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51.
News
Fifth International Deer Biology Congress 相似文献52.
The quality of the image produced by an outdoor optical system is affected by the presence of atmospheric aerosols between object and receiver. The properties of the point-spread function that result from aerosol particles were calculated by a new Monte Carlo code called MEDIA (an acronym for Modélisation des Effets de Diffusion Inhérents à l'Atmosphère). The influence of the scattering phase function's angular dependence on the irradiance of the focal plane of a detector was studied. Calculations were performed by use of Mie theory and of the Henyey-Greenstein formulation for the same asymmetry parameter and various detector optical characteristics and atmospheric conditions. Major variations were observed for strong forward-peaked scattering phase functions and a large detector field of view. 相似文献
53.
Jean-Christophe Zufferey Alexis Guanella Antoine Beyeler Dario Floreano 《Autonomous Robots》2006,21(3):243-254
Because of their ability to naturally float in the air, indoor airships (often called blimps) constitute an appealing platform
for research in aerial robotics. However, when confronted to long lasting experiments such as those involving learning or
evolutionary techniques, blimps present the disadvantage that they cannot be linked to external power sources and tend to
have little mechanical resistance due to their low weight budget. One solution to this problem is to use a realistic flight
simulator, which can also significantly reduce experimental duration by running faster than real time. This requires an efficient
physical dynamic modelling and parameter identification procedure, which are complicated to develop and usually rely on costly
facilities such as wind tunnels. In this paper, we present a simple and efficient physics-based dynamic modelling of indoor
airships including a pragmatic methodology for parameter identification without the need for complex or costly test facilities.
Our approach is tested with an existing blimp in a vision-based navigation task. Neuronal controllers are evolved in simulation
to map visual input into motor commands in order to steer the flying robot forward as fast as possible while avoiding collisions.
After evolution, the best individuals are successfully transferred to the physical blimp, which experimentally demonstrates
the efficiency of the proposed approach.
Jean-Christophe Zufferey and Alexis Guanella contributed equally to this work. 相似文献
54.
Antoine Mourad 《Multimedia Tools and Applications》1996,2(3):273-297
Disk striping is essential in Video-On-Demand servers to allow concurrent access for a large number of users to the same copy of a video object. On the other hand, disk striping makes the system more vulnerable to component failures. We propose a replication scheme for video content and an associated I/O scheduling algorithm that enables the system to tolerate a component failure. The scheme, called doubly-striped mirrors, compares favorably to other approaches for implementing redundancy such as RAID in terms of cost, bandwidth efficiency, buffer usage and system availability. 相似文献
55.
In the classical framework of formal languages, a refinement operation is modeled by a substitution and an abstraction by
an inverse substitution. These mechanisms have been widely studied, because they describe a change in the specification level,
from an abstract view to a more concrete one, or conversely. For timed systems, there is up to now no uniform notion of substitution.
In this paper, we study timed substitutions in the general framework of signal-event languages, where both signals and events
are taken into account. We prove that regular signal-event languages are closed under substitution and inverse substitution.
To obtain these results, we use in a crucial way a “well known” result: regular signal-event languages are closed under intersection.
In fact, while this result is indeed easy for languages defined by Alur and Dill’s timed automata, it turns out that the construction
is much more tricky when considering the most involved model of signal-event automata. We give here a construction working
on finite and infinite signal-event words and taking into account signal stuttering, unobservability of zero-duration τ-signals and Zeno runs. Note that if several constructions have been proposed in particular cases, it is the first time that
a general construction is provided. 相似文献
56.
In this paper, we define the notion of approximate bisimulation relation between two continuous systems. While exact bisimulation requires that the observations of two systems are and remain identical, approximate bisimulation allows the observations to be different provided the distance between them remains bounded by some parameter called precision. Approximate bisimulation relations are conveniently defined as level sets of a so-called bisimulation function which can be characterized using Lyapunov-like differential inequalities. For a class of constrained linear systems, we develop computationally effective characterizations of bisimulation functions that can be interpreted in terms of linear matrix inequalities and optimal values of static games. We derive a method to evaluate the precision of the approximate bisimulation relation between a constrained linear system and its projection. This method has been implemented in a Matlab toolbox: MATISSE. An example of use of the toolbox in the context of safety verification is shown. 相似文献
57.
No?l Xavier; Bechara Antoine; Dan Bernard; Hanak Catherine; Verbanck Paul 《Canadian Metallurgical Quarterly》2007,21(6):778
Individuals with alcoholism exhibit poor decision making as reflected by their continued alcohol use despite encountering problems and by low performance in laboratory tasks of decision making. Here, the authors investigated the relative contribution of several distinct processes of executive functions in performance on the Iowa Gambling Task (IGT; A. Bechara, A. R. Damasio, H. Damasio, & S. W. Anderson, 1994) in recently detoxified individuals with alcoholism. Compared to matched healthy participants, individuals with alcoholism showed below-normal scores in the last 20 trials of the IGT as well as on other tasks of executive functions, specifically those assessing the capacity to manipulate information stored in working memory, detect abstract rules, or inhibit prepotent responses. Prepotent response inhibition best predicted performance in the late trials of the IGT, that is, when participants have likely acquired knowledge about the reward/punishment contingencies of the task. These results underline the important role that response inhibition plays in decision making, especially in risky situations, when knowledge of the probability of a given outcome becomes available (i.e. decisions under risk). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
Antoine Le Mortellec Joffrey Clarhaut Yves Sallez Thierry Berger Damien Trentesaux 《Engineering Applications of Artificial Intelligence》2013,26(1):227-240
The use of electronic equipment and embedded computing technologies in modern complex transportation systems continues to grow in a highly competitive market, in which product maintainability and availability is vital. These technological advances also make fault diagnosis and maintenance interventions much more challenging, since these operations require a deep understanding of the entire system. This paper proposes a holonic cooperative fault diagnosis approach, along with a generic architecture, to increase the embedded diagnosis capabilities of complex transportation systems. This concept is applied to the fault diagnosis of door systems of a railway transportation system. 相似文献
59.
60.
As regards river restoration, it is fundamental to better link human pressures and environmental responses and to take into consideration not only target species or habitat but diverse ecological elements. This permits to assess sustainable restoration plan, especially concerning sediment augmentation below dams. The use of a hierarchical multicriteria approach on the Ain River permits us to assess a diagnosis of sediment deficit impact integrating several morphological (channel shifting, river bed degradation and river bed coarsening) and ecological components (Riparian and floodplain lake and fish communities). Our diagnosis also integrates a temporal and spatial approach better to link human pressures and environmental responses and to identify the dam effects amongst other drivers (e.g. grazing decline and channel regulation). The results confirm causality links between sediment deficit and slight channel bed degradation (0.01 m.year?1) or channel bed paving and thus highlight the impact of the dam on the drying of the riparian forest and on former channel community. However, the relationship between incision and reduction in active channel lateral mobility is more difficult to establish. The role of sediment deficit in the current variability of the riparian regeneration capacity and, thereby, landscape diversity along the lower valley remains unclear. This study also confirms the relevance of using different ecological indicators, notably because all components present different adjustment time scales, whereas some of them are more sensitive to other impacts. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献