Digital Commons Network^™

How Human Vs. Ai Chatbots Support Psychological Needs Of Students, Tymon T. Vu

Master's Theses

AI auto graders and virtual assistants are increasingly prevalent in educational set- tings. Although current literature demonstrates that AI chatbots can positively im- pact student motivation, there is little definitive evidence exploring whether these systems can replicate the effective motivational methods used by human teachers. Thus, in this experiment, we investigate how the perception of the identity of a tutor (AI versus human) impacts the psychological needs of students. 27 undergraduates taking introductory computer science courses were asked to explain code in plain English (EiPE). Participants received feedback from two tutors in within-subjects fashion: one human and one labeled as …

The Effects Of Maceration And Enzymes On The Chemical Characteristics Of Hard Apple Cider, Manou De Pelsmaeker

Master's Theses

The purpose of this study was to analyze the effects of maceration and pectinase enzymes on the base chemical, polyphenolic, and volatile characteristics of cider. The apples (Fuji) were milled and macerated for 0, 4, 12, 24, or 36 hours, both with and without an enzymatic pectinase addition. While base chemical characteristics such as sugar content and ABV were unaffected, the acidity of cider was influenced maceration and enzymes. Extended maceration time resulted in lower concentrations of malic acid, and enzymes resulted in a lower pH compared to the control. Polyphenols were extracted during maceration time, resulting in higher concentrations …

Deep Learning For Affect Recognition: A Comparative Study Of Physiological Sensor-Based And Facial Image-Based Approaches, Ravi Panchal, Ravi Panchal

Master's Theses

This thesis investigates deep learning approaches for affect recognition using wearable physiological signals and facial image data. The sensor-based component evaluates stress and affect recognition on the WESAD dataset using wrist-based physiological windows and examines multiple temporal modeling strategies, including convolutional, recurrent, hybrid CNN-LSTM, attention-based, ensemble, and time-frequency approaches.

The image-based component evaluates hard-label facial expression recognition on AffectNet+ using pre-trained ResNet-50, EfficientNet-B3, and ConvNeXt-Tiny architectures across Easy, Challenging, and Difficult subsets representing different levels of expression ambiguity.

Experimental results show that the proposed Multi-Branch Attention CNN-BiLSTM (MBA-CNN-BiLSTM) model achieves the strongest wearable stress- and affect-recognition performance among the evaluated …

Movement And Space Use Of Weaned Northern Elephant Seal (Mirounga Angustirostris) Pups During Their First At-Sea Foraging Migration, Katie Saenger

Master's Theses

The northern elephant seal (Mirounga angustirostris) is a marine mammal known for engaging in long foraging migrations at sea. Adult male northern elephant seals follow pathways along the western coast of North America towards Alaska and adult female northern elephant seals follow pathways to open ocean in the North Pacific. However, there is little information on weaned northern elephant seal pup foraging behavior during their first foraging migration. This lack of knowledge is significant because northern elephant seals have a mortality rate of >50% in the first year. This project aimed to better understand the at-sea migratory movement …

Reproducing And Evaluating Charger Surfing: Robustness Of Smartphone Charging-Line Side-Channels, Colby M. Watts

Master's Theses

Smartphones are frequently connected to external, untrusted charging hardware, creating opportunities for side-channel attacks that do not require malware or direct access to device data. Charger Surfing, a recently proposed charging-line power analysis side-channel attack, reported high accuracy in inferring touchscreen input from voltage measurements collected from a smartphone’s charging cable; however, the reproducibility and robustness of these results under different conditions remain unclear. This thesis presents an independent replication and evaluation of Charger Surfing, including the development of an end-to-end data collection pipeline consisting of a modified charging cable, oscilloscope-based recordings, custom Android app, automated trace processing, and convolutional …

An Evaluation Of Road Network Structure As A Predictor Of Traffic Volume, Colin M. Mcdonald

Master's Theses

This thesis evaluates the relationships between various graph theory metrics and taxi traffic volume for the cities of San Francisco, California and Porto, Portugal. We also evaluate a modified betweenness centrality metric which incorporates the count of distinct origin-destination pairs from the taxi data as the weight function. This thesis extends a paper by Pengyao Ye, Bo Wu, and Wenbo Fan by reducing circularity through a temporal train-test split and by comparing both line-graph and primal-graph formulations of betweenness centrality.

We found that past traffic volume is almost perfectly correlated with future traffic volume and that the modified betweenness centrality …

Sustainable Management Of Soilborne Pathogens In Strawberry Production Through Host Resistance And Sanitation Practices, Maria G. Alvarez Arredondo

Master's Theses

Strawberry production in California is significantly impacted by soilborne pathogens that reduce plant productivity and increase management costs. This research addressed management of these pathogens through two independent approaches: evaluation of host resistance in strawberry cultivars and assessment of sanitation practices for reducing pathogen movement between fields.

Macrophomina root rot, caused by Macrophomina phaseolina, was evaluated over two growing seasons (2024–2025 and 2025–2026) using field trials at California Polytechnic State University, San Luis Obispo. In Year 1, disease incidence varied widely among genotypes, with mortality ranging from 1.3% to 88.8% and an average mortality of 26.4%. Area under the …

Electrically Evoked Emg Decomposition Using The Perturbative Generalized Series Expansion, William R. Walker

Master's Theses

Electrically evoked electromyography records the muscle's response to nerve stimulation and has been used for clinical assessment of neuromuscular function, as well as treatments such as functional electrical stimulation or stroke rehabilitation. In every muscular contraction, an electrical signal is generated. These signals come from the summation of simultaneously recruited motor units, enabling decomposition techniques to reveal information about motor unit recruitment.  By improving the ability to decompose and analyze these signals, clinical treatments involving neuromuscular electrical stimulation can be optimized and better understood. Much of the research on EMG analysis focuses on voluntary EMG, leaving a gap in the …

Chemical And Sensory Consequences Of Oxidative And Reductive Handling Of White Wines, Amelia Pargellis

Master's Theses

In the 2024 and 2025 vintage four experiments were performed each with a different varietal, namely Albariño, Grenache blanc, Loureiro, and Vermentino. These experiments investigated the effects of hyperoxygenation, reductive winemaking techniques, while monitoring the oxidation-reduction potential.

Albariño grapes were made following two juice protocols, control/reductive (Reductive Control) and oxidative (HyOx). Reductive Control received antioxidants (50 ppm SO₂, 160 mg/L ascorbic acid) and CO₂ blanketing, and HyOx underwent hyperoxygenation at approximately 700 mL/L/h of air for two hours through a stainless-steel sparging stone with 10-µm pores. Juice was cold-settled and racked. Reductive Control juice was split into …

Integration Of Robotic Arm And Conveyor With Programmable Logic Controller, Drake A. Small

Master's Theses

To meet new curriculum demands brought on by Cal Poly's upcoming switch to semesters, a new, cross-disciplinary lab module was developed for EE 435 (Industrial Power Control and Automation). The module emphasizes career-applicable skills, preparing students for the field of controls engineering within the manufacturing industry. These skills include robotic control, computer networking and configuration, and embedded systems. The work focused on integrating a collaborative robot arm to pick-and-place boxes on a conveyor. A myCobot 320 Pi and an Ultimation Powered Roller MDR Conveyor were integrated with the existing PLC system using Modbus RTU and EtherNet/IP communication protocols, respectively. A …

Thermally Induced Color Changes In Iron Oxide Containing Coatings, Tabatha Whitfield

Master's Theses

Wildland-urban interface (WUI) fires and residential conflagrations present significant challenges for post-fire damage and fire propagation analysis. CAL FIRE observed reddening in architectural coatings during the 2025 Pacific Palisades fire with no determination of the cause. While heat-induced color change of infrastructure coatings has been studied, its potential use as a thermal exposure indicator in residential fire events remains largely unexplored. The objective of this study was to characterize the heat-induced color change of yellow iron oxide containing coatings subjected to thermal exposures, replicating residential fire conditions. The coatings were applied to commonly used building materials and exposed to direct …

A History Of The Underground Comix Scene: The Seriousness Of An Unserious Genre, Harris Darcie Shugart

Master's Theses

The Underground Comix Scene of the 1960s and 1970s was born out of an age of censorship. The Comics Code Authority, a regulatory body created by the Comics Magazine Association of America in 1954, established guidelines requiring publishing houses to self-regulate following a recommendation from the United States Senate Subcommittee on Juvenile Delinquency in 1953. Comix with an X, for their X-rated nature, represent an emerging counter-culture in the latter half of the 1960s and the 1970s, with an epicenter of San Francisco. These comix and their artists were not interested in obtaining the looming ‘Seal of Approval’ from the …

The Effects Of Carbon-Fiber Plates And Peba-Based Midsole Foam In Running Shoes On Lower-Limb Joint Kinetics And Kinematics In Recreational Female Runners, Jordan M. Allen

Master's Theses

The recent increase in long-distance running participation and the rapid advancement in footwear technology have created a need for research on injury prevention in this growing population of recreational runners. When “super shoes” were first introduced to the running scene, they caught the attention of runners worldwide with the rapid improvement in marathon performance [1]. Today, every major running brand offers its own version of a super shoe, each incorporating a carbon-fiber plate and PEBA-based midsole foam. While previous studies have shown the performance benefits of these shoes, a gap remains in the literature regarding how they impact knee, hip, …

Evaluation Of Laser Doppler Flowmetry And Transillumination Laser Speckle Contrast Imaging To Measure Blood Flow Change In Ischemia Mouse Hindlimb Models, Simon Park

Master's Theses

Peripheral Artery Disease (PAD), caused by plaque buildup and narrowing of the arteries, reduces blood flow to the extremities. Promoting collateral arteriogenesis can help redirect blood flow. However, simple growth of collaterals may not be enough to reverse PAD. Instead, the ability for the collaterals to vasodilate and control blood flow is important, meaning assessing collateral function is important for the arteriogenesis assesment. Although microscopy techniques can measure vasodilation, contrast limitations in larger vessels such as collaterals make blood flow measurements difficult. Techniques such as ultrasound or magnetic resonance imaging (MRI) can measure blood flow but have limitations with cost …

Crab: A Novel Clustering Score Using Clustering With Rivals And Buddies For Unsupervised Learning, Allen Choi

Master's Theses

Unsupervised clustering algorithms today are used across a wide variety of fields such as biology, engineering, and industry in order to classify observations into groups where labels are not provided. This can provide important latent information regarding the observations within groups, as well as insight regarding the groups themselves. In order to judge the optimal number of clusters for an unsupervised clustering algorithm, many methods exist such as the Elbow Method and Silhouette Score; however, these methods come with drawbacks and are not necessarily flexible across many unsupervised methods. We present a novel clustering score framework relying on a resampling-based …

Practical Multimodal Wearable Sensing For Functional Upper Extremity Primitive Classification With Application To Stroke Rehabilitation, Nicholas Weiss

Master's Theses

Stroke often causes long-term weakness and impaired motor control in the upper extremity (UE), making everyday tasks such as reaching, grasping, and moving objects more difficult. Restoring functional arm use is therefore a central goal of post-stroke rehabilitation. Measuring affected arm use continuously and objectively is important because isolated clinical assessments may not fully capture how the affected arm is used during therapy or daily life. Wearable sensors offer a promising approach for monitoring, but raw sensor signals are difficult to interpret directly. Functional movement primitives address this issue by describing UE behavior as smaller, task-agnostic movement units.

This thesis …

Dot Product Engine Based Neuromorphic Hardware For Continuous-Time Biomedical Signal Classification, Sanjeev Srinivasan

Master's Theses

Accurate diagnosis of pathological conditions from biomedical signals, such as electrocardiograms (ECGs) is often performed offline, making it time-consuming, costly, and inefficient, especially when abnormal patterns are rare and long-term monitoring generates large amounts of data. To address this, this work proposes a compact, scalable, and programmable neuromorphic system designed for real-time preliminary arrhythmia detection and classification using ECG signals, that can be extended to other biomedical signals. The proposed design processes ECG signals using a delta modulation-based spike encoder, followed by classification with a dot-product engine (DPE) based spiking neural network (SNN) processor and winner-take-all (WTA) circuit. The architecture …

`Youdrawitr`: Integrating Interactive Graphical Testing Into The `Ggplot2` Ecosystem, Alisa Krasilnikov

Master's Theses

`youdrawitR` is an R package inspired by the New York Times ‘You Draw It’ series, where readers are invited to sketch their own predictions before seeing the actual data. In a similar spirit, `youdrawitR` allows users to draw predicted values directly onto statistical graphics, creating a more engaging way to study how people interpret visual patterns. Earlier versions of the tool required knowledge of JavaScript D3 to extend or adapt the package, which created a barrier to entry for many statistical researchers. Further, the package was limited in scope, supporting only scatterplots. The redesigned `youdrawitR` builds on the familiar `ggplot2` …

Evaluation Of Solar Reflective Pigments For Use In Direct-To-Metal Coatings, William J. Diment

Master's Theses

Solar reflective coatings offer a promising strategy to mitigate the urban heat island effect by reducing absorption of near-infrared solar energy. This thesis project investigates the feasibility of incorporating near-infrared reflective pigments into waterborne direct-to-metal (DTM) latex coating systems while maintaining acceptable color comparison characteristics and coating performance. An all acrylic latex DTM formulation with titanium dioxide as the sole pigment was prepared and tinted with a variety of conventional and solar reflective commercial colorants across the yellow, red, blue, and green color ranges. Coatings were evaluated for solar reflectance, CIELAB color, gloss, contrast ratio, rheological behavior, accelerated ultraviolet weathering …

Effects Of Hot Water Dipping And Sub-Zero Saline Chilling On The Microbial Safety Of Broiler Carcasses And Recycled Chilling Water, Elen Zhu

Master's Theses

Broiler meat became the most widely consumed meat within the United States and across the world in 2019. The trend of increasing broiler consumption is expected to continue due to affordability, health benefits, and production efficiency. To meet the growing demand of broilers, a substantial number of birds need to be produced and processed while minimizing bacteria contamination, water consumption and wastewater generation.

In this study, the microbial safety (mesophilic aerobic bacteria, coliforms, and Escherichia coli) of broiler carcasses and post-chill water (red water) was assessed, using innovative processing techniques and red water recycling. A total of 144 broilers …

Independent And Combined Effects Of Early-Life Iron Deficiency And Antibiotic Exposure On Growth And Hematological Outcomes In A Piglet Model, Ginger M. Fitzpatrick

Master's Theses

Iron deficiency (ID) affects over 2 billion individuals globally. Children under 5 are at increased risk of ID due to rapid growth and are especially vulnerable to its negative consequences because of iron’s essential role in cognitive development and immune maturation. ID is the leading cause of iron deficiency anemia (IDA), with IDA affecting approximately 40% of children in this age group. Antibiotic (abx) exposure is also prevalent during early life and may disrupt growth and through gut dysbiosis, with increasing use posing additional risk in younger populations. Geographically, there is overlap in regions with high anemia prevalence and those …

Evaluation Of Ultraviolet-C Light For Control Of Mites And Western Tarnished Plant Bug In Strawberry & Interactive Lethal Effects Of Common Strawberry Fungicides And Adjuvants On Phytoseiulus Persimilis, Colin T. Koubek

Master's Theses

California strawberry production relies heavily on chemical pesticides to manage arthropod pests and diseases, but pesticide resistance, regulatory pressure, and the need to conserve biological control agents have increased interest in alternative pest management tools. This thesis evaluated ultraviolet-C (UV-C) light as a nonchemical management tool for key strawberry arthropod pests and assessed the compatibility of common strawberry fungicides and adjuvants with the predatory mite Phytoseiulus persimilis Athias-Henriot. The first objective was to determine the ovicidal and lethal effects of UV-C light on Lygus hesperus Knight eggs and nymphs. Laboratory and field ovicide assays were conducted using UV-C doses relevant …

Effect Of Viscoelastic Materials On Laminated Composite Beams For Vibration-Sensitive Automotive Enclosures, Nathan D. Neugeboren

Master's Theses

This study evaluates high-damping composite laminates for vibration-sensitive automotive components, with emphasis on motorcycle instrument clusters, the dashboard that houses the speedometer, indicator lights, and other rider information. Cantilever beam specimens were used as simplified test articles to compare analytical Euler-Bernoulli beam predictions, Autodesk Nastran finite element analysis, and sine-sweep experimental measurements. Metallic beams were first tested to validate modeling assumptions, FEA setup, and laboratory procedures. Analytical and FEA natural frequencies agreed within 0.6 % for ideal bonded metal beams, establishing a baseline for modal prediction. The method was then extended to carbon fiber, fiberglass, Kevlar, and hybrid laminates, with …

Development Of A Free-Floating Space Robotic Simulator, Truman: Terrestrial Robotic Unit For Multibody Analysis And Navigation, Jackson W. Cordova

Master's Theses

This work describes the development of a 3 Degree-of-Freedom (DOF) robotic manipulator for use on a free-floating planar air-bearing vehicle. The system developed aims to serve as a foundation for future space robotics research at the California Polytechnic State University (Cal Poly)’s Space Robotics Laboratory. Systems doc- umentation describes conceptual operation and architecture of the proposed system: Terrestrial Robotic Unit for Multibody Analysis and Navigation (TRUMAN). The key operation of TRUMAN is to study a self launch maneuver of a free-floating ve- hicle including 4 distinct phases: launch off a fixed rail, coast, reorientation using manipulator motion, and capture of …

Design And Evaluation Of An Assistive Powered Hand Orthosis For Grasp Activities For People Post-Stroke, Sydney Alexander

Master's Theses

After suffering a stroke, many survivors experience physical disability that affects their ability to complete daily tasks using their hands. Physical therapy is often pre scribed to people post-stroke, but is not fully effective at restoring hand function. The goal of this project was to design and fabricate an assistive device for people post-stroke to help with grasp and release. The device was designed to address com mon shortcomings of existing similar devices. State of the art devices in this domain were investigated to determine a set of design improvements. A novel motor-actuated hand orthosis was designed to decrease weight, …

Investigating The Structural Barriers And Opportunities For End-Of-Life Management Of Agricultural Plastic Waste Within California's Strawberry Industry, Rory M. O'Toole

Master's Theses

Agricultural plastic waste (APW) accounts for a significant and growing share of global plastic pollution, yet no study has documented how APW management functions across a specific crop system from production through end-of-life (EOL). This thesis addresses that gap by examining the structures and valuations that shape current EOL management of plastic mulch (PM) and drip tape (DT) in California's strawberry industry, one of the nation's most plastic-dependent crop systems. Drawing on an ethnographic approach that included 27 semi-structured interviews with stakeholders, as well as site visits, this study traces how APW is produced, valued, and discarded within a structurally …

Hamster: Hybrid-Actuated Mobile Spherical Terrain Exploration Rover, Winnie Gao

Master's Theses

The expansion of space exploration to increasingly challenging planetary environments requires mobility systems capable of extreme traversal capabilities and operational reliability. This thesis presents the design, development, and testing of a low-cost Hybrid-Actuated Mobile Spherical Terrain Exploration Rover (HAMSTER) intended for use on a planetary surface exploration mission. HAMSTER uses a pendulum-based actuation method for steering and an actuated internal shaft to propel the vehicle forward. The internal structure includes a two-tiered central case composed of the navigation control module, accelerometer, motor controller, primary DC motor, battery, voltage regulators, Raspberry Pi, pendulum servo motor, and drive shafts. Additive manufacturing through …

Trustworthy Intelligence Fusion For Search And Rescue: Designing Grounded And Secure Multi-Agent Ai For Mission Decision Support, Yayun Tan

Master's Theses

Search and rescue (SAR) operations require teams to integrate uncertain information under severe time pressure. Large language model (LLM)-based multi-agent systems (MAS) can support decision-making, but they also risk producing hallucinated outputs and processing unreliable or malicious data. This thesis addresses these risks through three linked studies. First, it proposes a modular eight-agent SAR MAS architecture that reflects the structure of real SAR missions by assigning specialized roles to different agents. Second, it introduces a post-hoc probabilistic verification framework that checks LLM agent outputs against a probabilistic knowledge graph built from historical SAR incidents.  Third, the thesis examines indirect adversarial …

Characterization Of The Thermally Driven Red Hue Effect In Coated And Uncoated Concrete Systems: Implications For Post-Fire Assessment In Wildland Urban Interface Communities, Juan C. Palominos Jr

Master's Theses

The increasing frequency and intensity of Wildland-Urban Interface (WUI) wildfires, such as the destructive 2025 Pacific Palisades Fire that destroyed over 6,000 structures, have underscored the urgent need for rapid post-fire safety assessment methodologies. This study sought to quantitatively characterize the Thermally Driven Red Hue Effect (TRHE), a unique, irreversible color shift observed in architectural coatings and concrete substrates, to determine its reliability as a permanent visual record of thermal exposure. Concrete substrates were formulated with three distinct coarse aggregates: gold granite (14.7% Fe), red cinder (22.4% Fe), and green rock (33.6% Fe) and coated with a 20 PVC waterborne …

Effects Of Irrigation And Nitrogen Management On Yield And Leaching Risk In Organic And Conventional Broccoli Fields, Shane Egerstrom

Master's Theses

Under regulatory pressures to reduce groundwater contamination by nitrate from fertilizer, such as those posed by the Central Coast Regional Water Quality Control Board’s Agricultural Order 4.0, a need exists to better understand interactions between irrigation and nitrogen (N) management. To increase N use efficiency (NUE), growers are encouraged to account for additional sources of N in their management plans, such as irrigation water N and preplant soil N. The availability of these N sources for plant uptake and how it is affected by other management conditions is not yet well documented. We conducted 6 field trials, 3 organic and …