1,721,216 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
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
Unit 10 - Mechanical design: forces, stresses and the preload paradigm
No full textThis units belongs to the fourth part of the course, focussed on magnet design. Here we discuss the pattern of the electromagnetic forces acting on a dipole and on a quadrupole coil.
We first give an analytical estimate of the accumulation of prestress in the midplane for dipoles and quadrupoles based on sector coils. We prove that for dipoles the azimuthal accumulation of stress on the edge of the aperture is simply given by a product of field, current density and magnet aperture. A geometric factor, has to be added to account for the stress increase inside the coil. We then discuss the relation between magnetic pressure and stress, showing that the relation that holds for solenoids is valid for the stress in the coil heads and for radial stress in the transverse plane.
After a brief introduction on mechanical properties, we discuss the preload paradigm, that requires that the coil is always under compression. </p
Unit 11 - Mechanical design: structures
No full textThis units belongs to the fourth part of the course, focussed on magnet design. Here we discuss the mechanical structure to support the dipole and quadrupole coils.
We start with the collar concept, introduced with Tevatron magnets. The principles and equation for dimensioning the collars are presented. We then introduce collared structures with a partial support of the iron yoke. The collars can be completely replaced by the iron as a supporting structure, as in RHIC dipole, MQXA and HL LHC D1 magnets. We then introduce the concept based on Al shells and bladder and keys. After discussing the equation governing the prestress increase due to the shell, we give the constraints on the shell thickness and we present few cases.
We then introduce the stress management concept, introduce for block coils and extended to sector coils. The canter cos theta design can be also seen as an extreme case of stress management. Finally we discuss the axial structures to support longitudinal forces.</p
Unit 4 - How to generate dipole and quadrupole fields with current lines
No full textThis unit belongs to the second part of the course, which is focussed on the physics of electromagnets in the case of current-dominated layouts.
In this unit we see how to arrange current lines to generate a constant field inside a circular aperture. We will give the classical solutions (intersecting ellipse, the wall dipole and the cos theta distribution), and we will focus on a sector coil, showing that the field is proportional to the current density and to the width of the coil.
We will then prove how using a few wedges we can successively set to zero the high order multipoles, finding analytical solutions that allow to understand why the magnet designers selected some layouts for Tevatron, RHIC and LHC magnets. The same approach will be used to describe the case of the quadrupole.
Using this first approximation, that neglects iron contribution or grading, we will discuss the combination of current density, field and coil width used in superconducting magnets.</p
Unit 8 - Magnetic design: short sample field of sector coils and sensitivities to parameters
No full textThis unit belongs to the fourth part of the course, which is focussed on magnet design.
In this unit we derive analytical equations for the short sample current and field of a dipole as a function of the main parameters: coil width, filling factor of the cable, and critical surface of Nb-Ti, approximated with linear fit. For the Nb3Sn analytical equations can also be derived through a hyperbolic fit.
We show that a fundamental parameter of the magnet design is the product between the slope of the critical surface and the slope of the loadline. This parameter separates "small" by "large" coils. Thanks to this parameter, one can derive the sensitivity of the short sample current/field on critical current, loadline slope, and copper fraction.
The same computations are done for a quadrupole, both for Nb-Ti and Nb3Sn. </p
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