231 research outputs found
JPKWIC - General key word in context and subject index report generator
JPKWIC computer program is a general key word in context and subject index report generator specifically developed to help nonprogrammers and nontechnical personnel to use the computer to access files, libraries and mass documentation. This program is designed to produce a KWIC index, a subject index, an edit report, a summary report, and an exclusion list
Radiation from polarized vacuum in a laser-particle collision
The probability of photon emission of a charged particle traversing a strong
field becomes modified if vacuum polarization is considered. This feature is
important for fundamental quantum electrodynamics processes present in extreme
astrophysical environments and can be studied in a collision of a charged
particle with a strong laser field. We show that for today's available 700 GeV
(6.5 TeV) protons and the field provided by the next generation of lasers, the
emission spectra peak is enhanced due to vacuum polarization effect by 30%
(suppressed by 65%) in comparison to the traditionally considered Compton
process. This striking phenomenon offers a novel path to the laboratory-based
manifestation of vacuum polarization.Comment: 6 pages, 1 figur
On the new and old physics in the interaction of a radiating electron with the extreme electromagnetic field
We show that an all-optical configuration of the laser-electron collision in
the configuration based on 10~PW-class lasers presents a viable
platform for reaching the range of parameters where a perturbative QED in
strong external electromagnetic field breaks. This case is contingently
referred to as a case of the nonperturbative QED; and this range of parameters
is the intriguing goal from an experimental point of view because of a possible
manifestation of a new physics of the interaction of a highly radiating
particle with a strong electromagnetic field. We show that the strong field
region can be reached by the electrons having the initial energy higher than 50
GeV. Our theoretical considerations are in agreement with three-dimensional
particle-in-cell simulations. While increasing of the electron energy raises
the number of electrons experiencing the strong field region, the observable
signature of photon emission radiative correction in the strong field is
expected to fade out when the electron energy surpasses the optimal value. This
threshold of electron energy is identified and the parameters for achieving the
nonperturbative limit of QED are provided.Comment: 6 pages, 2 figure
Highly Radiating Charged Particles in a Strong Electromagnetic Field
We consider highly radiating ultra-relativistic electrons in a strong
external electromagnetic field. High intensity radiative losses and consequent
-pair production, appearing in the frame of quantum electrodynamics,
determine indirectly mass operator of electrons in the strong field. We
calculate a leading term of the mass operator at asymptotically high energies
of electrons in a strong constant field. We do not use any perturbation theory
based on a low ratio of this mass operator to the electron mass , but only
the original small parameter of quantum electrodynamics, the fine structure
constant, . The analogous %but less nontrivial result is obtained for
the polarization operator for photon propagator. These results resolve at least
partially a very long-lasted controversy originating from traditional and
straightforward application of perturbative approaches for description of
highly radiating ultra-relativistic charged particles in a very strong
electromagnetic fields.Comment: 5 page
Analysis of the Role of Tortuosity and Infiltration Constants in the Beerkan Method
It has recently been proposed to couple the Beerkan method with the Beerkan
Estimation of Soil Transfer parameters (BEST) algorithm to facilitate the estima-
tion of soil hydraulic parameters from an infiltration experiment. Although this
simplified field procedure is relatively rapid and inexpensive, it has been doubt -
ed if the Beerkan method can represent a valid and reliable alternative to other
conventional methods. This study explored the impact of the tortuosity param-
eter (p) and two infiltration constants included in the BEST algorithm
using a sensitivity analysis applied to three experimental soils. The analysis that
was validated using the numerical model HYDRUS 2D/3D indicates that the
tortuosity is relatively insignificant compared to parameters b and g that have a
large impact on the estimation procedure
Analysis of Subsurface Gravel Layer Flow caused by Turbulent Open Channel Flow using 3-D PTV and Pressure Sensor Techniques (Untersuchung der Interaktion von Haupt- und Interstitialströmung mit Hilfe von 3-D PTV und piezoresistiven Drucksensoren)
Scaling dependence on the fluid viscosity ratio in the selective withdrawal transition
In the selective withdrawal experiment fluid is withdrawn through a tube with
its tip suspended a distance S above a two-fluid interface. At sufficiently low
withdrawal rates, Q, the interface forms a steady state hump and only the upper
fluid is withdrawn. When Q is increased (or S decreased), the interface
undergoes a transition so that the lower fluid is entrained with the upper one,
forming a thin steady-state spout. Near this transition the hump curvature
becomes very large and displays power-law scaling behavior. This scaling allows
for steady-state hump profiles at different flow rates and tube heights to be
scaled onto a single similarity profile. I show that the scaling behavior is
independent of the viscosity ratio.Comment: 33 Pages, 61 figures, 1 tabl
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