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431.
Harmonic components in load currents have a larger impact on the load noise level of transformers than might be expected from their amplitude. There are several reasons for this larger impact: (a) the interaction of higher harmonics with the large fundamental load current at power frequency, (b) the increasing sound radiation efficiency with increasing frequency, and (c) the greater sensitivity of the human ear to higher frequencies, which is considered in sound measurements by applying the A-weighting filter. This paper describes the process of generation, transmission, and emission of load noise in the presence of load harmonics. A calculation scheme is presented that is able to estimate the noise increase and the noise spectrum of electrical transformers under non-sinusoidal load conditions. The proposed calculation scheme is applied to three practical examples. 相似文献
432.
A. R. Dicker P. Campbell B. Cheal D. Gorelov J. Hakala D. J. S. Johnson A. Jokinen V. Kolhinen J. Koponen I. D. Moore H. Penttilä I. Pohjalainen M. Reponen S. Rinta-Antila V. Sonnenschein A. Voss 《Hyperfine Interactions》2014,227(1-3):139-145
The IGISOL (Ion Guide Isotope Separator On-Line) facility at the University of Jyväskylä accelerator laboratory has been upgraded and relocated to a purpose built laboratory. The new laboratory includes a dedicated MCC30 proton/deuteron cyclotron, which in conjunction with beams from the K130 cyclotron, will greatly increase the beam time available at the facility. Full off-line commissioning of the laser spectroscopy beam-line was achieved in February 2013 and on-line commissioning with radioactive beams was achieved in May 2013. Optical hyperfine resonance spectra were obtained for previously studied radioactive molybdenum isotopes and used to investigate our long term stability, efficiency and ability to successfully reproduce previous results from IGISOL III. A preliminary spectrum for the previously unmeasurable $^{107}$ Mo was collected, displaying the improved capabilities of the new facility. Both data-sets show that the laser-line is ready for future experiments. The IGISOL IV beams are cleaner and have a higher radioactive content compared to similar experiments at IGISOL III. 相似文献
433.
Mané E Voss A Behr JA Billowes J Brunner T Buchinger F Crawford JE Dilling J Ettenauer S Levy CD Shelbaya O Pearson MR 《Physical review letters》2011,107(21):212502
Collinear-laser spectroscopy with the bunched-beams technique was used for the study of neutron deficient Rb isotopes, out to (74)Rb (N = Z = 37) at TRIUMF. The measured hyperfine coupling constants of (76,78m)Rb were in agreement with literature values. The nuclear spin of (75)Rb was confirmed to be I = 3/2, and its hyperfine coupling constants were measured for the first time. The mean-square charge radius of (74)Rb was determined for the first time. This result has improved the isospin symmetry breaking correction term used to calculate the Ft value, with implications for tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. 相似文献
434.
Ricaud S Jaffres A Loiseau P Viana B Weichelt B Abdou-Ahmed M Voss A Graf T Rytz D Delaigue M Mottay E Georges P Druon F 《Optics letters》2011,36(21):4134-4136
We present the first demonstration of a Yb:CALGO thin-disk laser. In a slightly multimode configuration, we obtained up to 30?W of average power at a slope efficiency of 40% and an optical-to-optical efficiency of 32%. With a single-mode cavity, an average power of 25?W was achieved. A tuning range from 1018 to 1052?nm could be demonstrated by inserting a prism into the cavity. In the Q-switched regime, we obtained 1?mJ of pulse energy at a repetition rate of 100?Hz. 相似文献
435.
The linear and nonlinear optical response of graphene are studied within a quantum-mechanical, full-band, steady-state density-matrix model. This nonpurtabative method predicts the saturatable absorption and saturable four-wave mixing of graphene. The model includes τ(1) and τ(2) time constants that denote carrier relaxation and quantum decoherence, respectively. Fits to existing experimental data yield τ(2) < 1 fs due to carrier-carrier scattering. τ(1) is found to be on the timescale from 250 fs to 550 fs, showing agreement with experimental data obtained by differential transmission measurements. 相似文献
436.
The automated multi‐level sub‐structuring (AMLS) method is a powerful technique to determine a large number of eigenpairs with moderate accuracy of huge symmetric and definite eigenvalue problems in structural analysis. This paper is concerned with an adapted version of AMLS for eigenfrequency analysis of fluid–solid interaction systems. Although fluid–solid vibrations are governed by an unsymmetric eigenproblem, the modified AMLS method needs approximately the same computational effort. An error bound related to the eigenvalue approximations is proved. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
437.
A chiral Mn(salen) complex exhibiting two lactam binding sites at two rigid 1,5,7-trimethyl-3-azabicyclo[3.3.1]nonan-2-one skeletons is capable of enantioselective sulfoxidation due to spatially remote substrate hydrogen bonding. 相似文献
438.
Voss K Becker M Villinger A Emel'yanenko VN Hellmann R Kirchner B Uhlig F Verevkin SP Schulz A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(48):13526-13537
Room‐temperature ionic liquids containing the triply charged tricyanomelaminate (tcmel) ion [C3N6(CN)3]3? were synthesized. The 1‐methyl‐3‐methylimidazolium (MMIm), 1‐ethyl‐3‐methylimidazolium (EMIm), and 1‐butyl‐3‐methylimidazolium (BMIm) salts of the tricyanomelaminate ion have glass transition temperatures (?6, ?20, and ?30 °C) similar to those found for the analogous monomeric dicyanoamide salts. They are thermally stable up to over 200 °C and dissolve in polar organic solvents. Addition of B(C6F5)3 to M3[tcmel] (M=Na, MMIm, EMIm, BMIm) yields salts containing the very voluminous adduct ion [C3N6{CN ? B(C6F5)3}3]3? (tcmel_3B). The solid‐state structure of [MMIm]3[tcmel] shows only long cation ??? anion contacts but in large number, while the solid‐state structure of [Na(THF)3]3[tcmel_3B] ? 1.76 THF displays strong interactions of the sodium cation with the amido nitrogen atoms of the anion. Hence this adduct anion cannot be regarded as a weakly coordinating anion. A similar situation is found for the MMIm salt, [MMIm]3[tcmel_3B] ? 2.66 CH2Cl2, in which weak hydrogen bonds with the acidic proton of the MMIm ion are observed. On the basis of computations the energetics, structural trends, and charge transfer of adduct anion formation were studied. 相似文献
439.
Matovic NJ Stuthe JM Challinor VL Bernhardt PV Lehmann RP Kitching W De Voss JJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(27):7578-7591
Chamaelirium luteum is used in traditional medicine systems and commercial botanical dietary supplements for the treatment of female reproductive health problems. Despite the wide use of this herb, only very limited phytochemical characterisation is available. Our investigation of C. luteum roots led to the isolation of two new steroidal saponins 1 and 2 that contain an unusual aglycone 3 . The absolute configurations of these molecules were unable to be determined spectroscopically and thus the total synthesis of 3 was undertaken and achieved in 16 steps and 1.6 % overall yield from pregnenolone. The key step in the synthesis was the stereoselective installation of the side chain at C‐17 and C‐20, which employed anion‐accelerated oxy‐Cope methodology. The relative configuration of aglycone 3 was determined by X‐ray crystallography of an advanced synthetic intermediate. The absolute configuration was based upon that of the pregnenolone‐derived steroidal skeleton and determined to be 23R,24S. 相似文献
440.
Raman spectroscopy of apatite irradiated with swift heavy ions with and without simultaneous exertion of high pressure 总被引:1,自引:0,他引:1
J. Liu U.A. Glasmacher M. Lang C. Trautmann K.-O. Voss R. Neumann G.A. Wagner R. Miletich 《Applied Physics A: Materials Science & Processing》2008,91(1):17-22
Durango apatite was irradiated with energetic U ions of 2.64 GeV and Kr ions of 2.1 GeV, with and without simultaneous exposure
to a pressure of 10.5 GPa. Analysis by confocal Raman spectroscopy gives evidence of vibrational changes being marginal for
fluences below 5×1011 ions/cm2 but becoming dominant when increasing the fluence to 8×1012 ions/cm2. Samples irradiated with U ions experience severe strain resulting in crystal cracking and finally breakage at high fluences.
These radiation effects are directly linked to the formation of amorphous tracks and the fraction of amorphized material increasing
with fluence. Raman spectroscopy of pressurized irradiated samples shows small shifts of the band positions with decreasing
pressure but without a significant change of the Grüneisen parameter. Compared to irradiations at ambient conditions, the
Raman spectra of apatite irradiated at 10.5 GPa exhibit fewer modifications, suggesting a higher radiation stability of the
lattice by the pressure applied.
PACS 61.80.Jh; 62.50.+p; 07.35.+k 相似文献