Heated granular fluids: the random restitution coefficient approach

We introduce the model of inelastic hard spheres with random restitution coefficient $\alpha$, in order to account for the fact that, in a vertically shaken granular system interacting elastically with the vibrating boundary, the energy injected vertically is transferred to the horizontal degrees of freedom through collisions only, which leads to heating through collisions, i.e. to inelastic horizontal collisions with an effective restitution coefficient that can be larger than 1. This allows the system to reach a non-equilibrium steady state, where we focus in particular on the single particle velocity distribution $f(v)$ in the horizontal plane, and on its deviation from a Maxwellian. Molecular Dynamics simulations and Direct Simulation Monte Carlo (DSMC) show that, depending on the distribution of $\alpha$, different shapes of $f(v)$ can be obtained, with very different high energy tails. Moreover, the fourth cumulant of the velocity distribution quantifying the deviations from Gaussian statistics is obtained analytically from the Boltzmann equation and successfully tested against the simulations.Comment: 14 pages, 9 eps figure

Modal characterization of the ASCIE segmented optics testbed: New algorithms and experimental results

New frequency response measurement procedures, on-line modal tuning techniques, and off-line modal identification algorithms are developed and applied to the modal identification of the Advanced Structures/Controls Integrated Experiment (ASCIE), a generic segmented optics telescope test-bed representative of future complex space structures. The frequency response measurement procedure uses all the actuators simultaneously to excite the structure and all the sensors to measure the structural response so that all the transfer functions are measured simultaneously. Structural responses to sinusoidal excitations are measured and analyzed to calculate spectral responses. The spectral responses in turn are analyzed as the spectral data become available and, which is new, the results are used to maintain high quality measurements. Data acquisition, processing, and checking procedures are fully automated. As the acquisition of the frequency response progresses, an on-line algorithm keeps track of the actuator force distribution that maximizes the structural response to automatically tune to a structural mode when approaching a resonant frequency. This tuning is insensitive to delays, ill-conditioning, and nonproportional damping. Experimental results show that is useful for modal surveys even in high modal density regions. For thorough modeling, a constructive procedure is proposed to identify the dynamics of a complex system from its frequency response with the minimization of a least-squares cost function as a desirable objective. This procedure relies on off-line modal separation algorithms to extract modal information and on least-squares parameter subset optimization to combine the modal results and globally fit the modal parameters to the measured data. The modal separation algorithms resolved modal density of 5 modes/Hz in the ASCIE experiment. They promise to be useful in many challenging applications

Cooperative Resource Management in a IaaS

International audienceVirtualized IaaS generally rely on a server consolidation system to pack virtual machines (VMs) on as few servers as possible, for energy saving. However, two situations are not taken into account, and could enhance consolidation. First, since the managed VMs can be of various sizes (small, medium, large, etc.), VMs packing can be obstructed when sizes don't fit available spaces on servers. Therefore, we would need to "split" such VMs. Second, two VMs which host replicas of the same application server (for scalability) could be "fusion Ned" when they are located on the same physical server, in order to reduce virtualization overhead and VMs memory footprint. Split and fusion operations lead to the management of elastic VMs and requires cooperation between the application level and the provider level, as they impact management at both levels. In this paper, we propose a IaaS resource management system which implements elastic VMs based on split/fusion operations and cooperative management. We show its benefit with a set of experiments

Poverty, inequalities and social exclusion: what do we know and what can we do?

This report summarizes the main lessons from recent research on poverty and social exclusion from Quebec, Canada and abroad and examines the role of public policies in reducing poverty, inequalities and social exclusion

Energy-QoS Tradeoffs in J2EE Hosting Centers

International audienceNowadays, hosting centres are widely used to host various kinds of applications e.g., web servers or scientific applications. Resource management is a major challenge for most organisations that run these infrastructures. Many studies show that clusters are not used at their full capacity which represents a significant source of waste. Autonomic management systems have been introduced in order to dynamically adapt software infrastructures according to runtime conditions. They provide support to deploy, configure, monitor, and repair applications in such environments. In this paper, we report our experiments in using an autonomic management system to provide resource aware management for a clustered application. We consider a standard replicated server infrastructure in which we dynamically adapt the degree of replication in order to ensure a given QoS while minimising energy consumption

An Adaptable Framework to Deploy Complex Applications onto Multi-cloud Platforms

International audienceCloud computing is nowadays a popular technology for hosting IT services. However, deploying and reconfiguring complex applications involving multiple software components, which are distributed on many virtual machines running on single or multi-cloud platforms, is error-prone and time-consuming for human administrators. Existing deployment frameworks are most of the time either dedicated to a unique type of application (e.g. JEE applications) or address a single cloud platform (e.g. Amazon EC2). This paper presents a novel distributed application management framework for multi-cloud platforms. It provides a Domain Specific Language (DSL) which allows to describe applications and their execution environments (cloud platforms) in a hierarchical way in order to provide a fine-grained management. This framework implements an asynchronous and parallel deployment protocol which accelerates and make resilient the deployment process. A prototype has been developed to serve conducting intensive experiments with different type of applications (e.g. OSGi application and ubiquitous big data analytics for IoT) over disparate cloud models (e.g. private, hybrid, and multi-cloud), which validate the genericity of the framework. These experiments also demonstrate its efficiency comparing to existing frameworks such as Cloudify

Roboconf: a Hybrid Cloud Orchestrator to Deploy Complex Applications

International audienceThis paper presents Roboconf, an open-source distributed application orchestration framework for multi-cloud platforms, designed to solve challenges of current Autonomic Computing Systems in the era of Cloud computing. It provides a Domain Specific Language (DSL) which allows to describe applications and their execution environments (cloud platforms) in a hierarchical way in order to provide a fine-grained management. Roboconf implements an asynchronous and parallel deployment protocol which accelerates and makes resilient the deployment process. Intensive experiments with different type of applications over different cloud models (e.g. private, hybrid, and multi-cloud) validate the genericity of Roboconf. These experiments also demonstrate its efficiency comparing to existing frameworks such as RightScale, Scalr, and Cloudify

In-Hospital Evolution of Non Operated Aneurysmal Subarachnoid Hemorrhage at the Neurology Unit of Befelatanana University Teaching Hospital, Antananarivo

Subarachnoid hemorrhage is defined as a sudden irruption of blood in subarachnoid spaces. This study aims to determine the profile and in-hospital evolution of patients with post aneurysmal subarachnoid hemorrhage, who did not have surgical treatment in the Neurology Unit of Befelatanana University Hospital, Antananarivo, Madagascar. This study was a descriptive retrospective study within a period of 4 years, from January 1st, 2014 to December 31th, 2017. The study was carried out in hospitalized patients for subarachnoid hemorrhage with aneurysmal origin. We included 52 patients, with an average age of 48 years and a female predominance. They are housewives in majority of cases. 52% of the cases live in urban areas while 77% of cases have high blood pressure. The main clinical manifestation was a sudden headache, and intracranial aneurysm was located at the anterior communicating artery in 52% of cases. All patients benefited from drug treatments in majority of cases. Due to the lack of financial means, 60% had neurological complications. However, in-hospital mortality rate was at 13%. This study helps us to suggest to our patients medical treatment of their subarachnoid hemorrhage during hospitalization because of difficult access to surgery. It also aims to propose surgery outside the acute phase of the disease

AGRO-MORPHOLOGICAL CHARACTERIZATION OF TWO RICE VARIETIES FROM JAPAN; ORYSA SATIVA L. AND FOUR NERICAS VARIETIES IN AN AGRO-ECOLOGICAL ZONE OF THE TOWN OF YAOUNDE (CAMEROON); COMPARATIVE STUDY OF THEIR PERFORMANCES

International audienceThe performances of two rice species of the genus Oryza were evaluated by considering parameters such as the number of panicle per rice plant, the number of primary branches of the panicles, panicle length, the plant height, the number of grains and empty balls per panicle. It appears that O. sativa from Japan has a number of empty balls less than NERICA’s varieties from Africa. We also noted that O. sativa has the highest number of panicles per rice plant (a mean of 14.05 ± 6.14). However, the number of grains per panicle NERICA’s varieties was very high (a mean of 164 ± 38.82) and therefore they shows more attractive characters than Orysa sativa lines. The differences were statistically significant above all the parameters considered in both African and Japan rice studied. A significant correlation that was negative has been observed between the number of panicles per rice plant and the number of primary branches per panicle within the NERICA 9 variety (P <0.05). The correlation was highly significant and positive (P <0.001) between the number of primary branches per panicle and the number of grain per panicle. These results suggest another demonstration of the hybrid vigor of NERICA varieties