• 한국공간구조학회논문집
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• 제14권4호
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• pp.55-64
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• 2014

In this study, Intersecting Tensegrity System that is integrated solid compression members with tension members was presented. This system is set up by connecting upper and lower compression members of pyramid shape with exterior tension members. In this system, the solid compression members are intersected each other and connected by a tension member in the center. This system is a variation of Tensegrity system, has a improved feature that the system is able to induce prestresses in all of tension members easily by adjusting the distance of a tension member in the center. The proposed system was studied by modeling, and the structural behavior of the system was investigated by mechanical analysis of the model. Furthermore, the features of the structural behavior variations was investigated when the composition elements(total height, size of surface, intersection length, etc.) are changed variously. It was also showed that the system is able to be used as a temporary space structure system with a membrane roof of inverse conical shape.

• Journal of Advanced Marine Engineering and Technology
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• 제21권4호
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• pp.381-386
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• 1997

The offsetting method using geometric properties of B-spline control polygon is more faster than using of general normal vector in offset processing. But this method itself does not solve the prob¬lems of loop removal in normal offsetting. Generally the distance between neighborhood spans of B-spline control polygon is greater than the offset distance, the loops are occurred in offsetting. For generating of the more precision tool-path in NC machining, the loops of offset must be removed. In this paper, two methods for loop removal are introduced in offsetting of B-spline curve. One is using the intersection of B-spline control span which being occurred of the loop. The other is using two B-spline curve divisions divided from original B-spline curve or its offset curve. After the inter¬section point of loop was searched, the loop being removed to cusp. Also the method for filleting of cusp is inspected to more precision cutting. It is shown that the offsetting using B-spline control polygon is more effective in the sculptured surface machining.

• 대한전자공학회논문지
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• 제27권2호
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• pp.151-157
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• 1990

본 논문에서는 CSG 방식으로 나타내어진 3차원 입체를 신속하게 외형선 표시방식으로 그려줄 수 있는 방법을 제안한다. 두 개의 CSG 트리가 하나로 결합될때, 각 종속 트리에 해당하는 입체를 구성하는 다각형들간의 교차 부분을 계산하여 주어진 결합 연산자에 따라 합성 입체의 경계선 표현을 얻어내고, 이를 트리의 루트노드에 저장한다. 루트 노드에 저장된 경계선 표현은 입체를 외형선 표시방식으로 그려주는 부분과 다음 경계선 표현 계산에서 사용된다. 자유 곡면을 모델링하기 위하여 Bezier 곡면을 기본 입체의 하나로 취급하였고, 설계된 입체에 대한 실제적인 영상을 얻기 위하여 scan-line 알고리듬을 사용하였는데, 이 방식에서는 각 scan-line을 다각형들이 교차하지 않는 구간들로 나누고, 입체의 CSG 표현을 이용하여 각 구간을 묘화한다.

• 제어로봇시스템학회논문지
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• 제16권3호
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• pp.277-285
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• 2010

This paper describes an approach to analyze geometrical information of building images for understanding outdoor environment of autonomous navigation robot. Line segments and color information are used to classily a building with the other objects such as sky, trees, and roads. The line segments and their two neighboring regions are extracted from detected edges in image. The model of line segment (MLS) consists of color information of neighbor regions. This model rules out the line segments of non-building face. A building face converges into dominant vanishing points (DVPs) which include one vertical point and one of five horizontal points in maximum. The intersection of vertical and horizontal lines creates a facet of building. The geometrical characteristics such as the center coordinates, area, aspect ratio and aligned coexistence are used for extracting the windows in the building facet. In experiments, 150 building faces and 1607 windows were detected from the database of outdoor environment. We found that this result shows 94.46% detection rate. These experimental images were all taken in Ulsan metropolitan city in Korea under difference of viewpoints, daytime, camera system and weather condition.

• Steel and Composite Structures
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• 제18권3호
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• pp.739-756
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• 2015

This paper presents investigations on the hysteretic behavior of concrete-filled circular tubular (CFCT) T-joints subjected to axial cyclic loading at brace end. In the experimental study, four specimens are fabricated and tested. The chord members of the tested specimens are filled with concrete along their full length and the braces are hollow section. Failure modes and load-displacement hysteretic curves of all the specimens obtained from experimental tests are given and discussed. Some indicators, in terms of stiffness deterioration, strength deterioration, ductility and energy dissipation, are analyzed to assess the seismic performance of CFCT joints. Test results indicate that the failures are primarily caused by crack cutting through the chord wall, convex deformation on the chord surface near brace/chord intersection and crushing of the core concrete. Hysteretic curves of all the specimens are plump, and no obvious pinching phenomenon is found. The energy dissipation result shows that the inelastic deformation is the main energy dissipation mechanism. It is also found from experimental results that the CFCT joints show clear and steady stiffness deterioration with the increase of displacement after yielding. However, all the specimens do not perform significant strength deterioration before failure. The effect of joint geometric parameters ${\beta}$ and ${\gamma}$ of the four specimens on hysteretic performance is also discussed.

• Computers and Concrete
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• 제25권2호
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• pp.181-192
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• 2020

Nowadays, steel fiber reinforced concretes (SFRCs) are widely used in practical applications. Significant experimental research has thus been carried out to determine the constitutive equations that represent the behavior of SFRCs under multiaxial loadings. However, numerical modelling of SFRCs via FEM has been challenging due to the complexities of the implementation of these constitutive equations. In this study, following the literature, a plasticity model is constructed for the behavior of SFRCs that involves the Willam-Warnke failure surface with the relevant evolution laws and a non-associated flow rule for determining the plastic deformations. For the precise (yet rapid) integration of the constitutive equations, an explicit substepping scheme consisting of yield intersection and drift correction algorithms is employed and thus implemented in ABAQUS via UMAT. The FEM model includes various material parameters that are determined from the experimental data. Three sets of parameters are used in the numerical simulations. While the first set is from the experiments that are conducted in this study on SFRC specimens with various contents of steel fibers, the other two sets are from the experiments reported in the literature. The response of SFRCs under multiaxial compression obtained from various numerical simulations are compared with the experimental data. The good agreement between numerical results and the experimental data indicates that not only the adopted plasticity model represents the behavior of SFRCs very well but also the implemented integration scheme can be employed in practical applications of SFRCs.

• 열처리공학회지
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• 제34권3호
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• pp.116-121
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• 2021

This study was carried out to investigate the effect of transformation induced martensite on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy. α' and ε-martensite were formed by cold rolling, and these martensite were formed with according to the specific direction, surface relief and partially intersection. With an increasing degree of cold rolling, amount of α'-martensite was slowly increased, whereas amount of ε-martensite was rapidly increased. Volume fraction of ε-martensite formed by cold working was large than α'-martensite. Tensile strength was rapidly increase and elongation was rapidly decreased with an increasing of degree of cold rolling. This means that tensile strengh and elongation was greatly influenced by the volume fraction of ε-martensite formed by cold rolling then α'-martensite.

• International Journal of Precision Engineering and Manufacturing
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• 제8권3호
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• pp.64-70
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• 2007

Of all the rapid tooling (RT) methods currently available, thick-layer laminated tooling is the most suitable for large-scale, low-cost dies and molds. Currently, the determination of a lamina's contour or profile and the associated slicing algorithms are based on existing rapid prototyping (RP) data manipulation technology. This paper presents a new adaptive slicing algorithm developed exclusively for profiled edge laminae (PEL) tooling PEL tooling is a thick-layer RT technique that involves the assembly of an array of laminae, whose top edges are simultaneously profiled and beveled using a line-of-sight cutting method based on a CAD model of the intended tool surface. The cutting profiles are based on the intersection curve obtained directly from the CAD model to ensure geometrical accuracy. The slicing algorithm determines the lamina thicknesses that minimize the dimensional error using a new tool shape error index. At the same time, the algorithm considers the available lamination thicknesses and desired lamina interface locations. We demonstrate the new slicing algorithm by developing a simple industrial PEL tool based on a CAD part shape.

• 분석과학
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• 제11권3호
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• pp.151-155
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• 1998

100 mM NaCl+27 mM $MgCl_2$ 용액에서, 도데실황산나트륨 (SDS)의 유무에 따른 1.0 mM 메틸비올로겐 ($MV^{2+}$)의 전기화학적 거동을 연구하였다. ${\Delta}E_p$(산화와 환원 봉우리전위 값의 차이) 대 - log[SDS]로 도시한 그림에서 두 선의 교차점을 임계미셀농도 (CMC)로 결정하였다. $Mg^{2+}$가 첨가되면, 유리탄소전극에 대한 효과적인 $MV{\cdot}^+$의 접근이 가능해지고 미셀형성도 지연되었다.

• 한국수산과학회지
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• 제29권3호
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• pp.332-344
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• 1996

본 연구는 대마난류의 주류역인 동해 남부해역의 포항 연안의 6개 정점에서 1994년 4월 26일부터 29일까지 수층별로 채수하고, 이 해역에서 $^{210}Po$와 $^{234}Th$의 제거속도 혹은 체류시간과 제거과정을 알아보았다. $^{210}Po$는 대체적으로 연안쪽 정점들에서는 표면혼합층에서 낮고 수온약층을 포함한 하부층에서 다소 높지만, 바깥쪽 정점들에서는 표면혼합층에서 오히려 높아지는 경향을 보였다. 그러나 $^{210}Pb$는 수심이 깊어짐에 따라 점차 감소하는 경향을 보였다. 또한, 표면 혼합층에서는 대체적으로 $^{210}Po$가 어미핵종보다 부족량을 보이나, 수온약층을 포함한 하부층에서는 어미핵종과 거의 방사평형된 농도를 보이거나 약간의 과잉량을 보였다. $^{210}Pb$는 표면혼합층에서는 어미핵종인 $^{226}Ra$보다 과잉량을 보이나, 수온약층을 포함한 하부층에서는 약간 부족량을 보이거나 혹은 거의 방사평형된 농도를 보인다. $^{234}Th$는 표면혼합층과 수온약층이 그 하부층보다 현저히 낮다. $^{210}Po$의 체류시간은 $1\~4$년의 범위로 비교적 연안쪽의 정점들 (E3, E4, E5)이 바깥쪽에 위치한 정점들(E6, E7)보다 짧았다. 그러나 정점 E8에서는 약 10년으로 매우 길었으며, 이는 다른 정점들에 비해 표면혼합층이 두꺼운 관계로 하부 표면혼합층에서 재순환된 $^{210}Po$가 수직혼합되었기 때문일 것이다. 한편, $^{234}Th$의 체류시간은 $52\~74$일의 범위로 정점별 차이가 그다지 크지 않았으며, $^{210}Po$의 체류시간에 비해서 훨씬 짧았다. 표면혼합층 내에서 해수중 $^{234}Th$는 용존태의 수층별 제거속도상수가 총부유물질과 정의 상관성을 나타내는 것으로 보아 주로 비생물기원의 무기입자에 흡착되어 제거되고 있는 반면에, $^{210}Po$는 용존태의 제거 속도상수가 클로로필 $^{210}Po$와 정의 상관성을 나타내는 것으로 보아 주로 생물체 (주로 동${\cdot}$식물플랑크톤)에 흡수되어 제거되고 입자물질 농도에는 크게 영향을 받지 않는 것 같다.