A performance study of plane wave finite element methods with a Padé-type artificial boundary condition in acoustic scattering

This paper proposes an original numerical method and studies its performance for solving high-frequency scattering problems involving elongated scatterers. The approach is based on coupling a high-order Padé-type non-reflecting boundary condition with plane wave finite element formulations. It is shown that for some numerical examples the approximate solution of suitable accuracy can be obtained using a small number of degrees of freedom.     

Utilisation of attenuated total reflectance MIR and front-face fluorescence spectroscopies for the identification of Saint-Nectaire cheeses varying by manufacturing conditions

Twelve samples of cheeses (three types of Saint-Nectaire PDO cheeses and Savaron cheeses) differing by manufacturing and ripening conditions, from 12 different producers, were characterised by attenuated total reflectance mid-infrared (MIR) and front-face fluorescence spectroscopies, dynamic testing rheology and physico-chemical analysis. Fluorescence spectra (tryptophan residues, vitamin A and riboflavin) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region) and 1,500–900 cm⁻¹ (fingerprint region)) spectra were recorded on cheese samples. The potential of the data tables was investigated for discriminating the four different groups of cheeses. The results of factorial discriminant analysis (FDA) performed on the fluorescence and mid-infrared spectra showed a good discrimination of the four cheese groups. Considering cross-validation results, the best classifications (100%) were achieved from mid-infrared and fluorescence spectra, while only 91.7 and 72.2% of correct classification were obtained by applying FDA to rheology and physico-chemical data, respectively. Spectroscopic techniques could provide useful fingerprints and allow the identification of investigated cheeses according to manufacturing conditions. Simple and rapid spectroscopic methods offer a promising approach to the authentication of cheeses.     

Fifth International Deer Biology Congress

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Fifth International Deer Biology Congress     

Effects of aerosol scattering phase function formulation on point-spread-function calculations

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.     

Flying over the reality gap: From simulated to real indoor airships

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.     

Prediction of the rheology parameters of ripened semi-hard cheeses using fluorescence spectra in the UV and visible ranges recorded at a young stage

Storage modulus (G′), loss modulus (G″), strain, tan (δ) and complex viscosity (η*) of 20 semi-hard cheeses were measured by dynamic oscillatory analysis after 2, 30 and 60 days of ripening. On the same cheeses and at the same ages, tryptophan and riboflavin fluorescence spectra were recorded. The aim was to predict the rheology parameters of ripened cheeses from spectra recorded on these cheeses at a young stage. Using partial least square, tryptophan fluorescence spectra recorded at 20 °C on 2-days-old cheeses predicted G′, G″, strain, tan (δ) and η* measured at 80 °C on the 60-days-old cheeses with correlation coefficients (R) of 0.98, 0.97, 0.98, 0.98 and 0.97, respectively. Riboflavin fluorescence spectra gave slightly lower correlation coefficients of 0.88, 0.88, 0.92, 0.87 and 0.88, respectively. Dependent only on visible light, the riboflavin fluorescence spectra potentially provide viable and economic prediction of the rheology of ripe cheese.     

Doubly-striped disk mirroring: Reliable storage for video servers

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.     

Timed substitutions for regular signal-event languages

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.     

Approximate bisimulation relations for constrained linear systems

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.     

Response inhibition deficit is involved in poor decision making under risk in nonamnesic individuals with alcoholism.

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)