Les concessions à charge de remblais en Polynésie française ou les politiques face à la privatisation

Les concessions dites « à charge de remblais » autorisées par les pouvoirs publics permettent aux collectivités et aux particuliers d’utiliser l’espace maritime littoral en le remblayant. Les réglementations d’attribution de ces concessions sont traitées depuis les premiers textes et il n’y a plus actuellement que des dérogations. Les remblais sauvages et donc illicite au regard de la loi peuvent néanmoins être régularisés. Malgré des progrès en vue de mieux gérer ce problème de la privatisation du littoral, il est clair que les faits démontrent l’absence de volonté politique pour faire respecter l’inaliénabilité du domaine maritime. Les concessions bien que temporaires sont en fait définitives et le droit de passage de trois mètres de largeur sur la plage n’est jamais exigé. Les conséquences de ces remblais sont traitées dans le texte. Entre électoralisme et intérêt public, le pouvoir politique n’a pas encore eu le courage de faire appliquer la loi.Concessions, called ‘backfill load’, that are authorized by the authorities allow communities and individuals to use backfilled maritime areas for the public interest, or for the interests of riparian owners of the lagoon in order to enlarge their land. These concessions are issued according to regulations that have evolved in recent decades. There are currently no more concessions permitted except under special exemptions. Wild embankments that are therefore illegal in view of the law may nevertheless be regularized. Despite progress towards better management of the coastal privatization problem, there is clear evidence demonstrating a lack of political will to respect the inalienability of the maritime domain. The temporary concessions that are effectively final have never ensured the right of passage - three meters large - to the beach. Between electioneering schedules and public interest, political powers have lacked the courage to enforce these laws in spite of consequences of these embankments

Asynchronous decentralized accelerated stochastic gradient descent

In this work, we introduce an asynchronous decentralized accelerated stochastic gradient descent type of method for decentralized stochastic optimization, considering communication and synchronization are the major bottlenecks. We establish $\mathcal{O}(1/\epsilon)$ (resp., $\mathcal{O}(1/\sqrt{\epsilon})$) communication complexity and $\mathcal{O}(1/\epsilon^2)$ (resp., $\mathcal{O}(1/\epsilon)$) sampling complexity for solving general convex (resp., strongly convex) problems

Coherent Control of Isotope Separation in HD+ Photodissociation by Strong Fields

The photodissociation of the HD+ molecular ion in intense short- pulsed linearly polarized laser fields is studied using a time- dependent wave-packet approach where molecular rotation is fully included. We show that applying a coherent superposition of the fundamental radiation with its second harmonic can lead to asymmetries in the fragment angular distributions, with significant differences between the hydrogen and deuterium distributions in the long wavelength domain where the permanent dipole is most efficient. This effect is used to induce an appreciable isotope separation.Comment: Physical Review Letters, 1995 (in press). 4 pages in revtex format, 3 uuencoded figures. Full postcript version available at: http://chemphys.weizmann.ac.il/~charron/prl.ps or ftp://scipion.ppm.u-psud.fr/coherent.control/prl.p

Les modifications de la ligne de rivage dans les îles de la Société (Polynésie française) : un indicateur des pressions anthropiques en zone côtière

Dans les îles océaniques tropicales, la ligne de rivage naturelle correspond à une plage, à une falaise, à des galets ou rochers, à des zones de végétation basse ou haute. Le développement économique des îles et la croissance démographique de leurs populations ont pour conséquence une artificialisation de cette ligne de rivage pour utilité publique ou par des riverains qui cherchent à se protéger des actions de la mer, mais aussi à étendre leur emprise sur le lagon. Plusieurs îles de la Société ont fait l’objet d’une étude quantifiée de leurs lignes de rivage afin de déterminer leurs degrés d’anthropisation. Dans plusieurs d’entre elles, cette artificialisation est voisine ou dépasse 40 % du linéaire côtier. Elle est un bon indicateur des pressions anthropiques en zone côtière. L’évolution de cette tendance a pu être montrée à Moorea par des études menées à quinze ans d’intervalle. Des actions sont entreprises et doivent être développées pour mettre fin cette artificialisation aux conséquences néfastes pour l’environnement.In tropical oceanic islands, coastlines are usually either sandy, rocky or have cliffs, - or may have low or high vegetation. Developing island states with increasing human populations are modifying coastlines to form artificial or modified structures for public utility or by lagoonside residents hoping to protect their property from the sea or to gain extra land on the margins of the lagoon. Several French Society Islands have been examined to establish the extent of this coastal modification. In most of them, human activities have altered 40% or more of the coastline, and the percentage of modification is a good indicator of the human pressure  on the shoreline. The evolution of coastal modification has been documented on Moorea island during two field studies separated by a fifteen year period. Specific activities need to be developed and deployed to stop coastal modifications that result in damage to the environment

Shared Memory Pipelined Parareal

For the parallel-in-time integration method Parareal, pipelining can be used to hide some of the cost of the serial correction step and improve its efficiency. The paper introduces an OpenMP implementation of pipelined Parareal and compares it to a standard MPI-based variant. Both versions yield almost identical runtimes, but, depending on the compiler, the OpenMP variant consumes about 7% less energy and has a significantly smaller memory footprint. However, its higher implementation complexity might make it difficult to use in legacy codes and in combination with spatial parallelisation

Restauration d’une zone corallienne dégradée et implantation d'un jardin corallien à Bora Bora, Polynésie française

The restoration of coral reef habitats by coral transplantation is a hot topic in the news toda y due to the accelerating degradation of the coral reef ecosystem all over the world. There is much discussion about research programs for the transplantation of corals and about ac tuai field realizations and the motivation for coral reef restoration. But the implementation of such a project depends on a social request considering local or global cultural and economical situations . Projects are very costly and only applicable when important economical interests are involved such as the fight against erosion or tourism development. In the lagoon of Bora Bora in French Polynesia, a fringing zone, degraded by coral sand extractions, led to an erosion of the coast damaging local private property in a sec tor weil oriented toward tourism activities. The reconstruction of this degraded site (20,000 sq.m) required physically filling up holes, implementation of spurs, and putting into place artificial concrete structures to promote the natural colonization of corals and other reef organisms in order to reduce swell impacts. The creation of a coral reef garden was also part of the project with the transplantation of corals collected in the vicinity. Fifty groups of three different types of concrete blocks have been set out on the site and six others constitute the coral reef garden on which 311 coral colonies are transplanted. Two and a half years after this restoration, the project proved to be successful. The coral reef garden flourished; it showed much diversification and little mortality among the corals colonies, and the natural colonization on the concrete substrate was teeming with corals, seaurchins, mollusks, and fishes. But thirty months later, an exceptionally violent meteorological and oceanographical situation led to a catastrophic event which caused many transplanted coral as weil as natural colonies in the vicinity to be killed off. Lagoon waters temperatures were recorded as high as 34°C and of the 311 transplanted coral colonies only 119 survived, most of them bleached or partly dead. All colonies of the genus Acropora died, while those of the genus Psammocora survived. Methods for restoration and creation of coral reef gardens are highly controlled but they cannot always escape such catastrophic events such as the one in Bora Bora in December 2001. Physical restoration was successful but the biological transplantation of corals failed. Thus, when we consider how expansive a restoration project is, it is essential to conduct an historical inquiry on a potential coral transplantation site before implementing any projectLes problèmes de restauration de zones coralliennes, avec transplantations de coraux, sont à l'ordre du jour compte tenu de la dégradation accélérée de cet écosystème à la surface de la planète. Les motivations des recherches dans ce domaine et celles des projets de restauration sur le terrain sont évoquées. Elles répondent à une demande sociale exprimée en fonction de considérations culturelles et économiques. Les projets sont coûteux et ne peuvent concerner que des cas très limités avec des intérêts économiques importants (lutte contre l' érosion, développement du tourisme). À Bora Bora, en Polynésie française, une zone lagonaire frangeante, dégradée par des extractions de sédiment corallien, provoquait une érosion littorale. Son ré-aménagement comporte une restauration physique des lieux (comblement des fosses, réalisation d'épis...) et la mise en place de structures artificielles pour permettre la colonisation naturelle de coraux et autres organismes, afin de jouer le rôle de brise houle. Ce projet s'accompagne de la création d'un jardin corallien avec structures artificielles sur lesquelles sont fixés des transplants de coraux. Deux ans et demi après la fin des travaux, le jardin corallien affiche une communauté corallienne florissante et diversifiée avec très peu de mortalité des colonies transplantées, une croissance normale et la colonisation naturelle de coraux et d'autres organismes des récifs coralliens (oursins, mollusques, poissons). Cependant, un événement météorologique et océanographique exceptionnel, trente mois après la création du jardin corallien, a entraîné une forte mortalité des coraux transplantés comme ceux naturellement en place dans le secteur. Si les techniques nécessaires à la restauration de zones dégradées et à la création de jardins coralliens sont totalement maîtrisées, ces réalisations n'échappent pas aux variations temporelles des conditions de milieu qui peuvent être catastrophiques. Dans un tel cas, comme à Bora Bora en décembre 2001, la restauration physique reste à l'actif de l'opération, mais l'échec de la restauration biologique est à noter. Une étude historique, sur plusieurs décennies, des zones sujettes à des mortalités exceptionnelles s'impose donc avant tout choix de sites pour la réalisation de jardins coralliens dont les coûts sont très élevé

Semiclassical ionization dynamics of the hydrogen molecular ion in an electric field of arbitrary orientation

Quasi-static models of barrier suppression have played a major role in our understanding of the ionization of atoms and molecules in strong laser fields. Despite their success, in the case of diatomic molecules these studies have so far been restricted to fields aligned with the molecular axis. In this paper we investigate the locations and heights of the potential barriers in the hydrogen molecular ion in an electric field of arbitrary orientation. We find that the barriers undergo bifurcations as the external field strength and direction are varied. This phenomenon represents an unexpected level of intricacy even on this most elementary level of the dynamics. We describe the dynamics of tunnelling ionization through the barriers semiclassically and use our results to shed new light on the success of a recent theory of molecular tunnelling ionization as well as earlier theories that restrict the electric field to be aligned with the molecular axis

The listening talker: A review of human and algorithmic context-induced modifications of speech

International audienceSpeech output technology is finding widespread application, including in scenarios where intelligibility might be compromised - at least for some listeners - by adverse conditions. Unlike most current algorithms, talkers continually adapt their speech patterns as a response to the immediate context of spoken communication, where the type of interlocutor and the environment are the dominant situational factors influencing speech production. Observations of talker behaviour can motivate the design of more robust speech output algorithms. Starting with a listener-oriented categorisation of possible goals for speech modification, this review article summarises the extensive set of behavioural findings related to human speech modification, identifies which factors appear to be beneficial, and goes on to examine previous computational attempts to improve intelligibility in noise. The review concludes by tabulating 46 speech modifications, many of which have yet to be perceptually or algorithmically evaluated. Consequently, the review provides a roadmap for future work in improving the robustness of speech output

A quantitative theory-versus-experiment comparison for the intense laser dissociation of H2+

A detailed theory-versus-experiment comparison is worked out for H$_2^+$ intense laser dissociation, based on angularly resolved photodissociation spectra recently recorded in H.Figger's group. As opposite to other experimental setups, it is an electric discharge (and not an optical excitation) that prepares the molecular ion, with the advantage for the theoretical approach, to neglect without lost of accuracy, the otherwise important ionization-dissociation competition. Abel transformation relates the dissociation probability starting from a single ro-vibrational state, to the probability of observing a hydrogen atom at a given pixel of the detector plate. Some statistics on initial ro-vibrational distributions, together with a spatial averaging over laser focus area, lead to photofragments kinetic spectra, with well separated peaks attributed to single vibrational levels. An excellent theory-versus-experiment agreement is reached not only for the kinetic spectra, but also for the angular distributions of fragments originating from two different vibrational levels resulting into more or less alignment. Some characteristic features can be interpreted in terms of basic mechanisms such as bond softening or vibrational trapping.Comment: submitted to PRA on 21.05.200

Numerical simulation of skin transport using Parareal

In silico investigation of skin permeation is an important but also computationally demanding problem. To resolve all scales involved in full detail will not only require exascale computing capacities but also suitable parallel algorithms. This article investigates the applicability of the time-parallel Parareal algorithm to a brick and mortar setup, a precursory problem to skin permeation. The C++ library Lib4PrM implementing Parareal is combined with the UG4 simulation framework, which provides the spatial discretization and parallelization. The combination’s performance is studied with respect to convergence and speedup. It is confirmed that anisotropies in the domain and jumps in diffusion coefficients only have a minor impact on Parareal’s convergence. The influence of load imbalances in time due to differences in number of iterations required by the spatial solver as well as spatio-temporal weak scaling is discussed