204,957 research outputs found
Ultra-Short Optical Pulse Generation with Single-Layer Graphene
Pulses as short as 260 fs have been generated in a diode-pumped low-gain
Er:Yb:glass laser by exploiting the nonlinear optical response of single-layer
graphene. The application of this novel material to solid-state bulk lasers
opens up a way to compact and robust lasers with ultrahigh repetition rates.Comment: 6 pages, 3 figures, to appear in Journal of Nonlinear Optical Physics
& Material
Effects of horizontal vibration on hopper flows of granular materials
The current experiments investigate the discharge of glass spheres in a planar wedge-shaped hopper (45 degree sidewalls) that is vibrated hoizontally. When the hopper is discharged without vibration, the discharge occurs as a funnel flow, with the material exiting the central region of the hopper and stagnant material along the sides. With horizontal vibration, the discharge rate increases with the velocity of vibration as compared with the discharge rate without vibration. For a certain range of acceleration parameters (20-30 Hz and accelerations greater than about 1 g), the discharge of the material occurs in an inverted-funnel pattern, with the material along the sides exiting first, followed by the material in the core; the free surface shows a peak at the center of the hopper with the free surface particles avalanching from the center toward the sides. During the deceleration phase of a vibration cycle, particles all along the trailing or low-pressure wall separate from the surface and fall under gravity for a short period before reconnecting the hopper. For lower frequencies (5 and 10 Hz), the free surface remains horizontal and the material appears to discharge uniformly from the hopper
Effects of Horizontal Vibration on Hopper Flows of Granular Material
This study experimentally examines the flow of glass spheres in a wedge-shaped hopper that is vibrated hoizontally. When the hopper is discharged without vibration, discharge occurs as a funnel flow, with the material exiting the central region of the hopper and stagnant material along the sides. With vibration, the discharge of the material occurs in reverse, with the material along the sides exiting first, followed by the material in the central region. These patterns are observed with flow visualization and high-speed photography. The study also includes measurements of the discharge rate, which increases with the amplitude of the velocity of vibration
Comment on "Statistical Mechanics of Non-Abelian Chern-Simons Particles"
The second virial coefficient for non-Abelian Chern-Simons particles is
recalculated. It is shown that the result is periodic in the flux parameter
just as in the Abelian theory.Comment: 3 pages, latex fil
Probing molecular frame photoionization via laser generated high-order harmonics from aligned molecules
Present photoionization experiments cannot measure molecular frame
photoelectron angular distributions (MFPAD) from the outermost valence
electrons of molecules. We show that details of the MFPAD can be retrieved with
high-order harmonics generated by infrared lasers from aligned molecules. Using
accurately calculated photoionization transition dipole moments for
fixed-in-space molecules, we show that the dependence of the magnitude and
phase of the high-order harmonics on the alignment angle of the molecules
observed in recent experiments can be quantitatively reproduced. This result
provides the needed theoretical basis for ultrafast dynamic chemical imaging
using infrared laser pulses.Comment: 5 pages, 4 figure
Experimental investigation of the asymmetric spectroscopic characteristics of electron- and hole-doped cuprates
Quasiparticle tunneling spectroscopic studies of electron- (n-type) and hole-doped (p-type) cuprates reveal that the pairing symmetry, pseudogap phenomenon and spatial homogeneity of the superconducting order parameter are all non-universal. We compare our studies of p-type YBa2Cu3O7-delta and n-type infinite-layer Sr(0.9)Ln(0.1)CuO(2) (Ln = La, Gd) systems with results from p-type Bi2Sr2CaCu2Ox and n-type one-layer Nd1.85Ce0.15CuO4 cuprates, and attribute various non-universal behavior to different competing orders in p-type and n-type cuprates
Secondary pattern computation of an arbitrarily shaped main reflector
The secondary pattern of a perfectly conducting offset main reflector being illuminated by a point feed at an arbitrary location was studied. The method of analysis is based upon the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO) and geometrical theory of diffraction (GTD). Key features of the reflector surface is completely arbitrary, the incident field from the feed is most general with arbitrary polarization and location, and the edge diffraction is calculated by either UAT or by UTD. Comparison of this technique for an offset parabolic reflector with the Jacobi-Bessel and Fourier-Bessel techniques shows good agreement. Near field, far field, and scan data of a large reflector are presented
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