This thesis explores opportunities in the mathematical modelling of metal rolling processes, specifically asymmetrical sheet rolling. With the application of control systems in mind, desired mathematical models must make adequate predictions with short computational times. This renders generic numerical approaches inappropriate. Previous analytical models of symmetrical sheet rolling have relied on ad hoc assumptions about the form of the solution. The work within this thesis begins by generalising symmetric asymptotic rolling models: models that make systematic assumptions about the rolling configuration. Using assumptions that apply to cold rolling, these models are generalised to include asymmetries in roll size, roll speed and roll-workpiece friction conditions. The systematic procedure of asymptotic analysis makes this approach flexible to incorporating alternative friction and material models. A further generalisation of a clad-sheet workpiece is presented to illustrate this. Whilst this model was formulated and solved successfully, deterioration of the results for any workpiece inhomogeneity demonstrates the limitations of some of the assumptions used in these two models. Attention is then turned to curvature prediction. A review of workpiece curvature studies shows that contradictions exist in the literature; and complex non-linear relationships are seen to exist between asymmetries, roll geometry and induced curvature. The collated data from the studies reviewed were insufficient to determine these relationships empirically; and neither analytical models, including those developed thus far, nor linear regressions are able to predict these data. Another asymmetric rolling model is developed with alternative asymptotic assumptions, which shows non-linear behaviour over ranges of asymmetries and geometric parameters. While quantitative curvature predictions are not achieved, metrics of mechanisms hypothesised to drive curvature indicate these non-linear curvature trends may be captured with further refinement. Finally, coupling a curved beam model with a curvature predicting rolling model is proposed to model the ring rolling process. Both of these parts are implemented but convergence between them is not yet achieved. By analogy this could be extended with shell theory and a three-dimensional rolling model to model the wheeling process.

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Philosophiae Doctor - PhD / In this thesis, we present a multi-wavelength analysis of star-forming galaxies to shed new light on the evolution of the far-IR-radio relations in intermediate redshift (0.3 < z < 0.6) galaxy clusters and galaxy groups. The far-infrared (far-IR) emission from galaxies is dominated by thermal dust emission. The radio emission at 1.4 GHz is predominantly produced by non-thermal synchrotron radiation. The underlying mechanisms, which drive the far-IR-radio correlation, are believed to arise from massive star formation. A number of studies have investigated the relationship as a function of redshift in the field and have found no evolution out to at least z _ 2, however few works have been done in galaxy clusters. In nearby clusters, the median logarithmic ratio of the far-IR to radio luminosity is qFIR = 2.07_0.74, which is lower than the value found in the field, and there is an indication of an enhancement of radio emission relative to the far-IR emission. Understanding the properties of the far-IR-radio correlation in a sample of distant and massive cluster and groups plays an important role in understanding the physical processes in these systems. We have derived total infrared luminosities for a sample of cluster, group, and field galaxies through an empirical relation based on Spitzer MIPS 24 _m photometry. The radio flux densities were measured from deep Very Large Array 1.4 GHz radio continuum observations. We have studied the properties of the far-IR-radio correlation of galaxies at intermediate redshift clusters by comparing the relationship of these galaxies to that of low redshift clusters. We have also examined the properties of the galaxies showing radio excess to determine the extent that galaxy type or environment may explain the radio excess in galaxy clusters. We find that the ratio of far-IR to radio luminosity for galaxies in an intermediate redshift cluster to be qFIR = 1.72_0.63. This value is comparable to that measured in low redshift clusters. A higher fraction of galaxies in clusters show an excess in their radio fluxes when compared to low redshift clusters, and corroborates previous evidence of a cluster enhancement of radio excess sources at this earlier epoch as well. We have also investigated the properties of the far-IR-radio correlation for a sample of galaxy groups in the COSMOS field. We find a lower percentage of radio-excess sources in groups as compared to clusters. This provides preliminary evidence that the number of radioexcess sources may depend on galaxy environment. We also find that a larger fraction of radio-excess sources in clusters are red sequence galaxies.

Galaxies in the redshift range 1 < z < 3 existed during the most vigorous period of star formation in the history of the Universe. In the past 15 years, large rest-frame UV spectroscopic samples of z ~ 3 star-forming galaxies have been assembled. However, this particular redshift range, the so-called Redshift Desert, has only begun to be characterized. Most studies involve low resolution, low signal-to-noise spectra because the small angular size (δ ≤ 1") and faintness (RAB = 24 - 25.5) of high redshift galaxies limit what can be accomplished with a reasonable investment of observing time, even using the world's largest optical telescopes. One way to circumvent these two issues is to study gravitationally lensed galaxies. The magnification boost (up to a factor of 30x) and morphological distortion of a high redshift galaxy by an intervening mass concentration allow for the study of the high redshift Universe in unprecedented detail. I present a detailed analysis of the rest-UV spectrum of two gravitationally lensed galaxies: the 'Cosmic Horseshoe' (zsys = 2.38115) and the 'Cosmic Eye' (zsys = 3.07331). The characterization of the stellar populations and the interstellar gas geometry, kinematics, and composition which I achieve is a preview of the type of information that will be available for unlensed high redshift galaxies with the next generation of optical telescopes. I probe the lower redshift end of the Redshift Desert with a study of Fe ii and Mg ii features in the rest-frame near-UV spectrum of 96 star-forming galaxies in the redshift range 1 < z < 2. Stacked spectra are used to explore average outflow and line profile trends with stellar mass and reddening. I also investigate the phenomenon of emission filling of absorption lines which has implications for the line strength and velocity offset of interstellar absorption lines. Individual galaxies are used to assess the range of outflow velocities as well as the prevalence of emission filling in galaxies from this epoch. This is the first large scale study of fine-structure emission from Feii in high redshift galaxies, both in stacked and individual galaxy spectra. An alternative to investigating galaxies by collecting their light is to study them as seen in absorption against a cosmic backlight, such as a quasar. The Sloan Digital Sky Survey, an imaging and spectroscopic survey which covers about one-quarter of the night sky, has collected many thousands of quasar spectra. I search ~ 44,600 of these spectra, up through Data Release 4, for Mg ii λλ2796,2803 absorption doublets. The final catalog includes ~ 16700 Mgii absorption line systems in the redshift range 0.36 ≤ z ≤ 2.28. Measurements of the absorption redshift and rest equivalent widths of the Mg ii doublet as well as select metal lines are available in the catalog. This is the largest publicly available catalog of its kind and its combination of large size and well understood statistics make it ideal for precision studies of the low-ionization and neutral gas regions of galaxies. I conclude this thesis by suggesting several avenues for extending the studies of high redshift star-forming galaxies presented herein.

No description available.

Pseudomonas aeruginosa, a ubiquitous environmental bacterium and an opportunistic human pathogen, is one of the most and best studied biofilm-forming organisms and has emerged as a model organism in the study of surface- and biofilm-induced gene expression. P. aeruginosa forms biofilms through a series of interactions between the cells and adherence to surfaces, which is mediated by surface appendages such as flagella and type IV pili. A gene cluster, designated htpABCDEFGI, which appears to encode protein products with homology to those encoded by recently described novel pilus biogenesis and assembly systems, has been identified in P. aeruginosa PAO1. Since the pili produced by these systems, designated Flp, are associated with the ability of the bacteria to bind non-specifically to inert surfaces, the aims of this study were to characterize the transcriptional organization of the putative P. aeruginosa PAO1 htp gene cluster and to determine the functional importance of the htp gene cluster in the ability of P. Aeruginosa PAO1 to adhere to surfaces. In silico evidence has suggested that the pilin subunit gene flp is not part of the P. Aeruginosa htp gene cluster thought to encode proteins involved in the synthesis, assembly and export of these pili. To determine the transcriptional organization of this gene cluster, total RNA from P. aeruginosa PAO1 was analyzed by reverse transcriptase-polymerase chain reaction (RTPCR). Primers designed to amplify regions spanning gene junctions yielded amplicons at each individual gene junction from htpA to htpI, as well as an amplicon for flp. Moreover, corresponding sigma 70 (σ70) consensus sequences were identified in the intergenic region between the htpA and flp genes and promoter function of the flp and htpA upstream region was subsequently confirmed using lacZ reporter gene constructs transformed into P.aeruginosa PAO1. The results therefore indicated that the htp gene cluster is an operon transcribed as a polycistronic message, whilst the flp gene is transcribed independently as a monocistronic message. To determine the functional importance of thehtp gene cluster in P. aeruginosa PAO1, the htpD gene, encoding a putative NTPase, was inactivated by in vivo homologous recombination with an appropriately constructed allelic exchange vector to generate the isogenic mutant strain PAOHtpD. Comparative analysis of the wild-type P. aeruginosa PAO1 and mutant PAOHtpD strain revealed that the mutant strain was impaired in its ability to attach to a glass wool substratum and also in its ability to grow as a biofilm. Since the mutant PAOHtpD strain was not growth-impaired, these results indicate that the htp gene cluster plays a role in P. aeruginosa PAO1 biofilm development under the culturing conditions used in this study. Thus, it can be proposed that the flp and htp gene cluster of P. aeruginosa PAO1 may play a role in its ability to successfully colonize abiotic surfaces. / Dissertation (MSc)--University of Pretoria, 2010. / Microbiology and Plant Pathology / unrestricted

Tato diplomová práce se zabývá otázkami výroby závitů tvářecími a řezacímí závitníky. Její první část popisuje druhy závitníků, které se používají ve strojírenství. Pak se práce zaměřuje na otázky základních principů řezání závitů a tváření materiálu při obrábění. Dále se zaměřuje na porovnání řezných momentů a dalších veličin při aplikaci tvářecích závitníků v procesu obrábění. Výsledkem experimentu bylo zjíštění průběhů řezných momentů v závislosti na čase, který byly statisticky zpracovány a vyhodnoceny.

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This qualitative study explores how women in emerging adulthood make meaning of text messaging while developing an intimate heterosexual relationship. A focus group consisting of eight women was used in order to understand the way women interpret text messages during the formation of a romantic relationship. Data were analyzed using thematic analysis. Four themes emerged from the data: (1) what is the landscape?, (2) how do I figure it out?, (3) red flags, and (4) a red flag means. Participants described the context in which they enter relationships, and the role texting plays. Different strategies they used to make meaning of ambiguous text messages were discussed. Participants reported behaviors that were identified as red flags and how participants made meaning of those red flags Limitations, clinical implications, and future directions are identified and discussed. / Master of Science

A new methodology is proposed to obtain the forming limit diagram (or FLD) of sheet materials by utilizing routinely obtained experimental load versus displacement traces and incorporating finite element (FE) analysis of strain history to extract the characteristic points of diffuse and localized necking and further the limit strains. The experimental data from hemispherical punch stretching test such as limit dome height, maximum load and location of inflection point are utilized to adjust the load curves in the FE simulations. An optimization procedure to obtain various parameters in material definition has been established to obtain a good agreement between the FE-based and experimental punch load versus displacement curves. An analysis of FE model based strain history is then carried out to determine the limit strains. This approach avoids using experimental strain measurement in the vicinity of the neck on the dome specimens. The materials tested with the new methodology include automotive sheets AA6111-T4, AA6181-T4 and DP600. The one utilized for optimization of FE inputs was AA6111-T4. The proposed method for FLD determination considers out-of-plane displacement, punch-sheet contact and friction, and avoids the use of a rather arbitrary inhomogeneity factor to trigger localization such as in the Marciniak-Kuczynski method. A new criterion to determine the localized necking is proposed by seeking an inflection point m the major strain rate curve, or, maximum point in the second order of derivative of major strain, (ε1)max. The proposed localized necking criterion is compared with other two methods to determine the onset of localized necking. These are (i) Bragard criterion for post-test of deformation, and (ii) critical major strain (ε1)cr based on comparison of strain of material inside the localized site and its vicinity in the un-necked site. The new criterion of (ε1)max exhibits a more definite physical meaning towards developing an understanding of flow localization, formability and fracture. This new approach for obtaining FLDs is rapid and accurate and could be implemented easily for routine FLO generation in a lab setting with little user input and subjectivity. / Thesis / Doctor of Philosophy (PhD)