Depth-profiled Doppler broadening spectroscopy of positron annihilation on the cyclic fatigue-induced fracture surfaces of three amorphous Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ metallic glass specimens reveals the presence of a 30–50 nm layer of increased free volume that is generated by the propagating fatigue crack tip. The presence and character of this fatigue transformation zone...
The fundamental physics of turbulence in plasma is not well understood. Recent studies of the plasma deflagration accelerator in the High Temperature Gasdynamics Lab at Stanford University have demonstrated the presence of small scale instabilities that limit the lifetime of the jet/Z pinch and are not reproduced by coaxial plasma...
The microwave backscatter properties of surf zone waves are analyzed using field observations.
By utilizing a preexisting, independent, water surface discrimination technique, the microwave returns were
extracted along individual waveforms and the data from shoaling (steepening) waves, surf zone breaking
waves, and remnant foam were separated and quantified. In addition,...
Deformation of metallic glasses requires the existence of free volume to allow atomic movement under mechanical loading. Accordingly, the present research seeks to understand how free volume variations in alloys of identical compositions affect the fatigue and fracture behavior. By annealing below the glass transition temperature, the free volume of...
The Transient Reactor Test facility (TREAT) at Idaho National Laboratory (INL) is a unique reactor capable of stressing test fuel during a power pulse transient. TREAT fuel is composed of high enriched uranium (HEU) heterogeneous fuel; microscopic UO₂ fuel grains with an average radius of 10 μm are randomly distributed...
This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: https://doi.org/10.1016/j.elspec.2012.12.004
A new experimental apparatus was built at Oregon State University to perform high resolution stimulated Raman spectroscopy in a pulsed molecular jet at state densities of the order of 10¹¹ cm⁻³. The technique uses a stimulated Raman step to first populate a vibrational/rotational level and then a resonantly enhanced multiphoton...
Doppler-free saturation spectroscopy in an optically thick atomic vapor is used in an
optical-feedback configuration for two semiconductor diode laser systems. One laser
system consists of an unmodifed, commercially available diode laser. The other laser
system consists of a diode laser initially stabilized by optical feedback from a diffraction
grating....
In order to observe laser phase noise, this noise must be converted to
amplitude noise, which can be achieved using either an interferometer or an
absorption resonance in an atomic/molecular vapor or gas. When phase noise is
converted to amplitude noise, it is manifested as a heterodyne signal in the...
During the Internal Waves on the Continental Margin (IWAVES) field experiments of 1996 and 1997 off of Mission Beach, California (32.75° N), we observed energetic, dirunal-band motions across the entire study site in water depths ranging from 15 to 500 m and spanning a cross-shore distance of 15 km. The...
Previously unaddressed aspects of how equatorial currents affect long Rossby wave phase speeds are investigated using solutions of the shallow-water equations linearized about quasi-realistic currents. Modification of the background potential vorticity (PV) gradient by curvature in the narrow equatorial currents is shown to play a role comparable to the Doppler...
Relative lifetimes, and the closely related quadrupole moments (Q[subscript]i values), of the
six superdeformed (SD) bands in ¹⁹³Hg and the yrast SD band in ¹⁹²Hg were determined
by a Doppler-shift attenuation method measurement. The experiment was performed
using the Gammasphere array and Lawrence Berkeley National Laboratory's 88-inch
Cyclotron. The Q[subscript]i...
A continuous, low-velocity, nearly monochromatic atomic beam is created using
laser cooling and two-dimensional magneto-optic trapping. Rubidium atoms from an
effusive oven are slowed and cooled using Zeeman-tuned slowing. The scattering force
from a counter-propagating, frequency-stabilized diode laser beam is used to decelerate
the thermal beam of atoms to a...
Measurements of tidal currents on the central Oregon shelf are available from several sources, including recent high frequency (HF) coastal radar and Acoustic Doppler Profiler (ADP) deployments, and historical current moorings. In this paper we use a generalized inverse (GI) approach to compare these data to, and then assimilate them...
This study is mainly concentrated on examining the positive cloud-to-ground lightning activity associated with Mesoscale Convective Systems. Six MCS events which occurred during the O.K. PRE-STORM program in 1985 are studied. Data indicating the location and polarity of the cloud-to-ground lightning flashes from a lightning location network are analyzed in...
Wave breaking in the surf zone is an important forcing
mechanism on the generation of nearshore currents and in the driving
of sediment transport. At the same time, wave breaking can have
significant spatial and temporal variability that needs to be
accounted for in the description of nearshore processes. Remote...
Investigations of plasma production by a pulsed dye laser
microprobe were made. Comparisons between a Q- switched and a
pulsed dye laser system were made on the intensity of the continuum
produced by atmospheric breakdown. The dye laser system was
foundtominimize the production of the continuum which in turn
allowed...
The atmospheric sodium daytime abundance was measured for
Corvallis, Oregon, using direct absorption of sunlight by atmospheric
sodium atoms, as observed with an optical waveguide spectrum analyzer.
The disadvantage of the spectrum analyzer is that it can't resolve the
sodium D-lines (Its resolving power is 0.5 nm, which is approximately...
Techniques have been developed for measuring the
temperature, stable species concentrations, and atomic
radical concentrations during a transient combustion
event. They combine the features of direct sampling with
two spectroscopic techniques to produce relatively simple
diagnostic techniques to obtain time-resolved
measurements. In this study, a transient event was
provided by...
The high resolution stimulated Raman spectrometer at OSU was
modified to improve its sensitivity and to extend its range of
applications to low Raman shifts and to the spectroscopy of solids and
liquids. As part of the characterization of the spectrometer, optical
Stark effects on rotational and vibrational transitions of...
Carbon 1s photoelectron asymmetry parameters β for the chlorinated and the methyl carbon atom of CH₃CH₂Cl, CH₃CHCl₂, and CH₃CCl₃ have been measured using synchrotron radiation in the 340-600 eV energy range. We provide experimental evidence that the intramolecular scattering strongly affects beta values, even far from the ionization threshold. The...
A low velocity, low temperature beam of atoms is produced
from a two-dimensional magneto-optic trap known as an atomic
funnel. The funnel provides simultaneous spatial and velocity
compression of atoms and will provide a source for a three-grating
atomic interferometer. Rubidium atoms from an oven are slowed
by chirped cooling...
The life cycles of three Madden–Julian oscillation (MJO) events were observed over the Indian Ocean as part of the Dynamics of the MJO (DYNAMO) experiment. During November 2011 near 0°, 80°E, the site of the research vessel Roger Revelle, the authors observed intense multiscale interactions within an MJO convective envelope,...
We construct a Monte Carlo simulation in Python to calculate optical flashes at 5x10¹⁴ Hz peaking at 6x10³¹ erg s⁻¹Hz⁻¹St⁻¹ due to synchrotron radiation from the reverse shock of a gamma-ray burst’s jet. While analytical solutions to this problem exist, they rely on sweeping simplifications of what is necessarily a...
A method of treating resonance captures for few energy group
calculations is developed using the Narrow Resonance-Infinite
Absorber approximation to the resonance integral. The application
of this method is not restricted to this approximation, however,
as other approximations to the resonance integral could also be
used.
The approach presented defines...
The carbon is photoelectron spectrum of CO₂ has been measured with very high photon energy resolution. The natural lifetime of the carbon is hole state has been determined from a series of spectra taken at photon energies of 308, 320, and 330 eV. The measured values of the lifetimes show...
Repeated mesoscale surveys of waters over the shelf and slope off Oregon were
conducted during spring and summer of 2001 to study the spatial structure of the velocity
and hydrographic fields. The ocean response to wind forcing is compared between a
region of relatively simple topography with alongshore uniformity and...
The diurnal cycle of marine stratocumulus in cloud-topped boundary layers is examined using ship-based meteorological data obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx). The high temporal and spatial continuity of the ship data, as well as the 31-day sample size, allows the...
Because of the complicated form of the diffusion equation,
approximations are necessary to treat the energy dependence for
practical problems. The standard model is the few group approximation.
A second approximate form, the overlapping group or modal
method, is examined and more fully developed in this work to provide
an...
The scattering of optical rays by small spherical particles bears a strong resemblance to the
diffusion of fission neutrons in solid materials. This work explores the feasibility of
exploiting similarities between these two systems for the purposes of reactor component analysis, education, and outreach. After a brief overview of reactor-environment...
Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for...
A nonflame method for atomic absorption spectroscopy is
described. A helical tungsten filament from a commercially available
6-V, 4-A light bulb, heated to :incandescence in an argon atmosphere
is used to atomize 2-μl aqueous samples for metals analyses. Studies
of two hollow cathode lamp tungsten filament orientations, a
modulated light...
The US military is evaluating the capabilities of emerging technologies based on IEEE 802.16 standard as a potential commercial off-the-shelf solution to support the communication requirements of the future war.
In the last few years, development in military and telecommunication industries have focused on an intensive use of broadband systems,...
We report an experimental and theoretical study of single-molecule inner-shell photoemission measured over an extended range of photon energies. The vibrational intensity ratios I (nu = 1)/I (nu = 0) from the C 1s photoelectron spectra of carbon monoxide, although mostly determined by the bond length change upon ionization, are...
Observations off the New Jersey coast document the shoaling of three groups of nonlinear internal waves of depression over 35 km across the shelf. Each wave group experienced changing background conditions along its shoreward transit. Despite different wave environments, a clear pattern emerges. Nearly symmetric waves propagating into shallow water...
High resolution spectroscopy was used to study the properties of two simple polyatomic molecules, sulfur trioxide, SO₃, and carbon suboxide, C₃O₂. The fundamental modes and several hot bands of the ¹⁸O isotopic fonns of SO₃ (³²S¹⁸O₃ and ³⁴S¹⁸O₃) have been investigated using both infrared spectroscopy and coherent anti-Stokes Raman scattering...
The techniques of coherent anti-Stokes Raman spectroscopy (CARS)
and inverse Raman spectroscopy (IRS) are used to examine carbon dioxide
aggregation in a supersonic jet expansion. To promote the formation of
small clusters, a BMW injector valve is modified to permit its use as a
pulsed nozzle at very cold temperatures....