• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.201-211
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of aerated oil in fluid-film bearing. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The considered Parameters for the study of bubbly lubrication are oil aeration level, air bubble size, shaft misalignment and shaft speed. The results show that deliberate oil aeration can more clearly bring on the increasing load capacity under high-speed operation of plain journal hearing than previous normal speed operation. And the load capacity may be increased more by oil aeration under the conditions of shaft misalignment and the increasing speed.

• Tribology and Lubricants
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• v.17 no.4
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• pp.321-334
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• 2001

The influence of aerated oil on high-speed journal bearing Is examined by thermohydrodynamic lubrication theory to lubrication with mixtures of a Newtonian liquid and an ideal gas. For this purpose, analytical models for viscosity and density of aerated oil in fluid-film bearing are applied. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The results show that deliberate oil aeration can increase the load capacity of high-speed plain Journal bearing. And the load capacity is increased more by oil aeration under the conditions of shaft misalignment and higher speed.

• KSTLE International Journal
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• v.7 no.2
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• pp.35-44
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• 2006

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure, then the friction and load of journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Tribology and Lubricants
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• v.23 no.5
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• pp.207-218
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• 2007

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Biotechnology and Bioprocess Engineering:BBE
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• v.1 no.1
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• pp.32-35
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• 1996

Amoving aeration-membrane (MAM) bioreactor was employed for the production of 2$\mu$g/mL of tissue type Plasminogen Activator (tPA)in serum free medium from normal human fibroblast cells. This system could maintain high cell density for long periods of steady state conditions in perfusion cultivation. Under normal operating condition, shear stress was as low as 0.65 dynes/$\textrm{cm}^2$ at the agitation speed of 80 rpm. Even though cell density gradually decreased with increasing agitation speed, tPA production increased linearly with increasing shear stress within a moderate range. This culture system allowed production of 2$\mu$g tPA/mL while maintaining a high cell denisty of 1.0$\times$107 viable cell/mL.

• Tribology and Lubricants
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• v.17 no.3
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• pp.198-208
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• 2001

A Parametric study based on a computer analysis of the lubrication system of a four-cylinder gasoline engine is illustrated. Through the parametric study, the effects of various aeration levels on the change of oil flow rate and pressure are investigated. Also, at high oil temperature and low engine speed, the effect of oil aeration level on oil flow characteristics in lubrication system is investigated. The illustrated results may give to designers the guide lines of oil aeration level for the safe design of engine lubrication systems in terms of minimum pressure at crank oil bore.

• ALGAE
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• v.39 no.2
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• pp.109-127
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• 2024

High production and efficient harvesting of microalgae containing high omega-3 levels are critical concerns for industrial use. Aeration can elevate production of some microalgae by providing CO₂ and O₂. However, it may lower the production of others by generating shear stress, causing severe cell damage. The mixotrophic dinoflagellate Gymnodinium smaydae is a new, promising microalga for omega-3 fatty acid production owing to its high docosahexaenoic acid content, and determining optimal conditions and methods for high omega-3 fatty acid production and efficient harvest using G. smaydae is crucial for its commercial utilization. Therefore, to determine whether continuous aeration is required, we measured densities of G. smaydae and the dinoflagellate prey Heterocapsa rotundata in a 100-L semi-continuous cultivation system under no aeration and continuous aeration conditions daily for 9 days. Furthermore, to determine the optimal conditions for harvesting through centrifugation, different rotational speeds of the continuous centrifuge and different flow rates of the pump injecting G. smaydae + H. rotundata cells into the centrifuge were tested. Under continuous aeration, G. smaydae production gradually decreased; however, without aeration, the production remained stable. Harvesting efficiency and the dry weights of omega-3 fatty acids of G. smaydae + H. rotundata cells at a rotational speed of 16,000 rpm were significantly higher than those at 2,000-8,000 rpm. However, these parameters did not significantly differ at injection pump flow rates of 1.0-4.0 L min^-1. The results of the present study provide a basis for optimized production and harvest conditions for G. smaydae and other microalgae.

• KSTLE International Journal
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• v.2 no.2
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• pp.103-113
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The live oil surface tension is considered as functions of temperature, API gravity and air volume ratio. With changing eccentricity ratio, it is investigated the effects of air bubbles on the performance of a high-speed plain journal bearing. Just at the moderate eccentricity ratios, even if the involved aeration levels are not so severe and the entrained air bubble sizes are not so small, it is found that the bearing load and friction farce may be changed so visibly for the high speed bearing operation.

• KSTLE International Journal
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• v.2 no.1
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• pp.1-11
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• 2001

The influence of aerated oil on a high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. With changing eccentricity ratio, it is investigated the effects of air bubbles on the performance of a high-speed plain journal bearing. Just at the moderate eccentricity ratios, even if the involved aeration levels are not so severe and the entrained air bubble sizes are not so small, it is found that the bearing load and friction force may be changed so visibly for the high speed bearing operation.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.4
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• pp.29-43
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• 2000

This study is carried out to investigate the cahracteristics of green management practices and green speed(i.e., ball-roll distance) on 129 Golf Courses in Korea, and to explain the effects of managemet practices that affect green speed. Data collected from green-keepers were subjected to frequency, correlation analysis, and multi-regression analysis using SPSSWIN(Statistical Package for the Social Science). The results are as follows. 1. In spring mowing height, 3.5-4 mm appeared the highest frequency(44.4%) and 4-4.5mm mowing height appeared the high frequency(41.0%). In summer mowing height, 4.5-5mm appeared the highest frequency(51.3%). In fall mowing height, 4-4.5mm appeared the highest frequency(41.0%). 2. In N-fertilizing amount of February and November, 0(zero) g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of June and July 0-2 g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of March, May, August, and September 2-4 g/$m^2$ appeared the highest frequency. In N-fertilizing amount, of October 2-4 or 6-8 g/$m^2$ appeared the highest frequency. 3. In spring topdressing times, 3-6 times appeared the highest frequency(52.6%). In spring topdressing amount, more than 2mm appeared the highest frequency(35.9%). In summer topdressing tierms, 0-3times appeared the highest frequency(71.8%). In summer topdressing amount, 0.5-1mm appeared the highest frequency(46.2%). In fall topdressing times, 0-3times appeared the highest frequency(47.4%). In fall topdressing amount, more than 2mm appeared the highest frequency(35.9%). 4. In spring irrigation tiems, 3-4times/a week appeared the highest frequency (30.6%). In spring irrigation amount, the irrigation below 5mm/day under appeared the highest frequency(38.7%). In summer irrigation times, 4-7times/ a week appeared the highest frequency(38.9%). In summer irrigation amount, 5-10mm/a day appeared the highest frequency(45.2%). In fall irrigation times, 2-3times/a week appeared the highest frequency(36.1%). In fall irrigation amount, the irrigation below 5mm/a day under appeared the highest frequency(45.2%). 5. In spring aeration times, 2 times appeared the highest frequency(55.2%). In spring aeration depth, 5-10mm appeared the highest frequency(81.6%). In fall aeration times, 1 time appeared the highest frequency(82.5%). In fall aeration depth, 5-10mm appeared the highest frequency(86.8%). 6. In spring green speed, 1.98-2.28 or 2.59-2.89mm appeared the highest frequency(32.7%). In summer green speed, 1.98-2.28mm appeared the highest frequency (46.9%). In fall green speed, 1.98-2.28mm appeared the highest frequency(38.8%). 7. The factors which affect green speed were mowing height, N-fertilizing, season, topdressing, irrigation, and aeration. Vertical mowing did not affect green speed. The order of the relevant important factors was mowing height >: N-fertilizing > season > topdressing > irrigation > aeration. Mowing height and N-fertilizing were the most important factors in green speed. As mowing height decreased, green sped always increased. As total N-fertilizing amount decreased, green speed increased. In summer, green sped decreased remarkably. As topdressing times increased and the topdressing amount decreased, green sped increased. As irrigation times increased and irrigation amount decreased, green speed increased.