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21.
22.
There is a growing market for oligosaccharides as sweeteners, prebiotics, anticariogenic compounds, and immunostimulating
agents in both food and pharmaceutical industries. Interest in novel carbohydrate-based products has grown because of their
reduced toxicity and low immune response. Cellobiose is potentially valuable as a nondigestible sugar. The reaction of cellobiose,
as an acceptor with a sucrose as a donor, catalyzed by a dextransucrase from Leuconostoc mesenteroides B-512FMCM, produced a series of cellobio-oligosaccharides. This production system was optimized using a Box–Behnken experimental
design for 289 mM of sucrose and 250 mM of cellobiose and 54 U of the enzyme at pH 5.2 and 30 °C, to produce maximum yields
of oligosaccharide. 相似文献
23.
We consider piecewise smooth viscosity solutions to a Hamilton-Jacobi equation, for which the Hamiltonian is the maximum of
a finite number of smooth concave functions. We describe the possible types of “basic” singularities, namely jump discontinuities
in either the derivative of the solution or the Hamiltonian, which occur across a smooth hypersurface. Each such type of singularity
is described in terms of the properties of the Hamiltonian and the classical characteristics in the regions on either side
of the singularity. Where appropriate, singular characteristic equations of the types developed by Melikyan are formulated
which can be used in constructions. 相似文献
24.
T. Callan J. A. Russell Henderson A. R. Day W. I. Taggart C. Torres A. S. Capuchino L. Socias J. J. Fox und M. F. Barker 《Fresenius' Journal of Analytical Chemistry》1931,85(1-3):99-100
Ohne Zusammenfassung 相似文献
25.
26.
Martin V. Day 《Applied Mathematics and Optimization》1986,14(1):49-54
This paper is essentially an addendum to a previous paper [3] on the regularity properties of the Ventcel-Freidlin quasipotential function. We give here a proof of our conjecture regarding an exterior sphere condition for level sets.This work was supported in part by the National Science Foundation under grant DMS-8420755. 相似文献
27.
28.
Aerodynamic performance of an annular cascade of film cooled nozzle guide vanes under engine representative conditions 总被引:1,自引:0,他引:1
This paper addresses two important issues relevant to efficiency measurements in film-cooled annular cascades: the definition
of the ideal flow to be used in loss calculation, and the measurements that are necessary for such loss calculation. The paper
also addresses the question of the correct parameterisation of coolant density effects, showing that the momentum flux ratio,
rather than the blowing rate, is the most appropriate parameter.
Experiments examining the effect of extensive aerofoil surface film cooling on the aerodynamic efficiency of an annular cascade
of transonic nozzle guide vanes are reported. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios, momentum ratios and blowing rates
under ambient temperature conditions. Experiments are also conducted with air coolant to study the effect of density ratio
on efficiency. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown
facility which correctly models engine Reynolds and Mach numbers.
This work compares the measured aerodynamic efficiencies of uncooled vanes with those which employ an extensive amount of
cooling. The engine-representative cooling geometry investigated features 14 rows of cylindrical cooling holes, and a second
geometry where 8 of these rows are replaced by holes having a fan-shaped exit. The effects of adding trailing edge slot ejection
are also presented. By selectively blocking rows of holes, the cumulative effect on the mid-span efficiency of adding rows
of cooling holes has also been determined.
Experimental results are presented as area traverse maps (total pressure, isentropic Mach number and flow angles), from which
the relative changes in efficiency due to film cooling have been calculated. These calculations reveal that the presence of
foreign-gas coolant from the cylindrical-hole geometry increases the aerodynamic loss (relative to the uncooled baseline)
by 6.7%; and coolant from the fan-shaped holes increases the loss by 15%. The effects of different assumptions for the coolant
total pressure are shown to significantly change the measured loss; if the loss measurements are based on the mainstream total
pressure, rather than the total pressure in the coolant cavity, the respective increase in loss (relative to the uncooled
baseline) of cylindrical and fan-shaped holes is 4.5% and 12.5%. Experimental data is compared with loss predictions using
a Hartsel model.
Received: 4 December 1998/Accepted: 1 September 1999 相似文献
29.
Coastal erosion, accelerated by sea level rise, and subsidence are major Louisiana issues. With current sea-level-rise projections, coupled with the state's eroding barrier islands and coastal wetlands, the region's estuarine environments are in jeopardy of being lost, redefined, or permanently altered. As the coast erodes, Louisiana is endangered of losing valuable wetland's habitat. In addition, if the barrier islands disappear, the region's wetland-oriented oil and gas wells and associated infrastructure will be at risk to open Gulf conditions. If this should occur, each well, pipeline, and storage battery represents a potential environmental catastrophe. 相似文献
30.
Stephen Barlow Michael W. Day Seth R. Marder 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):303-304
The 1‐(2,3,4,5,1′,2′,3′,4′‐octamethylferrocen‐1‐yl)‐3‐(ruthenocenyl)allylium cation readily undergoes one‐electron oxidation to a dication in which an octamethylferrocenium moiety is bridged by a vinylene group to a [(η6‐fulvene)(η5‐cyclopentadienyl)ruthenium]+ moiety. In the title compound, 1‐(2,3,4,5,1′,2′,3′,4′‐octamethylferrocen‐1‐yl)‐3‐(ruthenocenylidene)prop‐1‐enium(2+) bis(tetrafluoroborate), [FeRu(C5H5)(C9H13)(C17H19)](BF4)2, the C—C bond lengths in the bridge (average for two independent molecules) are, starting from the ipso octamethylferrocenium carbon and ending at the exo carbon of the coordinated fulvene, 1.455 (6), 1.344 (3) and 1.449 (8) Å, indicating a localized electronic structure. 相似文献