1,721,491 research outputs found
Continuous variable entanglement of counter-propagating twin beams
No full textThis work describes the continuous variable entanglement of the counter-propagating twin beams generated in a Mirrorless Optical Parametric Oscillator (MOPO) below threshold, encompassing both their quadrature and photon-number correlation. In the first case, a comparison with the single-pass co-propagating geometry outlines a completely different stability of the two sources with respect to the phase-angle. In the second case, stimulated by the critical divergence of the correlation time evidenced by Corti et al., we address the issue of the temporal bandwidth of the intensity squeezing
Automazione di una fabbrica per la produzione di carta e derivati: il ruolo della rete di comunicazione. Confronto di soluzioni e archittetture BUS
No full textEfficient parametric generation in a nonlinear photonic crystal pumped by a dual beam
No full textWe investigate parametric down-conversion in a hexagonally poled nonlinear photonic crystal, pumped by a dual pump with a transverse modulation that matches the periodicity of the χ(2) nonlinear grating. A peculiar feature of this resonant configuration is that the two pumps simultaneously generate photon pairs over an entire branch of modes, via quasi-phasematching with both fundamental vectors of the reciprocal lattice of the nonlinearity. The parametric gain of these modes depends thus coherently on the sum of the two pump amplitudes and can be controlled by varying their relative intensities and phases. We find that a significant enhancement of the source conversion efficiency, comparable to that of one-dimensionally poled crystals, can be achieved by a dual symmetric pump. We also show how the four-mode coupling arising among shared modes at resonance can be tailored by changing the dual pump parameters
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
Efficiency and reliability of gravity die casting models for simulation based design
Full text linkSimulation of Gravity Die Casting (GDC) requires to couple different models for fluid dynamics, heat transfer and solidification, together with material physics properties. Very long calculation times are required since several heating and production cycles have to be run. The simplification of the simulation models is critical to have results in useful times for the design process. The present work discusses the solidification and heat transfer physics with simplification hypoth-eses. A simulation approach skipping the pouring model for the heating cycles is introduced. A realistic case study on an engine head GDC is presented to evalu-ate four possible simulation sequences. The results show that including the heat-ing cycles in the simulation is advisable. The simplified sequences reproduce the temperature field of the die with sufficient accuracy. The proposed simulation approach results in considerable time savings with respect to the actual simula-tions and even in little accuracy improvements
Wind tunnel tests on railway vehicles in the presence of windbreaks: Influence of flow and geometric parameters on aerodynamic coefficients
Full text linkCrosswind stability is one of the most studied topics in the field of train aerodynamics. The interaction between a train and strong crosswinds can lead to the train overturning. One way to reduce the train overturning risk is to equip the railway line with windbreak barriers. In this work, the results obtained during wind tunnel tests on an ETR1000 high-speed train in the presence of different types of windbreaks are shown. The goal is to underline the effects of different flow parameters and geometric parameters of the infrastructure's models on the train's aerodynamic coefficients. Comparing the different test results made it possible to provide indications on which parameters are important to avoid experimental errors and reproduce as much as possible the real full-scale phenomena. Particular attention shall be paid to the dimensions of the splitter plate because a limited upwind width can lead to underestimation of aerodynamic coefficients by more than 30%. The length of the barriers in front of the train is fundamental and too short length can lead to coefficients overestimation of about 25%. Finally, coefficients measured with only the upwind windbreak row are lower (up to 50%) than those measured with a two rows configuration
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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