• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.15-28
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• 1998

As an alternative for solving the incompressible Navier-Stokes equations, we present a vorticity-based integro-differential formulation for vorticity, velocity and pressure variables. One of the most difficult problems encountered in the vorticity-based methods is the introduction of the proper value-value of vorticity or vorticity flux at the solid surface. A practical computational technique toward solving this problem is presented in connection with the coupling between the vorticity and the pressure boundary conditions. Numerical schemes based on an iterative procedure are employed to solve the governing equations with the boundary conditions for the three variables. A finite volume method is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition . The velocity field is obtained by using the Biot-Savart integral derived from the mathematical vector identity. Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well-established for potential flow analysis. The calculated results with the present mettled for two test problems are compared with data from the literature in order for its validation. The first test problem is one for the two-dimensional square cavity flow driven by shear on the top lid. Two cases are considered here: (i) one driven both by the specified non-uniform shear on the top lid and by the specified body forces acting through the cavity region, for which we find the exact solution, and (ii) one of the classical type (i.e., driven only by uniform shear). Secondly, the present mettled is applied to deal with the early development of the flow around an impulsively started circular cylinder.

• 항공우주시스템공학회지
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• 제1권1호
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• pp.25-35
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• 2007

In this paper, the interlaminar crack problems of a fiber metal laminate (FML) under generalized plane deformation are studied using the theory of anisotropic elasticity. The crack is considered to be embedded in the matrix interlaminar region (including adhesive zone and resin rich zone) of the FML. Based on Fourier integral transformation and the stress matrix formulation, the current mixed boundary value problem is reduced to solving a system of Cauchy-type singular integral equations of the 1st kind. Within the theory of linear fracture mechanics, the stress intensity factors are defined on terms of the solutions of integral equations and numerical results are obtained for in-plane normal (mode I) crack surface loading. The effects of location and length of crack in the 3/2 and 2/1 ARALL, GLARE or CARE type FML's on the stress intensity factors are illustrated.

• Steel and Composite Structures
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• 제27권4호
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• pp.439-451
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• 2018

In the present investigation, a plane P (longitudinal) wave is made incident upon a transversely isotropic magnetothermoelastic solid slab of uniform thickness, interposed between two different semi-infinite viscoelastic solids. The transversely isotropic magnetothermoelastic sandwiched layer is homogeneous with combined effects of two temperature, rotation and Hall current in the context of GN Type-II and Type-III (1993) theory of thermoelasticity. The amplitude ratios of various reflected and refracted waves are obtained by using appropriate boundary conditions. The effect of energy dissipation on various amplitude ratios of longitudinal wave with angle of incidence are depicted graphically. Some cases of interest are also deduced from the present investigation.

• Journal of applied mathematics & informatics
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• 제40권3_4호
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• pp.393-407
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• 2022

In this paper, a diffusive predator-prey system with Beddington DeAngelis functional response and the modified Leslie-Gower type predator dynamics when a prey population is infected is considered. The predator is assumed to predate both the susceptible prey and infected prey following the Beddington-DeAngelis functional response and Holling type II functional response, respectively. The predator follows the modified Leslie-Gower predator dynamics. Both the prey, susceptible and infected, and predator are assumed to be distributed in-homogeneous in space. A reaction-diffusion equation with Neumann boundary conditions is considered to capture the dynamics of the prey and predator population. The global attractor and persistence properties of the system are studied. The priori estimates of the non-constant positive steady state of the system are obtained. The existence of non-constant positive steady state of the system is investigated by the use of Leray-Schauder Theorem. The existence of non-constant positive steady state of the system, with large diffusivity, guarantees for the occurrence of interesting Turing patterns.

• 한국지리정보학회지
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• 제7권1호
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• pp.62-74
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• 2004

백두대간은 국토의 근간이자 중요한 생태축이다. 그러나 최근 백두대간 지역을 대상으로 한 각종 개발요구가 증가함에 따라 이에 적절히 대응하기 위한 보전 전략 수립과 체계적인 관리의 필요성이 부각되고 있다. 이 연구는 백두대간 지역을 효율적으로 보호하기 위한 관리구역 설정을 제안하고자 수행하였다. 접근 방법은 백두대간의 적절한 관리범위 설정을 위해 수계 및 유역을 바탕으로 인간 간섭의 영향정도를 파악하는 것으로, 수치지도, Landsat TM 영상 등이 사용되었다. 준산악지형의 특성을 갖는 남덕유산~소사고개 구간을 대상으로 유역확장방식을 사용하여 유역차수에 따른 경작지, 도시, 나지, 수계, 산림 등의 토지이용상태의 변화를 추적하였다. 그 결과 유역확장방식은 백두대간 관리범위 설정기법으로 효율적이었으며, 관리범위는 마루금을 중심으로 무주(8차)와 거창(5차) 방향이 상이하게 설정되었다.

• Applied Microscopy
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• 제38권4호
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• pp.329-338
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• 2008

대극과 대극속 Meleuphorbia아절의 한계와 근연 분류군과의 유연관계를 규명하기 위해 Meleuphorbia아절에 속한 3종과 근연 분류군에 속하는 9종을 포함하여 총 12종의 화분을 광학 및 주사전자현미경으로 관찰하였으며, 8개의 정량 화분 형질을 이용한 수리분석을 바탕으로 2개의 유형으로 구분하였다: 화분의 표면 무늬가 미세유공상인 Type I (E. epicyparissias, E. inermis, E. pillansii, E. obesa, E. bubalina, E. meloformis, E. nesemanii, E. jansenvillensis), 화분의 표면 무늬가 추문상인 Type II (E. longituberculosa, E. monteiri, E. caput-medusae, E. grantii). 화분 형태학적으로 Meleuphorbia아절은 자연분류군이 아닐 가능성이 크며, Meleuphorbia아절에 속하는 종들은 Anthacantha아절, Treisia절, Medusea절에 속한 종들과 유연관계가 깊은 것으로 나타나, 이들을 함께 하나의 분류군으로 처리하는 것이 바람직하다.

• 한국환경복원기술학회지
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• 제18권1호
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• pp.127-133
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• 2015

Interests in ecosystem services have increased and a number of attempts to perform a quantitative valuation on them have been undertaken. To classify the ecosystem types landcover classification maps are generally used. However, some forest types on landcover classification maps have a number of errors. The purpose of this study is to verify the forest types on the landcover map by using a variety of field survey data and to suggest an improved method for forest type classifications. Forest types are compared by overlaying the landcover classification map with the 4th forest type map, and then they are verified by using National Forest Inventory, 3rd National Ecosystem Survey and field survey data. Misclassifications of forest types are found on the forest on the forest type map and farm and other grassland on the landcover map. Some errors of forest types occur at Daegu, Busan and Ulsan metropolitan cities and Gangwon province. The results of accuracy in comprehensive classification show that deciduous forest is 76.1%; coniferous forest is 54.0%; and mixed forest is 22.2%. In order to increase the classification accuracy of forest types a number of remote sensing images during various time periods should be used and the survey period of NFI and the National Forest Inventory and National Ecosystem Survey should be consistent. Also, examining areas with wide forest patch should be prioritized during the field survey in order to decrease any errors.

• Structural Engineering and Mechanics
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• 제6권2호
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• pp.143-159
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• 1998

The objective of this present work is to estimate the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, square symmetric laminates under the action in-plane positive (+ve) shear load. Two progressive failure analyses, one using the Hashin criterion and the other using a Tensor polynomial criterion, are used in conjunction with finite element method. First order shear deformation theory along with geometric non-linearity in the von Karman sense have been employed. Variation of failure loads and failure characteristics with five type of lay-ups and three types of boundary conditions has been investigated in detail. It is observed that the maximum difference between failure loads predieted by various criteria depends strongly on the laminate lay-up and the flexural boundary restraint. Laminates with clamped edges are found to be more susceptible to failure due to transverse shear (ensuing from the out of plane bending) and delamination, while those with simply supported edges undergo total collapse at a load slightly higher than the fiber failure load. The investigation on negative (-ve) in-plane shear load is in progress and will be communicated as part-II of the present work.

• 대한토목학회논문집
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• 제32권4A호
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• pp.217-225
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• 2012

본 연구에서는 비대칭 연결재를 갖는 조립식 압축부재의 연결재 종류에 따른 좌굴 거동을 알아보기 위한 실 대형 실험을 실시하였다. 압축부재인 H-300 형강 10 m 부재 3개를 볼트 연결하여 총 길이 30 m가 되도록 2 m 간격으로 2열 배치한 후 연결재 종류가 띠판, ㄷ형강, 복 ㄷ형강인 경우에 대하여 압축 실험을 실시하였다. 본 논문에서는 연결재 종류에 따른 실험 좌굴 하중을 평가하고 이를 유한요소해석 결과인 좌굴하중과 Timoshenko 식에 의한 좌굴하중과 비교 분석 하였으며, 연결재 종류에 따른 조립식 압축부재의 좌굴 거동으로 인한 종방향 변위, 횡방향 변위, 변형률 등을 분석하였다. 실험 결과 비대칭 연결재를 갖는 조립식 압축부재의 연결재가 띠판일 때 보다 복 ㄷ형강일 때의 좌굴 하중은 4.2%, ㄷ형강일 때는 36.6% 감소하는 것으로 나타났다.

• 물과 미래
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• 제29권2호
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• pp.143-151
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• 1996

중간류 유출, 지표표화지역, 흙수분저류량들의 동적 반응을 Richards 방정식을 이용한 수치실험을 통하여 유도하였다. 그리고 수치실험에서 경사면 모양, 토양종류, 경계조건 등을 변화시켜서 지표포화지역-중간류유출 동적 관계 및 지표포화지역-흙수분저류량 동적 관계를 결정하였다. 모의결과에 의하면, 지표포화지역-중간류유출 동적 관계 및 지표포화지역-흙수분 저류량 동적 관계는 각 관계들의 정상류 관계에 의해 근사적으로 설명될 수 있다. 그리고 강우양상이 단순한 펄스입력일지라도 중간류유출 및 지표포화지역의 동적 반응은 중복첨두치에 의해 특징지어지며, 중복첨두치의 발생에 대한 물리적 메케니즘은 "variable source area"의 개념을 이용하여 설명하였다.용하여 설명하였다.