Reduced order modelling in multimachine power systems

Conventional techniques used for the assessment of transient and dynamic stability in multimachine power systems require the solution of a large number of ordinary differential equations describing the dynamics of the system generating units. Detailed representation of generating units results in a system of equations that are numerically stiff and of large dimensionality. As a result, the digital simulation of the entire system becomes excessively complex and uneconomical in terms of computer time;It has been recognized that coherency identification is a fundamental step in obtaining reduced order dynamic equivalent models for power systems. Two methods of coherency identification are presented in this dissertation, one based on a slow coherency approach and the other based on modal analysis. Improvements in the slow coherency approach are accomplished by a sensitivity based identification of the set of group-reference generators in the system, leading eventually to the sets of coherent generators. The second method uses the undamped system equations having a system matrix A. The eigenstructure of A is used to obtain a set of coherency indices, based on the root-mean-square values of variations in angular differences between pairs of generators. These coherency indices are compared with a coherency threshold to determine coherent groups of generators. Numerical examples are presented to illustrate and validate both techniques;With regard to the dynamic stability of multimachine power systems, a method based on singular perturbation theory is proposed for the simulation of models of high dimensionality and widely varying time constants. In this method, the state vector is partitioned into subsets of slow and fast variables, a perturbation parameter, (epsilon), is selected and the equations are expressed in their singular perturbation form. The time responses of the system are obtained by the use of the asymptotic expansions of the outer solution and the boundary layer correction of the perturbed equations;A numerical example using a single machine-infinite bus system is used to illustrate and validate the method. While promising results were obtained, the need for additional refinements was made evident

Ingeniería social : el ataque silencioso

La seguridad informática en una organización depende en gran medida de la adquisición y de una adecuada configuración del hardware diseñado con ese propósito, además se debe tener un equipo de trabajo calificado para realizar las tareas de seguridad correspondientes. Sin embargo, las organizaciones olvidan que el eslabón más débil de su infraestructura informática son los usuarios de los sistemas y servicios de computadoras. Se cree que el servidor más seguro es el que está apagado, pero deja de ser cierto mientras exista un usuario que pueda encenderlo

Production of Customized Reactors by 3D Printing for Corrosive and Exothermic Reactions

This work presents a continuous reactor designed to be produced by 3D printing with the ultimate objective of performing fast, exothermic, and corrosive reactions. The dilution of sulfuric acid with water was used as a model for reactor design. A good mixing inside the reactor will promote the dilution and at the same time increase the heat transfer. Fast heat transfer is important to avoid vaporization of reactants/products and to control corrosion inside the reactor. The reactor was designed using a genetic algorithm to maximize the surface area of a prespecified reactor volume while ensuring a good mixing of the reactants. We have experimentally demonstrated that dilution of sulfuric acid can be done continuously in a Hartridge− Roughton mixer with lattices for enhanced heat transfer. Selected designs with internal and external lattices for enhanced heat exchange were manufactured by 3D printing using the Ti64 alloy. Different printing services were used to compare the quality of reactors that can be achieved by new industrial players that do not possess a 3D printer. One important item that should be considered when 3D printing is used for corrosive reactions is cross-contamination with other metals, since that can significantly affect the life and safety conditions of the reactors.publishedVersio

Analizando los resultados académicos en la Educación Superior en España

The development of the European Higher Education Area has been a process of modernization in many universities. Teaching methodologies have undergone a process of continuous change to meet the demands for high quality leading to a need for enhancement in the learning assessment methodologies as well. The objective of this study is to analyse student´s academic performance measured through coursework vs. final exam and to ascertain the factors that could explain the difference. Regression and variance analysis are carried out over the grades and responses to a questionnaire on a sample of 298 students of different subjects in a Spanish university. The results show that there are differences between continuous assessment and the final examination marks.Ministerio de Economía y Competitividad FFI2013-41235-

Innovative Process Cycle with Zeolite (MS13X) for Post Combustion Adsorption

This paper reports the integration of Electric swing adsorption (ESA) Process in a Natural Gas Combined Cycle. This process was investigated in the MATESA FP7 project financed by European Commission. The ESA process is modelled through ASPEN Adsorption using both heat and electricity for regenerating the sorbent. The overall heat duty of the sorbent is 4 MJ/kgCO2 where half of this is recovered in the regeneration cycle. The resulting CO2 avoided is around 90% with a net electric efficiency of about 40%. The low efficiency is consequence of the higher energetic value of electricity with respect to the thermal power typically adopted in MEA regeneration. Being the first attempt of simulating this process using multiple heat sources and the recent development of sorbents, significant improvements can be expected by ESA reducing the gap with conventional post-combustion CO2 capture technologies

Nonlinear ion-stopping calculations for a classical free-electron gas at high projectile energies

In this work, we solved the classical equations of motion and Poisson equation self-consistently, equivalent to the nonlinear Vlasov-Poisson equation, for a projectile moving in a static free-electron gas to calculate the full noncentral self-consistent electron-ion potential, and thus the ion stopping power. We investigated the origin of the Barkas effect, namely, the first nonlinear effect for projectiles at high velocities responsible for the difference between the energy-loss results for positively and negatively charged ions traversing the same target. This effect is strongly enhanced by the multipolar part of the electron-ion potential as first suggested by Lindhard [J. Lindhard, Nucl. Instr. and Meth. 132, 1438 (1976)]. Moreover, this effect is partially related to the nonconservation of the angular momentum in electron-ion collisions. These nonlinear calculations are applied to understanding the stopping of protons and antiprotons in Al at high projectile energie

Alta disponibilidad 24/7 : el reto

En la actualidad, las actividades diarias para los ne- gocios, instituciones, instituciones educativas o nivel de usuario común están directamente vinculadas a la red de redes, la Internet. Su desarrollo ha permitido a la mayoría de los servicios y aplicaciones, que hace años eran sólo para el modo cliente-servidor, ahora acceder desde cualquier lugar en cualquier dispositi- vo con conexión a Internet. Por lo tanto, ofrecer un ambiente que da conexiones y transacciones 7/24 es necesario para cada empresa e institución con servicios en línea. Sin embargo, es una premisa difícil de cumplir

Quenching of singlet oxygen by extract of peels of the fruit of syzygium cumini

Recent research has shown the importance of plant extracts as powerful antioxidants owing to the presence of chemically active components such as polyphenols, anthocyanins, flavonoids, among others. This synergy of the components becomes a possible alternative to the use of antioxidants of synthetic origin. In this study, Syzygium cumini fruit peel was used to determine the antioxidant activity against singlet oxygen. The extract showed appreciable amounts of phenolic groups (about 8.55 AGE mg/g fruit weight). HPLC-DAD characterization showed at least 3 anthocyanins of higher relative abundance (malvidin 3,5-diglucoside, delphinidin 3,5-diglucoside and petunidin 3,5-diglucoside). The percentage of quenching of singlet oxygen was determined at different concentrations of the ethanolic extract, finding a value of 60% at a concentration of 0.39 mg/mL.Recientes investigaciones demuestran la importancia de los extractos de origen vegetal como potentes antioxidantes, debido a la presencia de componentes químicamente activos, como los polifenoles, antocianinas, flavonoides, entre otros. Esta sinergia de los componentes se convierte en una posible alternativa frente al uso de antioxidantes de origen sintético. En este trabajo la cáscara de la fruta Syzygium cumini fue utilizada para determinar la actividad antioxidante frente al oxígeno singulete. El extracto mostró cantidades apreciables de grupos fenólicos (alrededor de 8,55 AGE mg/g peso fruta). La caracterización por HPLC-DAD muestra por lo menos 3 antocianinasde mayor abundancia relativa (la malvidina 3,5-diglucósido, la delfinidina 3,5- diglucósido y la petunidina 3,5-diglucósido). El porcentaje de desactivación del oxígeno singulete fue determinado a diferentes concentraciones del extracto etanólico, encontrándose un valor del 60% a una concentración 0.39 mg/mL