Mechanical Engineering Commons^™

Measurement Of Pollution Emissions From Natural Gas Stoves: Preparation For An Induction Cooktop Intervention Study, Jessica Zanella Lorensi

Dissertations and Theses

Humans spend ∼90% of their time enclosed in buildings. Indoors environments can be a source of pollutant which can affect health and productivity. Appliances that combust fossil fuels indoors, like stoves, are a critical source of a range of pollutants, like carbon monoxide (CO) and nitrogen dioxide (NO₂). In the US, the usual cooking fuel is natural gas (NG), presented in more than 30% of households in the country. Some studies in the literature linked cooking pollutants, including those specific to gas combustion, to various health conditions, including heart and respiratory diseases. Nitrogen dioxide, for example, can be …

Spatial Structure And Energy Content Of Wakes Behind Single And Arrayed Undulated Cylinders, Taiga Naomi Drucker-Boisvert, OndˇRej FerˇCák, Jérémie Auzoux, Sarah E. Smith, Zein Sadek, Rowan Moore, Christain T. Murphy, Trevor Dunt, Jennifer A. Franck, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Biologically inspired undulated cylinder geometries significantly influence wake structure and vortex-induced vibrations in turbulent flows, yet the underlying mechanisms are not fully understood. It is further unknown how these influences extend to multi-cylinder arrays, where interacting wakes accumulate and mix. This study examines the wake characteristics of an undulated cylinder and a smooth elliptic cylinder in single- and multi-cylinder array configurations, using particle image velocimetry and proper orthogonal decomposition (POD). Relative to the smooth elliptic cylinder, the undulated geometry induces pronounced spanwise-axial variability, characterized by enhanced near-wake mean momentum and weak far-wake signatures, consistent with reduced turbulent kinetic energy. While …

Improved Method Of Evaluating Gas-Phase Air Cleaners Considering Adsorption And Desorption Mechanisms To And From Internal Test Chamber Surfaces, Casey Douglas Coffland

Dissertations and Theses

Portable air cleaners are playing an increasingly important role in managing indoor air quality in response to pressing issues like wildfire smoke events. Smoke is a complex mixture of gases and particulate matter; while established test methods exist for particulate matter, the dynamic behavior of gaseous pollutants is not well accounted for in current test methods. This is because prevailing air cleaner testing methods typically treat background losses as irreversible, whereas gases can engage in partitioning to and from test chamber surfaces. Ignoring these sorption interactions causes inaccurate estimation of an air cleaner's impact.

A new approach has been developed …

Adaptive Design Strategies For A Dual-Shaft Pvc Shredder, Gavin Balderas

University Honors Theses

This capstone project involved the design and development of a mid-size plastic shredder, created to process strong, ductile PVC sheets up to ½" thick. This application falls between the capabilities of consumer grade plastic shredders and heavy-duty industrial machines. Over 400 million tons of plastic produced annually and less than 10% of it is recycled; there is an ever-growing need for plastic recycling accessibility and infrastructure. This project aimed to create a compact dual-shaft shredder that can shred thick PVC sheets while being powered by a 120V outlet. Research into blade geometry and orientations aided an iterative design process driven …

Rapid-Prototyping Nanofabrication: Lcd-Based Projection Lithography And Physical Vapor Deposition, Sabeel Saleem Mohammmed

University Honors Theses

The semiconductor industry's continued growth, driven in large part by demand for artificial intelligence hardware, has highlighted the need for greater workforce development in regions adjacent to major fabrication centers like Oregon's Silicon Forest. This capstone project lays the groundwork for a small scale and student led semiconductor fabrication lab at Portland State University by demonstrating two of the core steps in chip manufacturing: photolithography and thin film deposition. Rather than relying on conventional fixed reticles, this work explores a unique, low cost approach to patterning that uses an ultraviolet-compatible liquid crystal display (LCD) as a programmable reticle, allowing arbitrary …

Capstone Review: Warn Winch Proximity Sensor, Leana Girton

University Honors Theses

This thesis reviews the mechanical engineering capstone project that designed a winch proximity sensor for WARN Industries. WARN is very interested in developing this product for market as a safety and ease-of-use accessory, and working with Portland State University was the first step in this process. A group of four mechanical engineering and four electrical engineering capstone students collaborated to research sensor types, test the selected methods, and design and build a prototype. The final design implements an inductive ring, a mechanical button, and bluetooth signaling. The project succeeded in prototyping a proximity sensor for WARN, who will have access …

Coupled Ferroelectricity And Phonon Chirality, Xiang-Bin Han, Cong Yang, Rui Sun, Xiaotong Zhang, Thuc Mai, Zhengze Xu, Aryan Jouneghaninaseri, Xiaoning Jiang, Rahul Rao, Yi Xia, Multople Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

Recognizing the coupling between ferroelectricity and chirality in optically active ferroelectrics opens a route for manipulating chirality via ferroelectricity under an external electric field, enabling control over chirality-dependent quantum states. Here, we report the experimental demonstration of the coupling between ferroelectricity and phonon chirality in the molecular ferroelectric triglycine sulfate. By electrically switching the crystal chirality, we achieve reversible and device-compatible control of phonon chirality, as revealed by in situ time-resolved magneto-optical Kerr effect measurements. The Kerr rotation reverses with electric-field switching, while phonon chirality vanishes in the paraelectric phase and is tunable in the racemic ferroelectric state. Furthermore, density …

Isometric Force Characterization Of Braided Pneumatic Actuators, Ben Bolen, Mohammad Elzein, Lawrence Pang, Alexander Hunt

Mechanical and Materials Engineering Faculty Publications and Presentations

Artificial muscles such as braided pneumatic actuators (BPAs) offer many advantages for robotic systems, including high durability and strength-to-weight ratios. However, their use in robotic systems is still extremely limited, in part due to their poor force, length, and pressure characterization. In this work, a test setup is created to compare force produced by Festo fluidic BPAs with leading models. Our analysis of the data has resulted in (1) the development of new equations to calculate force as functions of pressure and contraction for Festo BPAs with uninflated diameters of 10 mm and 20 mm, and (2) a novel equation …

An Open-Source Linear Actuated-Quartz Tube Furnace With Programmable Ceramic Heater Movement For Laboratory-Scale Studies Of Combustion And Emission, Casey Coffland, Ryan Bixler, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

The Linear Actuated Quartz Tube Furnace (LA-QTF) is an instrument engineered to heat and combust materials under controlled conditions, capable of achieving flaming and smoldering states. A ceramic ring furnace is linearly actuated parallel to the length of a quartz tube. The mode of combustion depends on temperature, fuel composition, and oxygen availability; the LA-QTF regulates combustion by controlling the temperature and position of the ring furnace, and airflow within the tube. The LA-QTF can maintain temperatures between 23 °C and 530 °C for extended time periods, with stable temperatures over long-duration (∼120 min) experiments. Flow rate is dependent on …

Vegetated Canopy Heterogeneity Footprints In The Roughness Sublayer, Giulia Salmaso, Raul Bayoan Cal, Marc Calaf

Mechanical and Materials Engineering Faculty Publications and Presentations

Turbulent flows over horizontally homogeneous rough surfaces are categorized as rough‐wall boundary layer flows, while flows over homogeneous vegetated canopies are better described through a mixing‐layer analogy. At present, numerous studies have investigated canopy density as a transition mechanism between rough‐wall and mixing‐layer‐type flows. Yet, most considered canopies have been spatially homogeneous, with few exceptions investigating agricultural arrangements. However, most vegetated canopies are not homogeneously distributed, but instead contain gaps and spatial heterogeneities of different scales. In these cases, it remains unclear which are the dominant flow traits, and how spatial heterogeneity affects them. To help overcome these knowledge gaps, …

Cylindrical Versus Spherical Self-Similar Capillary Cavity Collapse, Karl Cardin, Christophe Josserand, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Drop tower experiments have been performed to study the capillary collapse of large high-aspect-ratio cavities. Cavities are formed by momentarily impinging the free surface of a liquid bath with a jet of air in the microgravity environment of a drop tower. The collapse may give rise to a jet and three distinct jetting regimes are identified. Simulations are performed to further investigate the phenomena. The abrupt emergence of a thin high velocity jet is observed experimentally and numerically at a specific initial cavity aspect ratio. Different power laws are identified in different regions of the cavity during the collapse providing …

Vacuum Modification Of The Surface Properties Of T15k6 Hard Alloy By Plasma–Chemical Synthesis Of Tin-Cu Coatings, Aleksandr Semenov, Dmitriy Tsyrenov, Nikolay Ulakhanov, Irina Semenova, Undrakh Mishigdorzhiyn, Wen Ma, Simon C. Tung, George E. Totten

Mechanical and Materials Engineering Faculty Publications and Presentations

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a …

Scale-Dependent Particle Transport Over Urban-Like Roughness In Turbulent Flow, Rae Riddle

Dissertations and Theses

This study employs direct numerical simulation (DNS) to investigate the dispersion of inertial particles in turbulent flow over three-dimensional urban-like roughness at Reτ = 200. Particles with Stokes numbers St = 5, 25, and 100 are tracked over cubic arrays with spanwise spacings Sy from 2h to 32h, where h = δ/8 and δ is the half-channel height, alongside a smooth-wall reference case. The results reveal scale-dependent particle responses characterized by three distinct regimes. First, high-inertia particles (St = 100) align strongly with mean secondary flows, exhibiting organized plumes above roughness elements. Their vertical transport peaks at intermediate spacing …

Asymmetric Airfoil Selection For A Small-Scale Vertical Axis Wind Turbine: A Numerical Study, Babak Ranjbaran, Yonatan Afework Tesfahunegn, Raul Bayoan Cal, Ármann Gylfason

Mechanical and Materials Engineering Faculty Publications and Presentations

Vertical-axis wind turbine (VAWT) efficiency depends mainly on the aerodynamic properties of the airfoils used in their blades. During each rotation of the turbine, the blade experiences a range of angles of attack (AOAs) with respect to the relative wind, resulting in a variation of its contribution to the overall performance of the turbine. This paper leverages the capabilities of XFoil for preliminary performance analysis and ANSYS Fluent for detailed Computational Fluid Dynamics (CFD) simulations. The initial selection of airfoils is based on geometric characteristics and their potential for high tangential force coefficients. The asymmetric airfoils were selected by maximizing …

Sweep Angle Effects Of Flow Over A Seal Whisker-Inspired Undulated Cylinder, Trevor Dunt, Christin T. Murphy, Ondrej Fercak, Raúl Bayoán Cal, Jennifer A. Franck

Mechanical and Materials Engineering Faculty Publications and Presentations

Flow over a seal whisker-inspired undulated cylinder at swept back angles is computationally investigated, comparing the vortex shedding, forces, and wake characteristics to those of an equivalent smooth geometry. Numerous prior studies have demonstrated that undulated cylinders can reduce mean drag and unsteady lift oscillations; however, none have isolated the effects of the sweep angle resulting from whisker positioning in flow. Inspired by the active control seals exert over their whiskers while navigating and sensing in unsteady aquatic environments, this study investigates how such orientation influences the hydrodynamic performance of the geometry. Simulations are performed of flow across a rigid, …

Characterizing Indoor Surface Voc Contamination After The 2025 Los Angeles Fires, Brett W. Stinson, Emily Lei, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

We quantify volatile organic compound (VOC) emissions from indoor surface swabs and portable air cleaner (PAC) filters collected in a home 30 days after the 2025 Los Angeles wildland-urban interface (WUI) fires. We calculate emissions for 17 fire-relevant compounds. Surface emissions exceeded those of clean controls, and emissions from a windowsill in a room without a PAC were ∼15× and ∼2× higher for benzene and toluene, respectively, than rates reported in the literature for comparable materials unaffected by smoke/soot. Particle filters installed in PACs at the start of the fire emitted aromatics at rates comparable to those reported in a …

High-Throughput Computational Framework For High-Order Anharmonic Thermal Transport In Cubic And Tetragonal Crystals, Zhi Li, Huiju Lee, Chris Wolverton, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

Accurate first-principles prediction of lattice thermal conductivity (κ L) remains challenging in identifying materials with extreme thermal behavior. While the harmonic approximation with three-phonon scattering (HA + 3ph) is now routine, reliable κ L prediction often requires higher-order anharmonic effects, including self-consistent phonon renormalization, three- and four-phonon scattering, and off-diagonal heat flux (SCPH + 3, 4ph + OD). We present a state-of-the-art high-throughput workflow that unifies these effects and apply it to 773 cubic and tetragonal crystals spanning diverse chemistries and structures. From 562 dynamically stable compounds, we assess the hierarchical impacts of higher-order anharmonicity. For around 60% of materials, …

Three-Dimensional Topographical Effects On The Generation Of Internal Lee Waves, Haosen H.A. Xu, Xiaowei Zhu, Kaiwen Zheng

Mechanical and Materials Engineering Faculty Publications and Presentations

Internal lee waves generated by the interaction between geostrophic flows and ocean-floor topography are recognized as an important pathway for transferring energy from large-scale circulation to small-scale mixing in the deep ocean; however, energy fluxes inferred from field observations often fall well below estimates based on classical linear theory. Here, we use direct numerical simulations to examine how three-dimensional (3D) topographic structure alters the generation and energy pathways of internal lee waves. We simulated idealized stratified flows impinging on twodimensional (2D) and 3D sinusoidal topography in a radiating regime. We used Reynolds decomposition based on spatial averaging to isolate wave-induced …

Scalar Source Localization Using Multi-Sensor Domains Of Dependence In Turbulent Channel Fow, Zejian You, Xiaowei Zhu, Qi Wang

Mechanical and Materials Engineering Faculty Publications and Presentations

Tracking hazardous events such as wildfire smoke, coastal oil spills, or chemical releases in natural environments is complicated by turbulent dispersion and molecular diffusion. This study presents a method to localize pollutant sources rapidly and accurately using infinite time-averaged measurements from a multi-sensor network, leveraging the duality between mean forward and adjoint scalar fields. The forward-adjoint duality states that measurements at the sensor (forward feld) are equal to the adjoint field at the source, providing crucial spatial information about the source. Consequently, the adjoint scalar fields can be interpreted as the domain of dependence for the sensor observations [1, 2]. …

Lattice Thermal Transport Beyond The Quasiparticle Approximation: Nontrivial Spectral Competition Between Three- And Four-Phonon Interactions, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

The breakdown of the quasiparticle approximation (QPA) for phonons in strongly anharmonic materials necessitates advanced first-principles frameworks for accurate lattice dynamics and thermal transport predictions. We develop a comprehensive beyond-quasiparticle approximation (BQPA) approach incorporating both three- (3ph) and four-phonon (4ph) interactions and apply it to investigate lattice thermal conductivity (κL) in MgO, PbTe, and AgCl – materials that span a broad spectrum of anharmonicity, from weak to severe anharmonic regimes with overdamped phonons. We reveal that while BQPA consistently increases κL relative to QPA due to phonon softening when considering only 3ph interactions, the inclusion of additional 4ph interactions hardens …

Concerted Rattling-Induced Strong Anharmonicity And Phonon Coherence Lead To Ultralow Glasslike Thermal Conductivity In Tlagte, Shantanu Semwal, Yi Xia, Chris Wolverton, Koushik Pal

Mechanical and Materials Engineering Faculty Publications and Presentations

Ordered crystalline compounds exhibiting ultralow and glass-like thermal conductivity are both fundamentally and technologically important, where phonon quasi-particles dominate their heat transport. Understanding the microscopic mechanisms that govern such unusual transport behavior is necessary to unravel the complex interplay of crystal structure, phonons, and collective excitations of these quasi-particles. Here, we use state-of-the-art first-principles calculations based on quantum density functional theory to investigate the origin of experimentally measured unusually low and glassy thermal conductivity in semiconducting TlAgTe that possesses disconnected chains of Tl atoms within its three-dimensional crystalline framework made up of distorted AgTe4 tetrahedra. Utilizing a unifying framework of …

Jhtdb-Wind: A Web-Accessible Large-Eddy Simulation Database Of A Wind Farm With Virtual Sensor Querying, Xiaowei Zhu, Shuolin Xiao, Ghanesh Narasimhan, Luia A. Martinez-Tossas, Michael Schnaubelt, Gerard Lemson, Hanxun Yao, Alexander S. Szalay, Dennice F. Gayme, Charles Meneveau

Mechanical and Materials Engineering Faculty Publications and Presentations

This paper introduces JHTDB-wind (https://turbulence.idies.jhu.edu/datasets/windfarms), a publicly accessible database containing large-eddy simulation (LES) data from wind farms. Building on the framework of the Johns Hopkins Turbulence Database (JHTDB), which hosts direct numerical and some large-eddy simulation datasets of canonical turbulent flows, JHTDB-wind stores the full space-time (4D) history of the flow and provides users the ability to access and query the data via a web-based virtual sensor interface. The initial dataset comprises LES results from a large wind farm with 6 X 10 turbines, modeled using a filtered actuator line method, under conventionally neutral atmospheric conditions. This data comprises one …

Effect Of Pore Structure On Void Formation In Lotus Type Porous Cu/Solder Joints, Jin-Kwan Lee, Keun-Soo Kim, Jae-Ho Shin, Seung-Min Cho, Sung Yi, Sang-Wook Kim, Soong-Keun Hyun

Mechanical and Materials Engineering Faculty Publications and Presentations

Void formation in solder joints is a critical reliability challenge in high-power electronics, as it degrades thermal dissipation and mechanical integrity. This study investigates a novel structural approach to mitigate this issue. The influence of an uni-directional porous structure in lotus-type porous Cu (Louts Cu) on void formation in solder joints was investigated. All pores in lotus Cu were infiltrated with SAC305 (Sn–3.0Ag–0.5Cu) solder paste. Then reflow soldering was performed under three different atmospheric conditions: air, nitrogen, and vacuum. The microstructure and void fraction were characterized. The shear strength was evaluated. The shear strength of Louts Cu joint was slightly …

Interfacial Gap Prediction In Laser Welding Of Pure Copper Overlap Joints Using Multiple Sensors., Hyeonhee Kim, Cheolhee Kim, Minjung Kang

Mechanical and Materials Engineering Faculty Publications and Presentations

In this study, a novel approach was proposed for predicting the interfacial gap in copper overlap joints by using deep learning and multi-sensor fusion. In this method, an image sensor, a spectrometer, and optical sensors tomography (OCT) sensors were used to develop and validate deep learning models under various gap conditions. The results revealed that the variation in melt pool dimensions, changes in keyhole behavior, intensity variations at specific wavelengths, and keyhole depth derived from the OCT data could be used to accurately predict the interfacial gap. Among the proposed models, a binary gap classification model achieved the highest accuracy …

First-Principles Theory Of Five-And Six-Phonon Scattering, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

igher-order phonon scatterings beyond fourth order remain largely unexplored despite their potential importance in strongly anharmonic materials at elevated temperatures. We develop a theoretical formalism for first-principles calculation of five- and six-phonon scatterings using Green’s function techniques based on a diagrammatic formalism, and systematically investigate multi-phonon interactions in Si, MgO, and BaO from room temperature to near melting points. Our calculations reveal dramatically different material-dependent behaviors: while five- and six-phonon processes remain negligible in Si even at high temperatures, they become increasingly important in MgO near its melting point (3100 K) and in BaO at intermediate temperatures (1200 K). Most …

Wind Farm Dynamics Over A Diurnal Cycle: Analysis Of A Comprehensive Large-Eddy Simulation, Web-Services Accessible Dataset, Shuolin Xiao, Xiaowei Zhu, Ghanesh Narasimhan, Dennice F. Gayme, Charles Meneveau

Mechanical and Materials Engineering Faculty Publications and Presentations

The 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 …

Al-Driven Interfacial Gap Prediction In Overlapped Al/Cu Laser Weld Joint For Battery Applications, Hyeonhee Kim, Sanghoon Kang, Cheolhee Kim, Yong Hoon Jang, Minjung Kang

Mechanical and Materials Engineering Faculty Publications and Presentations

The battery tab-to-busbar welding process forms the primary electrical path in battery packs and is directly linked to both performance and safety. Variations in jig alignment, material tolerance, and forming quality can cause small interfacial gaps that lead to weak welds. An artificial intelligence (AI)-driven method was proposed in this study for predicting interfacial gaps in aluminum-copper overlap joints by integrating deep learning with multi-sensor data. A charge-coupled device (CCD) camera, spectrometer, and optical coherence tomography (OCT) sensors were employed to develop and validate deep learning models under varying gap conditions. The results revealed that the variation in melt-pool dimensions, …

Enhancement Of Spin Transport Properties In Angled-Channel Graphene Spin Valves Via Hybrid Spin Drift-Diffusion, Samuel Olson, Kaleb Hood, Otto Zietz, Jun Jiao

Mechanical and Materials Engineering Faculty Publications and Presentations

Graphene has promise as a channel connecting separate units of large-scale spintronic circuits owing to its outstanding theoretical spin transport properties. However, spin transport properties of experimental devices consistently fall short of theoretical estimates due to impacts from the substrate, electrodes, or defects in the graphene itself. In this study, we fabricate both traditional non-local spin valves (NLSVs) and novel hybrid drift-diffusion spin valves (HDDSVs) to explore the impact of charge current and AC spin injection efficiency on spin transport. HDDSVs feature channel branches that allow investigation of charge-based spin drift enhancement compared to diffusion-only configurations. We investigate the modulation …

Pressure And Force Dynamics In Artificial Muscle Actuators: A State-Space And Optimization-Based Approach, Mohammad Elzein

Dissertations and Theses

This two-part investigation explores the dynamic behavior of braided pneumatic actuators (BPAs) under bio-inspired pulse modulation, with the aim of improving their biomimetic force output and control. The first study examines the effect of pulse length and inter-pulse timing on BPA performance, revealing that force output is highly sensitive to the temporal structure of input pulses mirroring biological muscle behavior. Using dual-pulse actuation schemes, the results demonstrate that force responses exceed the additive contributions of individual pulses, with peak amplification occurring consistently at a 27 ms inter-pulse gap. Shorter pulse lengths (10–20 ms) yielded the highest normalized force increases, up …

Transfer Learning-Based Multi-Sensor Approach For Predicting Keyhole Depth In Laser Welding Of 780dp Steel, Byeong-Jin Kim, Young-Min Kim, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

Penetration depth is a critical factor determining joint strength in butt welding; however, it is difficult to monitor in keyhole-mode laser welding due to the dynamic nature of the keyhole. Recently, optical coherence tomography (OCT) has been introduced for real-time keyhole depth measurement, though accurate results require meticulous calibration. In this study, deep learning-based models were developed to estimate penetration depth in laser welding of 780 dual-phase (DP) steel. The models utilized coaxial weld pool images and spectrometer signals as inputs, with OCT signals serving as the output reference. Both uni-sensor models (based on coaxial pool images) and multi-sensor models …