1,721,099 research outputs found
Critical K.A.M. circles and the Brjuno function
No full textThe authors consider a complex Hamiltonian map, and show how to approximate the critical value of the perturbation parameter at which a given KAM circle disappears by means of a function (the Brjuno function) which only depends on the continued fraction expansion of the rotation number
AN INTEGRATED SYSTEM FOR THE REAL-TIME DETECTION AND RECORDING OF ENGINE PARAMETERS OF AGRICULTURAL MACHINES DURING DYNO TESTS: DEVELOPMENT, SET-UP AND FIRST TESTS
No full textOne of the crucial points in the development of an experimental-test system is coordinating the acquisitions from the many connected measuring instruments. In general, there are two ways of addressing this issue, based respectively: (i) on an ex-post synchronization of the readings previously gathered during the tests, or (ii) on a properly-said synchronization of the instruments during the experimentation.
The first approach can give interesting results, even if it can be computationally heavy, having the experimenter to manage files with different formats, with data coming from instruments with different sampling frequencies and, maybe, having also non-synchronized internal clocks.
The second approach is certainly more effective, allowing the user to have, just at the end of a test session, ready-made data for any subsequent processing phase. However, it needs a lot of work for its implementation. Indeed, it requires the set-up (or the creation) of many hardware interfaces, the writing of software and, possibly, also the implementation of a simple and reliable user interface.
Such this latter approach has been followed in the creation of the control subsystem of the integrated test-system for agricultural machines, part of the equipment of the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano. This management subsystem, based on Labview, has a graphical user-interface able to: (1) simultaneously acquire data from a trailed PTOdyno, a fuel-consumption meter, an exhaust-gas chemical analyser, a datalogger with different thermocouples, (2) display in real time the value of the acquired quantities, (3) plot in real time the motor-performance graphs (torque, power as a function of engine speed) and other time-dependant graphs, (4) save the acquired data in a format compatible with the most common spreadsheets. After illustrating the main features of this acquisition system, we presented also its successful application in the test of a New Holland T4020V tractor
Set-up of integrated system for real-time detection and recording of many engine parameters of agricultural machines during Dyno tests
No full textIn the development of a transportable test-system for the on-site detection of many technical parameters concerning agricultural engines, two concurrent but conflicting needs have to be managed: (1) having a high degree of completeness (and compactness) of the equipment, (2) coordinating the acquisitions from several instruments by using a possibly unique acquisition clock (i.e., with the same time interval and acquisition instant). For the first point, the ideal solution is to have as many test-instruments as possible, however, all transportable with a single vehicle and, possibly, requiring a monophasic 230-VAC power supply (i.e., available in any civil building, including farms); instead, the second point may imply a much higher complexity to be addressed. Despite it, it is possible to select and purchase only instruments with the same type of data-output (e.g., serial), the acquisition rates can be very different, due to the different types of instruments and operating principles. Also, sometimes the data interfaces cannot even be available (e.g., for dynos) and it must be created ad hoc by arranging external integrated circuits to be connected to the test devices. In the present work we illustrate the solution that has been reached in the creation of an integrated mobile test-system for agricultural machines, part of the equipment of the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano. It is based on a LabVIEW system with a graphical user-interface able to: (1) simultaneously acquire data from a trailed PTO-dyno, a chrono-gravimetric fuel-consumption meter, an exhaust-gas chemical analyser and a datalogger with different thermocouples connected to it, (2) display in real time the value of any acquired parameter, (3) plot in real time the usual motor-performance graphs (torque and power as a function of the engine speed) and other time-dependant graphs, (4) save the acquired data in a format compatible with the most common spreadsheets (in particular, MS Excel). The torque and power data have been validated in a comparative test of the integrated system with the original software of the dyno, obtaining very small differences (lower than 3.1 %). The user interface has been developed in accordance with the good-design guidelines for software, thus resulting to be highly usable in carrying out its functions, i.e. having a high level of efficiency and effectiveness
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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