101,898 research outputs found
High performance wobbling subreflector for the MITO 2.6-m telescope
No full textThe Millimetre and Infrared Testa Grigia Observatory 2.6-m Cassegrain telescope has been designed to allow high-sensitivity observations in the millimeter spectral range. For this purpose, in order to reduce unwanted contributions from local foregrounds, we adopted a sky-chopping technique, by wobbling the telescope subreflector. We describe the design and performance of the wobbling system, which can endure external forced two and three fields square-wave modulation and includes features such as high frequency, high amplitude, high duty cycle, low microphonics, and high stability. © 1996 Optical Society of America
Power spectra and multifractal structure of the intensity fluctuations in the solar photosphere
No full textWe analyze the scaling properties of the intensity fluctuations in the solar photosphere. This analysis is based on monochromatic and white light images obtained at the THEMIS telescope with the Italian Panoramic Monochromator. We compute power spectra of the intensity fluctuations, showing that these spectra decrease with a power law with an exponent close to -17/3 in the range of scales smaller than 1.5 Mm. We also analyze the height dependence of the multifractal structure of the "dissipation" fields obtained from the intensity fields, in analogy with the dissipation of passive scalars in turbulent fluids. We show that in the higher photosphere the dissipation field become more intermittent and that it is characterized by more singular structures
The multiple jet impingement heat rejecter prototype for the GREGOR solar telescope
No full textHeat rejecter (HR) is a critical component of large aperture solar telescopes. It has the double task of acting as a Field Stop, to select the solar region to be studied, and as a heat rejecter to reduce the thermal load in the subsequent optics and keep the temperature of all internal surfaces within a few degrees of the ambient temperature. This last request is necessary to avoid the onset of internal convective air plumes and the subsequent generation of internal seeing. Since the thermal flux at the primary focus of a 4-m class telescope, as the European Solar Telescope (EST), is expected to be of the order of several MW=m2, even considering high HR reflectivity, the residual thermal load is conceivably high and a suitable Cooling Systems must be considered. Among the available cooling techniques, the most promising, and already applied in critical conditions such as for nuclear fusion reactor divertor, is the Multiple Jet Impingement (MJI) techniques. To fulfill the technological challenge of the HR for the next generation 4-m class European Solar Telescope (EST), a new prototype for the 1.5 meters GREGOR solar telescope has been developed as technological proof of concept. With the aim of testing this technique, a prototype of HR was realized to be mounted at the 1.5 meters GREGOR solar telescope at the at the Teide Observatory (Canary Islands, Spain). We present the HR thermal-hydraulic design based on the expected thermal load on the GREGOR primary focal plane (≃ 1500W) and the constraints on the HR temperature. The MJI technology consists in a series of nozzles impinging the liquid coolant on the backside of the field stop hot wall. The high cooling capabilities of MJI relies on the high Reynolds numbers achievable, even with modest velocity flow. In this work we describe our efforts to design, fabricate and test the prototype of an HR to characterize the MJI technology. More in detail, we show the results of the hydraulic and thermal tests carried out in the opto-electronics laboratory of the Physics Department of the University of Rome Tor Vergata
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Preliminary results on solar photospheric MHD turbulence studied via signed measures. (Based on THEMIS/IPM observations.)
No full textIn the present paper the autors report about the occurrence of sign-singularity in the solar photospheric MHD turbulence, using Dopplergrams provided during the past August 1997 by the Italian Panoramic Monochromator (IPM) at the THEMIS telescope (Tenerife)
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3346: Samuel G. Freedman, author, 2013
No full textPhotograph of author Samuel G. Freedman, at NT Daily Slash meeting in the Mayborn School of Journalism at UNT
The Car Sharing experience in Rome: when less is more
No full textCar Sharing (CS) in Rome started to be operative in March 2005, as a trial within an EC-funded project; despite its initial, modest implementation, the measure soon proved to be popular and therefore worth to be progressively enlarged across the city. Nowadays, CS is available in the most central neighbourhoods of the city, but more vehicles are expected to be operative in other areas very soon. A co-operation between the local CS operator (Agenzia Roma Servizi della Mobilità) and the “Sapienza” Department of Civil Engineering was started to develop such an expansion plan, according to an in-depth analysis of the operations run so far. For this purpose, a series of performance indicators has been defined and elaborated in order to assess the efficiency of CS not only under the operational point of view, but also in terms of achievable environmental benefits. Hence, the general approach has been two-pronged: on the one hand, operational indicators have been meant to provide values which may constitute a kind of threshold for the feasibility of the planned expansion to other areas; on the other, calculations of emissions of the CS fleet have been aimed at proving how a niche measure, as sharing cars, may positively contribute to improve air quality levels. If the former goal is clearly aimed at providing the local CS operator with sound reasons to upscale operations and place new resources at a given place rather than another in sight of major incomes, the latter is, on the contrary, focused on increasing the awareness, among the traditional drivers, of the need to switch towards more sustainable mobility patterns, in a city as Rome, where one of the highest motorization rates in Europe is recorded: 978 vehicles, including two-wheelers, every 1,000 in-habitants.
To have car-dependent citizens renouncing to their own vehicles in favor of paratransit seems, therefore, to be a very challenging task whose positive outcomes can go far beyond the simple promotion of an alternative mode of transportation, being less pollution and increased livability more important premium values for the built environment
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