Regional Decline of Coral Cover in the Indo-Pacific: Timing, Extent, and Subregional Comparisons

A number of factors have recently caused mass coral mortality events in all of the world's tropical oceans. However, little is known about the timing, rate or spatial variability of the loss of reef-building corals, especially in the Indo-Pacific, which contains 75% of the world's coral reefs

LES and FW-H Prediction of Aeroacoustic Noise for a SD 7037 Airfoil for Wind Turbine Applications

The aeroacoustic noise generated by wind turbines poses issues with the implementation of this renewable energy technology. The use of a fully analytical model for predicting airfoil noise could serve as a crucial tool in the design phase of new turbines or noise reduction technologies. This work uses a combination of Large Eddy Simulation (LES) and the Ffowcs-Williams and Hawkings (FW-H) acoustic model to predict the noise generated by a 2D segment of the SD 7037(c) airfoil. The simulations are performed at a static angle of attack (AOA) and at a Reynolds number typical for small scale wind turbines of Re = 4.3×10⁴. The flow and acoustic results are validated against experimental results conducted by the Wind Energy Group at the University of Waterloo. This model was able to accurately predict the flow field and acoustic results for the 0° AOA, and determined the source of the 4.1 kHz tone to be 2D vortex shedding from the trailing edge (TE) and the 3.4 kHz tone to come from the transition from 2D to 3D boundary layer behaviour. The 1° AOA simulation, while able to simulate the flow and broadband acoustic spectra, requires further investigation to simulate the complex boundary layer transition behaviours required to predict the 3.4 kHz tone. Overall, this method proved to be an effective predictive tool for airfoil self-noise at static AOAs.Natural Science and Engineering Research Council || Ontario Graduate Scholarship Program || TD Bank Graduate Scholarship in the Environment

Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs

Monolayers of transition metal dichalcogenides are promising materials for valleytronic applications, since they possess two individually addressable excitonic transitions at the non-equivalent $K$ and $K'$ points with different spins, selectively excitable with light of opposite circular polarization. Here, it is of crucial importance to understand the elementary processes determining the lifetime of these optically injected valley excitons. In this study, we perform microscopic calculations based on a Heisenberg equation of motion formalism to investigate the efficiency of the intervalley coupling in the presence (W based TMDCs) and absence (Mo based TMDCs) of energetically low lying momentum-dark exciton states. While we predict a valley exciton lifetime on the order of some hundreds of fs in the absence of low lying momentum-dark states we demonstrate a strong quenching of the valley lifetime in the presence of such states

Effect of diet versus diet and exercise on weight loss and body composition in class II and III obesity: A systematic review

Class II and III obesity (BMI >35 kg·m2) have increased dramatically in recent years. Current clinical guidelines suggest diet and exercise as first line treatment for adults throughout the spectrum of overweight and obesity. However, to date there is no systematic review that examines the effects of diet and exercise on this high risk population. This systematic review will examine the combined effects of diet versus diet and exercise on body composition in severe obesity. Medline and Cinahl were searched for randomised controlled trials comparing diet and exercise to diet alone. Studies published until July 2013 were included if they used reliable methods for analysing body composition in adults with BMI ≥ 35 kg·m2. Five of 459 studies met the inclusion criteria. Two studies, both in older adults, reported that exercise reduced lean mass loss during weight loss. Two studies showed that exercise facilitated (greater) fat mass loss. The remaining study reported no differences in body composition when exercise is added to energy restriction. Exercise training during energy restriction for individuals with BMI ≥35 kg.m2 may influence body composition outcomes but the evidence is limited. Further studies should focus on the efficacy of different exercise protocols during energy restriction for this population in order to better inform decision making for the treatment of severe obesity in respect to favourable body composition outcomes

Optimal path planning for nonholonomic robotics systems via parametric optimisation

Abstract. Motivated by the path planning problem for robotic systems this paper considers nonholonomic path planning on the Euclidean group of motions SE(n) which describes a rigid bodies path in n-dimensional Euclidean space. The problem is formulated as a constrained optimal kinematic control problem where the cost function to be minimised is a quadratic function of translational and angular velocity inputs. An application of the Maximum Principle of optimal control leads to a set of Hamiltonian vector field that define the necessary conditions for optimality and consequently the optimal velocity history of the trajectory. It is illustrated that the systems are always integrable when n = 2 and in some cases when n = 3. However, if they are not integrable in the most general form of the cost function they can be rendered integrable by considering special cases. This implies that it is possible to reduce the kinematic system to a class of curves defined analytically. If the optimal motions can be expressed analytically in closed form then the path planning problem is reduced to one of parameter optimisation where the parameters are optimised to match prescribed boundary conditions.This reduction procedure is illustrated for a simple wheeled robot with a sliding constraint and a conventional slender underwater vehicle whose velocity in the lateral directions are constrained due to viscous damping

Empirical Models of Transitions between Coral Reef States: Effects of Region, Protection, and Environmental Change

There has been substantial recent change in coral reef communities. To date, most analyses have focussed on static patterns or changes in single variables such as coral cover. However, little is known about how community-level changes occur at large spatial scales. Here, we develop Markov models of annual changes in coral and macroalgal cover in the Caribbean and Great Barrier Reef (GBR) regions

On the Exponentials of Some Structured Matrices

In this note explicit algorithms for calculating the exponentials of important structured 4 x 4 matrices are provided. These lead to closed form formulae for these exponentials. The techniques rely on one particular Clifford Algebra isomorphism and basic Lie theory. When used in conjunction with structure preserving similarities, such as Givens rotations, these techniques extend to dimensions bigger than four.Comment: 19 page

Visualising text co-occurrence networks

We present a tool for automatically generating a visual summary of unstructured text data retrieved from documents, web sites or social media feeds. Unlike tools such as word clouds, we are able to visualise structures and topic relationships occurring in a document. These relationships are determined by a unique approach to co-occurrence analysis. The algorithm applies a decaying function to the distance between word pairs found in the original text such that words regularly occurring close to each other score highly, but even words occurring some distance apart will make a small contribution to the overall co-occurrence score. This is in contrast to other algorithms which simply count adjacent words or use a sliding window of fixed size. We show, with examples, how the network generated can be presented in tree or graph format. The tree format allows for the user to interact with the visualisation and expand or contract the data to a preferred level of detail. The tool is available as a web application and can be viewed using any modern web browse