M-theory, a generalization of string theory, motivates the search for examples of volume minimizing cycles in Riemannian manifolds of G2 holonomy. Methods of calibrated geometry lead to a system of four coupled nonlinear partial differential equations whose solutions correspond to associa- tive submanifolds of R7, which are 3-dimensional and minimize volume in their real homology classes. Several approaches to finding new solutions are investigated, the most interesting of which exploits the quaternionic structure of the PDE system. A number of examples of associative 3-planes are explicitly given; these may possibly be projected to nontrivial volume minimizing cycles in, for example, the G2-manifold R6 × S1.

Reptile populations are suffering substantial global losses and roads are identified as one of the leading threats to their persistence. Currently, efforts to mitigate this threat are being implemented with various levels of success. I studied the effectiveness of exclusion structures (i.e., fencing) at preventing reptiles from gaining access to the road, and reducing road mortality. I also examined if population connectivity structures (i.e., ecopassages) were effective at reducing habitat and population fragmentation and allowing individuals to access habitats, resources, and mates on both sides of a major road (4 lane highway). I found that the fence was ineffective at preventing reptiles from gaining access to the road; however, reptiles were observed using the ecopassages to cross the road. Behavioural trials testing painted turtles’ (Chrysemys picta) willingness to use an ecopassage demonstrated that refusal was twice more likely than use of an ecopassage. I also examined the potential for roads to pose a physiological threat to roadside populations of reptiles by examining corticosterone (CORT), a stress hormone linked to negative health effects in cases of elevated levels over the long-term. To assess if individuals living near a major road had higher CORT levels than individuals from a less impacted population, I developed a novel means of measuring CORT from painted turtle claws in partnership with Dr. Gabriela Mastromonaco (Toronto Zoo). With long-term CORT levels considered as a proxy for chronic physiological stress, I did not find evidence that populations near roads had altered stress levels. However, this seminal study will provide the framework for further examination of more species, including species-at-risk, and a better understanding of effects of anthropogenic environments on wildlife health. As road ecologists strive to expand our understanding of the threats roads pose to reptiles, it is important that this field spans multiple disciplines, so that we can both understand the direct and indirect threats that roads cause and develop effective mitigation that preserves biodiversity within our anthropogenic landscape.

Excess water production is a major economic and environmental problem for the oil and gas industry. The cost of processing excess water runs into billions of dollars. Polymer gel technology has been successfully used in controlling water influx without damaging hydrocarbon production in conventional naturally fractured or hydraulically fractured reservoirs. However, there has been no systematic investigation on effectiveness and placement conditions of polymer gels for shutting off water flow from fractures with narrow apertures in shale and tight gas reservoirs. The existing polymer gels, like those based on Chromium(III) Acetate, as a crosslinker will exert very high extrusion pressure to effectively penetrate the narrow aperture fractures present in shale and tight gas reservoirs. This gives rise to a need for a new polymer gel system that can be used for selectively shutting off water flow from narrow aperture fractures in shale and tight gas reservoirs. The new gel system will have a longer gelation time than the existing polymer gels; this ensures minimum crosslinking of the gel by the time it reaches bottom hole. The gelant solution will be pumped at low pressure so that, it penetrates only pre-existing fractures in the formation with ease. This study for the first time focuses on developing an environmentally benign polymer gel system based on high molecular weight HPAM, as a base polymer and a commercial grade PEI as an organic crosslinker. Gel samples of different concentration ratios of the polymer and crosslinker were prepared and classified under Sydansk code of gel strength to find optimum concentration ratios that gave good gels. The gel system was characterized using Brookfield DV-III Ultra Rheometer and Fann-35 Viscometer.

We present an efficient algorithm for solving an interval coverage problem. Given n intervals of the same length on a line L and a line segment B on L, we want to move the intervals along L such that every point of B is covered by at least one interval and the sum of the moving distances of all intervals is minimized. As a fundamental computational geometry problem, it has applications in mobile sensor barrier coverage in wireless sensor networks. The previous work gave an O(n2) time algorithm for it. In this thesis, by discovering many interesting observations and developing new algorithmic techniques, we present an O(nlogn) time algorithm for this problem. We also show that Ω(n log n) is the lower bound for the time complexity. Therefore, our algorithm is optimal. Further, our observations and algorithmic techniques may be useful for solving other related problems.

In intelligent transportation systems, most of the research work has focused on lane change assistant systems. No existing work considers minimizing the interruption of traffic flow by maximizing the number of lane changes while eliminating the collisions. In this thesis, we develop qualitative and quantitative approaches for minimizing the interruption of traffic flow for three lane scenarios and show that we can extend our approach to any random number of lanes. The algorithm we propose in this thesis is able to achieve the maximum number of lane changes provided that only one vehicle per group (novel concept which is described in this thesis) is allowed to change lanes at a time. Simulation results show that our approach provides much better performance when compared with different lane change algorithms without incurring large overhead, and is hence suitable for online use.

No description available.

We provide geometric inequalities on $R^n$ and on general manifolds with nonnegative Ricci curvature by employing suitable monotone quantities along the flow of capacitary and $p$-capacitary potentials, as well as through related boundary value problems. Among the main achievements, we cite [(i)] a Willmore-type inequality on manifolds with nonnegative Ricci curvature leading in turn to the sharp Isoperimetric Inequality on $3$-manifolds with nonnegative Ricci curvature ; [(ii)] enhanced Kasue/Croke-Kleiner splitting theorems ; [(iii)] a generalised Minkowski-type inequality in $R^n$ holding with no assumptions on the boundary of the domain considered except for smoothness ; [(iv)] a complete discussion of maximal volume solutions to the least area problem with obstacle on Riemannian manifolds and its relation with the variational $p$-capacity.

This work was motivated by the famous Plateau\'s Problem which concerns the existence of a minimizing set of the area functional with prescribed boundary. In order to solve the Plateau\'s Problem, we make use of different theories: the theory of varifolds, currents and locally finite perimeter sets (Caccioppoli sets). Working on the Caccioppoli sets theory, it is straightforward to prove the existence of a minimizing set in some classical problems as the isoperimetric and Plateau\'s problems. If we switch the problem to find the regularity that we can extract of some minimizing set, we come across complicated ideas and tools. Although, the Plateau\'s Problem and other classical problems are well settled. Because of that, we have extensively studied the almost minimizing condition ((; r)-minimizing sets) considered by Maggi ([?]) which subsumes some classical problems. We focused on the regularity theory extracted from this almost minimizing condition. / This work was motivated by the famous Plateau\'s Problem which concerns the existence of a minimizing set of the area functional with prescribed boundary. In order to solve the Plateau\'s Problem, we make use of different theories: the theory of varifolds, currents and locally finite perimeter sets (Caccioppoli sets). Working on the Caccioppoli sets theory, it is straightforward to prove the existence of a minimizing set in some classical problems as the isoperimetric and Plateau\'s problems. If we switch the problem to find the regularity that we can extract of some minimizing set, we come across complicated ideas and tools. Although, the Plateau\'s Problem and other classical problems are well settled. Because of that, we have extensively studied the almost minimizing condition ((; r)-minimizing sets) considered by Maggi ([?]) which subsumes some classical problems. We focused on the regularity theory extracted from this almost minimizing condition.

Extensive computer use is creating a society where its citizens are communicating outside the norm of real life. These diversions from real life communication behavior have been named the Online Disinhibition Effect (ODE). The effect is a psychological model that is structured with different types of elements which can be triggered by different communication mediums. There are two sides of the effect; a benign, where compassion and a reveal of emotions are more likely, and a toxic, where anger, frustration and threats are in focus. In the online video game industry, ODE is active, but as the medium is different than regular internet use the effects are different as well. This paper looks at how online video games are affected by ODE. By using the most current disinhibition model made by Suler and looking at modern cyberpsychology in online games, this paper found eight features that have the possibility to decrease disinhibition amongst users. This paper concludes with a warning that games are becoming more immersive and without the proper authority features, games will increase their disinhibition effect amongst its users.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-13T17:29:47Z No. of bitstreams: 1 GeovanCampos.pdf: 458133 bytes, checksum: 442b76b0f10e2ef37624745cce5924a3 (MD5) / Made available in DSpace on 2017-06-13T17:29:47Z (GMT). No. of bitstreams: 1 GeovanCampos.pdf: 458133 bytes, checksum: 442b76b0f10e2ef37624745cce5924a3 (MD5) Previous issue date: 2016-03-31 / In this work, we talk about the article "Area-Minimizing Projective Planes in 3- Manifolds" due to Hubert Bray, Simon Brendle, Michael Eichmair and Andr´e Neves. In this article they consider a compact Riemannian 3-manifold (M; g) with positive scalar curvature and an embedded projective plane. In these conditions they prove a higher estimate of curvature, in term of infimum of the scalar curvature of (M; g), for the area of the projective plane that has the smallest area within the class of all surfaces Σ ⊂ M homeomorphic to projective plane. Furthermore, they prove that this inequality is great. More precisely, they get that if this equality hold in (M 3; g), so M is isometric to the three-dimensional projective space RP3 with constant sectional curvature. / Neste trabalho, dissertamos sobre o artigo "Area-minimizing Projective Planes in 3-Manifolds" devido a Hubert Bray, Simon Brendle, Michael Eichmair e André Neves. Neste artigo eles consideram uma 3-variedades Riemannianas compactas (M³, g) com curvatura escalar positiva e que admitem planos projetivos mergulhados. Nestas condições eles provam uma estimativa superior, em termo do ínfimo da curvatura escalar de (M; g), para a área do plano projetivo que possui a menor área dentro da classe de todas as superfícies Σ ⊂ M homeomorfas ao plano projetivo. Além disso, eles provam que esta desigualdade é ótima. Mais precisamente, eles obtém que se a igualdade ocorre então a variedade Riemanniana (M³, g) é isométrica ao espaço projetivo tridimensional RP3 coma métrica de curvatura seccional constante.