Free vibration of a three-layered sandwich beam using the dynamic stiffness method and experiment

In this paper, an accurate dynamic stiffness model for a three-layered sandwich beam of unequal thicknesses is developed and subsequently used to investigate its free vibration characteristics. Each layer of the beam is idealised by the Timoshenko beam theory and the combined system is reduced to a tenth-order system using symbolic computation. An exact dynamic stiffness matrix is then developed by relating amplitudes of harmonically varying loads to those of the responses. The resulting dynamic stiffness matrix is used with particular reference to the Wittrick-Williams algorithm to carry out the free vibration analysis of a few illustrative examples. The accuracy of the theory is confirmed both by published literature and by experiment. The paper closes with some concluding remarks. (c) 2007 Elsevier Ltd. All rights reserved

A guideline for the formation of sub-national climate-smart agriculture alliances in Tanzania

About the guideline: This document summarizes recommendations on best practices on how to form and operationalize of sustainable sub-national Climate Smart Agriculture (CSA) alliances for CSA actors in Tanzania. These are based on the experience and recommendations of existing District CSA Alliances and views from selected CSA actors in the country. It seeks to support ongoing efforts in the country to promote the adoption of CSA practices and technologies

Environmental Particle Emissions due to Automated Drilling of Polypropylene Composites and Nanocomposites Reinforced with Talc, Montmorillonite and Wollastonite

In this study, the effect on nanoparticle emissions due to drilling on Polypropylene (PP) reinforced with 20% talc, 5% montmorillonite (MMT) and 5% Wollastonite (WO) is investigated. The study is the first to explore the nanoparticle release from WO and talc reinforced composites and compares the results to previously researched MMT. With 5% WO, equivalent tensile properties with a 10 % weight reduction were obtained relative to the reference 20% talc sample. The materials were fabricated through injection moulding. The nanorelease studies were undertaken using the controlled drilling methodology for nanoparticle exposure assessment developed within the European Commission funded SIRENA Life 11 ENV/ES/506 project. Measurements were taken using CPC and DMS50 equipment for real-time characterization and measurements. The particle number concentration (of particles <1000nm) and particle size distribution (4.87nm - 562.34nm) of the particles emitted during drilling were evaluated to investigate the effect of the silicate fillers on the particles released. The nano-filled samples exhibited a 33% decrease (MMT sample) or a 30% increase (WO sample) on the average particle number concentration released in comparison to the neat polypropylene sample. The size distribution data displayed a substantial percentage of the particles released from the PP, PP/WO and PP/MMT samples to be between 5-20nm, whereas the PP/talc sample emitted larger particle diameters.The work is funded by and part of the European Commission Life project named Simulation of the release of nanomaterials from consumer products for environmental exposure assessment (SIRENA, Pr. No. LIFE 11 ENV/ES/596). The access and use of the facilities at the Flemish Institute for Technological Research (VITO) was funded by QualityNano Project through Transnational Access (TA Application VITO-TAF-382 and VITO-TAF-500) under the European Commission, Grant Agreement No: INFRA-2010-262163. Kristof is also thankful for partial funding by the School of Engineering at Robert Gordon University for his studentship

Beyond a unitary household measure: Does Gender matter in Legume Seed Systems among Smallholder Farmers?

We employ a non-unitary household model to analyze the main Pigeonpea seed channels for in Kenya. The paper is based on a household survey conducted on a 500 randomly selected households within three counties of Eastern Kenya. The study sites are based on the distance from the main trading center (county headquarters) which informs agro business infrastructure. We assess the participation in seed channels with regards to joint plots, women plots and male plots for Pigeonpeas legumes. More than half of the Pigeonpea plots (>50 %) in the sample are managed jointly by men and women; while around 10% are managed entirely by women. There were very few plots (<1%) managed by men alone. The main legumes seed sources are own saved seeds and cereal stockists. There is very limited sourcing from the certified seed channel (<10%), the certified seeds from agrovets are only acquired for joint plots. Using a multinomial logistic regression, we analyze the factors influencing the choice of Pigeonpea seed channels, encompassing characteristics of the wife of the household head. Literate wives and wives with high exposure to extension services were more likely to access seed from the agrovets, these variables were however not significant for the male head. Other significant determinants were total livestock unit, distance to the source of seed, amount of seed required, location of the household, and occupation. We conclude that targeting women farmers with knowledge and capacity building on the advantages of using certified seeds for legumes has the potential to enhance adoption of legumes in Eastern Kenya, education levels notwithstanding

Assessment of the face validity of two pain scales in Kenya: a validation study using cognitive interviewing

Background: Patients in sub-Saharan Africa commonly experience pain, which often is un-assessed and undertreated. One hindrance to routine pain assessment in these settings is the lack of a single-item pain rating scale validated for the particular context. The goal of this study was to examine the face validity and cultural acceptability of two single-item pain scales, the Numerical Rating Scale (NRS) and the Faces Pain Scale-Revised (FPS-R), in a population of patients on the medical, surgical, and pediatric wards of Moi Teaching and Referral Hospital in Kenya. Methods: Swahili versions of the NRS and FPS-R were developed by standard translation and back-translation. Cognitive interviews were performed with 15 patients at Moi Teaching and Referral Hospital in Eldoret, Kenya. Interview transcripts were analyzed on a question-by-question basis to identify major themes revealed through the cognitive interviewing process and to uncover any significant problems participants encountered with understanding and using the pain scales. Results: Cognitive interview analysis demonstrated that participants had good comprehension of both the NRS and the FPS-R and showed rational decision-making processes in choosing their responses. Participants felt that both scales were easy to use. The FPS-R was preferred almost unanimously to the NRS. Conclusions: The face validity and acceptability of the Swahili versions of the NRS and FPS-R has been demonstrated for use in Kenyan patients. The broader application of these scales should be evaluated and may benefit patients who currently suffer from pain