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631.
Johannes Tophøj Rasmussen Georges-Henri Cottet Jens Honoré Walther 《Journal of computational physics》2011,230(17):6742-6755
We present a novel multiresolution Vortex-In-Cell algorithm using patches of varying resolution. The Poisson equation relating the fluid vorticity and velocity is solved using Fast Fourier Transforms subject to free space boundary conditions. Solid boundaries are implemented using the semi-implicit formulation of Brinkman penalization and we show that the penalization can be carried out as a simple interpolation. We validate the implementation against the analytic solution to the Perlman test case and by free-space simulations of the onset flow around fixed and rotating circular cylinders and bluff body flows around bridge sections. 相似文献
632.
It is well known that the Kerr–NUT–AdS–dS black hole admits two linearly independent Killing vectors and possesses a hidden symmetry generated by a rank-2 Killing tensor. The near-horizon geometry of an extremal Kerr–NUT–AdS–dS black hole admits four linearly independent Killing vectors, and we show how the hidden symmetry of the black hole itself is carried over by means of a modified Killing–Yano potential which is given explicitly. We demonstrate that the corresponding Killing tensor of the near-horizon geometry is reducible as it can be expressed in terms of the Casimir operators formed by the four Killing vectors. 相似文献
633.
Nils Henry Williams Rasmussen 《Archiv der Mathematik》2011,97(2):135-140
We give a geometric construction of sub-linear systems on a K3 surface consisting of smooth curves C with infinitely many ${g^1_{{\rm gon}(C)}}$ ??s. 相似文献
634.
A. Gutierrez M. D. Ashkezari M. Baquero-Ruiz W. Bertsche C. Burrows E. Butler A. Capra C. L. Cesar M. Charlton R. Dunlop S. Eriksson N. Evetts J. Fajans T. Friesen M. C. Fujiwara D. R. Gill J. S. Hangst W. N. Hardy M. E. Hayden C. A. Isaac S. Jonsell L. Kurchaninov A. Little N. Madsen J. T. K. McKenna S. Menary S. C. Napoli P. Nolan K. Olchanski A. Olin P. Pusa C. Ø. Rasmussen F. Robicheaux R. L. Sacramento E. Sarid D. M. Silveira C. So S. Stracka J. Tarlton T. D. Tharp R. I. Thompson P. Tooley M. Turner D. P. van der Werf J. S. Wurtele A. I. Zhmoginov 《Hyperfine Interactions》2015,231(1-3):21-28
We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ~ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime. 相似文献
635.
We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25 °C. By measuring the excess partial molar enthalpy of Gly, HGlyEH_{\mathrm{Gly}}^{\mathrm{E}}, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}, in the presence of various samples (S). For S, tert-butanol (TBA), 1-propanol (1P), urea (UR), NaF, NaCl, NaBr, NaI, and
NaSCN were used. It was found that hydrophobes (TBA and 1P) reduce the values of HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}} considerably, but a hydrophile (UR) had very little effect on HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. The results with Na salts indicated that there have very little effect on HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. This contrasts with our earlier studies on 1P–S–H2O in that Na+, F− and Cl− are found as hydration centers from the induced changes on HIP-IPEH_{\mathrm{IP}\mbox{--}\mathrm{IP}}^{\mathrm{E}} in the presence of S, while Br−, I−, and SCN− are found to act as hydrophiles. In comparison with the Hofmeister ranking of these ions, the kosmotropes are hydration centers
and the more kosmotropic the higher the hydration number, consistent with the original Hofmeister’s concept of “H2O withdrawing power.” Br−, I− and SCN−, on the other hand, acted as hydrophiles and the more chaotropic they are the more hydrophilic. These observations hint that
whatever effect each individual ion has on H2O, it is sensitive only to hydrophobes (such as 1P) but not to hydrophiles (such as Gly). This may have an important bearing
towards understanding the Hofmeister series, since biopolymers are amphiphilic and their surfaces are covered by hydrophobic
as well as hydrophilic parts. 相似文献
636.
637.
S. T. Han E. N. Comfoltey M. A. Shapiro J. R. Sirigiri D. S. Tax R. J. Temkin P. P. Woskov D. A. Rasmussen 《International Journal of Infrared and Millimeter Waves》2008,29(11):1011-1018
We report the measurement of small losses in transmission line (TL) components intended for high-power millimeter-wave applications.
Measurements were made using two different low-power techniques: a coherent technique using a vector network analyzer (VNA)
and an incoherent technique using a radiometer. The measured loss in a 140 GHz 12.7 mm diameter TL system, consisting of 1.7 m
of circular corrugated waveguide and three miter bends, is dominated by the miter bend loss. The measured loss was 0.3 ± 0.1 dB
per miter bend using a VNA; and 0.22 ± 0.1 dB per miter bend using a radiometer. Good agreement between the two measurement
techniques implies that both are useful for measuring small losses. To verify the methodology, the VNA technique was employed
to measure the extremely small transmission loss in a 170 GHz ITER prototype TL system consisting of three lengths of 1 m,
63.5 mm diameter, circular corrugated waveguide and two miter bends. The measured loss of 0.05 ± 0.02 dB per miter bend may
be compared with the theoretical loss of 0.027 dB per miter bend. These results suggest that low-power testing of TL losses,
utilizing a small, simple TL system and a VNA, is a reliable method for evaluating performance of low-loss millimeter-wave
TL components intended for use in high-power applications. 相似文献
638.
Fabrício RS Pereira Andréa Alessio Maurício S Sercheli Tatiane Pedro Elizabeth Bilevicius Jane M Rondina Helka FB Ozelo Gabriela Castellano Roberto JM Covolan Benito P Damasceno Fernando Cendes 《BMC neuroscience》2010,11(1):1-13
Background
Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.Results
We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.Conclusions
We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds. 相似文献639.
Collective Band Structures and Identification of One-Phonon and Two-Phonon γ-Vibrational Bands in 109Tc
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GU Long ZHU Sheng-Jiang J. H. Hamilton A. V. Ramayya J. K. Hwang S. H. Liu WANG Jian-Guo Y. X. Luo J. O. Rasmussen I. Y. Lee XU Qiang E. Y. Yeoh W. C. Ma 《中国物理快报》2010,27(6):62-65
The high spin states of the neutron-rich 109Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252 Cf. The previously known yrast band based on the 7/2+ state is updated. A side band built on the 11/2+ state is expanded and a new band based on the 15/2+ state is identified. Band crossing in the yrast band occurs around fω≈ 0.36 MeV. This band crossing is associated with the alignment of two h11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2+ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2+ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed. 相似文献
640.
N. C. R. Holme L. Nikolova T. B. Norris S. Hvilsted M. Pedersen R. H. Berg P. H. Rasmussen P. S. Ramanujam 《Macromolecular Symposia》1999,137(1):83-103
Azobenzenes can serve as model compounds for the study of transcis isomerization in more complex molecules. We have performed time-resolved spectroscopy in solutions containing free azobenzene chromophores and diols with a view to obtaining the energy levels and lifetimes of the excited states. A transition route based on experimental results for the theoretically calculated energy level scheme is proposed. Physical observations of surface relief in thin films of azobenzene polymers when irradiated with polarized light are reported. These include two beam polarization holographic observations and single beam transmission measurements through a mask, followed by atomic force microscope and profiler investigations. It is concluded that none of the prevalent theories can explain all the observed facts. 相似文献