43 research outputs found
Bremsstrahlung of 350--450 MeV protons as a tool to study interaction off-shell
The bremsstrahlung cross section is calculated within the
method of coordinate space representation. It is shown that in the beam energy
range of 350--450~MeV a deep attractive NN-potential with forbidden states
(Moscow potential) and realistic meson exchange potentials (MEP) give rise to
the cross sections that differ essentially in shape: the cross sections nearly
coincide in the minima but differ by a factor of 5 approximately in the maxima.
Therefore, the reaction at energies 350--450~Mev can be
used to study interaction off-shell and to discriminate experimentally
between MEP and Moscow potential.Comment: 5 pages, latex, 4 PS figures. Talk presented by Andrey Shirokov at
the International Conference on Quark Lepton Nuclear Physics ``QULEN97'', May
20-23, 1997, Osaka, Japan; to be published in Nucl. Phys.
Long- and short-term earthquake prediction in Kamchatka
This paper presents the results of long- and short-term earthquake prediction obtained during 1971–1974. They can be summarized as follows:
The map of long-term prediction for the Kurile—Kamchatka zone compiled in 1965 and supplemented in 1972 by S.A. Fedotov is in good agreement (in four of four possible cases) with recorded seismicity.
The results obtained allow us to suppose that the areas for which the log (Ep/Es) of small earthquakes is low may be the areas of future large earthquakes.
Prediction of active periods for the Kamchatka earthquakes with M > 7 has been made on the basis of studying the correlation of seismicity with the lunar tide with a 18.6-year period. A possibility has been found for using the phenomenon of “induced foreshocks” for earthquake prediction, i.e., when a large remote earthquake induces small preceding events in the zone of preparation of a large earthquake.
The following three methods were used for operative short-term prediction of the time and place of future earthquakes with M > 5.5.
1.(1) Use of specific electrotelluric field anomalies, from 5 to 20 days in duration, which are recorded by a specially designed network of stations.
2.(2) Method of Vp/Vs anomalies. The anomalously high and low Vp/Vs values for a seismic station point to the possibility of large earthquakes near the latter.
3.(3) The earthquake statistics method described by Fedotov et al. in 1972.
Short-term seismic prediction is being made twice a week in two versions: Forecast I (for the whole of Kamchatka) and Forecast II (for each of six overlapping segments of the Kamchatka seismic zone).
This paper discusses the results of successful testing of short-term earthquake prediction during two years. During the “alarm” periods the probability of large earthquakes is double the average.
Paper presented at the Symposium on Earthquake Forerunners Searching, Tashkent, May 26–June 1, 1974
Hamiltonian Light-Front Field Theory: Recent Progress and Tantalizing Prospects
Fundamental theories, such as Quantum Electrodynamics (QED) and Quantum
Chromodynamics (QCD) promise great predictive power addressing phenomena over
vast scales from the microscopic to cosmic scales. However, new
non-perturbative tools are required for physics to span from one scale to the
next. I outline recent theoretical and computational progress to build these
bridges and provide illustrative results for Hamiltonian Light Front Field
Theory. One key area is our development of basis function approaches that cast
the theory as a Hamiltonian matrix problem while preserving a maximal set of
symmetries. Regulating the theory with an external field that can be removed to
obtain the continuum limit offers additional possibilities as seen in an
application to the anomalous magnetic moment of the electron. Recent progress
capitalizes on algorithm and computer developments for setting up and solving
very large sparse matrix eigenvalue problems. Matrices with dimensions of 20
billion basis states are now solved on leadership-class computers for their
low-lying eigenstates and eigenfunctions.Comment: 8 pages with 2 figure
Manifestation of three-body forces in three-body Bethe-Salpeter and light-front equations
Bethe-Salpeter and light-front bound state equations for three scalar
particles interacting by scalar exchange-bosons are solved in ladder
truncation. In contrast to two-body systems, the three-body binding energies
obtained in these two approaches differ significantly from each other: the
ladder kernel in light-front dynamics underbinds by approximately a factor of
two compared to the ladder Bethe-Salpeter equation. By taking into account
three-body forces in the light-front approach, generated by two exchange-bosons
in flight, we find that most of this difference disappears; for small exchange
masses, the obtained binding energies coincide with each other.Comment: 24 pages, 8 figures, submitted in Few-Body System
Explicitly Covariant Light-Front Dynamics and Relativistic Few-Body Systems
The wave function of a composite system is defined in relativity on a
space-time surface. In the explicitly covariant light-front dynamics, reviewed
in the present article, the wave functions are defined on the plane \omega \cd
x=0, where is an arbitrary four-vector with . The
standard non-covariant approach is recovered as a particular case for . Using the light-front plane is of crucial importance, while the
explicit covariance gives strong advantages emphasized through all the review.
The properties of the relativistic few-body wave functions are discussed in
detail and are illustrated by examples in a solvable model. The
three-dimensional graph technique for the calculation of amplitudes in the
covariant light-front perturbation theory is presented.
The structure of the electromagnetic amplitudes is studied. We investigate
the ambiguities which arise in any approximate light-front calculations, and
which lead to a non-physical dependence of the electromagnetic amplitude on the
orientation of the light-front plane. The elastic and transition form factors
free from these ambiguities are found for spin 0, 1/2 and 1 systems.
The formalism is applied to the calculation of the relativistic wave
functions of two-nucleon systems (deuteron, scattering state), with particular
attention to the role of their new components in the deuteron elastic and
electrodisintegration form factors and to their connection with meson exchange
currents. Straigthforward applications to the pion and nucleon form factors and
the transition are also made.Comment: latex.tar.gz file, 162 pages, 42 figures, to be published in Physics
Reports (next issues
Letter of interest for a neutrino beam from Protvino to KM3NeT/ORCA
The Protvino accelerator facility located in the Moscow region, Russia, is in a good position to offer a rich experimental research program in the field of neutrino physics. Of particular interest is the possibility to direct a neutrino beam from Protvino towards the KM3NeT/ORCA detector, which is currently under construction in the Mediterranean Sea 40 km offshore Toulon, France. This proposal is known as P2O. Thanks to its baseline of 2595 km, this experiment would yield an unparalleled sensitivity to matter effects in the Earth, allowing for the determination of the neutrino mass ordering with a high level of certainty after only a few years of running at a modest beam intensity of ≈ 90 kW. With a prolonged exposure (≈1500 kWyear), a 2σ sensitivity to the leptonic CP-violating Dirac phase can be achieved. A second stage of the experiment, comprising a further intensity upgrade of the accelerator complex and a densified version of the ORCA detector (Super-ORCA), would allow for up to a 6σ sensitivity to CP violation and a 10º−17º resolution on the CP phase after 10 years of running with a 450 kW beam, competitive with other planned experiments. The initial composition and energy spectrum of the neutrino beam would need to be monitored by a near detector, to be constructed several hundred meters downstream from the proton beam target. The same neutrino beam and near detector set-up would also allow for neutrino-nucleus cross section measurements to be performed. A short-baseline sterile neutrino search experiment would also be possible
Modeling and control principles for a tentacle-like surgical instrument
In this project a challenge in the field of minimally invasive surgery is addressed. Contemporary minimally invasive instruments usually consist of a rigid beam with an end effector on one side and a controlling mechanism on the other. These instruments work well for cases when the body can be entered in such a way that the target, on which to operate, is reachable in a straight line. When it is not possible to reach the target in a straight line, a new solution is necessary. This thesis proposes to replace the rigid beam with a robotic tentacle. The tentacle considered in this thesis is modeled after an Ionic Polymer-Metal Composite (IPMC) which is an Electro-Active Polymer (EAP), a material which mechanically deforms once put in an electric field. Electromechanical properties of the IPMC are combined with a layered geometric configuration of strips of IPMC to construct the tentacle. An electromechanical simulation model is constructed followed by the design of a curvature controller. The performance of the controller is analyzed in simulation. The results obtained from the simulation prove the concept of the robotic tentacle made of strips of IPMC as a possible solution to improve reaching capabilities of contemporary minimally invasive surgical instruments.Delft Centre for Systems and ControlMechanical, Maritime and Materials Engineerin