D'X,Y à X,Y,Z, de nouveaux outils pour l' étude architecturale et archéologique. Restitution 3D, lasergrammétrie et photogrammétrie : le cas de la citerne el-Nabih à Alexandrie

Actes du Colloque Virtual Retrospect 2009, Pessac (France) 18, 19 et 20 novembre 2009International audienceL’utilisation des nouvelles technologies 3D, appliquées au domaine de l’étude architecturale et archéologique, s’est généralisée au cours de ces dix dernières années. On a pu constater, du fait de la réduction des coûts d’acquisition et de la simplification de la mise en œuvre de ces techniques, que quelques responsables de chantier ont franchi le pas et troqué leur crayon gris et leur planchette pour un scanner laser 3D. Notre équipe CNRS, qui avait déjà acquis une certaine expérience dans le domaine de la restitution 3D appliquée à l’archéologie, a souhaité expérimenter l’apport de la lasergrammétrie et de la photogrammétrie sur l’un de ses chantiers en cours : la citerne el-Nabih à Alexandrie. Entamées en 2003, les campagnes de relevé et de fouilles touchent aujourd’hui à leur fin. À l’heure où démarre la phase du traitement des données de terrain, nous nous proposons de présenter succinctement les caractéristiques du chantier de la citerne el-Nabih, la méthode développée durant et après la fouille, et les premiers résultats de l’apport de l’utilisation de ces nouvelles technologies

Predicting the Next Best View for 3D Mesh Refinement

3D reconstruction is a core task in many applications such as robot navigation or sites inspections. Finding the best poses to capture part of the scene is one of the most challenging topic that goes under the name of Next Best View. Recently, many volumetric methods have been proposed; they choose the Next Best View by reasoning over a 3D voxelized space and by finding which pose minimizes the uncertainty decoded into the voxels. Such methods are effective, but they do not scale well since the underlaying representation requires a huge amount of memory. In this paper we propose a novel mesh-based approach which focuses on the worst reconstructed region of the environment mesh. We define a photo-consistent index to evaluate the 3D mesh accuracy, and an energy function over the worst regions of the mesh which takes into account the mutual parallax with respect to the previous cameras, the angle of incidence of the viewing ray to the surface and the visibility of the region. We test our approach over a well known dataset and achieve state-of-the-art results.Comment: 13 pages, 5 figures, to be published in IAS-1

Posterior and variational inference for deep neural networks with heavy-tailed weights

We consider deep neural networks in a Bayesian framework with a prior distribution sampling the network weights at random. Following a recent idea of Agapiou and Castillo (2023), who show that heavy-tailed prior distributions achieve automatic adaptation to smoothness, we introduce a simple Bayesian deep learning prior based on heavy-tailed weights and ReLU activation. We show that the corresponding posterior distribution achieves near-optimal minimax contraction rates, simultaneously adaptive to both intrinsic dimension and smoothness of the underlying function, in a variety of contexts including nonparametric regression, geometric data and Besov spaces. While most works so far need a form of model selection built-in within the prior distribution, a key aspect of our approach is that it does not require to sample hyperparameters to learn the architecture of the network. We also provide variational Bayes counterparts of the results, that show that mean-field variational approximations still benefit from near-optimal theoretical support.Comment: 41 page

Transnational labor regulation, reification and commodification: A critical review

Why does scholarship on transnational labor regulation (TLR) consistently fails to search for improvements in working conditions, and instead devotes itself to relentless efforts for identifying administrative processes, semantics, and amalgamations of stakeholders? This article critiques TLR from a pro-worker perspective, through the philosophical work of Georg Lukács, and the concepts of reification and commodification. A set of theoretically grounded criteria is developed and these are applied against selected contemporary cases of TLR. In the totality that is capitalism, reification of social relations of production conceals completely the experiences of workers. In TLR, managerialist and process-oriented scholarship is dominant, verifiable outcomes and positive improvements in conditions of employment are not sought, and worse, meaningless procedures are celebrated as positive achievements

When workplace unionism in global value chains does not function well : exploring the impediments

Improving working conditions at the bottom of global value chains has become a central issue in our global economy. In this battle, trade unionism has been presented as a way for workers to make their voices heard. Therefore, it is strongly promoted by most social standards. However, establishing a well-functioning trade union is not as obvious as it may seem. Using a comparative case study approach, we examine impediments to farm-level unionism in the cut flower industry in Ethiopia. For this purpose, we propose an integrated framework combining two lenses, namely a vertical one (governance and structure of global value chains) and a horizontal one (socio-economic context). We identify 10 impediments that point to three major dimensions contributing to unionisation. These three dimensions include awareness of and interest from workers, legitimacy of trade unions, and capacity of trade unions to act. Furthermore, our results suggest that private social standards may, in certain cases, be counterproductive for the efficient functioning of trade unions. Although we argue that there is no ‘quick fix’ solution to weak workplace unionism at the bottom of global value chains, we stress the importance of considering the dynamics of, and interactions between, the impediments when designing potential support measures that mitigate negative impacts

The Governance of Corporate Responses to Climate Change: An International Comparison

In response to pressures from governments, investors, non-governmental organisations and other stakeholders, many large corporations have adopted a variety of carbon and energy management practices, taken action to reduce their emissions and set targets to reduce their greenhouse gas emissions. Using the case of international retailers, this article examines whether, and under what conditions, non-state actors might be capable of assuming the governance roles that have historically been played by national governments. This article concludes that external governance pressures can, if they are aligned, robust and of sufficient duration, have a significant influence on internal governance processes and on corporate strategies and actions. However, the specific actions that are taken by companies – in particular those that require significant capital investments – are constrained by the ‘business case’. That is, companies will generally only invest capital in situations when there is a clear financial case (i.e. where the benefits outweigh the costs, when the rate of return meets or exceeds company targets) for action. That is, the extent to which external governance pressures can force companies to take action, in particular challenging or transformative actions that go beyond the boundaries of the business case, is not at all clear. This is particularly the case if the business case weakens, or if the opportunities for incremental change are exhausted. In that context, the power of non-state actors to force them to consider radical changes in their business processes and their use of energy therefore seems to be very limited

CSR and related terms in SME owner-managers' mental models in six European countries: national context matters

As a contribution to the emerging field of corporate social responsibility (CSR) cognition, this article reports on the findings of an exploratory study that compares SME owner–managers’ mental models with regard to CSR and related concepts across six European countries (Belgium, Italy, Norway, France, UK, Spain). Utilising Repertory Grid Technique, we found that the SME owner–managers’ mental models show a few commonalities as well as a number of differences across the different country samples. We interpret those differences by linking individual cognition to macro-environmental variables, such as language, national traditions and dissemination mechanisms. The results of our exploratory study show that nationality matters but that classifications of countries as found in the comparative capitalism literature do not exactly mirror national differences in CSR cognition and that these classifications need further differentiation. The findings from our study raise questions on the universality of cognition of academic management concepts and warn that promotion of responsible business practice should not rely on the use of unmediated US American management terminology

Symbolic character productions in the mousterian site of La Roche-Cotard in Langeais (Indre-et-Loire, France) and their geological context

Le site de La Roche-Cotard se trouve sur la rive droite de la vallée de la Loire à une vingtaine de kilomètres en aval de Tours. Le gisement, mis au jour en 1846, suite à l’extraction de matériaux, a été fouillé en 1912. Les recherches ont repris de 1975 à 1978, puis à partir de 2008.Les premières recherches, en 1975, permettent la découverte, devant l’entrée de la grotte, d’un lambeau de plage de Loire sur lequel les hommes de Néandertal ont allumé un feu, abandonné des pièces d’industrie lithique et une protofigurine, appelée par M. Lorblanchet « masque de La Roche-Cotard » (Marquet, Lorblanchet 2000, 2003). Un abri très bas est également découvert ; il contient un peu d’industrie lithique et un aménagement de blocs au sol.À partir de 2008, les nouvelles fouilles mettent au jour une petite grotte-abri comblée de sédiments, présentant également des indices d’occupation par l’homme de Néandertal. Elles poursuivent également le travail à l’intérieur de la cavité principale.L’examen approfondi des parois, effectué par J.-C. Marquet avec les appuis de M. Lorblanchet, P. Paillet et E. Man-Estier, permet de reconnaître quatre panneaux, trois de tracés digitaux et un de ponctuations. Ces traces sont visibles car il y a eu enlèvement de matière (au doigt ou à l’aide d’un instrument pouvant donner le même type de trace) sur la paroi de « craie tuffeau » (nom vernaculaire donné à cette roche) altérée, recouverte par un mince film de limon argileux. Sur l’un des panneaux, on observe une figuration circulaire, sur les deux autres des ensembles de tracés parallèles, organisés et rythmés. Quatre taches ocre rouge ont été repérées.Les études géométrique, granulométrique et morphologique des dépôts, ainsi que les datations des os par le 14C et des sédiments par la méthode OSL, montrent qu’après l’occupation par les hommes de Néandertal, l’entrée de la cavité a été occultée, pour n’être réouverte qu’en 1846 (voire seulement en 1912).Aucune datation directe des tracés n’est possible. Cependant, leur altération locale, les datations des os et des sédiments situés juste devant les panneaux et naturellement celle de la fermeture de l’entrée de la grotte après l’occupation par Néandertal autorisent à exclure un âge récent.Masque, tracés et traces de peinture dans une cavité inaccessible à Homo sapiens jusqu’en 1846, géométrie des dépôts, confèrent au site de La Roche-Cotard un très grand intérêt au moment où est sérieusement reconsidérée la question des compétences de l’homme de Néandertal.La Roche-Cotard site is located on the right side of the Loire valley, about 20 km down-river from Tours. The site, uncovered in 1846, following the extraction of materials, was excavated in 1912. Research was taken up again from 1975 to 1978, then from 2008 onwards.The first reprise of excavations in 1975 allowed for the discovery, at the entrance of a cave on a beach of the Loire on which Neanderthals have made fire, of stone tools and a proto-figurine that was named by M. Lorblanchet the “Mask of La Roche-Cotard” (Marquet & Lorblanchet, 2000, 2003). A very low shelter was also discovered, which contains some stone tools and a layout of blocks on the ground.The second reprise of excavations in 2008 allowed for the discovery of a small cave-shelter filled with sediments, presenting also indications of occupation by Neanderthals; but above all it enabled further work on the inside of the main cavity.Deeper examination of the cave walls, carried out by J.-C. Marquet, with the support of M. Lorblanchet, P. Paillet and E. Man-Estier, allowed for the recognition of three panels of finger flutings and a panel of point-marks. These marks are visible due to the removal of matter (by hand or with the aid of an instrument giving the same type of marks) on the weathered « tuffeau chalk » wall, recovered by a thin film of silty clay. On one of the panels can be observed a circular representation, on the other two, sets of parallel markings, organized and rhythmic. Four red ochre stains were also discovered.Geometric, granulometric and morphologic studies of the deposits, as well as 14C datings of bones and datings of sediments through the OSL method, show that following the occupation by Neanderthals, the entrance to the cave was blotted out and was only reopened in 1846, or even in 1912.No direct dating of the markings is possible. However, their localized weathering, datings of bones and sediments found just in front of the panels and naturally the closure of the cave’s entrance after the occupation by Neanderthals allows us to rule out the possibility of a recent age.Mask, markings and traces of painting in a cavity inaccessible to Homo sapiens until 1846, geometry of deposits, all add to the great interest in La Roche-Cotard site, at the very moment when we reconsider seriously the question of the competences of the Neanderthals