1,722,215 research outputs found
Unsupervised Legendre-Galerkin Neural Network for Solving Partial Differential Equations
No full textIn recent years, machine learning methods have been used to solve partial differential equations (PDEs) and dynamical systems, leading to the development of a new research field called scientific machine learning, which combines techniques such as deep neural networks and statistical learning with classical problems in applied mathematics. In this paper, we present a novel numerical algorithm that uses machine learning and artificial intelligence to solve PDEs. Based on the Legendre-Galerkin framework, we propose an unsupervised machine learning algorithm that learns multiple instances of the solutions for different types of PDEs. Our approach addresses the limitations of both data-driven and physics-based methods. We apply the proposed neural network to general 1D and 2D PDEs with various boundary conditions, as well as convection-dominated singularly perturbed PDEs that exhibit strong boundary layer behavior.
Path Planning for an Unmanned Aerial Vehicle Considering Dynamic Geo-fence in Urban Envrionment
No full textRecently, Unmanned Aerial Vehicles (UAVs) are widely used for various purposes such as aerial reconnaissance and delivery in urban areas. However, in some urban areas there are geo-fences where aerial vehicles cannot pass through. So, the importance of a path planning including obstacle avoidance has increased. In addition to the actual observable obstacles, it is also necessary to plan the route considering special areas or boundaries such as geofence. In this paper, we propose an algorithm to avoid dynamically changing geo-fence. To generate an efficient path which does not pass through the geofence, we add a time parameter. This proposed path planning algorithm considers not only obstacles on the map at present. The goal is to create an efficient path that also takes into account the geo-fence information dynamically generated over time, along with the speed of the UAV and the time it takes to pass through a specific location. Simulations are carried out to verify the performance of the proposed path planning algorithm
Viscosity approximation of the solution to Burgers' equations with shock layers
No full textViscous Burgers' equations with a small viscosity are considered and convergence of vanishing viscosity limit problem is investigated. We examine interior layers of a solution to viscous Burgers' equations, u(epsilon), as a viscosity parameter epsilon tends to zero. The inviscid model, i.e. when epsilon = 0, possesses the structure of scalar hyperbolic conservation laws, hence our studies deliver an important idea that arises in the field of shock discontinuities of nonlinear hyperbolic waves. The heart of the paper is to establish asymptotic expansions and utilize inner solutions of sharp transition, which are called a corrector function. With aid of corrector functions and energy estimates, we improve the convergence rate of ue to u(0) as O(epsilon(1/2)) in L-2(R) (O(epsilon) in L-loc(1)(R)) in the regions including shocks under an entropy condition
Autonomous Macro and Micro Bridge Inspection Using Aerial Vehicle Capable of Wall-Climbing
No full textSingle-gate electro-optic beam switching metasurfaces
No full textAbstract Electro-optic active metasurfaces have attracted attention due to their ability to electronically control optical wavefronts with unprecedented spatiotemporal resolutions. In most studies, such devices require gate arrays composed of a large number of independently-controllable local gate electrodes that address the local scattering response of individual metaatoms. Although this approach in principle enables arbitrary wavefront control, the complicated driving mechanism and low optical efficiency have been hindering its practical applications. In this work, we demonstrate an active beam switching device that provides highly directional beam profiles and significant and uniform optical efficiencies across diffraction orders separated by a large deflection angle. The device operates with only a single-gate bias applied to monolayer graphene, modulating its optical conductivity to control the optical efficiency of the device. The key performance metrics, the absolute and the relative efficiency, which are defined as the scattered power toward a certain angle θ normalized by the incident power and the net scattered power from the metasurface, respectively, are maximized by a genetic algorithm. Experimentally, the metasurface achieves 57° of active beam switching from the 0th to the −1st order diffraction, with absolute efficiencies of 0.084 and 0.078 and relative efficiencies of 0.765 and 0.836, respectively. Furthermore, an analytical framework using nonlocal quasinormal mode expansion provides deeper insight into the operating mechanism of active beam switching. Finally, we discuss the performance limitations of this design platform and provide insights into potential improvements
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
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