• The Journal of Korean Physical Therapy
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• 제25권5호
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• pp.297-302
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• 2013

Purpose: This study was conducted in order to investigate the kinematic gait parameter of lower extremities with different gait conditions (level walking, stair, ramp) in hemiplegic patients. Methods: Ten hemiplegic patients participated in this study and kinematic data were measured using a 3D motion analysis system (LUKOtronic AS202, Lutz-kovacs-Electronics, Innsbruk, Austria). Statistical analysis was performed using one-way repeated measure of ANOVA in order to determine the difference of lower extremity angle at each gait phase with different gait conditions. Results: Affected degree of ankle joint in the heel strike phase showed significant difference between level walking and climbing stairs, and toe off phase showed significant difference between level walking and climbing stairs, ramps, and climbing stairs. Affected degree of knee joint showed no significant difference in all attempts. Affected degree of hip joint in the toe off phase showed significant difference between level walking, ramps and stairs, and climbing ramps. Swing phase showed significant difference between sides for level walking and stairs, climbing ramps. Affected ankle joint of heel strike and toe off, and affected hip joint of toe off and the maximum angle of swing phase in the angle was increased. Unaffected side of the ankle joint, knee joint, and hip joint showed a significant increase in walking phase. Conclusion: These findings indicate that compared with level walking, different results were obtained for joint angle of lower extremity when climbing stairs and ramps. In hemiplegia patient's climbing ramps, stairs, more movement was observed not only for the non-affected side but also the ankle joint of the affected side and hip joint. According to these findings of hemiplegic patients when climbing stairs or ramps, more joint motion was observed not only on the unaffected side but also on the affected side compared with flat walking.

• 한국도로학회논문집
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• 제14권5호
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• pp.101-111
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• 2012

PURPOSES: Because expressway ramps are very complex segments where diverse roadway design elements dynamically change within relatively short length, drivers on ramps are required to drive their cars carefully for safety. Especially, ramps on expressways are designed to guarantee driving at high speed so that the risk and severity of traffic accidents on expressway ramps may be higher and more deadly than other facilities on expressways. Safe deceleration maneuvers are required on off-ramps, whereas safe acceleration maneuvers are necessary on onramps. This difference in required maneuvers may contribute to dissimilar patterns and severity of traffic accidents by ramp types. Therefore, this study was aimed at developing prediction models of the severity of traffic accidents on expressway on- and off-ramps separately in order to consider dissimilar patterns and severity of traffic accidents according to types of ramps. METHODS: Four-year-long traffic accident data between 2007 and 2010 were utilized to distinguish contributing design elements in conjunction with AADT and ramp length. The prediction models were built using the negative binomial regression model consisting of the severity of traffic accident as a dependent variable and contributing design elements as in independent variables. RESULTS: The developed regression models were evaluated using the traffic accident data of the ramps which was not used in building the models by comparing actual and estimated severity of traffic accidents. Conclusively, the average prediction error rates of on-ramps and offramps were 30.5% and 30.8% respectively. CONCLUSIONS: The prediction models for the severity of traffic accidents on expressway on- and off-ramps will be useful in enhancing the safety on expressway ramps as well as developing design guidelines for expressway ramps.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.102-111
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• 1996

For the air-fuel ratio control in a fuel injection SI engine, the Jump-Ramp control algorithm has been widely adopted by using the on/off type oxygen sensor. But the Jump-Ramp control method has limitation on treating the frequency and amplitude of the air-fuel ratio oscillation. This study suggests another feedback control logic named modulated fuel feedback control, which has a concept of pre-tuned air-fuel ratio oscillation. In the modulation method, the oxygen sensor output is not treated as on/off signal but as analog signal for feedback. By using the modulation method, the frequency and the amplitude of air-fuel ratio oscillation can be adjustable to some extent for improving the conversion efficiency of the Three-Way Catalyst. The result shows that the performance of the modulation method is better than that Jump-Ramp control method in reducing the amplitude of the air-fuel ratio oscillation as well as in increasing the frequency of the air-fuel ratio oscillation.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2007년도 제56회 학술발표회논문집
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• pp.310-318
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• 2007

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1187-1190
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• 2005

The ramp reset driving method proposed in [1] has been widely adopted because of its stability and high contrast ratio. However, when the conventional ramp reset method is used in PDPs of higher resolution, the long required time for reset often becomes a problem. In this paper, a new driving method that requires much less reset time and that significantly improves the contrast ratio is introduced. Using this new driving method, the required time for reset could be reduced to 150us from 350us of the conventional ramp reset method, and the contrast ratio is almost infinite because the luminance of the off-cell is almost zero.

• 대한교통학회지
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• 제20권7호
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• pp.107-116
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• 2002

충격흡수시설(Crash Cushion)은 고속도로 진출램프의 고어(Gore)지역과 같이 차량이 주행차로를 벗어나 도로상의 구조물과 충돌할 위험이 있는 곳에 설치하여 충돌 전 충격에너지를 흡수하는 역할을 하는 도로변 안전시설물이다. 시설의 설치효과를 높이기 위해서는 사고 발생 가능성을 고려하여 설치여부를 판단하는 기준이 필요하다. 그러나 현재의 충격흡수시설 설치기준은 이와 같은 과정을 제시하지 못하고 있다. 이에 착안하여 본 연구에서는 충격흡수시설의 설치여부 판단기준 개발을 위해 두 가지 형태의 연구를 수행하였다. 첫 번째는 고속도로 진출램프 사고예측모형의 개발이다. 충격흡수시설이 설치되는 고속도로의 고어(Gore)지역에서 발생되는 교통사고와 도로환경적 요인과의 관계를 고려한 사고예측모형을 개발하는 과정으로 교통통계 학자들 사이에서 교통사고의 특성을 잘 반영하여 준다고 알려진 음이항 분포를 사용하였다. 두 번째는 고속도로 진출행동모형의 개발이다. 운전자에 의한 고속도로 진출과정을 단계별로 가정하고 가정된 진출과정에 의해 발생되는 변수들과 사고와의 상관관계를 고려하여 운전행동모형을 개발하였다. 개발된 두 가지 형태의 모형으로 위험도를 수치화하고 편익-비용분석 과정을 통하여 충격흡수시설을 설치여부 판단기준을 제시하였다. 도로환경적 요인과 인적요인을 동시에 고려한 본 연구의 접근방법을 통해 효과적으로 충격흡수시설의 설치여부를 판단할 수 있다.

• 전기학회논문지
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• 제60권7호
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• pp.1299-1304
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• 2011

A wind turbine (WT) should be shut down as fast as possible to minimize its own damage in a storm-driven situation. Shutdown of a large wind farm requires a power grid to have a ramp-up capability large enough to balance between generation and consumption of electrical energy. This paper proposes a supervised shutdown algorithm of a wind farm to meet a required ramp-down rate in a grid code in the case of a storm-driven situation. The information on the speed and the direction of wind is measured at a wind mast (WM) installed around a wind farm. If the wind speed exceeds a cut-out speed, the number of WTs to be shut down simultaneously is decided to meet a required ramp-down rate of a grid-code. Arrival times to each WT from the WM are calculated and sorted in the order of time. Then a sequence of groups is generated. The shutdown start/end times of each group are decided to avoid superposition between adjacent two groups. The performance of the proposed shutdown algorithm is verified under various storm scenarios. Results indicate that the proposed algorithm can not only protect the wind farm in the case of a storm-driven situation but also meet the required ramp-down rate. In addition, the algorithm can produce more energy than that of a conventional shutdown algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1382-1383
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• 2011

결정질 실리콘 태양전지에서 전극 형성 공정은 Voc(Open-circuit voltage), Isc(Short-circuit current), Rser(Series resistance), Rshunt(Shunt resistance), FF(Fill factor) 특성에 영향을 주기 때문에 매우 중요하다. 하지만 paste와 선 공정에서의 조건에 따라 특성이 바뀌기 때문에 소성 공정을 최적화하기는 쉽지 않다. 본 연구에서는 Gravure Off-set printing 방식을 이용하여 결정질 실리콘 기판 표면에 미세 전극 형성 공정을 하고 소성 조건 최적화를 위해 peak 온도와 ramp-up 속도를 변화시켜 각 조건별 특성을 비교하였다. Peak 온도가 커질수록, contact resistance의 감소에 따라 Rser가 줄어들었다. 본 연구를 통해 Voc는 619mV, FF는 77.9%로 측정되는 Gravure Off-set 태양전지에 최적화된 소성 공정 조건을 확보하였다.

• 대한공간정보학회지
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• 제5권2호
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• pp.29-43
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• 1997

ITS 구축을 위한 고속도로축 통합최적제어모형은 진입램프미터링, 진출램프전환율 그리고 인접노면가로 g/C비 결정 등 3가지 제어 변수를 동시에 결정될 수 있도록 구축하였다. 또한 실시간 처리가 가능하도록 당초 비선형문제를 선형문제로 전환하기 위해 교통밀도 관계식을 두 개의 선형함수로 축약하고, SLP알고리즘을 사용한 컴퓨터 알고리즘도 제안하였다.

• 한국항공우주학회지
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• 제50권5호
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• pp.297-308
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• 2022

극초음속 영역에서 운용되는 대부분의 극초음속 공기흡입(Air-breathing) 비행체들에 스크램제트 엔진이 탑재되고 있다. 스크램제트(Scramjet) 엔진에서는 일반적인 가스터빈 엔진의 압축기 역할을 흡입구에서 발생하는 충격파가 대신 수행하기 때문에 충격파에 의한 전압력 손실이 매우 중요하게 여겨진다. 본 연구에서는 전압력 손실을 최소화하기 위해 등엔트로피 압축면을 적용한 외부 압축형 흡입구의 설계법을 제시하고, 동일한 조건의 Busemann 흡입구와 3개의 cone 각도를 가지는 외부 압축형 흡입구를 설계하였다. 이후 전산해석을 통해 비설계 조건에 대한 성능 특성을 비교하였다. 각 흡입구 형상은 3단 외부 압축형 흡입구의 길이에 맞춰 truncation을 진행하였으며, 경계층 보정을 수행하였다. 등엔트로피 외부 압축형 흡입구는 3단 외부 압축형 흡입구에 비해 설계점에서는 우수한 성능을 보였으나 일부 비설계 조건에서는 3단 외부 압축형보다 성능이 저하되는 현상이 발생하였다.