The low‐temperature crystal structure of bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF), C10H8S8, is similar to its high‐temperature structure. The room‐temperature central bond lengths of this molecule are often used as reference in empirical methods to estimate the charge carried by the (BEDT‐TTF)xn+ cations in the BEDT‐TTF molecule‐based organic conductors. We show that the method we previously reported can still be used with low‐temperature BEDT‐TTF salts data. Moreover, we confirm the purely thermal origin of the ordering of the ethylene group. 相似文献
This paper is concerned with the uniqueness and L1 continuous dependence of entropy solutions for nonlinear hyperbolic systems of conservation laws. We study first a class of linear hyperbolic systems with discontinuous coefficients: Each propagating shock wave may be a Lax shock, or a slow or fast undercompressive shock, or else a rarefaction shock. We establish a result of L1 continuous dependence upon initial data in the case where the system does not contain rarefaction shocks. In the general case our estimate takes into account the total strength of rarefaction shocks. In the proof, a new time-decreasing, weighted L1 functional is obtained via a step-by-step algorithm. To treat nonlinear systems, we introduce the concept of admissible averaging matrices which are shown to exist for solutions with small amplitude of genuinely nonlinear systems. Interestingly, for many systems of continuum mechanics, they also exist for solutions with arbitrary large amplitude. The key point is that an admissible averaging matrix does not exhibit rarefaction shocks. As a consequence, the L1 continuous dependence estimate for linear systems can be extended to nonlinear hyperbolic systems using a wave-front tracking technique. 相似文献
We prove that if D is a pseudoconvex domain with Lipschitz boundary having an exhaustion function such that is plurisubharmonic, then the Bergman projection maps the Sobolev space boundedly to itself for any .
Received March 10, 1999 / Published online May 8, 2000 相似文献
Patinas naturally formed on archaeological bronze alloys were characterized using light microscopy (LM), micro energy dispersive
X-ray fluorescence analysis (μ-EDXRF), time of flight secondary ion mass spectrometry (TOF-SIMS) and scanning electron microscopy
in combination with energy dispersive X-ray microanalysis (SEM/EDX). The examinations carried out on cross-sections of samples
have shown that in all samples the copper content in the corrosion layer is lower than in the bulk, while an increase of tin
and lead could be observed. Two different types of corrosion were found: first type, a corrosion formation leading to a three
layer structure was observed on lead bronze. The outer layer consists mainly of Cu(II) compounds and soil material, followed
by a fragmented layer of cuprous oxide and the surface layer of the alloy, where a depletion of copper and an enrichment of
tin and high amounts of Cl could be detected. The second type of corrosion is characterized by a two layer structure on the
tin bronze sample consisting of an outer layer with copper containing corrosion products and a layer with cracks, which reveals
a depletion of copper whereas tin and lead are enriched. Also high amounts of Si were detected in this surface layer. 相似文献
A nonconvex mixed-integer programming formulation for the Euclidean Steiner Tree Problem (ESTP) in Rn is presented. After obtaining separability between integer and continuous variables in the objective function, a Lagrange
dual program is proposed. To solve this dual problem (and obtaining a lower bound for ESTP) we use subgradient techniques.
In order to evaluate a subgradient at each iteration we have to solve three optimization problems, two in polynomial time,
and one is a special convex nondifferentiable programming problem.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
The Structured Total Least Squares (STLS) problem is a natural extension of the Total Least Squares (TLS) problem when constraints
on the matrix structure need to be imposed. Similar to the ordinary TLS approach, the STLS approach can be used to determine
the parameter vector of a linear model, given some noisy measurements. In many signal processing applications, the imposition
of this matrix structure constraint is necessary for obtaining Maximum Likelihood (ML) estimates of the parameter vector.
In this paper we consider the Toeplitz (Hankel) STLS problem (i.e., an STLS problem in which the Toeplitz (Hankel) structure
needs to be preserved). A fast implementation of an algorithm for solving this frequently occurring STLS problem is proposed.
The increased efficiency is obtained by exploiting the low displacement rank of the involved matrices and the sparsity of
the associated generators.
The fast implementation is compared to two other implementations of algorithms for solving the Toeplitz (Hankel) STLS problem.
The comparison is carried out on a recently proposed speech compression scheme. The numerical results confirm the high efficiency
of the newly proposed fast implementation: the straightforward implementations have a complexity of O((m+n)3) and O(m3) whereas the proposed implementation has a complexity of O(mn+n2).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Several threshold methods have been proposed for the purpose of estimating a bivariate extreme value distribution from a sample of data whose distribution is only in its domain of attraction. An integrated view of these methods is presented which leads to the introduction of a new asymptotically consistent estimator of the dependence function characterizing the extreme dependence structure. Through Monte Carlo simulations, the new estimator is also shown to do as well as its competitors and to outperform them in cases of weak dependence. To the authors' knowledge, this is the first time that the small-sample behavior of nonparametric bivariate threshold methods has ever been investigated. 相似文献
In the inviscid limit the generalized complex Ginzburg–Landau equation reduces to the nonlinear Schr?dinger equation. This
limit is proved rigorously with H1 data in the whole space for the Cauchy problem and in the torus with periodic boundary conditions. The results are valid
for nonlinearities with an arbitrary growth exponent in the defocusing case and with a subcritical or critical growth exponent
at the level of L2 in the focusing case, in any spatial dimension. Furthermore, optimal convergence rates are proved. The proofs are based on
estimates of the Schr?dinger energy functional and on Gagliardo–Nirenberg inequalities.
Received: 2 April 1999 / Accepted: 29 March 2000 相似文献
Summary: Well‐defined poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] diblock copolymers [P(EOm‐b‐AMPSn)], have been obtained by water‐based ATRP using α‐methoxy‐ω‐(2‐methylbromoisobutyrate) poly(ethylene oxide)s (MeO‐P[EO]m‐BriB with m ranging from 12 to 113) and CuBr · 2Bpy (Bpy for 2,2′‐bipyridyl) as macroinitiator and catalytic complex, respectively. Compared to direct polymerization in water, it has been demonstrated that the water/methanol (3:1, v/v) mixture is better suited for predicting the final number‐average molar mass from the initial monomer‐to‐macroinitiator molar ratio and achieving a quite narrow polydispersity, even at high monomer conversion ( ≈ 1.4 at 80% conversion). The effect of temperature, solvent mixture composition and addition of NaCl salt on the polymerization rate and extent of control over the copolymer molecular parameters have been highlighted as well.
Nanocomposites based on an ethylene–vinyl acetate copolymer (27 wt.‐% vinyl acetate) and multiwall carbon nanotubes (MWNTs) have been prepared by melt blending and their thermal degradation and flame retardant properties have been evaluated. Special attention has been paid to the influence of the nanotube nature on the flammability properties and more particularly on the time to ignition (TTI) as measured by cone calorimetry. It has been shown that there is a strong influence of the nature of carbon nanotubes on the fire behaviour of the composites, especially previous MWNTs crushing proved to substantially delay the TTI while maintaining much reduced heat release rate (HRR). Such a remarkable behaviour might be explained by the chemical reactivity of radical species present at the surface/extremities of crushed MWNTs during the combustion process.