• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.309-314
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• 2014

The structural layout of mechanical and civil structures is commonly obtained using conventional methods. For example, the shape of structures such as electric transmission towers and offshore substructures can be generated systematically. However, with rapid advancements in computer graphic technology, advanced structural analyses and optimum design technologies have been implemented. In this study, the structural shape of a jacket substructure for an offshore wind turbine is investigated using a topology optimization technique. The structure is subjected to multiple loads that are intended to simulate the loading conditions during actual operation. The optimization objective function is defined as one that ensures compliance of the structure under the given boundary conditions. Optimization is carried out with constraints on the natural frequency in addition to the volume constraint. The result of a first step model provides quick insights into the optimum layout for the second step structure. Subsequently, a 3D model in the form of the frustum of a quadrilateral pyramid is developed through topology optimization.

• Journal of Korean Association for Spatial Structures
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• v.8 no.6
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• pp.49-57
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• 2008

The seismic isolation systems could be used to reduce the seismic response of a structure. The natural period of a structure with seismic isolation system got be long to avoid the prominent seismic period. The purpose of this study is to analyzed the seismic behavior of the truss arch that is supported to column with LRB. Truss arch structures subjected to horizontal seismic have large horizontal and vertical response unlike seismic behavior of normal rahmen structures. When seismic load is applied to the truss arch with isolation systems, the horizontal acceleration response of the truss arch is reduced and the vertical seismic response is remarkably reduced. Also, the seismic behaviors of the truss arch with strengthen column as like lattice column are very similar to that of the truss arch supported to directly foundation. The Seismic Isolation system can be applied to reduce efficiently the seismic response of the spacial structure with not strong column.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.2
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• pp.96-103
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• 2015

Purpose: The purpose of this study was to spectrophotometrically evaluate the influence of porcelain layer thickness and substructure. Materials and Methods: Four groups of porcelain specimens (metal and ceramic substructure) was prepared for analysis. Color parameters were measured with spectrophotometer and color difference (${\Delta}E*$) were calculated. T-test and one-way ANOVA test were used to find out significant difference and Tukey test was used to identify where the difference ware. Results: Increasing the thickness of porcelain decreased values (P < 0.05). Increasing the thickness of porcelain on ceramic substructure decreased the $a^*$ (P < 0.05) but, the $b^*$ were not statistically different. Total color difference (${\Delta}E*$) were below 1 when the difference of porcelain thickness were 0.5 mm. Conclusion: The thickness of porcelain are the factor effecting on color. This study will help the color are controlled by changing the thickness of porcelain clinically.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.199-211
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• 2009

Development of underground space is actively performed globally for better life in the surface, and the scale of the space is increasing. Extreme care should be taken in the construction of the underground space in urban areas in order to avoid damage of adjacent structures and interference with existing underground space. In case of shallow tunnels, reinforcement of ground and structures is necessary to minimize the damage to structures due to excavation but any standard for optimum range of the reinforcement has not been established yet. In this paper, a series of numerical analyses have been performed for a 20 m diameter tunnel excavated underneath a structure to investigate the degree of damage of the structure according to vertical and horizontal spacing between the tunnel and structure. In addition to that, optimum range of reinforcement is presented for each case where reinforcement is required. It has been observed that the reinforcement is necessary for the ground condition adapted in the analyses as follows: (1) if horizontal spacing ($S_{H}$) approaches to 0D (D: equivalent diameter of tunnel) for vertical spacing (Sv) of 0.5D, and (2) if tunnel exists underneath the structure for vertical spacing (Sv) of 0.75D. The reinforcement is not necessary for Sv of 10 regardless of $S_{H}$. It also has been obtained that the optimum ranges of the reinforcement around structure foundation are 7 m in depth and whole width of the structure and 5 m beyond tunnel sidewall. These reinforcememt ranges have been confirmed to be enough for stability of the structure if types of reinforcement method is appropriately selected.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4329-4335
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• 2014

This study examined the effects of the shear bond strength when the surface condition of the metal and zirconia, each being the lower structures, was different when determining the bond strength (metal group) of the metal lower structure with upper ceramics, and the shear bond strength (zirconia group) of zirconia lower structure with the upper ceramics in prosthetic appliances of metal-ceramic crown and zirconia-ceramic crowns. The metal groups were divided into a total of four groups: the group with no condition on the metal surface(NM), the group with sand-blasting(SM), the group with applied opaque ceramics(OM), and the group with applied opaque ceramics and sand-blasting(SOM). The zirconia groups were also separated into four groups: the group with no condition(NZ), the group with sand-blasting(SZ), the group treated with ZirLiner on the zirconia surface(LZ), and the group applied with ZirLiner along and sand-blasting(SLZ). To examine the effects on the shear bond strength according to the surface condition of each of the four metal and zirconia groups, SPSS was used to conduct one-way ANOVA. For metal-ceramic crowns, it would be best to apply opaque ceramics after sand-blasting on the surface of the metal, the lower structure. For zirconia-ceramic crowns, it is recommended to apply the ZirLiner after sand-blasting on the surface of zirconia, the lower structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.107-115
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• 2011

In this study, the vibration analysis of the underground box structures induced train movement is studied. In order to perform these analysis, dynamic data, which was measured when subway is in service, are gained by attaching accelerometers on the structure such as lower beam, lateral wall and upper slab. Also, accelerometers are attached on the lower beams and side walls of the gravel ballast and concrete ballast sections in order to compare vibration due to ballast materials. The vibration results of upper slabs and lower beams reveal that the vibration on the upper slabs is greater than the lower beams. Also, the results of the crack gauge on the upper slab show that crack width dose not change due to vibration, These means that the effect of the vibration on the structure is very limited. In order to evaluate the vibration of the structure, acceleration unit is converted to velocity unit comparing with the existing velocity data gained from the platforms.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.33-44
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• 2023

Wind power is one of the most efficient and reliable energy sources in the transition to a low-carbon society. In particular, offshore wind power provides a high-quality and stable wind resource compared to onshore wind power while both present a higher installed capacity than other renewables. In this paper, we present our new program, the X-WIND program well suitable for the assessment of the substructure of offshore wind turbines. We have developed this program to increase the usability of analysis programs for offshore wind energy substructures by addressing the shortcomings of existing programs. Unlike the existing programs which cannot solely perform the substructure analyses or lack pre-post processors, our X-WIND program can complete the assessment analysis for the offshore wind turbines alone. The X-WIND program is embedded in AutoCAD so that both design and analysis are performed on a single platform. This also performs static and dynamic analysis for wind, wave, and current loads, essential for offshore wind power structures, and includes pre/post processors for designs, mesh developments, graph plotting, and code checking. With this expertise, our program enhances the usability of analysis programs for offshore wind energy substructures, promoting convenience and efficiency.

• Magazine of the Korea Concrete Institute
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• v.14 no.5
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• pp.15-20
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• 2002

갱폼이라 함은 주로 고층 아파트에서와 같이 평면상 상ㆍ하부 동일 단면 구조물에서 외부벽체 거푸집과 거푸집 설치ㆍ해체작업 및 미장ㆍ치장(견출) 작업발판용 케이지(cage)를 일체로 제작하여 사용하는 대형 거푸집을 말한다. 여기서 케이지는 갱폼에서 외부벽체 거푸집 부분을 제외한 부분으로 거푸집 설치ㆍ해체작업, 후속 미장, 치장(견출) 등 작업을 안전하게 수행하는데 필요한 작업발판, 안전난간 등으로 구성되어 갱폼 거푸집에 결합된 부분이며, 상부 케이지는 갱품 케이지의 4단 작업발판 중 거푸집 설치ㆍ해체작업용으로 사용되는 상부 2단 작업발판 구성 부분이고, 하부 케이지는 미장ㆍ치장(견출) 작업용으로 사용되는 하부 2단 작업발판 구성 부분을 말한다.(중략)

• Journal of Energy Engineering
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• v.20 no.2
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• pp.143-153
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• 2011

Offshore wind power(OWP) is one of the most promising renewable energy and gives higher output than onland one due to stronger and consistent wind in offshore. it offsets shortcoming of noise, spatial limit and less affects scenery, and can be built in larger size. Korea has plenty of offshore wind resources as it is surrounded by the sea in three directions. This review describes recent progress in offshore wind turbine and substructure technology. Market trend in local and overseas, Number of papers published and patents registered are analysed.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.83-90
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• 2009

The previous studies for dynamic behavior of spatial structure have been zoomed in on roof structure by numerical analytic method. But the roof structure of real spatial structures is supported by lower structure as column and wall. So, when earthquake is occurred, it is predicted that dynamic behavior of roof structure is affected by lower structure. Therefore, on this study, natural period characteristics of arch structures are analyzed according to section, length and the modulus of elasticity of brass column and polycarbonate column and additional mass of roof structure by the scale-down model of arch structure as the most simple structure of spatial structures. The changes of natural periods are generally alike. But, when Polycarbonate column is connected to roof structure, the change of natural period for change of section is relatively large. That means that change of section and section and length of column and additional mass of roof structure have less influence on change of stiffness because the modulus of elasticity of brass is relatively large.