Automated wordlength optimization framework for multi-source statistical interval-based analysis of nonlinear systems with control-flow structures

El uso de aritmética de punto fijo es una opción de diseño muy extendida en sistemas con fuertes restricciones de área, consumo o rendimiento. Para producir implementaciones donde los costes se minimicen sin impactar negativamente en la precisión de los resultados debemos llevar a cabo una asignación cuidadosa de anchuras de palabra. Encontrar la combinación óptima de anchuras de palabra en coma fija para un sistema dado es un problema combinatorio NP-hard al que los diseñadores dedican entre el 25 y el 50 % del ciclo de diseño. Las plataformas hardware reconfigurables, como son las FPGAs, también se benefician de las ventajas que ofrece la aritmética de coma fija, ya que éstas compensan las frecuencias de reloj más bajas y el uso más ineficiente del hardware que hacen estas plataformas respecto a los ASICs. A medida que las FPGAs se popularizan para su uso en computación científica los diseños aumentan de tamaño y complejidad hasta llegar al punto en que no pueden ser manejados eficientemente por las técnicas actuales de modelado de señal y ruido de cuantificación y de optimización de anchura de palabra. En esta Tesis Doctoral exploramos distintos aspectos del problema de la cuantificación y presentamos nuevas metodologías para cada uno de ellos: Las técnicas basadas en extensiones de intervalos han permitido obtener modelos de propagación de señal y ruido de cuantificación muy precisos en sistemas con operaciones no lineales. Nosotros llevamos esta aproximación un paso más allá introduciendo elementos de Multi-Element Generalized Polynomial Chaos (ME-gPC) y combinándolos con una técnica moderna basada en Modified Affine Arithmetic (MAA) estadístico para así modelar sistemas que contienen estructuras de control de flujo. Nuestra metodología genera los distintos caminos de ejecución automáticamente, determina las regiones del dominio de entrada que ejercitarán cada uno de ellos y extrae los momentos estadísticos del sistema a partir de dichas soluciones parciales. Utilizamos esta técnica para estimar tanto el rango dinámico como el ruido de redondeo en sistemas con las ya mencionadas estructuras de control de flujo y mostramos la precisión de nuestra aproximación, que en determinados casos de uso con operadores no lineales llega a tener tan solo una desviación del 0.04% con respecto a los valores de referencia obtenidos mediante simulación. Un inconveniente conocido de las técnicas basadas en extensiones de intervalos es la explosión combinacional de términos a medida que el tamaño de los sistemas a estudiar crece, lo cual conlleva problemas de escalabilidad. Para afrontar este problema presen tamos una técnica de inyección de ruidos agrupados que hace grupos con las señales del sistema, introduce las fuentes de ruido para cada uno de los grupos por separado y finalmente combina los resultados de cada uno de ellos. De esta forma, el número de fuentes de ruido queda controlado en cada momento y, debido a ello, la explosión combinatoria se minimiza. También presentamos un algoritmo de particionado multi-vía destinado a minimizar la desviación de los resultados a causa de la pérdida de correlación entre términos de ruido con el objetivo de mantener los resultados tan precisos como sea posible. La presente Tesis Doctoral también aborda el desarrollo de metodologías de optimización de anchura de palabra basadas en simulaciones de Monte-Cario que se ejecuten en tiempos razonables. Para ello presentamos dos nuevas técnicas que exploran la reducción del tiempo de ejecución desde distintos ángulos: En primer lugar, el método interpolativo aplica un interpolador sencillo pero preciso para estimar la sensibilidad de cada señal, y que es usado después durante la etapa de optimización. En segundo lugar, el método incremental gira en torno al hecho de que, aunque es estrictamente necesario mantener un intervalo de confianza dado para los resultados finales de nuestra búsqueda, podemos emplear niveles de confianza más relajados, lo cual deriva en un menor número de pruebas por simulación, en las etapas iniciales de la búsqueda, cuando todavía estamos lejos de las soluciones optimizadas. Mediante estas dos aproximaciones demostramos que podemos acelerar el tiempo de ejecución de los algoritmos clásicos de búsqueda voraz en factores de hasta x240 para problemas de tamaño pequeño/mediano. Finalmente, este libro presenta HOPLITE, una infraestructura de cuantificación automatizada, flexible y modular que incluye la implementación de las técnicas anteriores y se proporciona de forma pública. Su objetivo es ofrecer a desabolladores e investigadores un entorno común para prototipar y verificar nuevas metodologías de cuantificación de forma sencilla. Describimos el flujo de trabajo, justificamos las decisiones de diseño tomadas, explicamos su API pública y hacemos una demostración paso a paso de su funcionamiento. Además mostramos, a través de un ejemplo sencillo, la forma en que conectar nuevas extensiones a la herramienta con las interfaces ya existentes para poder así expandir y mejorar las capacidades de HOPLITE. ABSTRACT Using fixed-point arithmetic is one of the most common design choices for systems where area, power or throughput are heavily constrained. In order to produce implementations where the cost is minimized without negatively impacting the accuracy of the results, a careful assignment of word-lengths is required. The problem of finding the optimal combination of fixed-point word-lengths for a given system is a combinatorial NP-hard problem to which developers devote between 25 and 50% of the design-cycle time. Reconfigurable hardware platforms such as FPGAs also benefit of the advantages of fixed-point arithmetic, as it compensates for the slower clock frequencies and less efficient area utilization of the hardware platform with respect to ASICs. As FPGAs become commonly used for scientific computation, designs constantly grow larger and more complex, up to the point where they cannot be handled efficiently by current signal and quantization noise modelling and word-length optimization methodologies. In this Ph.D. Thesis we explore different aspects of the quantization problem and we present new methodologies for each of them: The techniques based on extensions of intervals have allowed to obtain accurate models of the signal and quantization noise propagation in systems with non-linear operations. We take this approach a step further by introducing elements of MultiElement Generalized Polynomial Chaos (ME-gPC) and combining them with an stateof- the-art Statistical Modified Affine Arithmetic (MAA) based methodology in order to model systems that contain control-flow structures. Our methodology produces the different execution paths automatically, determines the regions of the input domain that will exercise them, and extracts the system statistical moments from the partial results. We use this technique to estimate both the dynamic range and the round-off noise in systems with the aforementioned control-flow structures. We show the good accuracy of our approach, which in some case studies with non-linear operators shows a 0.04 % deviation respect to the simulation-based reference values. A known drawback of the techniques based on extensions of intervals is the combinatorial explosion of terms as the size of the targeted systems grows, which leads to scalability problems. To address this issue we present a clustered noise injection technique that groups the signals in the system, introduces the noise terms in each group independently and then combines the results at the end. In this way, the number of noise sources in the system at a given time is controlled and, because of this, the combinato rial explosion is minimized. We also present a multi-way partitioning algorithm aimed at minimizing the deviation of the results due to the loss of correlation between noise terms, in order to keep the results as accurate as possible. This Ph.D. Thesis also covers the development of methodologies for word-length optimization based on Monte-Carlo simulations in reasonable times. We do so by presenting two novel techniques that explore the reduction of the execution times approaching the problem in two different ways: First, the interpolative method applies a simple but precise interpolator to estimate the sensitivity of each signal, which is later used to guide the optimization effort. Second, the incremental method revolves on the fact that, although we strictly need to guarantee a certain confidence level in the simulations for the final results of the optimization process, we can do it with more relaxed levels, which in turn implies using a considerably smaller amount of samples, in the initial stages of the process, when we are still far from the optimized solution. Through these two approaches we demonstrate that the execution time of classical greedy techniques can be accelerated by factors of up to ×240 for small/medium sized problems. Finally, this book introduces HOPLITE, an automated, flexible and modular framework for quantization that includes the implementation of the previous techniques and is provided for public access. The aim is to offer a common ground for developers and researches for prototyping and verifying new techniques for system modelling and word-length optimization easily. We describe its work flow, justifying the taken design decisions, explain its public API and we do a step-by-step demonstration of its execution. We also show, through an example, the way new extensions to the flow should be connected to the existing interfaces in order to expand and improve the capabilities of HOPLITE.

Diseño de filtros helicoidales de altas prestaciones

El objetivo de este proyecto es el estudio detallado y fabricación de los filtros de cavidades con resonadores helicoidales. Este proyecto está motivado por el hecho de que es una tecnología cada vez más presente en el mercado y su uso resulta muy ´útil en aplicaciones donde se requiere que los componentes sean de tamaño reducido. Esto se debe a que las cavidades helicoidales son de las que presentan menor tamaño para una frecuencia dada. La estructura del proyecto se va a dividir en tres grandes bloques. El primero es el estudio teórico de esta tecnología. En la introducción se verán los principales usos de estos dispositivos, dando ejemplos comerciales, para luego poder compararlos con el prototipo que se ha construido. A continuación, en los primeros capítulos, se detallará la geometría de los resonadores, las ecuaciones que deben aplicarse para calcular las dimensiones y los elementos de diseño. Se comentarán algunas modificaciones opcionales que se pueden aplicar al filtro en el caso de que se requieran especificaciones especiales para la aplicación para la que esté destinado el dispositivo. En segundo lugar se procederá a diseñar modelos de filtros helicoidales para distintas bandas de frecuencia, con el programa de diseño CST Microwave Studio. Estos serán ajustados y parametrizados con el fin de obtener unos requerimientos que serán fijados previamente. Y por ´ultimo se mostrará como ha sido el proceso de prototipado del filtro de tres cavidades para la banda de FM que se ha llevado a cabo y estarán plasmadas las medidas que se han realizado para determinar las características que tiene el prototipo. Este proyecto está planteado como un manual para que el interesado en la fabricación de este tipo de filtros pueda afrontar el diseño desde el inicio y ser capaz de construir un prototipo que cumpla con las características que sean requeridas. ABSTRACT. The main purpose of this project is the detailed study of helical resonator filters and their manufacturing. This technology is increasingly present in the market, and its use is very convenient in applications where it is required for the components to be of reduced size. This is due to helical resonators being smaller than conventional cavity filters for a given frequency. The projects structure will be divided into three sections. First, the theoretical study of this technology will be presented. In the introduction, the main uses of these devices will be shown and commercial examples will be given, which can then be compared with the built prototype. Afterwards, in the first chapters, the geometry of the resonators, the required equations to calculate their dimensions and the design elements will be detailed. Some optional modifications that can be applied to the filter in the case of special specifications will be discussed. Second, some models of helical filters will be designed for different frequency bands, using the design software CST Microwave Studio. These will be adjusted and parameterized in order to meet requirements that will be set previously. Finally, the development of the prototyping process of a three cavities filter for the FM band will be shown, and the measurements that were made to determine the prototypes features will be reflected. This project is designed as a handbook; the individual concerned in the manufacture of these filters should be able to follow the design process from the start and build a prototype that has the required characteristics.

Providing Older Adults With Real-time Passenger Information via SMS

Peer reviewed

Voice-processing technologies--their application in telecommunications.

As the telecommunications industry evolves over the next decade to provide the products and services that people will desire, several key technologies will become commonplace. Two of these, automatic speech recognition and text-to-speech synthesis, will provide users with more freedom on when, where, and how they access information. While these technologies are currently in their infancy, their capabilities are rapidly increasing and their deployment in today's telephone network is expanding. The economic impact of just one application, the automation of operator services, is well over $100 million per year. Yet there still are many technical challenges that must be resolved before these technologies can be deployed ubiquitously in products and services throughout the worldwide telephone network. These challenges include: (i) High level of accuracy. The technology must be perceived by the user as highly accurate, robust, and reliable. (ii) Easy to use. Speech is only one of several possible input/output modalities for conveying information between a human and a machine, much like a computer terminal or Touch-Tone pad on a telephone. It is not the final product. Therefore, speech technologies must be hidden from the user. That is, the burden of using the technology must be on the technology itself. (iii) Quick prototyping and development of new products and services. The technology must support the creation of new products and services based on speech in an efficient and timely fashion. In this paper I present a vision of the voice-processing industry with a focus on the areas with the broadest base of user penetration: speech recognition, text-to-speech synthesis, natural language processing, and speaker recognition technologies. The current and future applications of these technologies in the telecommunications industry will be examined in terms of their strengths, limitations, and the degree to which user needs have been or have yet to be met. Although noteworthy gains have been made in areas with potentially small user bases and in the more mature speech-coding technologies, these subjects are outside the scope of this paper.

Projeto e desenvolvimento de uma arquitetura de baixo consumo de potência para microprocessadores.

O trabalho trata do projeto e do desenvolvimento de um processador de baixo consumo de potência, de forma simplificada, explorando técnicas de microarquitetura, para atingir menor consumo de potência. É apresentada uma sequência lógica de desenvolvimento, a partir de conceitos e estruturas básicas, até chegar a estruturas mais complexas e, por fim, mostrar a microarquitetura completa do processador. Esse novo modelo de processador é comparado com estudos prévios de três processadores, sendo o primeiro modelo síncrono, o segundo assíncrono e o terceiro uma versão melhorada do primeiro modelo, que inclui minimizações de registradores e circuitos. Uma nova metodologia de criação de padring de microcontroladores, baseada em reuso de informações de projetos anteriores, é apresentada. Essa nova metodologia foi criada para a rápida prototipagem e para diminuir possíveis erros na geração do código do padring. Comparações de resultados de consumo de potência e área são apresentadas para o processador desenvolvido e resultados obtidos com a nova metodologia de geração de padring também são apresentados. Para o processador, um modelo, no qual se utilizam múltiplos barramentos para minimizar o número de ciclos de máquina por instrução, é apresentado. Também foram ressaltadas estruturas que podem ser otimizadas e circuitos que podem ser reaproveitados para diminuir a quantidade de circuito necessário na implementação. Por fim, a nova implementação é comparada com os três modelos anteriores; os ganhos obtidos de desempenho com a implementação dessas estruturas foram de 18% que, convertidos em consumo de potência, representam economia de 13% em relação ao melhor caso dos processadores comparados. A tecnologia utilizada no desenvolvimento dos processadores foi CMOS 250nm da TSMC.

Desenvolvimento e otimização de antenas Vivaldi antipodais para aplicações a altas frequências.

Esta tese propõe a síntese e o estudo de uma nova técnica de cavidades de borda aplicada a antenas Vivaldi, com o intuito de melhorar suas características de diretividade. Embora as antenas do tipo Vivaldi possuam características diretivas, elas produzem radiações laterais indesejáveis, o que se reflete nos elevados índices de lóbulos laterais devido a correntes superficiais que fluem ao longo das bordas metalizadas nas laterais da antena. Estas correntes são a origem das radiações laterais que vêm sendo mitigadas pela aplicação de cavidades ressonantes, triangulares ou retangulares, que aprisionam tais correntes e, consequentemente, atenuam os lóbulos laterais, sem o incremento do lóbulo principal, uma vez que toda a energia dos lóbulos laterais é apenas confinada nos ressonadores e por isso literalmente perdida. Ao contrário desses esforços, este trabalho propõe cavidades radiantes tanto na forma de abertura exponencial, como na forma do fractais de Koch, que funcionam como radiadores auxiliares (antenas auxiliares), canalizando as correntes de borda e aproveitando-as para aumentar os níveis do lóbulo principal, mitigando os níveis de lóbulo lateral. A síntese desta nova técnica foi implementada em uma antena Vivaldi antipodal com características de baixa diretividade, como qualquer antena Vivaldi, o que foi corrigido e a aplicação da técnica de cavidades radiantes deu origem a duas novas antenas Vivaldis efetivamente diretivas. Os resultados foram obtidos através de simulações do modelo numérico no CST Microwave Studio e confirmados com medidas de laboratório, o que evidenciou a melhora das características de diretividade da antena pela aplicação da nova técnica de cavidades radiantes.

A Survey on FPGA-Based Sensor Systems: Towards Intelligent and Reconfigurable Low-Power Sensors for Computer Vision, Control and Signal Processing

The current trend in the evolution of sensor systems seeks ways to provide more accuracy and resolution, while at the same time decreasing the size and power consumption. The use of Field Programmable Gate Arrays (FPGAs) provides specific reprogrammable hardware technology that can be properly exploited to obtain a reconfigurable sensor system. This adaptation capability enables the implementation of complex applications using the partial reconfigurability at a very low-power consumption. For highly demanding tasks FPGAs have been favored due to the high efficiency provided by their architectural flexibility (parallelism, on-chip memory, etc.), reconfigurability and superb performance in the development of algorithms. FPGAs have improved the performance of sensor systems and have triggered a clear increase in their use in new fields of application. A new generation of smarter, reconfigurable and lower power consumption sensors is being developed in Spain based on FPGAs. In this paper, a review of these developments is presented, describing as well the FPGA technologies employed by the different research groups and providing an overview of future research within this field.

Augmented and Virtual Reality techniques for footwear

The use of 3D imaging techniques has been early adopted in the footwear industry. In particular, 3D imaging could be used to aid commerce and improve the quality and sales of shoes. Footwear customization is an added value aimed not only to improve product quality, but also consumer comfort. Moreover, customisation implies a new business model that avoids the competition of mass production coming from new manufacturers settled mainly in Asian countries. However, footwear customisation implies a significant effort at different levels. In manufacturing, rapid and virtual prototyping is required; indeed the prototype is intended to become the final product. The whole design procedure must be validated using exclusively virtual techniques to ensure the feasibility of this process, since physical prototypes should be avoided. With regard to commerce, it would be desirable for the consumer to choose any model of shoes from a large 3D database and be able to try them on looking at a magic mirror. This would probably reduce costs and increase sales, since shops would not require storing every shoe model and the process of trying several models on would be easier and faster for the consumer. In this paper, new advances in 3D techniques coming from experience in cinema, TV and games are successfully applied to footwear. Firstly, the characteristics of a high-quality stereoscopic vision system for footwear are presented. Secondly, a system for the interaction with virtual footwear models based on 3D gloves is detailed. Finally, an augmented reality system (magic mirror) is presented, which is implemented with low-cost computational elements that allow a hypothetical customer to check in real time the goodness of a given virtual footwear model from an aesthetical point of view.

Parametrizable Architecture for Function Recursive Evaluation

Paper submitted to the XVIII Conference on Design of Circuits and Integrated Systems (DCIS), Ciudad Real, España, 2003.

Combining the power of online crowdsourcing with creative writing user interfaces

The goal of this work was to provide professional and amateur writers with a new way of enhancing their productivity and mental well-being, by helping them overcoming writers block and being able to achieve a state of optimal experience while writing. Our approach is based on bringing together different components to create what we call a creative moment. A creative moment is composed by an image, a text, a mood, a location and a color. The color presented in the creative moment varied according to the mood that was associated to the creative moment. With the creative moments we hoped that our users could have a way to easily trigger their creativity and have a kick start in their work. The prototyping of a web crowdsourcing platform, named CreativeWall, and a Microsoft Word Add-In, that was used on the user study performed, is described and their implementations are discussed. The user study reveals that our approach does have a positive influence in the productivity of the participants when compared with another existing approach. The study also revealed that our approach can ease the process of achieving a state of optimal experience by enhancing one of the dimensions presented on the Flow Theory. At the end we present what we consider would be some possible future developments for the concept created during the development of this work.

Caraterização e modelação do comportamento mecânico da resina fotopolimerizada V-Flash FTI-GN

A utilização de tecnologias de prototipagem em objetos e estruturas do dia-a-dia é cada vez maior. Porém, os componentes que é possível fabricar estão em geral associados a protótipos demonstrativos não funcionais. Para ultrapassar estas limitações têm vindo a ser desenvolvidos novos materiais, procurando a melhoria das suas características mecânicas. A presente dissertação insere-se no projeto Firend®, que se tem vindo a desenvolver numa parceria entre a Academia Militar e outras instituições como o Instituto Superior Técnico e procura avaliar a viabilidade da utilização da técnica de deposição de resina fotopolimerizável por ultra-violeta no fabrico de projéteis para o transporte especial de agentes extintores, procurando caracterizar o desempenho deste material em condições operativas simulativas do disparo real. A pesquisa bibliográfica da presente dissertação baseou-se numa breve introdução aos materiais poliméricos. O trabalho teórico consistiu na modelação numérica através do método dos elementos finitos do ensaio de compressão utilizando o programa Deform® e na respetiva validação do modelo através de comparação dos resultados das simulações com dados experimentais existentes na literatura da especialidade. O trabalho experimental fundamentou-se no fabrico e preparação de provetes através da tecnologia de impressão 3D, na descrição das ferramentas utilizadas e do plano experimental. No final verificou-se a fratura de todos os provetes ensaiados e uma grande dispersão dos resultados, conseguindo-se apenas retirar uma tensão de segurança que não deve ser ultrapassada. De acordo com o estudo realizado o material ensaiado demonstrou-se não ser apropriado para a aplicação pretendida e recomenda-se a avaliação de outros materiais igualmente utilizados pelas técnicas de prototipagem rápida, tais como uma mistura de uma resina polimérica com um outro material com características mecânicas mais adequadas.

Experimental studies on the accuracy of wax patterns used in investment casting

Investment casting is often used to produce fully functional prototype components from sacrificial patterns. These patterns (prototypes) may be made using specialized rapid prototyping techniques such as stereolithography or three-dimensional printing. When multiple functional prototypes are required, interim tools for making wax patterns are employed. The objective of this research work was to determine the precision and accuracy of wax patterns produced using several prototype tools. Linear contraction was used to determine the accuracy as a function of the wax injection parameters used in low-pressure injection moulding. Wax patterns were produced using polyurethane and silicone rubber tools. It has been shown that the accuracy of patterns from both tools is similar. However, silicone tools produce patterns with much higher contraction than those produced by polyurethane tools. Unconstrained patterns dimensions contracted as much as 3.44 +/- 0.40 per cent and 1.70 +/- 0.60 per cent for silicone and polyurethane tools respectively. The constrained dimensions contracted by 2.20 +/- 0.20 per cent in the case of silicone tools and 1.40 +/- 0.20 per cent in the case of polyurethane tools.

Rapid manufacturing of aluminum components

A manufacturing technique for the production of aluminum components is described. A resin-bonded part is formed by a rapid prototyping technique and then debound and infiltrated by a second aluminum alloy under a nitrogen atmosphere. During thermal processing, the aluminum reacts with the nitrogen and is partially transformed into a rigid aluminum nitride skeleton, which provides the structural rigidity during infiltration. The simplicity and rapidity of this process in comparison to conventional production routes, combined with the ability to fabricate complicated parts of almost any geometry and with high dimensional precision, provide an additional means to manufacture aluminum components.

Electromagnetic fields inside a lossy, multilayered spherical head phantom excited by MRI coils: models and methods

The precise evaluation of electromagnetic field (EMF) distributions inside biological samples is becoming an increasingly important design requirement for high field MRI systems. In evaluating the induced fields caused by magnetic field gradients and RF transmitter coils, a multilayered dielectric spherical head model is proposed to provide a better understanding of electromagnetic interactions when compared to a traditional homogeneous head phantom. This paper presents Debye potential (DP) and Dyadic Green's function (DGF)-based solutions of the EMFs inside a head-sized, stratified sphere with similar radial conductivity and permittivity profiles as a human head. The DP approach is formulated for the symmetric case in which the source is a circular loop carrying a harmonic-formed current over a wide frequency range. The DGF method is developed for generic cases in which the source may be any kind of RF coil whose current distribution can be evaluated using the method of moments. The calculated EMFs can then be used to deduce MRI imaging parameters. The proposed methods, while not representing the full complexity of a head model, offer advantages in rapid prototyping as the computation times are much lower than a full finite difference time domain calculation using a complex head model. Test examples demonstrate the capability of the proposed models/methods. It is anticipated that this model will be of particular value for high field MRI applications, especially the rapid evaluation of RF resonator (surface and volume coils) and high performance gradient set designs.

The role of technology in the shift towards open innovation: the case of Procter & Gamble

As with all new ideas, the concept of Open Innovation requires extensive empirical investigation, testing and development. This paper analyzes Procter and Gamble's 'Connect and Develop' strategy as a case study of the major organizational and technological changes associated with open innovation. It argues that although some of the organizational changes accompanying open innovation are beginning to be described in the literature, more analysis is warranted into the ways technological changes have facilitated open innovation strategies, particularly related to new product development. Information and communications technologies enable the exchange of distributed sources of information in the open innovation process. The case study shows that furthermore a suite of new technologies for data mining, simulation, prototyping and visual representation, what we call 'innovation technology', help to support open innovation in Procter and Gamble. The paper concludes with a suggested research agenda for furthering understanding of the role played by and consequences of this technology.