488 research outputs found
A calculation of low-lying collective states in odd-even nuclei
We present results of a calculation of properties of low-lying collective quadrupole states in odd-even nuclei within the framework of the proton-neutron interacting boson-fermion model
Unexpected Magnetism of Small Silver Clusters
The ground-state electronic, structural, and magnetic properties of small
silver clusters, Ag (2n22), have been studied using a linear
combination of atomic Gaussian-type orbitals within the density functional
theory. The results show that the silver atoms, which are diamagnetic in bulk
environment, can be magnetic when they are grouped together in clusters. The
Ag cluster with icosahedral symmetry has the highest magnetic moment per
atom among the studied silver clusters. The cluster symmetry and the reduced
coordination number specific of small clusters reveal as a fundamental factor
for the onset of the magnetism.Comment: 4 pages, 4 figure
Phase diagram for a Cubic Consistent-Q Interacting Boson Model Hamiltonian: signs of triaxiality
An extension of the Consistent-Q formalism for the Interacting Boson Model
that includes the cubic QxQxQ term is proposed. The potential energy surface
for the cubic quadrupole interaction is explicitly calculated within the
coherent state formalism using the complete chi-dependent expression for the
quadrupole operator. The Q-cubic term is found to depend on the asymmetry
deformation parameter gamma as a linear combination of cos(3gamma) and
cos^2(3\gamma) terms, thereby allowing for triaxiality. The phase diagram of
the model in the large N limit is explored, it is described the order of the
phase transition surfaces that define the phase diagram, and moreover, the
possible nuclear equilibrium shapes are established. It is found that, contrary
to expectations, there is only a very tiny region of triaxiality in the model,
and that the transition from prolate to oblate shapes is so fast that, in most
cases, the onset of triaxiality might go unnoticed.Comment: 18 pages, 19 figure
Towards predictive models in food engineering: Parameter estimation dos and don'ts
1 póster.-- 29th EFFoST International Conference, 10-12 November 2015, Athens, GreeceRigorous, physics based, modeling is at the core of computer aided food process engineering. Models often
require the values of some, typically unknown, parameters (thermo-physical properties, kinetic constants,
etc). Therefore, parameter estimation from experimental data is critical to achieve desired model predictive
properties. Unfortunately, it must be admitted that often experiment design and modeling are fully
separated tasks: experiments are not designed for the purpose of modeling and models are usually derived
without paying especial attention to available experimental data or experimentation capabilities. When, at
some point, the parameter estimation problem is put on the table, modelers use available experimental
data to ``manually'' tune the unknown parameters. This results in inaccurate parameter estimates, usually
experiment dependent, with the implications this has in model validation.
This work takes a new look into the parameter estimation problem in food process modeling. First the
common pitfalls in parameter estimation are described. Second we present the theoretical background and
the numerical techniques to define a parameter estimation protocol to iteratively improve model predictive
capabilities. This protocol includes: reduced order modeling, structural and practical identifiability analyses,
data fitting with global optimization methods and optimal experimental design.
And, to finish, we illustrate the performance of the proposed protocol with an example related to the
thermal processing of packaged foods. The model was experimentally validated in the IIM-CSIC pilot plantThe authors acknowledge financial support from the EU (Project SPECTRAFISH), Spanish
Ministry of Science and Innovation (Project ISFORQUALITY) and CSIC (Project CONTROLA)Peer reviewe
The optical system of the Tenerife Microwave Spectrometer: a window for observing the 10-20 GHz sky spectra
The TMS optical system is based on a decentered dual-reflector system in a
Gregorian configuration to observe with an angular resolution of less than
. The primary goal of the present study is to evaluate the final
design and verify that it satisfies the design requirements. We aim for low
cross-polarization (-30 dB), low sidelobe (-25 dB) levels, and a stable beam in
terms of shape (low ellipticity) and size over a full octave bandwidth (10-20
GHz). We performed both ray-tracing and full-wave simulations using the CST
Studio software in order to investigate the system behaviour. We gave special
attention to the beam frequency variation and polarization leakage. We have
characterized the effects on the radiation pattern produced by the cryostat
window. We present the final design of the TMS optical system, as well as a
complete study of the system's performance in terms of cross-polarization,
sidelobes, ellipticity and beamwidth. We discuss the effects of sidelobes and
study the need for a baffle.Comment: 30 pages, 15 figures. Accepted for publication in JINS
The U(5)-O(6) transition in the Interacting Boson Model and the E(5) critical point symmetry
The relation of the recently proposed E(5) critical point symmetry with the
interacting boson model is investigated. The large-N limit of the interacting
boson model at the critical point in the transition from U(5) to O(6) is
obtained by solving the Richardson equations. It is shown explicitly that this
algebraic calculation leads to the same results as the solution of the Bohr
differential equation with a potential.Comment: Accepted in PR
Pensar el Laboratorio Internacional del Hábitat Popular: una apuesta a cuatro voces
Este texto relata cuatro experiencias de intervención provenientes de Francia y Colombia, en las cuales se manifiestaron distintas formas de abordaje y comprensión de los problemas asociados al hábitat popular. Se trata de identificar temas y espacios comunes en dichas experiencias,que permitan pensar los elementos constitutivos de un laboratorio internacional de hábitat popular. Por ello, el documento privilegia cuatro temas: las experiencias compartidas mismas,el concepto de lo "popular,las ideas para el diálogo de saberes, y las pistas metodológicas y los retos para la construcción del laboratorio Internacional del Hábitat popular
A Microwave Blackbody Target for Cosmic Microwave Background Spectral Measurements in the 10-20GHz range
The Tenerife Microwave Spectrometer (TMS) is a ground-based
radio-spectrometer that will take absolute measurements of the sky between
10-20 GHz. To ensure the sensitivity and immunity to systematic errors of these
measurements, TMS includes an internal calibration system optimised for the TMS
band, and cooled down to 4 K. It consists of an Aluminium core, composed of a
baseplate and a bed of pyramidal elements coated with an absorber material and
a metallic shield. The absorber coating is made of a commercial resin ECCOSORB
CR/MF 117. To achieve the high stability (+/- 1 mK/h), temperature homogeneity
(thermal gradients {AT = 0.999) requirements of
the reference unit, careful consideration has been given to the RF and thermal
properties of the materials, as well as their geometry. In summary, this paper
presents a comprehensive account of the design, characterisation, and test
results of the TMS reference system.Comment: 45 pages, 36 figures, JINS
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