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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.
391

[en] CRITERIA FOR DETERMINATION OF THE VOLTAGE STABILITY MARGIN FROM THE PERSPECTIVE OF THE OPERATION / [pt] CRITÉRIO PARA DETERMINAÇÃO DA MARGEM DE ESTABILIDADE DE TENSÃO SOB A PERSPECTIVA DA OPERAÇÃO

AMANDA ALVARENGA DIAS 12 November 2020 (has links)
[pt] Atualmente, o fenômeno de instabilidade de tensão representa uma das principais barreiras à operação estável das redes de energia elétrica, que tendem a crescer e a se tornarem cada vez mais interconectadas. A dificuldade de manter um perfil de tensão aceitável aumenta substancialmente e a estabilidade de tensão na operação dos sistemas elétricos deve ser preservada ao máximo, a fim de evitar os graves efeitos que a sua perda acarreta ao sistema. Esta dissertação atua na operação do sistema de energia elétrica, mais especificamente na área de operação em tempo real, onde é importante se conhecer a proximidade da condição operativa atual do sistema daquela que corresponde ao ponto crítico de estabilidade. Tal conhecimento permite que ações preventivas sejam realizadas no sentido de se evitar a instabilidade. O objetivo do trabalho é, a partir da comparação entre a margem sistêmica e a margem nodal, calculadas respectivamente pelo Fluxo de Potência Continuado e pelo método da Matriz D, determinar um critério para a margem de capacidade de carga, do ponto de vista de estabilidade de tensão, para a operação segura. No evento de cada contingência, calcula-se o maior crescimento de carga (margem), a partir do caso base, onde os índices nodais ainda são positivos. Define-se como margem mínima a menor dessas margens. A abordagem proposta foi avaliada através dos resultados obtidos com uma versão modificada do chamado sistema Nordic32. / [en] Currently, the phenomenon of voltage instability represents one of the main barriers to the stable operation of electric power networks, which tend to grow and become increasingly interconnected. The difficulty of maintaining an acceptable voltage profile increases substantially and the voltage stability in the operation of the electrical systems must be preserved to the maximum extent in order to avoid the serious effects that its loss entails on the system. This dissertation works in the operation of the electrical system, more specific in the area of operation in real time, where it is important to know the proximity of the operational condition of the current system that corresponds to the critical point of stability. Such knowledge allows preventive actions to be taken in order to avoid instability. The determination of appropriate margins for the various activities carried out in the electric power systems is not a trivial task, motivating the development of this dissertation. The objective of the work is from the comparison between a systemic margin and the nodal margin, calculated respectively by the Continued Power Flow and by the Matrix D method, to determine a criterion for the load capacity margin from the voltage stability point of view, for safe operation. In the event of each contingency, the largest growth (margin) is calculated from the base case, where the nodal indices are still positive. The smallest margin is defined as the minimum margin. The proposed approach was evaluated through the results obtained with a modified version of the so-called Nordic32 test system.
392

[en] USING ELECTRIC CIRCUIT EQUIVALENTS FOR VOLTAGE STABILITY ASSESSMENT / [pt] UTILIZAÇÃO DE CIRCUITOS ELÉTRICOS EQUIVALENTES NA AVALIAÇÃO DAS CONDIÇÕES DE ESTABILIDADE DE TENSÃO

LAURA CRISTINA PANIAGUA PALACIO 08 June 2015 (has links)
[pt] O surgimento do fenômeno de estabilidade de tensão na operação dos sistemas elétricos motivou centenas de pesquisadores a desenvolverem métodos que permitam detectar a proximidade à instabilidade de tensão, com eficiência computacional, e tomar medidas acertadas para garantir a operação confiável e segura. Neste trabalho são analisados diferentes métodos que permitem transformar sistemas de grande porte em circuitos simples: o circuito equivalente entre geradores e cargas, baseado no cálculo de correntes de curto-circuito, na técnica de redução de rede pela eliminação de barras intermediárias e no equivalente de Thévenin. É analisada a utilização destes equivalentes na avaliação das condições de estabilidade de tensão com sistemas-testes de 3 e 4 barras. Através de diferentes testes verificou-se que o circuito equivalente entre geradores e cargas e a técnica de redução de rede não podem ser usados para o cálculo de índices de avaliação das condições de estabilidade de tensão, enquanto que, usando circuito equivalente de Thévenin encontrou-se um método que funciona corretamente para barra de carga terminal, barra não-terminal e barra de tensão controlada por gerador. / [en] The emergence of voltage stability phenomenon in the operation of power systems has motivated hundreds of researchers to develop methods to detect the proximity to voltage instability, with computational efficiency and to take all necessary and appropriate measures to ensure reliable and safe operation. In this work, different methods that allow transforming large systems into simple circuits were analyzed, such as the equivalent circuit between generators and loads, based on the calculation of short-circuit currents; the network reduction technique for eliminating intermediate buses; and the Thévenin equivalent. The application of these equivalents on voltage stability assessment of 3 and 4 bus testing systems were extensively tested. At the end, it was verified that that the equivalent circuit between the generator and load, and the network reduction technique, cannot be used for calculating the voltage stability conditions evaluation indexes. However, using Thévenin equivalent circuit, it was found a proper method, which works correctly for terminal buses, transit buses and voltage-controlled buses.
393

SYSTEM-LEVEL SEISMIC PERFORMANCE QUANTIFICATION OF REINFORCED MASONRY BUILDINGS WITH BOUNDARY ELEMENTS

Ezzeldin, Mohamed January 2017 (has links)
The traditional construction practice used in masonry buildings throughout the world is limited to walls with rectangular cross sections that, when reinforced with steel bars, typically accommodate only single-leg horizontal ties and a single layer of vertical reinforcement. This arrangement provides no confinement at the wall toes, and it may lead to instability in critical wall zones and significant structural damage during seismic events. Conversely, the development of a new building system, constructed with reinforced masonry (RM) walls with boundary elements, allows closed ties to be used as confinement reinforcement, thus minimizing such instability and its negative consequences. Relative to traditional walls, walls with boundary elements have enhanced performance because they enable the compression reinforcement to remain effective up to much larger displacement demands, resulting in a damage tolerant system and eventually, more resilient buildings under extreme events. Research on the system-level (complete building) performance of RM walls with boundary elements is, at the time of publication of this dissertation, nonexistent in open literature. What little research has been published on this innovative building system has focused only on investigating the component-level performance of RM walls with boundary elements under lateral loads. To address this knowledge gap, the dissertation presents a comprehensive research program that covered: component-level performance simulation; system-level (complete building) experimental testing; seismic risk assessment tools; and simplified analytical models to facilitate adoption of the developed new building system. In addition, and in order to effectively mobilize the knowledge generated through the research program to stakeholders, the work has been directly related to building codes in Canada and the USA (NBCC and ASCE-7) as well as other standards including FEMA P695 (FEMA 2009) (Chapter 2), TMS 402 and CSA S304 (Chapter 3), FEMA P58 (FEMA 2012) (Chapter 4), and ASCE-41 (Chapter 5). Chapter 1 of the dissertation highlights its objectives, focus, scope and general organization. The simulation in Chapter 2 is focused on evaluating the component-level overstrength, period-based ductility, and seismic collapse margin ratios under the maximum considered earthquakes. Whereas previous studies have shown that traditional RM walls might not meet the collapse risk criteria established by FEMA P695, the analysis presented in this chapter clearly shows that RM shear walls with boundary elements not only meet the collapse risk criteria, but also exceed it with a significant margin. Following the component-level simulation presented in Chapter 2, Chapter 3 focused on presenting the results of a complete two-story asymmetrical RM shear wall building with boundary elements, experimentally tested under simulated seismic loading. This effort was aimed at demonstrating the discrepancies between the way engineers design buildings (as individual components) and the way these buildings actually behave as an integrated system, comprised of these components. In addition, to evaluate the enhanced resilience of the new building system, the tested building was designed to have the same lateral resistance as previously tested building with traditional RM shear walls, thus facilitating direct comparison. The experimental results yielded two valuable findings: 1) it clearly demonstrated the overall performance enhancements of the new building system in addition to its reduced reinforcement cost; and 2) it highlighted the drawbacks of the building acting as a system compared to a simple summation of its individual components. In this respect, although the slab diaphragm-wall coupling enhanced the building lateral capacity, this enhancement also meant that other unpredictable and undesirable failure modes could become the weaker links, and therefore dominate the performance of the building system. Presentation of these findings has attracted much attention of codes and standards committees (CSA S304 and TMS 402/ACI 530/ASCE 5) in Canada and the USA, as it resulted in a paradigm shift on how the next-generation of building codes (NBCC and ASCE-7) should be developed to address system-levels performance aspects. Chapter 4 introduced an innovative system-level risk assessment methodology by integrating the simulation and experimental test results of Chapters 2 and 3. In this respect, the experimentally validated simulations were used to generate new system-level fragility curves that provide a realistic assessment of the overall building risk under different levels of seismic hazard. Although, within the scope of this dissertation, the methodology has been applied only on buildings constructed with RM walls with boundary elements, the developed new methodology is expected to be adopted by stakeholders of other new and existing building systems and to be further implemented in standards based on the current FEMA P58 risk quantification approaches. Finally, and in order to translate the dissertation findings into tools that can be readily used by stakeholders to design more resilient buildings in the face of extreme events, simplified backbone and hysteretic models were developed in Chapter 5 to simulate the nonlinear response of RM shear wall buildings with different configurations. These models can be adapted to perform the nonlinear static and dynamic procedures that are specified in the ASCE-41 standards for both existing and new building systems. The research in this chapter is expected to have a major positive impact, not only in terms of providing more realistic model parameters for exiting building systems, but also through the introduction of analytical models for new more resilient building systems to be directly implemented in future editions of the ASCE-41. This dissertation presents a cohesive body of work that is expected to influence a real change in terms of how we think about, design, and construct buildings as complex systems comprised of individual components. The dissertation’s overarching hypothesis is that previous disasters have not only exposed the vulnerability of traditional building systems, but have also demonstrated the failure of the current component-by-component design approaches to produce resilient building systems and safer communities under extreme events. / Dissertation / Doctor of Philosophy (PhD)
394

Body-Safe Apocalypse : Sexual Materiality and Frameworks for Design During and Beyond Collapse / Body-Safe Apocalypse : Sexual Materiality and Frameworks for Design During and Beyond Collapse

Carr, Joshua (Ev) January 2023 (has links)
Following the Covid-19 pandemic, a relatively mild global disruption, our global society experienced large-scale shortages of high-tech materials, the increasing cost or absence of many commodities usually taken for granted, and the floundering of industries that facilitate our global industrial civilisation such as shipping and aviation. By comparison, catastrophic climate change stands to be far more devastating.  Body-Safe Apocalypse is an attempt to encourage a shift in thinking and practice away from the presumed possibility of eternal “sustainable” growth within a digital, high-tech global context and towards a practical, grounded framework of understanding, preparing for, and working beyond the collapse of global, high-tech, industrial civilisation. The method of exploration is through an analysis of sexual materiality, the contextualisation of sexual and broader materiality within a failing industrial civilisation, and the creation of a sex toy using materials and processes accessible in a collapsing/collapsed global civilisation.  As well as focusing on the craft and materiality of sexual practices in a collapse context, Body-Safe Apocalypse provides theoretical framework on collapse meant to address a current gap in design literature, critique on the current Western/anglo design paradigm that is yet to consider the catastrophic as non-speculative, and encouragement to designers to look into- and then beyond- the upheavals and endings of the systems most of us have built our lives/careers around and upon.
395

Violence Against the Elite : A Comparative Analysis of two Terminal Classic Mass Graves in Cancuén / Våld mot eliten : En komparativ analys av två massgravar från senklassiska perioden i Cancuén

Wallbing Kenney, Nayelli January 2023 (has links)
In this essay a comparative analysis will be conducted on two mass graves from the terminal classics in the Maya lowlands. This will be done by analysing interpretations of the Cancuén site in Guatemala. Cancuén was a major trading port city in the terminal classics’ southern lowlands. It flourished until its decline in the late 700’s CE. Around the year 800 CE a violent event led to the death of close to 50 elite individuals including the king of Cancuén. Two mass graves have been discovered in the hydraulic system of the city. Individuals in both mass graves represent a variety of ages and genders. A comparative analysis of osteological similarities and differences in the two graves will be based on osteological reports. Previously published work regarding interpretations of the mass graves will be used in an analysis of possible motives behind massacre. Trauma evident in the mass graves as well as their surrounding context suggests that a termination ritual took place after the massacre that the victims were subjected to. / I denna uppsats utförs en komparativ analys av två massgravar från senklassiska perioden i Mayarikets Cancuén, Guatemala. Cancuén var en hamnstad med stort inflytande i låglandet under den senklassiska epoken. Stadens tillväxt av influens och ekonomi skedde under det sena 700–talet e.vt. En våldsam händelse ca 800 e.vt ledde till döden av 50 individer av Cancuéns elit samt stadens egna kung. Två massgravar har påträffats i stadens hydraulsystem. Båda massgravar visar på en variation demografi för både sex och kön. En komparativ analys av osteologiska likheter och skillnader i massgravarna har baserats på osteologiska rapporter. Tidigare publikationer används i en analys av potentiella motivationer bakom massakern. Skeletal trauma i massgravarna samt dess omkringliggande kontext indikerar att en terminations ritual tagit palts efter massakern.
396

SN2005da: A Spectroscopic and Photometric Analysis of a Peculiar Type Ic Supernova

Williamson, Jacob 22 June 2017 (has links)
No description available.
397

Collapse Experiments and Assessment of Masonry Wall Buildings

Li, Kai January 2017 (has links)
No description available.
398

Observational Signatures of the Macroscopic Formation of Strange Matter during Core Collapse Supernovae

Zach, Juergen Johann 05 August 2003 (has links)
No description available.
399

The Aesthetics of Anxiety: Making in a Time of Environmental Collapse

Murphy, Laura L. 16 August 2012 (has links)
No description available.
400

Modellering och robusthetsanalys med parametrisk design : Effektivare visualisering av alternativa lastvägar vid bortfall av pelare

Kayhan, Özge, Mohamed, Zahra January 2020 (has links)
Today, 3D modelling and structural analysis of buildings are performed in various software. Collaboration between various software is common today but breaks the flow in the construction design phase. To achieve an uninterrupted flow in the construction design phase, a constellation of modelling and structural analysis is needed in a single software. To enable a constellation, there are today many developed digital methods for this.Parametric design is a digital method that is mostly used to handle complex shapes. In recent years, the parametric design has evolved even more and the algorithmic thinking in parametric design provides opportunities for performing structural analyses. The development includes various plug-in programs that have structural analysis capabilities. However, this degree project emphasizes that this can be achieved without a plug-in program that has structural analysis capabilities. With only one visualization program and a plug-in that handles visual programming, the ability to produce what is to be visualized with a script arises.The structural analysis in this thesis includes robustness analysis that is important in the context of progressive collapse, and only the alternative load path method is considered. Progressive collapse is an important analysis for buildings that arise due to known or unknown accident loads. To increase the redundancy of the bearing structure, the alternative load path method can be used, which is a branch under unknown accident loads.Robustness analysis is a time-consuming process and automation can make this more efficient. With parameter-driven modelling and robustness analysis, the constructor can indicate at an early stage possible structure failure before the building is completed. Early action also leads to a reduction in waste of material resources.The alternative load path method provides the possibility to analyze whether the building receives alternate load path in the event of loss of load-bearing elements. This research report analyses column loss. Automated visualization of alternate load path enables to be able to analyze the load redistribution after the loss of column.Today some buildings are at risk against the progressive collapse, people's lives and health are therefore at risk when all or part of the building collapses. That is why efficiency is needed. The research report showed that the script automated the modelling and robustness analysis of buildings. Two different loss scenarios were analyzed and the authors found different updated loading areas and load redistribution.

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