• Survey Research
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• v.5 no.2
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• pp.49-70
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• 2004

This paper is a broad review about general regression estimators, which are very useful when auxiliary variables are available in survey sampling. We investigate the process of development of general regression estimators from birth to suggestion of variance estimation method and examine some properties of general regression estimators by comparing with calibration and QR estimators. We also present some forms of general regression estimators available under complex sampling designs such as stratified sampling and cluster sampling. Finally, we comment some advantages as well as disadvantages of general regression estimators and theoretical and practical development in the future.

• Survey Research
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• v.3 no.2
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• pp.77-90
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• 2002

This study reports the results of a random sampling telephone survey conducted in the case of the Ulsan mayoral election 2002. We interview at least five times to a respondent who is randomly selected by means of the birthday method from a randomly sampled telephone number list of 1,233 households, We analyze the result of interviewing, such as absence and promise. And we compare the demographic variables of the surveyed sample and those of the population and we also compare the randomly selected sample's voting preference with outcome of the election in various ways. Finally, we discuss difficulty of random sampling with the birthday method and suggest some technical tips to conduct random sampling telephone survey.

• Korean Journal of Social Welfare
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• v.58 no.2
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• pp.251-271
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• 2006

The purposes of this study were to investigate the research utilization in social work practice and to examine the factors associated with research utilization. The subjects of this study were social workers participating in social work practice in Korea. The sampling methods used in this study was a multistage sampling strategy. Data were collected by sending mails and follow-up mails to the social workers. Data from 569 of social workers were finally analyzed by ordered regression analysis. The results showed that the level of research utilization by social workers in Korea was very low, but their attitude toward research was positive. The variables affecting research utilization were related to the research ability of social workers, but the variables of research related environment except type of organization were not significant. The variables for research ability of social workers are experiences of utilizing journal articles, experiences of re-education for research methodology, gender, attitude about research usefulness. The variables for research related environment are characteristics of agency setting. The implications of social work research are discussed.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.84-93
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• 2012

The study was conducted to analyze the spatio-temporal changes in water quality of the major 36 sampling stations of Nakdong River, depending on each station, season using the 17 water quality variables from 2000 to 2010. The result was verified to interpret the characteristics of water quality variables in a more accurate manners. According to the Principal component analysis (PCA) and Exploratory factor analysis (EFA) results; the results of these analyses were identified 4 factors, Factor 1 (nutrients) included the concentrations of T-N, T-P, $NO_{3}-N$, $PO_{4}-P$, DTN, DTP for sampling station and season, Factor 2 (organic pollutants) included the concentrations of BOD, COD, Chl-a, Factor 3 (microbes) included the concentrations of F.Coli, T.Coli, and Factor 4 (others) included the concentrations of pH, DO. The results of a Cluster analysis indicated that Geumhogang 6 was the most contaminated site, while tributaries and most of the down stream sites of Nakdong River were mainly affected by each nutrients (Factor 1) and organic pollutants (Factor 2). The verification consequence of Confirmatory factor analysis (CFA) from Exploratory factor analysis (EFA) result can be summarized as follows: we could find additional relations between variables besides the structure from EFA, which we obtained through the second-order final modeling adopted in CFA. Nutrients had the biggest impact on water pollution for each sampling station and season. In particular, It was analyzed that P-series pollutant should be controlled during spring and winter and N-series pollutant should be controlled during summer and fall.

• Journal of Korean Society for Quality Management
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• v.40 no.3
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• pp.245-258
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• 2012

Purpose: Recently, many quality issues are aroused in military forces, such as failures in K-series weapons, combat boots defects and 40mm ammunition explosion accident. To address these problems, the one and only government defense quality assurance agency, DTaQ(Defense Agency for Technology & Quality) tried to improve many quality assurance procedures and introduced new systems such as MRA(Manufacturing Readiness Assessment), TRA(Technology Readiness Assessment), and etc. However, as the amount of war supplies increasing every year, the resource(budget and manpower) for quality assurance is limited. Therefore, DTaQ had difficulty to handle the issue efficiently and effectively, and we propose the method to address this problem. Methods: The most popular quality assurance technique is a sampling method, in this research, we first review the many sampling techniques and compare the strength and weakness of each method. After then, we selected the most appropriate sampling techniques and applied the procedures in combat force support material and ammunition areas. Results: We can reduce the number of samples dramatically, thus the required amount of labor time and money can be saved. Also, the new sampling technique enforces the supplier to produce the product which meets the target value(desirable value). Conclusion: We can reduce the number of samples dramatically, thus the required amount of labor time and money can be saved. Also, the new sampling technique enforces the supplier to produce the product which meets the target value(desirable value). Lastly, since the new sampling method requires many numerical calculations, we developed a simple android OS smart-phone application which can be used easily in field.

• Journal of The Korea Institute of Healthcare Architecture
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• v.23 no.1
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• pp.7-14
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• 2017

Purpose: Since the large hospitals are one of the most intensive energy users among building types in Korea, it is important to investigate and apply appropriate energy conservation measures. There are many researches on energy conservation measures for HVAC system in hospitals, but only few useful guidelines for envelope design variables were existed. The building envelope is one of the important factors to building energy consumption and patients' comfort. The purpose of this study is to suggest the most influential envelope design variables for each end-use energy demand. Methods: 100 samples were generated by LHS(Latin Hypercube Sampling) method. After energy performance simulation, global sensitivity analysis was performed by the regression method. DesignBuilder, Simlab 2.2 and JEPlus were used in this process. Results: The most influencing variables are SHGC, SHGC and VT for heating, cooling, and lighting, respectively. However, the most influencing variable for total energy demand is WWR(Window to Wall Ratio). The analysis was conducted based on the coefficient of variance results. Implications: The six envelop design variables were ranked according to the end-use energy demand.

• Survey Research
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• v.9 no.1
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• pp.69-85
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• 2008

Stratification is a feature of the majority of field sample design. This paper considers the multivariate stratification strategy for multipurpose sample survey with several auxiliary variables. In a multipurpose survey, stratification procedure is very complicated because we have to simultaneously consider the efficiencies of stratification for several variables of interest. We propose stratification strategy based on factor analysis and cluster analysis using several stratification variables. To improve the efficiency of stratification, we first select the stratification variables by factor analysis, and then apply the K-means clustering algorithm to the formation of strata. An application of the stratification strategy in the sampling design for the Fisher Production Survey is discussed, and it turns out that the variances of estimators are significantly less than those obtained by simple random sampling.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.1-12
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• 2009

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.44-53
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• 2009

Numerical design optimization of a fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. Twenty training points are obtained by Latin Hypercube sampling for three design variables. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate. The film-cooling effectiveness has been successfully improved by the optimization with increased value of all design variables as compared to the reference geometry.

• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.23-31
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• 2008

The purpose of this study was to investigate proper sampling duration while executing quiet stance of feet together position and a preferred foot position with eyes open using COP variables through GRF system. The subjects participated in this study were twenty healthy elderly women individuals($68.9{\pm}6.8$ years). It represented that the sampling duration needed over 20 s in the FTP and over 60 s in the PFP during assessment of quiet stance. The sampling duration shorter than 20 s in the FTP and 60 s in the PFP may not provide the sample showing stability. Inversely if the sampling duration becomes longer, it can distort the sample showing stability. In the future, I expect more studies of the proper sampling duration through various groups and the study of characteristics of participants caused by more sampling duration.