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141.
Determining torque and current at locked rotor and various slips during the acceleration test on a synchronous machine is very tedious and time consuming. Induction and synchronous machines behave similarly during acceleration except that synchronous machine acceleration can include a pulsation torque. Because of the salient poles, conditions exist where the synchronous motor has minimum torque at quadrature axis and maximum torque at direct axis during locked rotor or stall. Since synchronous machines do not have large numbers of rotor bars in the amortisseur winding, like the induction motor has in the squirrel cage, their stall times tend to be shorter. Due to the shorter stall time and large starting torque, locked-rotor torque and current are generally determined from acceleration tests conducted at reduced voltage rather than by tests at stand-still. Data showing that saturation effects impact both torque and current are presented in this paper. The data shows that the voltage index that has to be applied to the torque and current measured at reduced voltage varies with speed and can be obtained from a series of acceleration tests 相似文献
142.
Marcus Frings 《Nexus Network Journal》2002,4(1):9-32
The never-ending—but always young—discussion about the Golden Section in architecture never lacks a hint at Luca Pacioli and
architectural theory. But what it always lacks is a thorough study of the Golden Section in architectural theory. This paper
aims to present this analysis. Marcus Frings traces the Golden Section from the mathematical and rather theoretical character
of Pacioli’s concept, the the treatises of Alberti, Serlio, and Palladio, to Adolf Zeising in the nineteenth century. and
to theorist Matila Ghyka and the practitioners Ernst Neufert and Le Corbusier in the twentieth. In the latter’s writings and
designs the Golden Section seems to play the role of a scholarly element which shows the master’s theoretical erudition, leading
to contemporary architects such as Ricardo Bofill. 相似文献
143.
The direct introduction of particulate matter into glow discharge atomic emission and mass spectrometry sources through a particle beam/momentum separator apparatus is described. Vacuum action through a narrow (0.0625 in. i.d.) stainless steel tube allows the introduction of discrete samples of NIST SRM 1648 urban particulate matter (UPM) and caffeine in powder form. Introduction of "ambient" airborne particulate matter is also possible. Particles passing through the aerodynamic momentum separator impinge on the heated (~200-250 °C) inner surface of the glow discharge plasma volume and are flash-vaporized. The resultant atoms/molecules are subjected to excitation/ionization collisions within the low-pressure (0.5-5 Torr of He or Ar) plasma, producing characteristic photon emission and/or signature ionic species. In this way, atomic emission and mass spectrometry identification of particle constituents is possible. Basic design aspects of the apparatus are presented, and demonstrations of atomic emission detection of the constituents in the NIST SRM illustrate the general characteristics of the approach. Transient atomic emission signals are captured for the introduction of preweighed, discrete samples, with the integrated areas used to construct analytical response curves. Limits of detection using this relatively simple atomic emission system are on the order of tens of nanograms for sample masses of ~50 μg. Mass spectrometric monitoring of introduced caffeine particles and a mixture of polycyclic aromatic hydrocarbons (PAHs) illustrates the ability of the glow discharge plasma to produce high-quality, library (electron impact) searchable mass spectra of molecular species while also yielding isotopic identification of elemental components of the UPM. Limits of detection for Fe in the NIST SRM are on the order of 175 ng of material, equivalent to ~7 ng of analyte Fe. It is believed that the small size, low power consumption, ease of operation, and multimode sampling capabilities (AES/MS) of the particle beam-glow discharge (PB-GD) apparatus hold promise for applications in continuous monitoring and discrete particle sampling. 相似文献
144.
Thierry Klein Isabelle Joumard Jacques Marcus Robert Cubitt 《Journal of Low Temperature Physics》1999,117(5-6):1353-1357
Small Angle Neutron Scattering has been used to observe diffraction from the flux line lattice in the fully isotropic (K, Ba)BiO
3
high T
c
superconductor. We show that the flux lines are ordered into a hexagonal lattice at low field (H < H
e
0.6T H
g (0) where H
g
is the second order vortex glass transition field). The diffracted intensity continuously drops to zero as the field is increased towards H
e
. Those observations are in good agreement with recent theoritical works which suggested that the formation of dislocations becomes favorable above H
e
leading to a glassy structure. The field H
e
lies close to the onset of the second peak in magnetization measurements indicating that this peak is related to the change in the vortex structure. 相似文献
145.
Marcus Fleck Alexander I. Lichtenstein Andrzej M. Ole Lars Hedin 《Journal of Superconductivity》1999,12(1):147-149
We investigate the consequences of an incommensurate magnetic order in doped La2–x
Sr
x
CuO4 using dynamical mean-field theory for the effective single-band model. The high-energy optical transitions are due to high-energy excitations across large Mott–Hubbard gap, while low-energy excitations involve a pseudogap induced by the local spin order. The latter lead to a strong drop in the scattering rate at low , in qualitative agreement with the experimental data. 相似文献
146.
The effect of converting from pravastatin to simvastatin on the pharmacodynamics of warfarin 总被引:1,自引:0,他引:1
Glycosylated amino acids and glycosylated human serum albumin reduce nitrite to nitric oxide under anaerobic conditions. The amount of nitric oxide produced was recorded by generation of nitrosoHb from deoxyHb. Without preincubation after the addition of sodium nitrite, glucose or a mixture of glucose with amino acid or serum albumin did not cause spectrophotometrically detectible transformation of deoxyHb into nitrosoHb. The generation of NO increased with an increase in content of colored "final" products of amino acid and serum albumin glycosylation in the incubation mixture. The incubation of blood plasma of patients with diabetes mellitus with nitrite also resulted in the increased production of NO as compared to blood plasma of healthy subjects. During the incubation of healthy subjects' blood plasma with nitrite a small amount of NO was produced. The removal of low-molecular-weight compounds was accompanied by a significantly decreased generation of NO by blood plasma. 相似文献
147.
Macedo Carlos Eduardo; Martinez Raquel Chacon Ruiz; Brand?o Marcus Lira 《Canadian Metallurgical Quarterly》2006,120(3):625
Chemical stimulation of the inferior colliculus (IC) with semicarbazide--an inhibitor of the gamma aminobutyric acid synthesizing enzyme--functions as an unconditioned stimulus in the conditioned place aversion test (CPA), and electrolytic lesions of the basolateral amygdala (BLA) enhance the aversiveness of the IC stimulation. This study examined the effects of inactivation of the BLA with muscimol on the conditioned and unconditioned fear using semicarbazide injections into the IC of rats subjected to conditioned (CPA) or unconditioned (open field) fear tests. In both tests, the rats were injected with semicarbazide or saline into the IC and muscimol or saline into the BLA. Muscimol decreased the CPA and increased the unconditioned fear elicited by IC injections of semicarbazide. These findings indicate that distinct modulatory mechanisms in the BLA are recruited during the conditioned and unconditioned fear triggered by IC activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
148.
A distance-measures approach to the problems of identification and approximation of queueing systems is presented. This approach combines ideas from statistical robustness, information-type measures, and parameter-continuity of stochastic processes. 相似文献
149.
Refusal to eat by the elderly, and subsequent malnutrition, occurs in both institutional and community settings. Causes include physiologic changes associated with aging, mental disorders such as dementia and depression, and medical, social, and environmental factors. Treatment approaches call for management of these causes while considering the roles that medicine, ethics, and culture play in the process. 相似文献
150.