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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Diffraction imaging of sediment drifts in the Canterbury Basin, New Zealand

Al-Hadab, Salah Ahmad 25 April 2013 (has links)
Analysis of scattered, or diffraction energy (the seismic response of small-scale objects) in the seismic data from Canterbury Basin, New Zealand reveals additional geological information about depositional patterns in sedimentary deposits. Diffrac- tion images from the seismic response for Canterbury Basin provide complementary interpretation tools to the conventional specular reflection images. To image diffrac- tions for a dataset from Canterbury Basin, I take the following steps: First, I attenuate multiples using a surface multiple prediction algorithm to predict multiples and apply regularized nonstationary regression to adaptively subtract the predicted multiples. Next, I separate diffractions using the plane-wave destruction method. The plane- wave destruction method removes conventional reflected energy in order to enhance the diffracted energy. I then apply a velocity continuation method on diffraction data to estimate migration velocities and then migrate the data using Kirchhoff migration in the dip-angle-gather domain. The resultant conventional and diffraction images are improved images suitable for geological interpretation of prograding sediment drifts. / text
2

Thermally Stimulated Current Study Of Traps Distribution In Tlgases Layered Single Crystals

Nasser, Hisham 01 July 2010 (has links) (PDF)
Trapping centres and their distributions in as-grown TlGaSeS layered single crystals were studied using thermally stimulated current (TSC) measurements. The investigations were performed in the temperature range of 10&ndash / 160 K with various heating rates between 0.6&ndash / 1.2 K/s. Experimental evidence has been found for the presence of three electrons trapping centres with activation energies 12, 20, and 49 meV and one hole trapping centre located at 12 meV. Their capture cross-sections and concentrations were also determined. It is concluded that in these centres retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. The optical properties of TlGaSeS layered single crystals have been investigated by measuring the transmission and the reflection in the wavelength region between 400 and 1100 nm. The optical indirect transitions with a band gap energy of 2.27 eV and direct transitions with a band gap energy of 2.58 eV were found by analyzing the absorption data at room temperature. The rate of change v of the indirect band gap with temperature was determined from the transmission measurements in the temperature range of 10&ndash / 300 K. The oscillator and the dispersion energies, the oscillator strength, and the zero-frequency refractive index were also reported. The parameters of monoclinic unit cell and the chemical composition of TlGaSes crystals were found by X-ray powder diffraction and energy dispersive spectroscopic analysis, respectively.
3

Thermally Stimulated Current Study Of Traps Distribution In Beta-tlins2 Layered Crystals

Isik, Mehmet 01 June 2008 (has links) (PDF)
Trapping centres in as-grown TlInS2 layered single crystals have been studied by using a thermally stimulated current (TSC) technique. TSC measurements have been performed in the temperature range of 10-300 K with various heating rates. Experimental evidence has been found for the presence of five trapping centres with activation energies 12, 14, 400, 570 and 650 meV. Their capture cross-sections and concentrations were also determined. It is concluded that in these centres retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of traps was revealed from the analysis of the TSC data obtained at different light excitation temperatures. The transmission and reflection spectra of TlInS2 crystals were measured over the spectral region of 400-1100 nm to determine the absorption coefficient and refractive index. The analysis of the room temperature absorption data revealed the coexistence of the indirect and direct transitions. The absorption edge was observed to shift toward the lower energy values as temperature increases from 10 to 300 K. The oscillator and the dispersion energies, and the zero-frequency refractive index were also reported. Furthermore, the chemical composition of TlInS2 crystals was determined from energy dispersive spectroscopic analysis. The parameters of monoclinic unit cell were found by studying the x-ray powder diffraction.

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