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Articles 31 - 38 of 38

Full-Text Articles in Physics

Spatiotemporally Periodic Driven System With Long-Range Interactions, Owen Dale Myers Jan 2015

Spatiotemporally Periodic Driven System With Long-Range Interactions, Owen Dale Myers

Graduate College Dissertations and Theses

It is well known that some driven systems undergo transitions when a system parameter is changed adiabatically around a critical value. This transition can be the result of a fundamental change in the structure of the phase space, called a bifurcation. Most of these transitions are well classified in the theory of bifurcations. Among the driven systems, spatiotemporally periodic (STP) potentials are noteworthy due to the intimate coupling between their time and spatial components. A paradigmatic example of such a system is the Kapitza pendulum, which is a pendulum with an oscillating suspension point. The Kapitza pendulum has the strange …


The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang Jan 2015

The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang

Graduate College Dissertations and Theses

Σ3{111} coherent twin boundary (CTB) in face-centered-cubic (FCC) metals and alloys have been regarded as an efficient way to simultaneously increase strength and ductility at the nanoscale. Extensive study of dislocation-CTB interaction has been carried out by a combination of computer simulations, experiments and continuum theory. Most of them, however, are based on the perfect CTB assumption. A recent study [Wang YM, Sansoz F, LaGrange T, et al. Defective twin boundaries in nanotwinned metals. Nat Mater. 2013;12(8):697-702.] has revealed the existence of intrinsic kink-like defects in CTBs of nanotwinned copper through nanodiffraction mapping technique, and has confirmed the effect of …


Numerical Simulations Of Reacting Flow In An Inductively Coupled Plasma Torch, Maximilian Dougherty Jan 2015

Numerical Simulations Of Reacting Flow In An Inductively Coupled Plasma Torch, Maximilian Dougherty

Graduate College Dissertations and Theses

In the design of a thermal protection system for atmospheric entry, aerothermal heating presents a major impediment to efficient heat shield design. Recombination of atomic species in the boundary layer results in highly exothermic surface-catalyzed recombination reactions and an increase in the heat flux experienced at the surface. The degree to which these reactions increase the surface heat flux is partly a function of the heat shield material. Characterization of the catalytic behavior of these materials takes place in experimental facilities, however there is a dearth of detailed computational models for the fluid dynamic and chemical behavior of such facilities. …


Density Functional Theory Study Of Dilute Transition Metal Phthalocyanines, Daniel Burrill Jan 2015

Density Functional Theory Study Of Dilute Transition Metal Phthalocyanines, Daniel Burrill

Graduate College Dissertations and Theses

Organometallic (OM) crystals are studied in fields ranging from spintronics to photovoltaics. This thesis focuses on studying a particular class of OM crystals known as transition metal-phthalocyanines (TM-Pc) - a molecular crystal composed of chains of planar OM molecules with a transition metal center and four coordinated pyrrole-aromatic rings joined by nitrogen atoms, similar to porphyrin. The structure resembles a dish rack pattern where the planar TM-Pcs of adjacent chains are oriented nearly perpendicular to each other. While TM-Pcs have been studied for decades due to their interesting optical properties and applications as dyes, there has been recent interest in …


Segregation Of Particles Of Variable Size And Density In Falling Suspension Droplets, Melissa Kathleen Faletra Jan 2014

Segregation Of Particles Of Variable Size And Density In Falling Suspension Droplets, Melissa Kathleen Faletra

Graduate College Dissertations and Theses

The problem of the falling under gravity suspension droplet was examined for cases where the droplet contains particles with different densities and different sizes. Cases examined include droplets composed of uniform-size particles with two different densities, of uniform-density particles of two different sizes, and of a distribution of particles of different densities. The study was conducted using both simulations based on Oseenlet particle interactions and laboratory experiments. It is observed that when the particles in the suspension droplet have different sizes and densities, an interesting segregation phenomenon occurs in which lighter/smaller particles are transported downward with the droplet and preferentially …


Electron Correlation Effects In Strained Dual-Layer Graphene Systems, Peter Karl Harnish Jan 2014

Electron Correlation Effects In Strained Dual-Layer Graphene Systems, Peter Karl Harnish

Graduate College Dissertations and Theses

In low dimensional systems, electron correlation effects can often be enhanced. This can be vital since these effects not only play an important role in the study of many-electron physics, but are also useful in designing new materials for various applications. Since its isolation from graphite in 2004, graphene, a two dimensional sheet of carbon atoms, has drawn considerable interest due to its remarkable properties. In the past few years, research has moved on from single to bi-, dual- and multi-layer graphene systems, each displaying their own multitudes of intriguing properties. In particular, multi-layer systems that are electronically decoupled, but …


Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves Jan 2014

Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves

Graduate College Dissertations and Theses

When bulk helium-4 is cooled below T = 2.18 K, it undergoes a phase transition to a superfluid, characterized by a complex wave function with a macroscopic phase and exhibits inviscid, quantized flow. The macroscopic phase coherence can be probed in a container filled with helium-4, by reducing one or more of its dimensions until they are smaller than the coherence length, the spatial distance over which order propagates. As this dimensional reduction occurs, enhanced thermal and quantum fluctuations push the transition to the superfluid state to lower temperatures. However, this trend can be countered via the proximity effect, where …


The Invention Of The Transistor, Bret E. Crawford Jan 1991

The Invention Of The Transistor, Bret E. Crawford

Graduate College Dissertations and Theses

Julius E. Lilienfeld filed for patents for three different designs for solid-state amplifying devices between 1926 and 1928, well before Bell Lab's discovery of the point-contact transistor in 1948. The American Physical Society named a prize in honor of Lilienfeld after receiving a substantial sum of money in 1982 from the will of his wife, Beatrice Lilienfeld, who believed her husband had not received sufficient credit for his scientific contributions. In order to investigate Lilienfeld's contribution to early efforts to replace the vacuum triode, we present the history surrounding these efforts, contributions and limitations of Lilienfeld's work, and details of …