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31.
Recent vehicular routing proposals use real-time road traffic density estimates to dynamically select forwarding paths. Estimating the traffic density in vehicular ad hoc networks requires the transmission of additional dedicated messages increasing the communications load. These proposals are generally based on unicast sender-based forwarding schemes. The greedy nature of sender-based forwarding can result in the selection of forwarders with weak radio links that might compromise the end-to-end performance. To overcome these limitations, this paper presents TOPOCBF, a novel contention-based broadcast forwarding protocol that dynamically selects forwarding paths based on their capability to route packets between anchor points. Such capability is estimated by means of a multi-hop connectivity metric. The obtained results demonstrate that TOPOCBF can provide good packet delivery ratios while reducing the communications load compared to unicast sender-based forwarding schemes using road traffic density estimates. 相似文献
32.
We introduce general sequences of linear operators obtained from classical approximation processes which are useful in the
approximation of the resolvent operators of the generators of suitable C
0-semigroups. The main aim is the representation of the resolvent operators in terms of classical approximation operators.
Work performed under the auspices of PRIN 2006–07 “Kolmogorov equations” (coordinator G. Da Prato) 相似文献
33.
Ricci Marina Evangelista Alessandro Di Roma Annalisa Fiorentino Michele 《Virtual Reality》2023,27(3):2281-2296
Virtual Reality - With the high growth and prosperity of e-commerce, the retail industry needs to explore new technologies that improve digital shopping experiences. In the current technological... 相似文献
34.
Sarv Ahrabi Sima Piazzo Lorenzo Momenzadeh Alireza Scarpiniti Michele Baccarelli Enzo 《The Journal of supercomputing》2022,78(9):12024-12045
The Journal of Supercomputing - We present a probabilistic method for classifying chest computed tomography (CT) scans into COVID-19 and non-COVID-19. To this end, we design and train, in an... 相似文献
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37.
Ugo Andreaus Michele Colloca Daniela Iacoviello Marcello Pignataro 《Structural and Multidisciplinary Optimization》2011,43(1):43-59
The objective of this paper was solving the optimization problem of lightweight stiffened structures modelled as a two-dimensional
domain in an efficient computational way. The underlying premise was that mass should be distributed in an efficient way,
so as to use a minimum amount of material to accomplish the mechanical function. This premise was expressed as a global, multi-objective
optimization problem in which stiffness and mass were conflicting objectives. Alternative local evolution rules were implemented
to update mass density or Young’s modulus at each step of the iterative procedure. The solution of the structural optimization
problem was accomplished by a novel automatic procedure consisting of two consecutive stages of control and optimization.
In the first stage of Proportional Integral Derivative (PID) control gains were manually selected whereas in the second stage
the finding of optimal values of control gains, target, and cost indices was allowed. In this study a bone-like material was
adopted and a thin slab was analysed as a sample problem. 相似文献
38.
Michele Barletta Silvio Ranise Luca Vigan�� 《Service Oriented Computing and Applications》2011,5(2):105-137
The specification of distributed service-oriented applications spans several levels of abstraction, e.g., the protocol for
exchanging messages, the set of interface functionalities, the types of the manipulated data, the workflow, the access policy,
etc. Many (even executable) specification languages are available to describe each level in separation. However, these levels
may interact in subtle ways (for example, the control flow may depend on the values of some data variables) so that a precise
abstraction of the application amounts to more than the sum of its per level components. This problem is even more acute in
the design phase when automated analysis techniques may greatly help the difficult task of building “correct” applications
faced by designers. To alleviate this kind of problems, this paper introduces a framework for the formal specification and
automated analysis of distributed service-oriented applications in two levels: one for the workflow and one for the authorization
policies. The former allows one to precisely describe the control and data parts of an application with their mutual dependencies.
The latter focuses on the specification of the criteria for granting or denying third-party applications the possibility to
access shared resources or to execute certain interface functionalities. These levels can be seen as abstractions of one or
of several levels of specification mentioned above. The novelty of our proposal is the possibility to unambiguously specify
the—often subtle—interplay between the workflow and policy levels uniformly in the same framework. Additionally, our framework
allows us to define and investigate verification problems for service-oriented applications (such as executability and invariant
checking) and give sufficient conditions for their decidability. These results are non-trivial because their scope of applicability
goes well beyond the case of finite state spaces allowing for applications manipulating variables ranging over infinite domains.
As proof of concept, we show the suitability and flexibility of our approach on two quite different examples inspired by industrial
case studies. 相似文献
39.
In this paper, we introduce and analyze a modification of the Hermitian and skew-Hermitian splitting iteration method for solving a broad class of complex symmetric linear systems. We show that the modified Hermitian and skew-Hermitian splitting (MHSS) iteration method is unconditionally convergent. Each iteration of this method requires the solution of two linear systems with real symmetric positive definite coefficient matrices. These two systems can be solved inexactly. We consider acceleration of the MHSS iteration by Krylov subspace methods. Numerical experiments on a few model problems are used to illustrate the performance of the new method. 相似文献
40.
Vittorio Bilò Angelo Fanelli Michele Flammini Luca Moscardelli 《Theory of Computing Systems》2011,49(1):24-45
We investigate the approximation ratio of the solutions achieved after a one-round walk in linear congestion games. We consider the social functions Sum, defined as the sum of the players’ costs, and Max, defined as the maximum cost per player, as a measure of the quality of a given solution. For the social function Sum and one-round walks starting from the empty strategy profile, we close the gap between the upper bound of \(2+\sqrt{5}\approx 4.24\) given in Christodoulou et al. (Proceedings of the 23rd International Symposium on Theoretical Aspects of Computer Science (STACS), LNCS, vol. 3884, pp. 349–360, Springer, Berlin, 2006) and the lower bound of 4 derived in Caragiannis et al. (Proceedings of the 33rd International Colloquium on Automata, Languages and Programming (ICALP), LNCS, vol. 4051, pp. 311–322, Springer, Berlin, 2006) by providing a matching lower bound whose construction and analysis require non-trivial arguments. For the social function Max, for which, to the best of our knowledge, no results were known prior to this work, we show an approximation ratio of \(\Theta(\sqrt[4]{n^{3}})\) (resp. \(\Theta(n\sqrt{n})\)), where n is the number of players, for one-round walks starting from the empty (resp. an arbitrary) strategy profile. 相似文献