• 한국건축시공학회지
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• 제7권4호
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• pp.145-151
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• 2007

In this paper, tests are carried out in order to investigate the strength development of concrete under various binder types, W/B and curing temperature ranged from $5{\sim}20^{\circ}C$. Fly ash and blast furnace slag were incorporated by as much as 30%, respectively. Strength development of concrete are estimated using Logistic model and strength ratio of concrete at 28days to that at early age are also investigated. According to experimental results, it is found that good agreements are obtained between measured values and calculated ones using logistic model below $20^{\circ}C$. Strength ratio of concrete at 28days to that at early age increases in case W/B decreases and curing temperature increases. Tables and graphs for strength ratio of concrete are provided in this paper. It is capable of obtaining and predicting the periods to attain design strength by considering increment factor of strength easily with the table and graphs presented in this paper. This paper presents the reference data to decide removal time of form, time to reach target strength and strength inspection of remicon whether the test specimens meet the specified criteria of compressive strength. Multi regression models with respect to the relationship between 7days compressive strength and 28 days compressive strength depending on W/B and admixture types are presented.

• 한국전산유체공학회지
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• 제13권1호
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• pp.21-27
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• 2008

A numerical study for laminar flow in the entrance region of helical tubes for uniform inlet velocity conditions is carried out by means of the finite volume method to investigate the effects of Reynolds number, pitch and curvature ratio on the flow development. This results cover a curvature ratio range of 1/10$\sim$1/320, a pitch range of 0.0$\sim$3.2, and a Reynolds number range of 125$\sim$2000. It has been found that the curvature ratio does significantly effect on the angle of flow development, but the pitch and Reynolds number do not. The characteristic angle $\phi_c(=\phi/\sqrt{\delta})$, or the non-dimensional length $\overline{l}(=l\sqrt{\delta}cos(atan\lambda)/d)$ can be used to represent the flow development for uniform inlet velocity conditions. In uniform inlet velocity conditions, the growth of boundary layer delays the flow development attributed to centrifugal force, and in which conditions the amplitude of flow oscillations is smaller than that in parabolic inlet velocity conditions. If the pitch increases or if the curvature ratio or Reynolds number decreases, the minimum friction factor and the fully developed average friction factor normalized with the friction factor of a straight tube and the flow oscillations decrease.

• 보건의료산업학회지
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• 제9권4호
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• pp.197-206
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• 2015

Objectives : This study presents comparison results of the correlations between ODA grants and health indicators among 23 countries in Asia. Methods : Data from 2005~2013 were collected through the World Development Indicator (WDI) provided by the World Bank (WB). The health-related variables used in this study included the maternal mortality ratio, infant mortality rate under five, infant mortality rate, incidence of tuberculosis, and prevalence of AIDS. Results : Based on the results, there were positive correlations between ODA grants and health indicators, which means that the overall ODA grants would drop when the health indicators improved. As for differences in the health indicators by income groups among the countries, there were differences in the maternal mortality ratio, infant mortality rate under five, infant mortality rate, and overall ODA grants. The maternal mortality ratio, infant mortality rate under five, and infant mortality rate were lower in the order of upper middle, lower middle, and poorest income countries. Conclusions : The findings raise a need for the integrated and horizontal development of Goals 4, 5 and 6 of MDGs in the ODA projects of health sector in the future.

• KIEAE Journal
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• 제11권2호
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• pp.3-8
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• 2011

This study was carried out for analysing the relationship of environmental factors and the reduction rate of land compensation of six urban development projects near waste landfill sites located in the Seoul metropolitan area. For a close investigation, 24 variables were selected but only 4 environmental variables were identified to have high correlation to the reduction rate of compensation. These are fine particles(PM10), bad smell, the ratio of a greening zone of land and park, and the distance in straight line from the landfill site. Two variables-PM10 and bad smell-were found to have an effect on the average reduction rate of land compensation by correlation analysis. On the other hand, the ratio of a greening zone and the distance in straight line from the landfill site have been rejected for the significance test. The result of regression analysis of six models for the search of affecting variables on the reduction rate of compensation is that PM10 and bad smell have the impact ratio of more than 0.5. But the ratio of greening zone and the distance from the landfill are not significant factors, having the impact ratio of 0.025~0.045 except one model.

• 한국추진공학회지
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• 제22권2호
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• pp.131-137
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• 2018

엔진 당량비의 제어오차가 요구범위를 불만족할 확률을 분석하였다. 당량비의 제어오차는 무작위 불확실요소와 인식론적 불확실요소로부터 동시에 영향을 받는다. 무작위 불확실요소는 일반적으로 확률 분포가 주어지므로 민감도 기반의 신뢰성 해석기법을 이용해 쉽게 해석이 가능하다. 확률분포를 알기 어려운 인식론적 불확실요소를 다루기 위해서는 새로운 접근법이 필요하다. 무작위 불확실요소에 대한 신뢰성 해석결과를 베이지안 추론에 이용함으로서 엔진 당량비의 제어오차가 요구범위를 불만족할 확률에 대한 확률분포를 구할 수 있었다. 이러한 접근은 무작위 불확실요소와 인식론적 불확실 요소가 동시에 존재하는 공학시스템 해석에 유용하게 사용될 수 있다.

• 아동학회지
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• 제38권1호
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• pp.117-126
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• 2017

Objective: The purpose of this study was to investigate young children's nonsymbolic magnitude comparison ability according to ratio limit and task condition. Methods: The participants included 40 3-year-old children, 42 4-year-old children, and 41 5-year-old children recruited from 4 childcare centers located in Seoul, Korea. All magnitude comparison tasks were composed of image material tasks and concrete material tasks. In addition, each magnitude comparison task varied with the ratio of the two quantities; 0.5 ratio, 0.67 ratio, 0.75 ratio. Results and Conclusion: The results revealed that 3-, 4-, and 5-year-old children could perform nonsymbolic magnitude comparison tasks without learning experiences. Also, 3-, 4-, and 5-year-old children could perform concrete material tasks better than image material tasks in nonsymbolic magnitude comparison tasks. Furthermore, children's performance on nonsymbolic magnitude comparison tasks indicated the ratio signature of the approximate number system. Children have a degree of numerical capacity prior to formal mathematics instruction. Also, children were influenced by task conditions or sense stimulus when they processed numerical information. Furthermore, the approximate number system can be used in understanding the ordinality of number.

• 기술혁신학회지
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• 제14권spc호
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• pp.1096-1127
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• 2011

본 연구는 TOD 시스템이 가져오는 경제적 파급효과에 대해 신규시장창출, 연구기획비용절감, 사업화 성공률 증대효과라는 세 가지 측면에서 정량적으로 추정하고자 하였으며 시스템 개발이 가져오는 효율성 제고라는 측면을 강조하여 패러미터들을 도출하고 시뮬레이션과 시나리오 분석을 실시하였다. 시나리오별로 (1) TOD 시스템 적용비율이 해당부문 R&D 기획과제의 1.4%라고 가정한 경우 R&D 기여율을 적용한 경제적 파급효과 편익의 총합은 2011년 가격기준으로 921.3억원으로 도출되며 연구개발 투입비용(2012-2017년까지 6년간 30억원이 투자되며 2011년 현재가치로는 149.9억원이 투입)을 감안하면 B/C ratio는 6.15으로 도출된다. 시나리오 (2) TOD 시스템 적용비율이 1.9%라고 가정한 경우 경제적 편익의 총합은 1,250.3억원, B/C ratio는 8.34, 시나리오 (3) TOD 시스템 적용비율이 0.9%라고 가정한 경우 경제적 편익은 592.2억원, B/C ratio는 3.95가 도출된다. 본 연구는 기술기회 탐색에 대한 새로운 시스템 개발이 가지는 경제적 효과에 대해서 사전적 타당성을 점검하였고, 시스템 관점에서 연구개발투자의 경제성 평가방법론에 대한 새로운 사례를 제공하였다는데 연구의 의의가 있다.

• 농촌의학ㆍ지역보건
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• 제47권4호
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• pp.255-267
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• 2022

Objectives: The purpose of this study was to analyze the factors affecting work-related musculoskeletal symptoms in farmers. Methods: In order to examine the factors affecting the musculoskeletal symptoms among farmers, data of 'Occupational Disease Survey for Farmers' was performed by the RDA(Rural Development Administration). Results: The odds ratio of work-related musculoskeletal symptoms among female farmers were 1.42(1.30-1.56) times higher than male farmers. The older aging and longer the agricultural work period, the higher odds ratio of musculoskeletal symptoms was shown. By major crops, all crop farmers showed higher odds ratio of musculoskeletal symptoms compared to rice crop farmers. As a result of examining the effective factors on the odds ratio of musculoskeletal symptoms by body parts, female farmers had higher odds ratio of musculoskeletal symptoms than male farmers by 1.38(1.26-1.51) times in waist, 1.58(1.44-1.74) times in knee, 1.32(1.05-0.67) times in hand/wrist, and 1.30(1.06-1.59) times in foot/ankle. By crops, animal husbandry farmers had higher odds ratio of musculoskeletal symptoms than rice crop farmers by 1.44(0.89-2.35) times in waist, and field crop farmers were 1.37(1.07-1.77) times higher in knee. Compared with rice crop farmers, odds ratio of the shoulder part the shoulder parts were 1.19(0.81-1.76) times higher in greenhouse crop farmers and 1.16(0.97-1.38) times higher in dry field crop farmers. Odds ratio of the hands/wrist parts were higher odds ratio of musculoskeletal symptoms than rice crop farmers by 1.69(1.00-2.87) times in greenhouse crop farmers. Conclusions: The results of this study would help to select the group that needs to be managed first, and could be used as basic data for the development of customized musculoskeletal disorders prevention programs.

• KDI Journal of Economic Policy
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• 제42권1호
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• pp.31-56
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• 2020

Does financial development contribute to economic growth? The literature finds that an expansion in financial resources is useful for economic growth if the degree of financial development is under a certain threshold; otherwise, the expansion is detrimental to growth. Almost every published study, however, considers country-panel data. Accordingly, the results are not directly applicable to the Korean economy. By examining Korean time-series data, this paper finds that there is an inverse U-shaped relationship between the per capita real GDP growth rate and private credit (as a percentage of nominal GDP)-a well-known measure of quantitative financial development, where the threshold is 171.5%. This paper also finds that private credit is positively associated with economic growth if the share of household credit out of private credit is less than 46.9%; otherwise, private credit is negatively associated with economic growth. As of 2016, the ratio of private credit to GDP and the ratio of household credit to private credit are both higher than the corresponding thresholds, which implies that policymakers should place more emphasis on qualitative financial development than on a quantitative expansion of financial resources.

• 환경영향평가
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• 제16권5호
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• pp.311-318
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• 2007

This study was conducted based on the 115 development projects of residential areas during 2001-2006 to investigate the current status of park green areas. Prior Environmental Review System (PERS) was categorized into regions, scales, and time of the projects, and regression model was used for a statistical analysis. The ratios of greenness of Seoul and Gyunggi province were greater than those of other regions whereas the ratios of greeness of Cheonnam, Chungbuk, and Jeonbuk provinces showed smaller percentage of green areas. Secondly as the scales of development get bigger areas of greenness become larger indicating a large scale residential development projects are favorable for securing green areas. Thirdly the correlation between planned area and green areas, and that between planned population and the ratio of greenness are relatively low (P>0.05). This implies green areas are not a good indicator but a concrete guideline for green areas. Fourthly the ratio of greenness of small scale project is not reached to 10% so that it is recommended to secure over one million $m^2$ areas for development project.