Île de Pâques | EPFL Graph Search

Lîle de Pâques, en rapanui Rapa Nui (« la grande Rapa », en référence à Rapa iti, « la petite Rapa »), en espagnol Isla de Pascua, est une île du Chili, de forme triangulaire, d'environ dans sa plus grande dimension, couvre , connue pour ses statues monumentales (les moaï) et son écriture océanienne unique (le rongorongo). Isolée dans le Sud-Est de l'océan Pacifique, elle se trouve à à l'est de l'île Pitcairn, site habité le plus proche, éloignement qui en fait le lieu habité le plus isolé du monde au même titre que l'archipel Tristan da Cunha. Elle est aussi éloignée de , à l'ouest-nord-ouest, de l'île Alejandro Selkirk, dans l'archipel Juan Fernández, ou encore à à l'ouest des côtes chiliennes de la région du Biobío (Concepción) et à à l'est-sud-est de Tahiti. Cette île est célèbre pour les vestiges mégalithiques de la civilisation autochtone : le patrimoine archéologique comprend statues de basalte, les moaï, de de hauteur moyenne, et près de empierrées supportant ces st

Benefits of a Diversified Energy Mix for Islanded Systems

Christophe Ballif, Lionel Benjamin Bloch, Marine Dominique C. Cauz, Laure-Emmanuelle Perret Aebi, Christian Rod

Achieving energy self-sufficiency is a major challenge for remote areas, especially islands. Various technologies have recently been developed to exploit renewable resources in such areas in order to reduce dependency on fossil fuels. This work focuses on the situation of Easter Island, a representative example of a remote area, and explores the pros and cons of three fully renewable energy mixes used to meet local requirements. This investigation reveals that, while a classic photovoltaic/battery combination allows demands to be met, the installations need to be oversized, leading to a 73% loss in the total energy produced. By adding alternative energy production sources such as wind turbines and pyrolysis, as well as alternative storage systems such as hydrogen-based storage, the energy loss is divided by a factor of 5. This more diverse energy mix enables a reasonable electricity price of 0.18 €/kWh, which is comparable to the current local prices. This work reinforces the importance of complementary energy production and storage systems to efficiently meet the energy requirements of islands.

2020

Race For Water Odyssey: Quantitative and Qualitative Assessment of Marine Plastic Debris Collected on Shorelines

Luiz Felippe De Alencastro, Florian Faure, Clément Levasseur, Frédéric Sciacca

With the help of the local people we met during the course of the 2015 Odyssey, the main objective, obtaining a collection of comparable data about marine plastic pollution using the NOAA internationally recognized protocol, has been achieved. It cannot be sufficiently stressed that not one of the 30 sampled shorelines during this worldwide journey was free from marine plastic debris. As for the recent identification of plastic debris in the Arctic and Antarctic areas, this observation confirms that plastic contamination in the oceans is ubiquitous. Whether in terms of macrodebris (>2.5 cm) or microplastics (< 5 mm) concentrations, Hawaii constitutes by far the 2015 Odyssey’s most notable hotspot. The highest macrodebris concentration registered at Kamilo Point in Hawaii (more than 3,500 macrodebris per 100 m2) was almost ten times greater than the second hotspot of the 2015 Odyssey, Pago Bay (372) on Guam Island in the Mariana Archipelago. Hawaii also constitutes the highest microplastics concentration hotspot with more than 94,000 particles per m2 collected once again at Kamilo Point again. For comparison, the second highest concentration, Ovahe beach on Easter Island, revealed more than 24,000 microparticles per m2. Unfortunately, based on their locations, marine macrodebris concentrations can suffer bias due to direct waste disposal (intentional or accidental) of tourists and/or local residents, and also because of the consecutive shoreline clean-up campaigns. Therefore, microplastic concentrations are a more reliable indicator to establish a comparison between study sites. On that basis, Northeast Pacific islands – especially the Hawaiian Archipelago – experience the most significant marine debris accumulation, followed by those of the South Pacific, Northeast Atlantic, Indian, Northwest Atlantic, Northeast Pacific and South Atlantic Oceans respectively. The macrodebris and microplastic average concentrations are summarized below in Figure 1. In qualitative terms, the hard plastic fragments category largely dominates the macroplastics content except for Palau and Chagos (BIOT). Other dominant categories are plastic foams, bottles and caps, and fishing lines and ropes. Foams were particularly predominant in Chagos, while bottles and caps constituted almost 70% of macrodebris in Palau. Besides, significantly higher bottle and cap concentrations were evidenced near the Asian continent. Fishing lines and ropes stood out particularly in Bermuda. Microplastic concentrations confirmed these trends with more than 80% of hard plastic fragments on every stopover, except Easter Island and Tristan da Cunha (around 60%). More specifically, Easter Island showed a significant concentration of pellets, while Bermuda confirmed a strong presence of fishing lines among the microparticles. Lastly, the polymer analysis of the hard plastic fragments ranging from 1 mm to 2.5 cm revealed the prevalence of polyethylene (PE) throughout all of the study sites, except for Tristan da Cunha where polypropylene (PP) dominated. Hawaii, Mariana, Palau and Mascarene also showed significant PP concentrations (between 31 to 47% of items). Other kinds of polymer such as EVA and PMP, have been evidenced especially on Tristan da Cunha, but also on the Azores and Mariana.

Race for Water Foundation2016

Poinçonnement des ponts-dalles précontraints

Thibault Clément, Miguel Fernández Ruiz, Aurelio Muttoni

Dans le domaine des ponts, les ponts-dalles appuyés sur de colonnes sont très souvent employés pour franchir des portées petites ou moyennes. Or dès que les portées commencent à devenir importantes, au-delà de 15 à 20 m environ, le recours à la précontrainte s’impose afin de contrôler les déformations et l’état de fissuration de l’ouvrage. Par rapport à la résistance au poinçonnement de ces structures, souvent étant l’état limite ultime déterminant de ces structures, la précontrainte induit généralement dans les régions d'appuis des efforts normaux de compression, ainsi que des moments et d’efforts tranchants dans le sens opposé à celui des charges permanentes. Ces actions ont une influence favorable sur la résistance au poinçonnement.

Schweiz. Verband der Strassen und Verkehrsfachleute (VSS)2013

Race For Water Odyssey: Quantitative and Qualitative Assessment of Marine Plastic Debris Collected on Shorelines

Luiz Felippe De Alencastro, Florian Faure, Clément Levasseur, Frédéric Sciacca

Race for Water Foundation2016