Showing papers by "General Electric published in 1968"

Syntax-Directed Transduction

Abstract: A transduction is a mapping from one set of sequences to another. A syntax-directed transduction is a particular type of transduction which is defined on the grammar of a context-free language and which is meant to be a model of part of the translation process used in many compilers. The transduction is considered from an automata theory viewpoint as specifying the input-output relation of a machine. Special consideration is given to machines called translators which both transduce and recognize. In particular, some special conditions are investigated under which syntax-directed translations can be performed on (deterministic) pushdown machines. In addition, some time bounds for translations on Turing machines are derived.

Thin Silicone Membranes-Their Permeation Properties and Some Applications

Abstract: While the permeation of gases through solid materials is often a nuisance and sometimes a hazard, in recent years several useful applications have been found for this phenomenon. For example, H, is purified by diffusion through Pd-Ag foils, 0, partial pressures are measured in instruments dependent on 0, permeating through a plastic membrane, and artificial lungs based on permeation of 0, and CO, through thin polymeric membranes are being developed. These applications are only the beginning, for recent advances in membrane technology portend uses as far afield as water desalination by reverse osmosis and the separation of azeotropes by membrane perm-vaporation. When one wishes to separate noncondensable gases by a membrane technique, his first consideration should be whether a silicone rubber membrane can be used. This stems from the unusually high permeability of silicone rubber, indicated in TABLE 1, a tabulation of 0, permeabilities in various membranes.

Tensile failure of fiber composites.

Abstract: Composite tensile-failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects

Superconductivity of Small Tin Particles Measured by Tunneling

Abstract: We have used tunneling to study the superconductivity of small Sn particles imbedded in an oxide film. In contradiction to existing theories, no lower size limit for superconductivity has been found down to a particle radius $\mathcal{r}=25$ \AA{}. The junction characteristic shows a large peak in resistance at zero bias even for normal particles. This resistance maximum can be explained in terms of a capacitor model of the particle.

Power converter circuits having a high frequency link

Abstract: 1,261,838. Static converters. GENERAL ELECTRIC CO. 9 April, 1969 [16 April, 1968], No. 18197/69. Addition to 1,261,392. Heading H2F. [Also in Division G3] In a power converter as claimed in parent Specification having a control circuit for selectively rendering conductive the solid state switching means in primary and secondary current paths at a switching rate frequency which is high compared with the supply frequency, there is further provided a phase shift circuit coupled to the control circuit to render conductive the primary and secondary current paths at a selected phase angle one with respect to the other, whereby to control the output voltage. The switches may be transistors as shown, Fig. 3, or Gate-turn-off thyristors (Fig. 10, not shown). Converter circuit, Fig. 3.-As in the parent Specification the load voltage e 2 is at the same low. frequency as the input side voltage e 1 , the input current being chopped by transistor switches and applied in opposite directions alternately through a ferrite core transformer 14 at a high frequency switching rate, e.g. 5-10 kHz. The h.f. current at the secondary side is reformed into a low frequency waveform by the secondary side transistor switches also operating at the h.f. rate. Reversibility of power flow through the converter is possible. Each switch means is bidirectional and as shown, Fig. 3, comprises an anti-parallel pair of' transistors Q1-Q2, Q3-Q4, Q5-Q6, Q7-Q8 respectively. Both transistors in a pair preferably receive base current from a control circuit 52 simultaneously and the circuit conditions determine which conducts or alternatively the base signals may be applied via logic circuits. Thus during the positive half cycles of low frequency input, Q2 conducts via diode 29 and in negative half cycles thereof, Q1 conducts via diode 28 and the transformer primary. In normal operation (i.e. 0 degree phase shift between input and output side switches) Q1, Q2 receive base signals at the same time as Q5, Q6 the transistors Q3, Q4, Q7 and Q8 being OFF. During the next h.f. half-cycles Q3, Q4, Q7, Q8 receive base signals and the others are OFF, and so on. D.C. supply.-The connection of the converter to a D.C. source is envisaged wherein the phase shift control is modulated to obtain a desired output waveform to a load. To obtain a sine wave the phase shift is changed between 0 and 180 degrees and then between 180 and 0 degrees according to a sine wave function. Alternatively the output may be D.C. Control circuit, Fig. 9.-An oscillator 58 supplies clock pulses at twice the h.f. switching rate to drive a flip-flop 59 connected to an amplifier 61 which provides base signals for the input side transistors Q1 to Q4. The oscillator pulses are also fed to a phase shifter 62 which actuates a second flip-flop 63 connected to a base signal drive amplifier 64 for the output side transistors. The output drive 63 is thus synchronized with the input drive 59 but is appropriately phase delayed by the shifter 62. Voltage regulation.-The output voltage is sensed by a transformer 48, is rectified and compared in a differential amplifier 68 with a pre-set level VR eg and fed to the phase shifter 62 which causes the output side transistor to change conduction states at a different time from the input side transistors, in either leading or lagging sense. Fig. 4 (not shown) illustrates the output voltage and transformer voltage waveforms for different degrees of phase difference between input and output transistor switches. For 90 degrees phase difference for instance the output voltage is zero. Current regulation.-Load current is sensed by a C.T. 49 and compared with a desired value IR eg in a circuit 71 and a difference value output operates the phase shifter 62 to adjust the output voltage and hence load current. Alternatively the load current signal is compared with a desired current limit value I Lim in circuit 71, the phase shifter operating to reduce the output voltage and current, overriding the voltage regulator. Overcurrent protection.-If overcurrent sensed persists for a time determined by a timer 73 (e.g. 20 low frequency input cycles) a base signal modifying circuit 74 sends a signal to drive amplifiers 61, 64 to cut off base signals to all the transistor switches, or to the input side transistors only, preferably at load current zero to minimize reactive current. Alternatively, circuit. 71 may operate the phase shifter 62 if excess current persists for a pre-set time, to give a full phase shift of 90 degrees between input and output side switching causing zero output voltage. After a time delay to allow reactive current to die all the transistors are turned OFF.

Collective Excitations and Magnetic Ordering in Materials with Singlet Crystal-Field Ground State

Abstract: The low-lying magnetic excited states ("Frenkel spin excitons") in rare-earth compounds with a singlet crystal-field ground state are studied. We consider the effect of exchange interaction between the ionic moments as it increases from zero towards the critical value necessary for magnetic ordering at zero temperature. For simplicity, we consider the two-level system where the first-excited crystal-field state is also a singlet. By employing a pseudospin formalism, we avoid many of the fundamental difficulties encountered in previous treatments which introduce fermion operators for each of the crystal-field states. Applying techniques similar to those used in treating standard spin problems such as the Heinsenberg ferromagnet, we obtain an improved collective-excitation spectrum with a gap which decreases as the exchange increases. The critical value of exchange for magnetic ordering found is substantially greater than that obtained from molecular-field theory, and also is somewhat greater than that found with the constant-coupling approximation.

Properties of Si x O y N z Films on Si

Abstract: The properties of silicon nitride, oxynitride, and oxide films formed by the pyrolysis of various mixtures of , , and are presented The variation in physical, optical, and electrical properties of this oxynitride series is examined The electrical and passivation properties of these films on Si are examined and compared with oxides These electrical data describe the general characteristics of nitride and oxynitride on top of Si and over thin (~300Aa) and thick (~1000Aa) thermal oxide films

Dynamic Stability Calculations for an Arbitrary Number of Interconnected Synchronous Machines

Abstract: Describing the small signal performance of a multi- machine synchronous power system by a set of differential equations of the form [x] = [A] [x] allows standard multivariable control theory to be used in dynamic stability studies. The construction of the [A] matrix for a multimachine power system involves the application of Kron's rotational transformation to the transmission network admittance matrix, and a matrix analysis of the synchronous machines using internal flux linkages as state variables.

Defects in Irradiated Silicon: Electron Paramagnetic Resonance and Electron-Nuclear Double Resonance of the Arsenic- and Antimony-Vacancy Pairs

Abstract: Two EPR spectra are observed in irradiated silicon (designated Si-$G23$ and Si-$G24$) which are identified with the neutral charge states of a lattice vacancy adjacent to a substitutional arsenic or antimony atom, respectively. EPR and ENDOR studies reveal a high degree of similarity between these defects and the phosphorus-vacancy pair (Si-$G8$) studied previously. Nuclear quadrupole interactions for the As and Sb atoms give additional information about the defect configuration, not available for the phosphorus-vacancy pair. For all three defects, a large static Jahn-Teller distortion occurs. Analysis of the response of the defects to externally applied stress allows an estimate of \ensuremath{\approx}1 eV for the magnitude of the Jahn-Teller stabilization energy. It is concluded that this energy is larger than the electron-electron interaction energies and comparable to (or greater than) the crystal-field energies for the electrons involved in the core of the defects. Studies of the group-V atom-vacancy reorientation kinetics reveal variations between the three defects that can be correlated with the elastic interactions between the oversize arsenic or antimony atoms and the tensile strain around the lattice vacancy. Comparison of the results with the annealing studies of electrical properties by Hirata et al. indicate that the annealing of each defect involves the migration of the pair as an entity through the lattice.

Phonon-Assisted Recombination of Free Excitons in Compound Semiconductors

Abstract: In this paper we study the band-edge optical transitions in "direct" semiconductors involving the interacting exciton-phonon system, especially the longitudinal-optical (LO)-phonon-assisted recombination of free excitons. By introducing an extended Green's-function approach to include propagation in and between the various bands in the exciton spectrum, we obtain rather directly the transition rate to lowest order in the exciton-photon coupling which contains the effects of the interactions between the exciton and lattice vibrations to all orders, and thus includes line broadening, shift, asymmetry, and all renormalizations. Under the appropriate conditions (sufficiently separated bands), this result is equivalent to an expression previously derived by Toyozawa, but has the virtue that all terms appearing in it (in particular, the asymmetry term) are given in precise and general expressions. The relation of the general result to that obtained by conventional perturbation theory is discussed. The radiative decay of free excitons by the one- LO- and two-LO-phonon-assisted processes are formulated in the framework of perturbation theory. The limitation of this approach and its relationship to that in which the exciton-photon interaction is treated more accurately are briefly discussed. It is also shown that the second-order perturbation-theory result for the one-phonon-assisted processes (both for absorption and emission), including the contributions from the full intermediate state (hydrogenic) spectrum, can be evaluated exactly in closed form. The one- and two-LO-phonon-assisted emission spectra for CdS are calculated for several temperatures up to 77\ifmmode^\circ\else\textdegree\fi{}K using only experimentally determined parameters and taking the anisotropy of the valence band into account. Except for the one-LO peak at $T=77\ifmmode^\circ\else\textdegree\fi{}$K, where the polariton effects are important, the calculated line shapes and widths, as well as the intensity ratio of peaks, are found to be in good accord with the observed spectra. The corresponding calculations for ZnO at 77\ifmmode^\circ\else\textdegree\fi{}K are in good agreement with experimental spectrum. The zero-LO exciton peak due to the one-acoustic-phonon-assisted process is calculated in weak exciton-photon coupling approximations for both the deformation potential and piezoelectric couplings. The widths of the calculated lines are orders of magnitude smaller than the observed widths, and we conclude that the difficulty lies in the use of the weak exciton-photon coupling approach.

The Void Fraction in Subcooled Boiling—Prediction of the Initial Point of Net Vapor Generation

Abstract: The satisfactory prediction of the vapor volume fraction in subcooled boiling depends in large part on the ability to predict the point where a significant amount of net vapor is first formed. A method for the prediction of this point is derived here and compared with experimental measurements at both low and high fluid velocities. The derived relationships for this point include the effect of fluid properties, geometry, and the liquid velocity. A comparison with the empirical formula of Bowring [2] for water is given.

An Algorithm for the Determination of the Economic Design of -Charts Based on Duncan's Model

Abstract: An algorithm for the determination of the economic design of -charts based on Duncan's model is described in this paper. This algorithm consists of solving an implicit equation in design variables n (sample size) and k (control limit factor) and an explicit equation for h (sampling interval). The use of this algorithm not only yields the exact optimum but also provides valuable information so that the sensitivity of the optimum loss-cost (L*) can be evaluated. Loss-cost contours are used to discuss the nature of the loss-cost surface and the effect of the design variables. The effect of two parameters, the delay factor (e), and the average time for an assignable cause to occur (1/λ), on the optimum design is evaluated. Numerical examples are used for illustrations.

Magnetic Equation of State for Nickel Near Its Curie Point

Abstract: The magnetization-field-temperature ($\ensuremath{\sigma}\ensuremath{-}H\ensuremath{-}T$) behavior of nickel both above and below its Curie point ${T}_{c}$ is found to obey an equation of state in which $\frac{\ensuremath{\sigma}}{{|1\ensuremath{-}\frac{T}{{T}_{c}}|}^{\ensuremath{\beta}}}$ is uniquely related to $\frac{H}{{|1\ensuremath{-}\frac{T}{{T}_{c}}|}^{\ensuremath{\beta}+\ensuremath{\gamma}}}$, where $\ensuremath{\beta}$ and $\ensuremath{\gamma}$ are the critical exponents for the temperature dependence of the spontaneous moment and initial susceptibility, respectively.

Theory of Two-Photon Spectroscopy in Solids

Abstract: The coefficient of absorption of two photons is calculated for a two-band model of a solid. The frequency and polarization dependence is evaluated for the case that one photon (laser) frequency is fixed while the second is varied. Wannier exciton states are explicitly included in both the intermediate and final states. Depending upon the symmetry of the two energy bands, the final state may either be an exciton $s$, $p$, or $d$ state. All three cases have different frequency and polarization dependences. The final formulas for the matrix element are complicated, and approximate formulas are given which are useful for many applications. It is shown that some of the two-photon spectroscopy experiments in semiconductors and alkali halides which have been reported so far can be explained by these calculations.

Metastable Immiscibility in the B2O3–SiO2 System

Abstract: Using the phase diagram and a simple solution model, a subliquidus miscibility gap was estimated for the B2O3-SiO2 system. The predicted coexistence boundary, showing a consolute temperature of 520°C, was flat and symmetrical and extended across the complete binary. Gradient furnace heat treatments of selected compositions in this system resulted in phase separation which corresponded closely to the coexistence boundary initially predicted. Calculations and preliminary experimental results indicate that temperatures and compositions exist wherein metastable three-liquid immiscibility occurs in R20–B203-SiO2systems.

Frequency and Duration Methods for Power System Reliability Calculations: I - Generation System Model

Abstract: As a goal, the evaluation and computation of electric power system reliability requires that a consistent technique be used for all portions?generation, transmission, and distribution. At present, a number of different methods are used for the generation system, while the frequency and duration of outages seems to be developing as a standard measure for the analysis of the distribution system. This paper and a subsequent one will present a reliability calculation method for the generation system that incorporates the frequency and duration of unit outages and includes consideration of the loads. This method leads to calculated generation reliability measures which are the availability, frequency of occurence, and mean duration of reserve states. These are cumulative states in that they specify system reserve conditions of a given magnitude or less. This paper is concerned with the procedure for calculating the availability, frequency, and outage duration for a number of generating units connected in parallel to form a single system. Numerical data are used to illustrate the technique and make comparisons with other methods.

Optimum radar signal processing in clutter

Abstract: This paper considers the joint optimization of a class of radar signals and filters in a number of clutter-pins-noise environments. The radar signal processor in this case will be optimum in the sense that its output at the time of target detection yields the maximum ratio of peak signal power to total interference power. If the interference at the input to this signal processor is a Gaussian random process, this processor also yields the maximum probability of detection for a given value of false-alarm probability. The signals used are pulse trains and the filters are tapped delay lines. The purpose of signal design is to determine the optimum complex weighting for each pulse of the pulse train. Filter design yields the optimum complex weighting for the output taps of the delay line. Filter design for a specified signal is considered first. This is followed by combined signal and filter design and matched filter design. Constrained signal and filter design is investigated last. It should be emphasized that the optimizations require a knowledge of the clutter time-frequency distribution. For practical situations, when the clutter distribution is unknown, an adaptive filter is proposed that automatically provides the optimum filter weights for a given transmitted signal. When the clutter has a range-time extent less than the equivalent range-time extent of the signal, filter design alone yields nearly optimum performance. As the clutter becomes extended in range-time, it is necessary to consider jointly the design of signal and filter to obtain an optimum radar signal processor. In this report it is suggested that the signal be designed under the assumption of the clutter being extended over a broad range of Dopplers and that the signal processor consist of a bank of adaptive filters. Then each filter output yields the maximum ratio of peak signal to total interference power for this signal design.

Method of forming interference fits by heat treatment

Abstract: An interference fit can be provided between metal components where at least one of the components is formed of a precipitation-hardenable metal alloy which undergoes a substantially permanent dimensional change in addition to a reversible dimensional change upon heat treatment at elevated temperatures. The interference fit itself will be irreversible if both components are formed of the preciptitation-hardenable alloy and reversible if only one of the components is formed of the alloy.

Effects of adsorption on the indentation deformation of non-metallic solids

Abstract: Marked changes in indentation microhardness have been observed in a wide range of non-metallic materials due to the presence of adsorbed water and other polar species. Opposite polar faces of crystals with non-centrosymmetric structures, including II–VI, III–V and IV–IV compounds, exhibit large differences in microhardness and anomalous indentation creep behaviour. Such differences are shown to be due to differential effects of water adsorption on the opposite polar faces rather than being an intrinsic polar mechanical property of the crystal. The usefulness of microhardness measurements for absolute determinations of crystallographic polarity of non-centrosymmetric crystals is discussed. Effects of environment on the extent of edge dislocation motion away from the indentation are examined. Possible mechanisms to explain the adsorption-induced changes in microhardness and related mechanical properties of non-metallic solids are critically discussed.

Grain Growth in UO2-Al,O3 in the Presence of a Liquid Phase

Abstract: The theory of grain growth in the presence of a liquid phase is examined using modifications of equations derived for coalescence of solid particles widely dispersed in a liquid. Although the grain diameter-time relation can still be represented by d3=kt, the absolute growth rates are increased as the amount of liquid is decreased. The grain growth kinetics in UO2 compacts containing 0.5 wtyo A12O3 were studied for temperatures between 1960° and 2200°C. The interrelation of grain size, temperature, and time is in agreement with that predicted by the theory.

Adhesive silicone rubber

Abstract: 1278798 Laminates GENERAL ELECTRIC CO 1 Aug 1969 [9 Aug 1968] 38786/69 Heading B5N [Also in Division C3] Laminates of polymethyl methaorylate to polymethyl methacrylate and polymethyl methacrylate to glass use as adhesive a curable selfbonding composition comprising (by wt.): (I) 100 parts of a vinyl terminated polysiloxane: in which R and R 1 are each C 1-8 alkyl radicals, mononuclear aryl radicals, cycloalkyl radicals with 5-7 ring carbon atoms or a mononuclear aralkyl radical (C 1-8 alkyl) with at least 50 mole per cent of R 1 being methyl, n has a value sufficient to provide a viscosity of 1000- 750,000 centistokes at 25‹ C.; (II) 0-50 parts of an organopolysiloxane comprising (R 11 ) 3 SiO 0.5 units and SiO 2 units where each R 11 is vinyl or has the same definition as R and R 1 and the ratio of (R 11 ) 3 SiO 0.5 units to SiO 2 units is 0A5 : 1 to 1:1 and where 2A5-10 mole per cent of the Si atoms contain silicon bonded vinyl groups; (III) 0-200 parts of an inorganic filler which is non-reinforcing for silicone elastomers; (IV) a Pt or Pt containing catalyst present so as to provide 10 -3 to 10 -6 gram atoms of Pt per Si-bonded vinyl radical; (V) an amount of a liquid organohydrogenpolysiloxane: sufficient to provide 0A5-1A2 Si-bonded hydrogen atoms per vinyl group in I (R is as previously defined), a=1A0-2A0; b=0A1-1A2 and a+b=2A0-2A67, there being at least two Sibonded H atoms per molecule; (VI) 0A1-1 part of a liquid vinyl siloxane hydrolysate: in which R 111 is C 1-8 alkyl, x > 3, y=0A1-0A4 and z=0A1-0A4; (VII) 0A1-85% of the weight of the entire composition of a halocarbon catalyst inhibitor which is a halocarbon having at least 2 carbon atoms and 3 halogen (atomic wt. 1 are methyl and phenyl or are all methyl. In preparing laminates at least one of the surfaces to be laminated may be coated with VI, the remaining ingredients being mixed and subsequently applied to the surfaces. Cure may take place at 50-110‹ C.

Resistor thin films formed by low-pressure deposition of molybdenum and tungsten

Abstract: High resistivity, low temperature coefficient of resistance films are formed by evaporating a molybdenum or tungsten source in a low-pressure atmosphere, e.g. 5 X 10 4 torr, of a nitrogen bearing gas, a carbon bearing gas or an inert gas and depositing a resistor film atop a preferably unheated dielectric substrate.

Enhancement of track etching rates in charged particle irradiated plastics by a photo-oxidation effect.

Abstract: THE use of appropriate etching solutions to reveal the paths of charged particles in irradiated insulating materials1 is a technique of increasing importance in several disciplines ranging from nuclear physics and space exploration to geology and archaeology (for reviews see ref. 2). Among the variety of dielectric solids useful for track-etching applications are plastic films, notably the cellulosics and polyesters, which are acutely sensitive to a variety of energetic charged particles3,4. The responsiveness of plastic particle detectors derives from the dramatic increase in chemical reactivity of the damaged area along the particle track. The etching rate along the track is generally 103 to 104 times that for the bulk polymer2–4. We report that exposure of a charged particle-bombarded polycarbonate film to ultraviolet energy in an oxygen atmosphere causes a significant acceleration in the etching rate for the damage region along a track, permitting immediate processing and analysis of the sample. Two approaches were utilized in this study of the sensitization of track etchability in polycarbonate film by this photo-oxidative treatment.