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Coulombic resonances in a zero-gap semiconductor : a variational approach to a problem of resonance in scatteringJoos, Béla. January 1978 (has links)
No description available.
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Deuteron break-up by protons at 100 MeV.Pan, Pi-Jung. January 1968 (has links)
No description available.
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Investigations of light scattering by Australian natural waters for remote sensing applicationsO'Bree, Terry Adam, s9907681@student.rmit.edu.au January 2007 (has links)
Remote sensing is the collection of information about an object from a distance without physically being in contact with it. The type of remote sensing of interest here is in the form of digital images of water bodies acquired by satellite. The advantage over traditional sampling techniques is that data can be gathered quickly over large ranges, and be available for immediate analysis. Remote sensing is a powerful technique for the monitoring of water bodies. To interpret the remotely sensed data, however, knowledge of the optical properties of the water constituents is needed. One of the most important of these is the volume scattering function, which describes the angular distribution of light scattered by a sample. This thesis presents the first measurements of volume scattering functions for Australian waters. Measurements were made on around 40 different samples taken from several locations in the Gippsland lakes and the Great Barrier Reef. The measurements were made by modifying an existing static light scattering spectrometer in order to accurately measure the volume scattering functions. The development of the apparatus, its calibration and automation, and the application of a complex series of post-acquisition data corrections, are all discussed. In order to extrapolate the data over the full angular range, the data was analysed using theoretical curves calculated for multi-modal size distributions using Mie light scattering theory applied to each data set. From the Mie fits the scattering and backscattering coefficients were calculated. These were compared with scattering coefficients measured using in situ sensors ac-9 and Hydroscat-6, and with values from the literature. The effect of chlorophyll a concentrations on the scattering coefficients was examined, and a brief investigation of the polarisation properties of the samples was also undertaken. Finally the angular effects on the relationship between the backscattering coefficient and the volume scattering function were investigated. This is important as in situ backscattering sensors often assume that measuring at a single fixed-angle is a good approximation for calculating the backscattering coefficient. This assumption is tested, and the optimal measurement angle determined.
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Balloon-borne X-ray observations of the southern skyThomas, Richard Murison January 1971 (has links)
vi, 165 leaves : ill., appendices / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1972) from the Dept. of Physics, University of Adelaide
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Theoretical discussion of stimulated Rayleigh-wing scattering in liquids and liquid mixturesFreeman, James A. Jr. January 1972 (has links) (PDF)
M.S. / Applied Physics / The theory of stimulated Rayleigh-wing scattering in anisotropic molecular liquids is discussed. This theory is extended to include liquid mixtures. When binary mixtures are considered, a singularity is found in the threshold condition in certain circumstances. This leads to the possibility of measuring the anisotropic polarizability difference for one of the liquids. In addition, the appearance of the singularity suggests a method of determining whether saturation plays an important role in stimulated Rayleigh-wing scattering.
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Developing models of aerosol representation to investigate composition, evolution, optical properties, and CCN spectra using measurements of size-resolved hygroscopicityGasparini, Roberto 16 August 2006 (has links)
A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) was used to measure size distributions, hygroscopicity, and volatility during the May 2003 Aerosol Intensive Operational Period at the Central Facility of the Atmospheric Radiation Measurement Southern Great Plains site. Hygroscopic growth factor distributions for particles at eight dry diameters ranging from 0.012 µm to 0.600 µm were measured. These measurements, along with backtrajectory clustering, were used to infer aerosol composition and evolution. The hygroscopic growth of the smallest and largest particles analyzed was typically less than that of particles with dry diameters of about 0.100 µm. Condensation of secondary organic aerosol on nucleation mode particles may be responsible for the minimal growth observed at the smallest sizes. Growth factor distributions of the largest particles typically contained a non-hygroscopic mode believed to be composed of dust. A model was developed to characterize the hygroscopic properties of particles within a size distribution mode through analysis of the fixed-size hygroscopic growth measurements. This model was used to examine three cases in which the sampled aerosol evolved over a period of hours or days. Additionally, size and hygroscopicity information were combined to model the aerosol as a population of multi-component particles. With this model, the aerosol hygroscopic growth factor f(RH), relating the submicron scattering at high RH to that at low RH, is predicted. The f(RH) values predicted when the hygroscopic fraction of the aerosol is assumed to be metastable agree better with measurements than do those predicted under the assumption of crystalline aerosol. Agreement decreases at RH greater than 65%. This multi-component aerosol model is used to derive cloud condensation nuclei (CCN) spectra for comparison with spectra measured directly with two Desert Research Institute (DRI) CCN spectrometers. Among the 1490 pairs of DMA/TDMA-predicted and DRI-measured CCN concentrations at various critical supersaturations from 0.02-1.05%, the sample number-weighted mean R2 value is 0.74. CCN concentrations are slightly overpredicted at both the lowest (0.02-0.04%) and highest (0.80-1.05%) supersaturations measured. Overall, this multi-component aerosol model based on size distributions and size-resolved hygroscopicity yields reasonable predictions of the humidity-dependent optical properties and CCN spectra of the aerosol.
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Flocculation of natural organic matter in Swedish lakesKlemedsson, Shicarra January 2012 (has links)
Flocculation is an important part of the carbon cycle. It is therefore crucial to understand how flocculation is regulated and how different environmental factors impact. A dilemma is that it has been found difficult to measure flocculation experimentally. In this thesis, flocculation of dissolved organic carbon in a Swedish lake was measured in a series of laboratory experiments. The method used was Dynamic Light Scattering (DLS). DLS is used to determine the size distribution profile of, for instance, small particles in suspension. DLS measures Brownian motion and relates it to the particle size by measuring the fluctuation in scattering intensity. It is not very effective to measure the frequency spectrum contained in the intensity fluctuations directly, so instead, a digital auto correlator is used. Since factors such as pH, salinity and calcium chloride content varies in lakes and is thought to have an impact on flocculation, this was investigated as well. As pH was changed in a range of 3 to 9, small changes in size distribution could be detected. Salinity and calcium chloride content have quite an impact on flocculation. Time also has a great impact, samples that were set to rest for a week showed a significant increase in particle size. For DLS to work, the samples need to be filtered of centrifuged to get rid of large particles. Different types of filters were tested to see which filter material was the best to use. When filtering the water we only want to filter out the large particles. Natural organic matter has a hydrophobic component which adsorbs to some filter types but not to others. It is crucial to know which filters this hydrophobic component adsorbs to, so that the loss of dissolved organic carbon during filtration can be minimalized.
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Attenuation models for material characterizationMaess, Johannes Thomas 18 November 2004 (has links)
Ultrasonic attenuation is a useful tool in characterizing the
damage state of different materials. The attenuation coefficients
for the incident longitudinal and transverse waves are both
derived from the scattering cross section of the material.
Scattering cross section is defined as the ratio of the scattered
energy to the incident energy. The incident wave field can be
scattered at inclusions, voids and material defects; there is also
grain boundary scattering in polycrystalline materials. For
accurate material characterization, it is important to distinguish
between the different types of scattering and to relate the
attenuation to its appropriate source. This study first solves the
single scatterer problem using either the Born approximation (for
difficult scatterer shapes and for anisotropic scatterers), or the
exact solution (in cases where it is necessary to provide an
accurate description of the viscoelastic behavior of the
surrounding effective medium). Multiple scattering effects are
investigated by a differential self-consistent scheme and a
self-consistent scheme. Both multiple scattering approaches are
applicable for each single scatterer solution. The differential
self-consistent scheme describes the scattering cross section
dependent on the volume fraction of the scatterers, and is
restricted to low volume fractions and materials, where the
surrounding material is clearly distinguished from the inclusions.
The self-consistent scheme is applicable to high volume fractions
of inclusions as well as to polycrystalline materials, where the
distinction between surrounding material and inclusions is not
possible.
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Applications of nonlinear dynamics in atomic and molecular systemsChoi, Ji Il 05 July 2007 (has links)
In this thesis we investigate what modern nonlinear-dynamical methods can tell us about some longstanding problems in atomic physics. It is well-known that it is very difficult to prevent electronic wavepackets from spreading, and that is where we bring in coherent states. We evaluate two strategies for forming coherent states in atomic physics problems with large Coriolis interactions : One involves the use of the "Cranked Oscillator" model to construct nondispersive wavepackets. We show that it is possible to keep the wavepackets from spreading while manipulating them with dipole fields with arbitrary time profiles. The second strategy involves using additional external fields to create a stable outer minimum far from the core. Whenever this minimum approximates a harmonic well it has its own subset of near-harmonic eigenstates and nearly-coherent states can be constructed. As examples of this strategy we study two-particle ion pair systems in a applied homogeneous magnetic field, and a weakly bound heavy-ion pair (Hydrogen positive and negative ions), where the nonspreading wavepacket corresponds to the motion of the drifting electron-ion or heavy ion pair in relative coordinates. We look for a Horseshoe Construction in the dynamics of the ionization of a highly excited two-electron atom by an classical-mechanical investigation.
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Giant resonance study by 6li scatteringChen, Xinfeng 15 May 2009 (has links)
Nuclear incompressibility Knm is an important parameter in the nuclear matter equation
of state (EOS). The locations of the isocalar giant monopole resonance (ISGMR) and
giant dipole resonance (ISGDR) of nuclei are directly related to Knm and thus can give
the most effective constraint on the value of the Knm. In order to determine Knm
accurately, a systematic study of the ISGMR and ISGDR over a wide range of nuclei is
necessary. Alpha inelastic scattering at small angles has been successfully used to study
the ISGMR of heavy and medium nuclei where the monopole resonance is concentrated
in a broad peak. For light nuclei (A<40), however, ISGMR strengths are more elusive
because the resonance is fragmented and extends to excitation energies above 35 MeV.
Other processes give a large physical background at high excitation energy in α inelastic
scattering, which makes it difficult to extract strength distributions in this range. As an
isoscalar projectile (N=Z), 6Li scattering could be an alternate way to study giant
resonances. A better ratio between the resonance peak and the continuum is expected in
6Li scattering due to the low particle emitting threshold. Another important motivation
for 6Li scattering study is to explore the possibility of expanding current research from
stable nuclei to radioactive nuclei with inverse reactions using 6Li as a target.
Data for elastic scattering of 240 MeV 6Li ions and inelastic scattering to low-lying states
and giant resonances was taken for 24Mg, 28Si and 116Sn. A data analysis procedure was
developed for double folding calculations. The optical potential parameters for 6Li + 24Mg, 6Li + 28Si and 6Li + 116Sn scattering systems were obtained by fitting elastic
scattering data. Multipole analyses were carried out for inelastic scattering to high lying
isoscalar giant resonances with multipolarities L=0 - 3. The results for the ISGMR and
ISGQR are in agreement with those obtained with 240 MeV α scattering, however the
agreement for the ISGDR and HEOR is not so good, indicating the uncertainty in
extracting these strengths. This work has shown that 240 MeV 6Li scattering is a viable
way to study the ISGMR and ISGQR and can be particularly useful in rare isotope
studies where 6Li can be used as the target.
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