An internal, 3-D, viscous numerical flow simulation was performed on the rectangular-to-circular transition, bifurcated, 2D high speed civil transport engine inlet at takeoff. The objective of the study was to obtain the causes of flow distortion at the inlet fan face. The inlet was modeled with the centerbody in the fully collapsed takeoff position. A single block, 14Ox40x40 Polar grid topology of a 1/4 symmetry volume of the inlet was used in the simulation. The calculation employed the well established, robust PARC3D CFD code, which uses the full three-dimensional, Reynolds averaged, Navier-Stokes equations in strong conservation form. The flow was considered to be turbulent over the entire flow region. The turbulence model incorporated into PARC3D is the algebraic Baldwin Lomax model. Limitations existed in the local region where the flow interacts with the nose cone due to the inherent limitations of the turbulence model. The results showed that the flow throughout the inlet was well behaved. The turbulent boundary layers were thin and stayed attached to the surfaces of the inlet throughout the entire flowfield. A high pressure recovery was observed at the fan face. Radial distortion at the fan face was caused by thin boundary layers on the nose cone and cowl surfaces. Circumferential distortion was caused by pressure gradients produced by the wake of the splitter plate, located just upstream of the fan. / Master of Science

Outside the world of music the transistor has supplanted the vacuum tube. Transistors do the same sort of job as vacuum tubes but they use germanium or silicon in their manufacture, thus the current is produced in a solid state, rather than a vacuum. Most electronic devices are built with solid state technology. Exceptions are some musical instrument amplifiers and some audiophile grade stereo gear. For the users of this equipment the transistor is unsatisfactory both spiritually and with respect to sound. The need for tubes has become specialized, to the point where designers are designing amplifiers to the specifications of available tubes. The relative scarcity of these gems makes the notion of manufacturing specific tubes under exacting conditions, in relatively small quantities, attractive. A place to make these glass jewels should respect their history, use, and the careful manufacturing techniques required to make them. It is the basilica of the church of the distorted guitar sound. / Master of Architecture

Volterra Series (VS) is often used in the analysis of mildly nonlinear circuits. In this approach, nonlinear circuit analysis is converted into the analysis of a series of linear circuits. The main benefit of this approach is that linear circuit analysis is well established and direct frequency domain analysis of a nonlinear circuit becomes possible. Sensitivity analysis is useful in comparing the quality of two designs and the evaluation of gradient, Jacobian or Hessian matrices, in analog Computer Aided Design. This thesis presents, for the first time, the sensitivity analysis of mildly nonlinear circuits in the frequency domain as an extension of the VS approach. To overcome efficiency limitation due to multiple mixing effects, Nonlinear Transfer Matrix (NTM) is introduced. It is the first explicit analytical representation of the complicated multiple mixing effects. The application of NTM in sensitivity analysis is capable of two orders of magnitude speedup. Per-element distortion decomposition determines the contribution towards the total distortion from an individual nonlinearity. It is useful in design optimization, symbolic simplification and nonlinear model reduction. In this thesis, a numerical distortion decomposition technique is introduced which combines the insight of traditional symbolic analysis with the numerical advantages of SPICE like simulators. The use of NTM leads to an efficient implementation. The proposed method greatly extends the size of the circuit and the complexity of the transistor model over what previous approaches could handle. For example, industry standard compact model, such as BSIM3V3 [35] was used for the first time in distortion analysis. The decomposition can be achieved at device, transistor and block level, all with device level accuracy. The theories have been implemented in a computer program and validated on examples. The proposed methods will leverage the performance of present VS based distortion analysis to the next level.

In an increasingly crowded frequency spectrum with strong interfering signals, the distortion performance, or the linearity, of RF circuits is key to their ability to reject strong intermodulation terms that can corrupt the weak but desired carrier signal. A standard figure-of-merit for small-signal linearity is the Input/Output Third Order Intercept Point (IIP3/OIP3), which represents the input/output power level at which the power of fundamental frequency (PFUND) become equal to that of the third-order intermodulation product (P3rd). Clearly, a higher IIP3 number yields improved linearity, and is highly desirable for many circuits. The thesis will focus on describing the issues that can stem in telecommunication systems from these non-linearities. These non-linearities can be modeled by using a rigorous mathematical expansion based on the Volterra Series. The thesis will "demystify" the Volterra series so that it could be readily understood by the circuit designer, without over burdening him with too much mathematics. Using this series, the distortion performance of an amplifier will be quantified based on IIP3 metrics as described above. Having identified sources of non-linearities, and quantifying the effect of each non-linearity on total IIP3 of an amplifier, the thesis will focus on mitigating these non-linearity sources to increase the overall IIP3 of an amplifier. The techniques discussed to do this are based on both novel device design as well as novel circuit techniques. The amplifiers under discussion will all be SiGe based, due to their exemplary RF performances (comparable to III-V devices) at the fraction of the cost.

This project consists of analyzing and finding solutions to the effect of non-linear distortionon the performance of a Massive Multiple Input Multiple Output (MIMO) system interms of Spectral Efficiency (SE) and Symbol Error Rate (SER). Massive MIMO is one ofthe technologies that are considered the backbone of the 5th generation of wireless communicationsand therefore this technology has gathered much interest from researchersand companies alike [19], as it is proven that this kind of system greatly improves thecapacity of the wireless connection [8]. Since Massive MIMO is still a relatively newtechnology and it is yet to be implemented for commercial use, there are several challengesthat arise when trying to implement such a system. One of these problems arisefrom the fact that the Power Amplifiers (PAs) in the transmitters of Massive MIMO systemsare non-linear and thus impose a distortion on the transmitted signals of the system[12]. The thesis aims to study this non-linear effect on the performance of massive MIMOsystems by first modelling the distortion effect on the transmitted signals using two differentnon-linear models. Moreover, closed-form expressions for one of the models areformed to facilitate the simulation of the non-linear model and facilitate the analysis ofthe distortion effect on the performance metrics. Then the established system model issimulated and based on the results, the effect of each of the power amplifier non-lineardistortion models on the performance metrics of the Massive MIMO system is studied.Furthermore, based on the analysis of the simulation results, a compensation mechanismis introduced to the Massive MIMO system in order to mitigate the distortion effect onthe system performance in terms of SER and SE.

Made available in DSpace on 2014-06-11T19:22:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-04-24Bitstream added on 2014-06-13T19:06:24Z : No. of bitstreams: 1 magnajr_jp_me_prud.pdf: 1562358 bytes, checksum: 707020e37c54b516d7377926b9cefee2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os avanços tecnológicos nos métodos de posicionamento, sobretudo os sistemas de posicionamento por satélite, fizeram com que diversos países atualizassem e/ou revisassem suas estruturas geodésicas fundamentais. Na busca de explorar a total potencialidade das novas tecnologias, as principais mudanças convergiram para a adoção de referenciais geocêntricos, de caráter global e cuja origem coincide com o centro de massa da Terra. A atualização de uma rede geodésica implica na mudança de coordenadas e, consequentemente, alteração da geometria da rede, evidenciando as distorções nela existentes. Para manter a integridade e topologia da rede geodésica é necessário que se proceda a uma modelagem das distorções. Neste contexto, este trabalho apresenta uma metodologia de modelagem de distorções entre realizações de sistemas de referência geodésicos, baseada na utilização de grades regulares. Amplamente utilizada, a modelagem baseada em grades é uma forma padronizada de se realizar a conversão entre referenciais sem a necessidade de aplicação de modelos complexos por parte dos usuários. Nessa dissertação, foram geradas grades de distorção com diferentes espaçamentos, cobrindo todo o território brasileiro, para a modelagem das distorções entre as redes SAD 69 (realização de 1996) e SIRGAS 2000. A geração e aplicação das grades esta pautada no desenvolvimento de aplicativos computacionais com utilização do método de Shepard na geração da grade e da função bilinear na interpolação das distorções a partir dos pontos da grade. A metodologia foi avaliada através de estações de teste, onde os resultados mostraram-se promissores. Nos melhores casos, houve redução de aproximadamente 50% no erro médio quadrático das coordenadas após a modelagem com um indicador médio de precisão de 0,179m. / The technological advances in the positioning methods, mainly in the satellite positioning systems conduced several countries to update and review their fundamental geodetic networks. In order to explore the full potential of these new technologies, the main changes converged to the adoption of geocentric reference systems, that are global and whose origin coincides with the Earth mass center. The geodetic network update implies in coordinate changes and, consequently, the network geometry changes, evidencing the existent distortions. To preserve the data set integrity and topology it is required a modeling of the distortions. In this context, this work presents a distortion modeling methodology between reference frames based on regular grids. Widely used, the modeling based on grids is a standardized and less complex way to accomplish the conversion between frames without the necessity to apply rigorous models by the user. In this research, distortion grids were generated with different sizes and covering all Brazilian s territory to model the distortion between the SAD 69 (1996) and SIRGAS 2000 frames. The grid generation and application are based on computational software development by the use of the Shepard s method in the grid generation and the bilinear function in the distortion interpolation from the grid points. The methodology was evaluated through test stations where the results were promising. In the best cases, the root mean squared error in the coordinates was reduced 50% after the modeling with an average precision indicator of 0,179m.

Orientador: Paulo de Oliveira Camargo / Orientador: Maurício Galo / Banca: João Carlos Chaves / Banca: Leonardo Castro de Oliveira / Resumo: Os avanços tecnológicos nos métodos de posicionamento, sobretudo os sistemas de posicionamento por satélite, fizeram com que diversos países atualizassem e/ou revisassem suas estruturas geodésicas fundamentais. Na busca de explorar a total potencialidade das novas tecnologias, as principais mudanças convergiram para a adoção de referenciais geocêntricos, de caráter global e cuja origem coincide com o centro de massa da Terra. A atualização de uma rede geodésica implica na mudança de coordenadas e, consequentemente, alteração da geometria da rede, evidenciando as distorções nela existentes. Para manter a integridade e topologia da rede geodésica é necessário que se proceda a uma modelagem das distorções. Neste contexto, este trabalho apresenta uma metodologia de modelagem de distorções entre realizações de sistemas de referência geodésicos, baseada na utilização de grades regulares. Amplamente utilizada, a modelagem baseada em grades é uma forma padronizada de se realizar a conversão entre referenciais sem a necessidade de aplicação de modelos complexos por parte dos usuários. Nessa dissertação, foram geradas grades de distorção com diferentes espaçamentos, cobrindo todo o território brasileiro, para a modelagem das distorções entre as redes SAD 69 (realização de 1996) e SIRGAS 2000. A geração e aplicação das grades esta pautada no desenvolvimento de aplicativos computacionais com utilização do método de Shepard na geração da grade e da função bilinear na interpolação das distorções a partir dos pontos da grade. A metodologia foi avaliada através de estações de teste, onde os resultados mostraram-se promissores. Nos melhores casos, houve redução de aproximadamente 50% no erro médio quadrático das coordenadas após a modelagem com um indicador médio de precisão de 0,179m. / Abstract: The technological advances in the positioning methods, mainly in the satellite positioning systems conduced several countries to update and review their fundamental geodetic networks. In order to explore the full potential of these new technologies, the main changes converged to the adoption of geocentric reference systems, that are global and whose origin coincides with the Earth mass center. The geodetic network update implies in coordinate changes and, consequently, the network geometry changes, evidencing the existent distortions. To preserve the data set integrity and topology it is required a modeling of the distortions. In this context, this work presents a distortion modeling methodology between reference frames based on regular grids. Widely used, the modeling based on grids is a standardized and less complex way to accomplish the conversion between frames without the necessity to apply rigorous models by the user. In this research, distortion grids were generated with different sizes and covering all Brazilian’s territory to model the distortion between the SAD 69 (1996) and SIRGAS 2000 frames. The grid generation and application are based on computational software development by the use of the Shepard’s method in the grid generation and the bilinear function in the distortion interpolation from the grid points. The methodology was evaluated through test stations where the results were promising. In the best cases, the root mean squared error in the coordinates was reduced 50% after the modeling with an average precision indicator of 0,179m. / Mestre

Accurately predicting fan performance, including bounds of operation, is an important function of any Computational Fluid Dynamics (CFD) package. The presented research uses a CFD code developed as part of the Computational Research and Engineering Acquisition Tools and Environment (CREATE), known as Kestrel, to evaluate a single stage compressor at various operating conditions. Steady-state, single-passage simulations are carried out to validate capabilities recently added to Kestrel. The analysis includes generating speedlines of total pressure ratio and efficiency, as well as radial total temperature and total pressure profiles at two axial locations in the compressor at various operating conditions and fan speeds, and simulation data from the single-passage runs is compared to experimental data. Time-accurate, full annulus simulations are also carried out to capture and analyze the processes leading to stall inception for both uniform and distorted inlet conditions. The distortion profile used contains a 90 degree sector of lower total pressure at the inlet. The observed fan behavior at stall inception is compared to previous research, and it is concluded that the inlet distortion significantly changes the behavior of the part-span stall cells that develop after stall inception. Understanding the physical processes that lead to stall inception allows fan designers to design more robust fans that can safely take advantage of the better performance associated with operating closer to stall.

Lens distortions appear in almost all digital images and cause straight lines to appear curved in the image. This can contribute to errors in position estimations and 3D reconstruction and it is therefore of interest to correct for the distortion. If the camera is available, the distortion parameters can be obtained when calibrating the camera. However, when the camera is unavailable the distortion parameters can not be found with the standard camera calibration technique and other approaches must be used. Recently, variants of Perspective-n-Point (PnP) extended with lens distortionand focal length parameters have been proposed. Given a set of 2D-3D point correspondences, the PnP-based methods can estimate distortion parameters without the camera being available or with modified settings. In this thesis, the performance of PnP-based methods is compared to Zhang’s camera calibration method. The methods are compared both quantitatively, using the errors in reprojectionand distortion parameters, and qualitatively by comparing images before and after lens distortion correction. A test set for the comparison was obtained from a camera and a 3D laser scanner of an indoor scene.The results indicate that one of the PnP-based models can achieve a similar reprojection error as the baseline method for one of the cameras. It could also be seen that two PnP-based models could reduce lens distortion when visually comparing the test images to the baseline. Moreover, it was noted that a model can have a small reprojection error even though the distortion coefficient error is large and the lens distortion is not completely removed. This indicates that it is important to include both quantitative measures, such as reprojection error and distortion coefficient errors, as well as qualitative results when comparing lens distortion correction methods. It could also be seen that PnP-based models with more parameters in the estimation are more sensitive to noise.

When a camera system in a car is mounted behind the windshield, light rays will be refracted by the windshield. The distortion can be significant, especially for wide field-of-view cameras. Traditional approaches handle the windshield distortion along with the calibration that calculates the intrinsic and extrinsic parameters. However, these approaches do not handle the windshield distortion explicitly, and to understand the image formation, it brings to understand more about the windshield distortion effect. In this thesis, data is collected from a camera system viewed with and without the windshield. The windshield distortion effect has been studied by varying the windshield’s tilt and the camera’s setup. Points are then found in both images and matched. From this, a distortion difference is calculated and analyzed. Next, a preliminary model of the windshield distortion effect is presented and evaluated. The results show that the model works well for all cases and the two windshields considered in this thesis.