• Journal of Korean Association for Spatial Structures
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• v.11 no.2
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• pp.71-79
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• 2011

Due to the self-equilibrium status of the cable system, the loss of the tensioning in the cable system results in other cables carrying larger tension forces than those initially calculated by structural engineers. Also, turn-buckle systems, which have been widely used to pre-tension and/or re-tension the cables, are limited to use for small cables and to provide a rough estimation for tension forces. In this study, the re-tensioning cable connection systems were developed to overcome the problems mentioned above. The main objective of the proposed system is to re-tension large cables and measure the exact amount of tension forces of the cable systems. This connection system is also combined with the wireless signal monitoring module so that engineers are able to measure the tension forces any place where the internet is available. This paper presents the development of the re-tensioning cable connection systems and experiment using the real-scale cable systems to verify the fe-tensioning and signal monitoring systems.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.345-360
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• 2002

This study was for analysing the sedimentary rock slope stability and providing the reinforcement method that can heighten stability. The study area consists of Cretaceous basalt or basaltic tuff belonging to Hak-Bong Basalt Formation in Ha-Yang Group. Nature of geological structure confirmed in this area ars bedding, joint and fault. Majority of geological structure that affect most relationship rock slope stability is bedding. It is shown that dip direction is 120~160/15~25. In other structure, joint sets are shown that dip direction of set 1 is 310~330/65~85 and set 2 is 230~250/70~85. Joint set 3 shows above 85$^{\circ}$ high angle on NE trend although do not show clear. Stability analysis about rock slope used kinematic analysis, limit equilibrium method and FLAC by numerical analysis method. FLAC is continuum model that use Fintie Defferentce Method, but could use Interfaces Module and get discrete model's analysis effect such as UDEC.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.517-524
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• 2012

In this study, the effects of the inelastic shear behavior of beam-column joint and the vertical distribution of lateral load are evaluated considering higher modes on the response of RC OMRF using the pushover analysis. A structure used for the analysis was a 5-story structure located at site class SB and seismic design category C, which was designed in accordance with KBC2009. Bending moment-curvature relationship for beam and column was identified using fiber model. Also, bending moment-rotation relationship for beam-column joint was calculated using simple and unified joint shear behavior model and moment equilibrium relationship for the joint. The results of pushover analysis showed that, although the rigid beam-column joint overestimated the stiffness and strength of the structure, the inelastic shear behavior of beam-column joint could be neglected in the process of structural design since the average response modification factor satisfied the criteria of KBC2009 for RC OMRF independent to inelastic behavior of joint.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.937-942
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• 2007

A new, systematic, simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple impedance matching among antenna components: i.e., transition, feed, and antenna. This new antenna design is possible due to the newly developed ultra-wideband transition. As design examples, wideband quasi-Yagi antennas are successfully designed and implemented in Ku- and Ka-bands with frequency bandwidths of 53.2% and 29.1%, and antenna gains of $4{\sim}5 dBi$ and $ 5{\sim}5.6 dBi$, respectively. The design method can be applied to other balanced antennas and their arrays.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.161-161
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• 2014

열플라즈마는 주로 아크 방전에 의해 발생시킨 전자, 이온, 중성입자(원자 및 분자)로 구성된 부분 이온화된 기체로, 국소열평형상태를 유지하여 구성입자가 모두 수천에서 수만도에 이르는 같은 온도를 갖는 고속의 제트 화염 형태를 이루고 있다. 이렇게 고온, 고열용량, 고속, 다량의 활성입자를 갖는 열플라즈마의 특성을 이용하여, 종래 기술에서는 얻을 수 없는 다양하고 효율적인 산업적 이용이 활발히 진행되고 있다. 용사코팅은 노즐 출구를 통해서 외부로 방출되는 열 플라즈마 화염을 이용하는 것으로 이 화염의 와류 특성으로 인하여 외기의 가스가 화염내부로 침투하는 특성을 가진다. 이러한 현상은 열원의 냉각효과 외에도 외기를 구성하는 기체 분자의 내부 유입을 의미하는 것으로 대기 상태에서 공정이 이루어진다면 열원 내로 유입되는 대기 내의 산소가 모재 표면과 반응하여 산화가 진행된다. 이러한 산화과정은 용사 코팅의 품질을 저하시키는 요인이 되므로, W, Ti 등과 같은 반응성이 높은 재료의 코팅은 산화과정을 방지하기 위하여 진공에서 코팅을 하여야만 한다. 진공 플라즈마용사코팅은 진공 또는 저압의 불활성 분위기 중에서 열플라즈마 화염에 용사재료를 투입하여 플라즈마 화염 내부에서 순간적으로 이를 용융시킨 후 고속으로 분출, 모재에 적층시키는 코팅공정이다. 이때 분말상의 용사재료를 고속으로 화염 중심에 투입하여 최대 에너지 전달이 이루어지도록 하는 것이 적층효율 및 코팅품질을 향상에 필수적이다. 하지만 플라즈마 화염 내부를 고속으로 이동하는 입자의 온도와 속도 및 궤적을 측정하여 제어하는 것은 매우 어렵기 때문에, 통상 형성된 코팅의 구조와 두께로부터 경험적으로 파라미터를 결정하는 것이 일반적이다. 본 연구에서는 초고속 레이저 카메라와 이미지 분석용 소프트웨어를 이용하여 플라즈마 화염내의 비행입자 궤적을 추적하고, 이를 통해 분말 이송가스의 유량이 코팅 효율 및 미세구조에 미치는 영향을 조사하였다. 플라즈마 화염은 중심부가 가장 높은 온도와 속도를 가지고 있기 때문에, 분말 이송가스의 유량이 적을 경우 투입된 분말은 단지 플라즈마 화염의 상부 경계면을 지나는 궤적을 갖게된다. 이로 인해 분말의 용융이 충분히 이루어지지 않아 적층 효율이 낮고 미용융 입자 및 기공이 많은 미세구조를 보였다. 이송가스 유량을 증가시키게 되면, 분말의 궤적은 플라즈마 화염의 중심부를 지나게 되어 적층 효율이 증가하고 미세구조 또한 개선되었다. 하지만 이송가스 유량이 지나치게 클 경우, 투입된 분말 입자는 플라즈마 화염을 조기에 관통하게 되어 비행궤적은 온도와 속도가 낮은 영역에 형성되었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.35-43
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• 2017

The minimum reinforcement ratio is an important design factor to prevent a brittle failure in RC flexural members. A minimum reinforcement ratio is presented by assuming an effective depth of cross-section and moment arm lever in CDC and KHBDC. In this study, it suggests that a rational method for minimum reinforcement ratio is calculated by material model and force equilibrium. As results, a minimum reinforcement ratio using a p-r curve in KHBDC is evaluated about 52~80% of recent design code's value and it induces an economical design. And also, a ductility capacity in case of placing this minimum reinforcement amount is evaluated about 89% of recent design code's value, but ductility in a member is 7 or more, so it has a sufficient ductility capacity. Therefore, it is judged that a minimum reinforcement ratio using p-r curve has a theoretical rationality, safety and economy in a flexural member design.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.61-66
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• 2005

In order to make submicron cell for spin-injection device, lift-off method using Pt stencil and wet etching was chosen. This approach allows batch fabrication of stencil substrate with electron-beam lithography. It simplifies the process between magnetic film stack deposition and final device testing, thus enabling rapid turnaround in sample fabrication. Submicron junctions with size of $200nm{\times}300nm$ and $500nm{\times}500nm$ 500 nm and pseudo spin valve structure of $CoFe(30{\AA})/Cu(100{\AA})/CoFe(120{\AA}$) was deposited into the nanojunctions. MR ratio was 0.8 and $1.1{\%}$, respectively and spin transfer effect was confirmed with critical current of $7.65{\times}10^7A/cm^2$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.53-60
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• 2016

This study discusses the thermal insulation capacity of variant of NO96 LNG (liquefied natural gas) cargo containment insulation system. Changing the insulation materials and the insulation layers of conventional GTT NO96 containment system, The thermal resistance and BOR(boil off rate) caused by the heat transfer between cryogenic and environmental temperature is discussed. Therefore, thermal analysis of LNG CCS(cargo containment system) is carried out to determine the insulation capabilities. Also, BOR is evaluated in terms of the total amount of heat invaded into CCS(cargo containment system). Variant of NO96 CCS such as NO96, NO96GW and NO96L3 membrane type during laden voyage is selected for the comparative study. Finite element model for heat transfer analysis is conducted by employing the equivalent thermal resistance model to simplify the complex insulation layers. Finally the results for each variant model are relatively compared and discussed to minimize the BOR.

• Computational Structural Engineering
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• v.10 no.4
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• pp.315-325
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• 1997

This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.307-314
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• 2009

The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.