Male cicada’s superior sound producing ability has been well studied by entomologists and ethologists. The secret behind the loud sound is the dual-resonator structure: the primary resonator is a series of buckled ribs/beams on its tymbal organ, while the secondary resonator is a large air cavity in the abdomen with a pair of openings. However, the understanding of the dual-resonator structure is incomplete, and few endeavors have been reported on developing cicada-inspired novel acoustic devices. To this end, this dissertation research aims to achieve a fundamental understanding of the cicada-inspired sound generating structures, and to apply the knowledge to develop a dual-resonator system with superior sound generating ability.First, a clamped-clamped buckled beam – the fundamental vibration source of the dual-resonator system – is modeled and tested for free vibration responses during the snap-through process between its bistable positions. It is found that the free vibration of the buckled beam is independent from actuation. In terms of the natural frequencies and the vibrational mode shapes, the free vibration is determined only by the geometry and material properties of the buckling beam. The experiment provides a comprehensive insight of the snap-through process and the induced free vibrations. Second, both analytical and experimental methods are used to investigate the buckling beam from an energy perspective, including the force needed for actuating the buckled beam, the work by the actuation force, the elastic energy of the buckling beam, and the sound radiation characteristics. Results show that although the actuation forces depend on its acting locations, the work by the force remains constant, which is equal to the elastic energy difference between the first symmetric buckling mode and the first anti-symmetric buckling mode. Acoustic analysis shows that the sound radiation is mostly generated from the first symmetric vibrational mode. Third, the dual-resonator system consisting of a buckling beam and a Helmholtz resonator is proposed. Considered as an equivalent two-degree-of-freedom vibration system, the dual-resonator system is modeled and studied for optimal sound output. Finally, a dual-resonator system is fabricated with the optimal parameters. Experimental characterization shows superior sound outputs of the dual-resonator system similar to what are observed in male cicadas. This dissertation sheds new lights on the structural-acoustic interaction of buckling beam and Helmholtz resonator that is found in the sound-producing organs of male cicadas and develops a cicada-inspired dual-resonator system for the first time. Findings from this research not only enhance the existing knowledge on male cicadas, but also pave the way for its engineering applications that require highly efficient sound radiation. / Mechanical Engineering

Thermal systems involve multiple components assembled to store or transfer heat for power, cooling, or insulation purpose, and this research focuses on modeling the performance of two novel thermal systems that are capable of functioning in environments subjected to high heat fluxes. The first investigated thermal system is a cascaded thermoelectric generator (TEG) that directly converts heat into electricity and offers a green option for renewable energy generation. The presented cascaded TEG allows harvesting energy in high temperatures ranging from 473K to 973K, and being a solid-state device with no moving parts constitutes an excellent feature for increase device life cycle and minimum maintenance in harsh, remote environments. Two cascaded TEG designs are analyzed in this research: the two-stage and three-stage cascaded TEGs, and based on the findings, the two-stage cascaded TEG produces a power output of 42 W with an efficiency of 8.3% while the three-cascaded TEG produces 51 W with an efficiency of 10.2%. The second investigated novel thermal system is a thermal protection system inspired by the porous internal skeleton of the cuttlefish also known as cuttlebone. The presented bio- inspired thermal protection has excellent features to serve as an integrated thermal protection system for spacecraft vehicles including being lightweight (93% porosity) and possessing high compressive strength. A large amount of heat flux is generated from friction between air and spacecraft vehicle exterior, especially during reentry into the atmosphere, and part of the herein presented research involves a thermomechanical modeling analysis of the cuttlebone bio-inspired integrated thermal protection system along with comparing its performance with three conventional structures such as the wavy, the pyramid, and cylindrical pin structures. The results suggest that the cuttlebone integrated thermal protection system excels the best at resisting deformation caused by thermal expansion when subjected to aerodynamic heat fluxes. / Doctor of Philosophy / Operating engineering systems in extremely hot environments often decreases systems' reliability, life cycle, and creates premature failure. This research investigates two novel thermal systems capable of functioning in high temperatures including a cascaded thermoelectric generator (TEG) and a bio-inspired thermal protection system. The first evaluated novel thermal systems is a cascaded TEG that directly converts waste heat into power, and being a solid-state device with no moving parts forms an excellent feature for device life cycle improvement and minimum maintenance in harsh, remote environments. The research findings show that the designed cascaded TEGs can produce power when subjected to high temperatures ranging from 473K to 973K. The remaining part of the research presented in this dissertation models the thermomechanical performance of a lightweight structure, which is inspired by the internal skeleton of the cuttlefish, also knows as the cuttlebone. The cuttlefish's natural ability to support high-deep sea pressure translates into possessing high compressive strength, and when added the fact of being lightweight (up to 93% porosity), the cuttlebone forms an excellent candidate to serve as integrated thermal protection for spacecraft vehicles. The last part of the presented research discuss the thermomechanical analysis of the cuttlebone when subjected to high aerodynamics heat flux generated from friction between the air and spacecraft vehicle exterior, and it was found that the cuttlebone structure resists deformation associated with the steep temperature gradient experienced by the spacecraft vehicle during travel.

Modern parallel computing techniques are subject to poor scalability. Their performance tends to suffer diminishing returns and even losses with increasing parallelism. Some methods of intelligent computing, such as neural networks and genetic algorithms, lend themselves well to massively parallel systems but come with other drawbacks that can limit their usefulness such as the requirement of a training phase and/or sensitivity to randomness. This thesis investigates the feasibility of a novel method of intelligent parallel computing by implementing a true multiple instruction stream, single data stream (MISD) computing system that is theoretically nearly perfectly scalable. Computational dreaming (CD) is inspired by the structure and dreaming process of the human brain. It examines previously observed input data during a 'dream phase' and is able to develop and select a simplified model to use during the day phase of computation. Using mazes as an example problem space, a CD simulator is developed and successfully used to demonstrate the viability and robustness of CD. Experiments that focused on CD viability resulted in the CD system solving 15% of mazes (ranging from small and simple to large and complex) compared with 2.2% solved by random model selection. Results also showed that approximately 50% of successful solutions generated match up with those that would be generated by algorithms such as depth first search and Dijkstra's algorithm. Experiments focusing on robustness performed repeated trials with identical parameters. Results demonstrated that CD is capable of achieving this result consistently, solving over 32% of mazes across 10 trials compared to only 3.6% solved by random model selection. A significant finding is that CD does not get stuck on local minima, always converging on a solution model. Thus, CD has the potential to enable significant contributions to computing by potentially finding elegant solutions to, for example, NP-hard or previously intractable problems. / Master of Science

The wings of most species of owl have been shown to possess three unique physical attributes which allow them to hunt in effective silence: a comb of evenly-spaced bristles along the wing leading-edge; a compliant and porous fringe of feathers at the trailing-edge; and a velvety down material distributed over the upper wing surface. This investigation focuses on the last of the mechanisms as a means to reduce noise from flow over surface roughness. A microscopic study of several owl feathers revealed the structure of the velvety down to be very similar to that of a forest or a field of crops. Analogous surface treatments (suspended canopies) were designed which simulated the most essential geometric features of the velvety down material. The Virginia Tech Anechoic Wall-Jet Facility was used to perform far-field noise and surface pressure fluctuation measurements in the presence of various combinations of rough surfaces and suspended canopies. All canopies were demonstrated to have a strong influence on the surface pressure spectra, and attenuations of up to 30 dB were observed. In addition, all canopies were shown to have some positive effects on far-field noise, and optimized canopies yielded far-field noise reductions of up to 8 dB across all frequencies at which roughness noise was observed. This development represents a new passive method for roughness noise control with possibility for future optimization and application to engineering structures. / Master of Science

The purpose of this thesis is to explore the performance of a bio-inspired plate undergoing oscillatory heave motions and active shape change. The shape change will be achieved using a panel embedded with Fluidic Flexible Matrix Composite (F2MC) tubes for actuation. A beam, or plate strip, model is presented as a means of verifying that F2MC tubes can effectively serve as a means of actuation. This model was actuated in air and water at several internal tube pressures. The static experimental deflections were compared to two beam models relying on Euler-Bernoulli and Timoshenko beam theories with concentrated tip moments and a distributed moment. It was found that the Euler-Bernoulli model with a concentrated tip moment best approximated the static experimental deflections. Following the success of the plate strip, and panel with 10 embedded F2MC tubes was manufactured. The plate panel was constructed with Dragon Skin Silicone and embedded with two rows of five F2MC tubes which provide the means of shape actuation. Experimental results from actuating the panel in static conditions showed that F2MC tubes are an effective means of prescribing a repeatable shape change to a silicone panel. Then, Classical Plate Theory and First-Order Shear Deformation Plate Theory were used with a concentrated tip moment at the free edge to provide a means of modeling the full panel. When comparing the static experimental results to the numerical models, it was found that the deflected plate shape could be most accurately predicted at lower pressures for upward deflection and higher pressures for downward deflections. When tested in unsteady conditions in a heaving experiment (0.5 Hz to 2.3 Hz), the force measured at frequencies above 1.5 Hz were up to 3.6 times greater than those measured for frequencies below 1.5 Hz. Additionally, the phase difference between the tip deflection and force with respect to the keel position decreased for force as frequency increased, while the opposite was true for the tip deflection. At 1.5 Hz, the tip deflection and force were equally out of phase with the keel. When the panel was subjected to an oscillatory heaving motion while asymmetrically actuated, it was found that faster heaving frequencies resulted in higher maximum force values for all actuation pressures, actuation directions, and depths below the free surface. However, when subjected to dual actuation by pressurizing the top and bottom tubes at the same pressure, the tip amplitude was highly dependent on specific combinations of heaving frequency, actuation pressure, and depth below the free surface. This indicates that the actuation pressure must be tuned to the depth and frequency of operation to obtain the desired tip amplitude for a given application. These findings further the knowledge of shape-changing F2MC panels operating near a free surface and lay a groundwork for developing flapping propulsors that mimic marine animals. / Master of Science / The purpose of this thesis is to explore the performance of a bio-inspired plate undergoing oscillatory (up and down) heave motions and active shape change. The active shape change is achieved using Fluidic Flexible Matrix Composite (F2MC) tubes, which act as an artificial muscles to deflect the panel. To verify that F2MC tubes are capable of prescribing a repeatable deflection, a simple beam model with two embedded tubes was manufactured and tested statically in air and water. It was found that the F2MC tubes were able to prescribe a repeatable deflection, and when comparing to two beam models, Euler-Bernoulli and Timoshenko, it was found that the Euler Bernoulli model with a concentrated tip moment best approximated the static experimental deflections. Following the success of the beam model with 2 embedded tubes, a panel was made with 10 embedded F2MC tubes, 5 along the bottom and 5 along the top, was created. This panel was tested statically and dynamically. Static results showed strong deflection repeatability. When subjected to heaving motions, it was found that the force in the system increased with increasing heaving frequency. The phase difference measured between the tip deflection and force with respect to the keel position decreased for force as frequency increased, while the opposite was true for the tip deflection. It was also observed that there exists a point where the tip deflection and force were equally out of phase with the keel. When the panel was subjected to dual actuation by pressurizing the top and bottom tubes at the same pressure, the tip amplitude was highly dependent on specific combinations of heaving frequency, actuation pressure, and depth below the free surface. This indicates that the actuation pressure must be tuned to the depth and frequency of operation to obtain the desired tip amplitude for a given application. These findings further the knowledge of shape-changing F2MC panels operating near a free surface and lay a groundwork for developing flapping propulsors that mimic marine animals.

Noise from fluid flow over rough surfaces is an important consideration in the design and performance of certain vehicles with high surface-area-to-perimeter ratios. A new method of noise control based on the anatomy of owls is developed and consists of fabric or fibrous canopies suspended above the surface. The method is tested experimentally and is found to reduce the total far-field noise emitted by the surface. The treatment also is found to reduce the magnitude of pressure fluctuations felt by the underlying surface by up to three orders of magnitude. Experimental investigations into the effects of geometric parameters of the canopies lead to an optimized design which maximizes noise reduction. The results obtained during the canopy experiment inspired a separate new device for the reduction of trailing edge noise. This type of noise is generated by flow past the wing of an aircraft or the blades of a wind turbine, and is a source of annoyance for those in surrounding communities. The newly developed treatment consists of small fins, or "finlets," placed near the trailing edge of an airfoil. The treatment is tested experimentally at near-full-scale conditions and is found to reduce the magnitude of far-field noise by up to 10 dB. Geometric parameters of the finlets are tested to determine the optimal size and spacing of the finlets to maximize noise reduction. Follow-up computational and experimental studies reveal the fluid mechanics behind the noise reduction by showing that the finlets produce a velocity deficit in the flow near the trailing edge and limit the magnitude and spanwise correlation lengthscale of turbulence near the trailing edge, factors which determine the magnitude of far-field noise. In a final experiment, the finlets are applied to a marine propeller and are found to reduce not only trailing edge noise, but also noise caused by the bluntness of the trailing edge. The results of this experiment show the potential usefulness of finlets to reduce noise from rotating systems, such as fans or propellers, as well as from structures which feature blunt trailing edges. / Ph. D. / As vehicles and other engineering structures, such as wind turbines, pass through the atmosphere or ocean, noise is produced when fluid is disturbed by their passage. The dominant source of this noise may be a certain geometrical or structural feature depending on the type of vehicle or structure in question. The noise from marine vehicles can be dominated by interaction between the fluid flow and any roughness present on the surface of the vehicle, and this is termed roughness noise. This noise can be detrimental to the performance and efficient operation of marine vehicles, and few options exist to suppress this noise apart from removing the roughness itself. As this is not always feasible if the structure’s design depends on the presence of roughness (for example, rivet heads which fasten structural components of the vehicle), other methods of noise control would be valuable. The noise from large, rotating wind turbines is dominated by interaction between the fluid flow and the sharp trailing edges of the turbine blades, termed trailing edge noise. This noise can travel significant distances from wind turbines and can be a source of annoyance for those living in nearby communities. New methods of noise control would significantly improve the quality of life in these communities and increase the viability and popularity of wind energy. This work takes inspiration from the anatomical features of silently-flying owls to develop new methods to control both roughness noise and trailing edge noise. Experiments and simulations were carried out to prove the effectiveness of these methods and to gain scientific understanding of the fluid mechanics responsible for noise reduction. The developments described in the present work give engineers new tools for designing future vehicles and wind turbines which operate more quietly and more efficiently.

In this study, structure-property relationships in the ironclad beetle (Zopherus nodulosus haldemani) exoskeleton are quantified to develop novel bio-inspired impact resistance technologies. The hierarchical structure of this exoskeleton was observed at various length scales for both the ironclad beetle pronotum and elytron. The exocuticle and endocuticle layers provide the bulk of the structural integrity and consist of chitiniber planes arranged in a Bouligand structure. The pronotum consists of a layered structure, while elytron consists of an extra layer with “tunnel-like” voids running along the anteroposterior axis along with smaller interconnecting “tunnel-like” voids in the lateral plane. Energy dispersive X-ray diffraction revealed the existence of minerals such as calcium carbonate, iron oxide, zinc oxide, and manganese oxide. We assert that the strength of this exoskeleton could be attributed to its overall thickness, the epicuticle layer thickness, the existence of various minerals embedded in the exoskeleton, and its structural hierarchy. The thickness of the exoskeleton correlates to a higher number of chitiniber planes to increase fracture toughness, while the increased thickness of the epicuticle prevents hydration of the chitiniber planes. In previous studies, the existence of minerals in the exoskeleton has been shown to create a tougher material compared to non-mineralized exoskeletons.

Mycorrhizal Networks (MNs) facilitate the exchange of resources including energy, water, nutrients, and information between trees and plants in forest ecosystems. This work explored MNs as an inspiration for new market models in transactive energy networks, which similarly involve exchanges of energy and information between buildings in local communities. Specific insights from the literature on the structure and function of MNs were translated into an energy model with the aim of addressing challenges associated with the proliferation of distributed energy resources (DERs) at the grid edge and the incorporation of DER aggregations into wholesale energy markets. First, a systematic review of bio-inspired computing interventions applied to microgrids and their interactions with modern energy markets established a technical knowledge base within the context of distributed electrical systems. Second, a bio-inspired design process built on this knowledge base to yield a structural and functional blueprint for a computational mycorrhizal energy market simulation. Lastly, that computational model was implemented and simulated on a blockchain-compatible, multi-agent software platform to determine the effect that mycorrhizal strategies have on transactive energy market performance. The structural translation of a mapped ectomycorrhizal network of Douglas-firs in Oregon, USA called the 'wood-wide web' created an effective framework for the organization of a novel mycorrhizal energy market model that enabled participating buildings to redistribute percentages of their energy assets on different competing exchanges throughout a series of week-long simulations. No significant changes in functional performance –- as determined by economic, technical, and ecological metrics – were observed when the mycorrhizal results were compared to those of a baseline transactive energy community without periodic energy asset redistribution. Still, the model itself is determined to be a useful tool for further exploration of innovative, automated strategies for DER integration into modern energy market structures and electrical infrastructure in the age of Web3, especially as new science emerges to better explain trigger and feedback mechanisms for carbon exchange through MNs and how mycorrhizae adapt to changes in the environment. This dissertation concludes with a brief discussion of policy implications and an analysis applying the ecological principles of robustness, biodiversity, and altruism to the collective energy future of the human species. / Doctor of Philosophy / Beneath the forest floor, a network of fungi connects trees and plants and allows them to exchange energy and other resources. This dissertation compares this mycorrhizal network (mycorrhiza = fungus + root) to a group of solar-powered buildings generating energy and exchanging it in a local community marketplace (transactive energy markets). In the analogy, the buildings become the plants, the solar panels become the leaves, and the electrical grid represents the mycorrhizal network. Trees and plants produce their own energy through photosynthesis and then send large portions of it down to the roots, where they can trade it or send it to neighbors via the mycorrhizal network. Similarly, transactive energy markets are designed to allow buildings to sell the energy they produce on-site to neighbors, usually at better rates. This helps address a major infrastructure challenge that is arising with more people adding roof-top solar to their homes. The grid that powers our buildings is old now and it was designed to send power from a central power plant out to its edges where most homes and businesses are located. When too many homes produce solar power at the same time, there is nowhere for it to go, and it can easily overload the grid leading to fires, equipment failures, and power outages. Mycorrhizal networks solve this problem in part through local energy balancing driven by cooperative feedback patterns that have evolved over millennia to sustain forest ecosystems. This work applies scientific findings on the structure and function of mycorrhizal networks (MNs) to energy simulation methods in order to better understand the potential for building bio-inspired energy infrastructure in local communities. Specifically, the mapped structure of a MN of douglas-fir trees in Oregon, USA was adapted into a digital transactive energy market (TEM) model. This adaptation process revealed that a single building can connect to many TEMs simultaneously and that the number of connections can change over time just as symbiotic connections between organisms grow, decay, and adapt to a changing environment. The behavior of MNs in terms of when those connections are added and subtracted informed the functionality of the TEM model, which adds connections when community energy levels are high and subtracts connections when energy levels are low. The resulting 'mycorrhizal' model of the TEM was able to change how much energy each connected household traded on it by changing the number of connections (more connections mean more energy and vice versa). Though the functional performance of the mycorrhizal TEM did not change significantly from that of a typical TEM when they were the context of decentralized computer networks (blockchains) and distributed artificial intelligence. A concluding discussion addresses ways in which elements of this new model could transform energy distribution in communities and improve the resilience of local energy systems in the face of a changing climate.

L’étude du fonctionnement de notre système nerveux et des mécanismes sensoriels a mené à la création de capteurs événementiels. Ces capteurs ont un fonctionnement qui retranscrit les atouts de nos yeux et oreilles par exemple. Cette thèse se base sur la recherche de méthodes bio-inspirés et peu coûteuses en énergie permettant de traiter les données envoyées par ces nouveaux types de capteurs. Contrairement aux capteurs conventionnels, nos rétines et cochlées ne réagissent qu’à l’activité perçue dans l’environnement sensoriel. Les implémentations de type « rétine » ou « cochlée » artificielle, que nous appellerons capteurs dynamiques, fournissent des trains d’évènements comparables à des impulsions neuronales. La quantité d’information transmise est alors étroitement liée à l’activité présentée, ce qui a aussi pour effet de diminuer la redondance des informations de sortie. De plus, n’étant plus contraint à suivre une cadence d’échantillonnage, les événements créés fournissent une résolution temporelle supérieure. Ce mode bio-inspiré de retrait d’information de l’environnement a entraîné la création d’algorithmes permettant de suivre le déplacement d’entité au niveau visuel ou encore reconnaître la personne parlant ou sa localisation au niveau sonore, ainsi que des implémentations d’environnements de calcul neuromorphiques. Les travaux que nous présentons s’appuient sur ces nouvelles idées pour créer de nouvelles solutions de traitement. Plus précisément, les applications et le matériel développés s’appuient sur un codage temporel de l’information dans la suite d'événements fournis par le capteur. / Studying how our nervous system and sensory mechanisms work lead to the creation of event-driven sensors. These sensors follow the same principles as our eyes or ears for example. This Ph.D. focuses on the search for bio-inspired low power methods enabling processing data from this new kind of sensor. Contrary to legacy sensors, our retina and cochlea only react to the perceived activity in the sensory environment. The artificial “retina” and “cochlea” implementations we call dynamic sensors provide streams of events comparable to neural spikes. The quantity of data transmitted is closely linked to the presented activity, which decreases the redundancy in the output data. Moreover, not being forced to follow a frame-rate, the created events provide increased timing resolution. This bio-inspired support to convey data lead to the development of algorithms enabling visual tracking or speaker recognition or localization at the auditory level, and neuromorphic computing environment implementation. The work we present rely on these new ideas to create new processing solutions. More precisely, the applications and hardware developed rely on temporal coding of the data in the spike stream provided by the sensors.

A Clusterização de dados em grupos oferece uma maneira de entender e extrair informações relevantes de grandes conjuntos de dados. A abordagem em relação a aspectos como a representação dos dados e medida de similaridade entre clusters, e a necessidade de ajuste de parâmetros iniciais são as principais diferenças entre os algoritmos de clusterização, influenciando na qualidade da divisão dos clusters. O uso cada vez mais comum de grandes conjuntos de dados aliado à possibilidade de melhoria das técnicas já existentes tornam a clusterização de dados uma área de pesquisa que permite inovações em diferentes campos. Nesse trabalho é feita uma revisão dos métodos de clusterização já existentes, e é descrito um novo método de clusterização de dados baseado na identificação de comunidades em redes complexas e modelos computacionais inspirados biologicamente. A técnica de clusterização proposta é composta por duas etapas: formação da rede usando os dados de entrada; e particionamento dessa rede para obtenção dos clusters. Nessa última etapa, a técnica de otimização por nuvens de partículas é utilizada a fim de identificar os clusters na rede, resultando em um algoritmo de clusterização hierárquico divisivo. Resultados experimentais revelaram como características do método proposto a capacidade de detecção de clusters de formas arbitrárias e a representação de clusters com diferentes níveis de refinamento. / DAta clustering is an important technique to understand and to extract relevant information in large datasets. Data representation and similarity measure adopted, and the need to adjust initial parameters, are the main differences among clustering algorithms, interfering on clusters quality. The crescent use of large datasets and the possibility to improve existing techniques make data clustering a research area that allows innovation in different fields. In this work is made a review of existing data clustering methods, and it is proposed a new data clustering technique based on community dectection on complex networks and bioinspired models. The proposed technique is composed by two steps: network formation to represent input data; and network partitioning to identify clusters. In the last step, particle swarm optimization technique is used to detect clusters, resulting in an hierarchical clustering algorithm. Experimental results reveal two main features of the algorithm: the ability to detect clusters in arbitrary shapes and the ability to generate clusters with different refinement degrees