Physical Sciences and Mathematics Commons^™

Machine Learning For Economists, John Luke Gallup

Economics Faculty Publications and Presentations

Explication of machine learning algorithms and their usefulness for economic research. The prediction algorithms of Random Forest, Gradient Boost Machines, Neural Networks and Support Vector Machines are built from simple steps applied at large scale to generate surprisingly precise nonlinear estimates. Although useful for processing and interpreting new forms of data, their application to economics research is limited because they do not provide readily interpretable evidence of the causes of outcomes.

The Johnson-Křížek-Mercier Elasticity Element In Higher Dimensions, Jay Gopalakrishnan, Johnny Guzman, Jeonghun J. Lee

Mathematics and Statistics Faculty Publications and Presentations

Mixed methods for linear elasticity with strongly symmetric stresses of lowest order are studied in this paper. On each simplex, the stress space has piecewise linear components with respect to its Alfeld split (which connects the vertices to barycenter), generalizing the Johnson–Mercier two-dimensional element to higher dimensions. Further reductions in the stress space in the three-dimensional case (to 24 degrees of freedom per tetrahedron) are possible when the displacement space is reduced to local rigid displacements. Proofs of optimal error estimates of numerical solutions and improved error estimates via postprocessing and the duality argument are presented.

Microbial Communities Of Selected Regions Of The Deep Springs Lake Aquifer System, Rania Zaki, Emma Bourne, Andrew Storino, Jay Nadeau

Physics Faculty Publications and Presentations

Deep Springs Lake is a small, isolated, highly alkaline soda lake in Inyo County of Eastern California, USA. It is a seasonally filled salt lake or playa, and is part of a closed aquifer system. Such closed systems are globally rare, occurring only in arid zones where annual evaporation is greater than annual rainfall. Deep Springs Lake’s hydrology and geology have been well studied, and it is home to a unique toad species, but its microbiome remains unexplored. Here we perform 16S, 18S, and ITS amplicon sequencing of the lake water, dried salt crust at the edges the lake, and …

Oregon State Rank Assessment For Plumed Clover (Trifolium Plumosum Var. Plumosum), Nora Dunkirk

Institute for Natural Resources Publications

Oregon state conservation status assessment for Plumed Clover (Trifolium plumosum var. plumosum) using NatureServe methodology, 2025.

Citizen's Rare Plant Watch 2025 Recap, Nora Dunkirk

Rae Selling Berry Seed Bank and Plant Conservation Program

Citizen's Rare Plant Watch (CRPW) is a community science program which takes volunteers out to visit populations of rare and threatened Oregon native plant species. Volunteers assess their health and viability, update the Oregon Biodiversity Information Center (ORBIC) state database for rare species, and help contribute to data driven management decisions throughout the state. Housed at Portland State University, this program is open to the public and attracts plant lovers from diverse backgrounds. Each spring, CRPW trains volunteers on methods of data collection, and this year we implemented new technology using Survey123 to streamline population assessments. We focus on species …

Online Decision Mamba, Trenton W. Ruf

Dissertations and Theses

Online in-context reinforcement learning enhances offline-trained policies through online fine-tuning. We introduce Online Decision Mamba (ODM), an architecture that replaces the attention mechanism in Online Decision Transformers (ODT) with the Mamba module to improve long-context sequence modeling and overall RL performance. We performed in-depth evaluations on MuJoCo (OpenAI Gym) and Atari benchmarks, comparing ODM against state-of-the-art offline and online baselines—including Decision Mamba (DM) and ODT. Our results show that ODM achieves competitive or superior performance, with particularly robust gains when initial datasets lack expert demonstrations. In the Qbert Atari environment, ODM shows context-length sensitivity similar to offline DM; however, we …

Systematics And Systems Theory: Reconstructability Analysis Of The Tetrad, Martin Zwick

Complex Systems Faculty Publications and Presentations

This talk discusses the relationship between systems theory, specifically Reconstructability Analysis, and Systematics, a systems theory-like framework of number symbolism developed by John G. Bennett, which he presented in his four-volume magnum opus, The Dramatic Universe. The talk, given to a community of people interested in Bennett's ideas, focuses on Martin Zwick's paper "Ideas and Graphs: the Tetrad of Activity" archived at https://archives.pdx.edu/ds/psu/36249.

Adaptive Image Acquisition Algorithms For Resource-Constrained Single-Photon Cameras, Yeganeh Jalalpour, Wu-Chi Feng

Computer Science Faculty Publications and Presentations

Emerging single-photon camera (SPC) technologies have unique challenges in data acquisition and processing. Unlike conventional sensors that produce a single 8- to 16-bit brightness value per pixel, SPCs record photon arrivals with many more samples per pixel, using high floating-point precision for each photon collected. This means that they must handle potentially millions of timestamps, especially at higher spatial resolutions and in the presence of ambient light, creating bottlenecks within the pixel circuitry. To address these challenges associated with SPCs, this paper proposes adaptive algorithms designed to efficiently distribute hardware resources among groups of pixels. By selectively subsampling the data …

Hint-Guided Video Frame Interpolation For Video Compression, Pan Tan, Wu-Chi Feng

Computer Science Faculty Publications and Presentations

Traditional video compression continues to advance, but the gainsin efficiency are diminishing and come at the cost of higher compu-tational complexity. Despite achieving competitive rate-distortionresults, current neural video codecs (NVCs) generally lack sup-port for a wide range of quality levels, often requiring multiplemodels to achieve flexible rate control, which increases both train-ing cost and deployment complexity. To address the limitations ofboth traditional codecs and current NVCs, we propose a hybridvideo compression framework that integrates traditional codecswith hint-guided video frame interpolation (VFI), a learning-basedtechnique for synthesizing intermediate frames. By using decodedreference frames and leveraging compressed-domain hints to guideinterpolation, our method improves …

Capstone Reflection: Developing A Muslim Prayer App For Psu Students, Jeremiah Su

University Honors Theses

This thesis examines the development process of the Muslim Student Association (MSA) App, a computer science capstone project. The app strives to help the Muslim community at Portland State University (PSU) and the Portland area by consolidating essential information for prayers, such as local prayer times, nearby masjids, and the direction of Qibla. The team behind this project was developed by 6 computer science developers, a majority of whom were from the Muslim culture and background. This paper describes the entire capstone development process from the perspective of a developer who is not rooted in Muslim customs. It also describes …

Experience From A Distance: Improving Transparency For The Multnomah Athletic Club, Matthew Penner

University Honors Theses

Portland is home to the largest and one of the most prestigious athletic clubs in the world: Multnomah Athletic Club. In many ways, it is the pinnacle of luxury and innovation, and over time, it finds any way to entice prospective members to pay the expensive upfront fee of $6000 and monthly membership fees exceeding $300. Due to the previous technological barrier, which was not being able to see the full extent of what amenities the club had to offer, the club faced major challenges in recruitment and marketing. Over two academic terms, a team of six computer science capstone …

Fractional Order Hierarchical Decompositions Using Multigrid Components, Panayot S. Vassilevski

Mathematics and Statistics Faculty Publications and Presentations

Motivated by the fractional order multilevel decompositions of finite element spaces developed previously, we exploit additive representations of popular multigrid (MG) cycles to design fractional order MG decompositions. The additive representations enable us to scale the individual hierarchical components thus ending up with fractional order hierarchical decompositions that are based on the readily available MG components. This results in a highly efficient and scalable (in terms of high-performance) fractional order hierarchical MG decompositions that we tested in the setting of finite element white noise sampling as an alternative to PDE-based white noise sampling using fractional order shifted Laplacians.

Security Vulnerabilities And Defense Tactics For Generative Ai Application Development, Kyle Klein

University Honors Theses

Generative AI (GenAI) applications such as OpenAI's ChatGPT leverage large language models (LLMs) trained on enormous amounts of data to accomplish tasks such as document editing, summarization, and query response. Chatbots and LLM programs that are equipped with retrieval-augmented generation (RAG) have the ability to draw upon data provided by developers and users to improve the quality of the program's responses. LLM technology has even expanded to generate images, audio, and video from user instructions. Designed around unpredictable user input and typically composed of many opaque components, LLM software products face a paradigm shift of new, constantly evolving security challenges. …

Future Vision And Action Recommendations, Sondoss Elsawah, Melissa Haeffner, Anthony Jakeman

Environmental Science and Management Faculty Publications and Presentations

Let us imagine a future world where water management is more fully integrated and supported by the science of sociohydrology and related metadisciplines. This is a vision for the future where the social, cultural, environmental, and economic values of water are explicitly considered through the lens of the science–water policy interface. The ultimate value of research will be measured by how much it supports improvements in water resources and hazards management and, in particular, completes and enriches the science–water policy interface.

Human-Drought Systems, Margaret Garcia, Elizabeth Koebele, Melissa Haeffner, Anne F. Van Loon, Newsha Ajami, Claudia Teutschbein, Marjolein Mens, Sylvain Massuel, Christopher White, Burcu Tezcan

Environmental Science and Management Faculty Publications and Presentations

Advancing our understanding of the processes linking social and hydrological systems is an essential step toward managing drought risk and increasing drought resilience. Over the past decade, numerous studies have advanced our understanding of human influences on drought propagation, drought responses and their immediate and long-term consequences, and decisions and conditions leading to drought resilience. These advances have been achieved through: (1) the development of datasets that document drought progression, hazards, risk, vulnerability, and adaptation capacity; (2) creation of new modeling methods and application of models to build and test theory; and (3) empirical analyses from in depth case studies …

Synthesis And Characterization Of Highly Stable Fisetin Encapsulated In Lecithin-Chitosan-Savie Nanoparticles, Hart Monyatovsky, Travis Anderson, Jay Nadeau

Physics Faculty Publications and Presentations

Senolytic drugs, of the class of polyphenolic flavonoids, have attracted attention for a wide variety of medical applications for which they may be delivered topically, orally, and/or intravenously. However, due to their hydrophobicity and sensitivity to light and oxygen, they have been proven difficult to package and deliver. Here we report a synthesis method for encapsulated fisetin using lecithin-chitosan ionic gelation with a recently reported surfactant that is an alternative to polyethylene glycol (PEG)-containing compounds. Called “Savie” for a contraction of its components, sarcosine-Vitamin E, this surfactant allows for production of sub-100 nm nanoparticles that are bench stable for at …

A Generalized Lehmer Conjecture For The Trace Of T ₃, Liubomir Chiriac, Erin Williams

Mathematics and Statistics Faculty Publications and Presentations

The expectation that Ramanujan’s tau function does not vanish, commonly known as Lehmer’s Conjecture, has inspired several extensions to broader settings. In this paper, we focus on one such direction, proposed by Rouse, concerning the non-vanishing of traces of Hecke operators Tn. We refine an algorithm originally introduced by Rouse to resolve the case n = 2, and, together with tools from our earlier work on the case n = 3 in level one, we settle the conjecture for T₃ in full generality. We also discuss an implication of our result for the non-vanishing of all coefficients of the …

Guided Modes Of Helical Waveguides, Jay Gopalakrishnan, Michael Neunteufel

Mathematics and Statistics Faculty Publications and Presentations

This paper studies guided transverse scalar modes propagating through helically coiled waveguides. Modeling the modes as solutions of the Helmholtz equation within the three-dimensional (3D) waveguide geometry, a propagation ansatz transforms the mode-finding problem into a 3D quadratic eigenproblem. Through an untwisting map, the problem is shown to be equivalent to a 3D quadratic eigenproblem on a straightened configuration. Next, exploiting the constant torsion and curvature of the Frenet frame of a circular helix, the 3D eigenproblem is further reduced to a two-dimensional (2D) eigenproblem on the waveguide cross section. All three eigenproblems are numerically treated. As expected, significant computational …

Climatic Controls On Soil Production, Transport And Chemical Erosion: Insights From Modelling Topography, Soils And Cosmogenic Nuclides At Little Lake, Oregon, Miles M. Reed, Ken L. Ferrier, Jill A. Marshall, Josh J. Roering, J. Taylor Perron

Geology Faculty Publications and Presentations

Predicting physical and chemical erosion rate responses to climate change are an ongoing challenge in geomorphology. A promising approach for investigating this is by measuring transient variations in physical and chemical erosion rates during climatically variable time periods, which can be accomplished by measuring cosmogenic nuclide concentrations and chemical depletion in sedimentary deposits. Interpreting such measurements warrants applying landscape evolution models that track variations in topography, cosmogenic nuclide concentrations and chemical depletion in soils. We applied a recently developed model that tracks these quantities at Little Lake, Oregon. Previous studies documented variations in cosmogenic nuclide concentrations and chemical depletion in …

Understanding The Role Of Sentiment And Emotion For Predicting Forced Displacement, Helge Marahrens, Ameeta Agrawal, Ali Arab, Katharine Donato, Yaguang Liu, Nathan Wycoff, Mohamed Ahmed, Colin Hwang, Lina Laghzaoui, Kate Liggio, Multiple Additional Authors

Computer Science Faculty Publications and Presentations

Digital trace data play an important role determining where and when people will move during migration crises because of their detailed temporal and spatial granularity. Yet, identifying variables that reliably serve as early indicators of movement remains a challenging task. Within this context, we conduct an in-depth analysis of two types of variables that can be constructed from social media data – sentiment and emotion. Sentiment is conceptually broad and easier to detect from social media posts, while emotion is conceptually nuanced and more difficult to determine. We investigate the potential of both sentiment and emotion of Twitter/X posts as …

Rare, Threatened And Endangered Zoology Species Of Oregon (2025), Jesse Laney, Eleanor P. Gaines, Lindsey K. Wise, Misty Nelson

Institute for Natural Resources Publications

This publication provides a 2025 update to the rare, threatened, and endangered zoology species of Oregon. Species lists are also provided in Excel format.

The Oregon Biodiversity Information Center (ORBIC) is part of the Institute for Natural Resources (INR) located at Portland State University (PSU). ORBIC maintains extensive databases of Oregon biodiversity, concentrating on rare and endangered plants, animals and ecosystems. Since its creation in 1979 as the Oregon Natural Heritage Program, ORBIC has been part of the Natural Heritage network. ORBIC is a constituent member of NatureServe, a non-profit organization with a mission to provide the scientific basis for …

A Case Study On The Effectiveness Of Llms In Verification With Proof Assistants, Barış Bayazıt, Yao Li, Xujie Si

Computer Science Faculty Publications and Presentations

Large language models (LLMs) can potentially help with verification using proof assistants by automating proofs. However, it is unclear how effective LLMs are in this task. In this paper, we perform a case study based on two mature Rocq projects: the hs-to-coq tool and Verdi. We evaluate the effectiveness of LLMs in generating proofs by both quantitative and qualitative analysis. Our study finds that: (1) external dependencies and context in the same source file can significantly help proof generation; (2) LLMs perform great on small proofs but can also generate large proofs; (3) LLMs perform differently on different verification projects; …

Digging Deeper With Deep Ram Networks, Andrew J. Wagner

Dissertations and Theses

While Deep Neural Networks (DNNs) have driven major breakthroughs in artificial intelligence, their internal complexity often makes their behavior hard to explain, resulting in the well-known “black box” dilemma. This thesis addresses the challenge of interpretability in DNNs and deep reinforcement learning (DRL) through two main contributions.

In Part I, we revisit and extend the use of Deep RAM Networks (DRNs) within the Arcade Learning Environment (ALE), showing that, with modern architectures and careful hyperparameter tuning, RAM-based agents can achieve performance competitive with established pixel-based baselines on Atari 2600 games, while offering additional advantages for research and analysis. We also …

Characterizing Meteorological Patterns For Oregon's Winter Elevated Pm2.5 Concentrations From 2000-2023, Arielle Golda Sherbak

Dissertations and Theses

Valleys and basins are uniquely susceptible to the buildup of air pollution during the wintertime due to cool, dense air pooling under favorable meteorological conditions, a common occurrence in the Intermountain West. In Oregon, wintertime anthropogenic air pollution is primarily from woodburning stoves and heaters and although efforts have been made to reduce wintertime pollution, stagnation events continue to result in decreased air quality. This analysis aims to understand the relationship between air pollution in six Oregon counties and the associated meteorology in the cool season (November-March) using a 2000-2023 climatology.

This is completed through a composite analysis using key …

The Fate Of Recycled Water In Restored Wetlands, Punyotoya Paul

Environmental Science and Management Professional Master's Project Reports

This research investigates the hydrological fate of treated wastewater or "recycled water" used for irrigation at a restored wetland site (Thomas Dairy) near Tigard, Oregon, that is managed by Clean Water Services (CWS). CWS is interested in understanding how treated wastewater moves through plants and soil in ecosystems that might be targeted for recycled water applications. Using a water balance approach, we evaluated irrigation inputs, soil infiltration dynamics, and hydraulic conductivity measurements across three soil types with different textures and other properties. Field measurements were collected using advanced sensors (TEROS and ATMOS devices) and laboratory tools (KSAT) to quantify soil …

Modeling Effective Shade For Oregon Streams Using Satellite Derived Vegetation Structure Metrics, Ella Wagner

Environmental Science and Management Professional Master's Project Reports

In the Pacific Northwest, rising stream temperatures threaten the survival of cold-water species, such as salmonids. The Oregon Department of Environmental Quality (DEQ) regulates stream temperature statewide through Total Maximum Daily Loads (TMDLs). To do this, the DEQ uses stream shade as a surrogate measurement for heat, as stream shade and stream temperature have a well-known strong relationship. This project focused on developing effective shade modeling and monitoring methods that increase the pace and scale of temperature TMDL implementation and tracking in Oregon. Stream shade can be measured in the field and modeled with computer models such as HeatSource, which …

Data-Driven Optimization And Parameter Estimation For A Metric Graph Epidemic Model With Applications To Covid-19 Spread In Poland: A Real-World Example Of Optimization For A Challenging Rosenbrock-Type Objective Function, Hannah Kravitz, Christina Duron, Brittani Nieves, Moysey Brio

Mathematics and Statistics Faculty Publications and Presentations

In this paper, we apply data-driven optimization to estimate key parameters in a metric graph-based epidemiological model, with the aim of analyzing the effect of road networks on the geographic spread of epidemics. As a case study, we fit our model to data from the COVID-19 pandemic in Poland during 2021. Our dataset integrates county-level daily case reports, national census information, and traffic flow studies. This framework allows us to examine the relative contribution of specific travel routes over time and infer unobserved transmission patterns in the presence of incomplete or unreliable case reporting. The optimization problem that arises from …

The Effect Of Mesoscale Frontal Waves On Landfalling Atmospheric Rivers And Their Associated Precipitation Over The Green River Watershed, Washington, Joseph Michael Riedl

Dissertations and Theses

In this study, the effect of mesoscale frontal waves (MFWs) on extreme precipitation (EP) in the Upper Green River Watershed (UGRW), Washington is investigated. 205 EP days (>95th percentile) are identified in the UGRW between the years 1980 and 2021. To characterize the range of large-scale meteorological conditions associated with EP days, the self-organizing map (SOM) approach is used to cluster daily integrated water vapor transport (IVT) on EP days. To further diagnose the meteorological drivers, composites of several other diagnostic fields are constructed for each SOM node and the preceding days. Together, these results illustrate common orientations of …

Orphan Basalts: Understanding The Origins Of Unassigned Eastern Oregon Basalts, Angela Rae Stetson

Dissertations and Theses

For more than a century, scientists have studied the geologic stratigraphy of eastern Oregon, which chronicles a rich history of volcanic activity spanning millions of years. Recent and ongoing geologic mapping of the northeastern Harney Basin -- along a corridor east of Highway 395 between the towns of Burns and John Day -- provides a more detailed understanding of an area originally mapped only in reconnaissance during the 1960s. At that time, geologic units were poorly delineated, often with entire quadrangles mapped as a single unit. For example, over 90% of the Calamity Butte quadrangle was previously mapped as 'Tba' …

Edge Percolation Centrality: A New Measure To Quantify The Influence Of Edges During Percolation In Networks, Christina Durón, Hannah Kravitz, Moysey Brio

Mathematics and Statistics Faculty Publications and Presentations

Numerous centrality measures exist to quantify the influence of edges within a network, with edge betweenness being one of the more well-known measures. However, such measures are inadequate in network percolation scenarios (e.g., the transmission of a disease over a transportation network of highways) as they fail to consider the changing percolation states of edges over time. This paper addresses this limitation by extending percolation centrality, a measure originally developed to evaluate the influence of vertices during a percolation process (i.e., a dynamic spread of a contagion) in the network, to the edge level. The proposed measure, edge percolation centrality, …