• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.3-11
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• 2002

This paper presents the trend of low voltage and high current technology for DC-DC converters. It can be said that the output voltage of the on-board power supply has been rapidly moving forward a low voltage in proportion to the minuteness of the semiconductors. As for as its speed is concerned, the change of the market situation seems to be faster than that of R&D for the low voltage and high current products put out by power supply manufacturers. Here, the present situation and the trend of non-isolated type step-down DC-DC converter and isolated type DC-DC converter called "Brick" will be taken up mainly from the fellowing point of view. -low voltage and high current keeping up with the current demand for the latest telecommunication networks and broadband. -build-up of the total solution for dispersion system power supply. In this paper, an explanation is given to mainly concerning to the newest products in the supplier's position.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.4
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• pp.369-374
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• 2009

In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are closely related to adhesion and stiction of interacting surfaces. In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained We introduced an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope. This method was used to calculate surface forces generated in the contact interface formed between diamond-like carbon coating and $Si_3N_4$ ball. This method is shown to effectively demonstrate the influence of capillary force in the contact area, especially in humid atmosphere.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.110-122
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• 1996

The objective of this study is to understand the dynamic characterictics of OHV type valve trains and to design and optimal cam profile which will improve engine performance. A numerical model for valve train dynamics is presented, which aims at both accuracy and computational efficiency. The lumped mass model and distributed parameter model were used to describe the valve train dynamics. Nonlinear characterictics in the valve spring behavior were included in the model. Comprehensive experiments were carried out concerning the valve train dynamics, and the model was tuned based on the test results. The dynamic model was used in designing an optimal cam profile. Because the objective function has many local minima, a conventional local optimizer cannot be used to find an optimal solution. A modified adaptive random search method is successfully employed to solve the problem. Cam lobe area could be increased up to 7.3% without any penalties in kinematic and dynamic behaviors of the valve train.

• Journal of the Korea Safety Management & Science
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• v.4 no.1
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• pp.37-47
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• 2002

Risk analysis is a formal deductive procedure for determining combinations of component failures and human errors that could result in the occurrence of specified undesired events at the system level. This method can be used to analyze the vast majority of industrial system reliability problems. This study deals with the application of knowledge-engineering and a methodology for the assessment ＆ measurement of reliability, availability, maintainability, and safety of industrial systems using FTA(fault tree analysis), A fuzzy methodology for fault-tree evaluation seems to be an alternative solution to overcome the drawbacks of the conventional approach (insufficient Information concerning the relative frequencies of hazard events). To improve the quality of results, the membership functions must be approximated based on heuristic considerations, The purpose of this study is to describe the knowledge engineering approach, directed to integrate the various sources of knowledge involved in a FTA.

• Journal of the Korea Safety Management & Science
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• v.4 no.4
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• pp.129-136
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• 2002

Utilization rate for the restrictive gate and required time and walking distance to board are to be a measure for the gate management and passenger's convenience estimation. So, the main purpose of the gate management are maximization of utilization rate and increment of airport terminal user's convenience through the efficient gate management. This study intends to maximize the utilization rate on usable gates and minimize the passenger's working distance in terminal by concerning about layout, terminal configuration, local passenger of the airport and formulate the gate assignment problem with integer linear programming problem. Then we obtained solution using optimization software LINGO and analyzed that maximize the number of assignment flights and minimize the passenger's walking distance.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.371-380
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• 1989

The purpose of this experiment is to elucidate the reaction mechanism concerning to the formation of crystalline BaTiO3 synthesized by adding the pH control agent(KOH soln) in TiCl4 and BaCl2 solution (Wet direct synthetic method). In this expeirment, it is identified that the amorphous barium-titanate having Ba-O-Ti bonding is formed above pH5 due to the -OH- ion and Ti-gel is formed below pH5 due to the polymerization of metatitanic acid. The bonding of the amorphous Ba-O-Ti is identified by FT-IR spectrum and crystallization temperature is about 82$0^{\circ}C$. If the pH of the above system according to the -OH- ion concentration is above 13.8, the polymerized metatitanic acid will be depolymerized and produce [TiO3]2+ion and crystalline BaTiO3 is formed by reacting the produced [TiO3]-- ion with the active Ba++ ion.

• The Journal of Information Technology and Database
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• v.7 no.1
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• pp.42-53
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• 2000

The major goal of this research is to develop an optimal route search algorithm for an intelligent route guidance system, one sub-area of ITS. ITS stands for intelligent Transportation System. ITS offers a fundamental solution to various issues concerning transportation and it will eventually help comfortable and swift moves of drivers by receiving and transmitting information on humans, roads and automobiles. Genetic algorithm, and fuzzy logic are utilized in order to implement the proposed algorithm. Using genetic algorithm, the proposed algorithm searches shortest routes in terms of travel time in consideration of stochastic traffic volume, diverse turn constraints, etc. Then using fuzzy logic, it selects driver-preference optimal route among the candidate routes searched by GA, taking into account various driver's preferences such as difficulty degree of driving and surrounding scenery of road, etc. In order to evaluate this algorithm, a virtual road-traffic network DB with various road attributes is simulated, where the suggested algorithm promptly produces the best route for a driver with reference to his or her preferences.

• 전기의세계
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• v.16 no.1
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• pp.19-28
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• 1967

Indigenous energy resources available in Korea are limited to the three major resources such as Korean anthracite, hydraulic potential and wood and straws. As reported in various reports concerning energy problem in Korea, unfortunately these three major resources are not only poor in quality but also limited in quantity. The amount of energy to be imported, which will be increased at a considerably high rate by years due to the shortage in the supply by domertic sources against the demand, is studied in the view-pint of sound and logical energy dependence upon the external sources. What would occur, if the imported energy would be exclusively limited to an energy source only, has an enough reason to be paid a significant consideration. As a result, the feasibility is discarded in favour of nuclear power plants after an extensive prospect for electric power development plan covering more than coming thirty years, i.e., up to the year of 2,000 A.D. In briefing, this paper indicates that a measures to accomodate as large amount of nuclear power plants as possible in the electric power system is not only inevitable for a sound solution of the severe energy problem with which Korea is to be confronted but also leads to the national benefit.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.829-831
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• 1996

This paper is concerning on a study on the object-oriented programming and its application to maintenance scheduling. The concept of object-oriented programming enables us to modify and reuse software with much ease. By introducing object-oriented programming to maintenance scheduling, we can develop a hierarchical and reusable software in maintenance scheduling. The maintenance scheduling problem becoming more and more large and complex can be dealt with the concept of object-oriented technique and we hope this concept will give a reasonable solution. And evolutionary computation will be developed as a optimization technique.

• Journal of Korean Society for Geospatial Information Science
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• v.11 no.4 s.27
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• pp.45-51
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• 2003

This study intended to extract the spatial data and attribute data from the images of terrestrial photographs to compile the digital map from the images using photogrammetric analysis. In this study, the plane map of present objective area was made using the single terrestial photographs and graphical method, and the spatial or attribute data for the facilities in the area was extracted. Also, it is concluded that the efficient techniques for acquiring spatial and attribute data of the building and road facilities in proper time for the concerning area were suggested.