1,721,210 research outputs found
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
Experimental simulation of the sharpening process of a disc blade and analysis of its dynamic response
No full textThe vibrations arising in the sharpening of large disc blades used in paper roll cutting machines are a crucial problem for paper manufacturing quality. In this work the results of an experimental investigation carried out on a reduced scale versatile test rig are presented and discussed. A series of tests were carried out varying the characteristic parameters of the process such as the grinding contact force, the contact friction, the grinding wheel and blade relative positions, and the sharpening time length. The Fourier transform was applied to the disc displacement signals and analyses of the waterfall plots obtained for the different cases show the influence of the operation and design parameters on the system dynamic behaviour
Simulation of the Vibratory Behavior of Slender Shafts Subject to Transverse Loads Moving in the Axial Direction
No full textIn various machines of the manufacturing industry, and in particular in paper converting machinery, there are shafts operating under conditions similar to that of a slender beam subjected to a transverse load moving in the axial direction. This condition can lead to vibrations and consequent deterioration of the machine performance and of the product quality. The problem has been theoretically studied in the literature since the 1990s. While shaft mass and stiffness are universally considered among the most influential parameters on its vibratory behavior, less obvious and not investigated in the literature is the influence of the spatial interval between two successive loads, an aspect that should be considered in the shaft design phase. In fact, if that is less than the length of the shaft, i.e., if there is more than one transverse load on the shaft at a given time, the vibration level may decrease with respect to the single-load configuration. This work describes the development of a mathematical model of a slender shaft hinged at its ends, representing the rotor of a paper roll perforating unit, with the SW Mathematica. The effect of a load moving axially at a given speed followed by similar loads after given spatial intervals was simulated investigating the influence of speed and load interval on shaft vibrations and resonance. The results showed how reducing the load interval can lead to a reduction of the shaft vibration which is a useful indication on possible design corrective actions
Theoretical and experimental investigation on the dynamic behaviour of disc blades during sharpening
No full textAnalisi delle vibrazioni nell'affilatura di lame a disco
No full textVibrations arising during the sharpening process of disc blades are a crucial problem in paper manufacturing for they can cause a considerable loss of quality and productivity in the paper cutting process. In the technical literature no specific works are reported but similar problems such as those related to grinding and brake discs are dealt with. In this work the results of an experimental investigation carried out on a paper cutting machine are presented and discussed. The sharpening process of a disc blade has also been simulated by means of the explicit code LS-DYNA, integrated with the finite element code ANSYS. Some phenomenological aspects have been studied highlighting the most important parameters affecting them such as stiffness, contact force and rotational speed
Random error propagation and uncertainty analysis in the dynamic characterization of Tilting Pad Journal Bearings
Full text linkIn this work a new statistical method for the determination of the dynamic coefficients of Tilting Pad Journal Bearings is described. The method is applied to the results obtained testing a 5 pads tilting pad journal bearing with 280 mm diameter. Tests were performed on an advanced experimental apparatus specifically realized for investigations on large size high performance bearings for turbomachinery. The linear coefficient identification procedure is based on the dynamic measurement of forces, accelerations and relative displacements of rotor and bearing, as function of excitation frequency for different operating conditions. The post-processing of the dynamic data is performed in the frequency domain using the Fast Fourier Transform. Along with a description of the experimental test and identification procedure, this paper presents a least-square minimization technique for determining the dynamic coefficients and a bootstrap statistical technique for estimating their confidence intervals
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
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