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Due to power system deregulations, transmission expansion not keeping up with the load growth, and higher frequency of natural hazards resulting from climate change, major blackouts are becoming more frequent and are spreading over larger regions, entailing higher losses and costs to the economy and the society of many countries in the world. Large-scale blackouts typically result from cascading failure originating from a local event, as typified by the 2003 U.S.-Canada blackout. Their mitigation in power system planning calls for the development of methods and algorithms that assess the risk of cascading failures due to relay over-tripping, short-circuits induced by overgrown vegetation, voltage sags, line and transformer overloading, transient instabilities, voltage collapse, to cite a few. How to control the economic losses of blackouts is gaining a lot of attention among power researchers. In this research work, we develop new Monte Carlo methods and algorithms that assess and manage the risk of cascading failure in composite reliability of deregulated power systems. To reduce the large computational burden involved by the simulations, we make use of importance sampling techniques utilizing the Weibull distribution when modeling power generator outages. Another computing time reduction is achieved by applying importance sampling together with antithetic variates. It is shown that both methods noticeably reduce the number of samples that need to be investigated while maintaining the accuracy of the results at a desirable level. With the advent of microgrids, the assessment of their benefits in power systems is becoming a prominent research topic. In this research work, we investigate their potential positive impact on power system reliability while performing an optimal coordination among three energy sources within microgrids, namely renewable energy conversion, energy storage and micro-turbine generation. This coordination is modeled when applying sequential Monte Carlo simulations, which seek the best placement and sizing of microgrids in composite reliability of a deregulated power system that minimize the risk of cascading failure leading to blackouts subject to fixed investment budget. The performance of the approach is evaluated on the Roy Billinton Test System (RBTS) and the IEEE Reliability Test System (RTS). Simulation results show that in both power systems, microgrids contribute to the improvement of system reliability and the decrease of the risk of cascading failure. / Ph. D.

Winter Storm Uri damaged parts of the United States, Mexico, and Canada in February of 2021. The State of Texas was heavily affected due to the institutional failure of Texas's primary power provider, the Electric Reliability Council of Texas (ERCOT). Despite similar previous storms that exposed weaknesses in the state's power grid system in 1999 and 2011, ERCOT did not make the necessary changes to prevent a future disaster. The purpose of this study is to advance the understanding of the concept of recreancy through the exploration of eight different dimensions of the concept: trust or distrust in institutions; institutional responsibility for disaster preparedness; responsibility for impacts of a disaster; effectiveness or ineffectiveness of institutions in responding to a disaster; an institution's capability of preventing a similar event in the future; an institution's willingness to make changes in their actions or behavior; confidence that an institution will prevent a similar event in the future; and responsibility for compensation for impacts of a disaster. To examine the composition of the concept of recreancy, I analyzed survey data collected in Texas during April and May of 2022. I aggregated and coded survey data according to the level respondents reported to agree with the survey indicators measuring dimensions of recreancy. I utilized Confirmatory Factor Analysis to analyze if the derived dimensions of recreancy measure recreancy, and if some are more salient than others. Confirmatory Factor Analysis revealed variability in the importance of different dimensions of recreancy, suggesting that some dimensions are more salient than others in shaping residents' perceptions of recreancy in the context of Winter Storm Uri. Further analysis revealed a preliminary model to operationalize recreancy, however further analysis is needed. / Master of Science / In February 2021, Winter Storm Uri devasted regions of the United States, Mexico, and Canada. The state of Texas experienced significant storm impacts due to the failure of its primary power provider, the Electric Reliability Council of Texas (ERCOT). ERCOT is responsible for overseeing and managing the state's power grid. Similar storms in 1999 and 2011 revealed weaknesses in the power grid's infrastructure—state officials mandated but did not require weatherization precautions to prevent future grid failures. ERCOT did not implement the suggested changes and the power grid failure during Winter Storm Uri left millions of Texas residents without access to power, heat, water, and other necessary services. This thesis explores residents' perceptions of ERCOT's institutional failure—recreancy—and aims to understand the concept of recreancy through the examination of eight dimensions: trust or distrust in institutions; institutional responsibility for disaster preparedness; responsibility for impacts of a disaster; effectiveness or ineffectiveness of institutions in responding to a disaster; an institution's capability of preventing a similar event in the future; an institution's willingness to make changes in their actions or behavior; confidence that an institution will prevent a similar event in the future; and responsibility for compensation for impacts of a disaster. I analyzed survey respondents' levels of agreement with each dimension and utilized Confirmatory Factor Analysis to assess the relative importance of the dimensions and if they accurately capture recreancy.

This diploma thesis covers a solution of designing the information system for HNS mechanix ltd. This company provides auditorial services of optical products. During the desining not only the requirements of functionality and attributes of the system itself but also implementation and developing tools are necessary to be followed. The system is required to be available as WWW service with multilevel user access.

An den automobilen Entwicklungsprozess werden zunehmend Anforderungen hinsichtlich der Verkürzung von Entwicklungszeiten, der Verringerung von Entwicklungskosten sowie der Verlagerung der Entwicklung hin zu frühen Entwicklungsphasen gestellt. Um diese Anforderungen zukünftig erfüllen zu können, ist es notwendig, geeignete Prozesse und Entwicklungsmethoden zu erarbeiten, die bereits in frühen Entwicklungsphasen zu robusten Konzepten führen. In der vorliegenden Arbeit wird dazu eine Fahrwerkauslegungsmethode für die Konzeptphase entwickelt, mit der es entsprechend des V-Entwicklungsmodells innerhalb von zwei Auslegungsschritten möglich ist, aus Gesamtfahrzeugeigenschaftszielen für Fahrdynamik und Fahrkomfort Subsystemziele für den Reifen, die Achskinematik und Achselastokinematik sowie für die Lenkung abzuleiten. Die entwickelte Auslegungsmethode basiert auf dem Target-Cascading-Ansatz und nutzt effektive Achscharakteristika, um die Wirkzusammenhänge innerhalb des Fahrwerks während der Auslegung aufzuzeigen. Mithilfe der in dieser Arbeit entwickelten Auslegungsmethodik ist ein wichtiger Beitrag zur zielgerichteten Ableitung von Fahrwerkeigenschaften geschaffen, der eine deutliche Verkürzung der Entwicklungszeiten und der damit einhergehenden Entwicklungskosten innerhalb der frühen Entwicklungsphase des Fahrwerks ermöglicht.:Vorwort und Danksagung Kurzfassung und Abstract Nomenklatur 1. Einführung 1.1. Motivation zur Entwicklung einer Fahrwerkauslegungsmethode für die Konzeptphase 1.2. Zielstellung und Struktur der Arbeit 1.3. Eingrenzung der Aufgabenstellung 2. Wissenschaftliche Grundlagen 2.1. Konzeptphase im Automobil-Entwicklungsprozess 2.2. Arbeitsraum des Fahrzeugs eines Normalfahrers 2.2.1. Fahrgeschwindigkeiten 2.2.2. Längs- und querdynamischer Arbeitsraum 2.2.3. Vertikaldynamischer Arbeitsraum 2.3. Objektivierung des Fahrverhaltens 2.3.1. Objektivierung der Längs- und Querdynamik 2.3.2. Objektivierung der Vertikaldynamik 2.4. Stand der Technik hinsichtlich Achsauslegungsmethoden 2.4.1. Klassische Auslegungsmethoden 2.4.2. Auslegungsmethoden auf Basis von Optimierungsalgorithmen 2.4.3. Wissensbasierte und strukturelle Auslegungsmethoden 2.4.4. Mischansätze 2.5. Zusammenfassung und Diskussion 3. Identifikation und Analyse relevanter Fahrwerkeigenschaften zur Integration in die Auslegungsmethode 3.1. Untersuchung der Subsystemeigenschaften der elektromechanischen Lenkung 3.2. Untersuchung der Subsystemeigenschaften der Achsen 3.2.1. Kinematische Achseigenschaften 3.2.2. Elastokinematische Achseigenschaften 3.2.3. Dämpfungseigenschaften der Achse 3.3. Untersuchung der Subsystemeigenschaften des Reifens 3.4. Zusammenfassung 4. Aufbau eines analytisch-physikalischen Wirkkettenverständnisses zwischen Gesamtfahrzeug- und Subsystemverhalten 4.1. Ableitung von Einfachmodellen zur Beschreibung der analytischen Wirkzusammenhänge 4.1.1. Einfachmodell zur Beschreibung der querdynamischen Wirkzusammenhänge 4.1.2. Einfachmodell zur Beschreibung der längs- und vertikaldynamischen Wirkzusammenhänge 4.2. Validierung der Einfachmodelle 4.2.1. Validierung des Einfachmodells zur Beschreibung der Querdynamik 4.2.2. Validierung des Einfachmodells zur Beschreibung der Längs- und Vertikaldynamik 4.3. Zusammenfassung 5. Entwicklung einer Achsauslegungsmethode für die Konzeptphase der Fahrwerkentwicklung 5.1. Strukturierung des Auslegungsprozesses 5.1.1. Definition und Herleitung der effektiven Achscharakteristika 5.1.2. Aufbau und Eigenschaften der effektiven Achscharakteristika 5.2. Detaillierung der Auslegungsmethode 5.2.1. Definition der objektiven Gesamtfahrzeugeigenschaften 5.2.2. Auslegung in Schritt 1 5.2.3. Auslegung in Schritt 2 5.2.4. Umsetzbarkeit der abgeleiteten Subsystemeigenschaften 5.3. Erweiterung und Automatisierung der Auslegungsmethode 5.3.1. Grundprinzip des Solution-Space-Algorithmus 5.3.2. Anpassung und Integration des Solution-Space-Algorithmus in die Achsauslegungsmethode 5.4. Zusammenfassung 6. Untersuchung und Evaluation der Achsauslegungsmethode anhand einer Beispielauslegung 6.1. Zielwertdefinition auf Basis einer Wettbewerbsanalyse 6.1.1. Längsdynamik 6.1.2. Querdynamik 6.1.3. Vertikaldynamik 6.1.4. Zusammenfassung der Zielanforderungen 6.2. Beispielauslegung auf Basis der manuellen Achsauslegungsmethode 6.2.1. Auslegung in Schritt 1 6.2.2. Auslegung in Schritt 2 6.2.3. Ergebnis der Auslegung, Umsetzbarkeit und Zielerreichung 6.3. Beispielauslegung auf Basis der erweiterten automatisierten Achsauslegungsmethode 6.3.1. Auslegung in Schritt 1 6.3.2. Auslegung in Schritt 2 6.4. Vergleich zu bisherigen Methoden 6.5. Zusammenfassung 7. Zusammenfassung und Handlungsempfehlung Literaturverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Anhang A.1. Konzepteigenschaften des Beispielfahrzeugs A.2. Kinematische Achseigenschaften des Beispielfahrzeugs A.3. Elastokinematische Achseigenschaften des Beispielfahrzeugs A.3.1. Einfluss der Längskraft auf die Radstellung A.3.2. Einfluss des Spinmoments auf die Radstellung A.3.3. Einfluss der Seitenkraft und des Sturzmoments auf die Radstellung A.3.4. Einfluss des Rückstellmoments auf die Radstellung A.3.5. Einfluss der Vertikalkraft auf die Radstellung A.4. Erstellung eines Allgemeinmodells zur Beschreibung des Fahrverhaltens A.5. Herleitung der verwendeten Simulationsmodelle A.5.1. Einfachmodell zur Beschreibung der Querdynamik A.5.2. Einfachmodell zur Beschreibung der Längs- und Vertikaldynamik A.6. Ableitung der Übersetzungen und Nachgiebigkeiten A.7. Vergleich des Fahrzeugverhaltens vor und nach der Auslegung mithilfe der entwickelten Auslegungsmethode

Doctor of Philosophy / Department of Electrical and Computer Engineering / Caterina Scoglio / Critical infrastructures are repeatedly attacked by external triggers causing tremendous amount of damages. Any infrastructure can be studied using the powerful theory of complex networks. A complex network is composed of extremely large number of different elements that exchange commodities providing significant services. The main functions of complex networks can be damaged by different types of attacks and failures that degrade the network performance. These attacks and failures are considered as disturbing dynamics, such as the spread of viruses in computer networks, the spread of epidemics in social networks, and the cascading failures in power grids. Depending on the network structure and the attack strength, every network differently suffers damages and performance degradation. Hence, quantifying the robustness of complex networks becomes an essential task. In this dissertation, new metrics are introduced to measure the robustness of technological and social networks with respect to the spread of epidemics, and the robustness of power grids with respect to cascading failures. First, we introduce a new metric called the Viral Conductance ($VC_{SIS}$) to assess the robustness of networks with respect to the spread of epidemics that are modeled through the susceptible/infected/susceptible ($SIS$) epidemic approach. In contrast to assessing the robustness of networks based on a classical metric, the epidemic threshold, the new metric integrates the fraction of infected nodes at steady state for all possible effective infection strengths. Through examples, $VC_{SIS}$ provides more insights about the robustness of networks than the epidemic threshold. In addition, both the paradoxical robustness of Barab\'si-Albert preferential attachment networks and the effect of the topology on the steady state infection are studied, to show the importance of quantifying the robustness of networks. Second, a new metric $VC_$ is introduced to assess the robustness of networks with respect to the spread of susceptible/infected/recovered ($SIR$) epidemics. To compute $VC_$, we propose a novel individual-based approach to model the spread of $SIR$ epidemics in networks, which captures the infection size for a given effective infection rate. Thus, $VC_$ quantitatively integrates the infection strength with the corresponding infection size. To optimize the $VC_$ metric, a new mitigation strategy is proposed, based on a temporary reduction of contacts in social networks. The social contact network is modeled as a weighted graph that describes the frequency of contacts among the individuals. Thus, we consider the spread of an epidemic as a dynamical system, and the total number of infection cases as the state of the system, while the weight reduction in the social network is the controller variable leading to slow/reduce the spread of epidemics. Using optimal control theory, the obtained solution represents an optimal adaptive weighted network defined over a finite time interval. Moreover, given the high complexity of the optimization problem, we propose two heuristics to find the near optimal solutions by reducing the contacts among the individuals in a decentralized way. Finally, the cascading failures that can take place in power grids and have recently caused several blackouts are studied. We propose a new metric to assess the robustness of the power grid with respect to the cascading failures. The power grid topology is modeled as a network, which consists of nodes and links representing power substations and transmission lines, respectively. We also propose an optimal islanding strategy to protect the power grid when a cascading failure event takes place in the grid. The robustness metrics are numerically evaluated using real and synthetic networks to quantify their robustness with respect to disturbing dynamics. We show that the proposed metrics outperform the classical metrics in quantifying the robustness of networks and the efficiency of the mitigation strategies. In summary, our work advances the network science field in assessing the robustness of complex networks with respect to various disturbing dynamics.

This thesis evaluates and develops a method for studying the occurrence of cascading effects between critical infrastructures. The thesis also analyzes how the results of previous research using the method may have been affected by certain aspects of the method. Applying different inclusion thresholds and exploring how material could be gathered differently, the thesis provides some tentative answers to the value of using newspaper articles when studying cascading effects. In addition, the thesis offers recommendations for future research and policy on the protection of critical infrastructures.

This thesis evaluates and develops a method for studying the occurrence of cascading effects between critical infrastructures. The thesis also analyzes how the results of previous research using the method may have been affected by certain aspects of the method. Applying different inclusion thresholds and exploring how material could be gathered differently, the thesis provides some tentative answers to the value of using newspaper articles when studying cascading effects. In addition, the thesis offers recommendations for future research and policy on the protection of critical infrastructures.

Urban service networks have come under increased pressure due to expansion of urban population, decrease of capital investment, growing interdependence, and man-made and natural hazards. This thesis introduces a simulation-based methodology for the estimation of the fragility of urban networks subjected to earthquake perturbation. The proposed Interdependent Fragility Assessment (IFA) algorithm abstracts the steps required for perturbation-induced damage propagation within and between networks through internal and interdependent links, respectively. Damage propagation uncertainty is accounted by considering conditional probabilities of failure for components and interdependent strengths measuring the likelihood of intersystemic failure propagation. The IFA algorithm is used in four applications. The first application subjected two simplified models of real interdependent urban power and water networks to selected seismic scenarios. Test results showed that interdependence presence worsens systemic fragility, but that the features of interdependence effects were jointly influenced by local fragility properties and interdependence strengths. A second application examined the role of cascading failures caused by component overloading in systemic fragility. The results showed that cascading failures worsen interdependence fragility, and that mitigation actions improving local component capacity have limited effect on controlling interdependent-induced fragility. Two additional conceptual mitigation measures, component fragility reduction ( CFR ) and interdependence redundancy enhancement ( IRE ), were explored. CFR , decreases component seismic fragilities while IRE adds interdependence links to dependent nodes. Test results showed that CFR outperforms IRE ; however, their combination achieved comparable fragility reductions. This outcome highlights the potential of synergistic mitigation policies in controlling interdependent systemic fragility. Finally, the IFA methodology was adapted to use a probabilistic seismic description for the estimation of unconditional systemic fragilities. The hazard description was obtained following an existing approach that uses importance sampling for the generation of intensity maps. The value of the hybrid methodology rests on its capacity to generate unconditional fragility estimates for direct use in risk assessment. Topics for future work include the development of more sophisticated models of cascading failure, the analysis of optimal mitigation actions using mitigation cost-structures and life-cycle costs, the extension of the IFA methodology for perturbation such as hurricanes and flooding, and interdependent fragility studies of theoretical network models.