1,721,001 research outputs found
Dataset for Organometallic Perovskite Metasurfaces
No full textDataset supporting:
Behrad Gholipour et al. Organometallic Perovskite Metasurfaces. Advanced Materials.</span
Phase Change Metamaterials for Fiber and Waveguide Integrated Compact Modulators with Built in Memory Functionality
Full text linkMachine learning focuses on the development of algorithms and models that enable
a dynamic approach to making predictions or decisions on large data-sets which
cannot be readily described by analytical models. Artificial neural networks (ANN)
have become the main approach to providing advance functionalities such as pattern
recognition, and inference calculations with improved performance through experience and iterative training cycles. Inspired by the structural organization of a biological brain, ANNs consist of interconnected layers of artificial neurons, or nodes,
where input signals are weighted, pooled, and passed on to the next layer for analysis. Leveraging the computational hardware performance gains in application specific
integrated circuits (ASICs) such as graphics processing units (GPUs), ANNs have
proliferated in applications ranging from image recognition, natural language processing, autonomous vehicles, and medical diagnosis. However, the computational
requirements for floating-point operations of increasingly complex ANN models have
far exceeded performance trends predicted by Moore’s Law. Additionally, data movement between arithmetic and memory modules on metallic interconnects in ANN
hardware accelerators does not scale in terms of energy consumption, latency, and
bandwidth. The incorporation of chalcogenide phase-change metamaterials on photonic platforms such as optical fibers and photonic integrated circuits (PICs) offers a
compact, reversible, and non-volatile device platform to realize a largely distributed
and parallel optical computing architecture to accelerate training and inference calculations of ANNs. We demonstrate a cuboid-based germanium antimony telluride
(GST) metamaterial integrated on the tip of an optical fiber with a high intensity
contrast and switchable group delay dispersion between amorphous and crystalline
phases for long haul telecommunication signal transmission across network nodes.
Similarly, by eliciting an all-dielectric metamaterial resonance in a subwavelength
structured GST grating, an optically or electrically addressable synaptic weight was
realized on photonic silicon nitride waveguides. The resonator’s wavelength tunability enables symmetric 30% transmission modulation for both positive and negative
weighting values across amorphous and crystalline phases. Lastly, benefiting from
the high infrared transparency and the large refractive index contrast between the
two phases (∆n > 2.0 for certain alloy compositions), the thin film inclusion of phasechange materials on photonic waveguide circuits enables efficient and ultra-compact
phase-shifter elements with memory functionalities. Furthermore, effective medium
metamaterial design concepts allow for specified dispersion engineering required for
low insertion loss (< 0.3dB) and compact footprint (Lπ = 5 − 20µm) designs. Such
non-volatile phase-shifters can be embedded within a cascaded MZI mesh to implement a programmable zero static energy consumption matrix vector multiplication
layer for an interconnected neural network
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
Optoelectronic Gas Sensing Platforms: From Metal Oxide Lambda Sensors to Nanophotonic Metamaterials
No full textReal‐time monitoring is critical to improving safety and efficiency in chemical factories, oil and gas reservoirs, refineries, as well as land/marine/air transportation infrastructure. The lack of real‐time knowledge of constantly changing conditions in these systems causes delayed responses to critical situations such as equipment failure, chemical spills, and fire hazards, resulting in operational downtime and possible environmental damage. Sensing of hydrocarbon levels is of paramount importance in all these systems. To this end, electrical lambda sensors based on metal oxides that rely on changes in the electrical conductivity (permittivity) of the active oxide layer as a result of exposure to a target gas species have been used traditionally. These devices can suffer from low sensitivity, slow response, and bulky designs. Traditional optical sensors based on optrode and nondispersive‐infrared technology provide greater sensitivity, a wider dynamic range, and multispecies sensitivity. Recently the emergence of nanophotonic metamaterials for sensing various species shows a very promising path forward for realizing highly miniaturized, fast‐response devices. Herein, a comprehensive review of the evolution of optoelectronic gas sensing technologies is presented, not just focusing on a device‐level perspective but also examining the underlying physics and material considerations that are critical to obtaining optimal device performance
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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