• Geomechanics and Engineering
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• 제16권2호
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• pp.169-176
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• 2018

An attempt has been made here to study the propagation of SH-type surface waves in an elastic medium, which is initially stressed and heterogeneous and has a point source inside the medium. The upper portion of the composite medium is a sandy layer. It is situated on an initially stressed heterogeneous half-space, whose density, rigidity and internal friction are function of depth. The analysis has been carried out by using Fourier transform and Green's function approach. The phase velocity has been investigated for several particular situations. It has been shown that the results of the study agree with those the case of Love wave propagation in a homogeneous medium in the absence of the sandy layer, when the initial stress is absent. In order to illustrate the validity of the analysis presented here, the derived analytical expression has been computed numerically, by considering an illustrative example and the variances of the concerned physical variables have been presented graphically. It is observed that the velocity of shear wave is amply influenced by the initial stress and heterogeneity parameters and the presence of the sandy layer. The study has an important bearing on investigations of different problems in the earth's interior and also in seismological studies.

• 한국해양공학회지
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• 제17권5호
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• pp.82-87
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• 2003

A practical method to investigate the sharing architecture of FMS, for small and medium enterprises, on distributed heterogeneous environmental conditions is investigated. Because the industrial FMS model requires a reasonable size for actual work-site flexible operation, the initial facility expense is very heavy. The support for flexible cooperation of FMS, with some external different FMS, can reduce expenditures and provide greater functionality. While most FMS provide their operation process using an adequate mechanism, when used in isolation, such as island of automation, there is increasing demand for FMS that can cooperate. By exchanging intermediate products and information with other external FMS, products can be produced that cannot be produced alone, such as those that require various processes. This study first considers the sharing architecture of FMS for small and medium enterprises, and investigates the effects of the general sharing architecture of FMS on distributed heterogeneous environments, by using transducer approach to agentification. In this study, set-up station or in-out station takes charge of the gateway of intermediate products, and routes them among distributed heterogeneous FMS plants. The transducer approach is applied to web agent and set-up agent established interfaces, with system controller and setup controller. In this study, the FMS-established sharing architecture is able to obtain not only the internal flexibility, but also the external flexibility.

• 충청수학회지
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• 제21권1호
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• pp.71-78
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• 2008

We introduce the homogenized differential systems for fissured medium equations representing the small temperature variation or densities of a fluid in a system consisting of two components.

• 대한기계학회논문집B
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• 제20권9호
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• pp.3015-3029
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• 1996

The notion of effective transport property of a heterogeneous medium implies that the medium is large enough that the ergodic theorem holds and local fluctuation of the property can be neglected. In case that the medium is not large enough compared to its characteristic microstructure length scale, the effective property fluctuates and differs from the value of the medium being large enough. As a representative transport phenomenon, diffusion was considered and the fluctuation of varying effective diffusion property, diffusion coarseness $C_k$, was defined as a quantifying parameter. Scaled effective diffusion property, $^*$>/k$_1$ and $C_k$ were computed for the two phase random media consisting of matrix of diffusion coefficient k$_1$ and spheres of diffusion coefficient k$_2$. Numerical simulations were performed by use of the so-called first passage time technique and data were collected for existing microstructure models of hard spheres(HS), overlapping spheres(OS) and penetrable concentric shells(PCS).

• Journal of applied mathematics & informatics
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• 제8권3호
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• pp.919-934
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• 2001

The concepts of material frame-indifference and material symmetry group with respect to isotropic scalar functions, as represented by energy functions, are discussed. An energy function for a structured heterogeneous (transversal isotropic) medium in large elastic deformations, which is known to satisfy the Ponyting’s effect [1], is highlighted. It is shown that the constitutive relation due to this energt function is material frame-indifferent.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.959-965
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• 2002

Effective hydraulic conductivity of a statistically anisotropic heterogeneous medium is obtained for steady two-dimensional flows employing stochastic analysis. Flow equations are solved up to second order and the effective conductivity is obtained in a semi-analytic form depending only on the spatial correlation function and the anisotropy ratio of the hydraulic conductivity field, hence becoming a true intrinsic property independent of the flow field. Results are obtained using a statistically anisotropic Gaussian correlation function where the anisotropy is defined as the ratio of integral scales normal and parallel to the mean flow direction. Second order results indicate that the effective conductivity of an anisotropic medium is greater than that of an isotropic one when the anisotropy ratio is less than one and vice versa. It is also found that the effective conductivity has upper and lower bounds of the arithmetic and the harmonic mean conductivities.

• Computers and Concrete
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• 제3권6호
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• pp.423-437
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• 2006

Stress wave propagation through concrete is simulated by finite element analysis. The concrete medium is modeled as a homogeneous material with smeared properties to investigate and establish the suitable finite element analysis method (explicit versus implicit) and analysis parameters (element size, and solution time increment) also suitable for rigorous investigation. In the next step, finite element analysis model of the medium is developed using a digital image processing technique, which distinguishes the mortar and aggregate phases of concrete. The mortar and aggregate phase topologies are, then, directly mapped to the finite element mesh to form a heterogeneous concrete model. The heterogeneous concrete model is then used to simulate wave propagation. The veracity of the model is demonstrated by evaluating the intrinsic parameters of nondestructive ultrasonic pulse velocity testing of concrete. Quantitative relationships between aggregate size and testing frequency for nondestructive testing are presented.

• 한국과학교육학회지
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• 제21권4호
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• pp.668-676
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• 2001

이질적으로 구성된 소집단 협동학습에서의 내적 과정을 이해하기 위해서 이 연구에서는 과학 수업에서의 협동학습 과정에서 나타나는 성취 수준별 상호작용 양상을 조사하였다. 성취 수준별 언어적 행동의 빈도를 비교하여 언어적 상호작용에의 참여 정도 및 방식을 조사하였다. 그리고 상호작용에 대한 학생들의 인식을 조사하여 성취 수준에 따른 상호작용 양상도 분석하였다. 조사 결과, 상위와 중위 학생 사이에는 언어적 행동의 빈도에 차이가 없었으며, 소집단의 언어적 상호작용은 상위와 중위 학생이 서로 협력하여 공동으로 의미를 구성해나가는 방식으로 일어났다. 상위와 중위 학생 사이의 활발한 상호작용은 학생들의 인식 조사를 통해서도 확인되었다. 즉, 과학수업에서의 협동학습 과정에서는 중위 학생도 적극적이고 활발하게 소집단 활동에 참여하고 있었다.

• 충청수학회지
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• 제19권4호
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• pp.335-347
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• 2006

The homogenization of non-stationary Navier-Stokes equations on anisotropic heterogeneous media is investigated. The effective coefficients of the homogenized equations are found. It is pointed out that the resulting homogenized limit systems are of the same form of non-stationary Navier-Stokes equations with suitable coefficients. Also, steady Stokes equations as cell problems are identified. A compactness theorem is proved in order to deal with time dependent homogenization problems.

• 한국지하수토양환경학회지:지하수토양환경
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• 제6권4호
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• pp.51-59
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• 2001

불균질 매질 내 분포하는 비 수용성 유기오염물(NAPL; non-aqueous phase liquid)을 계면활성제를 이용한 원위치 정화 방법으로 정화하는 칼럼 및 박스실험을 실시하였다. Ottawa 모래를 이용한 균질 칼럼실험을 통하여 NAPL에 대한 계면활성제용액의 정화 효율 증가를 검증하였고, 실제 오염지역의 토양을 이용한 칼럼실험을 통하여 불균질 토양에서의 정화 효율을 측정하였으며, 불균질 층리 구조와 단층구조를 모형화한 2차원 박스를 사용한 NAPL 정화 실험을 통하여 불균질 매질에서의 정화 효율을 규명하였다. LNAPL 오염원으로 o-xylene이, DNAPL 오염원으로 PCE(tetrachloroethylene)가 이용되었고, 계면활성제로는 비이온성 올리에마이드(oleamide)가, 매질로는 유류로 오염된 오염지역으로부터 채취한 실제토양과 Ottawa 모래가 실험에 사용되었다. 1% 계면활성제용액과 증류수를 주입하여 NAPL을 세정하였고 가스크로마토그래피(GC)를 이용하여 NAPL의 농도를 분석하였다. 균질 Ottawa 모래충진 칼럼의 경우 계면활성제를 주입할 경우가 증류수를 주입할 때보다 o-xylene의 최대유출농도가 약 460배, 불균질 토양의 경우 약 250배, 불균질 층상구조에서는 약 150배 증가를 나타내었다. 불균질 매질에서 계면활성제를 이용한 세정법(flushing method)으로 NAPL을 정화시, 균질 매질에서의 정화 효과보다는 정화 효율이 감소하나, 여전히 증류수만을 이용한 세정방법보다 훨씬 높은 정화 효과를 보이며, 빠른 시간 내에 NAPL이 정화되었음을 확인하였다. 본 실험을 통하여, 불균질 매질에서의 계면활성제를 이용한 토양세정방법의 효율성이 정량화 되었으며, 계면활성제를 이용한 채수주입법의 현장 적용가능성을 확인하였다.산이온의 탄소의 $\delta$$^{13}$C(PDB)값은 -6.2~0.0$\textperthousand$범위이며, 그 기원은 대수층인 지층내 탄산염암 또는 탄산염 광물의 용해에서 유래한 무기기원 탄소로 해석된다.다.으로 변화하였으며 치료 전에 반응하지 않던 항원에 새롭게 반응하는 항체가 나타나는 경우는 드물었다.ms of chlorophyll-a concentration estimation, however, the accuracy stays very similar compared to that of the CZCS-type algorithm. This is considered to be due to the nature of in-water algorithm which relies on spectral ratio of water-leaving radiances.ethanol의 혈중농도(血中濃度)가 높을수록 더 심(甚)한 혈압강하작용(血壓降下作用)을 나타내며, ethanol 로 인(因)한 이뇨작용(利尿作用)도 ethanol 량(量)이 증가(增加)함에 따라 뇨량(尿量)도 증가(增加)함을 보여 주었다.ults showed that the overall quality of Sullungtang significantly decreased as the parity increased for Hanwoo cows. The Sullungtang extracted from bones of heifer had the best sensory scores as well as nutritional quality when compared to those extracted from the cows with parity. Therefore,