The demand for using shell theories comes from its efficiency in computational and analytical cost. On another side, new materials that are orthotropic and/or anisotropic in nature are discovered and broadly used in many fields. Many advanced shell theories are developed for these new materials, particularly in the recent decades. A study about the accuracy of these shell theories is very meaningful to build confidence in them for further applications. This study requires a precise benchmark against which shell theories can be tested. This is the main research subjective in this dissertation: to build a set of solutions using the three dimensional (3D) theory of elasticity against which shell theories can be tested for accuracy. The contents of this dissertation to support this research include a comprehensive literature review for the shell theories and recent usage and to find the gaps which need to be filled. These gaps include, among others, the lack of studies on the accuracy of the theories used and the absence of results using the 3D theory, particularly for orthotropic materials. Some of these studies are conducted here. The deficiency of some commercial finite element packages is discussed here. The reasons for the absence of accurate results are investigated. The 3D theory and analyses of isotropic and orthotropic materials of hollow cylinders is investigated here for reliable results.

This thesis addresses a long-standing puzzle in empirical econometrics: Does the size distribution of income matter in the aggregate consumption function? Current opinion on whether distribution matters is divided. There is also a lack of consensus (among those who believe distribution effects exist) on the nature of such effects; that is, whether a decrease or an increase in income inequality is needed to stimulate aggregate demand. In this thesis, the previous or existing tests are challenged on the grounds that they do not properly take into account the causal link between the variability of the marginal, not the average, propensity to consume (with respect to the income level) and the existence of distribution effects. This particular link is taken care of, however, if one tests for the linearity (in income) of the micro relation underlying one's aggregate consumption function. The rejection of the linearity hypothesis will establish the existence of distribution effects. Ex post, if the nonlinear relation is such that the marginal propensity to consume declines with income, it also follows that an equalization in the income distribution produces greater aggregate consumption. The theoretical contribution of this thesis lies in the clarification of these issues. On the empirical side, this thesis cautions against the casual use of the term "distribution effects". In the current income-current expenditure framework of the Keynesians, it refers to "the effect of a redistribution of real disposable income" on aggregate real consumers' expenditure. In the Permanent Income Hypothesis framework, however, it could mean either "the effect of a redistribution of real disposable income" or "the effect of a redistribution of real permanent income" on aggregate real consumption. In this thesis, the distributions of real disposable income and real permanent income are alternatively assumed to follow the lognormal density, and two conclusions are empirically determined: I. The distribution of real disposable income matters in the current income-current expenditure framework---this result is statistically significant at a 10% level after the correction for serial correlation and simultaneity bias. In particular, the estimates indicate that the marginal propensity to consume declines with the level of real disposable income and, hence, a decrease in inequality would stimulate aggregate demand. II. The elasticity of consumption out of real permanent income is unity; therefore, the distribution of real permanent income does not matter in the Permanent Income Hypothesis framework---this result is statistically. significant at all conventional levels of significance both before and after the correction for serial correlation. Both findings are based on aggregative time-series data for Canada. The consumer unit in this thesis is an individual income-recipient, and the data period is 1947-1976. Maximum-likelihood procedures have been used in the estimation, with proper allowance for across-parameter constraints. In the event of correction for serial correlation, the autocorrelation coefficient is constrained to the open-interval (+1,-1). The results are also double-checked by examining many avenues that might affect the nature of the outcomes. Another contribution of this study is the compilation of data on the distribution of pre-tax personal income (in current dollars) in Canada under the lognormality hypothesis. The parameters of this distribution are determined using the minimum chi-square method. Estimates of the variance (of logarithms of income) parameter show a slight increase in income inequality over the period 1946 to 1976. The data on this parameter are used to approximate the variance of logarithms for the distribution of real disposable income (while establishing result I) and also the same for the distribution of real permanent income (while establishing the result II). / Thesis / Doctor of Philosophy (PhD)

Water-responsive biological materials make up a large fraction of the earth’s biomass. Organisms can exchange water with their environment to actuate organ movement, and this process has inspired engineers to mimic this for technological use. Hygroscopic biological materials are chemically and phylogenetically diverse, implying that there may be fundamental physical principles which can explain their mechanics. In this thesis I will detail the development of a theory, the hygroelastic model, that explains a number of surprising mechanical behaviors exhibited by the hygroscopic bacterial spore of Bacillus subtilis. The hygroelastic model relies on the idea that the nanoconfinement of water molecules near interfaces influences the mechanics of nanoporous biological materials. The effects associated with this restructuring are collectively referred to as Hydration Forces. I will explain how these forces give rise to the equilibrium, nonequilibrium, and hygroscopic mechanical behaviors of the bacillus subtilis spore. Further, I will explain how hydration forces predict a previously unrecognized mechanical transition in the spore that emerges under rapid compression. The predicted mechanical behaviors of the model were validated experimentally through the use of the Atomic Force Microscope (AFM). By modifying the traditional Hertz formula to account for a strain-dependent elastic modulus, we show that the hygroelastic model well explains the anomalous force-indentation curves collected on bacterial spores. We also confirm the existence of the mechanical transition which appears under rapid indentation. Using multiple AFM operational modes, we collected force-indentation curves across a wide range of contact times ranging from near a second to 10’s of microseconds. These experiments showed a rapid increase in elastic modulus occurring near the predicted timescale of the hygroelastic transition. Though these unique mechanical properties are uncommon in materials, the underlying assumptions of the hygroelastic theory are general. Because nanoporous hygroscopic matter is commonly found in nature, it is possible that hygroelastic model could be applied to a number of other biological structures as well. Notably, the hygroelastic model predicts that bacterial spores owe their elastic response to hydration forces, which emerge from a disruption of water structure near the porous interface. These ‘hydration solids,’ may represent a paradigm in materials. Their mechanical properties may find use in engineered materials, with tailored elasticity, dissipation, nonlinear response, and frequency response.

Energy awareness of database systems has emerged as a critical research topic, since energy consumption is becoming a major limiter for their scalability. Recent energy-related hardware developments trend towards offering more and more configuration opportunities for the software to control its own energy consumption. Existing research so far mainly focused on leveraging this configuration spectrum to find the most energy-efficient configuration for specific operators or entire queries. In this demo, we introduce the concept of energy elasticity and propose the energy-control loop as an implementation of this concept. Energy elasticity refers to the ability of software to behave energy-proportional and energy-efficient at the same time while maintaining a certain quality of service. Thus, our system does not draw the least energy possible but the least energy necessary to still perform reasonably. We demonstrate our overall approach using a rich interactive GUI to give attendees the opportunity to learn more about our concept.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Elemental titanium (Ti), niobium (Nb), zirconium (Zr), and iron (Fe) powders were used to fabricate four near-β alloys with non-toxic of composition Ti-34Nb-25Zr, Ti-34Nb-25Zr-0.4Fe, Ti-34Nb-25Zr-1.2Fe, and Ti-34Nb-25Zr-2Fe (wt. %) (TNZ and TNZF) using spark plasma sintering (SPS) of nano-crystalline powders attained by high energy ball milling. The fabricated alloys were compared to Ti-34Nb-25Zr (used as a benchmark alloy in this study) and comparison was made with the commercially used Ti base alloys produced either by conventional methods or powder metallurgy. The powder mixtures were milled for 5 hours using a Simoloyer high energy ball mill with a ball to powder ratio of 10:1 and a rotational speed of 1000 rpm. This was followed by sintering the mechanically alloyed powders at 1100 ºC for 10 minutes with a pressure of 50 MPa and a heating rate of 100 ºC/min using an H-HP D25 spark plasma sintering furnace (FCT System, Germany). The powders were characterised for particle size and crystal structure using SEM and XRD. The consolidated components were characterised with regards to density, microstructure, mechanical properties. The electrochemical behaviour of the alloys was investigated using a Digi Ivy DY2300 series potentiostat. Three corrosion medium, Sodium chloride (NaCl), phosphate buffered saline solution (PBS) and Dulbecco’s modified eagle’s medium that mimic the conditions in the human body were used. Mouse myoblast cell line (C2C12) was used to investigate the biocompatibility of the sintered alloys in 1010x5 mm specimens using standard colorimetric assay MTT. Both electrochemical and biocompatibility test were conducted in triplicates and the results compared with that of the benchmark. Results of mechanical alloying of powder mixtures demonstrated an inhomogeneous structure. Milling for 5 hours resulted in agglomeration of small Fe and Zr particles. Milling for 3 hours resulted in a better distribution of elements compared to longer milling times. Therefore, sintering powders milled for 3 hours would have yielded better results. The densification results were acceptable and ranged between 97-99% of theoretical densities. Although some porosity was observed, especially on the un-etched microstructure. An insignificant decrease in density was observed when 1.2 (wt. %) Fe was added. The sintered samples had microstructures which were not homogenous. However, the addition of Fe yielded a more homogeneous microstructure compared to the one with less Fe. Therefore, TNZF with 2 (wt. %) Fe had a more homogenous microstructure. Sintering at 1100 ºC resulted in undissolved niobium and titanium which were observed in the microstructure as dark and white areas. The hardness of the TNZF alloys were comparable and lied between 373 and 432 Hv. These hardness values are higher than other similar titanium-based alloys fabricated using conventional methods. The addition of Fe to TNZ showed an insignificant decrease in hardness. The addition of Fe was found to decrease the Young’s Modulus of TNZ from 119.1 to 80 GPa with an addition of 2 wt.% Fe. However, an unacceptable reduction (230.91 to 158.2 MPa) in strength was also noticed. Pseudo passivation was observed when the alloys were immersed in 0.9 % Sodium Chloride (NaCl) which could be attributed to the inhomogeneity in the microstructure. The possibility of pitting corrosion was also observed. The alloy containing 2 Fe (wt.%) was found to be more corrosion resistant than the other alloys. The TNZF alloys exhibited better corrosion resistance in 0. 9% NaCl compared to phosphate buffered solution (PBS) and DMEM. The corrosion behaviour in PBS and DMEM cannot clearly be explained from the graphs. The morphology of the corroded samples was almost the same for all the alloys in different corrosion media. The microstructures showed pits which could have been from the pores that acted as initiation sites for pitting. In cell culture for 1 and 7 days, the cell viability for TNZF alloys was greater than that of the control group (TNZ). A significant decrease in cell viability for TNZF was observed in cell culture for 4 days. The addition of Fe on TNZ do not cause toxic effects and show good cell adhesion, indicating in-vitro cytocompatibility. The greatest cell viability of 102±3.0 % for Ti-34Nb-25Zr-2Fe. The analysis of cell morphology indicated good cell-substrate interaction. The TNZF alloys developed in this study can be suitable candidates for orthopaedic implant application due to their low Young’s modulus, corrosion resistance and superior biocompatibility. However, the strength needs significant improvement. The advantage of this biomaterial, when compared to commercial alloys, is the absence of cytotoxicity elements such as Al and V.

My dissertation within macroeconomics puts special emphasis on uncovering the effects of market power within product and labor markets. I conduct these studies using novel empirical techniques and detailed granular data sets at the firm- and household-levels.In the first chapter, coauthored with Shruti Mishra, we consider how firms’ price-setting decisions are affected by the properties of their markup. We start by designing a general oligopoly framework that accounts for firm heterogeneity, firm granularity, and the effects of market share distribution. We use this structural model to decompose the effect of price on the quantity demanded into a direct price effect and an indirect effect coming from the impact of the market-level aggregates, such as market-level price. This decomposition allows us to take care of all the degrees of heterogeneity in a flexible manner. Under plausible assumptions, the most crucial of which we test in the data, all the information about the distribution of shares within the market will be accounted for by the variation of the market aggregates. Under these conditions, we can estimate the structural parameters that do not depend on the distribution of shares within the market. We use the model to inform our empirical strategy and apply it to the ACNielsen Retail Scanner Data. We test the assumptions put forward by the theory, estimate structural parameters and then use the decomposition formulas to calculate the elasticity of the firm’s demand and other parameters important for the markup variation. We find that elasticity depends sharply on the firm’s market share and decreases significantly as market shares increase. There is a positive dependence of demand elasticities on relative prices (superelasticity), in line with Marshall’s second law of demand. Additionally, elasticity depends on the levels of competitiveness within the market. Even if a firm’s market share stays the same, its elasticity decreases if the market becomes less competitive. Lastly, we apply our estimates to calculate the optimal pass-through of marginal costs into prices and strategic complementarity. We find that an individual firm’s pass-through is contained between zero and one, but depends sharply on the firm’s market share. We find that strategic complementarity between two firms depends on both of their shares and is not symmetric so the degree of strategic complementarity between a small and a large firm, between two small firms, between two large firms, or between large and small firms would all be different. We then assess the non-linear effects of the marginal cost shock on the price and find that pass-through depends positively on the size of the marginal cost shock. This means that the total effect of marginal cost shock on prices is non-linear and that firm prices are more responsive to marginal cost increases than to marginal cost decreases. For market leaders, the pass-through of a large negative marginal cost shock would be close to zero, while the pass-through of a large positive marginal cost shock would approach that of small firms. In the second chapter, coauthored with Rui Mano, Yannick Timmer, and Anke Weber, we study the effect of the firm granularity in the labor market on their hiring decisions. We argue that prevalence of firms controlling large vacancy shares plays an important role in the transmission of monetary policy to labor demand and wage growth and can partially explain the flattening of the wage Philips curve after the GFC. Accommodative monetary policy raises the marginal product of labor, incentivizing all firms to hire more. However, since the wage elasticity of labor demand is lower for high vacancy share firms, they can hire more workers without raising wages disproportionately. We study this effect in the Burning Glass Technology vacancy microdata and, consistently with this mechanism, show that accommodative monetary policy increases labor demand more for high vacancy share firms and that this comes without a disproportionate response in wages. In aggregate, this implies that due to the presence of firms controlling large vacancy shares, accommodative monetary policy can lead to a decline in the unemployment rate that is decoupled from an increase in wage growth. Quantitatively, a firm at the 50th percentile of vacancy share distribution increases its labor demand by ≈ 7% in response to a 10 basis point surprise monetary loosening while a firm at the 95th percentile of the vacancy share distribution increases labor demand by ≈ 9%. Moreover, the effect of monetary policy shocks on firms with high vacancy share is much more persistent, with effects economically large and statistically significant at least for eight quarters. At the same time, there is no comparable differential response of wages, so even though firms with high vacancy shares hire more, they don’t have to increase their wages by more. In this case, more hiring does not result in a comparable increase in wage inflation. This channel can partly explain the flattening of the wage Phillips curve and the “wage-less” recovery after the Global Financial Crisis.In the third and last chapter, coauthored with Shruti Mishra, we study the impact of wealth heterogeneity on labor supply decisions. In the standard model, the positive wealth effect should decrease the willingness to supply labor. In the macroeconomic setting, this means that the direction and the magnitude of the wealth effect will determine whether people search for jobs more actively after a monetary intervention. For example, if unemployed consumers are indebted, they experience a negative wealth effect after a monetary contraction, search for jobs more actively and increase their probability of finding a job, therefore, reducing the total unemployment response. The sign and magnitude of the overall effect of monetary policy on unemployment will therefore depend on whether unemployed consumers are indebted and the magnitude of their debt. To study this mechanism, we develop a theoretical framework with heterogeneous consumers and employment search efforts and then decompose the effect of the monetary policy shock on aggregate unemployment. We test the prediction of the model in both micro and aggregate data. To test the prediction of the model in the aggregate, we estimate the coefficient of the interaction term between the debt-to-income ratio and Romer and Romer monetary policy shock. For the microdata, we use a similar regression with unemployment and mortgage variables for individual consumers from the PSID panel dataset. Consistently with the proposed mechanism, we find that the intuitive negative effect on employment of the monetary contraction is virtually non-existent or even reversed for indebted consumers. The three chapters together paint a complex picture of the impact of market power on macroeconomic variables. First, product market power impacts price-setting decisions of the firms and affects the dynamic of prices and inflation, effectively leading less concentrated economies to behave as if they have more flexible prices. Second, firms that control large share of vacancies in their labor market conduct hiring differently from their smaller counterparts leading to more quantity expansion. Lastly, labor markets exhibit complex supply dynamics as well, with labor supply potentially intensifying during recessions, which might lead the bargaining power of firms to become countercyclical. All these effects hold first-order significance for macroeconomic dynamics and influence our ability to project the future or asses the effects of monetary policy.

M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Though aluminium (Al) is justifiably described as a green metal with an increasing rate of application in structures, designers still restrain themselves from its applications as a load-bearing skeleton in structure due to insufficient design guidelines. This insufficient information is more with channel sections that might experience lateral-torsional buckling (LTB) when used as a load-bearing skeleton in structures. This study investigates the effects on imperfections on LTB load-carrying stability for 6061-T6 Al alloy channel section arches and proposed design guidelines. The case study focused on freestanding circular fixed end arches subjected to a transverse point load at the shear centre. The software package Abaqus was used to study a total of 110 arch models from three separate channel sections with an additional 16 arch models for validation. Sixty-six channel arches were developed at a constant length, while the remaining 44 arches were formed at constant slender ratios using 11 discrete included angles. The FE analyses methods used for the investigation were validated with existing analytical methods and showed good agreement, despite the assumptions of the bilinear curve used for material nonlinearity, initial geometric imperfections and residual stresses that presented the imperfections of the models. The different investigated factors include slender ratios, change in cross-section area, imperfections, and angles. These factors were found to have substantial impacts on the prebuckling state, which turns to impact LTB behaviour and load-carrying capacity. From arches developed at constant span length, the arches with moderately included angles (50°≤2𝛼≤90°) were found suitable for the designs against LTB, followed by the shallow (2𝛼<50°) and deep arches (90°<2𝛼≤180°) respectively. For arches developed at constant slender ratios, the deep arches were found to be more suitable in the design against LTB, followed by the moderate and shallow arches, respectively. In addition, it was realised that the change in web-flange thickness, section depth and slender ratios, had significant effects on the LTB loads magnitudes and very insignificant effects on the general behaviour across the included angles. The same occurrence was also observed on the prebuckling analyses. All the investigated channel section arches showed the imperfections to have significant impacts on the LTB loads. Arches developed at constant span length showed the maximum elastic LTB loads to have overestimated the expected real LTB loads by approximately 48 percent. While the maximum elastic LTB loads of arches developed at 𝑆𝑟𝑥⁄= 60 and 90 showed that the real LTB loads were overestimated by about 39 and 14 percent, respectively. That said, the elastic LTB loads on average overestimated the real LTB loads by over 50 percent for the arches developed at the constant span length and by only 18 percent for arches developed at the constant slender ratios.

Although it is common to model modulus of elasticity (MOE) and modulus of rupture (MOR) of graded lumber as normal, lognormal, or Weibull distributions, recent theories and empirical practices have cast doubt on these models. Mathematical proofs have been used to shown how the MOR distributions of graded lumber can be derived from the MOR distributions of mill-run populations. The MOR distribution of a graded lumber subpopulation is "pseudo- truncated" and does not exhibit the same theoretical form as the mill-run population from which it was drawn. Therefore, it is essential to explore the properties of mill-run lumber populations and properly characterize their MOE and MOR distributions. To investigate this topic, this dissertation has three objectives: 1) to determine if the within-mill means and standard deviations of MOE and MOR in mill-run southern pine (Pinus spp.) lumber differ over time, 2) to determine the correlations among hand-held grain angle meter readings, MOE, and MOR in mill- run southern pine lumber, and 3) to model statistical distributions of MOE and MOR in mill-run red pine (Pinus resinosa) and spruce (Picea spp.) lumber. This research features four main sections: 1) an introduction summarizing the conclusions of each chapter, 2) a chapter investigating if there are statistically significant differences between the means and variances of MOE and MOR in mill-run southern pine lumber populations at the same mill over time, 3) a chapter evaluating the bivariate correlations among handheld grain angle meter readings, MOR, and three measures of MOE in mill-run southern pine lumber, and 4) a chapter modeling the distributions of MOE and MOR in mill-run red pine and spruce lumber populations and comparing those to previous work on mill-run southern pine lumber populations.

The ever-increasing demand for scalable database systems is limited by their energy consumption, which is one of the major challenges in research today. While existing approaches mainly focused on transaction-oriented disk-based database systems, we are investigating and optimizing the energy consumption and performance of data-oriented scale-up in-memory database systems that make heavy use of the main power consumers, which are processors and main memory. In this demo, we present energy-utility functions as an approach for enabling the operating system to improve the energy efficiency of scalable in-memory database systems. Our highly interactive demo setup mainly allows attendees to switch between multiple DBMS workloads and watch in detail how the system responds by adapting the hardware configuration appropriately.

During the casting of a concrete bridge deck, the temporary formwork is causing the underlying ground to deform if a shallow foundation solution is used. There are often demands on the maximum deformation of the superstructure when designing the foundation for the formwork.  To keep the deformations within the desired limits, several ground improvement methods like deep mixing columns or deep foundation methods like piling can be used. Permanent ground improvement methods are however expensive, and far from always needed. To reduce the need for unnecessary ground improvements, it is crucial to calculate the predicted deformations accurately during the design phase. The purpose of this thesis was to investigate how short-term deformations in clay under a formwork during bridge construction should be calculated more generally in future projects. Three different calculation models have here been used to calculate the ground deformations caused by the temporary formwork. A simple analytical calculation and two numerical calculations based on the Mohr Coulomb and Hardening Soil-Small constitutive models. The three calculation models were chosen based on their complexity. The analytical calculation model was the most idealised and the Hardening Soil-Small to be the most complex and most realistic model. Results show that the numerical calculation model Mohr Coulomb and the analytical calculation model gives the best results compared to the measured deformation. One of the most probable reasons for the result is that both of the models require a few input parameters that can easily be determined by well-known methods, such as triaxial-, routine- and CRS-tests. The more advanced Hardening soil small model requires many parameters to fully describe the behaviour of soil. Many of the parameters are hard to determine or seldom measured. Due to the larger uncertainties in the parameter selection compared with the other two models, the calculated deformation also contains larger uncertainties. / Vid gjutning av betongbrodäck kommer den underliggande marken att deformeras av den temporära formställningen, som tar upp lasterna medan betongen härdar. Det finns oftast krav på hur stora markdeformationerna maximalt får vara. För att hålla deformationerna inom gränserna kan diverse markförstärkningsmetoder, så som kalkcementpelare eller pålar, användas. Permanenta markförstärkningar är oftast väldigt dyra och inte alltid nödvändiga. Ett alternativ till att använda dyra markförstärkningar skulle kunna vara att beräkna den förutspådda deformationen med stor exakthet i projekteringsstadiet. Syftet med det här arbetet var att undersöka hur korttidsstätningar i lera vid en bronybyggnation ska beräknas mer generellt i framtida projekt.  I detta arbete har tre beräkningsmodeller använts för att beräkna markdeformationerna från den temporära formställningen. En enklare analytisk modell samt två numeriska beräkningsmodeller som baseras på Mohr Coulomb och Hardening Soil Small teorierna. De tre beräkningsmodellerna valdes utifrån deras komplexitet. Den analytiska beräkningen ansågs vara den mest förenklade modellen medan Hardening Soil-Small var den mest komplexa och realistiska modellen.   Resultatet visar att trots sin enkelhet så ger den numeriska beräkningsmodellen Mohr Coulomb och den analytiska beräkningen bäst resultat jämfört med de uppmätta deformationerna. En möjlig anledning till det goda resultatet är att modellerna endast kräver ett fåtal ingångsparametrar som kan bestämmas med hjälp av välkända fält- och laboratoriemetoder så som triaxialförsök, rutinlaboratorieförsök och CRS-försök. Den mer komplexa modellen Hardening Soil Small kräver flera ingångsparametrar för att kunna modellera jordens beteende. Många av parametrarna är svåra att bestämma då mätdata oftast saknas. Osäkerheterna i valet av ingångsparametrar för den mer komplexa hardening soil small modellen är större än de två andra studerade modellerna, vilekt även ger upphov till större osäkerheter i dem beräknade deformationerna.