General Electric

About: General Electric is a company organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Turbine & Rotor (electric). The organization has 76365 authors who have published 110557 publications receiving 1885108 citations. The organization is also known as: General Electric Company & GE.

On Finite Sample Distributions of Generalized Classical Linear Identifiability Test Statistics

Abstract: In the estimation of econometric simultaneous equations models, hypothesized necessary conditions for the identifiability of a single equation usually specify the exclusion of a number of variables from the structural equation in question. If the pre-determined variables are completely exogenous, if the disturbances in the equations are jointly normally distributed, and if a moderately high degree of precision can be obtained in reduced-form estimation, then the exact finite sample distribution of the generalized classical linear identifiability test statistic can be closely approximated by Snedecor's F with appropriate degrees of freedom.

Thermochemical Interaction of Thermal Barrier Coatings with Molten CaO–MgO–Al2O3–SiO2 (CMAS) Deposits

Abstract: Thermal barrier coatings (TBCs) are increasingly susceptible to degradation by molten calcium–magnesium alumino silicate (CMAS) deposits in advanced engines that operate at higher temperatures and in environments laden with siliceous debris. This paper investigates the thermochemical aspects of the degradation phenomena using a model CMAS composition and ZrO2–7.6%YO1.5 (7YSZ) grown by vapor deposition on alumina substrates. The changes in microstructure and chemistry are characterized after isothermal treatments of 4 h at 1200°–1400°C. It is found that CMAS rapidly penetrates the open structure of the coating as soon as melting occurs, whereupon the original 7YSZ dissolves in the CMAS and reprecipitates with a different morphology and composition that depends on the local melt chemistry. The attack is minimal in the bulk of the coating but severe near the surface and the interface with the substrate, which is also partially dissolved by the melt. The phase evolution is discussed in terms of available thermodynamic information.

Selecting uncertainty calculi and granularity: an experiment in trading-off precision and complexity

Abstract: The management of uncertainty in expert systems has usually been left to ad hoc representations and rules of combinations lacking either a sound theory or clear semantics. The objective of this paper is to establish a theoretical basis for defining the syntax and semantics of a small subset of calculi of uncertainty operating on a given term set of linguistic statements of likelihood. Each calculus will be defined by specifying a negation, a conjunction and a disjunction operator. Families of Triangular norms and conorms will provide the most general representations of conjunction and disjunction operators. These families provide us with a formalism for defining an infinite number of different calculi of uncertainty. The term set will define the uncertainty granularity, i.e. the finest level of distinction among different quantifications of uncertainty. This granularity will limit the ability to differentiate between two similar operators. Therefore, only a small finite subset of the infinite number of calculi will produce notably different results. This result is illustrated by an experiment where nine different calculi of uncertainty are used with three term sets containing five, nine, and thirteen elements, respectively.

Optical Constants of Silicon in the Region 1 to 10 ev

Abstract: The reflectance, ${|r(\ensuremath{\lambda})|}^{2}$, of single crystal silicon was measured in the range 1 to 11.3 ev. The phase, $\ensuremath{\theta}(\ensuremath{\lambda})$, was computed from these data using the Kramers-Kronig relation between the real and imaginary parts of the complex function $\mathrm{ln}r=\mathrm{ln}|r|+i\ensuremath{\theta}$. The optical constants, $n$ and $k$, were then determined from the Fresnel reflectivity equation. The real part of the refractive index, $n$, shows a sharp maximum of magnitude 6.9 at 3.3 ev. The extinction coefficient, $k$, shows maxima of magnitude 3.1 at 3.5 ev and 5.1 at 4.3 ev; optical absorption above 3 ev is associated with the onset of strong direct transitions. The results indicate that much useful information, applicable to band structure calculations for both silicon and germanium, could be obtained from limited reflectance studies (2 to 5 ev) on Ge-Si alloys.

Currents Limited by Space Charge between Concentric Spheres

Abstract: Limiting current between concentric spheres; calculation of the function $\ensuremath{\alpha}=f(\frac{r}{{r}_{0}})$ in the space charge equation $i=(\frac{4\sqrt{2}}{9})\frac{\sqrt{(\frac{e}{m})}{V}^{\frac{3}{2}}}{{\ensuremath{\alpha}}^{2}}$.---The coefficients of the first six terms of a series for $\ensuremath{\alpha}$ were determined, and ${\ensuremath{\alpha}}^{2}$ calculated from this series. The results were checked by an integration method which was also used to calculate values in the region where the series failed. For an emitter of radius ${r}_{0}$ inside a collector of radius $r$, values of ${\ensuremath{\alpha}}^{2}$ when $log(\frac{r}{{r}_{0}})g6.4$ are given by the equation $\frac{1}{2}{\ensuremath{\alpha}}^{2}=0.112 log (\frac{logr}{{r}_{0}})+\frac{1}{3}log (\frac{r}{{r}_{0}})+0.152.$ Where the collector is the inside sphere, values of ${\ensuremath{\alpha}}^{2}$ for $\frac{{r}_{0}}{r}g9$ are given by the equation ${(\frac{1}{2}{\ensuremath{\alpha}}^{2})}^{\frac{2}{3}}=1.11 (\frac{{r}_{0}}{r})\ensuremath{-}1.64$. It is shown that when the collector is the inside sphere the potential distribution near the collector is unaltered if the emitter is replaced by a non-emitting sphere with a diameter.677 times the original diameter.Limiting current between coaxial cylinders and between concentric spheres.---Equations are derived for the current in terms of the radius of curvature of the emitter. It is shown that at a surface in space four-fifths of the distance from the emitter to the collector the current density is independent of the radius of curvature when $\frac{r}{{r}_{0}} or \frac{{r}_{0}}{r}l2$; and in the case of coaxial cylinders with the emitter inside this holds true even when $\frac{r}{{r}_{0}}=20$.