• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.679-690
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• 2011

Since the elastic buckling problem of the plate has been studied both experimentally and theoretically, the buckling loads with various boundary conditions and loads can be easily determined. Currently, flange and web design specifications are based on the buckling stress and the post-buckling strength and include a safety-factor. Therefore, this study extended suchresearch to the linear buckling theory with ideal conditions and to the ultimate state with post-buckling. The current specifications are based on elastic buckling stress; and therefore, further research on the ultimate behavior of the plate is required. The ultimate strength design concept, which allows finite deflection, is used in this studyto maximize the post-buckling strength in a steel box. An empirical equation, which provides the ultimate strength of the steel box due to the change in the slenderness and optimum rigidity, are suggested based on the experiment results. Moreover, the appropriateness of the current design specifications was analyzed and discussed.

• Explosives and Blasting
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• v.21 no.2
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• pp.21-30
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• 2003

Currently, the shotcrete used as basic support in the tunnel excavation, has the advantages of maintaining high-level strength in condition of early shooting with thin thickness based on the excavation characteristics of rock mass. Therefore supreme equipment and materials were developed and the great strides have continued. Also, the development of measurement technology and the rocks behaviors of undergound are evaluated in detail and the designs of strength and thickness are made. The reinforcement materials development of new material is carried on. Most of the coal fly ash produced in Korea fire power plant is fly ash and bottom mash. Fly ash has been producing to be applied in many fields such as cement, aggregate, construction, civil, agriculture and fisheries. Also a lot of experiments are actively on the way. Therefore in this experiment, in order to use the fly ash mixed with concrete as a material of shotcrete, the experiment was performed in the best content to reduce the compression strength and the shooting rebound ratio of the excavated surface to use fly ash as a substitute material of concrete. As a result, when 15%.wt substitution was made to the fly ash, about 10% of compression strength and 6% of rebound ratio was reduced.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.125-132
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• 2014

Steel fiber is a effective composite for crack resistance and improve structural performance under tensile loading. This study presents an evaluation of crack resistance and structural performance in cement mortar with steel fiber and expansion agent through internal chemical prestressing. For this work, cement mortar samples with 10% replacement of cement binder with CSA (Calcium-Sulfo-Aluminate) expansion agent and 1% volume ratio of steel fiber are prepared. Including basic mechanical properties, initial cracking load and fracture energy are evaluated in cement mortar beam with notch. Initial cracking load and fracture energy in cement mortar with CSA and steel fiber increase by 1.75 and 1.41~1.53 times compared with those in cement mortar with steel fiber. With optimum mix design for steel fiber and CSA expansive agent, the composite with chemical prestressing can be applied to various members and effectively improve crack resistance to external loading.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.94-101
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• 2010

Recently, the interest of precast concrete is increased for rapid construction in construction fields. Experimental study about the shear performance of the joint between hollow core slabs which have internal core to reduce their weight was performed. Main test variables were thickness of the topping concrete and existence of the wiremesh. Total 8 specimens including 4 in-plane shear and 4 out of plane shear were tested. Test results were analyzed in terms of cracking load, failure load, failure aspect, stiffness and ductility, and compared its design load to develop optimum design details. Test results indicated that the shear performance of the non-shrinkage mortar specimen was similar to that of 30mm thickness topping concrete specimen, and the effect of wiremesh reinforcement did not affect the failure load or stiffness of the specimens but the increase of ductility. And this paper presents the comparison results of the test results and design load to provide the optimum detail of the joint design between the hollow core slabs.

• KDI Journal of Economic Policy
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• v.16 no.4
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• pp.47-80
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• 1994

본 연구는 우려나라 기업집단(企業集團)의 비용함수분석(費用函數分析)을 통해 제조업과 금융업간의 기술적 생산조건을 규명함으로써 제조산업(製造産業)과 금융업겸영(金融業兼營)의 효율성여부를 분석하고, 앞으로의 바람직한 금융소유지배규제정책방향(金融所有支配規制政策方向)을 모색하고 있다. 기업집단의 비용함수분석결과에 의하면 비금융제조업(非金融製造業)과 증권업(證卷業)간에는 범위(範圍)의 경제(經濟)(상호효율증진효과(相互效率增進效果))가 있는 반면 제조업(製造業)과 은행업(銀行業)이나 기타금융업과(其他金融業)의 사이에는 그런 관계가 부재(不在)하며, 우리나라 기업집단(企業集團)들은 평균적으로 규모가 과대하여 비효율(非效率)을 초래하고 있는 것으로 관찰되고 있다. 앞으로 우리 경제(經濟)의 개방화(開放化)와 금융자율화(金融自律化) 그리고 세계경제(世界經濟)의 통합화(統合化)가 진전됨에 따라서 제조업(製造業)과 증권업(證卷業)의 겸영(兼營)및 소유지배관계(所有支配關係)는 지속강화(持續强化)되겠지만 제조업(製造業)과 은행업(銀行業)과의 관계는 오히려 그 연계(連繫)가 약화(弱化)되며, 기업집단(企業集團)의 평균규모도 축소조정(縮小調整)될 것으로 전망된다. 이에 따라 장기적으로 금융소유규제정책(金融所有規制政策)은, 우선은 은행업과 제조업간의 소유지배를 허용하든 금지하든 어느 경우나 뚜렷한 자원배분(資源配分)의 왜곡(歪曲)이나 효율증진효과(效率增進效果)가 나타나지는 않기 때문에, 정부가 특정 소유구조를 강제하기보다는 은행(銀行)이나 기업(企業)들이 자체판단(自體判斷)에 의해 최적소유구조(最適所有構造)를 결정(決定)하도록 하되, 특정 소유지배관계(所有支配關係)의 형성이 금융산업 및 경제내에 경쟁저해적(競爭沮害的) 효과(效果)를 초래하지 않도록 하는 경쟁정책적(競爭政策的)차원에서 접근(接近)하는 것이 바람직할 것으로 판단된다. 그리고 소유집중(所有集中)에 따른 은행(銀行)의 안전(安全) 건전성(健全性) 저해효과(沮害效果)를 방지하기 위해서는 동일인(同一人) 여신한도(與信限度)의 엄격한 운용(運用) 등 건전감독기능(健全監督機能)을 보강해야 할 것이다.

• Polymer(Korea)
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• v.37 no.2
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• pp.204-210
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• 2013

Effects of additives (lubricant and antioxidant) and melt-blending condition (temperature, time and rotor speed) on the mechanical properties of polypropylene-based wood polymer composites (WPCs) were investigated. WPCs were prepared by melt-blending followed by compression molding. To understand melt-blending procedure, torque change of the WPC melt-blend was monitored. Maleic anhydride modified PP and nanoclay were used as a compatibilizer and a reinforcing filler, respectively. UTM and izod impact tester were used to measure the mechanical properties of the WPCs and a color-difference meter was used to measure the discoloration of the WPCs according to melt-blending condition. The mechanical properties showed that the optimized melt-blending condition was $170^{\circ}C$, 15 min, and 60 rpm. The mechanical properties of the WPCs decreased with increasing lubricant and antioxidant content. The two step method, adding wood flour later separately during melt-blending, was more effective than the typical one step method for improving the mechanical properties of the WPCs.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.88-97
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• 1998

Large aluminium extrusions can be used in rolling stocks and high speed vessels to reduce weight and labor cost. As sandwich plates with corrugated core have enough strength in transverse and longitudinal direction, welding lines to connect members are reduced and transverse members to strength longitudinal members are not required. However, for proper design of aluminium extrusion plates, understanding of structural behaviors of the exclusions are necessary. In this paper, at first, detailed finite element analysis is carried out to understand structural behavior. And then, simple theoretical formulas for design purpose are proposed using the orthotropic plate theory. Shear stresses resulting from end twisting which is characteristics of deep aluminium extrusion plates can also be calculated by the simple theoretical formula. Comparison with the results by detailed finite element analysis shows good accuracy of the proposed simple formulas. The simple formulas can be useful in repetitive analysis in the initial design stage.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.21-30
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• 2013

LB-Deck is one of the widely used member in interior part of girders as a permanent formwork in structures, but it is not easy to apply to the exterior part of girder due to the overturning and excessive deflection. Considering allowable deflection and safety of the exterior part, Precast Concrete Cantilever Deck (PCC-Deck) is proposed with normal LB-Deck in inner part and extended bars of LB-Deck in outer part. Both numerical analyses and experimental tests were compared to check the safety and allowable deflection for 6 types of PCC-Deck, and D-type (with 16 mm top bar, 6 mm lattice bar, 12 mm bottom bar) is suggested as an optimal structural reinforcement to the 28 kN of maximum load and 27.49 mm of final deflection. The load resisting ratio of D-type under working load of 10 kN was about 2.8 times and 77.5% of improvement was observed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.36-41
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• 2014

A floating offshore structure has high tendency to occur the buckling when compressive, bending and shear loads applied. When the buckling is occurred, in-plane stiffness of structure is remarkably decreased. And it has a harmful effect on the local structural strength as well as global structural strength. In the present study, it has been investigated the ultimate strength of tubular members which is located between a floater and a damping plate of the floating pendulum wave energy converter. Nonlinear finite element method is conducted using the initial imperfection according to 1st buckling mode which is obtained from the elastic buckling analysis. It is also noted the ultimate bending strength characteristic varying with a diameter, thickness and stiffeners of the tubular member.