Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 44). Also available in electronic version. Access restricted to campus users.

Results are reported from full-scale testing of a buried, deep-corrugated, large-span box culvert with a 2.4 m rise and 10.0 m span under controlled laboratory conditions. A total of twenty-one experiments were conducted on the structure, measuring its response without backfill, during backfilling, under a loaded tandem axle dump truck, and under simulated vehicle loading with force applied by an actuator. Surface strain measurements were used to calculate bending moments and thrusts, while deflections were monitored using an electronic theodolite. Tests conducted to a maximum force of truck loading specified by the Canadian Highway Bridge Design Code multiplied by a dynamic load allowance factor were performed at three cover depths. The maximum moment increased from 6 to 41 kNm/m as the cover was reduced from 1.5 to 0.45 m. This was attributed to less load distribution and decreased soil-structure system stiffness at shallower cover. The maximum bending moments were consistently observed directly beneath the applied force. Tests were also conducted at forces larger than the design values to identify the ultimate limit state(s) of the structure. An ultimate limit state was encountered at approximately 800 kN where the geotechnical resistance beneath the loading pads was exceeded. A subsequent test with the loading pad force spread over larger areas permitted larger forces to be applied. An ultimate limit state of the structure involving the formation of three plastic hinges occurred at 1100 kN. The plastic hinge initially formed at the crown, followed by hinges located at each shoulder. Post-test observations showed evidence of local buckling of the conduit wall, gaps between the plates at the seams, the tilting of bolts along the longitudinal seams, and surface cracks in the soil. Applying the material resistance factor of 0.9 to the ultimate load limit of 1100 kN measured for the structure yields a reserve capacity of 1.7 when compared to the fully factored load including dynamic load allowance and live load factors. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-12-23 11:56:12.314

Computing the collapse load and identifying the associated mechanism of block assemblage structures is an important task in historical restoration works. The research in this thesis is to contribute to the modelling and analysis of rigid block structures in dry frictional contact. The models can be applied to various structures such as masonry arches) vaults) domes, walls or piles in heritage buildings. Estimates of the collapse load are made by solving the underlying mathematical programming problems. 2-D and 3-D models are formulated and different contact assumptions (concavity and convexity) are investigated. Both associated and nonassociated flow rules are accounted for. The associative problem can be robustly solved by the bound theorems of classical plasticity theory. However, the result is often not valid. The nonassociated rule which shows up as a complementarity relationship in the governing system is the major challenge of the project. The 3-D model is more difficult to deal with as compared to the 2-D case. Proposed methods are presented to treat the nonlinear 3-D problem (Lorentz cone) by formulating it as a second-order cone problem or by piecewise linearizing the cone as a polyhedral. Various computational methods are proposed to obtain the best upper bound collapse load for the nonassociative model. One method formulates some extended complementarity problems that are able to restrict the domain of the collapse load variable to search for better solutions. The best method uses nonlinear programming) specifically mathematical programming with equilibrium constraints problems) to attempt to directly minimize the collapse load. Some enumerative schemes are also attempted to map out all the nonassociative solutions but proved to be computationally expensive. Various 2-D and 3-D examples are demonstrated for several different types of structures.

Phase change phenomena have been of interest mainly due to large latent heats associated with the phase transition and independency on external energy to drive the phase change process. When combined with micro/nano structures, phase change systems become a promising approach to address challenges in high heat flux thermal management. The objective of this thesis is to implement micro and nano structured surfaces for better understanding the underlying fundamentals of evaporation and boiling phase change heat transfer and enhancing the heat transfer performance. First, we study single bubble dynamics on superheated superhydrophobic (SHB) surfaces and the corresponding heat transfer mechanism of water pool boiling. Because of the large contact angle, such surfaces are ideal for correlating pool boiling with single bubble dynamics by accurately controlling the number of nucleation sites in a defined area. The fundamental parameters of single bubble dynamics are collected and put into the heat flux partitioning model. We find that latent heat transport and bulk liquid water convection contribute together to the heat removal on superhydrophobic surfaces. Next, we present a novel method to fabricate silicon nanowires by one-step metal assisted chemical etching (MACE) on micro-structured surfaces with desired morphologies. Patterned vertically aligned silicon nanowires are fabricated on dense cavity/pillar arrays due to trapped hydrogen bubbles serving as an etching mask. Uniformly grown silicon nanowires on structured surfaces can be fabricated if extra energy is introduced to remove the trapped bubbles. An enhanced pool boiling heat transfer performance on such structured surfaces is demonstrated. Finally, we study the ultimate limits of water evaporation in single 2D nanochannels and 1D nanopores. These ultimate transport limits are determined by the maximum evaporation fluxes that liquid/vapor interfaces can provide regardless of liquid supply or vapor removal rates. A hybrid nanochannel design is utilized to provide sufficient liquid supply to the evaporating meniscus and evaporated vapor is efficiently removed by air jet impingement or a vacuum pump. The effect of nanoscale confinement on evaporation flux has been investigated, with feature size ranging from 16 nm to 310 nm. An ultra-high heat flux of 8500 W/cm2 is demonstrated in a single 16-nm nanochannel at 40 °C. / 2017-09-09T00:00:00Z

It is the purpose of this thesis to indicate in more detail how various limits defined in analysis, as well as other concepts not ordinarily defined as limits, may be obtained as special cases of the Moore-Smith limit.

Climate changes have been observed in the Northern Hemisphere during the last century, causing a longer growing season and upslope expansion of forest, tree, and shrub limits. Here, a long-term historical perspective was used as a tool for investigating how climate change has impacted woody plants at the forest, tree, and shrub limits across the study region. For this, historical data about plant communities were used, including the position of the forest, tree, and shrub limits, gathered by the Reindeer Commission in Troms County (1914-1915). The historical data were compared to contemporary data from a re-visit study in 2022. In addition, variations in microclimatic factors were investigated by looking at the growing season length, distance to coast, slope, and aspect. Importantly, the growing season length was found to have increased across the study region with the largest increase along the coast. The increase in the growing season length led to an upslope shift in the vegetation limits, although not significantly so for the forest limit. The field layer had shifted from meadow to heath around the historical shrub limit, and non-significantly for the forest and tree limit zones, indicating that the alpine tundra is the most sensitive to the observed warming. Distance to coast and slope did not impact the shift in vegetation limits, while aspect impacted the forest limit shift. The results from this thesis indicate that future studies should expand their research beyond climate variables and explore factors such as herbivory and land use change

Master of Science / Department of Mathematics / David R. Auckly / In this report we present the main concepts of probability theory: sample spaces, events, random variables, distributions, independence, central limit theorem. Most of the material may be found in the notes of Bass. The work is motivated by wide range of applications of probability theory in quantitative finance.

Application of low hierarchy structures are becoming increasingly popular by enhancing job satisfaction and productivity of employees. On the other hand formation of hierarchy appears to be natural and beneficial in many cases. This study explores how low hierarchies could become and where the boundaries regarding job satisfaction lie as well as how these differ depending on formal position of employees. The inquiry is undertaken with a focus is on medium-sized companies in manufacturing industry in Germany where job satisfaction and productivity via such applications is vital. Extensive qualitative data was collected with a single-case approach; analysis was conducted qualitatively likewise. The lower limits of hierarchy are discovered to lie in various aspects mainly relating to supervision, recognition of good performance and promotion opportunities and to differ significantly with formal position. The study is believed to be unique and assist in shedding light into the area of beneficial and practical low hierarchy applications.

The LMVD Method of Planes has been used for many years by the New Orleans District of the U.S. Army Corps of Engineers to analyze the stability of flood control structures in the New Orleans hurricane protections system. The Method of Planes assumes a three-part, noncircular slip surface and generally does not satisfy any form of static equilibrium. In computing a factor of safety, the Method of Planes considers a balance of horizontal “resisting” and “driving” forces in computing a factor of safety. To better understand how the results of slope stability analyses with the Method of Planes compare with results from more rigorous procedures capable of analyzing slip surfaces with different shapes, a parametric study was performed by analyzing twenty earthen levee cross sections believed to represent the various levee configurations in southeastern Louisiana. Analyses were performed with a force equilibrium procedure that assumed a horizontal inclination for the interslice forces and Spencer’s (1967) procedure, and the results were compared with the solutions from the Method of Planes. The force equilibrium procedure with horizontal side forces was selected because the procedure is believed to yield results that are similar to results from the Method of Planes, and Spencer’s procedure was utilized because it is the only procedure considered in this study to completely satisfy static equilibrium. The analyses performed with the force equilibrium and Spencer’s procedures included analyses for the critical slip surfaces from the Method of Planes as well as analyses for critical circular and noncircular slip surfaces. It was shown with the results of the analyses that the shape of the assumed slip surface has a great effect on the differences in the factors of safety from Spencer’s procedure and the Method of Planes. / text

"On a stock exchange, trading activity has an impact on stock prices. Market agents place limit orders, which come in the form of bids and asks. These orders wait in the market to be executed when another agent agrees to fulfill the transaction. We examine an "inventory-based" quoting strategy model developed by Marco Avellaneda and Sasha Stoikov. We expand on their work by developing a method to calibrate the model to market data using limit order data provided by Morgan Stanley. We consider solving a least squares problem which fits the model to the data using a sensitivity parameter."