共查询到20条相似文献,搜索用时 78 毫秒
1.
We study here robust stability of linear systems with several uncertain incommensurate delays, more precisely the property usually called delay-dependent stability. The main result of this paper consists in establishing that the latter is equivalent to the feasibility of some Linear Matrix Inequality (LMI), a convex optimization problem whose numerical solution is well documented.The method is based on two main techniques:
- • use of Padé approximation to transform the system into some singularly perturbed finite-dimensional system, for which robust dichotomy has to be checked;
- • recursive applications of Generalized Kalman–Yakubovich–Popov (KYP) lemma to characterise by an LMI the previous property.
Keywords: Linear systems; Delay systems; Asymptotic stability; Robust stability; Delay-dependent stability; Semi-definite programming; Linear matrix inequalities 相似文献
2.
We present a simple new algorithm for triangulating polygons and planar straightline graphs, It provides "shape" and "size" guarantees:
- • All triangles have a bounded aspect ratio.
- • The number of triangles is within a constant factor of optimal.
3.
We show how to compute the modified moments of a refinable weight function directly from its mask in O(N2n) rational operations, where N is the desired number of moments and n the length of the mask. Three immediate applications of such moments are:
- • the expansion of a refinable weight function as a Legendre series;
- • the generation of the polynomials orthogonal with respect to a refinable weight function;
- • the calculation of Gaussian quadrature formulas for refinable weight functions.
Keywords: Refinable function; Orthogonal polynomials; Gaussian quadrature; Modified moments; Legendre series 相似文献
4.
Juan-Pablo Ortega 《Comptes Rendus Mathematique》2002,334(11):999-1004
During the last thirty years, symplectic or Marsden–Weinstein reduction has been a major tool in the construction of new symplectic manifolds and in the study of mechanical systems with symmetry. This procedure has been traditionally associated to the canonical action of a Lie group on a symplectic manifold, in the presence of a momentum map. In this Note we show that the symplectic reduction phenomenon has much deeper roots. More specifically, we will find symplectically reduced spaces purely within the Poisson category under hypotheses that do not necessarily imply the existence of a momentum map. In other words, the right category to obtain symplectically reduced spaces is that of Poisson manifolds acted upon canonically by a Lie group. To cite this article: J.-P. Ortega, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 999–1004. 相似文献
5.
We introduce a generalization of D-spaces, which we call linearly D-spaces. The following results are obtained for a T1-space X.
- – X is linearly Lindelöf if, and only if, X is a linearly D-space of countable extent.
- – X is linearly D provided that X is submetaLindelöf.
- – X is linearly D provided that X is the union of finitely many linearly D-subspaces.
- – X is compact provided that X is countably compact and X is the union of countably many linearly D-subspaces.
Keywords: D-space; SubmetaLindelöf; Linearly Lindelöf; Countably compact 相似文献
6.
We consider Lagrangian Floer cohomology for a pair of Lagrangian submanifolds in a symplectic manifold M. Suppose that M carries a symplectic involution, which preserves both submanifolds. Under various topological hypotheses, we prove a localization
theorem for Floer cohomology, which implies a Smith-type inequality for the Floer cohomology groups in M and its fixed point set. Two applications to symplectic Khovanov cohomology are included. 相似文献
7.
This paper is concerned with funding systems, i.e. systems which accumulate funds for the future payment of financial obligations. Commonly, such funding requires a balance between (1) the desire to minimise the contributions that need to be diverted from other use to the support of the Fund, and (2) the need to maintain reasonable solvency in the Fund.Such funding is discussed here in a general framework. Applications are numerous. The specific applications mentioned in the paper are:
- • Defined benefit retirement funding,
- • Maintenance of a prudential margin by a non-life insurer,
- • Dividend payment strategy.
8.
Time-series of statokinesigram (SKG) of healthy subjects and parkinsonians are investigated and compared. This is done by employing the chaos paradigm in order to obtain the main characteristics of the SKG. The interpretation of our findings is twofold:
- when a proper Theiler window is not used we find a virtual invariance of the chaos parameters when healthy subjects and parkinsonians are compared but a discrepancy of our values (correlation dimension equals to 1.4) with those found in previous works;
- when a proper Theiler window is used (more) appropriately, the SKGs do not show a convergence of the fractal dimension estimates; therefore nothing can be said in terms of chaoticity of system.
Article Outline
- 1. Introduction
- 2. Material
- 3. Methods: the paradigm of chaos
- 3.1. Limitations on the use of the non-linear time analysis
- 4. Results: dynamical analysis
- 5. Discussion and conclusions
- Acknowledgements
- References
1. Introduction
This work is born in the framework of the project “Celestina” coordinated by Prof. Paolo Pascolo (first author of this paper), who developed the methodological approach and theoretical basis and started the experimental acquisition which results are presented here. This paper continues and further develops the preliminary results presented in a previous paper [14].The statokinesigram (SKG) is the projection onto a 2-dimensional space of the trajectory of the centre of pressure (COP) of a person during erect stance (see Fig. 1). This sort of trajectories are the result of the (multi-dimensional) dynamical system underlying the human body, which is made up of a high number of links, is subject to the gravity and is also affected by perturbations such as breathing, blood circulation and muscular activity. Finally, on this system the central control acts to stabilize and limit the body oscillations. 相似文献9.
Christos Levcopoulos Drago Krznaric 《Journal of Algorithms in Cognition, Informatics and Logic》1998,27(2):303-338
This article settles the following two longstanding open problems:
- • What is the worst case approximation ratio between the greedy triangulation and the minimum weight triangulation?
- • Is there a polynomial time algorithm that always produces a triangulation whose length is within a constant factor from the minimum?
10.
Symmetry of graphs has been extensively studied over the past fifty years by using automorphisms of graphs and group theory which have played and still play an important role for graph theory, and promising and interesting results have been obtained, see for examples, [L.W. Beineke, R.J. Wilson, Topics in Algebraic Graph Theory, Cambridge University Press, London, 2004; N. Biggs, Algebraic Graph Theory, Cambridge University Press, London, 1993; C. Godsil, C. Royle, Algebraic graph theory, Springer-Verlag, London, 2001; G. Hahn, G. Sabidussi, Graph Symmetry: Algebraic Methods and Application, in: NATO ASI Series C, vol. 497, Kluwer Academic Publishers, Dordrecht, 1997]. We introduced generalized symmetry of graphs and investigated it by using endomorphisms of graphs and semigroup theory. In this paper, we will survey some results we have achieved in recent years. The paper consists of the following sections.
- 1. Introduction
- 2. End-regular graphs
- 3. End-transitive graphs
- 4. Unretractive graphs
- 5. Graphs and their endomorphism monoids.
Keywords: Graph; Endomorphism; Monoid; Generalized symmetry; End-regular; End-transitive; Unretractive 相似文献
11.
Julio Becerra Guerrero Fernando Rambla-Barreno 《Journal of Mathematical Analysis and Applications》2009,360(1):254-264
We prove that for every member X in the class of real or complex JB*-triples or preduals of JBW*-triples, the following assertions are equivalent:
- (1) X has the fixed point property.
- (2) X has the super fixed point property.
- (3) X has normal structure.
- (4) X has uniform normal structure.
- (5) The Banach space of X is reflexive.
Keywords: JB*-triple; Fixed point; Normal structure 相似文献
12.
Baumgarten N. Jung H. Mehlhorn K. 《Journal of Algorithms in Cognition, Informatics and Logic》1994,17(3)
The dynamic planar point location problem is the task of maintaining a dynamic set S of n nonintersecting (except possibly at endpoints) line segments in the plane under the following operations:
- • Locate (: point): Report the segment immediately above , i.e., the first segment intersected by an upward vertical ray starting at ;
- • Insert (: segment): Add segment to the collection of segments;
- • Delete (: segment): Remove segment from the collection of segments.
13.
Hung T. Nguyen Olga Kosheleva Vladik Kreinovich Scott Ferson 《International Journal of Approximate Reasoning》2009,50(8):1164
In many practical situations, we are not satisfied with the accuracy of the existing measurements. There are two possible ways to improve the measurement accuracy:
- • First, instead of a single measurement, we can make repeated measurements; the additional information coming from these additional measurements can improve the accuracy of the result of this series of measurements.
- • Second, we can replace the current measuring instrument with a more accurate one; correspondingly, we can use a more accurate (and more expensive) measurement procedure provided by a measuring lab – e.g., a procedure that includes the use of a higher quality reagent.
14.
Let (E,H,μ) be an abstract Wiener space and let DV:=VD, where D denotes the Malliavin derivative and V is a closed and densely defined operator from H into another Hilbert space . Given a bounded operator B on , coercive on the range , we consider the operators A:=V*BV in H and in , as well as the realisations of the operators and in Lp(E,μ) and respectively, where 1<p<∞. Our main result asserts that the following four assertions are equivalent:
- (1) with for ;
- (2) admits a bounded H∞-functional calculus on ;
- (3) with for ;
- (4) admits a bounded H∞-functional calculus on .
Keywords: Divergence form elliptic operators; Abstract Wiener spaces; Riesz transforms; Domain characterisation in Lp; Kato square root problem; Ornstein–Uhlenbeck operator; Meyer inequalities; Second quantised operators; Square function estimates; H∞-functional calculus; R-boundedness; Hodge–Dirac operators; Hodge decomposition 相似文献
15.
We show that a small neighborhood of a closed symplectic
submanifold in a geometrically bounded aspherical symplectic manifold has
non-vanishing symplectic homology. As a consequence, we establish the existence
of contractible closed characteristics on any thickening of the boundary
of the neighborhood. When applied to twisted geodesic flows on compact
symplectically aspherical manifolds, this implies
the existence of contractible periodic orbits for a dense set of
low energy values. 相似文献
16.
Shoshichi Kobayashi 《Results in Mathematics》2001,40(1-4):246-256
One of the sufficient conditions for a complex manifold to be (complete) hyperbolic (in the sense that its intrinsic pseudo-distance is a (complete) distance) is that it admits a (complete) Hermitian metric with holomorphic sectional curvature bounded above by a negative constant. The concept of hyperbolicity can be readily extended to almost complex manifolds. We will show that the above result for hyperbolicity can be generalized to the almost complex case. As an application, we prove that every point of an almost complex manifold has a complete hyperbolic neighborhood. In real dimension 4, this fact was established by Debalme and Ivashkovich [2] by a completely different method. 相似文献
17.
In a previous paper [H. Tsuiki, Y. Hattori, Lawson topology of the space of formal balls and the hyperbolic topology of a metric space, Theoret. Comput. Sci. 405 (2008) 198–205], the authors introduced the hyperbolic topology on a metric space, which is weaker than the metric topology and naturally derived from the Lawson topology on the space of formal balls. In this paper, we characterize spaces Lp(Ω,Σ,μ) on which the hyperbolic topology induced by the norm p coincides with the norm topology. We show the following:
- (1) The hyperbolic topology and the norm topology coincide for 1<p<∞.
- (2) They coincide on L1(Ω,Σ,μ) if and only if μ(Ω)=0 or Ω has a finite partition by atoms.
- (3) They coincide on L∞(Ω,Σ,μ) if and only if μ(Ω)=0 or there is an atom in Σ.
Keywords: Normed linear space; Lp; Uniformly rotund (convex); Locally uniformly rotund (convex); Atom; Metric space; Hyperbolic topology; Norm topology; Formal ball; Lawson topology 相似文献
18.
S. Bandyopadhyay B. Dacorogna 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2009,26(5):1717-1741
We discuss the existence of a diffeomorphism such that
φ*(g)=f