1,721,117 research outputs found
Interactions between molecules and surfaces
No full textPart 1The processing of semiconductor layer systems relies upon controlled plasma etching to achieve the desired device definition. The physics and chemistry of plasma etching are not completely understood, and many process parameters are still chosen empirically. In this thesis, in-situ ellipsometry, quadrupole mass spectrometry and optical emission spectrometry have been used to monitor the etching of silicon (100), germanium (100) and a heterostructure system comprising of Si (100) grown on Si1-xGex (100), where x=0.18. Information has been obtained on the etch rate, the layer thickness and the refractive index of the Si1-xGex layer using the in-situ diagnostic tools. Etching conditions were identified which gave uniform, smooth etching of the Si/Si1-xGex wafer system.The selective etching of Si over Si1-xGex was investigated, using CHF3 and SF6 to form etch inhibiting fluorocarbon polymer films. Si1-xGex was found to etch faster than Si in all of the experiments carried out. The best selectivity obtained for the etching of Si over Si1-xGex was 1:1.12.Nomarski microscopy was used to study the surface quality of the Si/Si1-xGex/Si wafers prior to etching. Surface roughness was attributed to relaxation of the Si1-xGex layer, leading to misfit dislocation defects. The presence of defects within the structure were confirmed using TEM and SEM.Semi-insulating polycrystalline silicon (SIPOS) thin films have been characterised using in-situ ellipsometry with plasma etching with CF4 as a process gas.The anisotropy of an etch is believed to be associated with the energy of ions impacting the wafer surface, and is therefore an area of particular interest. Experimental ion energy distributions (IED) have been recorded at the powered electrode. Theoretical IED were calculated using a FORTRAN program, and were in good agreement with the experimental IED.Part 2The rates of adsorption and desorption of methyl salicylate on various COLPRO wall coverings were measured. The adsorption and desorption curves have been fitted to an expression that can be derived for a simple adsorption/desorption model.</p
The vibration of rolling discs
No full textThe study presented is a fundamental investigation into the vibration of a rolling disc and an analysis of the sound which is then produced by the disc response. In order to characterise the disc's behaviour the free and forced vibration of a thin disc is analysed with the additional conditions which occur in rolling. These conditions include the geometric boundary conditions, the effect of the in-plane load, the change due to rotation of the disc and the effect of contact on the disc which in the first instance is modelled as a simple pinning constraint. Further in depth analysis is described for a more realistic model of the rolling contact including the effect of the contact stiffness and the creepage forces which may be present and simple contact models are proposed and corresponding responses predicted. Possible various sources of excitation are examined which cover the Rigid Body dynamics of the rolling disc, the effect of the contact model as a source of excitation and a preliminary consideration of the forces generated by contact of rough surfaces. An elementary representation is presented for the sound radiated by the rolling disc, assuming it is baffled, and its efficiency evaluated and the unbaffled disc radiation is also presented for a particular case
A perturbation method for locally damped dynamic systems
No full textIn the field of stochastic structural dynamics, perturbation methods are widely used to estimatethe response statistics of uncertain systems. When large built up systems are to be modelled inthe mid-frequency range, perturbation methods are often combined with finite element modelreduction techniques in order to considerably reduce the computation time of the response.Existing methods based on Component Mode Synthesis (CMS) allow the uncertainties in thesystem parameters to be treated independently in each of the substructures and the perturbationin the local parameters to be propagated to the full system global parameters. However, localtreatment of damping uncertainty is usually avoided by assuming proportional damping. Here,a perturbation method that includes local modal damping uncertainty and its propagation tothe global response is proposed. Local damping is accounted for in the CMS model by useof complex modes. A perturbation relationship between local and global modal properties isstated for non-classically damped systems
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
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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