10,098 research outputs found
Irrigated rice area estimation using remote sensing techniques: Project's proposal and preliminary results
The development of a methodology for annual estimates of irrigated rice crop in the State of Rio Grande do Sul, Brazil, using remote sensing techniques is proposed. The project involves interpretation, digital analysis, and sampling techniques of LANDSAT imagery. Results are discussed from a preliminary phase for identifying and evaluating irrigated rice crop areas in four counties of the State, for the crop year 1982/1983. This first phase involved just visual interpretation techniques of MSS/LANDSAT images
Fracturing highly disordered materials
We investigate the role of disorder on the fracturing process of
heterogeneous materials by means of a two-dimensional fuse network model. Our
results in the extreme disorder limit reveal that the backbone of the fracture
at collapse, namely the subset of the largest fracture that effectively halts
the global current, has a fractal dimension of . This exponent
value is compatible with the universality class of several other physical
models, including optimal paths under strong disorder, disordered polymers,
watersheds and optimal path cracks on uncorrelated substrates, hulls of
explosive percolation clusters, and strands of invasion percolation fronts.
Moreover, we find that the fractal dimension of the largest fracture under
extreme disorder, , is outside the statistical error bar of
standard percolation. This discrepancy is due to the appearance of trapped
regions or cavities of all sizes that remain intact till the entire collapse of
the fuse network, but are always accessible in the case of standard
percolation. Finally, we quantify the role of disorder on the structure of the
largest cluster, as well as on the backbone of the fracture, in terms of a
distinctive transition from weak to strong disorder characterized by a new
crossover exponent.Comment: 5 pages, 4 figure
Sampling system for wheat (Triticum aestivum L) area estimation using digital LANDSAT MSS data and aerial photographs
A procedure to estimate wheat (Triticum aestivum L) area using sampling technique based on aerial photographs and digital LANDSAT MSS data is developed. Aerial photographs covering 720 square km are visually analyzed. To estimate wheat area, a regression approach is applied using different sample sizes and various sampling units. As the size of sampling unit decreased, the percentage of sampled area required to obtain similar estimation performance also decreased. The lowest percentage of the area sampled for wheat estimation with relatively high precision and accuracy through regression estimation is 13.90% using 10 square km as the sampling unit. Wheat area estimation using only aerial photographs is less precise and accurate than those obtained by regression estimation
Integrated pests management on mangoes at the São Francisco river Valley, Brazil.
Aiming at a rational pest control for this crop, sampling strategies for monitoring and action threshold for the main mango pests were determined based on field and laboratory observations, national and international literature reviews, and tests/adaptations of IPM strategies already in use in other countries
- …