• Korean Journal of Soil Science and Fertilizer
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• v.46 no.5
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• pp.333-342
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• 2013

Soil compaction is affected by soil texture, organic matter (OM), strength (ST) and soil moisture, which is difficult to understand the degree and effects of related factors. The purpose of the study is to assess the impact of them on the compaction with bulk density (BD). The analysis was conducted with data collected from national-wide monitoring sites including 105 upland soils, 246 orchard soils, and 408 paddy soils between 2009 and 2012. The distributions of soil physical properties were measured. The correlation and multi linear regression analysis were performed between soil physical properties using SAS. The regression equation of BD(y) includes ST, gravitational water contents (GWC), and OM as variables commonly, having additional factors, clay content and sand content in paddy soil and upland soil for only subsoil (p<0.001). Our results show that the BD could be explained about 40~50% by various physical properties. The regression was mainly determined by ST in orchard and upland soil and by the GWC in paddy soil. To mitigate soil compaction, it is important to maintain the proper level of OM in upland soil and to consider the moisture condition with soil texture in paddy soil when making work plan. Furthermore, it would be recommended the management criteria classified by soil texture for the paddy soils.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.1-8
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• 2018

Whole body fatigue detection is an important phenomenon and the factors contributing to whole body fatigue can be controlled if a mathematical model is available for its assessment. This research study aims at developing a model that categorizes whole body exertion into fatigued and non-fatigued states based on physiological and perceived variables. For this purpose, logistic regression was used to categorize the fatigued and non-fatigued subject as dichotomous variable. Normalized mean power frequency of eight muscles from 25 subjects was taken as physiological variable along with the heart rate while Borg scale ratings were taken as perceived variables. The logit function was used to develop the logistic regression model. The coefficients of all the variables were found and significance level was checked. The detection accuracy of the model for fatigued and non-fatigues subjects was 83% and 95% respectively. It was observed that the mean power frequency of anterior deltoid and the Borg scale ratings of upper and lower extremities were significant in predicting the whole body fatigued when evaluated dichotomously (p < 0.05). The findings can help in better understanding of the importance of combined physiological and perceived exertion in designing the rest breaks for workers involved in squat lifting tasks in industrial as well as health sectors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1606-1616
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• 2011

The blood pressure measuring equipment, which is being supplied and used most widely by being recognized convenience and accuracy now generally, is oscillometric blood pressure monitor. However, a change in blood pressure is basically influenced by diverse elements such as each individual's physiological status and physical condition. Thus, the measurement of blood pressure, which used single element called oscillation in blood pressure of being conveyed to cuff, is not considered on physiological elements such as cardiovascular system status and blood vessel stiffness index, and on external elements, thereby being quite in error. Accordingly, this study detected diverse bio-signals and body informations in each individual as the measurement subject such as ECG, PPG, and Korotkoff Sound in order to enhance convenience and accuracy of measuring blood pressure in the complex measurement equipment, thereby having extracted regression method for compensation in error of oscillometric blood pressure measurement on the wrist, and having improved accuracy of measuring blood pressure. To verify a method of improving accuracy, the blood pressure value in each of SBP, DBP, MAP was acquired through 4-stage experimental procedure targeting totally 51 subjects. Prior to experiment, the subjects were divided into two groups such as the experimental group for extracting regression method and the control group for verifying regression method. Its error was analyzed by comparing the reference blood pressure value, which was obtained through the auscultatory method, and the oscillometric blood pressure value on the wrist. To reduce the detected error, the blood pressure compensation regression method was calculated through multiple linear regression analysis on elements of blood pressure, individual body information, PTT, HR, K-Sound PSD change. Verification was carried out on improving significance and accuracy by applying the regression method to the data of control group. In the experimental results, as a result of confirming error on the reference blood pressure value in SBP, DBP, and MAP, which were acquired through applying regression method, the results of $-0.47{\pm}7.45$ mmHg, $-0.23{\pm}7.13$ mmHg, $0.06{\pm}6.39$ mmHg could be obtained. This is not only the numerical value of satisfying the sphygmomanometer reference of AAMI, but also shows the lower result than the numerical value in SBP : $-2.5{\pm}12.2$ mmHg, DBP : $-7.5{\pm}8.4$ mmHg, which is the mean error in the experimental results of Brram's research for verifying accuracy of Omron RX-M, which shows relatively high accuracy among wrist sphygmomanometers. Thus, the blood pressure compensation could be confirmed to be made within significant level.

• Journal of Environmental Health Sciences
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• v.38 no.1
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• pp.42-50
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• 2012

The purpose of this study was to investigate the concentration and distribution characteristics of $PM_{10}$ at high schools classrooms in Ulsan and its surroundings. This study evaluated $PM_{10}$ levels in classrooms at 79 high schools in Ulsan from May 2008 to May 2009. The average $PM_{10}$ level was 63.8 ${\mu}g/m^3$, and the rate of exceeding the statutory maintenance limit was 16.0%. The average $PM_{10}$ level was higher in general schools (64.9 ${\mu}g/m^3$) compared to professional schools (59.2 ${\mu}g/m^3$), and private schools (66.6 ${\mu}g/m^3$) was higher than that of public schools (62.5 ${\mu}g/m^3$). The average $PM_{10}$ level (68.4 ${\mu}g/m^3$) in general classrooms was significantly (p < 0.01) higher than that in multi-purpose ones (54.6 ${\mu}g/m^3$), and first-year student classrooms (73.3 ${\mu}g/m^3$) was significantly (p < 0.05) higher than that in second or third grade ones (67.6 ${\mu}g/m^3$, 51.5 ${\mu}g/m^3$, respectively). The $PM_{10}$ level in schools in Dong-Gu in the vicinity of assorted industrial complexes was higher than that of schools located in other districts around the Ulsan Metropolitan Area. The regression model showed that $PM_{10}$ level was positively associated with number of students and relative humidity.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.666-674
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• 2016

This study examines the effect of consumption level on the life satisfaction of baby-boom generation and further examines the mediating effect of subjective expectation(standard of living and government policy). This research uses the panel survey to explore ageing society in 2012 made by Korean Labor Institute, which studied 1,756(born in 1955~1961). SPSS 21.0 Package was applied to analyze the date and multi-regression analysis was conducted. As a result, first, the findings show that as the consumption level increases, the life satisfaction of the baby-boom generation goes up. Second, the findings reveal that subjective expectation partially mediates the influences of consumption level on the life satisfaction of baby-boom generation. This study further discusses the theoretical and political implication of the direction properties on baby-boomer based upon the results of the study.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.2
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• pp.91-108
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• 2010

Universities are one of leading R&D institutes, however, their scarce security investment allows research information to leak outside. This paper proposes methods for improving security level of academic institutes to protect research information by analyzing security awareness and activities. To do that, we verified the current status of information security and awareness level by analyzing the survey which was conducted for a member of Seoul National University. As a result of statistical analysis using correlation, analysis of variance, multi regression and so on, we concluded that it is essential to improve security awareness, activities, professor's security level and management process for research labs. Thus, we suggest the following methods, security awareness and knowledge development through education, security management for research labs through provision, introduction of data protection softwares and physical control of visitors which are to be adopted to improve security level.

• Journal of Family Resource Management and Policy Review
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• v.21 no.1
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• pp.1-18
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• 2017

This study examined the predictors of life satisfaction of marriage migrant wives with school-aged children in South Korea. For this purpose, we draw data from the 2015 National Survey on Multi-cultural Families (NSMF). The target group was marriage migrant wives who were in a first marriage and had school-aged children (N=3,004). We used OLS regression to examine the predictors of the target group's life satisfaction with the SPSS 18.0 program. The results are as follows. First, marriage migrant wives with school-aged children had maintained their marriage for at least 14 years. They were satisfied with their relationships with both their spouses and their children. Also, they were satisfied with their spouse's child care roles. They did not support the multi-cultural policy of assimilation. Their Korean proficiency was slightly higher than the middle level. More than half had jobs and had not attended a parent meeting. Second, although they were satisfied with their everyday lives, their levels of life satisfaction were less than that of migrant wives with children below 5 years of age. Third, all variables explained 38.8% of the life satisfaction experienced by marriage migrant wives with school-aged children. Satisfaction with their spouses, subjective health, satisfaction of spouse's child care role, monthly family income, satisfaction with their children, experience attending a parents meeting, and Korean proficiency were positively associated with the life satisfaction of this target group. The findings of this study are significant because they can provide certain implications for family life education and policy within a multi-cultural society.

• Journal of Preventive Medicine and Public Health
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• v.39 no.1
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• pp.53-58
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• 2006

Objectives: We wanted to evaluate the main route of exposure to lead and cadmium for the general population in Korea by using multi-route and multi-media exposure assessment Methods: Samples of air at the homes, samples of the food and water and peripheral blood samples were collected from thirty volunteers living in Seoul (the metropolitan area), Yong-in (the suburban area) and Ansan (the industrial area) in 2001. Graphite furnace atomic absorption spectrometric methods were used for the determination of the Pb and Cd levels in the air, food, water and blood samples. Results: The average intake of lead through the air, drinking water and food were $5.06{\mu}g/day\;(26.3%)\;0.002{\mu}g/day\;(0.1%),\;and\;16.4{\mu}g/day\;(73.6%)$, respectively. The average intake of cadmium through the air, drinking water and food were $0.082{\mu}g/day\;(0.9%),\;0.001{\mu}g/day\;(0.007%),\;and\;12.61 {\mu}g/day\;(99.0%)$, respectively. The blood lead level was statistically higher in the male subjects than in the female subjects (3.39 and $2.22{\mu}g/dl$, respectively), and only gender was a significant variable on the multiple regression analysis for blood lead. Conclusions: This study showed that the intake of lead and cadmium through food was the major route of exposure. A policy to reduce the pollutants according to the exposure routes should be established. However, more studies will be needed to support these data for the general population.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.2
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• pp.1-14
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• 2021

It is highly challenging to measure the efficiency of electric vehicle charging stations (EVCSs) because factors affecting operational characteristics of EVCSs are time-varying in practice. For the efficiency measurement, environmental factors around the EVCSs can be considered because such factors affect charging behaviors of electric vehicle drivers, resulting in variations of accessibility and attractiveness for the EVCSs. Considering dynamics of the factors, this paper examines the technical efficiency of 622 electric vehicle charging stations in Seoul using data envelopment analysis (DEA). The DEA is formulated as a multi-period output-oriented constant return to scale model. Five inputs including floating population, number of nearby EVCSs, average distance of nearby EVCSs, traffic volume and traffic congestion are considered and the charging frequency of EVCSs is used as the output. The result of efficiency measurement shows that not many EVCSs has most of charging demand at certain periods of time, while the others are facing with anemic charging demand. Tobit regression analyses show that the traffic congestion negatively affects the efficiency of EVCSs, while the traffic volume and the number of nearby EVCSs are positive factors improving the efficiency around EVCSs. We draw some notable characteristics of efficient EVCSs by comparing means of the inputs related to the groups classified by K-means clustering algorithm. This analysis presents that efficient EVCSs can be generally characterized with the high number of nearby EVCSs and low level of the traffic congestion.

• Journal of the Korean Geographical Society
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• v.49 no.3
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• pp.405-422
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• 2014

Two important issues in hedonic model are to specify accurate model and delineate submarkets. While the former has experienced much improvement over recent decades, the latter has received relatively little attention. However, the accuracy of estimates from hedonic model will be necessarily reduced when the analysis does not adequately address market segmentation which can capture the spatial scale of price formation process in real estate. Placing emphasis on improvement of performance in hedonic model, this paper tried to segment real estate markets in Gangnam-gu and Jungrang-gu, which correspond to most heterogeneous and homogeneous ones respectively in 25 autonomous districts of Seoul. First, we calculated variable coefficients from mixed geographically weighted regression model (mixed GWR model) as input for clustering, since the coefficient from hedonic model can be interpreted as shadow price of attributes constituting real estate. After that, we developed a spatially constrained data-driven methodology to preserve spatial contiguity by utilizing the SKATER algorithm based on a minimum spanning tree. Finally, the performance of this method was verified by applying a multi-level model. We concluded that submarket does not exist in Jungrang-gu and five submarkets centered on arterial roads would be reasonable in Gangnam-gu. Urban infrastructure such as arterial roads has not been considered an important factor for delineating submarkets until now, but it was found empirically that they play a key role in market segmentation.