1,720,959 research outputs found
Studi teorici e sperimentali su maneggevolezza, stabilità e manovrabilità dei veicoli a due ruote
No full textThis dissertation is intended to address various issues relating to the dynamics of two-wheeled vehicles, especially as regards motorcycles.
After defining the scope of the dynamics of two-wheeled vehicles from a general point of view, its close correlation with the design and development of new vehicles as well as the safety of driving has been highlighted. Hence the need of theoretical and experimental studies on dynamics in its fundamental aspects, i.e. handling, stability and maneuverability, has been stressed.
In Section 1 the dynamics of two-wheeled vehicles has been dealt specifically as regards the handling and the stability.
As regards the handling, an extensive bibliography on the state of the art of the theoretical and experimental studies has been firstly reported (Chapter 2), in which a series of typical and well defined maneuvers has been considered as a matter of study. Among these the maneuver of "steady turning" has been dealt separately and in greater detail, as well representative of the cornering behavior of the vehicle and particularly suited to be tested with appreciable experimental reproducibility. In this regard a methodology has been developed (Chapter 3) in order to analyze "steady turning" test and assess vehicle behavior as concerns the different aspects of steering torque - Acceleration Index - and steering behavior - Steering Ratio - .
Similarly as regards the stability an extensive bibliography on the state of the art of theoretical and experimental studies has been firstly reported (Chapter 2), in which the main lateral vibration modes have been analyzed. "Weave" and "Wobble" have been considered separately and in greater detail being closely related to safety, in relation to the instability that may involve them under particular driving conditions and speeds. In this regard a methodology has been developed (Chapter 5) in order to analyze "weave" and "wobble" test and assess vehicle attitude in relation to stability at high speed - Damping Ratio -.
The above methods have been actually applied in an extended test session conducted in collaboration with Goodyear Dunlop Tires Europe BV group. The target was to characterize a series of sets of tires in relation to their influence on the handling (Chapter 4) and the stability (Chapter 6) of two sport-touring motorcycles.
The results obtained have been collected and summarized in a single exposure (Chapter 7). On one side they have been compared and correlated with the test riders evaluations, in order to ensure their compatibility and validity; on the other side they have been compared and correlated with some of the main parameters of tires, in order to obtain more insight for their development and design. In this sense the Acceleration Index, the Steering Ratio and the Damping Ratio have showed to be fully compatible with the riders evaluations, and acceptably sensitive in assessing the characteristics of the tires on vehicle performance.
In Section 2 the dynamics of the two-wheeled vehicles has been addressed specifically as regards the maneuverability.
An extensive bibliography on the state of the art of the theoretical and experimental studies concerning the maneuverability has been firstly reported (Chapter 2). Hence the Optimal Maneuver Method has been considered as a valuable tool in order to study the maneuverability of two-wheeled vehicles, making it possible to assess performance - LapTime - without any subjective influence of the test riders. In this regard, starting from the physical point of view of the maneuverability, the mathematical formulation of the Optimal Maneuver Method and its computer implementation has been described and developed in greater detail (Chapter 3).
Then the theoretical basis of the Optimal Maneuver Method and the results of the calculation-code have been checked by the actual comparison against a wide range of telemetric data collected during Campionato Italiano Velocità 2006 - categoria SUPERBIKE (Chapter 4), in order to verify its agreement with the reality and hence its applicability to motorcycles design problems.
After verifying objectively the effectiveness and reliability of the Optimal Maneuver Method, it has been really applied in a wide range of parametric studies and analyses concerning different aspects of the design of a racing motorcycle: the distribution of masses, the geometric configuration, the powertrain (Chapter 5). In this sense the Optimal Maneuver Method has proved to be extremely sensitive and reliable in the assessment of various parameters on the performance - LapTime - of the vehicle, and also with appreciable speed and simplicity
Steady turning of motorcycles
No full textWhen driving along a circular path, the rider controls a motorcycle mainly by the steering torque. If the steering torque is low and the vehicle is moderately over-steering, a good handling feeling is perceived by the rider. In this paper, non-linear steady turning results are analysed over a wide range of forward speeds and lateral accelerations, and different 'driving zones' are identified by considering the steering torque transition speeds and steering angle critical speed. A parametric linear model of steady turning, concerning both the steering torque and the steering angle, is developed and simple parametric expressions of transition speeds and the critical speed are obtained. Steady turning tests involving different motorcycles are presented, the transition speeds and critical speed are found by linear fitting, and the characteristics of the different driving zones are investigated. The primary purpose is to determine the conditions at which the operational safety and handling of the vehicle do not impose severe demands on rider skill for control and adequate path-following properties, i.e. to identify a 'preferable driving zone'
Motorcycle steering torque decomposition
No full textThis work addresses the decomposition of the motorcycle steering torque in its main components. Indeed the steering torque applied by the rider on the handlebar is the reaction to many contributes such as road-tyre forces, gyroscopic torques, centrifugal and gravity effects. Designers are interested in steering torque because it is very important when it comes to rider's feeling and vehicle's handling. A detailed and experimentally validated multibody model of the motorcycle is used herein to analyze the steering torque components at different speeds and lateral accelerations. First the road tests are compared with the numerical results for three different vehicles and then a numerical investigation is carried out to decompose the steering torque. Finally, the effect of longitudinal acceleration and deceleration on steering torque components is presented
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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