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[pt] O crescimento da produção de resíduos sólidos devido a evolução tecnológica, principalmente nos países em desenvolvimento, vem apresentando-se de maneira acelerada. Esta evolução acarreta na produção de novos produtos eletrônicos mais atualizados e, cada vez mais sofisticados quanto à composição química, com novas funcionalidades, tornando os antigos dispositivos obsoletos. O consumo exarcebado destes novos produtos contribui para um problema que ganha cada vez mais relevância no cenário mundial, o acúmulo de lixo eletrônico de origem urbana. O presente estudo contemplará como matéria prima amostras de placas de circuito impresso de computadores, conhecidas como PCIs, que são um padrão de barramentos, destinado a conectar periféricos à placa-mãe. Tendo em vista que nestes resíduos os teores de metais são tipicamente superiores àqueles de reservas naturais, torna-se interessante buscar rotas que viabilizem a reciclagem desses resíduos com a concomitante recuperação de constituintes de interesse ou concentração de precursores em distintos grupos para a posterior recuperação de metais. Nesta abordagem, foram realizadas análises termogravimétricas para acompanhar as melhores condições de processo e caracterização do material e produtos através de MEV/EDS. Assim, este material, tipicamente constituído por material orgânico (ex: plásticos como PVC) e constituintes inorgânicos (ex: metais e ligas metálicas), será submetido a um processamento térmico em forno tubular a 350 graus C em atmosfera inerte, seguido de etapas de concentração. A partir de 300 graus C a perda de massa se mantém constante, em torno de 30 por cento, e nas seguintes etapas aplicadas, 15 por cento da amostra total em constituintes metálicos com alto valor agregado, no caso Cu, Ni e Au, podem seguir para recuperação. / [en] The production of solid residues due to technological development has been increasing fast, mainly in developing countries. This growth leads to the manufacture of improved electronic products with varied functions, which not only are better versions of the old ones but also more sophisticated in their chemical compounds. The excessive consumption of the new devices contributes to an issue which has been increasing internationally: the accumulation of electronic waste. The raw material used in this study are samples of computer printed circuit boards (PCBs), which are a bus pattern that connects peripherals to the motherboard. Since the metal content in these residues are typically more elevated than in the ones located in natural reserves, it is interesting to find ways to recycle those residues while recovering components of interest or precursor concentrations in distinct groups for later metal recovery. Thermogravimetric analysis were performed on this approach in order to observe the best conditions of the process and the characterization of material and products was through SEM/EDS. Thus, this material, typically composed by organic material (such as plastic or PVC) and inorganic constituents (such as metals and alloys), undergoes a thermal processing in tubular furnace at 350 C degrees in inert atmosphere, followed by the concentration steps. The mass loss is constant from 300 C degrees on, around 30 percent. In the following steps, 15 percent of the total sample presents metallic components with high added value, such as Cu, Ni and Au, may be recovered.

[pt] O aumento do consumo de eletroeletrônicos e o desenvolvimento da tecnologia, proporcionou o surgimento de uma gama de produtos com diferentes funcionalidades, cada vez mais complexos e menores. As placas de circuito impresso (PCIs) são consideradas a parte principal dos dispositivos eletrônicos, sendo o cobre o seu componente elementar. O desenho e espessura das trilhas do circuito são determinantes para caracterizar a passagem de corrente elétrica nos equipamentos eletroeletrônicos e seu funcionamento está diretamente ligado a qualidade da confecção das trilhas do circuito. Este trabalho tem como objetivo estudar o processo de lixiviação do cobre, mediante a reação do ácido clorídrico, cloreto de cobre II e fluxo de ar. Além de investigar as condições experimentais ótimas do processo, que tem como principal característica a possibilidade de regeneração e reutilização da solução. Modelos para avaliar o efeito da concentração de ácido e fluxo de ar na corrosão das placas de circuito impresso foram desenvolvidos através da aplicação do planejamento experimental (pelo método clássico e por algoritmo genéticos em modelos polinomiais) e redes neurais artificiais. Visando encontrar as melhores condições experimentais para o sistema proposto, além de investigar a melhor técnica de predição do mesmo. Os resultados obtidos pelas previsões foram comparados com os resultados experimentais reais. As modelagens foram comparadas pela análise dos coeficientes de correlação (R2) e índices de erro (SSE, MSE e RMSE). Constatando-se que o modelo polinomial foi o mais adequado para prever a resposta. Através da investigação da superfície de resposta e curvas de contorno, foram identificadas as condições otimizadas para o processo. Das quais as concentrações ótimas de ácido clorídrico, cloreto de cobre II e fluxo de ar foram 1 mol.L-1, 0.3 mol.L-1 e 0.5 L/ min, respectivamente. / [en] The increased consumption of consumer electronics and the development of technology has led to the emergence of a range of products with different features, increasingly complex and smaller. Printed circuit boards (PCIs) are considered the main part of electronic devices, with copper being their elementary component. The design and thickness of the circuit tracks are crucial to characterize the passage of electric current in electronic equipment and its operation is directly linked to the quality of the circuit tracks. This work aims to study the copper leaching process through the reaction of hydrochloric acid, copper chloride II and airflow. In addition to investigating the optimal experimental conditions of the process, which has as its main feature the possibility of regeneration and reuse of the solution. Models to evaluate the effect of acid concentration and airflow on PCB corrosion were developed by applying experimental design (by the classical method and by the genetic algorithm in polynomial models) and artificial neural networks. Aiming to find the best experimental conditions for the proposed system, besides investigating the best prediction technique. The results obtained by the predictions were compared with the actual experimental results. The modeling was compared by analysis of correlation coefficients (R2) and error indices (SSE, MSE, and RMSE). Noting that the polynomial model was the most appropriate to predict the response. Through investigation of the response surface and contour curves, the optimized conditions for the process were identified. Of which the optimal concentrations of hydrochloric acid, copper chloride II and airflow were 1 mol.L-1, 0.3 mol.L-1 and 0.5 L / min, respectively.

Yes / Empirical results of an electrically small printed monopole antenna is described with fractional bandwidth of 185% (115 MHz–2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omnidirectionally to provide coverage over a large part of VHF, whole of UHF, entire of L-band and some parts of S-band. The antenna has dimensions of 48.32×43.72×0.8 mm3, which is corresponding with the electrical size of 0.235λ_0×0.211λ_0×0.003λ_0, where λ_0 is free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

Rising fuel costs and concerns about air pollution have significantly increased interest in electric vehicles (EVs). EVs are equipped with rechargeable batteries that can be fully recharged by connecting to an external electrical source. However, the wider adoption of EVs is hindered by the need for an on-board charger system that is both lightweight and efficient. EVs utilize two main charging methods: on-board chargers (OBC) for regular charging and off-board (fast) chargers for quick refills of battery pack. Most EVs currently use 400V battery packs paired with 6.6kW or 11kW OBCs, while larger vehicles with over 100 kWh battery packs employ 16.5kW or 19.2kW OBCs, constrained by household voltage and current limits. Some manufacturers are transitioning to 800V battery packs to lower costs and enhance fast charging capabilities, necessitating the development of 800V OBCs with high efficiency and power density. For household use, EVs can charge via OBC in a grid-to-vehicle transfer and can supply energy back to the home or grid (vehicle-to-grid) for emergency use or to support smart grid functionalities, requiring bidirectional OBCs. Advanced power semiconductor devices have been instrumental in advancing power conversion technology. The introduction of power semiconductor devices based on wide bandgap (WBG) materials marks a revolutionary shift, offering potential improvements over silicon-based devices. These WBG devices are capable of achieving higher efficiency, and higher power density in power conversion at higher operation frequency. Elevating the switching frequency diminishes the voltage-second across the transformer, facilitating the utilization of printed-circuit-board (PCB) technology for the windings as opposed to Litz wire implementations. Compared to traditional Litz wire-based transformers, the manufacturing process is significantly streamlined, and the management of parasitic is considerably more straightforward. Furthermore, the integration of resonant inductors with PCB-based transformer results in a reduction in the overall number of magnetic components and improved power density. This dissertation focuses on the DC/DC conversion stage of a bi-directional battery charger. It aims to achieve high power density and high efficiency using a PCB-based integrated transformer, enhancing manufacturing processes. The dissertation details the specific accomplishments in this area: Firstly, a two-stage on-board charger structure for 800 V battery EVs is proposed. The first stage is a four-phase bridgeless totem pole AC/DC converter working at critical conduction mode (CRM) so that soft switching can be achieved for all the fast switches. The second stage is single phase CLLC (1PCLLC) converter which is attractive due to its less component counts of devices and driver circuits. A novel matrix integrated transformer with controllable built-in leakage inductance for bi-directional 1PCLLC converter was proposed. Integrating three UI-core-based (1UI-based) elemental transformers with non-perfectly interleaved winding structures into one 3UI-based integrated transformer can reduce the core loss significantly with a smaller footprint compared with three EI-core-based integrated transformers. The proposed integrated magnetics can be scalable for higher voltage and higher power converters by assembling more 1UI-based elemental transformers. A SiC-based 1PCLLC converter prototype operating at 250-kHz switching frequency for 11-kW OBC applications was built with the proposed integrated transformer, and it can achieve a power density of 250 W/in3 with maximum efficiency of 98.4%. Secondly, the challenge of increased common mode (CM) noise after adopting PCB-based windings in the design was discussed. The inter-winding capacitors between the primary and secondary windings act as a conduction path for high dv/dt CM noise, which can lead to electromagnetic interference (EMI) issues. To address this, a winding cancellation method for an integrated matrix transformer in a 1PCLLC converter was proposed and validated. This approach was tested in an 11-kW 1PCLLC converter. The EMI measurement results align with the analysis, confirming the effectiveness of the proposed method, which achieved a reduction in CM noise by 17dB. Furthermore, the 1PCLLC converter, incorporating the proposed planar matrix integrated transformer and winding cancellation technique, attained a power density of 420 W/in³ and a peak efficiency of 98.5%. Thirdly, to enhance efficiency further, the 1PCLLC converter is substituted with the proposed three-phase CLLC (3PCLLC) resonant converter equipped with three-phase rectifiers. The 3PCLLC converter becomes more promising for high power applications as its lower RMS current stress and automatic current sharing capabilities. It can achieve soft switching under all conditions. In addition, due to the symmetrical resonant tank, it is more suitable for bi-directional operation. Variable DC-link voltage is adopted so that the DC/DC stage can always work at its optimized point, providing best efficiency for the entire battery voltage. An improved core structure for the three-phase integrated transformer was proposed to reduce the core loss and simplify the magnetic components by integrating three primary resonant inductors, three secondary resonant inductors and three transformers into one magnetic component. A systematic method of converter design which includes the design of integrated transformer, converter loss optimization was adopted to design an 11kW 3PCLLC resonant converter. A SiC-based 3PCLLC converter prototype operating at 250-kHz switching frequency for 11-kW OBC applications was built with the proposed integrated transformer, and it can achieve a power density of 330 W/in3 with peak efficiency of 98.7%. Fourthly, the power level of OBC continues to increase to make up the large capacitance battery pack inside the EVs to relief the concern of mileage range. To address this challenge of higher power, a scalable matrix integrated transformer for multi-phase CLLC converter was proposed. A universal method of integrating magnetizing inductance with built-in leakage inductance based on multiple perfectly coupled transformers (PCTs). The integration of built-in leakage inductance can be achieved by connecting several PCTs using a standardized core type for cost considerations or can be further integrated into a customized core with interleaved magnetomotive force polarities across transformer legs to achieve better flux distribution and smaller core loss. The proposed concept can be applied to single-input single-output, and multiple-inputs multiple-outputs integrated transformer applications. A 3x3 PCTs-based integrated transformer built with PCB windings was designed for a 3PCLLC resonant converter, which integrates three primary resonant inductors, three secondary resonant inductors, and three transformers into one magnetic core to simplify the complexity of the converter. The effectiveness of the proposed concept was demonstrated through a high-efficiency, high-power density 3PCLLC DC/DC converter for an 800V 16.5kW OBC. The designed converter can achieve a power density of 500 W/in3 and a peak efficiency of 98.8%. / Doctor of Philosophy / Rising fuel costs and concerns about air pollution have significantly increased interest in electric vehicles (EVs). EVs are equipped with rechargeable batteries that can be fully recharged by connecting to an external electrical source. However, the wider adoption of EVs is hindered by the need for an on-board charger system that is both lightweight and efficient. The dissertation presents advances in OBC technology to address these challenges, focusing on the development of efficient, high-power density OBCs suitable for various EV applications. EVs utilize two main charging methods: on-board chargers (OBC) for regular charging and off-board (fast) chargers for quick refills of battery pack. Most EVs currently use 400V battery packs paired with 6.6kW or 11kW OBCs, while larger vehicles with over 100 kWh battery packs employ 16.5kW or 19.2kW OBCs, constrained by household voltage and current limits. Some manufacturers are transitioning to 800V battery packs to lower costs and enhance fast charging capabilities, necessitating the development of 800V OBCs with high efficiency and power density. For household use, EVs can charge via OBC in a grid-to-vehicle transfer and can supply energy back to the home or grid (vehicle-to-grid) for emergency use or to support smart grid functionalities, requiring bidirectional OBCs. Advanced power semiconductor devices have been instrumental in advancing power conversion technology. The introduction of power semiconductor devices based on wide bandgap (WBG) materials marks a revolutionary shift, offering potential improvements over silicon-based devices. These WBG devices are capable of achieving higher efficiency, and higher power density in power conversion at higher operation frequency. Elevating the switching frequency diminishes the voltage-second across the transformer, facilitating the utilization of printed circuit board (PCB) technology for the windings as opposed to Litz wire implementations. Compared to traditional Litz wire-based transformers, the manufacturing process is significantly streamlined, and the management of parasitic is considerably more straightforward. Furthermore, the integration of resonant inductors with PCB-based transformer results in a reduction in the overall number of magnetic components and improved power density. Addressing cost concerns, a novel, cost-effective single-phase converter design was proposed, achieving high efficiency with integrated magnetics. Additionally, the research tackled the challenge of electromagnetic interference (EMI) through a winding cancellation technique, significantly reducing common-mode noise and further improving the converter's performance. The research introduces an improved core structure for a three-phase integrated transformer, significantly reducing core loss and simplifying the design by combining multiple components into a single unit. This approach facilitated the creation of a high-efficiency, SiC-based converter prototype, demonstrating remarkable power density and peak efficiency compared with state-of-the-art solutions. To accommodate the increasing power requirements of OBCs, a scalable, matrix integrated transformer design was developed for multi-phase converters, optimizing cost and performance. This design simplifies the converter architecture, enhancing efficiency and power density, and is adaptable to both single and multiple output applications. These advancements offer promising solutions to the challenges hindering the wider adoption of EVs. The dissertation underscores the potential of advanced power conversion technologies, including the application of WBG devices, integrated magnetics to streamline converter design and enhance both the efficiency and power density of battery chargers.

Microwave lenses support low-phase error, wideband, wide-angle scanning, and true-time delay (TTD) beam forming. They provide ideal performance for applications such as satellites, remote-piloted vehicles, collision-avoidance radars and ultra-wideband communications systems. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size beam-forming networks (BFNs). The microwave lens adopts a few beam ports to illuminate the prescribed receiving ports that feed energy into radiating antennas. Multi-beam patterns can be achieved by exciting multiple beam ports at a time. The design process starts with path-length equations from a limited number of beam-port foci assumptions. This constraint does not take into account the amplitude information; however, it allows an initial lens geometry to be solved. The resulted scanning angle of microwave lens is limited by the beam port contour, as such ± 90 degrees. In this dissertation, three contributions are made from the aspects of minimized phase errors, accurate and efficient simulation algorithms, and 360-degree scanning range extension. First, a minimum-phase-error, non-focal lens design method is proposed. It does not require a specific number of foci along the beam contour; however, minimum phase errors for all beam ports are able to be achieved. The proposed method takes into account flexible prescribed geometrical design parameters, and adopts numerical optimization algorithms to perform phase error minimization. Numerical results compared with the published tri-focal and quadru-focal lenses demonstrate the merits of the proposed method. Second, an accurate and fast simulation method for the microwave lens has been developed to predict the phase, amplitude, array factor, and power efficiency performance. The proposed method is compared to both full-wave simulation and measurement. Comparable results have been achieved. Third, a novel method for a 360-degree scanning microwave lens is proposed. This concept uses the beam ports and the receive ports in an interleaving sequence such that adjacent ports alternate beam and receive functions. The result is a lens that produces scanned beams on opposite sides of the structure resulting in a 360-degree scanning range. The structure can use multiple opposing facets or continuous circular-port and radiating-element contours. To prove the concept, a four-facet microstrip lens has been designed, simulated, fabricated, and tested. The comparison between full-wave simulation and measurement has demonstrated good agreement. / Ph. D.

Dual-band antenna elements that support dual-polarization provide ideal performance for applications including space-based platforms, multifunction radar, wireless communications, and personal electronic devices. In many communications and radar applications, a dual-band, dual-polarization antenna array becomes a requirement in order to produce an electronically steerable, directional beam capable of supporting multiple functions. The multiple polarizations and frequency bands allow the array to generate multiple simultaneous beams to support true multifunction radar. Many of the applications in spaced-based systems and personal electronic devices have strict restraints on the size and weight of the antenna element, favoring a low-profile, lightweight device. The research performed in this dissertation focuses on the design of a dual-band, dual-polarized antenna element capable of operating as an isolated element or in an array environment. The element contains two concentric, dual-polarized radiators. The low band radiator is a shorted square ring antenna, and the high band radiator is a square ring slot. Each constituent element achieves circular polarization through the introduction of triangular perturbations into opposing corners of the radiating element. This technique has been shown to introduce two, near-degenerate modes in the structure that – when excited in phase quadrature – combine to form circular polarization. The perturbations allow circular polarized operation with only a single feed point. The sense of the circular polarization is determined by the location of the feed point with respect to the perturbations. Both senses of circular polarization are excited by the introduction of orthogonal feeds for each of the two radiating elements. Thus, dual-ban, dual-circular polarization is obtained. The element achieves a low-profile from its printed circuit board realization. The high band square ring slot is realized in stripline. The orthogonal feeding transmission lines are printed on opposing sides of an electrically thin dielectric layer to allow them to cross without physically intersecting. This thin feeding substrate is sandwiched between two dielectric layers of matched dielectric constant. A ground plane is located on the top and bottom of the sandwiched dielectric structure, and the top ground plane contains the square ring slot with perturbed corners. Slotted stripline structures have been shown in the literature to excite a parallel-plate mode that can degrade overall performance of the antenna. Plated through holes are introduced at the outer perimeter of the square ring slot to short out this parallel-plate mode. The plated through holes (also called vias) serve as the shorting mechanism for the low band microstrip shorted square ring radiator. This element also contains triangular perturbations at opposing corners to excite circular polarization with a single feed point. In this element, orthogonal probe feeds are present to excite both senses of circular polarization. A dual-band, dual-polarized antenna element was built, tested, and compared to simulations. The constructed element operated at two distinct industrial, scientific, and medical (ISM) frequency bands due to their popularity in low power communications. The antenna element was realized in a multilayer printed circuit layout. A complex design procedure was developed and submitted to a printed circuit board company who manufactured the antenna element. The s-parameters of the antenna were measured using a Network Analyzer, and the results show good agreement with simulations. The radiation and polarization characteristics were measured in a compact range facility. These results also agreed well with simulations. The measured results verify the simulation models that were used in the simulations and establish a confidence level in the feasibility of constructing this element. The dual-band, dual-polarization nature of this element was established through the construction and measurement of this element. A novel size reduction technique was developed that allows for significant reduction of the element's footprint. This size reduction facilitates the placement of this element within an array environment. The loading technique utilizes a structure analogous to a parallel-plate capacitor to drastically reduce the overall size of the low frequency shorted square ring. The loading structure uses a substrate that is separate from that of the radiating elements. This allows the load to use a high dielectric material to achieve a high capacitance without requiring the radiating elements to be printed on high dielectric material that is potentially expensive and lossy at microwave frequencies. The two frequency bands were selected to be in separate industrial, scientific, and medical (ISM) bands. These frequency bands are increasingly popular in low power communication devices because unlicensed operation is permitted. The 2.45 GHz and 5.8 GHz ISM bands are commonly used for applications including Bluetooth technology, multiple 801.11 protocol, cellular phone technology, and cordless phones. The ISM bands were chosen for this antenna element due to their popularity, but this antenna is not restricted to these bands. The frequency ratio can be altered by controlling the dielectric constant used in the printed circuit board design, the parameters of the capacitive loading structure, and the size of the constituent elements that are used. After the size reduction technique is applied, the dual-band, dual-polarized elements can be placed in an array environment resulting in an array capable of generating both senses of circular polarization in the two, distinct ISM bands. This provides an aperture capable of supporting multiple functions. Depending on the applications required, the frequency bands of the antenna element can be altered to suit the particular system needs. The array analysis performed in this dissertation used a unique hybrid calculation technique that utilizes nine active element patterns to represent the patterns of the individual elements within a large antenna array. A common first look at array performance is achieved by multiplying the element pattern of an isolated element by an array factor containing the contributions of the geometrical arrangement of the antenna elements. This technique neglects mutual coupling between elements in the array that can alter the impedance match and radiation characteristics of the elements in the array. The active element pattern defines the radiation pattern of a given element in an array when all other elements are terminated in a matched impedance load. The active element pattern is unique for each element in an array. When these patterns are summed, the exact array pattern is obtained. While this technique has the advantage of accuracy, it is not ideal because it requires the simulation, calculation, or measurement of the pattern for each element in the array environment. The technique developed in this dissertation uses only nine active element patterns. These elements are then assigned to represent the active element patterns for all elements in the array depending on the geometrical region where the given element resides. This technique provides a compromise between the speed of using a single element pattern and the accuracy of using the unique active element pattern for each element in the array. The application of these two concentric, coplanar radiators along with the capacitive loading technique provides a unique contribution to the field of antenna engineering. The majority of dual-band antenna elements in the literature operate with a single polarization in each band. The ones that operate with dual-polarization in each band are typically limited to dual-linear polarization. Circular polarization is preferable to linear in many applications because it allows flexible orientation between the transmitting antenna and receiving antenna in a communications system, while also mitigating multipath effects that lead to signal fading. The ability to operate with two, orthogonal senses of circular polarization allows a system to reuse frequencies and double system capacity without requiring additional bandwidth. The uniqueness of this element lies in its ability to provide dual-circular polarization in two separate frequency bands for an individual element or an antenna array environment. The arrangement of the two element geometries with the addition of the novel capacitive loading technique is also unique. The performance of this element is achieved while maintaining the light weight, low profile design that is critical for many wireless communications applications. This dissertation provides a detailed description of the operation of this dual-band, dual-polarized antenna element. The design of the constituent elements is discussed for several polarization configurations to establish an understanding of the building blocks for this element. The dual-band, dual-polarized element is presented in detail to show the impedance match, isolation, and axial ratio performance. The capacitive loading technique is applied to the dual-band, dual-polarized element, and the performance with the loading in place is compared to the performance of the unloaded element. Next, there is an in-depth description of the array calculation technique that was developed to incorporate mutual coupling effects into the array calculations. This technique is then applied to the dual-band, dual-polarized array to show the performance of several array sizes. / Ph. D.

Composite materials have a wide range of applications in civil and structural engineering due to their advantages in mechanical properties and higher strengths over the base materials alone. Polymer-concrete composites are particularly attractive for use in industrial and infrastructure applications from combining the higher mechanical properties of the concrete in tension and the high tensile strength and ductile properties of the polymeric materials. However, these materials tend to be more expensive that typical concrete composites. This thesis explores the mechanical properties of two different polymer-concrete composites and their effectiveness in civil and structural applications: polymer concrete for rapid repair and 3D printed plastic-concrete composite members for energy absorption. The North Atlantic Treaty Organization (NATO) requires that emergency repair of military runways should be completed within 4 hours. In coordination with Luna Innovations Incorporated, a polymer concrete was developed by Luna for use as a rapid repair material for military runways to meet this requirement through its rapid heat curing. Its mechanical properties including its compressive and flexural strength, bond strength in various orientations, workability, modulus of elasticity, and coefficient of thermal expansion were tested and compared against another rapid repair material. The Tri-Service Pavements Working Group Manual recommendations for rigid repair materials were used as the requirements in determining whether the polymer concrete was an adequate rapid repair material. The polymer concrete formulation that was down-selected for further testing met these requirements for all tests except for the coefficient of thermal expansion. This was due to the resin itself having a high volumetric expansion when exposed to greater temperatures. As the polymer concrete is still under development, future tests are to be performed to determine the impact of the higher expansion on the surrounding runways. Additionally, inspired from naturally forming nacre found in some seashells, a 3D printed plastic-concrete beam structure was developed and tested in flexure to determine its energy absorption capabilities. The nacreous structure allows the material to experience a strain-hardening behavior, thus allowing for energy dissipation in the beam as it deflects from further applied load. It is theorized that the energy absorption capabilities would be suitable for withstanding the effects of dynamic loadings in structures, such as earthquake and blast loads. Multiple beam structures were developed and tested to determine the impact of percent-polymeric material and layout had on the energy dissipation. Overall, the specimens with more polymer in the cross-section demonstrated larger load vs. crack mouth displacement curves and fracture energy. These specimens demonstrated a higher toughness as well, making them more suitable for use in structural applications. As the project is still in development, future tests and analysis must be performed to determine their strength properties and feasibility as a structural material. The results of this thesis highlight the benefits of novel polymer composites in industrial and infrastructure applications, such as improved rapid setting characteristics and significantly enhanced mechanical and energy absorbing performance. Future work is needed to optimize these performance metrics, such as freeze thaw cycling, fatigue, and durability tests for the polymer concrete and analysis of moment capacity for the bioinspired nacreous composites. / Master of Science / Composite materials have a wide range of applications in civil and structural engineering due to their advantages in mechanical properties and higher strengths over the base materials alone. Polymer concrete composites are not as widely used due to their greater initial costs. However, they are very attractive in industrial and infrastructure applications because of the improved behavior in tension. This thesis explores the mechanical properties of two different polymer-concrete composites and their effectiveness in civil and structural applications: polymer concrete for rapid repair and 3D printed plastic-concrete composite members for energy absorption. The North Atlantic Treaty Organization (NATO) requires that emergency repair of military runways should be completed within 4 hours. In coordination with Luna Innovations Incorporated, a polymer concrete was developed by Luna for use as a rapid repair material for military runways to meet this requirement through its rapid heat curing. Its mechanical properties were tested and compared against another rapid repair material. The polymer concrete formulation that was down-selected for further testing met the requirements of the military for all tests performed except for the coefficient of thermal expansion. As the polymer concrete is still under development, future tests are to be performed to determine the impact of the higher expansion on the surrounding runways. Additionally, inspired from naturally forming nacre found in some seashells, a 3D printed plastic-concrete beam structure was developed and tested in bending to determine its energy absorption capabilities. The nacreous structure allows the material to experience a strain-hardening behavior, thus allowing for energy dissipation in the beam as it deflects from further applied load. It is theorized that the energy absorption capabilities would be suitable for withstanding the effects of earthquake and blast loads in structures. Multiple beam structures were developed and tested to determine the impact of percent-polymeric material and layout had on the energy dissipation. Overall, the specimens with more polymer in the cross-section demonstrated greater energy absorption capabilities. As the project is still in development, future tests and analysis must be performed to determine their strength properties and feasibility as a structural material. The results of this thesis highlight the benefits of novel polymer composites in industrial and infrastructure applications, such as improved rapid setting characteristics and significantly enhanced mechanical and energy absorbing performance. Future work is needed to optimize these performance metrics, such as freeze thaw cycling, fatigue, and durability tests for the polymer concrete and analysis of moment capacity for the bioinspired nacreous composites.

<p dir="ltr">Portable sensing enables an enhanced form of disease monitoring due to its accessible form-factors, low costs, and insights into user health, along with enhanced detection methods due to its many use cases for at-home or in-field applications. To that end, electrochemistry has been a widely used technique in characterization, detection, and diagnostics. Electrochemical Impedance Spectroscopy (EIS) is an electrochemical technique that enables electrode surface characterization through changes in impedance across a given frequency range making it sensitive to interactions at the electrode surface and enabling the detection and quantification of analytes. While EIS has been traditionally limited to benchtop potentiostats, advancements in integrated circuits (ICs) have since enabled the miniaturization of potentiostats for at-home or field applications. However, implementation of EIS in a portable format is still limited by discontinuous measurements, high cost, or designs not fit for portability. This work revolves around the development of a miniaturized potentiostat that can implement EIS to better accommodate the need for miniaturized sensing platforms. My design uses the AD5941 IC which is a single-chip potentiostat analog-front-end enabling a small form-factor that fits in the palm of the user’s hand. The device was able to characterize a resistor-capacitor circuit with errors as low as 0.33% and quantify the concentration of a redox active compound with a 6.2% error, providing agreeable results with a commercial benchtop potentiostat and demonstrating our device’s potential for diagnostic applications. Our working frequency range of 200 kHz – 0.15 Hz, coupled with high system configurability and a cost of $50 makes our device an accessible option for at-home and portable applications. Future work to implement truly wireless functionalities, such as WiFi or Bluetooth Low Energy, along with experimental testing of biological substances will create a truly robust platform for portable diagnostic and sensing applications.</p>

The FDR (Frequency Disturbance Recorder) is a data acquisition device for the power system. The device is portable and can be used with any residential wall outlet for frequency data collection. Furthermore, the FDR transmits calculated frequency data to the web for access by authorized users via Ethernet connection. As a result, Virginia Tech implemented Frequency Monitoring Network (FNET) with these FDR devices. FNET is a collection of identical FDRs placed in different measurement sites to allow for data integration and comparison. Frequency is an important factor for power system control and stabilization. With funding and support provided by ABB, TVA and NSF the FDRs are placed strategically all over the United States for frequency analysis, power system protection and monitoring. The purpose of this study is to refine the current FDR hardware design and establish a new design that will physically fit all the components on one Printed Circuit Board (PCB). At the same time, the software that is to be implemented on the new board is to be kept similar if not the same as that of the current design. The current FDR uses the Axiom CME555 development board and it is interfaced to the external devices through its communication ports. Even through the CME555 board is able to meet the demands of the basic FDR operations, there are still several problems associated with this design. This paper will address some of those hardware problems, as well as propose a new board design that is specifically aimed for operations of FDR. / Master of Science