1,387 research outputs found
Drag Reduction by Applying Speedstrips on Rowing Oars
No full textAbstractThe objective of this study was to determine the advantage of the application of speedstrips to rowing oars for a lightweight single sculler. The research method comprehended three steps: (1) the analysis of the rowing oar movement, (2) the determination of the change in drag and (3) the composition of a rowing model to establish the advantage that could be achieved. The parameters needed for the model: boat velocity, oar angle velocity and power delivered by the rower, were recorded on a real single sculler. The change in drag due to speedstrips on cylinders was determined by performing wind tunnel experiments. The rowing model (Matlab) simulates a race by using real stroke data of a world-class rower as input, while calculating the drag with the coefficients determined by the wind tunnel experiments. The output of the model is the final advantage by the application of speedstrips to rowing oars. Speedstrips induce a 0.1% advantage over a 2000 m race under calm wind conditions. The advantage increases up to .4% with a headwind velocity of 5 m s-1. For bigger boats, the advantage could be even more significant
Drag and Power-loss in Rowing Due to Velocity Fluctuations
No full textAbstractThe flow motions in the turbulent boundary layer between water and a rowing boat initiate a turbulent skin friction. Reducing this skin friction results in better rowing performances. A Taylor-Couette (TC) facility was used to verify the power losses due to velocity fluctuations PV′ in relation to the total power , as a function of the velocity amplitude A. It was demonstrated that an increase of the velocity fluctuations results in a tremendous decrease of the velocity efficiency eV . The velocity efficiency eV for a typical rowing velocity amplitude A of 20 – 25% was about 0.92 – 0.95%. Suppressing boat velocity fluctuations with 60% will increase boat speed with 1.6%. Riblet surfaces were applied on the inner and outer cylinder wall to indicate the drag reducing ability of such surfaces. The results of the measurements at constant velocity are identical as the results reported earlier, while the experimental configuration was different. This confirms once more the consistency of the TC-system for drag studies. The maximum drag reduction DR was 3.4% at a Reynolds number Res 4.7 × 104, which corresponds to a shear velocity in this TC-system with water of V 4.7 m/s. For typical rowing velocity fluctuations, the riblets maintain to reduce the drag with 2.8% and corresponds to a averaged velocity increase of 0.9%. The drag reducing ability of riblets is partly lost due to velocity fluctuations with high amplitudes (A > 20%). From these results, it is concluded that the friction coefficient Cf will vary within one cycle. Higher acceleration/deceleration leads to a additional level of turbulent kinetic energy
On the derivation of closed-form expressions for displacements, strains and stresses inside a poroelastic inclusion
No full textThis note provides the derivation of closed-form expressions for elastic displacements, strains, and stresses inside an inclusion. Jansen et al. (2019) and Wu et al. (2021) obtained correct expressions for the stresses inside an inclusion, but their derivation of these expressions contained mistakes. In this note, the correct derivation of expressions for the stresses inside an inclusion is presented and some of the results of the aforementioned studies are clarified.This note provides corrections to results published in: J.D. Jansen, P. Singhal, and F.C. Vossepoel. Insights from closed-form expressions for injection- and production-induced stresses in displaced faults. Journal of Geophysical Research - Solid Earth, 124:7193{7212, 2019. URL https://doi.org/10.1029/2019JB017932. H. Wu, V. Vilarrasa, S. De Simone, M. Saaltink, and F. Parisio. Analytical solution to assess the induced seismicity potential of faults in pressurized and depleted reservoirs. Journal of Geophysical Research - Solid Earth, 126: e2020JB020436, 2021. URL https://doi.org/10.1029/2020JB020436.Reservoir EngineeringMathematical PhysicsCivil Engineering & Geoscience
Fear the Machine?
No full textHealthCareHow do the technological changes caused by increased automation and A.I. affect workers�������� wages and jobs? This article summarizes PERC working paper 1801, PERC��������s Director Dennis W. Jansen and co-author Michael D. Bradley study the effects of automation and artificial intelligence on employment and labor income over multiple gen-erations
Twisted mass QCD thermodynamics: first results on apeNEXT
No full textCopyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.Ernst-Michael Ilgenfritz, Michael Müller-Preussker and Andre Sternbeck, Karl Jansen and Ines Wetzorke, Maria Paola Lombardo, Owe Philipsenhttp://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=3
Inter-Jurisdiction Migration and the Fiscal Policies of Local Governments
No full textHealthCare|PublicFinanceThe relationship between migration and the economy is of great interest to researchers, especially where migration and local government fiscal policy intersect. In order to attract immigrants or retain current residents, how do local governments choose to spend, and how do they choose to finance their spending? This article summarizes PERC working paper 1901, where Dennis W. Jansen, PERC��������s director, and PERC Research Scientist Liqun Liu, along with co-author Darong Dai analyze the effects of non-tax/debt-driven migration on the fiscal policies of local governments using a two-period model of two identical local governments that are connected by mutual migration
Frontmatter, Table of Contents, Preface, Organization, External Reviewers, List of Authors
No full textFrontmatter, Table of Contents, Preface, Organization, External Reviewers, List of Author
‘A Museum Label Is Not Enough!’: Diffraction, Urban Fascist Legacy, and Participatory Artivism from Contemporary Rome
No full textThrough the adoption of a methodology that combines ‘diffraction’ and personal experience, alongside an ecocritical interpretation of non-human bodies, this article demonstrates how literary works can be utilized to generate participatory ‘artivism’ initiatives in urban spaces, that intertwine the Roman districts EUR and Trastevere.
These Roman landscapes, both central and marginal, marked by an ambiguous and naturalized fascist legacy, risk promoting the appropriation of urban spaces and buildings by neo-fascist discourse. Bearing in mind a specific genealogy of the term ‘artivism’, the article foregrounds the double position of the author as both a scholar and an activist, and discusses (we) Are Not GIL, a participatory artivism action geared towards decolonizing the former GIL – Gioventù italiana del Littorio (Italian Youth of Littorio) building, in 2019. This endeavour, which involved a comparative and performative use of two literary texts by Ghermandi and Flaiano, played a pivotal role in dismantling the uniformity of institutional narratives pertaining to the fascist, colonial, and patriarchal legacies – prefiguring a participatory artistic practice and politics aimed at depatriarchalizing, decolonizing, and defascistizing the artistic heritage of the city of Rome
Classic selective sweeps revealed by massive sequencing in cattle.
No full textHuman driven selection during domestication and subsequent breed formation has likely left detectable signatures within the genome of modern cattle. The elucidation of these signatures of selection is of interest from the perspective of evolutionary biology, and for identifying domestication-related genes that ultimately may help to further genetically improve this economically important animal. To this end, we employed a panel of more than 15 million autosomal SNPs identified from re-sequencing of 43 Fleckvieh animals. We mainly applied two somewhat complementary statistics, the integrated Haplotype Homozygosity Score (iHS) reflecting primarily ongoing selection, and the Composite of Likelihood Ratio (CLR) having the most power to detect completed selection after fixation of the advantageous allele. We find 106 candidate selection regions, many of which are harboring genes related to phenotypes relevant in domestication, such as coat coloring pattern, neurobehavioral functioning and sensory perception including KIT, MITF, MC1R, NRG4, Erbb4, TMEM132D and TAS2R16, among others. To further investigate the relationship between genes with signatures of selection and genes identified in QTL mapping studies, we use a sample of 3062 animals to perform four genome-wide association analyses using appearance traits, body size and somatic cell count. We show that regions associated with coat coloring significantly (P<0.0001) overlap with the candidate selection regions, suggesting that the selection signals we identify are associated with traits known to be affected by selection during domestication. Results also provide further evidence regarding the complexity of the genetics underlying coat coloring in cattle. This study illustrates the potential of population genetic approaches for identifying genomic regions affecting domestication-related phenotypes and further helps to identify specific regions targeted by selection during speciation, domestication and breed formation of cattle. We also show that Linkage Disequilibrium (LD) decays in cattle at a much faster rate than previously thought
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