747 research outputs found
Seismic risk assessment of italian seaports: the case of Ancona (Italy)
A National research project was recently carried out to develop a robust methodology for the design and retrofit
of wharves structures located in areas of high to moderate seismicity. A detailed census of the Italian major
seaports was performed using purposely devised questionnaires and Ancona harbor was chosen for a detailed
investigation with the aim of providing risk assessment guidelines. This port has been selected as representative
of a moderate seismicity area (expected peak ground acceleration of 0.25 g with a return period of 475 yrs).
Ancona is the first harbor in the Adriatic sea, with more than a 1.500.000 passenger service and 150.000 trucks
transit. It is equipped with 30 wharfs, 25 of which built in 1965-1975.
To compute deterministic ground shaking scenarios, predictive empirical models have been used. At the same
time advanced numerical simulation have been carried out both at high (0.7-30 Hz) and low (0-1.3) frequency
ranges. The contributions of site effects and liquefaction have been also taken into account in damage estimation.
Standard risk assessment has been performed using the empirical curves implemented in HAZUS program
(NIBS, 2004), supported by recent studies (Lessloss, 2006, Del. 89) on damage observed after the 2003 event in
Lefkas (Greece)
Bailout Embeddings, Targeting of KAM Orbits, and the Control of Hamiltonian Chaos
We present a novel technique, which we term bailout embedding, that can be
used to target orbits having particular properties out of all orbits in a flow
or map. We explicitly construct a bailout embedding for Hamiltonian systems so
as to target KAM orbits. We show how the bailout dynamics is able to lock onto
extremely small KAM islands in an ergodic sea.Comment: 3 figures, 9 subpanel
Atmospheres of Magnetized Neutron Stars: Vacuum Polarization and Partially Ionized Models
We construct hydrogen atmosphere models for magnetized neutron stars in
radiative equilibrium with surface fields B=10^12-5x10^14 G and effective
temperatures T_eff a few x 10^5-10^6 K by solving the full radiative transfer
equations for both polarization modes in the magnetized hydrogen plasma. The
atmospheres directly determine the characteristics of thermal emission from
isolated neutron stars. We study the effects of vacuum polarization and bound
atoms on the atmosphere structure and spectra. For the lower magnetic field
models (B 10^12 G), the spectral features due to neutral atoms lie at extreme
UV and very soft X-ray energies and therefore are not likely to be observed.
However, the continuum flux is also different from the fully ionized case,
especially at lower energies. For the higher magnetic field models, we find
that vacuum polarization softens the high energy tail of the thermal spectrum.
We show that this depression of continuum flux strongly suppresses not only the
proton cyclotron line but also spectral features due to bound species;
therefore spectral lines or features in thermal radiation are more difficult to
observe when the neutron star magnetic field is > 10^14 G.Comment: 6 pages, 6 figures, submitted to Adv Sp Res: Proceedings of the 34th
COSPAR Scientific Assembly, E1.4 "High Energy Studies of Supernova Remnants
and Neutron Stars
Composite Fermion Description of Correlated Electrons in Quantum Dots: Low Zeeman Energy Limit
We study the applicability of composite fermion theory to electrons in
two-dimensional parabolically-confined quantum dots in a strong perpendicular
magnetic field in the limit of low Zeeman energy. The non-interacting composite
fermion spectrum correctly specifies the primary features of this system.
Additional features are relatively small, indicating that the residual
interaction between the composite fermions is weak. \footnote{Published in
Phys. Rev. B {\bf 52}, 2798 (1995).}Comment: 15 pages, 7 postscript figure
CKM Favored Semileptonic Decays of Heavy Hadrons at Zero Recoil
We study the properties of Cabibbo-Kobayashi-Maskawa (CKM) favored
semileptonic decays of mesons and baryons containing a heavy quark at the point
of no recoil. We first use a diagrammatic analysis to rederive the result
observed by earlier authors that at this kinematic point the meson decays
via transitions can only produce a or meson. The result is
generalized to include photon emissions which violate heavy quark flavor
symmetry. We show that photons emitted by the heavy quarks and the charged
lepton are the only light particles that can decorate the decays at zero recoil, and the similar processes of heavy baryons.
Implications for the determinations of the CKM parameter are
discussed. Also studied in this paper is the connection between our
diagrammatic analysis of suppression of particle emission and the formal
observation based on weak currents at zero recoil being generators of heavy
quark symmetry. We show that the two approaches can be unified by considering
the Isgur-Wise function in the presence of an external source.Comment: 27 pages, including 11 figures using macros FEYNMAN.te
The Kl3 scalar form factors in the standard model
We discuss the predictions of the standard model for the scalar form factors
of Kl3 decays. Our analysis is based on the results of chiral perturbation
theory, large Nc estimates of low-energy couplings and dispersive methods. It
includes a discussion of isospin violating effects of strong and
electromagnetic origin.Comment: 14 pages, presentation improved, several remarks and references
added, results unchanged, to be published in EPJ
Accretion, Outflows, and Winds of Magnetized Stars
Many types of stars have strong magnetic fields that can dynamically
influence the flow of circumstellar matter. In stars with accretion disks, the
stellar magnetic field can truncate the inner disk and determine the paths that
matter can take to flow onto the star. These paths are different in stars with
different magnetospheres and periods of rotation. External field lines of the
magnetosphere may inflate and produce favorable conditions for outflows from
the disk-magnetosphere boundary. Outflows can be particularly strong in the
propeller regime, wherein a star rotates more rapidly than the inner disk.
Outflows may also form at the disk-magnetosphere boundary of slowly rotating
stars, if the magnetosphere is compressed by the accreting matter. In isolated,
strongly magnetized stars, the magnetic field can influence formation and/or
propagation of stellar wind outflows. Winds from low-mass, solar-type stars may
be either thermally or magnetically driven, while winds from massive, luminous
O and B type stars are radiatively driven. In all of these cases, the magnetic
field influences matter flow from the stars and determines many observational
properties. In this chapter we review recent studies of accretion, outflows,
and winds of magnetized stars with a focus on three main topics: (1) accretion
onto magnetized stars; (2) outflows from the disk-magnetosphere boundary; and
(3) winds from isolated massive magnetized stars. We show results obtained from
global magnetohydrodynamic simulations and, in a number of cases compare global
simulations with observations.Comment: 60 pages, 44 figure
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
- …