temperature and soot of the visualized diesel engine's turbulent flow of flame was qualitatively measured. In combustion chamber, in order to judge the affect that the swirl has on the in-cylinder's current, was used two different heads with different values. Using the high speed camera, and the results were analyzed using the heat release rate produced by the pressure sensor. In order to measure the temperature and soot of the turbulent flames like that of the diesel flames two color methods were used temperature and the soot of the flames according to the conditions through analyzing the two wavelengths of the flames. It was possible to measure the highest temperature of the non-swirl head visualized engine which is approximately 2400K, and that swirl head engine managed up to 2100K. With respect to the visualized diesel engine soot, we got the grasp of the KL factor which bears the qualitative information of soot. This study is dedicated to suggesting the possibility of measuring not only the temperature but also soot of the diffusion flame of the diesel engine turbulent flames through such method.

• 한국운동역학회지
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• 제13권1호
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• pp.51-62
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• 2003

This study was attempted to kinematical characteristics of the El-grip swing with 1turn to el-grip in elite horizontal bar for the purpose of improving performance. The subjects were three males who were 2002 Busan Asian Games in men's team. The three dimensional motion analysis with DLT method was executed using three video cameras of analyzing the actual competition situation. In point of analyzing the actual competition situation, it is expected that gymnastics and coaches have the effective informations, and the following conclusion had resulted. 1. In case of release, It is impotant to make fast horizontal velocity of CM, high vertical position of CM, large hip and shoulder angle. Also It should be performed release motion of trunk rotation angle(+). 2. During LHR the action should be made at higher position than the CM and the shoulder joint is moving within $127{\pm}16.82$. It is important to make large lunk rotation angle. 3. During Hop, the RHR motion should be done in high position with short time and fast twisting action and to reduce the vertical speed is important.