289 research outputs found
First Principle Computation of Random Pinning Glass Transition, Glass Cooperative Length-Scales and Numerical Comparisons
As a guideline for experimental tests of the ideal glass transition (Random
Pinning Glass Transition, RPGT) that shall be induced in a system by randomly
pinning particles, we performed first-principle computations within the
Hypernetted chain approximation and numerical simulations of a Hard Sphere
model of glass-former. We obtain confirmation of the expected enhancement of
glassy behaviour under the procedure of random pinning, which consists in
freezing a fraction of randomly chosen particles in the positions they have
in an equilibrium configuration. We present the analytical phase diagram as a
function of and of the packing fraction , showing a line of RPGT
ending in a critical point. We also obtain first microscopic results on
cooperative length-scales characterizing medium-range amorphous order in Hard
Spere glasses and indirect quantitative information on a key thermodynamic
quantity defined in proximity of ideal glass transitions, the amorphous surface
tension. Finally, we present numerical results of pair correlation functions
able to differentiate the liquid and the glass phases, as predicted by the
analytic computations.Comment: Working draft, comments are welcom
La experiencia a favor del cambio
[Resumen] Objetivo: Explorar la percepción de la participación social en personas
mayores con déficit auditivo desde su perspectiva, identificando fortalezas
y barreras de comunicación y de información en su vida diaria,
profundizando en sus relaciones y de las personas de su entorno más
cercano, así como su desempeño ocupacional en salud y calidad de vida.
Metodología: Estudio de tipo cualitativo con enfoque fenomenológico
realizado en el período comprendido enseis meses. La muestra está
compuesta por 5 personas con déficit auditivo de una Residencia
Gerontológica. Las técnicas utilizadas fueron la entrevista y el uso de
audio.
Resultados: La mayoría de los participantes presentan problemas de
comunicación y acceso a la información oral, tanto con sus semejantes
como con los de su entorno más cercano (familia), referenciando una
limitación en la participación social. Se aprecia el importante papel de la
comunicación, el acceso a la información y los productos de apoyo (por
ej., las prótesis auditivas). Y, por tanto, se observa un desajuste entre los
recursos de apoyo y las necesidades de las personas mayores con déficit
auditivo.
Conclusiones:Las personas mayores con déficit auditivo perciben su
participación social como algo “normal”, debido a las circunstancias
personales y sociales. Se percibe que se encuentran en un estado de
acomodo en su “problema” para aquellas personas que portan prótesis
auditivas, en cambio, aquellas que no poseen de dichas prótesisTraballo fin de grao (UDC.FCS). Terapia ocupacional. Curso 2013/2014
An Ising Model for Metal-Organic Frameworks
We present a three-dimensional Ising model where lines of equal spins are
frozen in such that they form an ordered framework structure. The frame spins
impose an external field on the rest of the spins (active spins). We
demonstrate that this "porous Ising model" can be seen as a minimal model for
condensation transitions of gas molecules in metal-organic frameworks. Using
Monte Carlo simulation techniques, we compare the phase behavior of a porous
Ising model with that of a particle-based model for the condensation of methane
(CH) in the isoreticular metal-organic framework IRMOF-16. For both models,
we find a line of first-order phase transitions that end in a critical point.
We show that the critical behavior in both cases belongs to the 3D Ising
universality class, in contrast to other phase transitions in confinement such
as capillary condensation.Comment: 11 pages, 9 figure
Low-temperature anomalies of a vapor deposited glass
We investigate the low temperature properties of two-dimensional
Lennard-Jones glass films, prepared in silico both by liquid cooling and by
physical vapor deposition. We identify deep in the solid phase a crossover
temperature , at which slow dynamics and enhanced heterogeneity emerge.
Around , localized defects become visible, leading to vibrational
anomalies as compared to standard solids. We find that on average,
decreases in samples with lower inherent structure energy, suggesting that such
anomalies will be suppressed in ultra-stable glass films, prepared both by very
slow liquid cooling and vapor deposition.Comment: 10 pages including appendices, 8 figures. Version accepted for
Physical Review Material
Numerical detection of the Gardner transition in a mean-field glass former
Recent theoretical advances predict the existence, deep into the glass phase,
of a novel phase transition, the so-called Gardner transition. This transition
is associated with the emergence of a complex free energy landscape composed of
many marginally stable sub-basins within a glass metabasin. In this study, we
explore several methods to detect numerically the Gardner transition in a
simple structural glass former, the infinite-range Mari-Kurchan model. The
transition point is robustly located from three independent approaches: (i) the
divergence of the characteristic relaxation time, (ii) the divergence of the
caging susceptibility, and (iii) the abnormal tail in the probability
distribution function of cage order parameters. We show that the numerical
results are fully consistent with the theoretical expectation. The methods we
propose may also be generalized to more realistic numerical models as well as
to experimental systems.Comment: 17 pages, 16 figure
Growing timescales and lengthscales characterizing vibrations of amorphous solids
Low-temperature properties of crystalline solids can be understood using
harmonic perturbations around a perfect lattice, as in Debye's theory.
Low-temperature properties of amorphous solids, however, strongly depart from
such descriptions, displaying enhanced transport, activated slow dynamics
across energy barriers, excess vibrational modes with respect to Debye's theory
(i.e., a Boson Peak), and complex irreversible responses to small mechanical
deformations. These experimental observations indirectly suggest that the
dynamics of amorphous solids becomes anomalous at low temperatures. Here, we
present direct numerical evidence that vibrations change nature at a
well-defined location deep inside the glass phase of a simple glass former. We
provide a real-space description of this transition and of the rapidly growing
time and length scales that accompany it. Our results provide the seed for a
universal understanding of low-temperature glass anomalies within the
theoretical framework of the recently discovered Gardner phase transition.Comment: 12 pages, 20 figures. Accepted for publication in PNA
Unsupervised hierarchical clustering using the learning dynamics of RBMs
Datasets in the real world are often complex and to some degree hierarchical,
with groups and sub-groups of data sharing common characteristics at different
levels of abstraction. Understanding and uncovering the hidden structure of
these datasets is an important task that has many practical applications. To
address this challenge, we present a new and general method for building
relational data trees by exploiting the learning dynamics of the Restricted
Boltzmann Machine (RBM). Our method is based on the mean-field approach,
derived from the Plefka expansion, and developed in the context of disordered
systems. It is designed to be easily interpretable. We tested our method in an
artificially created hierarchical dataset and on three different real-world
datasets (images of digits, mutations in the human genome, and a homologous
family of proteins). The method is able to automatically identify the
hierarchical structure of the data. This could be useful in the study of
homologous protein sequences, where the relationships between proteins are
critical for understanding their function and evolution.Comment: Version accepted in Physical Review
Port-City Development: The Spanish Case
[Abstract]: The objective of this paper is to try to evaluate the port-city
relationship from its onset, taking into account the challenges
of port 4.0. Indicators such as the percentage of employees
participating in training programs, the percentage of female
employees in Galician ports, the percentage of merchandise
moved by private operators and the percentage of companies
with quality certification in Galician ports are evaluated. The
fourth revolution is based on the transition from current
fossil fuel-based energy models to alternative energy sources,
changes in the logistics and transport parameters and finally,
on the elimination of intermediation. The key component of
the third pillar of new Economy 4.0 is complete digitalization.
The optimum port-city solution must address the need of both
the urban planner and the port manager to evaluate potential
measures that would alleviate the pressure of dedicated port
facilities on the city and vice versa to the greatest extent possible
Industria agroalimentaria en Extremadura: obstáculos a la innovación, disposición a innovar y políticas públicas demandadas
The purpose of this paper is to analyse the barriers perceived by agribusiness companies in Extremadura; how these barriers influence their disposition to innovate and the type of public actions demanded by these companies in order to boost innovation. Data comes from an ad hoc survey conducted in 2013. The methodology used combines descriptive analysis with factor analysis and econometric analysis. Main results show that high costs and risks, lack of human resources and difficulties of appropriability are the barriers that reduce the probability to innovate, and that there are important differences among the perceived factors of obstacles and demands of public actions. This can be a reference to develop government policies specifically geared towards boosting innovation in this kind of industry.El objetivo de este trabajo es analizar las barreras percibidas por las empresas agroalimentarias en Extremadura; cómo estas barreras influyen en su disposición a innovar y el tipo de acciones públicas que demandan estas empresas para impulsar la innovación. Los datos provienen de una encuesta ad hoc realizada en 2013. La metodología utilizada combina el análisis descriptivo con el análisis factorial y econométrico. Los principales resultados muestran que los costes y riesgos elevados, la falta de recursos humanos y las dificultades de apropiabilidad son las barreras que reducen la probabilidad de innovar, y que existen diferencias importantes entre los factores de obstáculos percibidos y las demandas de las acciones públicas. Esto puede ser una referencia para desarrollar políticas gubernamentales orientadas específicamente a impulsar la innovación en este tipo de industria
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