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Cfd Simulations Of Bubble Column Equipped With Bundles Of Concentric Tubes, Glen C. DSouza 2020 The University of Western Ontario

Cfd Simulations Of Bubble Column Equipped With Bundles Of Concentric Tubes, Glen C. Dsouza

Electronic Thesis and Dissertation Repository

Bubble column reactors are multiphase contactors that have found several industrial applications owing to various attractive features including excellent thermal management, low maintenance cost due to simple construction and absence of moving parts. In order to attain desired performance for a given application, these reactors are usually equipped with internals such as vertical tube bundles to facilitate heat transfer. The column hydrodynamics and turbulence parameters are altered when the column is occluded with internals which adds to the complexity of the problem. The use of Computational Fluid Dynamics (CFD) tools for the study of multiphase flows has gained a lot ...


A Laser Induced Fluorescence Design For Renewable Energy Application, Shaimaa S. Mahdi, Intisar A. Hamad 2020 University of Baghdad| college of science for women|physics department

A Laser Induced Fluorescence Design For Renewable Energy Application, Shaimaa S. Mahdi, Intisar A. Hamad

Karbala International Journal of Modern Science

Biomass is considered to be one of the highest potential renewable energy sources to meet the requirements of energy in the world, where it can be used as an effective alternative for renewable energy sources, including electricity and heating, as well as fuel used in transport. One of the most common problems accompanying the usage of biomass through gasification processes to produce gases is the amounts of undesirable formed Tars. In this paper, a Laser Induced Fluorescence spectroscopy (LIF) method was incorporated to identify the produced Tar compounds at high temperature in the gasification technology. The effect of tars deposition ...


Motion Of Phase Boundary During Antiferroelectric–Ferroelectric Transition In A Pbzro3-Based Ceramic, Binzhi Liu, Xinchun Tian, Lin Zhou, Xiaoli Tan 2020 Iowa State University

Motion Of Phase Boundary During Antiferroelectric–Ferroelectric Transition In A Pbzro3-Based Ceramic, Binzhi Liu, Xinchun Tian, Lin Zhou, Xiaoli Tan

Materials Science and Engineering Publications

The in situ biasing transmission electron microscopy technique is employed to investigate the nucleation and growth of the ferroelectric phase during the electric field-induced phase transition in Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98}O3, a PbZrO3-based antiferroelectric ceramic. The first-order displacive phase transition is found to be highly reversible with the initial antiferroelectric domain configuration almost completely recovered upon removal of the applied field. In the forward transition from the antiferroelectric to ferroelectric phase, {100}c facets are dominant on the phase boundary; while in the reverse transition from the ferroelectric to antiferroelectric phase ...


Squeezing A Prism Into A Surface: Emulating Bulk Optics With Achromatic Meta-Surfaces, Odysseas Tsilipakos, Maria Kafesaki, Eleftherios N. Economou, Costas M. Soukoulis, Thomas Koschny 2020 Institute of Electronic Structure and Laser, Foundation for Research and Technology ‐ Hellas (FORTH‐IESL),

Squeezing A Prism Into A Surface: Emulating Bulk Optics With Achromatic Meta-Surfaces, Odysseas Tsilipakos, Maria Kafesaki, Eleftherios N. Economou, Costas M. Soukoulis, Thomas Koschny

Ames Laboratory Accepted Manuscripts

Metasurfaces promise to replace bulky prisms and lenses with 2D surfaces, revolutionizing wavefront control with technologically significant advantages in size, weight, and planar fabrication. However, conventional implementations suffer from large chromatic aberrations and cannot sustain performance over practical bandwidths of real‐world signals because of the limited phase modulation margin available in a surface. How can an infinitely thin surface generate the arbitrarily large, broadband phase delay that bulk phase accumulation can provide? Here, equivalence between bulk optics and certain multiresonant metasurfaces is demonstrated, where phase delay arises from trains of multiple resonances in the effective sheet conductivities of the ...


Substitutional And Interstitial Doping In Laco5 System For The Development Of Hard Magnetic Properties: A First Principles Study, Huseyin Ucar, Renu Choudhary, Durga Paudyal 2020 California State Polytechnic University - Pomona

Substitutional And Interstitial Doping In Laco5 System For The Development Of Hard Magnetic Properties: A First Principles Study, Huseyin Ucar, Renu Choudhary, Durga Paudyal

Ames Laboratory Accepted Manuscripts

We investigate here the changes in the electronic structure at the transition metal sites of the RE-TM5 structure (RE = Rare Earth, TM = Transition Metal) while doping the interstitial sites with nitrogen. LaCo5 compound is taken as the baseline compound owing to its critically needed intrinsic magnetic properties such as magneto-crystalline anisotropy energy (MAE) of ≈5 meV/fu [1] due to the contributions from the cobalt network. In addition, because of the lack of 4f electrons in lanthanum, complications originating from the treatment of the 4f localized electrons are absent in this compound; making it an ideal reference material to all ...


Viable Materials With A Giant Magnetocaloric Effect, Nikolai A. Zarkevich, Vladimir I. Zverev 2020 Ames Laboratory

Viable Materials With A Giant Magnetocaloric Effect, Nikolai A. Zarkevich, Vladimir I. Zverev

Ames Laboratory Accepted Manuscripts

This review of the current state of magnetocalorics is focused on materials exhibiting a giant magnetocaloric response near room temperature. To be economically viable for industrial applications and mass production, materials should have desired useful properties at a reasonable cost and should be safe for humans and the environment during manufacturing, handling, operational use, and after disposal. The discovery of novel materials is followed by a gradual improvement of properties by compositional adjustment and thermal or mechanical treatment. Consequently, with time, good materials become inferior to the best. There are several known classes of inexpensive materials with a giant magnetocaloric ...


Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner 2020 The Graduate Center, City University of New York

Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner

Dissertations, Theses, and Capstone Projects

One of the best tools we have for the edification of physics is the analogy. When we take our classical set of states and dynamical variables in phase space and treat them as vectors and Hermitian operators respectively in Hilbert space through the canonical quantization, we lose out on a lot of the intuition developed with the previous classical physics. With classical physics, through our own experiences and understanding of how systems should behave, we create easy-to-understand analogies: we compare the Bohr model of the atom to the motion of the planets, we compare electrical circuits to the flow of ...


Electronic Structure, Magnetic Properties, And Exchange Splitting Of Gadolinium Intermetallics, Brian Ensign, Renu Choudhary, Huseyin Ucar, Durga Paudyal 2020 Iowa State University and Ames Laboratory

Electronic Structure, Magnetic Properties, And Exchange Splitting Of Gadolinium Intermetallics, Brian Ensign, Renu Choudhary, Huseyin Ucar, Durga Paudyal

Ames Laboratory Accepted Manuscripts

We report here the electronic structure calculations of the magnetic moment, magneto-crystalline anisotropy energy (MAE), and density of states (DOS) of Gd-metal, GdAl2, GdAl3, GdCo2, GdCo3, and GdCo5. From the DOS, the exchange splitting energy is derived to map ferrimagnetic to paramagnetic phase transition (Curie temperature, TC). The employed theoretical method here is based on advanced density functional theory, specifically the linearized augmented plane wave method (LAPW) within the local spin density approximation (LSDA), including spin–orbit coupling (SOC) and Hubbard model parameter (U). DOS analysis of both Gd-Al and Gd-Co systems reveals a strong correlation between exchange splitting ...


Instability And Evolution Of The Magnetic Ground State In Metallic Perovskites Gdrh3c1-Xbx, Abhishek Pandey, A. K. Singh, Shovan Dane, K. Ghosh, I. Das, S. Tripathi, U. Kumar, R. Ranganathan, David C. Johnston, Chandan Mazumdar 2020 University of the Witwatersrand

Instability And Evolution Of The Magnetic Ground State In Metallic Perovskites Gdrh3c1-Xbx, Abhishek Pandey, A. K. Singh, Shovan Dane, K. Ghosh, I. Das, S. Tripathi, U. Kumar, R. Ranganathan, David C. Johnston, Chandan Mazumdar

Ames Laboratory Accepted Manuscripts

We report investigations of the structural, magnetic, electrical transport, and thermal properties of five compositions of the metallic perovskite GdRh3C1−xBx (0.00≤x≤1.00). Our results show that all five compositions undergo magnetic ordering at low temperatures, but the nature of the ordered state is significantly different in the carbon- and the boron-rich compositions, where the former shows signatures of an amplitude-modulated magnetic structure and the latter exhibits evidence of an equal-moment incommensurate antiferromagnetic ordering. We also observe a remarkable field-dependent evolution of conduction carrier polarization in the compositionally disordered compounds. The outcomes indicate that this system is ...


Aperiodically Ordered Nano-Graphene On The Quasicrystalline Substrate, M. Maniraj, L. Lyu, S. Mousavion, S. Becker, S. Emmerich, D. Jungkenn, Deborah L. Schlagel, Thomas A. Lograsso, S. R. Barman, S. Mathias, B. Stadtmüller, M. Aeschlimann 2020 University of Kaiserslautern

Aperiodically Ordered Nano-Graphene On The Quasicrystalline Substrate, M. Maniraj, L. Lyu, S. Mousavion, S. Becker, S. Emmerich, D. Jungkenn, Deborah L. Schlagel, Thomas A. Lograsso, S. R. Barman, S. Mathias, B. Stadtmüller, M. Aeschlimann

Ames Laboratory Accepted Manuscripts

Designing exotic structures in low dimensions is key in today's quest to tailor novel quantum states in materials with unique symmetries. Particularly intriguing materials in this regard are low dimensional aperiodic structures with non-conventional symmetries that are otherwise forbidden in translation symmetric crystals. In our work, we focus on the link between the structural and electronic properties of aperiodically ordered aromatic molecules on a quasicrystalline surface, which has largely been neglected so far. As an exemplary case, we investigate the self-assembly and the interfacial electronic properties of the nano-graphene-like molecule coronene on the bulk truncated icosahedral (i) Al–Pd ...


Vortex Cores In Narrow Thin-Film Strips, Vladimir G. Kogan, Masanori Ichioka 2020 Iowa State University and Ames Laboratory

Vortex Cores In Narrow Thin-Film Strips, Vladimir G. Kogan, Masanori Ichioka

Ames Laboratory Accepted Manuscripts

We study vortex current distributions in narrow thin-film superconducting strips with the help of analytic expression of the vortex current derived within the London theory. Using definition of the vortex core “boundary” as a curve where the current reaches the depairing value, vortex core size and shape are estimated as a function of vortex position in the strip. We show that the core size near the strip edges is smaller than in the rest of the strip, indicating that the Bardeen–Stephen flux-flow resistivity should be reduced near the edges. Moreover, at elevated temperatures, when the depairing current is small ...


Magnetic Phase Transitions In Eu(Co1-Xnix)(2-Y)As-2 Single Crystals, N. Sangeetha, Santanu Pakhira, D. H. Ryan, V. Smetana, A.-V. Mudring, David C. Johnston 2020 Ames Laboratory

Magnetic Phase Transitions In Eu(Co1-Xnix)(2-Y)As-2 Single Crystals, N. Sangeetha, Santanu Pakhira, D. H. Ryan, V. Smetana, A.-V. Mudring, David C. Johnston

Ames Laboratory Accepted Manuscripts

The effects of Ni doping in Eu(Co1-xNix)(2-y)As-2 single crystals with x = 0 to 1 grown out of self-flux are investigated via crystallographic, electronic transport, magnetic, and thermal measurements. All compositions adopt the body-centered-tetragonal ThCr2Si2 structure with space group I4/mmm. We also find 3%-4% of randomly distributed vacancies on the Co/Ni site. Anisotropic magnetic susceptibility chi(alpha) (alpha = ab, c) data versus temperature T show clear signatures of an antiferromagnetic (AFM) c-axis helix structure associated with the Eu+2 spins 7/2 for x = 0 and 1 as previously reported. The chi(alpha)(T) data ...


Fifth-Degree Elastic Energy For Predictive Continuum Stress–Strain Relations And Elastic Instabilities Under Large Strain And Complex Loading In Silicon, Hao Chen, Nikolai A. Zarkevich, Valery I. Levitas, Duane D. Johnson, Xiancheng Zhang 2020 East China University of Science and Technology

Fifth-Degree Elastic Energy For Predictive Continuum Stress–Strain Relations And Elastic Instabilities Under Large Strain And Complex Loading In Silicon, Hao Chen, Nikolai A. Zarkevich, Valery I. Levitas, Duane D. Johnson, Xiancheng Zhang

Aerospace Engineering Publications

Materials under complex loading develop large strains and often phase transformation via an elastic instability, as observed in both simple and complex systems. Here, we represent a material (exemplified for Si I) under large Lagrangian strains within a continuum description by a 5th-order elastic energy found by minimizing error relative to density functional theory (DFT) results. The Cauchy stress—Lagrangian strain curves for arbitrary complex loadings are in excellent correspondence with DFT results, including the elastic instability driving the Si I → II phase transformation (PT) and the shear instabilities. PT conditions for Si I → II under action of cubic axial ...


An Expanded Model Of Unmatter From Neutrosophic Logic Perspective: Towards Matter-Spirit Unity View, Florentin Smarandache, Victor Christianto, Robert Neil Boyd 2020 University of New Mexico

An Expanded Model Of Unmatter From Neutrosophic Logic Perspective: Towards Matter-Spirit Unity View, Florentin Smarandache, Victor Christianto, Robert Neil Boyd

Mathematics and Statistics Faculty and Staff Publications

In Neutrosophic Logic, a basic assertion is that there are variations of about everything that we can measure; the variations surround three parameters called T, I, F (truth, indeterminacy, falsehood) which can take a range of values. A previous paper in IJNS, 2020 shortly reviews the links among aether and matter creation from the perspective of Neutrosophic Logic. In any case, matter creation process in nature stays a major puzzle for physicists, scientists and other science analysts. To this issue neutrosophic logic offers an answer: "unmatter." This paper examines an extended model of unmatter, to incorporate issue soul solidarity. So ...


Electron Emission And Transport Properties Database For Spacecraft Charging Models, Phil Lundgreen 2020 Utah State University

Electron Emission And Transport Properties Database For Spacecraft Charging Models, Phil Lundgreen

Theses and Dissertations

Modeling the rate and likelihood of spacecraft charging during spacecraft mission is critical to determine mission length, proposed spacec­raft attitude, and spacecraft design. The focus of this work is the creation and utilization of a database of secondary electron yield (SEY) measurements for a host of materials to increase accuracy in spacecraft modeling. Traditional methods of SEY data selection for input into spacecraft charging codes typically include the use of compiled materials databases incorporated in charging codes or selecting values from a specific scientific study. The SEY database allows users to select data inputs based upon the details associated ...


Cooking Systems Using Aluminum Foam, Ryan Tetsuo Mizukami 2020 California Polytechnic State University, San Luis Obispo

Cooking Systems Using Aluminum Foam, Ryan Tetsuo Mizukami

Physics

In developing countries, the use of wood burning fires for cooking is cause for illness and death. With this in mind, research was conducted to develop a solar cooking device capable of cooking of soup within 15 mins in order to reduce the negative impacts of cooking with wood. Current methods of solar-based cooking, such as solar concentrators and solar tube ovens, are impractical. A small solar panel is a cost-effective way to produce energy but will not produce enough power to cook within a reasonable amount of time. Even if it is assumed that all of the energy produced ...


Developing Arduino Coding Curriculum, Tyler Brown, Riley Bucheitte, Timothy Kidd 2020 University of Northern Iowa

Developing Arduino Coding Curriculum, Tyler Brown, Riley Bucheitte, Timothy Kidd

Summer Undergraduate Research Program (SURP)

No abstract provided.


Reshaping Of Truncated Pd Nanocubes: Energetic And Kinetic Analysis Integrating Transmission Electron Microscopy With Atomistic-Level And Coarse-Grained Modeling, King C. Lai, Minda Chen, Benjamin Williams, Yong Han, Chia-Kuang Tsung, Wenyu Huang, James W. Evans 2020 Iowa State University and Ames Laboratory

Reshaping Of Truncated Pd Nanocubes: Energetic And Kinetic Analysis Integrating Transmission Electron Microscopy With Atomistic-Level And Coarse-Grained Modeling, King C. Lai, Minda Chen, Benjamin Williams, Yong Han, Chia-Kuang Tsung, Wenyu Huang, James W. Evans

Chemistry Publications

Stability against reshaping of metallic fcc nanocrystals synthesized with tailored far-from-equilibrium shapes is key to maintaining optimal properties for applications such as catalysis. Yet Arrhenius analysis of experimental reshaping kinetics, and appropriate theory and simulation, is lacking. Thus, we use TEM to monitor the reshaping of Pd nanocubes of ∼25 nm side length between 410 °C (over ∼4.5 h) and 440 °C (over ∼0.25 h), extracting a high effective energy barrier of Eeff ≈ 4.6 eV. We also provide an analytic determination of the energy variation along the optimal pathway for reshaping that involves transfer of atoms across ...


Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani 2020 Center for High Technology Materials

Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani

Optical Science and Engineering ETDs

Intracavity Phase Interferometry (IPI) using two correlated, counter-propagating frequency combs (pulse trains) in mode-locked lasers has evolved into a powerful technique for high-precision metrology. In this method a physical parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. Inside a laser cavity, that phase shift becomes a frequency shift (phase shift/round-trip time) applied to the whole frequency comb created by this pulse as it exits the cavity at each round-trip. This frequency shift is measured by interfering this comb with a reference comb created by a reference pulse circulating in the same ...


Strain‐Enhanced Metallic Intermixing In Shape‐Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics, Benjamin P. Williams, Allison P. Young, Ilektra Andoni, Yong Han, Wei-Shang Lo, Matthew Golden, Jane Yang, Lian‐Ming Lyu, Chun-Hong Kuo, James W. Evans, Wenyu Huang, Chia-Kuang Tsung 2020 Boston College

Strain‐Enhanced Metallic Intermixing In Shape‐Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics, Benjamin P. Williams, Allison P. Young, Ilektra Andoni, Yong Han, Wei-Shang Lo, Matthew Golden, Jane Yang, Lian‐Ming Lyu, Chun-Hong Kuo, James W. Evans, Wenyu Huang, Chia-Kuang Tsung

Chemistry Publications

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd‐Ni‐Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low‐temperature ...


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