Academic literature on the topic 'Distortion estimation'

Il principale obiettivo della tesi è stato lo sviluppo di un insieme di algoritmi per la valutazione di parametri vitali, come il respiro ed il battito cardiaco, utilizzando un radar UWB. La ricerca fa parte di un progetto più esteso, denominato NIMURRA (Non Invasive Monitoring by Ultra Wide Band Radar of Respiratory Activity of people inside a spatial environment), che il Dipartimento di Ingegneria dell’Informazione dell’Università Politecnica delle Marche ha messo a punto per conto dell’Agenzia Spaziale Italiana (ASI). Al progetto hanno contribuito anche gruppi di ricerca provenienti da altre università e alcune aziende che operano nel settore aerospaziale. Ne sistema basato su radar UWB, l’antenna trasmette una sequenza di impulsi ultracorti verso il soggetto monitorato e l’informazione cercata viene ottenuta attraverso opportuna elaborazione del segnale ricevuto. Quest’ultimo contiene anche segnali riflessi dovuti agli altri oggetti nell’ambiente simulato (clutter). Di essi si tiene conto attraverso un’adeguata caratterizzazione della risposta impulsiva del sistema. L’algoritmo deve eliminare i contributi dovuti al clutter, isolando l’eco generato dal torace umano. Dopo l’eliminazione del clutter, l’algoritmo identifica i punti di massimo dell’energia del segnale. E’ in corrispondenza di questi istanti, infatti, che risulta conveniente effettuare un’analisi in frequenza, basata sulla trasformata di Fourier o di sue versioni ottimizzate. Tale metodo consente di identificare la frequenza di respirazione dalla semplice rivelazione del picco dello spettro. La procedura è stata analizzata ed implementata sia dal punto di vista della modellizzazione analitica che della simulazione numerica. Oltre alla frequenza di respirazione, risulta anche auspicabile poter ricostruire lo spostamento della cavità toracica. Anche questo risultato può essere ottenuto attraverso lo sviluppo di opportuni algoritmi di elaborazione dei segnali. Tra le tecniche utilizzabili allo scopo, si rivela particolarmente efficace eseguire la correlazione tra il segnale ricevuto ed un segnale locale opportunamente scelto. La ricostruzione dello spostamento toracico richiede, ovviamente, un incremento dei tempi di elaborazione, anche se, come sottoprodotto, essa consente di ottenere anche la stima della frequenza di respirazione. La valutazione della frequenza cardiaca è, di norma, molto più complessa, in quanto le armoniche dovute al battito cardiaco sono “mascherate” dalla frequenza di respirazione (ed i suoi multipli) e dai prodotti di intermodulazione. Nell’ambito della tesi, sono comunque state messe a punto opportune operazioni di filtraggio, e valutata la loro efficacia in funzione dei valori relativi delle frequenze di interesse. Come accennato più sopra, una parte rilevante dell’attività di ricerca ha riguardato la messa a punto di programmi, in ambiente Matlab© per la simulazione e l’elaborazione dei segnali negli scenari di interesse. Accanto allo schema più convenzionale (e normalmente adottato, ad esempio nell’ambito del progetto NIMURRA) che prevede l’utilizzo di un radar esterno (a parete) si è anche studiato, pur con minor dettaglio, il caso di radar impiantato negli indumenti del soggetto sotto misura (e dunque solidale con la cavità toracica). Le caratteristiche essenziali del problema restano immutate, ma occorre tener conto del fatto che in questo caso il segnale utile è fornito dagli oggetti presenti nell’ambiente. Infine, si fatto il caso di soggetto sotto misura che si muove, in accordo con leggi deterministiche o aleatorie, compiendo brevi spostamenti nell’intorno della posizione di riferimento. In questo ulteriore scenario, il problema principale consiste nell’eliminazione del contributo nel segnale riflesso dovuto al movimento, e per raggiungere questo obiettivo l’algoritmo di elaborazione del segnale è stato opportunamente modificato. Gli algoritmi sono stati verificati anche a partire da misure reali effettuate presso i laboratori dell’Università La Sapienza di Roma, mostrando, in gran parte dei casi, un’ottima corrispondenza con i risultati di misure convenzionali (Es.: spirometro, per la valutazione della frequenza di respirazione).<br>This work purpose is the building of an algorithm that estimate the vital parameters from the received signal of an UWB antenna. The research was part of a large project found by the Italian Space Agency, where are included different research groups from different universities in Italy beside the group at Università Politecnica delle Marche. The algorithm was thought to measure the vital parameters of the astronauts before, during and after their mission. The project was entitled NIMURRA (Non Invasive Monitoring by Ultra wide band Radar of Respiratory Activity of people inside a spatial environment). The antenna transmits toward the person and due to the lack of directivity of it we will have the reflected waves also from the other objects. The environment and person reflected signals will be modeled firstly by the impulsive response. By performing a convolution with the reflected pulse we create the simulation matrix. The reflected signal from the human chest reaches the antenna attenuated by the propagation of it in air and distorted by the multiple reflections of the inner tissues of human body. The receiving antenna will gather also the other contributions from the static objects. These last contributions create the static clutter. The algorithm needs to eliminate these other contributions in order to let only the human chest echo. After elimination of the clutter it searches for the maximum of the energy of the signal. Performing a transformation of the column that holds the maximum of energy we find that the harmonic with the highest peak is that of the breath frequency. Another vital parameter of interest is the amplitude of the chest displacement. To make an estimation of the amplitude of the chest movement we need to reconstruct the chest movement form from the received signal. It can be done by performing a correlation between the received signal and a chosen signal that we call as reference signal. The estimation of breath frequency can be estimated also by making the transformation of the chest movement reconstructed and the peak with the highest energy belong to breath frequency. Heart frequency was another parameter of interest for us but its detection comes out a little difficult as it is hidden by the breath harmonics and intermodulation harmonics. The analytical study and modeling were transferred into Matlab code. This algorithm estimates the breath frequency and reconstructs the chest movement. It is possible to choose between the different scenarios of realization of measurements with UWB radar. The scenarios developed were two other beside the main branch with which we started. These other scenarios were when the antenna is on the person body and moves with the chest, it transmits toward the other objects around the person that holds it. The last scenario was when the person under observation with UWB performs small movements. The estimation of breath in this case will follow another path when firstly now we need to estimate the movement of the person. Then this movement is subtracted, by doing so we leave only the moving of the chest during respiration. The estimation of the breath follows after the same algorithm developed for the case of a standing person while the antenna radiates toward him.

Abstract This thesis presents several novel improvements to video coding algorithms, including block-based motion estimation, quantization selection, and video filtering. Most of the presented improvements are fully compatible with the standards in general use, including MPEG-1, MPEG-2, MPEG-4, H.261, H.263, and H.264. For quantization selection, new methods are developed based on the rate-distortion theory. The first method obtains locally optimal frame-level quantization parameter considering frame-wise dependencies. The method is applicable to generic optimization problems, including also motion estimation. The second method, aimed at real-time performance, heuristically modulates the quantization parameter in sequential frames improving significantly the rate-distortion performance. It also utilizes multiple reference frames when available, as in H.264. Finally, coding efficiency is improved by introducing a new matching criterion for motion estimation which can estimate the bit rate after transform coding more accurately, leading to better motion vectors. For fast motion estimation, several improvements on prior methods are proposed. First, fast matching, based on filtering and subsampling, is combined with a state-of-the-art search strategy to create a very quick and high-quality motion estimation method. The successive elimination algorithm (SEA) is also applied to the method and its performance is improved by deriving a new tighter lower bound and increasing it with a small constant, which eliminates a larger part of the candidate motion vectors, degrading quality only insignificantly. As an alternative, the multilevel SEA (MSEA) is applied to the H.264-compatible motion estimation utilizing efficiently the various available block sizes in the standard. Then, a new method is developed for refining the motion vector obtained from any fast and suboptimal motion estimation method. The resulting algorithm can be easily adjusted to have the desired tradeoff between computational complexity and rate-distortion performance. For refining integer motion vectors into half-pixel resolution, a new very quick but accurate method is developed based on the mathematical properties of bilinear interpolation. Finally, novel number theoretic transforms are developed which are best suited for two-dimensional image filtering, including image restoration and enhancement, but methods are developed with a view to the use of the transforms also for very reliable motion estimation.

Animal home range estimations are important for conservation planning and protecting the habitat of threatened species. The accuracy of home range calculations is influenced by the map projection chosen in a geographic information system (GIS) for data analysis. Different methods of projection will distort spatial data in different ways, so it is important to choose a projection that meets the needs of the research. The large number of projections in use today and the lack of distortion comparison between the various types make selecting the most appropriate projection a difficult decision. The purpose of this study is to quantify and compare the amount of area distortion in animal home range estimations when projected into a number of projected coordinate systems in order to understand how the chosen projection influences analysis. The objectives of this research are accomplished by analyzing the tracking data of four species from different regions in North and South America. The home range of each individual from the four species datasets is calculated using the Characteristic Hull Polygon method for home range estimation and then projected into eight projected coordinate systems of various scales and projection type, including equal area, conformal, equidistant, and compromise projections. A continental Albers Equal Area projection is then used as a baseline area for the calculation of a distortion measurement ratio and magnitude of distortion statistic. The distortion measurement ratio and magnitude calculations provide a measurement of the quantity of area distortion caused by a projection. Results show the amount distortion associated with each type of projection method and how the amount of distortion changes for a projection based on geographic location. These findings show how the choice of map projection can have a large influence on data analysis and illustrate the importance of using an appropriate PCS for the needs of a given study. Distorted perceptions can influence decision-making, so it is important to recognize how a map projection can influence the analysis and interpretation of spatial data.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Ghassan AlRegib; Committee Member: Elliot Moore; Committee Member: Monson H. Hayes; Committee Member: Paul A. Work; Committee Member: Ying Zhang. Part of the SMARTech Electronic Thesis and Dissertation Collection.