Commercial superalloys like Rene88DT are used in high temperature applications like turbine disk in aircraft jet engines due to their excellent high temperature properties, including strength, ductility, improved fracture toughness, fatigue resistance, enhanced creep and oxidation resistance. Typically this alloy's microstructure has L12-ordered precipitates dispersed in disordered face-centered cubic γ matrix. A typical industrially relevant heat-treatment often leads to the formation of multiple size ranges of γ¢ precipitates presumably arising from multiple nucleation bursts during the continuous cooling process. The morphology and distribution of these γ′ precipitates inside γ matrix influences the mechanical properties of these materials. Therefore, the study of thermodynamic and kinetic factors influencing the evolution of these precipitates and subsequent effects is both relevant for commercial applications as well as for a fundamental understanding of the underlying phase transformations. The present research is primarily focused on understanding the mechanism of formation of different generations of γ′ precipitates during continuous cooling by coupling scanning electron microscopy (SEM), energy filtered TEM and atom probe tomography (APT). In addition, the phase transformations leading to nucleation of γ′ phase has been a topic of controversy for decades. The present work, for the first time, gives a novel insight into the mechanism of order-disorder transformations and associated phase separation processes at atomistic length scales, by coupling high angle annular dark field (HAADF) - STEM imaging and APT. The results indicate that multiple competing mechanisms can operate during a single continuous cooling process leading to different generations of γ′ including a non-classical mechanism, operative at large undercoolings.

The need for the study arises from the assumption that the present liaison mechanism between architects in the private sector and the Transvaal Provincial Administration is deficient. The weaknesses are defined and presented by way of sub-problems and hypotheses arising therefrom. In order to limit the extent of the research and investigations, the study is confined to the liaison mechanism relating to primary schools only, within the Province of Transvaal. The data have been obtained from replies to questionnaires received from selected but individually unidentifiable architects in private practice as well as from answers to a standard set of questions verbally put to officials in various State departments. To further illustrate weaknesses in briefing and communication, a few case histories have been described. The assessment by related literature has largely been confined to the views of educationists, sociologists, economists and architects. In essence, these views accentuated the importance of sound communication, role expectation and role perception amongst the professionals representing the various disciplines engaged in the need for design and construction of educational buildings. Related literature leaves no doubt as to the importance of correct selection and acceptance of the architect as the leader of the professional team. A detailed investigation of the present liaison mechanism clearly reveals the areas of weakness which consequently affect efficiency as well as the steps that can be taken to improve the efficacy of the liaison mechanism. The progressive stages of a project from its inception to its completion are discussed in strict chronological order and in detail, leaving no doubt as to where the delays can and do occur. In conclusion, an effort is made to pinpoint the areas which need attention. Recommendations are also suggested in regard to eliminating any misunderstandings in role perception and expectation, and for the improvement and accuracy of the initial briefing. / Dissertation (MA))--University of Pretoria, 1983. / Digitised by the University of Pretoria, Library Services, 2012 / Architecture / unrestricted

In this project, the synthesis of carbon encapsulated copper nanoparticles using sustainable bioproducts as raw material was systematically studied. The synthesis mechanism, process parameters, and functionalization of carbon encapsulated copper nanoparticles were well established. In a preliminary study, carbon encapsulated copper nanoparticles were successfully synthesized at 1000 ºC, 1h, 20 ºC/min, and 1800 sccm argon gas flow rate using BCL-DI lignin as the carbon source. Carbon encapsulated copper nanoparticles were mainly located at defect sites. Copper was found not tightly encapsulated by graphene shells. The carbon encapsulated copper nanoparticles were uniformly distributed. The conversion of copper ions into copper atoms occurred at above 300 ºC, with the company of decomposition of BCL-DI lignin into CO, CO2, and hydrocarbon gases. The growth of graphene layers was proposed to start above 300 ºC. TEM images illustrated the onset of growth of graphene at the edge of the surface at 400 ºC, and the formation of graphene bands at 500 ºC. Copper catalyst continued to facilitate the decomposition of lignin functional groups at 600 ºC. Further increasing the temperature retarded the degradation of lignin, while assisted the reconstruction of the defective sites of the graphene layers, producing higher quality products. Plastic film phase of lignin dominated on the synthesis of carbon encapsulated copper nanoparticles, while gaseous phase had little impact. The orthogonal experiment revealed that temperature played the most important role in the growth of graphene: high temperature was preferred in order to obtain less defective sites. The optimum synthesis parameters were suggested as 1000 °C, 30 min duration time, 20 °C/min temperature rising ramp, and 1200 sccm argon gas flow rate. Post heat treatment was proved to be a feasible way to improve the crystallinity of graphite. Amorphous carbon was removed or converted into crystalline graphite under heat and oxygen. FTIR spectra confirmed the covalent linkages between carbon encapsulated copper nanoparticles and N-methyl-2-pyrrolidone and polyvinylpyrrolidone, indicating a successful functionalization. This study has presented a homogeneous carbon encapsulated copper nanoparticles solution in water and ethanol, and paved ways for further functionalization of CECNs.

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In this thesis photoluminescence measurements were made on ZnS:Mn thin-films with different concentration of Mn in order to observe the phenomenon of concentration quenching. A mathematical model, based on migration of energy among Mn centres and subsequent transfer to traps, is proposed to explain it. Probability of energy transfer to traps is considered independent of Mn concentration. It is consistent with experimental evidence reported in literature. Using this model we can give physical interpretation to the empirical decay-law for luminescence of Mn centres n(t) =n(0)exp[ - (t/r)a ] , where j and a change with Mn concentration. We are able to quantify the probability of energy loss to traps using Dexter's equation for dipole-dipole transfer. It is suggested that energy loss to the traps can be influenced by growth technique. / Thesis / Master of Engineering (ME)

Existing state-of-the-art legged robots often require complex mechanisms with multi-level controllers and computationally expensive algorithms. Part of this is owed to the multiple degrees of freedom (DOFs) these intricate mechanisms possess and the other is a result of the complex nature of dynamic legged locomotion. The underlying dynamics of this class of non-linear systems must be addressed in order to develop systems that perform natural human/animal-like locomotion. However, there are no stringent rules for the number of DOFs in a system; this is merely a matter of the locomotion requirements of the system. In general, most systems designed for dynamic locomotion consist of multiple actuators per leg to address the balance and locomotion tasks simultaneously. In contrast, this research hypothesizes the decoupling of locomotion and balance by omitting the DOFs whose primary purpose is dynamic disturbance rejection to enable a far simplified mechanical design for the legged system. This thesis presents a novel single DOF mechanism that is topologically arranged to execute a trajectory conducive to dynamic locomotive gaits. To simplify the problem of dynamic balancing, the mechanism is designed to be utilized in a quadrupedal platform in the future. The preliminary design, based upon heuristic link lengths, is presented and subjected to kinematic analysis to evaluate the resulting trajectory. To improve the result and to analyze the effect of key link lengths, sensitivity analysis is then performed. Further, a reference trajectory is established and a parametric optimization over the design space is performed to drive the system to an optimal configuration. The evolved design is identified as the Bio-Inspired One-DOF Leg for Trotting (BOLT). The dynamics of this closed kinematic chain mechanism is then simplified, resulting in a minimal order state space representation. A prototype of the robotic leg was integrated and mounted on a treadmill rig to perform various experiments. Finally, open loop running is implemented on the integrated prototype demonstrating the locomotive performance of BOLT. / MS / Existing state-of-the-art legged robots often require complex mechanisms with multi-level controllers and computationally expensive algorithms. Part of this is owed to the multiple degrees of freedom (DOFs) these intricate mechanisms possess and the other is a result of the complex nature of dynamic legged locomotion. The underlying dynamics of this class of non-linear systems must be addressed in order to develop systems that perform natural human/animal-like locomotion. However, the number of active DOF is merely a designers choice. To simplify the problem at both levels: design and controls of dynamic locomotion, we developed a novel mechanism that incorporates the benefits of higher DOF legs while accommodating the simplicity of single DOF leg. The preliminary design of the mechanism was designed with parameters (lengths of the femur,tibia) that were directly derived from a domestic dog. Synthesis of the mechanism suggested that the design was not suitable for an intended running-trot gait observed in biological counterparts. However, to gain a deeper understanding of the mechanism, it was necessary to perform a sensitivity analysis, as a result we arrived at a mechanism whose performance was better than the initial but still not satisfactory.With the insight gained through the analysis and an ideal gait design exercise, then an optimization on the design space was performed with carefully tuned bounds. The final result is a novel mechanism identified as Biologically inspired One DOF Leg for Trotting (BOLT) that is topologically arranged to execute a running-trot gait. Finally, the design choice presented with a challenge that has not been actively addressed. The dynamics of the mechanism can not be modeled using traditional methods due to presence of constraints that characterize the closed loops of the mechanism. We present an adaption of the Singularly perturbed dynamic model for systems that are hybrid in nature. The resulting dynamics are simplified, resulting in a minimal order state space representation, which is more amenable to model based control development in future. A prototype of the robotic leg was integrated and mounted on a treadmill rig to perform various experiments.Finally, open loop running is implemented on the integrated prototype demonstrating the locomotive performance of BOLT.

<p>I characterize optimal long term contracts offered by a monopolist to a buyer whose private valuation evolves according to a branching process with privately known transition probability. The optimal contract can be implemented in a simple way, and presents the buyer with a tradeoff between a high initial fixed fee and low future prices. In an interaction with a long time horizon, the relationship will terminate prematurely with probability close to one. Optimal mechanisms are quite different from models in which the transition probability is known, and the buyer's private information is his initial valuation. Optimal contracts resemble the structure of term life insurance contracts, and have features similar to actual interactions between retailers and suppliers.</p> / Dissertation

The administrative reform in all of the countries, all depends on via "the government reform" making the government performance results able to improve, and the government service outsourcing has become the most important strategy for government reform. Along with the rapid development of the information tech, and the popularization of the applications, introducing information tech to the government service of the high-efficiency, low cost, flexibility, fast response is the basic conditions for the modern government forging ahead into 21 centuries. "The government information service outsourcing" results in how to establish availably amid in the "partner relationship" a new topic in the long term, as well as under the condition of parts of information service providers lacking of the information professional knowledge with government agency to the government service. How to construct and lead to a "cooperation mechanism" strategic goal and reinforces efficiency is a successful key point to the outsourcing. The target of "cooperation mechanism" is "the management of the conflict" in the aspects of negatively, in addition to solving the conflicts that have appeared, also ought to think twice about the reason of the conflict, and avoid the possible conflicts. In the aspects of aggressively, it is to "move forward towards the whole target", whose aims consist in reaching to team up the goal availably. The purpose of the cooperation does not depend on the none of the conflicts, also, within the scope of cooperation. In other words, the cooperative "effectiveness" of one of both sides¡¦ achievement must meet with the following objectives in the meantime: first, it can't deviate from the whole goal; second, it must ensure to accomplish the whole objective benefits. Confronted with the conflicts appearing in the interval, this research proposes a new point of view as well as food for thoughts: ¡§Is there any chance these regarded as the reformed objects "bureaupathologies " cause critical factor of the conflict?". We refer to various organization theories and methods, originated from feeling have on the spot "examination mechanism", and we wish we could break through politician system constituent "black box" mode of every kind of "shell" block, and find out not appropriate "processing" hidden under the politician post authority. We expect to expel " bureaupathologies " to solve and reduce the development of the conflict. Now we think of Kaohsiung City property management system outsourcing as the individual cases study. We can illustrate practical manipulation inspection, propose the concrete conclusion and suggestions, and raise the capability of "Cooperation mechanism", in order to promote the success of ¡§government information service outsourcing".