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Influence of test conditions on post-peak deformation behavior of rock
No full textUnderstanding the post-peak deformation behavior of rock is important for underground rock
engineering. Laboratory property testing is commonly employed to investigate the post-peak
deformation behavior. However, the test conditions of laboratory testing, especially the Loading
System Stiffness (LSS) of stiff test machines, are usually varied and the influence of this
variation on the test results has not been fully elucidated. In addition, studying the influence of
test conditions on the post-peak deformation behavior of rock is crucial for interpreting test
results and subsequently applying the results to rock engineering design. The goal of this dissertation is to identify how the post-peak deformation behavior of a rock
specimen is affected by three major aspects of test conditions––the specimen geometry, the
contact conditions, and the LSS. To achieve this goal, an FEM/Explicit tool was employed to
carry out numerical experiments, in which the same material property was assumed for the rock
specimens and each wanted test condition was isolated for analysis. The well-observed slenderness effect and the recently-observed cross-sectional shape effect on
the Uniaxial Compressive Strength (UCS) of rocks were studied. The modeling results suggest
that the numerical tool and models are suitable for investigating the problem and the hoop
tension theory could be flawed. Next, the cross-sectional shape effect on the post-peak
deformation behavior was investigated. The modeling results reveal that although the influence
of the cross-sectional shape on the UCS of rocks is small, the cross-sectional shape affects the
post-peak deformation behavior considerably. The actual contact condition and the end effect in true triaxial compression tests were simulated while the legitimate intermediate principal stress (2) effect was excluded from the rock material contacts are frictional and the specimen in the 2 loading direction is squat. Thus, existing 3D
empirical failure criteria based on previous true triaxial compression test results may
overestimate the rock strength.
The influence of LSS on the post-peak stress–strain relations of stable rock failure was examined.
Key loading components of stiff test machines were considered in the numerical model. The
modeling results clarify that LSS affects the post-peak stress–strain curves of rocks even when
the failure process is stable. Unless LSS is either perfectly rigid or equivalent to the critical LSS
(), the post-peak stress–strain curves obtained under various LSS (with LSS > ) are varied and
all steeper than the one under an ideal loading condition. This dissertation demonstrates the cross-sectional shape effect in the post-peak deformation stage,
the long overlooked 2 effect caused by the end effect, and the variation of post-peak stress–
strain curves due to the LSS. This dissertation also makes a contribution to examining the hoop
tension theory and recognizing the correct choice of cross-sectional shape for test specimens,
offers insights into improving 3D empirical failure criteria and true triaxial test settings, and
suggests new requirements for developing stiff test machines in the future
Calibration and commissioning of the Helium and Lead Observatory
No full textThe Helium And Lead Observatory (HALO) is a dedicated supernova detector at SNOLAB
consisting of 79 tonnes of lead instrumented with 128 3He-filled neutron counters.
A burst of neutrinos from a supernova will interact with the lead and result in a burst of
neutrons, detectable by the counters. This burst can be identified as a supernova signal.
The previously existing HALO Monte Carlo simulation was revised to better represent
the detector and evaluate its supernova response. The composition of the paint used on
the lead blocks was estimated using new and previous measurements. Other geometry
updates were checked with neutron capture simulations to verify their implementation.
To verify the detection efficiencies of the Monte Carlo simulation, a 252Cf neutron source
was deployed in the 40 copper calibration tubes in the detector. The high neutron multiplicity
in Cf fissions allowed for the source strength to be determined along with the
neutron capture efficiency by an analysis of the relative population of the detected multiplicities.
This verified the Monte Carlo simulation’s results and gave an overall efficiency
for the detection of supernova-induced neutrons of (27.61 0.17)%.
Backgrounds to the detection of supernovae include neutrons leaking into the detector
from the lab, the spontaneous fission of uranium inside the detector, and muon-induced
spallation events in and around the detector. These factors along with the false positive
rates specified by the Supernova EarlyWarning System (SNEWS) limit the trigger threshold
to 4 neutrons detected in two seconds, giving a detection range of about 13.7 kpc for
supernovae with an average neutrino energy of 18 MeV and a pinching parameter of 2
Production and characterization of polystyrene resins containing fine activated carbon particles
No full textThe development of high capacity adsorbent using engineered activated carbon fines
technology, and their ability to extract gold from solution is presented. The unique
feature of these adsorbents is their ability to adsorb gold ions from low concentration
solutions like mine effluent as well as from leached solutions in gold mills.
Production of polystyrene ion exchange resins containing fine activated carbon
particles denoted, PSAC, (Polystyrene Activated Carbon) and their gold stripping
kinetics were studied. Polystyrene beads were prepared by simple suspension
polymerization. However, addition of fine activated carbon (AC) during suspension
polymerization was not successful in producing small beads, but rather a
conglomerated mass, which was then broken up and shaped into smaller beads. PSAC
beads were also produced by co-extrusion of polystyrene with activated carbon and by
physical adsorption of activated carbon onto raw polystyrene beads in an autoclave at
a temperature above the glass transition temperature of polystyrene. Stripping tests
were performed which identified the latter bead type as being the most promising
form of PSAC bead for future research. The work was aimed at optimizing the
production of the beads in terms of their physical and chemical properties. This work
led to the development of a new polystyrene/activated carbon ion exchange bead as an
alternative to pure activated carbon. A mini-elution column was also designed to carry
out the test work to study the performance of beads and loaded fine carbon stripping
parameters under typical industrial conditions. Further development of this research
may lead to a new method of stripping loaded fine carbon on mine sites as part of the
existing gold milling and extracting circuits
The Noojamadaa Project: using visual research methods to elicit Indigenous women’s perspectives on healthy relationships and support reconciliation in Canada
No full textIndigenous women experience higher rates of intimate partner violence (IPV), when compared
with non-Indigenous women. Little research has focused on Indigenous women's perspectives of
IPV. Three Northern Ontario First Nations communities wished to collaborate with researchers
on IPV research. To provide women’s perspectives on IPV, groups of participants were
established in each community (n=3). Participants (n=23) chose to approach research on
IPV from a strengths-based approach and, together with researchers, transformed the photovoice
method to research according to Indigenous worldviews. Gaataa’aabing is a new visual research
method which adapts to the cultural values of participants and emphasizes participant-desired
outcomes as a required result of research. Video footage and images from group sessions on IPV
were used to create an educational video that promotes cultural safety for service providers who
work with Indigenous women, shares Indigenous women’s perspectives on healthy relationships,
highlights strengths which might help address IPV, and works toward reconciliation
Knowledge of the effects of gestational alcohol consumption and FASD in an Ontarian sample
Get PDFThe current document is a two-paper manuscript-based thesis investigating what women in
Ontario know about drinking during the gestational period. Though there have been many studies
investigating what women in various countries and locations know about drinking during
pregnancy, there is a lack of recent data focusing on Ontario, Canada. Both papers use a surveybased
approach to answer the research questions posed in each respective manuscript. The first
paper explored what women currently know about drinking during pregnancy and what
individual characteristics may influence endorsement of drinking behaviours. The majority of
participants did not endorse drinking behaviours, however, a small but substantial portion of the
population still endorses drinking. The second manuscript addressed where individuals receive
their information about drinking during the gestational period. Results indicated that women in
Ontario saw information in print and news media, but would most prefer to get their information
from health care professionals. Implications in terms of education and prevention are discussed
Broadband optical wireless communications for the teleoperation of mining equipment
No full textThe current level of technological advancement of our civilization serving more than seven
billion human population requires new sources of biotic and abiotic natural resources. The
depletion and scarcity of high-grade mineral deposits in dry land are forcing the Natural Re-
sources industry to look for alternate sources in underwater environments and outer space,
requiring the creation of reliable broadband omnidirectional wireless communication systems
that allows the teleoperation of exploration and production equipment. Within these ob-
jectives, Optical Wireless Communications (OWC) are starting to be used as an alternative
or complement to standard radio systems, due to important advantages that optical wave-
lengths have to transmit data: potential for Terabit/s bit rates, broadband operation in
underwater environments, energy e ciency and better protection against interference and
eavesdropping. This research focus in two crucial design aspects required to implement
broadband OWC systems for the teleoperation of mining equipment: high bandwidth wide
beam photon emission and low noise omnidirectional Free-Space Optical (FSO) receivers.
Novel OWC omnidirectional receivers using guided wavelength-shifting photon concentra-
tion are experimented in over 100 meters range vehicle teleoperation
Integrated Multi-Parameter Exploration Footprints of the Canadian Malartic Disseminated Au, McArthur River-Millennium Unconformity U, and Highland Valley Porphyry Cu Deposits: Preliminary Results from the NSERC-CMIC Mineral Exploration Footprints Research Network
No full textMineral exploration in Canada is increasingly focused on concealed and deeply buried targets, requiring more effective tools to detect large-scale ore-forming systems and to vector from their most distal margins to their high grade cores. A new generation of ore system models is required to achieve this. The Mineral Exploration Footprints Research Network is a consortium of 70 faculty, research associates, and students from 20 Canadian universities working with 30 mining, mineral exploration, and mining service providers to develop new approaches to ore system modelling based on more effective integration and visualization of multi-parameter geological-structural-mineralogical-lithogeochemical-petrophysical-geophysical exploration data. The Network is developing the next generation ore system models and exploration strategies at three sites based on integrated data visualization using self-consistent 3D Common Earth Models and geostatistical/machine learning technologies. Thus far over 60 footprint components and vectors have been identified at the Canadian Malartic stockwork-disseminated Au deposit, 20–30 at the McArthur-Millennium unconformity U deposits, and over 20 in the Highland Valley porphyry Cu system. For the first time, these are being assembled into comprehensive models that will serve as landmark case studies for data integration and analysis in the today’s challenging exploration environment
Modeling of plasma dynamics during pulsed electron beam ablation of graphite.
No full textRecent advances in the field of plasma nanofabrication suggest that plasma-based technologies
may replace many of the conventional chemical and thermal routes in the synthesis of
nanomaterials (with at least one dimension below 100 nm) and thin films. In contrast to the
conventional processing routes, where only neutral species are involved, a plasma is made up of
energetic species including ions, electrons, and excited molecules in addition to neutrals. Due to
the highly energetic nature of interactions among these species and with other surfaces (substrates),
a plasma allows for the formation of materials at higher rates even though their concentrations
might be low as compared with those of neutral species in non-plasma based methods. While the
mechanisms of the various interactions in a plasma are undoubtedly complex and require a
fundamental understanding, they offer new opportunities for material nanofabrication. Pulsed electron beam ablation (PEBA) has recently emerged as a novel and promising technique
for high quality thin films growth. Pulsed electron beam film deposition consists of many physical
processes including target material heating, target ablation, plasma plume expansion, and film
growth on a substrate. Electron beam ablation is a complex process, which comprises heating,
phase change, and removal of a fine fraction from the target surface. Ablation strongly affects the
space distribution, composition, mass transfer processes, which in turn has a critical bearing on
the structure, stoichiometry and properties of thin films. Plasma plume expansion into an ambient
gas is a fundamental issue in PEBA as the quality of thin films deposited onto the substrate depends
on the composition, energy and density of particles ejected from the target. A one-dimensional heat conduction model is presented to investigate the heating and ablation of a
graphite target upon interaction with a polyenergetic electron beam. The effect of electron beam efficiency, power density, accelerating voltage, and Knudsen layer just above the target surface
during ablation are taken into account in the model. Phase transition induced during ablation is
considered through the temperature dependent thermodynamic properties of graphite. The
temperature distribution, surface receding velocity, melting depth, ablation depth, and ablated
mass per unit area are numerically simulated. Upon ablation, plasma expansion, induced by
interaction of a nanosecond electron beam pulse (~100 ns) with a graphite target in an argon
atmosphere at reduced pressure, was investigated by solving gas-dynamics equations. The spatiotemporal
profiles of the temperature, pressure, velocity, and density of the plasma plume are
numerically simulated for a beam efficiency of 0.6 and accelerating voltage of 15 kV. Each model
is validated by comparing some of the obtained simulation results with experimental data available
in the literature
The effects of learning on the eating responses of rats exposed to stress
No full textLiterature examining the relationship between stress and eating behaviour reveals that while both decreased and increased eating are observed in response to stress, it is unclear what factors determine whether an individual will typically decrease or increase eating during stress. The present study sought to explore whether decreased/increased eating in response to future stressors, could be elicited by prior associations between decreased/increased eating and the presentation of a stressor, through operant conditioning. The “Conditioned Non-Eaters” (CNE) group received punishment training while the “Conditioned Eaters” (CE) group received negative reinforcement training in response to a noise stressor, and the Control group received no operant training. Conditioning trials were followed by a series of five tests exposing subjects to no stress, the noise stimulus, threat of shock, restraint, and a tail-pinch. Results indicate that group differences in eating were observed during exposure to the noise stimulus following training, but not in the absence of stress, and consistent group differences to the noise stress were further observed during exposure to novel stressors. These findings suggest that past operant associations between eating and a specific stressor can generalize to other stressors, influencing individuals to respond to stress exposure in a way that has be reinforced in the past
"If we have the knowledge, then that is power to help our expectant moms": Northern Ontario health care students' knowledge and attitudes addressing alcohol consumption during pregnancy.
No full textThe current document is a paper-based dissertation investigating health care professionals’ knowledge, attitudes, and self-efficacy regarding fetal alcohol spectrum disorder (FASD) and alcohol consumption during pregnancy. This dissertation incorporates findings from a secondary data analysis of health care professionals in Ontario, as well as original data from health care students training in Northern Ontario. While previous research has demonstrated that health care professionals remain under-educated concerning FASD and alcohol use during pregnancy, limited research has investigated the knowledge and experiences of health care students. The first paper included is a secondary data analysis of the 2001-2002 Fetal Alcohol Syndrome Survey for Health Professionals. Ontario-specific data (N=834) were used to examine the awareness of FASD held by various provider groups in both rural and urban settings. Results from this study indicate that many physicians, midwives, and other health care professionals may have inconsistent knowledge regarding the impact of prenatal alcohol exposure, resulting in mixed messages for women of childbearing age about the safety of alcohol use during pregnancy. The second paper included is a qualitative analysis of scenario-based vignettes regarding alcohol use during pregnancy. Although almost all students (N=21) recognized that no alcohol consumption during pregnancy is the safest recommendation, many students noted that this advice is not always conveyed to pregnant women. Finally, the third paper included is also a qualitative analysis based on a thematic analysis of scenario-based vignettes and semistructured interviews. The third paper explores health care students’ (N=21) attitudes and beliefs about women who may continue to consume alcohol throughout their pregnancy and presents the often stereotypical and stigmatic perceptions of FASD and alcohol use during pregnancy held by health care professionals. Recommendations and implications for increasing students’ and professionals’ knowledge and self-efficacy regarding FASD management and prevention are discussed