From centralized to decentralized approach for optimal Controller of Discrete Manufacturing Systems

International audienceThis paper deals with a comparison of centralized and decentralized approaches to obtain an optimal controller for discrete manufacturing systems. It is based on a modular modeling of the plant to avoid combinatory explosion found in centralized structure and a synthesis algorithm. From the local Plant Elements, local constraints are defined to build local supervisors. Local constraints restrict the system behavior within a desired specification. Global constraints are added to establish high level supervisors. The resulting automata are translated in a normalized language for implementation in a Programmable Logic Controller

Two Cases of Study for Control Reconfiguration of Discrete Event Systems (DES)

International audienceIn this paper, we propose two cases of study for control reconfiguration of Discrete Event Systems. The main contributions are based on a safe centralized and distributed control synthesis founded on timed properties. In fact, if a sensor fault is detected, the controller of the normal behavior is reconfigured to a timed controller where the timed information replaces the information lost on the faulty sensor. Finally, we apply our contribution to a manufacturing system to illustrate our results and compare between the two frameworks

Numerical Study of Heat Transfer and Flow of Nanofluid Using Multi-Phase Mixture Model through Elliptical Tubes

دراسة عددية لنقل الحرارة وتدفق السوائل باستخدام تدفق مضطرب كامل التطور داخل أنبوب بيضاوي الشكل مع اختلاف نسبة المقطع العرضي لأنابيب وبثبات في مساحة سطح للأنبوب، وذلك باستخدام (AL2O3-ماء) مائع نانوي مع متوسط ​​حجم الجسيمات النانوية (20 نانومتر). وقد تم استخدام نموذج خليط متعدد المراحل لحساب عدد نسلت، سرعة المائع النانوي، والفارق في الضغط. حيث تم حل المعادلات للأشكال الهندسية ثلاثية الأبعاد (Navier-Stokes)، والطاقة، والنسبة الحجمية باستخدام برنامج (ANSYS fluent) مع طريقة حجم محدود (FVM). النتائج المحسوبة العددية تظهر قبولية معقولة بحدود خطأ مقداره تقريباً (10.34%) مقارنةً مع النتائج العملية السابقة. وقد استنتج من النتائج العددية أن زيادة في تركيز الدقائق النانوية سيزيد من عدد نسلت وله تأثير ضئيل على الزيادة في انخفاض الضغط. أنبوب بيضوي الشكل مع نسبة الأبعاد 0.25 هو الأفضل لاستخدام في العمليات التي يتم من خلالها تبديد الحرارة أو الحصول عليها من السوائل إلى المحيط. ولكنه يكون أقل فعالية في عملية نقل الموائع لمسافات بسبب كبر فرق الضغط عبر دخول وخروج المائع بالمقارنة مع أنابيب ذات مقاطع دائرية ضمن مدى معين من معدل التدفق.This paper presents a numerical study of heat transfer of a fully developed turbulent flow inside elliptical tube with different aspect ratio of constant surface area, by using (AL2O3-water) nanofluid with average nanoparticles diameter (20 nm). Multi-phase mixture model has been used to calculate the Nusselt number, nanofluid velocity, and pressure drop. “The three-dimensional Navier-Stokes”, energy, and volume fraction equations are solved by ANSYS fluent with “finite volume method (FVM)”. The numerical results show reasonable acceptance with error bounds approximately to (10.34%) upon pervious experimental works. It is found that the increase in nanoparticles “volume concentration (φ)” will increase the Nusselt number with little “pressure drop” rise. The elliptical tube with 0.25 aspect ratio gives best enhancement in heat transfer compared with circular tube with maximum Nusselt number (52.9%) and nanofluid volume concentration of 1.5%, but it is less effective in the process of transporting fluids to distance due to the high pressure drops between entry and exit of fluid compared to tube with circular sections within a certain range of Reynolds number (3000-9240)

CONTRIBUTION A LA COMMANDE DES SYSTEMES A EVENEMENTS DISCRETS TEMPORISES (SEDTS)

International audienceRESUME: Ce papier présente une approche de synthèse de commande sûre de fonctionnement des Systèmes à Evéne-ments Discrets Temporisés (SEDTs), à base de propriétés temporelles. Pour établir cette synthèse, la démarche propo-sée s'appuie sur la modularité des systèmes manufacturiers retrouvée dans les travaux (Qamsane et al., 2014a,b). Un exemple de système automatisé de production vient illustrer nos propos. MOTS-CLES: Systèmes à événements discrets temporisés, théorie de la supervision, commande distribuée, systèmes manufacturiers, modélisation

Obscured and unobscured AGN populations in a hard-X-ray selected sample of the XMDS survey

Our goal is to probe the populations of obscured and unobscured AGN investigating their optical-IR and X-ray properties as a function of X-ray flux, luminosity and redshift within a hard X-ray selected sample of 136 X-ray sources in the XMM Medium Deep Survey (XMDS) with wide multiwavelength coverage. The XMDS area is covered with optical photometry from the VVDS and CFHTLS surveys and infrared Spitzer data. Based on the X-ray luminosity and X-ray to optical ratio, 132 sources are likely AGN, of which 122 have unambiguous optical - IR identification. The observed optical and IR spectral energy distributions of sources are fitted with AGN/galaxy templates in order to classify them and compute photometric redshifts. 70% of the AGN are fitted by a type 2 AGN or a star forming galaxy template and are grouped together in a single class of ``optically obscured'' AGN. They have ``red'' optical colors and generally show significant X-ray absorption from X-ray spectra or hardness ratios (N$_H > 10^{22}$ cm$^{-2}$). Sources with SEDs typical of type 1 AGN have ``blue'' optical colors and exhibit X-ray absorption in about 30% of cases. We performed a stacking analysis for obscured and type 1 AGN. The stacked X-ray spectrum of obscured AGN is flatter than that of type 1 AGN and has an average spectral slope of Gamma = 1.6. The subsample of objects fitted by a galaxy template has an even harder stacked spectrum, with Gamma = 1.2 - 1.3. The obscured fraction is larger at lower fluxes, lower redshifts and lower luminosities. X-ray absorption is less common than ``optical'' obscuration and its incidence is nearly constant with redshift and luminosity. This implies that X-ray absorption is not necessarily related to optical obscuration.Comment: 33 pages, 21 figures, accepted for publication in A&

A stochastic sizing approach for sharing-based energy storage applications

In order to foster renewable energy integration, improve power quality and reliability, and reduce hydrocarbon emissions, there is a strong need to deploy energy storage systems (ESSs), which can provide a control medium for peak hour utility operations. ESSs are especially desirable at the residential level, as this sector has the most untapped demand response potential. However, considering their high acquisition, operation, and maintenance costs, isolated deployment of ESSs is not economically viable. Hence, this paper proposes a sharing-based ESS architecture, in which the demand of each customer is modeled stochastically and the aggregate demand is accommodated by a combination of power drawn from the grid and the storage unit when the demand exceeds grid capacity. The optimal size of ESSs is analyzed and an analytical method is developed for a group of customers with a single type of appliances. This framework is also extended to any network size with an arbitrary number of customers and appliance types, where the analytical method provides a tractable solution to the ESS sizing problem. Finally, a detailed cost-benefit analysis is provided, where the results indicate that sharing-based ESSs are practical and yield significant savings in terms of ESS size

The logN-logS relationship of normal X-ray emitting galaxies

Abstract. We have selected a flux limited serendipitous sample of galaxies from the crosscorrelation of the BMW (Brera Multiscale Wavelet) ROSAT HRI and the LEDA (LyonMeudon Extragalactic Database) Catalogues. This sample is used to study the X-ray properties of normal galaxies in the local universe. We also find that the logN-logS distribution we derived for a serendipitous subsample, optically and X-ray flux limited, is consistent with the euclidean slope in the flux range F X(0.5−2) ∼ 1.1 − 110 × 10 −14 erg cm −2 s −1 . We further show that the same law is valid over 4 decades, from the bright sample derived from the RASS data to the very faint detections in deep XMM -Newton fields

A sample of X-ray emitting normal galaxies from the BMW -- HRI Catalogue

We have obtained a sample of 143 normal galaxies with X-ray luminosity in the range $10^{38} - 10^{43}$ erg s$^{-1}$ from the cross-correlation of the ROSAT HRI Brera Multi-scale Wavelet (BMW -- HRI) Catalogue with the Lyon-Meudon Extragalactic Database (LEDA). We find that the average X-ray properties of this sample are in good agreement with those of other samples of galaxies in the literature. We have selected a complete flux limited serendipitous sample of 32 galaxies from which we have derived the logN-logS distribution of normal galaxies in the flux range $1.1 - 110 \times 10^{-14}$ erg cm$^{-2}$ s$^{-1}$. The resulting distribution is consistent with the euclidean -1.5 slope. Comparisons with other samples, such as the Extended Medium Sensitivity Survey, the ROSAT All Sky Survey, the XMM - Newton/2dF survey and the Chandra Deep Field Survey indicate that the logN-logS distribution of normal galaxies is consistent with an euclidean slope over a flux range of about 6 decades.Comment: Accepted for publication in A&A. 19 pages, 7 figures. Full resolution version of Figure 2 is available at http://www.brera.mi.astro.it/~tajer