Relación entre la estructura en estado recocido del acero grado construcción y las propiedades mecánicas después de un tratamiento térmico final

En esta investigación se analizó la influencia de diferentes estructuras obtenidas en el proceso de recocido para la vida útil de los elementos finales (baleros). Se observó, con base en los resultados, que existe una estrecha relación entre las estructuras (tamaño de carburos) en estado recocido y las propiedades mecánicas de elementos finales después del temple y revenido

The Spatial Distribution of Imperviousness in Watershed Hydrology

Urbanization affects the hydrology of watersheds often leading to increases in runoff volumes and peak flows. These impacts are mainly attributed to the presence of imperviousness on the landscape which inhibits the soil infiltration process. Normally, these impacts are studied at the hillslope scale and under lumped watershed conditions. The impacts at the watershed scale under more spatially distributed conditions have been studied less. Advancements in spatial observations and techniques, distributed hydrologic modeling, and greater understanding of the importance of scale in hydrology have increased the feasibility and need for including spatial data sets and methods into hydrologic investigations. This dissertation focuses on understanding the role and importance of the spatial distribution of imperviousness in watershed hydrology. The spatial distribution of imperviousness is investigated by incorporating various spatial datasets, techniques, and modeling approaches that are used routinely for the hydrology of natural watersheds but less frequently for urbanized conditions. The distribution of imperviousness is investigated based on three approaches. The first approach uses optimization concepts to study where imperviousness can be placed in the watershed to reduce negative impacts on flooding. The second approach develops, implements, and tests a hydrologic event-based model to study the influence of the spatial distribution of imperviousness on the hydrologic response. The last approach relates analytically the space-time variability of rainfall, runoff, and the routing process to the imperviousness pattern, and synthesizes the complex space-time variations into a simpler framework. From the first approach distinct patterns of imperviousness were obtained that embodied water resources objectives. For example, the clustering of imperviousness along the main channel was found to globally reduce peak flows along the stream network. The second approach indicated that the overall imperviousness pattern can have a considerable impact on the hydrologic response. The last approach showed that the spatial patterns of rainfall and imperviousness can interact to increase or decrease the average amount of rainfall excess. The main contribution from this research is a larger understanding of the role of the spatial distribution of imperviousness in watershed hydrology. It also demonstrates the usefulness of applying hydrologic knowledge of natural watersheds to anthropogenically-altered watersheds

Wenn und wie Lernerrollen ausgehandelt werden

Mejia Casas A. Wenn und wie Lernerrollen ausgehandelt werden. Bielefeld: Universität Bielefeld; 2013

Rural school in the tenza valley, rural education and agroecology reflections on rural “development”

The municipality of Sutatenza (Boyaca), constitutes an important reference for rural education in Colombia due to “Radio Sutatenza” (Educational Radio) and the People’s Cultural Action in the mid-twentieth century. Currently, in the same town, a process called the Campesina Community School del Valle de Tenza has been brewing, under an agroecological approach, guided in its work to the cultural and productive Andean farmers, their families and their young people to cultivate in them a return the field. This article addresses this educational experience for contrasting approaches of “development” with the perceptions and visions that emerge from the rural world, without being radically different, it raises important questions for the call for and controversy of development, from the local

Heavy metal concentration and distribution (Pb, Zn, Cu, Cd and Cr) in urban road sediments

RESUMEN: Este artículo presenta los resultados obtenidos de la recolección del sedimento depositado durante 65 días sobre superficies viarias (Torrelavega- España). Se distinguieron dos tipos de muestras: la aspirada directamente y la recolectada tras un barrido. Para cada tipo de muestra se determinó la granulometría y concentración de metales pesados. Los resultados sugirieron que la concentración de los metales pesados tiende a aumentar de forma exponencial con la disminución en la fracción de tamaño. La carga asociada de elementos metálicos aumenta de forma logarítmica con el aumento de lafracción de tamaño.ABSTRACT: This paper displays the obtained results of the collected sediment deposited during 65 days on road surfaces (Torrelavega-Spain). Two types of samples are distinguished: aspired directly and collected after sweeping. For each type of sample it was determined the particle size distribution and heavy metals concentration. The results suggest that the heavy metals concentration tends to increase exponentially form with the decrease in the size fraction. The associated loading of metallic elements exponentially increases with the size fraction.Los autores desean agradecer el apoyo financiero de la Agencia Española de Cooperación Internacional y Desarrollo (AECID), y la Universidad de Cantabria (España)

Searching For Empirical Evidence Of Complex Hydrological Behavior In Urbanizing Basins

Urban living accounts for approximately 50% of the worldwide population and this percentage will continue to rise in the decades to come. Urbanizing landscapes and their associated processes represent key aspects of coupled natural and human systems. Additionally, they can influence and cause impacts on regional broad-scale basin hydrology, stream and riparian ecosystems, and water quality. For this research, it is hypothesized that streamflow and water quality time series data for urbanizing basins may exhibit signs of complexity such as long range correlations, state transitions, and chaotic dynamics. To explore this hypothesis, we will use tools from statistical physics and ecology such as multifractal detrended fluctuation analysis, critical slowing down, and chaos-based time series analysis. We will apply these tools to streamflow, rainfall, and water quality data for nearly 40 stream gauges located in the metropolitan areas of cities across the US. It is expected that this analysis will reveal signs of complex behavior different from that already observed in natural basins, as well as new and unique behavior. The results from this research could help support and provide empirical evidence for developing improved data-driven models