Search results for "Transform"

showing 10 items of 3975 documents

A Hybrid Frequency-Space Approach for Shape Measurement by Shadow Moirè Technique with Carrier Fringe Pattern

2006

In this paper, a novel methodology to process fringe pattern is presented. The core of the signal processing technique is the use of the direction information, a modulo 2π quantity that locally informs about the direction along which fringes grow with maximum rate. By using this information, it was possible to perform adaptive, direction - and orientation-based operations on fringe images in order to remove unwanted effects, to enhance the contrast and to extract the phase information encoded. The method has been applied on shadow moiré interferograms with carrier fringes in order to measure the surface of small objects. The developed algorithm allows to process fringes whose phase informat…

Settore ING-IND/12 - Misure Meccaniche E TermicheHubert transform Shadow moiré Shape measurement
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Stability of Microgrids: An Application of Virtual Synchronous Generator

2022

The objective of this paper is to illustrate an alternative control algorithm for power converters which have the task of introducing the energy generated by systems based on the use of renewable sources such as, photovoltaic or wind power, in to small-sized networks, microgrids. Virtual Synchronous Generator can operate both in parallel to the main network as well as in isolated and autonomous conditions (islanding-mode). The contribute of this work is to drive a consolidate approach, made in time domain, in a more flexible and less time-consuming approach based on Park transformation.

Settore ING-IND/31 - ElettrotecnicaPark transformation Synchronverter Virtual synchronous generatorSettore ING-IND/32 - Convertitori Macchine E Azionamenti Elettrici
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A combined CWT-DWT method using model-based design simulator for partial discharges online detection

2009

The suppression of noises is fundamental in onsite Partial Discharge (PD) measurements. For this purpose, the wavelet transform analysis method has been developed and it is a powerful tool for processing the transient and suddenly changing signals. As the wavelet transform possesses the properties of multi-scale analysis and time-frequency domain localization, it is also particularly suitable to process the suddenly changing signals of the partial discharge pulse (PD). In this paper, an improved Wavelet denoising method developed by a model-based design software is presented. Simulations are provided as well as some results obtained during laboratory experiment and on-line PD measurements. …

Settore ING-IND/31 - ElettrotecnicaWaveletComputer scienceNoise reductionPartial dischargeModel-based designdiscrete wavelet transforms partial discharge measurements time-frequency analysis transientsElectronic engineeringSoftware designWavelet transformContinuous wavelet transformTime–frequency analysis2009 IEEE Conference on Electrical Insulation and Dielectric Phenomena
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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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Luby Transform Performance Tests on Time-Correlated Channel Model for Geo Free Space Optics Downlinks

2012

Settore ING-INF/03 - TelecomunicazioniSettore ING-INF/01 - ElettronicaFree Space Optics Luby Transform Codes Rateless Codes Channel Modeling Geo Free Space Optics Downlinks
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Performance Investigation of Fountaine Codes on a Simulated Terrestrial Free Space Optical Channel

2012

Settore ING-INF/03 - TelecomunicazioniSettore ING-INF/02 - Campi ElettromagneticiSettore ING-INF/01 - ElettronicaFree Space Optics Channel Modeling Fountain Codes Raptor Codes RaptorQ Codes Luby Transform Codes Rateless Codes
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Clifford Algebra based Edge Detector for Color Images

2012

Edge detection is one of the most used methods for feature extraction in computer vision applications. Feature extraction is traditionally founded on pattern recognition methods exploiting the basic concepts of convolution and Fourier transform. For color image edge detection the traditional methods used for gray-scale images are usually extended and applied to the three color channels separately. This leads to increased computational requirements and long execution times. In this paper we propose a new, enhanced version of an edge detection algorithm that treats color value triples as vectors and exploits the geometric product of vectors defined in the Clifford algebra framework to extend …

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniColor imagebusiness.industryComputer scienceColor image edge detectionClifford convolutionFeature extractionClifford algebraEdge detectionConvolutionsymbols.namesakeClifford Fourier transformFourier transformsymbolsCanny edge detectorComputer visionArtificial intelligenceClifford algebrabusinessAlgorithmImage gradient
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Copy–Move Forgery Detection by Matching Triangles of Keypoints

2015

Copy-move forgery is one of the most common types of tampering for digital images. Detection methods generally use block-matching approaches, which first divide the image into overlapping blocks and then extract and compare features to find similar ones, or point-based approaches, in which relevant keypoints are extracted and matched to each other to find similar areas. In this paper, we present a very novel hybrid approach, which compares triangles rather than blocks, or single points. Interest points are extracted from the image, and objects are modeled as a set of connected triangles built onto these points. Triangles are matched according to their shapes (inner angles), their content (c…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniComputer Networks and CommunicationsComputer scienceDelaunay triangulationbusiness.industryFeature vectorSURFFeature extractionScale-invariant feature transformPattern recognitionDelaunay TriangulationDigital Image ForensicVisualizationVertex (geometry)Copy-move ForgeryDigital imageComputer Networks and CommunicationHarriSIFTComputer visionArtificial intelligenceSafety Risk Reliability and QualitybusinessCopy-move Forgery; Delaunay Triangulation; Digital Image Forensics; Harris; SIFT; SURF; Computer Networks and Communications; Safety Risk Reliability and QualityTransformation geometryIEEE Transactions on Information Forensics and Security
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Composition of SIFT features for robust image representation

2010

In this paper we propose a novel feature based on SIFT (Scale Invariant Feature Transform) algorithm1 for the robust representation of local visual contents. SIFT features have raised much interest for their power of description of visual content characterizing punctual information against variation of luminance and change of viewpoint and they are very useful to capture local information. For a single image hundreds of keypoints are found and they are particularly suitable for tasks dealing with image registration or image matching. In this work we stretched the spatial coverage of descriptors creating a novel feature as composition of keypoints present in an image region while maintaining…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniComputer sciencebusiness.industryComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISIONImage registrationScale-invariant feature transformartificial intelligenceLuminanceimage annotationImage (mathematics)bag of wordsFeature (computer vision)SIFTvisual termsComputer visionArtificial intelligenceAffine transformationbusinessRepresentation (mathematics)semanticsImage representationFeature detection (computer vision)
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Real-time estimation of geometrical transformation between views in distributed smart-cameras systems

2008

In this paper, we present a method to automatically estimate the geometric relations among the different views of cameras with partially overlapping fields of view in a wireless video-surveillance system. The method uses the locations of the detected moving objects visible at the same time in two or more views. The correspondences among objects are found by comparing their appearance models based on dominant colour descriptors while the geometric transformation are computed iteratively and may be used to solve the consistent labelling problem. As a significant part of the processing is performed on the smart cameras, the method has been conceived by taking into account the limited resources…

Settore ING-INF/05 - Sistemi Di Elaborazione Delle InformazioniComputer sciencebusiness.industryGeometric transformationMotion detectiondistributed video surveillanceObject detectionData modelingTransformation (function)Computer visionSmart cameraArtificial intelligenceImage sensorbusinessHomography (computer vision)2008 Second ACM/IEEE International Conference on Distributed Smart Cameras
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