Wind tunnel and numerical study of a small vertical axis wind turbine

This paper presents a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine (VAWT). Wind tunnel tests were carried out to ascertain overall performance of the turbine and two- and three-dimensional unsteady computational fluid dynamics (CFD) models were generated to help understand the aerodynamics of this performance. Wind tunnel performance results are presented for cases of different wind velocity, tip-speed ratio and solidity as well as rotor blade surface finish. It is shown experimentally that the surface toughness on the turbine rotor blades has a significant effect on performance. Below a critical wind speed (Reynolds number of 30,000) the performance of the turbine is degraded by a smooth rotor surface finish but above the turbine performance is enhanced by a smooth surface finish. Both two bladed and three bladed it, rotors were tested and a significant increase in performance coefficient is observed for the higher solidity rotors (three bladed rotors) over most of the operating range. Dynamic stalling behaviour and the resulting large and rapid changes in force coefficients and the rotor torque are shown to be the likely cause of changes to rotor pitch angle that occurred during early testing. This small change in pitch angle caused significant decreases in performance. The performance coefficient predicted by the two dimensional computational model is significantly higher than that of the experimental and the three-dimensional CFD model. The predictions show that the presence of the over tip vortices in the 3D simulations is responsible for producing the large difference in efficiency compared to the 2D predictions. The dynamic behaviour of the over tip vortex as a rotor blade rotates through each revolution is also explored in the paper. (C) 2009 Elsevier Ltd. All rights reserved

I. Existence of Eigenvalues for Integral Equations; II. A Collocation Method for Boundary Value Problems

I. The existence of eigenvalues is shown for certain classes of integral equations with continuous kernels. A number of interesting and useful results are thereby treated in a unified and relatively elementary way. The simplicity of these new proofs make the results accessible to introductory courses on the theory of integral equations. II. Collocation with piecewise polynomial functions is developed as a method for solving two-point bour:rlary value problems. Convergence is shown for a general class of linear problems and a rather broad class of nonlinear problems. Some computational examples are presented to illustrate the wide applicability and efficiency of the procedure

Long-term corn and soybean response to phosphorus fertilization in Iowa

Efficient P fertilization practices are of great concern to Corn Belt farmers because of the agronomic and environmental implications of increasing soil-test P (STP) trends. This study evaluated (1) long-term STP trends for various initial STP levels and annual P application rates, (2) yields of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] as affected by P fertilization and STP. Yield and STP data were collected from three experiments established in Iowa during the 1970s on Webster (fine-loamy, mixed, mesic Typic Endoaquolls)-Nicollet (fine-loamy, mixed, mesic Aquic Hapludolls) soils, Webster-Canisteo (fine-loamy, mixed, calcareous, mesic Typic Endoaqualls) soils, and Kenyon (fine-loamy, mixed, mesic Typic Hapludolls) soils. Crops were grown in rotation each year until 2002. Three initial contrasting STP levels ranging from 17 to 75 mg kg−1 (Bray-P1) were created at two sites, and annual treatments of 0, 11, 22, and 33 kg P ha−1 were superimposed. At a third site, annual rates of 0, 22, and 45 kg P ha−1 were applied annually. Annual P rates required to maintain 16-20 mg kg−1 STP were similar at Webster-Nicollet-Canisteo soils (13-17 kg P ha−1), however, \u3e30 kg P ha−1 was required to maintain STP levels four times higher. At the Kenyon soil, a similar Phosphorus rate maintained a higher STP level (28 mg kg−1). Critical STP concentrations identified with linear-plateau and quadratic-plateau models across sites were 18-23 mg kg−1 for corn and 11-18 mg kg−1 for soybean. Results indicate that 10-15 years of cropping without P fertilization were required on high testing soils before yield response to P was observed. Abbreviations: AGRON, Agronomy and Agricultural Engineering Research Farm; NERF, Northeast Iowa Research Farm; NIRF, Northern Iowa Research Farm; STP, soil-test P

Ketenimines Generated from Ynamides: Versatile Building Blocks for Nitrogen-Containing Scaffolds

International audienceUsing ynamides as readily available starting materials, a single step can generate highly reactive ketenimines which can then undergo a variety of transformations. The choice of the method for generating the ketenimine dictates the outcome of the reaction that can, moreover, be precisely steered through minor variations of the starting material. This Concept gives an overview of the different existing methodologies for this objective, showcasing the diverse nitrogen-containing frameworks that can be obtained by this highly versatile strategy

Challenges Facing the Disabled People’s Movement in the UK: An Analysis of Activist’s Positions

This thesis explores disabled activist’s perceptions of the challenges to British disabled people thrown up by changes in policy and cuts to services made by the coalition government of 2010-2015. These themes are explored through a qualitative analysis of interviews conducted with 20 disabled activists. The thesis begins with a presentation of the history of the British Disabled People’s Movement, drawing on writers such as Hunt (1966, 1981), Campbell and Oliver (1996) and Barnes and Mercer (2006). This is followed by an overview of available evidence concerning current challenges to the standard of living of disabled people. The next chapter involves a discussion of methods in the form of a narrative account of the development of the thesis. This is followed by an interrogation of prominent methodologies in disability research, pointing to the strengths and drawbacks of the emancipatory disability research approach (Oliver, 1992; Bares 2008) by drawing on critical realist perspectives (Sayer, 1992; Lawson, 1999). Moving on to an analysis of interview data, the combination of challenges currently facing disabled people are explicated. To make sense of challenges revealed at individual, collective and ideological levels, the notion of ‘enforced individualism’ (Roulstone and Morgan, 2009) is drawn upon. It is argued that, taken together, these challenges comprise novel forms of disablism that coexist with older and more familiar forms of disablism associated with paternalism and oppression within institutions. Following examination of these challenges, attention turns to the political positions and responses that disabled people have adopted in reaction. To theorise such responses, Fraser’s (1995: 2003) analysis of injustice and resistance is applied to the political positions taken by participants. Later chapters reflect further on injustice and resistance, drawing again on Fraser, as well as the extension of the social model of disability presented by Thomas (1999; 2007; 2010; 2012), the political theory of Holloway (1991; 1993a; 1993b; 2005) and the political economy of Polanyi (1944). These theories serve to highlight the nature of contemporary anti-disablist resistance, and also provide a novel means of conceptualising the relationship of disability studies and disability activism

Daily irrigation attenuates xylem abscisic acid concentration and increases leaf water potential of Pelargonium×hortorum compared with infrequent irrigation

The physiological response of plants to different irrigation frequencies may affect plant growth and water use efficiency (WUE; defined as shoot biomass/cumulative irrigation). Glasshouse-grown, containerized Pelargonium × hortorum BullsEye plants were irrigated either daily at 100% of plant evapotranspiration (ET) (well-watered; WW), or at 50% ET applied either daily [frequent deficit irrigation (FDI)] or cumulatively every 4 days [infrequent deficit irrigation (IDI)], for 24 days. Both FDI and IDI applied the same irrigation volume. Xylem sap was collected from the leaves, and stomatal conductance (gs) and leaf water potential (Ψleaf) measured every 2 days. As soil moisture decreased, gs decreased similarly under both FDI and IDI throughout the experiment. Ψleaf was maintained under IDI and increased under FDI. Leaf xylem abscisic acid (ABA) concentrations ([X-ABA]leaf) increased as soil moisture decreased under both IDI and FDI, and was strongly correlated with decreased gs, but [X-ABA]leaf was attenuated under FDI throughout the experiment (at the same level of soil moisture as IDI plants). These physiological changes corresponded with differences in plant production. Both FDI and IDI decreased growth compared with WW plants, and by the end of the experiment, FDI plants also had a greater shoot fresh weight (18%) than IDI plants. Although both IDI and FDI had higher WUE than WW plants during the first 10 days of the experiment (when biomass did not differ between treatments), the deficit irrigation treatments had lower WUE than WW plants in the latter stages when growth was limited. Thus, ABA-induced stomatal closure may not always translate to increased WUE (at the whole plant level) if vegetative growth shows a similar sensitivity to soil drying, and growers must adapt their irrigation scheduling according to crop requirements

A Bourdieusian analysis of qualitative authorship in entrepreneurship scholarship

Empirically, this study builds on responses from leading qualitative entrepreneurship scholars.We carry out a Bourdieuan analysis of the field of entrepreneurship scholarship—particularly heterodox qualitative writing—and the way that scholars learn to play this game (habitus). It discusses unchallenged assumptions (doxa), commitment to shared stakes (illusio), the practice to achieve these stakes (practice), and the struggle for glories and riches (capital). By deploying Bourdieu’s frame, we have been able to expose key processes, structures, and relationships within qualitative entrepreneurship authorship. These offer four types of practical outcomes: guidance for good practice; insights into emotional aspects of authorship; warnings of potentially dysfunctional practices; and a celebration of our successes

IMPACTS OF SEMI SELF-CONTAINED LEARNING COMMUNITIES IN GRADE 6 ON STUDENTS’ ENGAGEMENT, ACHIEVEMENT, AND PERCEPTIONS OF THE CLASSROOM ENVIRONMENT: AN EVALUATION OF PROJECT SUCCESS

This study examines the impacts of business-as-usual departmentalization and semi self-contained learning communities on students’ engagement, achievement, and perceptions of the classroom environment in grade 6. The treatment condition in this randomized control trial is Project SUCCESS (e.g., Student Unified Curriculum Combining English, digital literacy, Science, and Social Studies) and departmentalization, or achievement through specialization (ATS), serves as the control condition. In the spring of 2016, grade 5 students were randomly assigned to Project SUCCESS (n = 87) and ATS (n = 313) for grade 6 in in two relatively large and low-income middle schools in the inner suburbs of a large metropolitan area. Multiple regression analyses on standardized test scores in reading on the Measures of Academic Progress (MAP-R) showed that Project SUCCESS had substantial and highly significant impacts on students’ literacy development in grade 6. Further, Project SUCCESS profoundly reduced the achievement gap between students who received free and reduced meals (FARMS) and students of higher socioeconomic status. Further, students in Project SUCCESS earned significantly higher cumulative grade point averages and placed significantly more value on interacting with peers than students in ATS. Finally, students in Project SUCCESS were less likely than the other students to indicate that their school had a negative performance goal structure where teachers treat students who get good grades better than other students, pay too much attention to grades and not enough to helping students learn, care only about the smart kids, and encourage students to compete against each other for grades