• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.99-108
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• 2006

Aerospace applications use pyrotechnic devices with many different functions. Functional shock, safety, overall system cost issue, and availability of new technologies, however, question the continued use of these mechanisms on aerospace applications. Release device is an important example of a task usually executed by pyrotechnic mechanisms. Many aerospace applications like satellite solar panels deployment or weather balloon separation need a release device. Several incidents, where pyrotechnic mechanisms could be responsible for spacecraft failure, have been encouraging new designs for these devices. The Frangibolt is a non explosive device which comprises a commercially available bolt and a small collar made of shape memory alloy (SMA) that replace conventional explosive bolt systems. This paper presents the modeling and simulation of Frangiblot by the change of bolt size and notch geometry. This analysis may contribute to improve the Frangibolt design.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.145-153
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• 2004

Conventional lead-rubber bearings may be unstable in case of strong ground motions. To address this problem, this paper proposed a new concept of isolation device wherein shape memory alloy wires were incorporated in an elastomeric bearing. A three-span continuous steel bridge was used for seismic analyses to compare the performance of lead-rubber and proposed bearings. The proposed bearings showed almost the same performance as the lead-rubber bearings. In particular, the proposed bearings limited relative displacement effectively with strong ground motions and recovered its original undeformed shape.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.587-597
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• 2007

Steel restrainer cables for multiple frame bridges in California in the United States have been shown to be effective in preventing unseating at internal hinges during the past several earthquakes. Consequently, the steel-cable-restrainer is being tested for applications on multiple-span-simply-supported (MSSS) bridges in the mid-American region. In addition, shape memory alloy (SMA) bars in tension are being studied for the same application, multiple frame bridges, the developed seismic forces are transferred to piers through the restrainers. However, in MSSS bridges, the seismic forces are transferred to abutments by the restrainers. Therefore, the abutment' behavior should also be investigated. In this study, we assessed the seismic performance of the three types of restrainers, such as steel restrainer cables, SMA in tension, and SMA in bending for an MSSS bridge from moderate to strong ground motion, bending test of an SMA bar was conducted and its analytical model was determined for this study. Nonlinear time history analyses were conducted to assess the seismic responses of the as-built and the retrofitted bridges. All three types of restrainers reduced the hinge opening and the SMA in tension was the most effective of the three devices in preventing the unseating, all restrainers produced damage on the abutment from the pulling action of the MSSS bridge due to strong ground motions, was found that the retrofit of the abutment in the pulling action is required in the installation of restrainers in MSSS bridges.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.445-452
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• 2014

This paper discusses the multifrontal direct solution method with out of core storage for large scale structural analysis in a limited computing resource. Large scale structural analysis requires huge amount of memory space and computation, so out of core solution method is needed in limited computing resource. In this research, out of core multifrontal solution algorithm which utilize the small size of physical memory and minimize the amount of access of low speed out of core storage is introduced. Three ideas, which are stack space in lower trianglar part of square factorization matrix, inverse stack data structure and selective data caching and recovery by data block size, are proposed.

• 전기의세계
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• v.30 no.12
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• pp.793-796
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• 1981

최근 우리나라에도 digital image processing에 대한 연구가 활발이 진행되고 있다. 또한 digital image processing의 생체공학에의 응용도 괄목할 만하다. 이러한 연구와 응용에 도움이 되고자 microcomputer를 이용한 image processor설계의 실례를 기술하고자 한다. 이 설계는 목적 image를 stationary image로 가정하여 TV카메라의 영상신호를 sample하여 computer 기억장치에 저장하므로 가격이 저렴하게 된다. 이러한 장치로서는 DMA연결 (Direct Memory Access interface)을 사용하여 빠른 data transfer를 달성할 수 있다. Digital image processing계는 기본적으로 microcomputer가 TV카메라와 TV모니터에 연결된 구조를 하고 있다. Computer가 기억장치에 저장된 data를 처리하여 필요한 정보를 얻게 된다. 이러한 data 처리를 하므로서 image를 사용자가 해석하기 쉽도록 image질을 향상시키거나 computer가 image를 인식하게 한다. 이와같이 처리된 image는 TV모니터를 통해서 볼 수 있다. 본지에서는 256x256개의 pixel들로 이루어지고, 각개의 pixel은 4개의 bit로 구성된 image processor의 설계를 기술한다.

• Journal of the Korean Chemical Society
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• v.25 no.2
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• pp.103-109
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• 1981

An inexpensive, yet convenient analog storage device was constructed. Sequentially MOSFET-switched 20 sample and holds equipped with a high input impedance preamplifier were parallelly matched to the digitally controlled shift register system in variable speeds up to 3 kHz. To verify its usefulness, square wave train, sinusiodal wave and some electrochemical data, such as fast-scan voltammogram and transient current-time curves of differential pulse polarography were tested.

• Journal of Korean Electronics
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• v.8 no.4
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• pp.46-52
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• 1988

• Journal of the Korean Institute of Telematics and Electronics
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• v.7 no.4
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• pp.20-29
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• 1970

• Journal of Korean Electronics
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• v.8 no.9
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• pp.94-100
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• 1988

• Composites Research
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• v.18 no.2
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• pp.38-45
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• 2005

Phase transformation behaviors and crystal structures of Nitinol shape memory alloy $(54.5Ni-45.5Tiwt\%)$ are investigated by varying annealing heat treatment conditions through DSC (Differential Scanning Calorimetry) and XRD (X-Ray Diffraction). Annealing heat treatment conditions were considered as heat treated times of 5min, 15min. 30m1n, and 45min, as well as heat treated temperatures of $400^{\circ}C,\;500^{\circ}C,\;525^{\circ}C,\;550^{\circ}C,\;575^{\circ}C,\;600^{\circ}C,\;700^{\circ}C,\;800^{\circ}C,\;and\;900^{\circ}C$ According to the results, annealing heat treatment conditions such as heat treated times and heat treated temperatures were found to affect significantly on phase transformation behaviors and crystal structures of Nitinol shape memory alloy.