This study was conducted to evaluate the risk of overweight and obesity in adolescents consuming snacks frequently from 2007~2009, Korean National Health and Nutrition Examination Survey (KNHANES). The subjects (12~14 years: n=523; 15~18 years: n=614) were presented with food frequency questionnaires, and they were classified according to their gender and frequency of snack consumption. In the age group of 12~14 years, boys and girls (boys OR: 1.11, 95% CI: 0.52~2.39, girls OR: 12.45, 95% CI: 2.26~68.51) who consumed yogurt frequently had a higher risk of overweight and obesity at the highest quartile frequency compared with the lowest quartile after adjustments for multiple confounding factors, including age, physical activity, frequency of eating out and snack consumption, and energy intake. In the age group of 15~18 years, girls (OR: 1.01, 95% CI: 0.34~2.99) consuming fried foods had a higher risk of overweight and obesity at the highest quartile frequency compared with the lowest quartile after adjustments for multiple confounding factors, including age, physical activity, frequency of eating out and snack consumption, and energy intake. Thus, we conclude that frequent consumption of yogurt and fried foods increases the risk of overweight and obesity in adolescents. These findings suggest that the risk of overweight and obesity is associated with the frequency of snack consumption.

Much of the data used in the analysis of environmental ecological data is being obtained over time. If the number of time points is small, the data will not be given enough information, so repeated measurements or multiple survey points data should be used to perform a comprehensive analysis. The method used for that case is longitudinal data analysis or mixed model analysis. However, if the amount of information is sufficient due to the large number of time points, repetitive data are not needed and these data are analyzed using time series analysis technique. In particular, with a large number of data points in the current situation, when we want to predict how each variable affects each other, or what trends will be expected in the future, we should analyze the data using time series analysis techniques. In this study, we introduce univariate time series analysis, intervention time series model, transfer function model, and multivariate time series model and review research papers studied in Korea. We also introduce an error correction model, which can be used to analyze environmental ecological data.

본 연구의 목적은 다층자료 매개효과의 분석 방법을 제안하는 것이다. 연구내용은 다층자료 매개효과의 통계방법 탐색, 분석절차 제안, 그리고 분석의 실례 제시 등 세 가지다. 첫째, MLM (multilevel modeling)과 MSEM (multilevel structural equation modeling) 중에서 어떤 방법이 다층자료의 매개효과 분석에 유용한지 탐색하였다. MSEM은 MLM 의 약점을 극복한 것으로서 유용한 다층 매개효과 분석방법이었다. 둘째, 다층자료 매개효과의 분석절차를 연구모형설 정, 전제조건 검토, 모형검증, 계수검증의 4단계로 전개하였다. 셋째, 매개효과 분석의 실례에 사용된 자료는 2,695명의 초중등 학생과 88명의 학급교사로 구성되었다. 분석 실례로 2층→2층→1층과 1층→1층→2층 두 가지를 제시하였다. 2층→2층→1층과 1층→1층→2층 모형은 완전매개모형이 지지되었지만, 2층→2층→1층 모형의 매개효과 계수만 95% 신뢰구간에서 유의하였다. 분석 실례에 사용된 Mplus 프로그램은 부록에 제시하였다. 연구결과를 기초로 본 연구의 의의와 제한점, 그리고 후속연구의 방향이 논의되었다.

Naval combat system developed in-country is progressing at an alarming rate since 2000. ROK navy will be achieved all vessels that have combat system in the near future. The importance of System Engineering and Integrated Logistics Support based on reliability analysis is increasing. However, reliability analysis that everyone trusted and recognized is not enough and applied practically for development of Defense Acquisition Program. In particular, Existing Reliability Analysis is focusing on reliability index (Mean Time Between Failure (MTBF) etc.) for policy decision of defense improvement project. Most of the weapon system acquisition process applying in the exponential distribution simply persist unreality due to memoryless property. Critical failures are more important than simple faults to ship’s operator. There are no confirmed cases of reliability analysis involved with critical failure that naval ship scheduler and operator concerned sensitively.Therefore, this study is focusing on Mean Time To Critical Failure (MTTCF), reliability on specific time and Operational Readiness Float (ORF) requirements related to critical failure of Patrol Killer Guided missile (PKG) combat system that is beginning of naval combat system developed in-country. Methods of analysis is applied parametric and non-parametric statistical techniques. It is compared to the estimates and proposed applications. The result of study shows that parametric and non-parametric estimators should be applied differently depending on purpose of utilization based on test of normality. For the first time, this study is offering Reliability of ROK Naval combat system to stakeholders involved with defense improvement project. Decision makers of defense improvement project have to active support and effort in this area for improvement of System Engineering.

본 연구는 다중빔 음향측심 자료를 바탕으로 침몰선박의 정확한 형상 및 해저지형에 대한 정보를 분석하였다. 다양한 영상 자료처리를 통해 현재 침몰선박의 상태를 분석하였다. 해당 자료와 과거 조사 자료의 비교를 통하여 침몰선박 상태 변화 및 주변지형의 변화를 해석하였다. 분석대상 선박 중 퍼시픽프랜드호의 경우 조류에 의한 침·퇴적으로 인해 선수-선미의 지형변화가 뚜렷하게 나타나는 특징을 알 수 있었다. 그리고 제7해성호의 경우 2011년 국립해양조사원 영상자료에서는 선수 일부가 유지된 상태였으나, 2015년 조사 영상에서는 선수 일부가 붕괴된 것을 확인할 수 있었다. 이는 오랜 기간 선박이 해저에 방치되면서 조류 및 화물의 하중 등과 지속적인 부식으로 선체가 붕괴된 것으로 추정된다. 따라서 잔존연료 유출 및 주변 해양오염이 발생할 수 있어 지속적인 모니터링이 필요할 것으로 판단된다. 침몰선박의 영상분석을 통해 침몰선박이 수심과 조류에 의한 영향을 많이 받은 지역일 경우 지질학적 특성과 퇴적물의 침·퇴적 양상에 따라 침몰선박의 구조 안전성에 상당한 영향을 줄 것으로 판단되며, 부식으로 인한 선체의 변화는 계속적으로 변화될 것으로 추정된다. 따라서 지질학적 특성을 고려한 잔존연료 유출 및 주변 환경 변화에 대하여 침몰선박의 변화에 따라 예측‧대응하는 기술의 개발이 필요하다.

This study investigates important parameters used to determine an effective peak ground acceleration (EPGA) based on the characteristics of response spectra of historical earthquakes occurred at Korean peninsula. EPGAs are very important since they are implemented in the Korean Building Code for the seismic design of new structures. Recently, the Gyeongju earthquakes with the largest magnitude in earthquakes measured at Korea took place and resulted in non-structural and structural damage, which their EPGAs should need to be evaluated. This paper first describes the basic concepts on EPGAs and the EPGAs of the Gyeongju earthquakes are then evaluated and compared according to epicentral distances, site classes and directions of seismic waves. The EPGAs are dependant on normalizing factors and ranges of period on response spectrum constructed with the Gyeongju earthquake records. Using the normalizing factors and the ranges of period determined based on the characteristics of domestic response spectra, this paper draw a conclusion that the EPGAs are estimated to be about 30 % of the measured peak ground accelerations (PGA).

This study proposes a methodology to analyse social networks among participating design engineers during product development projects. The proposed methodology enables product development managers or the participating design engineers to make a proper decision on product development considering the performance of participating design engineers. It considers a product development environment where an integrated product data management (PDM) system manages the product development data and associated product development processes consistently in its database, and all the design engineers share the product development data in the PDM database for their activities in the product development project. It provides a novel approach to build social networks among design engineers from an operational product development data in the PDM database without surveys or monitoring participating engineers. It automatically generates social networks among the design engineers from the product data and relationships specified by the participants during the design activities. It allows analysts to gather operational data for their analysis without additional efforts for understanding complex and unstructured product development processes. This study also provides a set of measures to evaluate the social networks. It will show the role and efficiency of each design engineers in the social network. To show the feasibility of the approach, it suggests an architecture of social network analysis (SNA) system and implemented it with a research-purpose PDM system and R, a statistical software system. A product configuration management process with synthetical example data is applied to the SNA system and it shows that the approach enables analysts to evaluate current position of design engineers in their social networks.

온난화와 같은 전지구적 변화는 기온과 강수 등 기상요소에 직접적으로 반영되어 곡물 수확량의 변화를 가져온다. 기후변화 시나리오에 기초한 선행연구들에서는 GCM (general circulation model)의 공간해상도 문제로 인하여 상세한 모의가 어려웠고, 시계열통계법을 활용한 연구들에서는 기후요소를 통합하여 수확량을 예측한 사례가 매우 드물었다. 이에 본 연구에서는 상세화된 기후재분석자료의 시계열모델링을 통하여 옥수수와 콩의 수확량 예측실험을 수행하였다. 미국 아이오와 주의 99개 카운티를 대상으로 1960년부터 2009년까지 50년간의 고해상도 기후재분석자료와 정부통계 수확량 DB를 구축하고, 시계열통계법인 VAR (vector autoregression)와 ARIMA (autoregressive integrated moving average)를 이용하여 다음해 수확량 예측실험을 10개 연도에 대해 수행하여 예측력을 평가하였다. VAR는 16-18%, ARIMA는 11-14% 의 오차율로 다음해의 수확량을 예측할 수 있는 것으로 집계되었으며, 옥수수의 경우 표토의 산성도, 심토의 점토와 나트륨 함유량 등의 토양특성 이 실제 수확량 및 예측정확도에 영향을 미치는 것으로 나타났다.

This study of small ＆ Medium-Sized construction sites construction disaster prevention technology conduction-site visits from the map results report by the inspector on-site advice and technical guidance for the analysis of deficiencies and potential construction of disaster revealed the potential factors causing an accident as follows. As a results, Should not be a once a month visits. Therefore should be changed at least twice a month to help prevent accidents of this system is to be judged.

PURPOSES: This study analyzed the lane-by-lane traffic flow characteristics in Korea by using real-world data, including congestion levels, for 2-, 3-, and 4-lane freeways. METHODS : On the basis of a literature review, lane flow and speed characteristics were analyzed using flow measurements and speed ratios. In addition, the effect of congestion levels on traffic flow were visualized using rescaled cumulative plots. RESULTS: Driver behavior varied depending on the congestion level. During free-flow conditions, the lane-use ratio of individual lanes varied largely, whereas during congestion, the ratio was nearly the same for all lanes (i.e., equilibrium). During maximum-flow and congestion conditions, the median lane was used more than the shoulder lane, whereas during all other conditions, the shoulder lane had a higher lane-use ratio. In 3- or 4-lane freeways, the lane-use ratio of the median lane always exceeded 1 and was the highest during free-flow conditions. CONCLUSIONS : The results of the present analysis can be used as an index to predict congestion before a lane is overcapacitated. Moreover, the results can be applied in variable lane guidance systems, such as car navigation systems and variable message displays, to control traffic flow.

Although the Hazen-Williams C factors are very important in the design, operation, and maintenance of water supply pipes, sufficient studies for them have been not reported in korea, which are based on experiments or measured data. Because of this, we have estimated C factors by measurement considering constraints in time precise safety diagnosis for multi-regional water supply system were performed. In this study, we confirmed constraints and variables characteristics of Hazen-Williams equation, and collected reliable C factors data of 174 by measurement, and analyzed their characteristics. According to collected data, the average value is 115.35, which is almost equal to the value of design standard or a little higher than it in korea. Also, among the equations suggested to determine C factor in the past, the C factors calculated by Sharp and Walski equation was closest to them in this study. In addition, to analyze collected C factors, use year and pipe diameter having high correlation with them were respectively divided into there categories. Analysis results showed that C factors evidently decreases depending on increases in use year, on the other hand, size of pipe diameter is proportional to value of them. In conclusion, this research showing evaluation and characteristics for C factors based on measured data will be used as practical reference in determining C factor in multi-regional water supply systems at a later date.

The effect of weir construction (2009~2011) was investigated on algal bloom dynamics and surrounding conditions in the Youngsan River by analyzing the long-term (2001~2014) data provided by the Water Information System, Ministry of Environment. The data include chlorophyll a and water properties such as total suspended solids (TSS), ammonium (NH4 +), nitrate (NO3-), orthophosphate (PO43-), total nitrogen (TN), total phosphorus (TP) and DIN/DIP molar ratio collected from 12 stations along the channel of the river. Temporal variations were examined using data collected monthly from 2001~2014 and Box-Whisker plot was used to examine the difference in algal bloom dynamics between before (2006~2008) and after (2012~2014) the weir construction. Pearson’s correlation analysis was also used to analyze the correlation of parameters. The results showed that TSS affecting water turbidity increased during the construction but decreased especially at the stations located in the upper and middle regions of the river after the construction. Ammonium concentrations increased whereas the concentrations of other nutrients decreased after the construction inducing an increase in N:P molar ratio. Chlorophyll a decreased suddenly during the construction but increased clearly after the construction at the stations where TSS decreased. This indicates that algal blooms can develop in the Youngsan River due to a decrease in turbidity that increases light penetration in water column although the concentrations of nutrients such as orthophosphate were reduced after the weir construction.

Conventional data envelopment analysis (DEA) models require that inputs and outputs are given as crisp values. Very often, however, some of inputs and outputs are given as imprecise data where they are only known to lie within bounded intervals. While a typical approach to addressing this situation for optimization models such as DEA is to conduct sensitivity analysis, it provides only a limited ex-post measure against the data imprecision. Robust optimization provides a more effective ex-ante measure where the data imprecision is directly incorporated into the model. This study aims to apply robust optimization approach to DEA models with imprecise data. Based upon a recently developed robust optimization framework which allows a flexible adjustment of the level of conservatism, we propose two robust optimization DEA model formulations with imprecise data; multiplier and envelopment models. We demonstrate that the two models consider different risks regarding imprecise efficiency scores, and that the existing DEA models with imprecise data are special cases of the proposed models. We show that the robust optimization for the multiplier DEA model considers the risk that estimated efficiency scores exceed true values, while the one for the envelopment DEA model deals with the risk that estimated efficiency scores fall short of true values. We also show that efficiency scores stratified in terms of probabilistic bounds of constraint violations can be obtained from the proposed models. We finally illustrate the proposed approach using a sample data set and show how the results can be used for ranking DMUs.