Size effects play a significant role in metal processing when the specimen dimensions are reduced. In this study, influence of size effects were investigated on two problem specific processes. First, numerical simulations of a small-scale forward extrusion with varying grain size were performed for both 2D and 3D cases. Here, grains were assigned to non-homogeneous properties in a random fashion. The computational geometry was obtained from Voronoi tessellation in MATLAB, and python-scripting in ABAQUS. Then the effects of size and property non-homogeneity were investigated. Second, a numerical model was simulated to predict final form shapes, punch load requirement, and thickness distribution of hemispherical bowl-shaped forming. The die, punch and cover plate were fabricated using stereolithographic apparatus (SLA). Numerically obtained punch load requirement, thickness distribution, von-Mises contours, and equivalent plastic strain contours were compared for different thickness specimens. Finally, the models were validated by experimental results.

In the city selected for this study, only 29% of inner-city students scored proficiently on standardized tests, whereas 71% of their peers at nearby suburban and affluent schools achieved the proficiency level. To address the gap, the local district implemented ability grouping in one charter school. The purpose of this ex post facto quasi-experimental study was to examine the effect of ability grouping among inner-city students in mathematics as an instructional intervention for improving student achievement. Ability grouping theory as an instructional strategy was used as the theoretical framework for this study. The criterion measure of mathematics improvement was provided by the test results from the Northwest Evaluation Association's Measure of Academic Progress (NWEA-MAP), a computer-adaptive assessment of mathematics. Using population data for 2012-2014 inner-city 8th graders who took the pretest and posttest NWEA-MAP (N = 234), two 1-way analyses of variances were used to test for mean differences in the NWEA-MAP improvement scores between ability-grouped (n = 115) and non-ability-grouped (n = 115) students, then specifically between students who were grouped as high ability (n = 55) and low ability (n = 55). The ability-grouped students had significantly higher improvement scores than did the nongrouped students. For those students who were ability grouped, no statistically significant difference existed in improvement between the high and low ability groups. A position paper was developed recommending student grouping to improve academic performance of inner-city school students. Positive social change will occur as the achievement gap is closed for students who attend inner-city schools.

La chimie du fluor suscite un intérêt croissant de la part des chimistes organiciens de par son exploitation industrielle dans les domaines pharmaceutique et agrochimique. Ainsi, depuis plusieurs années, de nouvelles méthodes permettant d'introduire de manière efficace et sélective des groupements fluorés - et plus particulièrement des fluoroalkyles - sur des molécules cibles sont activement recherchées. Les hydrazones sont des molécules largement utilisées en synthèse organique, notamment comme précurseurs de nombreux composés très recherchés par les industries pharmaceutiques ou agrochimiques, incluant les amines primaires et les hétérocycles azotés tels que les pyrazoles et les indoles. Dans le cadre de cette thèse, nous nous sommes intéressés à la fluoroalkylation des hydrazones. Les premières études ont visé la trifluorométhylation cupro-catalysée d'hydrazones d'aldéhydes et de cétones, lesquelles ont conduit respectivement à la formation d'hydrazones trifluorométhylées et de diimides alpha-trifluorométhylés. Par la suite, cette transformation a été entendue à la béta-trifluorométhylation régiosélective d'hydrazones alpha,béta-insaturées. Enfin, nous nous sommes intéressés au développement de réactions de difluoroalkylation d'hydrazones d'aldéhydes catalysées par le palladium ou le cuivre. Les divers composés obtenus lors de ces études se sont avérés être d'excellents précurseurs de cétones et d'indoles trifluorométhylés, d'alpha,alpha-difluoro-béta-cétoesters, ou encore d'alpha,alpha-difluorocétones / Fluorine chemistry is attracting the growing interest of organic chemists due to its industrial exploitation in the pharmaceutical and agrochemical fields. Thus, new methods for the effective and selective introduction of fluorinated groups – and particularly fluoroalkyls - on target molecules have been sought in recent years. Hydrazones are widely used reagents in organic synthesis, notably as precursors of many compounds pursued by the pharmaceutical or agrochemical industries, including primary amines and nitrogen heterocycles such as pyrazoles and indoles. This thesis work focused on the fluoroalkylation of hydrazones. The first studies have been directed toward the copper-catalyzed trifluoromethylation of aldehyde- and ketone-derived hydrazones, which led to the formation of trifluoromethylated hydrazones and alpha-trifluoromethylated azenes, respectively. Subsequently, this transformation was extended to the regioselective beta-trifluoromethylation of alpha,beta-unsaturated hydrazones. Finally, our interest focused on the development of difluoroalkylation reactions of aldehyde-derived hydrazones under palladium or copper catalysis. The various compounds obtained in these investigations have proven to be valuable precursors of trifluoromethylated ketones and indoles, alpha, alpha-difluoro-beta-ketoesters, as well as alpha,alpha-difluoroketones

[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] This thesis concerns the study of homogeneous factorisations of complete graphs with edge-transitive factors. A factorisation of a complete graph Kn is a partition of its edges into disjoint classes. Each class of edges in a factorisation of Kn corresponds to a spanning subgraph called a factor. If all the factors are isomorphic to one another, then a factorisation of Kn is called an isomorphic factorisation. A homogeneous factorisation of a complete graph is an isomorphic factorisation where there exists a group G which permutes the factors transitively, and a normal subgroup M of G such that each factor is M-vertex-transitive. If M also acts edge-transitively on each factor, then a homogeneous factorisation of Kn is called an edge-transitive homogeneous factorisation. The aim of this thesis is to study edge-transitive homogeneous factorisations of Kn. We achieve a nearly complete explicit classification except for the case where G is an affine 2-homogeneous group of the form ZR p x G0, where G0 is less than or equal to ΓL(1,p to the power of R). In this case, we obtain necessary and sufficient arithmetic conditions on certain parameters for such factorisations to exist, and give a generic construction that specifies the homogeneous factorisation completely, given that the conditions on the parameters hold. Moreover, we give two constructions of infinite families of examples where we specify the parameters explicitly. In the second infinite family, the arc-transitive factors are generalisations of certain arc-transitive, self-complementary graphs constructed by Peisert in 2001.

With the depletion of petroleum based fuels and the corresponding concerns of national energy security issues, natural gas as an alternative fuel in IC engine applications has become an attractive option. Natural gas requires minimum mixture preparation, and is chemically stable, both of which make it a suitable fuel for homogeneous charged compression ignition (HCCI) engines. Compared to petroleum based fuels, natural gas produces less green-house emissions. However, natural gas is hard to auto-ignite and therefore requires a higher compression ratio, some amount of intake heating, or some type of pre-ignition. In addition, natural gas usually has large differences in fuel composition from field to field, which adds more uncertainties for engine applications. The current study determines the auto-ignition characteristics, engine performance, and nitric oxides emissions as functions of major operating parameters for a natural gas fueled HCCI engine, and determines differences relative to gasoline fueled HCCI engines which have been studied for many years. These tasks have been done using both zero- and multi-dimensional engine simulations. By zero-dimensional simulation, the effects of varying equivalence ratios, engine speeds, compression ratio, EGR level, intake pressure and fuel compositions are determined and analyzed in detail. To be able to account for the in-cylinder inhomogeneous effect on the HCCI combustion, multi-zone models coupled with cold-flow CFD simulations are employed in addition to the single-zone model. The effects of non-homogeneous temperature and equivalence ratio stratification on the ignition timing, combustion phasing, and emissions formation have been studied and discussed. Finally, the preliminary two-dimensional axial-symmetric CFD simulations have been conducted to study the in-cylinder temperature and the species distributions, which provide better visualization of the natural gas auto-ignition process.

This doctoral thesis is about controlling the combustion timing of the combustion concept Homogeneous Charge Compression Ignition, HCCI, by means of variable valve timings. The HCCI research usually is regarded to have started in Japan during the later part of the 1970´s. The world of HCCI has since grown and HCCI is of today researched worldwide. Of particular interest from a Swedish point of view is that Lund Institute of Technology has emerged as one of the world leading HCCI laboratories. The idea with HCCI is to combine the Otto and Diesel engine. As in an Otto engine the charge is premixed but as in a Diesel engine the operation is unthrottled and the compression heat causes the ignition. The combustion that follows the ignition takes place homogeneously and overall lean. The result is ultra low NOx and particulate emissions combined with high total efficiency. A difficulty with the HCCI-concept is that it only works in a narrow area and that there is no direct way to control the Start Of Combustion, SOC. Out of this follows that timing/phasing of the combustion is one of the main difficulties with HCCI combustion concepts. This is particularly emphasized during transient operation and calls for feedback control of the combustion timing. This work investigates one method, the variable valve timing, to achieve feedback control of the combustion phasing. From the work it can be concluded that the variable valve timing can control the combustion phasing during engine transients. In order to improve the performance a non-linear compensation from ignition delay to valve timings has been suggested, incorporated in a control structure and tested in engine test. The engine test has been performed in a single cylinder engine based on a Scania truck engine. The speed range from 500 to 1750 rpm and the load range 1.26 and 10.5 bar of netIMEP has been covered with fair transient performance. / QC 20100629

<p>Granular materials are hard to understand due to their discrete and a-thermal nature. The mechanical response of a granular packing under external deformations, although highly relevant in industrial processes, is still poorly understood, partly due to the difficulty to generate a homogeneous granular packing. In this thesis, I present a novel shear apparatus that avoids the formation of inhomogeneities known as shear bands. This apparatus provides quasi-static, quasi-uniform simple shear deformation to a 2D model granular system under fixed packing fraction &phi. The position, orientation and forces for each particle are obtained at each shear step, using the photo-elastic technique. This model granular system exhibits coupling between the shear strain, &gamma, and the pressure, P, which we characterize by the `Reynolds pressure', and a `Reynolds coefficient', R(&phi) = (&partial^2 P/ &partial &gamma^2)/2. Under cyclic shear, this system evolves logarithmically slowly towards limit cycle dynamics, which we characterize in terms of pressure relaxation at cycle n: &Delta P &simeq - &beta ln(n/n_0). &beta depends only on the shear cycle amplitude, suggesting an activated process where &beta plays a temperature-like role. In addition, particles in the sheared system are diffusive. The translational and rotational diffusion, observed under stroboscopic view during cyclic shear, are observed to depend on the packing fraction but not on the stress states of the system. Finally, the structure of the force network, and how that connects to the mechanical behavior, is also briefly discussed.</p> / Dissertation

<p>The production of biodiesel (methyl esters) from vegetable oils represents analternative means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance and relevance due to increase in petroleum prices and the environmental advantages the process offers. Commercially, biodiesel is produced from vegetable oils, as well as from waste cooking oils and animal fats. These oils are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are usually converted into the respective mono alkyl esters by base-catalyzed transesterification with short chain alcohol, usually methanol. In the first part of this study, the transesterification reactions of three different vegetable oils / sunflower (SFO), soybean (SBO) and waste cooking oil (WCO) with methanol was studied using potassium hydroxide as catalyst in a conventional batch process. The production of biodiesel from waste cooking oil was also studied via continuous operation systems (employing the use of low frequency ultrasonic technology and the jet loop reactor). The characterisation of the feedstock used and the methyl ester products were determined by different analytical techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The effects of different reaction parameters (catalyst amount, methanol to oil ratio, reaction temperature, reaction time) on methyl ester/FAME yield were studied and the optimum reaction conditions of the different process systems were determined. The optimum reaction conditions for production of methyl esters via the batch process with the fresh oil samples (SFO and SBO) were established as follows: a reaction time of 60 min at 60 &ordm / C with a methanol: oil ratio of 6:1 and 1.0 KOH % wt/wt of oil / while the optimum reaction conditions for the used oil (WCO) was observed at a reaction time of 90 min at 60 &ordm / C, methanol: oil ratio of 6:1 and 1.5% KOH wt/wt of oil. The optimum reaction conditions for the transesterification of the WCO via ultrasound technology applied in a continuous system in this study were: a reaction time of 30 min, 30 &ordm / C, 6:1 methanol/oil ratio and a 0.75 wt% (KOH) catalyst concentration. The ultrasound assisted transesterification reactions performed at optimum conditions on the different oil samples led to higher yields of methyl esters (96.8, 98.32 and 97.65 % for WCO, SFO and SBO respectively) compared to methyl esters yields (90, 95 and 96 % for WCO, SFO and SBO respectively) obtained when using conventional batch procedures. A considerable increase in yields of the methyl esters in the ultrasound assisted reaction process were obtained at room temperature, in a remarkably short time span (completed in 30 min) and with a lower amount of catalyst (0.75 wt % KOH) while the results from the continuous jet loop process system showed even better results, at an optimum reaction condition of 25 min of reaction, a methanol: oil ratio of 4:1 and a catalyst amount of 0.5 wt%. This new jet loop process allowed an added advantage of intense agitation for an efficient separation and adequate purification of the methyl esters phase at a reduced time of 30 min. The use of homogeneous catalysts in conventional processes poses many disadvantages / heterogeneous catalysts on the other hand are attractive on the basis that their use could enable the biodiesel production to be more readily performed as a continuous process resulting in low production costs. Consequently, a solid base catalyst (KNO3/FA) prepared from fly ash (obtained from Arnot coal power station, South Africa) and a new zeolite, FA/Na-X synthesized from the same fly ash were used as solid base catalysts in the transesterification reactions in the conversion of a variety of oil feedstock with methanol to methyl esters. Since fly ash is a waste product generated from the combustion of coal for power generation, its utilization in this manner would allow for its beneficiation (as a catalytic support material and raw material for zeolite synthesis) in an environmentally friendly way aimed at making the transesterification process reasonably viable. Arnot fly ash (AFA) was loaded with potassium (using potassium nitrate as precursor) via a wet impregnation method while the synthesized zeolite FA/Na-X was ion exchanged with potassium (using potassium acetate as precursor) to obtain the KNO3/FA and FA/K-X catalysts respectively. Several analytical techniques were applied for characterization purposes. The results of the XRD and XRF showed that the AFA predominantly contained some mineral phases such as quartz, mullite, calcite and lime. The high concentration of CaO in AFA was apparent to be beneficial for the use of fresh fly ash as a support material in the heterogeneous catalysed transesterification reactions. XRD characterisation of KNO3/FA results indicated that the structure of KNO3/FA gradually changed with the increase in KNO3 loading. The catalyst function was retained until the loading of KNO3 was over 10 %. IR spectra showed that the KNO3 was decomposed to K2O on the fly ash support during preparation at a calcination temperature of 500 &ordm / C. The CO2-TPD of the KNO3/FA catalysts showed that two basic catalytic sites were generated which were responsible for high catalytic abilities observed in the transesterification reactions of sunflower oil to methyl esters. On the other hand, XRD results for the as- received zeolite synthesized from AFA showed typical diffraction peaks of zeolite NaX. SEM images of the FA /NaX showed nano platelets unique morphology different from well known pyramidal octahedral shaped crystal formation of faujasite zeolites and the morphology of the FA /KX zeolite did not show any significant difference after ion exchange. The fly ash derived zeolite NaX (FA /NaX) exhibited a high surface area of 320 m2/g. The application of the KNO3/FA catalysts in the conversion reactions to produce methyl esters (biodiesel) via transesterification reactions revealed methyl ester yield of 87.5 % with 10 wt% KNO3 at optimum reaction conditions of methanol: oil ratio of 15:1, 5 h reaction time, catalyst amount of 15 g and reaction temperature 160 &deg / C, while with the use of the zeolite FA/K-X catalyst, a FAME yield of 83.53 % was obtained for 8 h using the ion exchanged Arnot fly ash zeolite NaX catalyst (FA/KX) at reaction conditions of methanol: oil ratio of 6:1, catalyst amount of 3 % wt/wt of oil and reaction temperature of 65 &ordm / C. Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to uniquely demonstrate the utilization of South African Class F AFA both as a catalyst support and as a raw material for zeolite synthesis / these catalyst materials subsequently applied sucessfully as solid base catalysts in the production of biodiesel.</p>

Despite significant advancements in the understanding of fluid flows, combustion and material technologies, hypersonic flight still presents numerous technological challenges. In hypersonic vehicles turbulence is critical in controlling heat generation in the boundary layer, mixing inside the combustor, generation of acoustic noise, and mass flow in the intake. The study of turbulence in highly compressible flows is challenging compared to incompressible due to a drastic change in the behavior of pressure and a relaxation of the incompressibility constraint. In addition fluid flow inside a flight vehicle is complicated by wall-effects, heat generation and complex boundary conditions. Homogeneous shear flow contains most of the relevant physics of boundary and mixing layers without the aforementioned complicating effects. In this work we aim to understand and characterize the role of pressure, velocity-pressure interaction, velocity-thermodynamics interaction in the late-stage transition-to-turbulence regime in a high speed shear dominated flow by studying the evolution of perturbations in in a high Mach number homogeneous shear flow. We use a modal-analysis based approach towards understanding the statistical behavior of turbulence. Individual Fourier waves constituting the initial flow field are studied in isolation and in combination to understand collective statistical behavior. We demonstrate proof of concept of novel acoustic based strategies for controlling the onset of turbulence. Towards this goal we perform direct numerical simulations (DNS) in three studies: (a) development and evaluation of gas kinetic based numerical tool for DNS of compressible turbulence, and perform detailed evaluation of the efficacy of different interpolation schemes in capturing solenoidal and dilatational quantities, (b) modal investigation in the behavior of pressure and isolation of linear, non-linear, inertial and pressure actions, and (c) modal investigation in the possible acoustic based control strategies in homogeneously sheared compressible flows. The findings help to understand the manifestation of the effects of compressibility on transition and turbulence via the velocity-pressure interactions and the action of individual waves. The present study helps towards the design of control mechanisms for compressible turbulence and the development of physically consistent pressure strain correlation models.

In this thesis, after a general introduction, we first review some differential geometry to provide the mathematical background needed to derive the key equations in cosmology. Then we consider the Robertson-Walker geometry and its relationship to cosmography, i.e., how one makes measurements in cosmology. We finally connect the Robertson-Walker geometry to Einstein's field equation to obtain so-called cosmological Friedmann-Lemaître models. These models are subsequently studied by means of potential diagrams.