El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Bus Rapid Transit (BRT) is a bus-based public transport system that increase the effectiveness of public transportation through dedicated lanes with busways and independent stations. However, the low capacity at the stations and the high demand of the system increases the respiratory diseases risk caused by the interaction between pedestrians. This article proposes to make the main access point an entrance only and the access point at the opposite end of the platform an exit only, allowing one-way walking paths. This research is focused on the reduction of conflict points between pedestrians generated by walking flows in opposite directions. A BRT station located in the city of Lima was used as a case study for the investigation. It was identified for the peak hour that the area with the highest pedestrian interaction occurs in the station platform and boarding areas. The efficiency of the proposal is validated by using the Viswalk software. The results obtained show that the conflict points decreased by 68.5% and the pedestrian density by 45%. From that perspective, the pedestrian flows were optimized, and the risk of respiratory diseases was reduced.

A universal cycle (u-cycle) is a compact listing of a collection of combinatorial objects. In this paper, we use natural encodings of these objects to show the existence of u-cycles for collections of subsets, restricted multisets, and lattice paths. For subsets, we show that a u-cycle exists for the κ-subsets of an n-set if we let κ vary in a non zero length interval. We use this result to construct a "covering" of length (1+o(1))(n/κ) for all subsets of [n] of size exactly κ with a specific formula for the o(1) term. We also show that u-cycles exist for all n-length words over some alphabet ∑, which contain all characters from R ⊂ ∑. Using this result we provide u-cycles for encodings of Sperner families of size 2 and proper chains of subsets.

Given a configuration of t indistinguishable pebbles on the n vertices of a graph G, we say that a vertex v can be reached if a pebble can be placed on it in a finite number of "moves". G is said to be pebbleable if all its vertices can be thus reached. Now given the n-path Pn how large (resp. small) must t be so as to be able to pebble the path almost surely (resp. almost never)? It was known that the threshold th(Pn) for pebbling the path satisfies n2clgn≤th(Pn)≤n22lgn, where lg=log2 and c<1/2 is arbitrary. We improve the upper bound for the threshold function to th(Pn)≤n2dlgn, where d>1 is arbitrary.

Joining of uniformly-curved composite sandwich panel segments, typical in state of the art aerospace launch vehicles, should be mass-efficient. Adhesively bonded joints can provide increased mass-efficiency over mechanically-fastened joints. But, due to manufacturing sensitivities and certification requirements, conventional bonded joints can be improved upon by introducing structural redundancy. A longitudinal, durable redundant joint (DRJ) architecture featuring multiple adhesive load-paths, via a novel composite preform insert, was proposed to join composite sandwich panel segments of the interstage element for NASA's Ares V launch vehicle. A series of twenty-five static linear-elastic finite element models with plane strain solutions were developed to assess certain characteristics of a joint's structural response when subjected to a simplified circumferential hoop loading convention. Shear and normal stress distributions at the adherend-adhesive interface along the splice plate bondline of the DRJ are compared with those from a conventional splice joint (CSJ) configuration for a series of linearly increasing bondlines thicknesses and joint overlap lengths. The parameter studies indicate the DRJ configuration's adhesive peak stresses are independent of the joint overlap length at the joint edges. Also, simulated bonding defects, in the form of local adhesive gaps, due to manufacturing processes are investigated to determine the load path redistribution for the DRJ and CSJ configurations. Results for pristine versions of both configurations are included. The defective CSJ joint exhibits severe overloading of certain laminates, while the defective DRJ load redistributions are relatively mild. Between the two primary types of bondline gaps considered for the DRJ configuration, the gap corresponding to the splice plate, a more mature manufacturing operation and also a more easily inspected location than the insert-to-face sheet interface, is noted to be more severe. A direct joint-to-joint mass-comparison reveals a 164% increase in mass, per unit thickness, between the CSJ and DRJ. To put this in perspective, a second comparison is made using a four-segment sandwich panel barrel. A 3.51% increase in mass is observed between the CSJ and DRJ-based cylinders. Also, for a simplified sizing philosophy, based solely on the peak stresses in the adhesive domain, a CSJ may require a 1.5-inch longer joint overlap than a DRJ. The mass-estimate is recomputed, and the mass percent-increase of the segmented cylinder is reduced to 2.61% over a CSJ configuration. / Master of Science

Invasive plants are widely cited as a major threat to native plant communities, and the correlation between plant invasions and a subsequent decline in native species is well documented at some scales. However, one outstanding question is the degree to which invasive species are a driver of native plant declines versus a correlate of other drivers, such as habitat disturbance. These two hypotheses to explain the dominance of invasive species in communities have been termed the ‘driver’ and ‘passenger’ models, respectively. In order to understand the impacts of plant invasion on native plants we need more studies that consider the role of correlated environmental predictors, which may play unseen roles in the response and recovery of native plant communities frequently attributed to invasion alone. Using a large database of plant community and environmental data from sites across Southern Ontario, I used path analyses to examine the direct and indirect relationships between disturbance, exotic and native plant richness, and relative abundance. Counter to my initial predictions, I found support for both the partial passenger and partial driver models of invasive dominance, while full passenger models were outright rejected. The causal hypotheses consistent with the data indicated significant relationships between native and exotic species richness and native and exotic relative abundance across models. An exploratory analysis, which examined species-specific models, found that the data was consistent with seven out of twelve causal hypotheses. Models that could not be rejected were split almost evenly across full passenger, partial passenger, and partial driver models. Model support varied according to the species included in the dataset suggesting that the best fit underlying model of invasive dominance likely varies by species. While the partial passenger and partial driver models were recurrently consistent with the data, no single model described the underlying patterns of invasive dominance across all systems.

The Swedish educational system is full of possibilities but is also rather complicated because of that fact. There exist several different paths to reach the same goal but how do you find them and which one is the quickest? This project has tried to make it easier for students to find the right path from start to finish by presenting possible study paths. It has been done by collecting information about schools and programs and inserting it into a graph database which has then been traversed to extract the fastest paths from the starting point (e.g. elementary school) of a student to their goal (e.g. Doctor) based on a few arguments. Interviews with student counselors have been conducted in order to evaluate how practical the system is. A conclusion from these interviews is that the system is useful but halted by the fact the database contains too little information. The idea is good but the system would need to be scaled up to be more useful, which is expected when it is a prototype. To fill the database with all information necessary is left as a future work since it would be too time-consuming.

A mathematical model of a small fixed-wing aircraft was developed through application of parameter estimation techniques to simulated flight test data. Multiple controllers were devised based on this model for path following, including a self-scheduled linear parameter-varying (LPV) controller with path curvature as a scheduling parameter. The robustness and performance of these controllers were tested in a rigorous MATLAB simulation environment that included steady winds and gusts, measurement noise, delays, and model uncertainties. The linear controllers designed within were found to be robust to the disturbances and uncertainties in the simulation environment, and had similar or better performance in comparison to a nonlinear control law operating in an inner-outer loop structure. Steps are being taken to implement the resulting controllers on the unmanned aerial vehicle (UAV) testbed in the Nonlinear Systems Laboratory at Virginia Tech. / Master of Science

This thesis proposes a modification of trajectory shaping guidance to provide more accurate path convergence in curved paths. The object of this thesis is to apply this simple guidance law to platooning control to ensure all vehicles in the platoon converge to a desired constant radius path at a desired vehicle separation distance. To show the viability of this new guidance law, it is shown mathematically to be exponentially stable. It is also confirmed through simulations and on ground robots.

The Himalayan orogen provides a natural laboratory to test models of orogenic development due to large-scale continental collision. The Greater Himalayan Series (GHS), a lithotectonic unit continuous along the entire length of the belt, comprises the metamorphic core of the Himalayan orogen and underlies the highest topography. GHS rocks are exposed as a moderately north-dipping slab bounded below by the Main Central Thrust (MCT) and above by the South Tibetan Detachment System (STDS) of normal faults. Coeval reverse- and normal-sense motion on the crustal-scale MCT and STDS ductile shear zones allows the GHS to be modeled as an extruded wedge or channel of mid-crustal material. Due to this unique tectonic setting, the deformation path of rocks within the bounding shear zones and throughout the core of the GHS profoundly influences the efficiency of extrusion and exhumation processes. Attempts to quantify GHS deformation and metamorphic evolution have provided significant insight into Himalayan orogenic development, but these structural and petrologic studies are often conducted in isolation. Penetrative deformation fabrics developed under mid-upper amphibolite facies conditions within the GHS argue that deformation and metamorphism were coupled, and this should be considered in studies aimed at quantifying GHS teconometamorphic evolution. This work focuses on two projects related to the coupled deformation, thermal and metamorphic evolution during extrusion and exhumation of the GHS, focused on the lower and upper margins of the slab. A detailed examination of the P--T history of a schist collected from within the MCT zone of the Sutlej River, NW India, provides insight into the path experienced by these rocks as they traveled through the crust in response to the extreme shortening related to India-Asia collision. Combined forward thermodynamic and diffusion modeling indicates compositional zoning preserved in garnet has remained unmodified since growth and can be related directly to the P--T--X evolution of rocks from this zone. Classic porphyroblast--matrix relationships coupled with the above models provide a structural framework within which to interpret the microstructures and provide additional constraints on the relative timing of metamorphic and deformation events. A combined microstructural and quartz petrofabric study of rocks from the highest structural levels of the GHS in the Zanskar region was completed. This work provides the first quantitative estimate of temperatures attending normal-sense shearing along the Zanskar Shear Zone, the westernmost strand of the STDS. Results indicate penetrative top-N (extensional) deformation occurred at elevated temperatures and resulted in the telescoping of isothermal surfaces present during shearing and extrusion of GHS rocks. Simple geometric models invoking heterogeneous simple shear parallel to the overlying detachment require dip-slip displacement magnitudes on the order of 15--40 km, identical to estimates derived from nearby barometric analyses. Finally, focus is given to the rotational behavior of rigid inclusions suspended in a flowing viscous matrix from a theoretical perspective. Predictions of clast rotational behavior have been used to construct several kinematic vorticity estimation techniques that have become widely adopted for quantitative studies of naturally deformed rocks. Despite the popularity of the techniques, however, basic questions regarding clast-based analyses remain open. Therefore a numerical model was constructed and a systematic investigation of 2- and 3D clasts suspended in steady and non-steady plane-strain flows was undertaken to determine likely sources of error and the intrinsic strengths and limitations of the techniques. / Ph. D.

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