1,720,965 research outputs found
A Novel Scalable Digital Data Acquisition System for Industrial Condition Monitoring
No full textThis article introduces a novel data acquisition system aimed at condition monitoring (CM) of complex industrial machinery and plants. Current commercial solutions can be divided into two groups: 1) high resolution and 2) data rate rack systems or distributed systems usually at the price of lower performance. The proposed solution aims at filling this gap. It relies on a daisy-chain digital bus architecture, featuring a main node and a series of subordinate nodes, which have been designed to collect data from both analog and digital transducers. It follows that the system is highly scalable and easily reconfigurable: the number and the type of transducers, ranging from low-cost micro electromechanical systems to high quality piezoelectric sensors, can be optimized to match each specific measurement requirements, even after the installation of the system. The proposed technology supports up to 32 channels at 48 kS/s, and guarantees the perfect synchronization of all signals regardless of the transducer type and its position along the bus, allowing to perform advanced data analysis. The system performance is at first evaluated with laboratory tests, then in the scenario of CM of rolling bearing faults, demonstrating good sensitivity and coherence between different accelerometer types
A Novel Modular Data Acquisition System for Distributed Monitoring of Partial Discharge in Industrial Drives
No full textInsulation fault detection in rotating machinery using Partial Discharge (PD) has been a hot research topic over the last decades. In recent years, attention has also been paid to low voltage machines, following the advent of wide bandgap semiconductor devices. However, most of the solutions currently available are based on analog technology, which entails high costs, bulky wiring, and long installation times, making them unattractive for the market. This paper presents a low-cost, modular, and full-digital PD monitoring device, which implements a Capacitive Coupling (CC) front end for PD conditioning and an innovative, digital monitoring network, based on the Automotive Audio Bus (A2B), particularly suitable for deployment in large industrial plants, ensuring complete coverage and continuous monitoring of critical machinery without suffering of electromagnetic disturbances. The proposed system has been simulated in PSpice, then built and tested against a reference, consisting of a laboratory grade oscilloscope, using two different PD interfaces: CC and High Frequency Current transformer (HF-C). The comparison was carried out by subjecting a low voltage induction motor to a standard PD test to evaluate PD inception voltage detection with the different methods. The digital oscilloscope demonstrated a slightly better sensitivity concerning the onset PD voltage threshold, 1.3 - 1.35 kV. The proposed monitoring device on the other hand exhibits a greater robustness at transition voltages, being less prone to false positives. The two systems are equivalent at 1.4 kV while the proposed solution performs significantly better at higher voltages, with 6 PD events per cycle detected at 1.5 kV in place of 3. The HF-C transducer demonstrated even greater sensitivity at these voltage levels, with 7.6 PD detections per cycle at 1.5 kV. The results show that the proposed PD CC sensor has satisfactory sensitivity towards detecting onset of PD activity and appears less susceptible to noise than the digital oscilloscope CC sensor
Direction Specific Analysis of Psychoacoustics Parameters inside Car Cockpit: A Novel Tool for NVH and Sound Quality
Full text linkPsychoacoustics parameters are widely employed in automotive field for objective evaluation of Sound Quality (SQ) of vehicle cabins and their components. The standard approach relies on binaural recordings from which numerical values and curves are calculated. In addition, head-locked binaural listening playback can be performed. The Virtual Reality (VR) technology recently started to diffuse also in automotive field, bringing new possibilities for enhanced and immersive listening sessions, thanks to the usage of massive microphone arrays instead of binaural microphones. In this paper, we combine both solutions: the principal SQ parameters are derived from multichannel recordings. This allows computing a map of direction-dependent values of SQ parameters. The acquisition system consists in a spherical microphone array with 32 capsules and a multiple-lens camera for capturing a panoramic equirectangular background image. The audio recording is encoded into High Order Ambisonics (HOA) format for being compared with a classic omnidirectional microphone and into Spatial PCM Sampling (SPS) format for producing 360° equirectangular color maps. The SPS encoding is used to plot over the background image the distribution of SPL values in dB (A) and of the SQ parameters: by adding to them the directional information, it results into a novel 360° diagnostic tool for localizing the most annoying sources. Furthermore, the playback of the HOA soundtrack can be performed both on a loudspeaker rig inside an Ambisonics listening room or on binaural headphones attached to a Head Mounted Display (HMD), benefiting from head-tracking and personalized Head Related Transfer Functions (HRTFs), allowing to make quick subjective evaluations with a degree of realism unattainable with the older static binaural approach
A Novel Modular Data Acquisition System for Distributed Monitoring of Partial Discharge in Industrial Drives
Full text linkInsulation fault detection in rotating machinery using Partial Discharge (PD) has been a hot research topic over the last decades. In recent years, attention has also been paid to low voltage machines, following the advent of wide bandgap semiconductor devices. However, most of the solutions currently available are based on analog technology, which entails high costs, bulky wiring, and long installation times, making them unattractive for the market. This paper presents a low-cost, modular, and full-digital PD monitoring device, which implements a Capacitive Coupling (CC) front end for PD conditioning and an innovative, digital monitoring network, based on the Automotive Audio Bus (A(2)B), particularly suitable for deployment in large industrial plants, ensuring complete coverage and continuous monitoring of critical machinery without suffering of electromagnetic disturbances. The proposed system has been simulated in PSpice, then built and tested against a reference, consisting of a laboratory grade oscilloscope, using two different PD interfaces: CC and High Frequency Current transformer (HF-C). The comparison was carried out by subjecting a low voltage induction motor to a standard PD test to evaluate PD inception voltage detection with the different methods. The digital oscilloscope demonstrated a slightly better sensitivity concerning the onset PD voltage threshold, while the proposed monitoring device exhibits a greater robustness at transition voltages, being less prone to false positives. The two systems are equivalent at 1.4 kV while the proposed solution performs significantly better at higher voltages and the HF-C transducer demonstrated even greater sensitivity at these voltage levels. The results show that the proposed PD CC sensor has satisfactory sensitivity towards detecting onset of PD activity and appears less susceptible to noise than the digital oscilloscope CC sensor
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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