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.

Numerical Recirculating Flow Calculation Using a Body-Fitted Coordinate System

Abstract: A finite-difference algorithm for recirculating flow problem! in a body-fitted coordinate system is presented. A fully staggered grid system is adopted for the velocity components and the scalar variables. The strong conservation law form of the governing equations is written in the general curvilinear coordinates. The SIMPLE calculation procedure originally developed in Cartesian coordinates is extended to the present curvilinear coordinates. Two methods of evaluating the metric derivatives are discussed. Although both methods are formally of the same order of accuracy, it is shown that one performs the physical conservation laws more accurately than the other. The relative merits of three schemes, i.e., hybrid, second-order upwinding, and QUICK, for approximating the convection terms in the momentum equations are compared and the results are quite different from those in Cartesian coordinates in both accuracy and efficiency aspects. The effects of the grid distribution are also studied. Results obtained...

Characterization of Silicon Nitride Films

Abstract: Various "silicon nitride" films have been prepared from , N2, , and in an rf‐promoted glow discharge reaction. These films are described primarily through the use of infrared absorption. Aided by ultraviolet absorption, the inclusion of excess silicon or of oxygen in the films is readily followed. Changes in index of refraction, etch rates in HF acid, and electrical conductivity of the films are correlated with the optical absorption study. Comparisons of these films with those formed by pyrolysis or by reactive sputtering are made. Some reproducible physical properties of an amorphous film are stated.

Enhanced Interval Approach for Encoding Words Into Interval Type-2 Fuzzy Sets and Its Convergence Analysis

Abstract: Construction of interval type-2 fuzzy set models is the first step in the perceptual computer, which is an implementation of computing with words. The interval approach (IA) has, so far, been the only systematic method to construct such models from data intervals that are collected from a survey. However, as pointed out in this paper, it has some limitations, and its performance can be further improved. This paper proposes an enhanced interval approach (EIA) and demonstrates its performance on data that are collected from a web survey. The data part of the EIA has more strict and reasonable tests than the IA, and the fuzzy set part of the EIA has an improved procedure to compute the lower membership function. We also perform a convergence analysis to answer two important questions: 1) Does the output interval type-2 fuzzy set from the EIA converge to a stable model as increasingly more data intervals are collected, and 2) if it converges, then how many data intervals are needed before the resulting interval type-2 fuzzy set is sufficiently similar to the model obtained from infinitely many data intervals? We show that the EIA converges in a mean-square sense, and generally, 30 data intervals seem to be a good compromise between cost and accuracy.

Metal Artifact Reduction in CT: Where Are We After Four Decades?

Abstract: Methods to overcome metal artifacts in computed tomography (CT) images have been researched and developed for nearly 40 years. When X-rays pass through a metal object, depending on its size and density, different physical effects will negatively affect the measurements, most notably beam hardening, scatter, noise, and the non-linear partial volume effect. These phenomena severely degrade image quality and hinder the diagnostic power and treatment outcomes in many clinical applications. In this paper, we first review the fundamental causes of metal artifacts, categorize metal object types, and present recent trends in the CT metal artifact reduction (MAR) literature. To improve image quality and recover information about underlying structures, many methods and correction algorithms have been proposed and tested. We comprehensively review and categorize these methods into six different classes of MAR: metal implant optimization, improvements to the data acquisition process, data correction based on physics models, modifications to the reconstruction algorithm (projection completion and iterative reconstruction), and image-based post-processing. The primary goals of this paper are to identify the strengths and limitations of individual MAR methods and overall classes, and establish a relationship between types of metal objects and the classes that most effectively overcome their artifacts. The main challenges for the field of MAR continue to be cases with large, dense metal implants, as well as cases with multiple metal objects in the field of view. Severe photon starvation is difficult to compensate for with only software corrections. Hence, the future of MAR seems to be headed toward a combined approach of improving the acquisition process with dual-energy CT, higher energy X-rays, or photon-counting detectors, along with advanced reconstruction approaches. Additional outlooks are addressed, including the need for a standardized evaluation system to compare MAR methods.