1,720,966 research outputs found
Cavity Optomechanics Radiation pressure cooling of a micromechanical resonator
No full textAt the beginning of last century Einstein derived the statistics of the radiation pressure force fluctuactions acting on a moveable mirror. Later, pioneering experiments about the role of radiation pressure and its ability to provide cooling for large objects were carried on by Braginsky in the context of interferometers during the 60s. The dynamical influence of radiation pressure on a harmonically suspended end-mirror of a cavity was investigated, revealing that the retarded nature of the force provides either damping or anti-damping of mechanical motion. The first cavity optomechanical experiment in the optical domain demonstrated bistability of the radiation pressure force acting on a macroscopic end-mirror.\ud
The fundamental consquences of the quantum fluctuations of radiation pressure impose a limit on how accurately the position of a test mass can be measured and the standard quantum limit for continuous position detection was then established.\ud
The original task concerning my PhD Thesis is the observation of radiation pressure acting on a mechanical object due to light circulating inside a Fabry-Perot cavity. This evidence would trace the path to observe the standard quantum limit through optical methods allowing to perform quantum measurements, and the realization of coherent superposition of the states of macroscopic objects.\ud
A plethora of different systems was introduced starting from the last decades of the 20th century in order to explore both theoretically and experimentally the behaviour of optomechanical systems. On the experimental side the most part of the approaches were to miniaturize the investigated structure. Optomechanical effects of retarded radiation forces were observed in microscale setups. However, the task of producing high quality optical cavities below mm-scale remains quite challeging.\ud
The route that was followed is the membrane-in-the-middle setup. Previous theoretical proposals and experimental implementations have analysed the possibility of setting up this kind of research using a movable mirror as end mirror of the FP cavity. Later the research focused on a new interpretation of the problem, placing a SiN membrane (a few tens of nanometers of thickness) between the two mirrors.\ud
We performed a detailed study of dynamical back-action cooling and of radiation pressure induced modifications of the mechanical properties of the membrane. In particular we have studied how the mechanical susceptibility is modified by such interaction between radiation pressure and a driven cavity mode. We finally observed that the increase of mechanical damping is equivalent to cooling of the\ud
vibrational mode and we measured its effective temperature in three different ways, obtaining consistent results, in agreement with theoretical expectations
Method and system for identifying significant locations through data obtainable from a telecommunication network
No full textA method for identifying and locating at least one relevant location visited by at least one individual within a geographical area served by a wireless telecommunication network is proposed. The method comprising the following steps: selecting (203) a predetermined time period (T) over which the identifying and locating of the at least one relevant location have to be performed, selecting (206,209) a typology of relevant location to be identified and located, retrieving (218) recorded time and position data recorded by the telecommunication network and regarding events (e i ) in which a user equipment carried by the at least one individual interacted with the telecommunication network, computing (236) a probability that each event for which recorded time and position data have been retrieved occurred in the relevant location of the selected type based on the recorded time data, identifying and clustering (239) events occurred within a predefined distance from each other and having a similar probability, computing (242) a weight value for each cluster of events identified in order to take into account statistical aspects that affect the identification and the positioning of the selected relevant location, comparing (251) the weight value with a threshold weight value, if the weight value is equal to, or greater than, the threshold weight value, identifying (254) the relevant location as belonging to the selected typology of relevant location, and providing (230) an indication of the position of the at least one relevant location based on the recorded position data of the events of the cluster, or if the weight value is lower than the threshold weight value, identifying (224) the relevant location as not belonging to the selected typology of relevant location
Automatic identification of relevant places from cellular network data
Get PDFWe present a methodology to automatically identify users’ relevant places from cellular network data.1 In this work we used anonymized Call Detail Record (CDR) comprising information on where and when users access the cellular network. The key idea is to effectively cluster CDRs together and to weigh clusters to determine those associated to frequented places. The approach can identify users’ home and work locations as well as other places (e.g., associated to leisure and night life). We evaluated our approach threefold: (i) on the basis of groundtruth information coming from a fraction of users whose relevant places were known, (ii) by comparing the resulting number of inhabitants of a given city with the number of inhabitants as extracted by the national census. (iii) Via stability analysis to verify the consistency of the extracted results across multiple time periods. Results show the effectiveness of our approach with an average 90% precision and recall
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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