• 한국공간구조학회논문집
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• 제13권1호
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• pp.87-96
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• 2013

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

• 대한수학회지
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• 제44권5호
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• pp.1093-1102
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• 2007

In this note we survey some recent results on symmetric space, and related topics like rigidity, flexibility and geometry-topology aspect of symmetric space, specially in the line of hyperbolic 3-manifolds.

• Smart Structures and Systems
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• 제11권4호
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• pp.411-433
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• 2013

Due to its easy operation and wide applicability, the ambient vibration method is commonly adopted to determine the cable force by first identifying the cable frequencies from the vibration signals. With given vibration length and flexural rigidity, an analytical or empirical formula is then used with these cable frequencies to calculate the cable force. It is, however, usually difficult to decide the two required parameters, especially the vibration length due to uncertain boundary constraints. To tackle this problem, a new concept of combining the modal frequencies and mode shape ratios is fully explored in this study for developing an accurate method merely based on ambient vibration measurements. A simply supported beam model with an axial tension is adopted and the effective vibration length of cable is then independently determined based on the mode shape ratios identified from the synchronized measurements. With the effective vibration length obtained and the identified modal frequencies, the cable force and flexural rigidity can then be solved using simple linear regression techniques. The feasibility and accuracy of the proposed method is extensively verified with demonstrative numerical examples and actual applications to different cable-stayed bridges. Furthermore, several important issues in engineering practice such as the number of sensors and selection of modes are also thoroughly investigated.

• 한국공간구조학회논문집
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• 제16권1호
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• pp.73-84
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• 2016

This study analyzes the four composition elements : profile, anchorage and connection, material and member rigidity, stability, as the main composition design elements of flexure structure systems, in order to explore possibilities for more various structure designs in architectures with flexure structure system. It also examines typical design methods that use the mentioned four composition elements. At the results, this research presents an understanding of the differences between funicular shape and non-funicular shape and mechanical features of the shapes in the profile element, regarding to the ratio of rise height to span length(f/l). Also, the typical design methods are presented for the designable usages of the hinge joints and the fix joints, and for the applications of member rigidity expressed by the index of the ratio of member depth to span length(d/l). And it was presented that connection styles, addition of brace members, placement of shear walls are the main design methods in the stability element. This data would be useful to architectural designs concerning integrated design with structures.

• 한국지반신소재학회논문집
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• 제19권3호
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• pp.23-33
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• 2020

대구경 현장타설말뚝의 경우 수평지지특성은 중요한 요소이며 이를 증가시키기 위한 방안은 말뚝의 인접지반을 개량하여 강성을 증가시키는 방법과 말뚝 자체의 강성을 증가시키는 방법이 있다. 이중 말뚝체에 케이싱을 보강하여 강성을 증가시키는 방법이 많이 제안되고 있는 추세이지만 이와 관련된 연구는 거의 이루어지지 않고 있는 실정이다. 따라서 본 연구에서는 지반조건에 따라 대구경 현장타설말뚝의 적정 케이싱 보강길이를 평가하기 위해 비선형해석을 이용하여 지반조건별로 케이싱 보강길이에 따른 수평지지특성을 연구하였다. 그 결과 대구경 현장타설말뚝의 수평지지특성은 케이싱 보강 길이비(κ)가 1.2인 경우 가장 효과적이며 지반조건에 따라서는 느슨한 지반일수록 큰 보강효과를 나타내었다.

• 대한수학회보
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• 제53권2호
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• pp.399-410
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• 2016

In this paper, we study the relations between the Thurston metric and the hyperbolic metric on a closed surface of genus $g{\geq}2$. We show a rigidity result which says if there is an inequality between the marked length spectra of these two metrics, then they are isotopic. We obtain some inequalities on length comparisons between these metrics. Besides, we show certain distance distortions under conformal graftings, with respect to the $Teichm{\ddot{u}}ller$ metric, the length spectrum metric and Thurston's asymmetric metrics.

• 한국안전학회지
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• 제35권5호
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• pp.9-14
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• 2020

In order to realize high strength and light weight for various industrial facilities and structural materials, various new materials are applied to product design. Among them, CFRP has excellent specific strength and non-rigidity, and the scope of use is expanding throughout the industry, such as mobility products and building materials. GFRP is cheaper than CFRP, and has excellent specific strength and non-rigidity, and has excellent heat resistance and sound insulation, so it has been adopted as a core material for flooring and interior flooring. CFRP of twill weave structure has better resistance to deformation of fiber than plain weave structure, so the outermost layer is applied as twill weave structure in product design. After fabrication with DCB specimens, Mode I fracture toughness was evaluated according to the crack length. As the crack length increases, the energy release rate and stress intensity factor values tended to decrease overall.

• Advances in nano research
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• 제8권3호
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• pp.229-244
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• 2020

In this paper, modified Kelvin's model has been used to analyze the orthotropic vibration frequencies of single walled carbon nanotubes with clamped-clamped and clamped-free boundary conditions. For this system the governing equation is developed with wave propagation approach. Armchair, zigzag and chiral structures are considered for the vibrational analysis to investigate the effect of different modes, in-plane rigidity and mass density per unit lateral area. Throughout the computations, on decreasing the length-to-diameter ratios, the frequencies of said structure increases. In addition, by increasing three different value of in-plane rigidity resulting frequencies also increase and frequencies decrease on increasing mass density per unit lateral area. The results generated using computer software MATLAB to furnish the evidence regarding applicability of present model and also verified by available published literature.

• 한국기계가공학회지
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• 제12권5호
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• pp.36-41
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• 2013

One of the problems in grinding process using a machining center(MC) with a small diametric wheels is machining error due to decrease of the quill diameter. In this study, side-cut grinding is performed with a vitrified bonded CBN wheel on the machining center. Grinding experiments are performed at various grinding conditions including quill length, quill diameter and depth of cut. The effect on the grinding force, machining error and surface roughness due to the change of the quill rigidity are investigated experimentally. The slenderness ratio of the quill is significant factor to analyse the change of the grinding force and machining error.

• 폴리머
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• 제35권5호
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• pp.385-389
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• 2011

러빙공정에서는 러빙 시 공정변수와 배향막의 특성 그리고 러빙포의 물성이 중요한 변수로 작용한다. 이러한 변수들은 러빙밀도(rubbing density)와 러빙력(rubbing force)에 의해서 결정되는 러빙된 정도(크기)를 통하여 배향막의 배향성에 영향을 미치게 된다. 본 연구에서는 러빙 변수 중 러빙포의 물성이 러빙밀도(길이)와 러빙력에 미치는 영향에 대하여 알아보기 위하여 다른 물성(파일 밀도, 강직도)을 가지는 러빙포를 이용하여 러빙효과(정도)를 분석하였다. 러빙포의 파일 밀도가 커지고 강직도가 강할수록 러빙된 배향막의 이방성과 표면조도가 커졌으나 러빙효과의 형태는 서로 달랐다. 러빙포의 파일밀도는 러빙에 관여하는 파일의 수와 밀접한 관련이 되어 있어 러빙하는 밀도(길이) 영향을 미치지만 강직도는 러빙밀도(길이)보다는 러빙력과 보다 밀접하게 관련성이 있었다.