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981.
Jan Tobi? 《Chemical engineering science》2006,61(8):2447-2456
The pressure drop and the fluid velocity profiles were investigated experimentally and numerically in the model packings of complex geometry. The numerical estimations were performed by means of the hybrid method involving the use of structural macro-correlations. In this paper it has been demonstrated on several examples that the structural macro-correlations allow to predict the macro-scale flow behaviour in non-homogeneous packings. Finally, the recent mechanistic approaches to flow modelling in packed tubes of low tube-to-particle diameter ratio have been discussed. 相似文献
982.
合成氨装置脱碳工段采用NHD脱碳工艺,由于脱碳后的脱碳气中CO2含量偏高,造成H 2损耗较大,为此采用ZUPAC系列双向金属折峰式波纹填料和新型槽盘式液体分布器对脱碳塔进行改造。改造后,脱碳气中CO2体积分数从2.0%降至1.6%,年可增加经济效益1000万元左右。 相似文献
983.
Guan-Chiun?Lee Dong-Lin?Wang Yi-Fang?Ho Jei-Fu?ShawEmail author 《Journal of the American Oil Chemists' Society》2004,81(6):533-536
Lipase from Pseudomonas fluorescens efficiently catalyzed the alcoholysis of various TG in dry alcohols. For TG with short-chain FA, more MG were accumulated.
The yields of MG were affected by the alcohols used. The maximum yields of MG were as follows: 85% for monoacetin in n-butanol, 96% for monobutyrin in ethanol or n-butanol, 50% for monocaprylin in n-butanol, 48% for monolaurin in isopropanol, and 45% for monopalmitin in isopropanol. The MG produced were judged to be 2-MG
by TLC analysis. The presence of organic cosolvent affected the reaction rate of the lipase-catalyzed alcoholysis of TG. For
the alcoholysis of various TG in ethanol and cosolvent (1∶1, vol/vol), the rates had the following orders: (i) for tributyrin,
hexane > toluene > acetone > ethyl acetate > chloroform > acetonitrile > pyridine; (ii) for tricaprylin, hexane > acetone
> toluene > acetonitrile > ethyl acetate > pyridine > chloroform; and (iii) for trialurin, hexane > acetonitrile=acetone >
ethyl acetate > pyridine=chloroform > toluene. 相似文献
984.
985.
986.
Yue?Hung K.?M.?EL-KhatibEmail author Hazem?Tawfik 《Journal of Applied Electrochemistry》2005,35(5):445-447
Corrosion resistant treated metal bipolar plates with higher rigidity and electrical conductivity than graphite were developed and tested for PEM fuel cell applications. Six replicas of single cells were used three of which were made of graphite composites bipolar plates and the other three of the treated metallic plates. A Membrane Electrode Assembly (MEA) with 5.55 cm2 active electrode areas, 0.3 mg cm–2 Pt loading and Nafion membrane 115 was fitted to each cell and operated under identical conditions. The experimental testing was conducted at room temperature (20 °C). The average value of the data obtained for the three graphite cells was plotted. Similarly, the average value of the data obtained for the three treated metal cells was plotted on the same graph for comparison. Generally, the treated metal bipolar plate provided at least 12% saving in hydrogen consumption in comparison to graphite. This is attributed to the lower bulk and surface contact resistance of the metal used in this study in relation to graphite. The results of lifetime testing, conducted at room temperature under variable loading showed no indication of power degradation due to metal corrosion for at least 1500 hours. 相似文献
987.
The present study was designed to examine the effects of EFA deficiency (EFAD) on biochemical, functional, and structural
aspects of the kidney in growing and adult rats fed a normal or EFAD diet for 9 wk after weaning. Food and fluid intake (FI),
urine volume, and Na+ and K+ excretions were measured weekly from weeks 4 to 8 by placing the rats in individual metabolic cages for 24 h. At week 9,
Li+ and a 5% water load, respectively, were administered at 14 and 1.5 h prior to glomerular and proximal tubular function studies,
as assessed by 3-h creatinine (CCr) and Li+ (CLi+) clearances. Hematocrit and urine volume; serum and urine [Cr], [Li+], [Na+], and [K+]; and renal FA distribution were also measured. Data [corrected to 100 g/body weight (bw) and presented as means ±SEM] were
significant, at P<-0.05. Despite a similar ingestion of solids from weeks 4 to 7 (weeks 7 to 10 of life), the rats on the EFAD diet showed
a decreased body weight from week 5. From weeks 4 to 8, Fl and urine volume were similar for both groups, but the Fl increased
at week 6 in the EFAD group; 24-h Na+ and K+ excretions were similar at all weeks, except for an increase in the EFAD group for both ions at week 7. In the EFAD group,
CCr and CLi+ decreased by 27 and 56.3%, respectively (385.7±33.4 vs. 280±21.1, and 21.0±2.1 vs. 9.2±1.1 μL/min/100 g; n=9 vs. 10), the latter result suggesting increased proximal reabsorption. The 3-h Na+ and K+ excretions were similar, but the Li+ decreased (0.78±0.06×10−2 vs. 0.32±0.03×10−2 μeq/min/100 g) in the EFAD group, giving additional support to the suggestion. Renal structure was normal and similar for
both groups, but the EFAD group showed a more prominent proximal tubule brush border, together with heavier periodic acid-Schiff
staining in all specimens from weeks 5 to 9. In the EFAD group, FA of the n−9 and n−7 series were higher, but most of the
n−6 series were lower as a percentage of total lipids in the medulla and cortex. Medullary levels of 20∶4n−6 were maintained,
22∶4n−6 declined twice, arachidonic acid was maintained, and 20∶5n−3 was lower. The EFAD diet affected glomerular function,
proximal tubular structure and function, and FA distribution in the rat kidney. 相似文献
988.
Silvana?Martini Constantin?Bertoli Maria?Lidia?Herrera Ian?Neeson Alejandro?MarangoniEmail author 《Journal of the American Oil Chemists' Society》2005,82(5):305-312
An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead
of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in
concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples
were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was
followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships
were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC.
TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r
2>0.9) in a linear fashion (v=2.601 SFC+1433.0). 相似文献
989.
990.