1,721,031 research outputs found
Effects of working memory demand on short-term heart-rate- and pulse transit time-variability
No full textThe Sternberg memory scanning task provides a measure of processing and working memory retrieval speed. In this test, subjects are presented a set of stimuli of given length. After a delay, one item is presented, and subjects are asked to indicate whether or not the item was part of the set. Performance is assessed by speed and accuracy of the response.
Short-term heart rate variability (HRV) analysis is an eligible method for assessing the autonomic nervous system (ANS) mediated response of the cardiovascular system to working memory allocation and retrieval effort.
Pulse transit time (PTT), namely the interval between heart systole and arterial blood pulse (PPG) detected in peripheral sites, has also been related to mental stress.
The purpose of this study is to analyse HRV and PTT variability (PTTV) in response to a stepwise-increasing difficulty Sternberg task
Comparative analysis of heart- and pulse-rate variability during mental task execution: the role of pulse transit time variability
No full textHeart rate variability (HRV) analysis is an established method which provides valuable information on the autonomic nervous system’s (ANS) regulation of the cardiac rhythm. HRV is a time- and frequency-domain analysis which is based on the inter-beat interval series of normal sinus rhythm beats. Short-term HRV is computed over time frames of 5 minutes or less. It is widely used in biofeedback applications, in workload assessment and stress management.
In recent years different approaches have been proposed, in which the arterial blood pulse generated by cardiac contraction is used instead of the heart beat itself for generating the pulse-series. Although this approach simplifies signal acquisition as it only requires a photo-plethysmographic sensor (PPG) clipped to the earlobe or to a fingertip, the time occurring between heart contraction and propagation of the arterial blood pulse to the peripheral site may determine non-negligible differences between electrocardiogram-derived HRV and PPG-derived HRV indices.
Aim of this study is to present a comparative analysis of short-term indices of electrocardiogram-derived HRV and PPG-derived HRV, in an experimental setup reproducing the scenario of a sedentary working activity
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
Developments in Time-Frequency Analysis of Damaged Structures. Part II: Neural Pattern Recognition for the Interpretation of T-F Maps
No full textDep. Struct. Eng., DRG Internal Report n.2/199
Measurement and extraction of motion-related quantities in sport
No full textHuman movement analysis technology, including stereophotogrammetric motion
capture, 2D and 3D video camera reconstruction, global navigation satellite and local positioning systems (GNSS, and LPS), and magneto-inertial sensors (MIMUs) has revolutionized
the field of sports by providing scientists, coaches, and athletes with invaluable insights into
athletes’ movement patterns. Thanks to movement analysis, feedback on biomechanical inefficiencies may be obtained to optimize sports techniques and prevent the risk of injuries, and
athletes’ performances may be compared among peers or over time, aiding in the evaluation
of training interventions and performance progression. This chapter spans from describing
laboratory assessments, performed with motion capture in controlled conditions, to in-field
assessments, performed in ecological conditions by 2D/3D video analysis, positioning systems
and MIMU technologies allowing the digital reconstruction of the movement.
Due to their massive spread in the sports context, particular attention is devoted to MIMUs
integrating accelerometers, gyroscopes, and magnetic sensors. Their working principles and
a battery of tests useful for their metrological characterization, as well as their calibration
refinement process, are given. Sensor characteristics and good-practice procedures of relevance
in the sport context are also detailed. General indications on how to extract the main biomechanical kinematic parameters contributing to objective performance monitoring/evaluation
or to musculoskeletal injury assessment are provided either using sensor signals directly
(temporal parameters, phase segmentation and angular velocity or linear acceleration) or
through computation/modelling (3D absolute or relative orientation, namely joint kinematics,
or the linear velocity or position). Thereafter, a detailed analysis of joint angles, body positions, and biomechanical patterns during sporting activities is enabled, allowing the definition
of key performance indicators according to ad hoc technical analyses. Finally, running, being
the sports activity that has undergone the most extensive research and enjoys the highest
level of popularity, has been selected as the prime example for in-field analysis of signal
processing and feature extraction. The attention is focused on the identification and the biomechanical comparison of different foot strike patterns due to their possible close relationship
with running-related injuries
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
Developments in Time-Frequency Analysis of Damaged Structures. Part I: Comparison of Different Time-Frequency Transforms
No full textDep. Struct. Eng., DRG Internal Report n.1/199
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