• Journal of the Korean Solar Energy Society
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• v.26 no.2
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• pp.103-109
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• 2006

The Purpose of this work is to investigate a long-term thermal performance of active solar hot water heating system for the dormitory of university. For this, monitering system including temperature sensors, flow-meters was installed in this system. Measurement was continued for 13 months between April 1st 2004 and May 31th 2005. As results, hot water demand, daily and monthly hot water load distribution which are necessary for the solar system design were suggested. Also thermal stratification in solar buffer tank was observed in the point of increasement of system efficiency. The yearly solar fraction and system efficiency of this system are about 29.5% and 44.9% respectively.

• Wind and Structures
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• v.9 no.6
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• pp.493-503
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• 2006

The demand for energy in the world increases everyday. Blade energy which is wind turbine is a significant resource which must be appreciated in this field. Especially, in places where wind potential is high, the usage of wind energy is a beneficial factor for every country's economy. In this study, first, 6 different miniature rotor were produced by using 6 different NACA profiles. Rotors were produced with three blades. The electrical performance and the speed of start of action values that are provided from each rotor form were established by measuring them in the wind tunnel. The calculation of area and volumetric values of each profile and wind surfaces were made with AutoCad technical drawing program. As a result, it was searched whether there is any relation between electrical performance values and speed of start of motion that rotors produced and volumetric values of rotors. The aim of this study is to find out whether rotor blade volume is one of factors that influences rotor performance. The general tendency observed here is that the increase in the volume of rotor blade leads to an increase in the speed of start of motion and to a decrease in the rotor performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.401-401
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• 2009

Recently, demands for the development of compact, lightweight power supplies with higher power density and higher efficiency have been increased. Since Piezoelectric Transformer (PT) was emerged in device and material industry, it has been suggested as a viable alternative to the magnetic transformer in some applications. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). Also, PT can provide high voltage stepping ratio with good isolation and requires no copper windings saving copper usage especially for large voltage conversion differences. Conventional control of PT converter has mainly two-way. One is the pulse frequency modulation (PFM) control method and the other is the pulse width modulation (PWM) control with frequency fixed method. It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. And, also PT's resonant frequency moves according to the load condition. Therefore, selection of PT converter control method is very difficult. This paper analyzes general piezo-electric converter modeling and proposes a guide-line to selection of control method and stabilization control.

• Korean journal of food and cookery science
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• v.25 no.2
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• pp.219-226
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• 2009

Red ginseng extract was added to Yanggaeng to determine a practical use for the herb which has medical usage and functionality. We examined the antioxidant activity and quality characteristics of Yanggaeng prepared with different amounts (as ratios of 1%, 2%, 3% to the total materials) of red ginseng extract, as well as those of commercial red ginseng Yanggaeng. The antioxidant activity of the Yanggaengs samples was estimated by the DPPH free radical scavenging activity, $ABTS^{+\cdot}$ scavenging activity, and reducing power. The antioxidant activity of the Yanggaeng increased as a result of the addition of the red ginseng extract. Levels of polyphenol compounds and flavonoids increased according to the extract concentration. The quality characteristics of the red ginseng Yanggaeng were estimated in terms of pH, sugar content, viscosity, color, texture profile analysis, and sensory evaluations. With increasing concentrations of the extract, viscosity and sugar content increased, but pH decreased. In terms of the overall palatability, color, taste, flavor, and hardness, the 3% red ginseng Yanggaeng was determined as the best among the tested samples. Also, the 3% red ginseng Yanggaeng had higher scores than the commercial red ginseng Yanggaeng.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.157-164
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• 2001

The vehicle electric power system, which consists of two major components: a generator and a battery, which have to provide numerous electrical and electronic systems with enough electrical energy. A detailed understanding of the characteristics of the electric power system, electrical load demands, and the driving environment such as road, season, and vehicle weight is required when the capacities of the generator and the battery are to be determined for a vehicle. An easy-to-use and inexpensive simulation program may be needed to avoid the over/under design problem of the electric power system. A vehicle electric power simulator is developed in this study. The simulator can be utilized to determine the optimal capacities of generators and batteries. To improve the expandability and easy usage of the simulation program, the program is organized in modular structures, and is run on a PC. Empirical electrical models of various generators and batteries, and the structure of the simulation program are presented. For executing the vehicle electric power simulator, data of engine speed profile and electric loads of a vehicle are required, and these data are obtained from real driving conditions. In order to improve the accuracy of the simulator, numerous driving data of a vehicle are logged and analyzed.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.28.2-28.2
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• 2008

Recently, star sensors have been successfully used as main attitude sensors for attitude control in many satellites. This research presents the star visibility analysis for star trackers and the goal of this analysis is to make sure that the star tracker implementation is suitable to the mission profile and scenario and satisfies the requirement of attitude orbit control system. As a main optical attitude sensor imaging stars, accomodations of a star tracker should be optimized in order to improve the probability of the usage by avoiding the blinding (the unavailability) by the Sun and the Earth. For the analysis, a statistical approach and a time simulation approach are used. The statistical approach is based on the generation of numerous cases, to derive relevant statistics about Earth and Sun proximity probabilites for different lines of sight. The time simulation approach is performed for one orbit to check the statistical result and to refine the statistical result and accomodations of star trackers. In order to perform simulations first of all, an orbit and specific mission profiles of a satellite are set, next the earth proximity probability and the sun proximity probability are calculated by considering the attitude maneuvers and the geometry of the orbit, and then finally the unavailability positions are estimated. As a result, the optimized accomodations of two star trackers are suggested for the low earth orbit satellite.

• Journal of the Korean Society for information Management
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• v.18 no.3
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• pp.41-62
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• 2001

Effective resource management in the digital library should be implemented for the whole accessible sources on the network including multimedia one such as image files other than texts which focus on books. Contents management can be resource management of digital library in terms of wide scope, moreover, it\`s main function is to provide effectively tailor-made knowledge contents for users\` diversified objective of information usage. In this study, I examined main factors for more effective and advanced knowledge management including web resources under the current digital environment. First of all, I described closely several types of conceptualization and trails regarding more effective contents management and came up with advanced user-centered contents management system, i.e., user factors, intermediary factors, and finally service ones.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1259-1264
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• 2013

This study has focused on the application of magnetic assisted polishing for ELID ground surface of aluminum oxide ceramics. Aluminum oxide ceramics has been widely used as advanced materials for electric, optic, mechanic, chemical usage and so on. In this study, ELID grinding and magnetic assisted polishing technology was adopted for high-effective manufacturing and high quality surface of ceramic parts. The characteristic of MAP machining have been evaluated by the value of surface roughness and surface profile before and after magnetic assisted polishing. As the results of experiments, the surface roughness after magnetic assisted polishing has shown a significant improvement and the surface roughness was more improved when the feed rate of tool became slow.

• Journal of the Korean Home Economics Association
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• v.48 no.8
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• pp.113-128
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• 2010

The purposes of this study were 1) to divide consumers into segments according to their consumption attitude and subjective knowledge about natural dyed products 2) to develop a profile for each segment with respect to the media types, the preferred media programs, the information sources, the lifestyle activities and the demographics. Data(n = 213) was collected using questionnaires via the internet. By cluster analysis of the consumers' attitude and their subjective knowledge about natural dyed products, four groups were identified 1) the loyal consumption group (20.1%), 2) the conditional/reluctant consumption group(36.6%), 3) the negative/reluctant consumption group(24.2%) and 4) the non purchasers(19.1%). Several characteristics of these four groups were then compared by ANOVA and chi-square statistics. The results indicated that the consumption attitude and subjective knowledge could be the criteria for segmenting the consumers and that the segmented groups had unique consumer characteristics. Implications of this study were discussed.

• Journal of the Korean Vacuum Society
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• v.12 no.3
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• pp.162-167
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• 2003

To find the concentration according to the depth-direction of ions implanted in the sample, with sputtering of the sample surface, one needs the depth profiling of ion implanted in the sample. On measuring of depth profiling, the sputtering rate to affect depth direction, is calculated by SRIM simulation. When ion is implanted in the sample, the atomic density of the sample rises up a little, and it alters sputtering yield. This alteration then causes differences of sputtering rate to affect depth-direction, on measuring of depth profiling. With the usage of SRIM Monte Carlo simulation code, one calculates sputtering rate, with sputtering yield by the alteration of atomic density of the sample through ion implantation. As a result, it goes to prove that its difference affects depth distribution, on measuring of depth profiling.