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61.
We present measurements of Eulerian longitudinal velocity autocorrelations in homogeneous, isotropic, high-intensity (~9%) free-stream turbulence behind an active grid. Spatial correlations are measured using particle image velocimetry as well as with two-point hot-wire anemometry (HWA), while temporal correlations are measured using HWA. The temporal correlations are transformed into spatial correlations by using Taylor's ‘frozen’ hypothesis with both the mean as well as instantaneous velocities. A model relating Eulerian spatial and temporal autocorrelations is also used for this purpose. The differences from the measured spatial correlation resulting from the use of Taylor's hypothesis on the temporal correlation is quantified; even at this moderately high level of turbulent intensity, the result from the use of the instantaneous velocity as convection velocity is practically indistinguishable from that obtained using the mean velocity. Use of the model produces a good agreement between the estimates of the spatial correlation function. A relation between Eulerian spatial and temporal integral scales is also derived. 相似文献
62.
The acceleration effect of poly(ethylene oxide) on nucleophilic reactions was investigated. The enhancement of the reaction rate was interpreted by the cooperative solvation of alkali metal ions with ethereal oxygens of PEO resulting in active nucleophilic anions. In relation to the complex formation of alkali metal ions with PEO, the oligo(ethylene oxide) derivatives were prepared as the synthetic ionophores, which were able to transport alkali metal ions selectively through a liquid membrane against the alkali metal ion concentration. 相似文献
63.
A. Al-Kahtani Ahmed J. Jayaraju B. S. Sherigara H. S. Naik Bhojya J. Keshavayya 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1055-1063
The miscibility of dextran (Dex)/poly(vinyl pyrrolidone) (PVP) in solution has been investigated in different percentages of the blend components by employing viscosity, density, refractive index and ultrasonic velocity methods at 30 and 50°C, respectively. Ultrasonic velocity and adiabatic compressibility against blend compositions were plotted and found to be linear. The interaction parameters μ and α have been obtained by using the viscosity data. The results indicated that the Dex/PVP blends are miscible in the entire composition range and it was further confirmed by ultrasonic velocity, density, refractive index studies. In addition, the results revealed that the change in temperature has no significant effect on the miscibility of Dex/PVP polymer blend. 相似文献
64.
65.
Lemi Türker 《无机化学与普通化学杂志》2013,639(1):169-175
A physical model and a mathematical theory for the detonation pressures of explosives materials were developed. The pressure values are expressed as function of the detonation velocity (D) and the average mass (m) of the gaseous products, and are applied for various nitramines and aromatic nitro compounds including nitro pyrimidines and nitro triazines. Some regression equations were obtained and discussed. The pressure values show poor linear dependence on the average mass of the products but good dependence on the detonation velocities alone or Dm. Moreover, for the same Dm value nitramines should produce more pressure than aromatic nitro compounds. This work deals with pressure developed by explosion products and interrelates it with detonation pressure within the constraints of certain assumptions and pays attention to so far unnoticed relationships at least under certain circumstances. 相似文献
66.
67.
The geothermal steam turbines are exposed to mechanisms of corrosion/erosion that weakens its components and reduces their useful life. Due to this problem work has been done in application and characterization of coating in solid state by means of the technique of high-velocity Oxygen Fuel (HVOF), evaluating the corrosion rate (Vcorr) at high temperature of MCrAlY and Diamalloy 4006 coatings deposited on stainless steel SS304. Test was performance in an Autoclave at 170 0C using a modified geothermal fluid as electrolyte. Open circuit potential was monitoring during 24 hours until the system reached the equilibrium. After that, Polarization and Impedance Spectroscopy techniques were used to evaluate the specimens. For microstructure characterization; X–ray Diffraction (XRD), electron sweep microscope (SEM) and Optical microscope were applied. Results show that both coatings (Diamalloy 4006 and MCrAlY), have low current density compare with the substrate, which is an indicative of a lower corrosion rate due to the passive behavior of the species deposited on the Surface of the coating. 相似文献
68.
Approximate analytic expressions for the diffusiophoretic velocity of a spherical colloidal particle
Hiroyuki Ohshima 《Electrophoresis》2022,43(5-6):752-756
The general expression is derived for the diffusiophoretic velocity of a spherical colloidal particle of radius a in a concentration gradient of symmetrical electrolyte. On the basis of this expression, simple approximate analytic expressions for the diffusiophoretic velocity correct up to the order of 1/κa is derived, where κ is the Debye-Hückel parameter. It is found that the approximate expression correct to order unity can be applied for κa ≥ 50 with negligible errors, while the approximate expression correct to order 1/κa can be applied for κa ≥ 20 with negligible errors. 相似文献
69.
In this work, we used time-sliced ion velocity imaging to study the photodissociation dynamics of MgO at \mbox{193 nm}. Three dissociation pathways are found through the speed and angular distributions of magnesium. One pathway is the one-photon excitation of MgO(X\begin{document}$^1\Sigma^+$\end{document} ) to MgO(G\begin{document}$^1\Pi$\end{document} ) followed by spin-orbit coupling between the G\begin{document}$^1\Pi$\end{document} , 3\begin{document}$^3\Pi$\end{document} and 1\begin{document}$^5\Pi$\end{document} states, and finally dissociated to the Mg(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{u}$\end{document} )+O(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{g}$\end{document} ) along the 1\begin{document}$^5\Pi$\end{document} surface. The other two pathways are one-photon absorption of MgO(A\begin{document}$^1\Pi$\end{document} ) state to MgO(G\begin{document}$^1\Pi$\end{document} ) and MgO(4\begin{document}$^1\Pi$\end{document} ) state to dissociate into Mg(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{u}$\end{document} )+O(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{g}$\end{document} ) and Mg(\begin{document}$^1$\end{document} S\begin{document}$_\textrm{g}$\end{document} )+O(\begin{document}$^1$\end{document} S\begin{document}$_\textrm{g}$\end{document} ), respectively. The anisotropy parameters of the dissociation pathways are related to the lifetime of the vibrational energy levels and the coupling of rotational and vibronic spin-orbit states. The total kinetic energy analysis gives \begin{document}$D_0$\end{document} (Mg\begin{document}$-$\end{document} O)=21645\begin{document}$\pm$\end{document} 50 cm\begin{document}$^{-1}$\end{document} . 相似文献
70.
《印度化学会志》2021,98(12):100235
India has abundance of biomass such as rice husk, bagasse, wheat straw, sawdust etc. which is used as a main or auxiliary fuel in the fluidized bed combustor, gasifier and pyrolizer. Design of such fluidized bed equipments require the knowledge of minimum fluidization velocity (Umf), complete fluidization velocity (Ucf) and transport disengagement height (TDH). The present work reports the fluidization characteristic, Umf, Ucf and TDH of the individual size groups of sawdust and mixture thereof. The results indicate that the Umf and Ucf have a tendency to increase with increase in particle diameter, however the TDH shows the reverse trend. The sawdust particle size of 925 and 1200 μm showed significant difference between their Umf and Ucf, an essential parameter for controlled fluidization. Based on the experimental work new correlations for the prediction of Umf, Ucf and TDH for sawdust sample are proposed. The proposed correlations of Umf, Ucf and TDH are in good agreement with experimental values and the deviations found within the range of nearly ±10% for all the samples. 相似文献