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991.
We investigate the Painleve integrabiiity of nonautonomous nonlinear Schr6dinger (NLS) equations with both space-and time-dependent dispersion, nonlinearity, and external potentials. The Painleve analysis is carried out without using the Kruskal's simplification, which results in more generalized form of inhomogeneous equations. The obtained equations are shown to be reducible to the standard NLS equation by using a point transformation. We also construct the corresponding Lax pair and carry out its Kundu-type reduction to the standard Lax pair. Special cases of equations from choosing limited form of coefficients coincide with the equations from the previous Painleve analyses and/or become unknown new equations. 相似文献
992.
Flow actuation by a continuous/pulsed, direct-current (DC) surface glow discharge is explored. The discharge comprises an array of pin electrode pairs flush mounted on a dielectric actuator surface that lies adjacent to stagnant air. Strong electrostatic fields produced in the cathode sheath region of the discharge provides a motive force on the ions which in turn drag the background gas resulting in directed air flow from the anode to the cathode. The induced flow velocity is estimated by particle image velocimetry (PIV) at 10 Hz with TiO2 seeding. For a pulsed DC discharge with peak power of 5 W per electrode pair, the induced flow velocity reaches peak values of about 1.7 m/s which is comparable to dielectric-barrier discharge (DBD) or corona discharge actuators. The actuation effect quantified by the magnitude of induced velocity increases as the pulse frequency increases from 0 to 1 kHz. The actuation effect decreases for further increase in frequency above 1 kHz. Decreased actuation effect at high frequency is accompanied by structural change in the discharge. At fixed frequency of 1 kHz, flow actuation effect is highest for a square wave pulse with a duty cycle of 50% indicating that pulsed DC discharges produces better actuation than continuous DC with a corresponding reduction in energy consumption. 相似文献
993.
We consider a degenerate or a nearly degenerate dark matter sector where a sizable magnetic moment of a (almost) Dirac type neutral dark matter candidate N is anticipated. Then, due to soft photon exchange, the cross-section in direct detection of N can be enhanced at low Q2 region. We discuss the implication of this type of models in view of the recent CDMS II report. 相似文献
994.
New nonsingular positon, negaton and complexiton solutions for the coupled mKdV system are constructed by means of Darboux transformation with constant seed solution and given out both analytically and graphically. 相似文献
995.
Luc Huy Hoang Nguyen T. M. Hien W. S. Choi Y. S. Lee K. Taniguchi T. Arima S. Yoon X. B. Chen In‐Sang Yang 《Journal of Raman spectroscopy : JRS》2010,41(9):1005-1010
We have measured polarized Raman spectra of MnWO4 single crystals at low temperatures, and studied the temperature dependence of the various phonon modes. From our Raman studies of the MnWO4, a new transition temperature, ∼180 K, was found. We have completely assigned the symmetries of the 18 observed Raman modes of the MnWO4, as expected from a group theoretical analysis. These Raman modes have been classified into three groups according to weak, intermediate and strong temperature dependence of the modes in each group. Six internal modes have been identified by their weak temperature dependence of the Raman wavenumbers. The temperature dependence of the wavenumbers of the Bg modes in Mg O bonds, modes of intermediate temperature dependence group, shows an anomalous behavior under 50 K. The phonon modes of strong temperature dependence show an anomalous change at ∼180 K in the linewidths. This is believed to be a new transition temperature which involves the changes in the inter‐WO6 octahedra structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
Multisite quantitative magnetic resonance imaging (qMRI) of volume requires a small isotropic point spread-function (PSF) that is spatially, temporarily, and platform invariant. A phantom which will allow rapid assessment of this metric throughout the imaged volume without repositioning will assist certification of imaging sites for use in qMRI studies based on volume. This paper presents a phantom design for this purpose with a three-dimensional repeating pattern throughout its 800-cm3 volume. The image of the pattern from the phantom contains a series of positive signal points and lines which can be used to measure the PSF, gradient linearity, gradient orthogonality, and B0 homogeneity at multiple locations throughout its volume. The phantom is readily constructed, can be filled with any nuclear magnetic resonance signal-bearing liquid, and the design is scalable to cover larger volumes. 相似文献
997.
Sang Soo Shin Diane M. Armao Monty Shah Young Hoon Kim Chang Hee Lee Tara Rubinas Lauren M. Brubaker Richard C. Semelka 《Magnetic resonance imaging》2010
Purpose
To evaluate the clinical outcomes of conservative management by observation with MRI of patients with branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs).Materials and Methods
Twenty-three consecutive patients, who were followed up by MRI with magnetic resonance cholangiopancreatography (MRCP) over a period of more than 9 months after initial MRI examinations, were enrolled in this study. On MRI, number of lesions, the maximum diameter of BD-IPMNs, lesion location, the presence of associated dilatation of main pancreatic duct (MPD), the presence of enhancing mural nodules within the lesion and the presence of interval change were retrospectively reviewed on initial and follow-up MR images in consensus by two radiologists. All patients were evaluated to search for evidence of malignant progression of disease.Results
The follow-up period ranged from 10 to 96 months (mean, 37 months). On initial MRI with MRCP, a total of 39 lesions were found in 23 patients. The maximum diameter of BD-IPMNs ranged between 6 and 32 mm, with a mean of 12 mm. Thirty-four lesions (87%) of 19 patients remained unchanged in the maximum diameter. Five lesions (13%) of four patients showed an increase in the maximum diameter. Enhancing mural nodules were not found in any individual, neither on the initial MRI study nor on the follow-up studies. There was no patient who had evidence of local aggressive growth of tumor or evidence of metastases to distant sites.Conclusion
Our study suggests that branch-duct IPMNs without enhancing mural nodules are essentially benign and should be managed nonoperatively through observation by MRI. 相似文献998.
G. Kim A.R. Jeong W. Jo D.Y. Park H. Cheong G.M. Shin S.I. Yoo 《Physica C: Superconductivity and its Applications》2010,470(20):1021-1024
High temperature superconducting GdBa2Cu3O7 (GdBCO) thin films were grown by pulsed laser ablation. Textured MgO on metal substrates was used as a template for second generation wire applications. Growth conditions of GdBCO thin films were investigated for substrate temperature (Ts) and oxygen partial pressure (PO2) during deposition. Superconducting critical currents of the films were obtained in the films grown at 790–810 °C of Ts and at 100–700 mTorr of PO2. Scanning electron micrographs of the films revealed uniform and well-connected grains with some outgrown structures. X-ray θ–2θ scans of the films grown at 810 °C and 300–500 mTorr exhibited c-axis oriented texture. In-plane alignment and c-axis mosaic spread of the films were determined from X-ray Φ scans and rocking curves, respectively. Polarized Raman scattering spectroscopy was used to characterize optical phonon modes, oxygen content, cation disorder, and some possible second phases of the films. The Raman spectra of the films with large critical current density showed modes at 326–329 cm−1, 444–447 cm−1, 500–503 cm−1 related to vibration of oxygen atoms. Origin of small peaks near 600 cm−1 will be discussed as well. The information obtained from Raman scattering measurements will be useful for quality control of the conductors as well as optimization of the process conditions. 相似文献
999.
A flux fusion method was used to obtain the various sizes of Eu3+-activated Y2O3 red phosphors. The flux material was selected as an independent variable to control the physical properties of phosphor particles and their effects on the morphology and size distribution of phosphors were examined by scanning electron microscopy. The concentration of the flux materials and synthetic temperature were optimized for maximal photoluminescence intensity. Fluoride-based flux materials were found to work for the crystal formation of Eu3+-activated Y2O3. In particular, when a BaF2 flux was used during the reaction at 1450 °C for 3 h, the photoluminescence (PL) intensity of Eu3+-activated Y2O3 was 25% higher than that without a flux and spherical phosphors had a mean particle size of 4-5 μm. The morphology and size distribution of the synthesized Eu3+-activated Y2O3 phosphor were predominantly dependent upon the type and concentration of flux material and synthetic temperature. 相似文献
1000.
We study perturbations in the multifield axion N-flation model, taking account of the full cosine potential. We find significant differences from previous analyses which made a quadratic approximation to the potential. The tensor-to-scalar ratio and the scalar spectral index move to lower values, which nevertheless provide an acceptable fit to observation. Most significantly, we find that the bispectrum non-Gaussianity parameter f{NL} may be large, typically of order 10 for moderate values of the axion decay constant, increasing to of order 100 for decay constants slightly smaller than the Planck scale. Such a non-Gaussian fraction is detectable. We argue that this property is generic in multifield models of hilltop inflation. 相似文献