Boards of directors and bank performance in United Arab Emirates

This study presents an empirical analysis about corporate governance of financial institutions in United Arab Emirates (UAE). The purpose of this research is to analyze the influence of the structure of board of directors on the performance of these institutions. To examine the effect of control exerted by particular families on bank management, we estimated models where the dependent variable is return on assets (ROA) and return on equity (ROE), independent variables are board of directors variables, and control variables are bank management variables. Our results show that the control of corporate governance by a ruler's family within a board of directors has a positive effect on bank profitability. Our results indicate that control by a ruler's family through a bank's board of directors compensates for the inadequacy of UAE's corporate governance system.

Integrated program debugging, verification, and optimization using abstract interpretation (and the Ciao system preprocessor)

The technique of Abstract Interpretation has allowed the development of very sophisticated global program analyses which are at the same time provably correct and practical. We present in a tutorial fashion a novel program development framework which uses abstract interpretation as a fundamental tool. The framework uses modular, incremental abstract interpretation to obtain information about the program. This information is used to validate programs, to detect bugs with respect to partial specifications written using assertions (in the program itself and/or in system libraries), to generate and simplify run-time tests, and to perform high-level program transformations such as multiple abstract specialization, parallelization, and resource usage control, all in a provably correct way. In the case of validation and debugging, the assertions can refer to a variety of program points such as procedure entry, procedure exit, points within procedures, or global computations. The system can reason with much richer information than, for example, traditional types. This includes data structure shape (including pointer sharing), bounds on data structure sizes, and other operational variable instantiation properties, as well as procedure-level properties such as determinacy, termination, nonfailure, and bounds on resource consumption (time or space cost). CiaoPP, the preprocessor of the Ciao multi-paradigm programming system, which implements the described functionality, will be used to illustrate the fundamental ideas.

Conflict and cognitive control during sentence comprehension: recruitment of a frontal network during the processing of Spanish object-first sentences.

During sentence processing there is a preference to treat the first noun phrase found as the subject and agent, unless marked the other way. This preference would lead to a conflict in thematic role assignment when the syntactic structure conforms to a non-canonical object-before-subject pattern. Left perisylvian and fronto-parietal brain networks have been found to be engaged by increased computational demands during sentence comprehension, while event-reated brain potentials have been used to study the on-line manifestation of these demands. However, evidence regarding the spatiotemporal organization of brain networks in this domain is scarce. In the current study we used Magnetoencephalography to track spatio-temporally brain activity while Spanish speakers were reading subject- and object-first cleft sentences. Both kinds of sentences remained ambiguous between a subject-first or an object-first interpretation up to the appearance of the second argument. Results show the time-modulation of a frontal network at the disambiguation point of object-first sentences. Moreover, the time windows where these effects took place have been previously related to thematic role integration (300–500 ms) and to sentence reanalysis and resolution of conflicts during processing (beyond 500 ms post-stimulus). These results point to frontal cognitive control as a putative key mechanism which may operate when a revision of the sentence structure and meaning is necessary

Estrategias para el control microclimático del espacio entre edificaciones en clima cálido – húmedo

La presente investigación parte del problema en las zonas de clima cálido - húmedo en las cuales se producen impactos asociados a la incomodidad térmica producto de la intensa radiación solar, altas temperaturas y elevada humedad. Estos factores reducen la calidad de los espacios abiertos y desarrollan en la población una actitud de rechazo hacia el uso del microespacio urbano entre edificaciones en los desarrollos urbanos - conjuntos urbanos - , los mismos frecuentemente admiten soluciones que al parecer no contribuyen a la realización de las actividades comunes de esparcimiento de la población residente. Por lo tanto, el objetivo de la investigación es profundizar en la temática urbano - ambiental - social y el diseño urbano vinculada a la particularidad morfológica local, las condiciones microclimáticas, el uso del microespacio y los requerimientos de los usuarios. La finalidad de desarrollar estrategias de control microclimático del microespacio entre edificios en clima cálido - húmedo en búsqueda de soluciones óptimas que satisfagan las necesidades de los usuarios de los espacios exteriores en estas áreas residenciales. La investigación se centra en el estudio de las particularidades contextuales relacionadas con el microclima y las características urbanas - morfotipológicas, básicamente los factores microclimáticos (soleamiento y ventilación), los morfológicos y edificatorios y las características de las superficies (pavimentos). En coherencia con el objetivo propuesto el trabajo se desarrolla en cuatro fases: la primera aborda la revisión documental, literatura relevante e investigaciones relativas a la calidad ambiental, medio social, medio físico, el microespacio urbano, control y diseño sostenible, modelización proyectual y estrategias sostenibles; la segunda fase se refiere al marco contextual, características urbanas, datos climáticos locales, planes y procesos urbanos, tipologías y conformación urbana. En esta fase se describe el proceso de selección, análisis y evaluación urbano - ambiental de los casos de estudio (conjuntos residenciales). En la tercera fase se aborda el marco evaluativo y estudio de casos, consideraciones físicas, climáticas y valoración térmico - ambiental de los conjuntos residenciales seleccionados. En esta fase se aplican Técnicas Estadísticas y de Simulación Computacional y se analizan los resultados obtenidos. Finalmente, la cuarta fase propositiva incluye el establecimiento de Estrategias, Principios y Lineamientos de optimación térmica y se exponen las Conclusiones parciales de la tesis, alcances y perspectivas futuras. Finalmente, los resultados obtenidos en la investigación demuestran que el análisis en las experiencias de la realidad permiten comprobar que las situaciones y alteraciones ambientales sustanciales, los niveles de afectación térmica y las condiciones de confortabilidad e impacto derivan de las características urbanas, los componentes del microespacio y de las condiciones climáticas las cuales afectan el desarrollo de las actividades y el uso efectivo del microespacio entre edificios. El análisis de los factores morfo - climáticos incidentes y el estudio de los efectos de interacción contribuyen al establecimiento de Principios y Lineamientos para la evaluación y diseño sostenible del microespacio entre edificios y el uso correcto de los elementos del clima en estas áreas urbanas destinadas a la actividad social y al esparcimiento de la población residente. ABSTRACT This research starts from the problem of hot - humid climate zones where impacts related to thermal discomfort are produced as a result from the intense solar radiation and high temperatures and humidity. These factors reduce the quality of open spaces and people develop an attitude of rejection towards the use of urban microspace among buildings within urban developments - urban complexes - . Usually, these complexes admit solutions that apparently do not contribute to the achievement of common leisure activities in the resident dwellers. Therefore, the main purpose of this research is to deepen in the urban - environmental - social issue and urban design linked to the local morphological particularity, microclimate conditions, use of microspace and users’ requirements. In order to develop microclimate control strategies of microspace among buildings in hot - humid climate to look for optimal solutions that satisfy users’ needs of outdoors spaces in these residential areas. The research focuses in the study of contextual particularities related to microclimate and urban - morphotypological characteristics. Basically, microclimate (sunlight and ventilation), morphological and building factors as well as road surface characteristics. According to the proposed objective, this research is developed in four phases: the first one considers documentary review, relevant literature and researches related to environmental quality, social environment, physical environment, urban microspace, control and sustainable design, project modelling and sustainable strategies; while the second phase refers to contextual framework, urban characteristics, local climate data, plans and urban processes, typologies and urban structure. In this phase, the process of selection, analysis and urban - environmental evaluation of case studies (residential complexes) is described. The third phase approaches the assessment framework and case studies, physical and climate considerations as well as environmental - thermal evaluation of selected residential complexes. In this phase, statistical techniques and computational simulations are applied. Likewise, results obtained are analysed. Similarly, fourth and proposing phase includes the establishment of strategies, principles and guidelines of thermal optimization and partial conclusions of the thesis, scopes and future perspectives are exposed. Finally, from the results obtained, it is demonstrated that the analysis on reality experiences allow proving that situations and substantial environmental changes, levels of thermal affectations, comfort conditions and impact derive from urban characteristics, microspace components and from climate conditions which affect the development of activities and the effective use of microspace among buildings. The analysis of incidental morpho - climate factors and the study of interaction effects contribute to the establishment of principles and guidelines for the assessment and sustainable design of microspace among buildings as well as the correct use of climate elements in these urban areas oriented to social and leisure activities of resident population.

Digital Control Implementation to Reduce the Cost and Improve the Performance of the Control Stage of an Industrial Switched-Mode Power Supply

The main objective of this work is the design and implementation of the digital control stage of a 280W AC/DC industrial power supply in a single low-cost microcontroller to replace the analog control stage. The switch-mode power supply (SMPS) consists of a PFC boost converter with fixed frequency operation and a variable frequency LLC series resonant DC/DC converter. Input voltage range is 85VRMS-550VRMS and the output voltage range is 24V-28V. A digital controller is especially suitable for this kind of SMPS to implement its multiple functionalities and to keep the efficiency and the performance high over the wide range of input voltages. Additional advantages of the digital control are reliability and size. The optimized design and implementation of the digital control stage it is presented. Experimental results show the stable operation of the controlled system and an estimation of the cost reduction achieved with the digital control stage.

Single-Stage Grid-Connected Forward Microinverter with Boundary Mode Control

This paper presents a microinverter to be integrated into a solar module. The proposed solution combines a forward converter and a constant off-time boundary mode control, providing MPPT capability and unity power factor in a single-stage converter. The transformer structure of the power stage remains as in the classical DC-DC forward converter. Transformer primary windings are utilized for power transfer or demagnetization depending on the grid semi-cycle. Furthermore, bidirectional switches are used on the secondary side allowing direct connection of the inverter to the grid. Design considerations for the proposed solution are provided, regarding the inductance value, transformer turns ratio and frequency variation during a line semi-cycle. The decoupling of the twice the line frequency power pulsation is also discussed, as well as the maximum power point tracking (MPPT) capability. Simulation and experimental results for a 100W prototype are enclosed

PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented.

Torque control of switched reluctance motors

This paper presents the performance of an instantaneous torque control method. The simulation and experimental results illustrate the capability of Switched Reluctance Motors (SRM) being used in the motor drive industry. Based on experimental data, the advantages of this control method and its disadvantages in practical implementation were studied. The model used in the simulation is the linear magnetic model which has the 12/8 structure, the same structure as the experimental switched reluctance motor.

The internal structure of hydrogen-air difussion flames

The Internal Structure of Hydrogen-Air Diffusion Flames. Tho purpose of this paper is to study finite rate chemistry effects in diffusion controlled hydrogenair flames undor conditions appearing in some cases in a supersonic combustor. Since for large reaction rates the flame is close to chemical equilibrium, the reaction takes place in a very thin region, so thata "singular perturbation "treatment" of the problem seems appropriate. It has been shown previously that, within the inner or reaction zone, convection effects may be neglocted, the temperature is constant across the flame, and tho mass fraction distributions are given by ordinary differential equations, whore tho only independent variable involved is tho coordinate normal to the flame surface. Tho solution of the outer problom, which is a pure mixing problem with the additional condition that fuol and oxidizer do not coexist in any zone, provides t h e following information: tho flame position, rates of fuel consumption, temperature, concentrators of species, fluid velocity outside of tho flame, and the boundary conditions required to solve the "inner problem." The main contribution of this paper consists in the introduction of a fairly complicated chemical kinetic scheme representing hydrogen-oxygen reaction. The nonlinear equations expressing the conservation of chemical species are approximately integrated by means of an integral method. It has boen found that, in the case considered of a near-equilibrium diffusion flame, tho role played by the dissociation-recombination reactions is purely marginal, and that somo of the second order "shuffling" reactions are close to equilibrium. The method shown here may be applied to compute the distanco from the injector corresponding to a given separation from equilibrium, say ten to twenty percent. For the casos whore this length is a small fraction of the combustion zone length, the equilibrium treatment describes properly tho flame behavior.

Combining series elastic actuation and magneto-rheological damping for the control of agile locomotion

All-terrain robot locomotion is an active topic of research. Search and rescue maneuvers and exploratory missions could benefit from robots with the abilities of real animals. However, technological barriers exist to ultimately achieving the actuation system, which is able to meet the exigent requirements of these robots. This paper describes the locomotioncontrol of a leg prototype, designed and developed to make a quadruped walk dynamically while exhibiting compliant interaction with the environment. The actuation system of the leg is based on the hybrid use of series elasticity and magneto-rheological dampers, which provide variable compliance for natural-looking motion and improved interaction with the ground. The locomotioncontrol architecture has been proposed to exploit natural leg dynamics in order to improve energy efficiency. Results show that the controller achieves a significant reduction in energy consumption during the leg swing phase thanks to the exploitation of inherent leg dynamics. Added to this, experiments with the real leg prototype show that the combined use of series elasticity and magneto-rheologicaldamping at the knee provide a 20 % reduction in the energy wasted in braking the knee during its extension in the leg stance phase.

Program development using abstract interpretation (and the ciao system preprocessor)

The technique of Abstract Interpretation has allowed the development of very sophisticated global program analyses which are at the same time provably correct and practical. We present in a tutorial fashion a novel program development framework which uses abstract interpretation as a fundamental tool. The framework uses modular, incremental abstract interpretation to obtain information about the program. This information is used to validate programs, to detect bugs with respect to partial specifications written using assertions (in the program itself and/or in system librarles), to genérate and simplify run-time tests, and to perform high-level program transformations such as múltiple abstract specialization, parallelization, and resource usage control, all in a provably correct way. In the case of validation and debugging, the assertions can refer to a variety of program points such as procedure entry, procedure exit, points within procedures, or global computations. The system can reason with much richer information than, for example, traditional types. This includes data structure shape (including pointer sharing), bounds on data structure sizes, and other operational variable instantiation properties, as well as procedure-level properties such as determinacy, termination, non-failure, and bounds on resource consumption (time or space cost). CiaoPP, the preprocessor of the Ciao multi-paradigm programming system, which implements the described functionality, will be used to illustrate the fundamental ideas.

On-Chip Thermal Monitoring: Design, Placement and Interconnection of Temperature Sensors

La temperatura es una preocupación que juega un papel protagonista en el diseño de circuitos integrados modernos. El importante aumento de las densidades de potencia que conllevan las últimas generaciones tecnológicas ha producido la aparición de gradientes térmicos y puntos calientes durante el funcionamiento normal de los chips. La temperatura tiene un impacto negativo en varios parámetros del circuito integrado como el retardo de las puertas, los gastos de disipación de calor, la fiabilidad, el consumo de energía, etc. Con el fin de luchar contra estos efectos nocivos, la técnicas de gestión dinámica de la temperatura (DTM) adaptan el comportamiento del chip en función en la información que proporciona un sistema de monitorización que mide en tiempo de ejecución la información térmica de la superficie del dado. El campo de la monitorización de la temperatura en el chip ha llamado la atención de la comunidad científica en los últimos años y es el objeto de estudio de esta tesis. Esta tesis aborda la temática de control de la temperatura en el chip desde diferentes perspectivas y niveles, ofreciendo soluciones a algunos de los temas más importantes. Los niveles físico y circuital se cubren con el diseño y la caracterización de dos nuevos sensores de temperatura especialmente diseñados para los propósitos de las técnicas DTM. El primer sensor está basado en un mecanismo que obtiene un pulso de anchura variable dependiente de la relación de las corrientes de fuga con la temperatura. De manera resumida, se carga un nodo del circuito y posteriormente se deja flotando de tal manera que se descarga a través de las corrientes de fugas de un transistor; el tiempo de descarga del nodo es la anchura del pulso. Dado que la anchura del pulso muestra una dependencia exponencial con la temperatura, la conversión a una palabra digital se realiza por medio de un contador logarítmico que realiza tanto la conversión tiempo a digital como la linealización de la salida. La estructura resultante de esta combinación de elementos se implementa en una tecnología de 0,35 _m. El sensor ocupa un área muy reducida, 10.250 nm2, y consume muy poca energía, 1.05-65.5nW a 5 muestras/s, estas cifras superaron todos los trabajos previos en el momento en que se publicó por primera vez y en el momento de la publicación de esta tesis, superan a todas las implementaciones anteriores fabricadas en el mismo nodo tecnológico. En cuanto a la precisión, el sensor ofrece una buena linealidad, incluso sin calibrar; se obtiene un error 3_ de 1,97oC, adecuado para tratar con las aplicaciones de DTM. Como se ha explicado, el sensor es completamente compatible con los procesos de fabricación CMOS, este hecho, junto con sus valores reducidos de área y consumo, lo hacen especialmente adecuado para la integración en un sistema de monitorización de DTM con un conjunto de monitores empotrados distribuidos a través del chip. Las crecientes incertidumbres de proceso asociadas a los últimos nodos tecnológicos comprometen las características de linealidad de nuestra primera propuesta de sensor. Con el objetivo de superar estos problemas, proponemos una nueva técnica para obtener la temperatura. La nueva técnica también está basada en las dependencias térmicas de las corrientes de fuga que se utilizan para descargar un nodo flotante. La novedad es que ahora la medida viene dada por el cociente de dos medidas diferentes, en una de las cuales se altera una característica del transistor de descarga |la tensión de puerta. Este cociente resulta ser muy robusto frente a variaciones de proceso y, además, la linealidad obtenida cumple ampliamente los requisitos impuestos por las políticas DTM |error 3_ de 1,17oC considerando variaciones del proceso y calibrando en dos puntos. La implementación de la parte sensora de esta nueva técnica implica varias consideraciones de diseño, tales como la generación de una referencia de tensión independiente de variaciones de proceso, que se analizan en profundidad en la tesis. Para la conversión tiempo-a-digital, se emplea la misma estructura de digitalización que en el primer sensor. Para la implementación física de la parte de digitalización, se ha construido una biblioteca de células estándar completamente nueva orientada a la reducción de área y consumo. El sensor resultante de la unión de todos los bloques se caracteriza por una energía por muestra ultra baja (48-640 pJ) y un área diminuta de 0,0016 mm2, esta cifra mejora todos los trabajos previos. Para probar esta afirmación, se realiza una comparación exhaustiva con más de 40 propuestas de sensores en la literatura científica. Subiendo el nivel de abstracción al sistema, la tercera contribución se centra en el modelado de un sistema de monitorización que consiste de un conjunto de sensores distribuidos por la superficie del chip. Todos los trabajos anteriores de la literatura tienen como objetivo maximizar la precisión del sistema con el mínimo número de monitores. Como novedad, en nuestra propuesta se introducen nuevos parámetros de calidad aparte del número de sensores, también se considera el consumo de energía, la frecuencia de muestreo, los costes de interconexión y la posibilidad de elegir diferentes tipos de monitores. El modelo se introduce en un algoritmo de recocido simulado que recibe la información térmica de un sistema, sus propiedades físicas, limitaciones de área, potencia e interconexión y una colección de tipos de monitor; el algoritmo proporciona el tipo seleccionado de monitor, el número de monitores, su posición y la velocidad de muestreo _optima. Para probar la validez del algoritmo, se presentan varios casos de estudio para el procesador Alpha 21364 considerando distintas restricciones. En comparación con otros trabajos previos en la literatura, el modelo que aquí se presenta es el más completo. Finalmente, la última contribución se dirige al nivel de red, partiendo de un conjunto de monitores de temperatura de posiciones conocidas, nos concentramos en resolver el problema de la conexión de los sensores de una forma eficiente en área y consumo. Nuestra primera propuesta en este campo es la introducción de un nuevo nivel en la jerarquía de interconexión, el nivel de trillado (o threshing en inglés), entre los monitores y los buses tradicionales de periféricos. En este nuevo nivel se aplica selectividad de datos para reducir la cantidad de información que se envía al controlador central. La idea detrás de este nuevo nivel es que en este tipo de redes la mayoría de los datos es inútil, porque desde el punto de vista del controlador sólo una pequeña cantidad de datos |normalmente sólo los valores extremos| es de interés. Para cubrir el nuevo nivel, proponemos una red de monitorización mono-conexión que se basa en un esquema de señalización en el dominio de tiempo. Este esquema reduce significativamente tanto la actividad de conmutación sobre la conexión como el consumo de energía de la red. Otra ventaja de este esquema es que los datos de los monitores llegan directamente ordenados al controlador. Si este tipo de señalización se aplica a sensores que realizan conversión tiempo-a-digital, se puede obtener compartición de recursos de digitalización tanto en tiempo como en espacio, lo que supone un importante ahorro de área y consumo. Finalmente, se presentan dos prototipos de sistemas de monitorización completos que de manera significativa superan la características de trabajos anteriores en términos de área y, especialmente, consumo de energía. Abstract Temperature is a first class design concern in modern integrated circuits. The important increase in power densities associated to recent technology evolutions has lead to the apparition of thermal gradients and hot spots during run time operation. Temperature impacts several circuit parameters such as speed, cooling budgets, reliability, power consumption, etc. In order to fight against these negative effects, dynamic thermal management (DTM) techniques adapt the behavior of the chip relying on the information of a monitoring system that provides run-time thermal information of the die surface. The field of on-chip temperature monitoring has drawn the attention of the scientific community in the recent years and is the object of study of this thesis. This thesis approaches the matter of on-chip temperature monitoring from different perspectives and levels, providing solutions to some of the most important issues. The physical and circuital levels are covered with the design and characterization of two novel temperature sensors specially tailored for DTM purposes. The first sensor is based upon a mechanism that obtains a pulse with a varying width based on the variations of the leakage currents on the temperature. In a nutshell, a circuit node is charged and subsequently left floating so that it discharges away through the subthreshold currents of a transistor; the time the node takes to discharge is the width of the pulse. Since the width of the pulse displays an exponential dependence on the temperature, the conversion into a digital word is realized by means of a logarithmic counter that performs both the timeto- digital conversion and the linearization of the output. The structure resulting from this combination of elements is implemented in a 0.35_m technology and is characterized by very reduced area, 10250 nm2, and power consumption, 1.05-65.5 nW at 5 samples/s, these figures outperformed all previous works by the time it was first published and still, by the time of the publication of this thesis, they outnumber all previous implementations in the same technology node. Concerning the accuracy, the sensor exhibits good linearity, even without calibration it displays a 3_ error of 1.97oC, appropriate to deal with DTM applications. As explained, the sensor is completely compatible with standard CMOS processes, this fact, along with its tiny area and power overhead, makes it specially suitable for the integration in a DTM monitoring system with a collection of on-chip monitors distributed across the chip. The exacerbated process fluctuations carried along with recent technology nodes jeop-ardize the linearity characteristics of the first sensor. In order to overcome these problems, a new temperature inferring technique is proposed. In this case, we also rely on the thermal dependencies of leakage currents that are used to discharge a floating node, but now, the result comes from the ratio of two different measures, in one of which we alter a characteristic of the discharging transistor |the gate voltage. This ratio proves to be very robust against process variations and displays a more than suficient linearity on the temperature |1.17oC 3_ error considering process variations and performing two-point calibration. The implementation of the sensing part based on this new technique implies several issues, such as the generation of process variations independent voltage reference, that are analyzed in depth in the thesis. In order to perform the time-to-digital conversion, we employ the same digitization structure the former sensor used. A completely new standard cell library targeting low area and power overhead is built from scratch to implement the digitization part. Putting all the pieces together, we achieve a complete sensor system that is characterized by ultra low energy per conversion of 48-640pJ and area of 0.0016mm2, this figure outperforms all previous works. To prove this statement, we perform a thorough comparison with over 40 works from the scientific literature. Moving up to the system level, the third contribution is centered on the modeling of a monitoring system consisting of set of thermal sensors distributed across the chip. All previous works from the literature target maximizing the accuracy of the system with the minimum number of monitors. In contrast, we introduce new metrics of quality apart form just the number of sensors; we consider the power consumption, the sampling frequency, the possibility to consider different types of monitors and the interconnection costs. The model is introduced in a simulated annealing algorithm that receives the thermal information of a system, its physical properties, area, power and interconnection constraints and a collection of monitor types; the algorithm yields the selected type of monitor, the number of monitors, their position and the optimum sampling rate. We test the algorithm with the Alpha 21364 processor under several constraint configurations to prove its validity. When compared to other previous works in the literature, the modeling presented here is the most complete. Finally, the last contribution targets the networking level, given an allocated set of temperature monitors, we focused on solving the problem of connecting them in an efficient way from the area and power perspectives. Our first proposal in this area is the introduction of a new interconnection hierarchy level, the threshing level, in between the monitors and the traditional peripheral buses that applies data selectivity to reduce the amount of information that is sent to the central controller. The idea behind this new level is that in this kind of networks most data are useless because from the controller viewpoint just a small amount of data |normally extreme values| is of interest. To cover the new interconnection level, we propose a single-wire monitoring network based on a time-domain signaling scheme that significantly reduces both the switching activity over the wire and the power consumption of the network. This scheme codes the information in the time domain and allows a straightforward obtention of an ordered list of values from the maximum to the minimum. If the scheme is applied to monitors that employ TDC, digitization resource sharing is achieved, producing an important saving in area and power consumption. Two prototypes of complete monitoring systems are presented, they significantly overcome previous works in terms of area and, specially, power consumption.

A tutorial on program development and optimization using the Ciao preprocessor

We present in a tutorial fashion CiaoPP, the preprocessor of the Ciao multi-paradigm programming system, which implements a novel program development framework which uses abstract interpretation as a fundamental tool. The framework uses modular, incremental abstract interpretation to obtain information about the program. This information is used to validate programs, to detect bugs with respect to partial specifications written using assertions (in the program itself and/or in system libraries), to generate and simplify run-time tests, and to perform high-level program transformations such as multiple abstract specialization, parallelization, and resource usage control, all in a provably correct way. In the case of validation and debugging, the assertions can refer to a variety of program points such as procedure entry, procedure exit, points within procedures, or global computations. The system can reason with much richer information than, for example, traditional types. This includes data structure shape (including pointer sharing), bounds on data structure sizes, and other operational variable instantiation properties, as well as procedure-level properties such as determinacy, termination, non-failure, and bounds on resource consumption (time or space cost).

In situ control of As dimer orientation on Ge(100) surfaces

We investigated the preparation of single domain Ge(100):As surfaces in a metal-organic vapor phase epitaxy reactor. In situ reflection anisotropy spectra (RAS) of vicinal substrates change when arsenic is supplied either by tertiarybutylarsine or by background As4 during annealing. Low energy electron diffraction shows mutually perpendicular orientations of dimers, scanning tunneling microscopy reveals distinct differences in the step structure, and x-ray photoelectron spectroscopy confirms differences in the As coverage of the Ge(100): As samples. Their RAS signals consist of contributions related to As dimer orientation and to step structure, enabling precise in situ control over preparation of single domain Ge(100): As surfaces.

Control de vibraciones en pasarelas peatonales

En los últimos años se ha construido un gran número de pasarelas peatonales como respuesta a la demanda de nuevas vías de paso en las ciudades. Estas estructuras tienen requisitos constructivos menos exigentes en comparación con otros tipos de puentes, lo cual ha facilitado el desarrollo de diseños con nuevos esquemas resistentes, complicadas geometrías y el empleo de nuevos materiales. En general estas estructuras son esbeltas, ligeras y poco amortiguadas, lo que en ocasiones ha generado problemas de vi-braciones al paso de peatones una vez puestas en servicio. Las normativas actuales son cada vez más sensibles a esta problemática, recomendando diseños cuyas frecuencias naturales deben estar alejadas de los rangos de frecuencia de paso típicos de los peatones y fijando límites de confort en forma de valores máximos de aceleración permitidos, asegurándose así un correcto comportamiento de la estructura. En el presente artículo se analiza esta problemática desde un punto de vista práctico. Para ello se muestran los puntos clave de las normativas y guías de diseño de pasarelas que se pueden encontrar actualmente en la bibliografía, se presentan las técnicas que habitualmente se emplean en el análisis dinámico experimental de estas estructuras, y se comentan las soluciones a las que generalmente se recurre para mejorar su comportamiento dinámico. Por último, se muestran los trabajos llevados a cabo por el Centro Tecnológico CARTIF en colaboración con las Universidades de Valladolid y Castilla-La Mancha en la pasarela peatonal del Museo de la Ciencia de Valladolid. Estos trabajos incluyen: (1) el estudio dinámico de los tres vanos metálicos de dicha pasarela, (2) el diseño e implementación de un amortiguador de masa sintonizado en el vano más sensible a las vibraciones, (3) la implementación de un amortiguador de masa activo utilizando un excitador electrodinámico, y (4) el desarrollo de pruebas para la verificación del estado de servicio de la pasarela. In the last years, a wide number of footbridges have been built as demand response of more direct pathways in cities. These structures have lower building requirements as compared with standard bridges. This circumstance has facilitated the development of new structural design with complex geometries and innovative materials. As a result, these structures may be slender, light and low damped, leading to vibration problems once in service. The current codes take into account this problem, and recommend designs with natural frequencies away from the typical pedestrian pacing rates and fix comfort limits to guarantee the serviceability of the structure.This paper studies this problem from a practical point of view. Thus, the key points of codes and footbridges guidelines are showed, the typical experimental dynamic analysis techniques are presented, and the usual solutions adopted to improve the dynamic performance of these structures are discussed. Finally, the works carried out on the Valladolid Science Museum Footbridge by Centro Tecnológico CARTIF in collaboration with the Universities of Valladolid and Castilla-La Mancha are showed. These works include: (1) the dynamic study of the three steel spans of the footbridge, (2) the design and implementation of a tuned mass damper in the liveliest span, (3) the implementation of an active mass damper using an electrodynamic shaker, and (4) the development of field tests to assess the serviceability of such span.