• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.176-183
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• 2007

An experimental study was performed to investigate the effects of mixing quality, inlet pressure, nozzle diameter on CO emission and radiation characteristics in porous ceramic fiber radiant burners. Observations of combustion characteristics occurring inside the burner system which was insulated fiber mat, were investigated by measuring temperature, CO emission and radiation characteristics. Combustion was achieved at the firing rate of $88{\sim}99$ kcal/hr, inlet pressure of $100{\sim}250$mm$H_2O$. CO emissions were found to be strongly dependent on the operating conditions. There was a tendency that CO concentration increased as the firing rate increases. The reason for rise of CO concentration is that it becomes the relatively rich condition. The fiber burner exhibit significant both spectral intensity peaks in the bands at 2.5${\mu}m$ and 4.0${\mu}m$ relatively, There is a small difference in the variable mixing tube. However spectral intensity increased with the firing rate.

• 한국유체기계학회 논문집
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• 제18권1호
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• pp.37-43
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• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• Tuberculosis and Respiratory Diseases
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• 제48권5호
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• pp.766-772
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• 2000

배경 : 압력조절환기법(pressure control ventilation mode, PCV)에서 설정된 기도압의 달성은 기도저항이 일정한 조건에서 초기 흡기 유량 (inspiratory flow)에 의해 결정되며 압력상승시간(pressure rise time) 조절은 이 흡기 유량을 변동시킨다. 압력조절환기법에서 흡기 일환기량은 흡기 시간과 흡기 시간내 평균 흡기 유량에 따라 결정되므로 압력 도달 시간을 짧게 하면 초기 유량이 많아지게 되고 따라서 흡기되는 용적이 증가할 것으로 예상된다. 본 연구는 압력조절환기 법에서 압력상승시간을 줄이는 것이 흡기 일환기량 및 가스교환을 호전시키는지 알아보고자 하였다. 방법 : 호흡부전으로 기계호흡 중인 환자 13명(58$\pm$16세, 남 : 여=7 : 6)에서 Servo 300 (Simens-Elema, Solna, Sweden) 상의 압력상승시간 10%. 5% 및 30분 간 씩 적용하고 동맥혈 검사, 혈역동학적 지표(혈압, 분당맥박수) 및 호흡 지표(일회 호흡량, 최대 흡기유량, 최대 흡기압, 평균 기도압, 기도저항, 탄성도, 호기말 이산화탄소, 동맥혈가스)를 측정하였다. 결과 : 1) 압력상승시간이 10%, 5%, 0%로 변경시 일회 호흡량은 425$\pm$94 ml, 439$\pm$101 ml, 456$\pm$106ml로 증가되었다(p<0.001). 압력상승시간 단축에 따라 평균기도압 역시 증가되었다(각각 11.2$\pm$3.7cm $H_2O$, 12.0$\pm$3.7 cm $H_2O$, 12.5$\pm$3.8 cm $H_2O$; p<0.001). 2) pH는 10% 와 5% 보다 0%에서 높았으며(각각 7.40$\pm$0.08, 7.40$\pm$0.92, 7.41$\pm$0.96 ; p<0.0), $PaCO_2$도 10%와 5%에서 보다 0%에서 낮았다(각각 47.4$\pm$15.8 mm Hg, 47.2$\pm$15.7 mm Hg, 44.6$\pm$16.2 mm Hg ; p<0.01). 결론 : 압력조절환기법에서 압력상승시간의 단축은 일환기량과 평균기도압을 증가시키고, 동맥혈이산화탄소분압 저하 및 이에 따른 pH 상승 효과가 있었다. 압력조절 환기법에서 압력상승시간은 일환기량을 조절할 수 있는 한 변수로 사료된다.

• 항공우주기술
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• 제2권2호
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• pp.25-32
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• 2003

액체로켓용 터보펌프 인듀서에 대한 수치해석적 연구에 이루어졌다. 다수의 유동조건에서의 쉬라우드 표면 정압분포, 수두 및 효율에 대한 계산이 수행되었으며, 실험값과 비교하였다. 쉬라우드 정압의 분포는 실험과 비교하여 잘 일치하는 결과를 얻을 수 있었으나, 입구의 역류가 심한 지역에서는 실험값과 차이를 보였다. 전체 성능, 즉, 수두 및 효율은 대체로 실험값과 잘 일치하였지만, 고유량에서 계산값이 실험치에 비하여 낮게 예측하는 것이 확인되었다. 본 연구에 채택된 인듀서의 경우, 유량계수가 0.074일 경우에 수력성능이 최고가 되었으며, 유량계수가 0.085이상에서 입사각이 양의 값을 가지게 된다.

• 한국화재소방학회논문지
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• 제31권5호
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• pp.63-69
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• 2017

본 연구에서는 초고압 펌프의 개발과 같이 사용할 수 있는 초고압용 장거리 호스 개발에 관한 연구이며, 접근과 방수거리의 도달이 어려운 초고층 건물 및 대심도 터널의 화재진압에 효율적으로 적용이 가능함과 동시에 축광 성능을 포함하여 소방관의 화재 진압 시 퇴로 확보에도 도움이 될 수 있는 초고압용 호스의 개발에 관한 연구이다. 호스의 성능으로서 압력 3 MPa, 유량 2000 lpm을 목표로 초고압 호스를 개발하였으며, 2중의 자켓과 3중의 폴리우레탄 코팅 및 52의 경사를 사용하여 매우 촘촘하고 높은 고압에도 견딜 수 있는 초고압 소방호스를 개발하였다. 개발된 초고압 호스의 성능을 확보하기 위하여 구조 및 외관, 고압에서의 누수, 길이, 신장률, 박리시험, 마찰시험, 파단압시험 및 자유낙하 시험 등이 공인된 인증기관에서 수행되었으며 수행결과 성능에 이상이 없는 것으로 파악되었다. 또한 소방관의 화재진압 시 퇴로를 확보하기 위한 축광 성능의 초고압 호스에 추가하여 연구 및 개발하였으며, 휘도시험의 값으로 축광의 발광시험 개시부터 40분 후까지 휘도 측정치가 휘도시험의 기준 값 이상으로 충분히 확보되는 것을 확인할 수 있었다. 향후, 이와 같은 초고압용 소방용 호스가 상용화가 되어 현장에서 적용된다면 초고층 건물의 화재진압 및 장대터널에서의 화재진압에 있어서 현재 사용되고 있는 소방호스 보다 개선된 화재 진압 및 안전한 퇴로를 확보하는 측면에서 기여할 수 있을 것으로 판단된다.

• Journal of Biosystems Engineering
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• 제5권2호
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• pp.1-14
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• 1980

This study was carried out to investigate the effects of the counter-pressure setting and the roller speed of a rice whitening machine on the head rice recovery. milling capacity and milling efficiency, and also to find out the optimum operational conditions of the machine. The radial pressure inside the whitening chamber and the outlet axial pressure were measured to study their relationships with the head rice recovery, milling capacity and milling efficiency. The results of the study are summarized as follows. (1) The most important factor in rice whitening was the counter-pressure setting. It significantly affected the head rice recovery. (2) The roller speed significant affected the milling capacity and milling efficiency , but it did not affected the head rice recovery. (3) Both the radial pressure and the outlet axial pressure were affected by the counter-pressure setting but not by the roller speed. Both of them increased almost linearly with the counter-pressure setting. There was a significant correlation between the radial pressure and the outlet axial pressure. (4) The flow rate through the whitening chamber when the feed gate was fully opened increased with the roller speed, but it was not affected by the counter-pressure setting. (5) The head rice recovery decreased as the counter-pressure setting increased , but it was not affected by the roller speed. The reason could be explained by the fact that the radical pressure increased only with the counter-pressure setting. (6) The milling capacity increased with the counter-pressure setting and linearly with the roller speed. The milling efficiency generally increased with both the counter-pressure setting and the roller speed. However, the effect of roller speed was negligible at the higher counter-pressure setting. The temperature rise inside the whitening chamber was moderate with the mean of 11.3℃ (range 5.6-18.3℃) even though it increased slightly with the roller speed. Considering the head rice recovery and milling efficiency, the optimum operational conditions of the machine appeared to be the counter-pressure setting of 67g/㎠ and the roller speed of 1,050rpm. Neglecting the small difference in the head rice recovery , the greater milling capacity could be obtained at the counter-pressure setting of 85g/㎠ with the roller speed of 850-1050rpm.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.337-345
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• 2002

The present study addresses a computational result of unsteady gas flow through a critical nozzle. The axisymmetric, unsteady, compressible, Wavier-Stokes equations are solved using a finite volume method that makes use of the second order upwind scheme for spatial derivatives and the multi-stage Runge-Kutta integral scheme for time derivatives. The steady solutions of the governing equation system are validated with the previous experimental data to ensure that the present computational method is valid to predict the critical nozzle flows. In order to simulate the effects of back pressure fluctuations on the critical nozzle flows, an excited pressure oscillation with an amplitude and frequency is assumed downstream of the exit of the critical nozzle. The results obtained show that for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of critical nozzle, and thus giving rise to the applicable fluctuations in mass flow rate through the critical nozzle, while for high Reynolds numbers, the pressure signals occurring at the exit of the critical nozzle do not propagate upstream beyond the nozzle throat. For very low Reynolds number, it is found that the sonic line near the throat of the critical nozzle remarkably fluctuateswith time, providing an important mechanism for pressure signals to propagate upstream of the nozzle throat, even in choked flow conditions. The present study is the first investigation to clarify the unsteady effects on the critical nozzle flows.

• Journal of Chest Surgery
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• 제28권5호
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• pp.437-442
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• 1995

We developed an experimental model of brain death using dogs. Brain death was caused by increasing the intracranial pressure[ICP suddenly by injecting saline to an epidural Foley catheter in five female mongrel dogs[weight, 20-25Kg .Hemodynamic and electrocardiographic changes were evaluated continuously during the process of brain death. 1. Abrupt rise of ICP after each injection of saline followed by a rapid decline to a new steady-state level within 15 minutes and the average volume required to induce brain death was 7.6$\pm$0.8ml.2. Body temperature, heart rate, mean pulmonary arterial pressure, left ventricular[LV enddiastolic pressure and cardiac output was not changed significantly during the process of brain death, but there was an increasing tendency.3. Mean arterial pressure and LV maximum +dP/dt increased significantly at the time of brain death.4. Hemodynamic collapse was developed within 140 minutes after brain death.5. Marked sinus bradycardia followed by junctional rhythm was seen in two dogs and frequent VPB`s with ventricular tachycardia was observed in one dog at the time of brain death. Hyperdynamic state develops and arrhythmia appears frequently at the time of brain death. Studies on the effects of brain death on myocardium and its pathophysiologic mechanism should be followed in the near future.

• Tribology and Lubricants
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• 제38권6호
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• pp.281-286
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• 2022

In this study, the effects of Elasto-hydrodynamic lubrication pressure on the critical shoulder height of raceway in an angular contact ball bearing were investigated. Both 3D contact analyses using an influence function and the EHL analysis were conducted for the contact geometry between the ball and raceways. The pressure distributions by 3D contact analysis and EHL analysis for an example bearing were compared. The effect of ellipse truncation on the minimum film thickness also investigated from EHL analysis. The critical shoulder height in the dry contact and the EHL state were compared for various applied loads. It is shown that when the ellipse truncation occurs, the pressure spike for the EHL conjunction is higher than that for the dry contact, and its location moves more inward of the contact center. The steep pressure gradients would increase the flow rate, so in order to maintain flow continuity a significant reduction in film thickness and an abrupt rise in pressure occurs in the edge of shoulder. Significant reduction of the minimum film thickness occurs near the edge of shoulder. The critical shoulder heights in the EHL state are calculated as higher values compared with in the dry contact. This results shows that the determination of critical shoulder height by the EHL analysis is more proper.

• Tribology and Lubricants
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• 제38권5호
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• pp.185-190
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• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.