Airfoil Optimization for vertical axis wind turbines

This thesis addresses the process of airfoil optimization for vertical axis wind turbines (VAWT). The airfoils are designed for large scale turbines above 5 MW. The VAWT concept is relevant for offshore floating wind energy, because of its low center of gravity (stability) and their simplicity (low maintenance). An optimal tip speed ratio of 4-4.5 is chosen with an average Reynolds number of 5 million. The solidity c/R of the turbine is 0.1. These operation conditions are representative for the new generation VAWT. The goal of this thesis is to develop an optimization process for VAWT airfoils and to demonstrate it by designing an airfoil, while taking into account airfoil soiling. A literature review presents the previous research in VAWT airfoil design, showing that no consensus has been previously reached about VAWT airfoil design. From the literature review an optimization objective derived by Simão Ferreira [30] is chosen. The airfoil is optimized for aerodynamic and structural performance. The aerodynamics is assessed on airfoil level according to the objective of lift slope over drag. Structurally, the airfoil will be optimized for flapwise bending stiffness. Airfoil soiling is simulated on the airfoil by using turbulent transition. A genetic optimization tool for airfoils coupled with RFOIL, an airfoil analysis tool, is used to generate VAWT airfoils. The objective function values are calculated using the aerodynamic coefficients from RFOIL and the geometric properties of the airfoils. The optimization process is validated by analyzing the results with three different models for full VAWT analysis. These models are: 1) an inviscid panel model coupled with RFOIL, 2) a double wake panel model and 3) a CFD model. Three airfoils resulting from the optimization are tested using the aerodynamic models. The performance of the airfoils validates the objective functions, but performance for the soiled case is not satisfactory. These preliminary findings were presented at the 33rd Wind Energy Symposiumat the AIAA SciTech conference [32], the full paper can be found in appendix B Five different strategies are developed to optimize airfoils. The results are analyzed using a double wake panel model. The optimization strategy in which airfoils are optimized for soiled conditions results in the best performing airfoils. The RK2-27 is a demonstration airfoil resulting from this optimization strategy. The CP of this airfoil for a tip speed ratio of 4 and a solidity of 0.1 is 0.53 in the clean case and 0.45 in the soiled case. This was determined by both the inviscid panel model and the double wake panel model. The RK2-27 has an increased CP compared to the NACA 0018 of 0.04 in the clean case at the design operating conditions. The CP in the soiled case is only 0.02 lower than the NACA 0018. The maximum thickness of the airfoil increased by 50% from 18% to 27%. The RK2-27 has similar aerodynamic performance compared to the traditionally used NACA 0018, while structurally it performs significantly better.Wind EnergyAerospace Engineerin

Sustainable business model innovation: The role of boundary work for multi-stakeholder alignment

This study focuses on the boundary-spanning nature of sustainable business model innovation, studying multi-stakeholder engagement and alignment. Drawing on the concept of boundary work, we explore the different types of organizational boundary changes between focal companies and their external stakeholders, investigating specifically the process of exploring, negotiating, disrupting and realigning organizational boundaries. Based on an exploratory study of nine different sustainable business model initiatives from for-profit and non-profit organizations, our analysis shows how actors involved need to find alignment at normative, instrumental and strategic dimensions in order to achieve sustainable value creation. However, complexity for alignment emerges through different understandings of value, diverging interests, division of risks and responsibilities, and existing processes and activities that limits actors’ openness to align. Mutual boundary changes are thus necessary in the process of multi-stakeholder engagement in order to enhance organizations’ understanding of value and to capture the envisioned value. This paper functions as an agenda-setting paper, presenting first insights on how the boundary work lens can advance our understanding of alignment processes between focal organizations and their external stakeholders, required for sustainable business model innovation.Marketing and Consumer Researc

Evidence of linkage to chromosome 9q22.33 in colorectal cancer kindreds from the United Kingdom.

About 30% of all colorectal cancers are thought to have a genetic basis and the known predisposing genes can only account for a small fraction of cases. A previous report suggested that a colorectal cancer candidate gene, explaining at least 20% of colorectal cancer cases with family history, was located within a 25 cM region on chromosome 9q22.2-q31.3. We typed 16 polymorphic markers encompassing the region of putative linkage in 57 colorectal tumor families from the United Kingdom. Known Mendelian syndromes had been excluded. We found suggestive evidence of linkage, as positive parametric (HLOD = 1.23) and nonparametric (NPL = 1.21, P = 0.11) LOD scores were obtained by analysis of the whole family set. Enrichment for cases with a priori genetic etiology by analyzing families with at least one person affected at <45 years of age (n = 39 families) gave a maximum multipoint NPL score of 2.65 (P = 0.007). In this group, significant NPL scores >1.67 (P < 0.05) were found in a 6.5 cM region between D9S1851 and D9S277. With a more stringent threshold (NPL>2.4, P < 0.01), the linked region was 1.7 cM between D9S971 and D9S272/D9S173. Exclusion from the analysis of kindreds with a phenotype of multiple polyposis also found evidence of linkage in the same region (NPL = 2.47 at close to D9S277, P = 0.009). The type I transforming growth factor-beta receptor, a prime candidate gene, was excluded as a cause of disease. The results presented here further support the existence of a colorectal cancer susceptibility gene on chromosome 9q and refine its likely location

Is depression a disconnection syndrome? Meta-analysis of diffusion tensor imaging studies in patients with MDD

Background: Many studies using diffusion tensor imaging (DTI) have demonstrated impaired white matter integrity in patients with major depressive disorder (MDD), with significant results found in diverse brain regions. We sought to identify whether there are consistent changes of regional white matter integrity in patients with MDD, as shown by decreased fractional anisotropy in DTI. Method: A systematic search strategy was used to identify relevant whole brain voxel-based DTI studies of patients with MDD in relation to comparison groups. Relevant databases were searched for studies published between January 1994 and February 2011 using combinations of the terms "DTI" or "diffusion tensor;" "whole brain" or "voxel-based;" and "depress*." Using the studies that met our inclusion criteria, we performed a meta-analysis of the coordinates of decreased fractional anisotropy using the activation likelihood estimation (ALE) method, which detects 3-dimensional conjunctions of coordinates from multiple studies, weighted by sample size. We then used DTIquery software for fibre tracking to locate the fascicles involved in each region. Results: We included 11 studies with a combined sample of 231 patients with MDD and 261 comparison participants, providing 50 coordinates of decreased fractional anisotropy. Our meta-analysis identified 4 consistent locations of decreased fractional anisotropy in patients with MDD: white matter in the right frontal lobe, right fusiform gyrus, left frontal lobe and right occipital lobe. Fibre tracking showed that the main fascicles involved were the right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, right posterior thalamic radiation and interhemispheric fibres running through the genu and body of the corpus callosum. Limitations: The number of studies included was relatively small, and the DTI data acquisition and analysis techniques were heterogeneous. The ALE method cannot handle studies with no significant group differences. Conclusion: Voxel-based analysis of DTI studies of patients with MDD consistently identified decreased fractional anisotropy in the white matter fascicles connecting the prefrontal cortex within cortical (frontal, temporal and occipital lobes) and subcortical areas (amygdala and hippocampus). This is strong evidence for the involvement of these neural circuits in the pathology of MDD

Abnormal Regional Spontaneous Neural Activity in Treatment-Refractory Depression Revealed by Resting-State fMRI

Treatment-refractory depression (TRD) represents a large proportion of the depressive population, yet has seldom been investigated using advanced imaging techniques. To characterize brain dysfunction in TRD, we performed resting-state functional MRI (rs-fMRI) on 22 TRD patients, along with 26 matched healthy subjects and 22 patients who were depressed but not treatment-refractory (NDD) as comparison groups. Results were analyzed using a data-driven approach known as Regional Homogeneity (ReHo) analysis which measures the synchronization of spontaneous fMRI signal oscillations within spatially neighboring voxels. Relative to healthy controls, both depressed groups showed high ReHo primarily within temporo-limbic structures, and more widespread low ReHo in frontal, parietal, posterior fusiform cortices, and caudate. TRD patients showed more cerebral regions with altered ReHo than did NDD. Moderate but significant correlations between the altered regional ReHo and measures of clinical severity were observed in some identified clusters. These findings shed light on the pathophysiological mechanisms underlying TRD and demonstrate the feasibility of using ReHo as a research and clinical tool to monitor persistent cerebral dysfunction in depression, although further work is necessary to compare different measures of brain function to elucidate the neural substrates of these ReHo abnormalities. Hum Brain Mapp 32:1290-1299, 2011. (C) 2010 Wiley-Liss, Inc

Legitimising Racism: An Exploration of the Challenges Posed by the Use of Indigeneity Discourses by the Far Right

The disintegration of the British National Party (BNP) has removed the threat of the party securing a place in the political mainstream in the UK. But, in coming close to this objective it has succeeded in renewing and legitimising both its own claims to speak on behalf of the indigenous people of Britain, as well as the similar claims of other groups such as the English Defence League (EDL), the English Democrats and the Freedom Party. Rather than assessing the impact of the BNP in terms of the number of votes and councillors, this article contends that the renewal of racist discourse may enable far right views and ideologies to penetrate and gain acceptance in mainstream British society over the next decade. This article examines the re-shaping of the rhetoric of indigeneity by the BNP to legitimise racism. Using articles originally written for the BNP magazine Identity between 2006 and 2008 and extracted from the BNP website in advance of the 2010 elections, this article discursively analyses the way in which the BNP deploys the concept of indigeneity in its constructions of social groups in Britain. It is suggested that the potential (mis)use of indigeneity as a legitimising vehicle for racist and illiberal views and policies is exacerbated by the lack of clear definitional boundaries around the concept of indigeneity itself

Refinement of the basis and impact of common 11q23.1 variation to the risk of developing colorectal cancer.

The common single-nucleotide polymorphism (SNP) rs3802842 at 11q23.1 has recently been reported to be associated with risk of colorectal cancer (CRC). To examine this association in detail we genotyped rs3802842 in eight independent case-control series comprising a total of 10 638 cases and 10 457 healthy individuals. A significant association between the C allele of rs3802842 and CRC risk was found (per allele OR = 1.17; 95% confidence interval [CI]: 1.12-1.22; P = 1.08 x 10(-12)) with the risk allele more frequent in rectal than colonic disease (P = 0.02). In combination with 8q21, 8q24, 10p14, 11q, 15q13.3 and 18q21 variants, the risk of CRC increases with an increasing numbers of variant alleles for the six loci (OR(per allele) = 1.19; 95% CI: 1.15-1.23; P(trend) = 7.4 x 10(-24)). Using the data from our genome-wide association study of CRC, LD mapping and imputation, we were able to refine the location of the causal locus to a 60 kb region and screened for coding changes. The absence of exonic mutations in any of the transcripts (FLJ45803, LOC120376, C11orf53 and POU2AF1) mapping to this region makes the association likely to be a consequence of non-coding effects on gene expression