With the current trend of CO2 mitigation in process industries, the primary goal of this thesis is to promote biomass as an energy and reduction agent source to substitute fossil sources in the steel industry. The criteria for this substitution are that the steel process retains the same function and the integrated energy efficiency is as high as possible. This work focuses on advanced gasification of biomass and waste for substitution of fossil fuels in steel industry heat treatment furnaces. To achieve this, two approaches are included in this work. The first investigates the gasification performance of pretreated biomass and waste experimentally using thermogravimetric analysis (TGA) and a pilot plant gasifier. The second assesses the integration of the advanced gasification system with a steel heat treatment furnace. First, the pyrolysis and char gasification characteristics of several pretreated biomass and waste types (unpretreated biomass, steam-exploded biomass, and hydrothermal carbonized biomass) were analyzed with TGA. The important aspects of pyrolysis and char gasification of pretreated biomass were identified. Then, with the objective of studying the gasification performance of pretreated biomass, unpretreated biomass pellets (gray pellets), steam-exploded biomass pellets (black pellets), and two types of hydrothermal carbonized biomass pellets (spent grain biocoal and horse manure biocoal) were gasified in a fixed bed updraft gasifier with high-temperature air/steam as the gasifying agent. The gasification performance was analyzed in terms of syngas composition, lower heating value (LHV), gas yield, cold gas efficiency (CGE), tar content and composition, and particle content and size distribution. Moreover, the effects on the reactions occurring in the gasifier were identified with the aid of temperature profiles and gas ratios. Further, the interaction between fuel residence time in the bed (bed height), conversion, conversion rate/specific gasification rate, and superficial velocity (hearth load) was revealed. Due to the effect of bed height on the gasification performance, the bed pressure drop is an important parameter related to the operation of a fixed bed gasifier. Considering the limited studies on this relationship, an available pressure drop prediction correlation for turbulent flow in a bed with cylindrical pellets was extended to a gasifier bed with shrinking cylindrical pellets under any flow condition. Moreover, simplified graphical representations based on the developed correlation, which could be used as an effective guide for selecting a suitable pellet size and designing a grate, were introduced. Then, with the identified positive effects of pretreated biomass on the gasification performance, the possibility of fuel switching in a steel industry heat treatment furnace was evaluated by effective integration with a multi-stage gasification system. The performance was evaluated in terms of gasifier system efficiency, furnace efficiency, and overall system efficiency with various heat integration options. The heat integration performance was identified based on pinch analysis. Finally, the efficiency of the co-production of bio-coke and bio-H2 was analyzed to increase the added value of the whole process. It was found that 1) the steam gasification of pretreated biomass is more beneficial in terms of the energy value of the syngas, 2) diluting the gasifying agent and/or lowering the agent temperature compensates for the ash slagging problem in biocoal gasification, 3) the furnace efficiency can be improved by switching the fuel from natural gas (NG) to syngas, 4) the gasifier system efficiency can be improved by recovering the furnace flue gas heat for the pretreatment, and 5) the co-production of bio-coke and bio-H2 significantly improves the system efficiency. / <p>QC 20160825</p>

This thesis relates to the development of the Ambidextrous Robot Hand engineered in Brunel University. Assigned to a robotic hand, the ambidextrous feature means that two different behaviours are accessible from a single robot hand, because of its fingers architecture which permits them to bend in both ways. On one hand, the robotic device can therefore behave as a right hand whereas, on another hand, it can behave as a left hand. The main contribution of this project is its ambidextrous feature, totally unique in robotics area. Moreover, the Ambidextrous Robot Hand is actuated by pneumatic artificial muscles (PAMs), which are not commonly used to drive robot hands. The type of the actuators consequently adds more originality to the project. The primary challenge is to reach an ambidextrous behaviour using PAMs designed to actuate non-ambidextrous robot hands. Thus, a feasibility study is carried out for this purpose. Investigating a number of mechanical possibilities, an ambidextrous design is reached with features almost identical for its right and left sides. A testbench is thereafter designed to investigate this possibility even further to design ambidextrous fingers using 3D printing and an asymmetrical tendons routing engineered to reduce the number of actuators. The Ambidextrous Robot Hand is connected to a remote control interface accessible from its website, which provides video streaming as feedback, to be eventually used as an online rehabilitation device. The secondary main challenge is to implement control algorithms on a robot hand with a range twice larger than others, with an asymmetrical tendons routing and actuated by nonlinear actuators. A number of control algorithms are therefore investigated to interact with the angular displacement of the fingers and the grasping abilities of the hand. Several solutions are found out, notably the implementations of a phasing plane switch control and a sliding-mode control, both specific to the architecture of the Ambidextrous Robot Hand. The implementation of these two algorithms on a robotic hand actuated by PAMs is almost as innovative as the ambidextrous design of the mechanical structure itself.

Doctor of Philosophy / Department of Chemistry / Stefan H. Bossmann / The photochromic spirodihydroindolizine/betaine (DHI/B) system has been reinvestigated applying picosecond, microsecond, stationary absorption measurements, and NMR-kinetics. The first surprise was that the electronic structure of the betaines is quite different than commonly assumed. The photochemical ring-opening of DHIs to betaines is a conrotatory 1,5 electrocyclic reaction, as picosecond absorption spectroscopy confirms. The (disrotatory) thermal ring-closing occurs from the cisoid betaine. The lifetime of the transoid betaine is 60 s at 300 K, whereas the lifetime of the cisoid isomer is of the order of 250 microseconds. According to these results, the electrocyclic back reaction of the betaines to the DHI is NOT rate determining, as previously thought, but the cisoid-transoid-isomerization of the betaine. Although the presence of a second nitrogen atom increases the photostability of the spirodihydroindolizine-pyridazine/betaine-system remarkably, the photochemical reaction mechanism appears to be exactly the same for spirodihydroindolizine-pyridazine/betaine-system. A nondestructive photoswitch or an information recording systems has been explored using styryl-quinolyldihydroindolizines. Both isomers DHI and betaine are fluorescent. When the blue betaine is stabilized in a thin polymethyl methacrylate (PMMA) matrix, it is stable for several hours even in room temperature and very stable at 77K. Although irradiation of visible light = 532 nm allows the photo-induced reaction of the Betaine back to the DHI, a nondestructive read-out can be performed at λ = 645 nm upon excitation with λ = 580 nm. Image recording (write) and read-out, as well as information storage (at 77K) have been demonstrated. Charged and maleimide-functionalized DHI/B systems have beed synthesized for use as photochemical gates of the mycobacterial channel porin MspA. Positively charged and maleimide functionalized DHI groups that were attached to the DHI/B-system permit the binding of the photoswitch to selective positions in the channel proteins due to the presence of a cysteine moiety. An inexpensive new method for the large scale synthesis of coelenterazine is developed. A modified Negishi coupling reaction is used to make pyrazine intermediates from aminopyrazine as an economical starting material. This method permits the use of up to 1g coelenterazine per kg body weight and day, which turns the renilla transfected stem cells into powerful light sources.

Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend inrelation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the convertercircuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses whichare functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequencyband width with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8,15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is lessthan that of the two layered transformer because of the decreased radius for thesame amount of inductance.The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50Wand possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer fordriving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuitvitogether with the designed signal transformer is 0.37W. Both these signal andpower transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significanceof the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformerfor the given power transfer application have been proposed. The designed corebased planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency ofthe converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in thefrequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.In conclusion, the research in this dissertation proposed a solution for obtaining high power density converters by designing the highly integrated, high frequency(1 - 10MHz) coreless and core based planar magnetics with energy efficiencies inthe range of 92 - 97%. This solution together with the latest semiconductor GaN/SiC switching devices provides an excellent choice to meet the requirements of the next generation ultra flat low profile switch mode power supplies (SMPS).

Este trabalho tem como objetivo reunir, registrar, estudar e comparar as estratégias de controle utilizadas em inversores para fontes ininterruptas de energia, efetuado através de levantamento bibliográfico, englobando estratégias antigas (implementadas muitas vezes na forma analógica) e recentes (com implementação digital). É realizada comparação dos desempenhos, determinados analiticamente por modelamento e/ou por simulação computacional, entre algumas estratégias de controle. É apresentado um método para a implementação digital de um inversor monofásico para fontes ininterruptas de energia com transformador na saída. O método utilizado consiste de: Análise e modelagem dos controladores e planta, adotando-se critérios para o ajuste dos respectivos parâmetros; Simulação no modo de tempo contínuo; Roteiro da discretização para possibilitar implementação digital; Simulação em tempo discreto; Implementação em protótipo experimental. O controle é realizado com uma estratégia de múltiplas malhas, usando três malhas: uma malha interna de corrente usando controlador proporcional com compensação feedforward da perturbação da tensão de saída no controle da corrente e uma malha externa de tensão com um controlador proporcional + ressonante. Uma terceira malha de controle externa a malha de tensão é adicionada para prevenir a saturação do núcleo do transformador. O inversor é implementado através de um arranjo físico de baixa potência, possibilitando comparação dos resultados de simulação e experimentais. / This dissertation intends to collect, register, study and compare control strategies used in inverters for uninterrupted power supplies. Older control strategies, which use analogical control, as well as contemporary ones, which use digital control, were studied. A performance comparison between some strategies is made using analytical modeling and computational simulation. It is proposed a method for implementation of digital controller for a one-phase inverter with output transformer for uninterruptible power supplies applications. The method consists on: Analysis and modeling of plant and controllers, adopting criteria for parameters adjust; Continuous time computational simulation; Discretization guide for digital implementation; Discrete time computational simulation; Experimental prototype implementation. Control uses a multiloop approach, with three control loops: An internal current loop with proportional controller and feed-forward output voltage disturbance compensation, an external voltage loop using a proportional + resonant controller, and a third external loop to prevent the saturation of the output transformer. A low power experimental setup of the inverter is implemented, allowing comparison of simulated and experimental results.

Nesta tese foram investigadas as propriedades foto-switch de novas tríades constituídas por uma unidade central de Si(IV)-Ftalocianina e dois ligantes axiais azobenzênicos. A posição 4\' dos ligantes azobenzênicos apresenta substituintes (X) com diferentes propriedades eletrônicas e estéricas, a saber: -H; -CH3; -C(CH3)3; -OCH3; e -I. A tríade com substituinte -NO2 foi novamente investigada e incluída como tríade de maior caráter push-pull da série. Para efeito de comparação, também foram investigados hidróxiazobenzenos (HO-Azo-X) com os mesmos substituintes (X) na posição 4\' que os presentes nas tríades. Os HO-Azo-X apresentam propriedades espectroscópicas, fotoquímicas (fotoisomerização E&#8594;Z e Z&#8594;E) como também retorno térmico Z&#8594;E com características intermediárias entre a classe dos azobenzenos e dos amino-azobenzenos. Estas propriedades podem ser atribuídas à presença comum do substituinte hidróxi que apresenta um caráter doador, porém menos acentuado que a do grupo amino. Os espectros de absorção eletrônica das tríades apresentam uma banda B no UV e um conjunto de bandas Q na região visível do espectro eletromagnético. Observou-se a existência de um processo de agregação dos complexos dependente do substituinte 4\'. As tríades apresentam emissão de fluorescência quando excitadas tanto na banda B como na banda Q, com pequenos deslocamentos Stokes. Os rendimentos quânticos de fluorescência obedecem à regra de Kasha. Isto foi confirmado para os rendimentos quânticos corrigidos da banda B, os quais excluem a fração de luz absorvida pelos ligantes axiais nesta região de excitação. A excitação das tríades em THF resulta em photobleaching, que ocorre tanto na presença como na ausência de oxigênio, sendo mais efetivo neste último caso; temos que: a) na ausência de oxigênio provavelmente existe a formação de radicais acíclicos de THF que destroem a ftalocianina; b) na presença de oxigênio peróxidos estão envolvidos na degradação, tendo sido detectados e quantificados nas soluções das tríades após irradiação. Nos dois casos o estado excitado triplete é responsável pelo início do processo. Em benzeno puderam ser investigados a fotoisomerização E&#8594;Z, a isomerização fotossensibilizada Z&#8594;E, assim como a isomerização térmica (retorno térmico) Z&#8594;E. Os resultados mostram que a coordenação não altera as propriedades do estado excitado dos ligantes azobenzênicos evidenciado pela similaridade dos rendimentos quânticos e constantes de velocidade E&#8594;Z comparativamente aos HO-Azo-X. Entretanto, o retorno térmico Z&#8594;E, é muito mais lento comparativamente aos HO-Azo-X. A ligação Si-O nos complexos comparativamente a H-O nos HO-Azo-X e os momento de dipolo resultante devem ser os responsáveis por esse fenômeno. As isomerizações fotossensibilizadas Z&#8594;E são muito mais rápidas que as respectivas térmicas existindo diferenças de até 30 vezes nos valores das respectivas constantes. Todas as tríades apresentam o comportamento foto-switch de emissão que é controlado pelo estado E ou Z do ligante axial. Ao longo da série as variações de intensidade de emissão se situam entre 19 - 27% da intensidade inicial. O fato do processo Z&#8594;E nas tríades ocorrer através do processo térmico ou fotossensibilizado que é consideravelmente mais rápido faz destas tríades sistemas switches quase-biestáveis. Este controle cinético também potencializa a utilização destas tríades em sistemas de informação molecular binário. / In this work have been studied the photoswitch properties of new triads with one central Si(IV)-phthalocyanine and two axially coordinated azobenzenes. The 4\' position of the azobenzene ligands has substituents (X) presenting different electronic/steric contributions: -H; -CH3; -C(CH3)3; -OCH3; and -I. The triad with -NO2 substituent was reinvestigated and included as the triad with the major push-pull effect in the series. For comparative purposes have been investigated hydroxyazobenzenes (HO-Azo-X) with the same substituents (X) at the 4\' position of the triads. The HO-Azo-X compounds show spectroscopic, photochemical (photoisomerization E&#8594;Z and Z&#8594;E) and thermal Z&#8594;E reaction with intermediate properties that which shown by the class of azobenzene and aminoazobenzene compounds. These characteristics can be attributed to the hydroxyl-substituent present in all compounds, which has donor character, but less pronounced than the amino group. The electronic absorption spectra of the triads show a B band in the UV and a set of Q bands in the visible region of the electromagnetic spectrum. Could be noticed an aggregation behavior for these triads dependent on the 4\' substituent. The triads show fluorescence emission when excited at B or Q bands, presenting small Stokes shift. Fluorescence quantum yields are in accordance with Kasha\'s rule. Photobleaching is observed when THF solutions of the triads are irradiated. This photobleching occurs in presence or absence of oxygen, been most effective in this last case. Concerning the photobleaching process and presence/absence of oxygen: a) in absence of oxygen probably are formed THF acyclic radicals which lead to the destruction of the phthalocyanine; b) in the presence of oxygen, peroxides are involved in the degradation and peroxides were detected and quantified in THF solutions of the triads after irradiation. In both cases the excited triplet state is responsible for starting the steps that result in the observed bleaching. In benzene solutions could be investigated the E&#8594;Z photoisomerization, the Z&#8594;E photosensitized isomerization and Z&#8594;E thermal isomerization. The results show that coordination does not alter the excited state properties of the azobenzene ligands. This conclusion can be made by the similarity between the quantum yields and the E&#8594;Z rate constants values for the triads and HO-Azo-X compounds. Otherwise, the Z&#8594;E thermal isomerization is much slower for the triads comparatively to the HO-Azo-X compounds. The Si-O bound in the complexes compared to the H-O bond in the HO-Azo-X and the resulting dipole moments must be responsible for this phenomenon. The Z&#8594;E photosensitized isomerization reactions are much faster than the corresponding thermal ones existing up to 30 times differences on the respective constants. The investigated triads show photoswitch behavior concerning fluorescence emission which is controlled by the axial ligand E or Z state. The emission intensity variations along the series are found to be between 19 - 27% of the initial intensity. These triads can be classified as \"quasi\" bistable switches considering the Z&#8594;E process can be carried out by means a slow thermal or a fast photosensitized process. This kinetic control enable too the utilization of these triads in molecular binary information systems.

Heavy metals from natural and man-made sources can be a great threat to human and animal life. As small inorganic ions they are challenging to detect, usually requiring expensive and complicated machinery. Several heavy metals can accumulate in the human body, leading to long term toxic effects on the nervous system. Many bacteria have developed strategies to survive in heavy metal rich environments. One of these strategies is a bacterial operon containing genes for detoxification mechanisms controlled by a promoter and a regulatory protein. In this work some of these promoter-protein pairs, Pars-ArsR, PcopA-CueR, PmerTPAD-MerR and PzntA-ZntR from Escherichia coli have been employed in the design and construction of a set of biosensors aimed at the detection of heavy metals in drinking water. Biosensors usually employ biological recognition elements, transducing the signal from these to produce an output that can be integrated into electronic circuitry. The sensors presented in this work focus on reducing complexity and on providing a controlled sensor reaction. The arsenic biosensor ‘AsGard’ is based on the Pars-ArsR pair and functions by making the dissociation of an ArsR-mCherry fusion protein from its binding site in the Pars promoter visible. In the cell, ArsR dissociates from Pars upon binding of trivalent arsenic ions. Immobilising the relevant part of the Pars sequence on a solid plastic support allows for the mobilisation of previously bound ArsR-mCherry proteins in the presence of arsenic to become the sensor output. The AsGard sensor detects arsenic within minutes in a concentration range overlapping with the arsenic thresholds for drinking water as set by the World Health Organisation. Additional prototype sensors are presented bringing a reporter gene under the control of the aforementioned promoters. These sensors have been tested in vivo and in vitro in a cell free transcription translation system and partially detect metal concentrations close to relevant ranges. The Pars based sensor is tuneable in vitro by modifying the ratio of the supplied regulatory protein ArsR and is able to detect arsenic well within the relevant range. Spinach2, a fluorescent RNA aptamer, may make future designs independent from translation, drastically reducing complexity of cell free biosensors based on cis-trans transcriptional regulation.

Nesta tese foram investigadas as propriedades foto-switch de novas tríades constituídas por uma unidade central de Si(IV)-Ftalocianina e dois ligantes axiais azobenzênicos. A posição 4\' dos ligantes azobenzênicos apresenta substituintes (X) com diferentes propriedades eletrônicas e estéricas, a saber: -H; -CH3; -C(CH3)3; -OCH3; e -I. A tríade com substituinte -NO2 foi novamente investigada e incluída como tríade de maior caráter push-pull da série. Para efeito de comparação, também foram investigados hidróxiazobenzenos (HO-Azo-X) com os mesmos substituintes (X) na posição 4\' que os presentes nas tríades. Os HO-Azo-X apresentam propriedades espectroscópicas, fotoquímicas (fotoisomerização E&#8594;Z e Z&#8594;E) como também retorno térmico Z&#8594;E com características intermediárias entre a classe dos azobenzenos e dos amino-azobenzenos. Estas propriedades podem ser atribuídas à presença comum do substituinte hidróxi que apresenta um caráter doador, porém menos acentuado que a do grupo amino. Os espectros de absorção eletrônica das tríades apresentam uma banda B no UV e um conjunto de bandas Q na região visível do espectro eletromagnético. Observou-se a existência de um processo de agregação dos complexos dependente do substituinte 4\'. As tríades apresentam emissão de fluorescência quando excitadas tanto na banda B como na banda Q, com pequenos deslocamentos Stokes. Os rendimentos quânticos de fluorescência obedecem à regra de Kasha. Isto foi confirmado para os rendimentos quânticos corrigidos da banda B, os quais excluem a fração de luz absorvida pelos ligantes axiais nesta região de excitação. A excitação das tríades em THF resulta em photobleaching, que ocorre tanto na presença como na ausência de oxigênio, sendo mais efetivo neste último caso; temos que: a) na ausência de oxigênio provavelmente existe a formação de radicais acíclicos de THF que destroem a ftalocianina; b) na presença de oxigênio peróxidos estão envolvidos na degradação, tendo sido detectados e quantificados nas soluções das tríades após irradiação. Nos dois casos o estado excitado triplete é responsável pelo início do processo. Em benzeno puderam ser investigados a fotoisomerização E&#8594;Z, a isomerização fotossensibilizada Z&#8594;E, assim como a isomerização térmica (retorno térmico) Z&#8594;E. Os resultados mostram que a coordenação não altera as propriedades do estado excitado dos ligantes azobenzênicos evidenciado pela similaridade dos rendimentos quânticos e constantes de velocidade E&#8594;Z comparativamente aos HO-Azo-X. Entretanto, o retorno térmico Z&#8594;E, é muito mais lento comparativamente aos HO-Azo-X. A ligação Si-O nos complexos comparativamente a H-O nos HO-Azo-X e os momento de dipolo resultante devem ser os responsáveis por esse fenômeno. As isomerizações fotossensibilizadas Z&#8594;E são muito mais rápidas que as respectivas térmicas existindo diferenças de até 30 vezes nos valores das respectivas constantes. Todas as tríades apresentam o comportamento foto-switch de emissão que é controlado pelo estado E ou Z do ligante axial. Ao longo da série as variações de intensidade de emissão se situam entre 19 - 27% da intensidade inicial. O fato do processo Z&#8594;E nas tríades ocorrer através do processo térmico ou fotossensibilizado que é consideravelmente mais rápido faz destas tríades sistemas switches quase-biestáveis. Este controle cinético também potencializa a utilização destas tríades em sistemas de informação molecular binário. / In this work have been studied the photoswitch properties of new triads with one central Si(IV)-phthalocyanine and two axially coordinated azobenzenes. The 4\' position of the azobenzene ligands has substituents (X) presenting different electronic/steric contributions: -H; -CH3; -C(CH3)3; -OCH3; and -I. The triad with -NO2 substituent was reinvestigated and included as the triad with the major push-pull effect in the series. For comparative purposes have been investigated hydroxyazobenzenes (HO-Azo-X) with the same substituents (X) at the 4\' position of the triads. The HO-Azo-X compounds show spectroscopic, photochemical (photoisomerization E&#8594;Z and Z&#8594;E) and thermal Z&#8594;E reaction with intermediate properties that which shown by the class of azobenzene and aminoazobenzene compounds. These characteristics can be attributed to the hydroxyl-substituent present in all compounds, which has donor character, but less pronounced than the amino group. The electronic absorption spectra of the triads show a B band in the UV and a set of Q bands in the visible region of the electromagnetic spectrum. Could be noticed an aggregation behavior for these triads dependent on the 4\' substituent. The triads show fluorescence emission when excited at B or Q bands, presenting small Stokes shift. Fluorescence quantum yields are in accordance with Kasha\'s rule. Photobleaching is observed when THF solutions of the triads are irradiated. This photobleching occurs in presence or absence of oxygen, been most effective in this last case. Concerning the photobleaching process and presence/absence of oxygen: a) in absence of oxygen probably are formed THF acyclic radicals which lead to the destruction of the phthalocyanine; b) in the presence of oxygen, peroxides are involved in the degradation and peroxides were detected and quantified in THF solutions of the triads after irradiation. In both cases the excited triplet state is responsible for starting the steps that result in the observed bleaching. In benzene solutions could be investigated the E&#8594;Z photoisomerization, the Z&#8594;E photosensitized isomerization and Z&#8594;E thermal isomerization. The results show that coordination does not alter the excited state properties of the azobenzene ligands. This conclusion can be made by the similarity between the quantum yields and the E&#8594;Z rate constants values for the triads and HO-Azo-X compounds. Otherwise, the Z&#8594;E thermal isomerization is much slower for the triads comparatively to the HO-Azo-X compounds. The Si-O bound in the complexes compared to the H-O bond in the HO-Azo-X and the resulting dipole moments must be responsible for this phenomenon. The Z&#8594;E photosensitized isomerization reactions are much faster than the corresponding thermal ones existing up to 30 times differences on the respective constants. The investigated triads show photoswitch behavior concerning fluorescence emission which is controlled by the axial ligand E or Z state. The emission intensity variations along the series are found to be between 19 - 27% of the initial intensity. These triads can be classified as \"quasi\" bistable switches considering the Z&#8594;E process can be carried out by means a slow thermal or a fast photosensitized process. This kinetic control enable too the utilization of these triads in molecular binary information systems.

Hybrid models are those containing continuous and discontinuous behaviour. In constructing dynamic systems models, it is frequently desirable to abstract rapidly changing, highly nonlinear behaviour to a discontinuity. Bond graphs lend themselves to systems modelling by being multi-disciplinary and reflecting the physics of the system. One advantage is that they can produce a mathematical model in a form that simulates quickly and efficiently. Hybrid bond graphs are a logical development which could further improve speed and efficiency. A range of hybrid bond graph forms have been proposed which are suitable for either simulation or further analysis, but not both. None have reached common usage. A Hybrid bond graph method is proposed here which is suitable for simulation as well as providing engineering insight through analysis. This new method features a distinction between structural and parametric switching. The controlled junction is used for the former, and gives rise to dynamic causality. A controlled element is developed for the latter. Dynamic causality is unconstrained so as to aid insight, and a new notation is proposed. The junction structure matrix for the hybrid bond graph features Boolean terms to reflect the controlled junctions in the graph structure. This hybrid JSM is used to generate a mixed-Boolean state equation. When storage elements are in dynamic causality, the resulting system equation is implicit. The focus of this thesis is the exploitation of the model. The implicit form enables application of matrix-rank criteria from control theory, and control properties can be seen in the structure and causal assignment. An impulsive mode may occur when storage elements are in dynamic causality, but otherwise there are no energy losses associated with commutation because this method dictates the way discontinuities are abstracted. The main contribution is therefore a Hybrid Bond Graph which reflects the physics of commutating systems and offers engineering insight through the choice of controlled elements and dynamic causality. It generates a unique, implicit, mixed-Boolean system equation, describing all modes of operation. This form is suitable for both simulation and analysis.

"On-off control of hydraulic circuits enables significant improvements in efficiency compared with throttling valve control. A key enabling technology to on-off control is an efficient high speed on-off valve. This project aims to design an on-off hydraulic valve that minimizes input power requirements and increases operating frequency over existing technology by utilizing a continuously rotating valve design. This is accomplished through use of spinning port discs which chop the flow into pulses, with the relative phase between these discs determining the pulse duration. A mathematical model for determining system efficiency is developed with a focus on the throttling, leakage, compressibility, and viscous friction power losses of the valve. Parameters affecting these losses were optimized to produce the most efficient design under the chosen disc-style architecture. Using these optimum parameter values, a first generation prototype valve was developed and experimental data collected. The experimental valve matched predicted output pressure and flows well, but suffered from larger than expected torque requirements and leakage, resulting in a maximum efficiency of 38% at 1.0 duty ratio. Also, due to motor limitations, the valve was only able to achieve a 64Hz switching frequency versus the designed 100Hz frequency. Future design iterations will need to focus on controlling leakage, hydrodynamically balancing the spinning port disc axially to reduce torque requirements, developing a computational fluid dynamics model to gain further insight into the workings of the valve, and creating a control methodology for single and multiple high speed valves."