Inverting Permutations In Place

We address the problem of quickly inverting the standard representation of a permutation on $n$ elements in place. First, we present a naive algorithm to do it using $O(\log n)$ extra bits in $O(n^2)$ time in the worst case. We then improve that algorithm, using a small bit vector, to use $O(\sqrt n)$ extra bits in $O(n \sqrt n)$ time. Using a different approach, we present an algorithm to do it using $O(\sqrt n \log n)$ extra bits in $O(n \log n)$ time. Finally, for our main result, we present a technique that leads to an algorithm to invert the standard representation of a permutation using only $O(\log^2 n)$ extra bits of space in $O(n \log n)$ time in the worst case

Electron Yield Decay Curves for Analysis of Sample Charging and Neutralization

Excess charge on a material will affect the electron yield of the material. Electron yield is an attribute of materials which describe how the material behaves when irradiated with electrons. It is the ratio of the number of electrons going into the material over the number of electrons leaving the material. Understanding how a sample charges is important in both how it affects the electron yield and how it can be neutralized

Circular geopolymer concrete columns with composite rebars

Reinforced concrete (RC) is one of the most popular construction materials. Columns are critical to the safety as well as the performance of the structure. RC columns traditionally use Portland cement as a main ingredient for the cement as well as using steel bars and stirrups for reinforcement. One major problem encountered by RC columns is the corrosion of the reinforcement cages, which can result in deterioration of the concrete, loss of serviceability as well as, in extreme cases, brittle failure of the entire structure. This has resulted in the search for a product that will not corrode but still has similar behaviour. This search lead to the trial of glass fibre reinforced polymer (GFRP) material, which is made from high strength glass fibres surrounded by polymer matrices and shaped in the form of bars, tubes and grids. Another major problem is the issue of global warming. There is major concern over the amount of C O2 released by Portland cement. Due to modern day societies being extremely environmentally conscientious, an alternative product is needed to reduce this. This has resulted in the product which is known as geopolymer cement. Geopolymer concrete has been used in many projects around the world, and has been found to have the same strength as concrete. To test these two promising materials, six specimens were created, with the parameters of spacing between transverse reinforcement and type of transverse reinforcement varied. Each specimen was then tested through the application of axial loading with the internal longitudinal, internal transverse and external concrete strain recorded. The obtained resulted stated that both GFRP hoop and spiral ties are effective in pro- viding confinement to a GFRP reinforced geopolymer column. The results also show that the spiral ties are slightly more effective, due to having a higher ultimate load, ductility as well as confinement efficiency. These findings are why it is recommended that the spiral ties be used if GFRP reinforced geopolymer concrete is to be used within the construction industry. This study differs from other studies as the effect of the longitudinal GFRP bars on the behaviour of the specimen has been included. It was calculated that the longitudinal bars resulted in an increase in strength between 6-9% of the entire specimen. This contribution from the longitudinal bars is not quite as much as the contribution of steel reinforcement (12%) however, are still significant enough to avoid being neglected. A theoretical analysis was also performed to find an accurate equation to predict the axial capacity of the specimens. It was found that the equation 5.5 shown in this report was the most accurate from existing literature. This equation does not result in an accurate prediction of the capacity of the specimens. This was due to the strength reduction factor (α1) used being calculated for ordinary Portland cement concrete. An accurate prediction can be obtained if a strength reduction factor of 0.91 is used

Electron Yield of a Carbon Fiber Composite

As electron yield models continue to evolve and improve, a study of carbon fiber materials was conducted to try and understand more complex nanoscale structures and their influence on electron yield

Using Local Fishery Monitoring to Understand Small-Scale Coastal Fisheries in Tanzania

Nearshore marine fisheries provide the main source of protein for nearly 9 million people in the coastal villages of Tanzania, yet for decades the fisheries have shown signs of overexploitation. These fisheries are small-scale and co-managed by local coastal communities in groups known as Beach Management Units (BMUs). BMUs monitor individual fishing trip data (e.g. gear, vessel, taxa); however, these data have only been analyzed in nationally aggregated statistics and to our knowledge, are not presently used in management decision making. The present thesis aimed to identify the forms of data and information that local fishery monitoring can record about small-scale marine fisheries in Tanzania, and how that local monitoring data may be related to the spatial socio-ecological context of those fisheries. We collected all available fishing trip data from 2014 to 2017 from BMUs in fourteen villages in two spatially, socially, and ecologically distinct districts (Pangani and Rufiji) of the country. Our results found that each village had unique patterns of vessel-use, gear-use, and taxa landed, and that every village was specialized in some measure. Specifically, two villages in Pangani district landed octopus or parrotfish almost exclusively, suggesting potential trophic cascades after years of overexploitation. We then proposed a flexible modeling approach which incorporated the BMU landings data with spatial data to predict the spatial characteristics of the marine fisheries in Tanzania. The spatial models identified relationships between fishery landings and coral reef, seagrass, and mangrove habitat patch attributes, along with fisher density and a hydrologic index. Furthermore, the predicted spatial characteristics matched previously reported fishery characteristics in both districts. The maps developed by our modeling process provide a means for stakeholders and managers to understand the spatial distribution of their fisheries and in turn, focus on explicitly managing what, how, and where fishers operate. Overall, this thesis has shown that the catch data collected by BMUs were able to generate the first descriptions of village-based Tanzanian fishery characteristics. Thus, it is possible that the collection and analysis of local monitoring data can be used to promote the application of fishery regulations that are relevant to their socio-ecological context

Conjugacy and centralisers in Thompson's group T

PhD ThesisThe Thompson family of groups F < T < V are well-known as interesting (counter-) examples in group theory. Working algebraically with these objects is difficult, and yet the groups are computationally tractable. For instance, T and V are infinite simple groups; despite this, both are finitely presented. This thesis studies the middle group T, using the piecewise-linear function point of view. We present a solution to the conjugacy problem in this group, adapting the approach of Kassabov and Matucci1 to 1 Kassabov and Matucci 2012. the same problem in F. Conjugacy of elements in T was shown2 to 2 Belk and Matucci 2014. be decidable by Belk and Matucci; however our approach constructs explicit conjugators (when they exist). Later, we refine the description given by Matucci3 of nontorsion elements’ centralisers in T. 3 Matucci 2008, Chapter 7. * * * The first chapter introduces the world of Thompson’s groups. The sections on cyclic order, the generalised groups PLS,G and groupoid PL2, and on the Cantor space are particularly important for readers interested in the rest of the thesis. The second chapter discusses Thompson’s groups from a dynamical point of view. We summarise how F, T and V rerrange the interval, noting the distinction between dyadic and nondyadic points. Focussing on T, we introduce the rotation number and explain what we can learn from it. Amidst all this we present a number of intermediate results, forming a toolkit for use in later chapters. The third chapter studies conjugacy in T. We narrow the search space by finding constraints that a conjugator must satisfy. Next, we break the conjugacy problem into a search for a coarse and fine conjugator, the product of which—if they exist—is a bona fide conjugator. We solve these search problems,4 and thus solve the conjugacy problem in T. 4 Lemma 3.3.2 and Algorithms 3.3.5 and 3.4.8. In the fourth chapter, we study element centralisers in T via a particular group extension. We focus on nontorsion elements, providing small details missing from Matucci’s proof which identifies the extension’s kernel.5 We explain how to find the size of the extension’s quotient, by 5 Theorem 4.2.1 and Remark 4.2.2. reducing the problem to a search for coarse conjugators.6 6 Algorithm 4.2.3. The final chapter describes the extension structure of CT(α) in more detail.7 We do so by classifying α into one of four cases. In all but 7 Section 5.2. one case, this extension splits (as a wreath or direct product); in the remaining case, we identify8 exactly when the extension splits (again as 8 See Proposition 5.2.15 and the summary in in Theorem 5.3.2. a wreath product). In each case, we describe the centraliser’s structure9 9 Proposition 5.2.17. in terms of integer parameters. We then show how to construct10 an 10 Corollaries 5.2.6, 5.2.16, 5.2.18, 5.2.23 element of T whose centraliser has a given list of parameters

Surface Modification Influences on Electron Yield

Electron yield is sensitive to surface modifications such as charging effects, surface roughness, and contamination. Understanding these different surface modifications and how they influence electron yield is important to understand which measurements will accurately describe the yield of a material in its real-world environment

Update on drowning

Drowning is defined as the process of experiencing respiratory impairment from either submersion or immersion in liquid. Drowning morbidity and mortality are an under-recognised public health burden in southern Africa. Continuous concerted efforts are underway to improve awareness among recreational water users, but the prevention and management of drowning remain difficult to achieve owing to poor reporting and limited resources. Priorities for both prehospital and emergency department management of drowning victims include ensuring airway patency, adequate ventilation, supplemental oxygenation and rewarming for a pulsatile patient, and cardiopulmonary resuscitation with rewarming for a pulseless patient

Selective Foraging by \u3cem\u3ePogonomyrmex salinus\u3c/em\u3e (Hymenoptera: Formicidae) in Semiarid Grassland: Implications for a Rare Plant

Selective foraging by granivores can have important consequences for the structure and composition of plant communities, and potentially severe consequences for rare plant species. To understand how granivore foraging behavior affects common and rare plant species, diet selection should be viewed relative to the availability of alternative seed options, and with consideration of the individual attributes of those seeds (e.g., morphology, nutrient content). We examined the foraging decisions of Owyhee harvester ants, Pogonomyrmex salinus [Olsen], in semiarid grassland dominated by two species of grass, Poa secunda and Bromus tectorum, and two species of mustard, Sisymbrium altissimum and Lepidium papilliferum. The latter is a rare plant endemic to southwestern Idaho, and its seeds are readily consumed by P. salinus. We examined the diets of P. salinus colonies in June and July over three years and compared these values to the weekly availability of seeds on the ground in a 3-12 m radius around individual ant colonies. Small seeded species (P. secunda, S. altissimum and L. papilliferum) were usually overrepresented in the diet of ants relative to their availability, whereas the large seeds of B. tectorum were largely avoided despite being abundant and nutritious. The reduced travel time associated with carrying small seeds may overshadow differences in nutritional content among seed types, except in times when small seeds are in short supply. Lepidium papilliferum appears particularly vulnerable to seed predation, likely in part because it grows in dense patches that are easily exploited by foragers

Extracurricular Undergraduate Research: Student Perspectives and Experiences

This qualitative research examined the experiences and perspectives of undergraduate researchers to understand why they engaged in their research, what benefits they gained from the experience, and what challenges they faced in the conduct of their research