766 research outputs found
Exact asymptotics for fluid queues fed by multiple heavy-tailed on-off flows
We consider a fluid queue fed by multiple On-Off flows with heavy-tailed
(regularly varying) On periods. Under fairly mild assumptions, we prove that
the workload distribution is asymptotically equivalent to that in a reduced
system. The reduced system consists of a ``dominant'' subset of the flows, with
the original service rate subtracted by the mean rate of the other flows. We
describe how a dominant set may be determined from a simple knapsack
formulation. The dominant set consists of a ``minimally critical'' set of
On-Off flows with regularly varying On periods. In case the dominant set
contains just a single On-Off flow, the exact asymptotics for the reduced
system follow from known results. For the case of several
On-Off flows, we exploit a powerful intuitive argument to obtain the exact
asymptotics. Combined with the reduced-load equivalence, the results for the
reduced system provide a characterization of the tail of the workload
distribution for a wide range of traffic scenarios
La plate-forme "Corpus de langues parlées en interaction" (CLAPI) : historique, états des lieux, perspectives
http://lidil.revues.org/index139.htm
De l'un et du divers. La région Rhône-Alpes et la mise en récit de ses langues
International audienceEuropean regions, whether historically well-established ones or those of recent administrative construction, aim to acquire a legitimacy by means of spreading a genuine image and discourse of their own making. In France, the region Rhône-Alpes, a recent administrative unit where two regional languages are spoken, can but follow the trend. This article sets out to assess the ways in which the regional languages have recently been fitted in the regional council's institutional discourse on identification. The linguistic questions have become part of a carefully balanced discourse evolving around the issues of unity and diversity. The article asserts that those languages are enhanced for the sake of a regional discourse and one definite view of languages that eventually neglects the complex social processes in which speakers and promoters of these languages alike are involved.La région Rhône-Alpes constitue à première vue un exemple particulièrement emblématique de la création des régions françaises sur des critères administratifs apparemment arbitraires, imposés par le pouvoir central. Pourtant, au même titre que d'autres régions à l'identité plus marquée comme la Bretagne ou l'Alsace, le conseil régional de Rhône-Alpes a cherché à forger une image distinctive de la région (certains diront une identité), à la fois à destination des citoyens qui vivent sur son sol mais aussi dans une visée de commodification de cette image à travers des activités comme le commerce ou le tourisme. Par commodification, il faut entendre la transformation d'un objet, d'une idée, d'une construction sociale en marchandise échangeable et/ou négociable dans un marché donné (voir Heller, 2003 ; Duchêne, Heller, à paraître)
Lessons Learned from Designing the Montium - a Coarse-Grained Reconfigurable Processing Tile
In this paper we describe in retrospective the main results of a four year project, called Chameleon. As part of this project we developed a coarse-grained reconfigurable core for DSP algorithms in wirelessdevices denoted MONTIUM. After presenting the main achievements within this project we present the lessons learned from this project
Comparison of noise indicators in an urban context
Inter-Noise 2016, 45th International Congress and Exposition of Noise Control Engineering, HAMBOURG, ALLEMAGNE, 21-/08/2016 - 24/08/2016Noise is a major environmental issue, which gave birth in the last decades to the development of many engineering methods dedicated to both its estimation and mitigation. The specificity of the noise pollution problem lies in the complexity of human hearing and subjective assessment, and in the high spatiotemporal variation and rich spectral content of the noise generated by a wide variety of sources in urban context. Indicators that encompass all these dimensions are required for the description of sound environments and for the evaluation of noise mitigation strategies. This paper compares usual and more specific indicators, dedicated to environmental noise analyses, by means of a literature review. The comparison is based on the three following criteria: i) the ability of indicators to describe and physically categorize the urban sound environments, ii) the relevance of indicators for describing the perceptive appreciations of urban sound environments, iii) the ability of indicators to be estimated through classical or more advanced traffic noise estimation models. A discussion compares the pro and cons of the selected indicators in an operational scop
A theoretical and experimental spectroscopy study on methanol and ethanol conversion over H-SAPO-34
The elucidation of the structure-activity relation of zeolites or zeotype materials remains very challenging. Recent advances in both theoretical and experimental techniques provide new opportunities to study these complex materials and any catalytic reaction occurring inside. In order to establish new active reaction routes, the knowledge of formed intermediates is crucial. The characterization of such intermediates can be done using a variety of spectroscopic techniques. In this contribution, methanol and ethanol conversion over H-SAPO-34 is investigated using IR and UV-VIS measurements. Calculated adsorption enthalpies of methanol and ethanol in a large SAPO 44T finite cluster show the stronger adsorption of the larger alcohol by 14 kJ mol-1. Dispersion contributions are found to be crucial. IR spectra are calculated for the clusters containing the adsorbed alcohols and matched with experimental data. In addition, the cluster is also loaded with singly methylated cationic hydrocarbons as these are representative reaction intermediates. A detailed normal mode analysis is performed, enabling to separate the framework-guest contributions. Based on the computed data in situ DRIFT experimental peaks could be assigned. Finally, contemporary DFT functionals such as CAM-B3LYP seem promising to compute gas phase UV-VIS spectra
Plant Performance in Precision Horticulture: Optimal climate control under stochastic uncertainty
This paper presents a risk mitigating, time-varying feedback control
algorithm for crop production when state dynamics are subject to uncertainty.
The model based case study concerns a 40 day production round of lettuce in a
greenhouse where control input consists of daily and nightly temperature set
points. The control problem was formulated in terms of a stochastic Markov
decision process with the objective to maximize the expected net revenue at
harvest time.
The importance of time-varying feedback and of risk mitigation was
investigated by making a comparison with a controller that takes uncertainty
into account but is static and a controller which is dynamic but ignores the
uncertainty in the state dynamics. For the case of heat limited crop growth,
and strict requirements on harvest weight precision, the dynamic stochastic
controller outperformed the static controller in terms of both maximal expected
net revenue (by 19 %) and state precision at harvest time (with 50 % less
standard deviation). It also outperformed the deterministic controller for both
criteria (15 % in maximal expected net revenue and 8 % less standard
deviation). A detailed sensitivity analysis showed that such improvements in
performance levels are robust, since they hold over large ranges of uncertainty
in state dynamics, required harvest precision levels, starting days, and
initial weights.
The results provide insights in potential of dynamic feedback and risk
mitigation strategies for high precision requirements under uncertainty.
Although the results should be interpreted with caution, they illustrate the
considerable potential benefit for stochastic greenhouse climate control under
uncertainty when high precision is required
Sojourn time asymptotics in processor sharing queues
This paper addresses the sojourn time asymptotics for a GI/GI/• queue operating under the
Processor Sharing (PS) discipline with stochastically varying service rate. Our focus is on the
logarithmic estimates of the tail of sojourn-time distribution, under the assumption that the jobsize
distribution has a light tail. Whereas upper bounds on the decay rate can be derived under
fairly general conditions, the establishment of the corresponding lower bounds requires that the
service process satisfies a samplepath large-deviation principle. We show that the class of
allowed service processes includes the case where the service rate is modulated by a Markov
process. Finally, we extend our results to a similar system operation under the Discriminatory
Processor Sharing (DPS) discipline. Our analysis relies predominantly on large-deviations
techniques
Best practices for crop area estimation with Remote Sensing
This document gives recommendations on different ways to use Earth Observation as a tool for crop area estimation highlighting strengths and limitations. The document was discussed in a workshop hosted by the Joint Research Centre (JRC) of the European Commission in June 2008 and attended by 40 remote sensing practitioners and users.JRC.DG.G.3-Monitoring agricultural resource
IMPACT OF A HIGH LINEAR WEIGHT POLYMER CO-CONDITIONING WITH POLYALUMINIUM CHLORIDE ON DEWATERING AND CONVECTIVE DRYING OF URBAN RESIDUAL SLUDGE
This paper investigated the influence of Polyaluminium chloride (PAX) co-conditioning with a high linear weight polymer on the dewatering performance and the drying behavior of sludge. The CT linear polymer with a high molecular weight was used combined with PAX for sludge flocculation prior to mechanical dewatering and drying.
It was found that sludge conditioned with the couple PAX/ CT led to better flocculation/dewatering process regarding size flocs and specific resistance to filtration.
Concerning drying, it appeared that this chemicals combination led to improved drying rates with effect of a reduction of the drying time, when compared to polyelectrolyte used without PAX adding
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