Physics Commons^™

Dust Devils And Dustless Vortices On A Desert Playa Observed With Surface Pressure And Solar Flux Logging, Ralph D. Lorenz, Brian K. Jackson

Physics Faculty Publications and Presentations

Dust devils are convective vortices rendered visible by lofted dust, and may be a significant means of injecting dust into the atmosphere, on both Earth and Mars. The fraction of vortices that are dust-laden is not well-understood, however. Here we report a May/June 2013 survey on a Nevada desert playa using small stations that record pressure and solar flux with high time resolution (2 Hz): these data allow detection of vortices and an estimate of the dust opacity of the subset of vortices that geometrically occult the sun. The encounter rate of vortex pressure drops of 0.3 hPa ...

A Study Of Photon Trapping And The Ac Stark Effect In Photonic Crystals And Dispersive Materials, Iftekharul Haque

University of Western Ontario - Electronic Thesis and Dissertation Repository

In this thesis, we study light-matter interaction in the contexts of coherent population trapping (CPT) and the ac Stark effect in nanoparticles embedded (doped) in two important classes of reservoirs -- photonic crystals and dispersive materials. These materials have gaps in their energy spectra and are studied widely due to their unusual optical properties and potential for novel applications. We consider that the reservoirs are doped with an ensemble of five-level nanoparticles, each with a single Λ core (consisting of a lower doublet and an upper energy level), which interact with both the host reservoir and external radiation fields. We have ...

Torsion Free Biconformal Spaces: Reducing The Torsion Field Equations, James Thomas Wheeler

James Thomas Wheeler

Our goal is to solve the full set of torsion and co-torsion field equations of Euclidean biconformal space, with only the assumption of vanishing torsion. Here we begin by resolving the involution constraints, symmetry conditions and torsion field equation into a single equation for further study.

Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment, Justin Christensen

Physics Capstone Project

Dielectric materials subjected to energetic electron fluxes can emit light in several forms. We have observed three distinct types of emissions: (i) short-duration (<1 ms), high-intensity electrostatic discharge (ESD) or “arc” events; (ii) intermediate-duration, high-intensity events which begin with a bright arc followed by an exponential decay of intensity (~10 to 100 s decay constant), termed “flares”; and (iii) long-duration, low-intensity emission, or cathodoluminescence, that continues as long as the electron flux is on. These events were studied for bulk samples of bisphenol/amine epoxy, using an electron gun with varying current densities (0.3 to 5 nA/cm2) and energies (12 to 40 keV) in a high vacuum chamber. Light emitted from the samples was measured with a high-sensitivity visible to near-infrared video camera. Results of the spatial and temporal extent for each type of event are presented as well as a discussion of how absolute spectral radiance and rates for each type of event are dependent on incident electron current density, energy, and power density and on material type, temperature, and thickness. Applications of this research to spacecraft charging and light emissions are discussed.

Advantages Of A Finite Extensible Nonlinear Elastic Potential In Lattice Boltzmann Simulations, Tai-Hsien Wu, Dewei Qi

The Hilltop Review

A new structure, generalized lattice nonlinear spring model (GLNSM), which adopts non-linear FENE-LJ potential instead of harmonic potential, has been coupled with lattice Boltzmann simulation for solving fluid-solid interaction problem. In this article, a significant work is the relationship between the GLNSM (FENE-LJ potential) and Young’s modulus has been described in detail. A validation has also been presented to prove that GLNSM is reliable.

Variation Of The Linear Biconformal Action, James Thomas Wheeler

James Thomas Wheeler

We find the field equations of biconformal space in a basis adapted to Lagrangian submanifolds on which the restriction of the Killing metric is non-degenerate.

Studies In Torsion Free Biconformal Spaces. Case 2: \Gamma_{-} = 0, James Thomas Wheeler

James Thomas Wheeler

We show that the solutions for the symmetric part of the connection in homogeneous biconformal space also satisfy the more general field equations of curved biconformal spaces in the case when \gamma_{-} = 0.

Studies In Torsion Free Biconformal Spaces, James Thomas Wheeler

James Thomas Wheeler

We study whether the solutions for the symmetric part of the connection in homogeneous biconformal space also satisfy the more general field equation of curved biconformal spaces. We show that the six field equations for the torsion and co-torsion are satisfied by vanishing torsion together with the Lorentzian form of the metric when γ+ = 0.

Notes And Errata, David D. Nolte

David D Nolte

No abstract provided.

Fishing For New Physics With Massive Neutral Dibosons: Measurements Of Zz Production Cross Section And The Search For Invisible Higgs Boson Decays Beyond The Standard Model With The Cms Detector At The Lhc, Matthew Ervin Chasco

Physics Dissertations

No abstract provided.

Neutron Generation From 10mev Electron Beam To Produce Mo99, Innovative Research Publications Irp India, Borhani Zarandi, Mahmood, Tabbakh, Farshid, Amrollahi Bioki, Hojjat

Innovative Research Publications IRP India

In this paper MCNP4C code has been used to simulate of the photonuclear interaction induced by 10MeV electron beam is an approach for generating the high intensity neutrons. Since the results are depended on the target material, the calculations are performed for the targets made of high z elements of Pb, Ta and W in a simple geometry.

Historical Notes: Modern Dynamics, David D. Nolte

David D Nolte

Historical notes and historical biographies in the history of physics and the history of modern dynamics.

The Spatial Distribution Of Electric Field Intensity When The Motion Of Electric Charge In Absolute Space, Vildyan Yanbikov

Vildyan Yanbikov

When driving an electric or gravitational charge in absolute space. Field created by these particles will have a different distribution in space. In comparison with by a stationary charge. When the charge motion of the deformation field.

The Spatial Distribution Of Electric Field Intensity When The Motion Of Electric Charge In Absolute Space, Vildyan Yanbikov

Vildyan Yanbikov

При движении электрического или гравитационного заряда в абсолютном пространстве. Поля, создаваемого этими частицами, будет иметь другое распределение в пространстве. В сравнении со стационарным бесплатно. При движении заряда поля деформаций.

Gauge Transformations Of The Biconformal Connection, James Thomas Wheeler

James Thomas Wheeler

We study the changes of the biconformal gauge fields under the local rotational and dilatational gauge transformations.

Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre

Research Vignettes

In this worksheet we describe and illustrate a relatively simple set of new Rainich-type conditions on an n-dimensional spacetime which are necessary and sufficient for it to define a perfect fluid solution of the Einstein field equations. Procedures are provided which implement these Rainich-type conditions and which reconstruct the perfect fluid from the metric. These results provide an example of the idea of geometrization of matter fields in general relativity, which is a purely geometrical characterization of matter fields via the Einstein field equations.

Strain-Driven Growth Of Gaas(111) Quantum Dots With Low Fine Structure Splitting, Paul J. Simmonds

Physics Faculty Publications and Presentations

Symmetric quantum dots (QDs) on (111)-oriented surfaces are promising candidates for generating polarization-entangled photons due to their low excitonic fine structure splitting(FSS). However, (111) QDs are difficult to grow. The conventional use of compressive strain to drive QD self-assembly fails to form 3D nanostructures on (111) surfaces. Instead, we demonstrate that (111) QDs self-assemble under tensile strain by growing GaAs QDs on an InP(111)A substrate. Tensile GaAs self-assembly produces a low density of QDs with a symmetric triangular morphology. Coherent, tensile QDs are observed without dislocations, and the QDs luminescence at room temperature. Single QD measurements ...

Carbon Nanotube Sensors And Field Emitters, Ben Pound

Physics Capstone Project

Carbon nanotube (CNT) forests are arrays of free-standing CNTs, as seen in Fig. 1a. The goal of this project was to deposit 1,5-diaminonaphthalene (DAN) evenly on each CNT. The motivation is that CNTs cannot effectively participate in chemical reactions by themselves. However, DAN can bind to the CNT surface in such a way that it can participate in chemical reactions while staying on the CNT side wall¹. If DAN could be coated evenly on the CNTs throughout the forest, it could make a very sensitive biological sensor. A sensor is only as good as the number of detection ...

Neutral Density Behavior From 45-90 Km Based On Rayleigh Lidar Observations Above Usu, David Barton

Physics Capstone Project

There are over 900 nights of observations taken by the Rayleigh lidar above Utah State University from 1993 to 2004. The data have been reduced to give absolute temperatures and relative densities in the mesosphere, from 45-90 km (Herron, 2004, 2007). From the 11 years of relative density data an 11-year climatology of mesospheric densities above Logan, Utah has been created. From this climatology I have been able to normalize the 11 years of density data to the following models: the MSISe00 empirical model, the CPC (Climate Prediction Center) reanalysis model, the ERA Interim reanalysis model, and the NASA MERRA ...

Thermophonon, Nikolai A. Zarkevich

Ames Laboratory Software

ThermoPhonon is a stand-alone code, which can be integrated into other software packages. Typically, it is used together with a density functional theory (DFT) code (such as VASP, Wien2k, AbInit, SIESTA) and a phonon code (such as Phonopy or Phon). The workflow is the following.

• Molecular dynamics (MD) in a supercell at a given temperature T is performed using another code. After sufficient equilibration, the output in the form of atomic positions and forces for a large number of selected MD steps is recorded into a file. If needed, one can modify this file by applying additional constraints, such as ...