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41.
Poly (3-alkylthiophenes) (P3ATs) have made up of a family of conductive polymerswhich are soluble, fusible and processable, since the introduction of flexible alkyl sidechains"'. It is generally accepted that P3ATs can form similar layered structures. inwhich the thiophene rings possess planarity and the side chains act as spacers'-'. Whenthe number. of 'carbon atoms of alkyl side chains is more than 10, some orderlyarrangements will occur for side chains betWeen the' layers'. It has been w… 相似文献
42.
We consider site percolation on Z
d, directed edges going from any sZ
d to s+A
1,..., s+A
n, where A
1,..., A
n are the same for all sites and at least two of them are noncollinear. A site is closed if it belongs to p+Block, where p is a point in a Poisson distribution in R
dZ
d with a density and Block={sL: |s|M}+{sR
d: |s|}, where L is a linear subspace of R
d, |·| is the Euclidean norm, =max(|A
1|,..., |A
n|) and M is a parameter. We study the behavior of *, the critical value, and P
closed*, corresponding critical percentage of closed sites, when M. Denote R
d/L the factor space. Call two nonzero vectors U, V codirected if U=kV, where k>0. Theorem. If there are A
i and A
j whose projections to R
d/L are not codirected, then *1/M
dim(L) and P
closed* remains separated both from 0 and 1 when M. If projections of all A
1,..., A
n to R
d/L are codirected, then *1/M
dim(L)+1 and P
closed*1/M when M. 相似文献
43.
M. Keil T. Kolling K. Bergmann W. Meyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):55-64
The process of dissociative attachment (DA) of low-energy electrons ) to vibrationally excited sodium dimer molecules is studied with high electron energy resolution () in a supersonic molecular beam. A novel photoelectron source, based on two-step photoionization of the sodium atoms in the
beam, may deliver a current of up to 1 nA and has been used with a current of typically 0.2 nA in this experiment. The energy
dependence of the rate of sodium anion formation is determined by ion detection based on a time-of-flight analysis. The molecules
are selectively excited to levels using the technique of coherent population transfer by delayed pulses (STIRAP). The comparison of the experimental data with
recent resonance model calculations based on improved potential curves reveals generally good agreement for levels v
”>12. For some distinct differences between theoretical and experimental results persist.
Received: 21 November 1998 / Received in final form: 7 April 1999 相似文献
44.
基于面向对象技术的多媒体CAI素材库系统 总被引:1,自引:0,他引:1
建立实用、高效的多媒体CAI素材库是高效率、高质量开发CAI软件的基础和关键.本文从数据模型、面向对象分析和存储模式三方面入手,提出一种支撑CAI制作工具的素材库体系结构,并讨论该体系结构的特性和进一步研究的问题. 相似文献
45.
Chzhan M Kuppusamy P Samouilov A He G Zweier JL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,137(2):373-378
There has been a need for development of microwave resonator designs optimized to provide high sensitivity and high stability for EPR spectroscopy and imaging measurements of in vivo systems. The design and construction of a novel reentrant resonator with transversely oriented electric field (TERR) and rectangular sample opening cross section for EPR spectroscopy and imaging of in vivo biological samples, such as the whole body of mice and rats, is described. This design with its transversely oriented capacitive element enables wide and simple setting of the center frequency by trimming the dimensions of the capacitive plate over the range 100-900 MHz with unloaded Q values of approximately 1100 at 750 MHz, while the mechanical adjustment mechanism allows smooth continuous frequency tuning in the range +/-50 MHz. This orientation of the capacitive element limits the electric field based loss of resonator Q observed with large lossy samples, and it facilitates the use of capacitive coupling. Both microwave performance data and EPR measurements of aqueous samples demonstrate high sensitivity and stability of the design, which make it well suited for in vivo applications. 相似文献
46.
A. V. Dem'yanov I. V. Kochetov A. P. Napartovich S. Longo M. Capitei 《Plasma Chemistry and Plasma Processing》1996,16(1):121-140
The satbilit r of the pumping discharge for XeCI (Ne/Xe/HCI) lasers is investigated by using different one-dimensional models, considering both bulk discharge instabilities and filamentary ones. It is found that the bulk stability in a XeCl laser discharge can he improved, under certain conditions, due to the vihrational excitation of HCl molecules: this effect is studied by using different models for the HCl vihrational kinetics. It is established that the very short instability time found in experiments cannot he explained as a result of hulk instability of the discharge. On the other hand, a satisfactory comparison with experiments can he obtained by adding to the model a simplified microinstability which develops in the discharge. 相似文献
47.
48.
Christos A. Athanasiadis 《Journal of Algebraic Combinatorics》1996,5(1):5-11
The Laplacian of a directed graph G is the matrix L(G) = O(G) –, A(G) where A(G) is the adjaceney matrix of G and O(G) the diagonal matrix of vertex outdegrees. The eigenvalues of G are the eigenvalues of A(G). Given a directed graph G we construct a derived directed graph D(G) whose vertices are the oriented spanning trees of G. Using a counting argument, we describe the eigenvalues of D(G) and their multiplicities in terms of the eigenvalues of the induced subgraphs and the Laplacian matrix of G. Finally we compute the eigenvalues of D(G) for some specific directed graphs G. A recent conjecture of Propp for D(H
n
) follows, where H
n
stands for the complete directed graph on n vertices without loops. 相似文献
49.
L. Lammich S. Altevogt H. Buhr H. Kreckel S. Krohn M. Lange D. Strasser R. Repnow M. Grieser R. Schinke Z.-W. Qu H. Zhu D. Schwalm D. Zajfman A. Wolf 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):103-111
The fragmentation of LiH2
- anions after electron
impact was investigated at the heavy-ion storage ring TSR.
The main reaction channel was found to be electron detachment followed by a
breakup into LiH + H.
In the first ms after production of the molecular ions in a cesium
sputtering ion source, additional
contributions were observed in the Li + H2 and Li- + H2 channels,
hinting at an initial population of a short-lived state of the anion.
To gain a better understanding of the mechanisms underlying the observed
behavior of the system, ab initio calculations of relevant potential
energy surfaces were performed at selected geometries.
The experimental findings are discussed in the
light of these calculations. 相似文献
50.
基于Visual Basic 的面向对象的编程方法 总被引:2,自引:0,他引:2
黄一春 《浙江大学学报(理学版)》2000,27(3):302-306
本文从作为可视化编程和对象技术的Visual Basic语言的核心-对象着手,着重讨论了各种对象的特点,创建各种对象所采用的方法以及使用的场合,探讨了基于Visual Basic的面向对象的编程方法。 相似文献