• 한국유체기계학회 논문집
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• 제18권3호
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• pp.38-45
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• 2015

In this study, two computational methodologies were compared to consider an effective conjugate heat transfer analysis technique for the cooled vane with thermal barrier coating. The first one is the physical modeling method of the TBC layer on the vane surface, which means solid volume of the TBC on the vane surface. The second one is the numerical modeling method of the TBC layer by putting the heat resistance interface condition on the surface between the fluid and solid domains, which means no physical layer on the vane surface. For those two methodologies, conjugate heat transfer analyses were conducted for the cooled vane with TBC layer having various thickness from 0.1 mm to 0.3 mm. Static pressure distributions for two cases show quite similar patterns in the overall region while the physical modeling shows quite a little difference around the throat area. Thermal analyses indicated that the metal temperature distributions are quite similar for both methods. The results show that the numerical modeling method can reduce the computational resources significantly and is quite suitable method to evaluate the overall performance of TBC even though it does not reflect the exact geometry and flow field characteristics on the vane surface.

• 한국환경복원기술학회지
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• 제20권1호
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• pp.13-24
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• 2017

This study is to provide basic data on ecology and morpho-pedo milieu by analyzing diatom and grain size of Mt. Jeombong forest wetland. Sample was collected from 6 points and named sample 943, 932, 885, 881A, 881b, 849. Sample 934 could not identify diatom, and the soil layer was colluvium deposited by mass-movement process. Layer of sample 932 was developed in the lower velocity environment, and presence frequence of complete diatom was very low. Hydrological situation of sample 855 was analysed in oligosaprobien environments. Sample 881A was meso-saprobic environments, velocity was slow area that inhabit musci bryopsida and sphaerocarpus. Sample 881B was acidic wetland in oligosaprobien environments. Sample 849 was analysed in oligosaprobien environments. The results of soil and diatom analysis are well reflect on wet environments of mountain wetlands and also it will expected to be in the help of environmental changes study of mountain wetlands.

• 한국전산유체공학회지
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• 제4권2호
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• pp.57-66
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• 1999

Numerical Analysis has been done for the supersonic off-design jet flow due to the pressure difference between the jet and the ambient fluid. The difference of pressure generates an oblique shock or an expansion wave at the nozzle exit. The waves reflect repeatedly on the center axis and the sonic surface in the shear layer. The pressure difference is resolved across these reflected waves. In this paper, the axi-symmetric Navier-Stokes equation has been used with the κ-ε turbulence model. The second order TVD scheme with flux limiters, based on the flux vector split with the smooth eigenvalue split, has been used to capture internal shocks and other discontinuities. Numerical calculations have been done to analyze the off-design jet flow due to the pressure difference. The variation of pressure along the flow axis is compared with an experimental result and other numerical result. The characteristics of the interaction between the shock cell and the turbulence mixing layer have been analyzed.

• Computers and Concrete
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• 제22권2호
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• pp.133-142
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• 2018

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.

• 한국환경과학회지
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• 제15권1호
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• pp.45-58
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• 2006

In order to grasp physical characteristics of Ganajin Bay receiving the effluents from land, a comprehensive field surve)'has been conducted at the north of Wando and Gogeumdo in 2002. Water temperature was most high in September while most low in December. A high temperature in September was inferred to have caused by the dispersion of warm fresh water with favor of a dominant wind in autumn. However, salinity and sigma-t in situ was most low in September while most high in December. A low salinity (or density) in September turned out to reflect the influence of a dense rainfall in summer. Water temperature, salinity and density at the surface layer were lower than those at the bottom layer, except for December. Their horizontal profiles suggested the influence of effluents such as Tamjin River. Particularly, time series of water temperature acquired near the sluice and at the north channel of Wando tended to rise at the flood flow but fall at the ebb flow in accordance with the tide. The form ratio of the tide in the study area was $0.31\~0.32$ and the amplitude of the tide appeared to increase towards the west. Northeastward or southwestward flows prevailed in this area but the residual flows were all northeastward with a magnitude of $3\~4cm/s$.

• 대한지리학회지
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• 제44권4호
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• pp.463-480
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• 2009

전라북도 완주군 봉동읍에 위치한 만경강 하안단구 역층 상부에 퇴적되어 있는 뢰스-고토양 연속층을 대상으로 토양분석과 대자율 측정, 입도 및 원소분석을 행하여 퇴적물의 풍화 특성과 기원지를 검토하였다. 봉동단면은 상부에서 하부로 Layer 1(고토양), Layer 2(뢰스), Layer 3(고토양) 그리고 하안단구 역층으로 이루어진다. 대자율은 뢰스층과 고토양층 사이에 뚜렷한 차이를 보이며, 입도분석 결과는 봉동단면이 하천이나 사면이동이 아니라 바람에 의해 운반되었으며, 중국 뢰스고원이나 대천뢰스보다 상당히 세립질임을 보여준다. 토양분석 중 유기물 함량만이 대자율과 유사한 변화를 보이며, 건조 토색보다는 습윤 토색이 뢰스-고토양 연속층의 특성을 보다 잘 반영한다. 주원소 및 희토류 원소 분석 결과, 봉동단면의 뢰스물질은 중국 뢰스고원과 동일한 기원지 또는 재이동된 물질에 의해 형성되었으며, 퇴적 이후에는 고온다습한 우리나라 기후 환경에서 중국 뢰스고원보다 심하게 풍화작용을 받았다.

• 한국물환경학회지
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• 제28권2호
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• pp.292-299
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• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• 지질공학
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• 제24권4호
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• pp.511-523
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• 2014

확장공사 중 큰 규모의 붕괴가 발생한 사면에 대하여 현재와 확장공사 완료 후의 안정성을 평가하기 위하여 한계평형법과 유한차분법을 이용하여 안정해석을 실시하였다. 이 지역은 복잡한 공학적 특성을 갖는 붕적층이 존재하여 안정해석을 위한 해석모델 결정이 쉽지 않다. 따라서 실제 사면의 상태를 반영하는 해석모델을 만들기 위해 경계면(파괴면)의 형상과 지반강도정수를 변화시켜가며 역해석을 실시하여 최종적인 해석모델을 결정하였다. 대책공법으로 고려한 억지말뚝이 적용된 해석모델은 비교적 안정한 상태로 분석되었으며, 이러한 해석결과는 실제 사면의 상태와 일치하는 것이다. 또한 이 연구에서 제시된 해석모델과 지반물성은 향후 계획중인 사면 절취공사 시 지반의 안정성을 확보하는데 기초자료로 사용될 수 있을 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.509-514
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• 2001

The Fibre-optic Bragg grating (FBG) sensor is broadly accepted as a structural health monitoring device for Fibre reinforced plastic (FRP) materials by either embedding into or bonding onto the structures. The accuracy of the strain measured by using the FBG sensor is highly dependent on the bonding characteristics among the bare optical fibre, protective coating, adhesive layer and host material. In general, the signal extracted from the embedded FBG sensor should reflect the straining condition of the host structure. This paper presents a theoretical model to evaluate the differential strains between the bare fibre and host material with different adhesive thickness and modulus of the protective coating of the embedded FBG sensor.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.231-234
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• 2003

제주대학교 시험부지에 토양수채수기를 설치하고 2002년 11월부터 2003년 6월까지 토양수의 산소와 수소 동위원소 조성을 관측하였다. 토양수의 산소와 수소 동위원소 조성은 이 지역에 내리는 강수의 동위원소 조성을 반영하고 있음이 확인되었다. 중수소과잉값(d-값)으로 볼 때 연구지역에서 지하 30cm 깊이 토양까지 강수가 도달되는데 약 2개월 그리고 60cm 깊이까지 도달되는데 약 4개월의 겉보기체류시간이 소요되는 것으로 관찰되었다.