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Le thuya de Berbérie « Tetraclinis articulata Vahl », espèce résineuse endémique d’Afrique du Nord se trouve généralement sous forme de taillis. La valorisation de la biomasse de thuya, et en particulier de son bois peut être envisagée par la filière papetière par le biais d’une cuisson soude en présence d’anthraquinone (AQ). Le bois jeune de thuya (20 ans) se délignifie bien à l’aide d’une cuisson soude-anthraquinone dans les conditions habituellement appliquées aux résineux avec un temps total de cuisson de 145 min et une température de palier de 165 ◦C. Le rendement brut obtenu est égal à 43,3 % avec un indice Kappa de 33,6. Dans les mêmes conditions de cuisson, le bois âgé (60 ans) peut être lessivé mais se délignifie moins facilement., The coniferous trees of the thuya de Berbérie (Tetraclinis articulata Vahl), from the North Africa (Algeria) is commonly grown as a coppice stand. The biomass of thuya, and especially its wood, can be transformed in pulp by the paper and pulp industry throughout the soda cooking process with the help of the anthraquinone (AQ). The young wood (20 years-old) is well delignified in the soda–anthraquinone process, in the usual conditions applied to the resinous species, in the cooking time schedule of 145 min with the level of 165 ◦C of temperature. The pulp yield of raw material obtained is 43.3% (oven dried wood), with a kappa number of: 33.6. In the same cooking conditions, the mature wood (60 years-old) can be also treated, but with some lower delignification level.

The constantly increasing market request of high quality vehicles ask the automotive manufacturers to perform lifetime testing in order to verify the reliability levels of new products. In this paper, we deal with two difficulties in reliability assessment for mechanical parts. On one hand, there is the small number of parts available for testing. On the other hand, there is the problem of wear. In the automotive applications, mechanical components subjected to relative motion of parts have to be designed against wear. In this paper, the Bayesian estimation of Wiener process parameters (usually used to define the degradation process) is studied to improve the estimation accuracy in incorporating the available knowledge on the product. In particular, the finite element results and expert knowledge are considered as “a priori”. For wear prediction by FEM, a model based on Archard law was developed for the brake disc wear.

This paper introduces a new modeling method suitable for the simulation of shell fracture under impact. This method relies on an entirely meshless approach based on the smoothed particle hydrodynamics (SPH) method. The paper also presents the SPH shell formulation being used as well as the different test cases used for its validation. A plasticity model of the global type throughout the thickness is also proposed and validated. Finally, in order to illustrate the capabilities of the method, fracture simulations using a simplified fracture criterion are presented.

International audience; Noncooperative underwater acoustic (UWA) communication systems are prone to interfere with each other since the limited resource offered by the channel is not regulated by any standard. Mutual inteferences can significantly degrade the performances of such systems and it is necessary to find policies allowing UWA devices to access the same physical resource. In this paper, we consider noncooperative UWA OFDM systems competing to access the same portion of the spectrum. We show that an efficient decentralized power allocation strategy can be achieved when all the communication links apply a waterfilling policy only based on little knowledge about their environment. Numerical simulations performed with real UWA channels sounded at-sea demonstrate the relevance of our approach.

Aircraft performances at landing or takeoff depend strongly on runway surface conditions. There is a need to provide aircraft pilots with reliable information in view of determining landing performance. Currently, these information are based on a description of the type and the depth of contaminants on the runway surface. This paper presents a new method to improve the correlation between friction coefficients and braking coefficients measured respectively by ground vehicles and aircrafts. A three steps approach is proposed, using a friction model developed by ESDU, to weight the measured coefficients by factors taking into account the characteristics of the devices and of the contaminants. The friction ESDU model is used on contaminated surfaces. The methodology is applied to data collected from extensive friction tests conducted between 1996 and 2003 (Joint Winter Runaway Friction Measurement Program). Characteristics of ground friction measuring devices and aircrafts are provided as inputs for ESDU model. It was found that the correlation between weighted ground friction and braking coefficients is improved significantly compared with the correlation between unweighted coefficients. Advantages of the newly proposed method are discussed in terms of using ground friction coefficients as a promising alternative to determine Runway condition code for aircraft pilots.

In this paper, a study of an autonomous hybrid PV-Wind-battery system for a residential house of 4 persons in La Rochelle in France is presented. It includes system design optimization and performance evaluation in addition of its economic and environmental life cycle analysis. The results show a low environmental impact and a reasonable economic cost of the system.

A multi scale methodology is proposed for the study of the cellular material behavior under dynamic loading. The behavior of polymeric foams studied depends on the constitutive material and the morphology of the porous structure. The cellular material of this study is constituted of millimetric porous beads, these beads are themselves constituted of microscopic closed cells. The methodology proposed to model the multi scale morphology of the structure (the scales of beads and cells) of the cellular material; it consists in implementing simple mechanical models at the different scales to reproduce the complex physical phenomenon observed and to model the macroscopic response of the foam. The observation and the analysis of physical phenomenon is the first step of the multi scale modeling. This paper describes the experimental and numerical methods used to observe and describe the structure of the cellular material, and quantify deformations and damages of these structures at the scales of beads and cells. Two ways of modeling were investigated: a finite-element model to represent the bead structure and another approach, more original, by the use of a modified discrete element model to model the microscopic structure of the cells.

International audience; Due to operational constraints for underwater data acquisition, simulating realistic sonar data, like images, swath bathymetry profiles or interferometric signals, is crucial for tuning detection and classification algorithms according to sensors settings, sea-bottom nature and topography. Moreover, the robustness of any performance estimation or prediction can be greatly enhanced, as soon as such a simulation tool provides a modular and flexible underwater world representation (multiple sensors, environments and acquisition conditions). For signal and array processing, it is essential not only to generate the signal energy backscattered by a resolution cell, but also to produce a phase information that conveys its theoretical statistical properties. To this end, this paper proposes a Brownian motion-based approach to generate complex Gaussian signals from the contribution of a set of extended single scatterers inside a resolution cell. The resulting process preserves the conservation of energy when integrating on surfaces, as well as the decorrelation between different areas of the sea bottom, and the right interference between two sensors for interferometric applications.

This paper describes the design and the placement of piezoelectric actuators on switched reluctance motors by means of a genetic algorithm (nondominated sorting genetic algorithm II) for the purpose of reducing stator vibrations. Two distinct approaches are presented: one energy-related and the other based on a minimization of the resultant displacement. These methods lead to design and placement strategy for the piezoelectric actuators. A number of optimal actuators obtained using these kinds of approaches is also compared with mechanical finite-element simulations. At last, a solution is achieved in order to validate optimal placement using positive position feedback active filtering.

The excavation of an unexplored secondary agglomeration in Chevroches (France), from 2001 to 2002 has led to the discovery of a bronze dome of a type unknown in the Ancient world. It is inscribed with three lines in Greek transcribing Egyptian and Roman months, and the twelve signs of the Zodiac. This paper presents the first observations and some other finds from similar objects in Burgundy.

Fretting corrosion damages are commonly observed when two metallic bodies, which are in contact with each other, are subjected to oscillatory motions of low amplitude. Such kind of degradation mode is often responsible for limited durability of aeronautical joints. In the present paper, a multifunctional duplex coating based on Si–C–N and diamond-like carbon (DLC) materials, combining corrosion resistance and good tribological properties is described. Amorphous hydrogenated SiC, SiCN, SiC/DLC and SiCN/DLC were deposited on steel substrates by a plasma assisted chemical vapour deposition (PACVD) technique, using tetramethylsilane (TMS), ammonia (NH 3 ) or acetylene (C 2 H 2 ) as gas precursors. Nitrogen incorporation has shown to improve the corrosion protection ability of SiC coatings. The corrosion behaviour and the tribological performance in aqueous media of SiCN/DLC coating have therefore been investigated. A test rig has been designed to validate the fretting resistance of this duplex coating for aeronautic applications. It was found that the combination of a SiCN-based PACVD sublayer with a DLC topcoat could provide an enhanced solution to withstand both fretting and corrosion.

International audience; The main goal of Fault Tolerant Control Systems (FTCS) is to preserve the ability of the system to achieve the objectives that has been assigned when faults or failures occurred. The main goal of this work is to develop a fault tolerant control strategy that incorporates both reliability and dynamic performance of the system for control reconfiguration. Once a fault has been detected and isolated, the reconfiguration strategy proposed in this paper tries to find possible structures of the faulty system that preserve prespecified performance, calculate the system reliability, compute new controller gains and finally search the optimal structure that has the "best" control performance with the highest reliability. The proposed approach is illustrated through a hydraulic and thermal system of three tanks.

International audience; Dans la première partie de ce travail, on se propose de comparer le comportement rhéologique de bétons identifié à l'aide de différents rhéomètres, en utilisant une méthode de traitement des données permettant le tracé direct de la courbe d'écoulement du matériau. Dans une deuxième partie, les propriétés rhéologiques de bétons industriels sont étudiées au moyen d'un rhéomètre de forte capacité de couple muni d'une géométrie à ailettes. Les résultats permettent d'évaluer et de comparer les propriétés d'écoulement des bétons et de juger de la reproductibilité du procédé de fabrication. In the first section of this paper, the rheological behaviour of concretes obtained with different rheometers is investigated from a procedure allowing the plot of the flow curve of sheared material. Secondly, the rheological properties of industrial concretes are studied with a high torque vane rheometer. The flow properties of concrete are evaluated and compared, as well as the reproductibility of the making process of concrete.

cote interne IRCAM: Noisternig08a; None / None; National audience; Auralization is the process of making audible the acoustics of complex virtual architectural spaces in a realistic and accurate manner. This paper presents a novel real-time auralization software environment comprising a room acoustic modeler, a spatial renderer for auralization, and a visualization and scene graph unit for interactivity. The computation of early reflection paths within the geometric model is based on an efficient beam tracing algorithm capable of real-time detection of specular reflection paths in a static geometry with one or several moving listener(s). For “simple" rooms, the real-time performance is maintained even with dynamic geometries and sources. Results of the room acoustic model consisting of visible reflection paths and their accumulated material attenuation are sent to the audio renderer. From this geometrical and acoustical data, listener position-relative 3D room impulse responses are generated using a hierarchical-order Ambisonics approach. Finally, the spatialized audio output is presented to the listener via multiple loudspeakers or binaurally rendered over headphones. As higher order reflections are more diffuse in nature, they are encoded using lower Ambisonic orders, thereby reducing computational load. The environment combines high quality audio with visual rendering realized using the open source platforms Pure Data and VirChor respectively. This open source auralization framework provides direct audio-visual interaction in real-time and is suitable for VR environments.

International audience; In this paper, we consider MAC (media access control) protocols appropriate to the underwater acoustic networks. First, we consider a media access method based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol used in the wireless local area networks IEEE 802.11 (WiFi). In the underwater acoustic channel, the acoustic wave propagates very slowly with regard to the electromagnetic wave (about 1500 m s ). Therefore the propagation delay is significant and thus collisions present a high cost considering the delay of transmission and the available throughput. To avoid this problem, we consider a second protocol in which we integrate a WAIT command [1]. Finally we integrate to our proposition a power control mechanism in order to increase network performance (delay, throughput). The performance evaluation of the three propositions has been done in terms of available throughput of the underwater sensors, delay of transmission and collision probability. The proposed simulation system model is detailed.

International audience; In this paper, we derive mathematical expressions to assess reliability importance measures for a component in a common cause failure group (CCF). The main originality of this work is that the existing information on the cause of the component unavailability (intrinsic, unknown, CCF-related, maintenance) can be explicitly taken into account in the importance factor computation.; Cet article a pour objet de présenter des expressions permettant de calculer les facteurs d’importance fiabilistes d’un composant appartenant à un groupe de défaillance de cause commune (DCC). La possibilité de prendre en compte l’information sur la nature de la défaillance du composant considéré (intrinsèque, origine non identifiée, DCC, maintenance) lors du calcul des facteurs d’importance constitue la principale originalité de l’approche proposée

The extended finite element method (X-FEM) was used with success in the past few years for linear elastic fracture mechanics (LEFM). In the case of elastic–plastic fracture mechanics (EPFM), this method cannot be used without adequate asymptotic solutions to enrich the shape function basis. In this paper, we propose to use the well-known Hutchinson–Rice–Rosengren (HRR) fields to represent the singularities in EPFM. The analysis we are presenting is done in the context of confined plasticity, and shall be used to predict fatigue crack growth without remeshing. A Fourier analysis of the HRR fields is done in order to extract a proper elastic–plastic enrichment basis. Several strategies of enrichment, based on the Fourier analysis results, are compared and a six-enrichment-functions basis is proposed. This new tip enrichment basis is coupled with a Newton like iteration scheme and a radial return method for plastic flow. Numerical comparisons with and without unloading of fracture parameters are made with classical finite element results and show good agreements.

This paper is devoted to the presentation of the Extended Finite Element Method (X-FEM) compared to usual Finite Element Method for simulation of 3D fatigue crack propagation under complex loading. This type of situation is very typical of crack propagation in tribological environment. The X-FEM method will be presented in a first part, and two techniques allowing the discretization of cracks will be explained. The interaction integral concept, which allows to compute with a very good accuracy the stress intensity factors KI, KII, KIII, in complex situation will be presented. Once these tools are available, the method can be used very efficiently to simulate crack propagation without remeshing. This property is essential because it guarantees exact energy conservation when the crack is updated. The precise knowledge of individual stress intensity factors KI ,KII and KIII allows deciding the direction of the crack growth (using any crack propagation law). This tool can hence be used to identify the propagation laws in complex cases using comparison between experimental and numerical studies. One example of stress intensity factor computation using a 3D real crack measured by tomography will be shown. 3D crack propagation simulation will be presented. Very recent results will be given for small scale yielding and crack closure situations, which permit to explain, for instance, slowed down crack propagation due to overload.

During the excavation at Contraguda (Perfugas) in Northern Sardinia, a long blade workshop was found; it probably dates from the Late Neolithic/Chalcolithic (late 4th- 3rd millennium cal. ВС). The aim of this paper is to describe the different stages of this blade production in order to evaluate its position in the economic system of Mediterranean Late Neolithic communities. Based on the study of several thousand flint remains, this work allows us to propose a reconstruction of this blade production in seven stages: raw material supply near the site; selection of the nodules and core roughing out; transport of these pre-shaped blanks to the site; first blade flaking by indirect percussion; production of the long blades by pressure with a lever fitted with a copper point; production of other blanks (short blades and flakes) for common tools used on the site; abandoning of small cores. Some similarities could be established between this production and others from the South of France (Haute-Provence), especially the use of a lever fitted with a copper point. These long blades were not used on the site but were produced to be exported and only a few fragments, probably broken during production, were found on the site. This fact and the high technological level of this blade production testify to the importance of the production of prestige items at the end of the Neolithic period, which occurs in different parts of Europe., Les fouilles du site de Contraguda (Perfugas) dans le nord de la Sardaigne ont permis la découverte d'un atelier spécialisé dans la fabrication de grandes lames en silex, probablement daté du Chalcolithique (fin IV- IIIe millénaire cal. ВС). Le présent article vise à présenter la reconstitution des modalités de fabrication de ces grandes lames et à discuter de la place économique de cette production spécialisée, tant à une échelle locale que régionale. La haute technicité de cette production, en termes de savoir- faire et d'outillages (pression au levier, pointe métallique), souligne l'importance " extra-utilitaire " de ces produits aux caractéristiques exceptionnelles et place le site de Contraguda dans ce phénomène global d'émergence d'ateliers spécialisés à la fin du Néolithique dans différentes régions du vieux continent., Costa Laurent Jacques, Pélegrin Jacques. Une production de grandes lames par pression à la fin du Néolithique, dans le nord de la Sardaigne (Contraguda, Perfugas). In: Bulletin de la Société préhistorique française, tome 101, n°4, 2004. pp. 867-873.

International audience; This paper presents a general study of the stability of variable-mesh dynamic calculations using an energy approach. This study, whose scope is limited to the calculation of dynamic crack propagation with remeshing, enables us to establish the conditions which are necessary to ensure stability and allow control of energy transfers during the evolution of the mesh. The problem of the implicit calculation of the crack length is also presented. The results obtained on an sample problem are analyzed to illustrate the effectiveness of the proposed methods.

In this paper we focus on anaerobic digestion in a continuous bioreactor, a high yield waste water treatment process but which is intrinsequely unstable. After a brief description of the underlying model, based on two main steps (acidogenesis and methanogenesis), we propose a control law allowing to choose organic pollution level (Chemical Oxigen Demand, COD) inside a continuous anaerobic digester. This globally asymptotically stabilising control law, regulates a biologically based measurement of organic pollution. The closed loop system behavior is then illustrated on a noisy simulation and finally validated on a real life pilot process.

International audience; CMP aims at providing Universities, Research Laboratories and Industries with the facility to have their integrated circuits projects fabricated for prototyping and low volume production. During last 3 years, CMP introduced the access to new generation advanced technologies processes which are covering a wide spectrum of microelectronics, MEMS, and MCM technologies. In this paper we will describe and show some examples on how CMP Service succeeded transferring the knowledge of design techniques and methodology, targeting Deep Sub-Micron processes.

Because the aeration system in an activated sludge plant typically represents a large part of total energy requirements, designers and operators need accurate oxygen transfer information to make the aeration system as energy efficient as possible. This paper presents clean water tests performed at 38 wastewater treatment plants. The Specific Aeration Efficiency results (SAE, kgO2/kWh) are reported for: (1) large open channels (volume higher than 1000 m3), (2) small open channels, (3) total floor coverage cylindrical tanks, and (4) cylindrical tanks with grid arrangement. Some practical guidelines can be drawn, some of them being: (1) high SAE can be achieved at small aeration tanks (, L'aération représentant la part la plus importante de la dépense énergétique d'une station d'épuration à boues activées, les concepteurs et exploitants de station ont besoin d'éléments pertinents pour optimiser le transfert d'oxygène. Cette publication présente l'analyse de 38 mesures d'oxygénation en eau claire réalisées sur sites équipés de systèmes de diffusion d'air par fines bulles. Les apports spécifiques bruts de ces systèmes (ASB) sont présentés pour : i)des grands chenaux (volume supérieur à 1 000 m3), ii) des petits chenaux (volume inférieur à 1 000 m3), iii) des bassins cylindriques dont le fond est entièrement tapissé de diffuseurs (couverture plancher) et enfin iv) des bassins cylindriques où les diffuseurs sont groupés en raquettes sur une partie seulement du fond. Plusieurs recommandations pratiques peuvent être avancées dont les principales sont : 1) dans les bassins cylindriques, une couverture plancher avec un débit d'air par diffuseur modéré et fourni au moyen d'un surpresseur volumétrique permet d'obtenir de forts ASB, 2) le coût élevé d'investissement de cette configuration se justifie au regard des moins bonnes performances de transfert des configurations raquettes moins chères en investissement, enfin 3) les petits chenaux obtiennent des résultats d'A.S.B. satisfaisants mais n'atteignent pas les performances des bassins cylindriques en couverture plancher dans une gamme de volume équivalente.

International audience; The Microelectronics and Photonics Testbed (MPTB) carrying twenty-four experiments on-board a scientific satellite is in a high radiation orbit since November 1997. This paper presents SEU flight results on two commercial static RAMs includes in two of the MPTB experiments.

This paper presents an experimental investigation of the mean axial velocity and temperature excess of three-dimensional vertical and then horizontal wall jet, with opposite buoyancy forces. The initial Archimed number is used to establish an empirical model to estimate the maximum quantities of the jet, with reference to the inlet conditions. These measurements also enabled us to deduce the penetration law of the vertical jet and the separation distance law of the horizontal flow according to the inlet conditions.

Numerical simulation of creep rupture of a reactor pressure vessel in a severe hypothetical accident needs to perfectly take account of interactions between creep phenomena and damage. This paper presents a numerical method for solving constitutive equations of a material behaviour model coupling elastoviscoplasticity and creep damage through the effective stress concept. The numerical technique rests upon a semi-implicit time integration of the constitutive equations. The method is validated on both simple ID cases the results of which can be compared to other numerical or analytical solutions and in the case of an axisymmetric reference problem (RUPTHER 4 test) under thermal and mechanical loading. The efficiency of different tangent stiffness matrices is analysed.

An 8-year field experiment was conducted to determine the fertilizing properties of a lime and ferric chloridetreated urban sludge. This paper examines the absorption of some heavy metals by three successive corn crops grown 5 years after the first sludge application. At the time of the experiment, the total quantity of sludge delivered to the soil plots varied from 0 to 340 t dry matter per ha, and no additional sludge was applied during the 3 years. Metal assays were performed on both grain and leaves. Sludge applications had no significant effect on the metal composition of grain. However, in leaves, concentrations of cadmium, copper and zinc increased while that of iron and manganese decreased. Effects were usually minimal for leaves by the third corn harvest. The extraction of soil heavy metals using DTPA yielded mixed results, and only provided good estimates for two metals (cadmium and copper) during the first year of the study.