1,720,984 research outputs found
Torsional Vibration Analysis of a Test Rig Driveline Equipped with a Flexible Coupling
No full textThe paper deals with a case study from the automotive industry and relative to a test rig of internal combustion engines: the output shaft of the engine transmission is connected with an electromechanical brake by means of a transmission shaft which hosts a torsional coupling with rubber elements. The engine test cell was developed several years ago; over years, the engine operations and performance have been changed, in terms of output power and torque, entailing more severe dynamic loads affecting the driveline members. In this scenario, early failures of the rubber elements of the flexible coupling have occurred. The goal is to solve the problem by bringing the fewest possible modifications to the cell layout. An experimental campaign was thus carried out, with the aim of characterizing the current system dynamic behavior and finding possible modifications able to solve the problem. In particular, torsional vibration measurements have been achieved by a coder-based technique using high-quality optical sensors and equidistantly spaced markers (zebra tape) on the rotating components. The measured data were analyzed in the Time, Frequency, Time-Frequency, and Order domains. The paper presents the experimental setup, the data processing and the results obtained from tests performed on the original system and on a modified version of the transmission driveline, after changing the elastodynamic properties of the coupling
Displacement measurement on specimens subjected to non-Gaussian random vibrations in fatigue life tests
No full textHigh-cycle fatigue life tests conducted using controlled random vibrations are commonly used to evaluate failure in components and structures. In most cases, a Gaussian distribution of both the input vibration and the stress response is assumed, while real-life loads may be non-Gaussian causing the response to be non-Gaussian as well. Generating non-Gaussian drive signals with high kurtosis and a given power spectral density, however, does not always guarantee that the stress response will actually be non-Gaussian, because this depends on the adherence of the tested system to the Central Limit Theorem. On the other side, suitable measurement methods need to be developed in order to estimate the stress amplitude response at critical failure locations, and therefore to evaluate and select input loads. In this paper, a simple test rig with a notched cantilevered specimen was developed to measure the response and examine the kurtosis values in the case of stationary Gaussian, stationary non-Gaussian, and non-stationary non-Gaussian excitation signals. The Laser Doppler Vibrometry (LDV) technique was used for the first time in this type of test, to estimate the specimen stress amplitude response in terms of differential displacement at the notch section ends. A method based on the use of accelerometers to correct for the occasional signal drops occurring during the experiment is described and the results are discussed with respect to the ability of the test procedure to evaluate the output signal
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Protesi Mioelettrica a 5 gradi di libertà per Amputati di Spalla
No full textUna collaborazione fra Centro Protesi INAIL e dipartimento DIEM dell’Università di Bologna è volta alla realizzazione di una protesi mioelettrica d’arto superiore con elevata mobilità, che possa
aumentare l’autonomia funzionale di pazienti amputati al livello di spalla. Parole chiave del progetto sono funzionalità, portabilità, controllo user-friendly, costi sostenibili. La protesi comprende il prototipo di un’articolazione di spalla (costituita da due giunti rotoidali attuati ed un giunto rotoidale passivo), un gomito mioelettrico progettato all’INAIL, un’unità commerciale di
prono-supinazione del polso e una mano mioelettrica commerciale. Tale prototipo di braccio protesico può manipolare oggetti di 1 kg in tutto l’ampio spazio di lavoro (per una buona funzionalità) e ha dimensioni, peso ed estetica compatibili con l’arto sano (per una buona portabilità da parte del paziente). La semplicità dei meccanismi di spalla e gomito permette
di sostenere costi di produzione significativamente contenuti rispetto ai costi delle soluzioni protesiche commerciali.
Gli aspetti più innovativi del progetto sono legati alla motorizzazione dell’articolazione di spalla e all’implementazione di una tecnica di controllo basata sul comando vocale, che rende più flessibile e più immediato il governo dell’ausilio protesico da parte del paziente amputato di spalla
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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