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2019

Iowa State University

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Articles 1 - 30 of 723

Full-Text Articles in Engineering

Salt Mediated Self-Assembly Of Poly(Ethylene Glycol)-Functionalized Gold Nanorods, Hyeong Jin Kim, Wenjie Wang, Wei Bu, Md. Mir Hossen, Alejandra Londono-Calderon, Andrew C. Hillier, Tanya Prozorov, Surya Mallapragada, David Vaknin Dec 2019

Salt Mediated Self-Assembly Of Poly(Ethylene Glycol)-Functionalized Gold Nanorods, Hyeong Jin Kim, Wenjie Wang, Wei Bu, Md. Mir Hossen, Alejandra Londono-Calderon, Andrew C. Hillier, Tanya Prozorov, Surya Mallapragada, David Vaknin

Chemical and Biological Engineering Publications

Although challenging, assembling and orienting non-spherical nanomaterials into two- and three-dimensional (2D and 3D) ordered arrays can facilitate versatile collective properties by virtue of their shape-dependent properties that cannot be realized with their spherical counterparts. Here, we report on the self-assembly of gold nanorods (AuNRs) into 2D films at the vapor/liquid interface facilitated by grafting them with poly(ethylene glycol) (PEG). Using surface sensitive synchrotron grazing incidence small angle X-ray scattering (GISAXS) and specular X-ray reflectivity (XRR), we show that PEG-AuNRs in aqueous suspensions migrate to the vapor/liquid interface in the presence of salt, forming a uniform monolayer ...


Life-Cycle Assessment (Lca) Of Different Pretreatment And Product Separation Technologies For Butanol Bioprocessing From Oil Palm Frond, Nazira Mahmud, Kurt A. Rosentrater Dec 2019

Life-Cycle Assessment (Lca) Of Different Pretreatment And Product Separation Technologies For Butanol Bioprocessing From Oil Palm Frond, Nazira Mahmud, Kurt A. Rosentrater

Agricultural and Biosystems Engineering Publications

Environmental impact assessment is a crucial aspect of biofuels production to ensure that the process generates emissions within the designated limits. In typical cellulosic biofuel production process, the pretreatment and downstream processing stages were reported to require a high amount of chemicals and energy, thus generating high emissions. Cellulosic butanol production while using low moisture anhydrous ammonia (LMAA) pretreatment was expected to have a low chemical, water, and energy footprint, especially when the process was combined with more efficient downstream processing technologies. In this study, the quantification of environmental impact potentials from cellulosic butanol production plants was conducted with modeled ...


Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel Dec 2019

Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Adsorbed sulfur has been investigated on the Ag(110) surface at two different coverages, 0.02 and 0.25 monolayers. At the lower coverage, only sulfur adatoms are present. At the higher coverage, there are additional bright features which we identify as linear, independent AgS2 complexes. This identification is based upon density functional theory (DFT) and its comparison with experimental observations including bias dependence and separation between complexes. DFT also predicts the absence of AgS2 complexes at low coverage, and the development of AgS2 complexes around a coverage of 0.25 monolayers of sulfur, as is experimentally observed. To our ...


The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky Dec 2019

The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

Our 151Eu Mössbauer investigation of Eu2In and Eu2Sn shows that the europium in both materials is fully divalent. We confirm the distinct thermodynamic orders of the magnetic transitions and reveal a remarkable difference between the magnetic environments of the europium atoms in the two compounds. Possible structural and electronic origins for these differences are discussed using DFT calculations.


A Test System For Ercot Market Design Studies: Development And Application, Swathi Battula, Leigh Tesfatsion, Thomas E. Mcdermott Dec 2019

A Test System For Ercot Market Design Studies: Development And Application, Swathi Battula, Leigh Tesfatsion, Thomas E. Mcdermott

Economics Working Papers

The ERCOT Test System developed in this study is an open-source library of Java/Python software classes, together with a synthetic grid construction method, specifically designed to facilitate the study of ERCOT market operations over successive days. In default form, these classes permit a high-level modeling of existing ERCOT market operations. Users can conduct a broad range of computational experiments under alternative parameter settings. In addition, users can readily extend these classes to model additional existing or envisioned ERCOT market features to suit different research purposes. An 8-bus test case is used to illustrate the capabilities of the test system ...


Synthesis And Characterization Of Rapidly-Degrading Polyanhydrides As Vaccine Adjuvants, Sean M. Kelly, Akash Mitra, Srishti Mathur, Balaji Narasimhan Dec 2019

Synthesis And Characterization Of Rapidly-Degrading Polyanhydrides As Vaccine Adjuvants, Sean M. Kelly, Akash Mitra, Srishti Mathur, Balaji Narasimhan

Chemical and Biological Engineering Publications

There is a currently a need to develop adjuvants that are best suited to simultaneously enhance immune responses, induce immunologic memory, improve patient compliance (i.e., reduce doses and inflammation), and provide vaccine shelf stability for stockpiling and global deployment to challenging environments. Biodegradable polyanhydrides have been investigated extensively to overcome such challenges. It has been shown that controlling copolymer composition can result in chemistry-dependent immunomodulatory capabilities. These studies have revealed that copolymers rich in sebacic acid (SA) are highly internalized by antigen presenting cells and confer improved shelf stability of encapsulated proteins, while copolymers rich in 1,8-bis(p-carboxyphenoxy ...


Common Secondary And Tertiary Structural Features Of Aptamer–Ligand Interaction Shared By Rna Aptamers With Different Primary Sequences, Muslum Ilgu, Shuting Yan, Ryan M. Khounlo, Monica H. Lamm, Marit Nilsen-Hamilton Dec 2019

Common Secondary And Tertiary Structural Features Of Aptamer–Ligand Interaction Shared By Rna Aptamers With Different Primary Sequences, Muslum Ilgu, Shuting Yan, Ryan M. Khounlo, Monica H. Lamm, Marit Nilsen-Hamilton

Chemical and Biological Engineering Publications

Aptamer selection can yield many oligonucleotides with different sequences and affinities for the target molecule. Here, we have combined computational and experimental approaches to understand if aptamers with different sequences but the same molecular target share structural and dynamical features. NEO1A, with a known NMR-solved structure, displays a flexible loop that interacts differently with individual aminoglycosides, its ligand affinities and specificities are responsive to ionic strength, and it possesses an adenosine in the loop that is critical for high-affinity ligand binding. NEO2A was obtained from the same selection and, although they are only 43% identical in overall sequence, NEO1A and ...


Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya Dec 2019

Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya

Aerospace Engineering Publications

Energetic films were synthesized using stress altered nano-aluminum particles (nAl). The nAl powder was pre-stressed to examine how modified mechanical properties of the fuel particles influenced film reactivity. Pre-stressing conditions varied by quenching rate. Slow and rapid quenching rates induced elevated dilatational strain within the nAl particles that was measured using synchrotron X-ray diffraction (XRD). An analytical model for stress and strain in a nAl core–Al2O3 shell particle that includes creep in the shell and delamination at the core–shell boundary, was developed and used for interpretation of strain measurements. Results show rapid quenching induced 81% delamination at the ...


A Deep Learning Framework For Design And Analysis Of Surgical Bioprosthetic Heart Valves, Aditya Balu, Sahiti Nallagonda, Fei Xu, Adarsh Krishnamurthy, Ming-Chen Hsu, Soumik Sarkar Dec 2019

A Deep Learning Framework For Design And Analysis Of Surgical Bioprosthetic Heart Valves, Aditya Balu, Sahiti Nallagonda, Fei Xu, Adarsh Krishnamurthy, Ming-Chen Hsu, Soumik Sarkar

Mechanical Engineering Publications

Bioprosthetic heart valves (BHVs) are commonly used as heart valve replacements but they are prone to fatigue failure; estimating their remaining life directly from medical images is difficult. Analyzing the valve performance can provide better guidance for personalized valve design. However, such analyses are often computationally intensive. In this work, we introduce the concept of deep learning (DL) based finite element analysis (DLFEA) to learn the deformation biomechanics of bioprosthetic aortic valves directly from simulations. The proposed DL framework can eliminate the time-consuming biomechanics simulations, while predicting valve deformations with the same fidelity. We present statistical results that demonstrate the ...


A Transactive Energy Approach To Distribution System Design: Household Formulation, Swathi Battula, Leigh Tesfatsion, Zhaoyu Wang Dec 2019

A Transactive Energy Approach To Distribution System Design: Household Formulation, Swathi Battula, Leigh Tesfatsion, Zhaoyu Wang

Economics Working Papers

A household model is formulated to facilitate careful development and performance testing of bid-based transactive energy system (TES) designs with voluntary customer participation. The optimal general bid-function form for households with thermostatically controlled loads is derived from dynamic programming principles, based solely on general household thermal dynamic and welfare attributes. Quantitative forms are determined for these optimal bid functions, given quantitative forms for these attributes. These quantitative attributes are used to construct representative household types based on clusterings of correlated parameter values. Bid comparison, peak-load reduction, and load-matching test cases conducted for a 123-bus distribution system operating under a generic ...


Microstructure Evolution During Near-Tg Annealing And Its Effect On Shear Banding In Model Alloys, Meng-Hao Yang, Bei Cai, Yang Sun, Feng Zhang, Yi-Fan Wang, Cai-Zhuang Wang, Kai-Ming Ho Dec 2019

Microstructure Evolution During Near-Tg Annealing And Its Effect On Shear Banding In Model Alloys, Meng-Hao Yang, Bei Cai, Yang Sun, Feng Zhang, Yi-Fan Wang, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

By performing extensive molecular dynamics simulations, we investigate the deformation behavior in Al90Sm10 and Cu64.5Zr35.5 alloys after elongated isothermal annealing in the vicinity of the glass-transition temperature (Tg). Different microstructural response to the annealing process was observed: Al90Sm10 maintains the glassy structure with improved energetic stability, enhanced short-range order (SRO), and a more pronounced spatial network that extends beyond the first atomic shell, while Cu64.5Zr35.5 forms nanocrystalline Laves Cu2Zr phases. Shear banding occurs in both annealed systems under shear loading. For Al90Sm10, the spatial network formed by the local clusters characterizing the SRO of the system ...


Decision Making Under Uncertainty For Design Of Resilient Engineered Systems, Cameron A. Mackenzie, Chao Hu Dec 2019

Decision Making Under Uncertainty For Design Of Resilient Engineered Systems, Cameron A. Mackenzie, Chao Hu

Industrial and Manufacturing Systems Engineering Publications

Designing resilient engineered systems that can sense and withstand adverse events and recover from the effects of the adverse events is increasingly seen as an important goal of engineering design. This paper proposes a value-driven design for resilience (VD2R) framework in order to enable the assessment of system resilience and the optimization of decision variables (or design characteristics) that maximize the value of the system for a firm. The VD2R framework possesses three unique features that allow system resilience and value to be addressed in a theoretically founded and explicit way. First, it assesses the time-dependent resilience of an engineered ...


Assessing Plant Performance In The Enviratron, Yin Bao, Scott Zarecor, Dylan Shah, Taylor Tuel, Darwin A. Campbell, Antony V. E. Chapman, David Imberti, Daniel Kiekhaefer, Henry Imberti, Thomas Lubberstedt, Yanhai Yin, Dan Nettleton, Carolyn J. Lawrence-Dill, Steven A. Whitham, Lie Tang, Stephen H. Howell Dec 2019

Assessing Plant Performance In The Enviratron, Yin Bao, Scott Zarecor, Dylan Shah, Taylor Tuel, Darwin A. Campbell, Antony V. E. Chapman, David Imberti, Daniel Kiekhaefer, Henry Imberti, Thomas Lubberstedt, Yanhai Yin, Dan Nettleton, Carolyn J. Lawrence-Dill, Steven A. Whitham, Lie Tang, Stephen H. Howell

Agricultural and Biosystems Engineering Publications

Background: Assessing the impact of the environment on plant performance requires growing plants under controlled environmental conditions. Plant phenotypes are a product of genotype × environment (G × E), and the Enviratron at Iowa State University is a facility for testing under controlled conditions the effects of the environment on plant growth and development. Crop plants (including maize) can be grown to maturity in the Enviratron, and the performance of plants under different environmental conditions can be monitored 24 h per day, 7 days per week throughout the growth cycle.

Results: The Enviratron is an array of custom-designed plant growth chambers that ...


Viscoelastic Properties Of Shock Wave Exposed Brain Tissue Subjected To Unconfined Compression Experiments, Annastacia K. Mccarty, Ling Zhang, Sarah Hansen, William J. Jackson, Sarah A. Bentil Dec 2019

Viscoelastic Properties Of Shock Wave Exposed Brain Tissue Subjected To Unconfined Compression Experiments, Annastacia K. Mccarty, Ling Zhang, Sarah Hansen, William J. Jackson, Sarah A. Bentil

Mechanical Engineering Publications

Traumatic brain injuries (TBI) affect millions of people each year. While research has been dedicated to determining the mechanical properties of the uninjured brain, there has been a lack of investigation on the mechanical properties of the brain after experiencing a primary blast-induced TBI. In this paper, whole porcine brains were exposed to a shock wave to simulate blast-induced TBI. First, ten (10) brains were subjected to unconfined compression experiments immediately following shock wave exposure. In addition, 22 brains exposed to a shock wave were placed in saline solution and refrigerated between 30 minutes and 6.0 hours before undergoing ...


An Immersogeometric Formulation For Free-Surface Flows With Application To Marine Engineering Problems, Qiming Zhu, Fei Xu, Songzhe Xu, Ming-Chen Hsu, Jinhui Yan Nov 2019

An Immersogeometric Formulation For Free-Surface Flows With Application To Marine Engineering Problems, Qiming Zhu, Fei Xu, Songzhe Xu, Ming-Chen Hsu, Jinhui Yan

Mechanical Engineering Publications

An immersogeometric formulation is proposed to simulate free-surface flows around structures with complex geometry. The fluid–fluid interface (air–water interface) is handled by the level set method, while the fluid–structure interface is handled through an immersogeometric approach by immersing structures into non-boundary-fitted meshes and enforcing Dirichlet boundary conditions weakly. Residual-based variational multiscale method (RBVMS) is employed to stabilize the coupled Navier–Stokes equations of incompressible flows and level set convection equation. Other level set techniques, including re-distancing and mass balancing, are also incorporated into the immersed formulation. Adaptive quadrature rule is used to better capture the geometry of ...


Headland Turning Optimisation For Agricultural Vehicles And Those With Towed Implements, Xuyong Tu, Lie Tang Nov 2019

Headland Turning Optimisation For Agricultural Vehicles And Those With Towed Implements, Xuyong Tu, Lie Tang

Agricultural and Biosystems Engineering Publications

As an essential part of field coverage path planning process, mobile agricultural field equipment headland turning is a process that should be done in a manner that can maximise the equipment’s operational efficiency through minimising the time or travel distance during the turning. However, this headland turning trajectory optimisation task represents a challenging dynamic nonlinear optimisation problem which is difficult to solve by using traditional indirect numerical methods. In this research, we investigated the possibility of using direct numerical methods to solve such a nonlinear optimisation problem in a restricted parameter neighborhood with constraints. We developed the kinematic models ...


Machine Learning Approach For Prescriptive Plant Breeding, Kyle A. Parmley, Race H. Higgins, Baskar Ganapathysubramanian, Soumik Sarkar, Asheesh K. Singh Nov 2019

Machine Learning Approach For Prescriptive Plant Breeding, Kyle A. Parmley, Race H. Higgins, Baskar Ganapathysubramanian, Soumik Sarkar, Asheesh K. Singh

Mechanical Engineering Publications

We explored the capability of fusing high dimensional phenotypic trait (phenomic) data with a machine learning (ML) approach to provide plant breeders the tools to do both in-season seed yield (SY) prediction and prescriptive cultivar development for targeted agro-management practices (e.g., row spacing and seeding density). We phenotyped 32 SoyNAM parent genotypes in two independent studies each with contrasting agro-management treatments (two row spacing, three seeding densities). Phenotypic trait data (canopy temperature, chlorophyll content, hyperspectral reflectance, leaf area index, and light interception) were generated using an array of sensors at three growth stages during the growing season and seed ...


Pilot-Scale Assessment Of A Novel Farrowing Creep Area Supplementary Heat Source, Benjamin C. Smith, Brett C. Ramirez, Steven J. Hoff, Laura L. Greiner Nov 2019

Pilot-Scale Assessment Of A Novel Farrowing Creep Area Supplementary Heat Source, Benjamin C. Smith, Brett C. Ramirez, Steven J. Hoff, Laura L. Greiner

Agricultural and Biosystems Engineering Publications

Pre-weaning morality (PWM) is attributed to a poor creep area microclimate and causes major economic and productivity losses for the US swine industry. Piglets need supplementary heat to overcome a high surface area to body weight ratio and minimal thermoregulation. A pilot-scale study was conducted to evaluate a semi-enclosed heated microclimate (SEHM) as a supplementary heat source for farrowing creep areas over six farrowing cycles (from January to July 2019) in two rooms with 24 farrowing stalls in each room. Six SEHMs (each SEHM covers two stalls) were randomly distributed to each room and compared to heat lamps (HLs) for ...


A Meta-Analysis Of Global Fungal Distribution Reveals Climate-Driven Patterns, Tomáš Větrovský, Petr Kohout, Martin Kopecký, Antonin Machac, Matěj Man, Barbara Doreen Bahnmann, Vendula Brabcová, Jinlyung Choi, Lenka Meszárošová, Zander Rainier Human, Clémentine Lepinay, Salvador Lladó, Rubén López-Mondéjar, Tijana Martinović, Tereza Mašínová, Daniel Morais, Diana Navrátilová, Iñaki Odriozola, Martina Štursová, Karel Švec, Vojtěch Tláskal, Michaela Urbanová, Joe Wan, Lucia Žifčáková, Adina Howe, Joshua Ladau, Kabir Gabriel Peay, David Storch, Jan Wild, Petr Baldrian Nov 2019

A Meta-Analysis Of Global Fungal Distribution Reveals Climate-Driven Patterns, Tomáš Větrovský, Petr Kohout, Martin Kopecký, Antonin Machac, Matěj Man, Barbara Doreen Bahnmann, Vendula Brabcová, Jinlyung Choi, Lenka Meszárošová, Zander Rainier Human, Clémentine Lepinay, Salvador Lladó, Rubén López-Mondéjar, Tijana Martinović, Tereza Mašínová, Daniel Morais, Diana Navrátilová, Iñaki Odriozola, Martina Štursová, Karel Švec, Vojtěch Tláskal, Michaela Urbanová, Joe Wan, Lucia Žifčáková, Adina Howe, Joshua Ladau, Kabir Gabriel Peay, David Storch, Jan Wild, Petr Baldrian

Agricultural and Biosystems Engineering Publications

The evolutionary and environmental factors that shape fungal biogeography are incompletely understood. Here, we assemble a large dataset consisting of previously generated mycobiome data linked to specific geographical locations across the world. We use this dataset to describe the distribution of fungal taxa and to look for correlations with different environmental factors such as climate, soil and vegetation variables. Our meta-study identifies climate as an important driver of different aspects of fungal biogeography, including the global distribution of common fungi as well as the composition and diversity of fungal communities. In our analysis, fungal diversity is concentrated at high latitudes ...


Processing Of Alnico Magnets By Additive Manufacturing, Emma White, Emily Rinko, Timothy Prost, Timothy Horn, Christopher Ledford, Christopher Rock, Iver E. Anderson Nov 2019

Processing Of Alnico Magnets By Additive Manufacturing, Emma White, Emily Rinko, Timothy Prost, Timothy Horn, Christopher Ledford, Christopher Rock, Iver E. Anderson

Ames Laboratory Accepted Manuscripts

Permanent magnets without rare earth (RE) elements, such as alnico, will improve supply stability and potentially decrease permanent magnet cost, especially for traction drive motors and other increased temperature applications. Commercial alnico magnets with the highest energy product are produced by directional solidification (DS) to achieve a <001> columnar grain orientation followed by significant final machining, adding to the high cost. Additive manufacturing (AM) is an effective method to process near net-shape parts with minimal final machining of complex geometries. AM also, has potential for texture/grain orientation control and compositionally graded structures. This report describes fabrication of alnico magnets by ...


Incorporating The Standstill Distance And Time Headway Distributions Into Freeway Car-Following Models And An Application To Estimating Freeway Travel Time Reliability, Chaoru Lu, Jing Dong, Andrew Houchin, Chenhui Liu Nov 2019

Incorporating The Standstill Distance And Time Headway Distributions Into Freeway Car-Following Models And An Application To Estimating Freeway Travel Time Reliability, Chaoru Lu, Jing Dong, Andrew Houchin, Chenhui Liu

Civil, Construction and Environmental Engineering Publications

Standstill distances and following time headways are two important microsimulation model parameters associated with driver aggression. This paper investigates the distributions of standstill distances and time headways and incorporates these distributions into car-following models to estimate travel time reliability. By incorporating standstill distance and following headway into car-following models as stochastic parameters, a speed-density region can be generated, based on which various travel-time-reliability measures can be calculated. Key findings of this study are as follows: (1) Both standstill distances and time headways follow fairly dispersed distributions. Therefore, it is suggested that microsimulation models should include the option of allowing standstill ...


Boosting Verification Scalability Via Structural Grouping And Semantic Partitioning Of Properties, Rohit Dureja, Jason Baumgartner, Alexander Ivrii, Robert Kanzelman, Kristin Y. Rozier Nov 2019

Boosting Verification Scalability Via Structural Grouping And Semantic Partitioning Of Properties, Rohit Dureja, Jason Baumgartner, Alexander Ivrii, Robert Kanzelman, Kristin Y. Rozier

Aerospace Engineering Conference Papers, Presentations and Posters

From equivalence checking to functional verification to design-space exploration, industrial verification tasks entail checking a large number of properties on the same design. State-of-the-art tools typically solve all properties concurrently, or one-at-a-time. They do not optimally exploit subproblem sharing between properties, leaving an opportunity to save considerable verification resource via concurrent verification of properties with nearly identical cone of influence (COI). These high-affinity properties can be concurrently solved; the verification effort expended for one can be directly reused to accelerate the verification of the others, without hurting per-property verification resources through bloating COI size. We present a near-linear runtime algorithm ...


Inkjet Printing Of Magnetic Particles Toward Anisotropic Magnetic Properties, Karam Nashwan Al-Milaji, Ravi L. Hadimani, Shalabh Gupta, Vitalij K. Pecharsky, Hong Zhao Nov 2019

Inkjet Printing Of Magnetic Particles Toward Anisotropic Magnetic Properties, Karam Nashwan Al-Milaji, Ravi L. Hadimani, Shalabh Gupta, Vitalij K. Pecharsky, Hong Zhao

Ames Laboratory Accepted Manuscripts

Unique properties of one-dimensional assemblies of particles have attracted great attention during the past decades, particularly with respect to the potential for anisotropic magnetism. Patterned films can be created using inkjet printing; however, drying of particle-laden colloidal droplets on solid surfaces is usually accompanied by the well-known coffee-ring effect, deteriorating both the uniformity and resolution of the printed configurations. This study examines the effect of externally applied magnetic field on particle deposition patterns. Ferromagnetic Gd5Si4 particles were formulated in terpineol oil and directly deposited via magnetic field-assisted inkjet printing on a photopaper to generate patterned films with suppressed coffee-ring effect ...


In-Situ Tem Analysis Of The Phase Transformation Mechanism Of A Cu–Al–Ni Shape Memory Alloy, Tae-Hoon Kim, Gaoyuan Ouyang, Jonathan D. Poplawsky, Matthew J. Kramer, Valery I. Levitas, Jun Cui, Lin Zhou Nov 2019

In-Situ Tem Analysis Of The Phase Transformation Mechanism Of A Cu–Al–Ni Shape Memory Alloy, Tae-Hoon Kim, Gaoyuan Ouyang, Jonathan D. Poplawsky, Matthew J. Kramer, Valery I. Levitas, Jun Cui, Lin Zhou

Ames Laboratory Accepted Manuscripts

Minimizing phase transformation (PT) hysteresis is of crucial importance for reliability of shape memory alloy (SMA)-based devices, where the lattice strain/stress caused by thermal hysteresis leads to functional degradation. As a result, understanding structural factors that control PT pathway is critical for development of materials with high reversibility. In this study, two distinct PT mechanisms (from gamma'(1) martensite to beta(1) austenite phase) in Cu–Al–Ni SMAs were revealed by in-situ TEM observation. A growth-dominant conventional PT mechanism shows in the fast quench sample, whereas a nucleation-dominant PT mechanism that suppresses interface propagation and induces high ...


Use Of Neural Networks To Identify Safety Prevention Priorities In Agro-Manufacturing Operations Within Commercial Grain Elevators, Fatemeh Davoudi Kakhki, Steven A. Freeman, Gretchen A. Mosher Nov 2019

Use Of Neural Networks To Identify Safety Prevention Priorities In Agro-Manufacturing Operations Within Commercial Grain Elevators, Fatemeh Davoudi Kakhki, Steven A. Freeman, Gretchen A. Mosher

Agricultural and Biosystems Engineering Publications

The grain handling industry plays a significant role in U.S. agriculture by storing, distributing, and processing a variety of agricultural commodities. Commercial grain elevators are hazardous agro-manufacturing work environments where workers are prone to severe injuries, due to the nature of the activities and workplace. Safety incidents in agro-manufacturing operations generally arise from a combination of factors, rather than a single cause, therefore, research on occupational incidents must look deeper into identifying the underlying causes, through the application of advanced analyses methods. In occupational safety, it is possible to estimate and predict probability of safety risks through developing artificial ...


Implementation Of Pseudo-Turbulence Closures In An Eulerian–Eulerian Two-Fluid Model For Non-Isothermal Gas–Solid Flow, Cheng Peng, B. Kong, Jiazhong Zhou, B. Sun, Alberto Passalacqua, Shankar Subramaniam, Rodney O. Fox Nov 2019

Implementation Of Pseudo-Turbulence Closures In An Eulerian–Eulerian Two-Fluid Model For Non-Isothermal Gas–Solid Flow, Cheng Peng, B. Kong, Jiazhong Zhou, B. Sun, Alberto Passalacqua, Shankar Subramaniam, Rodney O. Fox

Mechanical Engineering Publications

The Eulerian–Eulerian two-fluid model is widely used for computational fluid dynamics simulations of gas–solid flows. For non-isothermal flows, the averaged conservation equations solved in the two-fluid model require closures for drag, gas–solid heat transfer, pseudo-turbulent velocity fluctuations and the pseudo-turbulent heat flux (PTHF). However, the pseudo-turbulence terms are usually neglected in two-fluid simulations due to the lack of accurate correlations. With the increase in computational power, closures for these terms are now available from particle-resolved direct-numerical simulation (PR-DNS). Here, the PTHF closure as well as the heat-transfer closure (i.e., the Nusselt number) extracted from PR-DNS are ...


Development Of Granular Roads Asset Management System, Shafkat Alam-Khan, Bora Cetin, H. David Jeong, Jeramy C. Ashlock, Mengwai Yaw Nov 2019

Development Of Granular Roads Asset Management System, Shafkat Alam-Khan, Bora Cetin, H. David Jeong, Jeramy C. Ashlock, Mengwai Yaw

InTrans Project Reports

Granular roads account for more than 75% of roads managed by Iowa counties. Granular roads experience rapid deterioration and more quickly develop various localized problems compared to paved roads. Frequent and regular maintenance is needed to keep the roadway performance at a desired reliability over its lifetime. Current granular road asset management practices are primarily on an ad hoc and reactive basis, which may not be the most efficient approach. The lack of a reliable and practical tool to estimate gravel loss over time, and thus the required amount of aggregate (rock) that needs to be purchased, is one of ...


Calorismart: Small-Scale Test-Stand For Rapid Evaluation Of Active Magnetic Regenerator Performance, Lucas Griffith, Agata Czernuszewicz, Julie Slaughter, Vitalij K. Pecharsky Nov 2019

Calorismart: Small-Scale Test-Stand For Rapid Evaluation Of Active Magnetic Regenerator Performance, Lucas Griffith, Agata Czernuszewicz, Julie Slaughter, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

We report operation of a device designed specifically for rapid experimental evaluation of performance of magnetocaloric materials in different magnetic fields using a compact active magnetic regenerator bed with a total volume of approximately 5 mL. Other features of the system include digital control of the rotating-permanent-magnet field source and custom dual-opposed syringe pump that enable precise tuning and coupling of the flow profile and the magnetic field profile. Performance of the device is demonstrated for flow volumes between 1 and 4 mL (utilization from 0.48 to 1.9), maximum magnetic fields of 1.13 and 1.45 T ...


Low Efficiency Roll-Off Phosphorescent Organic Light-Emitting Devices Using Thermally Activated Delayed Fluorescence Hosts Materials Based 1, 2, 4-Triazole Acceptor, Huixia Xu, Yaping Zhao, Jing Zhang, Di Zhang, Yanqin Miao, Joseph Shinar, Ruth Shinar, Hua Wang, Bingshe Xu Nov 2019

Low Efficiency Roll-Off Phosphorescent Organic Light-Emitting Devices Using Thermally Activated Delayed Fluorescence Hosts Materials Based 1, 2, 4-Triazole Acceptor, Huixia Xu, Yaping Zhao, Jing Zhang, Di Zhang, Yanqin Miao, Joseph Shinar, Ruth Shinar, Hua Wang, Bingshe Xu

Ames Laboratory Accepted Manuscripts

The host in phosphrescent organic light emitting devices (PhOLEDs), showing the thermally activated delayed fluorescence (TADF) charateristic, can effectively overcome the efficiency roll-off. Herein, six bipolar compounds with donor-π-acceptor (D-π-A) and D-π-A-π-D structures have been synthesized using 1,2,4-triazole derivative (TAZ) as an acceptor and phenothiazine (PTZ), phenoxazine (PXZ), and 9, 9-dimethylacridane (DMAC) as donors. The molecular structures were confirmed by 1H NMR, 13C NMR and X-ray single-crystal diffractions. The large steric hindrance endows these molecules with typical TADF features, including the small singlet-triplet energy splitting (Delta E-ST) of 0.08–0.30 eV and completely spatially separate highest ...


Designing Wind Turbine Rotor Blades To Enhance Energy Capture In Turbine Arrays, Benham Moghadassian, Anupam Sharma Nov 2019

Designing Wind Turbine Rotor Blades To Enhance Energy Capture In Turbine Arrays, Benham Moghadassian, Anupam Sharma

Aerospace Engineering Publications

An inverse design approach is proposed to compute wind turbine blade geometries which maximize the aggregate power output from a wind farm. An iterative inverse algorithm is used to solve the optimization problem. The algorithm seeks to minimize the target function, f = -CP,av, where CP,av is the average normalized mechanical power of all the turbines in the wind farm. An upper bound on the blade planform area, representative of the blade weight, is imposed to demonstrate how to incorporate constraints in the design process. The power coefficients (CP) of the turbines in the farm are ...