• 대한기계학회논문집
• /
• 제18권11호
• /
• pp.3021-3031
• /
• 1994

Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

• KIEAE Journal
• /
• 제12권3호
• /
• pp.53-60
• /
• 2012

This research is an illustrative research to verify the thermo environmental change created after introduction of indoor pond through abridged model test and simulation analysis. Especially, temperature and comfort level are analyzed by adjusting factors like size of water space, distance length, and location. Summary of the research is as follows. First, the most effective size of water space is 7% of the indoor size, from southern side. Temperature reduction effect is about $1.6^{\circ}C$(5.5%), and for the comfort level, it is found that pmv index increases 8%. Second, based on the simulation of distance length with the sphere, it is more effective as it is close to the surface. If distance length is more than 0.5m, there is no effect on reduction of temperature and comfort level of indoor environment. Lastly, for the analysis by location of the introduced water space, simulation is undertaken by dividing the water space (14% of the indoor size) with front, side, rear and center types. Temperature reduction effect is found to be : front type ($-1.53^{\circ}C$), side type ($-0.82^{\circ}C$), rear type ($-0.44^{\circ}C$), center type ($-0.28^{\circ}C$), respectively. The indoor environment change data by introduction of water space, found in this research, is at initial phase, but it is deemed to be a basic data to refer when planning actual water space.

• 수산해양기술연구
• /
• 제34권3호
• /
• pp.346-351
• /
• 1998

The purpose of this study is analyzing the performance of sea water cooling system under various refrigerant pipe length. In sea water cooling system, the increase of refrigerant pipe length cause increases of pressure drops. These pressure drops cause fresh gas in liquid pipe and increase specific volume in gas pipe outlet, so sea water cooling system capacity is decreased by decrease of refrigerant mass flow rate. Sea water cooling system capacity in refrigerant pipe length 70m is decreased more than 30% when compared with pipe length 10m and the decrease of the coefficient of performance is nearly 20%.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.288-293
• /
• 2001

This paper presents the water-hammer effect due to the rapid opening and closing of isolation valve and thruster valve in the spacecraft propulsion system. The single propellant feed system was modeled to investigate the maximum peak pressure due to the water-hammer effect. The test parameters are tank supply pressure, shape and throat length of orifice and line length. Kerosene was used as the inert simulant propellant liquid instead of hydrazine. As downstream line length after isolation valve increased from 1.5 to 2.5m, the maximum line-filling water-hammer peak pressure decreased, but the average time interval between peak pressures increased. The maximum line-filling water-hammer peak pressure with orifice was lower than without orifice, and the maximum line-filling water-hammer peak pressure with orifice at the back of isolation valve was lower than with orifice in front of isolation valve. Without orifice, the maximum water-hammer peak pressure due to the rapid opening and closing of the thruster valve was about 126% of tank supply pressure. With orifice, it decreased. As orifice throat length increased, it decreased. The maximum water-hammer peak pressure due to the rapid closing of the thruster valve with converging-diverging orifice was lower than normal orifice. It was found that the orifice as a means of pressure drop was very effective to reduce the water hammer peak pressure at the thruster valve. The results of this study can be used for the design of spacecraft liquid propulsion feed system.

• 생명과학회지
• /
• 제14권5호
• /
• pp.809-814
• /
• 2004

산성 전해수를 이용하여 콩나물을 생육시켰을 때 콩나물 관련 주요형질들의 반응을 조사하여 콩나물 재배수로 사용 가능성을 검토하였다. 산성전해수로 생육시킨 콩나물은 전체길이,뿌리길이, 하배축 길이 등이 짧아졌고, 하배축의 두께, 콩나물 개체당 무게 등은 늘어 난 것으로 평가되었다. 하배축 횡단면 관찰에서 산성전해수에서 자란 콩나물의 하배축내 세포가 대조구에 비해 커져 하배축의 두께가 두꺼워진 것으로 평가되었으며, 생육일수별 콩나물 주요 특성에서 콩나물 전체길이는 산성전해수에서 자란 콩나물의 전체 길이가 더 짧았으며, 수돗물에서 자란 콩나물은 생육 후 5일째 이후에 급격히 길이 신장을 하였으나 전해수에서 자란 콩나물은 길이 신장은 거의 변화가 없었다. 하배축의 신장은 콩나물 전체길이와 같은 경향을 보였는데 생육 후 5일째에는 품종간 신장의 차이가 관찰되었다. 뿌리 생육 특성은 전해수에서 생육시킨 콩나물은 생육 4일째에서 11일째까지 뿌리 길이의 차이가 없었으나 수돗물에서 생육시킨 콩나물의 뿌리길이는 생육일수가 증가함에 따라 급격하게 신장을 보였다. 하배축의 두께는 산성전해수에서 생육시킨 콩나물이 수돗물에서 생육시킨 콩나물보다 더 두꺼웠는데 생육 후 5일째까지 두께가 증가하다가 생육 후 5일째 이후부터 다소 감소하였으며, 콩나물 자엽의 무게는 산성전해수에서 생육시킨 콩나물의 자엽무게가 생육일수가 증가할수록 현저하게 증가하였으나 수돗물에서 생육시킨 콩나물은 생육 후 7일째까지는 거의 변화를 보이지 않았다. 콩나물의 생체중은 전해수에서 생육시킨 콩나물이 재배 후 7일 까지는 무거웠으나 11일째는 산성전해수와 수돗물에서 자른 콩나물의 생체중이 거의 비슷하였다.

• Structural Engineering and Mechanics
• /
• 제37권6호
• /
• pp.593-615
• /
• 2011

This study determines the water length effects on the modal behavior of a prototype arch dam using Operational and Analytical Modal Analyses. Achievement of this purpose involves construction of a prototype arch dam-reservoir-foundation model under laboratory conditions. In the model, reservoir length was taken to be as much as three times the dam height. To determine the experimental dynamic characteristics of the arch dam using Operational Modal Analysis, ambient vibration tests were implemented for empty reservoir and three different reservoir water lengths. In the ambient vibration tests, the dam was vibrated by natural excitations provided from small impact effects and the response signals were measured using sensitive accelerometers. Operational Modal Analysis software process signals collected from the ambient vibration tests, and Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques estimated modal parameters of the dams. To validate the experimental results, 3D finite element model of the prototype arch dam was modeled by ANSYS software for empty reservoir and three different reservoir water lengths, and dynamic characteristics of each model were determined analytically. At the end of the study, experimentally and analytically identified dynamic characteristics compared to each other. Also, changes on the natural frequencies along to water length are plotted as graphs. Results suggest that reservoir water complicates the modal behavior of the arch dam significantly.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.238.2-238.2
• /
• 2015

Surface modification of vertically-aligned carbon nanotube (VACNT) is essential in order to meet specific demands for particular applications such as field emission displays, heat dissipation device and potential sun energy conversion due to their superior electrical and thermal conductivity and strong light absorption. In this study, we observe the effect of exposure to water vapor on a different lengths of the surfaces of VACNT. The study was conducted on three different lengths of the VACNT: short length around $200{\mu}m$, medium-length around $500{\mu}m$, and high length around 1 mm. Water exposure time ranges between 2-10 min and temperature of the water ranges from 60 to 120 oC. The result of water vapor exposure mainly show that increasing the exposure time and water temperature give rise to increase of the speed of change on the surface of the VACNT. Especially, the shorter VACNT change their surface morphology most rapidly.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
• /
• pp.219-222
• /
• 1998

In this study, The water tree characteristics were investigated when crosslinking coagent was added in XLPE/EnBA blends. When XLPE was blended with EnBA, there was a decrease of water tree length as an increase of nBA contents in XLPE/EnBA20 blends. The effect of crosslinking coagent. A was better than those of other crosslinking coagents B, C and D in water tree retardation. In case of XLPE/EnBA/Crosslinking coagent blends, water tree length was increased as the crosslinking coagents were increased from 0.2 to 2 phr in 2.0 phr DCP content. To clarify the effects of crosslinking coagent, the DCP contents were changed from 1.5 to 2.0 par in the same crosslinking coagent contents. Then, there was a decrease of water tree length as an increase of crosslinking coagent contents in 1.5 and 1.8 phr DCP contents.

• 한국수자원학회논문집
• /
• 제48권8호
• /
• pp.673-683
• /
• 2015

하천 주변의 도시화와 이상기후 등으로 인해 기존의 하천 위주의 홍수방어는 한계를 보이고 있으며, 이에 따라 유역통합적인 홍수방어대책의 하나로 강변저류지 설치에 대한 요구가 증대되고 있다. 강변저류지를 치수대책에 포함시키기 위해서는 정량적인 홍수조절효과 산정이 필요하며, 이를 위해서는 강변저류지 홍수조절효과에 영향을 미치는 인자들의 불확실성을 줄이기 위한 노력이 필요하다. 특히 하천 수위 예측의 중요 변수인 하천 조도계수는 항상 불확실성을 포함하고 있으므로, 이를 고려한 설계방법이 필요하다. 따라서 본 연구에서는 상대적으로 설계자가 자유롭게 결정할 수 있는 설계인자인 강변저류지의 횡월류부 길이를 이용하여 하천 조도계수의 불확실성을 고려한 강변저류지 설계 기법을 제안하고자 한다. 이를 위해 HEC-RAS 부정류 수치모형을 이용하여 하천 조도계수와 횡월류부 길이 변화가 홍수조절효과에 미치는 영향을 검토하였고, 분석결과를 이용하여 하천의 수위 예측 불확실성을 고려한 횡월류부 길이를 결정하는 기법을 제시하였다. 본 연구에서 제시한 횡월류부 길이 결정 기법은 하천 수위 예측의 불확실성을 해결할 수 있기 때문에 강변저류지의 홍수조절효과를 좀 더 안전측으로 제시하는데 도움이 될 것으로 기대한다.

• Journal of Pharmaceutical Investigation
• /
• 제24권3호spc1호
• /
• pp.19-25
• /
• 1994

The single-pass perfusion technique was employed in order to investigate the effect of water flux from the rat jejunum in the normal experimental conditions. Our results suggested that water flux below ${\pm}0.75%/cm$ of jejunal length was considered normal. Water flux was $-0.131\;{\pm}\;0.311%/cm$ of jejunal length in a citrate buffer and should be corrected in order to determine the permeabilities of the compounds. Perfusion rate up to 0.5 ml/min had no effects on the permeability of ampicillin. Neither the effective permeabilities nor the wall permeabilities of aminopenicillins were influenced by water flux during experiments in rats.