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991.
The paper presents an exact analysis of the dispersion of an immiscible solute in a non-Newtonian fluid (known as an incompressible second-order fluid which shows viscoelastic behaviour) flowing slowly in a parallel plate channel in the presence of a periodic pressure gradient. Using a generalized dispersion model which is valid for all times after the solute injection, the diffusion coefficients K i (τ)(i=1,2,3,…) are obtained as functions of time τ in the case when the initial solute distribution is in the form of a slug of finite extent. The analysis leads to the novel result that K 2(τ) (which is a measure of the longitudinal dispersion coefficient of the solute) has a steady part S in addition to a fluctuating part D 2(τ) due to the pulsatility of the flow. It is found that S decreases with increase in the viscoelastic parameter M for given values of the amplitude λ and frequency ω of the pressure pulsation. On the other hand, it is found that at a fixed instant τ, the amplitude of D 2(τ) increases with increase in M for given values of λ and ω. Further it is shown that at a given instant τ, the amplitude of D 2(τ) decreases with increase in ω for given λ and M and the profile for D 2(τ) becomes progressively flatter with increase in ω. Finally the axial distribution of the average concentration θ m of the solute over the channel cross-section is determined at different instants after the solute injection for several values of M, λ and ω. The present study is likely to have important bearing on the problem of dispersion of tracers in blood flow through arteries. 相似文献
992.
We consider a particular case of the matrix Carleman problem for two pairs of functions in a ring and find a constructive
solution of this problem. In addition, we propose an algorithm for the construction of solutions for two infinite systems
of smooth transition and for a system of two singular equations of special type.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 5, pp. 662–671, May, 1997 相似文献
993.
Søren Riis 《Archive for Mathematical Logic》1997,36(3):157-188
For each there exists a model of which satisfies the Count() principle. Furthermore, if contains all prime factors of there exist and a bijective map mapping onto . A corollary is a complete classification of the Count() versus Count() problem. Another corollary shows that the pigeon-hole principle for injective maps does not follow from any of the Count() principles. This solves an open question [Ajtai 94].
Received August 16, 1994 / Revised version received April 29, 1996 相似文献
994.
S. P. Sosnyts'kyi 《Ukrainian Mathematical Journal》1997,49(10):1598-1606
Theorems on equilibrium instability of conservative systems with gyroscopic forces are proved. The theorems obtained are nonlinear
analogs of the Kelvin theorem. The equilibrium instability of the Chaplygin nonholonomic systems is considered.
Institute of Mathematics, Ukrainian Academy of Sciences, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49,
No. 10, pp. 1422–1428, October, 1997. 相似文献
995.
A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction. 相似文献
996.
Detailed pH-dependent steady state and picosecond time-resolved tryptophan fluorescence studies on thiocyanate and azide complexes
of horseradish peroxidase have been carried out. The fluorescence decay of the single tryptophan in these species was fitted
to a discrete three exponential model. Maximum entropy method analysis also gave three distinct regions of lifetime distributions.
The fast subnanosecond lifetime component was found to have > 97% amplitude contribution while other two longer lifetime components
have small contributions. Small contributions from the nanosecond lifetime components possibly arise from apoprotein impurity
or some small amount of disordered heme conformer of the protein. pH dependence of the fast picosecond lifetime components
was found to show a systematic behavior which has been interpreted in the light of obligatory conformation change associated
with activation of the enzyme at low pH. 相似文献
997.
998.
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, p. 2899, December, 1991. 相似文献
999.
1000.
V. Ya. Popkova L. E. Vinogradova L. A. Leites V. K. Osmanov 《Russian Chemical Bulletin》1991,40(10):2075-2078
The reaction of ammonia with 2-chloroperfluoro-1-cyclohexene-1-thiocyanate leads to 2-amino-7-iminoperfluoro-4,5,6-trihydrobenzo-1,3-thiazole (II) due to intramolecular heterocyclization in the Thorpe reaction with the concurrent exoiminization. Analysis of the IR spectra of (II) in CCl4 and in the solid phase indicated that molecules of (II) in the crystal form hydrogen-bonded centrosymmetric dimers (D), which are in equilibrium with free molecules of (II) in solution.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2366–2370, October, 1991.The authors express their gratitude to D. I. Zagorevskii for taking the mass spectrum of (II) and to L. S. German for a useful discussion of this work. 相似文献