1,721,056 research outputs found
Causes of Error for Turbine Radial Palette Measurement
No full textThis paper describes the project of an optical measurement system, an evolution of the system currently installed on the lathe for turbine palettes refinement in Ansaldo Energie, developed by the Politecnico di Milano. This article analyzes the most significant causes of errors found in designing an optical measurement system, proposing improvements that can optimize the system, both in terms of performance and reliability. The idea behind this work is to develop a system that can measure with an accuracy of 10m the difference of length of palettes of a turbine stadium in real time, while the turbine is turning on a refinement lathe
Interferometric instrument for thickness measurement on blown films
Full text linkReal-time measurement of plastic film thickness during production is extremely important to guarantee planarity of the final film. Standard techniques are based on capacitive measurements, in close contact with the film. These techniques require continuous calibration and temperature compensation, while their contact can damage the film. Different optical contactless techniques are described in literature, but none has found application to real production, due to the strong vibration of the films. We propose a new structure of low-coherence fiber interferometer able to measure blown film thickness during productions. The novel fiber-optic setup is a cross between an autocorrelator and a white light interferometer, taking the advantages of both approaches. View Full-Text
Optical instrument for thickness measurement
Full text linkIn modern metrology it is increasingly common to find the importance of thickness measurements in the production processes of compact materials (metals, plastics, paper, rubber, etc.). A quick and timely measurement is indispensable in those automated industrial processes capable of modifying the production parameters in real time in order to have the characteristics exactly suitable for the needs. The idea of the development of this kind of instrumentation it is starting from this. The requirements that the system will have to respect, including the importance of having a meter that must not be in contact with the plastic film and that can only be positioned on one side of it. These restrictions require the choice of a measurement methodology to be sought mainly in the optical field
Liquid level measurement through capacitive pressure sensor
Full text linkProperty of fluid and material compatibility limit the level sensor's fabrication, dynamic range and accuracy. Piezoresistive pressure sensing elements with media compatible diaphragm are limited in low pressure dynamic. In contrast, capacitive pressure sensing elements provide better solution in terms of dynamic range. In this paper, liquid level measurement is realized through a capacitive differential pressure sensor. A custom digital synchronous detection is implemented in order to optimize the measurement performances, gaining a sensitivity of 40 ppm/mm. Different operating frequencies have been defined and a DFT based feedback loop is proposed in addition to eliminate the impact of interferences at predefined frequency. The sensor characterization indicates linear response. The maximum error is limited to 0.3 mm in range of 0-200 mm as level displacement
High-sensitivity vibrometer based on FM self-mixing interferometry
No full textWe present a new optical instrument for vibrations measurement, based on a method to read the frequency modulation of a laser diode self-mixing interferometer. The laser source, when exposed to back-injection of its emitted power, is perturbed in frequency and amplitude (self-mixing effect). When the optical back-injection level is low, the self-mixing effect introduces a frequency and amplitude modulation (FM and AM) of the emitted optical field. We demonstrated with a prototype instrument that the performances of FM modulation, in terms of resolution, sensitivity and bandwidth, show an improvement of two order of magnitude with respect to well-known AM self-mixing interferometer
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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