Abstract: The automotive industry requires new sensors to improve automotive performance, comfort and safety. These sensors will need the electrical power for their operation, which could be supplied by future MEMS energy harvesting devices. We present the design of a MEMS-based piezoelectric vibration energy harvesting (PVEH) device. The design is formed of two cantilevers of trapezoidal shape (2500 x 1064 x 9 μm) that have two proof masses in their ends. The cantilevers and proof masses are designed of silicon with a PZT-5H film, considering the PiezoMUMPs fabrication process of MEMSCAP. This PVEH device can generate voltage when its structure is deformed at resonance under a vibration acceleration. Finite element method (FEM) models of the PVEH device are developed to predict its electrical and structural behavior at resonance under a vibration acceleration of 12 m/s2. The proposed device has a resonant frequency of 207.8 Hz, a maximum deflection of 201 μm and a generated voltage of 61.5 mV with an electrical resistive load of 10 kΩ. A PVEH devices array could be used to supply electrical power to sensors of modern and future automobiles.

Abstract This work introduces the Laplace Transform-Homotopy Perturbation Method (LT-HPM) in order to provide an approximate solution for Troesch’s problem. After comparing figures between exact and approximate solutions, as well as the average absolute relative error (AARE) of the approximate solutions of this research, with others reported in the literature, it can be said that the proposed solutions are accurate and handy. In conclusion, LT-HPM is a potentially useful tool.

Resumen Este artículo propone el método de perturbación homotópica con Transformada de Laplace para encontrar una solución aproximada al problema de Troesch. Después de comparar las figuras entre la solución aproximada y la exacta, así como el error relativo absoluto promedio (AARE) de las soluciones aproximadas en este estudio, con otras reportadas en la literatura, se puede decir que la solución propuesta es, además de práctica, precisa. Se concluye que el método LTHPM es potencialmente útil.

Abstract This article proposes a handy, accurate, invertible and integrable expression for Dawson’s function. It can be observed that the biggest relative error committed, employing the proposed approximation here, is about 2.5%. Therefore, it is noted that this integral approximation to Dawson’s function, expressed only in terms of elementary functions, has a maximum absolute error of just 7 × 10-3. As a case study, the integral approximation proposed here will be applied to a nonclassical heat conduction problem, contributing to obtain a handy, accurate, analytical approximate solution for that problem.

Resumen En este artículo se propone una expresión compacta y precisa de la función de Dawson, la cual es invertible e integrable. Se observa que el error relativo máximo que se encuentra empleando la aproximación aquí propuesta es del 2.5%. Por consiguiente, se hace notar que la aproximación a la integral de la función de Dawson, que se expresa solo en términos de funciones elementales, tiene un error absoluto máximo de 7 × 10-3. A manera de ejemplo, se aplicará la aproximación aquí propuesta a un problema no-clásico de conducción de calor para obtener una solución aproximada, compacta y precisa.

Because of the exponential characteristic of silicon diodes, exact solutions cannot be established when operating point and transient analysis are computed. To overcome that problem, the present work proposes a perturbation method which allows obtaining approximated analytic expressions of diode-based circuits. Simulation results show that numerical solutions obtained by using the proposed method are similar to those reported in literature, with the advantage of not requiring a user-selected arbitrary expansion point. Additionally, the method does not use the Lambert function W, reducing the proposed solution complexity, which makes it suitable for engineering applications.

In this article, Perturbation Method (PM) is employed to obtain an approximate solution for Troesch equation. In addition, we will describe the use of Laplace transform and Padé transformation to deal with the truncated series obtained by the PM method, in order to obtain handy approximations. Finally a table of comparison, between proposed solution, and other solutions reported in the literature: Adomian's Decomposition Method (ADM), Homotopy Perturbation Method (HPM), Homotopy Analysis Method (HAM) and exact numerical solution, shows that our solution is the most accurate one (Average Absolute Relative Error 1.705648354x10-8).

En este artículo el Método de Perturbación (PM) es empleado para obtener una solución aproximada para el problema de Troesch. Además describiremos el uso de la Transformada de Laplace y la Aproximación de Padé para trabajar con las series truncadas obtenidas por el Método de Perturbación, y así obtener soluciones aproximadas compactas. Finalmente se propone una tabla comparativa entre la solución propuesta y otras soluciones reportadas en la literatura: Método de Descomposición de Adomian, Método de Perturbación Homotópica, Método de Análisis Homotópico y la solución numérica exacta. Los resultados muestran que nuestra solución es la más exacta (Error Relativo Absoluto Promedio1.705648354x10-8).

The performance characteristics of a compliant mechanical displacement amplification mechanism, as well as the geometrical gain in forced regime, the geometrical gain in resonance and the resonance frequency are obtained by using optical interferometry and compared with values obtained using the finite element analysis software ANSYS. The operation principle and the limits of the compliant mechanism are described by numerical simulations in ANSYS. The similarity between the experimental results and numerical simulations show that the used methodology is adequate to describe its design and its mechanical performance.

Las características de desempeño de un mecanismo para amplificar desplazamientos mecánicos, como la ganancia geométrica en régimen forzado, la ganancia geométrica en resonancia y la frecuencia de resonancia, son obtenidas mediante interferometría óptica y comparados con los valores obtenidos mediante elemento finito en ANSyS. Se describe el principio de operación del mecanismo y mediante simulaciones numéricas en ANSyS, se obtienen los rangos de operación del mismo. La similitud entre los resultados experimentales y las simulaciones numéricas muestran que la metodología seguida es adecuada.

In this article, modified non-linearities distribution homotopy perturbation method (MNDHPM) is used in order to find power series solutions to ordinary differential equations with initial conditions, both linear and nonlinear. We will see that the method is particularly relevant in some cases of equations with non-polynomial coefficients and inhomogeneous non-polynomial terms.

En este artículo, el método modificado de perturbación homotópica con distribución de no linealidades (MNDHPM) es utilizado para encontrar soluciones en series de potencias de ecuaciones diferenciales ordinarias, tanto lineales como no lineales. Se verá que el método es particularmente relevante en algunos casos de ecuaciones con coeficientes no polinomiales e inhomogéneas con términos no homogéneos no polinomiales.

In this article we provide an exact solution to the nonlinear differential equation that describes the behaviour of a flow due to a stretching flat boundary due to partial slip. For this, we take as a guide the search for an asymptotic solution of the aforementioned equation.

This paper presents the design and integration of an electrical characterization system for Hall effect microsensors, which allows the detection and measurement of magnetic field perpendicular to the surface of the microsensors. The proposed system can control and maintain the communication of both the position of the excitation source and the magnitude of the magnetic field. This system includes a mechanism for surface movement θ-Z with two degrees of freedom, sensors, electronic instruments, a computer, interface cards and a graphical user interface (GUI) implemented in Lab- View®. The positioning of the system is made through two motors, a stepper motor, and a servomotor. Which perform the movements in the θ-Z surface. The Z axis has a resolution of 0.03 cm through a stepper motor and the θ axis has a resolution of 1 cm, which is obtained using a servomotor. As excitation source, we used neodymium iron boron (NdFeB) magnet, which has a magnetic field of 100 mT. The detection field is obtained with microsensors which had a response in the linear range of 1 mT to 100 mT. This system allows a single interface through the detection of magnetic field perpendicular to the surface of the microsensor, as well as the positioning of the excitation source in the θ-Z surface. The GUI has a control environment accessible to the end user. Furthermore, the system can be reconfigured for the characterization of other microsensors, changing only the excitation and detection modules. Its versatility will increment the life time ofour system characterization.

En este trabajo se presenta el diseño e integración de un sistema de caracterización eléctrica para microsensores de efecto Hall, el cual permite la detección y medición del campo magnético perpendicular a la superficie de los microsensores de efecto Hall. El sistema propuesto puede controlar y mantener la comunicación de la posición de la fuente de excitación y de la magnitud del campo magnético. Este sistema incluye un mecanismo de movimientos en la superficie θ-Z (dos grados de libertad), sensores, instrumentos electrónicos, una computadora, tarjetas de interfaz y una interfaz gráfica de usuario (IGU) implementada en Lab-View®. El posicionamiento del sistema se realizó por medio de dos motores, un motor paso a paso y un servomotor, los cuales efectúan los movimientos en la superficie θ-Z. El eje Z tiene una resolución de 0.03 cm mediante un motor paso a paso y el eje θ tiene una resolución de 1 cm que se obtiene con un servomotor. Como fuente de excitación se utilizó un magneto de Neodimio-Hierro-Boro (NdFeB) que genera un campo magnético máximo de 100 mT. La detección del campo magnético se obtiene con los microsensores de efecto Hall, los cuales presentaron una respuesta lineal en el rango de 1 mT a 100 mT. Este sistema permite a través de una sola interfaz la detección del campo magnético perpendicular a la superficie del microsensor, así como el posicionamiento de la fuente de excitación en la superficie θ-Z. La interfaz gráfica de usuario tiene un ambiente de control de fácil acceso para el usuario final. Además, el sistema puede reconfigurarse para la caracterización de otro tipo de microsensores, al cambiar únicamente los módulos de excitación y detección. Esta versatilidad permitirá obtener un mayor tiempo de vida útil del sistema de caracterización.

O alecrim é planta exótica e o interesse no seu cultivo tem crescido ao longo dos anos, pois pode ser utilizado tanto para fins medicinais como aromáticos; no entanto, o conhecimento fitotécnico sobre a espécie é bastante limitado. Dessa forma, o trabalho objetivou avaliar a influência da altura de corte e do intervalo destes sobre a produção de biomassa e no rendimento do óleo essencial de alecrim. O experimento foi realizado no Instituto Agronômico, em Campinas - SP, no período de janeiro de 2006 a julho de 2007. O delineamento experimental utilizado foi em blocos ao acaso, com 8 tratamentos em esquema fatorial 2 x 4, sendo duas alturas de corte (20 e 40 cm) e quatro intervalos entre cortes (60, 80, 100, 120 dias) e três repetições. Foram avaliadas as características altura da planta, massa seca da parte aérea, rendimento e qualidade do óleo essencial. Observou-se que maiores intervalos entre cortes proporcionaram maior altura da planta e maior massa seca da parte aérea. O rendimento e a qualidade do óleo essencial não foram afetados ao longo do período experimental.

Rosemary is an exotic plant and the interest in its cultivation has been growing along the years, because it can be used for medicinal or aromatic ends, however the agricultural knowledge about the species is quite limited. The goal of this research was to evaluate the influence of the cutting height and of the interval of these cuts on the biomass production and on the yield of the rosemary essential oil. The experiment was conducted at the Agronomical Institute, in Campinas - SP, from January 2006 through July 2007. It was organized in a completely randomized design with 8 treatments in a 2 x 4 factorial system, with two cutting heights (20 and 40 cm) and four intervals between cuts (60, 80, 100, 120 days) and three replications. Characteristics such as plant height, dry mass of the aerial part, yield and quality of its essential oil were evaluated. It was observed that longer intervals among cuttings provided longer height of the plant and greater dried mass of the aerial part. The yield and the quality of the essential oil were not affected throughout the experimental period.

The structural and electro-thermal analysis of a resonant structure for a magnetic sensor based on MEMS technology is presented in this paper. The effect of squeeze-film damping is included by mean of a theoretical model and using finite element software. In addition, analysis of the dynamic torsional model of magnetic structure is realized. The design of resonant structure considers a hollow rectangular configuration with thin beams of 20μm of width and 1.50μm of thickness suspended over a cavity that takes advantage of the Lorentz force principle allowing the detection of magnetic fields at levels of tens Gauss. The analytical results and simulations with finite element indicate that the vertical displacement has a linear behavior with low power consumption and a maximum Von Mises stress of 20.22MPa with a peak to peak voltage of 2 V.

The aim of the present paper is to study some direct results in simultaneous approximation for the linear combination of integral Baskakov type operators.

An adrenal mass found in the course of abdominal ecographic or computed tomography (CT) techniques performed for other reasons is a new diagnostic challenge. The patient in this case was asymptomatic and without previous illness. An ecographic study revealed an enlarged right adrenal gland, 66 by 33 mm. CT showed bilateral irregular enlargement of both adrenal glands. Nonadrenal malignancies and hyperfunctioning tumors were ruled out. A CT-guided biopsy was performed, and the histopathologic study was consistent with the diagnosis of histoplasmosis. The patient lived in an area endemic for this disease, and had daily contact with bird droppings. Histoplasmosis is a rare unsuspected cause of bilateral adrenal masses in the asymptomatic immunocompetent host.

El hallazgo de masas adrenales detectadas mediante técnicas ecográficas o tomográficas solicitadas por algún otro motivo, y por ello incidentales, constituye un nuevo desafío diagnóstico. El paciente que presentamos se encontraba asintomático y no refería antecedentes patológicos. Una ecografía mostró agrandamiento de la glándula suprarrenal derecha, que medía 66 por 33mm. La tomografía computada mostró agrandamiento irregular de ambas suprarrenales. Se descartaron neoplasias extra-adrenales y tumores hiperfuncionantes. Se realizó una biopsia guiada por tomografía, y el estudio histopatológico informó Histoplasma capsulatum. El paciente vivía en una zona endémica para esta enfermedad y, por exposición laboral, tenía contacto diario con excremento de aves. La histoplasmosis es una causa infrecuente de masas adrenales bilaterales en el huesped inmu-nocompetente.