1,721,716 research outputs found
Xenon irradiation of Ni3N/Si bilayers: Surface roughening and interface mixing and reactions
No full textThe irradiation effects in Ni3N/Si bilayers induced by 100-700 keV Xe ions at fluences up to 4 X 10(16) ions/cm(2) were investigated at 80 K and room temperature. The element depth profiles were measured via Rutherford backscattering (Ni,Si) and resonant nuclear reaction (N) analysis, the phase formation at the interface via x-ray diffraction, and the surface roughness by atomic force microscopy. The observed dissociation and preferential sputtering of Ni3N followed by nitrogen out-diffusion were related to the small binding energy of this compound. Mixing at the Ni3N/Si interface occurs via a combination of diffusion and reaction controlled transport processes and the interface broadening varies in second order with the ion fluence. At higher ion fluences, the formation of NiSi2 and Si3N4 phases at the interface was found
Epitaxial recrystallization of Rb-irradiated alpha-quartz during thermal annealing in air
No full textSolid phase epitaxial regrowth of the amorphized layer in alpha-quartz induced by Rb ion implantations has been studied by thermal annealing in air at 800 1200 K. The Rb+ ions were implanted at 175 keV to fluences of 1.0 x 10(16)-3.4 x 10(16) ionS/cm(2). The damage profiles and Rb depth distributions were measured by Rutherford back-scattering and channeling spectroscopy. Complete epitaxial recrystallization was achieved for the samples implanted with 2.5 x 10(16) Rb/cm(2) after a 1 h annealing in air at 1173 K. The regrowth process occurs in two steps and has activation energies of E-a(L) = 0.6 +/- 0.1 and E-a(H) = 3.6 +/- 0.4 eV. The recrystallization rate was found to increase for increasing implanted Rb fluence. The results are discussed by considering the topological structures and network connectivity Of SiO2. (C) 2002 Elsevier Science B.V. All rights reserved
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
Mixing and silicide formation during Xe-ion beam irradiations of Ta/Si bilayers
No full textThin Ta layers deposited on Si (100) substrates were irradiated with 475 keV Xe+ ions to fluences of (0.5-2) x 10(16) ions/cm(2) at temperatures between room temperature and 400 degreesC. By means of Rutherford Backscattering Spectrometry, the interface mixing and tantalum silicide formation were monitored as function of the ion fluence. TaSi2 phase formation was verified using X-ray diffraction. The interface broadening variance was found to depend linearly on the ion fluence and was explained with the help of a compound formation model involving global thermal spikes
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
Modeling the dependence of the distortion product otoacoustic emission response on primary frequency ratio
No full textWhen measured as a function of primary frequency ratio r=f(2)/f(1), using a constant f(2), distortion product otoacoustic emission (DPOAE) response demonstrates a bandpass shape, previously interpreted as the evidence for a cochlear second filter. In this study, an alternate, interference-based explanation, previously advanced in variants, is forwarded on the basis of experimental data along with numerical and analytical solutions of nonlinear and linear cochlear models. The decrease of the DPOAE response with increasing and decreasing ratios is explained by a diminishing overlap generation region and the onset of negative interference among wavelets of different phase, respectively. In this paper, the additional quantitative hypothesis is made that negative interference becomes the dominant effect when the spatial width of the generation (overlap) region exceeds half a wavelength of the DPOAE wavelets. Therefore, r is predicted to be optimal when this condition is matched. Additionally, the minimum on the low-ratio side of the DPOAE curve is predicted to occur as the overlap region width equals one wavelength. As the width of the overlap region depends on both tuning and ratio, while wavelength depends on tuning only, an experimental method for estimating tuning from either the width of the pass band or the optimal ratio of the DPOAE vs. ratio curve has been theoretically formulated and evaluated using numerical simulations. A linear model without the possibility of nonlinear suppression is shown to reasonably approximate data from human subjects at low ratios reinforcing the relevance of the proposed negative interference effect. The different dependence of the distortion and reflection DPOAE components on r as well as the nonmonotonic behavior of the distortion component observed at very low ratios are also in agreement with this interpretation
Atomic mixing and interface reactions in Ta/Si bilayers during noble-gas ion irradiation
No full textThis article focuses on the influence of chemical driving forces on the mixing and phase formation taking place at the interface of highly reactive metal/semiconductor systems under ion-beam irradiation. Ta/Si bilayers were irradiated with Ar, Kr, and Xe ions to fluences of (0.5-2.5) X 10(16) ions/cm(2) and at temperatures between liquid nitrogen and 400degreesC. The interface mixing and silicide formation were monitored as function of the ion mass and fluence by means of Rutherford backscattering spectrometry and x-ray diffraction. The interface broadening variance was found to depend linearly on the ion fluence and was explained with the help of a compound formation model involving local or global thermal spikes. The results are compared with those found in other silicide and germanide systems. The transition from local to global spikes was found to occur at the critical deposited damage energy of about 2.5 keV/nm
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
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