• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.38-45
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• 2008

This study presents a numerical procedure to optimize the compressor design to increase the surge margin of compressor with response surface method (RSM). The Box-Behnken design method is used to reduce the number of calculation for fitting the second-order response surface. In order to consider the increase of surge margin during numerical optimization without any calculation at the surge point, the slope of compressor characteristic curve at the design point is suggested as an objective function in the present optimization problem. Mean line performance analysis method is used to get the design and off-design characteristic curves of centrifugal compressor. The impeller exit angle, impeller exit height and impeller radius are chosen as design variables. The optimum shapes show the increase of surge margin for the surge margin optimization and increase of efficiency for the efficiency optimization in comparison with an initial shape.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.456-459
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• 2009

we studied a data acquisition and control system of a wind turbine for measuring and controlling a voltage fluctuations of a wind turbine system. The wind turbine system is installed out control area. So, it is so important for supervising to wind turbine of a maintenance, wind speed, optical resources wind turbine output, wind speed, wind direction, over voltage of a generator. This system can be supplied a data of over voltage, under voltage, voltage fluctuations of a wind turbine for controlling an EMS : Energy Management System or a SCADA : Supervision Control and Data Acquisition at a constitute of a wind farm. The of voltage fluctuation system of a wind turbine is improving an electric power supply power quality of a distribution line and unspecified individuals of used wind turbine.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1292-1301
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• 2001

The mean-line method using empirical models is the most practical method of predicting off-design performance. To gain insight into the empirical models, the influence of empirical models on the performance prediction results is investigated. We found that, in the two-zone model, the secondary flow mass fraction has a considerable effect at high mass flow-rates on the performance prediction curves. In the TEIS model, the first element changes the slope of the performance curves as well as the stable operating range. The second element makes the performance curves move up and down as it increases or decreases. It is also discovered that the slip factor affects pressure ratio, but it has little effect on efficiency. Finally, this study reveals that the skin friction coefficient has significant effect on both the pressure ratio curve and the efficiency curve. These results show the limitations of the present empirical models, and more resonable empirical models are reeded.

• Korean Journal of Remote Sensing
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• v.34 no.4
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• pp.703-708
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• 2018

In recent years, subsidence due to excessive groundwater withdrawal is a major problem in the Kathmandu Basin. In addition, on 25 April 2015, the basin experienced large crustal displacements caused by Mw 7.8 Gorkha earthquake. In this study, we applied StaMPS- Persistent Scatterer InSAR (StaMPS PS-InSAR) technique to estimate the spatio-temporal displacements in the basin after the mainshock. 34 Sentinel-1 C-band SAR data are used for measuring subsidence velocity during 2015-2017. We found the maximum subsidence velocity of about 9.02 cm/year and mean subsidence rate of about 8.06 cm/year in the line of sight direction, respectively, in the central part of the basin.

• Journal of the Korean Society of Clothing and Textiles
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• v.14 no.2
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• pp.73-84
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• 1990

The present research investigated perceptions of persons wearing Korean and Western clothing with reference to judgement of appropriateness of style in a variety of socially interacting contexts and relationship to social schemata and to general clothing interest. 180 male and 180 female students responded to open-ended and Likert-type questionnaires. The stimuli were 9 line drawings of male and female figures in traditional Korean and Western formal and informal attire. Data were analyzed by content analysis, frequency, percentage, and mean. Traditional Korean clothing was judged as inappropriate on the campus and in the office but appropriate in the ambiguous context. Korean traditional styles were related to person schemata, but Western styles were related to role schemata. Furthermore, Korean styles were considered to be 'impractical' and 'inactive.' A newly emerging perception of persons wearing Korean attire as 'individualistic' and 'radical activist' was discovered. Impressions of persons wearing traditional Korean clothing were partially related to subject's own clothing interest.

• Journal of Family Resource Management and Policy Review
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• v.7 no.2
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• pp.131-144
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• 2003

The purpose of this study was to examine the overspending in Korean urban households. Data for this study were from the 2001 Household Income and Expenditure Survey and consisted of a sample of 3,250 households. The mean of the spending to income ratio was 1.02 and 37% of the households spent more than 100% of their taken-home income. Multiple logistic regression was used to investigate the determinants of overspending. Education, job, household type, the number of earners, the number of children, life cycle, location, and home ownership were significant variables which influence the overspending. The results of this study is useful for financial planners and counselors to make a guide line for overspenders.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.64
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• pp.63-76
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• 2001

This paper presents a job-shop type flexible manufacturing system(FMS) scheduling problem and examines the effects of scheduling rules on the performance of FMS. Several machine and AGV scheduling rules are tested against the mean flow-time criterion. In this paper, I compare the rules under various experimental conditions by using an FMS simulation model. One of the objectives of this study is to discuss how the simulation-based scheduling problem can be operated. The other is to measure sensitivity of the rules to changes at inter arrival time, queue capacity, breakdown rates for machines and AGV, and AGV speed. Therefore, the results of simulation experiments were considered on FMS design and operating stages. A comprehensive bibliograph? is also presented in the paper.

• Journal of Environmental Health Sciences
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• v.19 no.4
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• pp.1-9
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• 1993

Since most people spend a large majority of their time indoors (at least in the industrialized countries), indoor air may affect human health more than outdoor air. This study was carried out to characterize the reference and equivalent methods against the low volume method which was promulgated by the Ministry of Health and Social Affairs. The Laser and Piezo air sampler offer the advantage of real time data and low labor costs. The arithmetic mean concentrations were found to be 102.9% (Laser-2 min method) and 65.9% (Piezo method) against low volume method (100%). The statistical analysis procedure for this comparision is linear regression. The linear regression line of low volume method had slopes of 0.5487 and 0.9697 and Y intercepts of 0.0266 and 0.0110 $\mu$g/m$^3$ about Laser (2 min) and (24 h) method respectively. And the correlation coefficients were 0.7271 and 0.9433.

• Journal of the Korean Home Economics Association
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• v.39 no.5
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• pp.15-26
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• 2001

The purpose of this study is to examine specific consumer problems in internet commerce and analyze them in the age of information. The way of sorting consumer problems in internet commerce from this study. For this empirical analysis, the data was collected 319 consumers by internet on-line survey from Feb. 13 to Feb. 20, 2000. The methods for study was frequency, percentage, mean, correlation, multiple regression using SAS PC program. The major findings of this study were as follows: 1. The level of consumer problem experiences in internet commerce was examined. The problems of privacy was the most problem and the problem of price was the second. Then delivery, advertisement, information was next, and the problem of quality, and A/S, change, cancel was the next consumer problem. 2. Among factors influence on experience consumer problem in internet commerce, the amount of usable money, information search were significant.

• 연구논문집
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• s.31
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• pp.77-88
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• 2001

In this paper, the critical vibration limits of a spindle unit for a high speed ball pen tip processing machine are studied. The vibration of the spindle is measured by FFT, and the influence of the vibration amplitude due to unbalance, bearing deflect, bite, and timing belts tension is analyzed. The critical vibration limits of the spindle is determined by the X, and Z directional vibrations of the spindle. Both FET and RMS values can be used to analyze the vibration characteristics of the spindle. From experimental results the limit line can be drawn for the spindle. The RMS value for the vibration limit is 3 G.