Concurrent Data Structures Linked in Time

Arguments about correctness of a concurrent data structure are typically carried out by using the notion of linearizability and specifying the linearization points of the data structure's procedures. Such arguments are often cumbersome as the linearization points' position in time can be dynamic (depend on the interference, run-time values and events from the past, or even future), non-local (appear in procedures other than the one considered), and whose position in the execution trace may only be determined after the considered procedure has already terminated. In this paper we propose a new method, based on a separation-style logic, for reasoning about concurrent objects with such linearization points. We embrace the dynamic nature of linearization points, and encode it as part of the data structure's auxiliary state, so that it can be dynamically modified in place by auxiliary code, as needed when some appropriate run-time event occurs. We name the idea linking-in-time, because it reduces temporal reasoning to spatial reasoning. For example, modifying a temporal position of a linearization point can be modeled similarly to a pointer update in separation logic. Furthermore, the auxiliary state provides a convenient way to concisely express the properties essential for reasoning about clients of such concurrent objects. We illustrate the method by verifying (mechanically in Coq) an intricate optimal snapshot algorithm due to Jayanti, as well as some clients

Desarrollo de un aplicativo para la visualización del volumen de tejido activo en estimulación cerebral profunda empleando un modelo no lineal de reducción de dimensionalidad

El Parkinson es una enfermedad con síntomas de desorden de movimiento, que puede ser tratada con la Estimulación Cerebral Profunda cuando los métodos convencionales con medicinas no son efectivos. Esta terapia implica la colocación de un electrodo en el ganglio basal, el tálamo, u otra estructura subcortical, el cual genera pulsos eléctricos de alta frecuencia en una región específica; el Volumen de Tejido Activo es la propagación espacial de la activación neuronal directa en respuesta a esta estimulación eléctrica, y es de suma importancia para los neurocirujanos contar con una herramienta que permita conocerlo; pero dado que la representación de estos volúmenes se realiza con estructuras de datos de alta dimensionalidad. es necesario trabajar con métodos de reducción de dimensionalidad para representar las estructuras en un espacio de características bidimensional. Para esto, este proyecto presenta, en primera instancia, un estudio para determinar el error de reconstrucción, obtenido con la medida de similitud Positive Matching Index, cuando se realiza el proceso de reducción sobre volúmenes simulados bajo condiciones isotrópicas y anisotrópicas, con las técnicas: Análisis de Componentes Principales y Análisis de Componentes Principales con Kernel. Y en segunda instancia, se desarrolló una solución informática que permite visualizar los volúmenes mientras se desplaza en un espacio de dos dimensiones. Finalmente se obtuvo, como resultados de investigación, los errores de reconstrucción en diferentes dimensiones, que permitieron determinar la eficiencia de estas técnicas; y una herramienta computacional que permite visualizar los volúmenes de tejido activo mientras se desplaza en un espacio bidimensional

El micro: un deporte de todos y para todos

Según estudios realizados por la Federación Colombiana de Fútbol de Salón, en Colombia existen al menos 1.2 millones de jugadores de este deporte, de los cuales una cuarta parte (300.000, aproximadamente) se encuentra en Bogotá. Tan sólo en la capital del país se juegan en un fin de semana más de 2.000 partidos oficiales y su liga es una de las más competitivas a nivel nacional. A continuación presento tres crónicas que retratarán de cerca la popularidad del microfútbol en la ciudad de Bogotá. Son más de 50 años de un deporte que llegó al país gracias al doctor Jaime Arroyave Rendón pero que en cuarenta minutos se reinventa en los pies de los ‘micreros’ bogotanos.According to an investigation made by the Colombian Football Hall Federation there are at least 1.2 million players of this particular activity and one fourth of this group (300.000 approximately) reside in Bogota. Every weekend, only in the capital’s country, more than 2.000 official matches are played and the city league is one of the most competitive leagues in the whole country. Three chronics are presented bellow with the purpose to portray closely the popularity of “microfútbol” in the city of Bogota. More than 50 years now since the arrival of this special sport by the hand of Jaime Arroyave Rendón, although it just takes 40 minutes to reinvent itself on the feet of the ‘micreros’ of this big city

Diseño de un clúster con computadoras dadas de baja, como alternativa de bajo costo frente a ordenadores de alto rendimiento, para empresas del Eje Cafetero

El aporte a las empresas de la región se puede realizar en diferentes formas, pero cuando se pueden reunir diferentes aspectos como la reutilización de elementos que han sido descartados, el alivio en los gastos de la organización, el apoyo al medio ambiente mediante la disminución de desechos de equipos tecnológicos y la posibilidad de contar con un sistema fruto de la unión de hardware y software que pueda generar unas capacidades aceptables, la propuesta es más atractiva, no solo desde el punto de vista empresarial, sino también desde el ambiental y social. En el presente documento se presenta una propuesta basada en el diseño de un clúster con equipos no activos en la empresa y se estudia su viabilidad, de tal forma que se tenga un sistema que pueda brindar beneficios como: ¿ Ayudar a reducir la contaminación generada por los desechos tecnológicos. ¿ Hacer uso eficiente de los recursos tecnológicos que puede poseer una empresa. ¿ Contar con un sistema de buenas prestaciones para la ejecución de aplicaciones que necesitan ordenadores de medio o alto rendimiento. En la metodología para el desarrollo del proyecto se encuentran el estudio teórico en lo relacionado a sistemas de clúster, conocer a partir de un grupo de empresas el escenario en el cual se puede desarrollar un proyecto como el propuesto, el diseño de un sistema clúster y los resultados obtenidos de la investigación que permita conocer la viabilidad de un proyecto de esta naturaleza

Functional anatomy, osteogenesis and bone microstructure of the appendicular system of African mole-rats (Rodentia: Ctenohystrica: Bathyergidae)

In comparison to their ecophysiological and behavioral aspects, the skeletal system of African mole-rats (Bathyergidae) has been relatively understudied. Only a few studies have assessed their skeletal system, but these have mostly focused on their cranial and dental systems, with little attention on their postcranial skeleton. This PhD thesis provides a considerable amount of information about the functional anatomy, morphological diversity and postnatal bone morphogenesis of the appendicular system of these subterranean mammals. African mole-rats are small mammals highly adapted to the hypogeous niche that feed on underground roots and tubers. They forage, mate, breed and to some extent even disperse underground. For this, they build extensive burrow systems primarily with their chisel-like teeth, but also using their forelimbs for scratch-digging. One of the most exceptional features of bathyergids is their wide spectrum of social organization, which is unique among mammals and ranges from solitary, social and eusocial. Here, the eusocial naked mole-rat, Heterocephalus glaber, has been the most studied species. The physiology of African mole-rats is also exceptional among rodents and other mammals, showing low metabolic rates and body temperatures, as well as slow somatic growth rates. They also show enhanced fitness and prolonged longevity, features that have been associated to a life protected from both climatic extremes and predation, as well as to intergenerational transfer of information, communal care of young and shared foraging endeavors in social species. For these reasons, bathyergids represent a unique animal model to explore their skeletal adaptations to fossoriality and life underground. The aim of this research was to assess the patterns of bone growth and development to understand how adults attain their final phenotype. A comprehensive sample (N = 506) of all six bathyergid genera including seven species and comprising individuals of both sexes and of different ontogenetic stages was studied. Stylopodial (humerus and femur) and zeugopodial (ulna and tibia-fibula) bones (n = 1133) were analyzed using multiple quantitative analyses of variance (ANOVA, MANOVA), ordination (PCA, DA) and regression (RMA, OLS, equality of slopes), as well as bone labeling techniques and detailed qualitative descriptions of their midshaft bone histology. Chapter 3 shows that the specialized phenotype of the only scratch-digger bathyergid Bathyergus suillus underwent considerable morphological changes during ontogeny, e.g. juveniles showed externally more robust bones with thin cortical walls, whereas adults presented slender bones with significantly thicker cross-sections. Such changes are probably related to the increased digging demands and agonistic behaviors of the developing young. However, other aspects of their anatomy expressed perinatally, such as greater external epicondylar robustness, well-developed olecranon, teres major and deltoid processes, suggest a major role of genetic factors in their development. This chapter applied for first time the conceptualization of developmental modules to long bones, and showed that the periosteal module had higher variability and tended to grow faster than the endochondral module. Chapter 4 analyzed the morphological diversity within Bathyergidae using comparative anatomy and morpho-functional indices and showed that most species shared a highly specialized fossorial morphology and that only the naked mole-rats were morphologically divergent (having a simplified phenotype), resembling the condition of non-fossorial closest relatives of the Bathyergidae. Nevertheless, the novel inclusion of three ecomorphological categories (solitary scratch-diggers, solitary chisel-tooth diggers and social chisel-tooth diggers) in this study, showed significant differences among the groups. In general, social species appeared to have a phenotype more specialized to increase digging ability and locomotor performance, whereas solitary species showed a relatively less specialized fossorial phenotype, and a diminished locomotor ability. This may contribute to foraging strategies in social species which are known to have more complex and relatively longer burrow systems as compared to solitary species. Chapter 5 assesses the ossification patterns of the endochondral and periosteal modules, and shows that in general most bathyergids have relatively similar endochondral growth rates, irrespective of social behavior or digging strategy, although the periosteal module showed relatively higher growth rates and a higher degree of variation as compared to the endochondral module, thus appearing to be considerably less dependent on body size and genetic factors. Naked mole-rats showed the lowest growth rates among bathyergids. Considering the basal phylogenetic position of H. glaber within the family, a neotenic condition is suggested for this species, and suggests accelerated bone growth rates for the evolution of the other bathyergids. Chapter 6 provides a comprehensive description of the pattern of bone modelling in bathyergids and includes an assessment of their bone dynamics using fluorochrome labeling. All bathyergids analyzed showed increased cortical bone thickening during ontogeny, as well as low rates of endosteal bone resorption. Also, all species showed high histodiversity, limited remodeling (i.e. development of secondary osteons) and they do not ever develop Haversian bone tissues. This thesis concludes that the combination of social strategy and type of excavation had an impact on the evolution of the bathyergid appendicular system. On one hand, it was evidenced that the development of fore- and hindlimbs are not constrained by intrinsic factors (as suggested for other mammals), and that the limbs develop at similar growth rates, resulting in relatively symmetrical limb proportions. This is suggested to improve locomotion within burrows and represents an adaptation to the subterranean lifestyle, which is also observed in other fossorial mammals. This thesis further discusses how environmental factors and specific behaviors and locomotor modes, may represent strong selective pressures on limb adaptation and evolution. Similarly, a proximo-distal pattern of variation was observed, where zeugopodial elements were more variable than stylopodial elements, probably because they are in direct interaction with the substrate, so they can evolve morphological adaptations for particular habitats and locomotor behaviors. Importantly, these adaptations are most likely mediated by heterochronic modifications of their ossification modules, especially intramembranous ossification, which is known to be more responsive to environmental factors, whilst the endochondral modules would be more conservative, perhaps because a stronger genetic regulation in postnatal life. Further research on long bone modules is necessary to understand the specificity of such changes. Despite the comparatively simplified phenotype of H. glaber, they showed a larger morphospace as compared to other bathyergids, indicating a wider intraspecific variability. This agrees with previous observations suggesting skeletal plasticity for this species. It is suggested that living in large colonies results in diminished selective pressures for limb specialization but has an impact on increasing trait variability within members of the colony. This study showed that the integration of multiscale techniques and multivariate analysis of combined skeletal phenotypes (i.e. forelimb + hindlimb) offer a better understanding of adaptations to the hypogeous environment. The findings of this study also highlight the importance of considering developmental modularity of long bones for assessment of bone adaptations, particularly for understanding the differential effects of intrinsic and extrinsic factors regulating endochondral and intramembranous ossification

Reterritorializing conflicting urban natures : Socio-ecological inequalities and the politics of spatial planning in Bogotá

Bogotá (Colombia) en su historia reciente ha enfrentado varios desafíos y conflictos ambientales que han ido de la mano con la posibilidad de re-imaginar un entorno urbano-rural menos hostil y más ecológico. A pesar de muchos inconvenientes, fragmentación social, política e institucional, dicha posibilidad ha estado presente y viva durante las últimas tres décadas entre diferentes grupos sociales a través de prácticas democráticas situadas en procesos de planificación y ordenamiento territorial. Dichas prácticas a su vez se relacionan con asuntos como la estructura ecológica local y regional. Esta tesis doctoral se propuso analizar un conjunto de conflictos ambientales contemporáneos en torno al ordenamiento del territorio y la naturaleza urbana en Bogotá (1990 a la actualidad). Al analizar casos de conflicto ambiental como la urbanización especulativa o con fines de lucro sobre áreas protegidas, actividades extractivas por materiales de construcción o el impacto de áreas de rellenos sanitarios en territorios urbanos-rurales, la investigación analizó las prácticas de planificación y ordenamiento territorial para repensarlas como una tarea política colectiva que apunta a prácticas más democráticas, y no sólo como un deber exclusivo de planificadores. Me propuse demostrar cómo los procesos de planificación y ordenamiento y su vínculo con asuntos ecológicos, son una fuente de conflicto ambiental y están a su vez relacionados con varias desigualdades socio-ecológicas. La cuestión clave es comprender la dialéctica entre los conflictos y la ordenación del territorio en un contexto de alta complejidad y biodiversidad.This doctoral dissertation analyzes a set of contemporary environmental conflicts around spatial planning and urban nature in Bogotá, Colombia (1990–present day). In this research I ask what the relations are between the spatial planning processes of recent history and contemporary urban environmental conflicts. To answer this, I focus on three questions. What have the specific roles of the government authorities, civil society, and different social actors been in the processes of urban planning and environmental concerns in Bogotá in recent decades? What have the environmental and social impacts of planning policies in Bogotá’s ecosystems been during the same timeframe? How have socio-ecological inequalities in the city been linked with Bogota’s spatial planning? This dissertation therefore analyzes the dialectic between conflict and spatial planning, exploring how urban nature and spatial planning processes are a source of environmental conflict related to socio-ecological inequalities in Bogotá. In this study I scrutinize environmental conflict as a key notion for identifying more productive ways of approaching such a dialectic in the production of urban territory. Although Bogotá’s region has faced several environmental challenges and inequalities, the possibility of reimagining a more just urban nature along with the conflicts and through situated knowledge has been alive in the last three decades among different social groups in planning practices. This research is situated in the Political Ecology of Urbanization (PEU) and adopts some elements of urban environmental history, establishing a dialogue between the analysis of qualitative research material with existing information from fields such as ecology and physical geography. Therefore, this doctoral dissertation introduces a historical reconstruction about the conflicting visions around urban nature in Bogotá in the last decades. The documentation of the visions over urban nature offers an empirical basis for the design of an alternative roadmap for the understanding and management of environmental conflicts related to (spatial) planning and urban nature in the Bogotá region and beyond.Finlandi

Digital repetitive control under varying frequency conditions

Premi extraordinari doctorat curs 2011-2012, àmbit d’Enginyeria IndustrialThe tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area and Repetitive Control has proven to be an efficient way to face this topic; however, in some applications the period of the signal to be tracked/rejected changes in time or is uncertain, which causes and important performance degradation in the standard repetitive controller. This thesis presents some contributions to the open topic of repetitive control working under varying frequency conditions. These contributions can be organized as follows: One approach that overcomes the problem of working under time varying frequency conditions is the adaptation of the controller sampling period, nevertheless, the system framework changes from Linear Time Invariant to Linear Time-Varying and the closed-loop stability can be compromised. This work presents two different methodologies aimed at analysing the system stability under these conditions. The first one uses a Linear Matrix Inequality (LMI) gridding approach which provides necessary conditions to accomplish a sufficient condition for the closed-loop Bounded Input Bounded Output stability of the system. The second one applies robust control techniques in order to analyse the stability and yields sufficient stability conditions. Both methodologies yield a frequency variation interval for which the system stability can be assured. Although several approaches exist for the stability analysis of general time-varying sampling period controllers few of them allow an integrated controller design which assures closed-loop stability under such conditions. In this thesis two design methodologies are presented, which assure stability of the repetitive control system working under varying sampling period for a given frequency variation interval: a mu-synthesis technique and a pre-compensation strategy. On a second branch, High Order Repetitive Control (HORC) is mainly used to improve the repetitive control performance robustness under disturbance/reference signals with varying or uncertain frequency. Unlike standard repetitive control, the HORC involves a weighted sum of several signal periods. With a proper selection of the associated weights, this high order function offers a characteristic frequency response in which the high gain peaks located at harmonic frequencies are extended to a wider region around the harmonics. Furthermore, the use of an odd-harmonic internal model will make the system more appropriate for applications where signals have only odd-harmonic components, as in power electronics systems. Thus an Odd-harmonic High Order Repetitive Controller suitable for applications involving odd-harmonic type signals with varying/uncertain frequency is presented. The open loop stability of internal models used in HORC and the one presented here is analysed. Additionally, as a consequence of this analysis, an Anti-Windup (AW) scheme for repetitive control is proposed. This AW proposal is based on the idea of having a small steady state tracking error and fast recovery once the system goes out of saturation. The experimental validation of these proposals has been performed in two different applications: the Roto-magnet plant and the active power filter application. The Roto-magnet plant is an experimental didactic plant used as a tool for analysing and understanding the nature of the periodic disturbances, as well as to study the different control techniques used to tackle this problem. This plant has been adopted as experimental test bench for rotational machines. On the other hand, shunt active power filters have been widely used as a way to overcome power quality problems caused by nonlinear and reactive loads. These power electronics devices are designed with the goal of obtaining a power factor close to 1 and achieving current harmonics and reactive power compensation.Award-winningPostprint (published version

Hacia la sustentabilidad del sistema prosumidor en el municipio de Apía, Risaralda

Apía es un municipio del departamento de Risaralda, centro occidente del territorio colombiano y punto clave del llamado eje cafetero. Actualmente el municipio vive un momento de gran importancia, una etapa de transición donde abogar por la ¿inteligencia¿ del territorio es permitirle al municipio decidir por el tipo de desarrollo al cual le quiere apostar. Hace unos pocos años comenzaron a emerger una serie de iniciativas cooperativistas que en el transcurso del tiempo permearía gran parte del circuito económico, haciendo de la articulación entre productores, transformadores y comercializadores, una meta de coherencia solidaria para con el territorio. El focalizar el trabajo de grado en este municipio, implicó asumir ciertos retos, y uno de ellos era devolverle a la complejidad misma del territorio su translúcida simplicidad en términos dialectitos, implícitos en el abordaje incluyente y participativo de dicha intervención. Un primer momento, requería conocer el estado del territorio, y para ello se urgía conocerlo a través de sus relaciones, de su lógica energética, material, simbólica y cognoscitiva; de este modo, el diagnóstico apuntaba a develar ¿aunque fuera someramente- las relaciones rur-urbanas del municipio en correlación con la manifestación intercooperacional del circuito económico. Encuestas, entrevistas y un taller diagnóstico participativo permitieron conocer las distintas perspectivas que desde los actores-autores esbozarían los principales problemas del circuito económico. Paralelo a esto se realizó un paseo-conversación que consistía en percibir como los patrones comportamentales en el municipio iban determinando las tendencias culturales del territorio. Partiendo del resultado obtenido en el diagnóstico, se procedió a analizarlo de manera participativa, pretendiendo generar a partir de este, los insumos necesarios para elaborar las estrategias. En este sentido, se desarrolló un taller de construcción de alternativas que daba cuenta