Search results for " Programming"
showing 10 items of 1616 documents
Browder's theorems through localized SVEP
2005
A bounded linear operator T ∈ L(X) on aBanach space X is said to satisfy “Browder’s theorem” if the Browder spectrum coincides with the Weyl spectrum. T ∈ L(X) is said to satisfy “a-Browder’s theorem” if the upper semi-Browder spectrum coincides with the approximate point Weyl spectrum. In this note we give several characterizations of operators satisfying these theorems. Most of these characterizations are obtained by using a localized version of the single-valued extension property of T. In the last part we shall give some characterizations of operators for which “Weyl’s theorem” holds.
Packing a Trunk
2003
We report on a project with a German car manufacturer. The task is to compute (approximate) solutions to a specific large-scale packing problem. Given a polyhedral model of a car trunk, the aim is to pack as many identical boxes of size 4 × 2 × 1 units as possible into the interior of the trunk. This measure is important for car manufacturers, because it is a standard in the European Union.
Spectral Asymptotics for $$\mathcal {P}\mathcal {T}$$ Symmetric Operators
2019
\(\mathcal {P}\mathcal {T}\)-symmetry has been proposed as an alternative to self-adjointness in quantum physics, see Bender et al. (J Math Phys 40(5):2201–2229, 1999), Bender and Mannheim (Phys Lett A 374(15–16):1616–1620, 2010). Thus for instance, if we consider a Schrodinger operator on Rn, $$\displaystyle P=-h^2\Delta +V(x), $$ the usual assumption of self-adjointness (implying that the potential V is real valued) can be replaced by that of \(\mathcal {P}\mathcal {T}\)-symmetry: $$\displaystyle V\circ \iota =\overline {V}, $$ where ι : Rn →Rn is an isometry with ι2 = 1≠ι. If we introduce the parity operator \(\mathcal {P}_\iota u(x)=u(\iota (x))\) and the time reversal operator \(\mathc…
XPL the Extensible Presentation Language
2009
The last decade has witnessed a growing interest in the development of web interfaces enabling both multiple ways to access contents and, at the same time, fruition by multiple modalities of interaction (point-and-click, contents reading, voice commands, gestures, etc.). In this paper we describe a framework aimed at streamlining the design process of multi-channel, multimodal interfaces enabling full reuse of software components. This framework is called the eXtensible Presentation architecture and Language (XPL), a presentation language based on design pattern paradigm that keeps separated the presentation layer from the underlying programming logic. The language supplies a methodology to…
A model of internal and external competition in a High Speed Rail line
2015
This paper is a contribution to evaluate structural and behavioral changes in railway passenger markets. The novel elements of our analysis are the following: (i) the consideration of inter-modal and intra-modal competition, (ii) the presence of public and private operators, and (iii) endogenous service frequency. After calibrating the model using actual data from two Spanish High Speed Rail lines, simulation exercises allow us to conclude the following. Privatization, whether entry occurs or not, would prompt an increase in prices and a reduction in the number of train services, eventually leading to welfare decreases, as compared with a regime where the incumbent rail operator remained pu…
Determining a Random Schrödinger Operator : Both Potential and Source are Random
2020
We study an inverse scattering problem associated with a Schr\"odinger system where both the potential and source terms are random and unknown. The well-posedness of the forward scattering problem is first established in a proper sense. We then derive two unique recovery results in determining the rough strengths of the random source and the random potential, by using the corresponding far-field data. The first recovery result shows that a single realization of the passive scattering measurements uniquely recovers the rough strength of the random source. The second one shows that, by a single realization of the backscattering data, the rough strength of the random potential can be recovered…
Reverse inheritance in statically typed object-oriented programming languages
2010
Reverse inheritance is a new class reuse mechanism, an experimental implementation of which we have built for Eiffel. It enables a more natural design approach, factorization of common features (members), insertion of classes into an existing hierarchy etc. Due to its reuse potential in Eiffel we consider exploring its capabilities in other industrial-strength programming languages like C++, Java and C#.
A grid representation for distributed virtual environments
2004
Fast Internet connections and the widespread use of high performance graphic cards are making Distributed Virtual Environments (DVE) very common nowadays. The architecture and behavior of these systems are very similar to new grid computing applications where concepts such as sharing and high scalability are extremely exploited. However, there are several key issues in these systems that should still be improved in order to design a scalable and cost-effective DVE system. One of these key issues is the partitioning problem. This problem consists of efficiently assigning clients (3-D avatars) to the arbiters (servers) in the system. As an alternative to the ad-hoc heuristic proposed in the l…
Exploring parallel capabilities of an innovative numerical method for recovering image velocity vectors field
2010
In this paper an efficient method devoted to estimate the velocity vectors field is investigated. The method is based on a quasi-interpolant operator and involves a large amount of computation. The operations characterizing the computational scheme are ideal for parallel processing because they are local, regular and repetitive. Therefore, the spatial parallelism of the process is studied to rapidly proceed in the computation on distributed multiprocessor systems. The process has shown to be synchronous, with good task balancing and requiring a small amount of data transfer.
Uniqueness of solutions for some elliptic equations with a quadratic gradient term
2008
We study a comparison principle and uniqueness of positive solutions for the homogeneous Dirichlet boundary value problem associated to quasi-linear elliptic equations with lower order terms. A model example is given by −Δu + λ |∇u| 2 u r = f (x) ,λ , r >0. The main feature of these equations consists in having a quadratic gradient term in which singularities are allowed. The arguments employed here also work to deal with equations having lack of ellipticity or some dependence on u in the right hand side. Furthermore, they could be applied to obtain uniqueness results for nonlinear equations having the p-Laplacian operator as the principal part. Our results improve those already known, even…