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排序方式: 共有1344条查询结果,搜索用时 15 毫秒
41.
Luis Henrique Gibeli Gean Davis Breda Rodrigo Sanches Miani Bruno Bogaz Zarpelão Leonardo de Souza Mendes 《International Journal of Network Management》2013,23(2):137-153
In the last century, owing to the constant evolution of technologies telecommunication networks have become increasingly robust, being able to support multiple services. These services are part of the heterogeneous network traffic that can be carried through the Internet. Many of these services, including VoIP, are latency sensitive. In other words, this means that their quality depends directly on the network quality of service. Since users tend to become more sensitive with the instability and unavailability of the network, it is important to improve traffic management. A particular type of data that could be used to improve VoIP traffic management is the Internet Protocol Detail Record (IPDR). IPDRs are tickets created by all VoIP call attempts which contain a group of information related to the call history. Because of its full range of information, IPDRs can be used to create VoIP traffic baselines. This paper presents the development of baselines based on IPDRs to support VoIP traffic management in open‐access Metropolitan Area Networks (MAN). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
42.
Leonardo Casetta 《Acta Mechanica》2016,227(6):1519-1532
The connection between geometry and dynamics is a canonical subject of analytical mechanics. A very traditional issue of this topic is the transformation of the mechanical problem at hand into a shortest-path problem. This means the mathematical translation of the dynamical problem into a problem of finding the geodesic of a certain space. In the classical domain of conservative systems, especially following the famous book of Lanczos, this translating bridge is established by the usual condition of constant total energy. By nature, the motion of a particle with position-dependent mass is not a conservative problem. Therefore, the classical geometrical theory of mechanics is not straightforwardly applicable. Given that, we here aim at developing the geometrical theory for the mechanics of a position-dependent mass particle. This is our intended contribution. To our best knowledge, the content of our single investigation is original within this variable mass context. Our theory will be developed in the light of the inverse problem of Lagrangian mechanics, which will accordingly sets the variational framework. From that, we will demonstrate the proper generalization of Euler-Maupertuis’ principle and the following generalization of Jacobi’s principle, which, analogously to the classical procedure, can be seen as intermediate steps to enter geometrical arguments. Then, the corresponding geodesic will appear. Finally, as a closing result, a theorem on the mathematical equivalence between such geodesic and the equation of motion of a position-dependent mass particle will be proved. Our investigation aims at providing the reader with a fundamental contribution to the geometry of variable mass mechanics. 相似文献
43.
Leonardo Crauss Daronco Valter Roesler José Valdeni de Lima Ricardo Balbinot 《Multimedia Tools and Applications》2012,61(3):571-597
This paper presents a study of quality on scalable video sequences coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the effects that transmission instability has in the quality of the videos and the relationship among three scalability methods (spatial, temporal and quality) in terms of quality. A set of experiments was performed to measure the subjective quality using the ACR-HRR methodology and recommendations from ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that the amount of instability is not as important as just the presence of instability, that video quality can be deteriorated due to instability and that temporal scalability usually produces videos with worse quality than spatial and quality scalabilities. 相似文献
44.
Sara Silva Stephen Dignum Leonardo Vanneschi 《Genetic Programming and Evolvable Machines》2012,13(2):197-238
Bloat can be defined as an excess of code growth without a corresponding improvement in fitness. This problem has been one
of the most intensively studied subjects since the beginnings of Genetic Programming. This paper begins by briefly reviewing
the theories explaining bloat, and presenting a comprehensive survey and taxonomy of many of the bloat control methods published
in the literature through the years. Particular attention is then given to the new Crossover Bias theory and the bloat control
method it inspired, Operator Equalisation (OpEq). Two implementations of OpEq are described in detail. The results presented
clearly show that Genetic Programming using OpEq is essentially bloat free. We discuss the advantages and shortcomings of
each different implementation, and the unexpected effect of OpEq on overfitting. We observe the evolutionary dynamics of OpEq
and address its potential to be extended and integrated into different elements of the evolutionary process. 相似文献
45.
46.
María J. Aguirre Mauricio Isaacs Betty Matsuhiro Leonora Mendoza Leonardo S. Santos Simonet Torres 《Food chemistry》2011
Anthocyanins in aged Cabernet Sauvignon red wines were studied by HPLC–MS. The major anthocyanin in 6, 7, and 8 year old red wine extracts was the dimer vitisin A produced by condensation of malvidin-3-O-glucoside mediated by pyruvic acid. In aged wine, the content of malvidin-3-O-glucoside decreased with age with a concomitant increase of vitisin A. The latter is accompanied by several condensation products with molecular weight up to 1500 m/z. Differential pulse voltammetry indicated that aged wines have lower antioxidant capacity than young wine (400 mV), but higher than malvidin-3-O-glucoside (483 mV). Tafel’s plots showed that the electrochemical process occurring in aged wines is different from young wines. Six, seven and eight year old wines show similar behaviour with plots of 234, 177 and 188 mV/dec, respectively. These values are higher than the expected 120 mV/dec corresponding to a first electronic transfer but smaller compared to the 523 mV/dec corresponding to young wine. 相似文献
47.
Edgar Leonardo Romero Marius Strum Wang Jiang Chau 《Journal of Electronic Testing》2013,29(2):223-236
The constant pressure for making functional verification more agile has led to the conception of coverage driven verification (CDV) techniques. CDV has been implemented in verification testbenches using supervised learning techniques to model the relationship between coverage events and stimuli generation, providing a feedback between them. One commonly used technique is the classification- or decision-tree data mining, which has shown to be appropriate due to the easy modeling. Learning techniques are applied in two steps: training and application. Training is made on one or more sets of examples, which relate datasets to pre-determined classes. Precision of results by applying the predictive learning concept has shown to be sensitive to the size of the training set and the amount of imbalance of associated classes, this last meaning the number of datasets associated to each class is very different from each other. This work presents experiments on the manipulation of data mining training sets, by changing the size and reducing the imbalances, in order to check their influence on the CDV efficiency. To do that, a circuit example with a large input space and strong class imbalance was selected from the application domain of multimedia systems and another one, with a small input space that affects the coverage occurrences, was selected from the communication area. 相似文献
48.
49.
Maurilio Toscano de Lucena Mário Ribeiro de Melo Júnior Mariana Montenegro de Melo Lira Célia Maria Machado Barbosa de Castro Leonardo Aguiar Cavalcanti Mariana Arruda de Menezes Flávia Cristina Morone Pinto José Lamartine de Andrade Aguiar 《Journal of materials science. Materials in medicine》2015,26(2):82
The development of a skin substitute suitable for immediately performing the function of the lost dermis and epidermis could result in a positive impact on the treatment of patients with extensive skin lesions. A biopolymer film was applied to skin wounds to investigate the biocompatibility and cutaneous reaction and to test its activity as a mechanical barrier and conductor in the healing process. Forty Wistar rats of both sexes were used in the present study. Two excisions were performed in the dorsal part of the skin flaps. The polysaccharide film was applied over one of the incisions and other incision was washed with saline. The time spent for complete healing of both lesions was virtually the same in both groups, during 21 days of observation. The film remained attached to the bed of the exposed wound for an average period of 6 days. There were no statistically significant differences with regard to lesion measurement area at assessment times of 2nd, 7th and 14th postoperative days. At day 21, the scar area showed a significant difference (0.0229). After 40 days, all wounds were completely healed. No statistically significant differences were found between the histological parameters assessed in the experimental and control groups. The cellulosic polysaccharide film integrated well with the tissue showing high biocompatibility and low skin reactivity. 相似文献
50.
Wesley Pacheco Calixto A. Paulo Coimbra Jesus Carlos da Mota Marcel Wu Wander G. da Silva Bernardo Alvarenga Leonardo da Cunha Brito Aylton Jose Alves Elder Geraldo Domingues Daywes Pinheiro Neto 《International Journal of Numerical Modelling》2015,28(1):78-95
This work presents a genetic operator developed from mathematical methods of curve extrapolation applied in solving problems in geoelectrical prospection. This operator will assist the production of fitter individuals in the population of a genetic algorithm in which inherent patterns of the best individuals of each generation are recognized. The proposed operator in conjunction with a real‐coded genetic algorithm is compared to five alternative optimization techniques known and used in the application to problems in geoelectrical prospection. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献