167 research outputs found
Estudio no destructivo del interior de piezas de valor histórico mediante gammagrafías
La tecnología de Tomografía de Hormigón Armado desarrollada por THASA ha sido aplicada al estudio de piezas ornamentales y otras de valor histórico con el objeto de examinar el interior de las mismas e investigar, en algunos casos, la existencia, configuración y condición de refuerzos metálicos y en otro caso, la existencia de huecos producidos por termitas en vigas de madera. En este trabajo se discuten detalles metodológicos y resultados alcanzados en los casos de las estatuas ubicadas en el coronamiento del Palacio de Tribunales en la Ciudad Autónoma de Buenos Aires, en dragones colgantes de las torres de la Basílica de Luján y en las vigas del techo de la Capilla Doméstica, construida en 1660 y declarada patrimonio de la humanidad por la UNESCO, ubicada en la manzana jesuítica en la Ciudad de Córdoba. El carácter pionero de la investigación de oquedades en madera realizada en este último caso hizo necesario la construcción de modelos de simulación que resultan de utilidad para otras aplicaciones similares
Application of a semi-microscopic core-particle coupling method to the backbending in odd deformed nuclei
In two previous papers, the Kerman-Klein-Donau-Frauendorf (KKDF) model was
used to study rotational bands of odd deformed nuclei. Here we describe
backbending for odd nuclei using the same model. The backbending in the
neighboring even nuclei is described by a phenomenological two band model, and
this core is then coupled to a large single-particle space, as in our previous
work. The results obtained for energies and M1 transition rates are compared
with experimental data for 165Lu and for energies alone to the experimental
data for 179W. For the case of 165Lu comparison is also made with previous
theoretical work.Comment: 16 pages including 8 figure(postscript), submitted to Phys.Rev.
DYNAMIC STRAY CURRENT MEASURING METHODS IN URBAN AREAS
In areas where urban tracks are used as public transportation,
dynamic stray currents cause high maintenance costs for the tracks and
metal structures near the tracks. Stray currents caused by rail vehicles
depend on many factors (traffic density, vehicle speed, acceleration and
deceleration, soil and track moisture), so it is very difficult to get a clear picture
of the harmfulness of the stray current based on the results of a single field
measurement. However, there are several measurement methods that can
be used to determine the presence of stray currents and predict appropriate
track maintenance actions. Some of these methods are described in this article,
namely the use of stray current mapper, measurement of rail potential and rail current, measurement at the stray current collection system, and the use of nondestructive sensors. In track construction, measuring the electrical potential
between rail and ground is one of the most common methods of detecting the
damaging influence of stray current
Influence of Impedance Interaction & Comparability on Spectral Aggregation (2-150 kHz) in DC Grids
The reported higher levels of conducted emissions in DC grids in the 2-150 kHz range are caused by the spectral aggregations resulting from the converter's switching harmonics. The dominant influence for these spectral aggregates is the impedance correlation between the DC-link capacitor and the converters. This paper analyses the impedance interaction & comparability between the DC-link and the DC/DC converters at the point of common coupling in the DC grid. Simulations with four DC-link capacitors and forty parallel DC/DC converters are conducted, with full (non-linear) and equivalent-source (linear) models for comparison. The dB/JV values for the first spectral aggregate decrease as the augmenting DC-side impedance becomes comparable with the smaller DC-link impedance, lowering the electromagnetic interference in the DC grid. This understanding may provide insights into the DC-link capacitor design from an electromagnetic compatibility perspective, and towards developing a framework for DC power quality standards in the 2-150 kHz range
Pantograph-To-OHL Arc: Conducted Effects in DC Railway Supply System
The electrical arc occurring in the sliding contact between the supply contact line and the current collector (pantograph) of an electrical locomotive is a fast transient phenomenon able to degrade progressively the line-To-pantograph contact quality and, consequently, the continuity of operation. In order to increase the energy efficiency of the railway system, an inexpensive solution is constituted by the detection of the arc event by the analysis of voltage and current measurements already available on-board train. An essential activity to reach this objective is to set up a reliable electrical model of the railway system in which the arc events originate. To this end, this paper presents a combination of experimental and simulation analysis for the development of an electrical model of a direct current (dc) 3 kV railway system, which is aimed at better understanding the propagation of conducted effects generated by arc events. First, a laboratory experimental activity is carried out to investigate the electrical dynamic characteristics of the arc in a controlled environment. Then, a model of the dc railway system is derived and validated by using the experimental data collected in a measurement campaign on-board train. Finally, a sensitivity analysis of the main model parameters is carried out
Rotationally Invariant Hamiltonians for Nuclear Spectra Based on Quantum Algebras
The rotational invariance under the usual physical angular momentum of the
SUq(2) Hamiltonian for the description of rotational nuclear spectra is
explicitly proved and a connection of this Hamiltonian to the formalisms of
Amal'sky and Harris is provided. In addition, a new Hamiltonian for rotational
spectra is introduced, based on the construction of irreducible tensor
operators (ITO) under SUq(2) and use of q-deformed tensor products and
q-deformed Clebsch-Gordan coefficients. The rotational invariance of this
SUq(2) ITO Hamiltonian under the usual physical angular momentum is explicitly
proved, a simple closed expression for its energy spectrum (the ``hyperbolic
tangent formula'') is introduced, and its connection to the Harris formalism is
established. Numerical tests in a series of Th isotopes are provided.Comment: 34 pages, LaTe
Role of axillary ultrasound in the preopertaive diagnosi of lymphonode metastases in patients affected by brest carcinoma
New features of collective motion of intrinsic degrees of freedom. Toward a possible way to classify the intrinsic states
Three exactly solvable Hamiltonians of complex structure are studied in the
framework of a semi-classical approach. The quantized trajectories for
intrinsic coordinates correspond to energies which may be classified in
collective bands. For two of the chosen Hamiltonians the symmetry SU2xSU2 is
the appropriate one to classify the eigenvalues in the laboratory frame.
Connections of results presented here with the molecular spectrum and
Moszkowski model are pointed out. The present approach suggests that the
intrinsic states, which in standard formalisms are heading rotational bands,
are forming themselves "rotational" bands, the rotations being performed in a
fictious boson space.Comment: 33 pages, 9 figure
B3 core biopsies should be assumed as positive findings for accuracy purposes Le biopsie percutanee B3 dovrebbero essere assunte come reperti positivi nella valutazione di accuratezza
- …