Search results for "Head"

showing 10 items of 1640 documents

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
researchProduct

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
researchProduct

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
researchProduct

Coloring-based resource allocations in ad-hoc wireless networks

2011

It is well known that CSMA/CA protocols exhibit very poor performance in case of multi-hop transmissions, because of inter-link interference due to imperfect carrier sensing. We propose to control such an interference by preallocating temporal slots in which different sets of network nodes are allowed to contend for the channel access. The approach is based on distributed coloring algorithms with limited signaling overhead that can be customized as a function of the network topology and traffic load.

Settore ING-INF/03 - Telecomunicazionibusiness.industryWireless ad hoc networkWireless networkComputer scienceDistributed computingComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSThroughputNetwork topologyInterference (wave propagation)coloring schemes; multi-hop wireless networksSettore ING-INF/04 - Automaticacoloring schemesOverhead (computing)Resource managementbusinesscoloring schememulti-hop wireless networksComputer networkCommunication channel2011 The 10th IFIP Annual Mediterranean Ad Hoc Networking Workshop
researchProduct

An Emotional Talking Head for a Humoristic Chatbot

2011

The interest about enhancing the interface usability of applications and entertainment platforms has increased in last years. The research in human-computer interaction on conversational agents, named also chatbots, and natural language dialogue systems equipped with audio-video interfaces has grown as well. One of the most pursued goals is to enhance the realness of interaction of such systems. For this reason they are provided with catchy interfaces using humanlike avatars capable to adapt their behavior according to the conversation content. This kind of agents can vocally interact with users by using Automatic Speech Recognition (ASR) and Text To Speech (TTS) systems; besides they can c…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniComputer sciencetalking head chatbot emotional AIMLSpeech synthesisAnimationcomputer.software_genreCyberwareASCIIChatbotIntelligent agentHuman–computer interactionGraphicscomputerNatural languageComputingMethodologies_COMPUTERGRAPHICS
researchProduct

Fast, Reliable Head Tracking under Varying Illumination: An Approach Based on Robust Registration of Texture-Mapped 3D Models

2000

An improved technique for 3D head tracking under varying illumination conditions is proposed. The head is modeled as a texture mapped cylinder. Tracking is formulated as an image registration problem in the cylinder's texture map image. The resulting dynamic texture map provides a stabilized view of the face that can be used as input to many existing 2D techniques for face recognition, facial expressions analysis, lip reading, and eye tracking. To solve the registration problem in the presence of lighting variation and head motion, the residual error of registration is modeled as a linear combination of texture warping templates and orthogonal illumination templates. Fast and stable on-line…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniHead tracking. image registration
researchProduct

A Pipeline for the Implementation of Immersive Experience in Cultural Heritage Sites in Sicily

2022

Modern digital technologies allow potentially to explore Cultural Heritage sites in immersive virtual environments. This is surely an advantage for the users that can better experiment and understand a specific site, also before a real visit. This specific approach has gained increasing attention during the extreme conditions of the recent COVID-19 pandemic. In this work, we present the processes that lead to the implementation of an immersive app for different kinds of low and high cost devices, which have been attained in the context of the 3dLab-Sicilia project. 3dLab-Sicilia’s main objective is to sponsor the creation, development, and validation of a sustainable infrastructure that int…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniVirtual heritageSettore INF/01 - InformaticaVR-headsetCultural heritageCAVEVirtual reality
researchProduct

A Graph-Based Method for PET Image Segmentation in Radiotherapy Planning: A Pilot Study

2013

Target volume delineation of Positron Emission Tomography (PET) images in radiation treatment planning is challenging because of the low spatial resolution and high noise level in PET data. The aim of this work is the devel- opment of an accurate and fast method for semi-automatic segmentation of me- tabolic regions on PET images. For this purpose, an algorithm for the biological tumor volume delineation based on random walks on graphs has been used. Va- lidation was first performed on phantoms containing spheres and irregular in- serts of different and known volumes, then tumors from a patient with head and neck cancer were segmented to discuss the clinical applicability of this algo- rith…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle Informazionimedicine.diagnostic_testRadiotherapybusiness.industryComputer sciencemedicine.medical_treatmentGraph basedHead and Neck cancerImage segmentationGraphGraphRadiation therapySegmentationPETPositron emission tomographymedicineSegmentationComputer visionSegmentation Graph PET Head and Neck cancer RadiotherapyArtificial intelligenceRadiation treatment planningbusinessImage resolution
researchProduct

Input for baroreflex analysis: which blood pressure signal should be used?

2022

The baroreflex (BR) is an important physiological regulatory mechanism which reacts to blood pressure perturbations with reflex changes of target variables such as the heart period (electrocardiogram derived RR interval) or the peripheral vascular resistance (PVR). Evaluation of cardiac chronotropic (RR as a target variable) and vascular resistance (target PVR) BR arms was in previous studies mainly based on the use of the spontaneous variability of the systolic or diastolic blood pressure (SBP, DBP), respectively, as the input signals. The use of other blood pressure measures such as the mean blood pressure (MBP) as an input signal for BR analysis is still under investigation. Making the a…

Settore ING-INF/06 - Bioingegneria Elettronica E InformaticaArterial baroreflex blood pressure cardiovascular variability spectral analysis transfer function head-up tilt mental arithmetic task muscle sympathetic nerve activity
researchProduct

Il ruolo del Consiglio europeo nella Brexit

2019

Il Consiglio europeo ha svolto un ruolo di primo piano nella Brexit. L’articolo cerca di spiegare che questo ruolo è stato più ampio rispetto a quello espressamente conferito dall’art. 50 TUE per affrontare poi due problemi: nello svolgere questo ruolo il Consi- glio europeo ha agito solo come istituzione dell’Unione europea o anche come vertice di capi Stato? E ha rispettato il principio dell’equilibrio istituzionale? The European Council has been playing a leading role in Brexit procedure. This article aims at showing how this role does not simply reflect the powers explicitly assigned to the European Council under Article 50 TEU. Two more questions are addressed: In performing its role h…

Settore IUS/14 - Diritto Dell'Unione EuropeaBrexit – Recesso dall’Unione europea – Consiglio europeo – Vertici di capi di stato o di governo – Equilibrio istituzionaleBrexit – Withdraw from the European Union – European Council – Summits of heads of State or Government – Institutional balance
researchProduct