Type

Database

Creator

Date

Thumbnail

Search results

64 records were found.

Malgré les problèmes que pose la délinquance juvénile au Sénégal, les réponses des décideurs semblent inefficaces, surtout pour les filles déviantes. Ainsi, l’objectif de notre étude est de déterminer les caractéristiques familiales, scolaires et des amis des adolescentes judiciarisées à Dakar en les comparant à celles de Montréal. Les enquêtes se sont déroulées à Dakar sur trente adolescentes interrogées avec un instrument adapté du MASPAQ. Les similitudes entre les échantillons concernent l’âge moyen et le statut judiciaire quasi-identiques, le milieu socio-économique défavorisé et la structure familiale en majorité monoparentale matricentrique. Les autres résultats concernent surtout les liens sociaux plus forts chez les dakaroises alors que l’activité marginale est plus importante chez les montréalaises. Les liens sociaux des dakar...
This paper explores our ability to map the extent of large floods in near real time using coarse resolution C-band radar remote sensing. The European Space Agency’s advanced synthetic aperture radar aboard the Envisat satellite, operating in global monitoring mode (GM), is considered for Australia due to its high temporal frequency, comprehensive coverage and ease of acquisition. Challenges are identified which relate both to the use of radar generally, and also in particular to GM data, in the demarcation of water and land. In Australia, the need for a better understanding of the expected backscatter response from inundated areas in tropical savanna, which covers one third of its landmass, is targeted. The backscatter responses to two large flood events in the tropical savanna of northern Australia are investigated, showing markedly d...
Southeast Australia is currently experiencing a severe multi-year drought caused by a significant rainfall deficit and record high temperatures. The vast system of lakes that occupy the Corangamite Catchment is affected by this drought with a significant drop in the water levels and a decline in water quality. Physical and chemical hydrological data are used in combination with remote sensing techniques to study (i) how drought conditions affect groundwater and lakes interaction, and (ii) how this, in turn, impacts on lakes quality. The data record spans over 14 years, and includes a pre-drought (1992- 1996) and drought (1997-2006) period. The drought has altered interaction of lakes with the groundwater system. By 2006, 10 of the 28 monitored lakes have changed from groundwater throughflow or discharge lakes to recharge lakes that are...
As in most of West and Central Africa, the rainfall regime over the Lake Chad basin has changed around 1970 from a humid to a dry period. This rainfall change is the cause of the changes in Lake Chad area. Lake Chad being a closed lake, its surface area has changed according to the lower water inputs from the watershed. The lake, which covered about 22000 km2 in the 1960s, is now divided into different individual seasonal or perennial lake basins. In the northern basin of the lake, the seasonally inundated area has varied from zero in dry years (as in 1985, 1987) to about 6000 km2 (1979, 1989 and 1999-2001). In the southern basin of the lake, the between year variability has markedly decreased. The changes in lake area and in the links between the lake basins have been modelled as a function of the river inputs. Satellite estimates o...
This paper examines the relationship of C-band radar backscatter from the Advanced Synthetic Aperture Radar on board the ENVISAT satellite with the local angle of incidence, whose influence on the received signal is significant, particularly in the modes of sensor operation that use the full swath of the orbit track. Linear regression is carried out for each pixel throughout a large time series of radar data over the whole of the state of Queensland, Australia, and at Great Salt Lake, Utah, USA. In the first case, the resultant coefficients are analysed for correlation against various parameters, with regolith showing the highest correlation. Class separability analysis shows the potential to use the resultant coefficients as a supplement to absolute threshold values in order to distinguish between classes of vegetation and/or ...
South-East Australia is currently experiencing a severe multi-year drought (not, vert, similar11 years of below long-term average rainfall between 1997 and 2008). To refine our understanding of the impacts of such climate stresses on lake systems, and to overcome the limitations of insufficient field based measurements, lake water levels and lake salinity values are combined with remote sensing data (Landsat-5TM) to analyse water and solute budgets for two large lakes in the Corangamite catchment. For these two lakes, data during pre-drought (1992–1996) and drought (1997–2006) periods are used to investigate the impact of the drought on lake and groundwater interaction and possible changes in mechanisms controlling the salinity of the lakes. For 26 other lakes in the Corangamite catchment with limited or no on-ground data, water and ev...
A simple and robust water balance model is developed for Lake Chad that simulates water levels and inundated areas according to the inflow (river discharge, precipitation) and outflow to the lake (evaporation, infiltration). In the model, Lake Chad is represented by three reservoirs (the southern basin connected to the north basin and the archipelago), whose water levels can be different during periods of low inputs (current situation) or similar during periods of surplus (pre-1973 situation). In accordance with field observations, the north basin is represented by a soil reservoir that must be filled before water can appear on the surface. The model uses seven optimized parameters: infiltration rate; depth of the soil reservoir; four exchange parameters between reservoirs; and the bottom level of the archipelago. It is calibrated on t...
Want to know more?If you want to know more about this cutting edge product, or schedule a demonstration on your own organisation, please feel free to contact us or read the available documentation at http://www.keep.pt/produtos/retrievo/?lang=en