Stand-alone flat-plate photovoltaic power systems: System sizing and life-cycle costing methodology for Federal agencies

A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems

Evaluating tree root distribution in a tree-based intercropping system with use of ground penetrating radar

Paper presented at the 13th North American Agroforesty Conference, which was held June 19-21, 2013 in Charlottetown, Prince Edward Island, Canada.In Poppy, L., Kort, J., Schroeder, B., Pollock, T., and Soolanayakanahally, R., eds. Agroforestry: Innovations in Agriculture. Proceedings, 13th North American Agroforestry Conference, Charlottetown, Prince Edward Island, Canada, June 19-21, 2013.Within agroforestry systems, tree root architecture is a driver of important ecological processes such as belowground nutrient flows and C storage. Yet the belowground component of trees remains largely under-studied due to methodological restraints. Conventional subsurface sampling can overlook the heterogeneity of root systems, while complete excavations are destructive and unrepeatable. Thus, there is a need to develop non-intrusive technologies, such as ground penetrating radar (GPR), to measure root systems in situ. In this study we used GPR to detect coarse root distributions below five tree species (Quercus rubra, Juglans nigra, Populus sp., Picea abies, and Thuja occidentalis) at a temperate tree-based intercropping site in Guelph, Ontario. GPR geo-imaged transects were collected in 4.5 _ 4.5m grids that were centered on 15 individual trees. Subsequently, tree roots were identified across all geo-images (visualized as radar signal reflections) providing 3-dimensional root distribution data for each target tree. Roots detected by GPR accounted for approximately 80% of large coarse roots (�1cm) and 40% of small coarse roots (<1cm) that were later exposed in a subset of matched soil profiles. Significant inter-specific variations of coarse rooting depth preferences were detected. Additionally, preliminary analyses indicate different tree rooting patterns below the crop rows. To determine fine root distributions, fine roots were extracted from soil cores collected from the tree root study plots. Preliminary analysis indicates fine root length densities vary across species predominately in the upper 20cm. Limitations will be identified and applications will be discussed of GPR to answer ecological questions within agroforestry systems. Notably, we will highlight results from our complementary study that used the same GPR data to effectively estimate belowground biomass.Kira A. Borden (1), Marney E. Isaac (2) and Sean C. Thomas (1) ; 1. Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada, M5S 3B3. 2. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4.Includes bibliographical references

Feasibility study for a Scanning Celestial Attitude Determination System /SCADS/ for three axis attitude determination at a Command and Data Acquisition /CDA/ station Final report

Scanning Celestial Attitude Determination System /SCADS/ for three axis attitude determination at Command and Data Acquisition /CDA/ statio

Questioning policy, youth participation and lifestyle sports

Young people have been identified as a key target group for whom participation in sport and physical activity could have important benefits to health and wellbeing and consequently have been the focus of several government policies to increase participation in the UK. Lifestyle sports represent one such strategy for encouraging and sustaining new engagements in sport and physical activity in youth groups, however, there is at present a lack of understanding of the use of these activities within policy contexts. This paper presents findings from a government initiative which sought to increase participation in sport for young people through provision of facilities for mountain biking in a forest in south-east England. Findings from qualitative research with 40 young people who participated in mountain biking at the case study location highlight the importance of non-traditional sports as a means to experience the natural environments through forms of consumption which are healthy, active and appeal to their identities. In addition, however, the paper raises questions over the accessibility of schemes for some individuals and social groups, and the ability to incorporate sports which are inherently participant-led into state-managed schemes. Lifestyle sports such as mountain biking involve distinct forms of participation which present a challenge for policy-makers who seek to create and maintain sustainable communities of youth participants

Evaluation of Coach-Based Technical Assistance: An Evolving Focus on Coachability and Goal Setting

In 2013, the National Institute of Food and Agriculture supported the creation of a professional development and technical assistance center to promote strong implementation and evaluation of University-led, community-based projects serving low-resource populations. Within this center, a coaching cadre was established to provide proactive and responsive technical assistance. Formative evaluation involving coaches and their primary contacts was used for refinement of coaching practices. Initially, coaches were encouraged to build strong interpersonal rapport. This set the stage for trusting, reciprocal interactions, but coaches recognized a need for targeted support and more tools for quality programming, evaluation, and sustainability. Greater emphasis was placed on goal-focused collaboration. Coaches received training and resources on topics such as goal setting, program quality, reduction of barriers (e.g., participant recruitment), and sustainability strategies. To assess coaching model enhancements, a survey of projects was expanded to gauge logic model usage, goal setting, strength of coaching relationships, and project implementation and sustainability progress. Overall, coaching was rated more favorably and effective when contact was consistent, inclusive of face-to-face interaction, met technical needs, and involved collaborative brainstorming and planning. Findings indicate coaching relationships strengthen over time and demand a collaborative, action-orientation to set goals, reduce barriers, and drive stronger outcomes

Spin states of zigzag-edged Mobius graphene nanoribbons from first principles

Mobius graphene nanoribbons have only one edge topologically. How the magnetic structures, previously associated with the two edges of zigzag-edged flat nanoribbons or cyclic nanorings, would change for their Mobius counterparts is an intriguing question. Using spin-polarized density functional theory, we shed light on this question. We examine spin states of zigzag-edged Mobius graphene nanoribbons (ZMGNRs) with different widths and lengths. We find a triplet ground state for a Mobius cyclacene, while the corresponding two-edged cyclacene has an open-shell singlet ground state. For wider ZMGNRs, the total magnetization of the ground state is found to increase with the ribbon length. For example, a quintet ground state is found for a ZMGNR. Local magnetic moments on the edge carbon atoms form domains of majority and minor spins along the edge. Spins at the domain boundaries are found to be frustrated. Our findings show that the Mobius topology (i.e., only one edge) causes ZMGNRs to favor one spin over the other, leading to a ground state with non-zero total magnetization.Comment: 17 pages, 4 figure

Practitioner accounts and knowledge production: an analysis of three marketing discourses

Responding to repeated calls for marketing academicians to connect with marketing actors, we offer an empirically-sourced discourse analysis of the ways in which managers portray their practices. Focusing on the micro-discourses and narratives that marketing actors draw upon to represent their work we argue that dominant representations of marketing knowledge production present a number of critical concerns for marketing theory and marketing education. We also evidence that the often promoted idea of a need to close the gap between theory - as a dominant discourse - and practice, as a way of doing marketing, is problematic to pursue. We suggest that a more fruitful agenda resides in the development of a range of polyphonic and creative micro-discourses of management, promoting context, difference and individual meaning in marketing knowledge production

Chitosan particles agglomerated scaffolds for cartilage and osteochondral tissue engineering approaches with adipose tissue derived stem cells

It is well accepted that natural tissue regeneration is unlikely to occur if the cells are not supplied with an extracellular matrix (ECM) substitute. With this goal, several different methodologies have been used to produce a variety of 3D scaffolds as artificial ECM substitutes suitable for bone and cartilage tissue engineering. Furthermore, osteochondral tissue engineering presents new challenges since the combination of scaffolding and co-culture requirements from both bone and cartilage applications is required in order to achieve a successful osteochondral construct. In this paper, an innovative processing route based on a chitosan particles aggregation methodology for the production of cartilage and osteochondral tissue engineering scaffolds is reported. An extensive characterization is presented including a morphological evaluation using Micro-Computed Tomography (μCT) and 3D virtual models built with an image processing software. Mechanical and water uptake characterizations were also carried out, evidencing the potential of the developed scaffolds for the proposed applications. Cytotoxicity tests show that the developed chitosan particles agglomerated scaffolds do not exert toxic effects on cells. Furthermore, osteochondral bilayered scaffolds could also be developed. Preliminary seeding of mesenchymal stem cells isolated from human adipose tissue was performed aiming at developing solutions for chondrogenic and osteogenic differentiation for osteochondral tissue engineering applications.Fundação para a Ciência e a Tecnologia (FCT)European NoE EXPERTISSUES (NMP3-CT-2004-500283)European STREP Project HIPPOCRATES (NMP3-CT-2003-505758