• 한국항공우주학회지
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• 제45권1호
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• pp.63-70
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• 2017

본 논문에서는 가항력돛을 이용한 궤도이탈 장치를 설계 및 제작하고 전개 특성을 연구하였다. 형상기억합금을 이용한 분리장치를 개발하고, 형상기억합금의 구동에 따라 테잎 스프링의 복원력을 이용해 구동되는 새로운 궤도이탈 장치를 설계하고 실험하였다. 가항력돛의 효율적인 수납 및 전개를 위해 origami flasher 방식 중 original ISO flasher 방식을 선정하였으며, 반복적인 실험을 하기 위해서 다른 재료들에 비해 저렴한 우주재료인 mylar film을 가항력돛의 재료로 사용하였다. 또한, 일회성 장치 신뢰성 평가 방법 중 하나인 FTA(fault tree analysis) 방법을 통해 장치의 신뢰도(0.997572)를 평가하고 가장 치명도가 높은 부분이 Roller failure임을 확인하였다. 최종적으로 가항력돛의 전개장치의 제작 및 실험을 통하여 향후 궤도이탈 장치의 개발 가능성을 확인하였다.

• 품질경영학회지
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• 제42권3호
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• pp.291-300
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• 2014

Purpose: The purpose of this study is to provide a statistical method from the data of ASRP's results and to apply to the reliability assessment of 155mm propelling charge, KM4A2. Methods: The accumulated data through ASRP for 155mm propelling charge were analyzed using regression analysis and MINITAB reliability analysis. The analysis methods used for this study were applied to statistical data types such as continuous data, binominal data. Results: The results of this study are as follows; The failure of 155mm propelling charge is mainly due to the broken charge bag, the decline of stabilizer content. The shelf-life(B5) regarding broken charge bag is 21.1years. The stabilizer content decrease with 0.0227%/year and safety storage period of propellant is 34.6years. Conclusion: The shelf-life of 155mm propelling charge determined by charge bag is estimated 21.1years.

• 한국정밀공학회지
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• 제21권8호
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• pp.180-187
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• 2004

The present study attempted to investigate the effects of supply of highly concentrated (30%) oxygen on human ability of visuospatial cognition and cerebrum lateralization. compared to air of normal oxygen concentration (21%). The experiment consisted of two runs, one fur visuospatial cognition test with normal air (21% of oxygen) and for visuospatial cognition test with more oxygen in the air (30% of oxygen). Each run was composed of four blocks and each block included eight control tasks and five visuospatial tasks. Functional brain images were taken from 3T MRI using the single-shot EPI method. The result of task performance showed the accuracy increased at 30%＇s concentration of oxygen rather than 21%＇s. There were more activations observed at the left and right hemisphere, but there was decrease cerebrum lateralization with 30% oxygen administration. Thus, it is concluded that the positive effect on the visuospatial cognitive performance level by the highly concentrated oxygen administration was due to increase of cerebrum activation and decrease of cerebrum lateralization

• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.127-138
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• 2011

장시간 저장 후 짧은 시간 동안 운용되는 특성을 갖는 보증 유도탄은 지속적인 신뢰도 저하를 개선하기 위해 주기적인 검사정책을 사용한다. 본 연구에서는 유도탄의 저장 신뢰도 유지를 위해 주기적 검사 개념을 기초로 검사장비의 불완전성에 따라 유도탄 구성품을 정비계단에 맞추어 분류하고, 검사 시 발생하는 손상확률과 정비과정의 불완전성에 의해 손상되는 확률을 고려하여 최적의 검사주기 산출과정을 제시한 기존 연구를 검토한다. 또한 검토된 기존 연구를 바탕으로 주기검사 과정에서 유도탄이 손상되는 확률과 유도탄의 운용 형태 및 정비 형태를 고려한 제약사항을 포함하는 시뮬레이션 모델을 설정하고, 시뮬레이션 전용 패키지를 활용하여 분석함으로써 실제 운용 환경에서 최적의 보증유도탄 검사주기, 주기검사소, 정비창을 설정함으로써 유사 유도탄체계에서 활용이 가능한 시뮬레이션모델을 제안한다.

• 대한의용생체공학회:의공학회지
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• 제26권1호
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• pp.1-7
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• 2005

This study aimed to investigate the hypothesis that administration of the air with 30% oxygen compared with normal air (21% oxygen) enhances cognitive functioning through increased activation in the brain. Seventeen college students (right­handed, average age of 24.3) were selected as subjects for this study. An oxygen supply equipment that provides 21% and 30% oxygen at a constant rate of 8L/min was developed. In order to measure the performance level of visuospatial and verbal cognition, two psychological tests were developed. The experiment consisted of two runs, one for cognition task with normal air (21% oxygen) and the other for cognition task with hyperoxic air (30% oxygen). Visuospatial and verbal tasks were presented while brain images were scanned by a 3T fMRI system using the single-shot EPI method. The results showed that there was an improvement in performance and also increased activation in several brain areas in the higher oxygen condition. These results suggest that while performing cognitive tasks, high concentrations of oxygen administration make oxygen administration sufficient, thus making neural network activate more, and the ability to perform cognitive tasks increase.

• 천문학회보
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• 제37권2호
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• pp.218.2-218.2
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• 2012

In the remote sensing researches, the reflected bright source such as snow, cloud have effects on the image quality of wanted signal. Even though those signal from bright source are adjusted in corresponding pixel level with atmospheric correction algorithm or radiometric correction, those can be problem to the nearby signal as one of the stray light source. Especially, in the step and stare observational method which makes one mosaic image with several snap shots, one of target area can affect next to the other snap shot each other. Presented in this paper focused on the stray light analysis from unwanted reflected bright source for geostationary ocean color sensor. The stray light effect for total 16 slot images each other were performed according to 8 band filters. For the realistic simulation, we constructed system modeling with integrated ray tracing technique which realizes the same space time in the remote sensing observation among the Sun, the Earth, and the satellite. Computed stray light effect in the results of paper demonstrates the distinguishable radiance value at the specific time and space.

• Journal of Astronomy and Space Sciences
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• 제23권4호
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• pp.453-464
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• 2006

일반적으로 웹 카메라는 PC간 화상통신을 위해 많이 쓰이고 있으나, 화소수도 적고 장시간 노출촬영도 불가능하기 때문에 천문용으로 사용하기에는 어려움이 있다. 하지만 장시간 노출이 필요 없는 달이나 행성 등을 촬영하기에는 부족함이 없기 때문에 아마추어 관측자들이 행성 촬영용으로 많이 이용하고 있다. 웹 카메라 중에 CCD를 사용한 Philips사의 ToUcam Pro II를 사용하여 행성촬영을 하였고, 촬영한 동영상은 상용 프로그램인 Registax를 이용하여 합성을 하였다. 또한 웹 카메라의 기본적인 특성을 알아보기 위해, CCD의 특성 분석에 활용하는 직선성, 이득 등의 특성을 살펴보았다. 행성 촬영할 때 기존에는 필름이나 디지털 카메라, CCD로 한 장씩 찍었지만, 웹 카메라로 촬영할 경우 동영상으로 촬영하여서 중은 이미지만을 골라서 합성하기 때문에, 훨씬 더 고해상도의 행성이미지 촬영이 가능하게 되었다. 행성관측 방법과 동영상 합성 방법 등에 대해 논의하기로 한다.

• 비파괴검사학회지
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• 제35권5호
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• pp.299-306
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• 2015

일반 위상배열 시스템에서는 다수의 압전소자를 가지는 탐촉자의 개별 소자에 인가하는 시간지연을 조절함으로써 초음파빔을 전자적으로 제어하고 초음파 영상을 획득한다. 반면, full matrix capture(FMC) 기술은 위상배열 탐촉자에 대해 하나의 소자에서 초음파를 입사시킨 신호를 모든 압전소자에서 수신하고, 이 방법으로 모든 가능한 송수신 조합의 신호 데이터를 수집하는 방법이다. 이 FMC 데이터는 후처리를 통해 초음파 영상으로 재구성될 수 있으며, 기존 위상배열 초음파 영상과 동등한 영상뿐만 아니라 가상적으로 관심영역의 모든 지점에 집속하여 분해능과 선명도가 향상된 total focusing method(TFM) 영상으로도 합성이 가능하다. 본 논문에서는 일반 위상배열장치를 이용하여 FMC가 가능하도록 시스템을 구현하고, 취득된 FMC 신호로부터 sector B-scan 및 TFM 이미지를 영상화하는 알고리즘에 대한 연구를 수행하였다.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.54-65
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• 1997

To quantify the LII signals from soot particle of flames in diesel engine cylinder, a new method has been proposed for correcting LII signal attenuated by soot particles between the measuring point and the detector. It has been verified by an experiment on a laminar jet ethylene-air diffusion flame. Being proportional to the attenuation, the ratio of LII signal at two different detection wavelengths can be used to correct the measured LIIsignal and obtain the unattenuated LII signal, from which the soot volume fraction in the flame can be estimated. Both the 1064-nm and frequency-doubled 532-nm beams from the Nd : YAG laser are used. Single-shot, one-dimensional(1-D) line images are recorded on the intensified CCD camera, with the rectangular-profile laser beam using 1-mm-diameter pinhole. Two broadband optical interference filters having the center wavelengths of 647 nm and 400 nm respectively and a bandwidth of 10 nm are used. This two-wavelength correction has been applied to the ethylene-air coannular laminar diffusion flame, previously studied on soot formation by the laser extinction method in this laboratory. The results by the LII measurement technique and the conventional laser extinction method at the height of 40 nm above the jet exit agreed well with each other except around outside of the peaks of soot concentration, where the soot concentration was relatively high and resulting attenuation of the LII signal was large. The radial profile shape of soot concentration was not changed a lot, but the absolute value of the soot volume fraction around outside edge changed from 4ppm to 6.5 ppm at r=2.8mm after correction. This means that the attenuation of LII signal was approximately 40% at this point, which is higher than the average attenuation rate of this flame, 10~15%.

• Design & Manufacturing
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• 제11권3호
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• pp.19-24
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• 2017

In these days, increase requirement of TEM (Transmission Electro Microscope) in not only scientific field but also industrial field. Because TEM can measure inner-structure of specimen a variety of materials like metal, bio. etc. When use TEM, specimen should be thin about 50nm. So making for thin specimen, use Ion milling device that include specimen holder. The holder generally made of Aluminium Aluminium holder is worn away easily. For this reason, using time of ion milling with aluminum holder is too short. To solve the problem, we replace aluminium holer to molybdenum alloy holder. In this paper, we design molybdenum alloy holer for CAM and modify CAD modeling for effective machining process. So we array a specimen 3 by 4 and setup orientation for one-shot machining process. Next we make a CAM program for machining. we making a decision two machining strategy that chose condition of tool-path method, step-down, step-over. etc. And then conduct machining using CNC milling machining center. To make clear difference between case.1 and case.2, we fixed machining conditions like feed-rate, main spindle rpm, etc. After machining, we confirm the condition of workpiece and analysis the problems case by case. Finally, case.2 work piece that superior than case.1 cutting with WEDM because that method can not ant mechanical effect on workpiece.