Ultrasound Nondestructive Evaluation (NDE) Imaging with Transducer Arrays and Adaptive Processing

This paper addresses the challenging problem of ultrasonic non-destructive evaluation (NDE) imaging with adaptive transducer arrays. In NDE applications, most materials like concrete, stainless steel and carbon-reinforced composites used extensively in industries and civil engineering exhibit heterogeneous internal structure. When inspected using ultrasound, the signals from defects are significantly corrupted by the echoes form randomly distributed scatterers, even defects that are much larger than these random reflectors are difficult to detect with the conventional delay-and-sum operation. We propose to apply adaptive beamforming to the received data samples to reduce the interference and clutter noise. Beamforming is to manipulate the array beam pattern by appropriately weighting the per-element delayed data samples prior to summing them. The adaptive weights are computed from the statistical analysis of the data samples. This delay-weight-and-sum process can be explained as applying a lateral spatial filter to the signals across the probe aperture. Simulations show that the clutter noise is reduced by more than 30 dB and the lateral resolution is enhanced simultaneously when adaptive beamforming is applied. In experiments inspecting a steel block with side-drilled holes, good quantitative agreement with simulation results is demonstrated

Rain-Fed Farming System at a Crossroads in Semi-Arid Areas of Tanzania: What Roles do Climate Variability and Change Play?

Positive changes, like adopting drought resistant crop varieties, in the rain-fed farming system (RFFS) in response to climate variability and change enhance system’s ability to support people’s living as opposed to negative changes, like lack of pastures, which put the system at risk of failure in supporting the living. Using participatory rural appraisal (PRA) and household survey, this paper examined the roles of climate variability and change in triggering changes in RFFS. Specifically, the paper: (i) assessed dominant crop and livestock farming system; (ii) assessed the change element of crop and livestock production systems; and (iii) examined factors for the changes in RFFS. A random sample of 388 households was used. Qualitative data analysis was done through content analysis. Binary logistic regression was used to assess factors that explain changes on RFFS. The results showed that dominant crops were different in each village. Secondly, some changes in crop varieties and in livestock grazing arrangements were noted in response to climate variability and change. Unlike the hypothesis (P>0.05), the results demonstrated that warming (ß = -10.61, Wald = 36.26, P ? 0.001) showed highest significant impact on likelihood of adopting new crop varieties relative to other factors. Similarly, drought (ß = 2.16, Wald = 6.82, P ? 0.009) showed highest impact on the likelihood of changing a grazing place. Yet, the changes were constrained by factors like natural resources protective policies, failure of crop varieties to withstand warming and drought, and poor land use management. Therefore, the RFFS was at a crossroads with implications on system sustainability and livelihoods. The government and private interventions should support farmers and agro-pastoralists to manage risks related to the changes in RFFS in response to climate variability and change. Keywords: Climate change, agro-pastoralism, livelihoods, semi-arid, Tanzani

Practical approach for sustainable solar eletrification of remote rural communities in eastern Africa : the case of Tanzania

Solar energy is one of the most important resources in the world, and advancements in solar energy technologies are making it more and more cost effective. Although the use of solar powered systems is rapidly increasing in many regions, the major barriers for wide spreads of such systems in remote rural areas of developing countries include lack of investment capital, cultural and technical barriers. This study was commissioned to assess the practicality of disseminating solar home lighting systems to remote rural villages in southern Tanzania, to identify specific barriers that may hinder adopting of such systems by wider communities in rural areas and recommend practical counteractive measures. The analysis used facts collected from key informants, focus group discussions and primary household-level data from 200 households in remote rural villages of Lindi and Mtwara regions. The study explored technical requirements, economic viability, and the policy and planning issues which may contribute to success or failure of an intervention. It was observed that the majority of respondents (80%) were enthusiastic towards acquiring solar kits for lighting their homes, especially those who happen to know these systems and were willing to pay between TAS 5000.00 ($3.3) and 10,000.00 ($ 6.6) as initial deposit to acquire a solar system,. In addition they were willing to pay TAS 5000 ($ 3.3) every month until the cost of the system is recovered. The payment is slightly lower than the cost they incur to buy kerosene and torch batteries for lighting. Despite, the willingness to acquire the lighting systems, it was observed that, success of such an intervention to large extent rely on availability of secure after sale services. The study could not identify any intentional government or other stakeholders’ strategies or policy measure to ensure sustainability of such interventions. Investigation on similar projects implemented in other parts of the country revealed that, conventional methods of providing aftersales services have had little success especially when applied to remote rural areas. Therefore the study recommends training of local people especially women who are deep rooted in the village and are unlikely to migrate from their villages to urban areas. The training should cover installation, repair, maintenance and spare parts procurement. Since most of rural dwellers in Tanzania are semi-illiterate, special approach for selection of trainees and ‘hands on’ training should be adopted to ensure comprehension of the course content. Barefoot approach which has been used successfully to train such technicians and has proved to be a workable solution for provision of training on aftersales services in Northern part of the country is recommended for other rural communities.RURAL COMMUNITIES- EAST AFRICACCIA

Vulnérabilité des systèmes agricoles et innovations techniques dans un contexte de variabilité climatique: cas des cultures de mil et de sorgho dans les zones sahélienne et soudano-sahélienne du Mali

Cette étude analyse la vulnérabilité des systèmes d’exploitation agricoles à base de mil et de sorgho à la variabilité climatique et l’adoption des innovations techniques dans les zones sahélienne et soudano- sahélienne du Mali. Sur la base d’enquêtes réalisées auprès de 360 exploitations agricoles dans les zones sahélienne et soudano-sahélienne, cette recherche a montré que la variabilité pluviométrique observée au cours des trois décennies dans les sites de recherche à travers des insuffisances et irrégularités des pluies est perçue 97% des producteurs comme le principal facteur de risque qui affecte la productivité des systèmes à base de mil et de sorgho. Elle est suivie par la pauvreté des sols 81%, et du manque d’équipement agricole, 47%. Les impacts de ces facteurs au niveau des exploitations agricoles se traduisent par une baisse des rendements des cultures, et de la fréquence des pénuries en denrées alimentaires qui sont observées par 98% des exploitations tous les ans et plus de 50% des producteurs tous les 3 ans. Pour réduire les vulnérabilités, des pratiques et innovations ont été adoptées par les exploitations agricoles au cours des 10 à 15 dernières années. Les principales portent sur le microdosage d’engrais, les variétés améliorées, le microdosage d’engrais, le trempage des semences, les techniques de conservation du sol et de l’eau, la fertilisation organique et la pratique de l’agroforesterie. Les entretiens semi-structurés (ISS) avec des questionnaires administrés auprès des chefs d’exploitation agricole familiale (EAF) ont été utilisés pour la collecte des données. Les statistiques descriptives, les matrices, et le cluster analyse ont été réalisés pour l’analyse des données avec les logiciels EXCEL et SPSS

Factors shaping on-farm genetic resources of sorghum [Sorghum bicolor (L.) Moench] in the centre of diversity, Ethiopia

Ethiopia is cited as one of the centres of sorghum diversity. In order to assess the on-farm genetic resources management of sorghum various research methodologies were employed. These were focus group interviews with 360 farmers, key informant interviews with 60 farmers and development agents and semi-structured interviews with 250 farmers. Besides, diversity fair was done with over 1200 farmers. For quantifying on-farm diversity, direct on-farm monitoring and participation with 120 farmers were made. Quantification of varietal diversity per farm was counted by a participatory zigzag sampling in the diagonal direction of the plot with the farmer and all encountered varieties were counted. Soil samples were taken from 120 farms and were subjected to analyses of soil pH, P, available nitrogen, organic matter and exchangeable potassium. Altitude and other related climatic data were collected. The number of varieties conserved by farmers ranged from one to twenty per farm and this is affected by socio-economic and biophysical factors. The mean numbers of 8.3 and 6.3 varieties were grown by Oromo and Amhara farmers respectively. The minimum and maximum range did not vary for both ethnic groups. There was no significant difference in the number of varieties held by various wealth groups. With respect to farm size as explained by the quadratic model, it significantly accounted and predicted for the variation in the number of varieties. The role of soil pH, P, available nitrogen, organic matter, and exchangeable potassium on-farm genetic diversity is described. P was a positive limiting factor for varietal diversity. As to the effect of crop ecology, there were higher number of varieties in the intermediate altitudes than in the lowland and highland. Both the quadratic and linear equation expressed that distance from the house and town and showed non-significant relationship to the number of varieties planted per farm. Varietal mixture is one of the strategies used by the farmers for improved on-farm genetic diversity management. Farmers' underlying principles for conserving genetic diversity is described. Three models developed, namely; Bioecogeographic genetic diversity model, Farmer induced genetic diversity model and Farmer-cum-bioecogeographic genetic diversity model are explaining the processes shaping on-farm genetic diversity of sorghum in Ethiopia