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Wind Farm Dynamics Over a Diurnal Cycle: Analysis of a Comprehensive Large-Eddy Simulation, Web-Services Accessible Dataset
No full textThe atmospheric boundary layer undergoes significant changes throughout a diurnal cycle, affecting wind turbine performance and wakes in wind farms. Wind farm large-eddy simulations (LES) under such conditions provide rich datasets to study the underlying dynamics and identify important trends. Here, we describe a comprehensive open dataset generated using LES of an eight-turbine wind farm consisting of four rows of two turbines. To avoid specifying either prescribed surface temperature or heat flux, a local one-dimensional soil heat conduction model is used with time-periodic solar surface heating, coupled to LES. After several days of low-resolution LES, an approximately time-periodic behavior is achieved, after which high-resolution LES is continued during a 24-h period. Analysis of the LES data reveals that wind turbine wakes have a significant impact on the temperature field and spatial surface heat flux patterns, exhibiting increased surface temperature behind the wind farm at night under the specific conditions of the simulation (dry unvegetated soil, clear sky). We observe that for a few morning hours the first row of wind turbines generates less power compared to the last row. Detailed analyses of the data using innovative web services facilitated data access tools reveal that during the morning transition, the presence of a low-level jet and the wind farm blockage effect combine to cause cooling and a reduction in wind speed at hub-height upstream of the wind farm. In addition, larger turbulence levels exist downstream in the wind farm, explaining the larger power production of downstream turbines
Mechanical Improvements and Control Implementation on a Biomimetic Quadruped Model
No full textRobotic development started billions of years after earth first began biological prototyping. While the evolutionary process in animals is quite different from robotic prototyping, it still remains no surprise that animals remain more agile, more efficient, and more adaptable than even the most advanced engineered robots to date, simply due to the sheer length of their improvement process. While bridging this improvement gap between deficits in robots and the abilities of animals is difficult, a specific subfield of robotics engineering has attempted to do so using biomimetic robotics. At Portland State, the Agile and Adaptive Robotics Lab (AARL) studies these biomimetic robotics. Its main biomimetic robotic platform, Muscle Mutt, is a quadruped actuated by artificial muscles and based on the proportions of a Whippet dog. While Muscle Mutt is structurally complete, it does not have a biologically-inspired control system to generate locomotion. Thus, this work details the electrical and control improvements to the Muscle Mutt and its test platform with the end goal of generating closed-loop, biologically-inspired air walking.
This work describes the implementation of a 3D printed adapter to fix Muscle Mutt’s non-functioning test treadmill platform. It also describes a force generation method in artificial muscles, called braided pneumatic actuators (BPAs), using neuron spike activations. It also details a novel method for modulating the mean force activation curve in BPAs using a noisy reset neuron model.
The work then chronicles the development of a virtual model of Muscle Mutt in MuJoCo, and the adaptation of a synthetic nervous system from a rat hind limb walking model in SNS-Toolbox to control the virtual model. Using spiking motoneurons to create activations in the virtual muscles, closed-loop, coordinated stepping in the fore and hind limbs is achieved in the simulated model of Muscle Mutt.
The Muscle Mutt robot is then connected to the synthetic nervous system, which was developed using the virtual model of Muscle Mutt. Adaptations of the network simulation for implementation in the physical robot are described, such as how sensory feedback from potentiometers and BPA pressure sensors is processed as biological muscle data for input in the synthetic nervous system (SNS). This biologically-inspired control scheme is able to generate rough, closed-loop stepping in the robot, suggesting the further utility of using spike activations from the synthetic nervous system to generate Muscle Mutt\u27s locomotion
From Cafes to Competitiveness: The Influence of Amenities on Office Values and Suburban Economic Development in Portland, OR
No full textThis dissertation examines the spatial and economic implications of urban amenities in the formation of suburban office markets in the post-pandemic period. The research applies principles from agglomeration theory, spatial econometrics, and urban planning to analyze the statistical relationships between amenity distribution, rent formation, and location behavior across central and non-central submarkets.
The research consists of three integrated papers focused on the Portland–Vancouver–Hillsboro, OR–WA Metropolitan Statistical Area (MSA). The first paper employs spatial econometric modeling, specifically a Spatial Autoregressive Model with Autoregressive Disturbances (SARAR), to examine the relationship between proximity to cafés and office rent levels in Portland’s central business district (CBD) and non-CBD areas. The findings indicate strong spatial dependence in office rent data and a clear divergence between urban and suburban markets. Proximity to cafés is associated with higher office rents in non-CBD areas, whereas in the CBD the effect is comparatively weaker, reflecting amenity saturation and congestion externalities that may diminish marginal returns from additional amenity concentration in dense urban cores. The second paper extends this analysis by incorporating a broader set of amenities categorized under the Accommodation and Food Services (NAICS 72) sector and applies Spatial Durbin Models (SDM) across four counties within the metropolitan region. The results demonstrate that amenity-driven rent premiums are more prominent in emerging suburban markets, particularly in Clackamas County, where localized amenity clustering contributes to higher office values, whereas the CBD area and other suburban counties exhibit weaker or statistically insignificant relationships. The third paper employs qualitative methods to explore how planners, brokers, and tenants interpret and mobilize amenity value within location strategies. Focusing on two submarkets in Lake Oswego, Oregon, it shows that amenity value is not fixed but interpreted through actor-specific logics: planners use it as a livability tool, brokers as marketable assets, and tenants as a workforce attraction strategy.
Together, this dissertation argues that amenities are not peripheral to economic geography, but constitute symbolic, spatial, and strategic infrastructure. Their presence signals quality, mediates spatial desirability, and supports place-making strategies in uneven office geographies. This dissertation contributes to the literature by offering an integrated, stakeholder-centered account of amenity logic, and by extending agglomeration theory into the interpretive domain of suburban development
The Matryoshka Doll Prior – Principled Multiplicity Correction in Bayesian Model Comparison
No full textThis paper introduces a general and principled construction of model space priors with a focus on regression problems. The proposed formulation regards each model as a “local” null hypothesis whose alternatives are the set of models that nest it. Assuming constant ratio of prior probabilities for any “local” null and its alternatives provides a natural isomorphism of model spaces (like a matryoshka doll), constituting an intuitive way to correct for multiplicity in Bayesian model selection and averaging problems. This isomorphism yields the Poisson distribution as the unique limiting distribution over model dimension under mild assumptions. We compare this model space prior theoretically and in simulations to widely adopted Beta-Binomial constructions. We show that the proposed prior yields a “just-right” multiplicity correction that induces a desirable complexity penalization profile
Exploring the Pathway from Customer Sexual Harassment to Instigated Incivility in Service Employees
No full textThe current study explores how and why customer sexual harassment (CSH) experienced by service workers may lead to instigated incivility towards customers in the same week. Specifically, following the tenets of Personality Systems Interaction theory (PSI) and the affective shift model, I hypothesized that week-level affective shifts mediate this relationship, such that upshifts in anxiety and downshifts in self-assurance govern changes in motivational and cognitive functions that impair the employee\u27s ability to provide good customer service. Further, supervisor preventive behaviors and psychological detachment are proposed as interventions that may lead to a departure from the mistreatment spiral by weakening the indirect effect of CSH on instigated incivility, drawing from the PSI theoretical mechanisms of systems conditioning and self-relaxation, respectively. The hypotheses proposed in this study were not supported. The theoretical and practical implications from this and other findings are discussed, as well as the limitations and opportunities for future research
Seasonal Bioavailability of Dissolved Organic Carbon Within Eight Urbanized Watersheds Across the Portland, OR, Metropolitan Area (Oregon, USA)
No full textThe bioavailability of dissolved organic carbon (DOC) measures how readily organic carbon compounds are utilized by heterotrophic microorganisms and depends on the size and molecular composition. DOC in aquatic systems are known to vary seasonally and across urbanization intensity; however, the effects of urbanization and seasonality on bioavailable DOC (BDOC) are not well understood. This study examines seasonal patterns in BDOC across a range of urbanization intensity within the Portland, OR, metropolitan area. We hypothesized that BDOC concentrations would decrease from the summer (dry season) through the spring (wet season). Water samples were collected seasonally from 20 stream sites located within eight watersheds between 2023 and 2024. Samples were filtered, inoculated with unfiltered water and incubated in the dark for 28 days. Significant differences in both concentrations and the bioavailable proportion of DOC were observed across seasons, with the direction of the change differing by watershed. For example, from fall 2023 to winter 2024, most watersheds decreased in BDOC concentration and in BDOC/DOC while the Willamette River and Lake Oswego increased in both BDOC concentration and BDOC/DOC. Between winter and spring 2024, Lake Oswego decreased in both BDOC concentration and BDOC/DOC, the Willamette increased in BDOC concentrations but decreased in BDOC/DOC, and the rest of the watersheds increased in both concentrations BDOC and BDOC/DOC. Overall, variability in seasonal changes in BDOC indicates that factors beyond seasonality influenced BDOC. Additional analysis of urban and hydrological factors will provide insight into the influence of urbanization on BDOC
Utilizing Roadkill Salvage to Bolster Chronic Wasting Disease Surveillance Data in Urban Areas
No full textChronic wasting disease (CWD) is a Transmissible Spongiform Encephalopathy that is always fatal to members of the deer family (Cervidae). CWD poses a unique challenge for wildlife managers as there is no cure or treatment for infected individuals, it remains transmissible and persistent in the environment, and symptoms become evident only after a long incubation period. The disease has yet to be detected in Oregon. CWD can impact trophic systems, economies, and sources of first foods. The Oregon Department of Fish and Wildlife’s (ODFW) CWD management plan includes increased surveillance through diversified sampling efforts, and public education and outreach. Monitoring for CWD is of particular importance in urban areas, as some studies have shown increased prevalence in urban areas in states where the disease is present. Cervids with CWD are more vulnerable to becoming roadkill, due to neurological symptoms, and emphasis has been placed on increasing samples in locations where hunter harvest isn’t possible. Within urban environments, ODFW relies heavily on roadkill salvage (RKS) animals to increase CWD detection probability. We obtained 20 and 13 CWD samples from RKS cervids in 2023 and 2024, respectively. We will present the spatial distribution of RKS samples obtained in the Portland metropolitan area for 2023-2024. Future RKS sampling efforts can be increased via partnerships with municipal governments and other state agencies. The public can help local deer and elk populations by not feeding them, adhering to ODFW regulations and by talking with their community about the impacts of CWD
Integrating Methods to Investigate Phytoplankton Dynamics Along Gradients of a Major Urban River
Get PDFWaterways that support human society and life on Earth host superabundant microorganisms which support all ecosystems and food webs: phytoplankton. This study aimed to identify and quantify phytoplankton in the Willamette River in order to understand the dynamics between different phyla. Building on previous studies, which showed that communities of phytoplankton change with the river environment, this work determined how eukaryotic and prokaryotic phytoplankton vary with one another while inhabiting the same river conditions. The approach involved sampling the Willamette river over a weekly time series and combined analytical techniques of qPCR, flow cytometry, and image cytometry to assess population composition and dynamics. The outcome provided a better understanding of causes and effects of changing community dynamics in a river. Combining qPCR, flow cytometry, and image cytometry revealed phytoplankton community structure more than any single approach could. Diatoms and subpopulations of picocyanobacteria were found to share correlations in community dynamics. Phycocyanin-producing organisms could be a major influence of the broad phytoplankton community. This work will generate hypotheses towards improved understanding of phytoplankton in river systems
Color Aberrations in Seven Bird Species in Costa Rica
Get PDFAlthough there are 935 species of birds in Costa Rica, scientific reports of pigmentation abnormalities in this group are limited. Nevertheless, several cases have been recently documented, including Leucism, Ino mutation, Progressive Graying, Dilution, and two unusual color aberrations in a toucan and a motmot. Here we describe seven cases of color aberrations observed over a period of five years in native birds of Costa Rica. An Eastern Wood-Pewee Contopus virens and a White-collared Manakin manacus candei were Brown. A Scintillant Hummingbird Selasphorus scintilla and a Talamanca Hummingbird, Eugenes spectabilis, also showed a Brown mutation, however, these two cases may be Ino. In addition, two cases of Progressive Graying were recorded in a Gray-necked Wood-rail Aramides cajaneus and a Great-tailed Grackle Quiscalus mexicanus. An indeterminate case was also observed in the Turkey Vulture Cathartes aura. Identifying plumage abnormalities in wild birds is challenging and can lead to misidentifications. However, documentation of color variation and behavior in birds can help inform future research. We encourage the reporting of observations of abnormally colored birds to further our understanding of this phenomenon
Continent Imaginaries Across Time Official Educational Discourse from the Progressive USA to UNESCO
Get PDFIn 1928, the United States Government published the Meriam Report. Almost a century later, the 2023 Global Education Monitoring (GEM) Report was released by UNESCO. In this paper I put these documents in conversation to trace the common ideological threads woven into the transition from a colonial era to our globalised world of mass schooling. The two reports seemingly have distinct emphases. A fixation on imperial expansion, Indigenous assimilation, and administrative progress gives way to the centrality of measurement, human rights, and building a transnational community. There are differences in form, vocabulary, grammar, and medium. But there is a unity in the insistence on modern education as the solution for social progress. By analysing the discursive practices of official reports, I show a persistence in the underlying narratives and symbols of education. These draw on shared – but contingent – social imaginaries of modernity which, once recognised, can open to alternative reimaginations