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There are many parameters that significantly affect the electrical performance of ceramic-core superconducting composite wire and tapes, which remain ambiguous and require more labor on their optimization. BSCCO 2212 has not been paid the attention and investment it deserves. In this regard, all optimization efforts were made for BSCCO 2223. In our work, a practical and inexpensive manufacturing method, thermally and mechanically optimized for Pb doped BiSrCaCuO 2212 superconducting multifilament (38 filaments) wires and tapes, was successfully employed. Optimized parameters can be classified under material, mechanical (deformation) and heat treatment (thermal) subgroups. Parameters involved with materials included investigation of deformation behavior of two different sheath metals; pure silver and 0.02% magnesia dispersion reinforced silver alloy. Pb doped BiSrCaCuO 2212 ceramic superconductor powder, the other source of material related parameters, was synthesized following the "Thermal Co-decomposition or Wet Mix" method. Fabrication of mono and multifilament wires with Oxide Powder in Tube (OPIT) method followed next. Optimization of drawing deformation was practiced to achieve the best ceramic grain alignment and smoother ceramic powder core/metal sheath interface in order to avoid "sausaging" in wires. Rolling of the wire products into tapes by following different deformation regimes was the other manufacturing stage of the project. Variable and constant reduction-per-pass deformation paths were employed to reveal their effects on our composites with distinct sheath material and filament formation. The search for the best (optimum) heat treatment schedule for our Bi2212 superconductor composites, a modified version of "step solidification partial melting", was employed successfully. A solution through tried recipes for the bubbling problem that occurred with our tapes was also addressed. Electrical performance tests of fully reacted wires were carried out in our laboratory and very promising results were attained.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 129-132). Also available in electronic version. Access restricted to campus users.

Objective: To assess the mechanical effects of nickel-titanium orthodontic archwire flaming and their distribution along the wire. Methodology: Two sizes of pre-formed austenitic nickel-titanium archwires were tested (n=10). The terminal 5mm of each wire was heated for five seconds using a butane lighter. Micro-hardness testing was used to determine the heat-affected zone for all wires. Cantilever bending was performed to assess the mechanical properties of heated wires. Results: The heat-affected zone was found to extend less than 2 mm past the flame boundary for all wires. For each wire gauge, the flamed zone was characterized by a lower and flatter super-elastic plateau and an increased tendency for plastic deformation when compared to controls. Conclusions: The limited ability of austenitic nickel-titanium orthodontic archwires to conduct heat past the boundary of the flamed region suggests no need to alter current clinical practice.

Objective: To assess the mechanical effects of nickel-titanium orthodontic archwire flaming and their distribution along the wire. Methodology: Two sizes of pre-formed austenitic nickel-titanium archwires were tested (n=10). The terminal 5mm of each wire was heated for five seconds using a butane lighter. Micro-hardness testing was used to determine the heat-affected zone for all wires. Cantilever bending was performed to assess the mechanical properties of heated wires. Results: The heat-affected zone was found to extend less than 2 mm past the flame boundary for all wires. For each wire gauge, the flamed zone was characterized by a lower and flatter super-elastic plateau and an increased tendency for plastic deformation when compared to controls. Conclusions: The limited ability of austenitic nickel-titanium orthodontic archwires to conduct heat past the boundary of the flamed region suggests no need to alter current clinical practice.

This thesis focuses on the methods and results of the workspace formulation of wire-actuated parallel manipulators. Four methods of workspace generation are studied. The null space method, based on the calculation of wire tensions, is used to formulate the workspaces of example manipulators. The results of this method are used to verify the results of the following methods. This thesis presents that the convex hull workspace formulation method, a geometric analysis of the manipulator’s Jacobian matrix, can be extended to manipulators that have an external wrench and/or gravity applied to the mobile platform. The convex hull method is applied to the example manipulators investigated with the null space method. The workspace envelope characterization, an analytical approach of defining the borders of the workspace using the formulation of the kernel of the manipulator’s Jacobian matrix, is applied to the example planar manipulators investigated with the previous methods. A new process, presented in this thesis, of identifying the contribution of each set of four wires/forces of a planar manipulator allows the workspace envelope characterization to be applied to redundant planar manipulators and planar manipulators that have an external wrench and/or gravity applied to the mobile platform. The discrete and analytical antipodal methods, based on theorems from multi-fingered grasping manipulators, are presented and applied to the example planar manipulators investigated with the previous methods. This research generalizes the use of these theorems, which determine wrench-closure poses of planar four-wire manipulators that share wire-connection points on the base or mobile platform, to the discrete and analytical workspace formulation of planar three-degree-of-freedom wire-actuated manipulators with no restrictions on the number of wires or the configuration of the manipulator. Comparing all methods investigated in this thesis, the null space method results in the workspace that takes into account the maximum and minimum wire tensions and is recommended for use in the design of both spatial and planar wire-actuated parallel manipulators. All the other methods presented in this thesis, have similar results when compared to the null space method but formulate the maximum workspace which assumes the wires can operate with very high to infinite wire tension. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-10-14 09:02:25.562

No description available.

This thesis describes the development and testing of two apparatuses; a vibrating wire viscometer to measure the viscosity of fluids over a wide range of temperature and pressure; and a microwave cavity resonator to measure dew points, gas phase densities, and liquid drop out volumes. Viscosity and density of downhole fluids are very important properties as their values can determine the economic viability of a petroleum reservoir. A vibrating wire viscometer has been developed with an electrically insulating tensioning mechanism. It has been used with two wires, of diameters (0.05 and 0.150) mm, to measure the viscosity of methylbenzene and two reference fluids with viscosities of (10 and 100) mPa·s at T = 298 K and p = 0.1 MPa, at temperatures in the range (298 to 373) K and pressures up to 40 MPa, where the viscosity covers the range (0.3 to 100) mPa·s, with a standard uncertainty < 0.6 %. The results differ from literature values by < ±1 %. The results demonstrate that increasing the wire diameter increases the upper operating viscosity range of the vibrating wire viscometer, a result anticipated from the working equations. For the microwave cavity resonator, the method is based on the measurements of the resonance frequency of the lowest order inductive-capacitance mode. The apparatus is capable of operating at temperatures up to 473 K and pressures below 20 MPa. This instrument has been used to measure the dew pressures of {0.4026CH4 + 0.5974C3H8} at a temperature range from 315 K up to the cricondentherm ˜ 340 K. The measured dew pressures differ by less than 0.5 % from values obtained by interpolation of those reported in the literature, which were determined from measurements with experimental techniques that have quite different potential sources of systematic error than the radio-frequency resonator used here. Dew pressures estimated from both NIST 14 and the Peng-Robinson equation of state lie within < ±1 % of the present results at temperature between (315 and 337) K while predictions obtained from the Soave-Redlich-Kwong cubic equation of state deviate from our results by 0.4 % at T = 315 K and these differences increase smoothly with increasing temperature to be -2.4 % at T = 337 K. Densities derived from dielectric permittivity measurements in the gas phase lie within < 0.6 % of the values calculated from the Soave-Redlich-Kwong cubic equation of state and about 1 % from values obtained with the Harvey and Prausnitz correlation based on a mixture reduced density. The calculations with Kiselev and Ely parametric crossover equation of state (based on Patel-Teja EOS) gave deviations < 0.7 %. Liquid volume fractions, in the 2-phase region, were measured from (0.5 to 7) cm3 in a total volume of about 50 cm3 at different isochors. The measured liquid volume fractions differ from values obtained with the Soave-Redlich-Kwong cubic equation of state by between 0 and 3 % at T < 326 K and about 8 % on approach to the critical region. The large deviations observed in the critical region were anticipated because of the known poor performance of the cubic equations of state with regard to the calculation of the liquid density in the vicinity of the critical temperature.

No description available.