61,433 research outputs found
Two Dimensional Numerical Model to Predict the Thermal-Chemical Degradation of a piece of Carbon Fibre Composite (CFC) due to Laser Ablation
No full textThere is a growing interest in using carbon fibre composites (CFC) as a high tech construction material. The reason for this is that CFCs have similar mechanical performance to that of the more traditionally used materials like aluminium alloys, whilst being considerable lighter. The benefits of using a lighter material are vast. However whilst CFC have similar structural properties to that of aluminium its electrical and thermal properties are very different. This becomes important if CFCs are placed in an environment where the pieces of CFC could be struck by lightning as this interaction will damage the panels [1]. Previous studies published by N. Jennings and C. J. Hardwick [2] and F Lago et. al. [3] have attempted to model the damage caused to a piece of CFC due to a lightning strike. However these models have only considered very simple degradation methods and also did not include gas transport. The study presented here is an expansion of what has been discussed previously [4]. A two dimensional numerical model has been built which is designed to predict the damaged caused to a piece of CFC due to a lightning strike. Initial verification of the model is conducted by decoupling the thermal physics from the electrical effects and damaging the pieces of CFC by using laser ablation. The two dimensional numerical model (2D) includes thermal chemical degradation of the polymer via pyrolysis, the resultant gas transport through the decomposing material and carbon fibre vaporisation. An image of the x-ray tomography results of the laser ablated CFC samples are shown in figure 1. The predictions from the 2D model provide a reasonable agreement with the experimental results. Although further expansion of the model, into three dimensions, is required before a true validation of the numerical predictions can be achieved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Al Velodromo" di Jean Metzinger: un'indagine non-invasiva dei materiali e della tecnica pittorica
No full textA cento anni di distanza dalla stagione cubista, a cento anni esatti dal saggio Du Cubisme pubblicato da Jean Metzinger e Albert Gleizes, ben conosciamo i canoni del movimento cubista e come la realtà venisse trasfigurata da quegli artisti.
Tuttavia ci chiediamo ancora come quei canoni si traducessero in concreto nelle opere: quali scelte di materiali, quali riflessioni sulla impostazione dello spazio abbiano condotto alla realizzazione dei dipinti.
Nel caso di Au Velodrome il soggetto è il movimento. Non è un insieme di oggetti statici, un ritratto in posa o un paesaggio. Di più: è un fatto di cronaca, riportato in fotografia sui giornali dell'epoca. L'artista ricorda e vuole far ricordare quelle fotografie, sovrapponendovi il suo modo di rappresentare la realtà.
Raccogliere informazioni inedite su questa fase di progettazione e poi di realizzazione dell'opera è stato lo scopo della campagna di studio dei materiali e della tecnica pittorica che si è eseguita con diagnostiche fisiche assolutamente non invasive, senza prelievi, cioè, di materiali, e senza contatto con l'opera stessa
Spray computers: Frontiers of self-organization
No full textThe two different approaches to self-organization in spray-computers are discussed. Direct engineering approaches to self-organization aim at defining distributed algorithm to lead a system to a final coherent global state. The method enables engineers to achieve a specific robust self-organized behavior. The reverse engineering approaches to self-configuration aim at achieving complex coordinated behaviors in spray computers by recreating the conditions enabling complex coordinated behaviors. The approach allows to rely on the results from other disciplines to explore a variety of complex coordiantion phenomena to be exploited in spary computers
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Grafting luminescent metal-organic species into mesoporous MCM-41 silica from europium(III)tetramethylheptanedionate, Eu(thd)3
No full textMixed systems with Eu(III) β-diketonates as optically active guest species, and mesoporous silicas MCM-41 as a host matrix have been investigated. The grafting of europium(III) onto the inner walls of unmodified MCM-41 has been achieved starting from Eu(thd)3 (thd = 2,2,6,6- tetramethyl-3,5-heptanedionate), using two routes: wet impregnation (WI) at room temperature,and chemical vapour infiltration (CVI) at 185 °C. In received hybrids, denoted Eu(thd)x@MCM- 41, the same maximum yield [Eu]/[Si] = 8.2 at% on average has been achieved with either methods. The molar ratio x = [thd]/[Eu] is 0.6 on average for WI samples, and 1.5 for CVI samples. In the latter, higher contents in thd compensate lower contents in silanols with respect to the former. Rationalizing the possible bonds exchanged at the silica surface leads to a great diversity of possible co-ordination schemes according to the expression Σ[Si(OH)nx (O)xEu(thd)3-x] (where Σ means that surface species are considered). Chromophore neutral ligands phenanthroline (phen) or bipyridine (bipy) have been added to induce efficient Eu3+ luminescence under 270–280 nm excitation, via the antenna effect. For the most favourable case, (phen)yEu(thd)x@MCM-41, the emission intensity at 612 nm under excitation at 270 nm is 2/3 that for the genuine heteroleptic complex Eu(thd)3(phen). Moreover the hybrid material is stable up to 440 °C
The safety and effectiveness of different methods of ear wax removal: a systematic review and economic evaluation
No full textEar wax (cerumen) is a natural secretion produced to protect the inner ear from dirt and other fragments by moving these particles towards the outer ear. If this process does not happen properly, wax may build up causing blockage in the ear canal and the possibility of impaction. People with a build up of ear wax may suffer from hearing loss, discomfort and, on occasions, infection. It may present problems in assessing hearing, blocking the view of the ear drum during medical examination and interfering with the fitting or function of hearing aids. Although it is thought to affect between 2% and 6% of the population in the England and Wales, some groups may be at a higher risk, such as those using hearing aids or with small ear canals and/or skin conditions. Recurrence is thought to be high among some of these groups. The consequences of the build up of ear wax in the ear canal are thought to be a common reason for consultation and cost in general practice with over 2 million consultations per year in the NHS.Methods of removal of ear wax include drops, flushing with water in general practice, and removal with suction or probes in specialist clinics. The relative safety and benefits of these different methods of removal remains uncertain. This research will systematically review published and unpublished evidence on the clinical and cost effectiveness of different methods for the removal of ear wax. Where appropriate, it will develop an economic model using data from this systematic review and other relevant sources to estimate the relative costs and benefits of different methods. In addition, the project will provide recommendations for future research to try to help answer any remaining areas of uncertainty
Self-archiving practice and the influence of publisher policies in the social sciences
No full textAuthors in different disciplines exhibit very different behaviours on the so-called ‘green’ road to open access, i.e. self-archiving. This study looks at the self-archiving behaviour of authors publishing in leading journals in six social science disciplines. It tests the hypothesis that authors are self-archiving according to the norms of their respective disciplines rather than following self-archiving policies of publishers, and that, as a result, they are self-archiving significant numbers of publisher PDF versions. It finds significant levels of
self-archiving, as well as significant self-archiving of
the publisher PDF version, in all the disciplines
investigated. Publishers’ self-archiving policies have
no influence on author self-archiving practice
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