abstract: This thesis dissertation presents design of portable low power Electrochemical Impedance Spectroscopy (EIS) system which can be used for biomedical applications such as tear diagnosis, blood diagnosis, or any other body-fluid diagnosis. Two design methodologies are explained in this dissertation (a) a discrete component-based portable low-power EIS system and (b) an integrated CMOS-based portable low-power EIS system. Both EIS systems were tested in a laboratory environment and the characterization results are compared. The advantages and disadvantages of the integrated EIS system relative to the discrete component-based EIS system are presented including experimental data. The specifications of both EIS systems are compared with commercially available non-portable EIS workstations. These designed EIS systems are handheld and very low-cost relative to the currently available commercial EIS workstations. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

The control of complex robotic platforms is a challenging task, especially in designs with high levels of kinematic redundancy. Novel variable impedance actuators (VIAs) have recently demonstrated that, by allowing the ability to simultaneously modulate the output torque and impedance, one can achieve energetically more efficient and safer behaviour. However, this adds further levels of actuation redundancy, making planning and control of such systems even more complicated. VIAs are designed with the ability to mechanically modulate impedance during movement. Recent work from our group, employing the optimal control (OC) formulation to generate impedance policies, has shown the potential benefit of VIAs in tasks requiring energy storage, natural dynamic exploitation and robustness against perturbation. These approaches were, however, restricted to systems with smooth, continuous dynamics, performing tasks over a predefined time horizon. When considering tasks involving multiple phases of movement, including switching dynamics with discrete state transitions (resulting from interactions with the environment), traditional approaches such as independent phase optimisation would result in a potentially suboptimal behaviour. Our work addresses these issues by extending the OC formulation to a multiphase scenario and incorporating temporal optimisation capabilities (for robotic systems with VIAs). Given a predefined switching sequence, the developed methodology computes the optimal torque and impedance profile, alongside the optimal switching times and total movement duration. The resultant solution minimises the control effort by exploiting the actuation redundancy and modulating the natural dynamics of the system to match those of the desired movement. We use a monopod hopper and a brachiation system in numerical simulations and a hardware implementation of the latter to demonstrate the effectiveness and robustness of our approach on a variety of dynamic tasks. The performance of model-based control relies on the accuracy of the dynamics model. This can deteriorate significantly due to elements that cannot be fully captured by analytic dynamics functions and/or due to changes in the dynamics. To circumvent these issues, we improve the performance of the developed framework by incorporating an adaptive learning algorithm. This performs continuous data-driven adjustments to the dynamics model while re-planning optimal policies that reflect this adaptation. The results presented show that the augmented approach is able to handle a range of model discrepancies, in both simulation and hardware experiments using the developed robotic brachiation system.

Humans have a complex musculoskeletal arrangement which gives them great behavioural flexibility. As well as simply moving their legs, they can modulate the impedance of them. Variable impedance has become a large field in robotics, and tailoring the impedance of a robot to a particular task can improve efficiency, stability, and potentially safety. Locomotion of a bipedal robot is a perfect example of a task for which variable impedance may provide such advantages, since it is a dynamic movement which involves periodic ground impacts. This thesis explores the creation of two novel bipedal robots with variable impedance joints. These robots aim to achieve some of the benefits of compliance, while retaining the behavioural flexibility to be truly versatile machines. The field of variable impedance actuators is explored and evaluated, before the design of the robots is presented. Of the two robots, BLUE (Bipedal Locomotion at the University of Edinburgh) has a 700mm hip rotation height, and is a saggital plane biped. miniBLUE has a hip rotation height of 465mm, and includes additional joints to allow hip adduction and abduction. Rapid prototyping techniques were utilised in the creation of both robots, and both robots are based around a custom, high performance electronics and communication architecture. The human walking cycle is analysed and a simple, parameterised representation developed. Walking trajectories gathered from human motion capture data, and generated from high level gait determinants are evaluated in dynamic simulation, and then on BLUE. With the robot being capable of locomotion, we explore the effect of varying stiffness on efficiency, and find that changing the stiffness can have an effect on the energy efficiency of the movement. Finally, we introduce a system for goal-based teleoperation of the robots, in which parameters are extracted from a user in a motion capture suit and replicated by the robot. In this way, the robot produces the same overall locomotion as the human, but with joint trajectories and stiffnesses that are more suited for its dynamics.

Combustion devices are prone to combustion instabilities. They arise from a constructive coupling between the unsteady heat release rate of the flame and the resonant acoustic modes of the entire system. The occurence of such instabilities can pose a threat to both performance and integrity of combustion systems. Although these phenomena have been known for more than a century, avoiding their appearance in industrial engines is still challenging. The objective of this thesis is threefold: (1) study the dynamics of the resonant acoustic modes, (2) investigate the flame response of a liquid rocket engine under unstable conditions using Large Eddy Simulation(LES) and (3) derive, use and study Time Domain Impedance Boundary Conditions (TDIBCs), i.e. boundary conditions modeling complex acoustic impedances.

O presente trabalho apresenta resultados de preparação, caracterização e aplicação de membranas de DNA e DNA-PEDOT:PSS como material transportador de buracos (HTM) em células solares sensibilizadas por corante (DSSC). As análises por UV-Vis das amostras revelaram 80% de transparência em 600 nm para o DNA-isolado e diminuindo para 62% em 550 nm para o DNA-2% PEDOT:PSS. As análises das amostras por FTIR revelaram os picos característicos tanto do DNA quanto do PEDOT:PSS, confirmando a incorporação deste último nas membranas. Os resultados de análises térmicas DSC evidenciaram a presença de Tg em -67ºC e o seu desaparecimento com a adição de PEDOT:PSS na formulação de HTM. As análises de TGA mostraram o aumento da estabilidade das amostras com a adição de PEDOT:PSS atingindo 200ºC. Todas as amostras apresentaram 19% de resíduos em 900ºC. As membranas a base de DNA também foram submetidas às medidas de condutividade iônica revelando o maior valor de 3,2x10-4 S/cm2 em temperatura ambiente e aumentando para 0,1x10-3 S/cm2 em temperatura de 75ºC, para a amostra de DNA-isolado. As amostras de DNA-PEDOT:PSS mostraram valores de condutividade de 4,67x10-5 S/cm2 para a amostra DNA -2% PEDOT:PSS, em temperatura ambiente e diminuíram com o aumento de porcentagem de PEDOT:PSS. Dos difratogramas de raios-X observou-se um aumento da cristalinidade das amostras com a adição de PEDOT:PSS sendo o maior valor encontrado de 77,8% foi para a amostra de DNA-10% PEDOT:PSS. As DSSCs apresentaram a diminuição de eficiência solar após a introdução de membranas de DNA de 2.04% para 1,49% fenômeno explicado em termos de aumento de reflectância e rugosidade das amostras que dificultou o transporte de carga e recombinação do par redox do eletrólito nas células solares sensibilizadas por corante. / This paper presents results of preparation, characterization and application of DNA and DNA-PEDOT:PSS-based membranes as hole-carrier material (HTM) in dye-sensitized solar cells (DSSC). The UV-Vis analysis of the samples revealed 80% of transparency at 600 nm for the isolated DNA and 62% at 550 nm for DNA-2% PEDOT:PSS. The FTIR analysis of the samples showed characteristic peaks of both the DNA and PEDOT:PSS, confirming its incorporation into membranes. The results of DSC analysis revealed the presence of Tg at -67ºC and its disappearance with the addition of PEDOT:PSS to the formulation of HTM. The TGA analysis showed increased stability of the samples with the addition of PEDOT:PSS reaching 200ºC. All samples showed 19% of ashes at 900ºC. The DNA-based membranes were also subjected to ionic conductivity measurements showing the highest value of 3.2x10-4 S/cm2 at room temperature and of 0.1x10-3 S/cm2 at 75ºC for the isolated DNA. Samples of DNA-PEDOT:PSS showed conductivity value of 4.67x10-5 S/cm2 for DNA-2% PEDOT:PSS sample at room temperature which decreased with increasing percentage of PEDOT:PSS. X-ray diffraction revealed an increase of the crystallinity of the samples with the addition of PEDOT:PSS and the highest value found was 77.8% for the sample of DNA-10% PEDOT:PSS. The DSSCs showed a reduction of solar efficiency from 2.04% to 1.49% after the introduction of DNA-based membranes. This phenomenon was explained in terms of increased reflectance and surface roughness of the samples that difficult the transport and recombination of charge carrier species.

Made available in DSpace on 2014-06-11T19:23:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-16Bitstream added on 2014-06-13T18:50:17Z : No. of bitstreams: 1 benites_ta_me_araiq_parcial.pdf: 365660 bytes, checksum: 563ff4de53643caf527ab2319e2ffd76 (MD5) Bitstreams deleted on 2014-11-14T12:17:01Z: benites_ta_me_araiq_parcial.pdf,Bitstream added on 2014-11-14T12:17:46Z : No. of bitstreams: 1 000721769.pdf: 1532537 bytes, checksum: 1f1f903eabe42a2227cf65971f622a31 (MD5) / O estudo das propriedades dielétricas das monocamadas automontadas de alcanotióis sobre o ouro (SAMs) é importante no campo da biotecnologia, já que essas camadas proporcionam uma estrutura fundamental na construção dos eletrodos quimicamente modificados, com sua principal aplicação na confecção dos biossensores. A análise das propriedades de bloqueio pelas SAMs é frequentemente feita por meio de técnicas eletroquímicas e de resposta em frequência, pois são extremamente eficazes no entendimento das características físico-químicas interfaciais de modificação desses filmes, além de apresentarem praticidade e velocidade de realização. Uma forma bastante apropriada de analisar a capacidade dielétrica das SAMs é quantificando a velocidade de transferência eletrônica frente a uma espécie eletroativa. Nesse trabalho foram caracterizadas monocamadas de diferentes espessuras em um meio com espécie eletroativa em concentrações variadas, a partir do cálculo da constante de transferência heterogênea de elétrons, feitas pelas metodologias propostas por diferentes autores e por uma metodologia inédita que será detalhada no corpo do trabalho / The study of the dielectric properties of self-assembled monolayers of alkanethiols on gold (SAMs) is of paramount importance to biotechnology, as these layers provide a fundamental structure in the construction of chemically modified electrodes, with its main application in fabrication of biosensors. The analysis of the blocking properties of SAMs is often done by electroanalytical techniques and frequency response, as they are extremely effective in understanding the physico-chemical interfacial modification of these films, and offer convenience and speed of execution. A very appropriate manner of evaluating the blocking ability of SAMs is quantifying dielectric constant and the heterogeneous electron transfer rate across from one electroactive species in solution. In this study monolayers of different thicknesses were characterized in a medium with electroactive species in different concentrations to calculate of the heterogeneous electron transfer constant by classical methods which were compared with a new methodology detailed in the present work

Submitted by Márcio Maia (marciokjmaia@gmail.com) on 2016-08-08T12:30:12Z No. of bitstreams: 1 arquivototal.pdf: 1568585 bytes, checksum: a2238a4716a4526680dc4b1d96c2e0b7 (MD5) / Made available in DSpace on 2016-08-08T12:30:12Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1568585 bytes, checksum: a2238a4716a4526680dc4b1d96c2e0b7 (MD5) Previous issue date: 2016-04-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Fuel cells (FC) are electrochemical devices that convert chemical energy from certain fuels into electrical energy, through oxidation-reduction reactions. They have a basic structure consisting of an electrolyte layer intercalating two electrodes: the cathode (positive electrode) and anode (negative electrode). In this work, cathode materials for solid oxide fuel cells (SOFC) were developed, such as lanthanum cobaltite doped with strontium and iron (La0,6Sr0,4Co0,2Fe0,8O3-8-LSCF6428) was synthesized by the modified polymeric precursors method, also known as modified Pechini method and compared the performance with the composite electrodes La0,6Sr0,4Co0,2Fe0,8O3-8/Ce0,9 Gd0,1O2-8 (LSCF6428/ CGO) and La0,6Sr0,4Co0,2Fe0,8O3-8/Ce0,9Gd0,1O2-8/Prox (LSCF6428/CGO/PROX). The method of synthesis consists in the use of commercial gelatin as polymerizing agent for metal ions. The powder obtained at 350 ° C / 2h was calcined at 800 and 1000 ° C / 4h and characterized by thermal gravimetric analysis (TG), particle size distribution, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The films of (LSCF6428), (LSCF6428 / CGO) and (LSCF6428 / CGO / PROX) were obtained by serigraph of calcined powders at 1000 ° C. The films were deposited on ceria substrates doped with gadolinia Ce0,9Gd0,1O2-8(CGO), sintered at 1150°C and characterized by impedance spectroscopy (in pure oxygen) between 600 and 800°C. The obtained results indicated that the method used was efficient in the formation of porous powders and with the perovskite crystalline structure. The crystallite size for the composite of LSCF6428 / CGO was of 336 (nm) for the LSCF6428 and 98 (nm) for the CGO, being also the expected for a powder calcined at 1000 ° C. The value of the area specific resistance (ASR) for the electrode of pure LSCF6428 at 750 ° C was of 0.25 ohms.cm2 quite plausible, especially because it was not made use of platinum, for the LSCF/CGO/ Prox was obtained an ASR of 0.02 ohms.cm2 at 750 ° C. / As células a combustível (CaC) são dispositivos eletroquímicos que transformam a energia química de determinados combustíveis em energia elétrica, por meio de reações de oxirredução. Possuem uma estrutura básica que consiste em uma camada de eletrólito intercalando dois eletrodos: cátodo (eletrodo positivo) e anodo (eletrodo negativo). Neste trabalho, foram desenvolvidos materiais catódicos para células a combustíveis de óxidos sólidos (SOFC), tais como, a cobaltita de lantânio dopada com estrôncio e ferro (La0,6Sr0,4Co0,2Fe0,8O3-δ – LSCF6428) foi sintetizado pelo método dos precursores poliméricos modificado, também conhecido como Pechini modificado e comparado o desempenho com o de eletrodos compósitos La0,6Sr0,4Co0,2Fe0,8O3-δ/Ce0,9Gd0,1O2-δ (LSCF6428/CGO) e La0,6Sr0,4Co0,2Fe0,8O3-δ/ Ce0,9Gd0,1O2-δ/PrOx (LSCF6428/CGO/PrOx). O método de síntese consiste na utilização da gelatina comercial como agente polimerizante para íons metálicos. O pó obtido a 350 °C/ 2h foi calcinado a 800 e 1000 °C/ 4h e caracterizados por analise termogravimétrica (TG), distribuição de tamanho de partícula, difração de raio X (DRX) e microscopia eletrônica de varredura (MEV). Os filmes de (LSCF6428), (LSCF6428/CGO) e (LSCF6428/CGO/PrOx), foram obtidos por serigrafia de pós calcinados a 1000 °C. Os filmes foram depositados sobre substratos de céria dopada com gadolínia Ce0,9Gd0,1O2-δ (CGO), sinterizados a 1150 °C e caracterizados por espectroscopia de impedância (em oxigênio puro) entre 600 e 800 °C. Os resultados obtidos indicaram que o método utilizado foi eficiente na formação de pós porosos e com a estrutura cristalina perovskita. O tamanho de cristalito para o compósito de LSCF6428/CGO foi de 336 (nm) para o LSCF6428 e 98 (nm) para o CGO, sendo, também o esperado para um pó calcinado a 1000 °C. O valor da resistência específica de área (REA) para o eletrodo de LSCF6428 puro a 750 °C foi de 0,25 ohms.cm2 bastante plausível, principalmente por não ter sido feito uso de platina, para o LSCF/CGO/PrOx foi obtido uma REA de 0,02 ohms.cm2 a 750 °C.

Made available in DSpace on 2014-10-09T12:34:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:48Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:50Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:00Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:21Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:31Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP