Transient Three-Dimensional Side Load Analysis of a Film Cooled Nozzle

Transient three-dimensional numerical investigations on the side load physics for an engine encompassing a film cooled nozzle extension and a regeneratively cooled thrust chamber, were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Ultimately, the computational results will be provided to the nozzle designers for estimating of effect of the peak side load on the nozzle structure. Computations simulating engine startup at ambient pressures corresponding to sea level and three high altitudes were performed. In addition, computations for both engine startup and shutdown transients were also performed for a stub nozzle, operating at sea level. For engine with the full nozzle extension, computational result shows starting up at sea level, the peak side load occurs when the lambda shock steps into the turbine exhaust flow, while the side load caused by the transition from free-shock separation to restricted-shock separation comes at second; and the side loads decreasing rapidly and progressively as the ambient pressure decreases. For the stub nozzle operating at sea level, the computed side loads during both startup and shutdown becomes very small due to the much reduced flow area

Synergy between the pre–T cell receptor and Notch: cementing the αβ lineage choice

Notch1 signaling suppresses B cell development and promotes T lineage commitment in thymus-seeding hematopoietic progenitors. Notch1 is also activated in early T cell progenitors, but the functions of these later Notch signals have not been clearly defined. Recent studies reveal that Notch signaling is not essential for pre–T cell receptor (TCR) expression or γδ lineage choice. Rather, pre-TCR signaling enhances progenitor competitiveness for limiting Notch ligands, leading to preferential expansion of TCRβ-bearing progenitors

“COMPARACIÓN DE COLECISTECTOMÍA LAPAROSCÓPICA 3 PUERTOS VS 4 PUERTOS”

RESUMEN: Introducción: La colecistitis es una enfermedad frecuente en nuestra población asociada a complicaciones graves en caso de no ser tratada o de presentar errores en su manejo, durante cuadros agudos o crónicos, es por ellos que se motiva la presente tesis donde analizaremos su manejo en un hospital de segundo nivel. Objetivo: El objetivo de esta tesis es comparar la cirugía laparoscópica 3 puertos versus 4 puertos, analizando el tiempo quirúrgico y las complicaciones trans y posoperatorias en el tratamiento de la colelitiasis en Hospital General “Dr. Gustavo Baz Prada” del 1 de enero del 2014 al 31 de diciembre del 2015. Material y Métodos: Se realiza un estudio analítico, transversal, retrospectivo y observacional. Universo de trabajo a los expedientes del archivo clínico del Hospital General “Gustavo Baz Prada” con manejo de colecistectomía laparoscópica ingresados del 1ro de enero del 2014 al 31 de diciembre del 2015. Resultados: Se recabaron los siguientes datos, se obtiene una muestra de 125 casos. De las cuales el 84% (105) fueron del sexo femenino y 16% (20) fueron del sexo masculino, se realizaron un total de 106 colecistectomías laparoscópicas abordadas con 3 puertos, contra un total de 20 colecistectomías abordadas con 4 puertos. De acuerdo al tiempo quirúrgico vemos que este se reduce de manera significativa en la disección teniendo una media el abordaje con 3 puertos de 87.78 ± 5.14 min (IC:95% con prueba t student, P=0.05) contra 61.05 ± 14.91 (IC:95% con prueba t de student, P=0.05) minutos del abordaje con 4 puertos. La principal complicación transquirurgia es la ruptura vesicular y posoperatoria la fuga biliar. Conclusiones: El abordaje con 3 puertos es una opción viable, cuando se practica por cirujanos expertos, mientras que el abordaje con 4 puertos se recomienda en cirujanos que inician su formación en este procedimiento

Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests and/or deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four degrees of ovalization of the nozzle: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The computed side load physics caused by the nozzle out-of-roundness and its effect on nozzle side load are reported and discussed

SpaceLab, an N-Body Particle-Particle Ballistic Collision Simulation Tool with Applications in Celestial Body Dynamics

This thesis conveys the key technical features and scientific applications of a particle-particle ballistic simulation tool (SpaceLab) as well as a high level overview of experiments it was designed for and executed on. SpaceLab simulates spherical particle interactions under any combination of self-gravity, sliding friction, rolling friction, Van-Der-Waals (VDW) cohesion force, elastic repulsion, and restitution. SpaceLab particle interactions are never instantaneous and ensure sufficient interaction time between particles to conserve energy not lost to restitution to within 1\% per collision. SpaceLab has been used to explore both the gravity dominated and VDW dominated scales, including hundreds of kilometer rubble-pile asteroids and micron sized dust grains comprised of up to 10,000 particles with desired material properties, size variation, and control over a wide range of initial conditions. High velocity projectiles are also facilitated with dynamic time-stepping to accurately simulate scenarios like the DART mission. Conglomerate objects and both scales are tested for resilience to collisions with various sized projectiles, speeds, and spins to define constraints for collision remnant growth. The data gained from these experiments may be used to determine what conditions facilitate the growth of asteroids into planets, or dust grains into larger objects significantly effected by gravity. We also verify that the tool's results agree with similar work in literature and attribute key differences to features we include that are still uncommon in the field, such as the inclusion of surface friction which we find to increase collision remnant bound mass due to increase dissipation of collision energy. Future development plans for performance improvement and user friendly interface are also briefly discussed. Figure \ref{fig:gum} shows a typical off-center collision of two clusters of particles which may be used to model rubble-pile asteroid collisions. These figures demonstrate a common scenario simulated with SpaceLab

La hacienda de la abuela

Work is undoubtedly one of the pillars of development and should be a source of economic growth for the country, a path to social mobility for individuals and a space for personal dignity. For work to fulfill these characteristics it must be well remunerated, enjoy the protections mandated by law, and be a job and be a satisfying task. for those who perform it on a daily basis. Entrepreneurship has become a popular term currently, but not all of entrepreneurs can succeed in entrepreneurial business. This paper talks about entrepreneur and entrepreneurship from three aspects, Characteristics of entrepreneurs like perseverance, dedication, self confidence, desire of achievement, and so on, help them obtain necessary capabilities to operate business in the venture world. Before starting an entrepreneurial business, entrepreneurs should exploit an appropriate opportunity. Opportunity identification is critical in the process of entrepreneurial world. And capturing necessary resources such as financial resources, human resources are also necessary. The last step is to balance opportunity, resources, and team so that the entrepreneurial business can be operated successfully

Aplicación informática para la asignatura de Matemática I en la carrera de Ingeniería de Sistemas Informáticos en la Facultad Multidisciplinaria Paracentral de la Universidad de El Salvador.

El desarrollo del proyecto “Aplicación informática para la asignatura de Matemática I en la carrera de Ingeniería de Sistemas Informáticos en la Facultad Multidisciplinaria Paracentral de la Universidad de El Salvador.” fue realizado como trabajo de graduación para optar al grado de ingeniero de sistema informático, en el Capítulo I se detalla los procesos actuales dentro de la asignatura de igual manera se describe la metodología para el desarrollo del proyecto, el presupuesto total del desarrollo de la aplicación y también se presenta el planteamiento del problema, en el Capítulo II se muestran los requerimientos informáticos, de desarrollo y operativos del sistema que se necesitan para la aplicación basándose en la metodología de desarrollo seleccionada, en el Capítulo III se presentan los estándares de diseño y base de datos, logrando así crear una herramienta que cumpla los objetivos planteados al inicio del proyecto. The development of the project "Computer application for the subject of Mathematics I in the Computer Systems Engineering career at the Paracentral Multidisciplinary Faculty of the University of El Salvador." It was carried out as graduation work to qualify for the degree of computer system engineer, in Chapter I the current processes within the subject are detailed in the same way the methodology for the development of the project is described, the total budget of the development of the application and the problem statement is also presented, in Chapter II the computer, development and operating requirements of the system that are needed for the application are shown based on the selected development methodology, in Chapter III the design standards are presented and database, thus creating a tool that meets the objectives set at the beginning of the project

Impacto del clima organizacional en el índice de productividad en empresas pymes latinoamericanas

Correlacionar la variable de clima organizacional con el impacto en la variable de productividad laboral de los colaboradores de dos empresas PYMES latinoamericanas. Objetivos específicos. • Establecer por medio de una encuesta el tipo de clima organizacional que maneja la empresa, para evaluar su conexión con la rotación y el ausentismo de los colaboradores de dos empresas PYMES latinoamericanas. Determinar cómo impacta el clima organizacional en la satisfacción laboral percibida por los colaboradores de dos empresas PYMES latinoamericanas. Establecer por medio de una encuesta, cómo influye el clima organizacional que maneja la empresa en la productividad de los colaboradores de dos empresas PYMES latinoamericana