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排序方式: 共有337条查询结果,搜索用时 15 毫秒
131.
132.
D.?YamaguchiEmail author H.?Mayama S.?Koizumi K.?Tsujii T.?Hashimoto 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):153-163
The unique structure of a set of self-assembled porous silica materials was
characterized through a combined small-angle scattering (CSAS) method using
small- and ultra-small angle neutron scattering as well as small-angle X-ray
scattering. The porous silica specimens investigated were prepared by a
sol-gel method under the presence of alkylketene dimer (AKD) template
particles and through calcination, which leads to the development of porous
silica having a mass-fractal structure over length scales from ~ 100 nm
to ~ 10 μm. Furthermore, the specimens posses a hierarchical
structure, which consist of a fractal porous structure, and also contain
primary silica particles less than 10 nm in size, which form a continuous
silica matrix. To characterize these complex structures, observation over a
broad range of length scales is indispensable. We propose a CSAS technique
that serves this purpose well. 相似文献
133.
A basic re-examination of the traditional dimensional analysis of microscopic and macroscopic multiphase flow equations in porous media is presented. We introduce a macroscopic capillary number
which differs from the usual microscopic capillary number Ca in that it depends on length scale, type of porous medium and saturation history. The macroscopic capillary number
is defined as the ratio between the macroscopic viscous pressure drop and the macroscopic capillary pressure.
can be related to the microscopic capillary number Ca and the LeverettJ-function. Previous dimensional analyses contain a tacit assumption which amounts to setting
= 1. This fact has impeded quantitative upscaling in the past. Our definition for
, however, allows for the first time a consistent comparison between macroscopic flow experiments on different length scales. Illustrative sample calculations are presented which show that the breakpoint in capillary desaturation curves for different porous media appears to occur at
1. The length scale related difference between the macroscopic capillary number
for core floods and reservoir floods provides a possible explanation for the systematic difference between residual oil saturations measured in field floods as compared to laboratory experiment. 相似文献
134.
135.
Instanton configurations of (1+1)-dimensions in an antiferromagnetic biaxial-anisotropy-spin-chain are obtained explicitly in the strong anisotropy limit, which interpolate between degenerate equilibrium orientations of the Néel vector along easy axis and are seen to be responsible for quantum tunneling. Macroscopic quantum coherence of the domain walls is demonstrated in terms of the instantons. 相似文献
136.
J. R. Anderson A. J. Berkley A. J. Dragt M. A. Gubrud P. R. Johnson C. J. Lobb R. C. Ramos F. W. Strauch F. C. Wellstood H. Xu 《Superlattices and Microstructures》2002,32(4-6)
We review briefly the problems that are driving the search for a quantum computer. These include, primarily, methods for encryption and decryption based on Shor’s algorithm for factoring large integers and the use of Pell’s equation for encryption. We also outline some of the approaches that have been suggested for implementing a quantum computer and then focus on Josephson-junction systems as qubits. We have been investigating the current-biased Josephson junction for this application, a suggestion we made about 2 years ago. We have studied macroscopic quantum tunneling and energy level spectroscopy, using microwaves, in single junctions and recently we have begun measurements of the two-quantum bit (qubit) system, i.e. two capacitively coupled junctions. Theoretical studies of energy levels and their dynamic evolution are also in progress. In the present report we discuss the basics of single Josephson junctions and compare their potential as qubits with the potentials of other systems. We also discuss our future plans to obtain greater isolation of the junctions from sources of decoherence and to develop realistic qubits. An important first step must be to exhibit quantum entanglement and measure coherence times. Then it must be shown that the states of the qubits can be initialized, that gate operations can be performed, and that the results can be read out. 相似文献
137.
Dr. Mengjiao Cheng Prof. Feng Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15763-15778
Macroscopic supramolecular assembly (MSA) is a new concept in supramolecular science with a focus on interfacial assembly of macroscopic building blocks, which has largely extended the applicable materials of supramolecular assembly and provided new solutions to fabricating tissue scaffolds, soft devices, etc. The precision of the assembled structures is of great interest; unlike molecular assemblies, MSA precision is highly dependent on the matching degree of assembled surfaces because of the large interactive area and group number, which result in remarkably increased kinetic possibilities and metastable assemblies. This Concept introduces the principle, history, and development of MSA, elaborates the low-precision challenge in MSA, summarizes the strategies for precise MSA based on the different thermodynamic stability of precise/imprecise structures and control over assembly kinetics, and finally demonstrates the applications of precise MSA structures in advanced manufacture such as tissue scaffolds. 相似文献
138.
《先进技术聚合物》2018,29(1):226-233
Macroscopic supramolecular assembly plays a key role to bridge the fundamental researches on molecular recognition to the potential applications as supramolecular materials. However, the challenge remains to promote the research from soft hydrogel system to semirigid objects or building blocks. Herein, the concept of flexible spacing coating was employed to modify the model polydimethylsiloxane building blocks, and reversible macroscopic assembly was successfully realized through introducing highly directional, dynamic, and reversible coordinate interactions as driving forces. The driving force for the macroscopic assembly was confirmed by introducing highly competitive ethylene diamine tetra acetic acid solution as an orthodox system to disassemble the assembled blocks. Moreover, the coordinate interaction was further understood through unique in situ measurements of binding forces between building blocks during assembly process. This work of macroscopic supramolecular assembly provides an in situ visible platform, which is significant to clarify the highly fascinating and facile coordinate interactions on the macroscopic assembly behavior. 相似文献
139.
A. Bershadskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):381-382
It is shown that a dimension-invariant form for fractal dimension D of random systems (where d is Euclidean dimension of the embedding space) is in good agreement with results of numerical simulations performed by different
authors for critical (p=p
c
) and subcritical (p<p
c
) percolation, for lattice animals, and for different aggregation processes.
Received: 9 July 1998 / Revised and Accepted: 12 July 1998 相似文献
140.
Fernando Ramôa Ribeiro Fernanda Alvarez Michel Guisnet Christian Marcilly 《Reaction Kinetics and Catalysis Letters》2002,77(2):301-308
The macroscopic distribution of platinum in extrudates of bifunctional PtHFAU/Al2O3 catalysts is shown to have a significant effect on their activity, stability and selectivity in n-hexane transformation under hydrogen pressure. The best catalysts are those for which platinum is homogeneously dispersed. n-Hexane transformation is proposed as a model reaction for estimating the macroscopic distribution of platinum in industrial catalyst pellets. 相似文献