• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.3
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• pp.22-34
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• 2004

An artificial disturbance like fragmentation in watershed forest has impacted a sustainability of watershed ecosystem, therefore this research quantified the landscape structure in the Geumho river watershed using landscape indices and GIS. Landscape indices were calculated from the forest distributed maps for 24 subwatersheds. Three common factors, which explained about 85% of the variation in the original data, were extracted by a factor analysis. The fragmentation gradient in forest landscape, which was calculated from the factor scores, was correlated with proportion of urban land (r=0.827, p<0.01, $R^2$=0.685), elevation (r=-0.637, p<0.01) and slope gradient (r=-0.593, p<0.01). The result of the study presented that the methodology and the values of landscape indices to assess the structural patterns of forest landscape for the Geumho river watershed management. Future research will be directed towards the detection of impacts of landscape patterns and their changes on the integrity of watershed environments.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1169-1175
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• 2011

The soil chemical properties, microbial community structures and biochemical properties of lettuce or cucumber-cultivated greenhouse soil samples were analyzed to assess soil health and characterize microbial distribution in 8 locations in Korea. Although most of chemical properties were within the soil management guidelines, the available phosphate, and the contents of exchangeable potassium and calcium were higher than those of recommended levels. In the culture-dependent analysis, 841 bacterial strains were isolated from the greenhouse soils and were identified at the genus level by 16S rRNA gene sequences analysis. The dominant bacterial genera were Bacillus (35.7%), Microbacterium (9.3%), Arthrobacter (5.7%) and Lysobacter (5.1%). The abundance of pseudomonads was highly variable depending on the soil samples. In the culture-independent analysis, soil microbial community was investigated by using phospholipid fatty acid (PLFA) method. Principal component analysis (PCA) showed that a specific grouping for microbial community structure in the greenhouse soils was not observed based on cultivated crops and investigated sites. The results revealed that the greenhouses soils examined are relatively sound managed in terms of soil chemical contents and microbial properties.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1358-1363
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• 2003

Due to the application of Integrated Head Assembly (IHA) in KSNP+ reactor design, an investigation of reactor internals integrity is carried out to assure that the adoption of IHA does not affect the safety of reactor operation. One of the postulated accident events is the R.V. closure head fall from 5.5m high directly above the reactor vessel that may occur during the refueling operation. The analysis model consists of lumped mass elements of the entire reactor vessel and internals. Because of extreme load, separate elastic-plastic analyses are done for the members that undergo plastic deformation. The analysis verified that the stresses of the reactor internals and the fuel assemblies are within the bound of allowable stress limits and the integrity of the fuel assemblies is maintained.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.79-85
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• 2016

A concrete silo plays an important role in subsurface low- and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.466-473
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• 2017

RC (Reinforced Concrete) member has varying service life due to varying diffusion characteristics with loading conditions even if it is exposed to constant exterior conditions. In the paper, quantitative parameters are obtained through adopting the previous results for effects of compressive, tensile, and cold joint on chloride diffusion in OPC (Ordinary Portland Cement) and GGBFS (Ground Granulated Blast Furnace Slag) concrete. Service life is evaluated in RC simple beam with 10.0m of span through increasing loading from self weight (2.5kN/m) to the loading to cracking moment (5.5kN/m). In OPC concrete without cold joint, service life changes to 89.4% for tensile region and 101% for compressive region with loadings while GGBFS concrete has 80.0% and 106%, respectively. For cold joint area, GGBFS concrete shows much reduced service life to 82~80% in compressive region and 69~61% in tensile region, which is caused by the lower diffusion in normal condition but relatively higher increasing cold joint effect than OPC concrete.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1137-1143
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• 2011

The IHX (intermediate heat exchanger) of a VHTR (very high-temperature reactor) is a core component that transfers the high heat generated by the VHTR at $950^{\circ}C$ to a hydrogen production plant. Korea Atomic Energy Research Institute manufactured a small-scale prototype of a PCHE (printed circuit heat exchanger) that was being considered as a candidate for the IHX. In this study, as a part of high-temperature structural integrity evaluation of the small-scale PCHE prototype, we carried out high-temperature structural analysis modeling and macroscopic thermal and elastic structural analysis for the small-scale PCHE prototype under small-scale gas-loop test conditions. The modeling and analysis were performed as a precedent study prior to the performance test in the small-scale gas loop. The results obtained in this study will be compared with the test results for the small-scale PCHE. Moreover, these results will be used in the design of a medium-scale PCHE prototype.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.191-200
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• 2011

A PHE (Process Heat Exchanger) is a key component of nuclear hydrogen system for massive production of hydrogen; the PHE transfers the very high temperature heat ($950^{\circ}C$) generated from the VHTR (Very High Temperature Reactor) to a chemical reaction. The Korea Atomic Energy Research Institute developed a small-scale gas loop for testing the performance of VHTR components and manufactured a modified PHE prototype for carrying out the testing in the gas loop. In this study, as a part of the evaluation of the high-temperature structural integrity of the modified PHE prototype which is scheduled to test in the gas loop, we carried out high-temperature structural analysis modeling, macroscopic thermal and structural analysis of the PHE prototype under the gas loop test conditions as a precedent study before carrying out the performance test in the gas loop. The results obtained in this study will be used to design the performance test setup for the modified PHE prototype.

• KDI Journal of Economic Policy
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• v.18 no.1
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• pp.149-215
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• 1996

현행 민영화정책이 공기업의 효율성제고를 최우선 목표로 설정한 것은 타당한 선택이었음에도 불구하고, 경제력집중 심화에 대한 우려와 주식시장의 제약 등을 이유로 민영화정책은 그 추진실적이 부진하고 향후 지속 여부가 불투명한 것이 현실이다. 본(本) 논문(論文)은 우리나라 공기업민영화를 둘러싼 논쟁의 핵심인 경제력집중(經齊力集中), 경쟁도입(競爭導入), 주식시장여건(株式市場與件) 등이 공기업민영화와 관련하여 어떻게 이해되어야 할 것이며, 바람직한 정책대응(政策對應)은 무엇인지를 논의하고 있다. 재산권이론(財産權理論)을 동원하여 주인(主人) 있는 경영(經營)의 의미를 재해석할 때, 기업지배(企業支配) 통제구조(統制構造)의 정착이 요원한 우리 현실에서 민영화가 기업효율을 제고하려면 민간대주주(民間大株主)의 지배(支配)를 인정하는 방식이 최선책(最善策)이며, 소유가 분산되고 전문경영체제(專門經營體制)를 도입하는 민영화방식은 지배구조(支配構造)의 실패가능성(失敗可能性) 때문에 차선책(次善策)이라고 평가된다. 그러나 효율성 차원의 최선책은 경제력집중이라는 국민경제적 비용을 초래하므로, 정부로서는 경제력 집중이라는 비용(費用)과 효율성이라는 편익(便益)을 조화시키는 방안을 모색할 수밖에 없다. 이 경우 정부가 고려할 보완책(補完策)으로는 감자후(減資後) 민영화(民營化)와 분할민영화(分割民營化)가 있다. 한편 자연독점의 특성이 뚜렷한 일부 네트워크사업분야를 제외하면, 민영화시 경쟁도입(競爭導入)은 기업효율성과 국민경제의 배분효율성을 제고하므로 정부로서는 당연한 선택일 것이다. 경쟁은 공기업의 인수자격규제에 있어서도 새로운 기준을 제시하는데, 민영화를 정부(政府)와 민간(民間)사이의 M&A로 이해하고 경쟁제한적(競爭制限的) 기업결합(企業結合)을 규제하는 공정거래법(公正去來法)의 정신(精神)이 인수자격규제기준이 되어야 하며, 업종전문화(業種專門化) 발상(發想)에 근거한 인수자격규제는 득보(得)다 실(失)이 클 것이다. 아직도 자생적 성장기반이 취약한 주식시장의 제약에 따라 민영화일정의 탄력적인 조정은 불가피하지만, 정부는 상장(上場)의 필요성(必要性)을 재검토하고, 매각(賣却)의 우선순위(優先順位)를 조정하며, 무엇보다도 양질(良質)의 주식(柱式) 공급(供給)이 수요(需要)를 창출하는 메커니즘을 개발해야한다. 이와 함께 본(本) 논문(論文)은 현행 추진체계(推進體系)에 내재된 민영화의 지연가능성이 심각한 문제임을 지적하였고, 대규모 공기업의 민영화가 대기업(大企業)의 새로운 전형(典型)을 창출하여 한국자본주의(韓國資本主義)의 건전한 발전을 앞당기는 역사적 기회라는 점을 강조하고 있다. 마지막으로 재벌인수가 가능한 경우와 규제되어야 할 각각의 경우에 대하여 민영화정책(民營化政策)의 '체크리스트'를 제시하고 있다.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.93-97
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• 2009

An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that the wave patterns are relatively clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaws. However, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Mode converted signals from a realistic piping mockup were acquired and analysed. We found mode conversions between a torsional guided wave T(0,1) mode and a flexural F(1,3) or longitudinal L(0,2) mode generated by a magnetostrictive strip transducer. Based on the experimental observations, an interpretation of the source of the mode conversion is discussed in a viewpoint of electromagnetic properties and structure of the strip transducer.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.3
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• pp.217-224
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• 2008

In deep geological disposal system, the integrity of a disposal canister having spent fuels is very important factor to assure the safety of the repository system. This disposal canister is one element of the engineered barriers to isolate and to delay the radioactivity release from human beings and the environment for a long time so that the toxicity does not affect the environment. The main requirement in designing the deep geological disposal system is to keep the buffer temperature below 100$^{\circ}C$ by the decay heat from the spent fuels in the canister in order to maintain the integrity of the buffer material. Also, the disposal canister can endure the hydraulic pressure in the depth of 500 m and the swelling pressure of the bentonite as a buffer. In this study, new concept of the disposal canister for the CANDU spent fuels which were considered to be disposed without any treatment was developed and the thermal stability and the structural integrity of the canister were analysed. The result of the thermal analysis showed that the temperature of the buffer was 88.9$^{\circ}C$ when 37 years have passed after emplacement of the canister and the spacings of the disposal tunnel and the deposition holes were 40 m and 3 m, respectively. In the case of structural analysis, the result showed that the safety factors of the normal and the extreme environment were 2.9 and 1.33, respectively. So, these results reveal that the canister meets the thermal and the structural requirements in the deep geological disposal system.