Foundation performance is controlled significantly by the stress-strain behavior of the underlying soils. For geomaterials, the small-strain shear modulus Gmax is a fundamental stiffness applicable to both monotonic static and dynamic loading conditions, as well to both drained and undrained loading. Yet, Gmax is too stiff for direct use in computing foundation displacements. The main objectives of this research are to: (1) explore the scaled parallelism between the stress-strain-strength behavior of the single soil element response and the load-displacement-capacity of a shallow foundation system supported on soil; (2) develop a methodology for evaluating the performance of vertically-loaded footings using a rational framework based on the small-strain modulus Gmax, large-strain strength ( and #964;max or su) and strain at failure ( and #947;f); and (3) calibrate the proposed method using a foundation database of full-scale load tests under both undrained and drained conditions. In geotechnical practice, foundation bearing capacity is handled as a limit plasticity calculation, while footing displacements are evaluated separately via elastic continuum solutions. Herein, a hybrid approach is derived that combines these two facets into a closed-form analytical solution for vertical load-deflection-capacity based on numerical studies. Here, a non-linear elastic-plastic soil model was developed to simulate the stress-strain-strength curves for simple shearing mode (LOGNEP) for each soil element. The model was encoded into a subroutine within the finite difference program FLAC. A large mesh was used to generate load-displacement curves under circular and strip footings for undrained and drained loading conditions. With proper normalization, parametric foundation response curves were generated for a variety of initial stiffnesses, shear strengths, and degrees of non-linearity in the soil stress-strain-strength response. Soil stress-strain non-linearity is described by a logarithmic function (Puzrin and Burland, 1996, 1998) that utilizes a normalized strain xL that relates strain at failure and #947;f, shear strength ( and #964;max or su), and small-strain stiffness Gmax, all having physical meaning. A closed-form algorithm is proposed for generating non-linear load-displacement curves for footings and mats within an equivalent elastic framework. The proposed method was calibrated using a database of well-documented footing load tests where soil input parameters were available from laboratory and/or in-situ field test results.

The goal of this research was to determine whether precast prestressed bridge elements with congested reinforcement could be cast using self-consolidating concrete (SCC) without vibration and yet comply with all parameters of strength, no honeycombing, and void-free surface finish. Eight wall panels and eight BT-72 13-ft long girder sections were fabricated in two precast plants. A qualitative and quantitative evaluation of the surface finish, and homogeneity of the concrete throughout the specimens was performed. Strength, creep, shrinkage and chloride permeability of the SCC field mixes were investigated. Good quality SCC mixes were produced for the walls and the BT-72 girder sections, which completely filled the specimens without the need of internal or external vibration, and resulted in a superior surface finish and a homogenous distribution of the aggregate throughout the section.

An anti-reflective (AR) lens is an ultrathin multilayered structure composing of AR coatings on a lens substrate. These coatings can be made by a spin-coating process with a nanocomposite of UV curable acrylic monomers and well dispersed metal oxide nanoparticles. The in-situ UV polymerization rate was reduced by oxygen inhibition and the absorption of UV energy by the metal oxide nanoparticles. There are few studies of the mechanical properties of ultrathin polymeric coatings that include the effects of substrates, the viscoelastic behaviors of polymers in submicron scales and the effects of multilayered coatings. With a coating system based on UV cured dipentaerythritol pentaacrylate on silicon wafer substrates, nanoindentation tests showed that the nominal reduced contact modulus increased with the indentation load and penetration depth due to the effect of the substrate, in quantitative agreement with an elastic contact model. Ultrathin polymeric coatings subjected to constant indentation loads exhibit shear-thinning during flow. None of the models examined completely described the elastic response of an ultrathin polymeric coating on a compliant plastic substrate. The effective modulus was a function of coating-substrate property, indenter tip size, coating thickness, adhesion and residual stress. It was logarithmic dependent on the ratio of the indentation depth to the coating thickness prior to coating fracture. An elastic model, assuming shear-lag and a plane-stress state, was used to estimate the interfacial strength between a submicron coating and a compliant substrate. The critical indentation load for the indentation-induced delamination of the coating from the substrate increased with the third power of the indentation depth and was a linear function of the reciprocal of the coating thickness. The interfacial strength was 70.4 MPa. Mechanical properties and fracture characteristics of CVD ceramic and nanocomposite coatings on polymer substrates were evaluated by nanoindentation and nanoscratching tests. The AR lenses made with polymer nanocomposite coatings have better mechanical properties due to the close match of properties between the coatings and the plastic substrate. The new approach to making AR lenses with polymer nanocomposites on plastic substrate is promising.

The objective of this study was to determine how final stocking influences tree growth and radial and longitudinal variation in wood properties at a Pinus radiata D. Don plantation located at one of the warmest forest sites in New Zealand, Forsyth Downs forest in Northland. This thesis addressed both the effect of stocking on stand basal area, height, diameter and branch diameter and the effect of stocking on wood properties microfibril angle (MFA), module of elasticity and density. Finally, how ring width influences wood properties and whether this variable accounts for the treatment effects was investigated. Stocking, height and ring number and all interactions between these variables significantly affected ring width. Ring width by itself was significant as a predictor of density, but when it was combined with other class level variables it was insignificant (i.e. does not account for treatment effects), and it did not add anything to a model with only class effects. There was a significant impact of ring number on density while ring width was insignificant in the same model. MFA was significantly affected by ring width, height and ring number in the tree, and all interactions, apart from the three way interaction, but not by stocking. Ring width was significant in the MFA model both by itself and when it was combined with other variables. Ring width accounted for the stocking effect. The best model of MOE included the class level effects of stocking, height and ring number within the tree, and all interactions between these variables, and ring width, as a continuous variable. While there was a significant effect between stockings this was relatively weak compared to the other main effects. Ring width largely accounted for the effect of stocking, but not that of ring number, or height.

No description available.

The sources of natural or virgin coarse aggregates are diminishing in alarming rate and its production is quite expensive, uses a lot of energy, and is not environmental friendly. Hence, utilizing the recycled aggregates like reclaimed or recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) on road pavement will not only preserve the natural aggregates but also reduce the negative environmental impact. It also helps to conserve the waste landfill sites. The major downside for the use of the recycled aggregate is the quality control during its production. This research characterizes RCA samples obtained from a demolished old foundation and RAP samples from old parking lot and determines their suitability as road pavement materials. Virgin aggregates, recycled aggregates, and several blended mixtures with 20 to 80% replacement of natural coarse aggregate or virgin aggregate (NCA or VA) by weight with RCA and RAP were prepared and tested for resilient modulus (Mr) and California Bearing Ratio (CBR) test. The durability of the virgin aggregate and recycled aggregate were also determined by micro-deval test. The resilient modulus value of 100% RCA and 100% VA was found to be very similar or higher but for 100% RAP the resilient modulus is higher than that of the 100%VA. The Resilient modulus of the RAP blended mixtures increases with the increase in the content of RAP percentage and for the RCA it was not consistent. The CBR values for the blended mixtures decreases with the increase in the percentage of the recycled aggregates. The micro-deval degradation test result for RCA was more than of VA due to presence adhere materials in RCA.

Master of Science / Department of Mathematics / Pietro Poggi-Corradini / This thesis contains three chapters split into two parts. In the first chapter, the discrete p-modulus of families of walks is introduced and discussed from various perspectives. Initially, we prove many properties by mimicking the theory from the continuous case and use Arne Beurling's criterion for extremality to build insight and intuition regarding the modulus. After building an intuitive understanding of the p-modulus, we proceed to switch perspectives to that of convex analysis. From here, uniqueness and existence of extremal densities is shown and a better understanding of Beurling's criterion is developed before describing an algorithm that approximates the value of the p-modulus arbitrarily well. In the second chapter, an exclusively edge-based approach to the discrete transboundary modulus is described. Then an interesting application is discussed with some preliminary numerical results. The final chapter describes four different takes of the Susceptible-Infected (SI) epidemic model on graphs and shows them to be equivalent. After developing a deep understanding of the SI model, the epidemic hitting time is compared to a variety of different graph centralities to indicate successful alternative methods in identifying important agents in epidemic spreading. Numerical results from simulations on many real-world graphs are presented. They indicate the effective resistance, which coincides with the 2-modulus for connecting families, is the most closely correlated indicator of importance to that of the epidemic hitting time. In large part, this is suspected to be due to the global nature of both the effective resistance and the epidemic hitting time. Thanks to the equivalence between the epidemic hitting time and the expected distance on an randomly exponentially weighted graph, we uncover a deeper connection- the effective resistance is also a lower bound for the epidemic hitting time, showing an even deeper connection.

No description available.

Organic solar cells promise a cheap and easy alternative to silicon photovoltaics, but there are many problems that must be solved before they can be a stable and efficient substitute. One such problem is the degradation of solar cells under exposure to light and oxygen. In response to evidence of change in electronic properties of polymer:PCBM solar cells, the mechanical properties of pristine PCBM films are investigated for analogous development using atomic force microscopy. Although no signicant change in the elastic modulus is detected, differences in material response indicate a skin effect which is beyond measurement sensitivity. Presence of a hard skin is verified in tapping phase imaging and spectroscopy.

No description available.