共查询到20条相似文献,搜索用时 31 毫秒
1.
Attila Dénes Yoshiaki Muroya Gergely Röst 《Mathematical Methods in the Applied Sciences》2020,43(17):9671-9680
We study the global stability of a multistrain SIS model with superinfection and patch structure. We establish an iterative procedure to obtain a sequence of threshold parameters. By a repeated application of a result by Takeuchi et al. [Nonlinear Anal Real World Appl. 2006;7:235–247], we show that these parameters completely determine the global dynamics of the system: for any number of patches and strains with different infectivities, any subset of the strains can stably coexist depending on the particular choice of the parameters. 相似文献
2.
A threshold start-up policy is appealing for manufacturing (service) facilities that incur a cost for keeping the machine
(server) on, as well as for each restart of the server from its dormant state. Analysis of single product (customer) systems
operating under such a policy, also known as the N-policy, has been available for some time. This article develops mathematical analysis for multiproduct systems operating
under a cyclic exhaustive or globally gated service regime and a threshold start-up rule. It pays particular attention to
modeling switchover (setup) times. The analysis extends/unifies existing literature on polling models by obtaining as special
cases, the continuously roving server and patient server polling models on the one hand, and the standard M/G/1 queue with N-policy, on the other hand. We provide a computationally efficient algorithm for finding aggregate performance measures, such
as the mean waiting time for each customer type and the mean unfinished work in system. We show that the search for the optimal
threshold level can be restricted to a finite set of possibilities.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
It has recently been shown by Rootzén and Tajvidi (Bernoulli, 12:917–930, 2006) that modelling exceedances of a random variable over a high threshold (peaks-over-threshold approach [POT]) can also in
the multivariate setup be done rationally only by a multivariate generalized Pareto distribution (GPD). The selection of a
proper threshold is, however, a crucial problem. The contribution of this paper is twofold: We develop first a non asymptotic
and exact level-α test based on the single-sample t-test, which checks whether multivariate data are actually generated by a multivariate GPD. Secondly, this procedure is utilized
for the derivation of a t-test based threshold selection rule in multivariate peaks-over-threshold models. The application to a hydrological data set
illustrates this approach.
相似文献
4.
R. G. Stepanov 《Theoretical and Mathematical Physics》2006,146(2):207-220
We study the 2N-component fermionic model on a hierarchical lattice and give explicit formulas for the renormalization-group transformation
in the space of coefficients that determine a Grassmann-valued density of the free measure. We evaluate the inverse renormalization-group
transformation. The de.nition of the renormalization-group fixed points reduces to a solution of a system of algebraic equations.
We investigate solutions of this system for N = 1, 2, 3. For α = 1, we prove an analogue of the central limit theorem for fermionic 2N-component fields. We discover an interesting relation between renormalization-group transformations in bosonic and fermionic
hierarchical models and show that one of these transformations is obtained from the other by replacing N with -N.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 146, No. 2, pp. 251–266, February, 2006. 相似文献
5.
Using the cavity equations of Mézard, Parisi, and Zecchina 23 ; Mézard and Zecchina, 24 we derive the various threshold values for the number of clauses per variable of the random K‐satisfiability problem, generalizing the previous results to K ≥ 4. We also give an analytic solution of the equations, and some closed expressions for these thresholds, in an expansion around large K. The stability of the solution is also computed. For any K, the satisfiability threshold is found to be in the stable region of the solution, which adds further credit to the conjecture that this computation gives the exact satisfiability threshold.© 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006 相似文献
6.
Yury A. Kutoyants 《Annals of the Institute of Statistical Mathematics》2012,64(2):383-413
We consider the problems of parameter estimation for several models of threshold ergodic diffusion processes in the asymptotics
of large samples. These models are the direct continuous time analogues of the well known in time series analysis threshold
autoregressive models. In such models, the trend is switching when the observed process attaints some (unknown) values and
the problem is to estimate it or to test some hypotheses concerning these values. The related statistical problems correspond
to the singular estimation or testing, for example, the rate of convergence of estimators is T and not ?T{\sqrt{T}} as in regular estimation problems. We study the asymptotic behavior of the maximum likelihood and Bayesian estimators and
discuss the possibility of the construction of the goodness-of-fit test for such models of observation. 相似文献
7.
Sequential Dynamical Systems (SDSs) are mathematical models for analyzing simulation
systems. We investigate phase space properties of some special classes of SDSs obtained
by restricting the local transition functions used at the nodes. We show that any SDS over the
Boolean domain with symmetric Boolean local transition functions can be efficiently simulated
by another SDS which uses only simple threshold and simple inverted threshold functions, where
the same threshold value is used at each node and the underlying graph is
d-regular for some integer
d. We establish tight or nearly tight upper and lower bounds
on the number of steps needed
for SDSs over the Boolean domain with 1-, 2- or 3-threshold functions at each of the nodes to
reach a fixed point. When the domain is a unitary semiring and each node computes a linear
combination of its inputs, we present a polynomial time algorithm to determine whether such an
SDS reaches a fixed point. We also show (through an explicit construction) that there are Boolean
SDSs with the NOR function at each node such that their phase spaces contain directed cycles
whose length is exponential in the number of nodes of the underlying graph of the SDS.AMS Subject Classification: 68Q10, 68Q17, 68Q80. 相似文献
8.
Daniel Arnaudon N. Crampé Anastasia Doikou Luc Frappat Eric Ragoucy 《Annales Henri Poincare》2006,7(7-8):1217-1268
We consider the N-site
integrable spin chain with periodic and open diagonal soliton-preserving boundary conditions. By employing analytical Bethe
ansatz techniques we are able to determine the spectrum and the corresponding Bethe ansatz equations for the general case,
where each site of the spin chain is associated to any representation of
In the case of open spin chain, we study finite dimensional representations of the quantum reflection algebra, and prove in
full generality that the pseudo-vacuum is a highest weight of the monodromy matrix.
For these two types of spin chain, we study the (generalized) “algebraic” fusion procedures, which amount to construct the
quantum contraction and the Sklyanin determinant for the
and quantum reflection algebras. We also determine the symmetry algebra of these two types of spin chains, including general
K and K+ diagonal matrices for the open case.
The case of open spin chains with soliton non-preserving boundary conditions is also presented in the framework of quantum
twisted Yangians. The symmetry algebra of this spin chains is studied. We also give an exhaustive classification of the invertible
matricial solutions to the corresponding reflection equation.
Communicated by Petr Kulish
Dedicated to our friend Daniel Arnaudon
Submitted: December 12, 2005; Accepted: January 23, 2006 相似文献
9.
Véronique Delouille Rainer Von Sachs 《Annals of the Institute of Statistical Mathematics》2005,57(2):235-253
We estimate nonlinear autoregressive models using a design-adapted wavelet estimator. We show two properties of the wavelet
transform adapted to an autoregressive design. First, in an asymptotic setup, we derive the order of the threshold that removes
all the noise with a probability tending to one asymptotically. Second, with this threshold, we estimate the detail coefficients
by soft-thresholding the empirical detail coefficients. We show an upper bound on thel
2-risk of these soft-thresholded detail coefficients. Finally, we illustrate the behavior of this design-adapted wavelet estimator
on simulated and real data sets.
Financial support from the contract ‘Projet d'Actions de Recherche Concertées’ nr. 98/03-217 from the Belgian government,
and from the IAP research network nr. P5/24 of the Belgian State (Federal Office for Scientific, Technical and Cultural Affairs)
is gratefully acknowledged. 相似文献
10.
Papers by Feddersen and Sandroni (Am Econ Rev, 2006a; Q J polit Sci, 2006b) and Coate and Colin (Am Econ Rev, 94:1476–1504,
2004) provide an explanation for turnout in large elections. These papers introduce ethical agents who are motivated to participate
when they determine that agents of their type are morally obligated to do so. Unlike previous duty-based models of participation,
ethical agents’ moral obligation to vote is determined endogenously as a function of the behavior of other agents. In order
to predict outcomes, a solution concept called consistency links agents’ preferences with actual behavior in a manner analogous to Nash equilibrium. In this paper, we address the foundational
problems in ethical participation models. We show the restrictions consistency imposes on the central notion of group identity,
the incentive constraints on ethical reasoning, and the existence and uniqueness of consistent profiles. 相似文献
11.
Based on kernel and wavelet estimators of the evolutionary spectrum and cross-spectrum we propose nonlinear wavelet estimators
of the time varying coefficients of a linear system, whose input and output are locally stationary processes, in the sense
of Dahlhaus (1997). We obtain large sample properties of these estimators, present some simulated examples and derive results
on the L
2-risk for the wavelet threshold estimators, assuming that the coefficients belong to some smoothness class.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
12.
We consider an M|E
N
|1 queue in which there are two essential on-line decisions that have to be taken. The first one is the decision to either accept or reject new jobs. The second one is the decision to either continue or abort the service of a job. We show that under certain regularity conditions, there exist optimal threshold policies for these two types of decisions. 相似文献
13.
Michael Krivelevich Benny Sudakov Prasad Tetali 《Random Structures and Algorithms》2006,29(2):180-193
We study a model of random graphs, where a random instance is obtained by adding random edges to a large graph of a given density. The research on this model has been started by Bohman and colleagues (Random Struct Algor 3 ; Random Struct Algor 4 ). Here we obtain a sharp threshold for the appearance of a fixed subgraph and for certain Ramsey properties. We also consider a related model of random k‐SAT formulas, where an instance is obtained by adding random k‐clauses to a fixed formula with a given number of clauses, and derive tight bounds for the non‐satisfiability of the thus‐obtained random formula. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2006 相似文献
14.
ABSTRACT. We investigate wildlife disease management, in a bioeconomic framework, when the wildlife host is valuable and disease transmission is density‐dependent. Disease prevalence is reduced in density‐dependent models whenever the population is harvested below a host‐density threshold a threshold population density below which disease prevalence declines and above which a disease becomes epidemic. In conventional models, the threshold is an exogenous function of disease parameters. We consider this case and find a steady state with positive disease prevalence to be optimal. Next, we consider a case in which disease dynamics are affected by both population controls and changes in human‐environmental interactions. The host‐density threshold is endogenous in this case. That is, the manager does not simply manage the population relative to the threshold, but rather manages both the population and the threshold. The optimal threshold depends on the economic and ecological trade‐offs arising from the jointly‐determined system. Accounting for this endogene‐ity can lead to reduced disease prevalence rates and higher population levels. Additionally, we show that ecological parameters that may be unimportant in conventional models that do not account for the endogeneity of the host‐density threshold are potentially important when host density threshold is recognized as endogenous. 相似文献
15.
《Journal of computational and graphical statistics》2013,22(3):610-625
This article proposes a probability model for k-dimensional ordinal outcomes, that is, it considers inference for data recorded in k-dimensional contingency tables with ordinal factors. The proposed approach is based on full posterior inference, assuming a flexible underlying prior probability model for the contingency table cell probabilities. We use a variation of the traditional multivariate probit model, with latent scores that determine the observed data. In our model, a mixture of normals prior replaces the usual single multivariate normal model for the latent variables. By augmenting the prior model to a mixture of normals we generalize inference in two important ways. First, we allow for varying local dependence structure across the contingency table. Second, inference in ordinal multivariate probit models is plagued by problems related to the choice and resampling of cutoffs defined for these latent variables. We show how the proposed mixture model approach entirely removes these problems. We illustrate the methodology with two examples, one simulated dataset and one dataset of interrater agreement. 相似文献
16.
Michael Molloy 《Random Structures and Algorithms》2014,45(3):498-512
–We consider two random graphs G1, G2, both on the same vertex set. We ask whether there is a non‐trivial set of vertices S, so that S induces a connected subgraph both in G1 and in G2. We determine the threshold for the appearance of such a subset, as well as the size of the largest such subset. © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 45, 498–512, 2014 相似文献
17.
We analyse the problem of finding instability thresholds and global non‐linear stability bounds for thermal convection in a linearly viscous fluid in a finite box. The vertical walls are maintained at different temperatures which gives rise to a non‐uniform temperature field in steady state. This problem was previously analysed by Georgescu and Mansutti (Int. J. Non‐Linear Mech. 1999; 34 :603–613). In our work we determine the linear instability threshold to be well above the global stability boundary found by an energy method. Since the perturbed system is not symmetric we expect this to be the case, and our analysis yields a parameter region where possible sub‐critical instabilities may be found. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
18.
In this paper we show that e/n is the sharp threshold for the existence of tight Hamilton cycles in random k ‐uniform hypergraphs, for all k ≥ 4. When k = 3 we show that 1/n is an asymptotic threshold. We also determine thresholds for the existence of other types of Hamilton cycles. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2013 相似文献
19.
We study an energy functional that arises in a simplified two-dimensional model for lipid bilayer membranes. We demonstrate that this functional, defined on a class of spatial mass densities, favours concentrations on ‘thin structures’. Stretching, fracture and bending of such structures all carry an energy penalty. In this sense we show that the models captures essential features of lipid bilayers, namely partial localisation and a solid-like behaviour. Our findings are made precise in a Gamma-convergence result. We prove that a rescaled version of the energy functional converges in the ‘zero thickness limit’ to a functional that is defined on a class of planar curves. Finiteness of the limit value enforces both optimal thickness and non-fracture; if these conditions are met, then the value of this functional is given by the classical Elastica (bending) energy. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Karl Weber 《Mathematische Nachrichten》1987,131(1):49-57
We consider two types of random subgraphs of the n-cube Qn obtained by independent deletion the vertices (together with all edges incident with them) or the edges of Qn, respectively, with a prescribed probability q = 1 — p. For these two probabilistic models we determine some values of the probability p for which the number of (isolated) k-dimensional subcubes or the number of vertices of a given degree k, respectively, has asymptotically a Poisson or a Normal distribution. The technique which will be used is that of Poisson convergence introduced by BARBOUR [1] (see also [4]). 相似文献