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With increasing demands in bone repair and replacement, this research investigates the microstructure, properties and performance of bovine bone, human bone, and synthetic materials. Doing so, experimental approaches were used to exam and compare bones, as well as mimicking nature by developing a synthetic material to repair bones. Experimentally, bovine bone, tumor-free human bone, and cancerous human bone were studied via the small scale mechanical loading test. Failure analysis was conducted via optical and electronic microscopic techniques. Characterization results were used to develop a synthetic material that possesses strength and strain needed as a bone material. Characterizing techniques include a small punch test, scanning electron microscope (SEM), optical microscope and x-ray diffraction (XRD) were used for experimental approach. The results showed that small punch tests in longitudinal and tangential directions showed different mechanical properties and failure mechanisms. Cancer cells in human bone caused the bone softening and lowered the density. Synthesized epoxy-silicone-geopolymer material had higher deformability than bone. Understanding obtained in this research helps us to develop better synthetic bone materials in future. This thesis is composed of six chapters. The first chapter covers as an introduction to understand the purpose and motivation of present studies, and this section followed by the details of the motivation and objectives of this research. The third chapter explains experimental approaches that were conducted to meet the objectives. The fourth chapter describes the results and the major discovery of the experiments, and the results will be discussed in the Chapter IV. Finally, the last chapter provides the conclusions and recommendations for future work.

Soft automation employs multi-functional robotic manipulators where dexterity, versatility and reconfigurability are now becoming key issues. For manipulators used in these circumstances, hyper-redundancy in configuration is essential. A typical application envisaged, is manipulator movement in unpredictable surroundings such as navigation amongst branches and foliage in automated fruit picking. This requires motion of a manipulator in an unmapped dynamic environment to find its way to the goal i.e. the fruit. To date, centralized control architectures have proven impractical for the control of redundant systems because the full environment needs to be mapped, there are time constraints on the computation required and, simultaneously, algorithms for obstacle avoidance must be enacted. Decentralized control of manipulators complements modular construction because the need for a full environment reconstruction in one master controller is bypassed by having localized sub-goals for each module. Time constraints are removed because the control algorithms are much simpler. Obstacle avoidance is localized. Manipulators constructed modularly are effective because they allow for reconfiguration and ease of fault diagnosis. For modular manipulators to be a more effective option as a subclass of robots, the conditions under which the interactive movements of modules are stable become a major issue. When a general review of hyper-redundant manipulators was undertaken, no published implementation of Modular Decentralized Control (MDC) was discovered. This thesis explored the use of a modular decentralized technique to create stable control of a redundant manipulator system. The computational burden was minimized by restricting inverse kinematics to within each module. Advantages of the approach taken were the ease of implementation of obstacle avoidance, reconfigurability and fault tolerance. Having firstly simulated a MATLAB version of stable motion using MDC on a modular manipulator with up to six identical modules, the technique was extended with state space analysis to redefine the limits of stable control of a hyper-redundant manipulator. The MDC study mapped motion profile types that were dependant on the initial manipulator configuration and goal position and, thereby, investigated possible instabilities in the system. A two-link, single degree of freedom system was initially explicated followed by an extension of the stability analysis to an n-module two degree of freedom system. A stability theory utilizing decentralized control was formed. Simulation results showed dynamic motion, path generation and obstacle avoidance capabilities in unmapped environments to be stable. The modeling redefined the bounds of stable control, showing that classical stability via Root Locus, now required only two roots from the characteristic equation to be stable for a selection of path trajectory to the goal to be found. The remaining roots could be unstable in traversing to the goal and settling at a marginal stability point when the goal was reached. The marginal stability was a reflection of the pseudo-independence given to each module in seeking the goal and differed radically from a standard Root Locus analysis and interpretation of stability. A hyper-redundant Reconfigurable Modular Manipulator System (RMMS) was designed and built to implement the MDC technique in a real world environment. From an initial design, five modules were constructed and control algorithms embedded appropriate to their position in a five-segment robotic manipulator. A stereoscopic vision system was attached to the end of the manipulator which supplied real time data on a goal in 3D Cartesian space. The data was supplied to the first module of the arm and subsequently to all others by localized homogenous transformation. The manipulator was tested for goal seeking, path following, obstacle avoidance, fault tolerance and reconfigurability. The arm produced stable motion and satisfied the criteria as hypothesized in the theory.

Doctor of Philosophy (Economics) / Auctions are an ancient economic institution. Since Vickrey (1961), the development of auction theory has lead to an extremely detailed description of the often desirable characteristics of these simple selling procedures, in the process explaining their enduring popularity. Given the pervasiveness of auctions, the question of how a seller should engineer the rules of these mechanisms to maximize her own profits is a central issue in the organization of markets. The seminal paper of Myerson (1981) shows that when facing buyers with Independent Private Values (IPVs) a standard auction with a specifically selected reserve price (or prices) is optimal, that is, maximizes a seller's expected profits among all conceivable selling mechanisms. In this model, it is assumed that the buyers have perfect information as to the existence of gains from trade. We shall argue that the consequences of this assumption for the design of the optimal auction are not well understood, which motivates our analysis. The three essays of this thesis relax the `known seller valuation' assumption by examining the optimal auction program when the seller (and principal) holds private information representing her reservation value for the good. In the first essay we provide an original technique for comparing ex ante expected profits across mechanisms for a seller facing N>1 potential buyers when all traders hold private information. Our technique addresses mechanisms that cannot be ranked point-by-point through their allocation rules using the Revenue Equivalence Theorem. We find conditions such that the seller's expected profits increase in the slope of each buyer's allocation probability function. This provides new intuition for the fact that a principal does not benefit from holding private information under risk neutrality. Monopoly pricing induces steep probability functions so the seller/principal benefits from announcing a fixed price, and implicitly her private information. An application is presented for the well known k double auction of the bilateral trade literature. In the second and third essays of this thesis, we extend the above framework to allow for informational externalities. Specifically, we allow for the situation in which the seller's private information represents a common value component in buyers' valuations. Thus the seller's private information (say regarding the quality of the good) is of interest to bidders independently of any strategic effects. In recent work Cai, Riley and Ye (2007) have demonstrated that a seller who holds private information about the quality of a good faces an extra consideration in designing an auction; the reserve price signals information to bidders. In a separating equilibrium signalling is costly in the sense that reserves are higher than would be optimal under complete information. We examine the returns to the seller in an English auction from using different types of secret reserve regimes. We find that immediate disclosure of a reserve is preferable to announcement after the auction in the form of a take-it-or-leave-it offer to the winning bidder. Sale occurs less often during the auction for a given reserve price strategy under secret reserve regimes, which increases the incentive for the seller to report more favourable information though the reserve price offer. Separating equilibria involving later announcement therefore generate even lower expected profits to the seller (signalling is more costly) than under immediate disclosure. In the third essay we compare the benchmark signalling equilibrium of immediate disclosure to a screening regime which we call the Right of Refusal. In this extreme form of a secret reserve the seller never announces the reserve price, she simply accepts or rejects the auction price. We find that the Right of Refusal dominates immediate disclosure if the seller's valuation is a sufficient statistic for the private information of interest. Thus a seller with market-relevant private preference information can benefit from not exercising monopoly price setting power. The result also provides conditions under which a competitive screening equilibrium is more efficient than a signalling mechanism. Broadly speaking, screening is better when the common value aspect in the preferences of the informed and uninformed parties are `aligned', and potential gains from trade to the uninformed party are significant. We believe this conclusion to be of particular interest to the design of privatization schemes.

Thesis (M.S.)--Ohio University, June, 2001. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, March, 1999. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, November, 2002. / Title from PDF t.p. Includes bibliographical references (leaves 77-79).

Thesis (M.S.)--Ohio University, June, 1997. / Title from PDF t.p.