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Direct Synthesis Of Graphene On Niobium And Niobium Nitride, Robin Ekeya, Otto Zietz 2018 Portland State University

Direct Synthesis Of Graphene On Niobium And Niobium Nitride, Robin Ekeya, Otto Zietz

Undergraduate Research & Mentoring Program

Since its isolation by mechanical exfoliation in 2004, graphene has attracted enormous interest from the scientific community not the least because of its unique physical and electronic properties. Among these, graphene’s ballistic electron transport and proximity induced superconductivity make graphene-superconductor (GS) hybrid structures a scientifically promising area.


Archaeology And Conservation Of The Middle Phrygian Gate Complex At Gordion, Turkey, Semih Gönen, Richard F. Liebhart, Naomi F. Miller, Elspeth Dusinberre 2018 Boğaziçi Üniversitesi

Archaeology And Conservation Of The Middle Phrygian Gate Complex At Gordion, Turkey, Semih Gönen, Richard F. Liebhart, Naomi F. Miller, Elspeth Dusinberre

Classics Faculty Contributions

In 2016, a project was undertaken at Gordion, Turkey, to stabilize and conserve the remains of a rubble platform built early in the Middle Phrygian period (ca. 800–700 b.c.e.) under the vast Gate Complex leading to the megarons on the Citadel Mound. In the process, aspects of Middle Phrygian building strategies came to light that enhanced our understanding gained from the original excavation in the 1950s. This article outlines the archaeology of the Middle Phrygian Gate Complex and the sophisticated internal structures that lent stability to the rubble platform upon which it was built, and examines the ...


Review Of Challenges And Advances In Modification Of Food Package Headspace Gases, Ziynet Boz, Bruce A. Welt, Jeffrey K. Brecht, William Pelletier, Eric McLamore, Gregory A. Kiker, Jason E. Butler 2018 University of Florida

Review Of Challenges And Advances In Modification Of Food Package Headspace Gases, Ziynet Boz, Bruce A. Welt, Jeffrey K. Brecht, William Pelletier, Eric Mclamore, Gregory A. Kiker, Jason E. Butler

Journal of Applied Packaging Research

Modified Atmosphere Packaging (MAP) has been widely used as an effective way to preserve foods. Fresh produce, meat and meat products, seafood, and dairy products can benefit from modified gaseous atmospheres, which are usually achieved by reducing oxygen and increasing carbon dioxide concentrations, within limits, defined by product tolerances. MAP of fresh produce is particularly challenging because products are living and respiring. Respiration rates depend on several factors including temperature, oxygen, and carbon dioxide concentrations. Balancing package permeation with respiration is challenging, often due to limited selection of practical packaging materials. Failing to remain within tolerance limits of products leads ...


Numerical Simulation Of Energy Localization In Dynamic Materials, Arkadi Berezovski, Mihhail Berezovski 2018 Tallinn University of Technology

Numerical Simulation Of Energy Localization In Dynamic Materials, Arkadi Berezovski, Mihhail Berezovski

Publications

Dynamic materials are artificially constructed in such a way that they may vary their characteristic properties in space or in time, or both, by an appropriate arrangement or control. These controlled changes in time can be provided by the application of an external (non-mechanical) field, or through a phase transition. In principle, all materials change their properties with time, but very slowly and smoothly. Changes in properties of dynamic materials should be realized in a short or quasi-nil time lapse and over a sufficiently large material region. Wave propagation is a characteristic feature for dynamic materials because it is also ...


Dislocations Interaction Induced Structural Instability In Intermetallic Al2cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu 2018 Xi'an Jiaotong University

Dislocations Interaction Induced Structural Instability In Intermetallic Al2cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu

Mechanical & Materials Engineering Faculty Publications

Intermetallic precipitates are widely used to tailor mechanical properties of structural alloys but are often destabilized during plastic deformation. Using atomistic simulations, we elucidate structural instability mechanisms of intermetallic precipitates associated with dislocation motion in a model system of Al2Cu. Interaction of non-coplanar <001> dislocation dipoles during plastic deformation results in anomalous reactions—the creation of vacancies accompanied with climb and collective glide of <001> dislocation associated with the dislocation core change and atomic shuffle—accounting for structural instability in intermetallic Al2Cu. This process is profound with decreasing separation of non-coplanar dislocations and increasing temperature and is likely ...


Molecular Doping Enabled Scalable Blading Of Efficient Hole-Transport-Layer-Free Perovskite Solar Cells, Wu-Qiang Wu, Qi Wang, Yanjun Fang, Yuchuan Shao, Shi Tang, Yehao Deng, Haidong Lu, Ye Liu, Tao Li, Zhibin Yang, Alexei Gruverman, Jinsong Huang 2018 University of North Carolina

Molecular Doping Enabled Scalable Blading Of Efficient Hole-Transport-Layer-Free Perovskite Solar Cells, Wu-Qiang Wu, Qi Wang, Yanjun Fang, Yuchuan Shao, Shi Tang, Yehao Deng, Haidong Lu, Ye Liu, Tao Li, Zhibin Yang, Alexei Gruverman, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

The efficiencies of perovskite solar cells (PSCs) are now reaching such consistently high levels that scalable manufacturing at low cost is becoming critical. However, this remains challenging due to the expensive hole-transporting materials usually employed, and difficulties associated with the scalable deposition of other functional layers. By simplifying the device architecture, hole-transport-layer-free PSCs with improved photovoltaic performance are fabricated via a scalable doctor-blading process. Molecular doping of halide perovskite films improved the conductivity of the films and their electronic contact with the conductive substrate, resulting in a reduced series resistance. It facilitates the extraction of photoexcited holes from perovskite directly ...


Characterization Of A Novel Variable Friction Connection For Semi-Active Cladding System, Yongqiang Gong, Liang Cao, Simon Laflamme, Spencer Quiel, James Ricles, Douglas Taylor 2018 Iowa State University

Characterization Of A Novel Variable Friction Connection For Semi-Active Cladding System, Yongqiang Gong, Liang Cao, Simon Laflamme, Spencer Quiel, James Ricles, Douglas Taylor

Civil, Construction and Environmental Engineering Publications

Cladding systems are conventionally designed to serve architectural purposes and protect occupants from the environment. Some research has been conducted in altering the cladding system in order to provide additional protection against natural and man-made hazards. The vast majority of these solutions are passive energy dissipators, applicable to the mitigation of single types of hazards. In this paper, we propose a novel semiactive variable friction device that could act as a connector linking a cladding panel to the structural system. Because of its semi-active capabilities, the device, here termed variable friction cladding connection (VFCC), could be utilized to mitigate different ...


Flow Patterns Through Vascular Graft Models With And Without Cuffs, Chia Min Leong, Gary B. Nackman, Timothy Wei 2018 Rensselaer Polytechnic Institute

Flow Patterns Through Vascular Graft Models With And Without Cuffs, Chia Min Leong, Gary B. Nackman, Timothy Wei

Mechanical & Materials Engineering Faculty Publications

The shape of a bypass graft plays an important role on its efficacy. Here, we investigated flow through two vascular graft designs±with and without cuff at the anastomosis. We conducted Digital Particle Image Velocimetry (DPIV) measurements to obtain the flow field information through these vascular grafts. Two pulsatile flow waveforms corresponding to cardiac cycles during the rest and the excitation states, with 10% and without retrograde flow out the proximal end of the native artery were examined. In the absence of retrograde flow, the straight end-to-side graft showed recirculation and stagnation regions that lasted throughout the full cardiac cycle ...


Applied Strength Of Materials For Engineering Technology, Barry Dupen 2018 Indiana University - Purdue University Fort Wayne

Applied Strength Of Materials For Engineering Technology, Barry Dupen

Manufacturing and Construction Engineering Technology Faculty Publications

No abstract provided.


Consuming Digital Debris In The Plasticene, Stephen R. Parks 2018 Virginia Commonwealth University

Consuming Digital Debris In The Plasticene, Stephen R. Parks

Theses and Dissertations

Claims of customization and control by socio-technical industries are altering the role of consumer and producer. These narratives are often misleading attempts to engage consumers with new forms of technology. By addressing capitalist intent, material, and the reproduction limits of 3-D printed objects’, I observe the aspirational promise of becoming a producer of my own belongings through new networks of production. I am interested in gaining a better understanding of the data consumed that perpetuates hyper-consumptive tendencies for new technological apparatuses. My role as a designer focuses on the resolution of not only the surface of the object through 3-D ...


Tunable Mechanical Metamaterials Through Hybrid Kirigami Structures, Doh-Gyu Hwang, Michael Bartlett 2018 Iowa State University

Tunable Mechanical Metamaterials Through Hybrid Kirigami Structures, Doh-Gyu Hwang, Michael Bartlett

Materials Science and Engineering Publications

Inspired by the art of paper cutting, kirigami provides intriguing tools to create materials with unconventional mechanical and morphological responses. This behavior is appealing in multiple applications such as stretchable electronics and soft robotics and presents a tractable platform to study structure-property relationships in material systems. However, mechanical response is typically controlled through a single or fractal cut type patterned across an entire kirigami sheet, limiting deformation modes and tunability. Here we show how hybrid patterns of major and minor cuts creates new opportunities to introduce boundary conditions and non-prismatic beams to enable highly tunable mechanical responses. This hybrid approach ...


An Integrated Microstructural-Nanomechanical-Chemical Approach To Examine Material-Specific Characteristics Of Cementitious Interphase Regions, Mahdieh Khedmati, Yong-Rak Kim, Joesph A. Turner, Hani Alanazi, Charles Nguyen 2018 University of Nebraska-Lincoln

An Integrated Microstructural-Nanomechanical-Chemical Approach To Examine Material-Specific Characteristics Of Cementitious Interphase Regions, Mahdieh Khedmati, Yong-Rak Kim, Joesph A. Turner, Hani Alanazi, Charles Nguyen

Mechanical & Materials Engineering Faculty Publications

Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region because it acts as a bridge transferring forces between aggregates and a binding matrix and is generally susceptible to damage. As alternative binding agents like alkali-activated precursors have obtained substantial attention in recent years, there is a growing need for fundamental knowledge to uncover interphase formation mechanisms. In this paper, two different types of binding materials, i.e., fly ash-based geopolymer and ordinary portland cement, were mixed with limestone aggregate to examine and compare the microstructures and nanomechanical properties of interphase region ...


An Integrated Microstructural-Nanomechanical-Chemical Approach To Examine Material-Specific Characteristics Of Cementitious Interphase Regions, Mahdieh Khedmati, Yong-Rak Kim, Joseph A. Turner, Hani Alanazi, Charles Nguyen 2018 University of Nebraska - Lincoln

An Integrated Microstructural-Nanomechanical-Chemical Approach To Examine Material-Specific Characteristics Of Cementitious Interphase Regions, Mahdieh Khedmati, Yong-Rak Kim, Joseph A. Turner, Hani Alanazi, Charles Nguyen

Mechanical & Materials Engineering Faculty Publications

Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region because it acts as a bridge transferring forces between aggregates and a binding matrix and is generally susceptible to damage. As alternative binding agents like alkali-activated precursors have obtained substantial attention in recent years, there is a growing need for fundamental knowledge to uncover interphase formation mechanisms. In this paper, two different types of binding materials, i.e., fly ash-based geopolymer and ordinary portland cement, were mixed with limestone aggregate to examine and compare the microstructures and nanomechanical properties of interphase region ...


An Integrated Model For The Probabilistic Prediction Of Yield Strength In Electron-Beam Additively Manufactured Ti-6al-4v, Thomas Kiel Ales 2018 Iowa State University

An Integrated Model For The Probabilistic Prediction Of Yield Strength In Electron-Beam Additively Manufactured Ti-6al-4v, Thomas Kiel Ales

Graduate Theses and Dissertations

A complete model for the prediction of the yield strength of Titanium 6Al-4V in an additively manufactured component is presented herein. A thermal model is presented utilizing the ABAQUS simulation software to provide the process leg of the materials tetrahedron. The thermal model is fed into an implementation of the Langmuir equation that has been adapted for use in the simulation of the Electron-Beam Additive Manufacturing (EBAM) process. The predicted chemistry provided by the Langmuir equation for the Ti-6Al-4V alloy is then used in a phenomenological equation for the prediction of yield strength; a design probability curve is generated through ...


Mixed Glass Former Effect In Borate And Thioborate Sodium-Ion Conducting Glass Systems, Brittany Curtis 2018 Iowa State University

Mixed Glass Former Effect In Borate And Thioborate Sodium-Ion Conducting Glass Systems, Brittany Curtis

Graduate Theses and Dissertations

As alternative energy sources continue to increase their production, there becomes a higher demand for cost-effective, safe, and energy efficient grid storage. Solid-state batteries are becoming of increased attention due to the demands for grid storage of alternative energy production, especially on days when these sources are under producing. As these solid-state batteries are being developed, many aspects of these batteries are being researched to optimize safety, cost-effectiveness and energy density. Current lithium-ion batteries have been scrutinized due to their safety concerns utilizing a flammable, liquid electrolyte. These concerns may be limited by replacing these organic, liquid electrolytes with an ...


Exploration Of Alnico Permanent Magnet Microstructure And Processing For Near Final Shape Magnets With Solid-State Grain Alignment For Improved Properties, Aaron Gregory Kassen 2018 Iowa State University

Exploration Of Alnico Permanent Magnet Microstructure And Processing For Near Final Shape Magnets With Solid-State Grain Alignment For Improved Properties, Aaron Gregory Kassen

Graduate Theses and Dissertations

Economic uncertainty in the rare earth (RE) permanent magnet (PM) marketplace as well as a quickly evolving electric drive motor market which has decided to leverage permanent magnet synchronous AC drive (PMAC) motors as the motor of choice, has driven renewed research in RE-free permanent magnets such as “alnico.” Alnico, essentially an Al-Ni-Co-Fe magnet alloy, was displaced for high energy density applications by RE-containing magnets in the 1970’s due to their high-energy performance and high coercivities.

The current PMAC development trajectory requires the development of a sustainable magnet material choice, which not only has impressive mechanical properties, such as ...


Precision Radio-Frequency And Microwave Dielectric Spectroscopy And Characterization Of Ionic Aqueous Solutions, Amin Gorji-Bandpy 2018 Iowa State University

Precision Radio-Frequency And Microwave Dielectric Spectroscopy And Characterization Of Ionic Aqueous Solutions, Amin Gorji-Bandpy

Graduate Theses and Dissertations

Excessive amounts of chemicals and ions flowing into water sources, which are mainly due to efflux from agricultural lands, cause serious environmental and human-health related concerns. The lack of affordable and real-time monitoring systems for these contaminants limits effective conservation and management strategies. To establish a basis for developing an effective, fast, real-time, and affordable sensing system, dielectric spectroscopy has been applied to characterize agriculturally-relevant aqueous solutions of most commonly found ions in tile drainage water. Dielectric spectra of aqueous sodium chloride (NaCl), sodium nitrate (NaNO3), and sodium sulphate (Na2SO4) ionic solutions, which are the common pollutants found in agricultural ...


Comparative Study Of Magnetic Properties Of Nanoparticles By High-Frequency Heat Dissipation And Conventional Magnetometry, V. Malik, J. Goodwill, Surya K. Mallapragada, Tanya Prozorov, Ruslan Prozorov 2017 Ames Laboratory

Comparative Study Of Magnetic Properties Of Nanoparticles By High-Frequency Heat Dissipation And Conventional Magnetometry, V. Malik, J. Goodwill, Surya K. Mallapragada, Tanya Prozorov, Ruslan Prozorov

Surya K. Mallapragada

The rate of heating of 15 nm uniformly-sized magnetic aqueous nanoparticles suspension by high-amplitude and high-frequency ac magnetic field induced by the resonating LC circuit was measured. The results are analyzed in terms of specific energy absorption rate (SAR). Fitting field amplitude and frequency dependences of SAR to the linear response theory, magnetic moment per particles was extracted. The value of magnetic moment was independently evaluated from dc magnetization measurements of a frozen colloid by fitting field-dependent magnetization to a Langevin function. The two methods produced similar results, which are compared to the theoretical expectation for this particle size. Additionally ...


Modeling Of Dislocation Channel Formation And Evolution In Irradiated Metals, Peter James Doyle 2017 University of Tennessee, Knoxville

Modeling Of Dislocation Channel Formation And Evolution In Irradiated Metals, Peter James Doyle

Masters Theses

Defect-free dislocation channel formation has been reported to promote plastic instability during tensile testing via localized plastic flow, leading to a distinct loss of ductility and strain hardening in many low-temperature irradiated materials. In order to study the underlying mechanisms governing dislocation channel width and formation, the channel formation process is modeled via a simple stochastic dislocation-jog process dependent upon grain size, defect cluster density, and defect size. Dislocations traverse a field of defect clusters and jog stochastically upon defect interaction, forming channels of low defect-density. Based upon prior molecular dynamics (MD) simulations and in-situ experimental transmission electron microscopy (TEM ...


Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan 2017 University of Nebraska-Lincoln

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method ...


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