• Journal of Korean Institute of Industrial Engineers
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• v.39 no.4
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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.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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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.

• Journal of English Language & Literature
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• v.57 no.6
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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.

• Journal of Korean Society of Transportation
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• v.26 no.6
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• pp.7-15
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• 2008

Due to the limitations in the statistical data, the existing studies adopted rough methodologies with strong assumptions in the estimation of international passenger travel demand forecast in the ASEAN region. This study aims to develop international passenger travel demand models using scientific methodologies. This study proposes a direct demand model using the immigration and emigration data between countries in the region. This is because of the difficulty of estimating trip generation and trip distribution separately due to the data limitation in the region. As there does not exist the mode choice model for the region, this study estimates a mode choice model using the Stated Preference technique. The mode choice model is separated into three categories of models according to the range of distance between the origin and destination of travel; this is to reflect the different behavior in mode choice according to the travel distance. The result of model estimations suggests that the estimated models produce resonable results statistically. It is expected that the proposed models are useful for the future travel demand estimation in the ASEAN region.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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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.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.171-181
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• 2010

The integrated transit fare system of Seoul metropolitan area has given positively evaluated with reduction of user cost and activating the transfer behavior from its opening year, July 2007. However, there were only few research about railway demand forecasting methodology, especially mode share, has conducted under the integrated fare system. This study focuses on the utility estimation by each mode under the integrated fare system, and on the coefficient actualization relates on travel time and travel cost estimation with Household Travel Survey Data 2006. Also the railway demand analysis methodology under various fare systems is presented. The methodology from this study is expected to improve accuracy and usefulness in railway demand analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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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.

• Korean Management Science Review
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• v.13 no.1
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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.

• Proceedings of the KSR Conference
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• 2008.11b
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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.

• Journal of Korean Society of Transportation
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• v.21 no.6
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• pp.43-55
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• 2003

This paper presents a new method for estimating potential transit ridership residential population and number of employees that have accesses to transit services. A standard procedure that can be used to determine transit accessibility by pedestrians ad automobiles are developed to improve its transit demand forecasting capability. The analysis results are compared with those from the traditional buffer method as well as the network ratio method. It was found that the proposed method is more accurate than the traditional methods. The new method can be used to better estimate the "Walk Access" transit trips and "Auto Access" transit trips in the Mode Choice Model.