Studies on scattering and thermodynamics of black holes in f(R) theory and Einstein's theory

One of the interesting consequences of Einstein's General Theory of Relativity is the black hole solutions. Until the observation made by Hawking in 1970s, it was believed that black holes are perfectly black. The General Theory of Relativity says that black holes are objects which absorb both matter and radiation crossing the event horizon. The event horizon is a surface through which even light is not able to escape. It acts as a one sided membrane that allows the passage of particles only in one direction i.e. towards the center of black holes. All the particles that are absorbed by black hole increases the mass of the black hole and thus the size of event horizon also increases. Hawking showed in 1970s that when applying quantum mechanical laws to black holes they are not perfectly black but they can emit radiation. Thus the black hole can have temperature known as Hawking temperature. In the thesis we have studied some aspects of black holes in f(R) theory of gravity and Einstein's General Theory of Relativity. The scattering of scalar field in this background space time studied in the first chapter shows that the extended black hole will scatter scalar waves and have a scattering cross section and applying tunneling mechanism we have obtained the Hawking temperature of this black hole. In the following chapter we have investigated the quasinormal properties of the extended black hole. We have studied the electromagnetic and scalar perturbations in this space-time and find that the black hole frequencies are complex and show exponential damping indicating the black hole is stable against the perturbations. In the present study we show that not only the black holes exist in modified gravities but also they have similar properties of black hole space times in General Theory of Relativity. 2 + 1 black holes or three dimensional black holes are simplified examples of more complicated four dimensional black holes. Thus these models of black holes are known as toy models of black holes in four dimensional black holes in General theory of Relativity. We have studied some properties of these types of black holes in Einstein model (General Theory of Relativity). A three dimensional black hole known as MSW is taken for our study. The thermodynamics and spectroscopy of MSW black hole are studied and obtained the area spectrum which is equispaced and different thermo dynamical properties are studied. The Dirac perturbation of this three dimensional black hole is studied and the resulting quasinormal spectrum of this three dimensional black hole is obtained. The different quasinormal frequencies are tabulated in tables and these values show an exponential damping of oscillations indicating the black hole is stable against the mass less Dirac perturbation. In General Theory of Relativity almost all solutions contain singularities. The cosmological solution and different black hole solutions of Einstein's field equation contain singularities. The regular black hole solutions are those which are solutions of Einstein's equation and have no singularity at the origin. These solutions possess event horizon but have no central singularity. Such a solution was first put forward by Bardeen. Hayward proposed a similar regular black hole solution. We have studied the thermodynamics and spectroscopy of Hay-ward regular black holes. We have also obtained the different thermodynamic properties and the area spectrum. The area spectrum is a function of the horizon radius. The entropy-heat capacity curve has a discontinuity at some value of entropy showing a phase transition.

Classification of recycled sands and their applications as fine aggregates for concrete and bituminous mixtures

As a result of the drive towards waste-poor world and reserving the non-renewable materials, recycling the construction and demolition materials become very essential. Now reuse of the recycled concrete aggregate more than 4 mm in producing new concrete is allowed but with natural sand a fine aggregate while. While the sand portion that represent about 30\% to 60\% of the crushed demolition materials is disposed off. To perform this research, recycled concrete sand was produced in the laboratory while nine recycled sands produced from construction and demolitions materials and two sands from natural crushed limestone were delivered from three plants. Ten concrete mix designs representing the concrete exposition classes XC1, XC2, XF3 and XF4 according to European standard EN 206 were produced with partial and full replacement of natural sand by the different recycled sands. Bituminous mixtures achieving the requirements of base courses according to Germany standards and both base and binder courses according to Egyptian standards were produced with the recycled sands as a substitution to the natural sands. The mechanical properties and durability of concrete produced with the different recycled sands were investigated and analyzed. Also the volumetric analysis and Marshall test were performed hot bituminous mixtures produced with the recycled sands. According to the effect of replacement the natural sand by the different recycled sands on the concrete compressive strength and durability, the recycled sands were classified into three groups. The maximum allowable recycled sand that can be used in the different concrete exposition class was determined for each group. For the asphalt concrete mixes all the investigated recycled sands can be used in mixes for base and binder courses up to 21\% of the total aggregate mass.

Black Boxes and Abstraction or A quick run through how computers work

How we get from transistors through to logic gates to ALUs and memory to the stored program and the fetch execute cycle through to machine code and high level languages. Inspired by Tanenbaum's approach in "Structured Computer Organozation"

Implementación del modelo toc “Black Penguin S.A.S”

La teoría de restricciones, más conocida como TOC, es una herramienta que permite el diagnóstico empresarial, identificando causas y efectos que afectan a la misma; en el desarrollo de esta tesis se realiza un diagnóstico TOC de la empresa BLACK PENGUIN S.A.S en el cual se considera la parte financiera donde se calculan y examinan las cuentas en términos TOC con medidores que ayudan a determinar las falencias en que incurre la empresa en su proceso productivo y de gestión administrativa, posteriormente se realiza una identificación de los efectos indeseables( EIDEs ) y las nubes de problema encontradas en la empresa, para de esta forma elaborar el árbol de realidad actual, y conocer el estado del arte de la organización. El desarrollo de diferentes análisis estratégicos como la cadena de valor y el análisis matricial servirán como punto de referencia para el desarrollo del Mejoramiento En Ambiente T.O.C.

Sands School : un centro asambleario en el que cada día es diferente.

Sands School es un centro de enseñanza privado inglés con un nuevo modelo educativo. Se trata de una comunidad abierta dónde todo el mundo tiene derecho a expresar y hacer valer su opinión. El proyecto promueve el compromiso entre los deseos, intereses y necesidades de los alumnos y exigencias del entorno social y educativo. La labor académica se desarrolla por la mañana dejando la tarde para actividades libres fuera de curriculum. La labor principal del profesorado consiste en combinar apoyo y orientación del trabajo de los alumnos hacia los objetivos para obtener el diploma a través de la individualización de la enseñanza.

Red, black, yellow, Peter, John, Mary...

Alumnos y alumnas de tres años empiezan a aprender un idioma nuevo en las aulas. Esta enseñanza de idiomas desde edades tempranas se manifiesta como la mejor fórmula para favorecer el aprendizaje de una lengua extranjera, en un ambiente donde los más pequeños sienten el placer de escuchar y practicar, aprendiendo a través del juego.