• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.39-45
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• 2006

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences overall operating condition of blast furnace such as gas flow, chemical reactions and temperature. because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process. In this model, cohesive zone is changed by solid temperature range, FVM is used for numerical simulation. To find location of cohesive zone whole calculation procedure is iterated Until cohesive zone is converged. Through this approach, shape of cohesive zone, velocity, composition and temperature within the furnace are predicted by model.

• 대한기계학회논문집A
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• 제38권4호
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• pp.401-407
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• 2014

본 논문에서는 3점 굽힘과 이중 외팔보 문제에 대하여 응집 요소를 사용한 유한요소 균열 진전해석을 수행하고 응집 법칙의 영향을 알아보았다. 응집 요소는 ABAQUS/Standard의 사용자 서브루틴(UEL)으로 구현하였으며 응집 법칙은 다항식 형태의 응집 트랙션-열림 변위의 관계식을 사용하였고 응집 법칙의 형상에 대한 영향을 알아 보기 위하여 다항식의 계수를 변화시켰다. 동일한 파손 에너지와 응집 강도를 갖지만 다른 형상의 응집 법칙에 대한 해석을 수행하고 변위-반력 곡선을 비교하여 균열 진전 거동의 변화를 알아보았다. 또한 요소 크기에 따른 균열 진전 해석 결과의 영향을 논의하였다.

• 생태와환경
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• 제44권1호
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• pp.66-74
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• 2011

This numerical study aims to investigate the effect of cohesive sediment on turbulence structure due to density stratification. The transport model for cohesive sediment incorporated with flocculation model has been selected and calculates the concentration, fluid momentum, and turbulence. From the model results, it is known that suspension of sediment decreases turbulence intensity. It is also found that cohesive sediment has a relatively weak effect on turbulence damping compared to noncohesive sediment. The low settling velocity and more suspension of cohesive sediment are considered to be mechanisms of this behavior. Richardson number determined with results of this study quantitatively shows that cohesive sediment causes less stable density stratification condition and, as a result, the turbulence structure is less damped compared to the case of noncohesive sediment.

• Advances in aircraft and spacecraft science
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• 제1권2호
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• pp.177-196
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• 2014

A theoretical exploration for determining the characteristic length of the cohesive zone for a double cantilever beam (DCB) specimen under mode I loading was conducted. Two traction-separation laws were studied: (i) a law with only a linear elastic stage from zero to full traction strength; and (ii) a bilinear traction law illustrating a progressive softening stage. Two analytical solutions were derived for the first law, which fit well into two existing solution groups. A transcendental equation was derived for the bilinear traction law, and a graphical method was presented to identify the resultant cohesive zone length. The study using the bilinear traction law enabled the theoretical investigation of the individual effects of cohesive law parameters (i.e., strength, stiffness, and fracture energy) on the cohesive zone length. Correlations between the theoretical and finite element (FE) results were assessed. Effects of traction law parameters on the cohesive zone length were discussed.

• 지질공학
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• 제19권3호
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• pp.409-415
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• 2009

일반적으로 흙의 투수계수를 예측하기 위하여 Kozeny-Carman 공식이 널리 적용되어왔다. 그러나 Kozeny-Carman 공식은 모래질 흙의 투수계수 예측에는 좋은 결과를 나타내나 점성토와 같은 세립토에는 적합하지 않다. 따라서 본 논문에서는 Kozeny-Carman 공식을 고려하여 점성토의 투수계수를 예측할 수 있는 이론식을 제시하였다. 이론식을 위해 해안가의 점성토와 댐의 심벽재로 사용하는 다짐 점성토의 토질특성에 대해 조사 분석하였다. 연구 결과, 토질특성과 투수계수 사이의 주요 관계 요소로, 해안가 점성토는 점토함유율, 다짐 점성토는 #200통과율과 관계가 있는 것으로 나타났다.

• 한국항공우주학회지
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• 제42권11호
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• pp.911-918
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• 2014

본 논문에서는 응집영역 모델링 방법에 의한 균열전파 해석에서 발생하는 연성추가문제의 효과적인 해결방법으로 사용자 부프로그램 UMPC를 이용한 응집요소의 선택적 활성화 기법을 연구 하였다. 먼저 균열의 발생 및 전파가 예상되는 지역의 일반요소들 사이에 응집요소를 삽입하고 응집요소를 구성하는 절점에 다중점 구속조건을 적용함으로써 응집 요소를 비활성화 시킨 상태로 해석을 시작한 후, 해석 도중에 특정 조건을 만족하는 절점들에 대해서만 다중점 구속조건을 해제하여 응집요소를 선택적으로 활성화하는 전략을 사용하였다. 응집요소의 초기강성 및 다중점 구속조건 해제 지표가 균열전파 거동 및 계산시간에 미치는 영향을 체계적으로 조사하였다.

• 한국연소학회지
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• 제14권4호
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• pp.1-6
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• 2009

Analysis of the internal state of the blast furnace is necessary to predict and to control the operating conditions. Especially, it is important to develop models of the blast furnace to predict the cohesive zone because shape of the cohesive zone influences overall operating conditions of blast furnace such as gas flow, chemical reactions and temperature. Because many previous blast furnace models have assumed cohesive zone to be fixed, it was not possible to evaluate the shape change of cohesive zone in relation with operating conditions such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace processes. In this model, cohesive zone is determined by the solid temperature. Finite volume method is employed for numerical simulation. To find location of the cohesive zone, entire calculation procedure is iterated until converged. Through this approach, shape of the cohesive zone, velocity and temperature within the furnace are predicted from the model.

• 한국수자원학회논문집
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• 제54권12호
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• pp.1275-1284
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• 2021

본 논문에서는 기계학습을 이용하여 비점성토 및 점성토 지반에서 시간에 따른 교각주위 국부세굴을 예측하였다. 기계학습 기법으로는 과적합 오차를 유발하지 않는다고 알려진 Support Vector Machines (SVM) 기법이 사용되었다. 비점성토 지반 및 점성토 지반에서 시간에 따라 발달하는 세굴심을 7개 및 9개의 변수를 각각 이용하여 표현하였다. 여러 실험을 통해 얻어진 시계열 자료를 이용하여 개발된 모형을 학습시키고 검증하였다. 계산된 평균절대비오차(MAPE)에 의하면 모형의 학습과 검증이 적절하게 수행된 것으로 나타났다. 실험 결과뿐 아니라 Choi and Cho 공식과 Briaud et al.이 제시한 SRICOS 방법에 의한 결과와 비교하였다. 본 연구를 통해 양질의 자료가 충분히 제공되는 경우 SVM 모형이 비점성토 및 점성토 지반 시간의존 국부세굴을 예측할 수 있음을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2038-2043
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• 2007

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences on overall operating condition of blast furnace such as gas flow, temperature distribution and chemical reactions. Because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process using the general purpose-simulation code. And Porous media is assumed for the gas flow and the potential flow for the solid flow. Velocity, pressure and temperature distribution for gas and solid are displayed as the simulation results. The cohesive zones are figured in 3 different operating conditions.

• 한국농공학회논문집
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• 제52권3호
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• pp.89-95
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• 2010

There is the freezing method as one of the ground improvement methods for excavating an underground tunnel, and due to its improved reliability, recently construction cases of applying this method into sandy soil grounds as well as cohesive soil grounds of cities have been reported. But, applying the freezing method into cohesive soil grounds could bring concerns of the expansion of the whole ground and the settlements from thawing of ground. In this study, the deformation strength characteristics of cohesive soil which received freezing and thawing hysteresis were examined using the sample collected from the site of cohesive soil ground applied with the freezing method and its structural characteristics were analyzed using an electronic microscope. And, the test with cohesive soil reconstituted from cohesive soil which received freezing and thawing hysteresis was carried out and its result was analyzed comparatively. The result of this test showed that the structure of natural clay was significantly changed due to freezing and thawing hysteresis.