Showing papers by "General Electric published in 1969"

Concepts of Synchronous Machine Stability as Affected by Excitation Control

Abstract: The phenomena of stability of synchronous machines under small perturbations is explored by examining the case of a single machine connected to an infinite bus through external reactance.

Hazard Plotting for Incomplete Failure Data

Abstract: Incomplete failure data consisting of times to failure on failed units and differing running times or unfailed units are called multiply censored. Data on units operating in the field, for example, are usually multiply censored. Presented in this paper ..

Tunneling, Zero-Bias Anomalies, and Small Superconductors

Abstract: We have prepared tunnel junctions which contain small Sn particles imbedded in the oxide barrier. The size distribution of the small particles has been determined from electron micrographs. The electrical characteristics of these junctions were measured in the temperature range 1-300\ifmmode^\circ\else\textdegree\fi{}K and in magnetic fields up to 100 kOe. All junctions show a large temperature-dependent resistance peak at zero bias and at low temperatures. The resistance peak increases in magnitude when the Sn particles are made superconducting. A simple model based upon the capacitance of the particles can account quantitatively for this behavior. We believe that a simple extension of this model can account for at least some of the previously reported zero-bias resistance anomalies. From the experiment, it is also possible to extract information about the superconductivity of small particles. We find that Sn particles down to at least a radius $r\ensuremath{\sim}25$ \AA{} are superconducting. The transition temperature of the particles increases with decreasing particle size and reaches 4.2\ifmmode^\circ\else\textdegree\fi{}K for particles with $r\ensuremath{\sim}70$ \AA{}, compared with ${T}_{c}=3.7\ifmmode^\circ\else\textdegree\fi{}$K for bulk Sn. In the radius range $rg100$ \AA{}, the critical field of the particles can be described in terms of a theory by De Gennes and Tinkham. Smaller particles have a much higher critical field, which increases more rapidly with decreasing radius than predicted by that theory.

On the generation of dislocations at misfitting particles in a ductile matrix

Abstract: The nucleation of a shear dislocation loop from the interface of a misfitting spherical particle in a deformable matrix is considered. The equilibrium shapes and positions of the nucleated dislocation have been calculated. There are two critical levels of misfit. The lower critical level, which is dependent on the particle size, must be reached before nucleation can occur. Above the upper critical level, which is virtually independent of the particle size, nucleation will always occur. Experimental measurements of the critical misfit show that the upper critical level describes the spontaneous generation of dislocations at coherent particles, whereas the lower level describes their generation at incoherent particles. Possible reasons for this are discussed.

Data structure diagrams

Abstract: Successful communication of ideas has been and will continue to be a limiting factor in man's endeavors to survive and to better his life. The invention of algebra, essentially a graphic technique for communicating truths with respect to classes of arithmetic statements, broke the bond that slowed the development of mathematics. Whereas "12+ 13=25 '' and "3+7= 10" and "14+(-2) = 12" are arithmetic statements, "a+b=c '' is an algebraic statement. In particular, it is an algebraic statement controlling an entire class of arithmetic statements such as those listed.

Vane assembly and temperature control arrangement

Abstract: A gas turbine engine vane assembly of the type adapted for use in an annular row of such assemblies and having spaced inner and outer platform portions for defining an annular hot gas stream flow path and a hollow airfoil extending therebetween. The airfoil is compartmentalized by a bridge member extending between the airfoil sidewalls and an impingement insert is provided for each compartment. Chordwise extending structural ribs are provided internally of the airfoil to strengthen the sidewalls and impingement baffles are provided outwardly of the platform portions for temperature control of these elements. Passageways are provided through the platforms to direct coolant to the downstream edges thereof and into the hot gas stream at an angle approximating the hot gas swirl angle.

Electron Correlation in Narrow Energy Bands. I. The Two-Pole Approximation in a Narrow S Band

Abstract: An improved version of Hubbard's treatment of correlation in a nondegenerate narrow band is obtained by the use of a new Green's-function decoupling scheme. The resulting one-electron Green's function has two poles on the real axis corresponding to a splitting of the electron bands due to the strong correlations between electrons on the same site. This is the same result that Hubbard obtained, but in our case the poles are shifted and their positions agree with the results of Harris and Lange, who used a moment technique. The theory is applied to a simple cubic lattice with nearest-neighbor interaction, and the lattice is found to be ferromagnetic in the strongly correlated limit for a sufficiently large number of electrons per atom. An examination of the low-density limit shows that the two-pole approximation does not reduce to Kanamori's $T$-matrix result, a failing which it shares with Hubbard's theory. A method is outlined for improving the theory so as to give the correct low-density result. In addition, the possibility of obtaining a minimum principle for the theory is explored.

Data base task group report to the CODASYL programming language committee, October 1969

Abstract: This report has been prepared by the Data Base Task Group which is an ad hoc committee of the CODASYL Programming Language Committee. The report details the recommendation of the Data Base Task Group to its parent committee. It consists of a proposal for a Data Description Language and a Data Manipulation Language. The Data Description Language is a language for describing a database. The Data Manipulation Language is language which, when associated with the facilities of a host language such as COBOL, PL/1, ALGOL, JOVIAL, FORTRAN..., allows manipulation of databases described by the Data Description Language. The specification of separate Data Description and Data Manipulation Languages is significant in that it allows databases described by the Data Description Language to be independent of the host languages used for processing the data. Of course, for this to be possible, the host language processors must be able to interface with such independent descriptions of data.

Crazing, yielding, and fracture of polymers. I. Ductile brittle transition in polycarbonate

Abstract: Most thermoplastics far below their glass transition give a brittle fracture when de-formed in uniaxial tension. Bisphenol-A polycarbonates are an exception and deform in a ductile manner. However, it has been observed in Izod impact studies of notched samples that the mode of failure changes from a ductile to a brittle fracture on annealing samples below Tg. It has been found that, when notched samples are stressed, a Griffith type flaw is formed under the notch. The criterion for the ductile brittle transition is evaluated in terms of σG (the stress required to propagate the Griffith flaw), and σy, the yield stress for the polymer. It has been found that the density and yield stress for the samples annealed at various temperatures are dependent upon previous thermal history and in particular on the molecular weiAght. On the basis of these measurements, it is concluded that many of the so-called anomalous effects observed with polycarbonate can be explained.

Solid state lamp assembly

Abstract: A light-emitting diode element is mounted on a supporting tab, in a depression thereof having polished tapered sides. A dimple is provided in the depression, at the underside of the diode, so that only a small area of the bottom surface of the diode is in contact with the tab, thereby maximizing internal light reflection at the bottom surface and thus increasing the amount of light usefully emitted through the top and sides of the diode. The polished tapered sides of the depression in the tab reflect upwardly the light emitted through the sides of the diode, so as to be useful along with light emitted through the top of the diode. The assembly is encapsulated in glass or plastic.

The Anodic Dissolution and Passivation of Zinc in Concentrated Potassium Hydroxide Solutions

Abstract: In this study, mainly two sets of experiments were carried out to obtain a better understanding of the tendency of the alkaline zinc electrode to passivate Either photomicrographs of the electrode surface were taken in‐situ at different potentials during an anodic voltage sweep or the two components of the electrode impedance were measured with a small signal of superimposed 1000 Hz AC The course of the passivation was found to depend strongly on the convective conditions in the electrolyte near the zinc electrode The conditions for the formation of two different types of solid films have been defined and their effects on the current‐potential curve have been determined Type I film is white, loose, and flocculent It forms in the absence of convection by precipitation from a supersaturated layer of zincate near the surface When the conditions for supersaturation are largely removed by stirring, the formation of the type II film can be observed The latter is more compact and appears to form directly at the surface rather than by precipitation Its color can range from light gray to black depending on the potential and time of formation The type II film is considered responsible for the transition from the active to the passive state of zinc in alkaline solution

Giant Moments in Ni-Cu Alloys Near the Critical Composition

Abstract: Neutron scattering experiments reveal that in weakly ferromagnetic Ni-Cu alloys near the critical composition the low-temperature spontaneous magnetization is inhomogeneously distributed in magnetic polarization clouds of large total moment (over ${8\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$) extending over many atoms.

Stability Analysis of a Symmetrical Induction Machine

Abstract: A stability study of an induction machine is performed by applying the root-locus criterion to the equations which describe the behavior of the machine during small displacements about a steady-state operating point. This investigation reveals that a symmetrical induction machine may become unstable at low speeds (low frequencies) even though balanced, constant amplitude, sinusoidal voltages are applied to the stator terminals. Regions of machine instability are established from the results of a digital computer study. The results of an analog computer study are included to illustrate the modes of operation which occur within these regions. Regions of instability for changes of system parameters are presented and discussed. Also, it is shown that the root- locus criterion can be utilized to identify regions of lightly damped operation.

Optical Absorption of Y 3 Al 5 O 12 from 10- to 55 000- cm − 1 Wave Numbers

Abstract: The optical absorption coefficient of synthetic single crystals of the garnet ${\mathrm{Y}}_{3}$${\mathrm{Al}}_{5}$${\mathrm{O}}_{12}$ has been measured from photon wave numbers of 10 to 55 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 300\ifmmode^\circ\else\textdegree\fi{}K. The wave-number range 10 to 900 ${\mathrm{cm}}^{\ensuremath{-}1}$ has been studied at 4\ifmmode^\circ\else\textdegree\fi{}K. The 17 theoretically predicted absorption peaks of the ${\mathrm{Y}}_{3}$${\mathrm{Al}}_{5}$${\mathrm{O}}_{12}$ lattice at 300\ifmmode^\circ\else\textdegree\fi{}K have been found at wave numbers of 123, 163, 223, 255, 293, 332, 373, 395, 430, 457, 510, 530, 570, 690, 722, 784, and 830 ${\mathrm{cm}}^{\ensuremath{-}1}$. The fourteenth, fifteenth, and sixteenth peaks are believed to be associated with the ${\overline{\ensuremath{ u}}}_{3}$ vibrations of the ${\mathrm{AlO}}_{4}$ groups in the lattice. The multiphonon lattice absorption bands extend upward to 2400 ${\mathrm{cm}}^{\ensuremath{-}1}$ wave numbers. Beyond 2400 ${\mathrm{cm}}^{\ensuremath{-}1}$ the crystal is transparent, with an absorption coefficient 0.1 ${\mathrm{cm}}^{\ensuremath{-}1}$ up to $\overline{\ensuremath{ u}}=30 000$ ${\mathrm{cm}}^{\ensuremath{-}1}$. From 30 000 to 52 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ the absorption appears to be dominated by trace impurities. The optical absorption increases rapidly for wave numbers above 52 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ and reaches an absorption coefficient of ${10}^{+3}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ at 54 300 ${\mathrm{cm}}^{\ensuremath{-}1}$ wave numbers (6.73 eV or 1840 \AA{}). Some comments are also made on the relationship of the lattice modes of yttrium aluminum garnet (YAG) to the phonon sidebands of electronic transitions of impurity ions in YAG.

The Dissolution of MgO and Mg ( OH ) 2 in Aqueous Solutions

Abstract: This paper reports studies of the rates of dissolution of natural Brucite, optical grade , and commercial in aqueous solutions. Natural Brucite dissolves by means of a surface reaction requiring protons, and while some protonated ions accelerate the dissolution no inhibitors were found. Dissolution of less perfect is normally diffusion limited; several substances which reduced the rate of dissolution of such were found. first reacts with water to form an layer and the rate is controlled by dissolution of the .

Multiple internal reflection face-pumped laser

Abstract: A miniaturized face-pumped, face cooled laser device is described wherein wave front distortion is minimized by the passage of a coherent beam of electromagnetic radiation through an elongated, rectangularly cross-sectioned laser body in an offaxial direction to effect multiple total internal reflections of the beam from fluid cooled, parallelly extending faces of the laser body. Because each ray of the coherent beam passes through substantially identical thermal environments during the reflective transmission of the beam through the laser body, the net distortion of the beam wave front is substantially reduced making the laser device particularly suitable for high-repetition rate, Q-switched operation. In a preferred embodiment, the beam is reflectively passed initially through only a portion of the cross-sectional area of the laser body to effect a first order compensation of beam distortion whereupon the beam is folded back one or more times along adjacent untraversed portions of the laser body for a second order compensation of beam distortion by additional averaging of the optical environment observed by the beam.

Polaritons at Surfaces

Abstract: We calculate the reflectivity of light incident upon the exposed face of a semi-infinite crystal, using the point-dipole model. This requires an accurate solution for the polariton modes near the crystal surface. The variation of the Lorentz local field, caused by the surface, is included in the calculations. The boundary conditions for the polariton modes are derived rigorously. This represents the first rigorous microscopic solution of polariton modes near ideal surfaces.

Critical Evaluation of the Literature Data on Beta Alumina and Related Phases: I, Phase Equilibria and Characterization of Beta Alumina Phases

Abstract: From a critical evaluation of the available data on the system Na2O-Al2O2 and particularly on β-Al2O3 some of the discrepancies in the literature were resolved, and plausible phase diagrams for the system were constructed. The diagrams define needed equilibrium data and are useful in putting into perspective the problems that have arisen with regard to synthesis and characterization of the 3–block and 3–block forms of β-Al2O3.

Fluid-cooled airfoil

Abstract: An improved fluid-cooled airfoil having spaced leading and trailing edge chambers and a serpentine passage therebetween. Coolant is delivered to the leading and trailing edge chambers, respectively, by an impingement insert and the portion of the serpentine chamber adjacent the trailing edge chamber. Various features, such as turbulence promoters, inclined trailing edge passages and film-cooling passageways, are provided to enhance the heat-transfer properties of the airfoil.

Fast response stepped-wave switching power converter circuit

Abstract: To obtain fast response to a cyclical AC or variable DC input reference signal by a stepped-wave power converter circuit comprising a plurality of equal or unequal inverter modules connected in series or parallel so that the module output voltages add algebraically, the composite instantaneous output stepped-wave voltage is compared with the instantaneous voltage values of the limits of a control band placed about the reference signal. One or more inverter modules are switched to produce a step change whenever the composite output voltage is outside the control band limits. An application is a fast response switching power amplifier for driving sonar transducers.

Light Scattering in Terms of Oscillator Strengths and Refractive Indices

Abstract: Quantum-mechanical expressions for nonresonance-dipole light-scattering cross sections are related to corresponding expressions for oscillator strengths and refractive indices. In particular, Rayleigh and Raman cross sections for atoms are expressed in terms of oscillator strengths and vector-coupling coefficients. Several of our results, including the relationship between Rayleigh scattering and refractive index, differ in general from the corresponding results of classical dispersion theory. We show that these differences arise from antisymmetric components Ckja = (Ckj − Cjk)/2 of the polarizability tensor, which have been neglected in the classical analyses. Calculated Rayleigh cross sections for cesium and aluminum atoms, and Raman cross sections for aluminum atoms are presented to illustrate our results. The antisymmetric contribution is found to be substantial in all of these cross sections; its most obvious effect is to cause the depolarization (for linearly polarized incident light) to exceed 34 over extended wavelength ranges away from resonance. On the other hand, for atoms initially in states of zero angular momentum, and molecules under conditions which allow the use of Placzek’s polarizability approximation, our results agree with those of classical dispersion theory.

Properties of deterministic top down grammars

Abstract: The class of context free grammars that can be deterministically parsed in a top down manner with a fixed amount of look-ahead is investigated. These grammars, called LL(k) grammars where k is the amount of look-ahead are first defined and a procedure is given for determining if a context free grammar is LL(k) for a given value of k. It is shown that e-rules can be eliminated from an LL(k) grammar, at the cost of increasing the value of k by one, and a description is given of a canonical pushdown machine for recognizing LL(k) languages. It is shown that for each value of k there are LL(k+l) languages that are not LL(k) languages. It is shown that the equivalence problem is decidable for LL(k) grammars. Additional properties are also given.