Testing a high-resolution satellite interpretation technique for crop area monitoring in developing countries

District-level crop area (CA) is a highly uncertain term in food production equations, which are used to allocate food aid and implement appropriate food security initiatives. Remote sensing studies typically overestimate CA and production, as subsistence plots are exaggerated at coarser resolution, which leads to overoptimistic food reports. In this study, medium-resolution (MR) Landsat 7 Enhanced Thematic Mapper Plus (ETM+) images were manually classified for Niger and corrected using CA estimates derived from high-resolution (HR) sample image, topographic and socioeconomic data. A logistic model with smoothing splines was used to compute the block-average (0.1°) probability of an area being cropped. Livelihood zones and elevation explained 75% of the deviance in CA, while MR did not add explanatory power. The model overestimates CA when compared to the national inventory, possibly because of temporal changes in intercropping and the exclusion of some staple crops in the national inventory.     

Relevant parameters involved in tribocharging of powders during dilute phase pneumatic transport

This work presents the results of an experimental study carried out on the tribo-charging of fine glass particles during their pneumatic conveying. The effect of several parameters such as the chemical nature of the transport pipe, the particles mean size, the solids flow rate, the air velocity and the relative humidity (RH) was examined. Experiments were carried out using several batches of monodisperse glass particles with mean particle sizes ranging from 75 μm to 500 μm. Both spherical and angular particles were used. Powders were conveyed through two types of pipe materials (Teflon and Nylon) at dilute loadings and varying relative humidities of air (0-90%). The total charge of conveyed powder was measured using a terminal Faraday cage. Furthermore, a series of four Faraday cages was used to measure the charge transfer between the wall and particles along the flow path. Greater electrostatic effects were observed for larger particles, higher air velocities, higher solids flowrate and lower RH.A simple model of charge transfer was also established in order to describe the time evolution of charges on the particles and the wall. Results showed that the tribocharging rate can be conveniently represented by an exponential-deceleration model.