• 한국공작기계학회논문집
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• 제17권2호
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• pp.23-29
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• 2008

This study analyzes the rolled circular rod strip with radius of loom and length of 350cm by using finite element analysis. The material strength and its durability of the rolled strip can be predicted through this study. As the penetration tolerance by contact decreases, the contact rigidity of strip increases. As the contact rigidity becomes the highest at the elapsed time of 1.2 second, the contact stress becomes the lowest. On the contrary, von-Mises stress becomes highest at this time. The total deformation on strip increases from the upper part of strip at the position near to rotating roll to the lower part of strip at the position near to fixing roll.

• 한국안광학회지
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• 제17권1호
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• pp.27-35
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• 2012

목적: 본 연구에서는 동일 재질 및 렌즈 파라미터를 가진 일반 소프트 콘택트렌즈와 써클 콘택트렌즈의 각막에서 중심안정위치와 움직임 양상을 비교하여 착색 여부에 따른 차이를 알아보고자 하였다. 방법: 눈물양이 정상인 20안을 대상으로 동일한 재질 및 파라미터의 일반 소프트 콘택트렌즈와 써클 콘택트렌즈를 각각 1일에 3시간씩 5일 동안 착용시키면서 각막에서의 중심안정위치와 반복적인 순목 후 콘택트렌즈의 이동거리 및 회전량을 측정하고 비교하였다. 결과: 일반 소프트 콘택트렌즈와 써클 콘택트렌즈 모두 착용 초기의 중심안정위치는 피팅 기준에서 벗어나는 경우가 있었으나 일반 소프트 콘택트렌즈의 경우는 착용 시간이 증가함에 따라 동공 중심으로 모이면서 모든 경우에도 피팅 기준에서 벗어나지 않는 적합한 중심안정위치로 변화되었다. 하지만, 써클 콘택트렌즈는 착용 시간이 증가하여도 수평 방향으로의 중심이탈이 여전히 존재하였다. 일반 소프트 콘택트렌즈와 써클 콘택트렌즈 모두 반복적인 순목 후 각막에서의 이동거리는 착용기간이 증가할수록 감소하였으나 두 콘택트렌즈 간에는 총 착용 기간이나 일일 착용 시간의 증가에 따른 차이는 통계적으로 유의하지 않았다. 반복적인 순목에 의한 써클 콘택트렌즈의 회전양은 착용기간이 증가하였을 때 일반 소프트 콘택트렌즈를 착용한 경우와 비교하여 통계적으로 유의한 차이가 있었다. 결론: 써클 콘택트렌즈의 각막에서의 위치 및 움직임은 일반 소프트 콘택트렌즈와 달라지며 이러한 차이는 착용기간이 증가하면 더 커짐을 밝혔다.

• 한국기계가공학회지
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• 제16권6호
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• pp.139-145
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• 2017

It is necessary to analyze the exact contact position and contact stress of the wheel-rail in order to predict damage to the wheel and rail. This study presents a wheel-rail contact analysis model that considers the deformation of the axle. When a wheel-rail contact analysis is performed using a full three-dimensional model of the wheelset and rail, the analytical model becomes very inefficient due to the increase in analysis time and cost. Therefore, modeling the element-coupling model of the wheel and rail as a three-dimensional element and the axle as a one-dimensional element is proposed. The wheel-rail contact characteristics in the proposed analysis model for straight and curved lines were analyzed and compared with the conventional three-dimensional analysis model. Considering the accuracy of the analysis results and time, the result shows that the proposed analytical model has almost the same accuracy as a full three-dimensional model, but the computational effort is significantly reduced.

• 구강회복응용과학지
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• 제26권2호
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• pp.197-204
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• 2010

본 실험의 목적은 인공 치관의 수복을 통해 인접치간 접촉강도의 경시적 변화를 관찰하는 것이다. 인공 치관을 통한 단일 치관 수복이 필요한 12명의 성인에서 치아 삭제 전과 인공치관 적합 후의 시간 경과에 따른 접촉강도를 측정하였다. 그 결과 적합 직후의 인접치간 접촉강도는 처음 삭제 전의 접촉강도보다 컸으며 1-2주 이내에 치아삭제 전의 접촉강도와 유사한 양으로 변화하였고 2-4주 후까지 인접치간 접촉강도는 거의 변화가 없고 일정한 접촉강도를 유지하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.407-412
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• 1998

In this work, a new time integration method is proposed using the generalized derivative concept to simulate the dynamic phenomena having sudden constraint occurring in dynamic contact/impact problems. By the adoption of the generalized derivative concept and jump assumption, discontinuity can be incorporated in time integration and as a result, the algorithm does not need any other special consideration of jumps in dynamic field variables due to sudden constraint like dynamic contact-release conditions. To observe the characteristics of the proposed time integration method, the stability and convergence analyses are carried out. In numerical tests, several dynamic contact/impact problems are analyzed by straightforward application of the proposed time integration method with the exterior penalty method.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2029-2037
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• 1997

In a web winding process, the contact roll plays many important roles including air-entrainment control and WIT(Wound In Tension) regulation. The behavior of contact roll significantly affects the winding tension characteristics specifically at the time of contact when the speeds of contact roll and the winding roll are not synchronized. A mathematical model for the web, the winding roll, and the contact roll is derived. By using the model derived, a nonlinear PID(NPID) controller is designed to control the winding tension at the time of contact and separation between the contact roll and the winding roll. Computer simulation study showed that the performance of the winding system with the NPID controller significantly improved compared with that of a system with PID controller.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1013-1015
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• 1995

The electrical properties of Al/TiN/Ti contact according to post anneal ins conditions are investigated at submicron contacts. $N^+$ contact resistance increases with increasing alloy temperature while $P^+$ contact resistance slightly decreases. The contact tentage current increases wi th increasing alloy temperature for both $N^+$ and $P^+$ contacts. The contact resistance and leakage current of $N^+$ contact increases with increasing alloy tide. $P^+$ contact resistance decreases with increasing alloy time but $P^+$ contact tentage current increases. The contact resistance and contact leakage current increases with increasing alloy cycles for both $N^+$ and $P^+$ contacts.

• 디지털산업정보학회논문지
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• 제9권2호
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• pp.41-54
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• 2013

In this paper, We collected location based services of the user's past moving paths through the GPS. Using the collected by location-based services through the analysis of the similarity between the user's of service level agreement recommended of mobile contact area(SLA) proposed that can be. S-RCA method based on Service Level Agreement of the users in order to provide the service user's path distance, time, and to predict the direction of the movement paths and collect. The data collected by the interests and requirements of users through classification with the same interests and the needs of users to move between the analysis of the similarity between the path is used to analyze the results of analysis of the path-specific tolerance range (distance, time, and space) is determined according to the difference in the contact area. From a small area of the error range for users first to recommended and through their smartphones recommended contact area (S-RCA) to meet with the other party to make a choice of recommended methods. We verify through experiments that proposed method(S-RCA) a valid and reliable mobile contact area were recommended.

• 한국정밀공학회지
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• 제16권6호
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• pp.148-159
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• 1999

A numerical method is presented for the dynamic analysis of spur gears rotating with very high angular speeds. For an efficient computation each gear is assumed to consist of a rotating rigid disk and an elastic tooth having mass, and finite element formulations are used for the equations of motion of the tooth. The geometric constraint is imposed between the rigid disk and the elastic tooth to fix them, and contact condition is imposed between the meshing teeth of the gears. At each iteration of each time step the Lagrange multiplier and contact force are revised by using the constraint error vector, and then the whole equations of motion are time integrated with the given Lagrange multiplier and contact force. For the accurate solution the velocity and acceleration constraints as well as the displacement constraint are satisfied by the monotone reductions of the constraint error vectors. Computing procedures associated with the iterative schemes are explained and numerical simulations are conducted with the spur gears.

• 신재생에너지
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• 제4권2호
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• pp.74-80
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• 2008

To improve the blue responses of screen-printed single crystalline silicon solar cells, we investigated an emitter etch-back technique to obtain high emitter sheet resistances, where the defective dead layer on the emitter surface was etched and became thinner as the etch-back time increased, resulting in the monotonous increase of short circuit current and open circuit voltage. We found that an optimal etch-back time should be determined to achieve the maximal performance enhancement because of fill factor decrease due to a series resistance increment mainly affected by contact and lateral resistance in this case. To elucidate the reason for the fill factor decrease, we studied the resistance analysis by potential mapping to determine the contact and the lateral series resistance. As a result, we found that the fill factor decrease was attributed to the relatively fast increase of contact resistance due to the dead layer thinning down with the lowest contact resistivity when the emitter was contacted with screen-printed silver electrode.