• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.165-170
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• 2004

The purpose of this work was to assess and quantify the beneficial effects of long-term gas exchange, at varying frequencies, for the development of a vibrating intravascular lung assistance device (VIVLAD), for patients suffering from acute respiratory distress syndrome (ARDS). The experimental design and procedure have been applied to the construction of a new device for assessing the effectiveness of membrane vibrations. An analytical solution has been developed for the hydrodynamics of flow through a bundle of sinusoidally vibrated hollow fibers, with the intention of gaining insight into how wall vibrations might enhance the performance of the VIVLAD. As a result, the maximum oxygen transfer rate was reached at the maximum amplitude and through the transfer of vibrations to the hollow fiber membranes. The device was excited by a frequency band of 7Hz at various water flow rates, as this frequency was the 2nd mode resonance frequency of the flexible beam. 675 hollow fiber membranes were also bundled, within the blood flow, into the device.

• 한국정밀공학회지
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• 제21권10호
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• pp.78-85
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• 2004

The particle amount monitoring technique using ultrasound is proposed to determine the proper maintenance time of the filter in the supply process of pure gas in the unit of oxygen plant. There are advantages that it is adaptable in high temperature and high pressure, and it is not disturbed by being exposed in the gas flow, and it can be implemented very economically. The applicability of the ultrasonic technique is pre-studied through the theoretical analysis for the dependency of attenuation of ultrasonic wave on the particles in the gas flow. For the purpose, absorption, scattering and dispersion models are considered, and the attenuation by absorption and the change rate of the propagation speed are calculated fur the specific range of particle size and the ultrasonic wave frequency. It was expected by simulation that the absorptive attenuation by particles was the most sensitive to the change of particle amount. The experimental result showed high correspondence with the theoretical expectation so that this ultrasound attenuation measurement was proved to be highly effective for monitoring the amount of floating particles in the gas flow.

• 한국표면공학회지
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• 제40권4호
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• pp.170-174
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• 2007

High Velocity Oxygen Fuel (HVOF) thermal spray coating of nano size WC-Co powder (nWC-Co) has been studied as one of the most promising candidate for the possible replacement of the traditional hard plating in some area which causes environmental and health problems. nWC-Co powder was coated on Inconel 718 substrates by HVOF technique. The optimal coating process obtained from the best surface properties such as hardness and porosity is the process of oxygen flow rate (FR) 38 FMR, hydrogen FR 57 FMR and feed rate 35 g/min at spray distance 6 inch for both surface temperature $25^{\circ}C\;and\;500^{\circ}C$. In coating process a small portion of hard WC decomposes to less hard $W_2C$, W and C at the temperature higher than its decomposition temperature $1,250^{\circ}C$ resulting in hardness decrease and porosity increase. Friction coefficient increases with increasing coating surface temperature from 0.55-0.64 at $25^{\circ}C$ to 0.65-0.76 at $500^{\circ}C$ due to the increase of adhesion between coating and counter sliding surface. Hardness of nWC-Co is higher or comparable to those of other hard coatings, such as $Al_2O_3,\;Cr,\;Cr_2O_3$ and HVOF Tribaloy 400 (T400). This shows that nWC-Co is recommendable for durability improvement coating on machine components such as high speed spindle.

• 한국수산과학회지
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• 제55권4호
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• pp.449-454
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• 2022

The oxygen consumption rate (OCR) based on the water temperature and body size of the sea squirt Halocynthia roretzi was examined to provide quantitative information about the metabolic response of the species. OCRs were measured using a closed flow-through respirometer at four different water temperatures (10, 15, 20 and 25℃) and two different body sizes (21.4±1.1 g and 150.5±1.3 g, wet weight) with triplicates of each treatment. OCR increased as water temperature increased at both body sizes, but decreased as body size increased regardless of the water temperature (P<0.001). The effect of body size evaluated as a power function ranged from 0.8055 to 0.8884. The highest Q₁₀ values in the small and large size groups ranged from 15 to 20℃ and 20 to 25℃, respectively. The metabolic daily energy loss rate via respiration at all tested temperatures ranged from 56.2 to 106.1 J g^-1 d^-1 in the small-size group and from 44.5 to 92.0 J g^-1 d^-1 in the large-size group. Our results indicate that the metabolic response of H. roretzi highly depends on fluctuating water temperature at a given life stage.

• 항공우주기술
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• 제8권2호
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• pp.140-148
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• 2009

발사체 추진시스템에서 CC(Combustion Chamber) 산화제 개폐밸브는 액체산소를 연소기로 공급 및 차단함으로써 연소를 개시 및 중단시킬 뿐만 아니라, 정상운영 상태에서는 연소기 내 안정된 연소가 가능하도록 일정한 유량의 액체산소를 공급한다. CC 산화제 개폐밸브 개발과 관련하여, TM(Technology Model)의 극저온 산화제 개폐밸브를 제작하여, 밸브의 정상적인 작동성능을 이미 확인한 바 있다. 반면 TM의 유량계수, Cv가 설계기준 값보다 상당히 작았기 때문에, 차기 개발 단계인 CC 산화제 개폐밸브 EM(Engineering Model)의 설계/제작을 통해 충분히 개선된 Cv 특성을 확보하기 위해 CFD 해석을 수행하였다. CFD 해석 결과, 밸브 출구 각도를 120o로 변경하고, 밸브의 부분적인 크기 증가와 스트록 길이를 증가시킴으로써 EM의 Cv를 상당히 향상시킬 수 있는 것으로 확인되었다. 유량시험을 통해 측정된 EM의 개선된 Cv는 최소 212로써, 기존 TM의 Cv값인 161보다 32%가량 증가된 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.299-304
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• 2004

In recent years, silicon carbide has emerged as an important material for MEMS application. In order to fabricate an SiC film based MEMS structure by using chemical etching method, high operating temperature is required due to high chemical stability Therefore, dry etching using plasma is the best solution. SiC film was deposited by thermal CVD at the temperature of 100$0^{\circ}C$ and pressure of 10 torr. SiC was dry etched with a reactive ion etching (RIE) system, using SF$_{6}$/O$_2$ and CF$_4$/O$_2$ gas mixture. Etch rate has been investigated as a function of oxygen concentration in the gas mixture, rf power, working pressure and gas flow rate. Etch rate was measured by surface profiler and FE-SEM. SF$_{6}$/O$_2$ gas mixture showed higher etch rate than CF$_4$/O$_2$ gas mixture. Maximum etch rate appeared at RF Power of 450W. $O_2$ dilute mixtures resulted in an increasing of etch rate up to 40％, and the superior anisotropic cross section was observe

• 한국항공우주학회지
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• 제30권1호
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• pp.114-123
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• 2002

케로신/액체산소 추진기관을 갖는 초음속 로켓의 플룸 유동장을 9 화학종 14 반응 모델과 연계된 레이놀즈 평균 Navier-Stokes 방정식을 이용하여 해석하였다. 유한속도 화학반응이 플룸 유동장에 미치는 영향을 고찰하기 위하여 그 결과를 화학적 동결유동 해석 결과와 비교하였다. 계산은 상용 CFD 소프트웨어인 FLUENT 5를 이용하여 수행하였다. 반응 유동 해석 결과는 노즐 내부에서의 화학반응에 따른 연소가스의 온도 증가로 인해 전체적으로 동결유동에 비해 더 높은 온도장을 나타내었다. 플룸에서의 모든 화학반응은 전단류와 배럴 충격파 반사지점 후방의 고온 영역에 국한되어 일어났으며 본 해석의 경우 플룸내에서의 유한속도 화학반응이 유동에 미치는 영향은 미약한 것으로 나타났다. 그러나 본 연구에서 이루어진 유한속도 화학반응을 고려한 플룸 해석을 통하여 플룸에서의 주된 화학 반응 및 이들의 반응 메커니즘을 확인할 수 있었다.

• 한국표면공학회지
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• 제47권3호
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• pp.109-115
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• 2014

High power impulse magnetron sputtering (HIPIMS), also known as the technology is called peak power density in a short period, you can get high, so high ionization sputtering rate can make. Higher ionization of sputtered species to a variety of coating materials conventional in the field of improving the characteristics and self-assisted ion thin film deposition process, which contributes to a superior being. HIPIMS at the same power, but the deposition speed is slow in comparison with DC disadvantages. Since recently as a replacement for HIPIMS modulated pulse power (MPP) has been developed. This ionization rate of the sputtered species can increase the deposition rate is lowered and at the same time to overcome the problems to be reported. The differences between the MPP and the HIPIMS is a simple single pulse with a HIPIMS whereas, MPP is 3 ms in pulse length is adjustable, with the full set of multi-pulses within the pulse period and the pulse is applied can be micro advantages. In this experiment, $In_2O_3$ : $SnO_2$ composition ratio of 9 : 1 wt% target was used, Ar : $O_2$ flow rate ratio is 4.8 to 13.0% of the rate of deposition was carried out at room temperature. Ar 40 sccm and the flow rate of $O_2$ and then fixed 2 ~ 6 sccm was compared against that. The thickness of the thin film deposition is fixed at 60 nm, when the partial pressure of oxygen at 9.1%, the specific resistance value of $4.565{\times}10^{-4}{\Omega}cm$, transmittance 86.6%, mobility $32.29cm^2/Vs$ to obtain the value.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.305-312
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• 2011

The use of a separator to control stack temperature in a molten carbonate fuel cell was studied by numerical simulation using a computational fluid dynamics code. The stack model assumed steady-state and constant-load operation of a co-flow stack with an external reformer at atmospheric pressure. Representing a conventional cell type, separators with two flow paths, one each for the anode and cathode gas, were simulated under conditions in which the cathode gas was composed of either air and carbon dioxide (case I) or oxygen and carbon dioxide (case II). The results showed that the average cell potential in case II was higher than that in case I due to the higher partial pressures of oxygen and carbon dioxide in the cathode gas. This result indicates that the amount of heat released during the electrochemical reactions was less for case II than for case I under the same load. However, simulated results showed that the maximum stack temperature in case I was lower than that in case II due to a reduction in the total flow rate of the cathode gas. To control the stack temperature and retain a high cell potential, we proposed the use of a separator with three flow paths (case III); two flow paths for the electrodes and a path in the center of the separator for the flow of nitrogen for cooling. The simulated results for case III showed that the average cell potential was similar to that in case II, indicating that the amount of heat released in the stack was similar to that in case II, and that the maximum stack temperature was the lowest of the three cases due to the nitrogen gas flow in the center of the separator. In summary, the simulated results showed that the use of a separator with three flow paths enabled temperature control in a co-flow stack with an external reformer at atmospheric pressure.

• 한국수산과학회지
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• 제56권5호
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• pp.660-666
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• 2023

This study aimed to examine the effect of external pop-up satellite archival tags (PSATs) attachment and water temperature on the oxygen consumption rate (OCR) of the olive flounder (mean body weight 2281.7 g). The OCRs of fish were measured under conditions of three different water temperature conditions (15, 20, and 25℃) and two different tagging methods [non-tagging, control; bio-logger external attachment with a miniature PSAT (dummy mrPAT), BEA] using a closed flow-through respirometer. The OCRs of fish linearly increased with the increase in water temperature in both the control and BEA (P<0.001); however, the OCRs of BEA were approximately 1.8-1.9 times lower than those of the control at each water temperature (P<0.001). The Q₁₀ values of the control and BEA were the highest in the water temperature range of 15 to 20℃, but sensitivity to water temperature changes was higher in BEA than in the control. The metabolic energy loss rate (MEL) of fish increased with increasing water temperature regardless of external tagging, but the MEL of the control was higher than that of BEA (P<0.001). These results demonstrate that OCR, thermal sensitivity, and energy expenditure are all affected in adult olive flounder with external PSAT attachment.