This dissertation details work aimed at better understanding topographic effects in earthquake ground motions. The experiment, conducted in Central-Eastern Utah, used frequent and predictable seismicity produced by underground longwall coal mining as a source of low-intensity ground motions. Locally-dense arrays of seismometers deployed over various topographic features were used to passively monitor seismic energy produced by mining-induced implosions and/or stress redistribution in the subsurface. The research consisted of two separate studies: an initial feasibility experiment (Phase I) followed by a larger-scale main study (Phase II). Over 50 distinct, small-magnitude (M[subscript 'L'] < 1.6) seismic events were identified in each phase. These events were analyzed for topographic effects in the time domain using the Peak Ground Velocity (PGV), and in the frequency domain using the Standard Spectral Ratio (SSR) method, the Median Reference Method (MRM), and the Horizontal-to-Vertical Spectral Ratio (HVSR) method. The polarities of the horizontal ground motions were also visualized using directional analyses. The various analysis methods were compared to assess their ability to estimate amplification factors and determine the topographic frequencies of interest for each feature instrumented. The MRM was found to provide the most consistent, and presumably accurate, estimates of the amplification factor and frequency range for topographic effects. Results from this study clearly indicated that topographic amplification of ground motions does in fact occur. These amplifications were very frequency dependent, and the frequency range was correctly estimated in many, but not all, cases using simplified, analytical methods based on the geotechnical and geometrical properties of the topography. Amplifications in this study were found to generally range from 2 to 3 times a reference/baseline site condition, with some complex 3D features experiencing amplifications as high as 10. Maximum amplifications occurred near the crest of topographic features with slope angles greater than approximately 15 degrees, and the amplifications were generally oriented in the direction of steepest topographic relief, with some dependency on wave propagation direction. / text

Thesis (MTech. degree in Water Care ) - Tshwane University of Technology, 2007. / This research project investigated the total nitrogen removal capabilities of a nitrification and denitrification system treating two medium strength municipal landfill leachates. The characteristics of the leachates differed as one was obtained from general waste (GLB+) and the other from mixed industrial and general waste (H:h). This project was commissioned to develop a leachate treatment philosophy and a leachate management plan for the Vissershok landfill site near Cape Town. The aim of this leachate treatment trial project was to establish leachate treatability of different types of leachate, characterise leachate and effluent quality, determine alkalinity requirements, assess hydraulic retention periods and sludge production and confirm whether leachate quality can inhibit successful treatment in a sequencing batch reactor system. The two units were operated as simple Sequencing Batch Reactors (SBRs) by treating the leachate in a biological treatment process. Both units were initially seeded with activated sludge obtained from a sewage treatment works. Provision was made to supplement carbonaceous nutrient and phosphorus to the system. In the first stage of the study a controlled nitrification system was maintained to treat ammoniacal-nitrogen and the next stage denitrification was used to treat nitrate and nitrite-nitrogen levels. A completely automated daily cycle was used to treat the leachate and altered according to process requirements. The results showed that during nitrification ammoniacal-nitrogen concentrations as high as 2032.4 mg/l were consistently reduced to less than 0.1 mg/l. Similarly, for denitrification, nitrate-and nitrite-nitrogen concentrations were also consistently reduced to less than 0.1 mg/l, with a methanol utilisation ratio of CH3OH:N at 4.80:1. Chemical oxygen demand (COD) removal efficiencies were in the range 57-65% depending on loading rates applied. In conclusion it was shown that: (a) the biodegradable organics (COD) was reduced considerably (b) complete nitrification and denitrification occurred (c) no constituents of the leachate caused inhibition of the biological process.

Decision makers often present military researchers with a most daunting challenge: to pursue, with some level of prophetic certainty, innovative concepts that will yield increased capabilities during future wars against forecasted threats in not-yet- determined locations. This conundrum is complicated further with the requirement that the proposed technology yield benefit throughout the various strata of military operations. In the maturation of an advanced capability enabled by a technological advancement, a groundbreaking design should simultaneously demonstrate performance overmatch against an envisioned foe while showing that the costs associated with development, procurement, and operation outweigh reverting to an incremental advancement in the conventional means of delivering combat power. This manuscript focuses on the construction and utilization of decision support tools for use by scientists and engineers charged with providing a quantitative evaluation of an advanced ground combat system. The concepts presented focus on the effects and synergy regarding the combat vehicle principal attributes of survivability, lethality, and mobility. Additionally, this study provides a framework for analysis of these attributes when screened at the tactical, operational, and strategic levels of war. These concepts are presented and demonstrated from both the candidate selection (or choice) perspective, and the concept development (or design) perspective. As an example of this approach, this study includes a comparison of conventional powder gun cannonry versus a specific type of electromagnetic launch device known as the railgun. The decision support tools formulated in this dissertation allow the user to distill, at a coarse level of fidelity, the parametric relationships between system survivability, lethality, and mobility for advanced weapon system concepts. The proposed methods are suited for evaluation at the nascent stages of development, when the information normally applied in standard methods is sparse. This general approach may also be valuable in contemporary acquisition strategies employed in urgent fielding efforts, where the immediacy of the problem can benefit from an expedient and efficient method of analyzing the coupled and synergistic effects of implementing a proposed technology. While advantage is typically measured in terms of performance overmatch at the platform level, the broadening of this consideration vertically to higher levels of military command can aid in identifying the competing issues and complementary relationships related to a technical approach. Finally, given the backdrop demonstration for the framework, this manuscript may serve as a brief summary of system fundamentals and design theory for direct fire powder gun cannonry and electromagnetic railguns. / text

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Quantum mechanics is a theory developed to explain both particle and wave-like properties of small matter such as light and electrons. The consequences of the theory can be counter-intuitive but lead to mathematical and physical theory rich in fascinating phenomena and challenging questions. This dissertation investigates the nature of quantum systems in Bernoulli distributed random potentials for systems on the one dimensional lattice {0, 1, ..., L, L+1} ⊂ Z in the large system limit L → ∞. For single particle systems, the behavior of the low energy states is shown to be approximated by systems where positive potential is replaced by infinite potential. The approximate shape of these states is described, the asymptotics of their eigenvalues are calculated in the large system limit L → ∞, and a Lifschitz tail estimate on the sparsity of low energy states is proven. For interacting multi-particle systems, a Lieb-Liniger model with Bernoulli distributed potential is studied in the Gross-Pitaevskii approximation. First, to investigate localization in these settings, a general inequality is proven to bound from below the support of the mean-field. The bound depends on the per particle energy, number of particles, and interaction strength. Then, the ground state for the one-dimensional lattice with Bernoulli potential is studied in the large system limit. Specifically, the case where the product of interaction strength and particle density is near zero is considered to investigate whether localization can be recovered.

When foundations are designed on weak clay layers, it is a common practice to modify the subgrade by installing stone columns. Currently used methods for determining the level of ground modification, represented by the percentage of soil replaced (replacement ratio), assume a rigid foundation. These analytical methods provide the designer with the potential settlement reduction based on the compressibility parameters of the subgrade and the replacement ratio. The deficiencies of these methods are the assumption of rigidity of the foundation and the consideration of the settlement reduction as the only design criterion. Furthermore, they do not consider the effects that ground modification has on differential settlement, moments, and shear forces within the slab. In order to determine the effects of ground modification on the overall performance of a flexible foundation, a computer program was formulated which compares a multitude of design parameters of the modified subgrade to those of the unmodified subgrade to determine the impact of ground modification. By performing this investigation, correlations were found between the replacement ratio and the settlement reduction factors. Similarly, correlations were also found between the ratio of the length of the foundation to the radius of relative stiffness, and the moments and shear forces generated within the slab. The use of the findings of this thesis would allow the design to make more informed decisions when designing foundations on modified subgrade resulting in safer and more economical designs.