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991.
蔡体录 《浙江大学学报(理学版)》1987,14(4):493-501
本文根据北仑港区的水文资料,运用三种不同方法进行初步的冲淤计算。计算成果与北仑港区地形测量资料比较一致。分析了水动力条件,床面切应力以及地形等资料,认为目前本区是处于稳定阶段,水流足能把来沙带走。 相似文献
992.
L. Sheng H.Y. Teng D.Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):209-213
Using the two-point conductivity formula, we numerically evaluate the giant magnetoresistance (GMR) in magnetic superlattices
with currents in the plane of the layers (CIP), from which the effect of the interfacial roughness and magnetization configuration
on the GMR is studied. With increasing interfacial roughness, the maximal GMR ratio is found to first increase and then decrease,
exhibiting a peak at an optimum strength of interfacial roughness. For systems composed of relatively thick layers, the GMR
is approximately proportional to ,where is the angle between the magnetizations in two successive ferromagnetic layers, but noticeable departures from this dependence
are found when the layers become sufficiently thin.
Received 21 September 1998 and Received in final form 22 December 1998 相似文献
993.
T. Ouchterlony I.V. Zozoulenko C.-K. Wang K.-F. Berggren C. Gould A.S. Sachrajda 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):361-370
We study the conductance of a square quantum dot, modeling the potential with a self-consistent Thomas-Fermi approximation.
The resulting potential is characterized by level statistics indicative of mixed chaotic and regular electron dynamics within
the dot in spite of the regular geometry of the gates defining the dot. We calculate numerically, for the case of a quantum
dot with soft confinement, the weak localization (WL) correction. We demonstrate that this confining potential may generate
either Lorentzian or linear lineshapes depending on the number of modes in the leads. Finally, we present experimental WL
data for a lithographically square dot and compare the results with numerical calculations. We analyze the experimental results
and numerical simulations in terms of semiclassical and random matrix theory (RMT) predictions and discuss their limitations
as far as real experimental structures are concerned. Our results indicate that direct application of the above predictions
to distinguish between chaotic and regular dynamics in a particular cavity can not always lead to reliable conclusions as
the shape and magnitude of the WL correction can be strongly sensitive to the geometry-specific, non-universal features of
the system.
Received 13 May 1998 相似文献
994.
Electrochemical quartz crystal microbalance study of ion transport accompanying charging-discharging of poly(pyrrole) films 总被引:1,自引:0,他引:1
György Inzelt Vilmos Kertész Ann-Sofi Nybäck 《Journal of Solid State Electrochemistry》1999,3(5):251-257
Electrochemical quartz crystal microbalance studies on poly(pyrrole) electrodes revealed a complex nature of the potential-dependent
sorption of ionic substances. It is found that the relative contribution of anions and cations to the overall charge transport
process depends upon several factors, such as the oxidation state of the polymer, the composition of the supporting electrolyte
as well as on the film thickness. The phenomena observed are discussed in terms of morphological transformations arising as
a result of interactions between the polymer and the mobile substances.
Received: 21 August 1998 / Accepted: 21 October 1998 相似文献
995.
Sun Y. petersen J. N. Bear J. Clement T. P. Hooker B. S. 《Transport in Porous Media》1999,35(1):49-65
A mathematical model describing microbial transport and growth in a heterogeneous aquifer domain, composed of overlapping subdomains of high-permeability and low-permeability materials, is developed. Each material is conceptually visualized as a continuum which occupies the entire considered spatial aquifer domain. Based on the assumption that advection in the low-permeability domain is negligible, the mathematical model is solved by using a publically available reactive transport code. The importance of modeling microbial transport and growth in such a dual-porosity system is demonstrated through a hypothetical case study. 相似文献
996.
Bal Guillaume Fannjiang Albert Papanicolaou George Ryzhik Leonid 《Journal of statistical physics》1999,95(1-2):479-494
We derive radiative transport equations for solutions of a Schrödinger equation in a periodic structure with small random inhomogeneities. We use systematically the Wigner transform and the Bloch wave expansion. The streaming part of the radiative transport equations is determined entirely by the Bloch spectrum, and the scattering part by the random fluctuations. 相似文献
997.
998.
H. Schneider S. Ehret C. Schönbein K. Schwarz G. Bihlmann J. Fleissner G. Tränkle G. Böhm 《Superlattices and Microstructures》1998,23(6):1289-1295
We have investigated the influence of the final states of bound-to-continuum transitions within the conduction band of asymmetric quantum well structures on the photocurrent. This influence manifests itself by an energy-dependent oscillation of the current direction. We observe pronounced oscillations at zero bias voltage in a double quantum well structure, induced by an asymmetric excitation into continuum states with positive and negative momentum, i.e. by a photogalvanic effect (PGE). If this effect is superimposed on an asymmetric backrelaxation, similar oscillations are observed in the spectrum when the latter asymmetry is compensated by an external electric field. Theoretically, we find a strong relation between the PGE and a quantum interference effect occurring in the continuum. 相似文献
999.
Photovoltaic phenomenon in tetracene and pentacene layers evaporated under the same conditions onto a glass substrate and provided with the same couple of electrodes is investigated. Comparison of the results obtained for both organic materials makes it possible to conclude that in spite of differences in mechanisms of charge carrier generation, the values of photovoltaic parameters are very similar. 相似文献
1000.
We have analyzed the frequency-dependent features of diffusive transport of mobile carriers by hopping in a disordered environment composed of varying energy barriers. We developed a simple approach based on the solution of the master equation for a gradient of concentration (chemical potential) under a sinusoidal perturbation. This method extends the well-known result of the steady state case, D = {1 / Γ}−1, to the frequency domain. The results of our calculations are in agreement with the approximate analytical solution of the CTRW formalism. We are able to determine the onset of frequency-dependent diffusivity in terms of probabilities of highest energy barriers. 相似文献