A note on linearized stability of Schwarzschild thin-shell wormholes with variable equations of state

We discuss how the assumption of variable equation of state (EoS) allows the elimination of the instability at equilibrium throat radius $a_0=3M$ featured by previous Schwarzschild thin-shell wormhole models. Unobstructed stability regions are found for three choices of variable EoS. Two of these EoS entail linear stability at every equilibrium radius. Particularly, the thin-shell remains stable as $a_0$ approaches the Schwarzschild radius $2M$. A perturbative analysis of the wormhole equation of motion is carried out in the case of variable Chaplygin EoS. The squared proper angular frequency $\omega_0^2$ of small throat oscillations is linked with the second derivative of the thin-shell potential. In various situations $\omega_0^2$ remains positive and bounded in the limit $a_0\rightarrow 2M$.Comment: Fifth version. 15 pages. Almost completely rewritten. Extended analysis. New reference

Charged anisotropic matter with linear or nonlinear equation of state

Ivanov pointed out substantial analytical difficulties associated with self-gravitating, static, isotropic fluid spheres when pressure explicitly depends on matter density. Simplification achieved with the introduction of electric charge were noticed as well. We deal with self-gravitating, charged, anisotropic fluids and get even more flexibility in solving the Einstein-Maxwell equations. In order to discuss analytical solutions we extend Krori and Barua's method to include pressure anisotropy and linear or non-linear equations of state. The field equations are reduced to a system of three algebraic equations for the anisotropic pressures as well as matter and electrostatic energy densities. Attention is paid to compact sources characterized by positive matter density and positive radial pressure. Arising solutions satisfy the energy conditions of general relativity. Spheres with vanishing net charge contain fluid elements with unbounded proper charge density located at the fluid-vacuum interface. Notably the electric force acting on these fluid elements is finite, although the acting electric field is zero. Net charges can be huge ($10^{19}\,C$) and maximum electric field intensities are very large ($10^{23}-10^{24}\,statvolt/cm$) even in the case of zero net charge. Inward-directed fluid forces caused by pressure anisotropy may allow equilibrium configurations with larger net charges and electric field intensities than those found in studies of charged isotropic fluids. Links of these results with charged strange quark stars as well as models of dark matter including massive charged particles are highlighted. The van der Waals equation of state leading to matter densities constrained by cubic polynomial equations is briefly considered. The fundamental question of stability is left open.Comment: 22 Latex pages, 17 figures, Inclusion of new paragraph at the end of Conclusion & some of the old captions of the Figures are replaced with new caption

DESARROLLO DE UN PROCESO DE SEPARACION Y RECUPERACION DE POLIMERO-ALUMINIO UTILIZANDO ACEITE RECICLADO, A PARTIR DE PELICULAS DE DESECHO RESULTANTES DE LA RECUPERACION DE CELULOSA EN EMPAQUES FLEXIBLES DE REPORTE DE INVESTIGACION

El presente proyecto surge con la necesidad de responder y dar solución a un problema de procesamiento y recuperación de aluminio y polímero que actualmente presenta la industria de recuperación de celulosa a partir de los envases tipo tetra pak para la producción de papel, y su posterior venta en las empresas papeleras como Kimberly & Klark entre otras. Todos los residuos que resultan después de la recuperación de la celulosa (papel) de este tipo de envases, son películas de aluminio y polímero, que resultan difíciles de separar porque se adhieren a través de adhesivos y extrución. Por lo que la separación mecánica no es una opción y se requiere el desarrollo de un nuevo proceso para una separación efectiva y de bajo costo. En este sentido el objetivo de este proyecto es el desarrollo de un nuevo proceso de separación del polímero y del aluminio para su posterior reciclaje. En este proyecto se propuso la utilización de un solvente que fuera lo mas barato posible y además que pudiera evitar contaminación ambiental, con este propósito se propuso utilizar aceite de canola reciclado (aceite de los restaurante que no utilizan o que ya no es útil para ellos y que tiran) , debido a su alta polaridad y posible disolución del polímero en este debido a esta propiedad

Escuela nueva: de las guías de aprendizaje al aprendizaje por proyectos

95 páginasEste trabajo de investigación acción que se desarrolla en el Centro Educativo Rural Los Animes del municipio de Urrao en el departamento de Antioquia, plantea la necesidad de revitalizar el modelo de escuela nueva a través del aprendizaje por proyectos, pues durante mucho tiempo la columna vertebral de este modelo pedagógico flexible han sido las guías de aprendizaje para dinamizar los procesos de enseñanza y aprendizaje en aulas multigrado de educación rural, causando un debilitamiento del saber pedagógico en los docentes, quienes han reducido su labor a la de facilitadores y verificadores de aprendizajes, por un lado para proveer material y recursos, y por otro para comprobar el desarrollo de las unidades didácticas que presentan las guías por parte de los estudiantes. Asimismo, a este debilitamiento de los saberes pedagógicos en los docentes, se suman los bajos niveles de desempeño en los estudiantes, quienes por mucho tiempo se han dedicado a realizar procesos de transcripción de las guías a sus cuadernos, sin provocar a través de la interacción, el trabajo colaborativo, el contacto con el entorno y la manipulación el desarrollo de habilidades y competencias, requiriéndose de una oxigenación en las prácticas de enseñanza para romper con la estructura didáctica implantada por las guías de aprendizaje

Modelo TPACK y Competencias Digitales de los Docentes en la Escuela Militar de Chorrillos Crl. Francisco Bolognesi – 2019

El objetivo de este trabajo de investigación consistió en identificar la correlación entre las variables, modelo TPACK y competencias digitales, en los docentes de la Escuela Militar de Chorrillos Crl. Francisco Bolognesi – 2019. En cuanto al campo metodológico, la investigación fue aplicada y tuvo un enfoque cuantitativo, contando con un nivel descriptivo y correlacional, caracterizándose por ser no experimental. Se recurrió a una muestra censal, siendo esta conformada por 64 educadores al igual que la población. Este grupo de educadores respondieron un cuestionario compuesto por 18 ítems, 9 para cada variable y se calculó en un escalamiento tipo Likert en base a 5 opciones de respuesta. La confiabilidad que demostró el instrumento fue de 0.917 que indicó una confiabilidad alta; así mismo, se validó por el juicio de expertos. Se hizo uso del coeficiente de correlación de Spearman para la corroboración de hipótesis. Finalmente, los resultados que se adquirieron confirmaron que existe una relación entre las variables estudiadas.The objective of this research work was to identify the correlation between the variables, TPACK model and digital competences, in the teachers of the Military School of Chorrillos Crl. Francisco Bolognesi – 2019. Regarding the methodological field, the The research was applied and had a quantitative approach, with a level descriptive and correlational, characterized by being non-experimental. One resorted to census sample, being made up of 64 educators as well as the population. This group of educators answered a questionnaire made up of 18 items, 9 for each variable and was calculated on a Likert-type scale based on 5 response options. The reliability that the instrument demonstrated was 0.917, which indicated a high reliability; likewise, it was validated by expert judgment. The correlation coefficient of Spearman for the corroboration of hypotheses. Finally, the results that were acquired confirmed that there is a relationship between the variables studied.ChosicaEscuela de PosGrad

Nanoporous Materials for Carbon Dioxide Separation and Storage

Global climate change is one of the most challenging problems that human beings are facing. The large anthropogenic emission of CO2 in the atmosphere is one of the major causes for the climate change. Coal-fired power plants are the single-largest anthropogenic emission sources globally, accounting for approximately one third of the total CO2 emissions. It is therefore necessary to reduce CO2 emission from coal-fired power plants. Current technologies for the post-combustion CO2 capture from flue gas streams can be broadly classified into the three categories: absorption, adsorption, and membrane processes. Despite challenges, CO2 capture by adsorption using solid sorbents and membranes offers opportunities for energy-efficient capture and storage of CO2. Nanoporous materials have attracted tremendous interest in research and development due to their potential in conventional applications such as catalysis, ion-exchange, and gas separation as well as in advanced applications such as sensors, delivery, and micro-devices. In the first part of this dissertation, we will study the synthesis of membranes using an emerging class of nanoporous materials, metal-organic frameworks (MOFs) for carbon dioxide (CO2) separations. Due to the unique chemistry of MOFs which is very different from that of zeolites, the techniques developed for the synthesis of zeolite membranes cannot be used directly. In order to overcome this challenge, a couple of novel techniques were developed: 1) "thermal seeding" for the secondary growth and 2) "surface modification" for the in situ growth. Membranes of HKUST-1 and ZIF-8, two of the most important MOFs, were prepared on porous α-alumina supports using thermal seeding and the surface modification techniques, respectively. The second part of this dissertation demonstrates a simple and commercially viable application of nanoporous materials (zeolite 5A and amine-functionalized mesoporus silica), storing CO2 as a micro-fire extinguishers in polymers. Materialist is observed that by dispersing these highly CO2-philic nanoporous materials in polymer matrices, the propagation of flame was greatly retarded and extinguished. This flame retarding behavior is attributed to the fact that CO2 released from the sorbents (zeolite 5A and mesoporous silica), blocks the flow of oxygen, therefore causing the fire to be effectively extinguished. Our results suggest that the binding strength of CO2 on sorbents play an important role. If the binding strength of CO2 is too low, CO2 releases too early, thereby ineffective in retarding the flame

Neutral perfect fluids of Majumdar-type in general relativity

We consider the extension of the Majumdar-type class of static solutions for the Einstein-Maxwell equations, proposed by Ida to include charged perfect fluid sources. We impose the equation of state $\rho+3p=0$ and discuss spherically symmetric solutions for the linear potential equation satisfied by the metric. In this particular case the fluid charge density vanishes and we locate the arising neutral perfect fluid in the intermediate region defined by two thin shells with respective charges $Q$ and $-Q$. With its innermost flat and external (Schwarzschild) asymptotically flat spacetime regions, the resultant condenser-like geometries resemble solutions discussed by Cohen and Cohen in a different context. We explore this relationship and point out an exotic gravitational property of our neutral perfect fluid. We mention possible continuations of this study to embrace non-spherically symmetric situations and higher dimensional spacetimes.Comment: 9 page

Investigating face perception in humans and DCNNs

This thesis aims to compare strengths and weaknesses of AI and humans performing face identification tasks, and to use recent advances in machine-learning to develop new techniques for understanding face identity processing. By better understanding underlying processing differences between Deep Convolutional Neural Networks (DCNNs) and humans, it can help improve the ways in which AI technology is used to support human decision-making and deepen understanding of face identity processing in humans and DCNNs. In Chapter 2, I test how the accuracy of humans and DCNNs is affected by image quality and find that humans and DCNNs are affected differently. This has important applied implications, for example, when identifying faces from poor-quality imagery in police investigations, and also points to different processing strategies used by humans and DCNNs. Given these diverging processing strategies, in Chapter 3, I investigate the potential for human and DCNN decisions to be combined in face identification decisions. I find a large overall benefit of 'fusing' algorithm and human face identity judgments, and that this depends on the idiosyncratic accuracy and response patterns of the particular DCNNs and humans in question. This points to new optimal ways that individual humans and DCNNs can be aggregated to improve the accuracy of face identity decisions in applied settings. Building on my background in computer vision, in Chapters 4 and 5, I then aim to better understand face information sampling by humans using a novel combination of eye-tracking and machine-learning approaches. In chapter 4, I develop exploratory methods for studying individual differences in face information sampling strategies. This reveals differences in the way that 'super-recognisers' sample face information compared to typical viewers. I then use DCNNs to assess the computational value of the face information sampled by these two groups of human observers, finding that sampling by 'super-recognisers' contains more computationally valuable face identity information. In Chapter 5, I develop a novel approach to measuring fixations to people in unconstrained natural settings by combining wearable eye-tracking technology with face and body detection algorithms. Together, these new approaches provide novel insight into individual differences in face information sampling, both when looking at faces in lab-based tasks performed on computer monitors and when looking at faces 'in the wild'