• Structural Engineering and Mechanics
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• 제5권1호
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• pp.105-113
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• 1997

This paper proposes a model for simulating concrete shrinkage taking into account aggregate restraint. In the model, concrete is regarded as a two-phase material based on shrinkage property. One is paste phase which undergoes shrinkage. Another is aggregate phase which is much more volumetrically stable. In the concrete, the aggregate phase is considered to restrain the paste shrinkage by particle interaction. Strain compatibility was derived under the assumption that there is no relative macroscopic displacement between both phases. Stresses on both phases were derived based on the shrinking stress of the paste phase and the resisting stress of the aggregate phase. Constitutive relation of paste phase was adopted from the study of Yomeyama, K. et al., and that of the aggregate phase was adopted from the author's particle contact density model. The equation for calculating concrete shrinkage considering aggregate restraint was derived from the equilibrium of the two phases. The concrete shrinkage was found to be affected by the free shrinkage of the paste phase, aggregate content and the stiffness of both phases. The model was then verified to be effective for simulating concrete shrinkage by comparing the predicted results with the autogeneous and drying shrinkage test results on mortar and concrete specimens.

• KDI Journal of Economic Policy
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• 제39권4호
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• pp.1-23
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• 2017

I measure aggregate productivity growth in manufacturing between 1995 and 2013 as defined by Petrin and Levinsohn (2012). I decompose aggregate productivity growth into technical efficiency improvements, resource reallocations, and net entry effects. I find that aggregate productivity growth slows down after 2004 and that the rapid drop in technical efficiency growth contributed most to the decline. In this paper, I focus on the role of young plants with regard to productivity growth of Korean manufacturing. I show that young plants account for nearly half of APG (48%), while their value-added share is 14 percent on average between 1995 and 2013. I find that productivity growth at young plants has been declining for the last ten years. The lower growth of continuing young plants contributes to this trend. These results stress the important role of young plants in aggregate productivity growth and imply that understanding the dynamics of young plants is necessary to form effective start-up policies.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.17-18
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• 2022

Carbon dioxide emissions in the construction sector account for 38% of all industries, and environmental destruction is occurring due to indiscriminate use of natural resources. The purpose of this study is to develop by-product aggregate Non-Sintered Cement(NSC) that can replace sand used as natural aggregate and Portland cement. Therefore, Ground Granulated Blast Furnace Slag, Type C Fly Ash and Type F Fly Ash are used to replace cement, and water granulated ferro-nickel slag(FNS) is used to replace aggregate. The flow, compressive strength and flexural strength of the formulation using sand as an aggregate and the formulation replacing 100% FNS were compared. As a result of the experiment, the formulation using FNS had higher overall strength than the formulation using sand, and as the substitution rate of Type C fly ash increased, the strength was the best. Formulation using FNS is more fluid than using sand. Through this study, we show the possibility of 100% substitution of FNS and its applicability to secondary concrete products of by-product aggregate NSC.

• 산업공학
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• 제3권1호
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• pp.21-29
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• 1990

This paper presents a linear programming formulation of the aggregate production planning problem for an optical instrument manufacturing company. Taking into account of the various requirements of the company, an L.P model is developed whose objective is to minimize the total cost of production during the planning horizon. The application results and its implications are well understood by the management and expected to be used as a guide line for future production planning.

• International Journal of Concrete Structures and Materials
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• 제10권1호
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• pp.61-73
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• 2016

In predicating the probability distribution of chloride diffusion coefficient of recycled aggregate concrete ($D_{RAC}$), the morphological characteristics of three phases, i.e., the old attached mortar, the natural aggregate and the new mortar, should all be taken into account. The present paper attempts to develop a probability density evolution method (PDEM) to achieve this. After verifying the derived PDEM results with experimental results, the effects of old attached mortar to the $D_{RAC}$ are examined in a quantitative manner. It is found that (1) the variation of the attached mortar content is much sensitive to $D_{RAC}$; (2) given the probability distribution of the content and chloride diffusion coefficient of old mortar, the probability distribution of DRAC can be analysed based on the PDEM; and (3) the critical chloride diffusion coefficient at a certain assurance rate can be obtained by the PDEM. The analysis results of this investigation will be valuable to the durability design for RAC.

• Computers and Concrete
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• 제12권5호
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• pp.627-650
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• 2013

This paper deals with application of a non-linear continuum model for reinforced concrete affected by alkali-aggregate reaction (AAR) to analysis of some nuclear structures. The macroscopic behaviour of the material affected by AAR is described by incorporating a homogenization/averaging procedure. The formulation addresses the main stages of the deformation process, i.e., a homogeneous deformation mode as well as that involving localized deformation, associated with formation of macrocracks. The formulation is applied to examine the mechanical behaviour of some reinforced concrete structures in nuclear power facilities located in Quebec (Canada). First, a containment structure is analyzed subjected to 45 years of continuing AAR. Later, an inelastic analysis is carried out for the spent fuel pool taking into account the interaction with the adjacent jointed rock mass foundation. In the latter case, the structure is said to be subjected to continuing AAR that is followed by a seismic event.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.565-570
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• 2001

Annually, Taiwan generates approximately 2 million tons of inorganic wastes in the form of sludge, fly ash and slug. To increase the added value of waste and maintain the increasingly insufficient supply of natural gravel, large public construction projects account for this large demand each year. future architectural trends are leading towards high-rise buildings. In light of the above, Center for Environmental, Safety and Health Technology Development, Industrial Technology Research Institute has developed the technology of manufacturing cold-bonding, sintering and bloating types of lightweight aggregates with a specific gravity ranging between 0.7~1.7, water absorption rate < 30%. The lightweight aggregate verified by physical property tests can be used as a substitute for the natural aggregate, which generally appears in replacing gravel in concrete, soundproofing and heat insulation materials. Doing so would not only moderate waste disposal problems, but also achieve the goal of resource recovery.

• 한국산학기술학회논문지
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• 제21권1호
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• pp.417-425
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• 2020

본 논문에서는 손해보험회사의 특별계정 의존도가 기업가치와 어떠한 관련성을 가지는지에 대하여 연구하였다. 심태섭 외(2015)에서도 언급하고 있듯이 보험회사의 특별계정은 일반계정과 다른 속성을 가진 계약으로 구성되어 있으므로, 보험회사의 특별계정 의존도에 따라 기업가치가 달라질 가능성이 있다. 이에 본 논문에서는 2011년도부터 2018년도까지 국내 상장 손해보험회사의 분기별 재무제표 자료와 주가자료를 이용하여 특별계정 의존도가 기업가치에 대해 갖는 관계를 분석하였다. 분석결과, 손해보험회사의 특별계정 의존도를 나타내는 변수는 손해보험회사의 기업가치에 대하여 유의적인 음(-)의 관련성을 가지는 것으로 나타났다. 이러한 연구결과는 손해보험회사의 특별계정 의존도가 높고 낮음에 따라 총괄계정 순자산과 순이익이 동일한 상황에서 해당 손해보험회사의 기업가치는 달라질 수 있음을 시사한다고 할 수 있다. 본 연구는 기업가치 극대화 관점에서 특별계정의 운용에 대한 경영적 시사점을 제공함과 아울러 특별계정의 운용성과를 보다 직접적으로 확인할 수 있는 공시제도가 필요할 것임을 시사한다.

• 자원환경지질
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• 제54권5호
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• pp.495-503
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• 2021

골재는 주택 및 도로·항만 등과 같은 SOC건설에 사용되는 주요한 천연자원이며 국가건설의 기본이 되는 기초자재이다. 골재가 공사원가에서 차지하는 비중은 약 4%에 불과하나, 골재는 건설공사 용적의 약 80%를 점유함으로서 건설공사의 양과 질을 좌우하는 필수요소이다. 하천, 수중, 하상, 바다, 육상 골재는 생산시 환경 문제와 제한된 부존량으로 인해 골재수급에 어려움이 발생할 경우 골재의 생산량을 급격하게 증가시키기 어려운 반면에 산림골재는 증산이 비교적 용이하다. 산림골재는 부존량이 풍부해 향후 다른 골재 감축시 대체 골재자원으로 유망하게 평가받고 있으며, 잘 짜여진 계획과 정책에 따라 골재수요에 유연하게 대응할 수 있는 효과적인 골재재원이다. 본 연구에서는 산림골재 개발에 큰 영향을 미치는 운반거리를 중심으로, 운반거리가 긴 경우와 짧은 경우에 대해서 산림골재 활성화 방안과 더불어 현재 산림골재 개발의 난제에 대한 대책을 제시하였다.

• 한국농공학회지
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• 제13권3호
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• pp.2342-2348
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• 1971

In concrete, the mater over aggregate is ever demanding each year in paralled with rapid development of Construction works from a couple of years ago. Want of most of them which is river gravel among aggregate has made us uneasy to get good gravel in quality. So far, we have counted on gravel, however, the time to turn the use of normal concrete into that of crushed concrete is closing at hand, I think. According to the results of study by Kaplan, Zeitman, Murdock, Hanada, Yamamodo, the shape of aggregate particle have a great effect on workability of concrete, as we know, is well known to the world. Crushed stone, particularly, is inconvenient to handle on account of jagged, angled particle form and rugged surface structure, give rise to inpediments in works, its unit water stands at about $15-20kg/m^3$, and w/c shows the increasing rate of approximately 5-10%, but it is unsuitable to use in terms of regidity. In order to research all of these, I have experimentalized and reviewed the physical character of aggregate and the regidity of concrete, in addition, its relative ratio of the elastic disposition as to gravel and crushed stone.