• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.529-534
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• 2014

Pyrotechnic devices are widely used for space appendages. However, a cube satellite requirements do not permit the use of explosive pyrotechnic device. A nichrome burn wire release has typically been used for holding and release of deployable appendages of the cube satellite due to its simplicity and low cost. However, relatively low mechanical constraint force and system complexity for application of multi-deployable systems are disadvantages of the conventional mechanism. To overcome these drawbacks, we developed a hinge driving segmented nut type holding and release mechanism based on the nichrome burn wire release. The functional performance of the mechanism has been verified through release function test, static load test and shock level measurement test.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.921-924
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• 2008

Several techniques, including transmission X-ray photography and AC-impedance spectroscopy, are available for evaluating the fiber dispersion in a fiber reinforced concrete Evaluating the fiber dispersion in fiber reinfored concrete needs since the fibers bridge crackseffectively. However, these equipment is very expensive. Therefore this paper presents the quantitative evaluation method based on the image analysis of sectional image taken using an ordinary digital camera. After detecting the fiber accurately, the fiber dispersion characteristics are represented by the coefficient such as the fiber dispersion coefficient, the number of fibers in unit area, and the distribution of the fiber orientation. Test were performed to evaluate the effectiveness of proposed method and the dispersion characteristics of fibers according placing method and flow direction. Additionally, the effect of fiber dispersion characteristics on mechanical properties was investigated. Test results shows that fiber aligned along the flow direction and more fibers placed and dispersion was better on the section parallel to the flow direction. And about 50% difference in the flexural tensile strength according to the placing method occured.

• Journal of Bio-Environment Control
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• v.18 no.2
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• pp.95-100
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• 2009

This study was conducted to develop an imaging processing system of inoculation processing of a lily callus. The image processing system was composed of a camera, a image processing board, and etc. And the illuminance always decided by setting up 55W/3 wavelength lamp respectively on all aspects and the side was maintained by the lighting part. The image characteristic was examined according to each frame of RGB,therefore the culture vessel was able to be separated with B frame. The required time was 2.2 seconds in one cycle from the image acquisition to obtaining the result. The recognition rate of the container was 100%, and the result of image processing showed that the recognition success rate of lily callus was 93%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.311-318
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• 2008

We propose new pulse shapes for FCC-compliant ultra-wideband (UWB) radios. The projections onto convex sets (POCS) technique is used to optimize temporal and spectral shapes of UWB pulses under the constraints of all of the desired UWB signal properties: efficient spectral utilization under the FCC spectral mask, time-limitedness, and good autocorrelation. Simulation results show that for all values of the pulse duration, the new pulse shapes not only meet the FCC spectral mask most efficiently, but also have nearly the same autocorrelation functions. It is also observed that our truncated (i.e., strictly time-limited) pulse shapes outperform the truncated Gaussian monocycle in the BER performance of binary TH-PPM systems for the same pulse durations. The POCS technique provides an effective method for designing UWB pulse shapes in terms of its inherent design flexibility and joint optimization capability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.27-35
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• 1998

In this paper, we propose a novel spectral-chopping model of Class-II$(1+D)^2$ -PRS system which reveals improved spectral efficiency. We build up the model having spectrum chopped by the amount of Nyquist over-rate, and then compare its characteristics with the conventional model in both the time-domain and the frequency-domain. When the transmission system operates above the Nyquist rate, the new model has better performance than the conventional PRS using its inherent speed-tolerance. According to our investigations, Class-II PRS shows more excellent effect in the spectral-chopping method than Class- I and W types analyzed previously. We ascertain that the over-rate of 26.675 obtained by the inherent speed-tolerance could be improved upto 40% using spectrum-truncation. These effects come from the fact that the raised-cosine spectrum of Class-II PRS has smaller Boss of frequency component and energy than any other types for the same amount of truncation. In order to validate these theoretical results, we present their sidelobe-trends confirming cancellation effects at the sampling instants and some experimental results showing their patterns of eye-openings and spectra.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.737-743
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• 2004

In this paper, we propose the call control scheme that can improve the capacity of the wireless system for the non-uniform traffic load distribution and the multiple types of services in multiple cells CDMA system. The number of mobile stations that can be served simultaneously in a base station is limited by the amount of total interference received in CDMA system. Further, the average number of mobile stations in each cell may not be uniformly distributed. Considering this factors, the call admission control scheme using the effective bandwidth concept is adapted in this paper. Thus, the bandwidth for a new call can be varied dynamically for reducing the blocking rate of new calls and the dropping rate of handoff calls. The suggested call control scheme is experimented through a simulation by dynamically assigning the bandwidth to new and handoff calls. The simulation results show that the proposed call control scheme can accommodate more mobile stations than the other methods in multiple cells environment.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.393-399
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• 2023

Upper limb amputees wear an upper limb prosthesis for both aesthetic purposes and functional necessity, and in particular, in the case of amputee with both hands, it is essential to wear a myoelectric prosthetic hand capable of gripping action. The prosthetic hand operated by the EMG signal of the remaining muscles is a public insurance benefit item of the Industrial Accident Compensation Insurance, and test method standards are needed to be developed for the safety of the user and the effectiveness of the product performance. In this study, we developed systems for measuring the gripping force of myoelectric hand prosthesis by a load cell and for durability test of the prosthesis over repeated use with a proximity sensor, and propose a test method standard. Since the international test method standard has not yet been established, it is expected that Korea will be able to play a leading role in this standardization field in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1D
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• pp.57-65
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• 2008

Joint of concrete pavement contributes to improvement of pavement performance by preventing occurrence of random cracking due to drying shrinkage and temperature changes of concrete slabs at early age. However, saw-cutting operations performed prior to sufficient concrete hardening develop micro-cracking of the concrete near the joints, which may develop to long-term distresses due to repetitious traffic and environmental loadings. To reduce the distresses, the joint crack inducers with heights of 100 mm, 150 mm, and 220 mm and the joint cracking slots with various depth were installed at a test section to investigate occurrence of the joint cracks and their behaviors over 5 months. As the results, higher efficiency of the crack inducing and larger behavior of the joint cracks were observed for the taller joint crack inducer. Higher efficiency of the crack inducing and improvement of the joint performance are warranted by additional investigation and reformation of the joint crack inducer.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.93.2-93.2
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• 2015

플라즈마를 포함한 반응성 가스 공정 분석용 사중극자 질량분석기의 필라멘트의 파손양상을 조사하였다. 또한 유전체 증착층이 이온원 성능에 미치는 영향을 분석하기 위하여 이온원의 일반적인 가동 전압 조건에서 Poisson방정식을 이용하여 전위를 수치 해석으로 구하였다. 사용중 파손된 필라멘트의 파단면을 주사전자현미경으로 관찰결과, 수직으로 절단되는 양상과 직경이 점차 작아지면서 erosion되는 두가지 양상을 보였다. 또한 파단면은 표면균열과 패시팅(faceting) 현상을 보였다. 필라멘트 사용시 가장 큰 문제는 패시팅(faceting)이다. 대부분의 결정에서는 다른 결정면보다 에너지 준위가 낮은 결정면이 존재한다. W 원자는 고온에서 확산 또는 증발하여 표면에서 다시 응축할 때 표면 에너지를 최소화하기 위한 독특한 평형 형상이 만들어 지는데 이것이 패시팅의 구동력이다. 이때 국부적으로 단면적이 감소하는 곳이 생기는데, 이 지점이 집중적으로 가열되고 증발이 가속화하여 파손된다. 파단면을 EDS 분석결과, 산화물을 포함한 F, Fe 및 C이 검출되었다. 이 F과 C는 공정중 사용된 CF4의 분해에 의한 것으로 생각되며, 파손된 필라멘트를 Ar 유도결합 플라즈마로 처리한 결과 이 F, Fe 및 C의 양이 감소하였다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.07a
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• pp.142-149
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• 1999

최근 주변첨단기술이 발달하여 수확, 접목 및 착유 등 농작업에 로봇을 응용하기 위한 연구가 수행되고 있다. 작업의 특성에 따라 응용되는 로봇기술도 차이는 있겠으나 수확용 로봇의 경우 대상물을 인식하고 위치를 검출하는 기술개발이 선행되어야만 대상물을 파지 또는 절단하여 수확이 가능하며, 대상물의 인식 및 위치 검출에는 영상처리기술이 많이 응용되고 있다. 따라서 수확로봇의 작업성능은 대상물을 얼마나 정확하게 인식하고 위치를 정확하게 검출하는 것이 중요하다. 그러나 작업대상이 일정한 조건에서 표준화 되어있는 일반 산업분야와는 달리 농산물의 수확작업현장은 대상물의 배치, 크기 및 형상 둥이 일정하지 않고 작업환경 또한 다양하여 외란의 영향을 많기 받기 때문에 시각장치의 개발은 매우 중요하다. (중략)