1,721,068 research outputs found
Luca Valerio: diffusione ed eredità delle sue opere giovanili
No full textQuesta tesi si focalizza sulle opere giovanili del matematico Luca Valerio (Napoli 1553 - Roma 1618), il Phylogeometricus Tetragonismus e il Subtilium indagationum liber primus seu quadratura circuli et aliorum curvilineorum, e in particolare sulla loro diffusione e la loro eredità nel contesto matematico del XVI secolo.
La tesi è divisa in due parti. La prima, dopo aver brevemente descritto l'ambiente scientifico romano del tardo Cinquecento e la figura dell'orientalista Giovanni Battista Raimondi, è dedicata allo studio delle idee di quadratura del cerchio presenti nel Phylogeometricus Tetragonismus di Valerio. Le idee del matematico Francesco Maurolico (Messina 1494 - Messina 1575) secondo le quali i rapporti fra retto e curvo siano “incogniti”, porteranno, attraverso discussioni che coinvolgeranno le figure di Raimondi e Valerio, all’idea di determinare la quadratura del cerchio mediante tentativi “innovativi”. In particolare mostreremo come il Phylogeometricus Tetragonismus di Luca Valerio sia strettamente correlato a un manoscritto di Raimondi intitolato Quadratura circuli (Biblioteca Nazionale Centrale di Firenze, fondo Magliabechiano, classe XI,41).
Nella seconda parte, invece, affronteremo il tema della diffusione e dell'eredità dei temi presenti nel Subtilium indagationum liber primus (1582). In particolare, descriveremo come il matematico e marchese Guidobaldo dal Monte (Pesaro 1545 - Pesaro 1607) abbia avuto modo di leggere e commentare alcuni passi di quest'opera e il suo punto di vista su questo lavoro ci permetterà di affrontare tematiche più generali. Infatti, seppure dell’impostazione dei primi lavori matematici di Valerio non rimarrà alcuna traccia esteriore ed evidente nel proseguimento dei suoi studi scientifici, attraverso canali secondari si svilupperà la concezione che il problema della determinazione dei centri di gravità di una figura sia equivalente alla quadratura della stessa.
Tutto ciò, però, si scontrerà coi limiti del linguaggio della geometria classica. La difficoltà di esprimersi con il linguaggio della teoria delle proporzioni porterà anche il Valerio più maturo ad abbandonare le sue idee più innovative e a regredire nella gabbia del paradigma greco.
Infine, in appendice di questa tesi, riporteremo le trascrizioni del manoscritto Quadratura circuli di Raimondi e delle note di Guidobaldo ad alcune proposizioni del Subtilium indagationum liber primus
Augmented visualization with depth perception cues to improve the surgeon's performance in minimally invasive surgery
No full textMinimally invasive techniques, such as laparoscopy and radiofrequency ablation of tumors, bring important advantages in surgery: by minimizing incisions on the patient's body, they can reduce the hospitalization period and the risk of postoperative complications. Unfortunately, they come with drawbacks for surgeons, who have a restricted vision of the operation area through an indirect access and 2D images provided by a camera inserted in the body. Augmented reality provides an "X-ray vision" of the patient anatomy thanks to the visualization of the internal organs of the patient. In this way, surgeons are free from the task of mentally associating the content from CT images to the operative scene. We present a navigation system that supports surgeons in preoperative and intraoperative phases and an augmented reality system that superimposes virtual organs on the patient's body together with depth and distance information. We implemented a combination of visual and audio cues allowing the surgeon to improve the intervention precision and avoid the risk of damaging anatomical structures. The test scenarios proved the good efficacy and accuracy of the system. Moreover, tests in the operating room suggested some modifications to the tracking system to make it more robust with respect to occlusions
NANOGrav Data Hints at Primordial Black Holes as Dark Matter
No full textThe NANOGrav Collaboration has recently published strong evidence for a stochastic common-spectrum process that may be interpreted as a stochastic gravitational wave background. We show that such a signal can be explained by second-order gravitational waves produced during the formation of primordial black holes from the collapse of sizeable scalar perturbations generated during inflation. This possibility has two predictions: (i) the primordial black holes may comprise the totality of the dark matter with the dominant contribution to their mass function falling in the range (10-15÷10-11)M⊙ and (ii) the gravitational wave stochastic background will be seen as well by the Laser Interferometer Space Antenna experiment
Crowdfunding: a systemic framework of benefits
No full textPurpose Crowdfunding (CF) is a fast-developing and multifaceted phenomenon at the intersection of entrepreneurship, technology, finance and sociology. Although it is an alternative way to fund innovative projects using the Internet, CF can provide great value other than money. Nevertheless, only few studies have been conducted to shed light on such additional benefits. The purpose of this article is to present an integrative model of benefits of CF for the successful undertaking and sustainability of an entrepreneurial initiative.
Design/methodology/approach Based on a systematic review of literature, a preliminary taxonomy is firstly identified. Industry experts, campaign creators, and the analysis of real cases are then used to progressively build a model of 11 areas and 85 categories of benefits deriving from crowdfunding.
Findings The article presents a comprehensive model of benefits of crowdfunding for the project, the start-up and the creator related to the following aspects: viability, costs, customer, demand, distribution, employees, fund, strategy, market, partners, personal, product.
Research limitations/implications The study does not distinguish among different forms of crowdfunding. Besides, only benefits are studied whereas potential drawbacks and challenges are not considered. Further research is thus needed to complement the framework along such two additional areas of investigation.
Originality/value The theoretical framework is an exhaustive snapshot of the benefits of a CF campaign and it can thus be assumed as a starting point for future researches and empirical studies. Moreover, the article can support platforms managers in the design of value-added tools aimed to improve attractiveness and project creators in campaign design and management
A Library for RTP Relaying and QoS Monitoring in Application Layer Multicast
No full textNative IP multicast would be the best solution to distribute live streaming contents among various destinations since the real-time nature of such applications usually imposes strict delay constraints. Application Layer Multicast (ALM) platforms are emerging as a solution to overcome the well- known lack of a globally supported native multicast. Since the development of ALM applications is slowed by complexity and portability issues, we designed an open source C library framework that takes care of RTP/RTCP technical details and fosters a modular and higher level design. Besides it frees ALM developers from spending time in porting operations from Unix to Windows operating systems
OpenSatRelaying: a hybrid approach to real-time audio-video distribution over the Internet
No full textIn spite of massive research efforts devoted to the advance of the technologies for large-scale live distribution of audio-video IP streams, no totally satisfying solutions seem to have emerged so far. CDNs are still expensive and P2P-TV systems face substantial delay limitations. As the deployment of a global terrestrial IP multicast infrastructure still looks far, turning the attention to satellite-based multicast would seem a sensible choice. However, the cost of such technology has been a stumbling block until now. That is where the CHARMS architecture comes in. It is designed to take advantage of the formidable properties of the satellite without requiring a generic user to install any sort of satellite receiver or dish. Its cornerstone is the recursive terrestrial relaying of satellite streams a number of properly equipped hosts are able to receive. The present paper relates about the results of the OpenSatRelaying project, aimed at the implementation and testing of the CHARMS architecture
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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