1,720,998 research outputs found
Development of a model to optimize the sand shape and post process parameters for parts produced by Direct Croning process
No full textThe complex sand cores and moulds for prototype sand, castings produced by Selective Laser Sintering (SLS), result fragile once they are removed from the supporting uncured sand. Therefore, they require Post Curing to become dimensionally stable and capable of successfully undergoing the rigors of the metal casting process. In this paper the effects of post curing process parameters on the performances of sand parts produce by SLS are investigated. The sand characteristics and Post Curing parameters choice must take into account the presence of two antagonistic needs: the decrease of gas production during the casting decreasing the presence of volatile components of the binder, and the improvement of the mechanical performances increasing the binder weight percentage (Subramanian K. & Al, 1995, ). Three different phenolic resin coated sands were investigated: 1) silica SiO2; 2) synthetic mullite 3Al2O32SiO2 ; 3) synthetic mullite + SiO2. The compressive strength of the sand specimen was reported VS time and temperature post process parameters. Increasing curing temperature and time, the mechanical performances improve up to a maximum value than decrease. A benchmark was defined and used to evaluate the post process parameters influence on dimensional and shape tolerance. The mechanical behaviour of a part reflects the micro joining mechanisms between the particles a model is proposed to understand how the post curing parameters can influence the performances of the SLS products.This paper examines also the reliability of stress distribution obtained by FEA, comparing the results with the experimental data obtained using the mullit+SiO2 sand. Finite Element Analysis (FEA) allows to construe the stress distribution in the grains contact as a function of the post process parameters, making it possible to define the grains shape optimising the mechanical properties of the obtained structure: the sand may be designed and its use can be optimised without long times and expensive tests
Multibody Modelling of Timing Belts Dynamics
No full textAlthough timing belt drives have recently been increasingly used in mechanical design, their behaviour is still considered to a large extent to be unpredictable, especially under varying operative conditions. The acoustic emission of the transmissions, above all, has been thoroughly investigated in past years, but noise still represents an unresolved problem for many applications and a concern for belt designers; therefore, the availability of good predictive models would be very useful for both design and application phases. The present work describes a multi-body numerical model that has been developed for the characterization of the dynamic behaviour of timing belt transmissions, with the final goal of assessing the acoustic radiation of a given design. Modelling and simulation have been performed by means of commercial software packages, but more additional programming was required to obtain dynamic models capable of simulating the complex behaviour of toothed belt transmissions. Several experimental tests have been performed to identify the many parameters that influence system dynamics and to validate the resulting computer aided engineering (CAE) model
A Novel Method for the design of prostheses based on Thermoelastic Stress Analysis and Finite Element Analysis
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Driving dynamics controller of a two wheel torque electric vehicle based on an integrated drive-by-wire system and absolute velocity sensing
No full textRecent advances in dependable embedded-system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to work to develop computer-controlled, by-wire subsystems with no mechanical link to the driver. These include steer-by-wire and brake-by-wire and are composed of mechanically decoupled sets of actuators and controllers connected through multiplexed in-vehicle computer networks. Actually, the success of such projects is highly dependant on the concurrent design of vehicle mechanics and control architecture and the mechatronic integrated approach is essential feature for the development of effective realisations; therefore, the availability of computer-aided modelling tools is basic requirement to assess beforehand system’s behaviour since the first design stages through dynamic simulation and virtual prototyping.
The present paper describes the architecture of a drive-by-wire controller that allows an electric city car to achieve good dynamic performances through a "joystick" human-machine interface; the independent motorization of the front wheels and a full-state sensorisation have been duly exploited to augment the standard capabilities of steer-by-wire vehicles. The referenced city-car has been studied by Tonino Lamborghini G.C. and Carrozzeria Suzzarese in cooperation with the University of Ancona, that developed a 7 d.o.f.’s model to assess controller’s performances by computer simulation, according to the different required performances or available sensing informatio
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
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