• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.1-9
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• 2003

In this paper, prototype of high-power-factor single-stage electronic ballast for fluorescent lamp is designed and implemented. A new low cost single stage high power factor electronic ballast for fluorescent lamps is based on integration of two-boost converter and LC type high frequency resonant inverter. The proposed ballast is combined by simple construction, because full bridge rectifier diode is eliminated and simple control circuit is applied. Boost converter operate in the voltage of positive and negative half cycle respectively at line frequency (60㎐), operation in discontinuous conduction mode performs high power factor. The experimental results show the good performance as PF 0.99, THD 15.4%, and CF 1.65 at output 63.5〔W〕.

• Journal of the Korean Society of Safety
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• v.22 no.1 s.79
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• pp.7-12
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• 2007

There are two kinds of design process for sprinkler system. one is pipe schedule system and the other is hydraulically designed system. We have inefficient results when we design by hydraulically designed system because the design process for sprinkler system is restricted by domestic fire code. Therefore, it is essential to do an introduction of hydraulically designed system which is based on engineering for enhancing reliability and efficiency of sprinkler system. This study presents points at issue by comparing and studying design standards of sprinkler system from Korea, Japan and NFPA, and presents improvement plans of national fire safety code of sprinkler system by processing, comparing and analyzing designs according to piping schedule and hydraulically designed system about domestic objects. Installation standards of sprinkler system have to be applied not by object buildings but by hazard classification. It is hard to design an efficient sprinkler system for fire control when water supply requirement of sprinkler systems allocated according to a size of a building because the same purpose but other buildings may request more water requirement or less. We should sublate the pipe schedule system from national fire safety code and need to introduce the hydraulically designed system. The pipe schedule system presents easy access because it is based on the forecasted engineering calculations but it is applied to only small buildings like NFPA due to its low reliability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.315-320
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• 2006

This paper describes access control, user authentication, and User Security and Encryption technology for the construction of database security system from network users. We propose model of network encrypted database security system for combining these elements through the analysis of operational and technological elements. Systematic combination of operational and technological elements with proposed model can construct encrypted database security system secured from unauthorized users in distributed computing environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.839-842
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• 2005

As various mobile technologies, sensor technologies, and remote control technologies are growing and quality of life is enhanced, researches and developments on home network are actively on going. Currently, some network service providers and construction corporations are going to provide home network service, but neither secure nor efficient, So, in this paper, we propose a security framework for providing various secure user authentication mechanisms and efficiently controlling services in home network. Namely, we are going to provide active home network security services with home gateway-based security policy, which locates on the gateway of each home.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.793-794
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• 2011

This paper presents a method of the circuit design of the multiple-valued digital logic switching functions based on the modular techniques. Fisr of all, we introduce the necessity, background and concepts of the modular design techniques for the digital logic systems. Next, we discuss the definitions that are used in this paper. For the purpose of the circuit design for the multiple-valued digital logic switching functions, we discuss the extraction of the partition functions. Also we describe the construction method of the building block, that is called the modules, based on each partition functions. And we apply the proposed method to the example, we compare the results with the results of the earlier methods. In result, we decrease the control functions, it means that we obtain the effective cost in the digital logic design for any other earlier methods. In the future research, we require the universal module that traet more partition functions and more compact module.

• Transactions on Electrical and Electronic Materials
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• v.5 no.1
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• pp.11-14
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• 2004

An rf triode magnetron sputtering system is designed and installed its construction in vacuum chamber. In order to calibrate the rf triode magnetron sputtering for thin films deposition processes, the effects of different glow discharge conditions were investigated in terms of the deposition rate measurements. The basic parameters for calibrating experiment in this sputtering system are rf power input, gas pressure, plasma current, and target-to-substrate distance. Because a knowledge of the deposition rate is necessary to control film thickness and to evaluate optimal conditions which are an important consideration in preparing better thin films, the deposition rates of copper as a testing material under the various sputtering conditions are investigated. Furthermore, a triode sputtering system designed in our team is simulated by the SIMION program. As a result, it is sure that the simulation of electron trajectories in the sputtering system is confined directly above the target surface by the force of E${\times}$B field. Finally, some teats with the above 4 different sputtering conditions demonstrate that the deposition rate of rf triode magnetron sputtering is relatively higher than that of the conventional sputtering system. This means that the higher deposition rate is probably caused by a high ion density in the triode and magnetron system. The erosion area of target surface bombarded by Ar ion is sputtered widely on the whole target except on both magnet sides. Therefore, the designed rf triode magnetron sputtering is a powerful deposition system.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.65-67
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• 1996

This paper presents the automatic construction and parameter optimization technique for the fuzzy logic controller using genetic algorithm. In general the design of fuzzy controller has difficulties in the acquisition of expert's knowledge and relies to a great extent on empirical and heuristic knowledge which, in many cases, cannot be objectively justified. Therefor the performance of the controller can be degraded in the case of plant parameter variations or unpredictable incident which the designer may lave ignored. And fuzzy logic controller parameters elicited form the expert may not be global. Some of these problems can be resolved by application of genetic algorithm. Finally, we provides the second order dead time plant to evaluate the feasibility and generality of our proposed method. Comparison shows that the proposed method can produce a fuzzy logic controller with higher accuracy and a smaller number of fuzzy roles than manually billed fuzzy logic controller.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.38-40
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• 2009

In order to achieve a gearless construction of the wind energy conversion system(WECS), a low-speed generator should be used. Of the various candidate machine types, radial-field, multi-pole, permanent magnet, synchronous machines may be used for low-speed applications. So, this paper deals with the design of direct-coupled, multi-pole radial field machines with permanent magnet(PM) excitation for wind power applications for cogging torque reduction through the determination of optimum pole arc/pitch ratio. On the basis of an equivalent magnetic circuit method(EMCM) and a space harmonic method(SHM), an initial design is performed considering restricted conditions. And then, a detailed design is made using a non-linear finite element analyses(FEA). Finally, test results concerning generating characteristics are given to confirm the validation of the design.

• Journal of Environmental Impact Assessment
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• v.20 no.3
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• pp.257-267
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• 2011

This paper examines the spatial and temporal variability in the shoreline boundary caused by artificial structures in Songdo Beach of South Korea. Quickbird Images of 2003, 2005, 2007, and 2010 extracted from Google Earth were used to identify changing trends of shoreline boundary. The most significant changes were observed in area where groins were extensively established, inducing the sand beach much narrower than before in almost 75% of the area($15070.72m^2$ in 2003 to $3877.46m^2$ in 2010). The Google Earth made it possible to identify area-wide patterns of shoreline change subject to many different type of artificial structures, which cannot be acquired by traditional field sampling. Groin heights, lengths and profiles can be modified during maintenance operations if the Google Earth monitoring indicates that the initial layout is not operating properly as a physical barrier to control sediment transport. It is anticipated that this research could be used as a valuable reference to confirm the outputs from past field researches for coastal processes to respond to storms in more visual and quantitative manner.

• Korean Journal of Community Nutrition
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• v.5 no.4
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• pp.697-708
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• 2000

The purpose of this study is to analyze the contents of the questionnaires used in dietary surveys and to evaluate each item in relation to the item construction strategy. Articles of which the contents were related to food, nutrition, diet, dietary behavior, and related areas. Published from 1997 to 1999 were searched fir and a total of 121 questionnaires were collected and analyzed. The questions in the questionnaires were classified into related areas and sub-areas. Among the keywords in the title of the articles, the term 'nutritional status'(or 'dietary intake status') was most frequently used. The terms such as dietary status, obesity, health, food habit, and dietary behavior were also frequency used. Major topics of the items in the questionnaires varied according to the life cycle of the subjects of the study. The topics most frequently asked in each lift cycle were as follows : overeating, snack, and food preference for preschool- and school-aged children ; anthropometry, weight control, and snack for middle and highschool students : meal skipping, smoking, and drinking for college students : disease, smoking, drinking, and exercise for adults : and smoking, drinking, disease and perceived health for the elderly. Inappropriate questions with complicated language, typographic and grammatic errors, unnecessary words, and negative questions were found. Therefore, care should be taken to construct each question so as to avoid possible misinterpretation. Also, a standardized questionnaire be developed for survey researchers.