1,721,013 research outputs found
Sliding mesh simulations of a wind turbine rotor with actuator line lattice-Boltzmann method
No full textSimulating entire wind farms with an actuator line model requires significant computational effort, especially if one is interested in wake dynamics and wants to resolve the tip vortices. A need to explore unconventional approaches for this kind of simulation emerges. In this work, the actuator line method is implemented within a lattice-Boltzmann flow solver, combined with a sliding mesh approach. Lattice-Boltzmann solvers have advantages in terms of performance and low dissipation, while the sliding mesh allows for local refinement of the blade and tip vortices. This methodology is validated on a well-documented case, the NREL Phase VI rotor, and the local refinement is demonstrated on the NREL 5 MW rotor. Results show good agreement with reference Navier–Stokes simulations. Advantages and limitations of the sliding mesh approach are identified
On Wind Turbine structural stiffness influence on wake flow
Full text linkIn this work we test a Fluid–Structure Interaction (FSI) method based on the SOWFA+
OpenFAST framework. The linear structural module of FAST is coupled to SOWFA’s
Actuator Line simulations to perform the aeroelastic analysis of a wind tunnel scaled
model (1:75) of the DTU 10 MW turbine. The objective is to give a quantitative
description of the turbine stiffness influence on the wake flow by varying the model
structural properties.
The simulations are performed in two different operating conditions: below rated
(TSR = 7.5) and above rated (TSR = 5.5). Turbulence is generated by positioning
disturbing elements at the inlet, analogously to what was done in the reference wind
tunnel tests. Results show that flexibility starts to have a considerable impact on the
wake velocity deficit when the tip deflection is somewhere between 4% and 12% of the
blade length.
Based on these results, an indication is given of when the accuracy obtainable with
the CFD-CSD coupling justifies the increased computational cost
Effect of ischemia on heart submitochondrial superoxide production
No full textNADH-dependent formation of superoxide anions (O2-) by rabbit cardiac submitochondrial particles (SMP) was stimulated after exposure of the isolated heart to 90 min of ischemic perfusion. This effect was more evident in the rotenone-inhibited region of the respiratory electron chain in comparison to the antimycin-inhibited region. The kinetic study of the NADH-dependent reaction showed that at the level of the rotenone-inhibited region, ischemia reduced Km value for NADH, differently from the antimycin-inhibited region where the kinetic constants remain unchanged. No significant changes of the Vmax values were observed in both SMP-producing O2- sites. The ischemic perfusions also produced a reduction of mitochondrial function, particularly evident when glutamate as substrate was studied
Deferoxamine Protects Stromal/Stem Cells of “Lull pgm System”-Processed Lipoaspirates Against Damages Induced by Mitochondrial Respiration Inhibition
No full textBackground: The ischemic environment of the receiving area compromises the outcome of autologous fat grafts. The aim of this study was to isolate and expand the stromal vascular fraction from patient lipoaspirates and investigate the gain in cell viability exerted by some protective agents against the blockage of mitochondrial respiration. Methods: The aspirates were (1) washed, using the “Lull pgm system,” (2) centrifuged and (3) decanted. The corresponding stromal vascular fractions were isolated, and after cell adherence selection, the stromal/stem cell subpopulations were exposed to Antimycin A for 1 h. Then, the protection induced by cell pretreatment with deferoxamine, diazoxide and IGF-1 was evaluated. Results: The residual cell viability of the “Lull pgm system”-washed samples was greater than that of the centrifuged samples (p < 0.05), and this advantage was maintained during the following 12 days of culture. The administration of 400 μM deferoxamine before Antimycin A treatment increased the number of viable cells from 56.5 to 80.8% (p < 0.05). On the contrary, the pretreatment with 250 μM diazoxide or 0.1 μg/ml IGF-1 did not exert any significant pro-survival action. Echinomycin abolished the positive effect of deferoxamine, suggesting that its protection involved HIF-1α. Conclusions: Adipose-derived stromal–stem cells survive the inhibition of mitochondrial respiration better if the lipoaspirate is washed using the “Lull pgm system” rather than centrifuged. Moreover, a significant contribution to cell survival can be obtained by preconditioning stromal–stem cells with deferoxamine. In a clinical perspective, this drug could be safely administered before surgery to patients undergoing autologous fat transfer. No Level Assigned: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266
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
Effect of oxygen radicals and hyperoxia on rat heart ornithine decarboxylase activity
No full textRat heart ornithine decarboxylase activity from isoproterenol-treated rats was inactivated in vitro by reactive species of oxygen generated by the reaction xanthine/xanthine oxidase. Reduced glutathione, dithiothreitol and superoxide dismutase had a protective effect in homogenates and in partially purified ornithine decarboxylase exposed to the xanthine/xanthine oxidase reaction, while diethyldithiocarbamate, which is an inhibitor of superoxide dismutase, potentiated the damage induced by O2- on enzyme activity. Dithiothreitol at concentrations above 1.25 mM had an inhibitory effect oupon supernatant ornithine decarboxylase activity, while at 2.5 mM it was most effective in the recovery of ornithine decarboxylase activity, after the purification of the enzyme by the ammonium sulphate precipitation procedure. The ornithine decarboxylase inactivated by the xanthine/xanthine oxidase reaction showed a higher value of Km and a reduction of Vmax with respect to control activity. The exposure of rates to 100% oxygen for 3 h reduced significantly the isoproterenol-induced heart ornithine decarboxylase activity. The injection with diethyldithiocarbamate 1 h before hyperoxic exposure further reduced heart ornithine decarboxylase activity. © 1982
A Steady-State Wind Farm Wake Model Implemented in OpenFAST
Full text linkWake models play a fundamental role in finding optimized solutions in wind farm control. In fact, they allow assessing how wakes develop and interact with each other with the agility required for real-time applications. In this paper, a Gaussian Wake Model (GWM) is implemented in the OpenFAST framework in a way such that its fidelity is increased with respect to previously implemented models, while enhancing its compatibility with control purposes. The OpenFAST tool is coupled with Floris, NREL's software based on the GWM, in order to simulate the wake effect on downstream machines (in the case where the downstream rotor is fully covered by the wake, only partially covered by the wake, of the wake is generated by the interaction of more than one turbine), while the rotor aerodynamics is calculated using the BEMT on the actual rotor flow field. We intend this work as a starting point for developing and testing open/closed-loop control logics that will work in real wind farms. To show the suitability of the implementation, the entire model is then compared to Floris
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
