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Articles 1 - 16 of 16
Full-Text Articles in Engineering
Extending The Functional Subnetwork Approach To A Generalized Linear Integrate-And-Fire Neuron Model, Nicholas Szczecinski, Roger Quinn, Alexander J. Hunt
Extending The Functional Subnetwork Approach To A Generalized Linear Integrate-And-Fire Neuron Model, Nicholas Szczecinski, Roger Quinn, Alexander J. Hunt
Mechanical and Materials Engineering Faculty Publications and Presentations
Engineering neural networks to perform specific tasks often represents a monumental challenge in determining network architecture and parameter values. In this work, we extend our previously-developed method for tuning networks of non-spiking neurons, the “Functional subnetwork approach” (FSA), to the tuning of networks composed of spiking neurons. This extension enables the direct assembly and tuning of networks of spiking neurons and synapses based on the network’s intended function, without the use of global optimization ormachine learning. To extend the FSA, we show that the dynamics of a generalized linear integrate and fire (GLIF) neuronmodel have fundamental similarities to those of …
Characterization And Manipulation Of Carbon Precursor Species During Plasma Enhanced Chemical Vapor Deposition Of Graphene, Otto Zietz, Samuel Olson, Brendan Coyne, Yilian Liu, Jun Jiao
Characterization And Manipulation Of Carbon Precursor Species During Plasma Enhanced Chemical Vapor Deposition Of Graphene, Otto Zietz, Samuel Olson, Brendan Coyne, Yilian Liu, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
To develop a synthesis technique providing enhanced control of graphene film quality and uniformity, a systematic characterization and manipulation of hydrocarbon precursors generated during plasma enhanced chemical vapor deposition of graphene is presented. Remote ionization of acetylene is observed to generate a variety of neutral and ionized hydrocarbon precursors, while in situ manipulation of the size and reactivity of carbon species permitted to interact with the growth catalyst enables control of the resultant graphene morphology. Selective screening of high energy hydrocarbon ions coupled with a multistage bias growth regime results in the production of 90% few-to-monolayer graphene on 50 nm …
The Optimization Of Machining Parameters For Milling Operations By Using The Nelder–Mead Simplex Method, Yubin Lee, Alin Resiga, Sung Yi, Chien Wern
The Optimization Of Machining Parameters For Milling Operations By Using The Nelder–Mead Simplex Method, Yubin Lee, Alin Resiga, Sung Yi, Chien Wern
Mechanical and Materials Engineering Faculty Publications and Presentations
The purpose of machining operations is to make specific shapes or surface characteristics for a product. Conditions for machining operations were traditionally selected based on geometry and surface finish requirements. However, nowadays, many researchers are optimizing machining parameters since high-quality products can be produced using more expensive and advanced machines and tools. There are a few methods to optimize the machining process, such as minimizing unit production time or cost or maximizing profit. This research focused on maximizing the profit of computer numerical control (CNC) milling operations by optimizing machining parameters. Cutting speeds and feed are considered as the main …
Fabrication And Characterization Of Flexible Three-Phase Zno-Graphene-Epoxy Electro-Active Thin-Film Nanocomposites: Towards Applications In Wearable Biomedical Devices, Mandeep Singh, Sanjeev Kumar, Shervin Zoghi, Debaki Sarcar, Saquib Ahmed, Shaestagir Chowdhury, Sankha Banerjee
Fabrication And Characterization Of Flexible Three-Phase Zno-Graphene-Epoxy Electro-Active Thin-Film Nanocomposites: Towards Applications In Wearable Biomedical Devices, Mandeep Singh, Sanjeev Kumar, Shervin Zoghi, Debaki Sarcar, Saquib Ahmed, Shaestagir Chowdhury, Sankha Banerjee
Mechanical and Materials Engineering Faculty Publications and Presentations
Perovskite oxides have been used as sensors, actuators, transducers, for sound generation and detection, and also in optical instruments and microscopes. Perovskite halides are currently considered as optoelectronic devices such as solar cells, photodetectors, and radiation detection, but there are major issues with stability, interfacial recombination, and electron/hole mobility. The following work looks into the fabrication of non-toxic ZnO-based lead-free alternatives to perovskite oxides for use as secondary sensors or electron transport layers along with perovskite halides for application in stacked biomedical wearable devices. Three-phase, lead-free, Zinc Oxide-Graphene-Epoxy electroactive nanocomposite thin films were fabricated. The volume fraction of the Graphene …
Parametric Investigation Of Effect Of Abnormal Process Conditions On Self-Piercing Riveting, Taek-Eon Jeong, Dong-Hyuck Kam, Cheolhee Kim
Parametric Investigation Of Effect Of Abnormal Process Conditions On Self-Piercing Riveting, Taek-Eon Jeong, Dong-Hyuck Kam, Cheolhee Kim
Mechanical and Materials Engineering Faculty Publications and Presentations
Self-piercing riveting (SPR) is one of the mechanical joining processes, and its application to Al/Fe dissimilar materials combination, which is hard to weld, is expanding in the automotive industry. The main process parameters in SPR are types of rivet and die, setting force, and rivet setting speed. Previously, the relationship between the main process parameters and output parameters such as cross-sectional characteristics and joint strength has been studied to optimize the SPR process. In practical applications, there are unexpected and abnormal process conditions such as poor fit-up, angular misalignment, edge offset distance, and inaccurate setting and pre-clamping forces, and their …
Ten Questions Concerning The Implications Of Carpet On Indoor Chemistry And Microbiology, Sarah R, Haines, Rachel I. Adams, Brandon E. Boor, Thomas A. Bruton, John Downey, Andrea R. Ferro, Elliott T. Gall, Multiple Additional Authors
Ten Questions Concerning The Implications Of Carpet On Indoor Chemistry And Microbiology, Sarah R, Haines, Rachel I. Adams, Brandon E. Boor, Thomas A. Bruton, John Downey, Andrea R. Ferro, Elliott T. Gall, Multiple Additional Authors
Mechanical and Materials Engineering Faculty Publications and Presentations
Carpet and rugs currently represent about half of the United States flooring market and offer many benefits as a flooring type. How carpets influence our exposure to both microorganisms and chemicals in indoor environments has important health implications but is not well understood. The goal of this manuscript is to consolidate what is known about how carpet impacts indoor chemistry and microbiology, as well as to identify the important research gaps that remain. After describing the current use of carpet indoors, questions focus on five specific areas: 1) indoor chemistry, 2) indoor microbiology, 3) resuspension and exposure, 4) current practices …
Utility-Scale Solar Pv Performance Enhancements Through System Level Modifications, Andrew D. S. Glick, Naseem Ali, Juliaan Bossuyt, Marc Calaf, Raúl Bayoán Cal
Utility-Scale Solar Pv Performance Enhancements Through System Level Modifications, Andrew D. S. Glick, Naseem Ali, Juliaan Bossuyt, Marc Calaf, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Performance of solar PV diminishes with the increase in temperature of the solar modules. Therefore, to further facilitate the reduction in cost of photovoltaic energy, new approaches to limit module temperature increase in natural ambient conditions should be explored. Thus far only approaches based at the individual panel level have been investigated, while the more complex, systems approach remains unexplored. Here, we perform the first wind tunnel scaled solar farm experiments to investigate the potential for temperature reduction through system-level flow enhancement. The percentage of solar irradiance converted into electric power depends upon module efficiency, typically less than 20%. The …
Utility-Scale Solar Pv Performance Enhancements Through System-Level Modifications, Andrew D. S. Glick, Naseem Ali, Juliaan Bossuyt, Marc Calaf, Raul Bayoan Cal
Utility-Scale Solar Pv Performance Enhancements Through System-Level Modifications, Andrew D. S. Glick, Naseem Ali, Juliaan Bossuyt, Marc Calaf, Raul Bayoan Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Performance of solar PV diminishes with the increase in temperature of the solar modules. Therefore, to further facilitate the reduction in cost of photovoltaic energy, new approaches to limit module temperature increase in natural ambient conditions should be explored. Thus far only approaches based at the individual panel level have been investigated, while the more complex, systems approach remains unexplored. Here, we perform the first wind tunnel scaled solar farm experiments to investigate the potential for temperature reduction through system-level flow enhancement. The percentage of solar irradiance converted into electric power depends upon module efficiency, typically less than 20%. The …
Data-Driven Modeling Of The Wake Behind A Wind Turbine Array, Naseem Ali, Raul Bayoan Cal
Data-Driven Modeling Of The Wake Behind A Wind Turbine Array, Naseem Ali, Raul Bayoan Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
The wake flow in a wind turbine array boundary layer is described using the Koopman operator. Dynamics of the flow are decomposed into the linear and forcing terms, and the low-energy delay coordinates are revealed. The rare events show the non-Gaussian long tails that capture the switching and bursting phenomena. The near-wake region shows the incoherent phase space region, where the dynamics are strongly nonlinear. The far-wake region is marked with the small non-Gaussian forcing term, and the dynamics are largely governed by linear dynamics. The data-driven predictive model is built based on the Hankel-based dynamic mode decomposition and treats …
A Dynamic Neural Network Designed Using Analytical Methods Produces Dynamic Control Properties Similar To An Analogous Classical Controller, Wade William Hilts, Nicholas Szczecinski, Roger Quinn, Alexander Hunt
A Dynamic Neural Network Designed Using Analytical Methods Produces Dynamic Control Properties Similar To An Analogous Classical Controller, Wade William Hilts, Nicholas Szczecinski, Roger Quinn, Alexander Hunt
Mechanical and Materials Engineering Faculty Publications and Presentations
Human balance is achieved using many concurrent control loops that combine to react to changes in environment, posture, center of mass and other factors affecting stability. Though numerous engineering models of human balance control have been tested, no methods for porting these models to a neural architecture have been established. It is our hypothesis that the analytical methods we have developed, combined with classical control techniques will provide a reasonable starting point for developing dynamic neural controllers that can reproduce classical control capabilities. In previous work, we tested this hypothesis and demonstrated that a biologically-constrained neural controller that replicates human …
Impact Of Cognitive Tasks On Co2 And Isoprene Emissions From Humans, Elliott T. Gall, Asit Kumar Mishra, Jiayu Li, Stefano Schiavon, Aurelie Laguerre
Impact Of Cognitive Tasks On Co2 And Isoprene Emissions From Humans, Elliott T. Gall, Asit Kumar Mishra, Jiayu Li, Stefano Schiavon, Aurelie Laguerre
Mechanical and Materials Engineering Faculty Publications and Presentations
The human body emits a wide range of chemicals, including CO2 and isoprene. To examine the impact of cognitive tasks on human emission rates of CO2 and isoprene, we conducted an across-subject, counterbalanced study in a controlled chamber involving 16 adults. The chamber replicated an office environment. In groups of four, participants engaged in 30 min each of cognitive tasks (stressed activity) and watching nature documentaries (relaxed activity). Measured biomarkers indicated higher stress levels were achieved during the stressed activity. Per-person CO2 emission rates were greater for stressed than relaxed activity (30.3 ± 2.1 vs 27.0 ± 1.7 g/h/p, p …
Openfoam Simulations Of Late Stage Container Draining In Microgravity, Joshua Thomas Mccraney, Mark M. Weislogel, Paul Steen
Openfoam Simulations Of Late Stage Container Draining In Microgravity, Joshua Thomas Mccraney, Mark M. Weislogel, Paul Steen
Mechanical and Materials Engineering Faculty Publications and Presentations
In the reduced acceleration environment aboard orbiting spacecraft, capillary forces are often exploited to access and control the location and stability of fuels, propellants, coolants, and biological liquids in containers (tanks) for life support. To access the ‘far reaches’ of such tanks, the passive capillary pumping mechanism of interior corner networks can be employed to achieve high levels of draining. With knowledge of maximal corner drain rates, gas ingestion can be avoided and accurate drain transients predicted. In this paper, we benchmark a numerical method for the symmetric draining of capillary liquids in simple interior corners. The free surface is …
Hot Deformation Data For Haynes 214, Haynes 230 And Inconel 740h, Benjamin Adam, Julie Tucker, Graham Tewksbury
Hot Deformation Data For Haynes 214, Haynes 230 And Inconel 740h, Benjamin Adam, Julie Tucker, Graham Tewksbury
Mechanical and Materials Engineering Faculty Publications and Presentations
This article presents the datasets gathered for the hot processing of three Ni-based superalloys intended for A-USC application, Haynes 214, Haynes 230 and Inconel 740H. Isothermal compression tests were conducted with a Gleeble 3500 at temperatures between 1000 C and 1200 C and strain rates between 0.01/s and 1/s to a full true strain of 0.7. The obtained true stress-true strain curves were used as basis for hot processing maps, linking temperature, stress and strain rate. Subsequently, all samples were sectioned through the geometric centre to provide microstructural information, captured using EBSD, as well as EDX for the evolution of …
Detailed Energy Efficiency Strategies For Converting An Existing Office Building To Nzeb: A Case Study In The Pacific Northwest, Ali Alajmi, Abby Short, Janna Ferguson, Kalina K. Vander Poel, Corey T. Griffin
Detailed Energy Efficiency Strategies For Converting An Existing Office Building To Nzeb: A Case Study In The Pacific Northwest, Ali Alajmi, Abby Short, Janna Ferguson, Kalina K. Vander Poel, Corey T. Griffin
Mechanical and Materials Engineering Faculty Publications and Presentations
This paper is an attempt to identify a methodology for converting conventional energy consumption buildings to net-zero energy buildings (NZEB). The first step was rather different from the usual energy audit, which is to analyze a facility’s energy consumptions from both macro- and micro-scales. To implement such an approach, a governmental office building (Metro) in Portland, OR, was chosen as a case study. After a building model was validated against a real measurement, it was then used to evaluate different energy efficiency strategies (EESs) so as to reduce the energy consumption. The EESs showed a reduction in energy use intensity …
Potential Of Module Arrangements To Enhance Convective Cooling In Solar Photovoltaic Arrays, B. Stanislawski, Fabien Margairaz, Raúl Bayoán Cal, Marc Calaf
Potential Of Module Arrangements To Enhance Convective Cooling In Solar Photovoltaic Arrays, B. Stanislawski, Fabien Margairaz, Raúl Bayoán Cal, Marc Calaf
Mechanical and Materials Engineering Faculty Publications and Presentations
When solar photovoltaic (PV) module temperatures rise during operation, commonly-installed modules experience an efficiency loss between 0.1 and 0.5% per degree above 25+C. Thus, extensive research has aimed to reduce the operating temperature of solar modules. However, many cooling solutions require additional cost or equipment that precludes their implementation in utility-scale PV plants. Based on previous studies of land-atmosphere interactions of surface thermal heterogeneity, we hypothesize that certain solar farm arrangements may enhance natural convective heat transfer between the solar modules and surrounding flow. Due to the strong non-linear relationship between module temperature and convective heat transfer, enhancing the convective …
Modelling Lagrangian Velocity And Acceleration In Turbulent Flows As Infinitely Differentiable Stochastic Process, Bianca Fontanin Viggiano, Jan Friedrich, Romain Volk, Mickael Bourgoin, Raúl Bayoán Cal, Laurent Chevillard
Modelling Lagrangian Velocity And Acceleration In Turbulent Flows As Infinitely Differentiable Stochastic Process, Bianca Fontanin Viggiano, Jan Friedrich, Romain Volk, Mickael Bourgoin, Raúl Bayoán Cal, Laurent Chevillard
Mechanical and Materials Engineering Faculty Publications and Presentations
We develop a stochastic model for Lagrangian velocity as it is observed in experimental and numerical fully developed turbulent flows. We define it as the unique statistically stationary solution of a causal dynamics, given by a stochastic differential equation. In comparison to previously proposed stochastic models, the obtained process is infinitely differentiable at a given finite Reynolds number, and its second-order statistical properties converge to those of an Ornstein-Uhlenbeck process in the infinite Reynolds number limit. In this limit, it exhibits furthermore intermittent scaling properties, as they can be quantified using higher-order statistics. To achieve this, we begin with generalizing …