• Economic and Environmental Geology
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• v.32 no.2
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• pp.161-167
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• 1999

Electric and electromagnetic surveys were conducted to investigate the deep structure of the Ulsan fault in Ipsil area, south of Kyeongju. On this study, especially high-frequency magnetotelluric method of electromagnetic survey in the frequency range of 10~100,000 Hz was mainly employed to study the deep subsurface configuration. High-frequency MT survey was performed at 70 points of spacing 30~50 m, making 3.8 km survey line. As a survey result, a 2-km-depth 2-D cross-section was achieved. It shows vertical and horizontal subsurface variations of resistivity values. Near-surface layer having low resistivity value becomes thicker eastward up to 800m. There is a steep low resistivity zone in the west side of survey line, and there exists two low resistivity zones dipping west in the east side of survey line. Two low resistivity zones are interpreted to be related to major movement pattern of the Ulsan fault. This suggests that major fault lines are developed on both peripheral sides of the broad fault zone.

• Nutrition Research and Practice
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• v.5 no.1
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• pp.66-72
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• 2011

The purpose of this study was to assess the metabolic profile and nutrient intake data in Korean adolescents according to exercise regularity using the forth Korean National Health and Nutrition Examination Survey from 2008 data. A total of 834 Korean adolescents (440 boys, 394 girls) aged 12 to 18 years were classified into exercising male (EM), non-exercising male (NM), exercising female (EF), and non-exercising female (NF) groups. EM exhibited significantly higher weight (P<0.001), waist circumference (WC) (P<0.01) and body mass index (EMI) (P<0.001) than NM. EF showed significantly greater height (P<0.01), weight (P<0.001), we (P<0.001), and BMI (P<0.001) than NF. Although ratios of macronutrient intake were within the appropriate range in all groups, energy, riboflavin, vitamin e and calcium were assessed as in adequate by the nutritional adequacy ratio (NAR) in all groups. Moreover, EF and NF had inadequate intake of vitamin A and iron according to NAR, respectively. There were significant correlations between height and NAR protein (r=0.249, P<0.001), and mean adequacy ratio (MAR) (r=0.177, P<0.01), and between weight and NAR protein (r=0.180, P<0.01), and MAR(r=0.136, P<0.05) in EM. On the other hand, there were significant correlations between weight and NAR protein (r=0.270, P<0.01), we and NAR protein (r=0.271, P<0.01), and BMI and NAR protein (r=0.326, P<0.01) in NM. There were significant correlations height and NAR Fe (r=0.153, P<0.05) in EF. However, there were no significant correlations between metabolic factors and nutritional adequacy in NF. Although we noted no significant differences in MAR between the groups, the exercising groups showed higher MAR values than the non-exercising groups. Therefore, practicing of ideal dietary behaviors appears to be induced through physical activity and regular exercise in Korean adolescents.

• The Korean Journal of Applied Statistics
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• v.21 no.3
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• pp.361-375
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• 2008

We propose proper methods to impute the item nonresponse in 4-8-4 rotation sample survey. We consider nonignorable nonresponse mechanism that can happen when survey deals with sensitive question (e.g. income, labor force). We utilize modeling imputation method based on Bayesian approach to avoid a boundary solution problem. We also estimate a interview time bias using imputed data and calculate cell expectation and marginal probability on fixed time after removing estimated bias. We compare the mean squared errors and bias between maximum likelihood method and Bayesian methods using simulation studies.

• Journal of the Korean Data and Information Science Society
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• v.13 no.2
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• pp.167-174
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• 2002

In the case of "nonignorable missing data", it is necessary to assume a model dealing with the missing on each situations. In this article, for example, we sometimes meet situations where data set are income amounts in a survey of individuals and assume a model as the values are the larger, a missing data probability is the higher. The method is to maximize using the EM(Expectation and Maximization) algorithm based on the (missing data) mechanism that creates missing data of the case of exponential distribution. The method started from any initial values, and converged in a few iterations. We changed the missing data probability and the artificial data size to show the estimated accuracy. Then we discuss the properties of estimates.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.84-92
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• 2019

While the Internet continues to integrate with modern lives, the risks of negative outcomes resulting from problematic use (PU) are also increasing. Although psychological well-being and use motivations have been shown to play major roles in Internet PU, understanding the moderating mechanism is critical for advanced knowledge. The present study employed survey data from users of a live video-game streaming service (LVGS) that is an area rarely been studied. Result concluded a positive moderating effect of escapism motive (EM) on the association between loneliness and the PU of LVGS, while the moderating mechanism between EM and stress was not indicated. A moderating effect of information seeking (IS) on the relationship between stress and the PU of LVGS was found negative, but no mechanism between IS and loneliness was indicated. This study highlights how the interplay of different motivation and pathologies may induce or prevent video-game-related addiction.

• Journal of the Korea Fashion and Costume Design Association
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• v.13 no.4
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• pp.1-14
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• 2011

This study is to analyze the image similarity and the preference for clothing stores in the 6 giant discount chains in Daejeon. The survey for this study was based on the questionnaires accomplished by 257 people through the multidimensional scaling. The results are as follows First, 6 clothing stores had 4 image groups located in 4 coordinates. CW(Costco Wholesale), NH(Nonghyup Hanaro-Mart), and SZ(Save Zone) had a similar distinct image, while HP(Home Plus) and EM(E-Mart), and LM(Lotte-Malt) also had similar differentiated images. Second, according to the preference analysis in terms of demographic characteristic, NH had the lowest preference from the people of all the different ages, while SZ had the highest. HP, EM, CW, and LM had their own preference in the following order: in the thirties, forties, and over fifties. Meanwhile, relatively, SZ is preferred by the people in their twenties and people over age fifty liked CW more. Third, according to the analysis of the preference for clothing stores in the giant discount chains in terms of educational background, clothing consumers who had high school degrees preferred NH and LM, people with 2 year college degrees liked HP and EM more, while 4-year college graduates and people with higher education had preference for SZ. Finally, according to the preference analysis in terms of income level, higher income groups preferred SZ and CW and lower income groups liked LH and LM more, while HP and EM had high preference from all kinds of income groups.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.110-115
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• 1998

Self-potential, VLF-EM and dipole-dipole resistivity methods have been widely used for exploration of conductive sulfide ore deposit, because of the convenience and low cost of field work and the reliability of their results. The geophysical responses for vein-type sulfide outcrop of Changkoom mine located in Bukwi-Myon, Jinan-Gun, Chollabuk-Do were investigated and compared with its drilling results. The geology around the survey area is composed of acidic volcanics and sediments of Yuchon Group. And sulfides bearing pyrite, pyrrotite, galena etc. are deposited in disseminated or vein type within acidic volcanics. Typical geophysical responses were detected from the above vein type ore body, respectively. From the shape and extent of S.P. anomaly, ore body is dipping westward and extending about 50 m. It is detected that the VLF EM response matching the outline of ore zone is considered as indication of dyke dipping westward. And also resistivity response indicating conductive dipping dyke is detected. From drilling results for outcrop and geophysical anomalies, the shape of ore body is vein type dipping about $70^{\circ}W$ and extending about 50 m.

• Geophysics and Geophysical Exploration
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• v.17 no.4
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• pp.187-201
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• 2014

Compared with the separated inversion of electromagnetic (EM) and seismic data, a joint inversion using both EM and seismic data reduces the uncertainty and gives the opportunity to use the advantage of each data. Seismic fullwaveform inversion allows velocity information with high resolution in complicated subsurface. However, it is an indirect survey which finds the structure containing oil and gas. On the other hand, marine controlled-source EM (mCSEM) inversion can directly indicate the oil and gas using different EM properties of hydrocarbon with marine sediments and cap rocks whereas it has poor resolution than seismic method. In this paper, we have developed a joint EM inversion algorithm using a cross-gradient technique. P-wave velocity structure obtained by full-waveform inversion using plane wave encoding is used as structure constraints to calculate the cross-gradient term in the joint inversion. When the jointinversion algorithm is applied to the synthetic data which are simulated for subsea reservoir exploration, images have been significantly improved over those obtained from separate EM inversion. The results indicate that the developed joint inversion scheme can be applied for detecting reservoir and calculating the accurate oil and gas reserves.

• Economic and Environmental Geology
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• v.33 no.6
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• pp.525-536
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• 2000

Electromagnetic and electric surveys were performed to reveal the deep structure of the Yangsan fault in the Bong-gye and Unyang areas, Kyeongnam Province, Korea. Especially, high-frequency magnetotelluric (HFMT) method of EM survey was mainly employed to study the deep subsurface configuration of Yangsan fault. HFMT survey was performed at 25 points of spacing 50 m, making 1.3 km survey line in Unyang area and 13 points of spacing 50 m, making 0.6 km survey line in Bong-gye area. Two 2-D cross-sections (Unyang and Bong-gye areas) were achieved as results. Electric survey by dipole-dipole array was performed to study the structure of shallow subsurface and compare the results with HFMT surveys. The results of HFMT and electric surveys show that Yangsan fault is a geologic boundary. It is very narrow and steep (about $80^{\circ}C$), and extends to 1~1.5 km depth.

• Korea journal of population studies
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• v.21 no.1
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• pp.162-183
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• 1998

This study examines the sampling bias that may have resulted from the large number of missing observations. Despite well-designed and reliable sampling procedures, the observed sample values in DSFH(Demographic Survey on Changes in Family and Household Structure, Japan) included many missing observations. The head administerd survey method of DSFH resulted in a large number of missing observations regarding characteristics of elderly non-head parents and their children. In addition, the response probability of a particular item in DSFH significantly differs by characteristics of elderly parents and their children. Furthermore, missing observations of many items occurred simultaneously. This complex pattern of missing observations critically limits the ability to produce an unbiased analysis. First, the large number of missing observations is likely to cause a misleading estimate of the standard error. Even worse, the possible dependency of missing observations on their latent values is likely to produce biased estimates of covariates. Two models are employed to solve the possible inference biases. First, EM algorithm is used to infer the missing values based on the knowledge of the association between the observed values and other covariates. Second, a selection model was employed given the suspicion that the probability of missing observations of proximity depends on its unobserved outcome.