First exact Geon found is a non-singular monopole, propagating as a primordial gravitational pp-wave

Geons are particle-like electrovacua. The concept is well-defined, but it still lacks a proper first example. Emerging as such is a self-confined exact 2-parameter pp-wave non-Dirac monopole {\cal G} with primordial Q/r^2 (r\geq r_o) field plus higher moments. {\cal G} has effective mass, independently-scaled NUT-like charge \kappa|Q|=2r_o as diameter, and spin. {\cal G} {\em cannot} have actual {\sc em} charge $Q$ (by \partial{\cal G}=0), Ricci-flat limits, nor spacetime or Dirac-string singularities, but Dirac's quantization condition holds. {\cal G}/2, as an upgraded `Kerr-Newman' alternative or {\cal S}_Q geon, carries actual charge Q confined by topology on a round-S^2[r_o] physical singularity on \partial{\cal S}_Q\neq0. {\cal G} and {\cal S}_Q offer exact analytic models in particle physics and cosmology, notably for primordial gravitational waves, inflation, and pre-galactic dynamics.Comment: 13 page

A new class of spatially homogeneous 4D string backgrounds

A new class of spatially homogeneous 4D string backgrounds, the $X(d\rightarrow)$ according to a recent classification, is presented and shown to contain only five generic types. In contrast to the case of $X(d\uparrow)$ (which contains as a subclass all possible FRW backgrounds), exact $SO(3)$ isotropy is always broken in the $X(d\rightarrow)$ class. This is due to the $H$-field, whose dual is necessarily along a principal direction of anisotropy. Nevertheless, FRW symmetry can be attained asymptotically for Bianchi-types $I$ and $VII_0$ in a rather appealing physical context. Other aspects of the solutions found for types $X=I,II,III,VI_{-1}$, and of the $VII_0$ case are briefly discussed.Comment: LaTeX, 13 pages, no figures

Bianchi-type string cosmology

Bianchi-type string cosmology involves generalizations of the FRW backgrounds with three transitive spacelike Killing symmetries, but without any a priori assumption of isotropy in the 3D sections of homogeneity. With emphasis on those cases with diagonal metrics and vanishing cosmological constant which which have not been previously examined in the literature, the present findings allow an overview and the classification of all Bianchi-type backgrounds. These string solutions (at least to lowest order in alpha prime) offer prototypes for the study of spatial anisotropy and its impact on the dynamics of the early universe.Comment: 12 pages, latex, 1 table, no figure

A performance and reliability model for thermal barrier coatings

A modeling technique for predicting the performance and reliability of TBC's is being developed at Solar Turbines Incorporated. The concept combines experimental coating property data with finite element analyses to predict the thermal and mechanical behavior of coating systems in service. A key feature of Solar's approach is the use of a four point flexure test to estimate coating strength distributions and to predict coating failure probability. This model was used to evaluate the effect of physical variations on coating performance in high heat flux rocket engine applications for NASA. Current work, promoted by Caterpillar Tractor Company for diesel engine applications, is being conducted to measure coating strength as a function of temperature, and future work will document strength degradation with time at temperature. Solar's interest lies in the application of TBCs to gas turbine engine components

General relativity reformed to a genuine Yang-Mills gauge theory for gravity

The theory of general relativity is reformed to a genuine Yang-Mills gauge theory of the Poincar\'e group for gravity. Several pathologies of the conventional theory are thus removed, but not every GR vacuum satisfies the Y-M equations. The sector of GR solutions which survive is fully classified and it is found to include the Schwarzschild black hole. Two other solutions presented here have no GR counterpart and they describe expanding Friedmann universes with torsion which vanishes only asymptotically. They are discussed along with novel theoretical possibilities, such as a well-defined energy-momentum tensor for the gravitational field, and novel perspectives for unification and quantization.Comment: Latex, 8pp, no figure

Rocket thrust chamber thermal barrier coatings

A research program was conducted to generate data and develop analytical techniques to predict the performance and reliability of ceramic thermal barrier coatings in high heat flux environments. A finite element model was used to analyze the thermomechanical behavior of coating systems in rocket thrust chambers. Candidate coating systems (using a copper substrate, NiCrAlY bond coat and ZrO2.8Y2O3 ceramic overcoat) were selected for detailed study based on photomicrographic evaluations of experimental test specimens. The effects of plasma spray application parameters on the material properties of these coatings were measured and the effects on coating performance evaluated using the finite element model. Coating design curves which define acceptable operating envelopes for seleted coating systems were constructed based on temperature and strain limitations. Spray gun power levels was found to have the most significant effect on coating structure. Three coating systems were selected for study using different power levels. Thermal conductivity, strain tolerance, density, and residual stress were measured for these coatings. Analyses indicated that extremely thin coatings ( 0.02 mm) are required to accommodate the high heat flux of a rocket thrust chamber and ensure structural integrity