This work focuses on both high fidelity experimental and numerical thermal hydraulic studies and advanced frequency decomposition methods. The major contribution of this work is a proposed method for spatio-temporal decomposition of frequencies present in the flow. This method provides an instantaneous visualization of coherent frequency ?structures? in the flow. The significance of this technique from an engineering standpoint is the ease of implementation and the importance of such a tool for design engineers. To validate this method, synthetic verification data, experimental data sets, and numerical results are used. The first experimental work involves flow through the side entry orifice (SEO) of a boiling water reactor (BWR) using non-intrusive particle tracking velocimetry (PTV) techniques. The second experiment is of a simulated double ended guillotine break in the prismatic block gas cooled reactor. Numerical simulations of jet flow mixing in the lower plenum of a prismatic block high temperature gas cooled reactor is used as a final data set for verification purposes as well as demonstration of the applicability of the method for an actual computational fluid dynamics validation case.

In 2002, Pensacola Beach was identified by the United States Lifesaving Association as being the most hazardous beach in the continental United States for beach drowning by rip currents. Recent studies suggest that the rip currents at Pensacola Beach are associated with a transverse bar and rip morphology that develops with the migration of the bars and recovery of the beachface following an extreme storm. Combined with an alongshore variation in wave forcing by transverse ridges on the inner-shelf, the bar cycle (of bar response and recovery to extreme storms) is hypothesized to create both rip current hotspots and periods of rip activity. However, it is unknown at what stage, or stages, the bar cycle is associated with the formation of these hotspots and the greatest number of rips. To determine how the accretional rip hazard varies in response to the nearshore bar cycle, this thesis will quantify the alongshore variation in the nearshore bar morphology on Santa Rosa Island from 1951 to 2004. Aerial photographs and satellite images are collected for the study area and nearshore features are digitized in ArcGIS and evaluated using wavelet analysis. Specifically, a continuous wavelet transform is used to the identify times and locations when a transverse bar and rip morphology is present or is in the process of developing. The findings suggest that the rip-scale variation in bar morphology (~100-250m) is superimposed on an alongshore variation consistent with the scale of the transverse ridges (~1000m). From the outer bar to the shoreline, and as the bar migrates landward, the variation becomes increasingly dominated by the rip-scale variation. Hotspots of rip current activity were found consistently between years at Fort Pickens Gate, San Souci, Holiday Inn, Casino Beach, Avenida 18 and Portofino, as clusters of rip-scale variation.

El análisis de Fourier es el método fundamental para la medida de armónicos e interarmónicos en señales eléctricas y es el principio de análisis que establece la International Electrotechnical Commission para los instrumentos de medida. Con el objetivo de superar las limitaciones que lo hacen poco efectivo en determinadas condiciones se han propuesto otras técnicas de análisis como las wavelets. En esta tesis doctoral se explora esta alternativa en el campo de la calidad del suministro de energía eléctrica.Como aportación principal se presenta un nuevo método de medida de armónicos e interarmónicos basado en la Transformada Wavelet Packet compatible con el estándar de medida IEC 61000-4-7 de 2002. El método propuesto utiliza un árbol de descomposición wavelet, que en sus distintos niveles suministra la medida de armónicos e interarmónicos de la señal, así como su contenido subarmónico e información de sus variaciones en el dominio temporal.Se exponen las características principales del método en cuanto a la elección de la función wavelet madre, el banco de filtros que implementa el árbol de descomposición wavelet y el postprocesado que posibilita la compatibilidad con el estándar de medida. Se analizan las prestaciones del método en la medida de armónicos e interarmónicos, tanto en condiciones estacionarias como en el caso de pérdida de sincronía por variación de la frecuencia fundamental o variación de la ventana de muestreo de la señal, presencia de componentes no síncronas con la frecuencia de la red o presencia de componentes de amplitud variable. Por último, se expone la información que aporta el método para la estimación temporal de las componentes frecuenciales medidas.El método desarrollado junto con el método de IEC, se ha implementado sobre un equipo electrónico para adquisición y procesado de señal utilizando técnicas de instrumentación virtual. Se expone la estructura y características del hardware utilizado y del software desarrollado así como los resultados obtenidos en la medida del espectro frecuencial de señales de diferente naturaleza.Por último se resumen las conclusiones obtenidas y se proponen futuras líneas de investigación motivadas por la realización de esta tesis doctoral. / Fourier analysis is the fundamental method for the measurement of harmonics and interharmonics in electrical power systems and is the method proposed by the International Electrotechnical Commission (IEC) for standard measurement instruments. With the objective of overcoming the limitations in certain conditions, other techniques of analysis such as wavelets have been proposed. This doctoral thesis investigates alternatives in the field of the quality of the provision of electrical energy. The main contribution of this thesis is the proposal of a new method of measurement of harmonics and interharmonics based on the Wavelet Packet Transform compatible with the standard IEC 61000-4-7 of 2002. The method proposed simultaneously uses different levels of the same wavelet decomposition tree for the measurement of harmonic, interharmonic and subharmonic components in the input signal as well as their time evolution.The basic characteristics of the method in terms of the choice of the mother wavelet function, the bank of filters that implements the wavelet decomposition tree and the postprocessing to make the method compatible with the measurement standard are explained. The benefits of the method in the measurement of harmonics and interharmonics are analyzed, both in stationary conditions and in the case of loss of synchrony due to variation of the base frequency or variation of the sampling window of the signal, presence of nonsynchronous components with the frequency of the network or presence of components of variable amplitude. Finally, the information that the method provides about the temporal estimation of the measured frequencial components is described.The method developed and the IEC method have been implemented on a virtual instrument. The hardware used and the software developed are explained studying the performance of the instrument under different measurement conditions.Finally the conclusions obtained are summarized and future lines of investigation motivated by this doctoral thesis are proposed.

Multiresolution analysis (MRA) has fairly recently become important, and even essential, to image processing and signal analysis, and is thus having a growing impact on image and signal related areas. As one of the most famous family members of the MRA, the wavelet transform (WT) has demonstrated itself in numerous successful applications in various fields, and become one of the most powerful tools in the fields of image processing and signal analysis. Due to the fact that only the scale information is supplied in WT, the applications using the wavelet transform may be limited when the absolutely-referenced frequency and phase information are required. The Stockwell transform (ST) is a recently proposed multiresolution transform that supplies the absolutely-referenced frequency and phase information. However, the ST redundantly doubles the dimension of the original data set. Because of this redundancy, use of the ST is computationally expensive and even infeasible on some large size data sets. Thus, I propose the use of the discrete orthonormal Stockwell transform (DOST), a non-redundant version of ST. This thesis will continue to implement the theoretical research on the DOST and elaborate on some of our successful applications using the DOST. We uncover the fast calculation mechanism of the DOST using an equivalent matrix form that we discovered. We also highlight applications of the DOST in image compression and image restoration, and analyze the global and local translation properties. The local nature of the DOST suggests that it could be used in many other local applications.

Image processing applications such as image denoising, image segmentation, object detection, object recognition and texture synthesis often require a multi-scale analysis of images. This is useful because different features in the image become prominent at different scales. Traditional imaging models, which have been used for multi-scale analysis of images, have several limitations such as high sensitivity to noise and structural degradation observed at higher scales. Parametric models make certain assumptions about the image structure which may or may not be valid in several situations. Non-parametric methods, on the other hand, are very flexible and adapt to the underlying image structure more easily. It is highly desirable to have effi cient non-parametric models for image analysis, which can be used to build robust image processing algorithms with little or no prior knowledge of the underlying image content. In this thesis, we propose a non-parametric pixel neighbourhood based framework for multi-scale image analysis and apply the model to build image denoising and saliency detection algorithms for the purpose of illustration. It has been shown that the algorithms based on this framework give competitive results without using any prior information about the image statistics.

The present work investigates the turbulent jet flow mixing of downward impinging jets within a staggered rod bundle based on previous experimental work. The two inlet jets had Reynold's numbers of 11,160 and 6,250 and were chosen to coincide with the available data. Steady state simulations were initially carried out on a semi-structured polyhedral mesh of roughly 13.2 million cells following a sensitivity study over six different discretized meshes. Very large eddy simulations were carried out over the most refined mesh and continuous 1D wavelet transforms were used to analyze the dominant instabilities and how they propagate through the system in an effort to provide some insight into potential problems relating to structural vibrations due to turbulent instabilities. The presence of strong standing horseshoe vorticies near the base of each cylinder adjacent to an inlet jet was noted and is of potential importance in the abrasion wear of the graphite support columns of the VHTR if sufficient wear particles are present in the gas flow.

This thesis is based on the modified JPEG encoding which uses a preprocessing called as Cubic Convolution Spline Interpolation to subsample the original image into lower resolution image, the subsampled image is encoded by JPEG. The modified JPEG can get very high compression ratio, it¡¦s quality is better than the JPEG file which has the same compressing ratio, but it still is not good enough. In this thesis we use the scalable wavelet encoding to encode the residual image, which is the difference between original and compression image. Due to the high compressing ratio and scalablity. We can attach the compressed residual image with modified JPEG compressed image to get the scalable compressed image whose compressing ratio can tun from 125 to 50 and always get better quality than optimal JPEG.

The paper proposes that Embedded Zreotree Wavelet algorithm and the architecture of the modified EZW algorithm will have the property of regularity, modularity ,and scalablity, and also posses the function , which can allow a detected watermark to be embedded. The methods to realize the algorithm and the function of watermark are to analyze the theory of algorithm and the order of output and input data and then to use queue and stack, the unit of memory, and the control of circuit. The modified EZW architecture needs a half less memory units than the original one, and functions nearly as effective as the original architecture. Besides, this paper points out that the whole architecture of the transform CODEC system can be applied properly to HDTV, MPEG-4 system, or QoS network.

In this paper a novel Hierarchical Sum of Double Difference metric, HSDD, was introduced. It was shown, as opposed to conventional Sum of Absolute Difference (SAD) metric, how this embedded-coding aware metric can jointly constrain the motion vector searching in both temporal and spatial (quad-tree) directions under multiresolution motion estimation (MRME) framework. The temporal-spatial co-optimization concept from HSDD brings us the motion compensation pyramid with better shape. The reward is that fewer bits are spent later for describing the isolated zeros. The compression performance of HSDD easily exceeds the performance of its competitors, especially when high compression ratios are used.

Abstract In radiation therapy, the beam angles and weightings are usually determined by a treatment planning planner. A uniform dose distribution depends on optimal radiation incident beam angle and individual beam weighting. In this study, simulated annealing with wavelet theory is adopted for solving the optimal beams¡¦ angles and weightings to accomplish a uniform dose distribution inside tumor lesion. Our method can increase the efficiency in solving the optimal angles and weightings in the process of simulated annealing.