287,210 research outputs found
Riemann zeros, prime numbers and fractal potentials
Using two distinct inversion techniques, the local one-dimensional potentials
for the Riemann zeros and prime number sequence are reconstructed. We establish
that both inversion techniques, when applied to the same set of levels, lead to
the same fractal potential. This provides numerical evidence that the potential
obtained by inversion of a set of energy levels is unique in one-dimension. We
also investigate the fractal properties of the reconstructed potentials and
estimate the fractal dimensions to be for the Riemann zeros and for the prime numbers. This result is somewhat surprising since the
nearest-neighbour spacings of the Riemann zeros are known to be chaotically
distributed whereas the primes obey almost poisson-like statistics. Our
findings show that the fractal dimension is dependent on both the
level-statistics and spectral rigidity, , of the energy levels.Comment: Five postscript figures included in the text. To appear in Phys. Rev.
Cryogenic loss monitors with FPGA TDC signal processing
Radiation hard helium gas ionization chambers capable of operating in vacuum
at temperatures ranging from 5K to 350K have been designed, fabricated and
tested and will be used inside the cryostats at Fermilab's Superconducting
Radiofrequency beam test facility. The chamber vessels are made of stainless
steel and all materials used including seals are known to be radiation hard and
suitable for operation at 5K. The chambers are designed to measure radiation up
to 30 kRad/hr with sensitivity of approximately 1.9 pA/(Rad/hr). The signal
current is measured with a recycling integrator current-to-frequency converter
to achieve a required measurement capability for low current and a wide dynamic
range. A novel scheme of using an FPGA-based time-to-digital converter (TDC) to
measure time intervals between pulses output from the recycling integrator is
employed to ensure a fast beam loss response along with a current measurement
resolution better than 10-bit. This paper will describe the results obtained
and highlight the processing techniques used.Comment: 7 pp. 2nd International Conference on Technology and Instrumentation
in Particle Physics 2011: TIPP 2011. 9-14 Jun 2011. Chicago, Illinoi
Competent genetic-evolutionary optimization of water distribution systems
A genetic algorithm has been applied to the optimal design and rehabilitation of a water distribution system. Many of the previous applications have been limited to small water distribution systems, where the computer time used for solving the problem has been relatively small. In order to apply genetic and evolutionary optimization technique to a large-scale water distribution system, this paper employs one of competent genetic-evolutionary algorithms - a messy genetic algorithm to enhance the efficiency of an optimization procedure. A maximum flexibility is ensured by the formulation of a string and solution representation scheme, a fitness definition, and the integration of a well-developed hydraulic network solver that facilitate the application of a genetic algorithm to the optimization of a water distribution system. Two benchmark problems of water pipeline design and a real water distribution system are presented to demonstrate the application of the improved technique. The results obtained show that the number of the design trials required by the messy genetic algorithm is consistently fewer than the other genetic algorithms
Mechanism of Gravity Impulse
It is well-known that energy-momentum is the source of gravitational field.
For a long time, it is generally believed that only stars with huge masses can
generate strong gravitational field. Based on the unified theory of
gravitational interactions and electromagnetic interactions, a new mechanism of
the generation of gravitational field is studied. According to this mechanism,
in some special conditions, electromagnetic energy can be directly converted
into gravitational energy, and strong gravitational field can be generated
without massive stars. Gravity impulse found in experiments is generated by
this mechanism.Comment: 10 page
X-ray Polarization Signatures of Compton Scattering in Magnetic Cataclysmic Variables
Compton scattering within the accretion column of magnetic cataclysmic
variables (mCVs) can induce a net polarization in the X-ray emission. We
investigate this process using Monte Carlo simulations and find that
significant polarization can arise as a result of the stratified flow structure
in the shock-ionized column. We find that the degree of linear polarization can
reach levels up to ~8% for systems with high accretion rates and low
white-dwarf masses, when viewed at large inclination angles with respect to the
accretion column axis. These levels are substantially higher than previously
predicted estimates using an accretion column model with uniform density and
temperature. We also find that for systems with a relatively low-mass white
dwarf accreting at a high accretion rate, the polarization properties may be
insensitive to the magnetic field, since most of the scattering occurs at the
base of the accretion column where the density structure is determined mainly
by bremsstrahlung cooling instead of cyclotron cooling.Comment: 7 pages, 8 figures, accepted by MNRA
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