Physical Sciences and Mathematics Commons^™

Magnetic Nanodoping: Atomic Control Of Spin States In Cobalt Doped Silver Clusters, Vicente Zamudio-Bayer, Konstantin Hirsch, Lei Ma, Kobe De Knijf, X. S. Xu, Arkadiusz Ławicki, Akira Terasaki, Piero Ferrari, Bernd Von Issendorff, Peter Lievens, Walt A. De Heer, J. Tobias Lau, Ewald Janssens

Department of Physics and Astronomy: Faculty Publications

The interaction of magnetic dopants with delocalized electron states can result in interesting many-body physics. Here, the magnetic properties of neutral and charged finite silver metal host clusters with a magnetic cobalt atom impurity were investigated experimentally by exploiting the complementary methods of Stern- Gerlach molecular beam deflection and x-ray magnetic circular dichroism spectroscopy and are accompanied by density functional theory calculations and charge transfer multiplet simulations. The influence of the number of valence electrons and the consequences of impurity encapsulation were addressed in free size-selected, singly cobalt-doped silver clusters CoAg^0,_n+ (n = 2–15). Encapsulation of the …

A Search For Chiral Asymmetry In Secondary Electron Emission From Cysteine Induced By Longitudinally Polarized Electrons, K. J. Ahrendsen, Kenneth Wayne Trantham, D. Tupa, T. J. Gay

Department of Physics and Astronomy: Faculty Publications

We performed experiments searching for chirality-dependent secondary electron emission for a 141 eV longitudinally spin-polarized electron beam incident on a thick solid cysteine target. We determined the secondary electron yield by measuring the positive current produced when the cysteine target was negatively biased. No spin-dependent effects to a level of 10⁻³ were found for the secondary electron emission yield.

Topological Hall Effect In Particulate Magnetic Nanostructure, Ahsan Ullah

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Conduction electrons change their spin direction due to the exchange interaction with the lattice spins. Ideally, the spins of the conduction electrons follow the atomic spin adiabatically, so that spins like S1, S2, and S3 can be interpreted as time-ordered sequences t1 < t2 < t3. Such spin sequences yield a quantum-mechanical phase factor in the wave function,  →ei, where  is known as the Berry phase. The corresponding spin rotation translates into a Berry curvature and an emergent magnetic field and subsequently, Hall-effect contribution known as the topological Hall-effect. This dissertation explores topological Hall-effect in particulate magnets, where noncollinear spins are stabilized by competition between different magnetic interactions. The topologically non-trivial spin textures in these nanostructures are flower states, curling states, vortex, and magnetic bubbles, which give rise to topological Hall-effect and have finite spin chirality and Skyrmion number Q. Topological Hall-effect is investigated in noninteracting nanoparticles, exchanges coupled centrosymmetric nanoparticles, exchanges coupled non-centrosymmetric nanoparticles which possess Dzyaloshinskii-Moriya interaction (DMI), and exchanged coupled Hard and soft magnetic films. Micromagnetic modeling, simulations, analytical calculations, and experimental methods are used to determine topological Hall-effect. In very small noninteracting nanoparticles, the reverse magnetic fields enhance Q due to the flower state until the reversal occurs, whereas, for particles with a radius greater than coherence radius, the Q jumps to a larger value at the nucleation field representing the curling state. The comparisons of magnetization patterns between experimental and computed magnetic force microscopy (MFM) measurements show the presence of spin chirality. Magnetic and Hall-effect measurements identify topological Hall-effect in the exchange-coupled Co and CoSi-nanoparticle films. The origin of the topological Hall-effect namely, the chiral domains with domain-wall chirality quantified by an integer skyrmion number in Co and chiral spins with partial skyrmion number in CoSi. These spin structures are different from the Skyrmions due to DMI in B-20 crystals and multilayered thin films with Cnv symmetry. In these films THE caused by cooperative magnetization reversal in the exchange-coupled Co-nanoparticles and peripheral chiral spin textures in CoSi-nanoparticles.

Advisor: Xiaoshan Xu

Search For Higgs Boson Decay To A Charm Quark-Antiquark Pair In Proton-Proton Collisions At √S =13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H → c[], produced in association with a leptonically decaying V (W or Z) boson is presented. The search is performed with proton-proton collisions at √s = 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb⁻¹. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for Z → c[] in VZ events, leading to its first observation at a hadron collider with a significance …

Growth And Emergent Functionalities Of Oxide Thin Films Utilizing Interface Engineering, Detian Yang

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Complex oxide interfaces have offered intriguing novel emergent phenomena and multiple functionalities through interfacial reconstructions of spin, orbital, charge, and lattice degrees of freedom. Interface engineering via manipulating interfacial interaction, defects and multiple interfacial quantum charges and orders constitutes the essential method and technique to achieve desired functionalities in oxide heterostructures. In this thesis, shown are two examples of utilizing interfacial reconstruction and interfacial strain engineering to achieve intrinsic exchange bias and realize epitaxial growth of mixed-valence hexagonal manganite thin films, respectively.

Firstly, we demonstrated intrinsic exchange bias induced by interfacial reconstruction in Ni_xCo_yFe_3-x-yO …

Azimuthal Correlations Within Exclusive Dijets With Large Momentum Transfer In Photon-Lead Collisions, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at √s_NN = 5.02 TeV, corresponding to an integrated luminosity of 0.38 nb⁻¹, collected with …

Electron Scattering From 1-Methyl-5-Nitroimidazole: Cross-Sections Formodeling Electron Transport Through Potential Radiosensitizers, Ana I. Lozano, Lidia Álvarez, Adrián García-Abenza, Carlos Guerra, Fábris Kossoski, Jaime Rosado, Francisco Blanco, Juan Carlos Oller, Mahmudul Hasan, Martin Centurion, Thorsten Weber, Daniel S. Slaughter, Deepthy M. Mootheril, Alexander Dorn, Sarvesh Sarvesh, Paulo Limão-Vieira, Rafael Colmenares, Gustavo García

Department of Physics and Astronomy: Faculty Publications

In this study, we present a complete set of electron scattering cross-sections from 1-Methyl-5- Nitroimidazole (1M5NI) molecules for impact energies ranging from 0.1 to 1000 eV. This information is relevant to evaluate the potential role of 1M5NI as a molecular radiosensitizers. The total electron scattering cross-sections (TCS) that we previously measured with a magnetically confined electron transmission apparatus were considered as the reference values for the present analysis. Elastic scattering cross-sections were calculated by means of two different schemes: The Schwinger multichannel (SMC) method for the lower energies (below 15 eV) and the independent atom model-based screening-corrected additivity rule with …

Search For Nonresonant Pair Production Of Highly Energetic Higgs Bosons Decaying To Bottom Quarks, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search for nonresonant Higgs boson (H) pair production via gluon and vector boson (V) fusion is performed in the four-bottom-quark final state, using proton-proton collision data at 13 TeV corresponding to 138 fb⁻¹ collected by the CMS experiment at the LHC. The analysis targets Lorentz-boosted H pairs identified using a graph neural network. It constrains the strengths relative to the standard model of the H self-coupling and the quartic VVHH couplings, κ_2V, excluding κ_2V = 0 for the first time, with a significance of 6.3 standard deviations when other H couplings …

Two-Particle Azimuthal Correlations In Γp Interactions Using Ppb Collisions At √SNn=8.16tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The first measurements of the Fourier coefficients (V_nΔ) of the azimuthal distributions of charged hadrons emitted from photon-proton (γp) interactions are presented. The data are extracted from 68.8nb⁻¹of ultra-peripheral proton-lead (pPb) collisions at √s_NN=8.16 TeVusing the CMS detector. The high energy lead ions produce a flux of photons that can interact with the oncoming proton. This γp system provides a set of unique initial conditions with multiplicity lower than in photon-lead collisions but comparable to recent electron-positron and electron-proton data. The V_nΔ coefficients are presented in ranges of event multiplicity and transverse momentum …

Search For Medium Effects Using Jets From Bottom Quarks In Pbpb Collisions At √SNn=5.02tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The first study of the shapes of jets arising from bottom (b) quarks in heavy ion collisions is presented. Jet shapes are studied using charged hadron constituents as a function of their radial distance from the jet axis. Lead-lead (PbPb) collision data at a nucleon-nucleon center-of-mass energy of √s_NN=5.02TeVwere recorded by the CMS detector at the LHC, with an integrated luminosity of 1.69nb⁻¹. Compared to proton-proton collisions, aredistribution of the energy inbjets to larger distances from the jet axis is observed in PbPb collisions. This medium-induced redistribution is found to be substantially larger forbjets than for …

Search For New Heavy Resonances Decaying To Ww, Wz, Zz, Wh, Or Zh Boson Pairs In The All-Jets Final State In Proton-Proton Collisions At √S=13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search for new heavy resonances decaying to WW, WZ, ZZ, WH, or ZHboson pairs in the all-jets final state is presented. The analysis is based on proton-proton collision data recorded by the CMS detector in 2016–2018 at a centre-of-mass energy of 13TeVat the CERN LHC, corresponding to an integrated luminosity of 138fb⁻¹. The search is sensitive to resonances with masses between 1.3and 6 TeV, decaying to bosons that are highly Lorentz-boosted such that each of the bosons forms a single large-radius jet. Machine learning techniques are employed to identify such jets. No significant excess over the estimated …

Search For Narrow Resonances In The B-Tagged Dijet Mass Spectrum In Proton-Proton Collisions At √S=13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search is performed for narrow resonances decaying to final states of two jets, with at least one jet originating from a b quark, in proton-proton collisions at √s = 13 TeV. The data set corresponds to an integrated luminosity of 138 fb⁻¹ collected with theCMS detector at the LHC. Jets originating from energetic b hadrons are identified through a b-tagging algorithm that utilizes a deep neural network or the presence of a muon inside a jet. The invariant mass spectrum of jet pairs is well described by a smooth parametrization and no evidence for the production of …

Probing Heavy Majorana Neutrinos And The Weinberg Operator Through Vector Boson Fusion Processes In Proton-Proton Collisions At √S = 13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at √s = 13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb⁻¹. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 …

Measurements Of Jet Multiplicity And Jet Transverse Momentum In Multijet Events In Proton–Proton Collisions At √S = 13tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

Multijet events at large transverse momentum (p_T) are measured at √ s = 13 TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3 fb⁻¹. The multiplicity of jets with p_T > 50 GeV that are produced in association with a high-p_T dijet system is measured in various ranges of the p_T of the jet with the highest transverse momentum and as a function of the azimuthal angle difference Δφ1,2 between the two highest p_T jets in the dijet system. The differential production …

Cauchy-Type Integral Method For Solving The Linearized One-Dimensional Vlasov-Poisson Equation, Frank M. Lee, Bradley A. Shadwick

Department of Physics and Astronomy: Faculty Publications

We present a method for solving the linearized Vlasov-Poisson equation, based on analyticity properties of the equilibrium and initial condition through Cauchy-type integrals, that produces algebraic expressions for the distribution and field, i.e., the solution is expressed without integrals. Standard extant approaches involve deformations of the Bromwich contour that give erroneous results for certain physically reasonable configurations or eigenfunction expansions that are misleading as to the temporal structure of the solution. Our method is more transparent, lacks these defects, and predicts previously unrecognized behavior.

Search For Nonresonant Higgs Boson Pair Production In The Four Leptons Plus Twob Jets Final State In Proton-Proton Collisions At √S = 13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of √s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fb⁻¹. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier μ, defined as the ratio of the observed HH production rate in the HH ⟶ ZZ*b[] ⟶ 4ℓb[] decay channel to the standard model (SM) …

Search For Nonresonant Higgs Boson Pair Production In The Four Leptons Plus Twob Jets Final State In Proton-Proton Collisions At √S = 13 Tev, Armen R. Tumasyan, Cma Collaboration

Department of Physics and Astronomy: Faculty Publications

The first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of √s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fb⁻¹. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier μ, defined as the ratio of the observed HH production rate in the HH ⟶ ZZ*bb[bar] ⟶ 4ℓb[bar] decay channel to the standard model (SM) …

Search For Top Squarks In The Four-Body Decay Mode With Single Lepton Final States In Proton-Proton Collisions At √S = 13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark ([]₁), is presented. The search targets the four-body decay of the []₁, which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino ( []⁰₁ ), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb⁻¹ of …

Optical Characterization Of Isothermal Spin State Switching In An Fe(Ii) Spin Crossover Molecular And Polymer Ferroelectric Bilayer, Saeed Yazdani, Kourtney Collier, Grace Yang, Jared Phillips, Ashley Dale, Aaron Mosey, Samuel Grocki, Jian Zhang, Anne E. Shanahan, Ruihua Cheng, Peter A. Dowben

Department of Physics and Astronomy: Faculty Publications

Using optical characterization, it is evident that the spin state of the spin crossover molecular complex [Fe{H₂B(pz)₂}₂(bipy)] (pz = tris(pyrazol-1-1y)-borohydride, bipy = 2,2′-bipyridine) depends on the electric polarization of the adjacent polymer ferroelectric polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) thin film. The role of the PVDF-HFP thin film is significant but complex. The UV–Vis spectroscopy measurements reveals that room temperature switching of the electronic structure of [Fe{H₂B(pz)₂}₂(bipy)] molecules in bilayers of PVDF-HFP/[Fe{H₂B(pz)₂}₂(bipy)] occurs as a function of ferroelectric polarization. The retention of voltage-controlled nonvolatile changes …

Search For Heavy Resonances And Quantum Black Holes In Eμ, Eτ, And Μτ Final States In Proton-Proton Collisions At √S = 13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search is reported for heavy resonances and quantum black holes decaying into eμ, eτ, and μτ final states in proton-proton collision data recorded by the CMS experiment at the CERN LHC during 2016–2018 at √s = 13TeV, corresponding to an integrated luminosity of 138 fb⁻¹. The eμ, eτ, and μτ invariant mass spectra are reconstructed, and no evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on the product of the cross section and branching fraction for lepton flavor violating signals. Three benchmark signals are studied: resonant τ sneutrino …

Symmetry Control Of Unconventional Spin–Orbit Torques In Iro2, Michael Patton, Gautam Gurung, Ding-Fu Shao, Gahee Noh, Joseph A. Mittelstaedt, Marcel Mazur, Jong-Woo Kim, Philip J. Ryan, Evgeny Y. Tsymbal, Si-Young Choi, Daniel C. Ralph, Mark S. Rzchowski, Tianxiang Nan, Chang-Beom Eom

Department of Physics and Astronomy: Faculty Publications

Spin–orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy-efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in-plane magnetic switching. Unconventional spin–orbit torques arising from novel spin current polarizations, however, have the potential to switch other magnetization orientations such as perpendicular magnetic anisotropy, which is desired for higher density spintronic-based memory devices. Here, it is demonstrated that low crystalline symmetry is …

Ultrafast Electron Diffraction Instrument For Gas And Condensed Matter Samples, Yibo Wang, Sajib Kumar Saha, Tianlin Li, Yanwei Xiong, Kyle Wilkin, Anil Adhikari, Michael Loes, Jehad Abourahma, Xia Hong, S. Adenwalla, Alexander Sinitskii, Martin Centurion

Department of Physics and Astronomy: Faculty Publications

We report the modification of a gas phase ultrafast electron diffraction (UED) instrument that enables experiments with both gas and condensed matter targets, where a time-resolved experiment with sub-picosecond resolution is demonstrated with solid state samples. The instrument relies on a hybrid DC-RF acceleration structure to deliver femtosecond electron pulses on the target, which is synchronized with femtosecond laser pulses. The laser pulses and electron pulses are used to excite the sample and to probe the structural dynamics, respectively. The new system is added with capabilities to perform transmission UED on thin solid samples. It allows for cooling samples to …

Néel Spin Currents In Antiferromagnets, Ding-Fu Shao, Yuan-Yuan Jiang, Jun Ding, Shu-Hui Zhang, Zi-An Wang, Rui-Chun Xiao, Gautam Gurung, W. J. Lu, Y. P. Sun, Evgeny Y. Tsymbal

Department of Physics and Astronomy: Faculty Publications

Ferromagnets are known to support spin-polarized currents that control various spin-dependent transport phenomena useful for spintronics. On the contrary, fully compensated antiferromagnets are expected to support only globally spin-neutral currents. Here, we demonstrate that these globally spin-neutral currents can represent the Néel spin currents, i.e., staggered spin currents flowing through different magnetic sublattices. The Néel spin currents emerge in antiferromagnets with strong intrasublattice coupling (hopping) and drive the spin-dependent transport phenomena such as tunneling magnetoresistance (TMR) and spin-transfer torque (STT) in antiferromagnetic tunnel junctions (AFMTJs). Using RuO₂ and Fe₄GeTe₂ as representative antiferromagnets, we predict that the …

Rehybridization Dynamics Into The Pericyclic Minimum Of An Electrocyclic Reaction Imaged In Real-Time, Y. Liu, D. M. Sanchez, M. R. Ware, E. G. Champenois, J. Yang, J. P. F. Nunes, A. Attar, Martin Centurion, J. P. Cryan, R. Forbes, K. Hegazy, M. C. Hoffmann, F. Ji, M.-F. Lin, D. Luo, S. K. Saha, X. Shen, X. J. Wang, T. J. Martínez, T. J. A. Wolf

Department of Physics and Astronomy: Faculty Publications

Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ and π bonds through a cyclic structure. This structure is known as a pericyclic transition state for thermal reactions and a pericyclic minimum in the excited state for photochemical reactions. However, the structure of the pericyclic geometry has yet to be observed experimentally.We use a combination of ultrafast electron diffraction and excited state wavepacket simulations to image structural dynamics through the pericyclic minimum of a photochemical electrocyclic ring-opening reaction in the molecule α-terpinene. The structural motion into the pericyclic minimum is dominated by rehybridization of two carbon …

Interfacial And Surface Magnetism In Epitaxial Nico2O4(001)/Mgal2O4 Films, Corbyn Mellinger, Xiao Wang, Arjun Subedi, Andy T. Clark, Takashi Komesu, Richard Rosenberg, Peter A. Dowben, Xuemei Cheng, Xiaoshan S. Xu

Department of Physics and Astronomy: Faculty Publications

NiCo₂O₄ (NCO) films grown on MgAl₂O₄ (001) substrates have been studied using magnetometry and x-ray magnetic circular dichroism based on x-ray absorption spectroscopy and spin-polarized inverse photoemission spectroscopy with various thicknesses down to 1.6 nm. The magnetic behavior can be understood in terms of a layer of optimal NCO and an interfacial layer (1.2 ± 0.1 nm), with a small canting of magnetization at the surface. The thickness dependence of the optimal layer can be described by the finite-scaling theory with a critical exponent consistent with the high perpendicular magnetic anisotropy. The interfacial layer …

Cms Pythia 8 Colour Reconnection Tunes Based On Underlying-Event Data, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

New sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the pythia 8 event generator, are obtained based on the default CMS pythia 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies √ s = 7 and 13 TeV, and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, …

Domain Wall Saddle Point Morphology In Ferroelectric Triglycine Sulfate, C. J. Mccluskey, A. Kumar, Alexei Gruverman, I. Luk’Yanchuk, J. M. Gregg

Alexei Gruverman Publications

Ferroelectric domain walls, across which there is a divergence in polarization, usually have enhanced electrical conductivity relative to bulk. However, in lead germanate, head-to-head and tail-to-tail walls are electrically insulating. Recent studies have shown that this is because, when oppositely oriented domains meet, polar divergence is obviated by a combination of domain bifurcation and suspected local dipolar rotation. To explore the uniqueness, or otherwise, of this microstructure, we have used tomographic piezoresponse force microscopy to map three-dimensional domain morphologies in another uniaxial ferroelectric system: triglycine sulfate. This mapping reveals an abundance of domain wall saddle points, which are characteristic of …

Magnetic Properties Of Polycrystalline Spinel Oxides From Solid State Reaction, Camden Olds

Honors Theses

Spinel crystal materials of nickel, cobalt, and iron oxides have seen abundant research for their strong conductivity, ferromagnetic and ferroelectric properties, and their catalytic uses. These can be synthesized by a number of means. This project explores the use of the solid state synthesis method, which benefits from simplicity, of this family of materials, looking for interesting phase shift lines in the triangle between of varying compositions of these three metals.

Nickel cobaltite and other related spinels were synthesized from two different solid state approaches and characterized using XRD and SQUID magnetometry. The range 0.5-0.6 of molar ratios of nickel …

Improper Ferroelectricity In Ultrathin Hexagonal Ferrites Films, Xin Li, Yu Yun, X. S. Xu

Department of Physics and Astronomy: Faculty Publications

Suppression of ferroelectricity in ultrathin films of improper ferroelectric hexagonal ferrites or manganites has been attributed to the effect of interfacial clamping; however, the quantitative understanding and related phenomenological model are still lacking. In this work, we report on the paraelectric-to-ferroelectric phase transition of epitaxial h-ScFeO₃ films with different thicknesses through in situ reflection highenergy electron diffraction. Based on the interfacial clamping model and the Landau theory, we show that the thickness-dependence of the ferroelectric Curie temperature can be understood in terms of the characteristic length of an interfacial clamping layer and the bulk Curie temperature. Furthermore, we found …

Assessment Of Bridge Pier Response To Fire, Vehicle Impact, And Air Blast, Chen Fang, Qusai Alomari, Daniel G. Linzell

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Highway bridges exposed to intentional or unintentional fire followed by combined vehicle impact and air blast are at risk of significant damage and, possibly, collapse. Limited studies examining the complex effects of these extreme demands on bridge support elements and parametrizing their response and damage are found in the open literature. Research that is presented is part of an ongoing numerical investigation examining round, multi-column, reinforced concrete (RC), bridge pier behavior subject to multi-hazard scenarios involving fire, vehicle impact, and air blast. Detailed nonlinear finite element analysis models of single columns and multi-column piers supported by a pile foundation system …