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41.
设{xn,n≥1}是同分布的两两NQD列,记Sn=∑i=1Xi^n.本文讨论了max |Si|/i(n≥1)的分布函数的上下界.作为应用,获得了随机变量supn≥|Sn|/n型的1阶矩及p(〉1)阶矩分别存在有限的充分必要条件,这是一个与独立同分布场合相一致的结果. 相似文献
42.
43.
针对水下小目标信息量有限而难以提取有效特征导致的检测性能不佳问题,提出了一种结合区域提取和融合Hu矩特征的改进卷积神经网络水下小目标检测方法。该方法包含区域提取和分类两个步骤。首先以马尔可夫随机场分割算法为基础进行区域提取,对潜在目标定位的同时降低伪目标对后续分类的干扰;然后提取潜在目标区域的Hu矩特征并融入卷积神经网络,形成一种形状特征表征能力更强的改进卷积神经网络用于分类。声呐实测数据处理结果表明,该方法可以有效提升对水下小目标的发现概率和正确报警率,与其他目标检测方法相比,该方法具有更好的检测性能和泛化性。 相似文献
44.
J. Cimpri? 《Journal of Functional Analysis》2011,260(10):3132-3145
We prove a general archimedean positivstellensatz for hermitian operator-valued polynomials and show that it implies the multivariate Fejer-Riesz theorem of Dritschel-Rovnyak and positivstellensätze of Ambrozie-Vasilescu and Scherer-Hol. We also obtain several generalizations of these and related results. The proof of the main result depends on an extension of the abstract archimedean positivstellensatz for ?-algebras that is interesting in its own right. 相似文献
45.
46.
In this paper, the authors consider the problem of which
(generalized) moment-angle manifolds admit Ricci positive metrics.
For a simple polytope $P$, the authors can cut off one vertex $v$ of
$P$ to get another simple polytope $P_{v}$, and prove that if the
generalized moment-angle manifold corresponding to $P$ admits a
Ricci positive metric, the generalized moment-angle manifold
corresponding to $P_{v}$ also admits a Ricci positive metric. For a
special class of polytope called Fano polytopes, the authors prove
that the moment-angle manifolds corresponding to Fano polytopes
admit Ricci positive metrics. Finally some conjectures on this
problem are given. 相似文献
47.
Given an undirected graph, a star partition is a partition of the nodes into subsets with at least two nodes so that the subgraph induced by each subset has a spanning star. Star partitions are related to well-known problems concerning domination in graphs and edge covering. We focus on the Constrained Star Partition Problem (CSP) that asks for finding a star partition of given cardinality. The problem is new and presents interesting peculiarities. We explore the relation between the cardinalities of star partitions and domatic bipartitions, showing that there are star partitions of any cardinality between minimum and maximum values, and that a similar but weaker result holds for domatic bipartitions. We study the computational complexity of different versions of star partition and domatic bipartition problems, proving that most of them, in particular CSP, constrained domatic bipartition and balanced domatic bipartition, are NP-complete. We also show that star partition problems are polynomial on trees and, more generally, on bounded treewidth graphs. We introduce an integer linear programming formulation that defines a polytope containing all the star partitions of a graph, showing that its vertices have only integral components for trees, which implies that linear programming can be used to solve weighted star partition problems on trees. 相似文献
48.
Stability Analysis for the Numerical Simulation of Hybrid Stochastic Differential Equations
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This paper is mainly concerned with the exponential stability of a class of hybrid stochastic differential equations–stochastic differential equations with Markovian switching (SDEwMSs). It first devotes to reveal that under the global Lipschitz condition, a SDEwMS is pth (p ∈ (0,1)) moment exponentially stable if and only if its corresponding improved Euler-Maruyama(IEM) method is pth moment exponentially stable for a suitable step size. It then shows that the SDEwMS is pth(p ∈ (0,1)) moment exponentially stable or its corresponding IEM method with small enough step sizes implies the equation is almost surely exponentially stable or the corresponding IEM method, respectively. In that sense, one can infer that the SDEwMS is almost surely exponentially stable and the IEM method, no matter whether the SDEwMS is pth moment exponentially stable or the IEM method. An example is demonstrated to illustrate the obtained results. 相似文献
49.
We study asymptotic stability of continuous-time systems with mode-dependent guaranteed dwell time. These systems are reformulated as special cases of a general class of mixed (discrete–continuous) linear switching systems on graphs, in which some modes correspond to discrete actions and some others correspond to continuous-time evolutions. Each discrete action has its own positive weight which accounts for its time-duration. We develop a theory of stability for the mixed systems; in particular, we prove the existence of an invariant Lyapunov norm for mixed systems on graphs and study its structure in various cases, including discrete-time systems for which discrete actions have inhomogeneous time durations. This allows us to adapt recent methods for the joint spectral radius computation (Gripenberg’s algorithm and the Invariant Polytope Algorithm) to compute the Lyapunov exponent of mixed systems on graphs. 相似文献
50.
E. Martínez F. J. Basterrechea F. Beitia F. Castaño M. T. Martínez L. Santos 《光谱学快报》2013,46(8):1007-1017
Franck-Condon factors and R-centroids for the B-X transition of I2 have been calculated from recent molecular parameters. From our radiative lifetimes and others reported in the literature, the validity of several proposed electronic transition moment functions has been checked. Acombination of the Bhale and Koffend functions seems to give the best fitting with the experimental radiative lifetimes. 相似文献