• 전자공학회논문지 IE
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• v.49 no.2
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• pp.40-45
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• 2012

In this paper, cooling system of power transformers is proposed for temperature optimized control. We predict the peak temperature of power transformer coils using load factors and construct a cooling system using weighting function. For the optimized temperature control for power transformer, a correlation function based on the load factor of a load current and the each temperatures for winding coils, for air and for oil is presented to predict the winding-coil peak temperature. Also, the results controlled by applying the power transformer is presented.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.296-301
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• 1996

이 연구의 목적은 원주방향 균열을 가진 페라이틱 배관의 파괴거동을 실험적으로 평가하는데 있다. 한계하중방법, SC.TNP 방법, R6방법, 그리고 ASME Code방법과 같은 여러 파괴거동 평가 방법의 타당성이 PWR 운전조건(압력:15.5MPa, 온도:228$^{\circ}C$)하에서의 직경 16인치의 대규모 배관파괴실험을 통해 조사된다. 모사지진하중, 단일주파수 사인함수하중, 정하중과 같은 여러 가지 형태의 하중이 배관의 하중지지능력에 미치는 영향이 조사된다. 또한 엘보우부위와 직관부의 영향과 표면균열 및 관통균일의 영향 등도 함께 조사된다. 결과는 다음과 같다. (1) 표면균열을 가진 배관의 파괴거동은 한계하중방법과 SC.TNP 방법에 의해 잘 예측할 수 있다. 반면 관통균열의 경우는 한계하중방법에 의해 잘 예측된다. (2) 모사지진하중하에서는 단일주파수 사인함수하중이나 정하중 하에서 보다 하중지지능력이 크게 예측된다. (3) 엘보우부위와 직관부, 관통균열과 표면균열 사이에 파괴거동에 대한 큰 차이는 없다.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.159-164
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• 2017

This paper presents the results of an investigation into the thermo-hydromechanical response of weathered granite soil. The effect of forced change temperature and relative humidity at the soil layer boundaries were monitored during heating. A series of load settlement test were performed on layers of compacted, unsatureated weathered granite soil with geosynthetic embedded at mid height before and after application of heat exchanger to the base of the soil layers. The results from this study indicated the potential for using embedded heat exchangers for the mechanical improvement of geotechnical systems incorporating weathered granite soil.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.335-342
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• 2000

The microhardness of rhenium sheets was determined as a function of indentation load and temperature. The temperature dependence of the microhardness between room temperatures and $1000 ^{\circ}C$was studied using a hot microhardness tester equipped with a Vickers indenter. The load dependence of the microhardness was investigated using oth a Vickers and a Knoop indenter. The indentation size effect (ISE) was well explained using the normalized Meyers law. The hardness of the annealed rhenium sheet approached that of the as-rolled sheets at large indentation loads because of work-hardening under the indenter during indentation. The hardness at zero load(obtained from extrapolation of the load dependence of the hardness) suggested that the hardness is controlled by two different mech-anisms having different thermal activation. At low temperature the activation energy for the mechanism controlling the hardness was approximately 0.02 eV , Whereas at higher temperatures that was approximately 0.15eV. The tranisi-tion temperature between the two different controlling mechanisms was about $250^{\circ}C$.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.297-306
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• 1999

In this research, the frost heave mechanism of the weathered tuff soil sampled from the area tying between Ulanbator and Beijing was studied. The frost heave tests were carried maintaining the constant temperature at both upper$(+5^{\circ}C)\; and\; lower(-5^{\circ}C)$ ends of the sample. Here, main emphasis is given on variation of the freezing point depression with the variation of applied overburden pressure. The expansion of ice lens and migration of the pore water towards freezing front were observed in the test. It was found that with the increase in overburden pressure there is decrease in heave rate and increase in the absolute value of a segregation-freezing temperature. Hence the equation between segregation-freezing temperature and overburden pressure could be suggested. Also the water content of the samples at the frozen side was shown to be higher than those at the unfrozen side. Similarly, the water at warmer part of the frozen tuff was found much higher than that of the cooler part.

• Environmental Analysis Health and Toxicology
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• v.21 no.3 s.54
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• pp.219-228
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• 2006

폴리우레탄, 폴리에스테르, 바이페놀, PVC 외 각종 농약 등을 생산하는 울산의 모 화학공장에서, 다양한 종류의 휘발성유기화합물질들(VOCs)이 배출되고 있다. 평균적인 휘발성유기화합물질의 배출 농도는 7283 ppm으로, 톨루엔, 페놀을 포함하여 Trimethyl-pentene, trimethyl-hexene, dimethyl-cyclohexane 등이 검출되었다. Trimethyl-pentene, trimethyl-hexene, dimethyl-cyclohexane등은 인화성이 강하며 화재를 일으킬 위험성이 매우 큰 것으로 알려져 있고, 특히 톨루엔과 페놀의 경우는 호흡이나 피부접촉 등을 통한 인체로의 유입이 있을 경우 유독성을 나타내게 된다. 이러한 VOCs제거를 위하여 겨울철 기간에 파이로트-규모의 바이오필터 적용 실험이 진행되어 졌다. 본 연구의 목적은 바이오필터 운영이 진행되는 가운데 온도, 함수비, 하중, 압력손실 등의 제한요소들이 미디어 내부에서 변화하는 상황에 대한 관찰 및 평가에 있다. 이러한 제한요소들은 바이오필터의 디자인과 오염물질 제거에 심대한 영향을 미치게 된다. 바이오필터는 옥외에 설치되어 총 44일간 운영되어 졌는데, 외부 영하온도의 영향을 최소화하기 위하여, 7cm두께의 파이버-글래스 소재 단열설비가 반응기 외부에 설치되었고 또한 $150^{\circ}C$의 스팀이 바이오필터 반응기와 단열설비 사이에 제공되어 졌다. 바이오필터 반응기 내부에는 23개의 온도 측정 센서와 함수비 센서, 공기샘플포트, 습도계 등이 각기 다른 장소에 설치되어 온도, 함수비 등의 제한요소 영향연구가 진행되었다. 미디어 내부 같은 높이의 서로 반대되는 위치에서 온도차가 13.7도에서 -8.3도까지 차이가 나는 것으로 관찰되었으며, 미디어 높이 위치의 변화에 따라서도 21도에서 2도가지 차이를 나타냈다. 바이오필터 함수비는 실험기간 동안 지속적으로 변화가 발생하였는데, 스팀이 제공되는 동안에는 미디어 함수비가 훨씬 빠른 속도로 증가됨이 관찰되어 졌다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.55-65
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• 1998

In industrial fields, RTP(rapid thermal processing) system is widely used for improving the oxidation and the annealing in semiconductor manufacturing process. The main control factors are temperature control of wafer and uniformity in the wafer. In this paper, we propose an $H^{\infty}$ controller design of RTP system satisfying robust stability and performance using weighted mixed sensitivity miniimization and loop shaping technique. And we need reduction technique because of the difficulty of implementation with the obtained high order controller for original model and reduced models, namely, Hankel, square-root balanced, and Schur balanced methods. An example is proposed to show the validity of the proposed method.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.19-29
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• 2013

Analysis via classical soil mechanics theory is either ineffective or inappropriate for fully describing stress distribution or failure conditions in cold regions, since mechanical properties of soils in cold regions are different from those reported in the classical soil mechanics theory. Therefore, collecting and analyzing technical data, and systematic and specialized research for cold regions are required for design and construction of the structure in cold regions. Freezing and thawing repeat in active layer of permafrost region, and a loading condition affecting the structure changes. Therefore, the reliable analysis of mechanical properties of frozen soils according to various conditions is prerequisite for design and construction of the structure in cold regions, since mechanical properties of frozen soils are sensitive to temperature condition, water content, grain size, relative density, and loading rate. In this research, the direct shear apparatus which operates at 30 degrees below zero and large-scaled low temperature chamber are used for evaluating shear strength characteristics of frozen soils. Weathered granite soil is used to analyzed the shear strength characteristics with varying freezing temperature condition, vertical confining pressure, relative density, and water content. This research shows that the shear strength of weathered granite soil is sensitively affected by various conditions such as freezing temperature conditions, normal stresses, relative densities, and water contents.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.30-33
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• 2009

본 논문에서는 형상기억합금의 특징적인 거동을 모사하기위한 구성방정식을 제안한다. 제안되는 구성방정식은 기존의 소성모델을 기초로 하는 현상학적인 모델로, 소성 경화이론에서 사용되는 항복곡면에 대응되는 상변이 곡면을 정의하여 형상기억합금의 비선형 거동을 모사한다. 단, 상변이 곡면이 1개만 존재하는 소성모델과는 다르게, 오스테나이트에서 마르텐사이트로의 정방향 상변이와 마르텐사이트에서 오스테나이트로의 역방향 상변이를 각각 해석하기위해 독립적인 2개의 상변이 곡면을 정의해주게 된다. 기계적 하중만이 아닌 열적 하중의 변화에도 비선형 거동을 보이는 형상기억합금의 특성을 반영하기위해 상변이 곡면은 응력과 온도의 함수로 정의되며, 이렇게 정의된 상변이 곡면을 바탕으로 리턴 매핑 알고리즘을 적용하여 열적하중과 기계적하중의 변화에 따른 형상기억합금의 거동을 모사하는 구성방정식을 제안하였다.

• Korean Journal of Materials Research
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• v.10 no.4
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• pp.305-311
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• 2000

Applicability of crack arrest load measured from the Charpy V-notch impact test has been investigated to predict the fracture toughness of nuclear reactor pressure vessel (RPV) steels (ASME SA508 Cl.3). The temperature dependence of the crack arrest load was well described by the type of exponential function characterized by an index temperature at which the crack arrest load is 2kN. The specific index temperature, which also well correlated with $T_{NDT}\;and\;T_{41J}$ is expected to be representative index temperature characterizing the crack arrest fracture toughness of RPV steels. Also, the crack arrest load correlated well with the stable crack length measured from the fracture surface. From the measurements of the crack arrest load and the stable crack length, the lower bound fracture toughness, $K_{Ia}$ of RPV steels could be predicted with sufficient accuracy.