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Search Results: 1 - 10 of 403624 matches for " Guy Mélard "
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Asymptotic properties of QML estimators for VARMA models with time-dependent coefficients: Part I
Abdelkamel Alj,Christophe Ley,Guy Mélard
Statistics , 2015,
Abstract: This paper is about vector autoregressive-moving average (VARMA) models with time-dependent coefficients to represent non-stationary time series. Contrarily to other papers in the univariate case, the coefficients depend on time but not on the length of the series $n$. Under appropriate assumptions, it is shown that a Gaussian quasi-maximum likelihood estimator is almost surely consistent and asymptotically normal. The theoretical results are illustrated by means of two examples of bivariate processes. It is shown that the assumptions underlying the theoretical results apply. In the second example the innovations are also marginally heteroscedastic with a correlation ranging from -0.8 to 0.8. In the two examples, the asymptotic information matrix is obtained in the Gaussian case. Finally, the finite-sample behaviour is checked via a Monte Carlo simulation study for $n$ going from 25 to 400. The results confirm the validity of the asymptotic properties even for short series and reveal that the asymptotic information matrix deduced from the theory is correct.
L’étude microtopographique et la visualisation 3D dans l’analyse de gravures préhistoriques – L’exemple des pierres gravées de La Marche
Nicolas Mélard
In Situ : Revue de Patrimoines , 2012, DOI: 10.4000/insitu.6837
Abstract: L’étude de pierres gravées préhistoriques pose depuis longtemps des problèmes de déchiffrement des motifs et de décodage des traces. La recherche archéologique se sert de plus en plus de moyens d’investigation empruntés des sciences naturelles tels la microscopie et plus récemment le relevé et la visualisation 3D. L’application de la microtopographie a permis d’appréhender de manière plus complète les pierres gravées de La Marche en ajoutant des éléments de compréhension en termes de composition et de construction des motifs (chronologie et morphologie des traits) ainsi qu’en termes de technologie (gestes et démarches des graveurs préhistoriques). De plus, il a été possible d’obtenir des informations sur l’histoire des supports avant et après la gravure (choix des matières premières, caractérisation des usures,…). The main difficulty in studying the engraved stones of the upper Paléolthic period is the decipherment and the understanding of the various overlapping traces on the surfaces. Scientific research in paleolithic art is trying since more than 20 years to use modern laboritory devises and techniques like the Scanning Electron Microscope and more recently the 3D scanning. For the engraved stones of the site of La Marche have been studied by 3D microtopography as a complementary technique. This non destructif protocole made a new approach of engraving technology and motif composition possible (chronology of the lines, traces morphology etc.). This leads to better understanging of the techniques and gestures used by prehistoric artists. Moreover studies of this type can give more informations obout the function and the history of the stones in a prehistoric rockshelter and by this way the role of theses stones in the life of the magdaleanian hunter-gatherer communities.
The Pragmatic Collective Interest as the Product of Civic Deliberation: The Case of Pesticide Management in Belgium
Fran?ois Mélard,Marc Mormont
Sustainability , 2013, DOI: 10.3390/su5052233
Abstract: Through the issue of pesticide management in Belgium, this article offers an empirical and conceptual grasp on what Ulrich Beck called the second-order reflexive modernity; that which is exercised among citizens when they are confronted with threatening and uncertain situations. To achieve this, we use two case studies of two public policy instruments, which we offer to the public for discussion: food product labelling, and the modelling of toxic effects linked to pesticide use. To this end, we organised two focus groups designed to encourage discussion, composed of citizens/practitioners. The results obtained plead in favour of a collective deconstruction-reconstruction of these tools and can lead to what we propose calling a “pragmatic collective interest.” This “pragmatic collective interest” can take the form of a new set-up or new associations that enable the coexistence of conflicting propositions and points of view, and a suspension of efforts to hierarchize causes and required solutions.
System Level Evaluation of Innovative Coded MIMO-OFDM Systems for Broadcasting Digital TV
Y. Nasser,J.-F. Hélard,M. Crussière
International Journal of Digital Multimedia Broadcasting , 2008, DOI: 10.1155/2008/359206
Abstract: Single-frequency networks (SFNs) for broadcasting digital TV is a topic of theoretical and practical interest for future broadcasting systems. Although progress has been made in the characterization of its description, there are still considerable gaps in its deployment with MIMO technique. The contribution of this paper is multifold. First, we investigate the possibility of applying a space-time (ST) encoder between the antennas of two sites in SFN. Then, we introduce a 3D space-time-space block code for future terrestrial digital TV in SFN architecture. The proposed 3D code is based on a double-layer structure designed for intercell and intracell space time-coded transmissions. Eventually, we propose to adapt a technique called effective exponential signal-to-noise ratio (SNR) mapping (EESM) to predict the bit error rate (BER) at the output of the channel decoder in the MIMO systems. The EESM technique as well as the simulations results will be used to doubly check the efficiency of our 3D code. This efficiency is obtained for equal and unequal received powers whatever is the location of the receiver by adequately combining ST codes. The 3D code is then a very promising candidate for SFN architecture with MIMO transmission.
Performance comparison of multi-user detectors for the downlink of a broadband MC-CDMA system
Fabrice Portier,R. Legouable,L. Maret,F. Bauer,N. Neda,J. -F. Hélard,E. Hemming,M. Des Noes,M. Hélard,the projet européen Matrice Collaboration
Mathematics , 2006,
Abstract: In this paper multi-user detection techniques, such as Parallel and Serial Interference Cancellations (PIC & SIC), General Minimum Mean Square Error (GMMSE) and polynomial MMSE, for the downlink of a broadband Multi-Carrier Code Division Multiple Access (MCCDMA) system are investigated. The Bit Error Rate (BER) and Frame Error Rate (FER) results are evaluated, and compared with single-user detection (MMSEC, EGC) approaches, as well. The performance evaluation takes into account the system load, channel coding and modulation schemes.
To the problem of the establishment of comparative relationships of Russian and foreign literature XIX–early XX centuries
Guy M. V.
Sociosfera , 2011,
Abstract: The basic premise of comparative and historical study of literatures of different nations is the idea of unity and regularity of the overall process of socio-historical development of mankind. Features of historical and typological similarities are found in the ideological and psychological content, the motives and plots, in poetic images and situations, particularly the genre of composition and artistic style.
La ville européenne: mutations des fonctions et recomposition des structures
Guy DI MéO
Mappemonde , 1989,
Abstract: Les villes d'Europe enregistrent une désindustrialisation au profit de leurs périphéries, et une nouvelle industrialisation basée sur les hautes technologies. Les fonctions tertiaires migrent aussi, mais sur des distances plus courtes, sans que les villes se dévitalisent. Cela remet en cause le modèle centre-périphérie et souligne la segmentation de l'espace urbain.
Identités et territoires : des rapports accentués en milieu urbain ?
Guy Di Méo
Métropoles , 2007,
Abstract: Phénomène social, presque toujours pluriel, les identités, individuelles ou collectives, se déclinent selon un continuum : du sujet humain aux territoires de la ville. La plupart des identités affichent une composante géographique, une spatialité qui les renforce et les rend plus prégnantes. Elles s’expriment donc, souvent, par ces médiations du social et du spatial que forment les lieux, les territoires, les paysages…Ceux de la ville s’avèrent particulièrement aptes à jouer ce r le, parce qu’ils s’imprègnent d’un sens social très puissant tenant à la forte densité humaine et mémorielle de ces espaces. En retour, les identités contribuent activement à toutes les constructions sociales d’espaces et de dispositifs urbains, réels ou sensibles. Les formes spatiales des identités, les dimensions identitaires des espaces s’interpénètrent selon une dialectique subtile. Elles se manifestent dans les représentations sociales par le truchement de schèmes symboliques qui associent objets, lieux, uvres, personnages et événements patrimoniaux. Si l’identité constitue une construction sociale de caractère idéologique et culturel, elle reste une structure fondamentale de l’humain et s’avère un outil politique de premier ordre. Individual or collective identities are social phenomena, mostly plural. From human subject to territory, they form a continuum. Most of them display a geographical component, a spatiality reinforcing and underlining them. Therefore, hey often appear through socio-spatial mediations, such as places, territories, landscapes…These of cities are particularly full of sens. In return, the identities actively contribute to those social constructions of spaces and geographical devices, either real or perceptible. Spatial forms of identity, identity dimensions of spaces interact according to a subtle dialectic. They appear in social representations by the means of symbolic schemes associating objects, places, works of art, characters and patrimonial events. As a social construction, identity has an undeniable ideological and cultural dimension ; but it is also a fundamental structure of the human element and a very important political tool.
Introdu o ao debate sobre a metropoliza o
Guy Di Méo
Confins , 2008, DOI: 10.4000/confins.5433
Abstract: La métropolisation est un phénomène universel caractérisé par la concentration, dans des aires urbaines désormais fluides et ouvertes, d’un nombre croissant d’habitants vivant au rythme de mobilités incessantes, utilisant les TIC et se consacrant de plus en plus à la production de services. L’interconnexion de ces métropoles au sein d’un réseau mondialisé en constitue l’une des originalités majeures. à la fois système productif globalisé très efficace et processus nouveau de valorisation/occupation des espaces, la métropolisation est aussi un instrument de classement des groupes sociaux au sein d’espaces toujours plus fragmentés. Cette introduction pointe les principales questions que posent aux sciences de l’espace géographique le processus de métropolisation et les formes d’innovation tant sociale que spatiale qu’il suscite. Traduction de l’article Introduction au débat sur la métropolisation , publié sur le site Hal-Shs http://halshs.archives-ouvertes.fr/halshs-00281654/fr/ Metropolization is a universal phenomenon characterized by the concentration of a growing number of inhabitants in fluid and open urban areas. Those inhabitants live to the rhythm of unceasing mobilities and use ICTs. Their activities are more and more devoted to the production of services. One of the main original aspects of the metropolises they live in is their interconnection within a global network. Metropolization is both a very efficient global productive system and a new process of space development/occupancy. It also provides a tool that can be used in order to classify social groups within more and more fragmented spaces. This introduction stresses the main questions linked to the process of metropolization and to the social and spatial innovation forms it generates in the sciences of geographical space. Traduction of Introduction au débat sur la métropolisation , published on the site Hal-Shs http://halshs.archives-ouvertes.fr/halshs-00281654/fr/ A metropoliza o é um fen meno universal caracterizado pela concentra o, em áreas urbanas doravante fluidas e abertas, de um número crescente de habitantes, utilizando as TICs e se dedicando cada vez mais ao setor de servi os. A interconex o destas metrópoles no seio de uma rede mundializada constitui uma das maiores originalidades desse processo. Sendo um sistema produtivo bastante eficaz e um processo novo de valoriza o/ocupa o de espa os, a metropoliza o é também um instrumento de classifica o dos grupos sociais no seio de espa os sempre fragmentados. Esta introdu o aponta as principais quest es que se imp e às
An approach for exploring interaction between two proteins in vivo
Guy M. Benian
Frontiers in Physiology , 2014, DOI: 10.3389/fphys.2014.00162
Abstract: We describe a strategy for exploring the function of protein-protein interactions in striated muscle in vivo. We describe our experience using this strategy to study the interaction of UNC-112 (kindlin) with PAT-4 (integrin linked kinase). Random mutagenesis is used to generate a collection of mutants that are screened for lack of binding or gain of binding using a yeast 2-hybrid assay. The mutant proteins are then expressed in transgenic C. elegans to determine their ability to localize in the sarcomere. We emphasize two advantages of this strategy: (1) for studying the interaction of protein A with protein B, when protein A can interact with multiple proteins, and (2) it explores the function of an interaction rather than the absence of, or reduced level of, a protein as can be obtained with null mutants or knockdown by RNAi. We propose that this method can be generalized for studying the meaning of a protein-protein interaction in muscle for any system in which transgenic animals can be generated and their muscles can be imaged.
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