• 한국데이터정보과학회:학술대회논문집
• /
• 2003.05a
• /
• pp.1-14
• /
• 2003

In man cases, the measurement error variances may be functions of the unknown true values or related covariate. In some cases, the measurement error variances increase in proportion to the value of predictor. This paper develops estimators of the parameters of a linear measurement error variance function under stratified multistage random sampling design and additional conditions. Also, this paper evaluates and compares the power of an asymptotically unbiased test with that of an asymptotically biased test. The proposed method are applied to blood sample measurements from the U.S. Third National Health and Nutrition Examination Survey(NHANES III)

• Journal of the Korean Home Economics Association
• /
• v.23 no.4
• /
• pp.123-141
• /
• 1985

The purposes of this study were 1)to examine the present and the preferred design characteristics of major interior furnishings in the Gamsil apartment area of Gangdong-Ku and to investigate the relationship between those characteristics and residents' socioeconomic and their physical housing characteristics, 2) to determine the past and the future factor structures for attributes of the major furnishing, and , 3) to examine the change between the degree of the past and the future consideration on each of the attributes. The data for the study were collected using self-administered questionnaire. Households in Gamsil apartment area of Gangdong-Ku were the population. A proportional stratified systematic random sampling was employed. 480 questionnaires were distributed and 258 were collected. Among them, SAS package. The staticstics used were frequency, percentage, χ\sup 2\-test, factor analysis, and paired t-test.

• Nuclear Engineering and Technology
• /
• v.44 no.1
• /
• pp.33-42
• /
• 2012

In the present study, CFD is employed to investigate phenomena occurring during a process of thermal stratification in U-bent pipes at transitional Reynolds number. URANS evaluation had been chosen for its low computational costs during transient analysis and for the evaluation of modeling performance in these conditions. Application of CFD at transitional Reynolds number and buoyancy driven flows indeed contains deeper uncertainties in relation to the range of applicability for hydrodynamic and thermal models. The methodology applied in the work points out, through validations with the basic problems constituting the complex stratified phenomenon, the applicability of the current turbulence modeling. Accurate predictions have been found in relation to transitional Reynolds number in bent pipes and region of stability induced by the gravitational field. On the other hand the defects introduced in the unstable region of the U bent pipe, are discussed in relation to the adopted modeling.

• Journal of Agricultural Extension & Community Development
• /
• v.13 no.2
• /
• pp.251-263
• /
• 2006

The purpose of this study was to analyze vocational competencies of rural youths. The study was carried out by focus group interview and questionnaire. The data were collected from 200 rural youths by stratified random sampling. The SPSSWIN / ver13 was used for analyzing data with t-test, ANOVA, and factor analysis. The major findings of this study were as follows; Firstly, rural youths showed higher competencies in handling and fixing machines, selecting seeds, where as rural youths showed lower competencies in goal setting, envisioning, acquiring agricultural policy information, management evaluation. Secondly, rural youths predicted optimistic future of their own farming even though the future of national farming should get smaller. Lastly, rural youths who are higher education, extending farming size, establishing farm had higher vocational competencies than other youths. Conclusionally, the study suggests adult-farmers give rural youths an opportunity to participate in decision making and farming.

• Journal of Environmental Science International
• /
• v.23 no.12
• /
• pp.2071-2082
• /
• 2014

In this study, the environmental consciousness of Daegu citizen on conservation planning considering the regional characteristics was investigated. Data were collected throughout a survey and 1400 people were selected using a stratified sampling method based on populations of Daegu administration district. Results wee followings; First, the levels of environmental consciousness were different dependent on districts' characteristics. Second, poor awareness on Daegu Agenda 21 (Clear and Green Daegu 21) were shown. Daegu Agenda 21 is the action plan for the sustainable environmental conservation activities of the City of Daegu. Third, waste was the most serious environmental problems of Daegu, air quality was second worst, and third was river water quality from the survey, but differentiated awareness was shown dependent on regional spatial factors and pollution emission factors. Last, a public environmental education was the most important issue to make invigorations and progress for future environmental policy.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.2
• /
• pp.680-688
• /
• 1996

In this paper, the unsteady state calculational model is proposed for the thermal stratification analysis in the feedwater line of the PWR plant. By defining dimensionless parameters in the two-dimensional polar coordinate system and applying SIMPLE algorithm, the temperature and flow profiles due to the thermal stratification are obtained. Base on the fact that the most significant condition occurs when the fluid temperature difference between the piping ends reaches as high as 166.deg. C, the present result shows that max. Dimensionless temperature difference of 0.6 (about l00.deg. C) obtained between hot and cold sections of pipe wall at dimensionless time 47.0.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.4
• /
• pp.481-496
• /
• 1996

The last Sea is a typical bark-arc basin consisting of basins, plateaus, ridges, and seamounts. The Ulleng Basin, located in the southwestern corner of the last Sea, contains thick Neogene sedimentary sequence. Analysis of over 2,500 km of single-channel seismic reflection data suggests that hemipelagic sedimentation prevailed over much of the basin during the late Miocene and pelagic sedimentation became more dominant during the Pliocene. During the Pleistocene terrigeneous sediments transported by turbidity currents and other gravity flows, together with continuous hemipelagic settling, resulted in well-stratified sedimentary layers. Influx of terrigenous sediments during the Pleistocene formed depocenters in the western and southern parts of the basins. In the Ulleung Interplain Gap, where the Ulleung Basin joins the deeper Japan Basin, sediment waves suggesting bottom current activities are seen.

• Communications for Statistical Applications and Methods
• /
• v.20 no.6
• /
• pp.455-466
• /
• 2013

In nested case-control studies, the most common way to make inference under a proportional hazards model is the conditional logistic approach of Thomas (1977). Inclusion probability methods are more efficient than the conditional logistic approach of Thomas; however, the epidemiology research community has not accepted the methods as a replacement of the Thomas' method. This paper promotes the inverse probability weighting method originally proposed by Samuelsen (1997) in combination with an approximate jackknife standard error that can be easily computed using existing software. Simulation studies demonstrate that this approach yields valid type 1 errors and greater powers than the conditional logistic approach in nested case-control designs across various sample sizes and magnitudes of the hazard ratios. A generalization of the method is also made to incorporate additional matching and the stratified Cox model. The proposed method is illustrated with data from a cohort of children with Wilm's tumor to study the association between histological signatures and relapses.

• Korean Journal of Hydrosciences
• /
• v.8
• /
• pp.111-123
• /
• 1997

A one-dimensional eddy diffusion model and a mixed-layer model are developed and applied to simulate the vertical temperature profiles in lakes. Also the running result of each method are compared and analyzed. In an eddy diffusion model, molecular diffusivity is neglected and eddy diffusivity which does not need lake-specific fitting parameter and constant lake's level are applied. The heat exchanges at the water surface and the bottom are formulated by the energy balance and zero energy gradient, respectively. In a mixed-layer model, two layers approach which has a constant thickness is adopted. The application of these models which use explicit finite difference and Runge-Kutta methods respectively demonstrates that the models simulate water temperatures efficiently.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.5
• /
• pp.22-30
• /
• 1999

Optimization of in-cylinder flow is regarded as one of the most important factors to realize stable stratified charge combustion in a Spark-ignited Direct Injection(SDI) engine. Therefore, Computational Fluid Dynamic(CFD) simulation technique were used to clarify the characteristics of in-cylinder flow of a SDI engine with top entry intake port. Also, CFD results were compared to experimental results using Laser Doppler Velocimetry(LDV), Particle Image Velocimetry(PIV) and good validations were met. As the results reverse tumble flow generated during intake process was preserved by configuration of curved piston while base and reverse tumbles were diminished at the end of compression stroke in case of flat top piston. In addition, it will be needed to optimize the fuel mixture distribution based on these results.