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This paper describes a recent case study of replacing an eddy-current clutch with a modem medium-voltage adjustable-speed drive (ASD) for a 2250-hp extruder application. It covers key issues, justification, factory and field measurements of torque-speed profile from 0.5 to 60 Hz, as well power quality analysis. The paper reviews manufacturers' capability to build medium-voltage ASDs that produce very high and stable torque at very low speed. Index Terms--Adjustable-speed drives, drive topologies, extruder.

Based on Chandra and ROSAT observations, we investigated the nearby poor cluster A194, which hosts two luminous radio galaxies, NGC 547 (3C 40B) and NGC 541 (3C 40A). We demonstrated the presence of a large X-ray cavity (r ~ 34 kpc) formed by the giant southern radio lobe arising from 3C 40B in NGC 547. The estimated age of the cavity is t = 7.9 x 107 years and the total work of the active galactic nucleus is 3.3 x 1059 erg, hence the cavity power is Pcav = 1.3 x 1044 erg s-1. Furthermore, in the Chandra images of NGC 545 and NGC 541 we detected sharp surface brightness edges, identified as merger cold fronts, and extended tails. Using the pressure ratios between inside and outside the cold fronts we estimated that the velocities of NGC 545 and NGC 541 correspond to Mach numbers of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed, respectively. The low radial velocities of these galaxies relative to the mean radial velocity of A 194 imply that their motion is oriented approximately in the plane of the sky. Based on these and earlier observations, we concluded that NGC 545 and NGC 541 are falling through the cluster, whose center is NGC 547, suggesting that A194 is undergoing a significant cluster merger event. Additionally, we detected 20 bright X-ray sources around NGC 547 and NGC 541, a surprisingly large number, since the predicted number of resolved low-mass X-ray binaries and cosmic X-ray background sources is 2.2 and 4.1, respectively. To explain the nature of additional sources, different possibilities were considered, none of which are satisfactory. We also studied the origin of X-ray emission in Minkowski's object (MO) and concluded that it is most likely dominated by the population of high-mass X-ray binaries rather than by hot diffuse interstellar medium. Moreover, in view of the galaxy dynamics in A194, we explored the possibility that the starburst in MO was triggered by its past interaction with NGC 541, and concluded that it may be a viable path. [ABSTRACT FROM AUTHOR]

Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN out-bursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. [ABSTRACT FROM AUTHOR]

Chandra x-ray observations of NGC 4342, a low-stellar mass (MK = –22.79 mag) early-type galaxy, show luminous, diffuse x-ray emission originating from hot gas with temperature of kT ∼ 0.6 keV. The observed 0.5-2 keV band luminosity of the diffuse x-ray emission within the D25 ellipse is L0.5-2 keV = 2.7 × 1039 erg s–1. The hot gas has a significantly broader distribution than the stellar light, and shows strong hydrodynamic disturbances with a sharp surface brightness edge to the northeast and a trailing tail. We identify the edge as a cold front and conclude that the distorted morphology of the hot gas is produced by ram pressure as NGC 4342 moves through external gas. From the thermal pressure ratios inside and outside the cold front, we estimate the velocity of NGC 4342 and find that it moves supersonically (M ∼ 2.6) toward the northeast. Outside the optical extent of the galaxy, we detect ∼17 bright () excess x-ray point sources. The excess sources are presumably LMXBs located in metal-poor globular clusters (GCs) in the extended dark matter halo of NGC 4342. Based on the number of excess sources and the average frequency of bright LMXBs in GCs, we estimate that NGC 4342 may host roughly 850-1700 GCs. In good agreement with this, optical observations hint that NGC 4342 may harbor 1200 ± 500 GCs. This number corresponds to a GC specific frequency of SN = 19.9 ± 8.3, which is among the largest values observed in full-size galaxies. [ABSTRACT FROM AUTHOR]