1,720,972 research outputs found
Advanced finite element model for predicting surface integrity in high-speed turning of AA7075-T6 under dry and cryogenic conditions
No full textSurface integrity of machined additively manufactured Ti alloys
No full textAdditive manufacturing processes (AM) offer the possibility to easily fabricate three-dimensional parts with high geometrical complexity. However, the additively manufactured components often require finishing operations, such as machining, showing a different machinability than those produced with conventional processes. Thus, it is crucial to study the effect of the manufacturer suggested cutting parameters on the surface integrity of the AM components, since they can behave differently than the correspondent wrought materials. The aim of the present work is to investigate the surface and subsurface modifications induced by turning operations performed on additively manufactured titanium alloys. The material under investigation is the grade 5 titanium alloy (Ti6Al4V) produced by three different methods namely, Electron Beam Melting (EBM), Direct Metal Laser Sintering (DMLS) and conventionally wrought processes. The effect of such processes on machinability and surface integrity is herein extensively studied (nano-hardness, plastically deformed layers, microstructural alterations etc.). In particular, the morphological, chemical and mechanical analyses on the pre- and post-machined samples highlight the influence of the production processes on their surface integrity underlying the need to properly redesign the machining parameters accordingly
Physics based modeling of machining Inconel 718 to predict surface integrity modification
No full textInconel 718 nickel-based super alloy is widely used in aerospace, nuclear and marine industries due to its important thermo-mechanical properties and excellent corrosion resistance. However, the possibility to produce parts with a superior surface quality (e.g. enhanced surface integrity) still represents a challenge for manufacturing industry since the standard processing parameters are not suitable when difficult-to-cut materials are involved. Thus, predictive models represent a useful tool to simulate the material behavior during machining. Physics based computational analysis is an excellent technique to analyze the micro-scale phenomena (e.g. dynamic recrystallization, density of dislocation changes) taking place during the plastic deformation processes. Thus, it represents an important tool to optimize the cutting process achieving the desired characteristics of the machined surface. This work presents a physics based model developed to assess the micro-mechanical behavior of Inconel 718 super alloy subject to severe machining operations. Results show the good capability of the model to properly deal with the main physical phenomena taking place during the process and to correctly predict the main surface modifications which affect the final product performance
3D finite element modelling of surface modification in dry and cryogenic machining of EBM Ti6Al4V alloy
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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
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
Crucial role of cytoskeleton reorganization in the negative inotropic effect of chromogranin A-derived peptides in eel and frog hearts
No full textVasostatins (VSs), i.e. the main biologically active peptides generated by the proteolytic processing of chromogranin A (CGA) N-terminus, exert negative inotropism in vertebrate hearts. Here, using isolated working eel (Anguilla anguilla) and frog (Rana esculenta) heart preparations, we have studied the role of the cytoskeleton in the VSs-mediated inotropic response. In both eel and frog hearts, VSs-mediated-negative inotropy was abolished by treatment with inhibitors of cytoskeleton reorganization, such as cytochalasin-D (eel: 10 nM; frog: 1 nM), an inhibitor of actin polymerisation, wortmannin (0.01 nM), an inhibitor of PI3-kinase (PI3-K)/protein kinase B (Akt) signal-transduction cascade, butanedione 2-monoxime (BDM) (eel: 100 nM; frog: 10 nM), an antagonist of myosin ATPase, and N-(6-aminohexil)-5-chloro-1-naphthalenesulfonamide (W7) (eel: 100 nM; frog: I nM), a calcium-calmodulin antagonist. These results demonstrate that changes in cytoskeletal dynamics play a crucial role in the negative inotropic influence of VSs on eel and frog hearts. (c) 2006 Elsevier B.V. All rights reserved
Influence of vasostatins, the chromogranin A-derived peptides, on the working heart of the eel (Anguilla anguilla): negative inotropy and mechanism of action
No full textWe have studied the effects of exogenous human recombinant Vasostatin-1 (VS-1), Vasostatin-2 (VS-2) and the human Chromogranin A (CGA) 7-57 synthetic peptides on the mechanical performance of the isolated and perfused working eel (Anguilla anguilla) heart. Under basal conditions, the three peptides decreased stroke volume (SV) and stroke work (SW), thus exerting negative inotropism. The VS-1-mediated negative inotropism was abolished by exposure to inhibitors of either Gi/o protein (pertussis toxin; PTx) or M1 muscarinic receptors (Pirenzepine) or calcium (Lantanum and Diltiazem) and potassium (Ba2+, 4-aminopyridine, tetraethylammonium, glibenclamide) channels, while it required an intact endocardial endothelium (EE). Using N-G-monomethyl-L-arginine (L-NMMA) as an inhibitor of nitric oxide (NO) synthase (NOS), and hemoglobin as a NO scavenger, we demonstrated the obligatory role of NO signaling in mediating the vasostatin response. Pretreatment with either a specific inhibitor of soluble guanylate cyclase (GC) 1H-(1,2,4)oxadiazolo-(4,3-alpha)quinoxalin-1-one (ODQ) or the inhibitor of the cGMP-activated protein kinase (PKG) KT5823, abolished the VS-1-mediated inotropism, indicating the cGMP-PKG component as a crucial target of NO signaling. Of note, VS-1 was effective in counteracting the adrenergic (Isoproterenol and Phenylephrine)-mediated positive inotropism. These findings provide the first evidence that vasostatins exert cardiotropic action in fish, thus suggesting their long evolutionary history as well as their species-specific mechanisms of action. (C) 2004 Elsevier Inc. All rights reserved
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