Geometric Aspects of Holographic Bit Threads

We revisit the recent reformulation of the holographic prescription to compute entanglement entropy in terms of a convex optimization problem, introduced by Freedman and Headrick. According to it, the holographic entanglement entropy associated to a boundary region is given by the maximum flux of a bounded, divergenceless vector field, through the corresponding region. Our work leads to two main results: (i) We present a general algorithm that allows the construction of explicit thread configurations in cases where the minimal surface is known. We illustrate the method with simple examples: spheres and strips in vacuum AdS, and strips in a black brane geometry. Studying more generic bulk metrics, we uncover a sufficient set of conditions on the geometry and matter fields that must hold to be able to use our prescription. (ii) Based on the nesting property of holographic entanglement entropy, we develop a method to construct bit threads that maximize the flux through a given bulk region. As a byproduct, we are able to construct more general thread configurations by combining (i) and (ii) in multiple patches. We apply our methods to study bit threads which simultaneously compute the entanglement entropy and the entanglement of purification of mixed states and comment on their interpretation in terms of entanglement distillation. We also consider the case of disjoint regions for which we can explicitly construct the so-called multi-commodity flows and show that the monogamy property of mutual information can be easily illustrated from our constructions.Comment: 48 pages, multiple figures. v3: matches published versio

Spectrum sharing in cognitive radio networks

Cognitive radio networks are the next step to tackle scarcity in wireless networks given the increasing demand of radioelectric spectrum where the proposed solution is to share said resource to improve this situation. In the present article, a review of the current state of spectrum sharing in cognitive radio networks. To achieve this purpose, the articles published over the last 4 years on the matter were reviewed including topics such as mobile networks and TV. Some studies and simulations proposed to share the spectrum is shown. The current state of the studies reveals that there has been significant progress in this research area yet it is necessary to continue similar studies and set in motion different schemes

Damage identification in structural health monitoring: a brief review from its implementation to the Use of data-driven applications

The damage identification process provides relevant information about the current state of a structure under inspection, and it can be approached from two different points of view. The first approach uses data-driven algorithms, which are usually associated with the collection of data using sensors. Data are subsequently processed and analyzed. The second approach uses models to analyze information about the structure. In the latter case, the overall performance of the approach is associated with the accuracy of the model and the information that is used to define it. Although both approaches are widely used, data-driven algorithms are preferred in most cases because they afford the ability to analyze data acquired from sensors and to provide a real-time solution for decision making; however, these approaches involve high-performance processors due to the high computational cost. As a contribution to the researchers working with data-driven algorithms and applications, this work presents a brief review of data-driven algorithms for damage identification in structural health-monitoring applications. This review covers damage detection, localization, classification, extension, and prognosis, as well as the development of smart structures. The literature is systematically reviewed according to the natural steps of a structural health-monitoring system. This review also includes information on the types of sensors used as well as on the development of data-driven algorithms for damage identification.Peer ReviewedPostprint (published version

Aplicación de gestión de mantenimiento preventivo para mejorar la productividad de la empresa Cinemark del Perú S.R.L, San Miguel, 2019

La presente investigación tuvo como objetivo principal determinar como la aplicación de gestión de mantenimiento preventivo mejora la productividad en el área de confitería de la empresa Cinemark del Perú S.R. L., para ello se implementó la disponibilidad, confiabilidad y mantenibilidad. Fue una investigación aplicada, de diseño cuasi-experimental. La población y la muestra fueron las maquinas pon corn en el área de confitería. La técnica empleada fue la observación, el instrumento fue la ficha de recolección de datos. La validación de los instrumentos se realizó a través del criterio de juicio de expertos. Para el análisis de los datos se utilizó el programa estadístico SPSS versión 25. Los resultados encontrados fueron: la productividad resultó 44.19 %; un valor menor luego de aplicar el nuevo método de trabajo que fue de 69.64 %; se concluyó que la aplicación de gestión de mantenimiento preventivo generó una mejora de 25.45 % en la productividad, en la empresa Cinemark 2019. Se recomendó seguir los procedimientos de mantenimiento preventivo, cumplir los cronogramas de mantenimiento para no presentar averías, determinando fallas a tiempo y poder contar con todos los equipos disponibles, a su vez ser eficientes en los servicios de mantenimiento y cumplir con lo establecido

Cluster Acceleration and Stabilization in Downflow Catalytic Reactors: Experimental and CPFD Simulation Studies

Particle cluster dynamics in downflow reactors are of great importance for the implementation of large scale, environmentally friendly catalytic processes. Studies should address particle cluster velocities, solids holdups, and individual cluster sizes to establish reliable models for the unit scale up. In this PhD dissertation, the individual characteristics of particle clusters, such as cluster size, velocity, and particle volume fraction, were measured in the feeding, intermediate, and fully developed flow sections of a cold-flow model unit using CREC-GS-Optiprobes. The downer unit employed in this research had a 0.051 m ID and a 2 m high acrylic column. The feeding section included a cyclone and a ring gas injector with eight nozzles angled at 45º. A fluid catalytic cracking (FCC) catalyst with a mean diameter of 84.4 μm and a density of 1722 kg/m3 was used. The operating conditions for the experiments were superficial gas velocities of 1.0-1.6 m/s and solids mass fluxes of 30-50 kg/m2s. The results obtained showed close to normal particle cluster size distributions near the feeding region, and skewed distributions with a higher frequency of short clusters in the fully developed flow section. Additionally, significant changes were noticed when clusters evolved from the feeding section to the fully developed flow section: the average cluster size changed from 7-9 particles to 3-4 particles, and 0.5-0.9 m/s cluster slip velocities in the downer entrance increased to 1.1-1.4 m/s in the stabilized region. Regarding the obtained findings, it was observed that the cluster slip velocity is a function of the measured axial cluster length. On the basis of the data obtained, it was also established a quasi-spherical shape for the clusters in the entry downer section and a strand shaped cluster for clusters in the stabilized downer region. Furthermore, by using computational fluid dynamics simulations (Multiphase Particle-in-Cell (MP-PIC) Method) and accounting for the experimentally determined cluster size distribution, a Hybrid Experimental-Numerical Cluster Model was postulated and successfully validated. Finally, and to establish the relevance of the fluid dynamic model, a fluidized catalytic cracking (FCC) pilot-scale downer unit, was simulated using the developed Hybrid MP-PIC Model and kinetics obtained in a CREC Riser Simulator. Radial and axial temperature distributions show the adequacy of the gas-solid feeder employed. This was the case given the very effective gas-solid mixing leading to quick gas-solid radial thermal stabilization. On this basis, it was proven that flow stabilization can be achieved in a 1-2 m downer unit length, and this for typical FCC operated with 5-7 C/O (catalyst/oil) ratios

Dirac materials in parallel non-uniform electromagnetic fields generated by SUSY: A new class of chiral Planar Hall Effect?

Within a Supersymmetric Quantum Mechanics (SUSY-QM) framework, the (3+1) Dirac equation describing a Dirac material in the presence of external parallel electric and magnetic fields is solved. Considering static but non-uniform electric and magnetic profiles with translational symmetry along the y-direction, the Dirac equation is transformed into two decoupled pairs of Schr\"odinger equations, one for each chirality of the fermion fields. Taking trigonometric and hyperbolic profiles for the vector and scalar potentials, respectively, we arrive at SUSY partner P\"oschl-Teller-like quantum potentials. Restricting to the conditions of the potentials that support an analytic zero-mode solution, we obtain a nontrivial current density in the same plane where the electric and magnetic fields lie, but perpendicular to both of them, indicating the possibility of realizing the Planar Hall Effect. Furthermore, this non-vanishing current density is the sum of current densities for the left- and right-chiralities, suggesting that the net current is a consequence of chiral symmetry.Comment: 10 pages, 6 figure

Uso de la inmunohistoquímica como herramienta epidemiológica para el diagnóstico de rabia bovina a partir de casos no conclusivos

Objetivo. Identificar el virus de la rabia en casos de encefalitis bovina a partir de muestras archivadas en el laboratorio sin diagnóstico conclusivo. Materiales y métodos. Doce muestras de cerebro bovino sospechosas de rabia, fueron procesadas por la técnica de inmunoperoxidasa indirecta, usando anticuerpos policlonales contra el agente viral. Resultados. Se demostró la presencia de antígenos virales en tres casos en forma de agregados pequeños en el citoplasma de las neuronas, con un patrón de forma redonda u oval y un número variable de corpúsculos de inclusión viral. Se discute sobre la importancia de los resultados en Colombia, la utilidad de la técnica en las difíciles condiciones de envío de muestras al laboratorio, además la posible relación de los casos negativos con herpesvirus bovino 5. Conclusiones. La utilización de la técnica de inmunohistoquímica para demostrar antígenos del virus rábico en encéfalos bovinos fijados en formol, puede ayudar en el perfeccionamiento del mapa epidemiológico de la enfermedad de la rabia en Colombia y puede disminuir el alto subdiagnóstico de otras enfermedades que afectan el sistema nervioso de los bovinos