Evolution of a non-cohesive granular bed subject to a succession of erosive turbidity currents

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2006.Includes bibliographical references (leaf 18).An experiment was performed to study the evolution of a non-cohesive granular bed subject to a succession of erosive turbidity currents to evaluate the applicability of a proposed interface model that prescribes a relationship between the bed shear stress and the local bed elevation and local bed slope. This study considered only the relationship between the local bed elevation and the shear stress by using non-cohesive plastic particles as bed sediment that was laid down in a subaqueous straight channel. The elevation of the plastic bed was measured before and after it was subjected to two erosive salt water turbidity currents using a high resolution displacement laser mapping system. These changes in elevation of the sediment bed are compared to determine whether a correlation exists between local bed elevation and bed erosion. The results from this experiment display a weak correlation between the erosion of the plastic bed and the initial local bed elevation when the initial elevation height is small relative to the thickness of the turbidity currents.(cont.) However, a strong correlation exists when the initial elevation height is approximately 2% to 6% of the turbidity current thickness. The strength of this correlation also depends upon the window size of the analysis which is shown to be associated with the downstream variability in bed roughness.by Roberto Carlos Rangel.S.B

Diversidad y equidad en la pedagogía salesiana

Don Pascual Chávez indica en el Aguinaldo 2013 que la afirmación «la educación es cosa del corazón» es una expresión analógica y simbólica; «no reducible a principio pedagógico sino, elemento de la espiritualidad apostólica de la Familia Salesiana, reconocida en la capacidad de amar y de hacerse amar». Este «amor» de carácter motivacional y relacional es la esencia del Sistema Preventivo de Don Bosco, frente al cual el salesiano «responde con competencia», como experto que practica la «profesionalidad pastoral». El texto La Pastoral Juvenil Salesiana indica que el Proyecto Educativo Salesiano responde a cuatro «dimensiones»; mientras que, para la acción en la Universidad menciona «pedagogías» ejecutadas por la Comunidad Educativa Pastoral (CEP), concepto que sobrepasa lo infraestructural ya que sus obras las consideran «casa». El P. Fernando Peraza dice que el sistema educativo salesiano se fundamenta en el “optimismo educativo” del que deriva la «prevención»: concepto promocional y hoy sintoniza con los conceptos y prácticas de la empatía, la asertividad y la resiliencia: reconoce la precariedad de la condición juvenil y su capacidad de alteridad, de rehabilitación y de enmienda

Optimization of Spacecraft Formations about Lagrange Points for the Next Generation Space Weather Prediction Mission

This thesis’s work serves as proof of concept for the Next Generation Space Weather Prediction Mission, a multi-spacecraft mission at various libration points whose objective is to forecast Space Weather hazards with a 12day warning time. This thesis deals with the design and control of orbits of spacecraft formations at different libration points. The systems studied are SunEarth, SunVenus, SunMercury, and SunMars. The orbit design and formation keeping control of the spacecraft are solved simultaneously using an optimization software called DIDO. Initial conditions are obtained through two different strategies. The first one, by placing the spacecraft in a tetrahedral formation and using Monte Simulations to find the initial velocities. The second strategy suggests holding velocities fixed while initial locations of the spacecraft are chosen randomly. All results are verified and validated by applying Pontryagin’s principle to the optimal control problem by “hand”, and then comparing the results with the outputs from the optimization software. L4 and L5 points of any systems are the easiest to work with due to their inherent stability. In most cases, the use of the L1norm of control as the cost function yields the lowest station-keeping cost. The culminating remark is that the Next Generation Space Weather Prediction Mission is feasible from an astrodynamics perspective

High Strain Rate Experiments of Energetic Material Binder

Energetic materials, in particular HMX, is widely used in many applications as polymer bonded explosives (PBX) and rocket propellant. However, when damaged, HMX is known to be an unstable substance which renders it a hazardous material and in some cases unreliable. Finding critical mechanical conditions at high rates that render various forms of energetic materials as unreliable would be vital to understand the effects that vibrations and compression forces have on energetic materials. A better understanding would enable the ability to develop improvements in the manufacturing of PBX and rocker propellant. The method utilized to evaluate the mechanical properties of the material involved a compression Kolsky bar where a projectile hits an incident bar at 5 meters per second. The incident bar then compresses a binding polymer specimen composed of Sylgard 184 at the other end. Strain gauges were applied to the incident bar to measure voltage changes due to strain. In addition, a load cell was placed behind the specimen to measure compression force histories. The specimens studied were varied to evaluate correlation between composition and mechanical behavior. The results from the experiments showed that the binders with a lower mixing ratio of base to curing agent made the bonding polymer stiffer and less prone to elastic deformation. The results also unveiled that the stiffer binder experienced a higher compression stress due to it’s limited elastic deformation. The results also show that, at the strain rates studied, none of the binders failed. However, the measured results provide insight to manufacturers to select proper binder for specific loads. Further research of the compression force on HMX within Sylgard 184 is needed to delineate whether a stiff or ductile binder is more reliable for PBX

Timotestin, un paradigma biológico o una fisiología programada: estudios in vitro

Tesis ( Doctorado en Ciencias con Especialidad en Microbiología) UANLUANLhttp://www.uanl.mx

Simplificando la comprensión de programas a través de la interconnexión de dominios

The program understanding task is usually time and effort consuming. In a traditional way the code is inspected line by line by the user without any kind of help. But this becomes impossible for large systems. Some software systems were created in order to generate automatically explanations, metrics, statistics and visualizations to describe the syntax and the semantic of programs. These kind of tools are Program Comprehension systems. One of the most important feature used in this kind of tool is the software visualization. We feel that would be very useful to define criterion to evaluate visualization systems that are used for program comprehension. The main objective of this paper is to describe and discuss a set of evaluation parameters for this kind of systems.FC