• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.857-858
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• 2010

• Earthquakes and Structures
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• 제16권4호
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• pp.437-453
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• 2019

This study investigates a new optimal placement method for viscous dampers between structures in order to prevent pounding of adjacent structures with different dynamic characteristics under earthquake effects. A relative displacement spectrum is developed in two single degree of freedom system to reveal the critical period ratios for the most risky scenario of collision using El Centro earthquake record (NS). Three different types of viscous damper design, which are classical, stair and X-diagonal model, are considered to prevent pounding on two adjacent building models. The objective function is minimized under the upper and lower limits of the damping coefficient of the damper and a target modal damping ratio. A new algorithm including time history analyses and numerical optimization methods is proposed to find the optimal dampers placement. The proposed design method is tested on two 12-storey adjacent building models. The effects of the type of damper placement on structural models, the critical period ratios of adjacent structures, the permissible relative displacement limit, the mode behavior and the upper limit of damper are investigated in detail. The results of the analyzes show that the proposed method can be used as an effective means of finding the optimum amount and location of the dampers and eliminating the risk of pounding.

• 한국안전학회지
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• 제28권6호
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• pp.49-56
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• 2013

The statistics of recent accidents in warehouses show that a heavy toll of lives were produced by various accidents, e.g. collision, overturn, fall, slip, exposure to harmful substances or environments, etc. Of significant concern amongst them is the collision, especially the collision between forklift and storage rack structure. Accordingly, this study focuses on behavioral characteristics of rack structure subjected to dynamic impact loading of a forklift. For this purpose, time-domain response analysis has been performed on a standard 2-bay six-story rack structure consisting of columns, beams and bracing members with perforated open section. In order to investigate the most critical scenario, the impact loads are applied in both down-aisle and cross-aisle directions, and the impact locations are also varied along the shelves of the palettes. In order to deal with storage distributions, three types of rack structures are further taken into account: original empty rack structure with no storage, half-loaded rack structure and fully-loaded rack structure. The numerical simulation results demonstrate that the dynamic characteristics of the rack structure are significantly dependent on the distribution of the storage goods and its natural period varies from 0.24sec to 1.06sec, approximately 4.4 times. Further, the parametric studies show that the forklift impact is most critical to the safety of the rack structure when it collides either at the base or at the top of the rack structure.

• 대한토목학회논문집
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• 제38권2호
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• pp.303-310
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• 2018

충격적인 헤드라인 중 하나는 심각한 연쇄추돌 교통사고(chain collision accident, CCA)이다. CCA의 진행과정은 시공간적으로 국부성을 가지며, 그 정보는 시간 임계적(time-critical)이다. 따라서 연쇄추돌을 감소시키기 위해서는 1차 사고 발생 직후 교통사고 정보를 운전자에게 신속하게 전파시켜야 한다. 국부적 긴급 정보전파의 유력한 대안 중 하나는 Ad hoc 통신에 기반을 둔 차량 간 통신(Inter-Vehicle Communication, IVC)이다. 이러한 IVC의 잠재력에도 불구하고, CCA 감소에 대한 IVC의 효과에 대한 연구는 현재까지 보고되지 않고 있다. 따라서 본 연구는 미시적 차량 시뮬레이터와 IVC 시뮬레이터가 결합된 병렬 플랫폼을 개발하고, 이를 이용하여 CCA 감소에 대한 IVC의 효과를 분석하였다. CCA를 감소시키기 위한 IVC기반 긴급 교통사고정보 전파의 가능성을 증명하기 위하여, IVC 장치의 시장 점유율과 교통량 시나리오에 따른 차량의 접근속도 감소, 사고정보의 전파속도, 그리고 CCA의 감소를 분석하였다. 분석결과, IVC 장비의 시장 점유율 10%와 50%에서 CCA는 40~60% 그리고 80~82%로 각각 감소될 수 있는 것으로 나타났다.

• 대한기계학회논문집
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• 제15권1호
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• pp.69-77
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• 1991

본 연구에서는 주로 약결합된 경우의 다로봇시스템에 대한 효과적인 운동조정 법을 개발하였다. 약결합된 경우의 다로봇시스템은 아크용접, 분사 도료, 금속면의 디버링, 복잡한 조립작업, 검사등 수많은 작업에 투입될 수 있다.그와 같은 작업들 은 대부분 연적경로제어(continuous path control)방법을 요구하고 있는데 다로봇시스 템인 경우 작업대 주위의 정지 혹은 이동 장애물이나 제로봇상호간의 충격포험성을 해 결할 수 있는 효과적인 장애물회피 능력을 추가적으로 요구하고 있다. 그리고 연적 경로제어 형태의 거의 대부분의 첨단부의 속도를 정속도로 유지해주어야만 한다. 따 라서 모든 로봇들을 지정된 경로의 이탈없이 가능한 최대등속도로 운동시키기 위한 다 로봇시스템의 충격회피운동제어 알고리즘을 개발하게되었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.396-408
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• 2019

The tubes which are applied in jacket platforms as the supporting structure might be collided by supply vessels. Such kind of impact will lead to plastic deformation on tube members. As a result, the ultimate strength of tubes will decrease compared to that of intact ones. In order to make a decision on whether to repair or replace the members, it is crucial to know the residual strength of the tubes. After being damaged by lateral impact, the simply supported tubes will definitely loss a certain extent of load carrying capacity under uniform axial compression. Therefore, in this paper, the relationship between the residual ultimate strength of the damaged circular tube by collision and the energy dissipation due to lateral impact is investigated. The influences of several parameters, such as the length, diameter and thickness of the tube and the impact energy, on the reduction of ultimate strength are investigated. A series of numerical simulations are performed using nonlinear FEA software LS-DYNA. Based on simulation results, a non-dimensional parameter is introduced to represent the degree of damage of various size of tubes after collision impact. By applying this non-dimensional parameter, a simplified formula has been derived to describe the relationship between axial compressive residual ultimate and lateral impact energy and tube parameters. Finally, by comparing with the allowable compressive stress proposed in API rules (RP2A-WSD A P I, 2000), the critical damage of tube due to collision impact to be repaired is proposed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1414-1419
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• 2011

In this paper we study the modeling to quantitatively assess the failure rate of USN system designed for fault-tolerant architecture, aiming at applying the world's best domestic USN technology to safety-critical railways. In order to apply the USN system to the safety-critical field like a train control sector that the failures of controllers may cause severe railway accidents such as train collision and derailment, the quantitative reliability and safety evaluation recommended in IEC 62278 must be preceded. We also develop the evaluation model for overall system failure rate for the distributed network structure, which is the characteristics of USN system. Especially, we allocate reliability targets to component units, and present an availability evaluation plan through the plan on the quantitative achievement of failure rate for sensor nodes, gateways, radio-communication network and servers, along with the failure rate model of the overall system considering network operational features.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.131.4-131
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• 2001

A lot of path planning algorithms have been developed to find the collision-free path with minimum cost. But most of them require complicated computations. In this paper, a thinning method, which is one of the image processing schemes, was adopted to simplify the path planning procedure. In addition, critical points are used to find the shortest-distance path among all possible paths from the start to the goal point. Since the critical points contain the information on the neighboring paths, a new path can be quickly obtained on the map even when the start and goal points change. To investigate the validity of the proposed algorithm, various simulations have been performed for the environment where the obstacles with arbitrary shapes exist. It is shown that the optimal paths can be found with relative easiness.

• 한국전산구조공학회논문집
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• 제36권2호
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• pp.113-120
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• 2023

본 논문에서는 LS-DYNA를 활용한 원자력발전소 설치 로드블록 차량 시뮬레이션 방법을 소개한다. 차량 강습 위협이 원자력 발전소의 설계기준위협으로 포함된 이후로 차량 강습을 대비하기 위한 차량 방벽(Anti-ram barrier)의 성능 평가 소요가 커지고 있다. 차량 방벽은 일반적으로 충돌 실험을 통하여 성능을 인증 받는다. 하지만 국내에서는 차량 방벽에 대한 성능 시험 시설이 마련되어 있지 않아, 시뮬레이션을 통한 차량 방벽 성능 검증이 필요하다. LS-DYNA는 충돌 시뮬레이션에 특화되어 있으며, NCAC를 비롯한 여러 기관에서 충돌 시험과의 타당성 검증을 완료한 수치 모델을 배포하고 있다. 본 논문에서는 로드블록의 가장 핵심적인 차량 차단막 모듈의 FE 모델을 구축하여 충돌 시뮬레이션을 수행하였다. 계산된 결과는 NCHRP 179의 차량 안전 시설 충돌 시뮬레이션 검증 기준을 준용하여 검증하였다. 그 결과 모래시계 에너지(hourglass energy)가 총 에너지의 5%를 넘지 않고 내부 에너지의 10%를 넘지 않는 것을 확인하였으며, added mass가 1% 미만으로 기준인 10%를 넘지 않는 것을 확인하였다. 향후 FE 모델을 활용하여 물리적 방벽의 성능을 평가하여 데이터 베이스를 구축할 예정이다.

• 전기학회논문지P
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• 제63권1호
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• pp.19-23
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• 2014

This paper describes the electron transport characteristics in $SF_6$-He gas calculated E/N values 0.1~700[Td] by the Monte Carlo simulation and Boltzmann equation method using a set of electron collision cross sections determined by the authors and the values of electron swarm parameters obtained by TOF method. This study gained the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients for $SF_6$-He gas at a range of E/N. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.