• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.769-776
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• 2013

The dynamic compliance characteristics of a prosthetic foot midgait are very important for natural performance in an amputee's gait and should be in a range that provides natural, stable walking. In this study, finite element analysis (FEA) and classical laminate theory were used to examine the mechanical characteristics of a carbon-epoxy composite laminate prosthetic foot as a function of variation in the lamination composition. From this analysis, an FEM model of a prosthetic keel, made from the composite material, was developed. The lamination composition of the keel was designed for improved stiffness. The prototype product was fabricated using an autoclave. Vertical loading response tests were performed to verify the simulation model. The results of the experiments were similar to those from simulations below the loading level of the gait, suggesting use of the proposed simulation model for prosthetic keel design.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.293-304
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• 1996

The Wolchul Mt. area is composed of a biotite granite and a pink feldspar granite. These granites are distinctly different in terms of their field occurrence, mineralogy, trace element and REE composition, as well as their isotope ages. The biotite granite has higher ferromagnesian elements and lower lithophile trace element abundances than the pink feldspar granite. The biotite granite has high Sr and Ba while the pink feldspar granite has high Rb. On the Rb-Sr-Ba diagram the biotite granite plots as a granodiorite while the pink feldspar granite belongs to a strongly differentiated granite. The ${\Sigma}$ LREE/ ${\Sigma}$ REE for the biotite granite is 0.95 and for the pink feldspar granite it is 0.88. The ratio shows a steep decrese in LREE while HREE is essentially constant. Based on the Eu/Sm, $[La/Lu]_{cN}$ and low Eu(-), the biotite granite has quartz diorite to granodiorite composition while the pink feldspar granite, with a relatively high Eu(-) anomaly, falls into the monzo- to syenogranite classification. The silica vs. trace element diagrams for the two granites indicate that the biotite granite could have formed near to a continental margin or volcanic island setting environment while the pink feldspar granite formed within a continental plate or as result of plate collision. The biotite granite has a U-Pb zircon age of 175 Ma, i.e. Middle Jurassic. The pink feldspar granite is younger, it has a K-Ar orthoclase age $93.6{\pm}1.5$ Ma which is Late Cretaceous age.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.1-8
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• 2020

Mobile elevating work platforms (MEWPs) consist of a work platform, extending structure, and chassis, and are used to move persons to working positions. MEWPs are useful but are composed of pieces of equipment, and accidents do occur owing to equipment defects. Among these defects, accidents caused by the fracture of bolts fixed to the extension structure and swing system are increasing. This paper presents a failure analysis of the fixing bolts of MEWP. Standard procedure for failure analysis was employed in this investigation. Visual inspection, chemical analysis, tensile strength measurement, microstructural characterization, fractography analysis by Optical Microscope(OM) and Scanning Electron Microscopy(SEM), and finite element analysis (FEA) were used to analyze the failure of the fixing bolts. Using this failure analysis approach, we found the root cause of failure and proposed a means for solving this type of failure in the future. First, the chemical composition of the fixing bolt is obtained by a spectroscopy chemical analysis method, which determined that the chemical composition matched the required standard. The tensile test showed that the tensile and yield strengths were within the required capacity. The stress analysis was carried out at five different boom angles, and it was determined that the fixing bolt of MEWP can withstand the loads at all the boom angles. The outcomes of the fatigue analysis revealed that the fixing bolt fails before reaching the design requirements. The results of the fatigue analysis showed primarily that the failure of the fixing bolt was due to fatigue. A visual inspection of the fractured section of the fixing bolt also confirmed the fatigue failure. We propose a method to prevent failure of the fixing bolt of the MEWP from four different standpoints: the manufacturer, safety certification authority, safety inspection agency, and owner.

• Journal of the Korea Convergence Society
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• v.12 no.11
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• pp.329-334
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• 2021

This thesis examined the characteristics of constructivism that brought about expanded expression of modern jewelry, and also organized how the constructivism was utilized for jewelry. The objective of this study is to examine the attempts of new materials based on constructivism and various expression styles, and also to understand the concept of constructivism developed into an element of complex formative expression. For this, this study organized the characteristics of constructivism that was initially expanded from Bau Haus in the aspect of expression through the composition of material and space, and also analyzed the jewelry artists' methods and attempts to express various materials. As a result, the constructivism showed the expansion of the formativeness of jewelry in the formative aspect of steric expression and in-depth concept through the composition of architectural pattern, visualization of space, and use of other materials, which becomes an example of basic formative element of modern jewelry design. However, it is limited to the material formative element of constructivism, so the expansion of design would be needed. Thus, there should be more researches on the expansion of various jewelry designs that could express the philosophy of constructivism.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.301-310
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• 2003

In order to design accurately sand compaction pile (SCP) method with low replacement area ratio, it is important to understand the mechanical interaction between sand piles and clays and its mechanism during consolidation process of the composition ground. In this paper, a series of numerical analyses on composition ground improved by SCP with low replacement area ratio were carried out, in order to investigate the mechanical interaction between sand piles and clays. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of composition ground improved by SCP. And, through the results of the numerical analyses, each mechanical behavior of sand piles and clays in the composition ground during consolidation was elucidated, together with stress sharing mechanism between sand piles and clays.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.9
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• pp.109-117
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• 2019

Since 'Hanok Expanse Support' has been started in Seoul, its target was expanded from renovation to new construction and from 'Hanok District' to all area in Seoul. The newly built hanok with Hanok Expanse Support had to follow the standards about the form of the hanok and adapt to modern lifestyle. However, the newly built hanok were planned with 'kan' since it retained the traditional wooden structure. So their composition of kan were considered to be influenced by the standards of each district and modern lifestyle. Therefore the aim of this study is to understand the architectural characteristics of newly built hanok in Seoul since 2000 focusing on the kan composition. Because of the differences in site conditions and the district unit plan, newly built hanok in Hanok District have more limited changes than Other District. However, kan is composed variously in horizontal and vertical ways to make the most space according to site conditions and most of the newly built hanok have opened courtyard rather than closed courtyard layout. With kan composition in various directions and kan added under the eaves, kan is highlighted in form. On the other hand, the composition of kan as an interior spatial element has changed and weakened because the lifestyle has changed compared to the traditional hanok and the 20th century urban hanok. Also the regular kan composition of Mom-chae and Nalgae-chae has changed. And kan is divided regardless to the wooden structure. Also, with the added kan under the eaves the main kan is dismantled inside. This paper indicates that although there is an undeniable premise that the case is restricted to hanok received Hanok Expanse Support on the condition of following the standards of the form of hanok, it is a part of the transitional changes that hanok is experiencing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.38-45
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• 2004

In this paper, a parallel visualization algorithm is proposed for efficient visualization of the massive data generated from large-scale parallel finite element analysis through investigating the characteristics of parallel rendering methods. The proposed parallel visualization algorithm is designed to be highly compatible with the characteristics of domain-wise computation in parallel finite element analysis by using the sort-last-sparse approach. In the proposed algorithm, the binary tree communication pattern is utilized to reduce the network communication time in image composition routine. Several benchmarking tests are carried out by using the developed in-house software, and the performance of the proposed algorithm is investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.64-67
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• 2000

Element distribution analysis and degradation characteristics of the ZnO varistors fabricated at the ambient sintering-process is investigated in this study. ZnO varistors made of Matsuoka's composition were fabricated by standard ceramic techniques. The ambient sintering-process is performed at the special electrical-furnace which is equipped with the vacuum system. The Gases of injection at sintering- process were oxygen, air, nitrogen and argon respectively. Element and quantitative analysis in the microstructure of ZnO varistors made use of EPMA equipment. Degradation characteristics were showed by DC degradation tests at $115{\pm}2\;^{\circ}C$ for period up to 13 h. From above analysis, it is found that at the DC degradation test the ZnO varistor sintered in oxygen atmosphere showed the excellent prop properties among them and these results could be explain by element and quantitative analysis in ZnO microstructure.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.197-201
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• 2009

A lot of work is carried out concerning to acicular ferrite formation in the weld metal of high strength and low-alloy steel. Those results are suggesting that oxides that contain titanium elements provides nucleation site of intragranular ferrite, referred as acicular ferrite. Thus, when intragranular ferrite is expected to form in heat-affected zone, oxide containing titanium element should be formed in the steel. However, normal steel is deoxidized by using aluminum element (Al-killed steel) with little oxygen content. It means almost oxygen is deoxidized with aluminum elements. In the present work, in order to form the acicular ferrite in the heat affected zone, with the same concept in the case of weld metal, the steel deoxidized with titanium element (titanium killed-steel) is prepared and the acicular ferrite formation is observed in detail by using laser-conforcal microscopy technique. The confocal technique makes it possible that the morphological change along the phase transformation from austenite to ferrite is in-situ tracked. Thus, the inclusion that stimulated the ferrite nucleation could be directly selected from the observed images, in the HAZ of the Ti-killed steel. The chemical composition of the selected inclusion is analyzed and the nucleation potential is discussed by changing the nucleation site with boron element. The potency for the ferrite nucleation is summarized and the existence of effective and ineffective manganese sulfide for nucleation is made clear.