求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

Photocatalytic Activity of Titanium Dioxide Nanoparticles Immobilized in the Polymer Network of Polyacrylamide Hydrogel

Composite hydrogels based on polyacrylamide immobilized nanoparticles of commercial (P25 brand) titanium dioxide and of titanium dioxide nanoparticles prepared by electric explosion of a wire were synthesized. The enthalpy of interaction at the polyacrylamide/TiO₂ interface was determined by microcalorimetry using the thermochemical cycle method. Interaction of polyacrylamide polymer chains with the surface of TiO₂ nanoparticles is energetically unfavorable. The absence of interactions between the hydrogel polymer network and surface of TiO₂ nanoparticles favors manifestation of the UV-induced photocatalytic activity of TiO₂ nanoparticles immobilized in the hydrogel. Immobilization in the polyacrylamide hydrogel matrix decreases the photocatalytic activity of P25 brand TiO₂ nanoparticles, but does not affect the photocatalytic activity of titanium dioxide nanoparticles prepared by the electric explosion method. The photocatalytic activity of TiO₂ nanoparticles immobilized in the bulk of polyacrylamide hydrogel evaluated by the decomposition of Methyl Orange dye is controlled by the diffusion rate of the dye molecules into the bulk of the hydrogel and depends also on the aggregation of TiO₂ nanoparticles in the hydrogel matrix.

     

Photoluminescence kinetics of wurtzite GaN quantum dots in an AlN matrix

The photoluminescence (PL) of GaN quantum dots in an AlN matrix is studied. It is found that the maximum of the PL line does not shift when the laser excitation power varies. The transient PL spectra indicate that the quenching kinetics is nonexponential and the quenching law depends on the spectral range. The experimental data are explained in the framework of a model taking into account the strong built-in electric field in wurtzite structures and the transport of charge carriers between them.     

Tracing of peroxy radicals in hexane cool flames

Stabilized hexane-air cool flames in a separately heated two-section reactor have been studied at T=480–770 K and P=30–63 kPa. ESR spectra of peroxy radicals were analyzed by the radical freezing technique and sonde sampling. Under these conditions high radical concentrations (>10¹⁴ cm^–3) are observed. With increasing pressure and temperature, the fraction of HO₂ radicals in the overall amount of radicals grows.

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480–770 , 30–63 . . , (>10¹⁴cm^–3). , HO₂ .

     

Radical concentrations and temperature oscillations in cool flame oxidation of butane

Damping and stable oscillation of free radical concentrations in butane oxidation have been found and studied experimentally by using a differential thermocouple. It has been established that maximum oscillations of radical concentrations slightly precede temperature maxima.

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Reaction of o-phenylenediamine with α-bromoacetylenic ketones

Conclusions 1,2-Di-(acylethynylaza)benzenes and 2-acylmethylenebenzo-1,3-imidazoline hydrobromides were obtained by the reaction of o-phenylenediamine with-bromoacetylenic ketones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1173–1175, May, 1984.     

Investigations in the field of vinyl ethers and esters of the furan series

Vinyl-furancarboxylate has been synthesized by the reaction of-furancarboxylic acid with acetylene and with vinyl acetate in the presence of various catalysts. The structure of the vinyl ester has been confirmed by IR spectra and by catalytic hydrogenation. The acid and alkaline hydrolyses of vinyl-furancarboxylate have been studied.