The increasing demand of the crops (soybean and corn) for biofuel production has increased the focus of the animal nutritionists to look for alternative feeds, which are economic and environmental friendly. To identify microalgae as suitable candidate as an alternative feed, growth response of Chlorella vulgaris was studied under varying concentrations of carbon dioxide (0.07, 1.4, 3.0 and 5.0%) and photon densities (39.19, 72.97, 105.41, 116.22, 135.14, 175.68 µmol/m 2 /s) by employing a photo-bioreactor. Swine wastewater was also investigated as nutritional source to economize the biomass production. Results showed that the higher biomass production was found to be at 3.0% CO2 compared to other CO2 concentrations. However, no difference in biomass production was found at 105.41 μmol/m 2 /s and above photon densities with 12 h of photoperiodicity. It was observed that C. vulgaris could easily grow in 200 times diluted swine wastewater and growth was found to be similar with that of artificial medium. Provided the conducive conditions for optimal growth, it has also the potentiality of depleting ammonia nitrogen (NH4-N) and orthophosphate (PO4 3-P) completely from the wastewater after 3~4 days of cultivation. Thus, growing C. vulgaris would not only solve the problem of animal feed, but also help in biological CO2 mitigation and wastewater treatment.

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The gas phase area in journal bearing is associated directly with bearing characteristics. Therefore, gas phase area observation have an ongoing by many researchers. This paper describes a new visualization method which can visualize oil film distribution and gas phase area on journal bearing. The distribution of oil supplied from two sites is visualized by two color oil, the blended color and gas phase area are measured by RGB representation. Moreover, the measured gas phase area compared to one by traditional visualization method. In this study, oil flow of wedge side under flooded lubrication, oil whip and starved lubrication condition are visualized. As results, it is found that the distribution of oil film under oil whip and starved lubrication condition have been changed by changing the amount of supply oil. Moreover, gas phase area by the new observation method agree rather well with a result of traditional experiment. Therefore, it was found that the new visualization method by using two color oil and RGB representation is possible to observe both gas phase area and blended oil color in journal bearing. １．緒 言 流体軸受にとって気相の領域を把握することは重要で ある．特に，ジャーナル軸受は気相の影響によって軸受特 性が変化することが知られている．例えば，軸受への供給 油量を減少させることで，すなわち，軸受内部をスターブ 状態にすることで気相領域が広がり， オイルホイップなど の不安定振動が抑制されることがわかっている 1) ．そのた め，気相の制御が可能であれば，回転機械の安全性に貢献 できるものと考える． ジャーナル軸受における気相は軸受の反負荷である末 広がり部での負圧の影響や，軸受端部からの大気吸い込み によって発生する．気相の領域を特定するためには軸受面 を直接観察する必要があり，透明な全周ジャーナル軸受を 撮影し，油膜と気相の境界を観察する方法が一般的である 2),3),4) ．逆くさび側（反負荷側）で発生する気相（キャビテ ーション）がくさび側（負荷側）に侵入する場合，軸受内 部は油膜とキャビテーションのスラグ流れとなる．キャビ テーションは非常に複雑な現象であり，わずかな軸の振動 によりその領域は時々刻々と変化する．そのため，従来の 方法で気相領域を特定するには工夫と時間を要する．以上 のことから，気相領域を実験的に特定する新たな測定法が 求められる． 一方で，ジャーナル軸受には潤滑油を供給するための給 油口が設置されており，その設置角度によっても軸受特性 が変化することがわかっている 5) ．一般的に，産業機械で 使用されている軸受の多くは潤滑油を内部に満遍なく供 給するため給油口が 2 箇所に設置されている．また，著者 らによるスターブ潤滑の研究では，給油口を 2 つ設置した 軸受において，給油口を 1 つ設置した軸受よりも安定化す る臨界供給油量が増加し，さらに，スターブ潤滑時に問題 となる局所的な温度上昇や油膜厚さの減少を抑制できる ことが実験的に明らかとなった 6) ．一方で，軸受内部の油 膜温度について理論的に検討する際，循環流や供給油の温 度およびキャビテーションの影響は無視できない．過去に 三井らは給油口 1 つの軸受に対し循環流と供給油の混合現 象やキャビテーション領域を適切にモデル化した熱流体 潤滑理論を構築し，精緻な実験によって得られた油膜温度 ─ 55 ─

In magnetic resonance imaging (MRI) , when radiofrequency (RF) is irradiated to a subject with metallic implant, it can generate heat by RF irradiation. Recently 3 T MRI scanner has spread widely and imaging for any regions of whole body has been conducted. However specific absorption rate (SAR) of 3 T MRI becomes approximately four times as much as the 1.5 T, which can significantly affect the heat generation of metallic implants. So, we evaluated RF heating of artificial hip joints in different shapes and materials in 1.5 T and 3 T MRI. Three types of artificial hip joints made of stainless alloy, titanium alloy and cobalt chrome alloy were embedded in the human body-equivalent phantom respectively and their temperature change were measured for twenty minutes by 1.5 T and 3 T MRI. The maximum temperature rise was observed at the bottom head in all of three types of artificial hip joints, the rise being 12ºC for stainless alloy, 11.9ºC for titanium alloy and 6.1ºC for cobalt chrome alloy in 1.5 T. The temperature rise depended on SAR and the increase of SAR had a good linear relationship with the temperature rise. It was found from the result that the RF heating of metallic implants can take place in various kinds of material and the increase of SAR has a good linear relationship with the temperature rise. This experience shows that reduction of SAR can decrease temperature of metallic implants.