On the dominance of roots of characteristic equations for neutral functional differential equations

We present a sufficient condition for a zero of a function that arises typically as the characteristic equation of a linear functional differential equations of neutral type, to be simple and dominant. This knowledge is useful in order to derive the asymptotic behaviour of solutions of such equations. A simple characteristic equation, arisen from the study of delay equations with small delay, is analyzed in greater detail. (C) 2009 Elsevier Inc. All rights reserved.

Extension of the characteristic equation to absorption chillers with adiabatic absorbers

Various researchers have developed models of conventional H2O–LiBr absorption machines with the aim of predicting their performance. In this paper, the methodology of characteristic equations developed by Hellmann et al. (1998) is applied. This model is able to represent the capacity of single effect absorption chillers and heat pumps by means of simple algebraic equations. An extended characteristic equation based on a characteristic temperature difference has been obtained, considering the facility features. As a result, it is concluded that for adiabatic absorbers a subcooling temperature must be specified. The effect of evaporator overflow has been characterized. Its influence on cooling capacity has been included in the extended characteristic equation. Taking into account the particular design and operation features, a good agreement between experimental performance data and those obtained through the extended characteristic equation has been achieved at off-design operation. This allows its use for simulation and control purposes.

Aproximação numérica – analítica para a modelagem da conversão termoquímica de combustíveis sólidos

Um algoritmo numérico foi criado para apresentar a solução da conversão termoquímica de um combustível sólido. O mesmo foi criado de forma a ser flexível e dependente do mecanismo de reação a ser representado. Para tanto, um sistema das equações características desse tipo de problema foi resolvido através de um método iterativo unido a matemática simbólica. Em função de não linearidades nas equações e por se tratar de pequenas partículas, será aplicado o método de Newton para reduzir o sistema de equações diferenciais parciais (EDP’s) para um sistema de equações diferenciais ordinárias (EDO’s). Tal processo redução é baseado na união desse método iterativo à diferenciação numérica, pois consegue incorporar nas EDO’s resultantes funções analíticas. O modelo reduzido será solucionado numericamente usando-se a técnica do gradiente bi-conjugado (BCG). Tal modelo promete ter taxa de convergência alta, se utilizando de um número baixo de iterações, além de apresentar alta velocidade na apresentação das soluções do novo sistema linear gerado. Além disso, o algoritmo se mostra independente do tamanho da malha constituidora. Para a validação, a massa normalizada será calculada e comparada com valores experimentais de termogravimetria encontrados na literatura, , e um teste com um mecanismo simplificado de reação será realizado.

Operational characteristics of four metering systems for agricultural fertilizers and amendments

The use of fertilizers and solid amendments in agriculture generates special interest for their effect on crop productivity, as well as for their environmental impact. The efficient use of these products demands knowing their physical and mechanical properties, the storing conditions effect and the operational characteristics of the metering systems used in the fertilizing equipment. In this context, the present study was developed with the purpose of evaluating the operational characteristics of different fertilizing metering systems and to determine the adequate metering system-product operational parameters, using powder lime, powder gypsum, granular 10-30-10 (N-P-K), and granular urea. Operational differences were established among four types of commercial fertilizer metering systems, including wire auger, star-shaped feed wheel, feed screw and ridged traction wheel. The study found that the unloading rate depends directly on the fertilizer metering system's rotating speed and is affected by particle size, repose angle, bulk density and moisture content of the applied product. The wire auger and star-shaped feed wheel metering systems were adequate for the distribution of powder products and the feed screw for granulated fertilizers. Furthermore, theoretical and experimental characteristic equations were established, defining curves for calibration and handling of the products plus the rotating speed range in which a better distributing behavior was achieved.

Two-dimensional background field gravity: A Hamilton-Jacobi analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A simplified method for determining the high frequency induction motor equivalent electrical circuit parameters to be used in EMI effect

The aim of this paper is to present a simple method for determining the high frequency parameters of a three-phase induction motor to be used in studies involving variable speed drives with PWM three-phase inverters, in which it is necessary to check the effects caused to the motor by the electromagnetic interference, (EMI) in the differential mode, as well as in the common mode. The motor parameters determination is generally performed in adequate laboratories using accurate instruments, such as very expensive RLC bridges. The method proposed here consists in the identification of the motor equivalent electrical circuit parameters in rated frequency and in high frequency through characteristic tests in the laboratory, together with the use of characteristic equations and curves, shown in the references to be mentioned for determining the motor high frequency parasite capacitances and also through system simulations using dedicated software, like Pspice, determining the characteristic waveforms involved in the differential and common mode phenomena, comparing and validating the procedure through published papers [01].

Caracterização hidráulica do microaspersor Eden Twister em posição normal e invertida

Pós-graduação em Agronomia (Ciência do Solo) - FCAV

Estudo clássico completo do formalismo de Hamilton-Jacobi

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Topologically massive Yang-Mills: A Hamilton-Jacobi constraint analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Inspeção de materiais compósitos utilizando ondas acústicas guiadas

Pós-graduação em Engenharia Elétrica - FEIS

Uso das ondas de Lamb e Scholte para caracterização de líquidos

Pós-graduação em Engenharia Elétrica - FEIS

Slabsim: Simulador de dispositivos ópticos integrados

En los diseños y desarrollos de ingeniería, antes de comenzar la construcción e implementación de los objetivos de un proyecto, es necesario realizar una serie de análisis previos y simulaciones que corroboren las expectativas de la hipótesis inicial, con el fin de obtener una referencia empírica que satisfaga las condiciones de trabajo o funcionamiento de los objetivos de dicho proyecto. A menudo, los resultados que satisfacen las características deseadas se obtienen mediante la iteración de métodos de ensayo y error. Generalmente, éstos métodos utilizan el mismo procedimiento de análisis con la variación de una serie de parámetros que permiten adaptar una tecnología a la finalidad deseada. Hoy en día se dispone de computadoras potentes, así como algoritmos de resolución matemática que permiten resolver de forma veloz y eficiente diferentes tipos de problemas de cálculo. Resulta interesante el desarrollo de aplicaciones que permiten la resolución de éstos problemas de forma rápida y precisa en el análisis y síntesis de soluciones de ingeniería, especialmente cuando se tratan expresiones similares con variaciones de constantes, dado que se pueden desarrollar instrucciones de resolución con la capacidad de inserción de parámetros que definan el problema. Además, mediante la implementación de un código de acuerdo a la base teórica de una tecnología, se puede lograr un código válido para el estudio de cualquier problema relacionado con dicha tecnología. El desarrollo del presente proyecto pretende implementar la primera fase del simulador de dispositivos ópticos Slabsim, en cual se puede representar la distribución de la energía de una onda electromagnética en frecuencias ópticas guiada a través de una una guía dieléctrica plana, también conocida como slab. Este simulador esta constituido por una interfaz gráfica generada con el entorno de desarrollo de interfaces gráficas de usuario Matlab GUIDE, propiedad de Mathworks©, de forma que su manejo resulte sencillo e intuitivo para la ejecución de simulaciones con un bajo conocimiento de la base teórica de este tipo de estructuras por parte del usuario. De este modo se logra que el ingeniero requiera menor intervalo de tiempo para encontrar una solución que satisfaga los requisitos de un proyecto relacionado con las guías dieléctricas planas, e incluso utilizarlo para una amplia diversidad de objetivos basados en esta tecnología. Uno de los principales objetivos de este proyecto es la resolución de la base teórica de las guías slab a partir de métodos numéricos computacionales, cuyos procedimientos son extrapolables a otros problemas matemáticos y ofrecen al autor una contundente base conceptual de los mismos. Por este motivo, las resoluciones de las ecuaciones diferenciales y características que constituyen los problemas de este tipo de estructuras se realizan por estos medios de cálculo en el núcleo de la aplicación, dado que en algunos casos, no existe la alternativa de uso de expresiones analíticas útiles. ABSTRACT. The first step in engineering design and development is an analysis and simulation process which will successfully corroborate the initial hypothesis that was made and find solutions for a particular. In this way, it is possible to obtain empirical evidence which suitably substantiate the purposes of the project. Commonly, the characteristics to reach a particular target are found through iterative trial and error methods. These kinds of methods are based on the same theoretical analysis but with a variation of some parameters, with the objective to adapt the results for a particular aim. At present, powerful computers and mathematical algorithms are available to solve different kinds of calculation problems in a fast and efficient way. Computing application development is useful as it gives a high level of accurate results for engineering analysis and synthesis in short periods of time. This is more notable in cases where the mathematical expressions on a theoretical base are similar but with small variations of constant values. This is due to the ease of adaptation of the computer programming code into a parameter request system that defines a particular solution on each execution. Additionally, it is possible to code an application suitable to simulate any issue related to the studied technology. The aim of the present project consists of the construction of the first stage of an optoelectronics simulator named Slabsim. Slabism is capable of representing the energetic distribution of a light wave guided in the volume of a slab waveguide. The mentioned simulator is made through the graphic user interface development environment Matlab GUIDE, property of Mathworks©. It is designed for an easy and intuitive management by the user to execute simulations with a low knowledge of the technology theoretical bases. With this software it is possible to achieve several aims related to the slab waveguides by the user in low interval of time. One of the main purposes of this project is the mathematical solving of theoretical bases of slab structures through computing numerical analysis. This is due to the capability of adapting its criterion to other mathematical issues and provides a strong knowledge of its process. Based on these advantages, numerical solving methods are used in the core of the simulator to obtain differential and characteristic equations results that become represented on it.

Approximate Riemann solutions of the two-dimensional shallow-water equations

A finite-difference scheme based on flux difference splitting is presented for the solution of the two-dimensional shallow-water equations of ideal fluid flow. A linearised problem, analogous to that of Riemann for gasdynamics, is defined and a scheme, based on numerical characteristic decomposition, is presented for obtaining approximate solutions to the linearised problem. The method of upwind differencing is used for the resulting scalar problems, together with a flux limiter for obtaining a second-order scheme which avoids non-physical, spurious oscillations. An extension to the two-dimensional equations with source terms, is included. The scheme is applied to a dam-break problem with cylindrical symmetry.