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The effect of urbanization on previously agricultural watersheds is an increasingly important issue for watershed planners. Urbanization increases runoff and pollutant loadings to the watershed outlet. Watershed planners in areas that previously had little impervious cover must now consider the effects of new roads and buildings on hydrologic processes. The ANSWERS-2000 watershed model was modified to simulate watersheds with mixtures of agricultural and urban areas. In addition, components were added to simulate atmospheric deposition and urban management practices, including wet ponds, dry ponds, and infiltration trenches. The modified model was evaluated on two watersheds in Blacksburg, Virginia, including a subwatershed of Stroubles Creek and a large parking lot on the Virginia Tech campus with a dry pond at its outlet. The model predicted the hydrology and pollutant losses for the year 1999 from the Stroubles Creek watershed within 50% of the observed values after calibration. Prediction errors were much higher for the parking lot and dry pond simulation of the period of time from August 1995 to February 1996. For the parking lot inflow to the dry pond, errors ranged from 0 to 100%. For the dry pond effluent, errors for runoff and sediment losses were -11.5 and 60.1%, respectively, and nutrient losses were poorly predicted (greater than 100% error). There was considerable uncertainty as to the quality of the observed data and this may account for some of the predicted sediment and nutrient loss errors. The modified model was applied to the Battlefield Green Watershed in Hanover County, Virginia to demonstrate the watershed response to development in that watershed. As simulated, sediment and nutrient losses were 30 to 50 times higher after development. The model is intended for use on watersheds with an impervious cover of 30% or less, due to the increased difficulty in accurately quantifying the hydrology of highly urbanized watersheds and because of uncertainty in atmospheric deposition rates on such watersheds. The pond subroutines are very simplified, and limit simulation to ponds with simple geometries. / Master of Science

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 110-115).

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Magíster en Ciencias, Mención Computación / El principal objetivo de esta tesis es encontrar casos tratables y buenas técnicas para computar Certain Answers sobre bases de datos de grafos incompletas, en tiempo polinomial. Las bases de datos de grafos surgen naturalmente de la necesidad de almacenar información de redes, tales como Facebook, mapas de rutas o la web. La idea de "incompletitud" viene de la falta de información completa, complejidad con la cual tenemos que trabajar a diario. Sobre estas bases de datos de grafos carentes de información completa, queremos realizar preguntas en la forma de consultas particulares y determinar si la pregunta puede ser contestada de la misma forma en cada posible completación de la base de datos. La respuesta a estas preguntas en cada posible completación de una base de datos de grafos incompleta es llamada Certain Answers. El problema de Certain Answers sobre bases de datos de grafos incompletas ya ha sido estudiado, y es conocido que este problema es en general co-NP completo. En esta tesis convertimos el problema de computar Certain Answers en un problema 3-SAT con su fórmula lógica booleana asociada. Podemos probar que bajo ciertas condiciones esta fórmula lógica tiene un número de variables que nos permite determinar si es satisfacible en tiempo polinomial. Luego, probamos que estas condiciones son exhaustivas: sin cualquiera de ellas el problema se vuelve co-NP completo otra vez. Para analizar más clases tratables del problema de Certain Answers, convertimos el problema Certain Answers en un problema de programación lineal entera. Con esta formulación de programación lineal, encontramos algunos casos tratables, algoritmos y heurísticas para resolverlo. Sin embargo, el principal logro es la nueva formulación en sí, porque nos permite usar las bien conocidas técnicas de programación lineal para encontrar más casos tratables y mejores heurísticas.

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RESUME Les problèmes du comportement dynamique des structures ont une importance technique considérable. Parmi de nombreuses applications plus particulièrement dans le domaine du Génie Civil pour lesquelles la prise en compte de leffet de la vitesse de déformation est nécessaire, on peut citer les problèmes de prévision de la durée de vie, destimation de la sûreté et de la fiabilité des structures. On sen sert dans lanalyse du comportement dynamique non linéaire des structures sollicitées au-delà de la limite élastique ; comme le cas des éléments dune structure exposée aux chocs ou dune structure soumise aux sollicitations violentes comme le cas des sollicitations sismiques. Leffet de la vitesse de déformation peut entraîner la mise hors service de la structure ou de ses éléments constitutifs et causer des dommages matériels et des pertes humaines. Ce comportement agit par le biais de la rupture fragile qui résulte dune réduction des déformations plastiques et de la capacité dissipative de la structure. Lors des séismes respectifs de Northridge 1995 et de Kobe 1994, divers types de ruptures sont identifiées au niveau de la jonction poutre poteau. Ces ruptures sont dûes essentiellement à linsuffisance de ductilité. Des programmes de recherche expérimentale ont été réalisés à travers le monde sur des structures prototypes pour évaluer entre autre l'effet de la vitesse de déformations sur le comportement des assemblages soudés. Au Japon et aux Etats-Unis, cette démarche expérimentale a été mise en ouvre afin didentifier les causes des ruptures dassemblages. En Europe, le progrès des connaissances sest poursuivi, grâce à des activités de recherche visant à lamélioration continue des codes parasismiques. Dans lobjectif détudier linfluence de la vitesse de déformation sur le comportement des structures en zone sismique un programme dessai complet est réalisé à lUniversité de Liège. Les simulations numériques sont conduites à laide du logiciel DRAIN-HASSOUNI dont la version dorigine est appelée DRAIN-2D et dans laquelle on a incorporé le modèle de PERZYNA pour tenir compte de linfluence de la vitesse de déformation.

Since the internet appears at the start of 1990s, the society has been changed. Nowadays, the internet has already become an essential part in modern life. The real world¡¦s interpersonal communication, sharing behavior and other interaction ways are all appeared in the internet virtual world. The Virtual Community verified this phenomenon. The Virtual Knowledge Community provided internet users convenient ways to seek useful information. Take the largest Virtual Knowledge Community in Taiwan¡ÐYahoo¡IKimo Knowledge¡Ï as example, its reaching rate exceeded Google Taiwan in only about one year, since the website was launched at the end of 2004. Obviously, the knowledge search service played a very important role in Taiwan. It seems that people can use this service originated from the concept of Web 2.0 to improve their own knowledge experience. However, the virtual world is fictitious because it is filled with good and bad information. Can people distinguish them? Will it influence the users¡¦ cognition and the ability to judge? The research is developed under this issue, adopting Content Analysis method to survey the Best Answers in Virtual Knowledge Community. It tried to prove and find out how the ability of people¡¦s information judgment under the Web 2.0 tendency is. The research found that the Best Answers in different categories are different in their argumentation structure. First, in the category of ¡§Evidence¡¨, the structure is obviously different between the ways Best Answers chosen. Best Answers chosen by asker pay much more attention to evidence than those chosen by voters. In addition, the category of ¡§Information Offering¡¨ played an important role in Best Answers. The significance is more conspicuous than Argumentation Backing and Emotionality Backing. Does it mean the answers provided more information will be chosen as Best Answer more easily? It also reminds us that even the internet and information technology bring this society many advantages and benefits, but we must train ourselves to have depth think and judgment ability, too. Or we will fall into Information Smog and lose our judgment ability.