1,721,031 research outputs found
Modulating Light-Matter Interactions by Quantum Engineering of 2D Materials for Optoelectronics Devices
No full textThe study of light-matter interactions has undergone remarkable transformations over the past century, evolving from classical electrodynamics to modern-day nanophotonics. The advent of two-dimensional (2D) materials has revolutionized this field, enabling the confinement and manipulation of light at scales previously thought impossible. From the discovery of graphene to the exploration of hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), 2D materials have unlocked novel polaritonic phenomena, including plasmon, phonon, and exciton-polaritons. These quasiparticles facilitate sub-wavelength optical confinement, surpassing the diffraction limit and offering new opportunities for photonic applications.
Building upon these advancements, this thesis explores the intricate physics of polaritonic modes in 2D materials, with a strong emphasis on Bound States in the Continuum (BICs), topological photonics, and ultraconfined resonances. We begin by establishing the fundamental principles governing phonon, plasmon, and exciton-polaritons in 2D materials. The concept of BICs is then introduced, highlighting their role in achieving lossless optical states and their emergence in hexagonal boron nitride (hBN) within the Reststrahlen bands. Our investigation delves into long-range coupled BICs in the Upper Reststrahlen Band (RB-2) and symmetry-protected topological BICs in the Lower Reststrahlen Band (RB-1), demonstrating their potential in enhancing optical robustness and waveguiding capabilities.
Beyond BICs, this thesis explores ultraconfined dielectric resonances in hBN, specifically at frequencies beyond the transverse optical phonon frequency, revealing new regimes of light confinement. The impact of substrate engineering is also examined, where nanolaminate oxide layers enable sub-nanometer phonon-polariton confinement, further expanding the design space for 2D material-based photonics. To experimentally validate these findings, we employ advanced nanofabrication techniques, including electron beam lithography and atomic layer deposition, ensuring precise realization of theoretical predictions.
As photonics continues to evolve, the principles outlined in this thesis will serve as a cornerstone for designing future material platforms capable of extreme light confinement and tailored wave interactions
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
TOPO-EUROPE – From the Deep Earth to the Surface of Continental Europe and Its Margins
Full text linkGeomagnetic field, global pattern
Full text linkThe geomagnetic field is generated in the fluid outer core region of the Earth by electrical currents flowing in the slowly
moving molten iron. In addition to sources in the Earth’s core, the geomagnetic field observable on the Earth’s surface has
sources in the crust and in the ionosphere and magnetosphere. The signal from the core dominates, accounting for over 95%
of the field at the Earth’s surface. The geomagnetic field varies on a range of scales, both temporal and spatial; the
description of the variations made here concentrates on the recent spatial and temporal variations of the field with origins in
the Earth’s core that can be surmised from observations made over the last four centuries
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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