Micro-Electro-Mechanical Systems (MEMS) varactors have the potential to replace conventional varactor diodes, due to their high loss and non-linearity, in many applications such as phase shifters, oscillators, and tunable filters. The objective of this thesis is to develop novel MEMS varactors to improve the capacitance tuning ratio, linearity, and quality factor. Several novel varactor configurations are developed, analyzed, fabricated and tested. They are built by using standard MEMS fabrication processes, as well as monolithic integration techniques in CMOS technology. The first capacitor consists of two movable plates, loaded with a nitride layer that exhibits an analog continuous capacitance tuning ratio. To decrease the the parasitic capacitance, a trench in the silicon substrate under the capacitor is adopted. The use of an insulation dielectric layer on the bottom plate of the MEMS capacitor increases the capacitors’ tuning ratio. Experimental and theoretical results are presented for two versions of the proposed capacitor with different capacitance values. The measured capacitance tuning ratio is 280% at 1 GHz. The proposed MEMS vararctor is built using the MetalMUMPs process. The second, third, and fourth capacitors have additional beams that are called carrier beams. The use of the carrier beams makes it possible to obtain an equivalent nonlinear spring constant, which increases the capacitors’ analog continuous tuning ratio. A lumped element model and a continuous model of the proposed variable capacitors are developed. The continuous model is simulated by commercial software. A detailed analysis for the steady state of the capacitors is presented. The measured capacitance tuning ratios of these three capacitors are 410%, 400% and 470%, respectively at 1 GHz. Also, the selfresonance frequency is measured and found to exceed 11 GHz. The proposed MEMS variable capacitors are built by the PolyMUMPs process. The fifth novel parallel-plate MEMS varactor has thin-film vertical comb actuators as its driver. Such an actuator can vertically displace both plates of the parallel-plate capacitor. By making use of the fringing field, this actuator exhibits linear displacement behavior, caused by the induced electrostatic force of the actuator’s electrodes. The proposed capacitor has a low parasitic capacitance and linear deflection due to the mechanically connected and electrically isolated actuators to the capacitor’s parallel-plates. The measured tuning capacitance ratio is 7:1 (600%) at 1 GHz. The fabricated MEMS varactor exhibits a self resonance frequency of 9 GHz and built by MetalMUMPs process. The sixth parallel-plate MEMS varactor exhibits a linear response and high tuning capacitance ratio. The capacitor employs the residual stress of the chosen bi-layer, and the non-linear spring constants from the suspended cantilevers to obtain a non-linear restoring force that compensates for the nonlinear electrostatic force induced between the top and bottom plates. Two existing techniques are used to widen the tuning range of the proposed capacitor. The first technique is to decrease the parasitic capacitance by etching the lossy substrate under the capacitor’s plates. The second technique is employed to increase the capacitance density, where the areas between the top and bottom plates overlap, by applying a thin film of dielectric material, deposited by the atomic layer deposition (ALD) technique. The measured linear continuous tuning ratio for the proposed capacitor, built in the PolyMUMPs process, is 5:1 (400%). The seventh and eighth MEMS variable capacitors have plates that curl up. These capacitors are built in 0.35 μm CMOS technology from the interconnect metallization layers. The plates of the presented capacitors are intentionally curled upward to control the tuning performance. A newly developed maskless post-processing technique that is appropriate for MEMS/CMOS circuits is proposed. it consists of dry and wet etching steps, developed to integrate the proposed MEMS varactors in CMOS technology. Mechanically, the capacitors are simulated by the finite element method in ANSYS, and the results are compared with the measured results. The seventh capacitor is a tri-state structure that exhibits a measured tuning range of 460% at 1 GHz with a flat capacitance response that is superior to that of conventional digital capacitors. The proposed capacitor is simulated in HFSS and the extracted capacitance is compared with the measured capacitance over a frequency range of 1 GHz to 5 GHz. The eighth capacitor is an analog continuous structure that demonstrates a measured continuous tuning range of 115% at 1 GHz with no pull-in. The measured quality factor for both CMOSbased capacitors is more than 300 at 1.5 GHz. The proposed curled-plate capacitors have a small area and can be realized to build a System-on-Chip (SoC). Finally, a tunable band pass filter that utilizes the MEMS variable capacitors in 0.18 μm CMOS technology from TSMC is designed, modeled and fabricated.

Recent attempts to increase the capacity of the compact disc (CD) and digital versatile disc (DVD) have explored the use of multilevel recording instead of binary recording. Systems that achieve an increase in capacity of about three times that of conventional CD have been proposed for production. Marks in these systems are multilevel and fixed-length as opposed to binary and variable length in CD and DVD. The main objective of this work is to evaluate the performance of multilevel ($M$-ary) runlength-limited (RLL) coded sequences in optical data storage. First, the waterfilling capacity of a multilevel optical recording channel ($M$-ary ORC) is derived and evaluated. This provides insight into the achievable user bit densities, as well as a theoretical limit against which simulated systems can be compared. Then, we evaluate the performance of RLL codes on the $M$-ary ORC. A new channel model that includes the runlength constraint in the transmitted signal is used. We compare the performance of specific RLL codes, namely $M$-ary permutation codes, to that of real systems using multilevel fixed-length marks for recording and the theoretical limits. The Viterbi detector is used to estimate the original recorded symbols from the readout signal. Then, error correction is used to reduce the symbol error probability. We use a combined ECC/RLL code for phrase encoding. We evaluate the use of trellis coded modulation (TCM) for amplitude encoding. The detection of the readout signal is also studied. A post-processing algorithm for the Viterbi detector is introduced, which ensures that the detected word satisfies the code constraints. Specifying the codes and detector for the $M$-ary ORC gives a complete system whose performance can be compared to that of the recently developed systems found in the literature and the theoretical limits calculated in this research.

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) has been developed and applied to clinical analysis studies due to its non-invasive properties. Because of the increasing clinical interests of applying MRS, a lot of post-processing tools has been developed, among which LCModel is one of the most popular. LCModel estimates the absolute metabolite concentrations in vivo according to the basis file, so basis files play an important role for the accuracy of absolute metabolite concentrations. The default basis sets of LCModel were made by phantom experiments. However, some special metabolites are difficult to get them, so the basis sets lack for these metabolites. In order to avoid this trouble, LCModel provides a special method called ¡§spectra offering¡¨. In this study, we use GAMMA Visual Analysis (GAVA) software to create basis sets and compare the shape of LCModel default basis sets with the shape of GAVA basis sets. Some metabolites which are not included in the LCModel phantom experiments are also generated. Finally, we estimate the absolute concentrations in normal subjects and patients by using these two kinds of basis sets respectively. Using LCModel ¡§spectra offering¡¨ method to append extra metabolites for LCModel basis sets is applicable to those metabolites of singlet resonance but not of J-coupling resonance in the meanwhile. Our results demonstrate that using GAVA simulation as the basis set leads to different quantitative results from using basis sets of in vitro. We believe that using GAVA simulation as the basis set would provide better consistency among all metabolites and thus achieve more accurate quantification of MRS.

Magnetic resonance (MR) has been developed and applied to clinical analysis studies due to its non-invasive properties. Because of the increasing interest of applying magnetic resonance spectroscopy imaging (MRSI) to clinical application, some post-processing softwares, like LCModel, provide a graphical user interface for convenient and efficient analysis. However, the features of combining MR imaging (MRI) with MRS information and browsing all analyzed results are not provided by LCModel. Our study proposed a method to implement the architecture for processing General Electric (GE), Siemens MRSI data sets and provides features including interactive display, selection and analysis of full 2D slices. For multi-console analysis, our tool also provides the combination of MRS, MRI, and data sets generated by LCModel, such as the projection of three planes and metabolite/spectra map, and therefore the three formats of data sets could be obtained from scanners of various manufactures. Especially, it is more complicated when processing GE data sets, so some mechanisms for processing are proposed, like the transformation, the three plane loc images detection and MRSI detection, etc. Additionally, our tool also has the advantage of the compatibility of further extended functionalities, which would be more flexible and useful for clinical applications.

<p> </p><p>Post-processing techniques are used to change a rendered image as a last step before presentation and include, but is not limited to, operations such as change of saturation or contrast, and also more advanced effects like depth-of-field and tone mapping.</p><p>Depth-of-field effects are created by changing the focus in an image; the parts close to the focus point are perfectly sharp while the rest of the image has a variable amount of blurriness. The effect is widely used in photography and movies as a depth cue but has in the latest years also been introduced into computer games.</p><p>Today’s graphics hardware gives new possibilities when it comes to computation capacity. Shaders and GPGPU languages can be used to do massive parallel operations on graphics hardware and are well suited for game developers.</p><p>This thesis presents the theoretical background of some of the recent and most valuable depth-of-field algorithms and describes the implementation of various solutions in the shader domain but also using GPGPU techniques. The main objective is to analyze various depth-of-field approaches and look at their visual quality and how the methods scale performance wise when using different techniques.</p><p> </p>

Phase-contrast magnetic resonance imaging (PC-MRI) can provide a complement to echocardiography for the evaluation of the fetal heart. Cardiac imaging typically requires gating with peripheral hardware; however, a gating signal is not readily available in utero. In this thesis, I present a technique for reconstructing time-resolved fetal phase-contrast MRI in spite of this limitation. Metric Optimized Gating (MOG) involves acquiring data without gating and retrospectively determining the proper reconstruction by optimizing an image metric, and the research in this thesis describes the theory, implementation, and evaluation of this technique. In particular, results from an experiment with a pulsatile flow phantom, an adult volunteer study, in vivo application in the fetal population, and numerical simulations are presented for validation. MOG enables imaging with conventional PC-MRI sequences in the absence of a gating signal, permitting flow measurements in the great vessels in utero.

Phase-contrast magnetic resonance imaging (PC-MRI) can provide a complement to echocardiography for the evaluation of the fetal heart. Cardiac imaging typically requires gating with peripheral hardware; however, a gating signal is not readily available in utero. In this thesis, I present a technique for reconstructing time-resolved fetal phase-contrast MRI in spite of this limitation. Metric Optimized Gating (MOG) involves acquiring data without gating and retrospectively determining the proper reconstruction by optimizing an image metric, and the research in this thesis describes the theory, implementation, and evaluation of this technique. In particular, results from an experiment with a pulsatile flow phantom, an adult volunteer study, in vivo application in the fetal population, and numerical simulations are presented for validation. MOG enables imaging with conventional PC-MRI sequences in the absence of a gating signal, permitting flow measurements in the great vessels in utero.

Orientador: Ruis Camargo Tokimatsu / Resumo: Ao longo das duas últimas décadas, a contribuição da manufatura aditiva passou da confecção de um mero protótipo de um produto, no início de seu desenvolvimento, para a confecção de qualquer produto direto, presente em todos os setores industriais. Com este avanço, diferentes tecnologias da manufatura aditiva surgiram com o intuito de melhorar alguns parâmetros de produção. Neste meio, a tecnologia de impressão tridimensional 3DP, por consequência de suas várias características intrínsecas, se destaca para atender o setor biomédico, através da técnica de biomodelagem, que contribuem imensamente de forma didática e prática para a performance de cirurgias. Porém, há algumas limitações finais nas peças obtidas por esta tecnologia que devem ser contornadas, focando-se no tratamento adicional necessário destas peças, o pós-processamento, de modo a aprimorá-las, conferindo então sucesso ao destino destas. Neste trabalho, adotou-se a tecnologia de manufatura aditiva 3DP para estudar como a adição de diferentes agentes infiltrantes influenciam no acréscimo de densidade aparente e resistência mecânica de amostras feitas de componentes de gesso, constituídas por corpos de prova cilíndricos e prismáticos, de modo a simular a melhor composição para biomodelos. Para isto, o pós-processamento foi dividido em duas etapas. Na primeira etapa, foram aplicados separadamente nas amostras, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento, e um à base de epóxi, por moldagem com... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Until recent times, weather forecasts were deterministic in nature. For example, a forecast might state ``The temperature tomorrow will be $20^\circ$C.'' More recently, however, increasing interest has been paid to the uncertainty associated with such predictions. By quantifying the uncertainty of a forecast, for example with a probability distribution, users can make risk-based decisions. The uncertainty in weather forecasts is typically based upon `ensemble forecasts'. Rather than issuing a single forecast from a numerical weather prediction (NWP) model, ensemble forecasts comprise multiple model runs that differ in either the model physics or initial conditions. Ideally, ensemble forecasts would provide a representative sample of the possible outcomes of the verifying observations. However, due to model biases and inadequate specification of initial conditions, ensemble forecasts are often biased and underdispersed. As a result, estimates of the most likely values of the verifying observations, and the associated forecast uncertainty, are often inaccurate. It is therefore necessary to correct, or post-process ensemble forecasts, using statistical models known as `ensemble post-processing methods'. To this end, this thesis is concerned with the application of statistical methodology in the field of probabilistic weather forecasting, and in particular ensemble post-processing. Using various datasets, we extend existing work and propose the novel use of statistical methodology to tackle several aspects of ensemble post-processing. Our novel contributions to the field are the following. In chapter~3 we present a comparison study for several post-processing methods, with a focus on probabilistic forecasts for extreme events. We find that the benefits of ensemble post-processing are larger for forecasts of extreme events, compared with forecasts of common events. We show that allowing flexible corrections to the biases in ensemble location is important for the forecasting of extreme events. In chapter~4 we tackle the complicated problem of post-processing ensemble forecasts without making distributional assumptions, to produce recalibrated ensemble forecasts without the intermediate step of specifying a probability forecast distribution. We propose a latent variable model, and make a novel application of measurement error models. We show in three case studies that our distribution-free method is competitive with a popular alternative that makes distributional assumptions. We suggest that our distribution-free method could serve as a useful baseline on which forecasters should seek to improve. In chapter~5 we address the subject of parameter uncertainty in ensemble post-processing. As in all parametric statistical models, the parameter estimates are subject to uncertainty. We approximate the distribution of model parameters by bootstrap resampling, and demonstrate improvements in forecast skill by incorporating this additional source of uncertainty in to out-of-sample probability forecasts. In chapter~6 we use model diagnostic tools to determine how specific post-processing models may be improved. We subsequently introduce bias correction schemes that move beyond the standard linear schemes employed in the literature and in practice, particularly in the case of correcting ensemble underdispersion. Finally, we illustrate the complicated problem of assessing the skill of ensemble forecasts whose members are dependent, or correlated. We show that dependent ensemble members can result in surprising conclusions when employing standard measures of forecast skill.

Submitted by Silvia Teixeira de Mello null (silviateixmello@gmail.com) on 2017-10-26T21:23:12Z No. of bitstreams: 1 DISSERTAÇÃO SILVIA MELLO 2017-3 CORRIGIDA 26-10.pdf: 3630355 bytes, checksum: 302fa9b705ffc11d7192a4b67392d0c6 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-10-31T18:59:52Z (GMT) No. of bitstreams: 1 mello_st_me_ilha.pdf: 3630355 bytes, checksum: 302fa9b705ffc11d7192a4b67392d0c6 (MD5) / Made available in DSpace on 2017-10-31T18:59:52Z (GMT). No. of bitstreams: 1 mello_st_me_ilha.pdf: 3630355 bytes, checksum: 302fa9b705ffc11d7192a4b67392d0c6 (MD5) Previous issue date: 2017-08-30 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Ao longo das duas últimas décadas, a contribuição da manufatura aditiva passou da confecção de um mero protótipo de um produto, no início de seu desenvolvimento, para a confecção de qualquer produto direto, presente em todos os setores industriais. Com este avanço, diferentes tecnologias da manufatura aditiva surgiram com o intuito de melhorar alguns parâmetros de produção. Neste meio, a tecnologia de impressão tridimensional 3DP, por consequência de suas várias características intrínsecas, se destaca para atender o setor biomédico, através da técnica de biomodelagem, que contribuem imensamente de forma didática e prática para a performance de cirurgias. Porém, há algumas limitações finais nas peças obtidas por esta tecnologia que devem ser contornadas, focando-se no tratamento adicional necessário destas peças, o pós-processamento, de modo a aprimorá-las, conferindo então sucesso ao destino destas. Neste trabalho, adotou-se a tecnologia de manufatura aditiva 3DP para estudar como a adição de diferentes agentes infiltrantes influenciam no acréscimo de densidade aparente e resistência mecânica de amostras feitas de componentes de gesso, constituídas por corpos de prova cilíndricos e prismáticos, de modo a simular a melhor composição para biomodelos. Para isto, o pós-processamento foi dividido em duas etapas. Na primeira etapa, foram aplicados separadamente nas amostras, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento, e um à base de epóxi, por moldagem com pá. Já na segunda etapa, foram aplicados nas amostras, também separadamente, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento e banho de imersão, e um à base de epóxi, por moldagem com pá. Além dos métodos de aplicação dos adesivos, as duas etapas se diferem também pelos binders utilizados para constituírem as amostras à base de gesso. Para ambas etapas, obteve-se o melhor resultado com o adesivo de cianocrilato de baixíssima viscosidade, capaz de provocar maiores variações de densidade aparente às amostras, além de maiores acréscimos de resistência. / Over the past two decades, the contribution of additive manufacturing has shifted from a mere prototype of a product at the beginning of its development to the production of any direct product present in all industrial sectors. With this advance, different technologies of the additive manufacturing appeared with the intention to improve some parameters of production. In this environment, three-dimensional printing 3DP technology, due to its various intrinsic characteristics, stands out to serve the biomedical sector through the biomodelling technique, which contribute immensely in a didactic and practical way for the performance of surgeries. However, there are some final limitations in the parts obtained by this technology that must be improved, focusing on the necessary additional treatment of these parts, the post-processing, in order to upgrade them, thus giving success to their destination. In this study, 3DP additive manufacturing technology was adopted to study how different infiltrating agents influence the increase in apparent density and mechanical strength of samples made of gypsum components, constituted by cylindrical and prismatic specimens, in order to simulate the best composition for biomodels. For this, the post-processing was divided in two stages. In the first stage, separately, four types of ethylcyanoacrylate-based adhesives were applied on the samples by dripping, and one epoxy-based adhesive was applied by shovel molding. In the second stage, also separately, four types of ethylcyanocrylate based adhesives were applied in the samples, by dripping and by dipping, and the epoxy-based, by shovel molding. Besides the adhesive application methods, the two stages also differ from the binders used to constitute the gypsum-based samples. For both stages, the best result was obtained by the cyanoacrylate adhesive with very low viscosity, capable of causing greater variations of apparent density and additions of strength to the samples.