Afrique du Sud

Résumé

LAfrique du Sud, en forme longue la république d'Afrique du Sud, est un pays d'Afrique australe. Sa capitale administrative est Pretoria. Il est frontalier à l'ouest-nord-ouest avec la Namibie, au nord et au nord-nord-est avec le Botswana, au nord-est avec le Zimbabwe, et à l'est-nord-est avec le Mozambique et l'Eswatini. Le Lesotho est pour sa part un État enclavé dans le territoire sud-africain. L'Afrique du Sud compte d’habitants en 2018 répartis en 80,2 % de Noirs, 8,8 % de Coloureds, 8,4 % de Blancs et 2,5 % d'asiatiques (sous-continent indien). Nation aux phénotypes très variés, l'Afrique du Sud est ainsi en Afrique le pays présentant la plus grande portion de populations dites coloureds, blanches et Asiatiques. Elle est souvent appelée « nation arc-en-ciel », notion inventée par l'archevêque anglican et militant des droits de l'homme sud-africain Desmond Tutu pour désigner la diversité de la nation sud-africaine et qui a remplacé le concept de société p

Source officielle

https://fr.wikipedia.org/wiki/Afrique_du_Sud

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Hydrogen Intensity and Real-Time Analysis Experiment: 256-element array status and overview

Jean-Paul Richard Kneib, Martin Kunz, Emma Elizabeth Tolley, Zeyu Zhang

The Hydrogen Intensity and Real-time Analysis Experiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the South African Radio Astronomy Observatory Square Kilometer Array site in South Africa. Each of the 6 m, f/0.23 dishes will be instrumented with dual-polarization feeds operating over a frequency range of 400 to 800 MHz. Through intensity mapping of the 21 cm emission line of neutral hydrogen, HIRAX will provide a cosmological survey of the distribution of large-scale structure over the redshift range of 0.775 < z < 2.55 over similar to 15,000 square degrees of the southern sky. The statistical power of such a survey is sufficient to produce similar to 7% constraints on the dark energy equation of state parameter when combined with measurements from the Planck satellite. Additionally, HIRAX will provide a highly competitive platform for radio transient and HI absorber science while enabling a multitude of cross-correlation studies. We describe the science goals of the experiment, overview of the design and status of the subcomponents of the telescope system, and describe the expected performance of the initial 256-element array as well as the planned future expansion to the final, 1024-element array. (C) 2022 Society of Photo Optical Instrumentation Engineers (SPIE)

SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS2022

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Fonctionnement et gestion des aquifères alluviaux de haute altitude

The Haute Sarine alpine valley is located at an average altitude of approximately 1'000 to 1'200 masl. It was formed in its southern part up to the area of Gstaad to the favour of a typical North-South tectonic fault according to the main structures of the Préalpes, then followed normal fault striking East-West to end up on the rock bolt of the Vanel hill. The late and postglacial period was marked by the deposition of glaciolacustrines, glaciofluviatile and flurecent fluviatile sediments which have filled the ice free valley bottom probably starting from a period older than the Bölling-Alleröd interstadial. The depth of this overdeepening varies between 20 and more than 50 m of depth. Drillings which we carried out could document series of typical glaciolacustrine sediments. The implementation of several geophysical survey methods (resistivity, seismic refraction and reflexion, well logs and pumping tests) enabled us to analyse several sources of information which we confronted between them in order to produce a 3D model of the quaternary deposits and their hydrological properties. Most of these sediments are relatively quite permeable and build a free groundwater reservoir that we subdivided into 3 parts. The basin of Gsteig in the south is closed, the valley having been blocked by a massive landslide that probably occurred in several successive stages starting at the first climate improvements. The second part, the basin of Feutersoey has not been retained as a potential important hydrogeologic resource based on our preliminary investigations. The last basin, that of Gstaad-Saanen is the largest and thickest. It is also in this basin that most of the tourist and industrial activities of the area are concentrated. The observation network was established in order to characterize the groundwater flows enabling us at the same time to carry out piezometric measurements and chemical as well as and bacteriological analyses. We also carried out a δ18O isotope analysis campaign. The whole of these approaches highlighted the particular characteristics of the groundwater recharge. The groundwater system is mainly fed by the Sarine and the precipitations infiltration. We also located an underground karstic feeding of evaporitic type. We finally propose a groundwater management and protection concept adapted to the particular situation of the Sarine alluvial mountain aquifer system on both quantitative and qualitative aspects. The high altitude alpine groundwater catchment areas such as the Haute Sarine represent as a whole a quality resource, with high potentials yet to be defined on a larger scale, for example by applying numerical modeling and by organizing and maintaining long term observation networks that will enable us to define a sustainable groundwater resource management within the alpine area.

EPFL2000

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Although rapid population growth will give them a significant weight in global urbanization by the middle of the century, African cities remain little known. As a result, they are essentially outside the global intellectual arena on urban issues, which justifies the need for more productive quantitative and qualitive research. This article is a contribution to the achievement of this objective. It aims to empirically analyze the evolution of urban planning studies in Africa, by identifying the trends that characterize existing scientific production. The paper thus provides a clear picture of existing scientific production on urban planning studies in Africa through a systematic review of the literature over the last four decades. The study is organized around four levels of analysis: temporal analysis, thematic analysis, methodological analysis, and geographical analysis. These analyzes are based on data drawn from 268 rigorously selected journal articles. Thus, the study highlights major trends in the evolution of urban planning studies in Africa. It specifically shows the slow quantitative evolution of the production of scientific journal articles, which should be strongly accelerated, the overwhelming predominance of South African and Anglo-American research institutions in this area, as well as the link between research main topics and methodological approaches on the one hand, and the realities on the ground on the other. The study finally discusses the reinvention of research on African cities in accordance with its specific context, through methodological tailoring and innovations. It also highlights the internationality of the research results with the low output of African institutions, and the effects of language barriers. Some possible solutions to the challenges highlighted by the study are provided in conclusion.

2020

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Fonctionnement et gestion des aquifères alluviaux de haute altitude

EPFL2000