Subwoofer Frequency Response Optimization by Means of Active Control

Most subwoofer systems have difficulties producing frequencies in the low end of the hearing spectrum due to the added power requirements and instabilities. Active controls can transform the audio signal without changing physical characteristics and ultimately generating a more impressive audio system. A Linkwitz transform crossover was implemented to extend the low end frequency response of a sealed enclosure. A graphical user interface in MATLAB was written to aid in selection of components, driver and enclosure volume. The circuit board was built and integrated with a home theater system inside of a couch and tested with a Real Time Analyzer. The Linkwitz crossover was shown to extend the frequency response, transient response and improve the subwoofer system while reducing the required enclosure volume

Estudio de voz sobre ip (VOLP) en redes umts

El presente trabajo tiene como objetivo analizar como se transmite VoIP (Voz sobre IP) sobre redes UMTS (Sistema universal de telecomunicaciones móviles). Explicaremos como funciona la tecnología VoIP, que es un servicio en tiempo real, y necesita de un QoS aceptable para su buen funcionamiento, mostraremos los problemas comunes al implementar VoIP y como evitarlos, además de los diferentes servicios que nos puede ofrecer, como por ejemplo: buzón de voz, llamadas en espera, control de acceso, etc. Luego analizaremos la implementación de VoIP en telefonía móvil (redes UMTS), la cual se lleva a cabo por medio de la arquitectura IMS (Subsistema Multimedia IP), que está encargada de todas las aplicaciones multimedia, que obligatoriamente necesitan transmitirse en tiempo real, como lo son: VoIP, teleconferencias, etc., veremos las ventajas principales de usar UMTS, como es el caso de su gran ancho de banda, movilidad y sobre todo con la implementación de IMS, nos ofrece un elevado QoS. Por último se realizarán pruebas para obtener los parámetros más importantes para una comunicación VoIP y así demostrar la buena calidad que tiene una comunicación VoIP al ser transmitida en un entorno 3G

Developing an Automatic Generation Tool for Cryptographic Pairing Functions

Pairing-Based Cryptography is receiving steadily more attention from industry, mainly because of the increasing interest in Identity-Based protocols. Although there are plenty of applications, efficiently implementing the pairing functions is often difficult as it requires more knowledge than previous cryptographic primitives. The author presents a tool for automatically generating optimized code for the pairing functions which can be used in the construction of such cryptographic protocols. In the following pages I present my work done on the construction of pairing function code, its optimizations and how their construction can be automated to ease the work of the protocol implementer. Based on the user requirements and the security level, the created cryptographic compiler chooses and constructs the appropriate elliptic curve. It identifies the supported pairing function: the Tate, ate, R-ate or pairing lattice/optimal pairing, and its optimized parameters. Using artificial intelligence algorithms, it generates optimized code for the final exponentiation and for hashing a point to the required group using the parametrisation of the chosen family of curves. Support for several multi-precision libraries has been incorporated: Magma, MIRACL and RELIC are already included, but more are possible

A REVIEW OF FORMULATIONS TO DESIGN AN ADHESIVE SINGLE-LAP JOINT FOR USE IN MARINE APPLICATIONS

The single adhesive joint has many applications in the shipbuilding industry, where it offers the advantage of joining materials (adherents) with different properties and characteristics using an adhesive. However, one disadvantage of this type of joint is the stress concentration at the ends of the joint, which directly affect the adhesive. Another disadvantage is the possible difference between the coefficients of thermal expansion of the adherents of the joint. Through compilation and classification of the formulas found in various publications, this study presents a state-of-the-art review of an adhesive single-lap joint that can be used in marine applications. It will consider the types of materials used as the adhesive and as the adherents, the possibility of varying the thicknesses of the adherents and the thickness of the adhesive, and the recommended design factors for each proposed methodology. This study proposes formulas to estimate the stresses for joints with balanced thicknesses and extrapolates the results for non-balanced joints; also, an equation is derived to calculate the minimum overlap joint length for ship lengthening, allowing the design process to be simplified. The results are expected to facilitate the design of single-lap joints in marine applications, such as reinforcing composite panels and lengthening of hulls and superstructures

Storm-Time Equatorial Thermospheric Dynamics and Electrodynamics

We present the first complete study of the dynamics of the equatorial upper atmosphere (180-350 km) during periods of strong magnetic activity driven by the Sun, which are generally referred as geomagnetic storms. These storms have the potential to considerably affect satellite-based communications and navigation systems among other severe technological challenges. We used large databases of two of the most important parameters at these altitudes, which are the velocities of the neutral and ionized gas (plasma) referred to as neutral winds and plasma drifts. These measurements were acquired in the Peruvian equatorial region by the Jicamarca radar and by a network of optical instruments nearby. In the first part, we derived average patterns of the neutral winds under weak geomagnetic activity conditions, or quiet times, for different seasons and compared them with predictions from current upper-atmospheric models. Then, we present, for the first time, the seasonal patterns of the night-time perturbations in the neutral winds at equatorial latitudes, and their variations for different solar-driven geomagnetic storms. These wind perturbations are strongest in the east-west direction and around midnight. They are strongest and longer lasting during and after extended periods of geomagnetic activity. We present a simple empirical model that significantly improves the prediction of the perturbations in the neutral winds compared with current models. In the second part, we derive the velocity perturbations in the plasma drifts along the vertical direction following 3 to 9 hours of geomagnetic activity. We show in detail that these vertical velocity perturbations are small and down-ward during the day and upward and stronger at night, and vary throughout the year and for different solar conditions. They are strongest near sunrise and sunset and during the equinoxes. In the last part of the thesis, we show the close relationship of the neutral wind and plasma drift velocities along the east-west direction during both geomagnetic quiet and disturbed conditions. Finally, we summarize our main results and make suggestions to improve the understanding of this important topic

Provision of Ancillary Services by Wind Power Generators

The current and future power systems foresee very deep penetration of renewable power plants into the generation mix, which will make the provision of ancillary services by renewables an ultimate necessity. This would be further emphasised when green power stations replace conventional power plants that rely on fossil fuels. In this context, many control methodologies could be applied to the controllers of the green generators to enable the provision of these services, mainly frequency support and voltage regulation. Most of the available models (i.e. in power system simulators) do not include such supplementary controls to provide ancillary services. Hence, this chapter exploits key examples of these controllers that proved to be efficient and widely accepted. In addition, this chapter considers their integration into the conventional controls of green generators, where the focus is on wind energy