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 & Signal. The organization has 76365 authors who have published 110557 publications receiving 1885108 citations. The organization is also known as: General Electric Company & GE.

Optimization of spoiled gradient‐echo phase imaging for in vivo localization of a focused ultrasound beam

Abstract: The parameters of a spoiled gradient-echo (SPGR) pulse sequence have been optimized for in vivo localization of a focused ultrasound beam. Temperature elevation was measured by using the proton resonance frequency shift technique, and the phase difference signal-to-noise ratio (SNR delta phi) was estimated in skeletal muscle and kidney cortex in 10 rabbits. Optimized parameters included the echo time equivalent to T2* of the tissue, the longest repetition time possible with a 20-s sonication, and the flip angle equivalent to the Ernst angle. Optimal SPGR phase imaging can detect a sonication beam with a peak phase difference of 0.55 radian, which corresponds to a temperature elevation of 7.3 degrees C. The sonication beam can be localized within one voxel (0.6 x 0.6 x 5 mm3) at power levels that are below the threshold for thermal damage of the tissue.

The Ubitron, a high-power traveling-wave tube based on a periodic beam interaction in unloaded waveguide

Abstract: The Ubitron is a high-power traveling-wave tube which makes use of the interaction between a magnetically undulated periodic electron beam and the TE 01 mode in unloaded waveguide. The electron-wave interaction exhibits the same type of first-order axial beam bunching characteristic of the conventional slow-wave traveling-wave tube; hence, it can be used in place of conventional O-type interaction in extended interaction klystrons and electron accelerators, as well as traveling-wave tubes. Experimental results are presented for the simplest physical embodiment of the Ubitron, which consists of an undulated pencil beam in a rectangular waveguide. Two of the unique features of this tube are very broad interaction bandwidth which results from the absence of a dispersive slow-wave circuit, and variable interaction phase velocity--hence, variable saturation power level. Among the physical embodiments of the Ubitron are a number of higher-order mode waveguide and beam configurations. These include plane, coaxial, and circular waveguides, all supporting the TE 01 mode, interacting with magnetically undulated sheet, hollow and cylindrical beams, respectively. The advantage of these configurations, which have not yet been tested experimentally, is that they provide a very large interaction area for beam placement. This property, plus the fact that the peak interacting field is far from the waveguide walls, makes the Ubitron an interesting prospect for high-power millimeter wave amplification.

On the Mechanics of Chip Segmentation In Machining

Abstract: The mechanics of chip segmentation, during machining of a cold rolled steel has been investigated from a phenomenological point of view using a high speed movie camera and an explosive quick stop device. The latter was used for obtaining chip root samples at various stages of segmentation for subsequent examination in the Optical and Scanning Electron Microscope (SEM). The chip segmentation process is found to arise as a result of instabilities in the cutting process and is further augmented by the dynamic response of part of the machine tool structure. This process involves a slow forward movement of the plastic boundary in the primary shear zone forming a ramp on the free surface of the chip followed by a rapid return of the plastic boundary back towards the tool forming a step on the chip segment as a result of partial fracture at the free surface. This process is characterized by large strains, low shear angles that oscillate cyclically and stick-slip friction on the rake face. The instability in the cutting process is proposed to be due to the negative stress—strain characteristics of certain materials at large strains, as Walker and Shaw [1] proposed, involving void formation around second phase particles, their propagation into microcracks in the primary shear zone and coalescence of these cracks leading to partial fracture. Evidence for this has been obtained in this investigation.

Transferrable, self-supporting pellicle for elastomer light valve displays and method for making the same

Abstract: An elastomeric light valve has a substrate with a principal surface on which is formed a multiplicity of pixels; each pixel includes a first set of pixel electrodes interdigitated with a second set of pixel electrodes. A silicone elastomer gel is disposed over both the principal substrate surface and the two sets of pixel electrodes. At least one silicone/polycarbonate self-supporting pellicle is disposed substantially completely over the gel layer; the pellicle and elastomer gel layer are heat cured to improve the response of the layers to electrostatic forces induced in the light valve by control voltages applied during operation of the light valve. A layer of gold is disposed over the at least one pellicle and a layer of silver is disposed over the gold layer to provide an exposed specular surface which is easily deformed and resilient to transverse stresses. Address-lines are provided for applying control voltages to the first and second sets of pixel electrodes responsive to a video signal; a bias voltage is applied to the gold and silver layers to provide optimum light valve sensitivity at lower control voltages.

Torque Production in Permanent-Magnet Synchronous Motor Drives with Rectangular Current Excitation

Abstract: Special features of torque production in self-controlled permanent-magnet (PM) synchronous motor drives with rectangular current excitation have been investigated. Addressed issues include the generation of undesired torque pulsations at low speeds and system operating locus limits imposed at high speeds by saturation of the current regulator. Attention is limited to motors in which sources of reluctance torque are suppressed by surface-mounting of the rotor magnets and skewing of the stator slots. Results from the low-speed investigation indicate that the pulsating torque can be minimized by a combination of steps including proper adjustment of the rotor magnet pole atc and effective use of rotor speed feedback compensation. High-speed saturated-regulator performance is significantly influenced by the 120 electrical degree inverter switch conduction intervals inherent with rectangular current excitation. The system torque-speed operating envelope can be expanded by several means, including on-line adjustment of the converter excitation phase angle a, but resulting performance trade-offs require careful scrutiny. A 15-kW prototype PM synchronous motor drive system has been used to confirm key analytical results.