The nonlinear evolution of magnetoacoustic waves in a nonadiabatic plasma is investigated analytically. The effect of plasma activity due to linear and quadratic heating and radiative cooling on propagating magnetoacoustic waves in a uniform plasma is considered. A nonlinear evolution equation is derived and stationary solutions are looked for the various combination of signs of the linear and quadratic heating-cooling terms, which determine the thermal activity of the plasma. It is shown that self-organizing magnetoacoustic waves (autowaves) exist in an active plasma. These wave have amplitudes that are independent from the initial conditions and function of plasma properties only. Their potential diagnostic purposes are discussed. Furthermore, magnetoacoustic autosolitary waves are shown to exist. They have been modeled using a novel perturbative technique, which allows to determine their propagation speed and shape. (C) 2010 American Institute of Physics. [doi:10.1063/1.3314721
Summary
Chemical enhanced oil recovery (EOR), including polymer and surfactant-based processes, is a method that operators consider to maximize oil recovery from onshore and offshore reservoirs. Because of the logistical, operational, and environmental differences and the footprint and required weight needed for additional injection and production equipment, offshore chemical EOR processes are challenged by greater complexity and costs as compared with onshore applications of the same technologies.
Chemical EOR commonly requires large volumes of injection chemicals, as well as demulsifiers to break produced-water/oil emulsions and inhibitors to control scale, resulting in high shipment and storage costs. The use of seawater and/or produced water for injection of the chemicals into offshore fields mandates stringent processing of both streams to allow optimal injectivity, sweep efficiency, and chemical effectiveness in the reservoir. Offshore production of saleable oil and clean water requires space- and weight-efficient oil/water-separation equipment. Currently, conventional methods for processing produced fluids fall short in both efficiency and compactness. High offshore drilling costs lead to relatively large well spacing and more difficulty in monitoring the EOR subsurface process, and lead to restrictions on the number of disposal wells. Finally, environmental restrictions limit the overboarding of toxic or poorly biodegradable EOR chemicals.
The industry is currently investigating the limiting factors pertinent to offshore chemical EOR. As a result of these efforts, new enabling chemistries and technologies are being examined for improving surface operations to allow cost-effective offshore chemical EOR to be performed in an environmentally sound and safe manner. Some of these recent chemical- and fluids-processing developments are described in this paper. Subsurface challenges to implementing offshore chemical EOR are also highlighted, along with potential solutions.
--This paper proposes a computationally efficient method, for accurate prediction of 3-dimensional (3D) high frequency eddy current loss in the rotor magnets of surface mounted permanent magnet machines employing the imaging method. 2D finite element analysis (FEA) is used to generate the information on radial and tangential 2D magnetic field variations (eddy current sources) within the magnet. The diffusion of eddy current sources along the axial plane of the magnet computed analytically is incorporated in the imaging method to establish the 3D eddy current source variations within the magnet. The modified method is validated with results from 3D time-stepped finite element analysis (FEA) for an 8-pole, 18-slot permanent magnet machine, evaluating its magnet loss considering axial and circumferential segmentation.Index Terms-Eddy current, finite element, permanent magnet machines.
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