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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Ambiente multim?todos para otimiza??o de opera??es em sistemas de distribui??o de energia el?trica generalizados / Multi-method environment for optimization of operations in generalized electricity distribution systems

Blengini Neto, Adolfo 16 February 2017 (has links)
Submitted by SBI Biblioteca Digital (sbi.bibliotecadigital@puc-campinas.edu.br) on 2017-03-23T14:50:03Z No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5) / Made available in DSpace on 2017-03-23T14:50:03Z (GMT). No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5) Previous issue date: 2017-02-16 / Pontif?cia Universidade Cat?lica de Campinas ? PUC Campinas / This study proposes the development of an environment for optimization of the operations of electrical distribution systems. The environment is proposed for the modern electrical distribution networks considering the possibility of inclusion of distributed generation and mesh topology. The environment is divided into three modules. The first module consists of standardizing the input and organization data of the network in memory using techniques of object-oriented software engineering. This approach simplifies the processes of nodal analysis of the circuits, improves the performance of the solution and allows reusing the objects and operations in other implementations. The second module is responsible for analyzing and represents network characteristics: topology, load model and distributed generation points. The third consists of the BFS, FW and OCF methods to perform the current flow calculation and allows the user to choose the desired algorithm, being able to present the currents and voltages in each iteration. The choice of different methods in the optimization environment allows the use of the most adherent method to the different network topologies, the types of load, the flexibility in the use of capacity constraints of the elements of the network and the inclusion of generation limits and voltage limits. In order to verify the adhesion and the efficiency of the environment, simulations were carried out on balanced three-phase circuits of primary distribution of 11, 33 and 400 buses with different load models, radial or mesh topology, with and without distributed generation. / Esta pesquisa prop?e-se ao desenvolvimento de um ambiente para otimiza??o da opera??o de sistemas de distribui??o de energia. O ambiente ? aderente ?s modernas redes de distribui??o de energia por considerar a possibilidade de inclus?o de gera??o distribu?da e topologia em malha. O ambiente est? dividido em tr?s m?dulos. O primeiro m?dulo consiste na padroniza??o dos dados de entrada e organiza??o da rede em mem?ria no formato de grafo utilizando t?cnicas de engenharia de software orientada a objetos. Este enfoque simplifica os processos de an?lises nodais dos circuitos, melhora o desempenho da solu??o e permite reaproveitar os objetos e opera??es em outras implementa??es. O segundo m?dulo ? respons?vel pela an?lise e representa??o das caracter?sticas da rede: topologia, modelo de cargas e pontos de gera??o distribu?da. O terceiro consiste dos m?todos BFS, FW e OCF para a execu??o do c?lculo do fluxo de corrente e d? a op??o ao usu?rio de escolha do enfoque desejado, podendo apresentar as correntes e tens?es em cada itera??o. A op??o de escolha de diferentes m?todos no ambiente de otimiza??o possibilita o uso do m?todo mais aderentes ?s diferentes topologias de rede, aos tipos modelos de carga, a flexibilidade no uso de restri??es de capacidade dos elementos da rede e a inclus?o de limites de gera??o e limites de tens?o. Com a finalidade de comprovar a ader?ncia e efici?ncia do ambiente foram realizadas simula??es em circuitos trif?sicos equilibrados de distribui??o prim?ria com 11, 33 e 400 barras com modelos de carga constante, topologia radial, anel, com e sem gera??o distribu?da.
32

Hosting capacity for photovoltaics in Swedish distribution grids

Walla, Tobias January 2012 (has links)
For planning issues, it is useful to know the upper limit for photovoltaics (PV) in the electrical grid with current design and operation (defined as hosting capacity) and how this limit can be increased. Future costs for grid reinforcement can be avoided if measures are taken to implement smart grid technology in the distribution grid. The aim of this project is to identify challenges in Swedish electricity distribution grids with a high penetration of local generation of electricity from PV. The aim is also to help Swedish Distribution System Operators (DSOs) to better understand hosting capacity issues, and to see which room for PV integration there is before there is need for actions to maintain power quality. Three distribution grids are modelled and simulated in Matlab: Rural area, Residential area and City (Stockholm Royal Seaport). Since the project is a cooperation between Uppsala University and Fortum, three different representative grids from Fortum’s grid software ”Power Grid” have been used as input to a flexible simulation program developed at Uppsala University. The simulation includes Newton-Raphson power-flow computing but has also been improved with a model of the temperature dependency of the resistance. The results show that there is room for a lot of PV systems in the Swedish grids. When using voltage rise above 1.1 p.u. voltage as limitation, the hosting capacity 60% PV electricity generation as a fraction of the yearly load were determined for the rural grid and the suburban grid. For the city grid, which is very robust, the hosting capacity 325% was determined. When using overload as limitation, the hosting capacities 70%, 20% and 25%, were determined for the same grids.
33

APPLICATION OF A GROUND-WATER FLOW MODEL TO THE MESILLA BASIN, NEW MEXICO AND TEXAS

Hamilton, Susan Lynne, Maddock, Thomas III January 1993 (has links)
It has been said that watersheds and aquifers ignore political boundaries. This phenomenon is often the reason for extensive regulation of surface -water and ground -water resources which are shared by two or more political entities. Regulation is often the result of years of litigation over who really owns the water, how much is owned, and how much is available for future use. Groundwater models are sometimes used as quantitative tools which aid in the decision making process regarding appropriation and regulation of these scarce, shared, water resources. The following few paragraphs detail the occurrences in the Lower Rio Grande Basin which led to the current ground -water modeling effort. New Mexico, Texas and Mexico have wrestled forever over the rights to the Lower Rio Grande and the aquifers of the Rio Grande Basin (Figure 1). As early as 1867, due to a flood event on the Rio Grande, Texas and Mexico were disputing the new border created by the migrating Rio Grande. During the 1890's, the users upstream from the Mesilla and El Paso Valleys were diverting and applying so much of the Rio Grande that the Mesilla and El Paso valley farmers litigated in order to apportion and guarantee the supply. In the recent past, disputes over who may use the ground -water resources of the region and the effect of surface- water uses on aquifer water levels resulted in litigation between El Paso, Texas, and New Mexico.
34

Fundamentální akciová analýza / Fundamental Share Analysis

Andrys, Michal January 2013 (has links)
The content of this thesis is the fundamental analysis of stocks whose bases are practically focused on the company New World Resources Plc. In the theoretical part of the thesis are presented approaches to the capital markets generally used to search for undervalued stocks and when appropriate to their business. The detail is given to the specifics of fundamental analysis. These data are used in the practical part of the work at different levels of fundamental analysis. The main part consists of the actual determination of the intrinsic value of the shares of New World Resources Plc on whose basis the work mentioned specific investment recommendation.
35

Fundamentální analýza vybrané akcie / Fundamental Analysis of Share Price

Pestr, Jiří January 2014 (has links)
This thesis is dedicated to fundamental analysis of the company ČEZ and tries to assess whether it is appropriate in the circumstances, to invest in the company or not. To determine the intrinsic value of a share in this work the use of dividend discount models, cash flow, profit models and other. Assessing the economic situation is then performed based on various ratios of the company's performance.
36

Fundamentální analýza vybrané akcie / Fundamental Analysis of Selected Stock

Kubiš, Martin January 2014 (has links)
The aim of this master`s thesis is to perform fundamental analysis and determine the intrinsic value of Pfizer Inc share. There are three main parts of fundamental analysis - global, industry and company analysis, which includes a financial analysis. Using the chosen methods the value of shares is determined. The calculated intrinsic value is then compared to the market price and the investment recommendation is proposed.
37

Lois de conservation pour la modélisation des mouvements de foule / Crowd motion modeling by conservation laws

Mimault, Matthias 14 December 2015 (has links)
Dans cette thèse, on considère plusieurs problèmes issus de la modélisation macroscopique des mouvements de foule. Le premier modèle consiste en une loi de conservation avec un flux discontinu, le second est un système mixte hyperbolique-elliptique et le dernier est une équation non-locale. D'abord, on utilise le modèle de Hughes une dimension pour décrire l'évacuation d'un couloir avec deux sorties. Ce modèle couple une loi de conservation avec un flux discontinu à une équation eikonale. On implémente la méthode de suivi de fronts, qui traite explicitement le comportement de la solution non-classique au point de rebroussement, afin d'obtenir des solutions de référence. Elles serviront à tester numériquement la convergence de schémas aux volumes finis classiques. Ensuite, on modélise le croisement de deux groupes marchant dans des directions opposées avec un système de lois de conservation mixte hyperbolique-elliptique dont le flux dépend des deux densités. Le système perd son hyperbolicité pour certainement valeurs de densité. On assiste à l'apparition d'oscillations persistantes mais bornées, ce qui conduit à la reformulation du problème associé dans le cadre des mesures de probabilités. Finalement, on étudie un modèle non-local de trafic piétonnier en deux dimensions. Le modèle consiste en une loi de conservation dont le flux dépend d'une convolution de la densité. Avec ce modèle, on résout un problème d'optimisation pour une évacuation d'une salle avec une méthode de descente, évaluant l'impact du calcul explicite du gradient de la fonction coût avec la méthode de l'état adjoint plutôt que son approximation par différences finies. / In this thesis, we consider nonclassical problems brought out by the macroscopic modeling of pedestrian flow. The first model consists of a conservation law with a discontinuous flux, the second is a mixed hyperbolic-elliptic system of conservation laws and the last one is a nonlocal equation. In the first chapter, we use the Hughes model in one space-dimension to represent the evacuation of a corridor with two exits. The model couples a conservation law with discontinuous flux to an eikonal equation. We implement the wave front tracking scheme, treating explicitly the solution nonclassical behavior at the turning point, to provide a reference solution, which is used to numerically test the convergence of classical finite volume schemes. In the second chapter, we model the crossing of two groups of pedestrians walking in opposite directions with a system of conservation laws whose flux depends on the two densities. This system loses its hyperbolicity for certain density values. We assist to the rising of persistent but bounded oscillations, that lead us to the recast of the problem in the framework of measure-valued solutions. Finally we study a nonlocal model of pedestrian flow in two space-dimensions. The model consists of a conservation law whose flux depends on a convolution of the density. With this model, we solve an optimization problem for a room evacuation with a descent method, evaluating the impact of the explicit computation of the cost function gradient with the adjoint state method rather than approximating it with finite differences.
38

Kontrollierte natürliche Lüftung in Büro- und Verwaltungsgebäuden: Ein Beitrag zur Steigerung von Energieeffizienz und Nutzerbehaglichkeit

Scheuring, Leonie 26 August 2022 (has links)
Es ist ein politisch erklärtes Ziel, den Ausstoß von klimaschädlichen Treibhausgasen weltweit zu verringern. Eine wesentliche Stellschraube im Gebiet des Bauwesens stellt hierbei die Einsparung von Energien zur Raumkonditionierung dar. Diese wird unter anderem über das Lüftungskonzept beeinflusst. Die Belüftung von Gebäuden ist zwingend notwendig, um die Emissionen der Baustoffe und die der Menschen, beispielsweise ihren CO2-Ausstoß über die Atmung, abzuführen und der Schimmelbildung vorzubeugen. Erfolgt die Belüftung über öffenbare Fenster – natürliche Lüftung – wird so allerdings energetisch aufwändig temperierte Raumluft mit untemperierter Außenluft ausgetauscht. Daraus können Wärmeverluste und thermisches Unbehagen resultieren. Energieeffiziente Technologien sind ventilatorgestützte Lüftungssysteme mit Wärmerückgewinnung. Doch nicht für alle Gebäudekonzepte und Nutzer stellen diese Lüftungskonzepte einen hohen Nutzerkomfort dar. Korrelationen zwischen Gebäuden mit ventilatorgestützten Lüftungsystemen und dem Sick-Building-Syndrom sind in der Literatur beschrieben, während hier für natürliche Lüftungskonzepte keine Korrelation besteht. Stattdessen wird in Nutzerbefragungen der natürlichen Lüftung eine hohe Akzeptanz zugeschrieben. Mit elektrisch angetriebenen Fenstern kann die natürliche Lüftung nutzerunabhängig gesteuert und so Wärmeverluste und thermisches Unbehagen kontrolliert werden. Bisher sind die Auslegungen solcher kontrollierten natürlichen Lüftungskonzepte noch sehr planungsintensiv. Das Ziel der Arbeit ist es, für Büro- und Verwaltungsgebäude Öffnungs- und Schließsignale einer kontrollierten natürlichen Lüftung zu geben. Diese zeichnen sich darüber aus, dass sie ein gesundes Raumklima, eine hohe Nutzerbehaglichkeit und Energieeffizienz über den Jahresverlauf schaffen und auf ihre Robustheit gegenüber Änderungen von Gebäuderandbedingungen überprüft sind. Für das Ziel wird ein über CO2- und Temperatursensoren gesteuertes Fenstersystem mittels dynamisch thermischer Gebäudesimulationen in vier Varianten von Schließsignalen auf thermische Behaglichkeit und Energiebedarf untersucht. Die Grundlage dazu stellt die bezüglich Entwurf, Konstruktion und Nutzung allgemeingültige Entwicklung eines Büroraums dar. Der Büroraum wird im Simulationsmodell abgebildet und in Realität errichtet. Die Kombination von Simulationsmodell und realem, als experimentellem Teststand ausgeführtem Büroraum ermöglicht verifizierte Ergebnisse. So werden vier Berechnungsmodelle für Luftvolumenströme von Fenstern über den Teststand verifiziert. Dazu dienen Luftwechselmessungen nach der Konstantinjektionsmethode an 173 Fensteröffnungen für fünf Außentemperatur- und elf Windgeschwindigkeitsbereiche. Das Berechnungsmodell nach DIN EN 16798-7 zeigt sich als realitätsnah. Da dieses Berechnungsmodell nicht im Gebäudesimulationsprogramm implementiert ist, wird eine Methode zur Implementierung entwickelt. Über das entwickelte Simulationsmodell zeigt sich, dass eine kombinierte CO2- und temperaturgesteuerte kontrollierte natürliche Lüftung nur zweimal im Jahr ihre Grenzwerte zur Fensteröffnung und -schließung variieren muss, um ganzjährig eine hohe Energieeffizienz und Nutzerbehaglichkeit zu schaffen. Die Schließsignale des sensorgesteuerten Fenstersystems werden in eine Zeitsteuerung überführt. Es zeigt sich, dass für die kühlen Monate jede Öffnung mit identischer Dauer angesetzt werden darf. In wärmeren Monaten muss die Öffnungsdauer in Abhängigkeit der Außentemperatur angepasst werden, so dass eine Zeitsteuerung mit einer Außentemperaturmessung gekoppelt werden muss. Die Ergebnisse zeigen, dass über eine Variation der Schließsignale einer kontrollierten natürlichen Lüftung die Energieeffizienz und die thermische Behaglichkeit wesentlich gesteigert werden und dass selbst bei geringen Windgeschwindigkeiten und Temperaturdifferenzen die Raumluftqualität stets gewährleistet ist. Für nahezu alle Standorte in Deutschland kann die kontrollierte natürliche Lüftung so den Kühlbedarf der untersuchten Büroräume eliminieren, ohne in einer sommerlichen Überhitzung der Räume zu resultieren. Die entwickelten und bezüglich Raumluftqualität und thermischer Behaglichkeit charakterisierten Sensor- und Zeitsteuerungen tragen dazu bei, die kontrollierte natürliche Lüftung als wartungsarme, technikreduzierte Alternative zu der ventilatorgestützten Lüftung zu etablieren.:1 Einleitung 2 Natürliche Lüftung 3 Kontrollmöglichkeiten der natürlichen Lüftung 4 Entwicklung der Untersuchungsmodelle 5 Voruntersuchungen 6 Sensorsteuerung für den Basisraum 7 Zeitsteuerung für den Basisraum 8 Übertragung auf unterschiedliche Gebäuderandbedingungen 9 Diskussion und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur 12 Abbildungsnachweis 13 Bezeichnungen 14 Anhang / It is a politically declared goal to reduce the emission of climate-damaging greenhouse gases worldwide. To support this goal by the building industry a key driver is the saving of energy for room conditioning. Among other factors, this is influenced by the ventilation concept. Also the ventilation of buildings is absolutely necessary in order to remove the emissions of the building materials and those of the people, for example their CO2 emissions through breathing as well as to prevent mould. However, if ventilation is carried out via openable windows - natural ventilation - then energetically expensive tempered room air is exchanged with cold outside air. This could result in heat loss and thermal discomfort. Mechanical ventilation systems with heat recovery are energy-efficient technologies. However, these ventilation concepts do not represent a high level of user comfort for all building concepts and users. Correlations between buildings with mechanical ventilation systems and sick building syndrome are described in the literature, while there is no such correlation for natural ventilation concepts. Instead, a high level of acceptance is attributed to it in user surveys. With electrically driven and controlled windows, natural ventilation can be controlled independently from the user, thus minimizing heat loss and thermal discomfort. So far, the design of such controlled natural ventilation concepts is still very planning-intensive. The aim of this work is to provide opening and closing signals for controlled natural ventilation in office buildings. These are characterized for their capability to create a high indoor air quality, high user comfort and high energy efficiency over the course of the year and are tested for their robustness against changes in building characteristics. To achieve this goal, a window system controlled by CO2 and temperature sensors is examined for its impact on thermal comfort and energy demand by means of building simulation tools with four variants of closing signals. As a basis for this examination an office room is utilized that conforms to the current standards in terms of design, construction and use. The office space is transferred to a simulation model and constructed in reality. The combination of the simulation model and the real office space, which is designed as an experimental test rig, enables verified results. Thus, four calculation models for air flow volumes of windows are verified via the test rig. Air exchange measurements according to the constant injection method on 173 window openings for five outdoor temperature and eleven wind speed ranges are used for this purpose. The calculation model according to DIN EN 16798-7 proves to be close to reality. Since this calculation model is not implemented in the building simulation program, a method for its implementation is developed. Using the developed simulation model, it is shown that a combined CO2- and temperature-controlled natural ventilation creates a high energy efficiency and user comfort throughout the year by varying its limit values for window opening and closing only twice a year. The closing signals of the sensor controlled window system are transferred to a time control system. It turns out that for the cold months, each opening could be set to the same opening time. In warmer months, the opening time must be adjusted depending on the outside temperature. Thus, a time control should be coupled with an outside air temperature measurement. The results show that by varying the closing signals of a controlled natural ventilation system, the energy efficiency and thermal comfort is significantly increased and that a high indoor air quality is always guaranteed even at low wind speeds and low temperature differences. For almost all locations in Germany, controlled natural ventilation can thus eliminate the cooling requirements in the office spaces studied without overheating in the summer. The developed sensor and time control systems are characterized by high indoor air quality and good thermal comfort. Thus, these systems are a contribution to promote controlled natural ventilation as a low-maintenance and technically reduced alternative to mechanical ventilation.:1 Einleitung 2 Natürliche Lüftung 3 Kontrollmöglichkeiten der natürlichen Lüftung 4 Entwicklung der Untersuchungsmodelle 5 Voruntersuchungen 6 Sensorsteuerung für den Basisraum 7 Zeitsteuerung für den Basisraum 8 Übertragung auf unterschiedliche Gebäuderandbedingungen 9 Diskussion und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur 12 Abbildungsnachweis 13 Bezeichnungen 14 Anhang

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