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1.
J. Jena 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,22(2):416-430
A Lie group of transformations method is used to establish self-similar solutions to the problem of shock wave propagation
through a relaxing gas and its interaction with the weak discontinuity wave. The forms of the equilibrium value of the vibrational
energy and the relaxation time, varying with the density and pressure are determined for which the system admits self-similar
solutions. A particular solution to the problem has been found out and used to study the effects of specific heat ratio and
ambient density exponent on the flow parameters. The coefficients of amplitudes of reflected and transmitted waves after the
interaction are determined. 相似文献
2.
A four-noded rectangular element with seven degrees of freedom at each node is developed for buckling analysis of laminated plate structures having any number of layers with a constant thickness of individual layers. The displacement model is so chosen that it can explain adequately the parabolic distribution of transverse shear stresses and the non-linearity of in-plane displacements across the thickness. A geometrical stiffness matrix is developed using in-plane stresses. A wide range of plates from thick to thin are examined under uniaxial loading conditions. The results are compared with the existing analytical and numerical solutions. The present formulations confirm its applicability for buckling analysis of a wide range of plates. 相似文献
3.
A poly(vinyl chloride)-based membrane composed of dithio-tetraaza macrocyclic compound as a neutral carrier with sodium tetraphenylborate (NaTPB) as an anion excluder and nitrobenzene (NB) as plasticizer was prepared and investigated as a Th(IV)-selective electrode. The electrode exhibits a Nernstian slope of 14.2 +/- 0.3 mV per decade over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with a detection limit of 8.0 x 10(-7) M between pH 3.5 and 9.5. The response time of the sensor is about 10 s and it can be used over a period of 5 months without any divergence in potential. The proposed membrane sensor revealed a good selectivity for Th(IV) over a wide variety of other metal ions and proved to be a better electrode in many respects than those reported in the literature. It was successfully applied as an electrode indicator as well as in the direct determination of thorium ions in standard and real samples. 相似文献
4.
Himansu Sekhar Sahoo S. Mahalakshmi Md. Hedayetullah Mir R. Raghunathan 《Tetrahedron letters》2007,48(5):761-765
A remarkable upfield shift of the pyα protons of complexed 2,2′-bipyridine in [cis-Pd(bpy)(NO3)2] is observed which is considered to originate from the anisotropic influence of suitably positioned coordinated nitrate anions around the Pd(II) centre of the molecule. A typical complexation-induced downfield shift is observed for the NH2 protons in [cis-Pd(en)(NO3)2] where ‘en’ stands for ethylenediamine. 相似文献
5.
Subnanosecond transient-dichroism experiments have been performed to investigate the rotational diffusion of dyes in solution. Dyes and solvents were chosen in a way to obtain information on the influence of size, shape and hydrogen-bonding abilities either of the solute or the solvent molecules. One finds slow orientational relaxation of di-anionic xanthene dyes in alcohols, while oblate cationic dyes rotate faster in spite of their comparable size. The rotational diffusion times for alcohol solutions exceed the theoretical values predicted by the Debye-Einstein model except for prolate molecules. For a solute molecule with internal mobility the rotational diffusion exhibits a partial slip behaviour. It is shown that the deviations from the Debye-Einstein model are restricted to alcohols since for other solvents either with or without strong hydrogen-bonding abilities the experimental values agree with the hydrodynamic model including the stick-boundary condition. Experiments on erythrosine B reveal the influence of size and shape of the attached solvent molecules. 相似文献
6.
In picosecond spectroscopy transient absorption methods are utilized to measure ground-state repopulation kinetics. Since linearly polarized light pulses from mode-locked lasers are used, the transient absorption characteristics in solutions are governed by the rotational diffusion of the absorbing molecules, too. The theory for isotropic diffusion is given and compared to a measurement on the rhodamine 6G molecule dissolved in solvents of different viscosity using a novel pulse spectrophotometer. 相似文献
7.
8.
Transient absorption spectroscopy on electronic levels of molecules in the liquid phase is governed by population kinetics as well as rotational diffusion. The goal of transient absorption experiments has been the true level kinetics free of rotation. Moreover, to extract the rotational time from transient photodichroism experiments the knowledge of true population kinetics is instrumental. Three methods for separating rotational and level kinetics are described theoretically, and one of them is performed experimentally using a repetitive picosecond spectrometer for the measurement of rotational behaviour of fluorescein 27 in solvents of different viscosity. 相似文献
9.
Reliable N-alkylations of secondary amines have been developed. By using DIAD and TPP (or PS-TPP) a variety of secondary amines can be converted to the corresponding tertiary amines in good to excellent yields with diverse alkylhalides; no formation of quaternary amine salts are observed. These protocols are amenable to combinatorial chemistry libraries, and are also useful for the syntheses of secondary amines by an acid lysis of the cleavable tertiary amino resins. 相似文献
10.
The mechanism and kinetics of the retardation of the permanganate-initiated polymerization of acrylonitrile by phenol have been studied in the temperature range of 30 to 45°C. The effect of monomer, metal ion, phenol, sulfuric acid, organic solvents, and some inorganic salts on the polymerization has been studied. The most remarkable observation in the present investigation was the negative intercept obtained from a plot of [M]/Rp versus 1/[M] of the rate mechanism, This observation appears to be a general phenomenon for all inhibiting substrates. A reaction mechanism has been suggested and a suitable rate law has been proposed. 相似文献