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541.
542.
543.
A Ti-TPyP reagent, i.e. an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, TiO(tpyp), was previously developed as a highly sensitive and specific reagent for determining hydrogen peroxide. In the present work, the reaction specificity of the TiO(tpyp) complex to hydrogen peroxide was clarified based on ab initio calculations. The results provide a well-grounded argument for determining hydrogen peroxide using the Ti-TPyP reagent experimentally. 相似文献
544.
In this study, the effect of the viscous dissipation in steady, laminar mixed convection heat transfer from a heated/cooled vertical flat plate is investigated in both aiding and opposing buoyancy situations. The external flow field is assumed to be uniform. The governing systems of partial differential equations are solved numerically using the finite difference method. A parametric study is performed in order to illustrate the interactive influences of the governing parameters, mainly, the Richardson number, Ri (also known as the mixed convection parameter) and the Eckert number, Ec on the velocity and temperature profiles as well as the friction and heat transfer coefficients. Based on the facts the free stream is either in parallel or reverse to the gravity direction and the plate is heated or cooled, different flow situations are identified. The influence of the viscous dissipation on the heat transfer varied according to the situation. For some limiting cases, the obtained results are validated by comparing with those available from the existing literature. An expression correlating Nu in terms of Pr, Ri and Ec is developed. 相似文献
545.
Carolina Cardoso Manica Songul Kaya Merdan 《Journal of Mathematical Analysis and Applications》2007,331(1):669-685
A suitable discretization for the Zeroth Order Model in Large Eddy Simulation of turbulent flows is sought. This is a low order model, but its importance lies in the insight that it provides for the analysis of the higher order models actually used in practice by the pioneers Stolz and Adams [N.A. Adams, S. Stolz, On the approximate deconvolution procedure for LES, Phys. Fluids 2 (1999) 1699-1701; N.A. Adams, S. Stolz, Deconvolution methods for subgrid-scale approximation in large eddy simulation, in: B.J. Geurts (Ed.), Modern Simul. Strategies for Turbulent Flow, Edwards, Philadelphia, 2001, pp. 21-44] and others. The higher order models have proven to be of high accuracy. However, stable discretizations of them have proven to be tricky and other stabilizations, such as time relaxation and eddy viscosity, are often added. We propose a discretization based on a mixed variational formulation that gives the correct energy balance. We show it to be unconditionally stable and prove convergence. 相似文献
546.
The paper presents finite element error estimates of a variational multiscale method (VMS) for the incompressible Navier–Stokes
equations. The constants in these estimates do not depend on the Reynolds number but on a reduced Reynolds number or on the
mesh size of a coarse mesh.
This work is partially supported by NSF grants DMS9972622, DMS20207627 and INT9814115. 相似文献
547.
Summary: Recent observations on phase transitions around the critical point showed that the critical exponents differed drastically from percolation results and classical results for pure hydrogel systems, depending on monomer concentration. In addition to pure hydrogels, the sol-gel phase transition during radical crosslinking copolymerization of acrylamide (AAm) and N-isopropylacrylamide (NIPA) hybrid was studied by using the steady state fluorescence (SSF) technique. N,N′-methylenebis(acrylamide) (BIS) and ammonium persulfate (APS) were used as crosslinker and initiator, respectively. Pyranine (trisodium 8-hydroxypyrene-1,3,6-trisulfonate acid, HPTS) was added as a fluoroprobe for monitoring the polymerization. It was observed that pyranine binds to AAm and NIPA chains on the initiation of the polymerization, thus the fluorescence spectra of the bonded pyranines shift to shorter wavelengths. Fluorescence spectra of the bonded pyranines allowed to monitor the sol-gel phase transition without disturbing the system mechanically and to test the universality of the sol-gel transition as a function of polymer concentration ratios. The observations around the gel point of PAAm-PNIPA hybrid show that the gel fraction exponent β obeyed the percolation result. 相似文献
548.
Orientation in Nematic Liquid Crystals Doped with Orange Dyes and Effect of Carbon Nanoparticles
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Some properties of nematic liquid crystal E7 doped with two disperse orange dyes used together and effect of addition of carbon nanoparticles (single walled carbon nanotube or fullerene C60) on them were studied. Two dyes (disperse orange 11 and 13) having high solubility and order parameter were used as co-dopants. A notable increase in order pa-rameter was obtained comparing to that of liquid crystal doped with single dye. When carbon nanoparticles were used as dopant, a decrease in order parameter was observed at low temperatures while it increased at high temperatures. When applied voltage changed, the order parameter abruptly increased in its threshold value and saturated in higher voltages as expected. An appreciable change in textures was not observed with addition of dopants. This addition gave rise to an increase in nematic-isotropic phase transition temperatures compared with that of pure liquid crystal. 相似文献
549.
In this study, laminar boundary layer flow over a flat plate embedded in a fluid-saturated porous medium in the presence of
viscous dissipation, inertia effect and suction/injection is analyzed using the Keller box finite difference method. The flat
plate is assumed to be held at constant temperature. The non-Darcian effects of convection, boundary and inertia are considered.
Results for the local heat transfer parameter and the local skin friction parameter as well as the velocity and temperature
profiles are presented for various values of the governing parameters. The non-Darcian effects are shown to decrease the velocity
and to increase the temperature. It is also shown that the local heat transfer parameter and the local skin friction parameter
increase due to suction of fluid while injection reverses this trend. It is disclosed that the effect of the viscous dissipation
for negative values of Ec (T
w
< T
∞) is to enhance the heat transfer coefficient while the opposite is true for positive values of Ec (T
w
> T
∞). The results are compared with those available in the existing literature and an excellent agreement is obtained. 相似文献
550.
This study investigates mixed convection heat transfer about a permeable vertical plate in the presence of magneto and thermal
radiation effects. The effects of the mixed convection parameter, the radiation–conduction parameter, the surface temperature
parameter, the magnetic parameter and the suction/injection parameter on the local skin friction and local heat transfer parameters
are presented and analyzed. 相似文献