Search results for "Width"

showing 10 items of 690 documents

Graph-based minimal path tracking in the skeleton of the retinal vascular network

2012

This paper presents a semi-automatic framework for minimal path tracking in the skeleton of the retinal vascular network. The method is based on the graph structure of the vessel network. The vascular network is represented based on the skeleton of the available segmented vessels and using an undirected graph. Significant points on the skeleton are considered nodes of the graph, while the edge of the graph is represented by the vessel segment linking two neighboring nodes. The graph is represented then in the form of a connectivity matrix, using a novel method for defining vertex connectivity. Dijkstra and Floyd-Warshall algorithms are applied for detection of minimal paths within the graph…

Settore INF/01 - Informaticabusiness.industryComputer sciencePath trackingGraph theoryImage segmentationGraph bandwidthRetinal Images Graphs Dijkstra Floyd-WarshallGraph (abstract data type)Computer visionArtificial intelligencebusinessBeta skeletonDijkstra's algorithmAlgorithmRandom geometric graphMathematicsofComputing_DISCRETEMATHEMATICS2012 25th IEEE International Symposium on Computer-Based Medical Systems (CBMS)
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End-to-end Bandwidth Estimation in the Wide Internet

2010

Settore ING-INF/03 - TelecomunicazioniBandwidth estimation
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The quest for bandwidth estimation techniques for large-scale distributed systems

2010

In recent years the research community has developed many techniques to estimate the end-to-end available bandwidth of an Internet path. This important metric can be potentially exploited to optimize the performance of several distributed systems and, even, to improve the effectiveness of the congestion control mechanism of TCP. Thus, it has been suggested that some existing estimation techniques could be used for this purpose. However, existing tools were not designed for large-scale deployments and were mostly validated in controlled settings, considering only one measurement running at a time. In this paper, we argue that current tools, while offering good estimates when used alone, migh…

Settore ING-INF/03 - TelecomunicazioniComputer Networks and Communicationsbusiness.industryComputer scienceScale (chemistry)Distributed computingTestbedNetwork congestionHardware and ArchitectureMetric (mathematics)Path (graph theory)bandwidth estimationBandwidth (computing)Overhead (computing)The InternetbusinessSoftwareACM SIGMETRICS Performance Evaluation Review
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Large-Scale Available Bandwidth Measurements: Interference in Current Techniques

2011

The end-to-end available bandwidth of an Internet path is a desirable information that can be exploited to optimize system performance. Several tools have been proposed in the past to estimate it. However, existing measurement techniques were not designed for large-scale deployments. In this paper we show that current tools do not properly work where multiple probing processes share a portion of a path. We provide experimental evidence to quantify the impact of mutual interference between measurements. We further analyze the characteristics of popular tools, quantifying (i) the impact of mutual interference, (ii) the total overhead imposed to the network and (iii) the intrusiveness of the m…

Settore ING-INF/03 - TelecomunicazioniComputer Networks and Communicationsbusiness.industryComputer scienceSystem of measurementReal-time computingAvailable BandwidthProcess (computing)Interference (wave propagation)ScalabilityBandwidth (computing)Overhead (computing)The InternetElectrical and Electronic EngineeringbusinessDimensioning
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Rateless Codes Performance Analysis in Correlated Channel Model for GEO Free Space Optics Downlinks

2012

Settore ING-INF/03 - TelecomunicazioniFree Space Optics (FSO) technologies for satellite communications offer several advantages: wide bandwidth high rate capability immunity to electromagnetic interference and small equipment size. Thus they are suitable for inter-satellite links deep space communications and also for high data rate ground-to-satellite/satellite-to-ground communications. Nevertheless FSO links suffer impairments that cause power signal degradation at the receiver. Scattering and absorption cause power signal attenuations predictable by suitable deterministic models. Optical turbulence causes random irradiance fluctuations which can generate signal fading events and can thereby only be predicted by statistical models. Attenuation and fading events can corrupt FSO links and so it would be recommended to add mitigation error codes on the communication link. FSO channel can be described as an erasure channel: fading events can cause erasure errors. We have identified in rateless codes (RCs) a suitable solution to be employed in FSO links. RCs do not need feedback and they add a redundant coding on the source data that allows the receiver to recover the whole payload despite erasure errors. We implemented two different of rateless codes: Luby Transform (LT) and Raptor. We analyzed their performances on a simulated turbulent GEO FSO downlink (1 Gbps - OOK modulation) at a 106 μm wavelength and for different values of zenith angles. Assuming a plane-wave propagation and employing Hufnagel-Valley we modeled the downlink using: 1) a temporal correlated channel model based on Gamma-Gamma probability distribution and 2) an irradiance covariance function that we converted on a time function using Taylor frozen eddies hypothesis. Our new channel model is able to simulate irradiance fluctuations at different turbulence conditions as it will be shown in the full paper. We will also report performance results of LT and Raptor codes at overhead range varying between 0 and 50% and for different values of source packets.Settore ING-INF/01 - Elettronica
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A Fog-Based Application for Human Activity Recognition Using Personal Smart Devices

2019

The diffusion of heterogeneous smart devices capable of capturing and analysing data about users, and/or the environment, has encouraged the growth of novel sensing methodologies. One of the most attractive scenarios in which such devices, such as smartphones, tablet computers, or activity trackers, can be exploited to infer relevant information is human activity recognition (HAR). Even though some simple HAR techniques can be directly implemented on mobile devices, in some cases, such as when complex activities need to be analysed timely, users’ smart devices can operate as part of a more complex architecture. In this article, we propose a multi-device HAR framework that exploits the fog c…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniExploitComputer Networks and CommunicationsComputer sciencebusiness.industryBandwidth (signal processing)Activity tracker020206 networking & telecommunicationsCloud computing02 engineering and technologyActivity recognitionHuman–computer interactionHuman activity recognition mobile crowdsensing fog computing0202 electrical engineering electronic engineering information engineering020201 artificial intelligence & image processingSmart environmentbusinessMobile deviceWearable technologyACM Transactions on Internet Technology
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Investigation on Cascode Devices for High Frequency Electrical Drives Applications

2019

In the last years a widespread development in the market of electrical drives employing high-speed electrical machines has occurred in various industrial fields, due to the extremely high power density that can be reached. Nevertheless, to maintain output power quality without using bulky filtering networks, DC-AC converters should be controlled by means of higher PWM switching frequencies. New switching device technologies, such as Field Effect Transistors based on SiC and GaN, are therefore gathering momentum in order to comply with the higher working frequencies. To operate under high frequencies and at the same time at high voltage levels, alternative circuital configurations for switch…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniMomentum (technical analysis)High voltage deviceComputer sciencebusiness.industry020209 energyCascode020208 electrical & electronic engineeringElectrical engineeringHigh voltage02 engineering and technologyConvertersSettore ING-IND/32 - Convertitori Macchine E Azionamenti ElettriciHigh frequencyPower transistors0202 electrical engineering electronic engineering information engineeringField-effect transistorPower semiconductor deviceCascodebusinessFrequency modulationPulse-width modulation
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Propagation Channels for mmWave Vehicular Communications : State-of-the-art and Future Research Directions

2018

Vehicular communications essentially support automotive applications for safety and infotainment. For this reason, industry leaders envision an enhanced role for vehicular communications in the fifth generation of mobile communications technology. Over the years, the number of vehicle- mounted sensors has increased steadily, which potentially leads to more volume of critical data communications in a short time. Also, emerging applications such as remote/autonomous driving and infotainment such as high-definition movie streaming require data-rates on the order of multiple Gb/s. Such high data rates require a large system bandwidth, but very limited bandwidth is available in the sub-6 GHz cel…

Signal Processing (eess.SP)FOS: Computer and information sciencesComputer scienceComputer Science - Information Theoryfrequency bandsAutomotive industry02 engineering and technologyFOS: Electrical engineering electronic engineering information engineering0202 electrical engineering electronic engineering information engineeringajoneuvotElectrical and Electronic EngineeringElectrical Engineering and Systems Science - Signal ProcessingHigh data rateta213business.industryInformation Theory (cs.IT)Bandwidth (signal processing)020206 networking & telecommunicationsMicrowave transmissionwireless communicationComputer Science ApplicationsvehiclesExtremely high frequencylangaton viestintätaajuusalueetCellular frequenciesMobile telephonybusinessTelecommunicationsCommunication channelIEEE Wireless Communications
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Wide bandwidth impedance meter using low rate random sampling

2008

A novel impedance measurement method based on random sampling of voltage and current signals is proposed. This technique dramatically reduces the sampling frequency requirements, thus circumventing the limitations imposed by maximum speed of the analog to digital converter and the signal processing unit. The lowering of the sampling frequencies allows the design and the implementation of an almost all digital architecture by using a simple microprocessor based embedded system and a digital frequency synthesizer. The basic principles are presented, and the implemented algorithms are described. Experimental results show the instrument performances compared to others commercial alternatives.

Signal processingEngineeringDigital down converterbusiness.industryBandwidth (signal processing)Electrical engineeringSampling (statistics)Analog-to-digital converterlaw.inventionMicroprocessorlawElectronic engineeringbusinessElectrical impedanceVoltage2008 Ph.D. Research in Microelectronics and Electronics
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In-Fiber Fractional Signal Processing: Recent Results and Applications

2018

The implementation of mathematical operators using photonic signal processing –as for example, conventional differentiators and integrators– is particularly well suited to overcome the speed and bandwidth limitations of electronics. In the Laboratory of Fiber Optics of the University of Valencia we work on the development of in-fiber time-domain fractional operators and their applications. In the last years we have made some specific proposals to perform photonic fractional differentiation (PFD), photonic fractional integration (PFI), photonic fractional Hilbert transform (PFHT), and photonic fractional Fourier transform (PFFT), using fiber-based technologies. Recently, we have been able to…

Signal processingOptical fiberComputer sciencebusiness.industryBandwidth (signal processing)Physics::Optics02 engineering and technology021001 nanoscience & nanotechnology01 natural sciencesFractional Fourier transformlaw.inventionMathematical Operators010309 opticsDifferentiatorlawIntegrator0103 physical sciencesElectronic engineeringPhotonics0210 nano-technologybusiness2018 20th International Conference on Transparent Optical Networks (ICTON)
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