A MAS-Based Cloud Service Brokering System to Respond Security Needs of Cloud Customers

Cloud computing is becoming a key factor in computer science and an important technology for many organizations to deliver different types of services. The companies which provide services to customers are called as cloud service providers. The cloud users (CUs) increase and require secure, reliable and trustworthy cloud service providers (CSPs) from the market. So, it’s a challenge for a new customer to choose the highly secure provider. This paper presents a cloud service brokering system in order to analyze and rank the secured cloud service provider among the available providers list. This model uses an autonomous and flexible agent in multi-agent system (MASs) that have an intelligent behavior and suitable tools for helping the brokering system to assess the security risks for the group of cloud providers which make decision of the more secured provider and justify the business needs of users in terms of security and reliability

MEMS calorimetric transducers for flow separation detection and control

International audienceRobust micro machined high temperature gradient calorimetric (HTGC) transducers were developed for flow separation control. Based on thermal principle, the transducers measure the mean and fluctuating bidirectional shear stress that is particularly useful for flow separation detection. More than a hundred micro-sensors were simultaneously micro-machined using MEMS technology. A flexible array of calorimetric micro-sensors was implemented with miniaturized electronics on a flap model also equipped with pulsed jet actuators. Flow control experiments were successfully conducted as the natural separation occurring on the model was detected the HTGC micro sensors and controlled by pulsed jet actuation

Magnetic particle embedded in a piezoelectric matrix: analysis and applications

We take into consideration a nonlinear magnetostrictive particle embedded in a piezoelectric matrix in order to obtain (stress mediated) magneto-electric effects with applications to memory cells. The micromechanical analysis is conducted through the magneto-electro-elastic Eshelby tensor in an anisotropic environment. The results show the equilibrium orientations of magnetization versus the applied fields and the boundary conditions. In particular, a bi-stable behaviour (controlled by the applied electric field) can be obtained and it could be useful for applications to memory cells design

Intrinsic versus shape anisotropy in micro-structured magnetostrictive thin films for magnetic surface acoustic wave sensors

International audienceThis work aims at studying the interaction between surface acoustic waves (SAW) and micro-structured magnetostrictive layers under a magnetic field with a perspective to develop magnetic field sensors. The impact of the competition between the strong intrinsic magnetic anisotropy of the magnetic material and the shape anisotropy of the interdigitated transducer (IDT) fingers introduced by the micro-structuration is investigated. Therefore, the macroscopic and microscopic magnetic properties of the IDT and their influence on the magneto-acoustic response are studied. A SAW resonator with the IDTs made of the magnetostrictive thin film was elaborated and the magnetic surface acoustic wave (MSAW) response under a magnetic field was performed and discussed. Depending on the energy balance, the anisotropy gets modified and a correlation with the MSAW sensitivity to an externally applied magnetic field is made

Original MEMS wall shear stress sensors developed for separation detection and active flow control on a flap model

Active flow control systems are developed to promote air safety, reduce energetic consumption or increase airplanes efficiency. Sensors are needed to measure flow parameters at high frequencies with a high spatial resolution and micro-electro-mechanical system (MEMS) sensors are potential candidates for precise and located measurements. We present an original MEMS thermal flow sensor designed for flow control and separation detection. The general aim of the work is to run active flow control experiments integrating several MEMS sensors into a motorized deflectable flap model where the actuation is provided by pulsed jets, following previous work performed by Chabert et al. [1].   The micro-sensor is sensitive to the wall shear stress and flow direction [2]. It can be flush mounted to the wall for separation detection and flow control applications. The micro-fabrication process is CMOS-compatible meaning that it allows on-chip integration for designing very small devices. The micro-sensor structure combines suspended wires, free from the substrate, and micro-bridges used as mechanical supports. Designed to be set perpendicularly to the flow, the sensor presents three parallel heated wires. The central wire is structured with multiple layers with a heater, made of gold, and a sensing wire, placed under the heater and made of Ni/Pt multilayer. This central sensing wire is designed to measure the wall shear stress. The other two sensing wires, placed on both side of the central wire, allow flow direction sensing when considering the temperature variation between them as the wire upstream is more cooled than the wire downstream. The micro-wires dimensions, 3 µm width for 1 mm length, and the fact that they are suspended over a 20-µm-deep cavity, allow a high gradient of temperature for low power consumption (8 °C/mW for the central wire and 5 °C/mW for the lateral wires). The micro-sensor was characterized in a turbulent boundary layer wind tunnel by measuring the resistance variations, simultaneously with the wall shear stress fluctuations, measured by near wall hot-wire anemometry. The sensor demonstrates a resistance variation up to 0.3 % for 2.4 Pa for the central wire. The flow direction measurements were performed using the resistance difference between the two lateral wires. The purpose is to provide a way to detect the presence of a flow separation since in such a situation, the velocity field near the wall is reversed. The sensor setup in the wind tunnel enables to rotate it from 0° to 180°, considering that, at 90°, the wires are parallel to the flow. The results demonstrate the sensor ability to detect the flow direction: the resistance difference is +0.25 ? for 0°, 0 for 90° and -0.25 ? for 180°, all for a wall shear stress of 1 Pa. A second set of experiments were performed by adding an obstacle on the wind tunnel wall, upstream of the MEMS sensor, to cause flow separation at the sensor location. The central wire of the sensor, designed for wall shear stress measurements, present an expected behavior: the sensor detects the decrease of wall shear stress in a separated flow. And the lateral wires detect the flow direction inversion, providing an additional information compared to conventional hot-film sensors.  The results demonstrate the sensor ability to measure the wall shear stress and to detect flow separation. Currently, the sensors integration in the flap model is in progress and open-loop active flow control experiments will begin at ONERA Lille. The first results will be presented in the full paper. References: [1] T. Chabert, Thèse, Université Pierre et Marie Curie - Paris VI, 2014. [2] C. Ghouila-Houri et al., Appl. Phys. Lett., vol. 109, no. 24, p. 241905, Dec. 2016

Sensibilité des dispositifs à ondes élastiques de surface réalisés sur des structures monocouches de quartz et structure bicouche de ZnO/Si aux déformations mécaniques (application au capteur de pression)

Dans ce mémoire nous avons présenté une étude théorique et expérimentale de dispositifs à ondes élastiques de surface (OES) appliqués à la réalisation de capteurs de pression sur substrat en quartz et de manière plus originale sur structure bicouche ZnO/Si. Dans la partie expérimentale nous avons mis en œuvre un banc de mesure permettant la caractérisation sous pression. Nous avons développé et optimisé les procédés technologiques nécessaire pour la réalisation des dispositifs OES à l'aide des outils de simulation des procédées microélectronique SILVACO. Nous avons aussi optimisé la croissance de couches minces piézoélectriques de ZnO par le procédés de pulvérisation magnétron. Concernant la modélisation nous avons développé un ensemble de codes dans l'environnement MATLAB pour modéliser la propagation des OES en régime linéaire et non linéaire. Nous avons validé ce travail de modélisation dans le cas du quartz et nous l'avons extrapolé ensuite à l'étude de la structure ZnO/Si.The aim of this thesis is the devellopment of a pressure sensor using surface acoustic wave device. A theoretical and exprimental study of the sensor perfomed on quartz substrate and ZnO/Si structure are presented. Concerning the experimental study we have developped an experimental set-up wich permit testing under pressure. We have developed and optimized the SAW process manufacturing using SILVACO (soft for process simulation). We have also optimized the ZnO piezoelectric film deposition by using a DC planar magnetron sputtering system. Concerning the theoretical study we have developed a set of computer code in MATLAB environnement. For linear surface acoustic wave propagation a Jones and campbel method is used. For nonlinear surface acoustic wave propagation a Tierstein perturbation procedure was used. Both devices performed on quartz and ZnO/Si structure were investigated.NANCY1-SCD Sciences & Techniques (545782101) / SudocSudocFranceF