Homeownership may be the American Dream, but renting is the American reality for nearly half of Portland, Oregon’s residents. In Oregon, where I conducted fieldwork from 2014 to 2017, a statewide ban on rent control, the prevalent use of no-cause evictions, and the lack of renters’ protections pushed Portland residents, especially renters, into a Housing State of Emergency. Many renters in this housing crisis are forced to rent and face the threat of being repeatedly displaced as their apartment units change hands from investor-to-investor. These investor landlords used no-cause evictions to remove tenants from their homes and to quickly empty entire apartment buildings, flip the buildings, and increase their rate of return. As gentrification increased the rent in Portland, it also push low-income people and communities of color as they moved to the suburbs in search of scarce low-income rental housing. Employing ethnographic methods of participant observation and in-depth interviewing, this dissertation explores the inequalities built into the rental housing system for different groups of vulnerable tenants in Portland. A qualitative analysis revealed that families of color and low-income residents not only experience serial displacement as renters, but also serial segregation. / 2020-09-06

Digitized by Kansas Correctional Industries

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 112-126).

No description available.

Thesis (Ph.D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 112-126) Also available in print.

The conventional car suspension system uses isolated shock absorbers that are only capable of dissipating energy in the form of heat. Each shock absorber in a hydraulic interconnected suspension is connected by hydraulic circuits, allowing the electrified hydraulic fluid to be used to counteract undesirable body motion and enhance dynamic performance as a whole. An established idea with good potential for managing body rolling and separating the warp mode from other dynamic modes is the hydraulic interconnected suspension. While certain active or semi-active suspension technologies enable the shock absorbers to compensate for the effects of the road disturbances using external power input, hydraulic linked suspension is still passive and lacks adaptivity. In order to adjust the suspension's damping properties to rapidly changing road conditions, active suspensions, like electromagnetic shock absorbers, utilize the magnetofluid's variable viscosity. In some circumstances, the energy requirement of an active suspension might amount to kilowatts, which lowers the vehicle's fuel efficiency. This research proposes a novel energy-harvesting hydraulically interconnected shock absorber (EH-HISA) system to find a balanced solution to dynamic performance and energy efficiency by incorporating energy harvesting ability to a passive hydraulically interconnected suspension. Improved energy efficiency and vehicle dynamics performance are provided by the features which combine energy harvesting with hydraulic interconnection. AMESim is used to build a single diagonal hydraulic circuit model, which is then validated in a bench test. The theoretical model's validity was established by the bench test results, and the model was then applied to estimate system performance. To verify the effectiveness of the entire system design, a full car model outfitted with EH-HISA is created. For model simulation, various dynamic input scenarios—including sinusoidal input and double lane change tests—are applied. The EH-HISA achieves average lateral acceleration improvements of 38% over traditional suspensions and 11% compared to a prior design (EHHIS proposed by Chen et al.) and average energy harvesting ability improvements of 133 % while maintaining acceptable anti-rolling dynamics in the double lane change test. The EH-HISA also improves the anti-rolling ability by 30 % as compared to traditional suspensions. The power generated is found to reach maximum of 210 W at 2 Hz and 20 mm sinusoidal input. Bench tests are performed on the EH-HISA prototype to validate the simulation results. Damping force and energy harvesting experimental data is measured and compared with the simulation results to validate the effectiveness of the system. / Master of Science / The vehicle industry has always sought improved road handling dynamics and riding comfort. The vehicle body may move in a variety of ways, including roll, pitch, and bounce; each of these motions can endanger passengers' safety and lead to passenger fatigue. Oil shock absorbers that are isolated from the rest of the vehicle's suspension system can only dissipate energy by forcing oil via dampening valves. A hydraulic interconnected suspension can connect each shock absorber using hydraulic circuits so that the energized hydraulic fluid can be used to reduce unwanted body motion and enhance the overall riding experience. A tried-and-true idea, the hydraulic interconnected suspension (HIS), has shown promising results in stabilizing the vehicle body on unsteady roads. While active suspensions, like electro-magnetic shock absorbers, can employ an external power source to compel them to adjust to rapidly changing road conditions, hydraulic linked suspension is still passive and unadaptive. In some circumstances, the energy requirement of an active suspension might amount to kilowatts, which lowers the vehicle's fuel efficiency. Additionally, there is always a chance that a system that is actively receiving power will malfunction as a result of a power outage. This research offers a new type of energy-harvesting hydraulically interconnected shock absorber (EH-HISA) system to achieve a balanced solution to dynamic performance and energy efficiency. The combined energy-harvesting and HIS system provide improved energy efficiency as well as vehicle dynamics performance. Each system is composed of two distinct diagonal hydraulic circuits which interconnect the shock absorbers of the diagonal wheels in a vehicle. AMESim is used to build a single diagonal hydraulic circuit model, which is then validated in experiments, as a starting point for investigating the effectiveness of the overall system. The theoretical model's validity was established by the outcomes of the bench tests, and the model was then utilized to predict system performance. A full car model is created based on the tested single diagonal hydraulic circuit model to assess the performance of the entire system architecture. Different road condition scenarios are used for model simulation, which includes sinusoidal input and double lane change test. The EH-HISA achieves average lateral acceleration improvements of 38% over traditional suspensions and 11% compared to a prior design (EHHIS proposed by Chen et al.) and average energy harvesting ability improvements of 133 % while maintaining acceptable anti-rolling dynamics in the double lane change test. The EH-HISA also improves the anti-rolling ability by 30 % as compared to traditional suspensions. The power generated is found to reach maximum of 210 W at 2 Hz and 20 mm sinusoidal input. Bench tests are performed on the EH-HISA prototype to validate the simulation results. Damping force and energy harvesting experimental data is measured and compared with the simulation results to validate the effectiveness of the system.

No description available.

In recent years, there have been significant changes in power systems due to the integration of renewables, distributed generation, switched power loads, and energy storage systems, etc. Locally these AC/DC microgrids include both DC generation (such as solar PV) and AC generation (such as wind generation), various DC and AC loads, converters and inverters, and energy storage systems, such as storage batteries and supercapacitors. DC systems are often characterized as low inertia systems whereas AC generation and systems are usually high inertia and high time constant systems. As such, various components of the microgrid will have different temporal characteristics in case of disturbances, such as short circuit, load switchings, etc. which may lead to instability of the microgrid. This research develops the first principle model for coupling the AC and the DC subsystem of an integrated AC/DC microgrid utilizing the dq-framework. The developed model is highly nonlinear and captures the dynamic interaction between the AC and DC subsystems of the microgrid. Lyapunov stability is used to evaluate the stability of the complete system. Simulation results show that the AC and DC subsystems are tightly dynamically coupled so that any disturbance in one subsystem induces transients in the other subsystem. Induced transients due to pulse loads on the AC and DC subsystems clearly show that generator damper winding alone may not be enough to mitigate transients in the microgrid. Addition of prime mover and excitation system controllers for the generator improves the transients primarily on the AC subsystem. Thus, a battery storage with a charge/discharge controller was also added to the DC subsystem. Simulations of the AC/DC microgrid with all three controllers validate the smooth operation of the system for all types of disturbances. The proposed method can be extended in modeling microgrid with multiple generators and various types of loads. / Electrical and Computer Engineering

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Doctor of Philosophy / Department of Electrical and Computer Engineering / Caterina Scoglio / Society increasingly depends on networks for almost every aspect of daily life. Over the past decade, network science has flourished tremendously in understanding, designing, and utilizing networks. Particularly, network science has shed light on the role of the underlying network topology on the dynamic behavior of complex systems, including cascading failure in power-grids, financial contagions in trade market, synchronization, spread of social opinion and trends, product adoption and market penetration, infectious disease pandemics, outbreaks of computer worms, and gene mutations in biological networks. In the last decade, most studies on complex networks have been confined to a single, often homogeneous network. An extremely challenging aspect of studying these complex systems is that the underlying networks are often heterogeneous, composite, and interdependent with other networks. This challenging aspect has very recently introduced a new class of networks in network science, which we refer to as multilayer and interconnected networks. Multilayer networks are an abstract representation of interconnection among nodes representing individuals or agents, where the interconnection has a multiple nature. For example, while a disease can propagate among individuals through a physical contact network, information can propagate among the same individuals through an online information-dissemination network. Another example is viral information dissemination among users of online social networks; one might disseminate information received from a Facebook contact to his or her followers on Twitter. Interconnected networks are abstract representations where two or more simple networks, possibly with different dynamics over them, are interconnected to each other. For example, in zoonotic diseases, a virus can move from the network of animals, with some transmission dynamics, to a human network, with possibly very different dynamics. As communication systems are evolving more and more toward integration with computing, sensing, and control systems, the theory of multilayer and interconnected networks seems to be crucial to successful communication systems development in cyber-physical infrastructures. Among the most relevant dynamics over networks is epidemic spreading. Epidemic spreading dynamics over simple networks exhibit a clear example where interaction between non-complex dynamics at node level and the topology leads to a complex emergent behavior. A substantial line of research during the past decade has been devoted to capturing the role of the network on spreading dynamics, and mathematical tools such as spectral graph theory have been greatly useful for this goal. For example, when the network is a simple graph, the dominant eigenvalue and eigenvector of the adjacency matrix have been proven to be key elements determining spreading dynamics features, including epidemic threshold, centrality of nodes, localization of spreading sites, and behavior of the epidemic model close to the threshold. More generally, for many other dynamics over a single network, dependency of dynamics on spectral properties of the adjacency matrix, Laplacian matrix, or some other graph-related matrix, is well-studied and rigorously established, and practical applications have been successfully derived. In contrast, limited established results exist for dynamics on multilayer and interconnected networks. Yet, an understanding of spreading processes over these networks is very important to several realistic phenomena in modern integrated and composite systems, including cascading failure in power grids, financial contagions in trade market, synchronization, spread of social opinion and trends, product adoption and market penetration, infectious disease pandemics, and outbreak in computer worms. This dissertation focuses on spreading processes on multilayer and interconnected networks, organized in three parts. The first part develops a general framework for modeling epidemic spreading in interconnected and multilayer networks. The second part solves two fundamental problems: introducing the concept of an epidemic threshold curve in interconnected networks, and coexistence phenomena in competitive spreading over multilayer networks. The third part of this dissertation develops an epidemic model incorporating human behavior, where multi-layer network formulation enables modeling and analysis of important features of human social networks, such as an information-dissemination network, as well as contact adaptation. Finally, I conclude with some open research directions in the topic of spreading processes over multilayer and interconnected networks, based on the resulting developments of this dissertation.