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排序方式: 共有1497条查询结果,搜索用时 343 毫秒
241.
In this paper, the problem of positivity and exponential stability for linear singular positive systems with time delay is addressed. By using the singular value decomposition method, necessary and sufficient conditions for the positivity of the system are established. Based on that, a new sufficient condition for exponential stability of the system is derived. All of the criteria obtained in this paper are presented in terms of algebraic matrix inequalities, which make the conditions can be solved directly. A numerical example is given to show the usefulness of the proposed results. 相似文献
242.
243.
This study explored two undergraduate precalculus students’ understandings of the idea of logarithm as they completed conceptually oriented exploratory lessons on exponential and logarithmic functions. The students participated in consecutive, individual teaching experiments that focused on Sparky – an animated mystical saguaro that doubled in height every week. The exponential lesson focused on developing students’ conceptions of growth factors and tupling (e.g., doubling) periods as a foundational understanding for conceptualizing logarithms and logarithmic properties meaningfully. This paper characterizes conceptions that are productive for students to acquire in introductory lessons on exponential and logarithmic growth, and discusses two understandings that were revealed to be foundational for students’ development of productive meanings for exponents, logarithms and logarithmic properties. 相似文献
244.
We develop the exact WKB analysis of an M2P1T (merging two simple poles and one simple turning point) Schrödinger equation. In Part II, using a WKB-theoretic transformation to the algebraic Mathieu equation constructed in Part I, we calculate the alien derivative of its Borel transformed WKB solutions at each fixed singular point relevant to the simple poles through the analysis of Borel transformed WKB solutions of the Legendre equations. In the course of the calculation of the alien derivative we make full use of microdifferential operators whose symbols are given by the infinite series that appear in the coefficients of the algebraic Mathieu equation and the Legendre equation. 相似文献
245.
246.
Let and let wρ(x)|x|ρexp(-Q(x)), where and is an even function. In this paper we consider the properties of the orthonormal polynomials with respect to the weight , obtaining bounds on the orthonormal polynomials and spacing on their zeros. Moreover, we estimate An(x) and Bn(x) defined in Section 4, which are used in representing the derivative of the orthonormal polynomials with respect to the weight . 相似文献
247.
Alexander L. Stolyar 《Queueing Systems》2008,59(1):1-35
We consider a discrete-time model where multiple queues, each with its own exogenous arrival process, are served by a server
whose capacity varies randomly and asynchronously with respect to different queues. This model is primarily motivated by the
problem of efficient scheduling of transmissions of multiple data flows sharing a wireless channel.
We address the following problem of controlling large deviations of the queues: find a scheduling rule, which is optimal in
the sense of maximizing
where Q
i
is the length of the i-th queue in a stationary regime, and a
i
>0 are parameters. Thus, we seek to maximize the minimum of the exponential decay rates of the tails of distributions of weighted
queue lengths a
i
Q
i
. We give a characterization of the upper bound on (0.1) under any scheduling rule, and of the lower bound on (0.1) under
the exponential (EXP) rule. We prove that the two bounds match, thus proving optimality of the EXP rule. The EXP rule is very parsimonious
in that it does not require any “pre-computation” of its parameters, and uses only current state of the queues and of the
server.
The EXP rule is not invariant with respect to scaling of the queues, which complicates its analysis in the large deviations
regime. To overcome this, we introduce and prove a refined sample path large deviations principle, or refined Mogulskii theorem, which is of independent interest.
相似文献
(0.1) |
248.
249.
The purpose of this paper is to establish the exponential decay properties of the solutions for the nonlinear multiharmonic equation where the condition plays the role of a boundary value condition. 相似文献
250.
In this paper, a nonlinear impulsive neutral integro-differential equation with time-varying delays is considered. By establishing a singular impulsive delay integro-differential inequality and transforming the n-dimensional impulsive neutral integro-differential equation to a 2n-dimensional singular impulsive delay integro-differential equation, some sufficient conditions ensuring the global exponential stability in PC1 of the zero solution of an impulsive neutral integro-differential equation are obtained. The results extend and improve the earlier publications. An example is also discussed to illustrate the efficiency of the obtained results. 相似文献