12,520 research outputs found
Lifting of Steel Coils in Bore-Vertical Orientation
Lifting of coils with the bore in the vertical orientation could give rise to safety issues if the coil integrity is compromised during the slitting and packing operation. Coil telescoping (whereby the inner wraps of the coil spiral out) is known to occur during lifting, which could pose as a serious threat to the safety of personnel involved. In this type of incident, the coil straps are also broken when their breaking strength is exceeded and the whole coil would unwrap itself at an elevated position. Back tension is applied to the strip while shearing wide strip into narrower slits; this allows sufficient radial pressure to be built up within the bulk of the narrow coils. Upon unloading, the radial pressures at the innermost and outermost wraps decrease to zero but the bulk of the inter-wrap pressure within the coil remains largely unchanged. The interwrap frictional forces developed within the coil enable the coil to retain its integrity under its own weight. It is found that the radial pressures developed within the slit coil play the most crucial role in providing sufficient frictional resistance to support the weight of the coil wraps during lifting with the bore in the vertical orientation. In addition, the inter-wrap pressures near the footprint of the mechanical lifting device, near the bore, have the most significant influence in preventing coil telescoping
Pulsed THz radiation due to phonon-polariton effect in [110] ZnTe crystal
Pulsed terahertz (THz) radiation, generated through optical rectification
(OR) by exciting [110] ZnTe crystal with ultrafast optical pulses, typically
consists of only a few cycles of electromagnetic field oscillations with a
duration about a couple of picoseconds. However, it is possible, under
appropriate conditions, to generate a long damped oscillation tail (LDOT)
following the main cycles. The LDOT can last tens of picoseconds and its
Fourier transform shows a higher and narrower frequency peak than that of the
main pulse. We have demonstrated that the generation of the LDOT depends on
both the duration of the optical pulse and its central wavelength. Furthermore,
we have also performed theoretical calculations based upon the OR effect
coupled with the phonon-polariton mode of ZnTe and obtained theoretical THz
waveforms in good agreement with our experimental observation.Comment: 9 pages, 5 figure
Front Stability in Mean Field Models of Diffusion Limited Growth
We present calculations of the stability of planar fronts in two mean field
models of diffusion limited growth. The steady state solution for the front can
exist for a continuous family of velocities, we show that the selected velocity
is given by marginal stability theory. We find that naive mean field theory has
no instability to transverse perturbations, while a threshold mean field theory
has such a Mullins-Sekerka instability. These results place on firm theoretical
ground the observed lack of the dendritic morphology in naive mean field theory
and its presence in threshold models. The existence of a Mullins-Sekerka
instability is related to the behavior of the mean field theories in the
zero-undercooling limit.Comment: 26 pp. revtex, 7 uuencoded ps figures. submitted to PR
Entangling two superconducting LC coherent modes via a superconducting flux qubit
Based on a pure solid-state device consisting of two superconducting LC
circuits coupled to a superconducting flux qubit, we propose in this paper that
the maximally entangled coherent states of the two LC modes can be generated
for arbitrary coherent states through flux qubit controls.Comment: 5 pages, 2 figure
Binary Nonlinearization of Lax pairs of Kaup-Newell Soliton Hierarchy
Kaup-Newell soliton hierarchy is derived from a kind of Lax pairs different
from the original ones. Binary nonlinearization procedure corresponding to the
Bargmann symmetry constraint is carried out for those Lax pairs. The proposed
Lax pairs together with adjoint Lax pairs are constrained as a hierarchy of
commutative, finite dimensional integrable Hamiltonian systems in the Liouville
sense, which also provides us with new examples of finite dimensional
integrable Hamiltonian systems. A sort of involutive solutions to the
Kaup-Newell hierarchy are exhibited through the obtained finite dimensional
integrable systems and the general involutive system engendered by binary
nonlinearization is reduced to a specific involutive system generated by
mono-nonlinearization.Comment: 15 pages, plain+ams tex, to be published in Il Nuovo Cimento
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