3,122 research outputs found
Localization transition induced by learning in random searches
We solve an adaptive search model where a random walker or L\'evy flight
stochastically resets to previously visited sites on a -dimensional lattice
containing one trapping site. Due to reinforcement, a phase transition occurs
when the resetting rate crosses a threshold above which non-diffusive
stationary states emerge, localized around the inhomogeneity. The threshold
depends on the trapping strength and on the walker's return probability in the
memoryless case. The transition belongs to the same class as the
self-consistent theory of Anderson localization. These results show that
similarly to many living organisms and unlike the well-studied Markovian walks,
non-Markov movement processes can allow agents to learn about their environment
and promise to bring adaptive solutions in search tasks.Comment: 5 pages, 5 figures + 4 pages of Supplemental Information. Accepted in
Physical Review Letter
Frequency and voltage partitioning in presence of renewable energy resources for power system (example: North Chile power network)
This paper investigates techniques for frequency and voltage partitioning of power network based on the
graph-theory. These methods divide the power system into distinguished regions to avoid the spread of disturbances
and to minimize the interaction between these regions for frequency and voltage control of power system. In case
of required active and reactive power for improving the performance of the power system, control can be performed
regionally instead of a centralized controller. In this paper, renewable energy sources are connected to the power
network to verify the effect of these sources on the power systems partitioning and performance. The number of
regions is found based on the frequency sensitivity for frequency partitioning and bus voltage for voltage partitioning to disturbances being applied to loads in each region. The methodology is applied to the north part of Chile power
network. The results show the performance and ability of graph frequency and voltage partitioning algorithm to divide
large scale power systems to smaller regions for applying decentralized controllers.Peer ReviewedPostprint (published version
Bound states in the continuum: localization of Dirac-like fermions
We report the formation of bound states in the continuum for Dirac-like
fermions in structures composed by a trilayer graphene flake connected to
nanoribbon leads. The existence of this kind of localized states can be proved
by combining local density of states and electronic conductance calculations.
By applying a gate voltage, the bound states couple to the continuum, yielding
a maximum in the electronic transmission. This feature can be exploited to
identify bound states in the continuum in graphene-based structures.Comment: 7 pages, 5 figure
Análisis de una propuesta de evaluación en relación con la estructura conceptual de la proporcionalidad
La presente propuesta es una aproximación reflexiva y critica de las prácticas evaluativas que se vienen desarrollando en la enseñanza básica y media en las instituciones de carácter privado de la ciudad de Cali, sustentada desde nuestra propia experiencia como docentes en ejercicio y estudiantes de último semestre en Licenciatura de Matemáticas y FÃsica de la Universidad del Valle, y apoyada en el análisis de unas actividades piloto de intervención y evaluación matemática, en torno a diferentes nociones y conceptos relacionados con la estructura conceptual del tópico de proporción y proporcionalidad en los grados de séptimo de educación básica y décimo de educación media que se realizaron a fin de plantear una serie de interrogantes cruciales en torno a la evaluación, dado su carácter organizador, dinamizador y potencializador del currÃculo. Esta propuesta se apoyará en el marco metodológico de los organizadores del currÃculo, donde la evaluación es un eje fundamental en el análisis didáctico que permite la articulación y organización de un currÃculo significativo para los intereses de los educandos
Radiative decay Z_H-> \gamma A_H in the little Higgs model with T-parity
In the little Higgs model with T-parity (LHTM), the only tree-level
kinematically allowed two-body decay of the Z_H boson is Z_H-> A_H H and thus
one-loop induced two-body decays may have a significant rate. We study the
Z_H-> \gamma A_H decay, which is induced at the one-loop level by a fermion
triangle and is interesting as it depends on the mechanism of anomaly
cancellation of the model. All the relevant two- and three-body decays of the
Z_H gauge boson arising at the tree-level are also calculated. We consider a
small region of the parameter space where the scale of the symmetry breaking f
is still allowed to be as low as 500 GeV by electroweak precision data. We
first analyze the scenario of a Higgs boson with a mass of 120 GeV. We found
that the Z_H->\gamma A_H branching ratio can be of the order of a tree-level
three-body decay and may be at the reach of detection at the LHC for f close to
500 GeV, but it may be difficult to detect for f=1 TeV. There is also an
scenario where the Higgs boson has an intermediate mass such that the Z_H-> A_H
H decay is closed, the Z_H-> \gamma A_H gets considerably enhanced and the
chances of detection get a large boost.Comment: 19 pages, 9 figures, 2 table
Patrimonio minero-metalúrgico de Rodalquilar: MetodologÃa de catalogación y resultados
Para estudiar y conservar el Patrimonio, es necesario desarrollar una metodologÃa para la catalogación y valoración de los elementos patrimoniales. Un caso real catalogación de una antigua zona minera; Rodalquilar (AlmerÃa) en el Sudeste de España, es el objetivo del presente trabajo
Momentum and energy preserving integrators for nonholonomic dynamics
In this paper, we propose a geometric integrator for nonholonomic mechanical
systems. It can be applied to discrete Lagrangian systems specified through a
discrete Lagrangian defined on QxQ, where Q is the configuration manifold, and
a (generally nonintegrable) distribution in TQ. In the proposed method, a
discretization of the constraints is not required. We show that the method
preserves the discrete nonholonomic momentum map, and also that the
nonholonomic constraints are preserved in average. We study in particular the
case where Q has a Lie group structure and the discrete Lagrangian and/or
nonholonomic constraints have various invariance properties, and show that the
method is also energy-preserving in some important cases.Comment: 18 pages, 6 figures; v2: example and figures added, minor correction
to example 2; v3: added section on nonholonomic Stoermer-Verlet metho
Hysteresis of nanocylinders with Dzyaloshinskii-Moriya interaction
The potential for application of magnetic skyrmions in high density storage
devices provides a strong drive to investigate and exploit their stability and
manipulability. Through a three-dimensional micromagnetic hysteresis study, we
investigate the question of existence of skyrmions in cylindrical
nanostructures of variable thickness. We quantify the applied field and
thickness dependence of skyrmion states, and show that these states can be
accessed through relevant practical hysteresis loop measurement protocols. As
skyrmionic states have yet to be observed experimentally in confined
helimagnetic geometries, our work opens prospects for developing viable
hysteresis process-based methodologies to access and observe skyrmionic states.Comment: 4 pages, 2 figure
Continuidad del cuidado: adulto mayor con diabetes tipo 2 y su cuidador
ResumenObjetivoAplicar la continuidad del cuidado en la persona con diabetes tipo 2 (DT2) y su cuidador, posterior al egreso hospitalario a través de intervenciones de enfermerÃa domiciliaria que contribuyan a mejorar el estilo de vida.MétodoSe trata un proceso de enfermerÃa a un adulto mayor con DT2 y a su cuidador primario, mediante una valoración de enfermerÃa inicial y la medición del conocimiento de la enfermedad a través del Cuestionario de Conocimiento en Diabetes-24 y estilo de vida, con el Instrumento para Medir el Estilo de Vida en Diabéticos. La identificación de necesidades con la taxonomÃa NANDA permitió intervenciones de tipo informacional, de relación y gestión basadas en la Clasificación de Intervenciones de EnfermerÃa para la continuidad del cuidado. Las intervenciones educativas fueron ejecutadas en sesiones periódicas, bajo consentimiento informado de los participantes, a través de una metodologÃa interactiva. La efectividad fue evaluada con una valoración final de la persona con DT2 y cuidador.ResultadosSe observó un incremento del nivel de conocimientos de la enfermedad y una mejora en el estilo de vida, de la persona con DT2 y su cuidador, en los dominios: nutrición, actividad fÃsica, emociones y adherencia terapéutica.ConclusiónLa continuidad del cuidado en la persona con DT2 y su cuidador es una herramienta indispensable para mejorar el estilo de vida y nivel de conocimientos, disminuir el riesgo de complicaciones y evitar reingresos hospitalarios.AbstractObjectiveTo establish the continuity care on persons suffering from diabetes type 2 (DT2) and their caregiver following hospital discharge, through home-visit interventions which can contribute to the improvement of lifestyles.MethodThe nursing process was performed on a patient with DT2 and the corresponding primary caregiver through a nursing assessment which included the use of the 24-Diabetes Knowledge Questionnaire and the Instrument to Measure Lifestyles in patients with Diabetes Type 2. The identification of needs through the NANDA taxonomy allowed informational, relational and managerial interventions based on the Nursing Interventions Classification. The educational interventions were performed during periodic sessions under the informed consent of the participants and through an interactive methodology. The effectiveness was assessed through a final evaluation of the patient and corresponding caregiver.ResultsAn increment in the level of knowledge of the illness and an improvement in the lifestyle of the person with DT2 and the corresponding caregiver, in the nutrition, physical activity, emotions, and therapeutic adherence domains were observed.ConclusionThe continuity care on the person with DT2 is a critical tool to improve the lifestyle and level of knowledge, and to reduce the risk of complications and hospital re-entries
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