• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 추계학술대회 논문집
• /
• pp.73-78
• /
• 2001

In this paper, overall planning and design procedure for the marine transportation are examined. For this purpose, marine transportation analysis for the North Nemba deck structure has been carried out. The results of analysis with the rigid barge transportation are compared to those with the barge considering its flexibility. The environmental conditions, especially waves, are shown to be the most important factor which affected on the structural strength, deformation and fatigue damage.

• 대한토목학회논문집
• /
• 제26권5A호
• /
• pp.909-915
• /
• 2006

콘크리트의 자기수축을 예측하기 위해 기존 수화도와 자기수축의 진행 속도 차이를 불포화공극 생성 속도로 가정하고 시멘트 페이스트의 자기수축 실험을 통하여 물-결합재비에 반비례하는 불포화공극 보정계수를 산정할 수 있었다. 이를 자기수축 기여 성분과 미기여 성분이 고려된 변형 Pickket 모델을 이용하여 콘크리트의 자기수축을 예측하였으며, 실험값 및 기존 Tazawa 모델과 일치하는 경향을 나타내어 불포화공극 보정계수에 의한 자기수축 예측이 타당함을 알 수 있었다. 그러나 강도의 함수로 설정된 기존 CEB-FIP 자기수축 예측 모델의 경우 최종 자기수축률과 자기수축 발현 시간함수에 대하여 다소의 수정이 필요할 것으로 판단된다.

• 대한한방소아과학회지
• /
• 제24권3호
• /
• pp.138-149
• /
• 2010

Objectives: The purpose of this study is to estimate genetic and environmental factors which can effect growth, and predict final height using this factors. Methods: Correlation analysis and regression analysis were conducted between measurements of height and Genetic & environmental factors through survey from 1352 child & adolescent patients. Results: Factors which have correlation with height percentile are MPH(Mid-Parental Height), NBW(Neonatal body weight), anorexia, dyspepsia, atopic dermatitis, frequency of breakfast and quality of sleeping time. MPH has moderate relation, NBW and anorexia have fair relation, and other factors have linear but poor relation. Regression equation from factors which have correlation and height percentile has 26.9% of predictive power. Regression equation considering only genetic factor has 20.4%. MPH has the most effect on height percentile. Anorexia has more effect than NBW. Other factors also have small and similar effect. Conclusions: Height of parents has the most effect on growth, anorexia, dyspepsia, atopic dermatitis, frequency of breakfast and quality of sleeping time also has effect.

• 국제강구조저널
• /
• 제18권4호
• /
• pp.1242-1251
• /
• 2018

Not all loads contribute to fatigue crack propagation in the welded detail of steel bridges when they are subjected to variable amplitude loading. For fatigue assessment, therefore, non-contributing stress cycles should be truncated. However, stress range truncation is not considered during typical fatigue reliability assessment. When applying the first order reliability method, stress range truncation occurs mismatch between the expected number of cycles to failure and the number of cycles obtained at the time of evaluation, because the expected number of cycles only counts the stress cycles that contribute to fatigue crack growth. Herein, we introduce a calibration factor to coordinate the expected number of cycles to failure to the equivalent value which includes both contributing and non-contributing stress cycles. The effectiveness of stress range truncation and the proposed calibration factor was validated via case studies.

• 한국산학기술학회논문지
• /
• 제19권12호
• /
• pp.7-13
• /
• 2018

콘크리트 강도는 시멘트, 물, 자갈, 모래 그리고 혼화재 등 내부영향요인뿐만 아니라 실제 현장에서 발생하는 현장기온과 타설지연시간 등 외부영향요인의 영향을 받게 된다. 본 연구의 목적은 콘크리트 배합설계 시 내부영향요인과 외부영향요인을 고려하여 현장 콘크리트 타설시 최적의 콘크리트 강도를 확보하는 것이다. 본 연구에서는 내부영향요인과 외부영향요인에 대한 수준을 정의하고, 모두 24개의 조합에 대한 콘크리트 강도 테스트를 한 후 콘크리트 강도예측 뉴럴 네트워크 모델을 개발했다. 본 콘크리트 강도예측 뉴럴 네트워크 모델은 현장 콘크리트 타설 시 현장기온과 타설지연시간을 고려하여 콘크리트 강도를 예측하는 기능을 제공한다. 본 콘크리트 강도예측 뉴럴 네트워크 모델은 내부영향요인과 외부영향요인을 분석하고 실제 현장에서 콘크리트를 타설할 때 양생온도와 타설지연시간을 뉴럴 네트워크 입력변수로 처리하여 콘크리트 강도를 예측하는 기능을 제공한다. 시공사는 콘크리트 강도예측 결과를 활용하여 콘크리트 배합을 조정함으로써 현장타설 콘크리트 강도를 관리할 수 있을 것이다.

• Geomechanics and Engineering
• /
• 제33권2호
• /
• pp.141-154
• /
• 2023

This study investigated the effect of water retention characteristics between aged and fresh Municipal Solid Waste (MSW) on the stability of the landfill. A series of transient numerical modeling for the slope of an MSW landfill was performed considering the variation of water retention characteristics due to leachate circulation. Four different scenarios were considered in this analysis depending on how to obtain hydraulic conductivity and the aging degree of materials. Unsaturated hydraulic properties of the MSW used for the modeling were evaluated through modified hanging column tests. Different water retention properties and various landfill conditions, such as subgrade stiffness, leachate injection frequency, and gas and leachate collection system, were considered to investigate the pore water distribution and slope stability. The stability analyses related to the factor of safety showed that unsaturated properties under those varied conditions significantly impacted the slope stability, where the factor of safety decreased, ranging between 9.4 and 22%. The aged materials resulted in a higher factor of safety than fresh materials; however, after 1000 days, the factor of safety decreased by around 10.6% due to pore pressure buildup. The analysis results indicated that using fresh materials yielded higher factor of safety values. The landfill subgrade was found to have a significant impact on the factor of safety, which resulted in an average of 34% lower factor of safety in soft subgrades. The results also revealed that a failed leachate collection system (e.g., clogging) could result in landfill failure (factor of safety < 1) after around 298 days, while the leachate recirculation frequency has no critical impact on stability. In addition, the accumulation of gas pressure within the waste body resulted in factor of safety reductions as high as 24%. It is essential to consider factors related to the unsaturated hydraulic properties in designing a landfill to prevent landfill instability.

• KDI Journal of Economic Policy
• /
• 제24권1호
• /
• pp.113-190
• /
• 2002

The purpose of this paper is to perform empirical studies on the impact of pollution intensity on international competitiveness using 1993 and 1998 data, and to estimate the change in environmental regulation level faced by the firms during 1993~1998. Collecting relevant data and providing them for further studies in the area are another purposes of the paper. The first method is the regression of various indices of international competitiveness on factor costs, such as labor, capital, R&D and pollution abatement costs. Goal of the regression analysis is to estimate the scarcity and comparative advantage effect of each production factor, especially environmental resource. Regression results show that those industries which employ more environmental resource have higher comparative advantage in both years, which implies that Korean firms are endowed with abundant environmental resource compared to other countries. The second method is to compute the relative scarcity indices(HOVL indices) of production factors, proposed by Leamer based on Vanek's generalized Hecksher-Ohlin Theorem. This method estimates the relative scarcity of production factors by computing factor costs embodied in import and export of commodities. This method shows similar results as the regression method; i.e., trade pattern of production factors implies that the manufacturing sector in Korea is endowed with abundant environmental resource compared to other countries. Considering population density, water resource endowment, intensity of economic activity per unit area and current air and water pollution levels, it is evident that Korea is never endowed with abundant environmental resource compared to other countries. Then the abundance of environmental resource revealed by the trade patterns of commodities and production factors implies that Korea's environmental regulation level is excessively generous compared to environmental capacity, and that this increased the environmental resource endowment supplied to firms and thus distorted the inter-industry comparative advantages. Both regression and HOVL methods, on the other hand, show that overall environmental regulation level faced by the firms has been strengthened during 1993~1998.

• International Journal of Concrete Structures and Materials
• /
• 제8권4호
• /
• pp.269-278
• /
• 2014

When concrete is being transported through a pipe, the lubrication layer is formed at the interface between concrete and the pipe wall and is the major factor facilitating concrete pumping. A possible mechanism that illustrates to the formation of the layer is the shear-induced particle migration and determining the rheological parameters is a paramount factor to simulate the concrete flow in pipe. In this study, numerical simulations considering various rheological models in the shear-induced particle migration were conducted and compared with 170 m full-scale pumping tests. It was found that the multimodal viscosity model representing concrete as a three-phase suspension consisting of cement paste, sand and gravel can accurately simulate the lubrication layer. Moreover, considering the particle shape effects of concrete constituents with increased intrinsic viscosity can more exactly predict the pipe flow of pumped concrete.

• 한국지반공학회논문집
• /
• 제32권6호
• /
• pp.27-40
• /
• 2016

기존의 강우에 의한 사면붕괴 기준들은 지형학적 특성, 임상특성, 불포화 지반 조건 등을 반영하지 않아 사면 파괴 예측 지표로 활용하기에는 많은 문제점을 가지고 있다. 본 연구에서는 강우패턴, 지형학적 특성(경사, 토심), 공학적 특성(불포화 지반 특성), 임상특성(식생 뿌리에 의한 영향, 수목하중) 등을 반영할 수 있는 불포화 사면 안정성 해석 방법을 제안하였다. 뿌리보강과 수목하중을 고려하지 않는 사면의 안전율 평가는 안전율을 과다 평가하는 것으로 나타났다. 제안된 안정성 해석 방법에 의하여 강우에 의한 불포화사면의 안전율에 대한 데이터베이스를 구축하고, 이를 GIS와 연계하여 울주군 산사태위험 지정지역에 적용하여 강우에 대한 사면 위험성을 정량적으로 분석하였다. 산사태위험지역은 강우에 의한 사면의 안전율이 낮거나, 대부분 안전율 감소가 급격하게 발생한 지점의 하류에 위치하고 있음을 알 수 있다.

• 국제학술발표논문집
• /
• The 9th International Conference on Construction Engineering and Project Management
• /
• pp.119-127
• /
• 2022

Most of the construction works are conducted outdoors, so the construction workers are affected by weather conditions such as temperature, humidity, and wind velocity which can be evaluated the thermal comfort as environmental factors. In our previous researches, it was found that construction accidents are usually occurred in the discomfort ranges. The safety management, therefore, should be planned in consideration of the thermal comfort and measured by a specialized simulation tool. However, it is very complex, time-consuming, and difficult to model. To address this issue, this study is aimed to develop a framework of a prediction model for improving the prediction accuracy about outdoor thermal comfort considering environmental factors using machine learning algorithms with hyperparameter tuning. This study is done in four steps: i) Establishment of database, ii) Selection of variables to develop prediction model, iii) Development of prediction model; iv) Conducting of hyperparameter tuning. The tree type algorithm is used to develop the prediction model. The results of this study are as follows. First, considering three variables related to environmental factor, the prediction accuracy was 85.74%. Second, the prediction accuracy was 86.55% when considering four environmental factors. Third, after conducting hyperparameter tuning, the prediction accuracy was increased up to 87.28%. This study has several contributions. First, using this prediction model, the thermal comfort can be calculated easily and quickly. Second, using this prediction model, the safety management can be utilized to manage the construction accident considering weather conditions.