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31.
We say that a vertexx of a graph is predominant if there exists another vertexy ofG such that either every maximum clique ofG containingy containsx or every maximum stable set containingx containsy. A graph is then called preperfect if every induced subgraph has a predominant vertex. We show that preperfect graphs are perfect, and that several well-known classes of perfect graphs are preperfect. We also derive a new characterization of perfect graphs. 相似文献
32.
The results of the electronic structures and conduction properties of four novel donor-acceptor polymers based on polysilole, obtained on the basis of ab initio Hartree-Fock crystal orbital method using their optimized geometries, are reported. The repeat unit of these polymers consists of bicyclopentadisilole unit bridged by an electron-accepting group Y(Y=CCH2 in PSICH, CO in PSICF, CCF2 and CC(CN)2 in PSICN). All the polymers on the basis of their geometries and π-bond order values are found to have benzenoid-type electronic structures. Comparison of the important electronic properties such as ionization potential, electron affinity and band-gap of these polymers indicates PSICN to be the best candidate for intrinsic conductivity and reductive (n-) doping while PSICH is predicted to be the best candidate for oxidative (p-) doping. All these polymers are estimated to have band-gap values ranging between 1 and 2 eV. The low band-gap values of these polymers are rationalised on the basis of the patterns of their frontier orbitals. 相似文献
33.
Yue Liu Masahito Ohta Grozdena Todorova 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2007
We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity. 相似文献
34.
We will give some conditions for Sobolev spaces on bounded Lipschitz domains to admit only trivial isometries. 相似文献
35.
X.L. Zhong 《Applied Surface Science》2006,253(2):417-420
Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated on Pt/Ti/SiO2/Si(1 0 0) substrates by chemical solution deposition (CSD), and the dependence of ferroelectric and dielectric properties of the as-deposited BLT thin films on excess Bi content in precursor sols was studied. It is found that the prepared BLT thin film shows the best polarization-electric field, capacitance-voltage and dielectric constant (?r)-frequency characteristics, when the value of excess Bi content in precursor sols is 10%. In detail, its remnant polarization (2Pr) value is 40 μC/cm2, the capacitance tunability is 21% measured at room temperature under conditions of an applied voltage of 8 V and measurement frequency of 10 kHz, and the ?r is 696 at 100 kHz frequency. 相似文献
36.
Hiromichi Hashimoto 《Journal of Differential Equations》2007,237(2):491-525
We consider a hyperbolic-parabolic singular perturbation problem for a quasilinear equation of Kirchhoff type, and obtain parameter-dependent time decay estimates of the difference between the solutions of a quasilinear dissipative hyperbolic equation of Kirchhoff type and the corresponding quasilinear parabolic equation. For this purpose we show time decay estimates for hyperbolic-parabolic singular perturbation problem for linear equations with a time-dependent coefficient. 相似文献
37.
We have combined a home-built capacitance sensor with a commercial scanning force microscope to obtain a Scanning Capacitance Microscope (SCM). The SCM has been used to study Nitride-Oxide-Silicon (NOS) heterostructures which offer potential applications in charge storage technology. Charge writing and reading on a submicrometer scale is demonstrated with our SCM setup. In addition, SCM appears to be very useful for the characterization of subsurface defects in semiconductor devices which are inaccessible by most of the other scanning probe microscopies. Finally, we introduce a novel spectroscopic mode of SCM operation which offers combined voltage-dependent and spatially resolved information about inhomogeneous charge distributions in semiconductor devices. 相似文献
38.
We study the large-time behavior and rate of convergence to the invariant measures of the processes dX
(t)=b(X)
(t)) dt + (X
(t)) dB(t). A crucial constant appears naturally in our study. Heuristically, when the time is of the order exp( – )/2 , the transition density has a good lower bound and when the process has run for about exp( – )/2, it is very close to the invariant measure. LetL
=(2/2) – U · be a second-order differential operator on d. Under suitable conditions,L
z has the discrete spectrum
- \lambda _2^\varepsilon ...and lim \varepsilon ^2 log \lambda _2^\varepsilon = - \Lambda \hfill \\ \varepsilon \to 0 \hfill \\ \end{gathered} $$
" align="middle" vspace="20%" border="0"> 相似文献
39.
Much recent work has been done to investigate convergence of modified continued fractions (MCF's), following the proof by Thron and Waadeland [35] in 1980 that a limit-periodic MCFK(a
n
, 1;x
1), with
andnth approximant
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