Engineering Commons^™

Biomechanical And Sensory Feedback Regularize The Behavior Of Different Locomotor Central Pattern Generators, Kaiyu Deng, Alexander J. Hunt, Nicholas Szczecinski, Matthew Tresch, Hillel J. Chiel, Charles Heckman, Roger Quinn

Mechanical and Materials Engineering Faculty Publications and Presentations

This work presents an in-depth numerical investigation into a hypothesized two-layer central pattern generator (CPG) that controls mammalian walking and how different parameter choices might affect the stepping of a simulated neuromechanical model. Particular attention is paid to the functional role of features that have not received a great deal of attention in previous work: the weak cross-excitatory connectivity within the rhythm generator and the synapse strength between the two layers. Sensitivity evaluations of deafferented CPG models and the combined neuromechanical model are performed. Locomotion frequency is increased in two different ways for both models to investigate whether the model’s …

Study On The Spatiotemporal Dynamic Of Ground-Level Ozone Concentrations On Multiple Scales Across China During The Blue Sky Protection Campaign, Haoji Wu, Lin Pei, Xiaowei Zhu, Bin Guo, Dingming Zhang, Multiple Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

Surface ozone (O3), one of the harmful air pollutants, generated significantly negative effects on human health and plants. Existing O3 datasets with coarse spatiotemporal resolution and limited coverage, and the uncertainties of O3 influential factors seriously restrain related epidemiology and air pollution studies. To tackle above issues, we proposed a novel scheme to estimate daily O3 concentrations on a fine grid scale (1 km × 1 km) from 2018 to 2020 across China based on machine learning methods using hourly observed ground-level pollutant concentrations data, meteorological data, satellite data, and auxiliary data including digital elevation model (DEM), land use …

Prediction Of Curing Time/Shear Strength Of Non-Conductive Adhesives Using A Neural Network Model, Kyung-Eun Min, Jae-Won Jang, Jun-Ki Kim, Sung Yi, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

Electronic packaging has been developed with high resolution and fine interconnection pitches. Non-conductive adhesives (NCAs) have been growing with the increase of I/O pad count and density, along with fine pad bond pitch interconnections. Prediction and optimization of NCA characteristics are inherently complicated due to various and extensive materials composing NCAs. In this study, a framework predicting the curing time and shear strength of an NCA is established by a neural network model. NCA formulations with 4 resins, 3 hardeners, 8 catalysts, and a coupling agent were selected from in-house experiments, and an artificial neural network (ANN) with one dense …

A Novel Voc Breath Tracer Method To Evaluate Indoor Respiratory Exposures In The Near- And Far-Fields; Implications For The Spread Of Respiratory Viruses, Hooman Parhizkar, Mark Fretz, Aurelie Laguerre, Jason Stenson, Richard Corsi, Kevin Van Den Wymelenberg, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

Background

Several studies suggest that far-field transmission (>6 ft) explains a significant number of COVID-19 superspreading outbreaks.

Objective

Therefore, quantifying the ratio of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks.

Methods

In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 0.76 m (2.5 ft), 1.52 m (5 ft), 2.28 m (7.5 ft) from the participant, as well as in the …

Wind Tunnel Research, Dynamics, And Scaling For Wind Energy, Majid Bastankhah, Raul Bayoan Cal, Nicholas Hamilton

Mechanical and Materials Engineering Faculty Publications and Presentations

The interaction of wind turbines with turbulent atmospheric boundary layer (ABL) flows represents a complex multi-scale problem that spans several orders of magnitudes of spatial and temporal scales. These scales range from the interactions of large wind farms with the ABL (on the order of tens of kilometers) to the small length scale of the wind turbine blade boundary layer (order of a millimeter). Detailed studies of multi-scale wind energy aerodynamics are timely and vital to maximize the efficiency of current and future wind energy projects, be they onshore, bottom-fixed offshore, or floating offshore. Among different research modalities, wind tunnel …

Wind Plant Controls, Nicholas Hamilton, Dennice Gayme, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

The development of operational strategies for wind farms as an integrated plant system to achieve a variety of goals from elevating power production to reducing maintenance needs has generated a great deal of interest in recent years. Achieving these operational goals requires an estimate of the energy available and the wind conditions affecting each turbine. The importance of the aerodynamic interaction of wind turbines with the dynamic atmospheric resource means that wakes (the momentum deficit due to power extraction) and their interactions through the farm have the largest influence on the available energy. Predicting the influence of wakes and their …

Remote Sensing Evidence For Significant Variations In The Global Gross Domestic Product During The Covid-19 Epidemic, Bin Guo, Wencai Zhang, Lin Pei, Xiaowei Zhu, Pingping Luo, Weili Duan

Mechanical and Materials Engineering Faculty Publications and Presentations

Coronavirus disease 2019 (COVID-19) has been spreading rapidly and is still threatening human health currently. A series of measures for restraining epidemic spreading has been adopted throughout the world, which seriously impacted the gross domestic product (GDP) globally. However, details of the changes in the GDP and its spatial heterogeneity characteristics on a fine scale worldwide during the pandemic are still uncertain. We designed a novel scheme to simulate a 0.1° × 0.1° resolution grid global GDP map during the COVID-19 pandemic. Simulated nighttime-light remotely sensed data (SNTL) was forecasted via a GM(1, 1) model under the assumption that there …

Visualization Of Cathode Spot Control Using Laser Irradiation And Oxide Addition In Wire Arc Additive Manufacturing Of Titanium Alloys, Tae Hyun Lee, Cheolhee Kim, Je Hoon Oh, Dong Hyuck Kam

Mechanical and Materials Engineering Faculty Publications and Presentations

Arc instability is one of the most critical problems in gas-metal-arc (GMA) based wire arc additive manufacturing of titanium (Ti) alloys. It can result in a poor bead surface, surface oxidation, and spattering. In particular, the relocation of the cathode spot area is the main cause of big spatters because of the high thermal energy of the molten droplet at the molten pool surface. In this study, two cathode spot control techniques were applied using auxiliary laser heating and prelaid oxides, and the behaviors of the cathode spots and arc were visualized using high-speed photography. When the laser beam was …

Increased Panel Height Enhances Cooling For Photovoltaic Solar Farms, Sarah E. Smith, Bianca Viggiano, Naseem Ali, Timothy J. Silverman, Martin Obligado, Marc Calaf, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Solar photovoltaic (PV) systems suffer substantial efficiency loss due to environmental and internal heating. However, increasing the canopy height of these systems promotes surface heat transfer and boosts production. This work represents the first wind tunnel experiments to explore this concept in terms of array flow behavior and relative convective heat transfer, comparing model solar arrays of varied height arrangements - a nominal height, extended height, and a staggered height configuration. Analyses of surface thermocouple data show average Nusselt number (𝑁𝑢) to increase with array elevation, where panel convection at double height improved up to 1.88 times that of the …

Technoeconomic Analysis Of Changing Pv Array Convective Cooling Through Changing Array Spacing, Matthew Prilliman, Sarah E. Smith, Brooke Stanislawski, Janine M.F. Keith, Timothy J. Silverman, Marc Calaf, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Accuracy in photovoltaic (PV) module temperature modeling is crucial to achieving precision in energy performance yield calculations and subsequent economic evaluations of PV projects. While there have been numerous approaches to PV temperature modeling based on both the steady-state and transient thermal assumptions, there have been few attempts to account for changing convective cooling on PV module surfaces resulting from changes in the PV system layout. Changes in system row spacing, in particular, can have a meaningful impact on module electrical efficiency and subsequent economic performance, even when considering additional costs from the changes in row spacing. Using a heat …

Identifying Population Hollowing Out Regions And Their Dynamic Characteristics Across Central China, Bin Guo, Yi Bian, Lin Pei, Xiaowei Zhu, Dingming Zhang, Wencai Zhang, Xianan Guo, Qiuji Chen

Mechanical and Materials Engineering Faculty Publications and Presentations

Continuous urbanization and industrialization lead to plenty of rural residents migrating to cities for a living, which seriously accelerated the population hollowing issues. This generated series of social issues, including residential estate idle and numerous vigorous laborers migrating from undeveloped rural areas to wealthy cities and towns. Quantitatively determining the population hollowing characteristic is the priority task of realizing rural revitalization. However, the traditional field investigation methods have obvious deficiencies in describing socio-economic phenomena, especially population hollowing, due to weak efficiency and low accuracy. Here, this paper conceives a novel scheme for representing population hollowing levels and exploring the spatiotemporal …

A Lacunarity-Based Index For Spatial Heterogeneity, Ryan H. Scott, Hawwa Falih Kadum, G. Salmaso, Marc Calaf, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Characteri zing spatial heterogeneity is fundamental in numerous areas, yet defining spatial patterns often depends on qualitative assessments or a priori knowledge. Lacunarity analysis is a popular occupancy-based method for identi fy ing relevant length scales in spatially heterogeneous systems. From lacunarity, we identify the ex istence of a point which encapsulates the spatial heterogeneity of a given system. This value sati sfies the conditions for the lac unarity cutoff function and forms the bas is of a heterogeneity index. We evaluate the behavior of both parameters in mono fractal, clustered, and periodic systems. ln addition, we demonstrate the broad …

Ti–6al–4v Alloy Deposition Characteristics At Electrode-Negative Polarity In The Cold Metal Transfer–Gas Metal Arc Process, Tae Hyun Lee, Dong Hyuck Kam, Je Hoon Oh, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

Although wire arc additive manufacturing (WAAM) of Ti alloys using gas metal arc yields a high deposition rate, cathode spots exhibit unstable behavior. In this study, the cold-metal-transfer process and an electrode-negative (EN) polarity were used in the WAAM process of the Ti–6Al–4V alloy. High-speed imaging was performed to investigate the mechanisms to stabilize cathode plasma jets, arc plasma, and molten metal transfer in the EN polarity. Arc plasma and cathode jets had the same direction, and sound cathode jets were shrouded by arc plasma in the EN mode. The metal transfer was also stabilized by balanced plasma formation under …

Thermophysical Properties Of Inorganic Phase-Change Materials Based On Mncl2·4h2o, Kyung-Eun Min, Jae-Won Jang, Jun-Ki Kim, Chien Wern, Sung Yi

Mechanical and Materials Engineering Faculty Publications and Presentations

Manganese (II) chloride tetrahydrate, classified as an inorganic phase-change material (PCM), can be used as a thermal energy storage material, saving and releasing thermal energy during its phase transitions. In this study, thermophysical properties, such as phase change temperatures, latent heat, and thermal conductivities, of four types of MnCl₂·4H₂O PCMs were investigated under single and dual phases (liquid-, solid-, and dual-phase PCMs) using differential scanning calorimetry (DSC) and a heat flow meter. PCMs with a liquid or dual phases exhibited superheating issues, and their melting temperatures were 7 to 10 °C higher than the reference melting …

Wake Bifurcations Behind Two Circular Disks In Tandem Arrangement, Jianzhi Yang, Xiaowei Wu, Minghou Liu, Changjian Wang, Yuxin Wu, Zhihe Shen

Mechanical and Materials Engineering Faculty Publications and Presentations

The wake bifurcations behind two circular disks in tandem arrangement are investigated through numerical simulations. The separation distance between the disks, S/d, is chosen at 1, 2, 4, and 6, and the Reynolds number, Re, lies in the range of 100 Re 500. The wake dynamics are examined in terms of the flow structures as well as drag and lift coefficient characteristics. Seven main wake regimes are observed in the considered (Re, S/d) space: steady state (SS), Zig-zig (Zz) mode, standing wave mode, periodic state with reflectional symmetry breaking (RSB), periodic state with double-helical (DH) structures shedding, periodic state with …

How Advances In Low-G Plumbing Enable Space Exploration, Mark M. Weislogel, John Graft, Andrew P. Wollman, Karl Cardin, Logan Torres, J. E. Goodman, J. C. Buchli

Mechanical and Materials Engineering Faculty Publications and Presentations

In many ways, plumbing is essential to life support. In fact, the advance of humankind on Earth is directly linked to the advance of clean, healthy, reliable plumbing solutions. Shouldn’t this also be true for the advancement of humankind in space? Unfortunately, the reliability of even the simplest plumbing element aboard spacecraft is rarely that of its terrestrial counterpart. This state of affairs is due entirely to the near-weightless “low-g” state of orbiting and coast spacecraft. But the combined passive capillary effects of surface tension, wetting, and system geometry in space can be exploited to replace the passive role of …

Characteristics Of The Wake Of An Inclined Prolate Spheroid In Uniform Shear Flow, Zhe Wang, Jianzhi Yang, Helge I. Andersson, Xiaowei Wu, Yuxin Wu, Liping Wang, Minghou Liu

Mechanical and Materials Engineering Faculty Publications and Presentations

Flow around an inclined 5:2 prolate spheroid with the incidence angle α = 45° is numerically investigated in a uniform shear flow. The Reynolds number based on the inflow center velocity Uc and the volume-equivalent sphere diameter De of the spheroid are considered at Re = 480, 600, 700, and 750. The non-dimensional shear rate K is ranged from 0 to 0.1. Five qualitatively different wake modes are observed, including a new mode characterized by multi-periodic shedding of hairpin vortices with regular rotation of the separation region. In general, the wake transition is suppressed with increasing shear rate. …

Measuring Volatile Emissions From Moss Gametophytes: A Review Of Methodologies And New Applications, Danlyn L. Brennan, Leslie M. Kollar, Scott Kiel, Timea Deakova, Aurélie Laguerre, Stuart F. Mcdaniel, Sarah Eppley, Elliott T. Gall, Todd Rosenstiel

Center for Life in Extreme Environments Publications

Mosses inhabit nearly all terrestrial ecosystems and engage in important interactions with nitrogen-fixing microbes, sperm-dispersing arthropods, and other plants. It is hypothesized that these interactions could be mediated by biogenic volatile organic compounds (BVOCs). Moss BVOCs may play fundamental roles in influencing local ecologies, such as biosphere–atmosphere–hydrosphere communications, physiological and evolutionary dynamics, plant–microbe interactions, and gametophyte stress physiology. Further progress in quantifying the composition, magnitude, and variability of moss BVOC emissions, and their response to environmental drivers and metabolic requirements, is limited by methodological and analytical challenges. We review several sampling techniques with various analytical approaches and describe best practices …

Secondary Motions Above A Staggered Multi-Scale Rough Wall, Bianca Viggiano, Juliaan Bossuyt, N. Ali, Johan Meyers, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Wind tunnel experiments were performed to investigate turbulent flow over an array of heterogeneous roughness elements using stereoscopic particle image velocimetry. Nine streamwise planes, covering one periodic cell of a multi-scale roughness element that is arranged in a staggered pattern, are combined to quantify mean flow features and Reynolds stresses. Dispersive stresses, arising from spatial variations in the temporally averaged mean velocity, are also presented. The results highlight that the roughness elements create a large deficit pathway along the surfaces. Outer scaling of the time-averaged streamwise velocity presents features which are nearly independent of the roughness element type, with parameters …

Effects Of Electrode Negative Pulsing Ratio In Direct Energy Deposition Via Variable-Polarity Cold Metal Transfer Process On The Deposition Behavior And Microstructural Characteristics, Tae Hyun Lee, Cheolhee Kim, Minjung Kang

Mechanical and Materials Engineering Faculty Publications and Presentations

Interest in research on the application of variable-polarity cold metal transfer mode in wire-based direct energy deposition has been growing; particularly popular are investigations into the respective influences of polarity, amplitude of the arc current, and polarity variation sequence on the quality of the final product manufactured via additive manufacturing. The application of the electrode-negative phase is more capable of yielding relatively large droplets and increasing the weight of the deposited material. However, the proportions of the electrode positive phase are typically larger than those of the electrode-negative phase because it maintains arc stability and droplet transfer. This discrepancy has …

Per-Person And Whole-Building Voc Emission Factors In An Occupied School With Gas-Phase Air Cleaning., Brett W. Stinson, Aurélie Laguerre, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

Using real-time measurements of CO and volatile organic compounds (VOCs) in the air handler of an occupied middle school, we quantified source strengths for 249 VOCs and apportioned the source to the building, occupants and their activities, outdoor air, or recirculation air. For VOCs quantified in this study, there is a source to the outdoors of 8.6 ± 1.8 g/h in building exhaust air, of which 5.9 ± 1.7 g/h can be attributed to indoor sources (the building and occupants and their activities). The corresponding whole-building area emission factor from indoor sources is 1020 ± 300 μg/(m h), including reactive …

Novel Fabrication Of Silver-Coated Copper Nanowires With Organic Compound Solution, Suhyun Lee, Chien Wern, Sung Yi

Mechanical and Materials Engineering Faculty Publications and Presentations

Copper nanowires and Cu-Ag nanowires have various potential applications, such as transparent conductive film, flexible electronics, and conductive filler. In this study, we developed a new green fabrication method for silver-coated copper nanowires using methylsulfonylmethane (DMSO2), which is an environmentally friendly chemical at the food-grade level, to replace toxic chemicals, including ammonia, in the silver coating process. Copper nanowires were synthesized under various reaction temperatures and concentrations of hydrazine (N2H4), ethylenediamine (EDA), sodium hydroxide (NaOH), and copper precursor. The reaction temperature higher than 70 C caused the oxidation of copper products and evaporation of the sample solution. The optimal conditions …

Analyzing Modeled Torque Profiles To Understand Scale-Dependent Active Muscle Responses In The Hip Joint, Fletcher Young, Hillel J. Chiel, Matthew Tresch, Charles Heckman, Alexander J. Hunt, Roger Quinn

Mechanical and Materials Engineering Faculty Publications and Presentations

Animal locomotion is influenced by a combination of constituent joint torques (e.g., due to limb inertia and passive viscoelasticity), which determine the necessary muscular response to move the limb. Across animal size-scales, the relative contributions of these constituent joint torques affect the muscular response in different ways. We used a multi-muscle biomechanical model to analyze how passive torque components change due to an animal’s size-scale during locomotion. By changing the size-scale of the model, we characterized emergent muscular responses at the hip as a result of the changing constituent torque profile. Specifically, we found that activation phases between extensor and …

Entrainment, Diffusion And Effective Compressibility In A Self-Similar Turbulent Jet, Thomas Basset, Bianca Viggiano, Thomas Barois, Mathieu Gibert, Nicolas Mordant, Raúl Bayoán Cal, Romain Volk, Mickael Bourgoin

Mechanical and Materials Engineering Faculty Publications and Presentations

An experimental Lagrangian study based on particle tracking velocimetry has been completed in an incompressible turbulent round water jet freely spreading into water. The jet is seeded with tracers only through the nozzle: inhomogeneous seeding called nozzle seeding. The Lagrangian flow tagged by these tracers therefore does not contain any contribution from particles entrained into the jet from the quiescent surrounding fluid. The mean velocity field of the nozzle seeded flow, ⟨Uφ⟩, is found to be essentially indistinguishable from the global mean velocity field of the jet, ⟨U⟩, for the axial velocity while significant deviations are found for the radial …