• 항공우주기술
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• 제5권2호
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• pp.174-180
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• 2006

액체로켓엔진에서 연료와 산화제를 가압하는 역할을 하는 핵심부품인 터보펌프는 극저온 산화제와 구동 터빈의 고온 환경이 동일 축에 분포하고 있으며 내부 회전부 간극이 매우 작고 회전속도가 높아 기계적으로 대단히 열악한 환경에서 동작한다. 따라서 사고 위험도를 낮추기 위한 구조 해석 및 시험이 필수적인데, 본 연구에서는 특히 터보펌프 케이징의 구조해석 및 응력 측정이 이루어졌다. 기존의 단품 레벨에서의 해석에서 벗어나 연료펌프와 산화제펌프의 케이징 조립체 레벨에서 내압기밀시험 조건에 대한 구조해석이 이루어졌으며 이를 통하여 케이징 간 체결효과 및 실 부분의 접촉 압력을 성공적으로 고려할 수 있었다. 또한, 연료펌프 케이징에 나타나는 높은 수준의 응력 집중 현상을 해석과 측정을 병행함으로써 성공적으로 예측하였다.

• 한국세라믹학회지
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• 제35권1호
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• pp.88-96
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• 1998

The structural and electrical properties of titanium dioxide(TiO2) thin films deposited on p-type (100) si and 4$^{\circ}$off(100) Si substartes by metalorganic chemical vapor deposition (MOCVD) have been studied with post rapid thermal annealing. TiO2 thin films of anatase phase were grown at 300-500$^{\circ}C$ using titanium post rapid thermal annealing at a temperature of 800$^{\circ}C$ for 30sec. rutile phase was observed in the condition of the deposition temperature over 350$^{\circ}C$ in the ambient air atmosphere and at 500$^{\circ}C$ in cacuu,. SEM and AFM study show-ed surface roughness were increased slightly from 40${\AA}$to 55${\AA}$ after annealing due to grain growth and phase transformation. From capacitane-voltage measurement of Al/TiO2./p-Si structure after annealing we obtained ideal capacitance-voltage characteristics of MOS structure with dielectric constant of 16-22 in case of (100) Si and about 30- in case of 4$^{\circ}$off(100) Si but showed the higher leakage current.

• 한국전산구조공학회논문집
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• 제15권3호
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• pp.409-420
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• 2002

본 논문에서는 상시진동계측 결과를 활용하여 교랑의 이동하중해석을 수행하기 위한 구조재해석 기법을 제시하였다. 구조재해석을 위해 필요한 실구조물의 고유진동수와 모우드 형상은 직접퓨리에 분석을 통해 구하고, 감쇠비는 Random Decrement기법을 이용하는 방법을 사용하였다. 또한, 계측 모우드 형상을 구조재해석에 필요한 자유도로 보간하기 위한 보간법을 제시하였다. 더불어, 제시된 구조재해석기법을 이동질량 모형에 기초한 주행하중 해석에 적용하여 이를 직접 해석한 결과와 비교하였다 해석결과는 상시진동 계측의 결과만을 이용하여 수행된 구조재해석 결과도 교량의 실제 응답을 잘 표현할 수 있음을 보여주고 있다.

• Advances in environmental research
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• 제1권1호
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• pp.69-82
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• 2012

Based on the measurement data of the particulate matter with an aerodynamic diameter of less than or equal to a nominal 10 ${\mu}m$ (PM10) by the ${\beta}$-ray absorption method (BAM) equipped with an inlet heater and the gravimetric method (GMM) at two coastal sites in Korea, the optimal inlet heater temperature was estimated. By using a gas/particle equilibrium model, Simulating Composition of Atmospheric Particles at Equilibrium 2 (SCAPE2), water content in aerosols was estimated with varying temperature to find the optimal temperature increase to make the PM10 concentration by BAM comparable to that by GMM. It was estimated that the heated air temperature inside the BAM should be increased up to $35{\sim}45^{\circ}C$ at both sites. At this temperature range, evaporation of volatile aerosol components was minor. Similar ($30{\sim}50^{\circ}C$) temperature range was also obtained from the calculation based on the absolute humidity which changed with ambient absolute humidity and chemical composition of hygroscopic species.

• 제어로봇시스템학회논문지
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• 제15권5호
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• pp.519-524
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• 2009

This paper describes a new sensor system for 3D environment perception using stereo structured infrared light sources and a camera. Environment and obstacle sensing is the key issue for mobile robot localization and navigation. Laser scanners and infrared scanners cover $180^{\circ}$ and are accurate but too expensive. Those sensors use rotating light beams so that the range measurements are constrained on a plane. 3D measurements are much more useful in many ways for obstacle detection, map building and localization. Stereo vision is very common way of getting the depth information of 3D environment. However, it requires that the correspondence should be clearly identified and it also heavily depends on the light condition of the environment. Instead of using stereo camera, monocular camera and two projected infrared light sources are used in order to reduce the effects of the ambient light while getting 3D depth map. Modeling of the projected light pattern enabled precise estimation of the range. Two successive captures of the image with left and right infrared light projection provide several benefits, which include wider area of depth measurement, higher spatial resolution and the visibility perception.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.92-96
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• 2009

A new precursor [$Zr(acac)_{3}(H_{2}O)_{2}$] was synthesized by Sonochemical technique and used to deposit thin $ZrO_{2}$ film on quartz and ceramic substrate via ultrasonic aerosol assisted chemical vapour deposition (UAACVD) at 300 ${^{\circ}C}$ in oxygen environment followed by annealing of the sample for 2-3 minutes at 500 ${^{\circ}C}$ in nitrogen ambient. The molecular structure of the precursor determined by single crystal X-ray analysis revealed that the molecules are linked through intermolecular hydrogen bonds forming pseudo six and eight membered rings. DSC and TGA/FTIR techniques were used to determine thermal behavior and decomposition temperature of the precursor and nature of evolved gas products. The optical measurement of annealed $ZrO_{2}$ film with tetragonal phase shows optical energy band gap of 5.01 eV. The particle size, morphology, surface structure and composition of deposited films were investigated by XRD, SEM and EDX.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.768-773
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• 2004

When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is underexpanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with nonequilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics can not even know. In the present study, the effect of the nonequilibrium condensation on the underexpanded moist air jet impinging on a vertical flat plate is investigated experimentally. Flow visualization and impact pressure measurement are performed for various relative humidities and flat plate positions. The obtained results show the plate shock and Mach disk are dependent on the nozzle pressure ratio and the relative humidity, but for a given nozzle pressure ratio, the diameters of the plate shock and Mach disk depend on the stagnation relative humidity. The impact pressure deviation from the flow of without condensation is large, as the relative stagnation humidity increases.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.493-502
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• 2012

Syngas laminar burning velocity measurements were carried out at atmospheric pressure and ambient temperature using the Bunsen flame configuration with nozzle burner as a fundamental study on flame stability of syngas fuel. Representative syngas mixture compositions ($H_2$:CO) such as 25:75%, 50:50% and 75:25% and equivalence ratios from 0.5 to 1.4 have been conducted. Average laminar burning velocities have been determined by the stabilized nozzle burner flames using the angle method, radical surface area method and compared with the data obtained from the other literatures. And the results of each experimental methodologies in the various composition ratios and equivalence ratios were coincided with the result of numerical simulation. Especially, it was confirmed that there was necessary to choice a more accurate measurement methodology even the same static flame method for the various composition ratios of syngas fuel including hydrogen. Also, it was reconfirmed that the laminar burning velocities gradually increased with the increasing of hydrogen content in a fuel mixture.

• 한국지능시스템학회논문지
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• 제11권1호
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• pp.58-64
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• 2001

정밀을 요하는 자동차 부품의 측정 시스템은 온도에 따라 보상이 필수적이다. 부품의 측정값의 신뢰도를 유지하기 위해서 단순히 제품의 합격 영역을 상온에서 51.786~51.819mm로 했을 때, 온도가 상온에서 따러져 있는 경우 그 부품의 측정영역을 신뢰하기가 어려워진다. 본 논문에서는 이 문제를 해결하기 위해서 2개의 카메라를 사용하여 한쪽은 표준 제품을 두고, 다른 쪽은 실제 제품을 둠으로서 온도에 따라 달라지는 표준 제품의 측정값의 Offset를 실제 제품에 반영함으로써 측정값을 보상하려고 하였다. 자동차의 부품은 여러 가지가 있으나, 이 중에서 현재 공장에서 측정에 어려움을 겪고 있는 에어콘 스윗치인 마그네트 코일 하우징을 대상으로 하였다. 특히 측정 대상이 크고, 카메라의 화소수가 40만 이하일 경우, 측정의 중요한 포인트는 화소수와 배경과 대상의 구별이다. 이를 정확히 알아내는데, FCM (Fuzzy C-means) 알고리듬이 좋은 결과를 주지만 속성 공간에서 유사성만을 고려하고, 공간영역에서 유사성은 고려되지 않기 때문에 FCM은 \"equal evidence\"와 \"ignorance\"를 구분하지 못한다. 이를 개선하기 위해서 FCM를 수정하여 먼저 FCM로 처리하고 이를 바탕으로 PCM (Possibilistic C-means)를 사용하였다. 결과를 모니터에 보여주고, RSC-232 포트를 통하여 신호를 마이크로 프로세서에 전달하여 제품의 양호(good), 불량(bad)을 판별하는 신호를 발생하게 하였다.을 판별하는 신호를 발생하게 하였다.

• 한국세라믹학회지
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• 제28권8호
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• pp.603-610
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• 1991

An oxygen deficient perovskite (CaLa)(MgMn)O5.43, with the cubic unit cell parameter of 3.826$\AA$, was prepared 115$0^{\circ}C$ for 10 hrs under the ambient oxygen gas pressure. The average oxidation state of manganese was determined to be 3.86 by the iodometric titration, so that the perovskite could be formulated as (CaLa) ({{{{ { MgMn}`_{ chi } ^{II } }}{{{{ { Mn}`_{ y} ^{III } }}{{{{ { Mn}`_{1- chi -y } ^{IV } }})O5.43 (2x+y=0.14). From X-ray photoelectron spectroscopy, the manganese ions in the lattice are mostly tetravalent, but two paramagnetic configurations were observed in the EPR spectrum: One sharp isotropic signal with hyperfines (ΔH 50 G, g=1.997$\pm$0.002 and │A│=82(4)$\times$10-4 cm-1) and a broad isotropic one (ΔH 1600 G, g=1.994$\pm$0.002), those which correspond respectively to Mn(II) and Mn(IV) ions. According to the magnetic susceptibility measurement, it follows the Curie-Weiss law from 20 K up to room temperature with $\mu$eff=5.23 $\mu$B, which is relatively larger than spin-only value({{{{ { mu }`_{eff} ^{s.o } }}=4.04 $\mu$B) due to the effect of weak ferromagnetic coupling. Such a result is in accord with a theory of semicovalence exchange.