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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.

Synthesis of alkaline earth transition metal sulfides

Rees, David Alan January 2000 (has links)
No description available.

The crystallographic texture and morphology of nickel oxide layers grown on textured nickel and nickel alloy substrates

Woodcock, Thomas George January 2003 (has links)
No description available.

High resolution powder diffraction studies of molecular solids

Rodriguez, Asiloe Jasmina Mora January 1996 (has links)
No description available.

Strategies for protein crystal growth-screening and optimization

Haire, Lesley Findlay January 1996 (has links)
No description available.

Solid state studies of ternary oxides and sulphides

Atkins, Alison J. January 1996 (has links)
No description available.

A study of deformation twinning in magnesium alloy AZ31B

Majkut, MARTA 12 March 2013 (has links)
Crystals with a hexagonal close-packed crystal structure are inherently anisotropic, and have a limited number of independent slip systems, which lead to strong deformation textures and reduced formability in polycrystalline products. In magnesium (Mg), all of the easy slip systems have a Burgers vector in the <a> direction making twinning necessary for arbitrary shape changes. The most common twinning system which allows extension along the c-axis is {10-12}<10-11>. A good predictor of slip is the global Schmid factor, which resolves the externally applied force onto the slip plane and direction of a crystal. The critically resolved shear stress (CRSS) at which a grain twins is not readily measured by experiment and the CRSS for twin initiation often appears larger than for twin propagation. In polycrystals, twin variants with both low and high Schmid factors have been observed indicating that this Schmid factor is inappropriate to predict twinning and more local effects play an important, though still uncertain role. In this work, experiments were devised to dynamically study extension twinning in a polycrystalline Mg alloy AZ31B with a strong basal rolling texture by tensile deformation parallel to the plate normal. Three-dimensional X-ray diffraction using a synchrotron source was used to map the centre-of-mass positions, orientations, and grain-resolved elastic strain tensors of over 1000 grains in-situ up to a true strain of 1.4%. The majority of twins formed in grains with a high local Schmid factor; however, low-ranked twin variants were common. The average grain-resolved stress did not always select the highest twin variant and resulted in some negative Schmid factors. The internal stress state of parent grains and twinned grains did not differ significantly within the large measurement uncertainties. The misorientations between grains ideally oriented for twinning and their nearest neighbours could not explain cases of no twin activity. Results suggest that the controlling factors for twin formation are much more local and not captured within the spatial resolution of the technique. Complimentary measurement of the strain rate sensitivity during twinning, by instantaneous strain rate change tests, suggest that basal slip is a part of this local process. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-03-12 13:40:26.039

Residual stress measurement using X-ray diffraction

Anderoglu, Osman 17 February 2005 (has links)
This paper briefly describes the theory and methods of x-ray residual stress measurements. Residual stresses can be defined as the stresses which remain in a material in the absence of any external forces. There are many stress determination methods. Some of those methods are destructive and some are nondestructive. X-ray residual stress measurement is considered as a nondestructive method. X-ray diffraction together with the other diffraction techniques of residual stress measurement uses the distance between crystallographic planes as a strain gage. The deformations cause changes in the spacing of the lattice planes from their stress free value to a new value that corresponds to the magnitude of the residual stress. Because of Poisson’s ratio effect, if a tensile stress is applied, the lattice spacing will increase for planes perpendicular to the stress direction, and decrease for planes parallel to the stress direction. This new spacing will be the same in any similarly oriented planes, with respect to the applied stress. Therefore the method can only be applied to crystalline, polycrystalline and semi-crystalline materials. The diffraction angle, 2&#952;, is measured experimentally and then the lattice spacing is calculated from the diffraction angle, and the known x-ray wavelength using Bragg's Law. Once the d-spacing values are known, they can be plotted versus 2 sin &#968;, ( &#968; is the tilt angle). In this paper, stress measurement of the samples that exhibit a linear behavior as in the case of a homogenous isotropic sample in a biaxial stress state is included. The plot of d vs. 2 sin &#968; is a straight line which slope is proportional to stress. On the other hand, the second set of samples showed oscillatory d vs. 2 sin &#968; behavior. The oscillatory behavior indicates the presence of inhomogeneous stress distribution. In this case the xray elastic constants must be used instead of E and &#957; values. These constants can be obtained from the literature for a given material and reflection combination. It is also possible to obtain these values experimentally. Calculation of the residual stresses for these samples is beyond the scope of this paper and will not be discussed here.

Self-assembly of proteins at interfaces and two-dimensional protein crystallization /

Edwards, Todd Criswell. January 1999 (has links)
Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves [74]-85).

Measurement and assessment of residual stresses for probabilistic fatigue life predictions

Zhu, Wuxue January 1996 (has links)
No description available.

Structural studies of dye molecules adsorbed on silver halide crystals

Hammond, Deborah Bernice January 1995 (has links)
No description available.

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