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排序方式: 共有251条查询结果,搜索用时 15 毫秒
1.
Motion control with permanent-magnet AC machines 总被引:9,自引:0,他引:9
Jahns T.M. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(8):1241-1252
Motion control techniques have been developed to exploit the high efficiency and extremely fast dynamic response capabilities of permanent-magnet AC (PMAC) machines. Control techniques are reviewed separately for the two major classes of PMAC machines referred to as trapezoidal (i.e., brushless DC) and sinusoidal machines. While trapezoidal PMAC machine drives are distinguished by their controls simplicity and minimal sensor requirements, sinusoidal PMAC machine drives offer opportunities for extremely smooth torque production and extended high-speed operating ranges. Advanced PMAC machine control topics including sensor elimination techniques and robust servocontrol algorithms are reviewed, concluding with a discussion of PMAC machine drive application trends 相似文献
2.
Ekkehard H. Lutz 《Journal of the American Ceramic Society》1994,77(5):1274-1280
Plasma spraying, originally a surfacing technology used for ceramic coating of metal and nonmetal substrates, is suitable for producing large, full ceramic bodies, such as plates and tubes, in situ to almost the desired dimensions; i.e., conventional methods of designing by molding and casting green bodies followed by sintering are not required. These "plasma ceramics" exhibit characteristic mechanical and thermomechanical properties. Their porous laminar grain structure results in low E -modulus and strength, and in extreme thermal shock resistance, which is enhanced by the comparably high fracture resistance of the material. Because of these properties and their low hardness, plasma ceramics can be easily machined with almost conventional methods of metal processing. 相似文献
3.
In the field of flue gas cleaning, active coke plays an important role as adsorbant and catalyst. In the temperature range usually prevailing downstream of the air preheater of power plants, SO2 becomes adsorbed on carbonaceous materials and in a consecutive step is catalysed by the carbonaceous surface and converted to sulphuric acid. The quality demands for a cyclic regenerative process for SO2 removal are fulfilled by the active coke which is used in the BF-process. The same active coke catalyses the reaction of NO with NH3 to N2 and steam. This is the basis for processes for simultaneous SO2 and NOx removal. By the addition of ammonia the SO2 removal by active coke is improved. Two processes are described and results from the laboratory and from the demonstration plant for the BF-process are presented. These show that SO2 removal efficiences exceed 95% and NO conversions of > 80% can be realized without problems. The cost of the processes using active coke with ammonia addition are comparable with those of wet flue gas desulphurization processes without any additional equipment should NO have to be removed. 相似文献
4.
We demonstrate the planar integration of Talbot array illuminators designed to generate one-dimensional spot arrays. The array illuminator basically consists of a phase grating and a cylindrical diffractive lens integrated as a single diffractive optical element onto a transparent glass substrate. We discuss various design aspects, and we focus on problems typical for planar-integrated free-space optics like the tilted optical axis of the system. Experimental results and measurements, which were obtained from planar-integrated setups fabricated as surface-relief structures on a transparent glass substrate by use of standard photolithography, are included. 相似文献
5.
Ekkehard Lange 《Journal of Low Temperature Physics》1996,105(3-4):645-650
The anomalous properties of the Hall constant in the normal state of high-Tc superconductors are investigated within the Hubbard model. In Mori theory, the frequency dependent Hall constant is given as the sum of its infinite frequency limit and a memory function contribution. The first term (R
H
) was already considered by Shastry et al.1 In perturbation theory and in the limit of infinite spatial dimensions, the memory function contribution causes the Hall constant to change sign as a function of doping () and to decrease as a function of temperature, if we allow U to be 2W (U: Coulomb repulsion; W: bandwidth). In the limit U , the memory function is calculated via its moments. For frequencies W U, this leads to a decrease of R
H
by a factor of (1 + )/2. 相似文献
6.
Ekkehard Diedrich 《Datenschutz und Datensicherheit - DuD》2011,35(1):72-73
DuD ReportVeranstaltungsbesprechungen
Stefan Hügel transparenz.arbeit.kontrolle, Gemeinsame Jahrestagung von FIfF und DVD K?ln, 5.–7. November 2010 相似文献7.
Future high-performance computing (HPC) architectures will consist of whole parallel computing systems integrated on chip-level and boards mounted with lots of computing chips and chip-external main memory. Photonic networks on board and photonic network on chips (NoCs) offer the potential to fulfill the high bandwidth requirements in such systems. In addition they need less power, offer better EMC capabilities and can reduce cabling effort compared to electronic networks. Due to their non-blocking property Clos networks are frequently used in HPC architectures. Therefore we investigated how a photonic on-board Clos network can be realized using Coarse Wavelength-Division-Multiplexing (CWDM) techniques with state-of-the art components based on fiber technology. In addition we present a new photonic Clos NoC architecture based on Wavelength Interchanging (WI) elements, optical waveguide structures, mode-locked laser sources, nanophotonic microrings and passive optical deflection elements to reduce the number of switches. We discuss the benefits and drawbacks for using different optical technologies for such an architecture. 相似文献
8.
Bert Schlatterer und Ekkehard Weiset 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1982,175(6):392-398
Zusammenfassung Es wird über Sulfonamidbefunde in Nieren und Muskulatur geschlachteter Tiere (36 Rinder, 3 Schweine) berichtet. Gewebeproben wurden vor und nach der Gewebefraktionierung mit einem durch Trimethoprim modifizierten Hemmstofftest (Teststamm:Bac. subtilis BGA) auf Hemmaktivität sowie mit einer dünnschichtchromatographischen Methode (DC) auf Sulfonamide untersucht. Als Indikatorreakti on für die Darstellung der Sulfonamide diente deren Derivatisierung mit Fluorescamin (Fluram) nach zweidimensionaler Trennung. Insgesamt wurden 11 verschiedene Sulfonamide identifiziert. An Hand von Dosis-Wirkungsbeziehungen wurde gezeigt, daß das mit Trimethoprim modifizierte Testsystem mit Ausnahme der enteral angewandten und kaum absorbierbaren Substanzen allen sonst untersuchten Sulfonamiden gegenüber mittel- bis hochgradig sensitiv ist. Hierbei liegt die minimale Hemmkonzentration im Agarlochtest (50 l) zwischen 10 und 25 Nanogramm je Sulfonamid. Der Vergleich der Ergebnisse von mikrobiologischem Test und chemischer Analyse zeigte bei dem vorliegenden Untersuchungsmaterial, daß knapp 30% der mit dem modifizierten Hemmstofftest positiv reagierenden Nierenproben aufgrund des DC-Befundes nicht als sulfonamidhaltig anzusehen waren, während umgekehrt bei den Muskelproben nahezu 30% der mit Hilfe der DC als sulfonamidhaltig erkannten Proben durch den mikrobiologischen Test nicht erfaßt wurden.
Analysis of sulfonamides in tissues of slaughtered animals. Comparison of results from a microbiological test and from thin layer chromatographic analysis after derivatization with fluorescamin
Summary Sulfonamide residues in kidneys and muscles of slaughtered animals (36 cattle, 3 pigs) are reported. Tissue samples were examined prior to and after separation first for inhibitory activity by an inhibition test modified by addition of trimethoprim and subsequently for sulfonamides by thin layer chromatography (TLC). Sulfonamides were demonstrated by derivatisation with fluorescamine (Fluram) after two dimensional separation. A total of 11 different sulfonamides was identified. It could be demonstrated by dosage-activity relationships that the test system modified with trimethoprim was moderately to highly sensitive to all examined sulfonamides with the exception of the enterally applied and hardly absorbable substances. In this test (agar diffusion test, 50 l per well) the minimal inhibotory concentration is between 10 and 25 ng for each of the sulfonamides. Comparing the microbiological test with the chemical analysis it could be demonstrated that nearly 30% of the kidney samples which were positive in the modified inhibition test did not contain sulfonamides according to interpretation of the TLC. On the other hand nearly 30% of the muscle samples containing sulfonamides (found by TLC) did not react to the microbiological test.相似文献
9.
Applications of sol-gel-processed interphase catalysts 总被引:2,自引:0,他引:2
10.
Welchko B.A. Wai J. Jahns T.M. Lipo T.A. 《Industry Applications, IEEE Transactions on》2006,42(1):113-120
This paper proposes a control method to the magnet flux in an interior permanent-magnet (IPM) motor following short-circuit-type faults in either the inverter drive or motor stator windings. Phase-based control is employed to implement the flux-ing-control method so that it is possible to take advantage of a zero-sequence current in order to minimize the current in the shorted phase. It is shown that phase-based control results in a smaller induced current than when employing a synchronous-frame dq0 current regulator. The induced torque is also less than that when employing a purposely commanded symmetrical short circuit in response to a short-circuit-type fault. In the paper, the complete magnet-flux-ing-control algorithm is derived with reference to the proposed phase-current-control method. The impact of controlling the zero-sequence current on the resulting phase currents is presented. Both simulation and experimental results are presented, verifying the operation of the proposed methods. 相似文献