1,721,128 research outputs found
Performance Investigation of Airfoils for Axial Flow Fans in Low Solidity Cascades Operating at High Inlet Flow Angles
No full textAxial flow fans are usually characterized by blade sections with low solidity and high inlet flow angles. Two main approaches are followed in the preliminary design phase, to take into account blade interaction effects: the use of available airfoil cascades data (or related correlations) and that of isolated airfoil data together with interference coefficients. The working conditions of low solidity airfoil cascades with highly tangential inflow are not widely studied in the literature, leaving the designer the possibility to rely on limited cascade data or often on the use of isolated airfoil data, with the assumption of negligible interference effects. A systematic investigation of the above working conditions for airfoil cascades is performed with Reynolds-averaged Navier-Stokes simulations. Three different airfoils are used to evaluate the influence of the design lift coefficient and maximum blade thickness. The results provide a better insight into the aerodynamic behavior of airfoil sections in such operating conditions, showing that interactions cannot be neglected. The use of metamodeling coupled with computational fluid dynamics (CFD) simulations is presented as a suitable tool for treating interference effects within the fan design process. The main findings of the present work can be used as a support for design choices as well as for developing design strategies both for the fan blades and for the airfoil sections
Thoracic computed tomography in the progressive fibrotic phenotype
No full textPURPOSE OF REVIEW: To discuss rationale and methods for determining progressive lung fibrosis on thoracic computed tomography (CT) and describe limitations and challenges. RECENT FINDINGS: Identifying patients with progressive lung fibrosis is important to determine optimal treatment. Serial high-resolution computed tomography is a method of determining disease progression. A number of studies are reviewed in this article, that have explored various parameters (both visual and automated) that signify progressive fibrosis on CT. SUMMARY: To reliably use serial CT as a marker of disease progression in fibrotic lung disease, clinicians and radiologists need to be aware of the optimal methods for identifying changes in disease extent, and understand their limitations
An Experimental Study of the Effects of the Test Configuration on the Noise Generated by Axial Flow Fans
No full textThe present paper concerns the effect of the test configuration on the noise generated by axial flow fans employed for automotive cooling systems. During the development of a fan, a number of noise tests are usually taken on different configurations, whose characteristics
depend on the design step. Often, significant discrepancies are observed between the results of different tests, resulting in difficulties in transferring and generalizing the measured SPL level spectra. Such differences regard both the broad band noise and the tonal one. In the present paper the effects of the following aspects are considered: the rotor balancing
method, the geometrical tolerances, the rotor mounting system on simplified configurations (with and without downstream stator) and the production configuration (a stationary plastic shroud) without heat exchangers. The balancing method affects the high frequency part of
the SPL spectrum, due to the broad band noise, while the mounting system may affect the OASPL and the low frequency part of the SPL spectrum, due to the tonal noise. The
geometrical tolerances do not affect the generated noise
Medical-expulsive therapy for distal ureterolithiasis: randomized prospective study on role of corticosteroids used in combination with tamsulosin-simplified treatment regimen and health-related quality of life
No full text
Analysis of the Design Bounds in Performance Limits for Industrial Axial Flow Fans
No full textThe design of an industrial axial flow fan can take great advantage from the knowledge of performance limits and favourable design choices determined from its specific fluid-dynamic characteristics.
As for other turbomachinery types, this fact is generally experienced through the entire design flow-path, from the preliminary design phase to the final optimization. Correlations, data and charts available from literature as well as proprietary database, exploited with many techniques (including machine learning) are resources in widespread use for this purpose. Despite the fluid-dynamics of axial flow fans can be considered a well-known topic, nevertheless some specific points (e.g. the maximum achievable total-to-static efficiency) can be the subject of discussions, misunderstanding or bad design choices. The present work addresses this problem in two parts. In the first part a simple 1D model is built, for fans with and without stator, from classical theory of axial fans for pressure rise coefficient, head coefficient, flow angles and diffusion efficiency. The most relevant quantities (e.g. total-to-total efficiency, total-to-static efficiency), obtained with the 1D model, are plotted on hill charts as a function of the non-dimensional pressure rise and flow coefficient. This tool provides information that can be used for preliminary design evaluations, to understand and exploit the impact of the main design choices on the basic flow characteristics and the related performance. In the second part of the work a numerical investigation is presented on the main 3D flow characteristics that are observed to limit, both in CFD simulations and experimental tests, the performance of industrial axial fans at high-pressure rise and low-to-medium flow coefficients. Simulations results highlighted that local critical swirl ratios exist for the hub and the tip regions which, when exceeded, lead with different flow topology changes to a strong performance degradation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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