1,720,990 research outputs found
Characterization of the unsaponifiable matter of coffee by means of GC/MS[Determinazione del profilo compositivo della frazione insaponificabile del caffè mediante GC/MS]
No full textThe lipid fraction of green and roasted coffee beans can be considered as a fingerprint in order to characterize coffee varieties. In particular, the analysis of the unsaponifiable fraction plays a key role to characterize different varieties of green coffee and different commercial blends. Moreover, during the roasting process several components disappear while others are generated; the roasting temperature and time, as well as the blend characteristics can affect the unsaponifiable profile. The aim of this work was the study of the unsaponifiable fraction of green and roasted coffee obtained using two different roasting temperatures. Eight samples of green coffee, four arabica and four robusta coffee beans and their roasted derivatives obtained at different roasting temperatures, and four different coffee blends were studied. The analysis of the unsaponifiable fraction was performed with GC/FID (Gas chromatography/Flame ionization detection) and GC/MS (Gaschromatography/Mass spectrometry). The unsaponifiable lipid fractions of green, arabica and robusta coffee was characterised by the presence of several diterpenes such as kahweol, cafestol, 16-O-methylkahweol, and 16-O-methylcafestol. gamma-Tocopherol, cholesterol, campesterol, 24-methylencholesterol, stigmasterol, beta-sitosterol and cicloartenol were also identified. The roasting process generated the dehydrated kahweol, and cafestol derived products. In arabica coffee a neoformation diterpene called diterpene E was identified
Full Wave Computation of the Electromagnetic Field in Chaotic Reverberation Chambers
No full textThe geometry deformation of a rectangular shaped reverberation chamber (RC) improves the field mixing and the chaoticity within the RC, in addition to traditional stirring techniques. We noted how the position and number of hemispherical diffractors affect the RC, evaluating their typical key performance parameter such as the number of uncorrelated stirrer positions. Full wave finite-difference time-domain simulations were performed for the analysis
Near Field Optimization Algorithm for Reconfigurable Intelligent Surface
No full textReconfigurable intelligent surface (RIS) is a type of wireless communication technology that uses a reconfigurable surface, such as a wall or building that is able to adjust its properties by an integrated optimization algorithm in order to optimize the signal propagation for a given communication scenario. As a reconfiguration algorithm the multidimensional optimization of the GNU scientific library was analyzed to evaluate the performance of the smart surface in the quality of signal reception. This analysis took place by means of electrodynamic simulations based on the finite difference time domain method. Through these simulations it was possible to observe the efficiency of the algorithm in the reconfiguration of the RIS, managing to focus the electromagnetic waves in a remarkable way towards the point of interest
Time Reversal for Reverberation Chamber Performance Evaluation
No full textTime Reversal (TR) technique has been proposed to evaluate the capability of a scatterer to improve the electromagnetic (EM) field chaos within a reverberant environment. After TR application, the signal reconstructed in the sampling point of the field has been analyzed to evaluate its focusing ability in time and space. This method can be applied during the design phase of a reverberation chamber (RC) to numerically evaluate the agitator goodness in the project. In this regard, it could be useful to experimentally verify the stirrer performance applied to the temporal response of the measured chamber
Flexible FDTD Simulation for the Wireless Earphone Exposure Evaluation
No full textThe electromagnetic field penetration into a human head is computed when a wireless earphone is dressed. The computation done by a home made FDTD code able to account for tissues permittivity and for a real feeding of the earphone antenna. We adopted a human head model developed on the Zubal Phantom downloaded from SourceForge. Permittivity values are assigned to each tissue accounting for the Cole-Cole frequency dependence
Time Reversal in Reverberating Environments for Electromagnetic Focusing in Biological Bodies
No full textThis paper proposes the time reversal as an electromagnetic focusing technique for improving deep biological tissues heating. The analysis occurred by full-wave FDTD simulations considering a body of a 6-year-old boy placed within a reverberant environment. The excitation was a pulse at the central frequency of 433.9 MHz. After the time reversal application, the distribution of the computed electromagnetic field shows excellent results in terms of strong spatial focusing within the human body. Examples are given for the head and limb
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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