• 한국지하수토양환경학회지:지하수토양환경
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• 제22권2호
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• pp.10-16
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• 2017

Recently, the gap between demand and supply of natural aggregate has increased owing to the depletion of aggregate sources. Therefore, policy support is necessary for the stable supply of aggregate resources. Public and construction works experience problems when they do not receive a steady supply of aggregate. Further, instabilities in aggregate supply lead to increases in aggregate prices, and consequently construction costs. As a result, the likelihood of poor construction using low-grade aggregate increases. It is therefore crucial to put measures in place that deal with these issues. This study aims to reduce the load imposed by aggregate use on the environment by recycling soil dredged from sewage ducts to reduce the gap between supply and demand of fine aggregate. The dredged soil is assessed using an applicability test for quality characteristics and solidification with basic properties. This study aims to secure the safety of dredging soil and solidified objects through interior physical and chemical analyses and to utilize it as a base material for concrete solidification in the future.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.65-68
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• 2009

Recycled aggregate by the recycling construction waste has a lot of advantage such as the developing the alternative resource and protecting of environment. However, recycled aggregate is used as the low quality grade, because the technic to remove old mortar from aggregate is low level. To use the recycled aggregate as high quality grade, it is important to develop the technic to produce the high quality recycled aggregate. To manufacture the high quality recycled aggregate, old mortar attached on the aggregates should remove efficiently. Therefore, in this study, we suggested the optimum condition to remove old mortar effectively using sulfuric acid and low speed wet rotary mill for high quality recycled fine aggregate. The results shows that the recycled aggregate satisfy on the standards of KS F 2573 in density, absorption and solid volume when, adequate condition of sulfuric mole ratio and aggregate ratio are make.

• 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.

• 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.

• 한국건축시공학회지
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• 제7권2호통권24호
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• pp.85-92
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• 2007

In the past, recycled aggregate was used very limitedly in low value-added areas such as the base layer of roads. However, in response to the shortage of natural aggregate, high consciousness of resource saving and changed idea on environment, the quality of recycled aggregate has been improved considerably, and the percentage of recycled construction waste is increasing every year compared to simple landfill or incineration. Recently the Act on the Promotion of Construction Waste Recycling was enacted on December 2003 for the efficient use of recycled aggregate, and the Standards for the Quality of Recycled Aggregate for Concrete (Proposal) were announced in order to use and manage recycled aggregate according to quality. According to the Standards for the Quality of Recycled Aggregate for Concrete (Proposal), it is recommended to substitute recycled coarse aggregate and fine aggregate below 30% each. However, compared to the trend of recycling, the recycling rate of aggregate is still quite low. It is because of low performance of recycled aggregate, users' lack of understanding, etc. These problems basically come from the decrease of strength of recycled concrete resulting from the use of recycled aggregate, and recycled aggregate is still considered not reliable because there have been not many cases of actual application. If the basic problem of strength decrease is solved and data on recycled aggregate is provided through actual field placing, we may maximize the use of recycled aggregate. Thus, in order to maximize the use of recycled aggregate that satisfy the recycled aggregate quality standards, the present study made a mock-up similar to real structures, evaluated its performance and examined the field applicability of recycled aggregate concrete.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.519-533
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• 2005

The numerical simulations on the influence of mesoscopic structures on the macroscopic strength and fracture characteristics are carried out based on that the concrete is assumed to be a three-phase composite composed of matrix (mortar), aggregate and bond between them by using a numerical code named MFPA. The finite element program is employed as the basic stress analysis tool when the elastic damage mechanics is used to describe the constitutive law of meso-level element and the maximum tensile strain criterion and Mohr-Coulomb criterion are utilized as damage threshold. It can be found from the numerical results that the bond between matrix and aggregate has a significant effect on the macroscopic mechanical performance of concrete.

• 한국정보과학회논문지:데이타베이스
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• 제33권6호
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• pp.563-577
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• 2006

스트림 처리기는 다수의 연속질의에서 제한된 자원을 효율적으로 이용하기 위하여 자원공유 기법을 이용한다. 기존의 기법은 계층구조를 유지하여 집계질의를 처리한다. 그래서 삽입연산은 계층구조 재구성 비용이 필요하다. 또한 검색연산은 서로 다른 슬라이딩 윈도우 크기에 속하는 집계정보 검색비용이 필요하다. 그래서 본 논문에서는 보다 빠른 질의 처리를 위해 선형 자료구조를 사용한다. 제안기법은 팬(Pane)크기 결정단계와 팬 생성단계, 팬 삭제단계로 구성된다. 팬 크기 결정단계는 정확한 집계정보를 유지하기 위한 최적 팬 크기를 결정하는 단계이며, 팬 생성단계는 스트림 버퍼로부터 팬 크기만큼의 데이타에 대한 집계정보를 저장하는 단계이다. 팬 삭제단계는 더 이상 연속질의가 사용하지 않는 팬을 삭제하는 단계이다. 제안 기법은 선형 자료 구조를 이용하므로 계층구조를 이용하는 자료 구조에 비해 자원을 적게 사용한다. 또한 스트림 데이타가 입력되어도 팬 크기에 해당하는 집계정보만 계산하면 되므로 집계정보 삽입비용이 감소하고, 서로 다른 슬라이딩 윈도우 크기에 대해서도 선형검색으로 집계정보 검색비용이 감소한다. 성능평가를 통하여 제안기법이 적은 메모리 사용 결과를 보였으며, 질의 처리 속도가 증가하였다.

• 정보처리학회논문지C
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• 제15C권1호
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• pp.37-44
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• 2008

이동 네트워크 환경에서 MN(Mobile Node)의 핸드오버 후 새로운 경로 상에 자원을 예약할 때 시그널링 지연을 최소화하기 위해서는 이전 경로와 새로운 경로가 만나는 지점에 있는 노드인 크로스오버 노드(Crossover Node:CRN)를 발견하는 것이 중요하다. 일반적으로 크로스오버 노드의 발견은 MN과 CN(Correspondent Node)간 설립된 종단간 SID(Session ID)를 주요키로 사용하여 이루어지지만, HMIPv6(Hierarchical Mobile IPv6) 네트워크에서 MAP(Mobility Anchor Point)과 HA(Home Agent)간 군집(Aggregate) 세션 단위로 자원예약을 하는 경우에는 이와 같은 일반적인 방법의 적용이 어렵다. 군집 예약을 할 때에는 종단간 SID와는 별도로 군집 SID를 사용하는데, MN의 핸드오버 후 이전 MAP과 HA간 설립된 세션의 군집 SID가 새로운 MAP과 HA간 설립된 세션의 군집 SID와 달라서 SID를 이용하여 크로스오버 노드를 발견할 수 없기 때문이다. 이에, 본 논문에서는 HMIPv6 네트워크에서 차세대 네트워크 시그널링 프로토콜인 NSIS(Next Step in Signaling)를 이용하여 자원을 예약하는 경우 군집 예약이 이루어진 MAP과 HA간 터널상에서 크로스오버 노드를 발견하고, 크로스오버 노드를 발견한 즉시, 군집 예약된 자원의 갱신이 지역적으로 이루어지도록 하는 방안을 제안한다. 시뮬레이션을 통해, 시그널링 메시지가 항상 터널의 끝 노드까지 전달되는 기존 방안에 비해 제안하는 방안이 자원 예약을 위한 시그널링 지연을 단축시키고, 핸드오버 동안의 평균 처리율을 향상시킴을 알 수 있었다.

• Advances in concrete construction
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• 제4권4호
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• pp.243-261
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• 2016

This research study focuses on utilizing sandstone which is overburden waste rock in coal mines to use in concrete as a replacement of fine aggregate. Physical properties of sandstone like water absorption, moisture content, fineness modulus etc., were found to be similar to conventional fine aggregate. Scanning Electron Microscope (SEM) analysis was carried out for analysing elemental composition of sandstone. There was no sulphur content in sandstone which is a good sign to carry the replacement. Fine aggregate was replaced with sandstone at 25%, 50%, 75% and 100% by volume and moulds of concrete cubes and cylinders were prepared. Compressive strength of concrete cubes was tested after 3, 7 and 28 days and split tensile & flexural strength was determined after 28 days. The strength was found to be increasing marginally with increase in sandstone content. Fine aggregate that was replaced by 100% sandstone gave highest strength among all the replacements for the compressive, split tensile and flexural strengths. Though increase in strength was marginal, still sandstone can be an effective replacement for sand in order to save the natural resource and utilize the waste sandstone.

• 한국건설순환자원학회지
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• 제4권3호
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• pp.15-23
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• 2009