1,721,481 research outputs found
Challenging entropic gravity /by Jonathan James Roveto.
No full textA recent paper by Erik Verlinde [1] argues that gravity should be viewed not as a fundamental force, but as an emergent thermodynamic phenomenon due to some yet undetermined microscopic theory. Using well-established thermodynamic principles along with the holographic principle, Verlinde proposes that gravity can be seen as an entropic force as opposed to a fundamental one. Using this idea, Verlinde claims to be able to derive Newton s 2nd law, Newton s law of universal gravitation, and Einstein gravity. We present a challenge to this reformulation of gravity. Our contention is that a detailed examination of Verlinde s argument shows that such a theory cannot correctly give Newton s laws or Einstein gravity. We find that the Poisson equation for Newtonian gravity is not uniquely determined using Verlinde s theory. We are also able to show that Verlinde s theory does not uniquely determine Einstein s field equations. Specific calculations can also be done in the Reissner-Nordstrom and Schwarzschild metrics to show that the entropy of these black holes do not agree with accepted values of these entropies._x000D_We will begin by introducing results by Hawking, Unruh, and Bekenstein that motivate the relationship between gravity and thermodynamics. We then summarize Verlinde s proposal of gravity being a thermodynamic phenomenon. From this new theory, we can make calculations using the Schwarzschild and Reissner-Nordstrom metrics to determine if Verlinde s theory is compatible with well-known calculations for the temperature and entropy of black holes with these metrics. Finally, we will present a detailed explanation as to why we believe Verlinde s derivation of the Poisson equation and Einstein s field equations is flawed
Microstructural characterisation of duplex 316 weld metals : the effects on mechanical and high temperature properties
No full textSeveral 316 manual metal arc weld metals produced with commercial and experimental consumEbles, have been aged between 600-850oC. This resulted in the progressive dissolution of the δ-ferrite with the appearance of austenite, M_23C_6, MX and intermetallics σ, X and η phase. The amount and distribution of the secondary phases were strongly dependent on small compositional variations including C, Cr, Mo, Si and residual Nb, Ti and V. In addition, the morphologies of the M_23C_6 and intermetallics σ and X were sensitive to the ageing temperature. During the δrightarrowy transformation, the δ-ferrite becomes progressively enriched in Cr, Mo and Si and depending on the local composition of the δ-ferrite, eventually transforms to intermetallic σ or X. A model has been formulated in which the rate of δ-ferrite dissolution is controlled by solute diffusion along the δ/y boundary. The effect of ageing and the subsequent microstructural transformations on the tensile, impact and creep properties, have been discussed in terms of changes in the precipitate distribution and morphology. Although the effect of secondary phases on the tensile properties were relatively small, the precipitate distribution and morphology had a large effect on both the creep properties and the ambient impact toughness. In the creep tests, the duplex deposits of nominally the same composition exhibited very large differences in minimum creep rate, with the rutile deposits being approximately 2-3 orders of magnitude stronger than the duplex deposits. A correlation between the minimum creep rate and weld metal composition has been established for all the duplex deposits. The model implies that the variations in rupture properties are largely controlled by the residual levels of Nb, Ti and V present in the deposits. It has been shown that the formation of carbide and intermetallics is not necessarily a pre-requisite factor for the embrittlement of the weld metal. The present study indicates that the sensitivity of the weld metal to embrittlement by carbide and intermetallics is dependent on the matrix ductility or the MX particle dispersion. Low ductility fracture occurred when the δ/y or y/y grain boundaries were outlined by continuous films of carbide and intermetallic, in the presence of hardened grain interiors.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Synthesis of cycloheptanes using radical cyclisations of methylenecycloproprane derivatives
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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