La transdisciplinarite comme approche innovante de recherche action; le cas du projet syprobio

L’agriculture biologique et le commerce équitable en Afrique de l’Ouest centrés autour du coton, introduits depuis 1999, ont démontré un vrai potentiel d’augmenter les revenus et d'améliorer la sécurité alimentaire des petits productrices et producteurs. Actuellement, plus de 16'000 producteurs produisent le coton et d’autres cultures vivrières dans leurs systèmes de production en bio dans la sous-région. La diversification de ces cultures biologiques dans la rotation ou la combinaison de ces cultures avec celles d'arbres (agroforesterie) et de l’élevage visent à protéger la productivité en dépit des changements anticipés des conditions climatiques. A travers l'amélioration de la fertilité des sols et la diversification des systèmes de production, l'agriculture biologique a également un potentiel reconnu de contribuer à l'adaptation au changement climatique

Statistical approach of factors controlling drainage network patterns in arid areas. Application to the Eastern Anti Atlas (Morocco)

International audience12 13 Abstract: 14 Several studies have revealed that the complexity in the distribution of drainage network patterns is not 15 random and controlled by major parameters, variable in space but also throughout geological time. Drainage 16 networks in the Eastern Anti-Atlas of Morocco consist of complex spatial arrangements with various types of 17 patterns, such as trellis, angular, dendritic and parallel. The objective was to distinguish, quantify and rank 18 the relationship that may exist between the different drainage networks patterns, geology and 19 geomorphology. A total of 230 basins were extracted from the ASTER-GDEM Elevation Data (USGS), which 20 were assigned 16 parameters reflecting their topography, morphometry, slope and geology. The statistical 21 treatment of the dataset (16 variables x 230 observations) was carried out through principal component 22 analysis (PCA), linear discriminant analysis (LDA) and agglomerative hierarchical clustering (AHC), in order to 23 investigate the complexity of drainage network patterns and their distribution. The PCA showed that the 24 topographical, slope and geological parameters, i.e. primarily the parameter associated with structural 25 control, best explains the variation in the type of the drainage pattern. The LDA made it possible to distinguish 26 between the four types of drainage patterns with a success rate of 90%, using 3 discriminant functions that 27 were better correlated with geological and slope parameters. LDA and AHC statistical treatments show 28 confusion between the parallel, trellis and angular patterns, on the one hand, due to similar factors 29 responsible for their formation, and on the other because of transitions phenomenon from one drainage 30 pattern to another over time or space. Such possible drainage network shifting may be explained by the 31 geological events that have occurred in the Eastern Anti Atlas from Lower Mesozoic to the Quaternary. 32 3

Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa

BACKGROUND: The Onchocerciasis Control Program (OCP) in West Africa has been closed down at the end of 2002. All subsequent control will be transferred to the participating countries and will almost entirely be based on periodic mass treatment with ivermectin. This makes the question whether elimination of infection or eradication of onchocerciasis can be achieved using this strategy of critical importance. This study was undertaken to explore this issue. METHODS: An empirical approach was adopted in which a comprehensive analysis was undertaken of available data on the impact of more than a decade of ivermectin treatment on onchocerciasis infection and transmission. Relevant entomological and epidemiological data from 14 river basins in the OCP and one basin in Cameroon were reviewed. Areas were distinguished by frequency of treatment (6-monthly or annually), endemicity level and additional control measures such as vector control. Assessment of results were in terms of epidemiological and entomological parameters, and as a measure of inputs, therapeutic and geographical coverage rates were used. RESULTS: In all of the river basins studied, ivermectin treatment sharply reduced prevalence and intensity of infection. Significant transmission, however, is still ongoing in some basins after 10–12 years of ivermectin treatment. In other basins, transmission may have been interrupted, but this needs to be confirmed by in-depth evaluations. In one mesoendemic basin, where 20 rounds of four-monthly treatment reduced prevalence of infection to levels as low as 2–3%, there was significant recrudescence of infection within a few years after interruption of treatment. CONCLUSIONS: Ivermectin treatment has been very successful in eliminating onchocerciasis as a public health problem. However, the results presented in this paper make it almost certain that repeated ivermectin mass treatment will not lead to the elimination of transmission of onchocerciasis from West Africa. Data on 6-monthly treatments are not sufficient to draw definitive conclusions

Blind time domain equalization of SC-FDMA signal

International audienceIn this paper a new equalizer for Single Carrier FDMA (SCFDMA)[1][2] is described. This signal is currently proposed for mobile radio uplink communications in 3G Long Term Evolution (3G LTE). In this system, equalization is performed thanks to the addition of a Cyclic Prefix (CP), as in OFDM system, and pilots regularly inserted for channel estimation which leads to the useful throughput degradation. To reduce this degradation a new structure of blind time domain equalizer, shared in two parts, is proposed in this paper : The filtering itself which is a linear time domain filtering performed before any demodulation device in the receiver side, and the MMSE criterion algorithm performed in the time domain after user selection and demodulation. The results are very convincing both in terms of Mean Square Error and in throughput gain compared to the performances of Zero-Forcing technique(ZF) used in literature

Mobile radio channels' Estimation for SC-FDMA systems by means of adequate Noise and Inter-carrier Interference filtering in a transformed domain

WOSInternational audienceThis paper proposes a new channel estimation technique for mobile radio multipath channels in the context of SCFDMA1[ 1],[2],[3],[4] system. SC-FDMA is currently adopted for mobile radio uplink communications in 3G LTE2 because of its low PAPR3. In this system, 1/7 SC-FDMA time symbols are dedicated to perform the channel estimation. This is sufficient when the channel can be considered as constant over the 7 symbol periods. But it is clear that transmission channel can change rapidly over time, typically when the user (UE) moves with an important enough velocity, thus introducing Doppler effect and therefore Inter-Carrier Interference (ICI). Our proposition deals with this situation, and consists in filtering the channel noise and ICI perturbation through a new transformed domain. This approach is based on the variation rate of the channel's frequency response and the nature of the noise and ICI component in the Transformed domain. The performances obtained are very convincing since we have up to 3 dB gain compared to the simple interpolation solution encountered in the literature

A SEMI-BLIND TIME DOMAIN EQUALIZATION OF SCFDMA SIGNAL

This paper proposes a new semi blind equalizer structure for Single Carrier FDMA (SC-FDMA)[1][2]. SC-FDMA is currently adopted for mobile radio uplink communications in 3G Long Term Evolution (3G LTE). In this system, a Zero-Forcing(ZF) equalization is performed thanks to the addition of a Cyclic Prefix (CP), as in OFDM system, and pilots regularly inserted for channel estimation which lead to the useful throughput degradation. To reduce this degradation we propose in this paper a new structure of semi blind equalizer in time domain based on [3]. A ZF criterion and a simple Minimum Mean Square Error (MMSE) are combined to reduce the number of pilots inserted and to outperform the ZF optimum mean square error. This equalizer is shared in two parts: The filtering itself which is a linear time domain filtering performed before any demodulation device in the receiver side, and the criterion algorithm performed in the time domain after user selection and demodulation which is sometimes a ZF criterion and sometimes MMSE criterion. The results are very convincing both in terms of Mean Square Error and in throughput gain compared to the performances of Zero- Forcing technique used in literature

Environmental impact assessment of settlement and development in the upper leraba basin: Burkina faso,cote d'ivoire,and mali

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Channel Estimation Technique by Hidden Signal: Application in the SC-FDMA Context

International audienceThis paper deals with a new channel estimation technique for Single Carrier FDMA (SC-FDMA) currently adopted for mobile radio uplink communications in 3GPP LTE standard. The principle is to exploit the statistical advantages of a specific signal added in the transmitter to estimate the channel coefficients. In contrast to a pilots signal, the added signal covers the entire useful signal band during all of the communication delay. The advantage of this proposal is to estimate the channel by kipping the same spectral efficiency. This proposal is compared to Zero-Forcing Estimator with LS equalizer and MMSE equalizer. The results are very convincing in term of symbol error rate; the gain is up to 2.5 dB

Enviromental impact assessment of settlement and development in the upper leraba basin : burkina faso, cote d'Ivoire, and Mali

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