1,720,984 research outputs found
A weighted Hybridizable Discontinuous Galerkin method for drift-diffusion problems
Full text linkIn this work we propose a weighted hybridizable discontinuous Galerkin method
(W-HDG) for drift-diffusion problems. By using specific exponential weights
when computing the product in each cell of the discretization, we are
able to mimic the behavior of the Slotboom variables, and eliminate the drift
term from the local matrix contributions, while still solving the problem for
the primal variables. We show that the proposed numerical scheme is well-posed,
and validate numerically that it has the same properties as classical HDG
methods, including optimal convergence, and superconvergence of postprocessed
solutions. For polynomial degree zero, dimension one, and vanishing HDG
stabilization parameter, W-HDG coincides with the Scharfetter-Gummel finite
volume scheme (i.e., it produces the same system matrix). The use of local
exponential weights generalizes the Scharfetter-Gummel scheme (the
state-of-the-art for finite volume discretization of transport dominated
problems) to arbitrary high order approximations.Comment: 28 pages, 4 figures, 4 table
Detecting striations via the lateral photovoltage scanning method without screening effect
Full text linkData-driven solutions of ill-posed inverse problems arising from doping reconstruction in semiconductors
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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
Modellierung und Simulation von vakanzenbasiertem Ladungstransport in innovativen Halbleiterbauteilen
No full textIn response to the climate crisis, there is a need for technological innovations to reduce the escalating CO2 emissions. Two promising semiconductor technologies in this regard, perovskite-based solar cells and memristive devices based on two-dimensional layered transition metal dichalcogenide (TMDC), can potentially contribute to the expansion of renewable energy sources and the development of energy-efficient computing hardware.
Within perovskite and TMDC materials, ions dislocate from their ideal position in the semiconductor crystal and leave void spaces. So far, the precise influence of these vacancies and their dynamics on device performance remain underexplored. Therefore, this thesis is dedicated to comprehensively examining the impact of vacancy-assisted charge transport in innovative semiconductor devices through a theoretical approach by modeling and simulating systems of partial differential equations. We start by deriving drift-diffusion equations using thermodynamic principles, including Maxwell-Stefan diffusion and the grand canonical ensemble of an ideal lattice gas. Particular attention is directed towards accurately limiting vacancy accumulation. Furthermore, we formulate drift-diffusion models to describe charge transport in perovskite solar cells and TMDC memristors. We discretize the transport equations via the finite volume method and establish the existence of discrete solutions using the entropy method. Our study concludes with simulations conducted with ChargeTransport.jl, an open source software tool developed in the programming language Julia. These simulations investigate the large time behavior of discrete solutions for both transport models. Additionally, we explore the influence of volume exclusion effects on charge transport in perovskite solar cells and compare our simulation results with experimental measurements found in literature for TMDC-based memristive devices
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
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