• 한국정보과학회논문지:데이타베이스
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• 제31권2호
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• pp.83-90
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• 2004

본 논문에서는 순환적인 검색공간과 장애물이 존재하는 검색공간에서 객체들을 클러스터링할 때 고려해야하는 CCD(Clustering with Circular Distance) 문제와 COD(Clustering with Obstructed Distance) 문제를 연구하였다. 그리고 다차원 검색공간에서 삽입이나 삭제가 빈번히 발생하는 객체들을 효율적으로 클러스터링하기 위한 새로운 클러스터링 알고리즘을 제안하였다. 제안한 클러스터링 알고리즘에는 CCD 및 COD 문제를 해결하기 위한 거리 함수가 정의된다. 그리고 최소의 연산 시간으로 높은 공간 국부성을 갖는 클러스터들을 생성하기 위한 클러스터링 방법이 포함된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2059-2065
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• 2008

In this paper, quasi-static crushing tests of composite circular tubes under axial compression load are conducted to investigate the energy absorption characteristics. Circular tubes used for this experiment are glass/epoxy (GFRP) composite tubes, which is fabricated by the filament winding method. One edge of the composite tube is chamfered to reduce the initial peak load and to prevent catastrophic failure during crushing process. Two suggested trigger mechanisms for the composite tubes are investigated. Crushing modes are mainly affected by thickness/diameter ratio, and average crushing loads are mainly affected by their cross-sections. Energy absorption characteristics vary significantly as a function of the tube geometry, trigger mechanism, t/D ratio and the cross-sectional shape.

• 전자공학회논문지B
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• 제31B권6호
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• pp.91-103
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• 1994

As CAD systems are introduced in the filed of engineering design, the necessities for automatic drawing input are increased . In this paper, we propose a method for realizing automatic drawing input by separation of text regions and graphic regions, extraction of line vectors from graphic regions, and recognition of circular arcs and circles from line vectors. Sizes of isolated regions, on a drawing are used for separating text regions and graphic regions. Thinning and maximum allowable error method are used to extract line vectors. And geometric structures of line vectors are analyzed to recognize circular arcs and circles. By processing text regions and graphic regions separately, 30~40% of vector information can be reduced. Recognition of circular arcs and circles can increase the utilization of automatic drawing input function.

• 한국전문물리치료학회지
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• 제15권4호
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• pp.50-58
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• 2008

The purpose of this study was to investigate the effects of the task-oriented training according to the application time with the change of motor and cognition function. Focal ischemic brain injury was produced in Sprague-Dawley rats (20 rats, $250{\pm}50$ g) through middle cerebral artery occlusion (MCAo). Before MCAo induction, all rats were trained in treadmill training and Morris water maze training for 1 week. Then they were randomly divided into groups: Group I : MCAo induction ($n_1$=5), Grop II: the application for simple treadmill task training after. MCAo induction ($n_2$=5). Group III: the application for Morris water maze cognitive task training after MCAo induction ($n_3$=5). Group IV: the application for progressive treadmill task training and Morris water maze cognitive task training after MCAo induction ($n_4$=5). Modified limb placing tests (MLPTs) and motor tests (MTs) were performed to test motor function and then Morris water maze acquisition test (MWMAT) and Morris water maze retention test (MWMRT) were performed to test cognitive function. For MTs, there were significant interactions among the groups with the time (p<.001). Group IV showed the steeper increasing pattern than those in other Groups on the 7th and 14th day. For MLPTs, there were significant interactions among the groups with the time (p<.001). The scores in Group III. IV had showed the more decreasing pattern than those in Group I, II since the 7th day and 14th day. For MWMAT, there were significant interactions among the groups with the time (p<.001). Group II found the Quadrant circular platform showed the steeper decreasing pattern than that in Group I on the 9th, 10th, 11th and 12th day. Group III. IV found the quadrant circular platform showed the slower decreasing pattern than that in Group I, II, For MWMRT, there were significant differences among the four groups (p<.001). The time to dwell on quadrant circular platform in Group IV on the 13th day was the longest compared with other groups. These results suggested that the combined task training was very effective to improve the motor and cognition function for the rats affected on their focal ischemic brain injury.

• 한국산학기술학회논문지
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• 제20권5호
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• pp.530-537
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• 2019

본 논문에서는 시스템함수 및 변복조의 개념을 3차원 복원 문제에 적용하는 알고리즘을 제안한다. 시스템의 유일한 특성을 정의하는 시스템 함수 (또는 시스템 응답)를를 일반적인 신호처리 또는 제어시스템에서 결정하듯이, 본 논문에서는 적절한 입력과 출력신호를 선택한 다음 3차원 물체의 특성을 결정짓는 시스템 함수를 결정한다. 본 논문에서는 3차원 복원 문제를 두 가지 방법의 시스템 함수 문제로 풀어 나간다. 첫 번째 방법은 입력과 출력 신호를 각각 3차원 물체의 면에 투영된 원형 빛 패턴과 카메라(2차원 이미지 면)가 획득한 패턴이 투영된 3차원 물체의 이미지로 정의하여 3차원 물체의 특성을 나타내는 시스템 함수를 정의 하는 것이다. 두 번째 방법은 입력과 출력 신호를 각각 복원되어야 할 3차원 물체의 좌표와 카메라가 획득한 빛 패턴이 투영된 3차원 물체의 이미지로 정의하여 입력 신호를 추정하는 문제로 해석하는 것이다. 첫 번째 방법은 일반적인 입출력 함수의 비(ratio)로부터 시스템 함수를 구하는 것이고 두 번째 방법은 신호의 변조와 복조 과정으로부터 원래의 전송된 신호 (입력) 를 추정하는 것처럼 입력 신호인 3차원 물체의 좌표를 추정하는 것이다.

• 대한조선학회논문집
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• 제43권3호
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• pp.285-293
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• 2006

Three-dimensional and time-dependent solution for the fluid flow and heat transfer past a circular cylinder with fins is obtained using accurate and efficient spectral methods. A Fourier expansion with a corresponding uniform grid is used along the circumferential direction. A spectral multi-domain method with a corresponding Chebyshev collocation is used along r-z plane to handle fins attached to the surface of a circular cylinder. At the Reynolds number of 300 based on a cylinder diameter, results with fins are compared with those without fins in order to see the effects of the presence of fins on three-dimensional and unsteady fluid flow and heat transfer past a bluff body. The detail structures of fluid flow and temperature field are obtained as a function of time to investigate how the presence of fins changes heat transfer mechanism related to the vortical structure in the wake region.

• Advances in materials Research
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• 제5권4호
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• pp.299-318
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• 2016

Analytical investigations were performed of a longitudinal crack representing a cylindrical surface in circular shafts loaded in torsion with taking into account the non-linear material behavior. Both functionally graded and multilayered shafts were analyzed. It was assumed that the material is functionally graded in radial direction. The mechanical behavior of shafts was modeled by using non-linear constitutive relations between the shear stresses and shear strains. The fracture was studied in terms of the strain energy release rate. Within the framework of small strain approach, the strain energy release rate was derived in a function of the torsion moments in the cross-sections ahead and behind the crack front. The analytical approach developed was applied to study the fracture in a clamped circular shaft. In order to verify the solution derived, the strain energy release rate was determined also by considering the shaft complimentary strain energy. The effects were evaluated of material properties, crack location and material non-linearity on the fracture behavior. The results obtained can be applied for optimization of the shafts structure with respect to the fracture performance. It was shown that the approach developed in the present paper is very useful for studying the longitudinal fracture in circular shafts in torsion with considering the material non-linearity.

• Geomechanics and Engineering
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• 제22권1호
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• pp.11-23
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• 2020

In this study, a new analytical-numerical procedure is developed to give the stresses and strains around a circular tunnel in rock masses exhibiting different stress-strain behavior. The calculation starts from the tunnel wall and continues toward the unknown elastic-plastic boundary by a finite difference method in the annular discretized plastic zone. From the known stresses in the tunnel boundary, the strains are calculated using the elastic-plastic stiffness matrix in which three dimensional Hoek-Brown failure criterion (Jiang and Zhao 2015) and Mohr-Coulomb potential function with proper dilation angle (i.e., non-associated flow rule) are employed in terms of stress invariants. The illustrative examples give ground response curve and show correctness of the proposed approach. Finally, from the results of a great number of analyses, a simple relationship is presented to find out the closure of circular tunnel in terms of rock mass strength and tunnel depth. It can be valuable for the preliminary decision of tunnel support and for prediction of tunnel problems.

• Structural Engineering and Mechanics
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• 제64권5호
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• pp.591-610
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• 2017

This paper is concerned with the static analysis of variable thickness of two directional functionally graded porous materials (FGPM) circular plate resting on a gradient hybrid foundation (Horvath-Colasanti type) with friction force and subjected to compound mechanical loads (e.g., transverse, in-plane shear traction and concentrated force at the center of the plate).The governing state equations are derived in terms of displacements based on the 3D theory of elasticity, assuming the elastic coefficients of the plate material except the Poisson's ratio varying continuously throughout the thickness and radial directions according to an exponential function. These equations are solved semi-analytically by employing the state space method (SSM) and one-dimensional differential quadrature (DQ) rule to obtain the displacements and stress components of the FGPM plate. The effect of concentrated force at the center of the plate is approximated with the shear force, uniformly distributed over the inner boundary of a FGPM annular plate. In addition to verification study and convergence analysis, numerical results are displayed to show the effect of material heterogeneity indices, foundation stiffness coefficients, foundation gradient indices, loads ratio, thickness to radius ratio, compressibility, porosity and friction coefficient of the foundation on the static behavior of the plate. Finally, the responses of FG and FG porous material circular plates to compound mechanical loads are compared.

• 한국해양공학회지
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• 제27권5호
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• pp.51-62
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• 2013

The water wave interactions on any three-dimensional structure of arbitrary geometry can be calculated numerically through the use of source distribution or Green's function techniques. However, such a method can be computationally expensive. In the present study, the water wave interactions in floating circular cylinder arrays were investigated numerically using the eigenfunction expansion method with the three- dimensional potential theory to reduce the computational expense. The wave excitation force, added mass coefficient, radiation damping coefficient, and wave run-up are presented with the water wave interactions in an array of 5 or 9 cylinders. The effects of the number of cylinders and the spacing between them are examined because the water wave interactions in floating circular cylinder arrays are significantly dependent upon these.