Quality-weld parameters for microwelding techniques and equipment

Limited-amplitude, controlled-decay process improves the reliability of microwelding. The system consists in building a capacitor-discharge welder for control of the shape of the weld pulse. Standard welders may be modified

Intermolecular Forces and the Glass Transition

Random first order transition theory is used to determine the role of attractive and repulsive interactions in the dynamics of supercooled liquids. Self-consistent phonon theory, an approximate mean field treatment consistent with random first order transition theory, is used to treat individual glassy configurations, while the liquid phase is treated using common liquid state approximations. The transition temperature $T^{*}_{A}$, the temperature where the onset of activated behavior is predicted by mean field theory, the lower crossover temperature $T_{c}^{*}$ where barrierless motions actually occur through fractal or stringy motions, and $T^{*}_{K}$, the Kauzmann temperature, are calculated in addition to $T^{*}_{g}$, the glass transition temperature that corresponds to laboratory cooling rates. Both the isobaric and isochoric behavior in the supercooled regime are studied, providing results for $\Delta C_{V}$ and $\Delta C_{p}$ that can be used to calculate the fragility as a function of density and pressure, respectively. The predicted variations in the $\alpha$-relaxation time with temperature and density conform to the empirical density-temperature scaling relations found by Casalini and Roland. We thereby demonstrate the microscopic origin of their observations. Finally, the relationship first suggested by Sastry between the spinodal temperature and the Kauzmann temperatures, as a function of density, is examined. The present microscopic calculations support the existence of an intersection of these two temperatures at sufficiently low temperatures.Comment: Submitted to J. Phys. Chem. A, June 2007 Replaced with accepted version Sept. 200

Flight testing the fixed-wing configuration of the Rotor Systems Research Aircraft (RSRA)

The Rotor Systems Research Aircraft (RSRA) is a unique research aircraft designed to flight test advanced helicopter rotor system. Its principal flight test configuration is as a compound helicopter. The fixed wing configuration of the RSRA was primarily considered an energy fly-home mode in the event it became necessary to sever an unstable rotor system in flight. While it had always been planned to flight test the fixed wing configuration, the selection of the RSRA as the flight test bed for the X-wing rotor accelerated this schedule. This paper discusses the build-up to, and the test of, the RSRA fixed wing configuration. It is written primarily from the test pilot's perspective

Quality weld parameters for microwelding techniques and equipment Final report

Amplitude controlled welding process for electronic circuit module

Study of cryogenic propellant systems for loading the space shuttle

Computer programs were written to model the liquid oxygen loading system for the space shuttle. The programs allow selection of input data through graphic displays which schematically depict the part of the system being modeled. The computed output is also displayed in the form of graphs and printed messages. Any one of six computation options may be selected. The first four of these pertain to thermal stresses, pressure surges, cooldown times, flow rates and pressures during cooldown. Options five and six deal with possible water hammer effects due to closing of valves, steady flow and transient response to changes in operating conditions after cooldown. Procedures are given for operation of the graphic display unit and minicomputer

On the Theory of Killing Orbits in Space-Time

This paper gives a theoretical discussion of the orbits and isotropies which arise in a space-time which admits a Lie algebra of Killing vector fields. The submanifold structure of the orbits is explored together with their induced Killing vector structure. A general decomposition of a space-time in terms of the nature and dimension of its orbits is given and the concept of stability and instability for orbits introduced. A general relation is shown linking the dimensions of the Killing algebra, the orbits and the isotropies. The well-behaved nature of "stable" orbits and the possible miss-behaviour of the "unstable" ones is pointed out and, in particular, the fact that independent Killing vector fields in space-time may not induce independent such vector fields on unstable orbits. Several examples are presented to exhibit these features. Finally, an appendix is given which revisits and attempts to clarify the well-known theorem of Fubini on the dimension of Killing orbits.Comment: Latex, 19 pages, no figur

Self-similar static solutions admitting a two-space of constant curvature

A recent result by Haggag and Hajj-Boutros is reviewed within the framework of self-similar space-times, extending, in some sense, their results and presenting a family of metrics consisting of all the static spherically symmetric perfect fluid solutions admitting a homothety.Comment: 6 page

The provision of technical education in Sunderland prior to 1908

The period dealt with by this survey is from 1825 to 1908, those being the dates, respectively, of the first foundation of the Sunderland mechanics’ Institutes and the end of the first phase of Sunderland technical college’s development. The mechanics institute, which was declining by 1856, was succeeded, in 1855, by a navigation school which operated under south konoington regulations until 1864. That year, a science and art school, established in 1861, was closed, and another was opened in 1869. This last developed into a central school of art and science offering dry and evening courses, maintained a continuous existence for nearly forty years; and evolved into two major institutions for art and technical education respectively. From 1873 onwards the work of this school was supplemented by varying members of science and art evening classes provided mainly through private enterprises. The development of these institutions is traced in detail- with particular performance to such questions as the type of instruction given and by who, the subjects taken, contemporary view on technical education, methods of administration, and the status of teachers- against the background of nineteenth century economic development in Sunderland and in relation to development on the national scene. The local development dealt with show clearly the change of public opinion with regard to provision of technical education facilities that take place during periods. Such provision, during most of the nineteenth century was regarded as the concern of private enterprise, but by 1903, local authority provision dominated the field. The local administrative reorganisation which accepted this change of view is also dealt with. The survey concluded by driving general conclusions about such matters as the curriculum, the types and numbers of students, their motive for attendances, accuses of expansion and the aims of technical education during the period