Generic Battery Model based on a Parametric Implementation

Batteries are a common element used in many electronic applications. Therefore, the analysis and simulation of these applications requires a battery model in order to validate the behavior of the whole system. Since batteries are based on different technologies, a modeling approach valid for any technology is a potential good alternative. Since there are similarities among the different technologies, it is possible to address the modeling of batteries as generic energy storage elements with particular differences. This work presents a battery model valid for different technologies based on a parametric implementation

A simplified capacitive model for center-tapped multi-windings transformers

A simplified capacitive model for transformers with center-tapped windings has been developed. A Finite Element Analysis (FEA) tool is used to compute the electric energy in the windings of the transformer in order to obtain the required parameters of the model. Due to its reduced number of elements it can be easily used to model the capacitive effects in symmetrical (center-tapped) multi-winding magnetic components such as transformers for Push-Pull (PP), Half-Bridge (HB) and Full-Bridge (FB) applications. Some experimental results are compared with simulations

Selection of the appropriate winding setup in planar inductors with parallel windings

The use of parallel windings in high frequency planar inductors is a common practice. Since the planar technology, commonly PCB layers, limits the maximum layer thickness, the use of parallel windings is usually required in order to reduce the current density and losses. The distribution of the current through each parallel winding depends on the winding positioning and the frequency effects. This effect is especially important in gapped inductors, because the energy stored in the gap region determines the current distribution through the windings. Therefore, the winding positioning is a critical task in order to obtain a balanced current distribution through all the parallel winding

Automatized connection of the layers of planar transformers with parallel windings to improve the component behavior

Transformers with parallel windings are commonly used to reduce the losses in the windings. Windings losses depend on the winding positioning and the frequency effects because each winding affects the current sharing of itself and the neighboring windings. In this paper a methodology for determining the connections of the parallel windings that reduces the power losses (and temperature) in the windings of multi-winding transformers is presented. Other applications of the method, such as balanced current sharing and voltage drop reduction are also explored. In this paper a methodology for determining the connections of the parallel windings that reduces the power losses (and temperature) in the windings of multi-winding transformers is presented. Other applications of the method, such as balanced current sharing and voltage drop reduction are also explored

Estimation of wall shear stress using 4D flow cardiovascular MRI and computational fluid dynamics

Electronic version of an article published as Journal of mechanics in medicine and biology, 0, 1750046 (2016), 16 pages. DOI:10.1142/S0219519417500464 © World Scientific Publishing CompanyIn the last few years, wall shear stress (WSS) has arisen as a new diagnostic indicator in patients with arterial disease. There is a substantial evidence that the WSS plays a significant role, together with hemodynamic indicators, in initiation and progression of the vascular diseases. Estimation of WSS values, therefore, may be of clinical significance and the methods employed for its measurement are crucial for clinical community. Recently, four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has been widely used in a number of applications for visualization and quantification of blood flow, and although the sensitivity to blood flow measurement has increased, it is not yet able to provide an accurate three-dimensional (3D) WSS distribution. The aim of this work is to evaluate the aortic blood flow features and the associated WSS by the combination of 4D flow cardiovascular magnetic resonance (4D CMR) and computational fluid dynamics technique. In particular, in this work, we used the 4D CMR to obtain the spatial domain and the boundary conditions needed to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. Similar WSS distributions were found for cases simulated. A sensitivity analysis was done to check the accuracy of the method. 4D CMR begins to be a reliable tool to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. The combination of both techniques may provide the ideal tool to help tackle these and other problems related to wall shear estimation.Peer ReviewedPostprint (author's final draft

Uso de Herramientas de Simulación Electrónica como Apoyo Docente en Electrónica de Potencia

El objetivo de este trabajo es el mostrar cómo las herramientas de simulación electrónica pueden apoyar didácticamente al profesor en la enseñanza de asignaturas relacionadas con la electrónica de potencia. Se va a presentar un ejemplo guiado de uso de este tipo de herramientas en para el diseño del circuito de control de un convertidor CC/CC para una aplicación de alimentación dual en el entorno del automóvil. Para diseñar el circuito de control es necesario determinar en primer lugar la respuesta en frecuencia del convertidor. Se va a hacer uso del programa Simplorer con la biblioteca SMPS Library como herramienta de simulación para este ejemplo. Existen modelos en dicha biblioteca que permiten obtener la respuesta en frecuencia del circuito de forma directa. Este artículo explica los pasos que deben seguirse para diseñar el circuito de control de un convertidor Buck multi-fase usando tanto modelos promediados como modelos conmutados

Teaching Magnetic Design using CAD tools

Design of magnetic components is a multivariable problem. There are many different combinations of shapes, sizes and materials for the core with many diameters for the wires. So it is difficult to find the optimum design without a great number of iterations. Analytically only a few combinations are usually studied but it is very easy to take into account all the combinations using a CAD tool [1]. In this work the CAD tool used is PExprt (ANSYS [2]) which is being developed at UPMCEI

A Piezoelectric Minirheometer for Measuring the Viscosity of Polymer Microsamples

This paper describes the electromechanical design, operating principles and performance of a rheometer able to characterize the rheological behavior of microsamples of viscoelastic materials, such as polymer solutions, melt, and rubbers. It was developed with a view to portability, robustness, and ease of operation for very small samples. The rheometer operates by subjecting the samples to small-amplitude sinusoidal strain rates via an inverse piezoelectric actuator and detecting the stress response of the material via a direct piezoelectric sensor. The device operates under frequency-sweep mode in a very wide range of frequencies. Required sample sizes are typically three orders of magnitude smaller than for conventional rheometers. Owing to its lack of moving parts, the rheometer has an extremely simple design and is insensitive to vibration. Measurements on pressure-sensitive adhesives and other polymeric systems are presented and validated against a standard cone-and-plate rheometer

Power losses calculations in windings of gapped magnetic components

A model is proposed for the calculation of the winding losses at the beginning of the design process of high frequency transformers and inductors. Although this kind of losses have been subject of investigation for years, their analytical calculation in gapped components is still limited, and the use of numerical analysis tools, such as finite elements analysis (FEA) tools, are commonly needed for winding characterization. A general 2-D equivalent analytical model for windings losses calculation in gapped magnetic components that shows very good results compared with FEA calculation is presented. The model can be integrated in design and optimization tools in order to evaluate the influence of the gap on the windings at the very early stages of the design process

Decision support system for cardiovascular problems

The DISHEART project aims at developing a new computer based decision support system (DSS) integrating medical image data, modelling, simulation, computational Grid technologies and artificial intelligence methods for assisting clinical diagnosis and intervention in cardiovascular problems. The RTD goal is to improve and link existing state of the art technologies in order to build a computerised cardiovascular model for the analysis of the heart and blood vessels. The resulting DISHEART DSS interfaces computational biomechanical analysis tools with the information coming from multimodal medical images. The computational model is coupled to an artificial neural network (ANN) based decision model that can be educated for each particular patient with data coming from his/her images and/or analyses. The DISHEART DSS system is validated in trials of clinical diagnosis, surgical intervention and subject-specific design of medical devices in the cardiovascular domain. The DISHEART DSS also contributes to a better understanding of cardiovascular morphology and function as inferred from routine imaging examinations. Four reputable medical centers in Europe took an active role in the validation and dissemination of the DISHEART DSS as well as the elaboration of computational material and medical images. The integrated DISHEART DSS supports health professionals in taking promptly the best possible decision for prevention, diagnosis and treatment. Emphasis was put in the development of userfriendly, fast and reliable tools and interfaces providing access to heterogeneous health information sources, as well as on new methods for decision support and risk analysis. The use of Grid computing technology is essential in order to optimise and distribute the heavy computational work required for physical modelling and numerical simulations and especially for the parametric analysis required for educating the DSS for every particular application. The four end user SMEs participating in the project benefits from the new DISHEART DSS. The companies COMPASS, QUANTECH and Heartcore will market the DSS among public and private organizations related to the cardiovascular field. EndoArt will exploit the DISHEART DSS as a support for enhanced design and production of clinical devices. The partnership was sought in order to gather the maximum complementary of skills for the successful development of the project Disheart DSS, requiring experts in Mechanical sciences, Medical sciences, Informatic, and FEM technique to grow up the testes.Postprint (published version