1,720,998 research outputs found
Silicon photomultipliers: characterization and application to fluorescence flucturation spectroscopy.
Full text linkThis thesis originates from and develops around Silicon Photomultipliers (SiPMs): starting from a description of the working principles of these devices, this work presents a review on this technology and on some of its possible applications.
The great part of this work took place within the framework of an international scientific and industrial collaboration (RAPSODI1, a project funded by the European Commetee), with the aim of developing three radiation detectors using the SiPM technology; in order to find the optimal sensor for each application, an exhaustive protocol to provide a characterization of the performances of the main SiPM parameters (gain, photo-detection efficiency, dark count rate, optical cross-talk, breakdown voltage dependence from temperature) has been provided.
In order to further improve the knowledge on Silicon PhotoMultipliers, a phenomenological model describing the statistics of Geiger-Müller avalanches for impinging photons with known probability distribution has been elaborated: this model takes into account the contribution given by the thermally generated avalanches and by the cross-talk, thus providing a model for the SiPM deviations from the ideal bernoullian detection.
Last, a feasibility study on the possibility of using this sensors as detecting technology in Fluorescence Fluctuation Spectroscopy (FFS) biophysical experiments had been conducted. In FFS experiments the parameters describing the system under study (proteins ligated with fluorophores in a solution) are measured from the deviations of the fluorescence intensity around its mean value: the use of fast (with a sub-nanosecond temporal resolution) detectors with an large photon number resolution can costitute an improvement of the experimental conditions. Thus a dedicated setup had been commissioned and SiPMs demonstrated to be able to perform an effective Photon Counting Histogram (one of the FFS techniques) measurement.
1RAdiation Protection with Silicon Optoelectronic Devices and Instruments – COOP 3299
MalwareStats: Improving Static Analysis of Modern Malware through Statistical Characterization of Samples
No full textThe continued growth in number and complexity of malware is a well
established fact. Malware are no longer simple pieces of code that rely on
unsuspecting users to spread and thrive. They can change, adapt and hide
themselves from analysts, using very sophisticated techniques. Static analysis is
complex and time consuming, and it could be difficult to deduce every possible
malicious behavior, yet it is often very effective because it hinders the capability
of malware to detect the analysis environment. The purpose of this work is to
illustrate an open web-based project the authors are developing, and to show
how its results can provide valuable assistance to the phase of static analysis.
The goal is to support analysts in their exploration of code features, enabling
them to make more focused, statistically motivated and structured decisions
Raising Risk Awareness on the Adoption of Web 2.0 Technologies in Decision Making Processes
Full text linkIn the recent past, the so-called “Web 2.0” became a powerful tool for decision making processes. Politicians and managers, seeking to improve participation, embraced this technology as if it simply were a new, enhanced version of theWorldWideWeb, better suited to retrieve information, opinions and feedbacks from the general public on subjects like laws, acts and policies. This approach was often naive, neglecting the less-obvious aspects of the technology, and thus bringing on significant security problems. This paper shows how, in the end, the result could easily be the opposite of what was desired. Malicious attackers, in fact, could quite easily exploit the vulnerabilities in these systems to hijack the process and lead to wrong decisions, also causing the public to lose trust in the systems themselves
Decentralized detection of network attacks through P2P data clustering of SNMP data
No full textThe goal of Network Intrusion Detection Systems (NIDSs) is to protect against attacks by inspecting network traffic packets, for instance, looking for anomalies and signatures of known attacks. This paper illustrates an approach to attack detection that analyzes just the standard statistics automatically generated by the Simple Network Management Protocol (SNMP) through unsupervised distributed data mining algorithms. We describe the design of a decentralized system composed of a peer-to-peer network of monitoring stations: each of them continuously gathers SNMP statistical observations about the network traffic and runs a distributed data clustering algorithm in cooperation with other stations. This progressively leads to the construction of a traffic model capable to detect undergoing attacks on later observations, including potentially previously unknown attacks. To estimate the accuracy of the described system, we performed an extensive number of distributed data clustering processing on data sets of SNMP observations generated from real traffic
WEB MANAGEMENT OF ELECTRIC VEHICLE FLEETS
No full textAn architecture for enabling the internet connection of a fleet of electric vehicles is presented in the paper. The connection is based on the on-board integration of an Arduino platform with the CAN-bus communication network of the vehicle powertrain. The system allows a plurality of networking interface: GPRS, LAN, Wi-fi for the present and Wi-Max, LTE for the future. The proposed system manages the main powertrain parameters and warning/fault condition. Local and remote data storage is possible, such as direct web interface of the vehicle powertrain. Data post processing from the remote server allows the implementation of an automatic diagnostic procedure for the detection of incipient faults in the powertrain
Photon-number statistics and correlations with Silicon photomultipliers
No full textWe present the characterization of a multi-pixel detector (SiPM, Hamamatsu) in the presence of dark-count and cross-talk effects. Our description yields a self-consistent calibration of the device, based on the light under investigation, which is used to evaluate shot-by-shot detected-photon numbers including dark-counts and cross-talk. The analysis allows us to reliably reconstruct the detected-photons statistics of different light states by taking into account the modifications introduced by detector features. Finally we quantify photon-number correlations in bipartite states and use the data to produce conditional states: only if dark-count and cross-talk effects can be neglected, the experimental results match theory
Photon-number statistics with Silicon photomultipliers
No full textWe present a description of the operation of a multi-pixel detector in the presence of non-negligible dark-count and cross-talk effects. We apply the model to devise self-consistent calibration strategies to be performed on the very light under investigation
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
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