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Very Uniform (very + uniform)
Selected AbstractsAl and Zn Foams Blown by an Intrinsic Gas SourceADVANCED ENGINEERING MATERIALS, Issue 6 2010M. Mukherjee A method was developed to produce Al- and Zn-based foams with a uniform distribution of small cells. Pre-alloyed AlMg50 powder containing hydrogen was used as a replacement for the usual blowing agent TiH2. AlMg50 powder released gas uniformly in the entire sample, caused the nucleation of a large number of cells and led to simultaneous growth that finally resulted in a uniform cell structure. The expansion behavior of these foams was studied by means of in situ X-ray radioscopy. The macrostructure of the solidified foams was then analyzed through optical microscopy and X-ray tomography and proved to be very uniform. The high strength of the foams was demonstrated by uni-axial compression tests. [source] Studies on different combined microwave drying of carrot piecesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2010Wei-Qiang Yan Summary Three different combined microwave (MW) drying methods were compared, namely microwave-assisted vacuum drying (MWVD), microwave-assisted freeze drying (MWFD), microwave-enhanced spouted bed drying (MWSD), in terms of drying rate, drying uniformity, product colour, rehydration ratio, retention of , - carotene and vitamin C, and energy consumption. The drying rate of MWVD and MWSD were much faster than that of MWFD. The largest drying rate was obtained in MWSD with 3.5 W g,1. In general, the colour of MWSD products was very uniform. Rehydration ratio of MWFD carrot pieces was almost the same as the freeze-dried (FD) products and better than MWVD and MWSD products. In addition, the highest retention of carotene and vitamin C was observed in MWFD carrot pieces. No significant differences were observed in carotene and vitamin C between MWVD and MWSD products. However, the energy consumption in MWFD was the highest. [source] Control of pore structure and size in freeze-dried collagen spongesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 4 2001Heike Schoof Abstract Because of many suitable properties, collagen sponges are used as an acellular implant or a biomaterial in the field of tissue engineering. Generally, the inner three-dimensional structure of the sponges influences the behavior of cells. To investigate this influence, it is necessary to develop a process to produce sponges with a defined, adjustable, and homogeneous pore structure. Collagen sponges can be produced by freeze-drying of collagen suspensions. The pore structure of the freeze-dried sponges mirrors the ice-crystal morphology after freezing. In industrial production, the collagen suspensions are solidified under time- and space-dependent freezing conditions, resulting in an inhomogeneous pore structure. In this investigation, unidirectional solidification was applied during the freezing process to produce collagen sponges with a homogeneous pore structure. Using this technique the entire sample can be solidified under thermally constant freezing conditions. The ice-crystal morphology and size can be adjusted by varying the solute concentration in the collagen suspension. Collagen sponges with a very uniform and defined pore structure can be produced. Furthermore, the pore size can be adjusted between 20,40 ,m. The thickness of the sponges prepared during this research was 10 mm. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 352,357, 2001 [source] GEITLERINEMA SPECIES (OSCILLATORIALES, CYANOBACTERIA) REVEALED BY CELLULAR MORPHOLOGY, ULTRASTRUCTURE, AND DNA SEQUENCING,JOURNAL OF PHYCOLOGY, Issue 3 2009Maria Do Carmo Bittencourt-Oliveira Geitlerinema amphibium (C. Agardh ex Gomont) Anagn. and G. unigranulatum (Rama N. Singh) Komárek et M. T. P. Azevedo are morphologically close species with characteristics frequently overlapping. Ten strains of Geitlerinema (six of G. amphibium and four of G. unigranulatum) were analyzed by DNA sequencing and transmission electronic and optical microscopy. Among the investigated strains, the two species were not separated with respect to cellular dimensions, and cellular width was the most varying characteristic. The number and localization of granules, as well as other ultrastructural characteristics, did not provide a means to discriminate between the two species. The two species were not separated either by geography or environment. These results were further corroborated by the analysis of the cpcB- cpcA intergenic spacer (PC-IGS) sequences. Given the fact that morphology is very uniform, plus the coexistence of these populations in the same habitat, it would be nearly impossible to distinguish between them in nature. On the other hand, two of the analyzed strains were distinct from all others based on the PC-IGS sequences, in spite of their morphological similarity. PC-IGS sequences indicate that these two strains could be a different species of Geitlerinema. Using morphology, cell ultrastructure, and PC-IGS sequences, it is not possible to distinguish G. amphibium and G. unigranulatum. Therefore, they should be treated as one species, G. unigranulatum as a synonym of G. amphibium. [source] Phase distributions in a gas,liquid,solid circulating fluidized bed riserTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010S. A. Razzak Abstract The distributions of the three phases in gas,liquid,solid circulating fluidized beds (GLSCFB) were studied using a novel measurement technique that combines electrical resistance tomography (ERT) and optical fibre probe. The introduction of gas into a liquid,solid circulating fluidized bed (LSCFB), thus forming a GLSCFB, caused the increase of solids holdup due to the significantly decreased available buoyancy with the lower density of the gas, even with a somewhat increased liquid velocity due to the decreased liquid holdup giving space for the gas holdup. The gas passed through the riser in the form of bubbles, which tended to flow more through the central region of the riser, leading to more radial non-uniformity in radial holdup of the phases. The gas velocity has the most significant effect on the gas phase holdup. While the gas velocity also has an obvious effect to the solids holdups, the liquid flow rate had a much more considerable effect on the phase holdups. The solids circulation rate also had a significant effect on the phase holdups, with increasing solids circulation rate causing much more increased solids holdup in the central region than close to the wall. A correlation was developed for the relative radial distributions of solids holdup in GLSCFB, as such radial profiles were found similar over a wide range of operating conditions, like those in a typical gas,solid circulating fluidized beds (GSCFB). Finally, the axial solids profiles in a GLSCFB was found to be much closer to those in an LSCFB which are very uniform, than those found in a GSCFB which are less uniform and sometime having a S shape. Water was used as the continuous and conductive phase, air was the gas phase and glass bead and lava rock particles were used as the solid and non-conductive phase. Les distributions des trois phases des lits fluidisés circulants gaz-liquide-solide (LFCGLS) ont été étudiées à l'aide d'une technique de mesure originale qui combine la tomographie à résistance électrique (ERT) et la sonde à fibre optique. L'introduction de gaz dans un lit fluidisé circulant liquide-solide, formant par conséquent un lit fluidisé circulant gaz-liquide-solide, a provoqué une retenue de solides en raison de la diminution importante de la flottabilité disponible avec la densité moindre du gaz, même avec une vitesse de liquide quelque peu accrue causée par la retenue de liquide diminuée qui donne de l'espace pour la retenue de gaz. Le gaz passé dans la colonne de montée sous forme de bulles, qui avaient tendance à circuler davantage dans la région centrale de la colonne, donne une non-uniformité plus radiale dans la retenue radiale des phases. La vitesse du gaz a aussi un effet évident sur les retenues des solides; le débit du liquide a un effet beaucoup plus considérable sur les retenues des phases. Le taux de circulation des solides avait également un effet important sur les retenues des phases, le taux de circulation des solides croissant causant beaucoup plus de retenues de solides accrues dans la région centrale que près du mur. Une corrélation a été créée pour les distributions radiales relatives de la retenue des solides dans le LFCGLS, puisque de tels profils radiaux ont été trouvés semblables sur une vaste gamme de conditions d'utilisation, comme celles dans un LFCGS typique. Enfin, on a découvert que les profils des solides axiaux dans un LFCGLS sont beaucoup plus près que ceux d'un LFCLS qui sont très uniformes, que ceux découverts dans un LFCGS, qui sont moins uniformes et qui ont à peu près la forme d'un « S ». [source] | |||||||||||||