• 대한산업공학회지
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• 제39권4호
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• pp.253-259
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• 2013

Investment scenarios in the transportation network design problem usually contain installation or expansion of multi-mode transportation links. When one applies the mode choice analysis and traffic assignment sequentially for each investment scenario, it is possible that the travel impedance used in the mode choice analysis is different from the user equilibrium cost of the traffic assignment step. Therefore, to estimate the travel impedance and mode choice accurately, one needs to develop a combined model for the mode choice and traffic assignment. In this paper, we derive the inverse demand and the excess demand functions for the multi-mode multinomial logit mode choice function and develop a combined model for the multi-mode variable demand traffic assignment problem. Using data from the regional O/D and network data provided by the KTDB, we compared the performance of the partial linearization algorithm with the Frank-Wolfe algorithm applied to the excess demand model and with the sequential heuristic procedures.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.13.2-13.2
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• 2009

Electrostatic printing either it is drop-on-demand or continuous has immense applications in non-contact printing systems such as solar cells, flexible printed circuits, RFIDs and bio applications. In this paper a laboratory manufactured nozzle has been designed for the experimental investigation of electrostatic dripping and atomization of liquid. Dripping and atomization conditions such as voltage, nozzle tip diameter, distance between counter electrode and flowrate has been indentified for the designed nozzle. Furthermore it is also demonstrated that the diameter of a generated droplet could be reduced from a significantly large size to a narrow size distribution which can be controlled by volumetric flow rate and applied voltage. This study will help in classify the conditions between different electrostatic dripping mode such as drop-on-demand formation, jet mode and finally the atomization mode based on the laboratory fabricated nozzle head.

• 영어영문학
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• 제57권6호
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• pp.911-938
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• 2011

The present study examined the effect of two variables of task complexity, reasoning demand and time pressure, each from the resourcedirecting and resource-dispersing dimension in Robinson's (2001) framework of task classification. Reasoning demand was operationalized as the two types of texts to read and summarize, expository and argumentative. Time pressure was operationalized as the two modes of performance, oral and written. Six university students summarized the two types of text orally and twenty four students from the same school summarized them in the written form. Results from t test and ANCOVA showed that in the oral mode, reasoning demand tends to heighten the complexity of the language used in the summary in competition with accuracy but such an effect disappeared in the written mode. It was interpreted that the degree of time pressure is not the only difference between the oral and written modes but that the two modes may be fundamentally different cognitive tasks, and that Robinson's (2001) and Skehan's (1998) models were differentially supported by the oral mode of tasks but not by the written mode of the tasks.

• 대한교통학회지
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• 제26권6호
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• pp.7-15
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• 2008

기존의 아세안지역 국가간 여객통행수요예측에 있어 적용된 방법론은 자료의 한계로 인하여 모형을 이용하기보다는 개략적인 분석방법론과 가정위주로 이루어져 왔다. 본 연구에서는 아세안 지역의 국가간 여객통행 수요예측을 위해 개발된 모형을 제시한다. 통행발생과 통행분포 모형을 개별적으로 추정하기에는 해당지역의 통계자료구축이 미흡한 상태이기 때문에 국가간 출입국 통계자료를 이용하여 통행발생과 통행분포를 동시에 고려하는 직접수요모형을 개발하였다. 또한 현재 연구대상지역의 경우 국가간 통행에 대한 수단선택모형이 존재하지 않기 때문에 본 연구에서는 수단분담율 산정을 위해 명시선호기법을 이용하여 수단분담모형을 추정하였다. 통행거리에 따른 수단선택행태의 차이를 반영하기 위해 세 개의 거리대로 구분하여 수단분담모형을 추정하였다. 추정결과 모형의 설명력과 변수의 유의성 측면에서 대체적으로 양호한 결과가 도출되었다. 본 연구에서 구축한 모형은 향후 아세안지역의 통행수요예측에 있어 참고자료로 활용될 수 있을 것으로 기대된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.351-352
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• 2009

On-demand ejection of ultra-fine droplets that uses both electrohydrodynamic (EHD) force and mechanical actuation is presented. The liquid meniscus was controlled by a piezoelectric actuator and droplets were ejected by EHD force. Through these effects, it was possible to obtain a high operational jetting frequency of 5kHz with a short delay-time (about 50 us) when compared with existing on-demand EHD jetting methods, such as the pulsating jet mode (3-10 msec) and the pulsed-voltage cone-jet mode(3.6 msec). Also, we obtained ultra-fine droplets at a volume that was at the femto-liter level simultaneously. The jetting characteristics were examined for both hydrophobicity and hydrophilicity of the surface of a capillary.

• 대한교통학회지
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• 제28권2호
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• pp.171-181
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• 2010

2007년 7월부터 시행되고 있는 수도권 대중교통 통합요금제는 이용자의 통행비용 절감 및 활발한 환승행위의 유도로 긍정적인 평가를 얻고 있다. 그러나 수도권 대중교통 통합요금제를 고려한 철도 수요예측 방법론, 특히 수단분담과 관련된 연구가 많지 않았다. 이에 본 연구는 수도권 대중교통 통합요금제를 반영할 수 있는 수단별 효용산정기법을 제시하였으며, 2006년 가구통행실태조사 자료를 활용하여 통행시간과 통행비용 산정에 적용되는 계수를 현실화하였다. 그리고 다양한 요금제를 적용하기 위한 철도 수요예측 방법론을 제시하였다. 본 연구에서 제시한 철도 수요예측 방법론은 철도 수요예측의 정확성과 유용성을 향상시키는데 기여할 수 있을 것으로 기대된다.

• 전기학회논문지
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• 제56권6호
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• 경영과학
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• 제13권1호
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• pp.47-55
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• 1996

Rapid globalization of production and marketing functions makes choice of international transportation mode of great importance. In this paper, transportation mode is characterized by two factors, mean and variability of transportation lead time. We developed a simple mathematical model to estimate the relative impact of mean lead time, lead time variance and demand variance on the required average inventory level under specified service rates.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1833-1838
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• 2008

With the opening of a KTX on April 1st, 2004, Gwangmyung Station was opened. It is a station for KTX only. As it is not located at the center of a city, it doesn't have as good access mode system as Seoul, Deajun Station. In addition, because it is constructed within a limited development district, the development of catchment areas is not enough. At the beginning of the opening, demand falls short of their expectation so Importance of Access Mode System is issued. For the revitalization of Gwangmyung Station, Korea National Railroad focuses on the construction of Access Mode System such as the beginning of shuttle bus service between Kwan-ak and Gwangmyung station on June, 2005, opening of shuttle electric train between Yongsan and Gwangmyung station December, 2006, and the completion of parking tower in Gwangmyung station. After opening to Access Mode System, demand has been increasing. As market is changing, the railway line capacity between Seoul and Siheung reaches a limit, this research tries to review the way to setup sufficient Access Mode System.

• 대한교통학회지
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• 제21권6호
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• pp.43-55
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• 2003

본 연구에서 대중교통 수요예측과정에서 교통죤(TAZ)내의 거주인구, 직장인 등 대중교통이용가능 잠재수요 추정을 개선하기 위한 새로운 방법이 제시되었다. 대중교통을 이용하기 위해서는 보행 또는 승용차(Park & Ride or Kiss & Ride)로 대중교통에 접근하는 바, 제시된 방법이 보행에 의한 대중교통 잠재수요 및 승용차에 의한 대중교통 잠재수요를 추정하는 데 있어 기존의 buffer method 및 network ratio method보다 합리적이고 개선된 방법임을 보여주고 있다. 본 연구에서 제시된 방법은 교통수단선택모형(mode choice model)의 적용과정에서 대중교통 수요예측을 개선할 수 있을 것으로 기대된다.