• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• 한국결정성장학회지
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• 제15권5호
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• pp.188-192
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• 2005

High $T_c(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y[(YNS)-123]$ superconductors with/without $CeO_2$ additive were systematically investigated by the zone melt growth process in air. Cylindrical green rods of (YNS)-123 oxides were fabricated by cold isostatic pressing (CIP) method using rubber mould. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.5}Nd_{0.25}Sm_{0.25})_2BaCuO_5[(YNS)211]$ nonsuperconducting inclusions were uniformly dispersed in large $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y$[(YNS)123] superconducting matrix. In this study, optimum melting temperature and growth rate were $1100^{\circ}C$ and 3 mm/hr, respectively. The directionally melt-textured (YNS)-123 sample with $CeO_2$ additive showed an onset critical temperature $(T_c)\;T_c{\geq}93K$ and sharp superconducting transition.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.245-248
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• 2005

This paper is concerned with manufacturing technology of thin foil tensile specimen using CIP(Cold Isostatic Press) and measurement of precision mechanical property. This thin foil tensile specimen manufacturing technology is a method that can make a metal thin foil specimen for micro tensile testing. We can get a burr free micro metallic thin foil specimen using this technology. For testing mechanical property of this micro thin foil, we use a nano scale material testing machine that was developed by KITECH. In this paper, micro tensile specimens of nickel and copper thin foil are fabricated with CIP and precision mechanical properties of these materials could be measured. We will expect that precision mechanical property of micro/nano material and component. Micro and Nano mechanical property can be measured using this technology and mechanical property data base of micro/nano material and component can be constructed.

• 한국분말재료학회지
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• 제30권1호
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• pp.35-40
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• 2023

In this study, a graphite block is fabricated using artificial graphite processing byproduct and phenolic resin as raw materials. Mechanical and electrical property changes are confirmed due to the preforming method. After fabricating preforms at 50, 100, and 150 MPa, CIP molding at 150 MPa is followed by heat treatment to prepare a graphite block. 150UP-CIP shows a 12.9% reduction in porosity compared with the 150 MPa preform. As the porosity is decreased, the bulk density, flexural strength, and shore hardness are increased by 14.9%, 102.4%, and 13.7%, respectively; and the deviation of density and electrical resistivity are decreased by 51.9% and 34.1%, respectively. Therefore, as the preforming pressure increases, the porosity decreases, and the electrical and mechanical properties improve.

• 콘크리트학회논문집
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• 제26권4호
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• pp.533-543
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• 2014

최근 들어, 지하주차장과 같은 모듈화 건물에 프리캐스트 콘크리트와 현장타설 콘크리트가 함께 사용되는 복합공법의 사용이 증가하고 있다. 일반적으로 프리캐스트 콘크리트는 공장에서 선 제작되기 때문에 재료의 효율성을 극대화하기 위해 프리텐션을 도입하여 사용한다. 현행 구조기준이 긴장력이 가해진 단일 단면의 전단 강도식은 제시하지만 긴장력이 가해진 프리캐스트와 현장타설 콘크리트 합성단면의 전단강도식은 제시하지 못하고 있는 실정이다. 따라서 긴장력이 가해진 합성 부재의 전단강도 실험을 통해 긴장력이 전단강도에 미치는 영향과 합성부재의 전단강도 산정시 고려해야할 사항에 대해 알아보았다. 변수로는 콘크리트의 면적비, 긴장재의 긴장력, 전단 경간비, 그리고 전단철근비를 고려하였다. 실험 결과를 분석해보면, 전단강도는 긴장력 크기와 긴장력이 가해진 단면의 면적비가 커질수록 증가하였고 전단경간비가 증가할수록 감소하였다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.259-260
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• 2004

• 한국세라믹학회지
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• 제33권4호
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• pp.471-477
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• 1996

During Bi(Pb)-Sr-Ca-Cu-O superconductor wire fabrication the effect of the initial packing density on the final characteristics of superconductor wire was systematically studied. To increase the powder packing density with uniform distribution of superconducting core a billet insertion method processed by CIP was applied instead of the commonly used vibration and ramming method of powder insertion into silver sheath. Compared with the vibration and ramming method the billent insertion technique processed by CIP cause the 30% incre-specimen with 130${\mu}{\textrm}{m}$(core thickness : 45 ${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$for 200hrs. shows specimen with 130${\mu}{\textrm}{m}$ (core thickness ; 45${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$ for 200 hrs. shows maximum 34A for Ic and 16, 700 A/cm2 for Ic measured at 77K and 0T. Also the sample rolled 3 times shows maximum 7, 2A for Ic and 11, 000 A/cm2 for 77K and 0T. Based on X-ray experimental results the formation of Bi-2223 and texture were significantly well developed at the interface between the superconducting core and silver sheath as compared with those of the interior area of superconducting core.

• 한국해안·해양공학회논문집
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• 제33권3호
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• pp.93-100
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• 2021

고정된 격자시스템에서 임의형상의 불투과 경계를 갖는 물체와 유체와 연성해석이 가능한 IB(Immersed Boundary)법이 개발 된 이후로 다양한 CFD 모델에서 IB법의 활용이 증가하고 있다. 기존의 IB법의 대부분은 구조물의 경계면에서 산정되는 유체력으로부터 수치적으로 경계조건을 만족시키는 directing-forcing법이나 구조물 내부에 가상셀을 위치시켜 보간을 통해 경계조건을 만족시키는 ghost-cell법들로 알고리즘이 복잡하다. 본 연구에서는 고정된 격자시스템에서 가동물체형 구조물 해석이 가능함과 더불어 3차원으로의 확장도 용이한 SIB(Simplified Immersed Boundary)법을 제안하였다. 본 연구에서 제안한 SIB법은 각 상(phase)의 밀도함수가 국소질량의 중심과 함께 이동하는 것으로 가정한 단일유체모델(one-field model for immiscible two-phase fluid)을 기초로 하였다. 또한 이동하는 고체상태의 구조물을 취급하기 위해 고체의 밀도함수를 이용한 체적가중평균법을 적용하고, 수치확산을 방지하기 위해 이류계산에는 CIP법을 적용하였다. 제안된 SIB법의 해석성능을 검토하기 위해 자유수면으로 낙하하는 물체에 대한 수치모의를 수행하였다. 수치해석결과는 자유수면으로 낙하하는 물체를 양호하게 재현하였다.

• 한국동물위생학회지
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• 제30권1호
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• pp.13-21
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• 2007

An atmospheric pressure chemical ionization (APcI) LC/MS/MS method was developed for the simultaneous analysis of fluoroquinolones (norfloxacin, ciprofloxacin, enrofloxacin, danofloxacin) residues in eggs. The spiked and blank samples were extracted from whole eggs using 50mM phosphate buffer (pH 7.4). The extract was cleaned up by passage though $Oasis^{(R)}$ MAX extraction cartridge for solid-phase extraction followed by elution with 4% formic acid in methanol. The extract of sample was separated on a Waters $Atlantis^{TM}$ $dC_{18}$ reversed-phase column ($4.6{\times}150mm,\;5{\mu}m$) and analyzed by APcI positive mode mass spectrometry. The mobile phase consists of aqueous 0.2% nonafluoropentanoic acid (NFPA) and methanol. Multiple reaction monitoring (MRM) using the precursor to product ion combinations of m/z $320\;{\dashrightarrow}\;302,\;332\;{\dashrightarrow}\;314,\;360\;{\dashrightarrow}\;342$ and m/z $358\;{\dashrightarrow}\;340$ were used to quantify norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR) and danofloxacin (DAN), respectively. The limits of quantification (LOQ) were 7.8ppb for NOR, 8.5ppb for CIP, 8.9ppb for ENR, and 4.8ppb for DAN. Average recoveries of fortified sample at levels of 0.025 to 0.1 ppm were estimated 71.29% for NOR, 75.27% for CIP, 85.51% for ENR and 81.22% for DAN. These results could be applied for the confirmation and quantification in eggs.

• 한국강구조학회 논문집
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• 제26권1호
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• pp.11-20
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• 2014

2001년 이후 앵커의 설계는 Concrete Capacity Design(CCD) 방법이 적용되고 있는데, 국내 기준에서는 지진하중에 대한 콘크리트의 파열파괴강도를 정적 파괴강도의 75%로 제한하고 있다. 본 연구에서는 무근콘크리트에 매입된 선설치앵커의 동적 전단하중에 대한 콘크리트 파열파괴강도 평가하기 위한 실험을 수행하였다. 이를 위해 직경 20 mm의 앵커에 대해 정적 하중과 동적 편진하중에 대한 실험을 각각 3개의 시험체에 대해 수행하였으며, 앵커의 연단거리는 120 mm를 적용하였다. 동적 실험은 15 cycle의 편진하중을 1 Hz의 속도로 재하하였으며 반복하중단계의 크기를 키워가면서 최종 파괴 시까지 가력하였다. 실험으로부터 동적 전단하중에 의한 콘크리트 파열파괴강도는 정적하중에 의한 것과 거의 같은 파괴강도를 보였다.