Showing papers by "ParisTech published in 2009"

QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials

Abstract: QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). The acronym ESPRESSO stands for opEn Source Package for Research in Electronic Structure, Simulation, and Optimization. It is freely available to researchers around the world under the terms of the GNU General Public License. QUANTUM ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively parallel architectures, and a great effort being devoted to user friendliness. QUANTUM ESPRESSO is evolving towards a distribution of independent and interoperable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.

High yield fabrication of fluorescent nanodiamonds

Abstract: A new fabrication method to produce homogeneously fluorescent nanodiamonds with high yields is described. The powder obtained by high energy ball milling of fluorescent high pressure, high temperature diamond microcrystals was converted in a pure concentrated aqueous colloidal dispersion of highly crystalline ultrasmall nanoparticles with a mean size less than or equal to 10 nm. The whole fabrication yield of colloidal quasi-spherical nanodiamonds was several orders of magnitude higher than those previously reported starting from microdiamonds. The results open up avenues for the industrial cost-effective production of fluorescent nanodiamonds with well-controlled properties.

The role of propeller aerodynamics in the model of a quadrotor UAV

Abstract: We study models of a quadrotor UAV. These models include various aerodynamic effects of the propellers and their interactions with the motion of the rigid body of the UAV. Two main assumptions are formulated: the twisting of the propellers is such that the local angle of attack is constant along the blades in stationary flight, and, secondly, that the local induced velocity is also constant along the blades. Under these assumptions (which correspond to an optimal hovering rotor), we conclude that the flexibility of the propellers plays an important role in the dynamics of the UAV (including the effects of the vertical location of the center of gravity), and that it is interesting to account for it when designing a closed loop controller.

Temporal Integration for Audio Classification With Application to Musical Instrument Classification

Abstract: Nowadays, it appears essential to design automatic indexing tools which provide meaningful and efficient means to describe the musical audio content. There is in fact a growing interest for music information retrieval (MIR) applications amongst which the most popular are related to music similarity retrieval, artist identification, musical genre or instrument recognition. Current MIR-related classification systems usually do not take into account the mid-term temporal properties of the signal (over several frames) and lie on the assumption that the observations of the features in different frames are statistically independent. The aim of this paper is to demonstrate the usefulness of the information carried by the evolution of these characteristics over time. To that purpose, we propose a number of methods for early and late temporal integration and provide an in-depth experimental study on their interest for the task of musical instrument recognition on solo musical phrases. In particular, the impact of the time horizon over which the temporal integration is performed will be assessed both for fixed and variable frame length analysis. Also, a number of proposed alignment kernels will be used for late temporal integration. For all experiments, the results are compared to a state of the art musical instrument recognition system.

Greta: an interactive expressive ECA system

Abstract: We have developed a general purpose use and modular architecture of an Embodied Conversational Agent (ECA) called Greta. Our 3D agent is able to communicate using verbal and nonverbal channels like gaze, head and torso movements, facial expressions and gestures. It follows the SAIBA framework [10] and the MPEG4 [6] standards. Our system is optimized to be used in interactive applications.

Fatigue crack initiation detection by an infrared thermography method

Abstract: In this paper, the study of the temperature variation during fatigue tests was carried out on different materials (steels and aluminium alloys). Tests were performed at ambient temperature using a piezoelectric fatigue system (20 kHz). The temperature field was measured on the surface of the specimen, by means of an infrared camera. Just at the beginning of the test, it was observed that the temperature increased, followed by a stabilization which corresponds to the balance between dissipated energy associated with microplasticity and the energy lost by convection and radiation at the specimen surface and by conduction inside the specimen. At the crack initiation, the surface temperature suddenly increases (whatever the localization of the initiation), which allows the determination of the number of cycles at the crack initiation and the number of cycles devoted to the fatigue crack propagation. In the gigacycle fatigue domain, more than 92% of the total life is devoted to the initiation of the crack. So, the study of the thermal dissipation during the test appears a promising method to improve the understanding of the damage and failure mechanism in fatigue and to determine the number of cycles at initiation.

Ocarina: An Environment for AADL Models Analysis and Automatic Code Generation for High Integrity Applications

Abstract: Developing safety-critical distributed applications is a difficult challenge. A failure may cause important damages as loss of human life or mission's failure. Such distributed applications must be designed and built with rigor. Reducing the tedious and error-prone development steps is required; we claim that automatic code generation is a natural solution. In order to ease the process of verification and certification, the user can use modeling languages to describe application critical aspects. In this paper we introduce the use of AST as a modeling language for Distributed Real-time Embedded (DRE) systems. Then we present our tool-suite ocarina which allows automatic code generation from AST models. Finally, we present a comparison between ocarina and traditional approaches.

Comprehensive post-event survey of a flash flood in Western Slovenia: observation strategy and lessons learned

Abstract: The limited extent of the areas affected by flash floods and strong spatial and temporal gradients of rainfall cause conventional measurement networks of rain and discharges to be inadequate for an effective observation of these events. The documentation of flash floods urges post-event survey strategies encompassing accurate radar rainfall estimation, field observations of the geomorphic processes associated to the flood, indirect reconstruction of peak discharges and interviews of eyewitnesses. This paper describes the methods applied and the results achieved in the survey of a flash flood that occurred on 18th September 2007 in the Selka Sora watershed (Western Slovenia). The documentation of this flash flood reveals high peak flood discharges and unit peak discharges and a complex flood response. Observations on geomorphic activity show widespread erosion and debris flows, although generally involving relatively small debris volumes. Relevant amounts of large wood were mobilised, with a large variability of the intensity of supply processes. The field study of the Selka Sora flash flood outlines the importance of geomorphological surveys as a prerequisite for flood discharge reconstruction in mountainous watersheds with active sediment dynamics, the basic role of the accounts of eyewitnesses of the flood, and the need of qualitycontrolled weather radar, which permit coupling field observations with rainfall-runoff modelling.

Tracking costs of virulence in natural populations of the wheat pathogen, Puccinia striiformis f.sp. tritici

Abstract: Costs of adaptation play an important role in host-parasite coevolution. For parasites, evolving the ability to circumvent host resistance may trade off with subsequent growth or transmission. Such costs of virulence (sensu plant pathology) limit the spread of all-infectious genotypes and thus facilitate the maintenance of genetic polymorphism in both host and parasite. We investigated costs of three virulence factors in Puccinia striiformis f.sp.tritici, a fungal pathogen of wheat (Triticum aestivum). In pairwise competition experiments, we compared the fitness of near-isogenic genotypes that differed by a single virulence factor. Two virulence factors (vir4, vir6) imposed substantial fitness costs in the absence of the corresponding resistance genes. In contrast, the vir9 virulence factor conferred a strong competitive advantage to several isolates, and this for different host cultivars and growing seasons. In part, the experimentally derived fitness costs and benefits are consistent with frequency changes of these virulence factors in the French pathogen population. Our results illustrate the variation in the evolutionary trajectories of virulence mutations and the potential role of compensatory mutations. Anticipation of such variable evolutionary outcomes represents a major challenge for plant breeding strategies. More generally, we believe that agro-patho-systems can provide valuable insight in (co)evolutionary processes in host-parasite systems.

Simplified environmental study on innovative bridge structure.

Abstract: The aim of this paper is to present a simplified life cycle assessment on an innovative bridge structure, made of wood and ultra high performance concrete, which combines mechanical performance with minimum environmental impact. The environmental analysis was conducted from cradle to grave using the Life Cycle Assessment method. It was restricted to energy release and greenhouse gas emissions. Assumptions are detailed for each step of the analysis. For the wood end-of-life, three scenarios were proposed: dumping, burning, and recycling. Results show that the most energy needed is in the production phase, which represents 73.4% of the total amount. Analysis shows that the renewable energy is about 70% of the production energy. Wood, through its biomass CO2, contributes positively to the environmental impact. It was concluded that no scenario can be the winner on both impacts. Indeed, the end-of-life wood recycling gives the best impact on CO2 release, whereas burning wood, despite its remarkable energy impact, is the worst. According to the emphasis given to each impact, designers will be able to choose one or the other.

Comparison of methods to assess quadriceps muscle volume using magnetic resonance imaging

Abstract: Purpose To compare the precision of four methods to estimate the volume of quadriceps muscles using axial MRI. Materials and Methods Entire legs of 10 healthy young subjects were scanned using a 1.5 Tesla magnetic resonance imaging scanner and 4-mm-thick sections without any gaps. Quadriceps muscles were outlined on all of the slices to obtain the MRI reference standard measure of quadriceps muscle volume. This MRI reference standard was compared with the volume estimated using (i) the truncated cone formula, (ii) the Cavalieri method, (iii) a cubic spline interpolation of missing cross sectional areas, and, (iv) the deformation of a parametric specific object. For each method, 3 to 21 slices were used. Results The average volume error was significantly (P < 0.001) different in comparing the four methods (4.4%, 2.3%, 1.1%, and 1.2%, respectively). In addition, the number of slices required to reach a given volume error was significantly (P < 0.001) different across all methods (respectively, 12, 9, 5, and 7 slices required to reach a volume error of 1.1%). Conclusion While methods based on interpolation and deformation of a parametric specific object have not been used in literature, these two methods are the most precise approaches to reach a given level of precision. J. Magn. Reson. Imaging 2009;30:1116–1123. © 2009 Wiley-Liss, Inc.

Experimental and theoretical cooling velocity profile inside laser welded metals using keyhole approximation and Boubaker polynomials expansion

Abstract: In this paper we are concerned with the t-dependent cooling velocity during laser welding sequences. The temperature profile has been yielded by using keyhole approximation for the melted zone and solving the heat transfer equation. A polynomial expansion has been adopted as a guide to determining the cooling velocity during welding cut-off stage. A thorough comparison with experimental results and recently published profiles has been carried out.

Geographic limits of a clonal population of wheat yellow rust in the Mediterranean region.

Abstract: Most plant pathogens present complex life cycles, in which the clonal reproduction may impede the delimitation of population entities. By studying the genetic structure of the wheat yellow rust caused by Puccinia striiformis f.sp. tritici (PST), we highlighted difficulties impeding population delimitation in highly clonal species. Despite the high dispersal potential of PST, southern France isolates were shown to be divergent from a northwestern European population. A 2-year survey was performed in the Mediterranean region to assess the geographic distribution of southern isolates: 453 isolates collected in 11 countries were genotyped using 15 simple sequence repeat markers. A subsample was analysed for virulence against 23 resistance genes. The dominant strain in the western Mediterranean region was further studied with amplified fragment length polymorphism markers to test for a geographic substructure. Both 'individual'- and 'population'-centred analyses of polymorphism markers revealed two south-specific groups: a predominant group, with a broad variability and a wide distribution in both western and eastern Mediterranean countries, and a minor group in the western Mediterranean. The east-west gradient of genetic diversity suggested gene flow from the Middle East with subsequent founder effects and genetic divergence, and demonstrated the local survival of a western Mediterranean population. The high frequency of the resistance gene Yr8 observed in cultivars from Tunisia and Algeria may contribute to maintain the north/south structure observed in France. In addition to migration and local adaptation, the dynamics of clonal lineage diversification and replacement should be considered to define population entities in strongly clonal species.

An optimized resistor pattern for temperature gradient control in microfluidics

Abstract: In this paper, we demonstrate the possibility of generating high-temperature gradients with a linear temperature profile when heating is provided in situ. Thanks to improved optimization algorithms, the shape of resistors, which constitute the heating source, is optimized by applying the genetic algorithm NSGA-II (acronym for the non-dominated sorting genetic algorithm) (Deb et al 2002 IEEE Trans. Evol. Comput. 6 2). Experimental validation of the linear temperature profile within the cavity is carried out using a thermally sensitive fluorophore, called Rhodamine B (Ross et al 2001 Anal. Chem. 73 4117–23, Erickson et al 2003 Lab Chip 3 141–9). The high level of agreement obtained between experimental and numerical results serves to validate the accuracy of this method for generating highly controlled temperature profiles. In the field of actuation, such a device is of potential interest since it allows for controlling bubbles or droplets moving by means of thermocapillary effects (Baroud et al 2007 Phys. Rev. E 75 046302). Digital microfluidics is a critical area in the field of microfluidics (Dreyfus et al 2003 Phys. Rev. Lett. 90 14) as well as in the so-called lab-on-a-chip technology. Through an example, the large application potential of such a technique is demonstrated, which entails handling a single bubble driven along a cavity using simple and tunable embedded resistors.

An enthalpy-based thermal lattice Boltzmann model for non-isothermal systems

Abstract: An enthalpy-based thermal lattice Boltzmann model is introduced for simulating a class of strongly coupled thermo-hydrodynamic problems. The novelty of the model lies in the formulation of an enthalpy density distribution function to simulate the temperature field, in place of the existing internal energy density distribution function. The proposed model has a clear advantage over the earlier internal energy density distribution function based thermal lattice Boltzmann model, in a sense that it can simulate certain classes of thermofluidic transport problems without facing mathematical difficulties in handling with additional energy source terms.

Towards a functional classification of pathogenic FOXL2 mutations using transactivation reporter systems

Abstract: Mutations of FOXL2 are responsible for the Blepharophimosis-Ptotsis-Epicantus-inversus Syndrome (BPES), involving complex eyelid malformations often associated with premature ovarian failure (POF). Loss-of-function mutations are expected to lead to BPES associated with POF, whereas hypomorphic mutations would lead to BPES without ovarian dysfunction. However, multiple exceptions to the genotype-phenotype correlation have been described and missense mutations in the forkhead domain can lead to either type of BPES. This renders almost impossible the prediction of a POF condition from a given genotype. Moreover, no clear-cut correlation between nuclear and/or cytoplasmic aggregation or cytoplasmic retention of mutant FOXL2 forms and the BPES type has been established thus far. Here, we dissect the molecular and functional effects of 10 FOXL2 mutants, known to induce BPES associated with POF or not. We found a correlation between the transcriptional activity of FOXL2 variants on two different reporter promoters and the type of BPES. We used this functional classification framework to explore the behavior of 18 missense mutations leading to BPES of unknown type. The reporters used enabled us to assess the risk of POF associated with these mutations. Moreover, we document a previously overlooked correlation between subcellular mislocalization and aggregation of mutant FOXL2 and the type of BPES, known or predicted using our reporter assays. Thus, intranuclear aggregation and cytoplasmic mislocalization of mutant FOXL2 may be considered as loose predictors of ovarian dysfunction. The functional classification tool described here is a first step towards circumventing the lack of a clear-cut genotype-phenotype correlation in BPES.

Participation in online interaction spaces: Design-use mediation in an Open Source Software community

Abstract: This research aims at characterizing emerging roles fostering design-use mediation during the Open Source Software (OSS) design process through the analysis of participation. Studying OSS is of particular interest: (1) to investigate socio-technical settings supporting user participation to the design process, which is considered to be the major strength of OSS design; (2) to gain insights into supporting the changing nature of the software industry, which is becoming more and more distributed and global, and which is thus increasingly making use of OSS design tools and methods. In this research, we characterized effective roles of participants, i.e. participation, on the basis of activities analysis in three online interaction spaces (discussion, documentation and implementation) during a continuous “pushed-by-users” design process of the Python project. Participation is targeted through a methodology articulating: (1) structural analyses (organization of the discussions, regularity and involvement of participants, quotes-based social network) in usage-oriented and development-oriented mailing lists of the projects’ discussion space; (2) actions to the code and documentation made by participants in the implementation and documentation spaces. Besides the importance of the users’ contribution to the process, OSS design is fostered by some key-participants, the cross-participants, who act as boundary spanners between the developers and the users, helping them to go beyond some barriers to participation. These findings can be reinforced developing software to automate the structural analysis of discussions and actions to the code and documentation.

Motion detection: Fast and robust algorithms for embedded systems

Abstract: This article introduces a new hierarchical version of a set of motion detection algorithms called ΣΔ These new algorithms are designed to preserve as much as possible the computational efficiency of the basic ΣΔ estimation, in order to target real-time implementation for low power consumption processors and embedded systems