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.

Currents Limited by Space Charge between Coaxial Cylinders

Abstract: Limiting current between coaxial cylinders; calculation of the function $\ensuremath{\beta}=\mathbf{f}(\frac{\mathbf{r}}{{\mathbf{r}}_{\ensuremath{\circ}}})$ in the space charge equation $i=\frac{(\frac{2\sqrt{2}}{9})\sqrt{(\frac{e}{m})}{V}^{\frac{3}{2}}}{(r{\ensuremath{\beta}}^{2})}$. Two different infinite series were obtained for $\ensuremath{\beta}$ and the coefficients for fourteen terms of each were determined. These two sets were checked against each other. Thus values of ${\ensuremath{\beta}}^{2}$ were obtained accurate to 1 in 10,000. These were checked by an integration method which was also used to calculate values in the region where the series failed. For a cathode of radius ${r}_{0}$ inside an anode of radius $r$, ${\ensuremath{\beta}}^{2}$ increases from 1 at $\frac{r}{{r}_{0}}=11.2$ to a maximum value 1.0946 at $\frac{r}{{r}_{0}}=42$, decreases to a minimum value 0.9990 at $\frac{r}{{r}_{0}}=30,000$, and becomes 1 at $\frac{r}{{r}_{0}}=\ensuremath{\infty}$. The customary assumption ${\ensuremath{\beta}}^{2}=1$ has therefore led to errors up to 9.5 per cent in previous calculations, but this error is usually about equal and opposite to that introduced by neglecting the effect of initial velocities. For the cathode outside the anode, ${\ensuremath{\beta}}^{2}$ is given very closely by the equation ${\ensuremath{\beta}}^{2}=4.6712 (\frac{{r}_{0}}{r}) {[{log}_{10}(\frac{{r}_{0}}{r})\ensuremath{-}{log}_{10}\sqrt{2}]}^{\frac{3}{2}}$, for $\frac{{r}_{0}}{r}g10$. The empirical constant \ensuremath{\surd}2 is interpreted to mean that the potential distribution near the anode is unaltered if the hot cathode is replaced by a cold cylinder having one half the cross-section of the original cathode. The correction for initial velocities is less for a cylindrical cathode inside an anode than for parallel planes. In the inverted case it is much greater than in the case for parallel planes, and the effect of the tangential component of the initial velocity may greatly decrease the current that flows.

Three-dimensional segmentation of MR images of the head using probability and connectivity.

Abstract: We describe a three-dimensional (3D) segmentation method that comprises (a) user interactive identification of tissue classes; (b) calculation of a probability distribution for each tissue; (c) creation of a feature map of the most probable tissues; (d) 3D segmentation of the magnetic resonance (MR) data; (e) smoothing of the segmented data; (f) extraction of surfaces of interest with connectivity; (g) generation of surfaces; and (h) rendering of multiple surfaces to plan surgery. Patients with normal head anatomy and with abnormalities such as multiple sclerosis lesions and brain tumors were scanned with a 1.5 T MR system using a two echo contiguous (interleaved), multislice pulse sequence that provides both proton density and T2-weighted contrast. After the user identified the tissues, the 3D data were automatically segmented into background, facial tissue, brain matter, CSF, and lesions. Surfaces of the face, brain, lateral ventricles, tumors, and multiple sclerosis lesions are displayed using color coding and gradient shading. Color improves the visualization of segmented tissues, while gradient shading enhances the perception of depth. Manipulation of the 3D model on a workstation aids surgical planning. Sulci and gyri stand out, thus aiding functional mapping of the brain surface.

Thermal conductivity of isotopically modified single crystal diamond.

Abstract: We present new experimental results on the thermal conductivity of isotopically enriched $^{12}\mathrm{C}$ diamond crystals at low temperatures. To our knowledge, the measured value for a 99.9% $^{12}\mathrm{C}$ crystal at 104 K, 410 W/cm K, is the highest measured thermal conducitivity for a solid above liquid nitrogen temperature. Our measured temperature dependent conductivities for the isotopically enriched diamond and natural abundance diamond specimens are well described by Callaway's theoretical model. We predict that the thermal conductivity of a 99.999% $^{12}\mathrm{C}$ diamond crystal should exceed 2000 W/cm K at \ensuremath{\sim}80 K.