• 대한수학회지
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• 제45권2호
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• pp.467-477
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• 2008

In this paper, we provide a criterion for Chow stability in terms of log canonical threshold of the Chow form in the Grassmannian.

• 대한수학회보
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• 제50권3호
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• pp.1029-1040
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• 2013

In this paper, we give sufficient conditions on a canonical genus 4 curve for it to be Chow (semi)stable.

• 한국전산유체공학회지
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• 제7권1호
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• pp.10-19
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• 2002

The non-staggered(collocated) grid approach in which all the solution variables are located at the centers of control volumes is very popular for incompressible flow analyses because of its numerical efficiency on the curvilinear or unstructured grids. Rhie and Chow's paper is the first in using non-staggered grid method for SIMPLE algorithm, where pressure weighted interpolation was used to prevent decoupling of pressure and velocity. But it has been known that this non-staggered grid method has stability problems when pressure fields are nonlinear like in natural convection flows. Also Rhie-Chow scheme generates large numerical diffusion near curved walls. The cause of these unwanted problems is too large pressure damping term compared to the magnitude of face velocity. In this study the magnitude of pressure damping term of Rhie-Chow's method is limited to 1∼10% of face velocity to prevent physically unreasonable solutions. The wall pressure extrapolation which is necessary for cell-centered FVM is another source of numerical errors. Some methods are applied in a unstructured FV solver and analyzed in view of numerical accuracy. Here, two natural convection problems are solved to check the effect of the Rhie-Chow's method on numerical stability. And numerical diffusion from Rhie-Chow's method is studied by solving the inviscid flow around a circular cylinder.

• 한국ITS학회 논문지
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• 제16권2호
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• pp.73-82
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• 2017

회귀모형은 현실세계 모사를 위해 우리가 흔히 활용하고 있는 통계적 방법이다. 교통분야에서도 계획이나 공학부문에 활발하게 활용되고 있지만 여러 개의 모형이 구축될 경우 개별모형의 유의성 검증에 치중하여, 모형 간의 유사성을 검증하는 단계가 부재했다. 따라서 본 연구에서는 두 선형회귀모형 간의 유사성 확인을 위해 "차우(Chow) 검정"이라는 통계적 검정 방법을 적용하였다. 차우검정은 서로 다른 두 회귀모형에서 산출된 모수의 추정값을 근거로 하여, 두 모형 사이에 어떤 유사성이 존재하는지를 통계적으로 검증하는 기법으로 오래전부터 활용되고 있는 기법이다. 차우검정의 적용성을 확인하기 위해 우선, 우천시 주야간 고속도로 교통데이터를 수집하여 각각의 속도-밀도 회귀모형을 개발하였으며 차우검정을 통해 우천시 주야간 두 모형간의 유사성을 검증함으로써 이러한 통계적 절차가 객관적인 자료분석 과정에서 중요한 역할을 수행할 수 있음을 입증하였다. 본 연구에서는 선형회귀모형들에 대한 차우검정의 적용성을 확인해 보았으며, 향후 비선형 모형간의 유사성 검증 작업이 이어질 수 있을 것으로 기대한다.

• Journal of the Korean Data and Information Science Society
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• 제21권5호
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• pp.945-950
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• 2010

As the U.S. Congress has continued to debate over the health care reform pushed by President Obama, there is an ample reason to believe that the systematic risk of the health care industry, especially health care plan providers, is increasing. This study measures and compares the systematic risk of two health care industry indexes and one portfolio of health care plan providers from before and after the introduction of the health care legislation into Congress in September, 2009. The Capital Asset Pricing Model (CAPM) is used to measure the systematic risk, and a dummy variable approach and the Chow test are used to formally compare the systematic risk from before and after the introduction of the legislation.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권4호
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• pp.320-329
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• 2016

An implicit method of solving the six degree-of-freedom rigid body motion equations based on the second order Adams-Bashforth-Moulten method was utilised as an improvement over the leapfrog scheme by making modifications to the rigid body motion solver libraries directly. The implementation will depend on predictor-corrector steps still residing within the hybrid Pressure Implicit with Splitting of Operators - Semi-Implicit Method for Pressure Linked Equations (PIMPLE) outer corrector loops to ensure strong coupling between fluid and motion. Aitken's under-relaxation is also introduced in this study to optimise the convergence rate and stability of the coupled solver. The resulting coupled solver ran on a free floating object tutorial test case when converged matches the original solver. It further allows a varying 70%-80% reduction in simulation times compared using a fixed under-relaxation to achieve the required stability.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권3호
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• pp.268-272
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• 2006

A dense, pellicular UpFront adsorbent ($p=1.5 g/cm^3$, UpFront Chromatography, Cophenhagen, Denmark) was characterized in terms of hydrodynamic properties and protein adsorption performance in expanded bed chromatography. Cibacron Blue 3GA was immobilised into the adsorbent and protein adsorption of bovine serum albumin (BSA) was selected to test the setup. The Bodenstein number and axial dispersion coefficient estimated for this dense pellicular adsorbent was 54 and $1.63{\times}10^{-5}m^2/s$, respectively, indicating a stable expanded bed. It could be shown that the BSA protein was captured by the adsorbent in the presence of 30% (w/v) of whole-yeast cells with an estimated dynamic binding capacity $(C/C_o = 0.01)$ of approximately 6.5 mg/mL adsorbent.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권5호
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• pp.466-469
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• 2006

The bed stability of Streamline DEAE (p = 1.2 g/mL) in a 20mm (i.d.) glass expanded bed contactor, and its performance on the recovery of glucose 6-phosphate dehydrogenase (G6PDH) from unclarified yeast homogenate were investigated. A residence time distribution study showed that a stable expanded bed was achieved. The theoretical plate and Bodenstein numbers determined were 25 and 53, respectively. A recovery yield of 87% and purification factor of 4.1 were achieved in the operation using 5% (w/v) biomass concentration feedstock. The performance of the anion exchange EBAC was still considerable good at a biomass concentration as high as 15% (w/v).

• 소비문화연구
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• 제15권1호
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• pp.93-118
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• 2012

본 연구는 예비적 저축행동 이론의 관점에서 가구주 근로유형이 가계저축에 미치는 영향을 분석하고, 근로유형별 가계저축에 미치는 영향 요인을 파악하고자 하였다. 실증분석 자료는 2009년도 한국복지패널조사(KOWEPS) 자료로, 가구주 근로유형이 상용직과 비상용직(임시직, 일용직, 공공근로)인 가계로 한정하여 2009년도 한국복지패널조사 가구 총 6,207가구 중 2,463가구를 본 연구의 실증분석에 사용하였다. 실증분석 결과, 가구주의 근로유형은 가계저축에 통계적으로 유의미한 영향을 미치는 것으로 나타났으나 예비적 저축행동 이론에서 제시하는 기대와는 일치하지 않았다. 즉, 상용직 가구주 가계가 임시직, 일용직 혹은 공공근로의 비상용직 가구주 가계보다 더 많은 예비적 저축을 하였고, 나아가 더 많은 예비적 자산을 축적하는 것으로 나타났다. 가구주 근로유형별 가계저축에 영향을 미치는 요인을 살펴본 결과, 가구주 근로유형별로 영향 요인 및 정도에 차이가 존재하기는 하였으나 주로 월평균 총소비지출, 부채 유무, 순자산, 빈곤 여부, 가구원수, 기초보장 유무가 유의미한 영향을 미치는 것으로 나타났다. 여기에서 특히 주목할 만한 것은 예비적 저축에 대한 기초보장의 정적 영향이었다.