• 한국지반공학회지:지반
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• 제14권4호
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• pp.103-116
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• 1998

순수전단강도를 추정하기 위해 150 세트의 삼축시험 결과를 분석하였다. 내부마찰각은 Hoek와 Brown의 파괴조건계수 m이 증가하는데 따라 비 선형적으로 증가하였으나 순수전단강도 비례계수 1c는 비선형적으로 감소하였다. 압축강도의 전단강도에 대한 비는 내부마찰각의 비에 역비례하였다. 전단강도는 m에 반비례하였으나 내부마찰각은 비례하였다. 또 단축강도는 c에 비례하였다. 회 귀분석의 해석에 있어서 전단강도가 m과 단축압축강도의 주요 영향요소로 나타났다. 전단강도의 비례계수는 RMR의 증가에 따라 비선행적으로 증가하였으나 내부마찰각은 선형적으로 감소하였다.

• Communications for Statistical Applications and Methods
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• 제3권2호
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• pp.77-83
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• 1996

This paper is concerned with an estimation problem for the AR(1) process $Y_t, t=0, {\pm}1, {\cdots}$with time carying autoregressive coefficient, where coefficient itself is also stochastic process. Attention is directed to the problem of finding a consistent estimator of ${\Phi}$, the mean level of autoregressive coefficient. The asymptotic distribution of the resulting consistent estimator of ${\Phi}$, is them discussed. We do not assume any time series model for the time varying autoregressive coefficient.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.24-32
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• 2004

The characteristics of heat transfer from horizontal cylinder immersed in both a riser and downcomer of a circulating fluidized beds were investigated experimentally under different values of solids mass flux, superficial air velocity, particle size diameter, and different bed materials. The test results indicated that local heat transfer coefficients in both riser and downcomer are strongly influenced by angular position, and mass flux, as well as by particle size and bed materials. The local heat transfer coefficients around a circumference of the cylinder inside a riser and downcomer of a CFB exhibited a general tendency to increase with decreasing particle size and increasing solids mass flux and vary with different bed materials. Also the averaged heat transfer coefficient calculated from local heat transfer coefficient exhibited the same trend as a local i.e increase with decrease particle size and increasing solids mass flux and vary with varying bed materials. The general trend for a riser local heat transfer coefficient is decrease with increase angle until ${\Phi}$ = 0.5-0.6 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Also the general trend for a local heat transfer coefficient in downcomer is to increase with increase the angle until ${\Phi}$= ${\theta}/{\Pi}$ = 0.3-0.5 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Comparison the results of the heat transfer in the riser and downcomer of a circulating fluidized beds shows that they have approximately the same trend but the values of heat transfer coefficients in riser is higher than in downcomer.

• 응용통계연구
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• 제29권1호
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• pp.257-266
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• 2016

비선형 모형인 확률계수 자기회귀 모형의 모수를 추정하기 위해 전체 데이터를 부표본으로 나누어 확률계수 ${\phi}(t)$가 초기값, ${\phi}(0)$를 갖는 특별한 경우를 제안하고 추정하였다. 모의 실험으로 부표본으로 나누어 확률계수 자기회귀 모형을 추정하는 더 바람직함을 확인하였다. 실증분석에서는 한국 Mumps 자료를 선형 모형인 자기회귀 모형과 확률 계수 자기회귀 모형에 각각 적합시켜 모수를 추정하고, PRESS 값을 비교하여 확률계수 자기회귀 모형의 예측이 더 우수함을 보였다.

• 태양에너지
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• 제6권1호
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• pp.31-36
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• 1986

In this paper heat transfer characteristics in air-solid packed bed with spherical steel particles are studied experimentally. The effect of particle sizes (${\phi}1.5,\;{\phi}2.5,\;{\phi}3.96,\;{\phi}4.75,\;{\phi}5.95,\;{\phi}7.15$), bed sizes (${\phi}50,\;{\phi}60,\;{\phi}70,\;{\phi}80$) and mass flow rate are investigated. Also heat transfer effect of the bed with particles and without particles is compared in terms of heat transfer coefficient. As a result of this experiments, the following relation is obtained in the range of the Reynolds numbers 40 between 1500. $Nu= 0.8755\;Re^{0.6367}$ (40

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.725-732
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• 2003

It was achieved that Rowecell test for this undisturbed sample was picked by Block sampler($\phi$:250mm, L:500mm) and hydraulic piston sampler($\phi$:76mm, L:850mm) in the marine clay of YONGYUDO and YEONGJONGDO in this research. Ratio of coefficient of consolidation was analyzed through comparison with C$\_$h/ by CPTu and C$\_$v/ and C$\_$h/ by existent consolidation test. According to analysis, coefficient of consolidation of block sample is fairly greater than coefficient of consolidation of piston sample. And the bigger diameter of undisturbed sample, sample disturbance could know decreasing. Coefficient of consolidation by Rowecell test measured more greatly than coefficient of consolidation by existent consolidation test. Rowecell test could know decreasing consolidation rate because of smear effect by Mandrel injection. Also, C$\_$h/ by CPTu shows deviation by each analysis method, selection of suitable analysis method judged by important leading in the coefficient of consolidation.

• 한국터널지하공간학회 논문집
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• 제11권2호
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• pp.117-129
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• 2009

원형수직터널에서 3차원적인 아칭효과를 고려한 토압산정을 위해 여러 연구가 수행되었고 실내시험 및 수치해석을 통해 이를 검증하였으나, 다층지반과 c-${\phi}$지반에서의 적용이 어려웠다. 본연구에서는 c-${\phi}$지반에서의 토압 산정을 위해 c-${\phi}$지반에서 적용 가능한 토압계수 산정식을 구하였으며, 기존 토압식을 수정 제안하였다. 점착력이 토압에 미치는 영향을 파악하기 위해 지반을 가정하여 각 경우별로 토압을 산정하여 비교하였으며, 다층지반에서 파괴면을 가정하는 방법으로 토압을 구하였다. 이 논문은 두 개의 연속된 논문(Companion paper)의 첫 번째로서 모델개발을 위한 이론전개를 다루고 있으며, 대형 모형실험에 의한 실증은 두 번째 논문에서 다룰 것이다.

• 한국전기전자재료학회논문지
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• 제20권7호
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• pp.611-614
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• 2007

The changes in the work $function({\Phi}_w)$ in the MgO protective layers after $plasma(Ar,\;H_2)$ treatment have been studied using ${\Upsilon}-focused$ ion beam $({\Upsilon}-FIB)$ system. The ${\Phi}_w$ was determined as follows: Ar-plasma $treatment({\Phi}_w=4.52eV)$, $H_2-plasma$ $treatment({\Phi}_w=5.65eV)$, and non-plasma $treatment({\Phi}_w=4.64eV)$. The results indicated that the H-plasma could not make any effective physical etching due to the small masses of hydrogen atoms and molecules while the hydration of H-plasma could grow some contaminating materials on the surface of MgO.

• International Journal of Fluid Machinery and Systems
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• 제5권2호
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• pp.65-71
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• 2012

The objective of the present investigation is to explore the possibility of improving the performance of a centrifugal fan at low Reynolds numbers using a simple passive means, namely Gurney flap (GF). GFs of 1/$8^{th}$ inch brass angle (3.175 mm) corresponding to 15.9% of blade exit height or 5.1% of blade spacing at the impeller tip are attached to the impeller blade tip on the pressure surface. Performance tests are carried out on the centrifugal fan with vaneless diffuser at five Reynolds numbers (viz., 0.30, 0.41, 0.55, 0.69, $0.82{\times}10^5$, i.e., at five speeds respectively at 1,100, 1,500, 2,000, 2,500 and 3,000 rpm) without and with GF. Static pressures on the vaneless diffuser hub and shroud are also measured for each speed at four flow coefficients [${\phi}$=0.23 (below design flow coefficient), ${\phi}$=0.34 (design flow coefficient), ${\phi}$=0.45 (above design flow coefficient) and ${\phi}$=0.60 (above design flow coefficient)] with and without GF. From the performance curves it is found that the performance of the fan improves considerably with GFs at lower Reynolds numbers and improves marginally at higher Reynolds number. Similar improvements are observed for the static pressures on the diffuser hub and shroud. The effect of Reynolds number on the performance and static pressures is considerable. However the effect is reduced with GFs.

• 대한수학회보
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• 제54권1호
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• pp.43-50
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• 2017

Let A(n) denote the largest absolute value of the coefficients of n-th cyclotomic polynomial ${\Phi}_n(x)$ and let p < q < r be odd primes. In this note, we give an infinite family of cyclotomic polynomials ${\Phi}_{pqr}(x)$ with A(pqr) = 3, without fixing p.