• Steel and Composite Structures
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• 제10권2호
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• pp.129-149
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• 2010

The objective of this study is to formulate a general 3D material-structural analysis framework for the thermomechanical behavior of steel-concrete structures in a fire environment. The proposed analysis framework consists of three sequential modeling parts: fire dynamics simulation, heat transfer analysis, and a thermomechanical stress analysis of the structure. The first modeling part consists of applying the NIST (National Institute of Standards and Technology) Fire Dynamics Simulator (FDS) where coupled CFD (Computational Fluid Dynamics) with thermodynamics are combined to realistically model the fire progression within the steel-concrete structure. The goal is to generate the spatial-temporal (ST) solution variables (temperature, heat flux) on the surfaces of the structure. The FDS-ST solutions are generated in a discrete form. Continuous FDS-ST approximations are then developed to represent the temperature or heat-flux at any given time or point within the structure. An extensive numerical study is carried out to examine the best ST approximation functions that strike a balance between accuracy and simplicity. The second modeling part consists of a finite-element (FE) transient heat analysis of the structure using the continuous FDS-ST surface variables as prescribed thermal boundary conditions. The third modeling part is a thermomechanical FE structural analysis using both nonlinear material and geometry. The temperature history from the second modeling part is used at all nodal points. The ABAQUS (2003) FE code is used with external user subroutines for the second and third simulation parts in order to describe the specific heat temperature nonlinear dependency that drastically affects the transient thermal solution especially for concrete materials. User subroutines are also developed to apply the continuous FDS-ST surface nodal boundary conditions in the transient heat FE analysis. The proposed modeling framework is applied to predict the temperature and deflection of the well-documented third Cardington fire test.

• Childhood Kidney Diseases
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• 제11권2호
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• pp.247-254
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• 2007

목 적 : 세계적으로 급성 신부전을 가진 소아중환자의 경우 신대체요법으로서 CRRT가 우선적으로 적용되고 있는데 국내에서 CRRT에 대한 치료 결과나 이에 미치는 예후인자에 대한 연구가 드문 설정이다. 이에 저자들은 CRRT를 시행 받은 소아 환자군을 대상으로 치료결과와 예후인자를 알아보기 위해 본 연구를 시행하였다. 방 법 : 2003년 1월부터 2006년 12월까지 세브란스 어린이병원 소아과에서 CRRT를 시행 받은 소아 중환자 32명을 대상으로 하여 환자들이 입상적 특징과 생존율, 그리고 이에 미치는 예후인자를 생존군과 사망군으로 나누어 비교하였다. 결 과 : 총 32명의 평균 나이는 7.5세로 범위는 생후 4일에서 16살까지였고 평균 몸무게는 25.8kg로 최소 3.2kg 최고 63kg였다. 기저 질환 중 조혈모세포이식과 악성종양 환자군이 가장 많았고, 이 군에서 생존율이 가장 낮았다. 전체 생존자는 11명으로 생존율은 34.4%였고 예후인자에 대한 연구에서 CRRT 시작시 PRISM III 점수($9.8{\pm}5.3$ vs. $26.7{\pm}7.6$, P<0.0001), 승압제 사용 수 ($2.1{\pm}1.2$ vs. $3.0{\pm}1.0$, P=0.038)와 수분 저류 정도 (%FO, $5.2{\pm}6.0$ vs. $15.0{\pm}8.9$, P=0.002)가 사망군보다 생존군에서 의미 있게 낮았다. 또 다중 회귀분석을 통해 높은 수분 저류만이 독립적 위험인자임을 확인하였다. 결 론 : 저자는 이 연구를 통해 소아 급성 신부전 환자에서 생존율이 환자의 중증도와 체내 수분 저류와 연관성이 높다는 것을 확인하였고, 환자의 전신상태가 보다 좋을 때 특히 수분 저류가 시작되기 전에 CRRT를 빨리 시작하는 것이 생존율을 높일 수 있다는 결론을 얻을 수 있었다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.86-95
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 한국결정성장학회지
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• 제1권1호
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• pp.74-81
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• 1991

Czochralski 단결정 성장계에서 유체동의 표면 복사열전달을 고려하여 온도분포를 모사하였다. 복사열전달 고려시 표면요소들의 view factor를 고려하였다. 고-액의 2상은 고상에 가상적으로 매우 큰 점성을 부여하여 연속의 단상으로 처리하였으며 응고시 잠열은 반복열량 방출법을 개발하여 처리하였다. 본 연구에서 개발한 응고 모델을 증명하기 위하여 Ca 금속의 용융에 적용하여 실험결과와 비교한 결과 잘 맞는다는 것을 알아낸 후 본 모사 프로그램을 Cz계에서 Al금속의 단결정 성장에 적용하였다.

• 대한족부족관절학회지
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• 제21권3호
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• pp.113-116
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• 2017

Synovial fistula of the ankle joint is an uncommon complication from an ankle sprain. This may likely result in an unhealed wound around the ankle joint due to continuous leakage of joint fluid. However, in the event of an open wound on the lower leg, and not on the joint, it may be difficult to consider synovial fistula as a cause of the open wound. We experienced an interesting case with an unhealed open wound on the lower leg due to a synovial fistula of the ankle joint following an ankle sprain. We obtained good results after a treatment using a self-produced suction drainage device on the unhealed open wound.

• Environmental Engineering Research
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• 제23권1호
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• pp.76-83
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• 2018

Spatial moment analysis has been performed on the concentration of the first species in a multispecies solute transport in porous media. Finite difference numerical technique was used in obtaining the solute concentration. A constant continuous source of contaminant was injected at the inlet of the domain. Results suggest that the decaying of solute mass increases as the magnitude of mean fluid velocity increases. The dispersion coefficient is highly time dependent under decaying of solutes with a complex behavior of mixing of solutes. The solute mobility and mixing varies non-linearly with time during its initial period, while the same ceases with higher decay rates of the first species much faster.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.619-624
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• 2004

This paper applies the fuzzy logic controller to a semiactive seat suspension system in order to obtain the better ride comfort in constraint of specific rattle space. The seat suspension system used for this research is a scissors-type one with the MR (Magnetic Rheological) fluid damper. Since a seat suspension system with a driver can not be exactly modeled, it is effective to control with the fuzzy logic controller. The rule was carefully tuned to effectively reduce the vibration transmitted to a driver. The on-road ride was realized on a hydraulic excitor and the result shows that the fuzzy controller has reduced the vibration of a seat suspension system compared to the continuous skyhook controller.

• 대한소아치과학회지
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• 제21권2호
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• pp.587-592
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• 1994

The dentigerous cyst originates through alteration of the reduced enamel epithelium after amelogenesis is completed, with accumulation of fluid between the layers of the enamel epithelium or between this epithelium and the tooth crown. It is always associated with unerupted teeth. There are two methods of treament which are generally accepted. One is the enucleation of the cystic sac in its entirety, the other is the Partch operation, or the marsupialization, by which the cyst is uncovered or "deroofed" and the cystic lining made continuous with the oral avity or surrounding structures. The present case report showed that in instance of dentigerous cyst & odontogenic keratocyst surgical enucleation followed by careful excision of all cyst wall was successfully carried out and recovery and healing were rapid and uncomplicated.

• 한국전산유체공학회지
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• 제6권4호
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• pp.8-14
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• 2001

The phenomena of two-phase suspension flows appear widely in nature and industrial processes. Hence, it is of great importance to understand the mechanism of the gas-solid two-phase flows. In the present study, the numerical simulation has been approached by utilizing the Eulerian-Lagrangian methodology for describing the characteristics of the fluid and particulate phases in a vertical pipe and a 90°square-sectioned bend. The continuous phase(gas phase) is described by the Eulerian formulation and a κ-ε turbulence model is employed to find mean and turbulent properties of the gas phase. The particle properties(velocity and trajectory) are then described by a Lagrangian approach and computed using the mean velocity and turbulent fluctuating velocity of the gas phase. The predictions are compared with measurements by laser-Doppler velocimeter for the validation. As a result, the calculated results show good agreements.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.45-47
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• 2005

We have investigated the mixing behavior of a tubular heat exchanger reactor using CFD and compared its mixing performance with different type of reactors such as jet mixer and continuous stirred tank reactor (CSTR). The mixedness in each reactor was quantified introducing a statistical average value, the coefficient of variation (CoV), which is a normalized standard deviation of concentration of a component over the whole fluid domain. Through the analysis of the flow pattern and turbulent energy distribution, we suggested a simple but effective way to improve the mixing performance of the tubular heat-exchanger reactor, which include the addition of the internals and/or the increase of the recycle flow rate. It was found that the CoV value of the tubular reactor could be nearly equivalent to that of CSTR by applying those two alternatives suggested here.