This research focuses on developing a cognitive radio that could operate reliably in unforeseen communications environments like those faced by the disaster and emergency response communities. Cognitive radios may also offer the potential to open up secondary or complimentary spectrum markets, effectively easing the perceived spectrum crunch while providing new competitive wireless services to the consumer. A structure and process for embedding cognition in a radio is presented, including discussion of how the mechanism was derived from the human learning process and mapped to a mathematical formalism called the BioCR. Results from the implementation and testing of the model in a hardware test bed and simulation test bench are presented, with a focus on rapidly deployable disaster communications. Research contributions include developing a biologically inspired model of cognition in a radio architecture, proposing that genetic algorithm operations could be used to realize this model, developing an algorithmic framework to realize the cognition mechanism, developing a cognitive radio simulation toolset for evaluating the behavior the cognitive engine, and using this toolset to analyze the cognitive engineà ­s performance in different operational scenarios. Specifically, this research proposes and details how the chaotic meta-knowledge search, optimization, and machine learning properties of distributed genetic algorithm operations could be used to map this model to a computable mathematical framework in conjunction with dynamic multi-stage distributed memories. The system formalism is contrasted with existing cognitive radio approaches, including traditionally brittle artificial intelligence approaches. The cognitive engine architecture and algorithmic framework is developed and introduced, including the Wireless Channel Genetic Algorithm (WCGA), Wireless System Genetic Algorithm (WSGA), and Cognitive System Monitor (CSM). Experimental results show that the cognitive engine finds the best tradeoff between a host radio's operational parameters in changing wireless conditions, while the baseline adaptive controller only increases or decreases its data rate based on a threshold, often wasting usable bandwidth or excess power when it is not needed due its inability to learn. Limitations of this approach include some situations where the engine did not respond properly due to sensitivity in algorithm parameters, exhibiting ghosting of answers, bouncing back and forth between solutions. Future research could be pursued to probe the limits of the engineà ­s operation and investigate opportunities for improvement, including how best to configure the genetic algorithms and engine mathematics to avoid engine solution errors. Future research also could include extending the cognitive engine to a cognitive radio network and investigating implications for secure communications. / Ph. D.

Geckos and other insects have fascinated scientists and casual observers with their ability to effortlessly climb up walls and across ceilings. This capability has inspired high capacity, easy release synthetic adhesives, which have focused on mimicking the fibrillar features found on the foot pads of these climbing organisms. However, without a fundamental framework that connects biological and synthetic adhesives from nanoscopic to macroscopic features, synthetic mimics have failed to perform favorably at large contact areas. In this thesis, we present a scaling approach which leads to an understanding of reversible adhesion in both synthetic and biological systems over multiple length scales. We identify, under various loading scenarios, how geometry and material properties control adhesion, and we apply this understanding to the development of high capacity, easy release synthetic adhesive materials at macroscopic size scales. Starting from basic fracture mechanics, our generalized scaling theory reveals that the ratio of contact area to compliance in the loading direction, A/C, is the governing scaling parameter for the force capacity of reversible adhesive interfaces. This scaling theory is verified experimentally in both synthetic and biological adhesive systems, over many orders of magnitude in size and adhesive force capacity (Chapter 2). This understanding is applied to the development of gecko-like adhesive pads, consisting of stiff, draping fabrics incorporated with thin elastomeric layers, which at macroscopic sizes (contact areas of 100 cm2) exhibit force capacities on the order of 3000 N. Significantly, this adhesive pad is non-patterned and completely smooth, demonstrating that fibrillar features are not necessary to achieve high capacity, easy release adhesion at macroscopic sizes and emphasizing the importance of subsurface anatomy in biological adhesive systems (Chapter 2, Chapter 3). We further extend the utility of the scaling theory under shear (Chapter 4) and normal (Chapter 5) loading conditions and develop simple expressions for patterned and non-patterned interfaces which describe experimental force capacity data as a function of geometric parameters such as contact area, aspect ratio, and contact radius. These studies provide guidance for the precise control of adhesion with enables the development of a simple transfer printing technique controlled by geometric confinement (Chapter 6). Force capacity data from each chapter, along with various literature data are collapsed onto a master plot described by the A/C scaling parameter, with agreement over 15 orders of magnitude in adhesive force capacity for synthetic and biological adhesives, demonstrating the generality and robustness of the scaling theory (Chapter 7).

Because origami has proved to be a tremendously rich source of inspiration in engineering, interest in solving some of the challenges that affect origami-inspired design has been significant. One such challenge involves ensuring that origami-inspired mechanisms are rigid-foldable or capable of moving without requiring links to bend or distort. Because rigid-foldability is essential in mechanisms that are constructed using rigid materials, access to methods of engineering this characteristic are highly desirable. This research addresses this need by developing methods for the design of origami-inspired mechanisms that are rigid-foldable. Methods for modifying crease patterns to achieve this are described and compared. Methods for achieving rigid-foldability using thick materials are also developed. Proofs of a process for generating new variations of existing thick-origami models are developed and demonstrated on multiple models. The possibility of using compliant panels to create rigid-foldability is also studied.Because of the relationship between mechanism stiffness and rigid-foldability, means of managing the pattern stiffness are also examined. The design of compliant, deployable stiffeners is studied to permit a comparison of different stiffener types. This comparison is used to identify dominant configurations that are most advantageous for a deployable mechanism. The use of thick-origami models are also considered. The geometry of two varieties of a cantilever tube are optimized to support a cantilever beam.

Traditional methods for dermal wound closure such as sutures and staples are invasive and can result in soft tissue trauma, increasing the likelihood of localized inflammation and infections. Alternately, while tissue adhesive alternatives can effectively seal and adhere to the wounds, they can also present safety concerns relating to immunogenic responses and tissue toxicity. Herein, we fabricate injectable, adhesive, and cytocompatible poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA)-dopamine (DA) hydrogels co-crosslinked via hydrazone and self-polymerized dopamine crosslinks that exhibit high water retention, improved tissue adhesiveness, and effective tissue regeneration properties. POEGMA-DA hydrogels exhibit independently tunable gelation properties based on their dual crosslinking mechanism, allowing for gelation as fast as 24 s (allowing for injection and rapid filling of irregularly-shaped wounds) while achieving relevant compressive moduli of up to 37 kPa and in vitro skin adhesion strengths of up to 1.2 kPa. The POEGMA-DA hydrogels induced no significant inflammation while demonstrating high interfacial adhesiveness in a stented skin excisional mouse model, enabling efficient dermal tissue regeneration by supporting collagen remodelling and enabling the regeneration of hair follicles, sebaceous glands, and blood vessels at the excision site over the 14-day study timeline. As such, injectable POEGMA-DA hydrogels represent a relevant non-toxic and adhesive alternative wound closure system for treating deep dermal wounds. / Thesis / Master of Applied Science (MASc) / Effective wound healing and subsequent tissue regeneration after a physical injury requires a moist sterile environment, the presence of oxygen, nutrients and enzymes, an efficient blood supply to the wound site, and a controlled inflammatory response to initiate the healing process. External methods of closing the wound to prevent infection aid in faster healing like sutures, staples, and liquid sealants which can result in infections and/or the stimulation of an inflammatory response that can hinder tissue restoration. Hydrogels, water-swellable polymer networks, represent an alternative solution that can both suppress infection while simultaneously promoting wound healing. Hydrogels have a similar structure to soft tissues like skin and can thus provide a supportive environment for cells to promote tissue regeneration and restore tissue structure and function. The swelling of hydrogels in water is highly beneficial for providing moisture at the wound site; however, this high degree of water retention also means they have a hard time sticking to tissues. To address this challenge, hydrogels can be modified with a component naturally derived from marine mussels that allows them to stick to their wet habitats, helping hydrogels to stick to the wound site while healing. In this thesis, mussel-inspired hydrogels are designed and can spontaneously gel and stick to a wound site to accelerate the restoration of the structure and function of skin. These biodegradable and injectable hydrogels are effective in accelerating wound closure with minimal evidence of scarring while suppressing negative inflammatory reactions and restoring the structure of skin by promoting the regeneration of hair follicles, sebaceous glands and blood vessels.

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