• 한국항공운항학회지
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• 제16권4호
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• pp.26-34
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• 2008

This article provides a comprehensive treatment of cracks in non-homogeneous structural materials such as functionally graded materials (FGMs). It is assumed that the material properties depend only on the coordinate perpendicular to the crack surfaces and vary continuously along the crack faces. By using laminated composite plate model to simulate the material non-homogeneity, we present an algorithm for solving the system based on Laplace transform and Fourier transform techniques. Unlike earlier studies that considered certain assumed property distributions and a single crack problem, the current investigation studies multiple crack problem in the FGMs with arbitrarily varying material properties. As a numerical illustration, transient thermal flow intensity factors for a metal-ceramic joint specimen with a functionally graded interlayer subjected to sudden heating on its boundary are presented. The results obtained demonstrate that the present model is an efficient tool in the fracture analysis of non-homogeneous material with properties varying in the thickness direction.

• Earthquakes and Structures
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• 제9권4호
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• pp.753-766
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• 2015

An investigation has been carried out for the propagation of torsional surface waves in an inhomogeneous prestressed layer over an inhomogeneous half space when the upper boundary plane is assumed to be rigid. The inhomogeneity in density, initial stress (tensile and compressional) and rigidity are taken as an arbitrary function of depth, where as for the elastic half space, the inhomogeneity in density and rigidity is hyperbolic function of depth. In the absence of heterogeneities of medium, the results obtained are in agreement with the same results obtained by other relevant researchers. Numerically, it is observed that the velocity of torsional wave changes remarkably with the presence of inhomogeneity parameter of the layer. Curves are compared with the corresponding curve of standard classical elastic case. The results may be useful to understand the nature of seismic wave propagation in geophysical applications.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1699-1710
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• 2001

The characteristics of methanol and methanol blended (M85) sprays were investigated under atmospheric conditions at various temperature, ranging from on-vaporizing to vaporizing ambient conditions (298∼353 K). From laser scattering images, the macroscopic characteristics of the spray, such as the spray tip penetration and the spray angle, were determined. Entropy concept was introduced to represent homogeneity and PIV analysis was adopted to determine the fluid dynamic information at each location of the spray. The correlation between entropy and vorticity strength enabled us to find their relations. The effect of ambient composition, mainly of viscous effect as affected by CO$_2$levels, was investigated using PIV and entropy analysis. Spray width and entropy value were found to tend to decrease at increased CO$_2$levels.

• 대한기계학회논문집
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• 제5권4호
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• pp.257-265
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• 1981

A modified subsonic wind tunnel was employed to investigate the turbulent flow of a valve jet. To effectuate this experimental study, an actual valve and valve seat of a diesel engine were equipped at its outlet (ref. Fig. 3) Theoretically, using the equation of motion of Navier-Stokes in the chlindrical coordinates, the turbulent equation of motion for the incompressible fluid was derived with three assumptions; steady flow (.delta./.delta.t=0), axisymmetry and revolutionary homogeneity(.delta./.delta..phi.=0), no ensemble revolution (V.iden.0). Experimentally, mean and fluctuation velocities have been measured in the redial direction. With a assumption of a non-dimensional velocity distribution equation, a sami-emperical similarity profile equation of the jet flow have been derived, whose empirical constants were deterimed graphically with the data obtained.

• Computers and Concrete
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• 제9권3호
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• pp.171-178
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• 2012

This paper presents numerical studies of stiff fiber pullout behaviors of fiber reinforced cementitious composites based on a progressive damage model. The ongoing debonding process is simulated. Interfacial stress distribution for different load levels is analyzed. A parametric study, including bond strength and the homogeneity index on the pullout behaviors is carried out. The numerical results indicate that the bond stress decreases gradually from loaded end to embedded end along fiber-cement interface. The debonding initially starts from loaded end and propagates to embedded end as load increasing. The embedded length and bond strength affect the load-loaded end displacement curves significantly. The numerical results have a general agreement with the experimental investigation.

• Journal of Microbiology and Biotechnology
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• 제14권4호
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• pp.863-867
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• 2004

$\alpha$-Galactosidase from A. oryzae DR-5 was induced in the presence of melibiose, raffinose, galactose, and locust bean galactomannan. The enzyme was purified to homogeneity by precipitation with acetone followed by ion-exchange chromatography using DEAE-Sephacel. The purified enzyme showed a single band in both nondenaturing-PAGE and SDS-PAGE. The enzyme was a glycoprotein in nature by activity staining. The molecular weight of the purified enzyme was 93-95 kDa by SDS-PAGE. The enzyme exhibited the optimum pH and temperature at 4.7 and $60^\circ{C}$, respectively. $\alpha$-Galactosidase activity was strongly inhibited by $Ag^{2+}, Hg^{2+}, Cu^{2+}$, and galactose. EDTA, 1,10-phenanthraline, and PMSF did not inhibit the enzyme activity, whereas N-bromosuccinimide completely inhibited enzyme activity. Investigation by TLC showed complete hydrolysis of stachyose and raffinose in soymilk in 3 h at pH 5.0 and $50^\circ{C}$.

• 한국수학교육학회지시리즈A:수학교육
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• 제38권1호
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• pp.1-14
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• 1999

It has already been fifty years since the Korean peninsula was divided into two nations, South and North Korea. Owing to forming different political and social structures with each other, we can conjecture that there are much heterogeneity in education. On the assumption that education plays important role in coming to an accommodation and in restoring homogeneity of the Korean race after unification, we consider the investigation of the contents of mathematics text-book of secondary schools as a meaningful research to make provision against unification. In this paper, we shall investigate the learning contents, and the teaming substances and sequences in mathematics of secondary schools between South and North Korea by falling into four regions; algebra and statistics, analysis and geometry. By grasping the special features of terms, teaming subject matters and learning substances, and clarifying their distinctions, we shall present some reforms measure of distinctions.

• 한국제4기학회:학술대회논문집
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• 한국제4기학회 2002년도 한몽 제1차 합동세미나 발표요지
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• pp.94-95
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• 2002

South Korea is divided into five ecoprovinces and sixteen ecoregions. The criteria for ecoprovince classification are ecosystem connectivity and cultural homogeneity. Ecoregions are classified by cluster analysis. The variables used in the analysis are latitude, longitude, seasonal mean temperature, and seasonal precipitation. The large forest fires occurred in the specific ecoregions including Kangwon coastal ecoregion, WoolYoung coastal ecoregion, Hyungsan Taehwa coastal ecoregion, Upper Nagdong river basin ecoregion and Southeastern inland ecoregion. The largest forest fire in the korean history occurred in Kangwon coastal ecoregion in the year 2000. The fire devastated the forestland over 25,000ha. Korea Forest Service, Ministry of Environment, Province Kangwon and NGO organized an investigation committee for the restoration of the burnt area. The committee suggested restoration principles and also forged a restoration strategy of the Kangwon burnt area.

• 한국강구조학회 논문집
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• 제28권5호
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• pp.313-323
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• 2016

본 연구에서는 SM490TMC(120mm) 강재를 대상으로 7종의 각종 시험을 실시하여 소재특성을 KS 및 강구조설계기준과 비교하였으며, 강도의 두께에 대한 균질성을 검토하였다. 각종 시험결과, SM490TMC(120mm) 강재는 KS를 만족하는 것으로 나타났다. 특히 인장시험결과, 1/4지점 및 전두께에 대한 기계적 성질은 KS 및 강구조설계기준을 만족하며, 2/4지점 및 두께방향에 대한 기계적 성질은 1/4지점의 85%이상으로 나타났다. 따라서 SM490TMC(120mm) 강재는 강도의 균질성 기준을 만족하며, 120mm의 경우에도 강구조설계기준에서와 같이 항복강도를 점감하지 않아도 되는 것으로 판단된다.

• 한국수자원학회논문집
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• 제49권5호
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• pp.439-450
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• 2016

본 연구에서는 미계측유역에서의 수공구조물의 설계를 위한 홍수량을 추론하는데 있어, 공간자료 확장기법에 의해 모의된 다지점의 첨두홍수량 자료를 이용한 지역홍수빈도분석의 가능성을 검토하였다. 충주댐 상류유역을 대상으로 지역홍수빈도분석의 표준방법인 지수홍수법을 중심으로 공간확장 자료의 활용에 대한 타당성을 입증하고, 대상유역 내 22개 지점의 확장자료를 이용하여 지역홍수빈도분석을 수행하였다. 지역의 동질성 가정을 구체적으로 검토하기 위해 수문학적 개념의 누가유역과 독립적인 자체유역으로 구분하여 분석을 시도하였다. 자체유역에 대한 지역의 동질성 분석결과는 이질지역으로 평가되었으며, 이러한 가장 큰 원인은 강우의 공간적인 불균등한 분포에서 기인한 것으로 분석되었다. 지역확률분포형을 선정하기 위해 적합성척도와 Floodfreq (Cost action ES0901)에서 제시한 가중이동평균(WMA) 방법으로 검토한 결과, 홍수빈도해석에 널리 이용되는 GEV 분포가 적정 확률분포형으로 채택되었으며, 그에 따른 유역의 무차원 성장곡선(분위수)을 제시하였다. 본 연구는 미계측유역에 대한 빈도홍수량 추정을 위해 지역홍수빈도분석을 중심으로 국내 관측자료의 한계를 극복하기 위한 시도이다.