Environmental controls on bioturbation processes in marine benthic habits

Through bioturbation, the macrofauna mediate chemical, physical and biological processes in marine benthic ecosystems. Because of the importance of bioturbation as ecosystem mediator, various studies have been conducted on bioturbation intensity and depth, and the relation of bioturbation processes to environmental condition and ecosystem state. This thesis builds on those previous studies, using a standard field and analytical protocol and by expanding the geographical scale to three climatic regions along Canada’s East Coast and Arctic margins, the Arctic Archipelago, the coastal Subarctic (Labrador Fjords), and the temperate continental climate zone (Gulf of Maine and adjacent Scotian shelf/slope). This Ph.D. study provides a comprehensive assessment of environmental influences on bioturbation along gradients in latitude and ocean depth. Bioturbation intensity, mixing depth, and bioturbation structures were studied in relation to the quantity and quality of potential food sources (organic matter) and substrate characteristics to gain an understanding of the environmental controls on bioturbation in these regions. The three main research chapters of this thesis are divided based on the contrasting climatic and geographical regions studied. The analytical approach included seabed sampling with a boxcorer, describing the sedimentary fabric and bioturbation structures by X-radiography, estimating bioturbation intensity and depth applying a biodiffusion model to particle tracer profiles of ²¹⁰Pbₓs, ²²⁸Thₓs, ²³⁴Thₓs, and chlorophyll-a, and analyzing benthic organic matter and substrate characteristics. Strong regional and cross-climatic relations of bioturbation processes with combinations of environmental factors were observed. In particular, bioturbation depth and the vertical extent of bioturbation structures responded to the environmental patterns observed and, therefore, represented potentially applicable predictors of environmental conditions and ecosystem state. The results of this Ph.D. study may be further extended to other geographical regions with similar environmental characteristics to predict the effects of benthic habitat alterations through environmental stresses on a global scale. Integrated with biological data produced by fellow CHONe scientists the presented data may provide valuable information about functional roles of macrofaunal species and community traits in marine benthic ecosystems along Canada’s extensive East Coast and Arctic margins.

Regional flood frequency analysis for Newfoundland and Labrador using the L-Moments index-flood method

The L-moments based index-flood procedure had been successfully applied for Regional Flood Frequency Analysis (RFFA) for the Island of Newfoundland in 2002 using data up to 1998. This thesis, however, considered both Labrador and the Island of Newfoundland using the L-Moments index-flood method with flood data up to 2013. For Labrador, the homogeneity test showed that Labrador can be treated as a single homogeneous region and the generalized extreme value (GEV) was found to be more robust than any other frequency distributions. The drainage area (DA) is the only significant variable for estimating the index-flood at ungauged sites in Labrador. In previous studies, the Island of Newfoundland has been considered as four homogeneous regions (A,B,C and D) as well as two Water Survey of Canada's Y and Z sub-regions. Homogeneous regions based on Y and Z was found to provide more accurate quantile estimates than those based on four homogeneous regions. Goodness-of-fit test results showed that the generalized extreme value (GEV) distribution is most suitable for the sub-regions; however, the three-parameter lognormal (LN3) gave a better performance in terms of robustness. The best fitting regional frequency distribution from 2002 has now been updated with the latest flood data, but quantile estimates with the new data were not very different from the previous study. Overall, in terms of quantile estimation, in both Labrador and the Island of Newfoundland, the index-flood procedure based on L-moments is highly recommended as it provided consistent and more accurate result than other techniques such as the regression on quantile technique that is currently used by the government.

Active suspension development based on energy analysis

This research focuses on developing active suspension optimal controllers for two linear and non-linear half-car models. A detailed comparison between quarter-car and half-car active suspension approaches is provided for improving two important scenarios in vehicle dynamics, i.e. ride quality and road holding. Having used a half-car vehicle model, heave and pitch motion are analyzed for those scenarios, with cargo mass as a variable. The governing equations of the system are analysed in a multi-energy domain package, i.e., 20-Sim. System equations are presented in the bond-graph language to facilitate calculation of energy usage. The results present optimum set of gains for both ride quality and road holding scenarios are the gains which has derived when maximum allowable cargo mass is considered for the vehicle. The energy implications of substituting passive suspension units with active ones are studied by considering not only the energy used by the actuator, but also the reduction in energy lost through the passive damper. Energy analysis showed less energy was dissipated in shock absorbers when either quarter-car or half-car controllers were used instead of passive suspension. It was seen that more energy could be saved by using half-car active controllers than the quarter-car ones. Results also proved that using active suspension units, whether quarter-car or half-car based, under those realistic limitations is energy-efficient and suggested.

Impacts of newly established non-indigenous green crab (Carcinus maenas) on native fauna in Placentia Bay, Newfoundland

The recent invasion of the European green crab (Carcinus maenas) populations in Placentia Bay, Newfoundland and Labrador (NL) raises great concern about potential impacts on local fisheries and native biodiversity. Green crab are highly adaptable and in both native and invaded areas, green crab are well established predators that can outcompete other similarly sized decapods. The main objectives of this thesis were to: 1) identify the native species that green crab compete with for resources; 2) determine the depths and substrate types in which these interactions likely occur; 3) assess the indirect effects of green crab on native crustaceans and their changes in behavior; 4) assess the impacts of green crab on benthic community structure; 5) compare the NL population with other Atlantic Canadian populations in terms of competitive abilities; and 6) compare morphological features of the NL population with other Atlantic Canadian populations. I found that green crab overlap in space and diet with both rock crab (Cancer irroratus) and American lobster (Homarus americanus), potentially leading to a shift in habitat. Laboratory studies on naïve juvenile lobster also suggested shifts in behavior related to green crab, in that lobster decreased foraging activity and increased shelter use in the presence of green crab. Benthic community analyses showed fewer species in mud, sand, and eelgrass sites heavily populated by green crab compared to sites without green crab, although results depended on the taxa involved and I could not eliminate environmental differences through a short term caging study. Foraging ability of green crab varied in intraspecific competition experiments, with populations from NL and Prince Edward Island dominating longer-established populations from Nova Scotia and New Brunswick. Additional studies excluded claw size as a factor driving these results and behavioral differences likely reflected differences in invasion time and population genetics. Overall, green crab in Placentia Bay appear to be altering community structure of benthic invertebrates through predation and they also appear to indirectly impact native crustaceans through competition.

Effects of seasonally varying temperature and salinity on the dynamics of sea lice (Lepeophtheirus salmonis)

Sea lice (Lepeophtheirus salmonis) are an economically significant parasite in salmonid aquaculture. They exhibit temperature-dependent development rates and salinity-dependent mortality, which can greatly impact sea lice population dynamics, but no deterministic models have incorporated these seasonal variables. To understand how seasonality affects sea lice population dynamics, I derive a delay differential equation model with temperature and salinity dependence. I find that peak reproductive output in Newfoundland and British Columbia differs by four months. A sensitivity analysis shows sea lice abundance is most sensitive to variation in mean annual water temperature and salinity, whereas it is lease sensitive to infection rate. Additionally, I investigate the effects of production cycle timing on sea lice management and find that optimal production cycle start times are between the 281st and 337th days of the year in Newfoundland. I also demonstrate that adjusting follow-up treatment timing in response to temperature can improve treatment regimes. My results suggest that effective sea lice management requires consideration of local temperature and salinity patterns.

Time-domain simulation of wave-induced ship motions by a Rankine panel method

In this thesis, a numerical program has been developed to simulate the wave-induced ship motions in the time domain. Wave-body interactions have been studied for various ships and floating bodies through forced motion and free motion simulations in a wide range of wave frequencies. A three-dimensional Rankine panel method is applied to solve the boundary value problem for the wave-body interactions. The velocity potentials and normal velocities on the boundaries are obtained in the time domain by solving the mixed boundary integral equations in relation to the source and dipole distributions. The hydrodynamic forces are calculated by the integration of the instantaneous hydrodynamic pressures over the body surface. The equations of ship motion are solved simultaneously with the boundary value problem for each time step. The wave elevation is computed by applying the linear free surface conditions. A numerical damping zone is adopted to absorb the outgoing waves in order to satisfy the radiation condition for the truncated free surface. A numerical filter is applied on the free surface for the smoothing of the wave elevation. Good convergence has been reached for both forced motion simulations and free motion simulations. The computed added-mass and damping coefficients, wave exciting forces, and motion responses for ships and floating bodies are in good agreement with the numerical results from other programs and experimental data.

A PHR system with policy-based fine-grained access control and revocation mechanism

Collaborative sharing of information is becoming much more needed technique to achieve complex goals in today's fast-paced tech-dominant world. Personal Health Record (PHR) system has become a popular research area for sharing patients informa- tion very quickly among health professionals. PHR systems store and process sensitive information, which should have proper security mechanisms to protect patients' private data. Thus, access control mechanisms of the PHR should be well-defined. Secondly, PHRs should be stored in encrypted form. Cryptographic schemes offering a more suitable solution for enforcing access policies based on user attributes are needed for this purpose. Attribute-based encryption can resolve these problems, we propose a patient-centric framework that protects PHRs against untrusted service providers and malicious users. In this framework, we have used Ciphertext Policy Attribute Based Encryption scheme as an efficient cryptographic technique, enhancing security and privacy of the system, as well as enabling access revocation. Patients can encrypt their PHRs and store them on untrusted storage servers. They also maintain full control over access to their PHR data by assigning attribute-based access control to selected data users, and revoking unauthorized users instantly. In order to evaluate our system, we implemented CP-ABE library and web services as part of our framework. We also developed an android application based on the framework that allows users to register into the system, encrypt their PHR data and upload to the server, and at the same time authorized users can download PHR data and decrypt it. Finally, we present experimental results and performance analysis. It shows that the deployment of the proposed system would be practical and can be applied into practice.

Novel double-sided linear generator for the wave energy conversion

The direct drive point absorber is a robust and efficient system for wave energy harvesting, where the linear generator represents the most complex part of the system. Therefore, its design and optimization are crucial tasks. The tubular shape of a linear generator’s magnetic circuit offers better permanent magnet flux encapsulation and reduction in radial forces on the translator due to its symmetry. A double stator topology can improve the power density of the linear tubular machine. Common designs employ a set of aligned stators on each side of a translator with radially magnetized permanent magnets. Such designs require doubling the amount of permanent magnet material and lead to an increase in the cogging force. The design presented in this thesis utilizes a translator with buried axially magnetized magnets and axially shifted positioning of the two stators such that no additional magnetic material, compared to single side machine, is required. In addition to the conservation of magnetic material, a significant improvement in the cogging force occurs in the two phase topology, while the double sided three phase system produces more power at the cost of a small increase in the cogging force. The analytical and the FEM models of the generator are described and their results compared to the experimental results. In general, the experimental results compare favourably with theoretical predictions. However, the experimentally observed permanent magnet flux leakage in the double sided machine is larger than predicted theoretically, which can be justified by the limitations in the prototype fabrication and resulting deviations from the theoretical analysis.

Magnetic ordering in Er₂Ti₂O₇ and elastic softening in Tb₂Ti₂O₇

Geometric frustration occurs in the rare earth pyrochlores due to magnetic rare earth ions occupying the vertices of the network of corner-sharing tetrahedra. In this research, we have two parts. In the first one we study the phase transition to the magnetically ordered state at low temperature in the pyrochlore Er₂Ti₂O₇. The molecular field method was used to solve this problem. In the second part, we analyse the crystal electric field Hamiltonian for the rare earth sites. The rather large degeneracy of the angular momentum J of the rare earth ion is lifted by the crystal electric field due to the neighboring ions in the crystal. By rewriting the Stevens operators in the crystal electric field Hamiltonian ᴴCEF in terms of charge quadruple operators, we can identify unstable order parameters in ᴴCEF . These may be related to lattice instabilities in Tb₂Ti₂O₇.

Computational fluid dynamics (CFD) based approach to consequence assessment of accidental release of hydrocarbon during storage and transportation

This thesis investigated the risk of accidental release of hydrocarbons during transportation and storage. Transportation of hydrocarbons from an offshore platform to processing units through subsea pipelines involves risk of release due to pipeline leakage resulting from corrosion, plastic deformation caused by seabed shakedown or damaged by contact with drifting iceberg. The environmental impacts of hydrocarbon dispersion can be severe. Overall safety and economic concerns of pipeline leakage at subsea environment are immense. A large leak can be detected by employing conventional technology such as, radar, intelligent pigging or chemical tracer but in a remote location like subsea or arctic, a small chronic leak may be undetected for a period of time. In case of storage, an accidental release of hydrocarbon from the storage tank could lead pool fire; further it could escalate to domino effects. This chain of accidents may lead to extremely severe consequences. Analyzing past accident scenarios it is observed that more than half of the industrial domino accidents involved fire as a primary event, and some other factors for instance, wind speed and direction, fuel type and engulfment of the compound. In this thesis, a computational fluid dynamics (CFD) approach is taken to model the subsea pipeline leak and the pool fire from a storage tank. A commercial software package ANSYS FLUENT Workbench 15 is used to model the subsea pipeline leakage. The CFD simulation results of four different types of fluids showed that the static pressure and pressure gradient along the axial length of the pipeline have a sharp signature variation near the leak orifice at steady state condition. Transient simulation is performed to obtain the acoustic signature of the pipe near leak orifice. The power spectral density (PSD) of acoustic signal is strong near the leak orifice and it dissipates as the distance and orientation from the leak orifice increase. The high-pressure fluid flow generates more noise than the low-pressure fluid flow. In order to model the pool fire from the storage tank, ANSYS CFX Workbench 14 is used. The CFD results show that the wind speed has significant contribution on the behavior of pool fire and its domino effects. The radiation contours are also obtained from CFD post processing, which can be applied for risk analysis. The outcome of this study will be helpful for better understanding of the domino effects of pool fire in complex geometrical settings of process industries. The attempt to reduce and prevent risks is discussed based on the results obtained from the numerical simulations of the numerical models.

People and big cats (Panthera onca and Puma concolor) of the Atlantic Forest, Brazil

Conservation of large felids is not only about collecting ecological information; it is also about understanding people’s values, beliefs, attitudes and behaviour. The overarching goal of this thesis is to assess the relationship between people and jaguars and pumas. Specifically by contributing to the understanding of public acceptance of big cats, as well as the forces (cognitive and social) that influence people’s acceptability. Self-administered questionnaires (n=326) were applied to rural residents outside two protected areas in the State of Sao Paulo: Intervales and PETAR state parks. Findings showed that the acceptability of killing big cats varied accordingly to attitudinal type (positive and negative). Additionally, acceptability of jaguars and pumas was influenced by existence values, attitudes and park credibility. Human dimensions research helped in understanding the relationship between people and the big cats, highlighting the need, for example, to improve the credibility of the parks in the communities and to decrease the fear of jaguars and pumas.

The effects of foam rolling on muscular co-activation around the knee joint

The major objectives of this thesis were to determine if foam rolling had any effect on antagonist muscle activation and whether those changes would alter muscular co-activation patterns. The results from this thesis along with current literature will help clinicians to develop adequate exercise prescription for rehabilitative and pre-activity purposes. The existing literature has shown that foam rolling or roller massagers can increase range of motion (ROM), improve performance, and alter pain perception, however little research exists regarding changes in muscle activation following foam rolling. This study developed a reliable method for measuring muscle activation around the knee joint and using that method found that foam rolling the quadriceps can impair hamstrings muscle activation likely due to greater levels of perceived pain when rolling the quadriceps.

Design, development and control of a new generation high performance linear actuator for parallel robots and other applications

The main focus of this research is to design and develop a high performance linear actuator based on a four bar mechanism. The present work includes the detailed analysis (kinematics and dynamics), design, implementation and experimental validation of the newly designed actuator. High performance is characterized by the acceleration of the actuator end effector. The principle of the newly designed actuator is to network the four bar rhombus configuration (where some bars are extended to form an X shape) to attain high acceleration. Firstly, a detailed kinematic analysis of the actuator is presented and kinematic performance is evaluated through MATLAB simulations. A dynamic equation of the actuator is achieved by using the Lagrangian dynamic formulation. A SIMULINK control model of the actuator is developed using the dynamic equation. In addition, Bond Graph methodology is presented for the dynamic simulation. The Bond Graph model comprises individual component modeling of the actuator along with control. Required torque was simulated using the Bond Graph model. Results indicate that, high acceleration (around 20g) can be achieved with modest (3 N-m or less) torque input. A practical prototype of the actuator is designed using SOLIDWORKS and then produced to verify the proof of concept. The design goal was to achieve the peak acceleration of more than 10g at the middle point of the travel length, when the end effector travels the stroke length (around 1 m). The actuator is primarily designed to operate in standalone condition and later to use it in the 3RPR parallel robot. A DC motor is used to operate the actuator. A quadrature encoder is attached with the DC motor to control the end effector. The associated control scheme of the actuator is analyzed and integrated with the physical prototype. From standalone experimentation of the actuator, around 17g acceleration was achieved by the end effector (stroke length was 0.2m to 0.78m). Results indicate that the developed dynamic model results are in good agreement. Finally, a Design of Experiment (DOE) based statistical approach is also introduced to identify the parametric combination that yields the greatest performance. Data are collected by using the Bond Graph model. This approach is helpful in designing the actuator without much complexity.