1,721,135 research outputs found
A dynamic analysis of the LO noise transfer mechanism in a Rb-cell frequency standard
No full textThe authors are also affiliated with the Istituto' Tstitntu Nazioniln di fisica dolla Matoria. Kroqumicy noise of the local oscillator aL ovoti harmonies of the nmdulatirm frequency is known to contribute to the short-turrii instability of passive frequency sLnricifivdK [1]-[3], The moclianism by wtiicli tliiij noise trtuisfor takes place in Rb-cell standard is described here in a comprehensive approach that melticluK both signal theory methods [3] tmcl n tinie-tlcpcnclcnt quantum mechan-ical analysis. The resulting calculated transfer cocfUcionts fiir the various oven ha.rrntmic:s HFCJ discussed in relationship with measured coefficients in an actnal experiment [2]. © 2000 IEEE
Geomagnetic Time Variations and High Definition Study of Space Magnetic Effects Induced by Artificial Submerged Sources
No full textWe describe a technique for high definition marine coastal survey in which we have used to locate possible artificial magnetic sources, such as wrecks, in the Eastern Ligurian Sea. The data were recorded with a marine proton magnetometer using a high density grid ….Marina Militare Italiana, Witehead Alenia Sistemi SubacqueiPublished221 - 2281.8. Osservazioni di geofisica ambientaleN/A or not JCRope
Geomagnetic Time Variations and High Definition Study of Space Magnetic Effects Induced by Artificial Submerged Sources
No full textWe describe a technique for high definition marine coastal survey in which we have used to locate possible artificial magnetic sources, such as wrecks, in the Eastern Ligurian Sea. The data were recorded with a marine proton magnetometer using a high density grid ….Marina Militare Italiana, Witehead Alenia Sistemi SubacqueiPublished221 - 2281.8. Osservazioni di geofisica ambientaleN/A or not JCRope
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
Microgravity vertical gradient measurement in the site of VIRGO interferometric antenna (Pisa plain, Italy)
No full textThe site of the European Gravitational Observatory (EGO) located in the countryside near Pisa (Tuscany, Italy) was investigated by a microgravity vertical gradient (MVG) survey. The EGO site houses the VIRGO interferometric antenna for gravitational waves detection. The microgravity survey aims to highlight the gravity anomalies of high-frequency related to more superficial geological sources to obtain a detailed model of the lithologic setting of the VIRGO site, this will allow an estimate of the noise induced by seismic waves and by Newtonian interference. This paper presents the results of the gradiometric survey of 2006 in the area of the interferometric antenna. MVG measurements allow us to enhance the high frequency signal strongly associated with the shallow structures. The gradient gravity map shows a main negative pattern that seems related to the trending of the high density layer of gravel revealed in geotechnical drillings executed along the orthogonal arms during the construction of the VIRGO complex. Calibrating the relationship between the vertical gradient and the depth of the gravel interface we have computed a model of gravity gradient for the whole VIRGO site, defining the 3D distribution of the top surface of this layer. The latter shows a NE-SW negative pattern that may represent a palaeobed alluvial of the Serchio from the Bientina River system
A metrologic method of anomaly field amplitude bottom reduction in undersampled geomagnetic marine surveys
No full textWe show the results obtained by means of a seabed reduction technique on the intensity of geomagnetic anomaly fields applied to a synthetic case and then to the real case of a geomagnetic survey of eastern Ligurian Sea (Italy). The eastern Ligurian Sea has very intense short waves anomaly fields and a sea bed that varies greatly in depth. As a result the geomagnetic space signal is characterized by a very large spectral content; in these conditions it is not possible to obtain a full sampled marine survey and vertical continuation analytic procedures and standard numerical bottom reduction based on a single vertical incremental parameter, whichever is applicable, fails to give accurate results. The present technique, which has been fine-tuned over 4 years of experimentation in environmental researchs, aims to provide a simple and efficient means to reduce the distortion of geomagnetic anomalies field caused by the variation of distance between survey plane and magnetic outcrop source position. The compensation procedure is based on evaluation, by comparison of two measurements carried out at different altitudes, of the mean vertical increment typical of each anomaly field principal frequency component bands. The component anomaly fields are then corrected by application of the corresponding vertical increments and lastly, the anomaly geomagnetic field reduced to the sea-bed is computed as Inverse Fourier Transform of a spectrum built as synthesis of the component anomaly fields' spectra. The results obtained have shown a notable increase in definition of anomaly field intensity without the production of appreciable distortions or false geomagnetic echoes.Hydrographic Institute of the Italian Navy,Published63-792.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveJCR Journalreserve
A metrologic method of anomaly field amplitude bottom reduction in undersampled geomagnetic marine surveys
No full textWe show the results obtained by means of a seabed reduction technique on the intensity of geomagnetic anomaly fields applied to a synthetic case and then to the real case of a geomagnetic survey of eastern Ligurian Sea (Italy). The eastern Ligurian Sea has very intense short waves anomaly fields and a sea bed that varies greatly in depth. As a result the geomagnetic space signal is characterized by a very large spectral content; in these conditions it is not possible to obtain a full sampled marine survey and vertical continuation analytic procedures and standard numerical bottom reduction based on a single vertical incremental parameter, whichever is applicable, fails to give accurate results. The present technique, which has been fine-tuned over 4 years of experimentation in environmental researchs, aims to provide a simple and efficient means to reduce the distortion of geomagnetic anomalies field caused by the variation of distance between survey plane and magnetic outcrop source position. The compensation procedure is based on evaluation, by comparison of two measurements carried out at different altitudes, of the mean vertical increment typical of each anomaly field principal frequency component bands. The component anomaly fields are then corrected by application of the corresponding vertical increments and lastly, the anomaly geomagnetic field reduced to the sea-bed is computed as Inverse Fourier Transform of a spectrum built as synthesis of the component anomaly fields' spectra. The results obtained have shown a notable increase in definition of anomaly field intensity without the production of appreciable distortions or false geomagnetic echoes.Hydrographic Institute of the Italian Navy,Published63-792.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveJCR Journalreserve
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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