Research is presented that evaluates a semi-passive treatment system for remediation of contaminated groundwater with elevated dissolved metal concentrations, including selenium and sulphate, at the Wolverine Mine, Yukon. Laboratory up-flow columns were used to treat simulated mine impacted waters. Five columns were filled with varying compositions of gravel and creek substrate organics, and were un-amended or amended with manure, sewage sludge, zero-valent iron, or wood chips and alfalfa. Selenium, sulphate and other parameters of concern were lowered in column effluents, most effectively by the control column and by the columns amended with sewage sludge. Column effluent metal and sulphate concentrations provided evidence that co-precipitation, adsorption and microbially mediated redox reactions were the predominant biogeochemical mechanisms operating within the columns. Based on this research, recommendations are made to further the design of a semi-passive treatment system that may be installed at the mine site upon closure.

O uso de materiais inteligentes em problemas de controle de vibração tem sido investigado em diversas pesquisas ao longo dos últimos anos. Apesar de que diferentes materiais inteligentes estão disponíveis, o piezelétrico tem recebido grande atenção devido à facilidade de uso como sensores, atuadores, ou ambos simultaneamente. As principais técnicas de controle usando materiais piezoelétricos são os ativos e passivos. Circuitos piezelétricos passivos são ajustados para uma frequência específica e, portanto, a largura de banda efetiva é pequena. Embora os sistemas ativos possam apresentar um bom desempenho no controle de vibração, a quantidade de energia externa e hardware adicionado são questões importantes. As técnicas SSD (Synchronized Switch Damping) foram desenvolvidas como uma alternativa aos controladores passivos e controladores ativos de vibração. Elas podem ser técnicas semi-ativas ou semi-passivas que introduzem um tratamento não linear na tensão elétrica proveniente do material piezelétrico e induz um aumento na conversão de energia mecânica para energia elétrica e, consequentemente, um aumento no efeito de amortecimento. Neste trabalho, o controle piezoelétrico semi-passivo de uma pá piezelétrica engastada é apresentado e comparado com outros controladores. O modelo não linear electromecânico de uma pá com piezocerâmicas incorporados é determinado com base no método variacional-assintótico (VAM). O sistema rotativo acoplado não linear é resolvido no domínio do tempo, utilizando um método de integração alfa-generalizado afim de garantir a estabilidade numérica. As simulações são realizadas para uma vasta gama de velocidades de rotação. Em primeiro lugar, um conjunto de resistências (variando desde a condição de curto-circuito para a condição de circuito aberto) é considerada. O efeito da resistência ótima (que resulta em máximo amortecimento) sobre o comportamento do sistema é investigado para o aumento da velocidade de rotação. Mais tarde, a técnica SSDS é utilizada para amortecer as oscilações da pá com o aumento da velocidade de rotação. Os resultados mostram que a técnica SSDS pode ser um método útil para o controle de vibrações de vigas rotativas não lineares, tais como pás de helicóptero. / The use of smart materials in vibration control problems has been investigated in several researches over the last years. Although dierent smart materials are available, the piezoelectric one has received great attention due to ease of use as sensors, actuators, or both. The main control techniques using piezoelectric materials are the active and passive ones. Passive piezoelectric networks are adjusted for specic target frequencies and, therefore, the eective bandwidth of such systems is small. Although active systems can achieve good vibration control performance, the amount of external power and added hardware are important issues. The synchronized switch damping (SSD) technique was developed in order to address the issues of passive damping methodologies as well as the issues of active control systems. The SSD can be classied as semi-passive technique or semi-active technique that introduce the nonlinear treatment of the piezoelectric element voltage output and induce an increase in mechanical to electrical energy conversion and, consequently, the shunt damping eect. In this work, the semi-passive piezoelectric control of a rotating cantilever beam response is presented and compared with other controllers. The nonlinear electromechanical model of a rotating beam with embedded piezoceramics is derived based on the variational-asymptotic method (VAM). The coupled non-linear rotary system is solved in the time-domain by using a generalized-alpha integration method in order to guarantee numerical stability. The simulations are performed for a wide range of rotating speeds. First, a set of load resistances (ranging from short circuit condition to open circuit condition) is considered. The eect of optimum load resistance (for maximum damping) on the elastic behavior of the beam is investigated for increasing rotating speed. Later, the synchronized switch damping on short (SSDS) technique is employed to damp the nonlinear oscillations of the rotating beam with increasing rotating speed. Results show that the SSDS technique can be a useful method of control for nonlinear rotating beams such as helicopter blades.

Os materiais inteligentes têm sido utilizados em problemas de controle de vibrações e conversão de energia mecânica em energia elétrica. Apesar das diferentes opções existentes, os piezelétricos têm recebido grande atenção devido a facilidade de instalação, além de possibilidade de uso como sensores ou atuadores. Em termos de sistemas de controle utilizando materiais piezelétricos, dois grandes grupos podem ser encontrados: os controladores passivos e os ativos. Os controladores ativos utilizam o efeito piezelétrico inverso e apresentam bom desempenho na redução de vibrações. Entretanto, apresentam desvantagens relacionadas à complexidades de uma lei de controle, necessidade de equipamentos externos e, potencialmente, exigem elevada potência de atuação. Por outro lado, os controladores passivos utilizam circuitos elétricos simples, compostos somente por elementos elétricos passivos. Apesar de serem de fácil implementação prática, apresentam bom desempenho em faixas restritas de frequências. Os controladores semi-passivos, surgiram como uma alternativa aos pontos negativos dos controladores passivos e ativos. Nestes novos sistemas, o material piezelétrico instalado na estrutura a ser controlada é conectado e desconectado a um circuito shunt de forma sincronizada com as vibrações mecânicas. Em geral, a conversão eletromecânica de energia é amplificada, assim como o efeito shunt damping. Dessa forma, os circuitos chaveados têm sido utilizados tanto como controladores semi-passivos quanto em problemas de coleta piezelétrica de energia. Neste trabalho, o controle piezelétrico semi-passivo de oscilações aeroelásticas lineares e não lineares, assim como a coleta piezelétrica de energia a partir das mesmas condições, são investigados experimentalmente. Uma seção típica com dois graus de liberdade e acoplamento eletromecânico é utilizada nos experimentos. Dois tratamentos não lineares do sinal elétrico proveniente dos piezelétricos são utilizados. Primeiro, o chaveamento a partir da condição de circuito aberto para uma resistência muito baixa, próxima ao curto circuito, e posteriormente, o chaveamento da condição de circuito aberto para um indutor. Um circuito chaveador autônomo (que não depende de fontes externas de energia) é apresentado. O desempenho dos dois sistemas no controle de flutter, e também de oscilações em ciclo limite, são discutidos. Os resultados mostraram um aumento na velocidade de flutter de até 8,8% e 11,5%, com chaveamento em uma resistência e em um indutor, respectivamente. No caso de coleta de energia a partir de oscilações aeroelásticas lineares e não lineares, o desempenho dos circuitos chaveados são comparados entre si, e com o caso em que uma resistência é considerada no domínio elétrico, resultando em um aumento da potência elétrica de até 101%, para chaveamentos em resistência, e 227%, para chaveamentos em um indutor. / Smart materials have been used in vibration control and also in energy harvesting problems. Although different materials are available, piezoelectric one has received most attention due to ease of installation and possibility of use as sensors or actuators. In general, there are two large categories of vibration control techniques using piezoelectric materials: passive and active control. In active control the reverse piezoelectric effect is used. In general, they present good performance in vibration reduction over a range of frequencies. However, active control has the disadvantages of additional complexities of a control law, additional hardware and the potentially large amount of power required. On the other hand, piezoelectric passive controllers use simple electric circuits composed by passive electrical elements. Although they are simple to implement, the performance of the controlled system is sensitive to the exciting frequency. The semi-passive controllers are a recent alternative to the drawbacks of passive and active controllers. In semi-passive systems, the piezoelectric element is switched in and out of a shunt impedance, in a synchronous way with mechanical vibrations. In general, the electromechanical energy conversion is enhanced as well as the shunt effect damping. Therefore, the switching techniques have been used both in semi-passive control problems and in piezoelectric energy harvesting problems. In this work, semi-passive techniques are experimentally investigated in aeroelastic control and piezoaeroelastic energy harvesting cases. An electromechanically coupled aeroelastic typical section is used in the experiments. Two techniques are investigated, the synchronized switching damping on short and the synchronized switching damping on inductor. An autonomous switching circuit (that does not requires external source of energy) is presented resulting in a self-powered flutter controller. The performance of the two semi-passive techniques is discussed for the linear case, flutter control, as well as limit cycle oscillations control. The linear flutter speed is increased by 8.8% and 11.5% when the SSDS and SSDI techniques are used, respectively. In the case of energy harvesting from linear and nonlinear aeroelastic oscillations, the performance of switching techniques is investigated and compared to the case of simple load resistance in the electrical domain. The power output is increased by 101% for the SSDS case and 227% for SSDI case.

<p>This thesis is analysis-based survey in which our task was to find out the suitability of </p><p>IEEE 802.15.4 for the RFID systems in terms of power. We studied the different RFID </p><p>systems. We analyzed the IEEE 802.15.4 to see how much this protocol can facilitate the </p><p>RFID application, but we just considered the 2.4 GHz physical band as Free2move uses </p><p>this band for its RFID products. Since semi-passive1 RFIDs are the closest competitors </p><p>of the active RFID, so we also compared the IEEE 802.15.4 with ISO 18000-4 (mode2) </p><p>to find out their pros and cons. </p><p>We also tried to evaluate the hardware architecture proposed by Free2move. We </p><p>compared proposed hardware components with other competitors available in the market. </p><p>The main point of focus during hardware evaluation remained its power efficiency. As </p><p>concluding part we have proposed an idea for using the IEEE 802.15.4 standard in semi- </p><p>passive RFIDs.</p>

This thesis is analysis-based survey in which our task was to find out the suitability of IEEE 802.15.4 for the RFID systems in terms of power. We studied the different RFID systems. We analyzed the IEEE 802.15.4 to see how much this protocol can facilitate the RFID application, but we just considered the 2.4 GHz physical band as Free2move uses this band for its RFID products. Since semi-passive1 RFIDs are the closest competitors of the active RFID, so we also compared the IEEE 802.15.4 with ISO 18000-4 (mode2) to find out their pros and cons. We also tried to evaluate the hardware architecture proposed by Free2move. We compared proposed hardware components with other competitors available in the market. The main point of focus during hardware evaluation remained its power efficiency. As concluding part we have proposed an idea for using the IEEE 802.15.4 standard in semi- passive RFIDs.

O uso de materiais inteligentes em problemas de controle de vibração tem sido investigado em diversas pesquisas ao longo dos últimos anos. Apesar de que diferentes materiais inteligentes estão disponíveis, o piezelétrico tem recebido grande atenção devido à facilidade de uso como sensores, atuadores, ou ambos simultaneamente. As principais técnicas de controle usando materiais piezoelétricos são os ativos e passivos. Circuitos piezelétricos passivos são ajustados para uma frequência específica e, portanto, a largura de banda efetiva é pequena. Embora os sistemas ativos possam apresentar um bom desempenho no controle de vibração, a quantidade de energia externa e hardware adicionado são questões importantes. As técnicas SSD (Synchronized Switch Damping) foram desenvolvidas como uma alternativa aos controladores passivos e controladores ativos de vibração. Elas podem ser técnicas semi-ativas ou semi-passivas que introduzem um tratamento não linear na tensão elétrica proveniente do material piezelétrico e induz um aumento na conversão de energia mecânica para energia elétrica e, consequentemente, um aumento no efeito de amortecimento. Neste trabalho, o controle piezoelétrico semi-passivo de uma pá piezelétrica engastada é apresentado e comparado com outros controladores. O modelo não linear electromecânico de uma pá com piezocerâmicas incorporados é determinado com base no método variacional-assintótico (VAM). O sistema rotativo acoplado não linear é resolvido no domínio do tempo, utilizando um método de integração alfa-generalizado afim de garantir a estabilidade numérica. As simulações são realizadas para uma vasta gama de velocidades de rotação. Em primeiro lugar, um conjunto de resistências (variando desde a condição de curto-circuito para a condição de circuito aberto) é considerada. O efeito da resistência ótima (que resulta em máximo amortecimento) sobre o comportamento do sistema é investigado para o aumento da velocidade de rotação. Mais tarde, a técnica SSDS é utilizada para amortecer as oscilações da pá com o aumento da velocidade de rotação. Os resultados mostram que a técnica SSDS pode ser um método útil para o controle de vibrações de vigas rotativas não lineares, tais como pás de helicóptero. / The use of smart materials in vibration control problems has been investigated in several researches over the last years. Although dierent smart materials are available, the piezoelectric one has received great attention due to ease of use as sensors, actuators, or both. The main control techniques using piezoelectric materials are the active and passive ones. Passive piezoelectric networks are adjusted for specic target frequencies and, therefore, the eective bandwidth of such systems is small. Although active systems can achieve good vibration control performance, the amount of external power and added hardware are important issues. The synchronized switch damping (SSD) technique was developed in order to address the issues of passive damping methodologies as well as the issues of active control systems. The SSD can be classied as semi-passive technique or semi-active technique that introduce the nonlinear treatment of the piezoelectric element voltage output and induce an increase in mechanical to electrical energy conversion and, consequently, the shunt damping eect. In this work, the semi-passive piezoelectric control of a rotating cantilever beam response is presented and compared with other controllers. The nonlinear electromechanical model of a rotating beam with embedded piezoceramics is derived based on the variational-asymptotic method (VAM). The coupled non-linear rotary system is solved in the time-domain by using a generalized-alpha integration method in order to guarantee numerical stability. The simulations are performed for a wide range of rotating speeds. First, a set of load resistances (ranging from short circuit condition to open circuit condition) is considered. The eect of optimum load resistance (for maximum damping) on the elastic behavior of the beam is investigated for increasing rotating speed. Later, the synchronized switch damping on short (SSDS) technique is employed to damp the nonlinear oscillations of the rotating beam with increasing rotating speed. Results show that the SSDS technique can be a useful method of control for nonlinear rotating beams such as helicopter blades.

Os materiais inteligentes têm sido utilizados em problemas de controle de vibrações e conversão de energia mecânica em energia elétrica. Apesar das diferentes opções existentes, os piezelétricos têm recebido grande atenção devido a facilidade de instalação, além de possibilidade de uso como sensores ou atuadores. Em termos de sistemas de controle utilizando materiais piezelétricos, dois grandes grupos podem ser encontrados: os controladores passivos e os ativos. Os controladores ativos utilizam o efeito piezelétrico inverso e apresentam bom desempenho na redução de vibrações. Entretanto, apresentam desvantagens relacionadas à complexidades de uma lei de controle, necessidade de equipamentos externos e, potencialmente, exigem elevada potência de atuação. Por outro lado, os controladores passivos utilizam circuitos elétricos simples, compostos somente por elementos elétricos passivos. Apesar de serem de fácil implementação prática, apresentam bom desempenho em faixas restritas de frequências. Os controladores semi-passivos, surgiram como uma alternativa aos pontos negativos dos controladores passivos e ativos. Nestes novos sistemas, o material piezelétrico instalado na estrutura a ser controlada é conectado e desconectado a um circuito shunt de forma sincronizada com as vibrações mecânicas. Em geral, a conversão eletromecânica de energia é amplificada, assim como o efeito shunt damping. Dessa forma, os circuitos chaveados têm sido utilizados tanto como controladores semi-passivos quanto em problemas de coleta piezelétrica de energia. Neste trabalho, o controle piezelétrico semi-passivo de oscilações aeroelásticas lineares e não lineares, assim como a coleta piezelétrica de energia a partir das mesmas condições, são investigados experimentalmente. Uma seção típica com dois graus de liberdade e acoplamento eletromecânico é utilizada nos experimentos. Dois tratamentos não lineares do sinal elétrico proveniente dos piezelétricos são utilizados. Primeiro, o chaveamento a partir da condição de circuito aberto para uma resistência muito baixa, próxima ao curto circuito, e posteriormente, o chaveamento da condição de circuito aberto para um indutor. Um circuito chaveador autônomo (que não depende de fontes externas de energia) é apresentado. O desempenho dos dois sistemas no controle de flutter, e também de oscilações em ciclo limite, são discutidos. Os resultados mostraram um aumento na velocidade de flutter de até 8,8% e 11,5%, com chaveamento em uma resistência e em um indutor, respectivamente. No caso de coleta de energia a partir de oscilações aeroelásticas lineares e não lineares, o desempenho dos circuitos chaveados são comparados entre si, e com o caso em que uma resistência é considerada no domínio elétrico, resultando em um aumento da potência elétrica de até 101%, para chaveamentos em resistência, e 227%, para chaveamentos em um indutor. / Smart materials have been used in vibration control and also in energy harvesting problems. Although different materials are available, piezoelectric one has received most attention due to ease of installation and possibility of use as sensors or actuators. In general, there are two large categories of vibration control techniques using piezoelectric materials: passive and active control. In active control the reverse piezoelectric effect is used. In general, they present good performance in vibration reduction over a range of frequencies. However, active control has the disadvantages of additional complexities of a control law, additional hardware and the potentially large amount of power required. On the other hand, piezoelectric passive controllers use simple electric circuits composed by passive electrical elements. Although they are simple to implement, the performance of the controlled system is sensitive to the exciting frequency. The semi-passive controllers are a recent alternative to the drawbacks of passive and active controllers. In semi-passive systems, the piezoelectric element is switched in and out of a shunt impedance, in a synchronous way with mechanical vibrations. In general, the electromechanical energy conversion is enhanced as well as the shunt effect damping. Therefore, the switching techniques have been used both in semi-passive control problems and in piezoelectric energy harvesting problems. In this work, semi-passive techniques are experimentally investigated in aeroelastic control and piezoaeroelastic energy harvesting cases. An electromechanically coupled aeroelastic typical section is used in the experiments. Two techniques are investigated, the synchronized switching damping on short and the synchronized switching damping on inductor. An autonomous switching circuit (that does not requires external source of energy) is presented resulting in a self-powered flutter controller. The performance of the two semi-passive techniques is discussed for the linear case, flutter control, as well as limit cycle oscillations control. The linear flutter speed is increased by 8.8% and 11.5% when the SSDS and SSDI techniques are used, respectively. In the case of energy harvesting from linear and nonlinear aeroelastic oscillations, the performance of switching techniques is investigated and compared to the case of simple load resistance in the electrical domain. The power output is increased by 101% for the SSDS case and 227% for SSDI case.

South Africa (SA) currently faces a major pollution problem from mining impacted water, including acid rock drainage (ARD), as a consequence of the mining activities upon which the economy has been largely built. The environmental impact of ARD has been further exacerbated by the country's water scarce status. Increasingly scarce freshwater reserves require the preservation and strategic management of the country's existing water resources to ensure sustainable water security. In SA, the primary focus on remediation of ARDcontaminated water has been based on established active technologies. However, these approaches are costly, lead to secondary challenges and are not always appropriate for the remediation of lower volume discharges. Mostly overlooked, ARD discharges from diffuse sources, associated with the SA coal mining industry, have a marked impact on the environment, similar to those originating from underground mine basins. This is due to the large number of deposits and their broad geographic distribution across largely rural areas of SA. Semi-passive ARD treatment systems present an attractive alternative treatment approach for diffuse sources, with lower capital and operational costs than active systems as well as better process control and predictability than traditional passive systems. These semi-passive systems typically target sulphate salinity through biological sulphate reduction catalysed by sulphate reducing bacteria (SRB). These anaerobic bacteria reduce sulphate, in the presence of a suitable electron donor, to sulphide and bicarbonate. However, the hydrogen sulphide product generated is highly toxic, unstable, easily re-oxidised and poses a significant threat to the environment and human health, so requires appropriate management. An attractive strategy is the reduction of sulphate to sulphide, followed by its partial oxidation to elemental sulphur, which is stable and has potential as a value-added product. A promising approach to achieve partial oxidation is the use of sulphide oxidising bacteria (SOB) in a floating sulphur biofilm (FSB). These biofilms develop naturally on the surfaces of sulphide rich wastewater streams. Its application in wastewater treatment and the feasibility of obtaining high partial oxidation rates in a linear flow channel reactor (LFCR) has been described. The use of a floating sulphur biofilm overcomes many of the drawbacks associated with conventional sulphide oxidation technologies that are costly and require precise operational control to maintain oxygen limiting conditions for partial oxidation. In the current study a hybrid LFCR, incorporating a FSB with biological sulphate reduction in a single reactor unit, was developed. The integration of the two biological processes in a single LFCR unit was successfully demonstrated as a ‘proof of concept'. The success of this system relies greatly on the development of discrete anaerobic and microaerobic zones, in the bulk liquid and at the airliquid interface, that facilitate sulphate reduction and partial sulphide oxidation, respectively. In the LFCR these environments are established as a result of the hydrodynamic properties associated with its design. Key elements of the hybrid LFCR system include the presence of a sulphate-reducing microbial community immobilised onto carbon fibres and the rapid development of a floating sulphur biofilm at the air-liquid interface. The floating sulphur biofilm consists of a complex network of bacterial cells and deposits of elemental sulphur held together by an extracellular polysaccharide matrix. During the Initial stages of FSB development, a thin transparent biofilm layer is formed by heterotrophic microorganisms. This serves as ‘scaffolding' for the subsequent attachment and colonisation of SOB. As the biofilm forms at the air-liquid interface it impedes oxygen mass transfer into the bulk volume and creates a suitable pH-redox microenvironment for partial sulphide oxidation. Under these conditions the sulphide generated in the bulk volume is oxidised at the surface. The biofilm gradually thickens as sulphur is deposited. The produced sulphur, localised within the biofilm, serves as an effective mechanism for recovering elemental sulphur while the resulting water stream is safe for discharge into the environment. The results from the initial demonstration achieved near complete reduction of the sulphate (96%) at a sulphate feed concentration of 1 g/L with effective management of the generated sulphide (95-100% removal) and recovery of a portion of the sulphur through harvesting the elemental sulphur-rich biofilm. The colonisation of the carbon microfibres by SRB ensured high biomass retention within the LFCR. This facilitated high volumetric sulphate reduction rates under the experimental conditions. Despite the lack of active mixing, at a 4-day hydraulic residence time, the system achieved volumetric sulphate reduction rates similar to that previously shown in a continuous stirred-tank reactor. The outcome of the demonstration at laboratory scale generated interest to evaluate the technology at pilot scale. This interest necessitated further development of the process with a particular focus on evaluating key challenges that would be experienced at a larger scale. A comprehensive kinetic analysis on the performance of the hybrid LFCR was conducted as a function of operational parameters, including the effect of hydraulic residence time, temperature and sulphate loading on system performance. Concurrently, the study compared the utilisation of lactate and acetate as carbon source and electron donor as well as the effect of reactor configuration on system performance. Comparative assessment of the performance between the original 2 L LFCR and an 8 L LFCR variant that reflected the pilot scale design with respect to aspect ratio was conducted. Pseudo-steady state kinetics was assessed based on carbon source utilisation, volumetric sulphate reduction, sulphide removal efficiency and elemental sulphur recovery. Additionally, the hybrid LFCR provided a unique synergistic environment for studying the co-existence of the sulphate reducing (SRB) and sulphide oxidising (SOB) microbial communities. The investigation into the microbial ecology was performed using 16S rRNA amplicon sequencing. This enabled the community structure and the relative abundance of key microbial genera to be resolved. These results were used to examine the link between process kinetics and the community dynamics as a function of hydraulic residence time. Results from this study showed that both temperature and volumetric sulphate loading rate, the latter mediated through both sulphate concentration in the feed and dilution rate, significantly influenced the kinetics of biological sulphate reduction. Partial sulphide oxidation was highly dependent on the availability and rate of sulphide production. Volumetric sulphate reduction rates (VSRR) increased linearly as hydraulic residence time (HRT) decreased. The optimal residence time was determined to be 2 days, as this supported the highest volumetric sulphate reduction rate (0.21 mmol/L.h) and conversion (98%) with effective sulphide removal (82%) in the 2 L lactate-fed LFCR. Lactate as a sole carbon source proved effective for achieving high sulphate reduction rates. Its utilisation within the process was highly dependent on the dominant metabolic pathway. The operation at high dilution rates resulted in a decrease in sulphate conversion and subsequent increase in lactate metabolism toward fermentation. This was attributed to the competitive interaction between SRB and fermentative bacteria under varying availability of lactate and concentrations of sulphate and sulphide. Acetate as a sole carbon source supported a different microbial community to lactate. The lower growth rate associated with acetate utilising SRB required longer start-up period and was highly sensitive to operational perturbations, especially the introduction of oxygen. However, biomass accumulation over long continuous operation led to an increase in performance and system stability. Microbial ecology analysis revealed that a similar community structure developed between the 2 L and 8 L lactate-fed LFCR configurations. This, in conjunction with the kinetic data analysis, confirmed that the difference in aspect ratio and scale had minimal impact on process stability and that system performance can be reproduced. The choice of carbon source selected for distinctly different, highly diverse microbial communities. This was determined using principle co-ordinate analysis (PCoA) which highlighted the variation in microbial communities as a function of diversity and relative abundance. The SRB genera Desulfarculus, Desulfovibrio and Desulfomicrobium were detected across both carbon sources. However, Desulfocurvus was found in the lactate-fed system and Desulfobacter in acetate-fed system. Other genera that predominated within the system belonged to the classes Bacteroidetes, Firmicutes and Synergistetes. The presence of Veillonella, a lactate fermenter known for competing with SRB, was detected in the lactate-fed systems. Its relative abundance corresponded well with the lactate fermentation and oxidation performance, where an apparent shift in the dominant metabolic pathway was observed at high dilution rates. Furthermore, the data also revealed preferential attachment of selective SRB onto carbon microfibers, particularly among the Desulfarculus and Desulfocurvus genera. The microbial ecology of the floating sulphur biofilm was consistent across both carbon sources. Key sulphur oxidising genera detected were Paracoccus, Halothiobacillus and Arcobacter. The most dominant genera present in the FSB were Rhizobium, well-known nitrogen fixing bacteria, and Pannonibacter. Both genera are members of the class Alphaproteobacteria, a well-known phylogenetic grouping in which the complete sulphur-oxidising, sox, enzyme system is highly conserved. An aspect often not considered in the operation of these industrial bioprocess systems is the microbial community dynamics within the system. This is particularly evident within biomass accumulating systems where the proliferation of non-SRB over time can compromise the performance and efficiency of the process. Therefore, the selection and development of robust microbial inoculums is critical for overcoming the challenges associated with scaling up, particularly with regards to start-up period, and long-term viability of sulphate reducing bioreactor systems. In the current study, long-term operation demonstrated the robustness of the hybrid LFCR process to maintain relatively stable system performance. Additionally, this study showed that process performance can be recovered through re-establishing suitable operational conditions that favor biological sulphate reduction. The ability of the system to recover after being exposed to multiple perturbations, as explored in this study, confirms the resilience and long-term viability of the hybrid process. A key feature of the hybrid process was the ability to recover the FSB intermittently without compromising biological sulphate reduction. The current research successfully demonstrated the concept of the hybrid LFCR and characterised sulphate reduction and sulphide oxidation performance across a range of operating conditions. This, in conjunction with a clearer understanding of the complex microbial ecology, illustrated that the hybrid LFCR has potential as part of a semi-passive approach for the remediation of low volume sulphate-rich waste streams, critical for treatment of diffuse ARD sources.

Advanced materials such as carbon fiber, composite materials et al. are more and more used in modern industry. They make the structures lighter and stiffer. However, they bring vibration problems. Researchers studied numerous methods to eliminate the undesirable vibrations. These treatments are expected to be a compact, light, intellectual and modular system. Recently, a nonlinear technique which is known as Synchronized Switch Damping (SSD) technique was proposed. These techniques synchronously switched when structure got to its displacement extremes that leading to a nonlinear voltage on the piezoelectric elements. This resulting voltage showed a time lag with the piezoelectric strain thus causing energy dissipation. Based on the developed SSD techniques, a new synchronized switch damping e.g. Synchronized Switch Damping with Energy Transfer (SSDET) was proposed in this document. This method damped the vibration by using the energy from other vibrating form. The objectives of the work reported in this document were threefold. The first one consisted of introduction of SSDET principle and developing its control law. This part aimed at establishing the mathematical model and verifying the proposed method by mathematical tools. Then, the experimental validations were carried out. Three experiments with different configurations demonstrated that SSDET can be implemented not only between structures but also vibrating modes in one structure. A SSDET scheme with multi-patches was also investigated for improving the damping. Finally, a bidirectional SSDET concept was introduced based on the original SSDET technique. This technique be regarded as a multimode control SSDET. Since it privileged the target vibration while keeps a decent control effect on the source vibration.

No description available.