1,721,068 research outputs found
Density functional theory studies of solid density plasmas
Full text linkIn warm dense matter (WDM) and dense plasma physics, Density Functional Theory (DFT) has become a standard approach over the past many years for simulating transport properties, equations of state, interpreting experimental measurements and many other applications. The main chapters, two to four, of this thesis cover original work by the author on three topics: excited state pseudopotentials, time-dependent DFT (TDDFT) and many-body theory.
For an excited state pseudopotential, a specific excited ion core configuration is generated by externally imposing a set of occupation numbers in the same way as can be rigorously done for a non-interacting electron system. In chapter 2 results and a physical argument are presented seeking to justify this process when generating excited configurations of bound electron systems.
Those electrons that might be considered as `free' within a plasma exhibit not only single-particle excitations, as one might label with a set of single-particle occupation numbers, but also significant collective behaviour i.e. plasmons. TDDFT linear-response theory is applied in chapter 3 as a rigorous means of modelling the general dynamic and wavelength-dependent response properties, and fluctuations, for quantum plasma systems. With help from the Langreth rules a fluctuation-dissipation relation for the electron dynamic structure factor is derived. Finally, the dynamic structure factor is computed for compressed Beryllium and CH plasma, with favourable comparison to experimental data and simulations by previous authors.
In chapter four the free-free opacity of solid density Al plasma is considered. Both the tensor nature of the dielectric function, in the form of local field corrections, and an accurate description of bound-state properties, in the form of correct binding energies, are required to reproduce experimental room temperature measurements. Commonly used exchange-correlation functionals are insufficient for predicting the energy gap between bound states and the continuum in a linear response theory context. To this end, the author has implemented and demonstrated finite-temperature many-body quasi-particle calculations in the Abinit code. These many-body calculations are expensive however they are a potential future source of accurate theoretical predictions, covering a wide range of plasma conditions to which other, perhaps simpler models might be benchmarked
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Isochoric generation and spectroscopic diagnosis of high energy-density systems
Full text linkAdvances in both optical laser and X-ray Free Electron Laser (XFEL) facilities have extended the regimes accessible in laser targets. Petawatt lasers such as Orion at AWE can be routinely used to drive targets to extreme conditions of multi-keV temperatures. Isochoric heating with an XFEL to temperatures of 100’s of eV has been demonstrated and well described on prototypical metals and low-Z mixtures, and the bright, tunable x-ray source is often used as a probe in Warm Dense Matter (WDM) and High Energy-Density (HED) studies. X-ray diagnostics are often used to characterise the conditions present in such a laser target, with stringent demands on collection efficiency to yield significance in signal/noise in order to characterise systems with potentially large spatio-temporal gradients.
This thesis describes a set of experiments to isochorically generate and characterise WDM and HED systems relevant to astrophysical plasmas and Inertial Confinement Fusion. The focus of this work is on using measured X-ray Emission Spectroscopy or Resonant Inelastic X-ray Scattering (RIXS) spectra to bound the conditions present in the laser target, and using Single Photon Counting informed techniques to maximise the signal/noise in recovered spectra. Accurate accounting of the single photon response of x-ray detectors is used to detail the absolute value and error on recovered spectral intensity, and from that to inferred plasma parameters. The particular systems considered in this work are nanowire targets irradiated at relativistic intensities, RIXS measurements of warm-dense nickel, and nano-focused XFEL heating of solid density iron.
The recovered plasma conditions mapped from experimental data are shown to correspond well to Particle-In-Cell and Density Functional Theory, benchmarking simulation capacity and offering insights into factors affecting the target’s response to laser drive. The results and methods presented here could inform and complement future efforts to investigate warm- and hot-dense systems, as a diagnostic capability or elucidating a navigable route toward ultra-HED systems
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
