• Journal of Advanced Navigation Technology
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• v.2 no.2
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• pp.143-156
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• 1998

Incheon International Airport(IIA) is planned to open in about two years. Korean government has an ambition to make IIA a major hub airport in Northeast Asia. The most essential and required condition for an airport to be a successful hub airport in a certain region is to have more efficient flight service network than the other airports in the same region. IIA should compete with Japanese airports to be a major hub in Northeast Asia because Japanese government also has a plan to expand greatly the airport capacity in Tokyo area and Kansai airport in Osaka. It is necessary for both IIA and Korean national air carriers to compose efficient flight service network considering hub competition with Japanese major airports. As the liberalization of international air transport industry would give more marketing freedom to airlines, they would plan the flight service network and flight schedule based on market analysis instead of governmental regulations. In the economically liberalized environment, it is very required to analyze air passengers' flight choice behaviour in order to induce other carriers and passengers through IIA's attractive flight service network. Disaggregate model is more appropriate than aggregate model to analyze consumers' behaviour. The information derived from disaggregate choice model of air passengers could be utilized in devising efficient flight network and schedule plan. Value of travel time or trade off ratio between flight frequency and travel time which could be estimated from discrete choice model could be utilized for scheduling an efficient flight plan for airlines and composing efficient flight service network for IIA.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.315-320
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• 2010

To improve not only the basic performance but also the fail-safe performance, power consumption of the main landing gear for helicopters, a semi-active control landing gear using hybrid MR damper, was introduced in this paper. This damper of the configuration to install a permanent magnet in a electromagnet MR damper, was designed by the trade-off study on permanent magnet location and a magnet field analysis. Force control algorithm which keep the sum of air spring force and damping force at a specified value during landing, was used for the controller. The drop simulations using ADAMS Model for this semi-active control landing gear, were done. The improvement of the preceding performances as the result to evaluate the landing performance by the simulations, has been confirmed.

• The Journal of Information Systems
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• v.25 no.3
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• pp.31-60
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• 2016

Purpose In 2016, the market size of mobile(m-) shopping goes beyeond more than half of a total of online shopping. People use smartphones as the main device for m-commerce. Under the circmustances, this study attempts to address why people prefer to use smartphone-based m-commerce. In other words, it is necessary to understand the main value that smartphone-based m-commerce creates. Drawing on the studies of consumption value, this study focuses on utilitarian value in predicting customers' continuance intention in the context of smartphone-based m-commerce, recognizing that utilitarian value is a key extrinsic motivation in the goal-oriented, performance-oriented shopping contexts. Furthermore, this study identifies factors affecting customers' utilitarian value from the perspective of benefits and costs, following the notion that it represents the result of evaluating a trade-off of benefits and costs caused by smartphone-based m commerce. More specifically, in this study, ubiquitous service, location-based service (LBS), transaction speed, and price utility belong to the benefit dimension, whereas technology anxiety and cognitive effort belong to the cost dimension. Design/methodology/approach To test the proposed hypotheses, the study conducted partial least squares (PLS) analysis with a total of 294 data collected on users with experience in smartphone-based m-commerce. Findings The results show that first, utilitarian value is increased by the benefits, such as ubiquitous service, transaction speed, and price utility. However, LBS has no direct effect on utilitarian value. Second, the noteworthy finding is that ubiquitous service and LBS greatly increase transaction speed. Third, technology anxiety and cognitive effort considered as the cost dimension are negatively associated with utilitarian value but their impacts on it are non-significant. Finally, the results support the argument that utilitarian value is a determinant of continuance intention. Overall, the findings imply that utilitarian value greatly depends on the peception on benefits rather than the aspect of cost in smartphone-based m-commerce. Overall, the findings offer new insight into the studies of m-commerce by considering and verifying the impacts of its benefits and costs simultaneously.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.550-563
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• 1999

A wavelet-Galerkin scheme based on the time-dependent Maxwell's equations is presented. Daubechies wavelet with two vanishing wavelet moments is expanded for basis function in spatial domain and Yee's leap-frog approach is applied. The shifted interpolation property of Daubechies wavelet family leads to the simplified formulations for inhomogeneous media without the additional matrices for the integral or material operator. The stability condition is formulated. The dispersion characteristics are analyzed and compared with those of finite difference time domain and multiresolution time domain methods. The analyses show the excellent trade-off between the regularity and the support width of the basis function. Although the basis function has only two vanishing wavelet moments, it is enough to provide negligible dispersive error in the numerical analysis and its compact support enables only several involved terms per nodes. The storage effectiveness, execution time reduction and accuracy of this scheme are demonstrated by calculating the resonant frequencies of the homogeneous and inhomogeneous cavities.

• Journal of the Korean Geographical Society
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• v.36 no.4
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• pp.434-443
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• 2001

Differing from the existing method to optimize the statistical proximity, the new optimization method was developed to maximize the spatial proximity among the unit areas of choropleth map. 25 choropleth maps were made using 5 classification methods(maximum BEI, maximum TEI, equal interval, natural break, n-tile) for 5 classes(3∼7) and were analyzed to elucidate the effectiveness of classification methods on the basis of 3 evaluation indeces (TEI, BEI, $C_{F}$). The results from the maximum TEI and maximum BEI were evaluated as relatively stable and effective compared to those from other classification methods. But they showed the opposite trends owing to the trade-off relationships. Meanwhile, the resets from the natural break method got higher marks, which was also identified through the analysis using a new $alpha$-index.x.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.3
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• pp.263-267
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• 2014

Super junction trench gate power MOSFETs have been receiving attention in terms of the trade-off between breakdown voltage and on-resistance. The vertical structure of super junction trench gate power MOSFETs allows the on-resistance to be reduced compared with conventional Trench Gate Power MOSFETs. The heat release of devices is also decreased with the reduction of on-resistance. In this paper, Lattice Temperature of two devices, Trench Gate Power MOSFET and Super junction trench gate power MOSFET, are compared in several temperature circumstance with the same Breakdown Voltage and Cell-pitch. The devices were designed by 100V Breakdown voltage and measured from 250K Lattice Temperature. We have tried to investigate how much temperature rise in the same condition. According as temperature gap between top of devices and bottom of devices, Super junction trench gate power MOSFET has a tendency to generate lower heat release than Trench Gate Power MOSFET. This means that Super junction trench gate power MOSFET is superior for wide-temperature range operation. When trench etching process is applied for making P-pillar region, trench angle factor is also important component. Depending on trench angle, characteristics of Super junction device are changed. In this paper, we focus temperature characteristic as changing trench angle factor. Consequently, Trench angle factor don't have a great effect on temperature change.

• Composites Research
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• v.25 no.2
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• pp.54-61
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• 2012

In this study, a specific structural design procedure for 2 MW class glass/epoxy composite wind turbine system towers is newly proposed through load case study, trade-off study, optimal structural design and structural analysis. Optimal tower design is very important because its cost is about 20% of the wind turbine system's cost. In the structural design of the tower, three kinds of loads such as wind load, blades, nacelle and tower weight and blade aerodynamic drag load should be considered. Initial structural design is carried out using the netting rule and the rule of mixture. Then the structural safety and stability are confirmed using a commercial finite element code, MSC NASTRAN/PATRAN. The finally proposed tower configuration meets the tower design requirements.

• Journal of the Korean Geographical Society
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• v.40 no.6 s.111
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• pp.653-670
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• 2005

The purpose of this study is to explore a spatial agglomeration characteristics and innovative milieu of the shoemaking industry in Seoul. In order to explain it, currently discussed dynamic agglomeration economies approach is applied and as an example, shoemaking industry in Seoul has been analyzed. The result of this research can be boardly summarized into two points. Frist, agglomeration economy is changing from urbanization economy to localization economy in this newly rising core of shoemaking industry which is Sung-Su dong area. Also, cooperative effects based on collective efficiency between companies and people are being generated within the area. This is largely affected by networking infrastructure between companies and people within the area, non-trade dependency and social capital acclamation. Secondly, the lack of institutional agglomeration formation in this area is considered to be the obstacle for the long-term development and innovation spin-off. This means recognition switch-over and institutional concern and support is needed in the future from the public sector.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1293-1300
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• 2011

The configurations of the evaporator and condenser of a water chiller can be determined from the trade-off between the heat transfer area, which is related to the capital cost and the pressure drop, which is associated with the operational cost. In this study, the design of the water chiller focused on minimizing the water pressure drop of both condenser and evaporator for given cooling capacity and requirements. Commercial enhanced tubes were employed to simulate real-life conditions. The results of the present analysis were compared with those obtained by HTRI software for verifying them. The results indicated that a reduction in the water pressure drop, which is associated with the short length of a tube, can be effected by decreasing the number of tube passes and increasing the number of tubes and the tube diameter. However, using a large number of tubes with smaller diameters can reduce the capital cost because the tubes are short. The reduction of the capital cost is due to the fact that a small-diameter tube has low internal thermal resistance and hence contributes to a decrease in the overall thermal resistance per unit length.

• Journal of ILASS-Korea
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• v.24 no.4
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• pp.157-162
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• 2019

This numerical study was analyzed to predict the flammability limits of biodiesel and diesel fuels in the high temperature and pressure conditions. To achieve this, the biodiesel fuel was simulated with the chemical species of n-heptane (n-C₇H₁₆), methyl decanoate (C₁₁H₂₂O₂), and methyl-9-decenoate (C₁₁H₂₀O₂), and the diesel fuel was substituted the chemical species of n-heptane. The closed 0-D homogeneous reactor model which was employed the 1100 K of ambient temperature and 35 atm of ambient pressure was used for the simulation of constant volume combustion, and the equivalence ratio was changed from 0.3 to 2.5 conditions. In addition, a comparative analysis study was conducted with the results of HCCI engine simulation and flammability limits according to the changes of equivalence ratio. The results of combustion temperature, pressure, and ignition delay were increased when the equivalence ratio elevated from 0.3 to 1.3 conditions because the increase in fuel oxidation rate affects the chemical reaction of the overall combustion process. Furthermore, the CO and NO_X production under the rich combustion conditions are considered to have a trade off relationship since the OH radicals and O₂ chemical species are greatly affected the CO and NO_X production and oxidation processes.