• 대한기계학회논문집
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• 제12권2호
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• pp.359-372
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• 1988

본 연구에서는 두 노즐간의 거리와 분사압력을 변화시켜 하류로 전개되는 이중분무의 분무형태를 살펴보았다.

• 한국전산유체공학회지
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• 제19권4호
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• pp.80-85
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• 2014

High-volume low-speed (HVLS) fans are one category of ceiling fan installed in large enclosings such as warehouses, large barns and health clubs in order to generate comfortable air circulation. As a rotary blade, aerodynamic performance of a HVLS fan is predominantly related to its airfoil(s), and the pitch and twist angles. This paper first, investigates the effects of airfoil on the performances of three different HVLS fans with NACA 5414, 6413 and 7415 airfoils. The fans have six untwisted blades with the diameter of 6 m and rotate at 60 RPM. The blades pitch angels are $12^{\circ}$, $12^{\circ}$ and $13^{\circ}$, respectively. The results are presented in the form of the aerodynamic forces and moments, volumetric flow rate and streamlines. Regarding the volumetric flow of air, the results show that the model with NACA 7415 has the best performance. Hence, two other HVLS fans with the same airfoil but, with four and five blades are studied in order to investigate the effects of number of blades. From the point of view of air circulation still the six-bladed fan is the best one; however, the five-bladed fan is more efficient in power consumption.

• 공업화학
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• 제28권4호
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• pp.437-441
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• 2017

본 연구에서는 방화용 실란트의 첨가제로 사용되는 팽창흑연의 부피팽창률과 경도특성을 개선하기 위해 팽창흑연에 다양한 수지를 코팅한 후 그 특성을 고찰하였다. 수지의 코팅률을 나타내는 평균코팅두께는 수지의 건조속도와 점도의 영향으로 초산비닐계수지 > 아크릴수지 > 우레탄수지 > 수용성라텍스의 순으로 크게 나타났다. 또한 수지의 종류에 따라 코팅된 팽창흑연의 부피팽창률은 우레탄수지 > 수용성라텍스 > 아크릴수지 > 초산비닐계수지의 순으로 컸으며, 경도는 초산비닐계수지 > 아크릴수지 > 수용성라텍스 > 우레탄수지의 순으로 증가함을 알 수 있었다. 이는 코팅처리를 하지 않은 팽창흑연에 비해 부피팽창률은 감소하나 경도가 현저하게 증가되어 방화첨가제로 사용이 가능함을 알 수 있었다. 반응표면분석법에 의한 최적화실험 결과 아크릴수지의 최적코팅 조건은 수지의 첨가량 37.6 wt%과 코팅 교반속도 441.4 rpm이었다.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.120-127
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• 2019

Purpose: This study was designed to evaluate the dosimetric performance of Mobius3D by comparison with an aSi-based electronic portal imaging device (EPID) and Octavius 4D, which are conventionally used for patient-specific prescription dose verification. Methods: The study was conducted using nine patients who were treated by volumetric modulated arc therapy. To evaluate the feasibility of Mobius3D for prescription dose verification, we compared the QA results of Mobius3D to an aSi-based EPID and the Octavius 4D dose verification methods. The first was the comparison of the Mobius3D verification phantom dose, and the second was to gamma index analysis. Results: The percentage differences between the calculated point dose and measurements from a PTW31010 ion chamber were 1.6%±1.3%, 2.0%±0.8%, and 1.2%±1.2%, using collapsed cone convolution, an analytical anisotropic algorithm, and the AcurosXB algorithm respectively. The average difference was found to be 1.6%±0.3%. Additionally, in the case of using the PTW31014 ion chamber, the corresponding results were 2.0%±1.4%, 2.4%±2.1%, and 1.6%±2.5%, showing an average agreement within 2.0%±0.3%. Considering all the criteria, the Mobius3D result showed that the percentage dose difference from the EPID was within 0.46%±0.34% on average, and the percentage dose difference from Octavius 4D was within 3.14%±2.85% on average. Conclusions: We conclude that Mobius3D can be used interchangeably with phantom-based dosimetry systems, which are commonly used as patient-specific prescription dose verification tools, especially under the conditions of 3%/3 mm and 95% pass rate.

• 에너지공학
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• 제23권4호
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• pp.230-235
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• 2014

본 연구에서는 프로토 타입 베인 팽창기가 적용된 초소형 유기 랭킨사이클을 구성하고, 팽창기 전단 온도가 약 $110^{\circ}C$이고, 냉매유량을 일정하게 유지한 조건에서 베인 팽창기 회전수를 변화시키면서, 팽창기 출력, 효율 및 팽창기 전후단 압력, 온도 등을 측정하였다. 베인 팽창기 성능 측정 결과 팽창기 회전수가 증가됨에 따라 팽창기 출력 및 효율이 증가하였다. 팽창기 전효율은 500 rpm 회전수 조건에서 6~7%이고, 1000 rpm 에서는 11~12%임을 보였다. 팽창기 전효율이 낮은 원인은 팽창기 체적효율이 낮기 때문인 것으로 분석되었으며, 향후 체적효율을 향상시키기 위해 팽창기 누설을 개선하기 위한 연구가 진행될 예정이다.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1383-1389
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• 2011

본 연구는 태양열 발전에 사용하는 공기식 다채널 체적식 흡수기의 일관성 있는 열전달 해석에 초점을 두고 있다. 이를 위해 흡수 소재 물성과 채널 형상 변화의 영향을 몬테카를로 광선추적법에 기반한 광학 모델과 전도, 대류, 복사를 고려한 1 차원 열전달 모델에 동시에 반영하였다. 광학 모델 결과는 채널 반경 대비 길이의 형상비가 매우 커서 대부분의 태양 에너지는 15 mm 이내의 짧은 길이에서 흡수됨을 증명하고 있다. 복사 열손실 분류를 통해 채널의 낮은 흡수율에서는 방사 손실은 줄지만 반사손실이 증가하여 흡수기 효율이 감소하는 것을 보였다. 큰 채널 반경이나 작은 질량 유량으로 인해 흡수기 평균 온도가 상승할 때, 방사 손실과 반사 손실 모두 증가하지만 방사 손실의 영향이 더 큰 것으로 나타났다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.426-429
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• 2001

The continuous production of L -proline was studied using L-histidine auxotrophic mutant of Corynebacterium acetoacidophilum under various substrate limited conditions. Among the $NH_4\;^+$ $PO_4\;^3$ and L -histidine limited conditions, the highest production of L -proline was observed under the L-histidine limited condition. Under $NH_4\;^+$ and $PO_4\;^3$ limited conditions, no or poor L-proline production was observed, respectively. For the kinetic parameters under L -histidine limitation the specific rate of L -proline production was increased with dilution rate upto $0.1hr^{-1}$ but decreased above $0.1hr^{-1}$. The volumetric rate of L -proline production was showed similar pattern with specific rate. The dried cell weight was gradually increased according to decrease the dilution rate. Specific rate of glucose consumption was proportionally increased with dilution rate. The results of continuous culture (higher production of L-proline at dilution rate $0.1hr^{-1}$) will be used in fed-batch culture for the control of cell growth rate and mass production of L-proline.

• 한국환경보건학회지
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• 제24권2호
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• pp.57-67
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• 1998

The characteristics of anaerobic degradation of phenol were studied in a fluidized bed reactor using a granular activated carbon as media. Increasing the phenol loading rate with variation of feed concentration was considered as an experimental variable. In the present anaerobic fluidized-bed reactor, the removal efficiency of phenol and COD was maintained about 93-99% and 91-96%, respectively, up to 3.6 kg-phenol/$m^3\cdot d$ of the phenol loading rate, but it was abruptly decreased under 5.0 kg-phenol/$m^3\cdot d$. The volumetric production of biogas per removed phenol was decreased linearly between 0.80-1.27 m$^3$ gas/kg-phenol (0.35-0.56 m$^3$-gas/kg-COD), increasing the phenol loading rate, and the methane content of biogas was 55-60% as similar to that estimated theoretically up to 3.6 kg-phenol/$m^3\cdot d$. But the production rate and methane content of biogas were suddenly decreased at the loading rate of 5.0 kg-phenol/$m^3\cdot d$. Therefore, the anaerobically biodegradable phenol loading rate of the present reactor was 3.6 kg-phenol/$m^3\cdot$ d in order to accomplish over 90% of the removal efficiency.

• 환경위생공학
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• 제12권2호
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• pp.1-12
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• 1997

This research aims to develop biofilm process for the nutrient removal of piggery wastewater. The developed process is the four stage anoxic-oxic biofilm process with recirculation of the final effluent. In summery, the results are as follows: 1. Nitrification in the piggery wastewater built up nitrite because of the high strength ammonia nitrogen. The nitrification of nitrobacter by free ammonia was inhibited in the total ammonia nitrogen loading rate with more than 0.2 kgNH$_{3}$-N/m$^{3}$·d. 2. The maximal total ammonia nitrogen removal rate was obtained at 22$\circ $C and without being affected by the loading rate. But total oxidized nitrogen production rate was largely affected by loading rate. 3. Autooxidation by the organic limit was a cause of the phosphorus release in the aerobic biofilm process. But the phosphorus removal rate was 90 percent less than the influent phosphorus volumetric loading rate of above 0.1 kgP/m$^{3}$·d. Therefore, the phosphorus removal necessarily accompanied the influent loading rate. 4. On the anoxic-oxic BF process, the total average COD mass balance was approximately 67.6 percent. Under this condition, the COD mass removal showed that the cell synthesis and metabolism in aerobic reactor was 42.8 percent and that the denitrification in anoxic reactor was 10.7 percent, respectively.

• 대한환경공학회지
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• 제33권12호
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• pp.868-873
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• 2011

산소전달률은 음폐수, 축산폐수 그리고 매립지 침출수와 같은 고농도 폐수처리를 호기성 공정으로 처리할 시 그 성과를 결정하는 아주 중요한 요소이다. 본 논문에서는, Jet Loop Reactor (JLR)를 이용하여 공기유량과 동력량을 운전조건의 변수로 두고 미생물의 농도에 따른 산소소비율(Oxygen uptake rate, OUR)과 물질전달계수(Volumetric mass transfer coefficient, $K_L{\cdot}a$)를 측정하였으며, 산출된 $K_L{\cdot}a$ 값의 결과를 가지고 통계학적인 분석을 통하여 비선형 회귀 모형을 제안하여 보았다. 연구 결과, 미생물 농도를 높게 유지시켜야 하는 고농도 폐수를 적용할 경우에는, 동력량과 공기량은 산소전달률의 중요한 인자이며, 마지막으로 최종 비선형 회귀모형을 동력량과, 공기량 그리고 점성계수의 함수로 나타내보았다.