International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / The Army development and test community must demonstrate the functionality and reliability of gun-launched projectiles and munitions systems, especially newer smart munitions. The best method to satisfy this requirement is to combine existing optical and tracking systems data with internal data measured with on-board instrumentation (i.e. spin, pitch, and yaw measurements for standard items and terminal sensor, signal processor, and guidance/navigation system monitoring for smart munitions). Acquisition of internal data is usually limited by available space, harsh launch environments, and high associated costs. A technology development and demonstration effort is underway to provide a new generation of products for use in this high-g arena. This paper describes the goals, objectives, and progress of the Hardened Subminiature Telemetry and Sensor System (HSTSS) program.

The emerging need for smart and wearable electronic systems are driving new electronics technology paradigms in miniaturization, functionality and cost.The operating voltages and power levels for devices in these systems are becoming increasingly varied with increased diversity of devices to serve these heterogeneous functions. Power convertor technologies are incorporated into various parts of these systems to step-up or step-down battery voltages and currents to address these diverse needs. Hence, multiple power converters, each requiring several passive components, are used to create stable power-supplies. This is placing significant challenges in ultra-miniaturized and ultra-efficient power management technologies. A typical power convertor consists of magnetic components such as inductors perform the basic energy storage and delivery functions from the source to the load. These power components are still at microscale in lithography and milliscale in component size. They occupy a large volume fraction of the power circuitry. Power convertors therefore, are a major bottleneck to system miniaturization. There is, thus, a need for ultra-miniaturized and high-performance power inductors for scaling down such power convertors. The critical parameters governing the size and performance of power inductors are its inductance density and power handling capability. These parameters are limited by the magnetic properties of the present inductor core materials. A new approach to inductor cores that achieves the best magnetic properties and yet allows integration of power inductors into ultra-thin substrates to meet the emerging needs for performance and size is therefore required. The objective of this research is to model, design and synthesize a novel multilayered ferromagnetic-polymer composite structure for inductor cores with high permeability and saturation magnetization.The multilayered composite structure consists of thin magnetic layers interspersed with ultra-thin polymers. A fabrication approach to integrate the composite structure in inductor devices is also demonstrated.

<p> In this thesis, we develop manifestly covariant methods for 4 dimensional, <i> N</i> = 1 superconformal field theories. First, we generalize the embedding formalism in conformal field theories (CFTs) to <i>N</i> = 1 superconformal field theories (SCFTs). As applications we construct manifestly superconformally covariant expressions for land 3-point correlation functions involving the supercurrent multiplet or the global symmetry current superfield. Next, we combine this superembedding formalism with the shadow formalism in CFTs into a new method for computing superconformal blocks appearing in 4-point functions of SCFTs. This new method, called the supershadow formalism, expresses a superconformal block as manifestly covariant integrations over a product of 3-point functions. The supershadow formalism is much more efficient computationally than the brute force methods used previously in the literature. We obtain the superconformal blocks appearing in the 4-point functions of general scalar operator and then specialize to the 4-point functions involving chiral and global symmetry current multiplets. The results in the chiral case can be further generalized to <i> N</i> = 2 SCFTs. Finally, we present a systematic algorithm to extract the correlation functions of conformal primary component operators from the superfield correlation functions. We implemented this algorithm in <i> Mathematica</i> and applied it to the superfield 2-point function between general operators, from which we obtain all the component 2-point functions and all possible shortening conditions for a <i>N</i> = 1 superconformal multiplet. We also discuss a few potential directions for future researches. </p>

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

The interfacial properties of a surfactant in a CO₂-aqueous system at a temperature above 100 °C, and how they influence foams are essentially unknown. A cationic surfactant, C₁₂₋₁₄N(EO)₂ in the protonated state below pH 5.5, was demonstrated to be soluble in an aqueous phase with up to 22% total dissolved salt (TDS) at 120 °C. Moreover, the strong solvation in brine (high cloud point) and simultaneous affinity for CO₂ led to significant adsorption of the surfactant at the CO₂-water interface. Given that the surfactant favored the brine phase over the CO₂ phase, the preferred curvature was a CO₂-in-water (C/W) macroemulsion (foam). The surfactant stabilized foam in the presence of crushed calcium carbonate at ~ pH 4 upon suppressing the dissolution of calcium carbonate upon addition of Ca²⁺ and Mg²⁺ according to the common ion effect. Cationic alkyltrimethylammonium surfactants with an alkyl tail of average carbon number less than 15 were soluble in 22% TDS brine up to 120 oC. The head group was properly balanced with a C₁₂₋₁₄ hydrocarbon tail for a sufficiently dense surfactant layer at the CO₂-water interface to reduce the interfacial tension. For C₁₂₋₁₄N(CH₃)₃Cl the solubility in brine and the surfactant adsorption were sufficient to stabilize C/W foam at 120 °C in both a crushed calcium carbonate packed bed (76 Darcy) and a capillary tube at the downstream of the bed. The stability of the foam at high temperature may be attributed to the high surfactant adsorption at the interface. The use of nonionic surfactants as a foam stabilizer is usually limited by their poor aqueous solubility at elevated temperatures, particularly at high salinity. A nonionic surfactant C₁₂₋₁₄(EO)₂₂ with high degree of ethoxylation gave higher salt tolerance at elevated temperature. The surfactant stabilize C/W foam at 80 °C in the presence of 90 g/L NaCl brine in a 30 Darcy sand pack, which has not yet been reported by a nonionic surfactant. Both the formation of strong foam in the porous media and the low of oil-brine partition coefficient suggest C₁₂₋₁₄(EO)₂₂ is a potential candidate for a CO₂ EOR field trial. / text

<p>In this thesis, we propose and analyze a fast method for computing the solution of the Helmholtz equation in a bounded domain with a variable wave speed function. The method is based on wave splitting. The Helmholtz equation is first split into one--way wave equations which are then solved iteratively for a given tolerance. The source functions depend on the wave speed function and on the solutions of the one--way wave equations from the previous iteration. The solution of the Helmholtz equation is then approximated by the sum of the one--way solutions at every iteration. To improve the computational cost, the source functions are thresholded and in the domain where they are equal to zero, the one--way wave equations are solved with GO with a computational cost independent of the frequency. Elsewhere, the equations are fully resolved with a Runge-Kutta method. We have been able to show rigorously in one dimension that the algorithm is convergent and that for fixed accuracy, the computational cost is just O(ω^1/p) for a p-th order Runge-Kutta method. This has been confirmed by numerical experiments.</p>

High alloy Fe-Cr-Ni-C austenitic stainless steels have become the principal alloys for use in steam-methane reforming furnaces within the petrochemical industry. Each furnace contains a large array of vertically oriented centrifugally cast tubes through which a mixture of methane and steam is flowed across a nickel-oxide catalyst in order to obtain a mixture of hydrogen, carbon monoxide and carbon dioxide and water commonly known as synthesis gas (or syngas). Generally, the tubes operate at temperatures between 850-1050°C, internal pressures between 1-3.5MPa and are expected to withstand service lives in excess of 100,000 hours. The combination of high temperatures and moderate stresses causes creep to be the dominant failure mechanism experienced by these tubes in service. The HP austenitic alloys are the latest in a series of heat resisting (H-series) stainless steels developed to provide high temperature strength, ductility, and corrosion resistance in the oxygen, carbon, and sulphur rich environments typical of these furnaces. Extensive work has been carried out to optimise HP alloys’ microstructure in order to maximise the alloy’s creep resistance. Strength increases have largely been realized through the use of niobium and/or titanium additions, which modify the primary precipitates (formed during solidification) and secondary precipitates (formed during exposure to the service temperatures). These strength increases have typically been observed during laboratory accelerated creep testing of the ‘modified’ HP alloys where the temperature and/or stress is increased to achieve failure of the material within reasonable time period (typically between 1000-2000 hours). However, since the duration of typical accelerated creep tests often represent less than 2% of the tubes’ actual service life, uncertainty surrounds the validity of using this testing method as the basis to predict the tubes actual service life. This uncertainty has largely arisen due to the significant microstructural evolution that occurs within these alloys during prolonged service exposure and is not captured within the typical accelerated testing time-frame. In the present work, the microstructures of HP alloys modified with a single addition of niobium (HP-Nb) and dual additions of niobium and titanium (HP-NbTi) have been characterized in the as-cast condition and after long-term (10,000 hours) isothermal laboratory ageing at 1000, 1050 and 1100°C. The main focus of this study is to provide further insight into the microstructural features that increase the HP-NbTi alloy’s creep resistance in comparison to the HP-Nb alloy when performing accelerated creep testing and determine if these microstructural features remain stable during long-term ageing. The microstructure and crystallography of the primary and secondary precipitates in each alloy have been studied in detail using light optical microscopy, high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (EBSD, SAD and CBED), Powder X-ray Diffraction and energy dispersive X-ray spectroscopy. Specific attention has been paid to the niobium-rich and niobium-titanium-rich phases that form as a direct result of HP alloy’s modification with niobium and titanium. The current research is part of a wider project conducted in collaboration with Quest Integrity Group Ltd. (Wellington, New Zealand) that aims to characterize the microstructural and mechanical properties of the HP-Nb and HP-NbTi alloys during long-term service exposure. The microstructural characterization presented in this thesis will subsequently be used by Quest Integrity Group to build a comprehensive understanding of the relationship between HP-Nb and HP-NbTi alloy’s microstructure and creep properties. This understanding will allow Quest Integrity Group to more accurately predict the service life of HP-Nb and HP-NbTi alloy tubes within steam-methane reforming furnaces.

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