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61.
Gábor Hetyei 《Graphs and Combinatorics》2002,18(3):533-564
62.
Let be a lattice in a noncompact simple Lie Group G, where . Suppose acts analytically and ergodically on a compact manifold M preserving a unimodular rigid geometric structure (e.g. a connection and a volume). We show that either the action is isometric or there exists a "large image" linear representation of . Under an additional assumption on the dynamics of the action, we associate to a virtual arithmetic quotient of full entropy.
Received: December 14, 2000 相似文献
63.
Summary This paper is concerned with the study of a newM/G/1 retrial queueing system in which the delays between retrials are exponentially distributed random variables with linear intensityg(n)=α+nμ, when there aren≥1 customers in the retrial group. This new retrial discipline will be calledlinear control policy. We carry out an extensive analysis of the model, including existence of stationary regime, stationary distribution of the
embedded Markov chain at epochs of service completions, joint distribution of the orbit size and the server state in steady
state and busy period. The results agree with known results for special cases. 相似文献
64.
In this paper, we derive a stochastic model for the HIV epidemic in homosexual populations involving age and race. To account for effects of different mixing patterns, a low risk selection rule is introduced. The model is then formulated in terms of chain multinomial distributions by means of which the means are derived. Some simulation studies by computer indicate clearly that age and race have a significant impact on the HIV epidemic. 相似文献
65.
A study of ultrasonic velocities and internal friction has been carried out in Pb-Bi alloys in the concentration range of
0 to 49.5 atomic % Bi using the composite oscillator technique. From the velocity and density data a set of elastic constants
namely, Young’s modulus, rigidity modulus, bulk modulus and Poisson’s ratio are estimated. The results are interpreted in
terms of the phase changes occurring in the alloy system. Internal friction is found to be more sensitive than the elastic
constants to the phase changes. 相似文献
66.
Cédric Rousseau 《Bulletin of the Brazilian Mathematical Society》2005,36(3):379-391
Let A be a symmetric hyperbolic matrix in SL(2, ℤ) and Γ the subgroup of SL(2, ℤ) generated by A. We aim to study the infinitesimal rigidity of the standard action of Γ on the torus
. More precisely, we will consider the Sobolev Ws–infinitesimal rigidity of this action (that is to determine if the cohomology space H1(Γ,Ws (T M)) is trivial or not), and show that it is Ws–infinitesimally rigid only if 0 ≤ s < 1. A consequence will be that this action is not C∞–infinitesimally rigid.
*I would like to thank A. El Kacimi for introducing me this problem about which we had many fruitful discussions. 相似文献
67.
** Email: giorgio.vittadini{at}unimib.it*** Email: simona.minotti{at}unicatt.it In this paper we propose a methodology for measuring the relativeeffectiveness of healthcare services (i.e. the effectof hospital care on patients) under general conditions, in which:) a healthcare outcome underlies qualitative and quantitativeobservable indicators; ß) we are interested in studyingthe simultaneous dependency of multiple outcomes on covariates(where the outcomes can also be correlated to each other); )the relative effectiveness is adjusted for hospital-specificcovariates; ) we hypothesise a general distribution for randomdisturbances and the random parameters of relative effectiveness.For this topic, a generalisation of the SURE (seemingly unrelatedregression equations) multilevel model is proposed. The solutionsare obtained by means of Bayesian inference methods. Since thereis currently no software available to estimate this model, anSAS procedure based on Markov Chain Monte Carlo methods hasbeen developed by the authors, in line with Goldstein &Spiegelhalter (1996, J. R. Stat. Soc. Ser. A, 159, 385443),Spiegelhalter et al. (1996, Bayesian Using Gibbs Sampling Manual.Cambridge: MRC Biostatistic Unit, Institute of Public Health)and Albert & Chib (1997, J. Am. Stat. Assoc., 92, 916925).In addition, a new theoretical result regarding the joint posteriordistribution for the parameters is provided. The model proposedhas been implemented for an effectiveness study of a selectionof Lombard hospitals. 相似文献
68.
The objective is to derive the probability distribution of the frequency of occurrence of a subsequence within a nucleotide
sequence under the hypothesis that the four nucleotides occur at random and with equal probability.
We also consider the Compound Poisson approximation for the same distribution. The exact probability distribution can be obtained
by the finite Markov chain imbedding technique introduced by Fu and Koutras (1994), however we can manage the case as well
if the probabilities are not all equal. The compound Poisson approximation by Stein-Chen's method can be used to develop an
approximate probability distribution with proper setting of the definition of the sets of dependence. Such structure gives
a bound on the total variation distance, which tends to get relatively larger as the frequency goes up.
AMS 2000 Subject Classification: Primary: 60E05; Secondary: 60J10 相似文献
69.
The germanate compound Cu2Sc2Ge4O13 has been synthesized by solid-state ceramic sintering techniques between 1173 and 1423 K. The structure was solved from single-crystal data by Patterson methods. The title compound is monoclinic, a=12.336(2) Å, b=8.7034(9) Å, c=4.8883(8) Å, β=95.74(2), space group P21/m, Z=4. The compound is isotypic with Cu2Fe2Ge4O13, described very recently. The structure consists of crankshaft-like chains of edge-sharing ScO6 octahedra running parallel to the crystallographic b-axis. These chains are linked laterally by [Cu2O6]8− dimers forming a sheet of metal-oxygen-polyhedra within the a-b plane. These sheets are separated along the c-axis by [Ge4O13]10− units. Cooling to 100 K does not alter the crystallographic symmetry of Cu2Sc2Ge4O13. While the b, c lattice parameter and the unit cell volume show a positive linear thermal expansion (α=6.4(2)×10−6, 5.0(2)×10−6 and 8.3(2)×10−6 K−1 respectively), the a lattice parameter exhibits a negative thermal expansion (α=−3.0(2)×10−6 K−1) for the complete T-range investigated. This negative thermal expansion of a is mainly due to the increase of the Cu-Cu interatomic distance, which is along the a-axis. Average bond lengths remain almost constant between 100 and 298 K, whereas individual ones partly show both significant shortages and lengthening. 相似文献
70.
We provide an asymptotic formula for the number of labelled essential DAGs an and show that limnan/an=c, where an is the number of labelled DAGs and c13.65, which is interesting in the field of Bayesian networks. Furthermore, we present an asymptotic formula for the number of labelled chain graphs.Acknowledgment. I would like to thank Prof. Peter Grabner for his support and very helpful discussions, which where constitutive for this article. I am also thankful to the referees for their comments.This Research was supported by the Austrian Science Fund (FWF), START-Project Y96-MATFinal version received: January 28, 2004 相似文献