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1.
2.
It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes
the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of
fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant
coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in
the N→∞ limit) of an
isolated
N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.
An erratum to this article can be found at 相似文献
3.
《Journal of solid state chemistry》2004,177(7):2366-2372
Proton exchange reactions have been performed on tetragonal tungsten bronze-like NaNbWO6 by using nitric acid as an exchanging agent. The characterization of the exchange reaction products has been made by means of chemical analysis, X-ray diffraction, thermal analysis, and IR spectroscopy. The exchange reaction takes place topotactically and the following formula is proposed for the obtained phase of variable composition: Na1−xHxNbWO6·yH2O (0<x?0.46 and 0?y?0.12). Impedance spectroscopy on the present proton exchanged samples indicated that these samples behaved as solid electrolytes under high humidity. As an example, the compound with the composition Na0.68H0.32NbWO6·0.1 H2O exhibits ionic conductivity of 8×10−3 and 1×10−2 S cm−1 at 70°C and 90°C, respectively. 相似文献
4.
Johan Revstedt 《国际流体数值方法杂志》2004,45(7):775-795
The flow around spherical, solid objects is considered. The boundary conditions on the solid boundaries have been applied by replacing the boundary with a surface force distribution on the surface, such that the required boundary conditions are satisfied. The velocity on the boundary is determined by extrapolation from the flow field. The source terms are determined iteratively, as part of the solution. They are then averaged and are smoothed out to nearby computational grid points. A multi‐grid scheme has been used to enhance the computational efficiency of the solution of the force equations. The method has been evaluated for flow around both moving and stationary spherical objects at very low and intermediate Reynolds numbers. The results shows a second order accuracy of the method both at creeping flow and at Re=100. The multi‐grid scheme is shown to enhance the convergence rate up to a factor 10 as compared to single grid approach. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
5.
Krzysztof Pawaowski 《K-Theory》1998,13(1):41-55
The paper presents a procedure for constructing smooth actions of finite perfect groups on spheres with fixed point sets having certain prescribed properties (Theorem A); in particular, having any prescribed configuration of Chern and Pontryagin numbers (Corollary C). The main ingredients used are equivariant thickening and equivariant surgery. 相似文献
6.
A highly selective solid phase extraction sorbent for pre-concentration of sameridine made by molecular imprinting 总被引:5,自引:0,他引:5
Summary A novel approach to solid phase extraction, based on the use of a highly selective molecularly imprinted polymer, is presented.
The versatility of this type of sorbent for solid phase extraction was demonstrated in a model batch-wise pre-concentration
of sameridine prior to gas chromatography. Problems associated with leakage of remaining imprint molecules during the desorption
phase could be eliminated by the use of a close structural analogue of sameridine as the imprint species. It was found that
a major benefit of the imprinted polymer was its specificity, which lead to distinctly cleaner chromatographic traces and
ability to improve sensitivity by extracting sameridine from larger sample volumes. 相似文献
7.
The direct growth of ZnSe–CdSe solid solution onto metallic cathodes by electrodeposition from acidic aqueous sulphate solutions
is described. The plating process is studied by simple voltammetry, while the structure and composition of the electrolytic
deposits are investigated by X-ray diffraction. The experimental d-spacing values of the as-grown mixed lattice are compared to data from reference Zn
x
Cd1-x
Se pellets of standard composition, produced by a sintering method. The findings are supplemented with energy-dispersive X-ray
(EDX) elemental analysis. Thereupon, the variation of the mole fraction x in Zn
x
Cd1-x
Se, and the solid phase constitution of the electrodeposits are determined and correlated to the electrochemical conditions
of growth. The resulting films contain admixtures of CdSe compound and metallic Cd. 相似文献
8.
In this paper, we discuss non-elementary subgroups and discontinuous subgroups of PU(1,n; C), and give their geometric characterizations. 相似文献
9.
We have investigated the free energy of formation for AgxIn1-x and AgxSn1-x liquid binary alloys at temperatures 1173 and 1250 K, respectively. A microscopic theory based on the first order perturbation has been applied. The interionic interaction and a reference liquid are the fundamental components of the theory. The interionic interaction is described by a local pseudopotential. A liquid of hard spheres (HS) of two different effective diametres and charges is used to describe the reference system. The results of the calculations for energy of formation agree very well with the available experimental data. Our calculations also reveal that a simple perturbative approach along with appropriate effective pair potentials can produce nearly quantitative results for the concerned alloys. 相似文献
10.
Uptake of trace elements into fish otoliths is governed by several factors such as life histories and environment in addition to stock and species differences. In an attempt to elucidate the elemental signatures of rare earth elements (REEs) in otoliths, a solid phase extraction (SPE) protocol was used in combination with electrothermal vaporization (ETV) as a sample introduction procedure for the determinations by inductively coupled plasma quadrupole mass spectrometry (ICP-MS). Effects of various parameters, such as carrier gas flow rate, atomization temperature and chemical modification, were examined for optimization of the conditions by ETV-ICP-MS. Atomization was achieved at 2800 °C. Lower temperatures (i.e. 2600 °C) resulted in severe memory problems due to incomplete atomization. Palladium was used as a chemical modifier. It was found that an increase in Pd concentration up to 0.5 μg in the injection volume (70 μl) led up to four-fold enhancement in the integrated signals. This phenomenon is attributed to the carrier effect of Pd rather than the stabilization since no significant losses were observed for high temperature drying around 700 °C even in the absence of Pd. Preconcentration was performed on-line at pH 5 by using a mini-column of Toyopearl AF-Chelate 650M chelating resin, which also eliminated the calcium matrix of otolith solutions. After preconcentration of 6.4 ml of solution, the concentrate was collected in 0.65 ml of 0.5% (v/v) HNO3 in autosampler cups, and then analyzed by ETV-ICP-MS. The method was validated with the analysis of a fish otolith certified reference material (CRM) of emperor snapper, and then applied to samples. Results obtained from otoliths of fish captured in the same habitat indicated that otolith rare earth element concentrations are more dependent on environmental conditions of the habitat than on species differences. 相似文献