Circuit model for diffuse multipath and electromagnetic absorption prediction in rooms

We present a room electromagnetics-based theory which primarily models the diffuse multipath components (DMC) power density with a simple circuit model, and afterwards includes the line-of-sight (LOS) component to predict the total exposure in a realistic environment. Given a human absorption cross section (ACS) and its location from a transmitter (Tx), the average whole-body specific absorption rate (SAR(wb)) can be determined by the proposed circuit model for ultra-wideband (UWB) and wireless local area network (WLAN) systems. The SAR(wb) in humans in a realistic office environment for both UWB and WLAN systems is investigated as part of application. The theory is simulated with the Advanced Design System (ADS) software, and excellent agreement between theoretical and simulated values are obtained in terms of relative errors (<2%). The model may be very useful for SAR(wb) prediction in realistic complex indoor environments

The DMC contribution in the human absorption in an indoor environment

Room electromagnetics theory is applied to determine the influence of the diffuse multipath components (DMC) in the human specific absorption rate at 2.8 GHz. The whole-body absorption is determined for an exposure to a Line Of Sight (LOS) component plus the DMC. Both experimental and numerical results show that the contribution of the DMC in the whole-body absorption can not be neglected. The whole-body specific absorption rate (SAR) may be due up to 90% to the DMC in an indoor environment

The possibility of a rice green revolution in large-scale irrigation schemes in Sub-Saharan Africa

This paper investigates the potential of and constraints to a rice Green Revolution in Sub-Saharan Africa's large-scale irrigation schemes, using data from Uganda, Mozambique, Burkina Faso, Mali, Niger, and Senegal. The authors find that adequate irrigation, chemical fertilizer, and labor inputs are the key to high productivity. Chemical fertilizer is expensive in Uganda and Mozambique and is barely used. This is aggravated when water access is limited because of the complementarities between fertilizer and irrigation. Meanwhile, in the schemes located in four countries in West Africa's Sahel region, where water access is generally good and institutional support for chemical fertilizer exists, rice farmers achieve attractive yields. Some countries'wage rate is high and thus mechanization could be one solution for this constraint. Improvement of credit access also facilitates the purchase of expensive fertilizer or the employment of hired labor.Crops&Crop Management Systems,Irrigation and Drainage,Water Supply and Systems,Regional Economic Development,Water and Industry

Physical-statistical modeling of dynamic indoor power delay profiles

This paper presents a physical-statistical radio channel power delay profiles model for room-to-room communication systems combining the room electromagnetic theory for modeling deterministic channel components with a geometry-based stochastic channel model with time-variant statistics for modeling stochastic components. The deterministic channel component, i.e., mean power delay spectrum, is comprised of specularly reflected paths plus diffuse components due to scattering and diffraction. The specular components are modeled with a set Dirac function, whereas the diffuse components modeling approach is a room electromagnetic theory-based model. Dynamic indoor communication channels are characterized by a non-stationary time-and delay-fading process due to changes in the environment. We analyze and model the time-delay variability of channels using K-factor for small-scale variations and the t-location scale distribution parameters for large-scale variations. It turns out that these parameters cannot be assumed to be constant in time and delay. After modeling of time-delay variations of the first order statistics, we generate channel realizations with appropriate second order statistics. As the result, the presented model enables to describe the evolution of the power delay profile in the time domain

Policy and Institutional effects on market participation by smallholder rice farmers: case studies in Burkina Faso, Mali and Niger

Rice sector contributes significantly to secure households with regard to their food needs but also to the creation of employments and income generation. The sector development and its evolution over the years have been marked by various policies and approaches. These development stages of the sector constitute nothing but the impact of the number of factors such as the rice policies put in place. A collaborative multi-country pilot study on policy and institutional arrangements effects on irrigated rice production and commercialization was conducted by WARDA and its country partners of Burkina Faso, Mali, and Niger. In-depth surveys were carried out at both village and household levels to collect qualitative and quantitative data on irrigated rice production, commercialization, and irrigated schemes governance. A common critical constrain cited by the producers in these countries is the commercialization of their product and their inability to take advantage of the market opportunities. Using village and household levels survey data on irrigated rice production and commercialization, this paper attempts to examine the impact of policy and institutional factors in market participation by smallholder rice producers. A farm level supply is estimated using the quantity of rice marketed as the dependant variable and factors such as output and inputs price, and policy and institutional variables as independent ones. The preliminary results indicate that most significant explanatory variable is the average irrigated rice plot (Mali and Niger) and total area of other crops grown by the producer.Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Environmental Economics and Policy, Farm Management, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Institutional and Behavioral Economics, International Relations/Trade, Labor and Human Capital, Marketing, Production Economics, Research and Development/Tech Change/Emerging Technologies, Research Methods/ Statistical Methods,