• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1031-1036
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• 2000

In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

• Progress in Superconductivity
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• 제13권1호
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• pp.47-51
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• 2011

Mono-atomic-layer graphene is an interesting system for studying the relativistic carrier transport arising from a linear energy-momentum dispersion relation. An easy control of the carrier density in graphene by applying an external gate field makes the system even more useful. In this study, we measured the Josephson current in a device consisting of mono-layer graphene sheet sandwiched between two closely spaced (~300 nm) aluminum superconducting electrodes. Gate dependence of the supercurrent in graphene Josephson junction follows the gate dependence of the normal-state conductance. The gate-tunable and relatively large supercurrent in a graphene Josephson junction would facilitate our understanding on the weak-link behavior in a superconducting-normal metal-superconducting (SNS) type Josephson junction.

• Design & Manufacturing
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• 제2권4호
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• pp.11-15
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• 2008

In the sheet metal forming using a high speed press machine, driving device, such as crank, link, and knuckle mechanism, has to be designed in consideration of impact at a moment when press die contact with material, because the impact affects a dimensional accuracy of products and a life span of press die. In this study, dynamic analysis was performed using numerical simulation in order to verify the impact reduction effect for proposed double knuckle mechanism by estimating rolling and pitching moment of slide.

• 로봇학회논문지
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• 제8권2호
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• pp.136-142
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• 2013

In nature, many small insects are using jumping as a survival strategy. Among them, fleas jump in a unique method. They use an elastomer, 'Resilin', an extensor muscle and a trigger muscle. By contracting the extensor muscle, the elastic energy, that makes a flea to jump, is stored in the resilin. After storing energy, the trigger muscle begins contracting and pulling the extensor muscle. When the extensor muscle crosses the rotational joint, direction of torque generated from the extensor muscle reverses, 'torque reversal mechanism'. Simultaneously, the elastic energy stored in the resilin releases rapidly and is converted into the kinetic energy. It makes a flea to jump 150 times its body length. In this paper, miniaturized jumping robot using flea-inspired catapult mechanism is presented. This mechanism is based on the 4-bar linkage and the reversal joint and is actuated by Shape Memory Alloy (SMA) coiled springs describing the flea's muscle. The robot prototype is fabricated by SCM process using glass fiber prepregs and a sheet of polyimide film. The prototype is 20mm link length, 34mm width and 2.0g weight and can jump 103cm.

• 한국산림과학회지
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• 제88권2호
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• pp.157-168
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• 1999

본 연구는 브라질의 서부에 있는 Mato Grosso do Sul 주의 Jangada 농장과 Jamaica 농장에 유칼리나무 식재계획(植栽計劃)을 원활히 추진하기 위해 인공위성사진을 이용하여 식생분류(植生分類) 및 토지이용구분(土地利用區分), 경사도(傾斜度) 및 영구자연보존지역(永久自然保存地域) 등을 분석한 결과이다. Mato Grosso do Sul 주의 서쪽에 위치하는 이 지역은 볼리비아와 파라과이의 국경근처에 있기 때문에 지정학적(地政學的)으로 매우 중요하다. 또한 물품수출이 파라과이강을 통해서 아르헨티나의 수도인 부에노스아이레스 까지 도달될 수 있고 브라질의 남동지역과 안데스산맥에 연한 국가들을 연결하는 국도(國道)와 철도(鐵道)가 존재한다. 농장의 산림(山林) 피복지역(被服地域)의 일차해석을 위한 기초로서 Radambrasil프로젝트 SF-21 Campo Grande로부터 얻은 식생지도가 사용되었고, 그 이후에 현장조사(現場調査)가 수행되었다. 최초의 이미지해석이 이루어진 후에 사용급과 토지점유에 대한 개념정의가 이루어 졌으며 스펙트럼분류가 행해졌다. Jangada 농장과 Jamaica 농장에 있어서 산림지역 Savanna와 초원지역 Savanna가 전체 총면적의 68% 정도를 차지하고 있다. 현재로서 만족한 연구결과에도 불구하고 이미 이루어진 평가결과(評價結果)에 기초하여 프로젝트 발전을 위한 수정(修正)과 보완(補完)이 요구된다. 특히 토양(土壤)과 지형(地形)을 포함해서 환경인가에 대한 상세한 분석이 병행되어야 할 것이다.