251 research outputs found

    Experiments on identification and control of inflow disturbances in contracting streams

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    Vorticity from all surfaces and isolated objects in the vicinity of the fan intake, including the outside surfaces of the fan housing, were identified as the major sources for disturbances leading to blade passing frequency noise. The previously proposed mechanism based on atmospheric turbulence is refuted. Flow visualization and hot wire techniques were used in three different facilities to document the evolution of various types of disturbances, including the details of the mean flow and turbulence characteristics. The results suggest that special attention must be devoted to the design of the inlet and that geometric modeling may not lead to adequate simulation of the in flight characteristics. While honeycomb type flow manipulators appear to be effective in reducing some of the disturbances, higher pressure drop devices that generate adequate turbulence, for mixing of isolated nonuniformities, may be necessary to suppress the remaining disturbances. The results are also applicable to the design of inlets of open return wind tunnels and similar flow facilities

    Kawasaki Disease Shock Syndrome vs Classical Kawasaki Disease: A Meta-analysis and Comparison With SARS-CoV-2 Multisystem Inflammatory Syndrome.

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    BACKGROUND: The emergence of increasing reports worldwide of a severe inflammatory process and shock in pediatric patients resembling Kawasaki disease (KD) and more specifically Kawasaki disease shock syndrome (KDSS), prompted us to explore KDSS in a preamble of a systematic comparison between the two conditions. METHODS: We completed a systematic review of KDSS and performed a meta-analysis comparison between reported KDSS cases and KD controls. RESULTS: A total of ten case-control series were included in the meta-analysis. KDSS patients were older (38.4 ± 30.6 vs. 21.9±19.5 months; P<0.001) compared to standard KD with equal sex distribution and completeness of clinical diagnostic criteria. KDSS present higher CRP (59.4±29.2 mg/dL vs. 20.8±14.8 mg/dL; p<0.001), lower albumin (2.7±0.5 g/dL vs. 3.3±0.5 g/dL; p<0.01), and lower platelets (255±149 109/L vs. 394±132 109/L; p<0.001) but only borderline higher WBC's (p=0.06). Differences in ALT, AST and ESR were non-significant. The odds of IVIG resistance (44.4% vs. 9.6%; (p<0.001) and the hospital length of stay (10.9±5.8 vs. 5.0±3.0 days; p<0.001) were higher in KDSS as were the odds of coronary artery abnormalities (33.9% vs. 8.6%; p<0.001). CONCLUSION: This first meta-analysis on KDSS versus KD represents a basis for future works on KDSS and opens the opportunity for future multicenter studies in the search of causal relationships between presenting elements and the eventual complications of KDSS. The similarities between SARS-CoV-2 multisystem inflammatory syndrome in children (MIS-C) and KDSS open new horizons to the understanding of the etiology and pathophysiology related to KDSS

    Obtaining accurate mean velocity measurements in high Reynolds number turbulent boundary layers using Pitot tubes

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    This article reports on one component of a larger study on measurement of the zero-pressure-gradient turbulent flat plate boundary layer, in which a detailed investigation was conducted of the suite of corrections required for mean velocity measurements performed using Pitot tubes. In particular, the corrections for velocity shear across the tube and for blockage effects which occur when the tube is in close proximity to the wall were investigated using measurements from Pitot tubes of five different diameters, in two different facilities, and at five different Reynolds numbers ranging from Re_θ = 11 100 to 67 000. Only small differences were found amongst commonly used corrections for velocity shear, but improvements were found for existing near-wall proximity corrections. Corrections for the nonlinear averaging of the velocity fluctuations were also investigated, and the results compared to hot-wire data taken as part of the same measurement campaign. The streamwise turbulence-intensity correction was found to be of comparable magnitude to that of the shear correction, and found to bring the hot-wire and Pitot results into closer agreement when applied to the data, along with the other corrections discussed and refined here

    Statistical Properties of Turbulence: An Overview

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    We present an introductory overview of several challenging problems in the statistical characterisation of turbulence. We provide examples from fluid turbulence in three and two dimensions, from the turbulent advection of passive scalars, turbulence in the one-dimensional Burgers equation, and fluid turbulence in the presence of polymer additives.Comment: 34 pages, 31 figure

    Scaling in Wall Turbulence: Scale Separation and Interaction (Invited Paper)

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    High Reynolds number pipe flow data are used to demonstrate the importance of several conditions related to scale separation that are either assumed in the classical theories or may be used in light of recent results in wall turbulence to infer a minimum Reynolds number condition above which scaling results may be suitable for extrapolation. Results from the Princeton Superpipe have suggested Re_τ > 5000 as the minimum Reynolds number for which key properties of pipe flow reach a “fully-developed” condition, based on observations of streamwise mean and turbulent velocity structure. Additional values related to finer constraints on the structural development are also discussed. A “skeleton” of wall turbulence is introduced, based on structural components identified as having a dominant role in the dynamics of near-wall turbulence in recent experiments by a variety of authors. Possible interaction mechanisms between these components are described alongside some outstanding questions concerning scale separation and interaction

    A comprehensive dataset of annotated brain metastasis MR images with clinical and radiomic data.

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    Brain metastasis (BM) is one of the main complications of many cancers, and the most frequent malignancy of the central nervous system. Imaging studies of BMs are routinely used for diagnosis of disease, treatment planning and follow-up. Artificial Intelligence (AI) has great potential to provide automated tools to assist in the management of disease. However, AI methods require large datasets for training and validation, and to date there have been just one publicly available imaging dataset of 156 BMs. This paper publishes 637 high-resolution imaging studies of 75 patients harboring 260 BM lesions, and their respective clinical data. It also includes semi-automatic segmentations of 593 BMs, including pre- and post-treatment T1-weighted cases, and a set of morphological and radiomic features for the cases segmented. This data-sharing initiative is expected to enable research into and performance evaluation of automatic BM detection, lesion segmentation, disease status evaluation and treatment planning methods for BMs, as well as the development and validation of predictive and prognostic tools with clinical applicability

    Framing the Real: Lefèbvre and NeoRealist Cinematic Space as Practice

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    In 1945 Roberto Rossellini's Neo-realist Rome, Open City set in motion an approach to cinema and its representation of real life – and by extension real spaces – that was to have international significance in film theory and practice. However, the re-use of the real spaces of the city, and elsewhere, as film sets in Neo-realist film offered (and offers) more than an influential aesthetic and set of cinematic theories. Through Neo-realism, it can be argued that we gain access to a cinematic relational and multidimensional space that is not made from built sets, but by filming the built environment. On the one hand, this space allows us to "notice" the contradictions around us in our cities and, by extension, the societies that have produced those cities, while on the other, allows us to see the spatial practices operative in the production and maintenance of those contradictions. In setting out a template for understanding the spatial practices of Neo-realism through the work of Henri Lefèbvre, this paper opens its films, and those produced today in its wake, to a spatio-political reading of contemporary relevance. We will suggest that the rupturing of divisions between real spaces and the spaces of film locations, as well the blurring of the difference between real life and performed actions for the camera that underlies much of the central importance of Neo-realism, echoes the arguments of Lefèbvre with regard the social production of space. In doing so, we will suggest that film potentially had, and still has, a vital role to play in a critique of contemporary capitalist spatial practices
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