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81.
82.
Übersicht Die zusätzlichen Stromwärmeverluste im Läufer ändern sich bei einem Drehzahlstellantrieb je nach Betriebsweise des Umrichters beträchtlich. Im Blockbetrieb ist der Gesamtverlust kaum vom Lastzustand (Schlupf) abhängig. Im Synchronismus sind die Verluste jedoch ungleichmäßig auf die einzelnen Läuferstränge oder Stäbe verteilt. Die Maxima und Minima der Stabverluste stehen im Synchronismus etwa im Verhältnis 10:1 zueinander. Die Verluste in dem am stärksten beaufschlagten Läuferstab liegen nicht wesentlich niedriger als im Bemessungsbetrieb. Die gesamten zusätzlichen Stromwärmeverluste wachsen bei konstanter Speisefrequenz quadratisch mit der Spannung. Im Feldschwächbereich nehmen sie in Abhängigkeit von der Speisefrequenz ungefähr nach der Funktion 1/1,52 ab.
Additional rotor I2R-losses and their spatial distribution in three-phase windings respectively rotor bars of induction motors fed from six-step U-invertors
Contents Additional rotor I2R-losses in speed variable drives with induction motors change very strongly with the operation mode of the invertor. During block-operation the sum of these additional losses is nearly independent of the load (slip). But at synchronous speed the losses are distributed very unequally among the phase windings respectively the rotor bars. The ratio of maximum to minimum bar losses is approximately 10:1. The highest ohmic loss in a bar is nearly the same as the rated bar loss. The additional rotor I2R-losses change with the square of the voltage. In the field weakening range the losses drop with the frequency approximately following the function 1/1,52.相似文献
83.
The experimentally determined chromaticities and reflectance spectra of films consisting of uniform ellipsoidal or spherical colloidal hematite particles are compared with calculated values and are found to be in good agreement. The theoretical treatment of the light-scattering problem involves the Mie theory for the spheres and the T-matrix method for the ellipsoids. The reflectance spectra for the pigment films are calculated through the use of the Kubelka-Munk analysis. 相似文献
84.
Building brains for bodies 总被引:10,自引:2,他引:8
We describe a project to capitalize on newly available levels of computational resources in order to understand human cognition. We are building an integrated physical system including vision, sound input and output, and dextrous manipulation, all controlled by a continuously operating large scale parallel MIMD computer. The resulting system will learn to think by building on its bodily experiences to accomplish progressively more abstract tasks. Past experience suggests that in attempting to build such an integrated system we will have to fundamentally change the way artificial intelligence, cognitive science, linguistics, and philosophy think about the organization of intelligence. We expect to be able to better reconcile the theories that will be developed with current work in neuroscience. 相似文献
85.
Algorithm for the determination of intrinsic optical constants of metal films: application to aluminum 总被引:2,自引:0,他引:2
Rakić AD 《Applied optics》1995,34(22):4755-4767
Optical and electron-energy-loss data for evaporated-aluminum films have been critically analyzed and used in an iterative, self-consistent algorithm that represents a combination of the Kramers-Kronig analysis and the semiquantum-model application. The novel values of the intrinsic optical functions of aluminum have been determined in a wide spectral range from 200 μm (6.2 meV) to 0.12 nm (10 keV). These functions are in accordance with recent calculations by Lee and Chang [Phys. Rev. B 49, 2362 (1994)], with dc conductivity measurements, and are in good agreement with both peak positions and line widths obtained from electron-energy-loss experiments. The results are examined for internal consistency by inertial and f-sum rules. 相似文献
86.
The anodic stability of an electrodeposited ruthenium electrode was measured by anodic galvanostatic polarization in 0.5 mol dm–3 H2SO4 solution. The role of water and adsorbed hydroxyl groups in electrode stability was determined by means of thermogravimetric analysis. A continuous weight loss due to water removal and condensation of hydroxyl groups was detected between 120 and 430 °C. The loss of a hydrous component of the oxide layer was in direct correlation with the increase of the anodic stability. Between 430 and 480 °C a weight gain was detected on the thermogravimetric curve. It was attributed to the formation of the ruthenium oxide layer in a higher oxidative state. This finding was confirmed by X-ray photoelectron spectroscopy measurements. 相似文献
87.
B. Kaluderović 《Journal of Materials Science》1995,30(7):1839-1844
Carbon-carbon composites were prepared with commercially available carbonized and graphitized fibres, with a mixture of pitch and phenolic resin as a binder and pitch as an impregnant. The contents of pitch in mixtures were: 0, 10, 20 and 30 wt %. The influence of pitch content in the mixture and fibre type on mass loss, shrinkage and mechanical properties of the composites was examined. With an increase of pitch content mass loss and shrinkage increased, while mechanical properties decreased. After three densification cycles, flexural strength increased with increasing pitch content in the binder, especially for composites with graphitized fibres. 相似文献
88.
Compagnucci Ivan Corradini Flavio Fornari Fabrizio Polini Andrea Re Barbara Tiezzi Francesco 《Software and Systems Modeling》2023,22(3):969-1004
Software and Systems Modeling - The Internet of things has been adopted in several sectors both influencing how people work and enhancing organizations’ business processes. This resulted in... 相似文献
89.
Knowledge and Information Systems - Pattern mining is a fundamental data mining task with applications in several domains. In this work, we consider the scenario in which we have a sequence of... 相似文献
90.
Iovine Andrea Lops Pasquale Narducci Fedelucio de Gemmis Marco Semeraro Giovanni 《Journal of Intelligent Information Systems》2022,58(2):337-362
Journal of Intelligent Information Systems - Conversational Recommender Systems have received widespread attention in both research and practice. They assist people in finding relevant and... 相似文献