1,721,070 research outputs found
Scattering iterative method based on generalized wave variables for the implementation of audio circuits with multiple one-port nonlinearities
No full textThe Scattering Iterative Method (SIM) is a recently developed fixed-point method relying on Wave Digital (WD) principles for the discrete-time simulation of electrical networks containing multiple one-port nonlinearities. Due to its robustness and efficiency, SIM proved itself to be suitable for the digital emulation of nonlinear audio circuits in Virtual Analog applications. The existent SIM formalization uses voltage wave variables. In this paper, we extend such a formalization to accommodate circuit descriptions based on generalized wave variables, including voltage, current, and power-normalized waves, as particular cases. A SIM-based WD implementation of a passive audio compressor employing the newly introduced generalized wave framework is presented, along with an analysis of the SIM convergence speed considering different types of waves and two different initialization strategies
Development of predictive models for short-term prediction of disability progression in multiple sclerosis
Full text linkMultiple Sclerosis (MS) is an autoimmune degenerative disease of the central nervous system, in which chronic inflammation leads to demyelination with transient or permanent axon damage. Symptoms of MS include problems with vision, movement, sensation and balance, which can be intermittent or progressively increasing over time until bringing to permanent disability. Predictive models of MS disability progression can be very useful to support the clinician in choosing the best care for each patient. The aim of this work is to develop predictive models of short-term MS disability progression. Data are part of the Multiple Sclerosis Outcome Assessments Consortium (MSOAC) Placebo database, which includes longitudinal demographic and clinical data of 2465 MS patients who were enrolled in the control arm of different MS clinical trials. Variables collected in the first visit were used to predict a binary outcome of disability progression at 6 months and 18 months from the baseline, using a logistic regression model. Disability progression was defined as a 1.5 increase in the Expanded Disability Status Scale (EDSS) value compared to the baseline time. 20 input variables were considered in each model, including demographics, medical history, functional tests, questionnaires, and MS phenotype. Preprocessed data were split into a training and a test set with an 80%-20% proportion. Logistic regression models were trained on the training set, using over-/undersampling techniques for balancing the classes. The identified models were tested on the test set by assessing the area under the receiver operating characteristic curve (AUC). Prediction performance on the test set was satisfactory, although not optimal, with AUC equal to 0.74 at 6 months and 0.71 at 18 months. These prediction performances are comparable with results obtained by other literature studies on smaller cohorts. Future developments of this work include the use of other machine learning techniques for model training, the application of feature selection and variable ranking techniques, the incorporation of new variables (e.g., imaging variables), and the external validation of the models on new populations
Antiderivative Antialiasing Techniques in Nonlinear Wave Digital Structures
Full text linkThe Wave Digital Filter (WDF) formalism is becoming a popular approach for the digital emulation of audio circuits. Nonlinear WDFs, like other kinds of discrete-time nonlinear filters used in Virtual Analog modeling applications, are often affected by aliasing distortion. Recently formalized Antiderivative Antialiasing (ADAA) methods are capable of significant aliasing reduction even with low oversampling factors. This paper discusses different strategies to integrate pth-order ADAA methods into stateful WDFs with a single one-port or multiport nonlinearity while preserving the modularity property typical of traditional WDFs. The effectiveness of the proposed approach is verified by applying the discussed ADAA techniques to three nonlinear audio circuits containing diode-based nonlinearities and a BJT transistor
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
Largely shared neural codes for biological and nonbiological observed movements but not for executed actions in monkey premotor areas
Full text linkThe neural processing of others' observed actions recruits a large network of brain regions (the action observation network; AON) in which frontal motor areas are thought to play a crucial role. As the discovery of mirror neurons (MNs) in the ventral premotor cortex, it has been assumed that their activation was conditional upon the presentation of biological rather than nonbiological motion stimuli, supporting a form of direct visuomotor matching. Nonetheless, nonbiological observed movements have rarely been used as control stimuli to evaluate visual specificity, thereby leaving the issue of similarity among neural codes for executed actions and biological or nonbiological observed movements unresolved. Here, we addressed this issue by recording from two nodes of the AON that are attracting increasing interest, namely, the ventrorostral part of the dorsal premotor area F2 and the mesial presupplementary motor area F6 of macaques while they 1) executed a reaching-grasping task, 2) observed an experimenter performing the task, and 3) observed a nonbiological effector moving in the same context. Our findings revealed stronger neuronal responses to the observation of biological than nonbiological movement, but biological and nonbiological visual stimuli produced highly similar neural dynamics and relied on largely shared neural codes, which in turn remarkably differed from those associated with executed actions. These results indicate that, in highly familiar contexts, visuomotor remapping processes in premotor areas hosting MNs are more complex and flexible than predicted by a direct visuomotor matching hypothesis
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