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981.
The present study investigates convective heat/mass transfer and flow characteristics inside a cooling passage of rotating gas-turbine blades. The rotating duct with and without rib turbulators are used. The ribs of 70° attack angle are attached on leading and trailing surfaces in a staggered arrangement. A naphthalene sublimation technique is employed to determine detailed local heat transfer coefficients using the heat and mass transfer analogy. Additional numerical calculations are conducted to analyze the flow patterns in the cooling. The local heat/mass transfer and the flow pattern in the passage are changed significantly according to rib configurations, duct turning geometry and duct rotation speed. The results show that the duct rotation generates the heat transfer discrepancy between the leading and trailing walls due to the secondary flows induced by the Coriolis force. The heat/mass transfer on the ribbed duct shows 80% higher than the smooth duct because the ribs attached on the walls disturb the mainflow resulting in recirculation and secondary flows near the rib with the secondary flow generated by rotation. The overall heat transfer pattern on the leading and trailing walls for the first and second passes depend on the rotating speed and the turning geometry, but the local heat transfer trend is affected mainly by the rib arrangeements. 相似文献
982.
We prove the existence of unique solutions to Dirichlet boundary value problems for linear second-order uniformly parabolic operators in either divergence or non-divergence form with boundary blowup low-order coefficients. The domain is possibly time varying, non-smooth, and satisfies an exterior measure condition. 相似文献
983.
K Choi M Haque H W Lee Y K Cho Y H Kwak 《The Journal of the Operational Research Society》2013,64(8):1258-1268
The construction industry is one of the largest sectors in the US economy, yet little is known about the key macroeconomic parameters that affect its industry’s structure and performance. The main objectives of this research are (1) to analyse the macroeconomic performance of construction industry as a whole and at 14 of its sub-sectors in terms of labour productivity, gross margin, and worker's wages; and (2) to develop a quantitative model that predicts a firm's profitability by analysing various levels of labour productivity. The results of a non-linear regression analysis based on the comprehensive US Economic Census data show that the construction industry’s sub-sectors with the highest productivity are the most profitable with regard to the gross margins that they are able to generate. This study and its model will help decision makers better assess macroeconomic performance and conduct trend analysis of the construction industry to serve as a basis for developing strategic roadmap for the future. 相似文献
984.
Steklov expansions for a harmonic function on a rectangle are derived and studied with a view to determining an analog of the mean value theorem for harmonic functions. It is found that the value of a harmonic function at the center of a rectangle is well approximated by the mean value of the function on the boundary plus a very small number (often 3 or fewer) of specific further boundary integrals. These integrals are coefficients in the Steklov representation of the function. Similar approximations are found for the central values of solutions of Robin and Neumann boundary value problems. The results follow from analyses of the explicit expressions for the Steklov eigenvalues and eigenfunctions. 相似文献
985.
Low and high molecular weight fucoidans (F(5-30K) and F(>30K)) were chemically modified through the addition of sulfate groups, and the effect of oversulfation on the in vitro anticancer activity was investigated. After the addition of sulfate groups, a considerable increase of 35.5 to 56.8% was observed in the sulfate content of the F(5-30K) fraction, while the sulfate content of the F(>30K) fraction increased to a lesser extent (from 31.7 to 41.2%). Significant differences in anticancer activity were observed between the oversulfated F(5-30K) and F(>30K) fractions, with activities of 37.3-68.0% and 20.6-35.8%, respectively. This variation in the anticancer activity of oversulfated fucoidan derivatives was likely due to differences in their sulfate content. The results suggest that the molecular conformation of these molecules is closely related to the extent of sulfation in the fucan backbones and that the sulfates are preferably substituted when the fucoidan polymers are in a loose molecular conformation. 相似文献
986.
987.
988.
Asymmetrical-flow field flow fractionation (AFFF) separates constituents based on hydrodynamic size and is emerging as a powerful
tool for obtaining high-resolution information on the size, molecular weight, composition, and stability of nanoscale particles
in liquid media. We employ a customized AFFF system combining on-line detectors for multi-angle light scattering, dynamic
light scattering, and UV–Vis absorption. Our objective is to develop optimized measurement protocols for the characterization
of gold nanoparticles (GNPs), which are widely utilized in biomedical research and other nanotechnology applications. Experimental
conditions have been optimized by controlling key parameters, including injection volume and solids concentration, mobile
phase composition, membrane type and pore size, and ratio of channel-to-cross-flow rates. Individual citrate-stabilized GNP
components (nominally 10, 20, 30, 40, and 60 nm) and GNPs functionalized with polyethylene glycol were separated from multicomponent
GNP mixtures by AFFF and subsequently characterized. We discuss the effects due to variations in measurement parameters and
GNP surface modification on observed retention, recovery, and peak resolution. 相似文献
989.
Here we describe an anion excluding ion‐permeable membrane, which we evaluate on an O2‐electroreducing cathode poised at a strongly oxidizing potential, near the reversible potential of the O2/H2O half cell. The bioelectrocatalyst of the O2 cathode consists of the cross‐linked electrostatic adduct of a polycationic redox hydrogel and bilirubin oxidase (BOD), a polyanion at neutral at pH 7.3. If an uncured Nafion dispersion is applied on this bioelectrocatalyst, the polyanionic Nafion displaces the BOD in the electrostatic adduct, de‐wiring the BOD. We show here that insertion of a polycationic poly(acrylamide‐co‐vinylimidazole) (PAA‐PVI) between the bioelectrocatalyst and the Nafion prevents the dewiring of BOD. The resulting bi‐layer membrane effectively excludes the urate, thiocyanate and NADH anions. 相似文献
990.
Dong Wook Shin Ji-Won Choi Won-Kook Choi Yong Soo Cho Seok-Jin Yoon 《Electrochemistry communications》2009,11(3):695-698
The influence of Sn substitution in LiMn2O4 thin films as a cathode has been studied via solution deposition to improve the electrochemical performance of thin film lithium batteries. LiSn0.025Mn1.95O4 thin films showed the most promising performance, i.e. a high capacity retention of 77% at 10 C after the 500th cycle, due to the increased average Mn valence state. The thin films of LiSnx/2Mn2?xO4 (x ? 0.10) showed significant precipitation of SnO2 and SnO after the cycling evaluation. 相似文献