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.

Generalized Structure of a Multilevel PWM Inverter

Abstract: A generalized structure of a multilevel voltage source thyristor inverter is proposed. The multilevel concept is used to decrease the harmonic distortion in the output waveform without decreasing the inverter power output. A simple uniform PWM control of the output voltage is seen to be sufficient to practically remove all remaining harmonics. Harmonic analysis of n-step waveform is given, and the experimental results obtained on a three-step inverter are presented.

Morpho butterfly wing scales demonstrate highly selective vapour response

Abstract: Tropical Morpho butterflies are famous for their brilliant iridescent colours, which arise from ordered arrays of scales on their wings. Here we show that the iridescent scales of the Morpho sulkowskyi butterfly give a different optical response to different individual vapours, and that this optical response dramatically outperforms that of existing nano-engineered photonic sensors. The reflectance spectra of the scales provide information about the nature and concentration of the vapours, allowing us to identify a range of closely related vapours–water, methanol, ethanol and isomers of dichloroethylene when they are analysed individually. By comparing the reflectance as a function of time for different vapours, we deduce that wing regions with scale structures of differing spatial periodicity give contributions to the overall spectral response at different wavelengths. Our optical model explains the effect of different components of the wing scales on the vapour response, and could steer the design of new man-made optical gas sensors.

Stereo from uncalibrated cameras

Abstract: The problem of computing placement of points in 3-D space, given two uncalibrated perspective views, is considered. The main theorem shows that the placement of the points is determined only up to an arbitrary projective transformation of 3-space. Given additional ground control points, however, the location of the points and the camera parameters may be determined. The method is linear and noniterative, whereas previously known methods for solving the camera calibration and placement problem to take proper account of both ground-control points and image correspondences are unsatisfactory in requiring either iterative methods or model restrictions. As a result of the main theorem, it is possible to determine projective invariants of 3-D geometric configurations from two perspective views. >

The use of semiconductors in thermoelectric refrigeration

Abstract: In the past the possibility of thermoelectric refrigeration has been considered, but all attempts to produce a practical refrigerator have failed owing to lack of suitable thermocouple materials. In this paper it is proposed that semiconductors should be used and the factors governing their selection are discussed. It is concluded that the semiconductors should be chosen with high mean atomic weights and that they should be prepared with thermoelectric powers lying between 200 and 300 μVC-1. Preliminary experiments have led to the production of a thermocouple consisting of bismuth telluride, Bi2Te3, and bismuth, capable of maintaining 26 C of cooling.

Excitons in Metals: Infinite Hole Mass

Abstract: The optical conductivity is evaluated for interband transitions between a flat valence band and a parabolic conduction band. The conduction band is filled with electrons to a Fermi energy ${\ensuremath{\mu}}_{F}$. The conductivity is calculated assuming that the electron-hole interaction is attractive, static, and short range. The final-state interactions between the electron and hole cause a divergence in the conductivity at the interband threshold. This divergence appears to go as a power law. For this case of an infinite hole mass, the exciton binding energy vanishes, since the singularity in the scattering amplitude occurs just at threshold.