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.

Sintering Crystalline Solids. II. Experimental Test of Diffusion Models in Powder Compacts

Abstract: During sintering in alumina powder compacts, the density has been found to increase linearly with the logarithm of time, and the grain size increases with the one-third power of time. Incorporation of the time dependence of grain size increase into late-stage bulk diffusion sintering models (from Part I )[R. L. Coble, J. Appl. Phys., 32, 787 (1961)] leads to corrected models by which a semilogarithmic behavior is predicted. The presence of density gradients in normally fabricated pellets makes impossible the deduction of whether theoretical density will be achieved from the early stages of the course of densification. Diffusion coefficients calculated from the intermediate and later stages of sintering bear order-of-magnitude agreement with those calculated from the initial-stage sintering measurements in alumina. All diffusion coefficients from sintering data are higher than Kingery’s measured diffusion coefficients for oxygen. It is hypothesized that the sintering process must then be controlled by bulk diffusion of aluminum ions while the oxygen transport takes place along the grain boundaries. In controlling the sinterability of alumina to theoretical density, it appears that magnesia does not ‘inhibit’ discontinuous grain growth, but instead increases the sintering rate such that discontinuous growth nuclei do not have time to form.

Phase-aberration correction using signals from point reflectors and diffuse scatterers: basic principles

Abstract: Methods for correction of phase aberrations induced by near-field variations in the index of refraction are explored. Using signals obtained from a sampled aperture (i.e. transducer array), phase aberrations can be accurately measured with a correlation approach similar to methods used in adaptive optics and radar. However, the method presented here has no need for a beacon or an ideal point reflector to act as a source for estimating phase errors. It uses signals from random collections of scatterers to determine phase aberrations accurately. Because there is no longer a need for a beacon signal, the method is directly applicable not only to medical ultrasound imaging but also to any coherent imaging system with a sampled aperture, such as radar and sonar. >

Complete PCB congener distributions for 17 Aroclor mixtures determined by 3 HRGC systems optimized for comprehensive, quantitative, congener-specific analysis

Abstract: Three HRGC systems (1: 30m DB-XLB capillary with MS-SIM detection; 2: 60m DB-XLB capillary with full-scan, ion-trap MS detection; and 3: Parallel dual-column DB-17 and series-coupled HP5/HT5 with ECD detection) were used to completely characterize multiple lots of 8 different-numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensitivity and more Aroclor congener coelutions than the dual-column ECD system, the MS systems enabled measurement of more congeners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent of ortho-chlorine substitution. The tables of congener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations of single-level calibration precluded measurement of all congeners to the ±10% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener-specific PCB analysis.

Field-weakening performance of brushless synchronous AC motor drives

Abstract: The paper examines the theoretical and practical limitations to the field-weakening performance of surface permanent magnet, synchronous reluctance and interior permanent magnet motors when driven from an inverter with a limited volt-ampere rating. It is shown that the 'optimal' field-weakening performance consists of an infinite constant-power speed range but is limited to an inverter utilisation of about 0.7. The new concept of the interior permanent magnet parameter plane is introduced. This graphically illustrates the effect of varying the drive parameters on the shape of the field-weakening characteristic. The interior permanent magnet parameter plane is used to show that there are three types of optimal field-weakening designs. When practical factors and considerations are taken into account, the optimal high-saliency interior permanent magnet motor design is the most promising for applications requiring a wide field-weakening range. A 7.5 kW design was built and a constant-power speed range exceeding 7.5:1 was demonstrated.

A Survey of Condition Monitoring and Protection Methods for Medium-Voltage Induction Motors

Abstract: Medium-voltage (MV) induction motors are widely used in the industry and are essential to industrial processes. The breakdown of these MV motors not only leads to high repair expenses but also causes extraordinary financial losses due to unexpected downtime. To provide reliable condition monitoring and protection for MV motors, this paper presents a comprehensive survey of the existing condition monitoring and protection methods in the following five areas: thermal protection and temperature estimation, stator insulation monitoring and fault detection, bearing fault detection, broken rotor bar/end-ring detection, and air gap eccentricity detection. For each category, the related features of MV motors are discussed; the effectiveness of the existing methods are discussed in terms of their robustness, accuracy, and implementation complexity. Recommendations for the future research in these areas are also presented.