• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1383-1390
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• 2009

This study conducted a series of drained triaxial test in order to determine the critical state parameters of a high compressible Jeju sand. Jeju sand is classified into mixed sand containing both siliceous and calcareous materials and has high extreme void ratios due to the angularity of grains and the intra-particle voids of hollow particles. It is observed that the behavior of Jeju sand is similar to that of general calcareous sand. The friction angle of Jeju sand at critical state gradually decreases with increasing the mean effective stress. Test result shows that the particle crushing resulted from stress during shear causes the reduction of void ratio at critical state.

• 설비공학논문집
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• 제11권1호
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• pp.125-132
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• 1999

Studies are being done to replace conventional refrigerants with alternatives that have low or no ozone depletion and greenhouse warming Potentials, yet possess appropriate pro perties for a refrigeration cycle. To achieve this goal, a consistent set of thermodynamic properties of the working fluid is required. A common problem with the possible alternative refrigerants is that sufficient experimental data do not exist, thus making it difficult to develp complete equations of state that can predict properties in all regions including the vapor-liquid equilibrium. One solution is the use of the generalized equation of state correlations that can predict thermodynamic properties with a minimum number of characteristic parameters. Characteristic parameters required for the generalized equation of state are, in general, critical temperature, critical pressure, critical volume and normal boiling temperature. In this study, estimation of these characteristic parameters of refrigerants by group contribution method is developed.

• 한국지반공학회논문집
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• 제36권4호
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• pp.5-15
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• 2020

본 논문은 점성토의 응력-변형률 관계를 모사하기 위해 한계 상태 이론을 기반으로 하여 수정한 Modified Cam-Clay 파괴면을 제안한다. 평균유효응력과 von Mises 응력의 공간에서 타원형상의 파괴면을 가지는 Modified Cam-Clay 모델의 경우, 강성 및 발달법칙 미적용시, 비배수 전단조건하에 한계상태 평균유효응력은 선행압밀 평균유효응력의 절반이 되며, 이는 실제 점성토의 거동과 차이가 있다. 본 연구에서는 선행압밀 평균유효응력은 점성토의 압밀이력으로 정량화되고, 한계상태 평균유효응력은 점성토의 현재 간극비로 산정되어, 이 둘간의 비율이 고정되지 않는 찌그러진 형태의 파괴면을 제안한다. 제안된 파괴면을 항복평면으로 가정하고, 비배수 삼축압축 거동을 모사한 결과, 실내 실험 결과와 유사한 결과를 얻을 수 있었다

• Structural Engineering and Mechanics
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• 제46권3호
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• pp.337-352
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• 2013

Seismic performance of critical facilities has been focused on the structural components over the past decade. However, most earthquake damages were observed to the nonstructural components during and after the earthquakes. The primary objective of this research was to develop the seismic fragility of the piping system incorporating the nonlinear Tee-joint finite element model in the full scale piping configuration installed in critical facilities. The procedure for evaluating fragility curves corresponding to the first damage state was considered the effects of the top floor acceleration sensitivities for 5, 10, 15, and 20 story linear RC and steel building systems subjected to 22 selected ground motions as a function of ground motion uncertainties. The result of this study revealed that the conditional probability of failure of the piping system on the top floor in critical facilities did not increase with increased level of story height and in fact, story level in buildings can tune the fragilities between the building and the piping system.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2638-2651
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• 2020

Nozzle corner cracks present at the intersection of reactor pressure vessels (RPVs) and inlet or outlet nozzles have been a persistent problem for a number of years. The fracture analysis of such nozzle corner cracks is very important and critical for the efficient design and assessment of the structural integrity of RPVs. This paper aims to perform an engineering critical assessment of RPVs with nozzle corner cracks subjected to several transients accompanied by pressurized thermal shocks. The critical crack size of the RPV model with nozzle corner cracks under transient loading is evaluated on failure assessment curve. In particular, the influence of cladding on the crack initiation of nozzle corner crack under thermal transients is studied. The influence of primary internal pressure and secondary thermal stress on the stress field at nozzle corner and SIF at crack front is analyzed. Finally, the influence of different crack size and crack shape on the final critical crack size is analyzed.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.315-318
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• 2009

Some particular bound state energies of an electron, under Coulomb potential field, confined in a two-dimensional circle and a three-dimensional sphere are analytically derived. The derivation shows that the electron cannot be bound in a negative energy state when the circle (or sphere) is smaller than a certain critical size. The critical size dependency on the strength of Coulomb potential and the angular momentum of the electron is also analytically derived. This system mimics quantum dots. Therefore the derivation provides new information on a minimum critical size of quantum dots with hydrogenic impurity.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.1071-1080
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• 2020

This study aims to explore the critical success factors of the Water Public-Private Partnership (PPP) Projects in developing country with evidence from Indonesia. We all know that water is a basic need and therefore it becomes very important for the governments especially in the developing countries to develop and formulate a comprehensive water policy to deliver and manage the water services in the most appropriate manner as well tackle several challenges such as budget and project efficiency. In this context, PPP is a promising scheme to address the water problems, hence it becomes important to reveal the success factors of water PPP projects. An Analytic Hierarchy Process (AHP) questionnaire built from delphi methods is used to capture the perception of the relevant stakeholders in relation to the success factors. The results of this study show the most critical success factors in PPP water projects is the support and acceptance of the stakeholders from the community, whereas the private and public entities are the the second and third important factors. These findings contribute to the success of the PPP stakeholders by enhancing the policy-making decision process and by executing the water policies to support the development of PPP in the Water Sector.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1459-1462
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• 2008

In this paper we describe solutions to address critical challenges in direct fabrication of amorphous silicon thin film transistor (TFTs) arrays for active matrix flexible displays. For all flexible substrates a manufacturable handling protocol in automated display-scale equipment is required. For metal foil substrates the principal challenges are planarization and electrical isolation, and management of stress (CTE mismatch) during TFT fabrication. For plastic substrates the principal challenge is dimensional instability management.

• 한국추진공학회지
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• 제26권5호
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• pp.24-34
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• 2022

초임계 영역에서 작동하는 탄화수소 연료를 사용하는 재생냉각채널의 냉각성능을 예측하기 위해서는 타당한 물성 예측이 필수이다. 본 연구는 고분자 탄화수소의 임계 압축인자에 따라 밀도와 비열을 적절하게 예측하기 위해 2-파라미터 상태방정식인 SRK(Soave-Redlich-Kwong) 및 PR(Peng-Robinson) 상태방정식과 이를 합한 3-파라미터 상태방정식인 RK-PR 상태방정식에 대한 비교 분석을 수행하였다. 대표적으로 낮은 임계압축 인자를 갖는 n-dodecane 연료와 높은 임계압축 인자를 갖는 JP-10 연료를 선정하여 두 연료의 열역학적 물성을 예측할 때 적합한 상태방정식을 제시하였다. 마지막으로 밀도와 비열의 예측 결과를 NIST REFPROP 데이터와 비교하여 검증하였다.

• 대한수학회보
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• 제59권4호
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• pp.961-977
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• 2022

In this paper, we consider the following Kirchhoff type equation on the whole space $$\{-(a+b{\displaystyle\smashmargin{2}{\int\nolimits_{{\mathbb{R}}^3}}}\;{\mid}{\nabla}u{\mid}^2dx){\Delta}u=u^5+{\lambda}k(x)g(u),\;x{\in}{\mathbb{R}}^3,\\u{\in}{\mathcal{D}}^{1,2}({\mathbb{R}}^3),$$ where λ > 0 is a real number and k, g satisfy some conditions. We mainly investigate the existence of ground state solution via variational method and concentration-compactness principle.