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991.
J. J. Gonzalez A. Gleizes S. Vacquié P. Brunelot 《Plasma Chemistry and Plasma Processing》1993,13(2):237-271
A physical model of two zones (constricted arc and cathode jet) of a 1-MW transferred arc in air is presented. It is based on the solution al conservation equations by a finite-differenee method. Turbulence is treated with Prandtl's approximation, whereas radiative transfer is solved considering a nonhontogeneous medium, with the hypothesis of gray spectral bands. The in of radiative transfer on the temperature field is illustrated using two-band and four-band radiation models. We also show the influence of several parameters on plasma jet properties: current intensity between 500 and 1500 A; gas mass /low rate between 10 and 90g/s, vortex injection. The arc characteristics are analyzed in accordance with physical mechanisms such as heat conduction, radiation, turbulence, convection, and miring of cold gas. 相似文献
992.
Wieslaw Wiczk Peggy S. Eis Mayer N. Fishman Michael L. Johnson Joseph R. Lakowicz 《Journal of fluorescence》1991,1(4):273-286
The end-to-end distance distribution of a flexible molecule was recovered from steady-state fluorescence energy transfer measurements using the method suggested by Cantor and Pechukas (Proc. Natl. Acad. Sci. USA
68, 2099–2101, 1971). In this method, the Förster distance (R
0) is varied by attaching different donor-acceptor (D-A) pairs to the flexible linker of interest. Distance distributions are then recovered from energy transfer efficiency measurements on the set of D-A pairs with differentR
0 values. Thirteen D-A pair compounds were synthesized withR
0 values ranging from 6 to 32 Å. Each compound contained a tryptamine donor linked by an alkyl chain (10 carbons) to 1 of 13 acceptors. Using these compounds, we have experimentally confirmed the Cantor and Pechukas method for recovering distance distributions. The measured transfer efficiencies, as a function ofR
0, were fit to the transfer efficiencies predicted for both Gaussian and skewed Gaussian distance distributions. The data support the existence of a skewed Gaussian distribution, and we believe that this is the first experimental observation of an asymmetric distribution for a flexible molecule using fluorescence resonance energy transfer measurements. Finally, the experimentally recovered distance distribution was found to be in good agreement with the distribution predicted from the rotational isomeric state model of Flory (Statistical Mechanics of Chain Molecules, John Wiley & Sons, New York, 1969, Chaps. 1, 3, and 5) but not with the predicted distribution for a freely rotating or freely jointed chain. 相似文献
993.
James Allen Fill 《Journal of Theoretical Probability》1992,5(1):45-70
LetX(t), 0t<, be an ergodic continuous-time Markov chain with finite or countably infinite state space. We construct astrong stationary dual chainX
* whose first hitting times yield bounds on the convergence to stationarity forX. The development follows closely the discrete-time theory of Diaconis and Fill.(2,3) However, for applicability it is important that we formulate our results in terms of infinitesimal rates, and this raises new issues. 相似文献
994.
设q为质数幂,m为大于1的正整数,p_(1),p_(2)为不同的奇质数满足gcd(q,p_(1)p_(2))=1且m|gcd(p_(1)-1,p_(2)-1).本文基于m次剩余的思想,给出码长为p_(1)p_(2)的m次剩余码的两种构造.对每种构造,分别给出其为
相似文献
995.
中立型时滞微分方程解的零点距估计 总被引:7,自引:1,他引:7
考虑中立型时滞微分方程〔x(t)+P(t)x(t-r)‘+Q(t)x(t-σ)=0,其中P(t),Q(t)∈C(│t0,∞),R^+),r,σ∈R^+,本文对上述方程解的相邻零点间的距离作了新的估计。 相似文献
996.
Tomá s Domí nguez Benavides Genaro Ló pez Acedo Hong-Kun Xu 《Proceedings of the American Mathematical Society》1996,124(3):831-838
Some random fixed point theorems for set-valued operators are obtained. The measurability of certain marginal maps is also studied. The underlying measurable space is not assumed to be a Suslin family.
997.
The turbulence in the ocean and atmosphere is most of the time non-homogeneous in nature. These spatial changes could affect the structure of the turbulence. In this work a classification is proposed to determine the intermittency and mixing ability. The variation of the structure functions and the scaling exponent in decaying non-homogeneous turbulence produced by a grid and by a jet is measured with a sonic velocimeter SONTEK3-D. We use Extended Self Similarity (ESS) to obtain better estimates of the scaling exponents of the structure functions of order up to the 6th. We study the variation of the absolute scaling exponents p and relative scaling exponents ¯p as a function of distance from the source of turbulence. In most cases, the absolute scaling exponent 3 is shown to vary as function of the separation distance l. On the other hand the relative scaling exponents ¯p depend on the location of the flow and in most cases the deviations from the Kolmogorov 1941 scaling are related to the intermittency. 相似文献
998.
Arnold Janssen 《Journal of Theoretical Probability》1990,3(2):349-360
In this note we obtain a local central limit theorem and an expansion of length two for the Kac processY
(t) that describes the position of a particle at timet after collisions. In particular, we obtain a rate of convergence for the distance of total variation for the distributions oft
–1/2
Y
(t) and the Wiener process at timet. The results apply to the probabilistic solutions of abstract telegraph and heat equations which heavily rely on the Kac and Wiener processes. Under very mild assumptions we establish a rate of convergence for a singular perturbation problem of an abstract heat equation. 相似文献
999.
Using the Verwey-Overbeek potential (VO) function the various liquid-state properties of SiO2 sols in dilute salt solutions have been evaluated under the mean spherical model approximation (MSMA). The structure factors of these SiO2 sols predicted by this model are compared with results obtained from small-angle neutron scattering experiments by Ramsay et al. Fourier transformation of these structure factors have been performed to obtain the radial distribution functions (RDF), and from these RDF's we computed coordination numbers of the sol particles. The interparticle distanced
c of sol particles has been obtained from the peak position in structure factorS(k) by using the Bragg's equation. The surface potential
s
of the oxide sols has been determined from the amplitude (A) of the VO potential. The present calculations clearly indicate some sort of ordering in the sols system. It is gratifying to note that the present theoretical calculations could reproduce the available observed results very satisfactorily with respect to structure factor and other data. 相似文献
1000.
Piotr Dobryszycki Dorota Krzyzanowska Marian Kochman 《Journal of Chemical Sciences》1991,103(3):435-440
The range of flexibility of the rabbit muscle aldolase molecule was studied using fluorescent labelled aldolase. The protein
molecule was specifically labelled on the opposite sites of the enzyme subunit with the fluorescence energy donor and acceptor
residues. Labelled aldolase with full enzymatic activity was used as a tool in the FRET studies between IAEDANS — donor or
Cys-289 and IAF — acceptor on Cys-239. A range of Forster distance (R) was obtained by collisional quenching of the donor emission. The experiments of donor fluorescence quenching with wide range
of acrylamide concentrations have shown the changes of donor-acceptor distances. In the absence of quencher the D-A distance
distribution in characterized by an average value of 40.4 ?, and a half-width of 0.13 ?. A dramatic increase in half-width
to 17.7? is observed after expositions of the enzyme to high acrylamide concentrations (0.13 M-0.68 M). 相似文献