University of New Brunswick
  • Fredericton, New Brunswick, Canada
Recent publications
Statistical continuum mechanics theory was used to simulate the inelastic stress of polycrystalline materials using two-point statistics. For the experimental part, the Electron beam melting (EBM) technique (Arcam EBM Q10 additive machine) was used to fabricate cylindrical rods of Ti-6Al-4V both in horizontal and vertical directions. Electron backscatter diffraction (EBSD) technique was employed to achieve statistically reliable orientation maps of vertically and horizontally printed samples. In this study, high strain rate compression tests at six different strain rates were performed, and the stress-strain curves were generated. This work is amongst the first attempts to model the microstructure of additively manufactured hexagonal alloys under compressive loadings using the statistical continuum mechanics theory. The model is capable of simulating reasonably large microstructures (statistically representative) with a practical computational cost and accuracy, unlike numerical models that require a high computational cost. It should be noted that in additive manufacturing, due to large grains and high anisotropy, microstructures used in the simulations should be large enough to include sufficient information from the material’s structure. Therefore, using finite element models would be very challenging here. On the other hand, the statistical continuum mechanics theory uses the statistical representation of the material’s characteristics for solving the governing equations with Green’s function that enables this methodology to use more microstructure characteristic information without having a noticeable change to the computational cost. The proposed model in this study uses different microstructure characteristics such as crystal grain orientation, total slip systems, active slip systems, gain morphology, and chemical phases that are obtained from EBSD images for simulating the inelastic mechanical behavior of polycrystalline materials. Although this model simulates polycrystalline materials by considering various crystal and grain information, unlike numerical methods, it doesn’t simulate the grain interactions well and we cannot study local deformation and crack nucleation sites. This model works very well for simulating the overall behavior of material instead of each individual grain and failure analysis. This model has shown a good combination of computational cost and accuracy in which the error between the simulated and experimental strength for vertical and horizontal samples was 6.21% and 8.07%, respectively.
We have been analyzing the zenith total delay (ZTD) time series provided by six REPRO3 International GNSS Service (IGS) Analysis Centers (ACs), namely, COD, ESA, GFZ, GRG, JPL, and TUG, to compare their long-term trends. Long-term here means 20 years or longer. About thirty stations have been selected globally for this purpose. The estimated ZTD time series have gone through a process of homogenization using ERA-5 derived ZTDs as reference. The homogenized data is then averaged to daily values to minimize potential influences coming from different estimation strategies adopted by individual Analysis Centers as well as to mitigate the inherent autocorrelation. Similar averaging is applied to the ERA-5 ZTDs. Two combinations, using weighted mean and (a robust) least median of squares, are being generated from the six homogenized ACs. The combinations serve as quality control to each ACs. Analysis of the trends generated from each one of the seven ZTD time series is performed looking at their similarities in both time and frequency domains. This paper showcases the methodology and early results as presented during the second International Symposium of Commission 4: Positioning and Applications. Early results are based on station ALBH in Canada, showing an inter-AC scatter is 0.47 mm/decade for the trends, 0.11 mm for the annual amplitudes, and 0.29° for the annual phase.
Alkali‐silica reaction continues to be a challenging durability issue for portland cement‐based concrete. While myriad of preventive options is known to reduce the risk of ASR, changes in availability and consistency of materials make either prescriptive or performance‐based approaches difficult to develop and then quickly adapt. In general, the research community has supported industry with practical solutions based on empirically derived relationships, mostly from accelerated test methods and to a lesser extent realistic exposure/field structures. It is time to increase the level of science behind our approach. The research team represented in this talk is investigating a new methodology that combines the alkali availability needed to initiate ASR (aggregate specific) with the available alkali from the total cementitious blend. The relationship between reactivity of a supplementary cementitious material and the ASR expansion is also explored. This keynote lecture will: 1) Explore performance‐based testing versus prescriptive approaches and why a hybrid approach should be considered ASR prevention; 2) Evaluate the relationship between accelerated laboratory tests, outdoor exposure blocks and field structures; 3) Examine the use of “non‐traditional” supplementary cementitious materials and/or chemical admixtures to prevent alkali‐silica reaction; 4) Propose future research needs and; 5) Make recommendations for how best to prevent alkali‐silica reactivity following the proposed approach.
This paper critically examines ‘kitchen sink regression’, a practice characterised by the manual or automated selection of variables for a multivariable regression model based on p values or model-based information criteria. We highlight the pitfalls of this method, using examples from perinatal/neonatal medicine, and propose more robust alternatives. The concept of directed acyclic graphs (DAGs) is introduced as a tool for describing and analysing causal relationships. We highlight five key issues with ‘kitchen sink regression’: (1) the disregard for the directionality of variable relationships, (2) the lack of a meaningful causal interpretation of effect estimates from these models, (3) the inflated alpha error rate due to multiple testing, (4) the risk of overfitting and model instability and (5) the disregard for content expertise in model building. We advocate for the use of DAGs to guide variable selection for models that aim to examine associations between a putative risk factor and an outcome and emphasise the need for a more thoughtful and informed use of regression models in medical research.
This study delves into the interplay between crystallographic texture, microstructure, and mechanical behavior in pulse laser powder bed-fused (LPBF) 316L stainless steel subjected to uniaxial tensile loading. The as-built microstructure exhibits a hierarchical arrangement spanning macro, micro, and nanoscales, showcasing chemical uniformity and minimal elemental segregation owing to the rapid cooling rate intrinsic to LPBF, distinct melt pool formations, and the emergence of nanosized silicon-rich oxides. The additive manufacturing process induces a network of dislocations, imparting twinning-induced plasticity (TWIP) behavior to 316L stainless steel. This is characterized by a distinctive five-stage strain hardening process. Maintained pre-existing dislocation networks enhance nanotwin creation, fostering interactions between different types of dislocations. Deformation-induced nanotwins contribute to a sustained elevated strain hardening rate through two stages. This effect is reinforced by the development of pronounced < 111 > and α-fiber textures, aligned with the tensile direction. Additionally, the alloy's high yield strength is attributed to the dense dislocation cell population. These dislocation cells, coupled with distributed nanooxide inclusions, facilitate the formation of nanometer-scale ductile dimples, effectively impeding crack propagation and mitigating defects compared to conventional manufacturing methods. In summary, plastic deformation hinges on dislocation glide and deformation-induced twinning, culminating in a final microstructure featuring diverse twin types and highly misoriented dislocation boundaries. This comprehensive understanding sheds light on the intricate relationship between microstructural attributes and mechanical performance in LPBF 316L stainless steel.
In the past few years, privacy concerns have grown, making the financial models of businesses more vulnerable to attack. In many cases, it is hard to emphasize the importance of monitoring things in real-time with data from Internet of Things (IoT) devices. The people who make the IoT devices and those who use them face big problems when they try to use Artificial Intelligence (AI) techniques in real-world applications, where data must be collected and processed at a central location. Federated learning (FL) has made a decentralized, cooperative AI system that can be used by many IoT apps that use AI. It is possible because it can train AI on IoT devices that are spread out and do not need to share data. FL allows local models to be trained on local data and share their knowledge to improve a global model. Also, shared learning allows models from all over the world to be trained using data from all over the world. This article looks at the IoT in all of its forms, including “smart” businesses, “smart” cities, “smart” transportation, and “smart” healthcare. This study looks at the safety problems that the federated learning with IoT (FL-IoT) area has brought to market. This research is needed to explore because federated learning is a new technique, and a small amount of work is done on challenges faced during integration with IoT. This research also helps in the real world in such applications where encrypted data must be sent from one place to another. Researchers and graduate students are the audience of our article.
Amidst the widespread consciousness and several awareness programs to combat the adverse impact of greenhouse gas emissions on the climate, Net-zero energy buildings (NZEB) have emerged as one of the potential solutions. Various factors, including the need for heavy initial capital investment, weather conditions, government regulations, policies, training and development, technology, and so forth, were figured out by carrying out a literature review and interviewing the area experts. Further, investigating the inter-contextual relationships helps to have key success factors of NZEBs in India that are multidimensional in nature. To achieve this goal, the Interpretive Structural Modelling (ISM) approach was employed to compute the mutual influence of the ten key success factors in the Indian context. The results report that favorable weather conditions, government policies, and regulations are the most crucial factors for the NZEB sectoral development in Indian contexts.
Winter cold slows ectotherm physiology, potentially constraining activities and ecological opportunities at poleward latitudes. Yet, many fishes are winter-active, facilitated by thermal compensation that improves cold performance. Conversely, winter-dormant fishes (e.g., cunner, Tautogolabrus adspersus) become inactive and non-feeding overwinter. Why are certain fishes winter-dormant? We hypothesized that winter dormancy is an adaptive behavioural response arising in poleward species that tolerate severe, uncompensated constraints of cold on their physiological performance. We predicted that below their dormancy threshold of 7-8°C, exercise and metabolic performance of cunner is greatly decreased, even after acclimation (i.e., shows above-normal, uncompensated thermal sensitivity, Q10>1-3). We measured multiple key performance metrics (e.g., C-start maximum velocity, chase swimming speed, aerobic scope) in cunner after acute exposure to 26-2°C (3°C intervals using 14°C-acclimated fish) or acclimation (5-8 weeks) to 14-2°C (3°C intervals bracketing the dormancy threshold). Performance declined with cooling and the acute Q10 of all six performance rate metrics was significantly greater below the dormancy threshold temperature (Q10(8-2°C)acute=1.5-4.9, mean=3.3) than above (Q10(14-8°C)acute=1.1-1.9, mean=1.5), inferring a cold constraint. However, 2°C acclimation (temporally more relevant to seasonal cooling) improved performance, abolishing the acute constraint (Q10(8-2°C)acclimated=1.4-3.0, mean=2.0; also c.f. Q10(14-8°C)acclimated=1.2-2.9, mean=1.7). Thus, dormant cunner show partial cold-compensation of exercise and metabolic performance, similar to winter-active species. Responsiveness to C-start stimuli, however, was greatly cold-constrained even following acclimation, suggesting dormancy involves sensory limitation. Thermal constraints on metabolic and exercise physiology are not significant drivers of winter dormancy in cunner. In fact, compensatory plasticity at frigid temperatures is retained even in a dormant fish.
Objective The objective of this scoping review is to identify, categorize, and map the types of supports and services available to at-risk mothers and their children in maternity residences. A secondary objective is to identify and map the measures used to evaluate the efficacy of these supports and services. Introduction Pregnant and parenting women and their children experiencing complex challenges related to the social determinants of health, including unstable housing and poverty, are at high-risk for long-term negative health and socioeconomic outcomes. Maternity residences may provide supports and services that improve this population’s outcomes, however, there is little understanding of what services are offered and how efficacious they may be. A comprehensive overview of supports and services in maternity residences, as well as identifying the measures used to evaluate the efficacy of the supports and services, will provide the foundation to evaluate these services and outcomes and inform the development of future maternity residential programs. Inclusion criteria Studies including pregnant and parenting women and gender-diverse individuals who are housed in, or accessing the services of, maternity residences in politically stable high-income countries due to challenges rooted in the social determinants of health will be considered for inclusion. We define maternity residences as any agency with a residential component offering supports/services to this population Methods This review will be conducted in accordance with JBI methodology for scoping reviews. The data will be analyzed using a quantitative descriptive analysis approach. The data analysis and discussion will informed by the Social Determinants of Health, Reproductive Justice, Harm Reduction, and Health in All Policies frameworks.
This article explores the intersections between gender, disability and care labour in the slaveholding societies of the British Caribbean from 1788 to 1834. Considered economic burdens by slaveholders, aged and disabled bondswomen were made productive through caring for their enslaved peers, many of whom were themselves temporarily unproductive due to pregnancy, illness, age or impairment. Although slaveowners devalued aged and disabled bondswomen, and assigned them inferior labour positions, in actuality, slaveowners concealed an economic logic: disabled and aged bondspeople were efficient but of a different kind, and their productivity was essential to the healthscape of the plantation. This article explores The History of Mary Prince as a first‐hand account of an enslaved woman who experienced episodic impairment and long‐term disability and who practiced self‐care and received care from multiple different women.
Integrated sensing and communication (ISAC) is regarded as an important paradigm in future networks. In this work, we consider that the ISAC device can offload its collected sensing data to multiple edge-servers for remote processing via multi-access mobile edge computing (MEC). To this end, we formulate a joint optimization problem of the beamforming for radar sensing and the beamforming for offloading transmission, with the objective of maximizing the energy efficiency of ISAC device, which is defined as the ratio between the total information collected from the radar echo signal and the energy consumption of the ISAC device. Despite the non-convexity of the formulated joint optimization problem, we propose an efficient algorithm to find the optimal solutions. Numerical results are provided to evaluate the effectiveness of our proposed algorithm and demonstrate the performance advantage of our proposed multi-access MEC empowered ISAC.
The clustering problem of big data in the era of artificial intelligence has been widely studied. Because of the huge amount of data, distributed algorithms are often used to deal with big data problems. The distributed computing model has an attractive feature: it can handle massive datasets that cannot be put into the main memory. On the other hand, since many decisions are made automatically by machines in today's society, algorithm fairness is also an important research area of machine learning. In this paper, we study two fair clustering problems: the centralized fair $k$ -center problem with outliers and the distributed fair $k$ -center problem with outliers. For these two problems, we have designed corresponding constant approximation ratio algorithms. The theoretical proof and analysis of the approximation ratio, and the running space of the algorithm are given.
Objective Growing evidence suggests that inner-city residents actively navigate their food landscape to meet a wide range of socio-economic needs. Given the increasing focus of health policies on sugar-sweetened beverages (SSB) through price-based strategies, it is critical to understand purchasing habits of populations with higher SSB intake. This study examined urban Indigenous adults’ SSB shopping behaviour and experiences. Methods We conducted a community-based participatory research study using semi-structured interviews with a purposive sample of Indigenous adults (≥ 18 years old) from the North End neighbourhood of Winnipeg. Interviews were audio recorded, transcribed verbatim, and thematically analyzed. Results All 20 participants (women = 10; men = 8; two-spirit = 2) consumed SSB on a regular, daily basis either at the time of the interview or at a prior period in their lives. Themes defining residents’ SSB shopping behaviour and experiences of shopping for SSB included balancing on the redline , specifically (1) balancing SSB purchasing constraints and facilitators with savvy shopping approaches and (2) balancing (stereo)typical reactions with resilient coping approaches . Residents procured SSB in various stores within and beyond the boundaries of the North End neighbourhood. SSB is a considerable, reoccurring expense, requiring savvy price-shopping strategies in order to access. Indigenous adults experience judgement and stereotyping when purchasing SSB, including intersecting racial, class, and weight stigma. Conclusion Purchasing SSB is perceived as a source of judgement when outside of inner-city neighbourhoods. Policymakers should consider how policies directed at SSB, which are consumed by Indigenous and food-insecure populations in greater quantities, may magnify existing racial, class, and weight-based discrimination.
Ionospheric convection patterns from the Super Dual Auroral Radar Network are used to determine the trajectories, transit times, and decay rates of three polar cap patches from their creation in the dayside polar cap ionosphere to their end of life on the nightside. The first two polar cap patches were created within 12 min of each other and traveled through the dayside convection throat, before entering the nightside auroral oval after 104 and 92 min, respectively. When the patches approached the nightside auroral oval, an intensification in the poleward auroral boundary occurred close to their exit point, followed by a decrease in the transit velocity. The last patch (patch 3) decayed completely within the polar cap and had a lifetime of only 78 min. After a change in drift direction, patch 3 had a radar backscatter power half‐life of 4.23 min, which reduced to 1.80 min after a stagnation, indicating a variable decay rate. 28 minutes after the change in direction, and 16 min after coming to a halt within the Clyde River radar field‐of‐view, patch 3 appeared to reach its end of life. We relate this rapid decay to increased frictional heating, which speeds up the recombination rate. Therefore, we suggest that the slowed patch motion within the polar cap convection pattern is a major factor in determining whether the patch survives as a recognizable density enhancement by the time the flux tubes comprising the initial patch cross into the nightside auroral oval.
Dietary self-monitoring is a behaviour change technique used to help elicit and sustain dietary changes over time. Current dietary self-monitoring tools focus primarily on itemizing foods and counting calories, which can be complex, time-intensive, and dependent on health literacy. Further, there are no dietary self-monitoring tools that conform to the plate-based approach of the 2019 Canada Food Guide (CFG), wherein the recommended proportions of three food groups are visually represented on a plate without specifying daily servings or portion sizes. This paper explored the perceptions of end-users (i.e., general public) and Registered Dietitians of iCANPlate TM —a dietary self-monitoring mobile application resembling the CFG. Qualitative data were collected through virtual focus groups. Focus group questions were based on the Capability, Opportunity, Motivation-Behaviour (COM-B) theoretical framework to explore perceptions of using the CFG and currently available dietary self-monitoring tools. The prototype iCANPlate TM (version 0.1) was presented to gain feedback on perceived barriers and facilitators of its use. Focus group discussions were audio recorded and verbatim transcribed. Trained researchers used thematic analysis to code and analyze the transcripts independently. Seven focus groups were conducted with Registered Dietitians (n = 44) and nine focus groups with members from the general public (n = 52). During the focus groups, participants mainly discussed the capabilities and opportunities required to use the current iteration of iCANPlate TM . Participants liked the simplicity of the application and its capacity to foster self-awareness of dietary behaviours rather than weight control or calorie counting. However, concerns were raised regarding iCANPlate TM ’s potential to improve adherence to dietary self-monitoring due to specific characteristics (i.e., insufficient classifications, difficulty in conceptualizing proportions, and lack of inclusivity). Overall, participants liked the simplicity of iCANPlate TM and its ability to promote self-awareness of dietary intakes, primarily through visual representation of foods on a plate as opposed to reliance on numerical values or serving sizes, were benefits of using the app. Findings from this study will be used to further develop the app with the goal of increasing adherence to plate-based dietary approaches.
We study spin models on Euclidean black hole backgrounds. These resemble the Ising model, but are inhomogeneous with two parameters, the black hole mass and the cosmological constant. We use Monte-Carlo methods to study macroscopic properties of these systems for Schwarzschild and anti-deSitter black holes in four and five dimensions for spin-1/2 and spin-1. We find in every case that increasing the black hole mass causes the spins to undergo a second order phase transition from disorder to order and that the phase transition occurs at sub-Planckian black hole mass.
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5,215 members
David Wagner
  • Faculty of Education
Hilary du Cros
  • Department of Humanities & Languages
Ted Mcdonald
  • Department of Economics
Tommi Linnansaari
  • Canadian Rivers Institute, Department of Biology and Faculty of Forestry and Environmental Management
100 Tucker Park Road, E2L 4L5, Fredericton, New Brunswick, Canada