Carbon dioxide is considered to be the major source of GHG responsible for global warming; man-made CO₂ contributes approximately 63. 5% to all greenhouse gases. The cement industry is responsible for approximately 5% of global anthropogenic carbon dioxide emissions emitting nearly 900 kg of CO₂ for every 1000 kg of cement produced! Amine absorption processes in particular the monoethanolamine (MEA) based process, is considered to be a viable technology for capturing CO₂ from low-pressure flue gas streams because of its fast reaction rate with CO₂ and low cost of raw materials compared to other amines. However, MEA absorption process is associated with high capital and operating costs because a significant amount of energy is required for solvent regeneration and severe operating problems such as corrosion, solvent loss and solvent degradation. This research was motivated by the need to design size and cost analysis of CO₂ capture process from cement industry. MEA based absorption process was used as a potential technique to model CO₂ capture from cement plants. In this research four cases were considered all to reach a CO₂ purity of 98% i) the plant operates at the highest capacity ii) the plant operates at average load iii) the plant operates at minimum operating capacity and iv) switching to a lower carbon content fuel at average plant load. A comparison among four cases were performed to determine the best operating conditions for capturing CO₂ from cement plants. A sensitivity analysis of the economics to the lean loading and percent recovery were carried out as well as the different absorber and striper tray combinations.

As reserves of conventional crude oil are depleted, there is a growing need to develop unconventional oils such as heavy oil and bitumen from oil sands. In terms of recoverable oil, Canadian oil sands are considered to be the second largest oil reserves in the world. However, the upgrading of bitumen from oil sands to synthetic crude oil (SCO) requires nearly ten times more hydrogen (H₂) than the conventional crude oils. The current H₂ demand for oil sands operations is met mostly by steam reforming of natural gas. With the future expansion of oil sands operations, the demand of H₂ for oil sand operations is likely to quadruple in the next decade. As natural gas reforming involves significant carbon dioxide (CO₂) emissions, this sector is likely to be one of the largest emitters of CO₂ in Canada. <br> <br>In the current H₂ plants, CO₂ emissions originate from two sources, the combustion flue gases from the steam reformer furnace and the off-gas from the process (steam reforming and water-gas shift) reactions. The objective of this study is to develop a process that captures CO₂ at minimum energy penalty in typical H₂ plants. <br> <br>The approach is to look at the best operating conditions when considering the H₂ and steam production, CO₂ production and external fuel requirements. The simulation in this study incorporates the kinetics of the steam methane reforming (SMR) and the water gas shift (WGS) reactions. It also includes the integration of CO₂ capture technologies to typical H₂ plants using pressure swing adsorption (PSA) to purify the H₂ product. These typical H₂ plants are the world standard of producing H₂ and are then considered as the base case for this study. The base case is modified to account for the implementation of CO₂ capture technologies. Two capture schemes are tested in this study. The first process scheme is the integration of a monoethanolamine (MEA) CO₂ scrubbing process. The other scheme is the introduction of a cardo polyimide hollow fibre membrane capture process. Both schemes are designed to capture 80% of the CO₂ from the H₂ process at a purity of 98%. <br> <br>The simulation results show that the H₂ plant with the integration of CO₂ capture has to be operated at the lowest steam to carbon (S/C) ratio, highest inlet temperature of the SMR and lowest inlet temperatures for the WGS converters to attain lowest energy penalty. H₂ plant with membrane separation technology requires higher electricity requirement. However, it produces better quality of steam than the H₂ plant with MEA-CO₂ capture process which is used to supply the electricity requirement of the process. Fuel (highvale coal) is burned to supply the additional electricity requirement. The membrane based H₂ plant requires higher additional electricity requirement for most of the operating conditions tested. However, it requires comparable energy penalty than the H₂ plant with MEA-CO₂ capture process when operated at the lowest energy operating conditions at 80% CO₂ recovery. <br> <br>This thesis also investigates the sensitivity of the energy penalty as function of the percent CO₂ recovery. The break-even point is determined at a certain amount of CO₂ recovery where the amount of energy produced is equal to the amount of energy required. This point, where no additional energy is required, is approximately 73% CO₂ recovery for the MEA based capture plant and 57% CO₂ recovery for the membrane based capture plant. <br> <br>The amount of CO₂ emissions at various CO₂ recoveries using the best operating conditions is also presented. The results show that MEA plant has comparable CO₂ emissions to that of the membrane plant at 80% CO₂ recovery. MEA plant is more attractive than membrane plant at lower CO₂ recoveries.

In this research the effects of the fabrication processes of MEA on the output power of a DMFC stack are studied by changing hot-pressing conditions including pressure, temperature and time. Additionally, the effects of the various treatments of the MEAs on the output voltage and power are also studied after the hot-pressing process of MEA is finished. In the first experimental study the catalyst of cathode is 4.0mg/cm unsupported HP Pt black, Anode is 4.0mg/cm 80% HP Pt-Ru Alloy (1: 1), membrane is Nafion 117, and bipolar plates is heterogeneous carbon fiber bipolar plate developed by our fuel cell laboratory. The MEA for single cell includes the area of membrane 3*3 cm2 the active area of electrode 1.5*1.5 cm2. Under the hot-pressing conditions 120 oC, 100 bar and 90s, the maximum power density can reach a value of 18 mW/cm2 at the conditions of methanol concentration 3 M, air-breathing, and room temperature After several experiments, we observed that performances of MEAs decayed with time. So we designed a series of experiments to inspect the various possible reasons and try to solve this problem. The cylindrical DMFC is one of the most important developments in our lab. However, the MEAs made for plate-type DMFC do not fit the cylindrical DMFC stack properly. The electrodes easily pealed off from the membrane and the contact resistance increases after certain periods. So the hot-pressing device had been redesigned to fit the cylindrical DMFC stack. After that the total power of the 6-cell stack with total active area 15 cm2 can reach a value 135 mW. If the performance of each cell of the 6-cell stack is uniform, we expect that the total power of this stack can reach a higher value 195 mW, which can be applied to some portable electronic products.

A mathematical model for a proton exchange membrane fuel cell is the focus of this thesis. Modeling and simulations are carried out with an aim to understand the influence of operational and geometrical parameters on the inner reaction and performance of a proton exchange membrane fuel cell, and discuss the distributions of physical phenomena in membrane and catalyst layer. Than, the results of modeling are compared and analyzed with the experiments, and discuss the reasons of influences of the performance of PEMFC. The results show that activation overpotential is the major reason of influence of the performance at low current density (less than ), and diffusion and ohmic overpotential are substantially increased at high current density (great than ). The membrane of higher membrane conductivity and more thin, increasing pressure of cathode gas and use oxygen can enhance the performance of a PEMFC. The performance almost no influence for the catalyst layer over 0.3£gm. The catalyst layer thin and uniform can decrease coating of this layer. The results of modeling and experiments show that experiments have contact resistance between materials, and the performance slightly lower than performance of modeling, and the differences that at high current density great than low current density.

Membrane electrode assembly (MEA) is the foundation of the single cell as well as the core of the fuel cell when generating electricity. Its work efficiency is the key factor for single cell performance. This study aims to understand the variation between the conventional method and the decal method during the MEA process. By observing the microstructure morphology of electrode and the performance of single cell, as well as analyzing internal resistance and its stabilization, the advantages and disadvantages of MEA in the two methods is analyzed. The decal condition is 135¢XC, 15 kg/cm , 2.5 min at a high temperature (50¢XC 3M methanol), in air-breathing under atmosphere system. The maximum power density is approximately 22.5 mW/cm which is very close to the result of conventional method. The decal method is better than the conventional method particularly in regards to the high current density performance. It shows that there is an efficient influence of the decal method on the methanol mass transfer and it also improves its polarization and enlarges the current. If the single cell is operated in the high temperature, the fuel mass transfer can be advanced in the decal method and its performance can be raised. However, in the manufacturing process, more time has to be spent when producing the MEA. This experiment can be used as a reference on the single cell operation environment and manufacturing time for future studies.

Fuel cells are electrochemical energy devices that convert the chemical energy in a fuel into electrical energy. Although they are more efficient, clean, and reliable than fossil fuel combustion systems, they have not been widely adopted because of manufacturing challenges and high production cost. The most expensive component of a fuel cell is the membrane electrode assembly (MEA), which consists of an ionomer membrane coated with catalyst material. Best performing MEAs are currently fabricated by depositing and drying liquid catalyst ink on the membrane, however, this process is limited to individual preparation by hand due to the membrane’s rapid water absorption that leads to shape deformation and coating defects. This work models the swelling and drying phenomena of the membrane and coating during manufacturing, and then applies the results to develop and control a continuous coating line for the production of defect free fuel cell MEAs. A continuous coating line can reduce the costs and time needed to fabricate the MEA, incentivizing the commercialization and widespread adoption of fuel cells. Membrane swelling is a three-dimensional, transient, coupled mass transfer, heat transfer, and solid mechanics problem. Existing models describe the membrane’s behavior in operating conditions, but none predict the behavior during manufacturing. This work develops a novel physics-based model that describes the behavior of the membrane and coating in a continuous manufacturing scenario and incorporates effects that are missing from existing models. A model that can predict wrinkles, the most commonly observed defect during manufacturing, is presented. Simulation results from the above models are used to design and develop an improved continuous MEA coating process that includes pre-swelling and two-stage drying of the coated membrane. A prototype pilot-scale coating line to implement and test the improved coating process is designed and constructed. Finally, a Linear-Quadratic-Gaussian type controller is developed using the physics-based model of the manufacturing process to optimally control the temperature and humidity of the drying zones, and its effectiveness when implemented on the coating line is discussed. / text

This work investigates the volatilities of amine solvents used in post-combustion CO₂ capture from coal-fired power plants. Amine volatility is one of the key criteria used in screening an amine solvent for CO₂ capture: (1) amine losses up the stack can react in the atmosphere to form ozone and other toxic compounds; (2) volatility losses can result in greater solvent make-up costs; (3) high losses will require the use of bigger water wash units, and more water, to capture fugitive amines prior to venting - these translate to higher capital and operating costs; (4) volatilities need to be measured and modeled in order to develop more accurate and robust thermodynamic models. In this work, volatility is measured using a hot gas FTIR which can determine amine, water, and CO₂ in the vapor headspace above a solution. The liquid solution is speciated by NMR (Nuclear Magnetic Resonance). There are two key contributions made by this research work: (1) it serves as one of the largest sources of experimental data available for amine-water volatility; (2) it provides amine volatility for loaded systems (where CO₂ is present) which is a unique measurement not previously reported in the literature. This work studied the volatility of 20 alkanolamines in water at 0.5 - 1.1 molal (m) in water (< 1.5 mol% amine) at zero loading (no CO₂) from 40 ° - 70 °C. An empirical group contribution model was developed to correlate H[subscript 'amine'] to molecular structures of both alkylamines and alkanolamines. The model incorporated additional functional groups to account for cyclic structures and to distinguish between different types of alkyl groups based on the attached neighboring groups. This model represented the experimental H[subscript 'amine'], which spanned five orders in magnitude, to well within an order of magnitude of the measured values. The second component of this research involves upgrading the AspenPlus® v.7.3 model of MDEA-PZ-CO₂-H₂O system primarily by improving MDEA thermodynamics for MDEA-H₂O, MDEA-CO₂-H₂O, and MDEA-PZ-CO₂-H₂O. A key modification was made to include the carbonate (CO₃²⁻) species into the model chemistry set which greatly improved the fit of CO₂ solubility for MDEA-CO₂-H₂O at ultra lean loading ([alpha]) for 0.001 < [alpha] < 0.01. With MDEA-PZ-H₂O, no MDEA-PZ cross interaction parameters were needed to match the blend volatility. Ultimately, both the blend volatility, at unloaded and loaded conditions, along with speciation were adequately represented by the upgraded model. The final component of this research involves screening the volatilities of novel amines at unloaded and nominal lean loading condition from 40 ° - 70 °C (absorber operating conditions). The volatility of tertiary and hindered amines, such as MDEA and AMP, respectively, is not a strong function of loading because these amines are unable to form stable carbamates. Conversely, the volatility of mono-amines and of diamines decreases by ~3 and 5-20 times, respectively, due to a much greater extent of carbamate-forming speciation. PZ or a blend having a diamine promoted by PZ would be favorable for CO₂ capture due to the low volatility of the diamines in loaded solution. . Finally, in order of increasing degree of salting out as reflected by the increasing magnitude of the system asymmetric amine activity coefficient, 7 m MDEA < 4.8 m AMP ~ 7 m MDEA/2 m PZ < 8 m PZ < 7 m MEA. / text

We have developed a high-throughput system of closed-loop electrical stimulation and optical recording that facilitates the rapid characterization of extracellular stimulus-evoked neural activity. The ability to selectively stimulate a neuron is a defining characteristic of next-generation neural prostheses. Greater stimulus control and differential activation of specific neuronal populations allows for prostheses that better mimic their biological counterparts. In our system, we deliver square current pulses using a microelectrode array; automated real-time image processing of high-speed digital video identifies the neuronal response; and a feedback controller alters the applied stimulus to achieve a targeted response. The system controller performs directed searches within the strength-duration (SD) stimulus parameter space to build probabilistic neuronal activation curves. An important feature of this closed-loop system is a reduction in the number of stimuli needed to derive the activation curves when compared to the more commonly used open-loop system: this allows the closed-loop system to spend more time probing stimulus regions of interest in the multi-parameter waveform space, facilitating high resolution analysis. The stimulus-evoked activation data were well-fit to a sigmoid model in both the stimulus strength (current) and duration (pulse width) slices through the waveform space. The 2-D analysis produced a set of probability isoclines corresponding to each neuron-electrode pairing, which were fit to the SD threshold model described by Lapique (1907). We show that stimulus selectivity within a given neuron pair is possible in the one-parameter search space by using multiple stimulation electrodes. Additionally, by applying simultaneous stimuli to adjacent electrodes, the interaction between stimuli alters the neuronal activation threshold. The interaction between simultaneous multi-electrode multi-parameter stimulus waveforms creates an opportunity for increased stimulus selectivity within a population. We demonstrated that closed-loop imaging and micro-stimulation technology enable the study of neuronal excitation across a large parameter space, which is requisite for controlling neuronal activation in next generation clinical solutions.

Willfully controlling the focus of an extracellular stimulus remains a significant challenge in the development of neural prosthetics and therapeutic devices. In part, this challenge is due to the vast set of complex interactions between the electric fields induced by the microelectrodes and the complex morphologies and dynamics of the neural tissue. Overcoming such issues to produce methodologies for targeted neural stimulation requires a system that is capable of (1) delivering precise, localized stimuli a function of the stimulating electrodes and (2) recording the locations and magnitudes of the resulting evoked responses a function of the cell geometry and membrane dynamics. In order to improve stimulus delivery, we developed microfabrication technologies that could specify the electrode geometry and electrical properties. Specifically, we developed a closed-loop electroplating strategy to monitor and control the morphology of surface coatings during deposition, and we implemented pulse-plating techniques as a means to produce robust, resilient microelectrodes that could withstand rigorous handling and harsh environments. In order to evaluate the responses evoked by these stimulating electrodes, we developed microscopy techniques and signal processing algorithms that could automatically identify and evaluate the electrical response of each individual neuron. Finally, by applying this simultaneous stimulation and optical recording system to the study of dissociated cortical cultures in multielectode arrays, we could evaluate the efficacy of excitatory and inhibitory waveforms. Although we found that the proximity of the electrode is a poor predictor of individual neural excitation thresholds, we have shown that it is possible to use inhibitory waveforms to globally reduce excitability in the vicinity of the electrode. Thus, the developed system was able to provide very high resolution insight into the complex set of interactions between the stimulating electrodes and populations of individual neurons.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-11-22T21:32:18Z No. of bitstreams: 1 BrunoDeSouzaMaggi_TESE.pdf: 1944735 bytes, checksum: 3f8ff31d8a9b2321520912386e5a28f1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-11-24T22:46:45Z (GMT) No. of bitstreams: 1 BrunoDeSouzaMaggi_TESE.pdf: 1944735 bytes, checksum: 3f8ff31d8a9b2321520912386e5a28f1 (MD5) / Made available in DSpace on 2017-11-24T22:46:45Z (GMT). No. of bitstreams: 1 BrunoDeSouzaMaggi_TESE.pdf: 1944735 bytes, checksum: 3f8ff31d8a9b2321520912386e5a28f1 (MD5) Previous issue date: 2017-08-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Nesta proposta esperamos resolver as seguintes quest?es: 1. existe diferen?as na colora??o entre machos e f?meas de Tropidurus hispidus? 2. as f?meas utilizam caracter?sticas da colora??o para escolher parceiros? 3. a colora??o dos machos prediz o resultado de disputas em contextos agon?sticos? Tropidurus hispidus Spix (1825) a maior esp?cie do grupo Torquatus. Os lagartos desse g?nero s?o diurnos, extremamente abundantes, heli?filos, forrageadores senta-e-espera, territoriais, ocorrendo predominantemente em forma??es abertas. Utilizamos um espectrofot?metro para mensurar as vari?veis de cor e uma modelagem visual, utilizando os dados de sensibilidade visual do lagarto Podarcis mularis. Estes dados foram usados para responder a primeira quest?o. Para responder as quest?es 2 e 3 realizamos dois experimentos controlados, no qual pareamos os machos pelo tamanho. No primeiro, de escolha dos machos pelas f?meas, dois machos foram colocados em um terr?rio dividido em tr?s partes, cada macho ficava em um compartimento e n?o tinham contato visual entre eles e a f?meas no outro compartimento com total acesso visual aos dois machos. Para o segundo, de intera??es agon?sticas entre machos, os animais foram colocados em um terr?rio durante 30 min e neste per?odo foram registrado todos os comportamento para determinar os vencedores em cada rodada. Primeiramente, as vari?veis de cor foram usadas para diferenciar machos de f?meas. Nossos primeiros resultados mostraram claramente que T. hispidus exibe dicromatismo sexual e que este ? percebido por conspec?fico. Das onze ?reas do corpo usadas para comparar machos e f?meas, nove mostraram diferen?as significativas. Para a regi?o dorsal e cabe?a, o croma vermelho ? a vari?vel que mais discrimina machos de f?meas. J? para a regi?o ventral da coxa, cloaca, flanco, barriga e garganta o brilho ? a que melhor distingue machos de f?meas. Para a base da cauda a matiz ? o que melhor discrimina os sexos?. Ainda, o croma UV na regi?o ventral da base da cauda, tamb?m distingue os sexos. A modelagem visual mostrou que essas diferen?as s?o percebidas por outro lagarto, confirmando os dados de espectrofotometria. No experimento de escolha pelas f?meas a regi?o e a vari?vel que melhor discriminaram escolhidos e n?o escolhidos, foram, respectivamente ventral da coxa e croma 8. Para o experimento de competi??o entre os machos as regi?es barriga e colar, bem como as vari?veis croma azul, 3 e 8, melhor discriminaram vencedores e perdedores. Isso nos mostra que a diferen?a entre machos e f?meas v?o al?m das descritas na literaturas e que a colora??o tem um papel importante na competi??o inter e intrasexual. Com isso esperamos ter contribu?do para uma melhor compreens?o da evolu??o do design do sinal e como agem a sele??o intra- e intersexual neste processo. / In this study our goals were to address the following issues: Are there differences in coloration between males and females of Tropidurus hispidus? Do females use color traits to choose between mates? Does male coloration predict the outcome of agonistic encounters? Tropidurus hispidus Spix (1825), the larger species of the Torquatus group. Tropidurus are diurnal, extremely abundant, heliophiles, sit-and-wait foragers, and territorial lizards occurring predominantly in open areas. We used a spectrophotometer to measure color variables and visual modeling using visual sensitivity data for Podarcis mularis. This data was used to answer the first question. To answer questions 2 and 3 we performed two controlled experiments with size-paired males. First, we conducted a female mate-choice experiment where males were placed in a terraria enclosure with three separated parts. We assigned each male to a compartment in which they did not have mutual visual contact. Next, we assigned females to the third compartment that enabled visual contact to both the males. The second experiment consisted of an agonistic interaction set up where we placed a pair of males in a single terraria enclosure for 30 min. During the experiment period we recorded behavioral displays in order to determine winners of each trial. Separately, we used color variables to differentiate males from females. Our first results clearly showed that T. hispidus exhibits sexual dichromatism and that it is perceived as conspecific. Of the eleven areas of the body used to compare males and females, nine showed significant differences. For the dorsal region and head, the red chroma is the variable that most discriminates males from females. While for the ventral region of the thigh, cloaca, flank, belly and throat the glow is the one that best distinguishes males from females. For the base of the tail the tint better discriminates. The UV chroma in the ventral region of the tail base also distinguishes the sexes. The visual modeling showed that these differences are likely perceived by other lizards, confirming spectrophotometry data. In the experiment of choice by the females the region and the variable that discriminated best chosen and not chosen were respectively thigh ventral and chroma 8. For the competition experiment between the males the belly and collar regions, as well as the blue, 3 And 8 chroma variables, better discriminated winners and losers. This shows us that the difference between males and females goes beyond those described in literatures and that coloring plays an important role in inter and intra-sexual competition. With this we hope to have contributed to a better understanding of the evolution of the signal design and how the intra- and intersexual selection act in this process in T. hispidus.