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排序方式: 共有182条查询结果,搜索用时 15 毫秒
31.
Nils Dyrset Eirik Selmer-Olsen
ystein Havrevoll Harsha Ratnaweera Ivar Storr Stein-Erik Birkeland 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1998,73(3):175-182
A continuous process for treatment of dairy wastewater with immobilized lactic acid bacteria has been demonstrated at pilot scale. A strain of Lactobacillus plantarum was selected on the basis of a high conversion rate of lactose at low pH, a high affinity of lactose at low concentrations, and the ability to retain activity for a long time immobilized in alginate beads. Lactose was converted to lactic acid, which lowered the pH and precipitated milk proteins. The proteins were separated together with milk fat by flotation with carboxy methyl cellulose (CMC) or chitosan and gave a solid phase of approx. 10% dry matter (23% protein and 68% fat). The total chemical oxygen demand (CODt) removed varied from 65 to 78% for CMC and 49 to 82% for chitosan. The precipitated material was used as a feed supplement for pigs to provide up to 30% of the total energy intake. No adverse effects on the pig's performance were observed. The energy feed value of the precipitate was estimated to be 2·0 feed units (FUs) per kg dry matter. © 1998 Society of Chemical Industry 相似文献
32.
By means of a Gleeble machine, the flow stress at steady-state creep in an AA3103 aluminium alloy has been measured for temperatures and strain rates relevant for thermally induced deformations in DC casting. The strain rate has been determined by measuring the global radial strain rate at the specimen center by an extensometer, and the stress has been set equal to the force in the axial direction divided by the cross-section area. The parameters of Garofalo's equation have been fitted to the resulting steady-state stress and strain rate. Such a method is based upon the assumption of homogeneous stress and strain rate fields. In the Gleeble machine, the specimens are heated by the Joule effect leading to axial temperature gradients, and the specimen geometry is noncylindrical. The resulting inhomogeneities in the stress and strain rate fields are studied by finite element modeling, and it is shown that although they can be significant, the global radial strain rate and the axial force divided by the cross-section area at the specimen center can be relatively close to what the respective strain rate and stress values would have been if the conditions actually were homogeneous. 相似文献
33.
Keith Rozenburg Ivar E. Reimanis Hans-Joachim Kleebe Ron L. Cook 《Journal of the American Ceramic Society》2008,91(2):444-450
The sintering kinetics of a pure magnesium aluminate spinel, MgAl2 O4 , and that doped with LiF were determined through the use of the master sintering curve technique developed by Su and Johnson. 20 Powders with 0%, 0.5%, and 1.0% by mass LiF were densified in a vacuum hot press under a range of unaxial pressures. After the sintering mechanisms in each temperature and pressure regime were determined, an optimized vacuum hot-pressing schedule was formulated for spinel powders doped with 1.0% by mass of LiF. In addition to forming a transient liquid phase, the presence of LiF leads to the formation of oxygen vacancies that promote late-stage sintering in MgAl2 O4 . 相似文献
34.
Simon Ivar Andersen 《Petroleum Science and Technology》2013,31(11-12):1551-1577
ABSTRACT Solid petroleum asphaltenes have been fractionated according to solubility in toluene/n-heptane mixtures of increasing toluene content. A large hysteresis was observed between this dissolution and the precipitation from the crude oil. In order to shed light on the solution mechanism, the fractions obtained have been analyzed using size exclusion chromatography (SEC-HPLC-UV-vis), VPO, elemental analysis, UV-vis adsorption spectroscopy and phenol interaction values and methylene content by FTir. Less polar non-associating low molecular weight species are dissolved and a specific extraction of porphyrins is observed. An increased association in the insolubles is indicated. More basic interaction sites are available on the asphaltenes in both fractions relative to the native asphaltene. From the SEC chromatograms it was seen that the soluble fractions did not associate as the insoluble fractions even when making up more than 60 % of the total asphaltenes. 相似文献
35.
Artur Noole Maksim Oeka Tnis Pehk Mario
eren Ivar Jrving Mark R. J. Elsegood Andrei V. Malkov Margus Lopp Tnis Kanger 《Advanced Synthesis \u0026amp; Catalysis》2013,355(5):829-835
3‐Chlorooxoindoles have emerged as versatile precursors in the synthesis of spirocyclopropyl oxindoles. High enantio‐ and diastereoselectivity was attained under conditions of both iminium/enamine and H‐bonding catalysis. 相似文献
36.
37.
Lovaas (see record 1987-16420-001) has been criticized for overstating the outcome of an intensive behavioral intervention for young autistic children. Part of the criticism reflects skepticism of Lovaas's view that it is possible to overcome autistic children's deficits. However, Lovaas's study built on a substantial body of research that has suggested just such a possibility. It also contained a number of methodological features that provide evidence supporting his interpretation of the outcome, notably, unbiased control groups and multiple pretreatment and follow-up measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Ivar E. Reimanis John J. Petrovic Hisayuki Suematsu Terrence E. Mitchell 《Journal of the American Ceramic Society》1996,79(2):395-400
A composite consisting of elongated α-Si3 N4 crystallites (5–50 (Am in diameter) embedded in an amorphous Si3 N4 matrix was synthesized by chemical vapor deposition. The hardness and indentation fracture toughness of the amorphous matrix and of the composite have been evaluated at temperatures from ambient to 1200°C. It was found that the crystallites have relatively little influence on the hardness and indentation fracture toughness when the surrounding matrix is amorphous. However, a 1400°C heat treatment of the material results in a matrix consisting of small crystals (100 nm in diameter) surrounded by carbon-containing regions which appear to be amorphous in the TEM; TEM and EELS in nearby triple points revealed the presence of amorphous carbon. After heat treatment, the indentation fracture toughness at ambient and at 1200°C is increased due to extensive microcracking. The Vickers hardness at 1200°C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed. 相似文献
39.
Plant availability of inorganic and organic selenium fertiliser as influenced by soil organic matter content and pH 总被引:11,自引:0,他引:11
Susanne Eich-Greatorex Trine A. Sogn Anne Falk Øgaard Ivar Aasen 《Nutrient Cycling in Agroecosystems》2007,79(3):221-231
The objective of the present study was to investigate the influence of soil organic matter content and pH on plant availability
of both inorganic and organic selenium (Se) fertilisers. Further, the risk of Se leaching after application of inorganic Se
fertiliser was evaluated. A new interpretation of an older field study at different sites in Southern Norway showed that organic
C was correlated with grain Se concentration in wheat, barley and oats, explaining up to 60% of the variation in Se concentration.
Pot experiments with a peat soil, a loam soil and a peat/loam soil mixture were conducted for the present study at a range
of pH values between pH 5 and 7. Below pH 6, Se uptake from added Se fertiliser was higher in the soil types with high organic
matter content than in the loam. The opposite occurred at a soil pH above 6, where Se uptake was higher in the loam than in
the peat soil. A simple leaching experiment after one growing season confirmed the findings of the pot experiments that Se
availability in the loam soil with a relatively low organic matter content increased with increasing pH, whereas it decreased
in the peat soil. Neither Se yeast, nor pure Se methionine, used as organic Se fertiliser, resulted in any significant uptake
of Se when added at concentrations similar to the inorganic Se applications. 相似文献
40.
K. Rozenburg I. E. Reimanis H.-J. Kleebe Ron L. Cook 《Journal of the American Ceramic Society》2007,90(7):2038-2042
Reactions between LiF and MgAl2 O4 at temperatures up to 1500°C are examined with a variety of tools, including differential scanning calorimetry, thermo-gravimetric analysis, X-ray diffraction, and scanning electron microscopy. LiAlO2 and MgF2 are found to be the active reaction products at these temperatures. A transient liquid phase comprising MgF2 and LiF forms at intermediate temperatures, but then is consumed at higher temperatures during the reformation of MgAl2 O4 . If processed as an uncompacted powder mixture, all of the initial LiF in the system eventually vaporizes at temperatures exceeding 1300°C. A new reaction sequence relevant to the densification of LiF-doped MgAl2 O4 spinel is proposed. 相似文献