Konstanz, Univ., Diplomarb., 1999.

Universiẗat, Diss., 2003--München.

Master-Arbeit Univ. St. Gallen, 2007.

Techn. Universiẗat, Diss., 2001--Dresden.

Universiẗat, Diss., 2004--Heidelberg.

Universiẗat, Diss., 2004--Köln.

Universiẗat, Diss., 2005--Köln.

A study has been made of the elasticity associated with the martensite transformation in the polycrystalline β-phase alloy of composition Cu-33.6 wt. % Zn-4 wt. % Sn tested at room temperature. The mechanical properties of the material undergoing the stress induced martensite transformation have been examined. These properties are influenced by the elastic anisotropy of the bcc β-phase, the development, preferential distribution and morphology and the mechanical properties of the transformation product. The elastic shape change associated with the elastically accommodated, stress-induced martensitic transformation was always found to be accompanied by some plastic deformation. A relationship between the β-grain size, the sample thickness and the deformation response was observed. Specimens with grains extending through the sample thickness exhibited large reversible strains (∼2.5%), whereas specimens with a much smaller grain size/thickness ratio (<1) exhibited only limited transformation elasticity. The morphology of the thermal martensite and the Ms temperature was also found to be influenced by the ratio grain size/thickness (g.s./t). A lower Ms temperature was associated with a decreasing g.s./t ratio; only self-accommodating burst martensite was observed in very fine grained material. The Af temperature increased with a decreasing g.s./t ratio. Repeated loading (cycling) reduced the hysteresis of the stress strain curve for all g.s./t ratios tested, but was always accompanied by plastic deformation of the matrix and the development of non-reversible deformation martensite. The experimentally determined habit plane for the thermal and the stress induced martensite were in moderate agreement with the planes predicted by the phenomenological martensite theory (W.L.R.) assuming a {110} <1Ī0> microscopic shear. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Cette thèse traite de deux problèmes dans le cadre du programme de Langlands. Pour le premier problème, dans la situation de $\GL_2 $ et un cocaractère non minuscule, nous fournissons un contre-exemple (sous certaines hypothèses naturelles) à la conjecture de Rapoport-Zink, communiquée par Laurent Fargues. Le deuxième problème concerne un résultat dans le programme de Langlands $p$-adique. Soit $A$ une algèbre $\qp$-affinoïde, au sens de Tate. Nous développons une théorie d'un espace localement convexe en $A$-modules parallèle au traitement dans le cas d'un corps par Schneider et Teitelbaum. Nous montrons qu'il existe une application d'intégration liant une catégorie de représentations localement analytiques en $A$ -modules et des modules de distribution séparés relatif. Il existe une théorie de cohomologie localement analytique pour ces objets et une version du Lemme de Shapiro. Dans le cas d'un corps, ceci a été substantiellement développé par Kohlhaase. Comme une application, nous proposons une correspondance de Langlands $p$-adique en families: Pour un $(\varphi, \Gamma)$-module trianguline et régulière de dimension 2 sur l'anneau de Robba relatif $\Robba_A$ nous construisons une $\GL_2(\qp)$-représentation localement analytique en $A$-modules. Il s'agit d'un travail en commun avec Joaquin Rodrigues. / This thesis deals with two problems within the Langlands program. For the first problem, in the situation of $\GL_2$ and a non-minuscule cocharacter, we provide a counter-example (under some natural assumptions) to the Rapoport-Zink conjecture, communicated to us by Laurent Fargues.The second problem deals with a result in the $p$-adic Langlands program. Let $A$ be a $\qp$-affinoid algebra, in the sense of Tate. We develop a theory of locally convex $A$-modules parallel to the treatment in the case of a field by Schneider and Teitelbaum. We prove that there is an integration map linking a category of locally analytic representations in $A$-modules and separately continuous relative distribution modules. There is a suitable theory of locally analytic cohomology for these objects and a version of Shapiro's Lemma. In the case of a field this has been substantially developed by Kohlhaase. As an application we propose a $p$-adic Langlands correspondence in families: For a regular trianguline $(\varphi,\Gamma)$-module of dimension 2 over the relative Robba ring $\Robba_A$ we construct a locally analytic $\GL_2(\qp)$-representation in $A$-modules. This is joint work with Joaquin Rodrigues.

Thesis ((MSc. (Physics)) -- University of Limpopo, 2018 / The mechano-chemical technique was employed to synthesise the undoped, cobalt and indium single and double doped ZnO nanoparticles powder samples. The x-ray diffraction (XRD), scanning electron microscopy (SEM), raman spectroscopy (RS), ultraviolet-visible spectroscopy (UV-vis), and photoluminescence (PL) spectroscopy were employed to characterise the prepared samples. The XRD and energy dispersive spectroscopy (EDS) results confirmed that the prepared samples were of hexagonal wurzite form. In addition, it was found that the diffraction pattern for In-ZnO nanoparticles display an additional peak which was associated with In3+ dopant. The peak suggest that In3+ ions prefer the interstitial site in the hexagonal ZnO structure. Doping the ZnO nanoparticles with Co and In did not significantly affect the lattice parameters but the average grain sizes of the nanoparticles were found to be reduced. The morphology of the samples revealed by the SEM images appear to be more spherical. The Raman modes obtained from the excitations wavelength of 514.532 nm further indicated that the prepared samples were of hexagonal ZnO structures. The energy band gap of the prepared samples were calculated from the UV-vis data which showed that the doped ZnO nanoparticles had smaller energy band gap compared to the undoped ZnO nanoparticles. The excitation wavelength of 350 nm were used in the PL study where various defects related emissions were observed for the doped and undoped ZnO nanoparticles. The kenosistec station equipment was used to investigate the prepared samples for gas sensing application. Ammonia (NH3), methane (CH4) and hydrogen sulphide (H2S) gases were probed. In all the response curves observed, the undoped and double doped ZnO nanoparticles are being favoured at a temperature range 200 – 350oC. In addition, the double doped ZnO nanoparticles was found to be more sensitive to CH4 at low temperatures and low v concentrations. / National Research Foundation (NRF) and Council for Scientific and Industrial Research (CSIR)