1,721,045 research outputs found
Training an object detector using only positive samples
No full textAccurate pedestrian detection has an important role in automotive applications because, by issuing warnings to the driver and acting actively on the car brakes, it can save human lives and decrease the probability of injuries. In order to achieve adequate accuracy, detectors require training sets containing a very large number of negative samples, which can be challenging for the training algorithms of models like support vector machines (SVM). A common approach to deal with such large datasets is Hard Negative Mining (HNM), which avoids working on the full set by growing an active pool of mined samples. A more recent method is the Block-Circulant Decomposition, which achieves the accuracy of HNM at a lower computational cost by reformulating the problem in the Fourier domain. The method however results in additional memory, required during training by the FFT transform, which could be reduced significantly by using only the positive examples. To address the problem, this paper proposes two main contributions: (1) it shows that the circulant decomposition method works with the same performances when only the positive samples are used in the training phase (2) it compares the performance of a detection pipeline based on HOG features trained with either both all negative and positive samples or with only positive samples on the INRIA pedestrian dataset
Conductor losses calculation in two-dimensional simulations of H-plane rectangular waveguides
Full text linkThis paper presents a novel numerical approach to simulate H-plane rectangular-waveguide microwave circuits considering a reduced quasi-2D simulation domain with benefits for computational cost and time. With the aim to evaluate the attenuation of the full height 3D component, we propose a modified expression for the waveguide top/bottom wall conductivity. Numerical 2D simulations are validated against results from full wave 3-D commercial electromagnetic simulator. After a benchmark on a simple straight waveguide model, the method has been successfully applied to an asymmetric un-balanced power splitter, where an accurate power loss prediction is mandatory. Simulation time and memory consumption can be reduced by a factor ten and seven respectively, in comparison with complete 3D geometries. Finally, we show that, also for quasi-2D E-bend waveguide, a case where the translational H-plane symmetry is broken, the error on conductor losses computation is mitigated by our approach since the method remains still valid in a first approximation
No-reference quality assessment of in-capture distorted videos
Full text linkWe introduce a no-reference method for the assessment of the quality of videos affected
by in-capture distortions due to camera hardware and processing software. The proposed method
encodes both quality attributes and semantic content of each video frame by using two Convolutional
Neural Networks (CNNs) and then estimates the quality score of the whole video by using a Recurrent
Neural Network (RNN), which models the temporal information. The extensive experiments
conducted on four benchmark databases (CVD2014, KoNViD-1k, LIVE-Qualcomm, and LIVE-VQC)
containing in-capture distortions demonstrate the effectiveness of the proposed method and its ability
to generalize in cross-database setup
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
Fabrication and Characterization of Woodpile Waveguides for Microwave Injection in Ion Sources
No full textIn this article, we study the propagation of high-power RF fields along an air channel realized in a dielectric photonic crystal (PC) woodpile. The resulting hollow-core dielectric waveguide is suitable for high-power applications at 18 GHz and can be used as a dc-break for microwave ion sources. The infinite-periodic electromagnetic bandgap (EBG) waveguide structure has been truncated and coupled to a standard metallic rectangular waveguide operating in the fundamental TE10 mode. The fabricated waveguide structure exhibits a very low insertion loss (IL) of 0.5 dB over a transmission bandwidth of 260 MHz around the operating frequency of 18.25 GHz. A six-period structure has been manufactured, and the experimental characterization exhibits a very good agreement with the simulation results
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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