Schmutz M.,Bordeaux Montaigne University |
Blondel A.,Bordeaux Montaigne University |
Revil A.,Colorado School of Mines |
Revil A.,University of Savoy
Geophysical Research Letters | Year: 2012
We have investigated the complex conductivity of oil-bearing sands with six distinct oil types including sunflower oil, silicone oil, gum rosin, paraffin, engine oil, and an industrial oil of complex composition. In all these experiments, the oil was the non-wetting phase. The in-phase (real) conductivity follows a power law relationship with the saturation (also known as the second Archie's law) but with a saturation exponent n raging from 1.1 to 3.1. In most experiments, the quadrature conductivity follows also a power law relationship with the water saturation but with a power law exponent p can be either positive or negative. For some samples, the quadrature conductivity first increases with saturation and then decreases indicating that two processes compete in controlling the quadrature conductivity. One is related to the insulating nature of the oil phase and a second could be associated with the surface area of the oil/water interface. The quadrature conductivity seems to be influenced not only by the value of the saturation exponent n (according to the Vinegar and Waxman model, p = n-1), but also by the surface area between the oil phase and the water phase especially for very water-repellent oil having a fractal oil-water interface. Copyright 2012 by the American Geophysical Union.
Loosli F.,University of Geneva |
Le Coustumer P.,Bordeaux Montaigne University |
Le Coustumer P.,University of Bordeaux 1 |
Stoll S.,University of Geneva
Water Research | Year: 2013
The behavior of manufactured TiO2 nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO2 nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO2 nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO2 nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO2 nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO2 nanoparticles. © 2013 Elsevier Ltd.
Leguillon D.,University Pierre and Marie Curie |
Martin E.,Bordeaux Montaigne University
International Journal of Fracture | Year: 2013
The final aim of the two parts of this study is to quantify the gain in strength of a layered heterogeneous structure caused by the elastic contrast between the layers, especially if no crack deflection is observed at the interface. In part I, the analysis focus on an example, the 3 point-bending of a bimaterial made of a compliant and a stiff layer; whereas part II is dedicated to the 3-point bending of a homogeneous beam embedding a thin stiff film. Baptized "step-over" and "jump-through", two original mechanisms of crack crossing the interface are proposed herein. They rely on a coupled criterion involving both energy requirement and stress condition. It is established from asymptotic expansions and the theory of singularities. This criterion is able to respond to the paradox posed by the traditional tools of brittle fracture mechanics which might carelessly conclude to a quasi infinite strength enhancement. The subtitle of this first part might be: can a crack pass through an interface? © 2012 Springer Science+Business Media Dordrecht.
Yang B.,Bordeaux Montaigne University |
Dai M.,Bordeaux Montaigne University
Pattern Recognition | Year: 2012
The problem of image reconstruction from its statistical moments is particularly interesting to researchers in the domain of image processing and pattern recognition. Compared to geometric moments, the orthogonal moments offer the ability to recover much more easily the image due to their orthogonality, which allows reducing greatly the complexity of computation in the phase of reconstruction. Since the 1980s, various orthogonal moments, such as Legendre moments, Zernike moments and discrete Tchebichef moments have been introduced early or late to image reconstruction. In this paper, another set of orthonormal moments, the Gaussian-Hermite moments, based on Hermite polynomials modulated by a Gaussian envelope, is proposed to be used for image reconstruction. Especially, the papers focus is on the determination of the optimal scale parameter and the improvement of the reconstruction result by a post-processing which make Gaussian-Hermite moments be useful and comparable with other moments for image reconstruction. The algorithms for computing the values of the basis functions, moment computation and image reconstruction are also given in the paper, as well as a brief discussion on the computational complexity. The experimental results and error analysis by comparison with other moments show a good performance of this new approach. © 2011 Elsevier Ltd All rights reserved.
Yang B.,Bordeaux Montaigne University |
Dai M.,Bordeaux Montaigne University
Signal Processing | Year: 2011
Orthogonal moments are powerful tools in pattern recognition and image processing applications. In this paper, the GaussianHermite moments based on a set of orthonormal weighted Hermite polynomials are extensively studied. The rotation and translation invariants of GaussianHermite moments are derived algebraically. It is proved that the construction forms of geometric moment invariants are valid for building the GaussianHermite moment invariants. The paper also discusses the computational aspects of GaussianHermite moment, including the recurrence relation and symmetrical property. Just as the other orthogonal moments, an image can be easily reconstructed from its GaussianHermite moments thanks to the orthogonality of the basis functions. Some reconstruction tests with binary and gray-level images (without and with noise) were performed and the obtained results show that the reconstruction quality from GaussianHermite moments is better than that from known Legendre, discrete Tchebichef and Krawtchouk moments. This means GaussianHermite moment has higher image representation ability. The peculiarity of image reconstruction algorithm from GaussianHermite moments is also discussed in the paper. The paper offers an example of classification using GaussianHermite moment invariants as pattern feature and the result demonstrates that GaussianHermite moment invariants perform significantly better than Hus moment invariants under both noise-free and noisy conditions. © 2011 Elsevier B.V.
Demazeux S.,Bordeaux Montaigne University
International Journal of Epidemiology | Year: 2014
This article traces the historical decisions, concepts and key professional collaborations that laid the foundations for the formation of American psychiatric epidemiology during the 20th century, up to the discipline's institutional consolidation, circa 1980, when the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) was published. Thomas Kuhn's 'disciplinary matrix' is mobilized as a framework that allows the institutional and intellectual construction of a discipline to be analysed as separate but intertwined components, without assuming that the two evolve in tandem. The identification of the strengths as well as the frailties and internal divisions of the discipline as it developed reveals a paradoxical situation: a time lag between psychiatric epidemiology's institutionalization and public recognition, on the one hand; and the weak coherence of its intellectual components, on the other hand. We briefly trace the origins of split among the discipline's aetiological models of mental disorders and suggest that the lack of coherence among them has prevented psychiatric epidemiology from achieving the status of a normal scientific discipline, in the Kuhnian sense. Without a more explicit attention to the intellectual rationale of the discipline, psychiatric epidemiology will continue to maintain a strong institutional dimension and weak intellectual matrix. © The Author 2014; all rights reserved.
Ducrot A.,Bordeaux Montaigne University |
Magal P.,Bordeaux Montaigne University
Nonlinearity | Year: 2011
The aim of this paper is to investigate the spatial invasion of some infectious disease. The contamination process is described by the age since infection. Compared with the classical Kermack and McKendrick's model, the vital dynamic is not omitted, and we allow some constant input flux into the population. This problem is rather natural in the context of epidemic problems and it has not been studied. Here we prove an existence and non-existence result for travelling wave solutions. We also describe the minimal wave speed. We are able to construct a suitable Lyapunov like functional decreasing along the travelling wave allowing to derive some qualitative properties, namely their convergence towards equilibrium points at x = ∞. © 2011 IOP Publishing Ltd & London Mathematical Society.
Agency: European Commission | Branch: H2020 | Program: MSCA-IF-EF-ST | Phase: MSCA-IF-2014-EF | Award Amount: 185.08K | Year: 2016
The RecRoad project aims to reconstruct the Roman road going from Aquileia, in the north-east of Italy, to Singidunum, on the Danube river. This was one of the main road axes of the Empire and it connected the Venetian area with the Pannonia Superior and the Danubian limes: the road was longer than 450 miles, passing through the Alps, it ran along the river Sava, crossing its course several times. The roads general layout can be followed in the itinerary sources but an attempt to accurately reconstruct the course of the road on the ground has never been tried before and may greatly improve our knowledge of the evolution of the territories that it crossed over the time. After an in-depth study of the original itinerary of the road, the project aims also at the analysis of the consequences of its construction on the landscape from different point of view (culture, settlement dynamics, religion, trade, ), so that better comprehension of the territorial and cultural connections, will be possible. To reach these goals, the project will consider and use all the sources and the new technologies avalaible to archaeologists, in a multi-disciplinary approach. All the collected and generated information will be geo-referenced and published in an online Atlas. The main output of the project will be an interactive atlas available online, where it will be possible to visualize the reconstructed route in its geographical context, the reliability degree of the individual segments and the sources that were identified with reference to the single stretch of the road to which they pertain. In addition, new strategies and initiatives for the protection and knowledge dissemination will be developed. For the first time, all the sources today avalaible to archaeologists will be used to identify the original track of a Roman road and to study the importance of the consequences that its presence had on the territory and on the way ancient people conceived the landscape where they lived.
Agency: European Commission | Branch: H2020 | Program: ERC-STG | Phase: ERC-2016-STG | Award Amount: 1.49M | Year: 2017
PATRIMONIVM aims at conducting the first comprehensive and multidisciplinary socio-economic study of the properties of the Roman emperors from Octavian/Augustus to Diocletian (44 BC AD 284) using a complete documentary base for the entire Roman world. Imperial properties were extended throughout the empire and included residences, cultivated land, pastureland, woods, mines, quarries, luxury items and slaves. This immense richness was a key element for the maintenance of the position of supreme power, since the emperor could use it to carry out all sort of public expenditure and to confer benefactions to individuals and communities. Moreover, large imperial possessions (vast landed estates, quarries) had relevant local economic repercussions. Since their owner was both the head of the empire and a global economic player, we can trace a tendency to trans-regional uniformity in the patterns of exploitation and a positive effect on the economic and, in a certain way, cultural integration of peripheral areas. No major survey of the available documentation has been produced since the beginning of the 20th century and many questions about the acquisition and use of the properties remain unanswered. The project aims at filling this gap creating a powerful online relational database of all published sources; every record will contain geodata and will be related to separate databases of all known persons (administrators, peasants etc.), regions and bibliographic references. A multidisciplinary and comparative study, developed through the projects rich scientific activity, will allow to understand the role of the properties as a structuring factor of Roman economy and as a vector of human mobility and socio-cultural transformation. Innovative hypotheses on imperial investments, the role of the emperors freedmen and other aspects will be tested. A series of five books, among which an authoritative history of the imperial properties, will disseminate the projects results.
Agency: European Commission | Branch: H2020 | Program: MSCA-IF-EF-ST | Phase: MSCA-IF-2014-EF | Award Amount: 185.08K | Year: 2015
The main goal of this project is to investigate out-of-equilibrium Cu-As alloys, i.e. 0-10 wt.% As in the range used in the transition period between Stone and Metal ages. The research protocol is made of several steps: equilibrium and out-of-equilibrium phase diagrams in the above mentioned range, evaluation of mechanical properties of Cu-As alloys in the most common metallurgical states (as-cast, annealed, cold-hardened, recrystallized), and estimation of the loss of As during metallurgical transformations (melting/casting, homogenisation and recrystallisation annealing) according to the number of iterations and of the treatment temperature and dwell time. The fulfilment of these objectives is of high importance for materials science applied to archaeology dealing with development and usage of this very first alloy produced by human kind. The applicant will acquire and share with the scientific community new knowledge in the production, thermomechanical treatment and consequent properties of the misknown arsenical bronzes. She will use her metallurgical experience and archaeological knowledge (both matured in the field of tin-bronzes) applied to production, treatment and analyses of arsenical bronze. The additional knowledge the applicant will obtain within the project is related to the domain of phase diagrams creation and the usage of DTA, DSC and XRPD, under the supervision of experienced researchers from inorganic chemistry and metallurgy. The project as a whole will provide for the first time: 1) out-of-equilibrium phase diagrams for the Cu-As system 2) determination of chemical, physical and mechanical properties of arsenical bronze in the range of 0-10 wt.% arsenic 3) a comprehensive overview on the actual loss of arsenic during metallurgical transformations. The proposed project constitutes an excellent career-springboard for the applicant, being then the sole expert on the usage of arsenical bronze in the field of European archaeometallurgy.