Este trabalho é uma síntese da transformada de Fourier na forma discreta e uma de suas principais aplicações à computação gráfica, a restauração de imagens corrompidas por movimento, seja do aparelho óptico ou da própria imagem.

The aim of this PhD thesis is to incorporate deformation twinning in a fullield viscoplastic crystal plasticity model based on fast Fourier transform in an effort to gain insights into its role on strain localization. This work is motivated by current experimental evidences on the important role that dislocation reactions at the twin interface play on damage initiation in materials during plastic deformation. We began first by investigating the role of slip on stress localization. To this end, we simulated the effect of macroscopic deformation path, which dictates a macroscopic stress state, as well as pre-existing microstructure in typical ferritic steel, where plastic deformation is accommodated by slip mechanism. The results show that the width of localized strain rate regions near grain boundaries is a function of the deformation path, and there is a positive correlation between local Taylor factor and local stress field, which slightly depends on deformation path. For the incorporation of mechanical twinning in twinning-induced plasticity (TWIP) steel, we implemented predominant reorientation scheme (PTR) in vpFFT, which was implemented previously in the mean field VPSC. The comparison between experimental and simulation results indicates that twin volume fraction, final texture, and stress-strain curve were satisfactorily predicted. Despite that predominant twin reorientation scheme was not suitable to capture lamellar shape of twins in the microstructure, twin domains were predicted to form and grow at or close to grain boundary regions. Finally, we surveyed current literature, which aimed at capturing the characteristic lamellar morphology of twins. Literature review shows several unsuccessful crystal plasticity simulations in capturing twin nucleation and twin lamellar shape at measocale. These inabilities can be attributed to i) twin nucleation that is controlled by local atomistic configurations and stress fluctuations at the grain boundaries, and ii) the random or stochastic nature of twin nucleation, which has been proved by EBSD observation. Based on the EBSD observations, twin nucleation depends on both microstructural (e.g, grain size, dislocation density) and loading conditions ( e.g, stress, strain). Furthermore, the propensity, frequency, and morphology of deformation twins are different among grain with the same orientation and applied boundary conditions.

<p>The purpose of this master thesis work is to design a device that measures the loudness of sound for different frequencies. This device is divided in three parts; a microphone that captures the sound, one A/D converter that samples the sound and one FPGA which analyse the data using an FFT algorithm.</p><p>LEDs connected to the FPGA are used to indicate different output levels. A db(A) filter is applied that weights each frequency, before the different outputlevels are measured for each frequency. </p><p>This system is supposed to be a subsystem to a larger system that is developed in a company. However, because of the risk that competitors might be able to guess the next product move of the company, the company is anonymous in this report. All the components used are paid for by the company and in return the company gets an idea of the complexity of the system and a basis for future design decisions.</p>

The purpose of this master thesis work is to design a device that measures the loudness of sound for different frequencies. This device is divided in three parts; a microphone that captures the sound, one A/D converter that samples the sound and one FPGA which analyse the data using an FFT algorithm. LEDs connected to the FPGA are used to indicate different output levels. A db(A) filter is applied that weights each frequency, before the different outputlevels are measured for each frequency. This system is supposed to be a subsystem to a larger system that is developed in a company. However, because of the risk that competitors might be able to guess the next product move of the company, the company is anonymous in this report. All the components used are paid for by the company and in return the company gets an idea of the complexity of the system and a basis for future design decisions.

Infrared target tracking devices (called IR seeker) are important part of the heat seeking missiles. They are based on a simply principle that heat produced by the operation of each machine emits strong infrared radiation. Take an aircraft for an example, an exhaust of the combustion engines produce much heat. The IR radiation is then detected and processed by the IR seeker which then guides the missile to the desired target. There are many kinds of IR seeker. In this thesis we focus on ¡§reticle¡¨ and ¡§image¡¨ types of IR seekers. In the early 1950s, the IR technology is limited to a single detector. To be able to locate the target, a rotating reticle was placed before the detector. The pattern on the reticle introduces a specific modulation onto the output signals of the IR seeker thus giving the missile the equivalent of an IR eye. This is the built-in feature of the familiar sidewinder heat seeking missiles. In recent years, technology has greatly improved. The so called ¡§image¡¨ IR seeker uses a focal plane arrays (FPA), similar to the charge coupled device (CCD) of digital camera, to capture the IR image generated from the target. These high definition images are then processed by the computer and help the missile to track its targets. We studied both types of IR seekers and developed approximation methods to generate IR signatures as well as algorithms to locate and identify the target. The ¡§image seeker¡¨ is technologically more advanced and can detect and track several targets simultaneously. Its inversion methods are however, simpler and easier to implement. From the simulation results, we can correctly locate of the target position. Due to the limited input information, more elaborate efforts are needed for the ¡§reticle seekers¡¨ because different reticle have different characteristics and need to be handled differently. To speed up the calculation, we use 2-D Fast Fourier transform of the reticle pattern and IR images of the target for both generation of detector waveforms and for target location. The overall results are satisfactory and meet the IR seeker simulator¡¦s requirements.

In this thesis, an FFT (Fast Fourier Transform) hardware circuit is designed for OFDM systems. A new memory table permutation deletion method, which can reduce the size of memory storing twiddle factors table, is proposed. The architecture of the FFT circuit is based on the faster split-radix algorithm with SDF (Single-path Delay Feedback) pipeline structure. The bits number of the signal is carefully selected by system simulation to meet the system requirements. Based on the simulation results, a small area FFT circuit is carried out for OFDM systems.

Vibrations in machines increase friction on moving parts which cause chafing that will tear down the fabric of the machine components when given time, thus monitoring and analysis of machine vibrations are important for preventive maintenance. Vibration analysis utilizes time domain as well as frequency domain analysis for which there have been analog solutions for quite some time. This work has been about moving a predominantly analog mixed signal system onto an FPGA and making it mostly digital. Vibration analysis on an FPGA have its own challenges and benefits compared to other methods. The inherent parallelism of the FPGA makes it suitable for high performance signal analysis. This report shows through two proof-of-concept solutions that the translation of a predominantly analog system is viable, economic and can deliver improved performance. The two solutions have utilized two different units from Xilinx, the Spartan-6 FPGA and the Zynq-7000 system on chip FPGA. The solution implemented on Spartan-6 produces a result in 9.32 ms and the other implementation based on Zynq-7000 produces a result in 9.39 ms, which is more than a 10-fold increase in performance of the current system. The results obtained show that both solutions can perform the calculations for the proof of concept within 20% of the allotted time. Costs of both solutions as well as other qualities of each solution are presented in this paper.

The convolution operation is a powerful tool which is widely used in many disciplines.Lately is has seen much use in the area of computer vision, particularly with convolutionalneural networks. For these use cases, convolutions need to be run repeatedly many timeswhich necessitates specialized hardware. Our work empirically investigates the efficiencyof some of the most prominent convolution methods used, such as the Fast FourierTransform and the Winograd method, and compares these to a baseline convolutionimplementation. These comparisons are made in both one and two dimensions, and forseveral different floating point data types.

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Dieser Artikel präsentiert einen neuartigen Ansatz für die vorbeugende Instandhaltung von Planetengetrieben durch Integration von Beschleunigungssensoren in die Planeten. Die Beschleunigungssensoren zeichnen Daten von 36 Sekunden pro Stunde bei einer hohen Abtastrate von 10 kHz auf, was die Sammlung von hochauflösenden Vibrationsdaten zur Analyse ermöglicht. Ziel der Studie ist die Entwicklung eines Rahmens für die vorbeugende Instandhaltung unter Verwendung von Clustering- Techniken, analytischen Berechnungen und numerischen Simulationen sowie eines digitalen Zwillings für effektives Monitoring und die Instandhaltungsplanung von Planetengetrieben.