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Characterization of microstructure and high strain rate deformation response of C250 maraging steel fabricated by directed energy deposition process
No full textC250 maraging steel, known for its high strength and good toughness, is ideal for applications requiring exceptional high strain rate properties. Its carbon-free composition is suitable for the directed energy deposition-arc (DED-Arc) method, an additive manufacturing (AM) process with a low cost and high deposition rate. However, the thermal cycles in DED-Arc significantly impact the microstructure of C250 alloy. This could lead to undesirable high strain rate properties, necessitating post-fabrication heat treatment. Research gaps remain in understanding the microstructure and dynamic deformation response of DED-Arc fabricated C250 steel. Besides, AM enables fabricating complex geometries, but accurate constitutive models governing the stress-strain relationship of materials are essential for reliable finite element analysis (FEA) predictions of dynamic deformation. Yet, no reliable models have been proposed to predict the dynamic deformation behaviors of DED-Arc built C250 alloy. Therefore, this study aims to investigate the microstructure and dynamic deformation responses of DED-Arc built C250 steel at different strain rates and temperatures and to develop appropriate constitutive models based on the observed flow behavior.
Microstructure analyses indicate the absence of strengthening precipitates and the presence of retained austenite phase in as-built DED-Arc C250 steel, leading to inferior dynamic mechanical performance compared to heat-treated wrought C250 alloy. However, commercial heat treatment significantly improves the dynamic mechanical performance of heat-treated DED-Arc C250 steel, making it comparable to that of the heat-treated wrought C250 alloy. This substantial improvement is mainly attributed to the formation of nano-sized, needle-shaped, and coherent Ni3Mo strengthening precipitates during the heat treatment.
Modifications are made to the Johnson-Cook constitutive models to predict the dynamic deformation behaviors of as-deposited and heat-treated DED-Arc C250 alloy, respectively. These modifications consider the variable thermal softening effects and coupled effects of strain rate and strain in the flow behavior of the as-deposited specimen. In the heat-treated condition, the modified model accounts for the combined effects of strain rate and strain, as well as joint influences of strain rate and temperature on the flow behavior at elevated temperatures. The enhanced predictive capability of the modified Johnson-Cook models is further validated through verification tests under new dynamic compression conditions.February 202
Developing a set of emergency department performance measures to evaluate delirium care quality for older adults: a modified e-Delphi study
No full textBackground
Older adults are at high risk of developing delirium in the emergency department (ED); however, it is under-recognized in routine clinical care. Lack of detection and treatment is associated with poor outcomes, such as mortality. Performance measures (PMs) are needed to identify variations in quality care to help guide improvement strategies. The purpose of this study is to gain consensus on a set of quality statements and PMs that can be used to evaluate delirium care quality for older ED patients.
Methods
A 3-round modified e-Delphi study was conducted with ED clinical experts. In each round, participants rated quality statements according to the concepts of importance and actionability, then their associated PMs according to the concept of necessity (1–9 Likert scales), with the ability to comment on each. Consensus and stability were evaluated using a priori criteria using descriptive statistics. Qualitative data was examined to identify themes within and across quality statements and PMs, which went through a participant validation exercise in the final round.
Results
Twenty-two experts participated, 95.5% were from west or central Canada. From 10 quality statements and 24 PMs, consensus was achieved for six quality statements and 22 PMs. Qualitative data supported justification for including three quality statements and one PM that achieved consensus slightly below a priori criteria. Three overarching themes emerged from the qualitative data related to quality statement actionability. Nine quality statements, nine structure PMs, and 14 process PMs are included in the final set, addressing four areas of delirium care: screening, diagnosis, risk reduction and management.
Conclusion
Results provide a set of quality statements and PMs that are important, actionable, and necessary to a diverse group of clinical experts. To our knowledge, this is the first known study to develop a de novo set of guideline-based quality statements and PMs to evaluate the quality of delirium care older adults receive in the ED setting
Knowledge Synthesis Research in the Rady Faculty of Health Sciences
No full textKnowledge synthesis, which includes systematic reviews, scoping reviews, and rapid reviews, is an important form of research for the Rady of Faculty of Health Sciences. But how is this research completed, what services are available to support students and researchers doing this work, and what does published KS from the RFHS look like over the last six years?
Librarians from the Neil John Maclean Health Sciences Library have collaborated with RFHS faculty, students, and researchers on hundreds of reviews, consulted on innumerable projects, answered thousands of knowledge synthesis questions, and provided hours of in-class and online instruction. Since 2018 we have also offered a multi-part workshop series that allows attendees to add it to their Experience Record.
We also recently completed a research study that identified all published KS research produced by the RFHS community since 2017. This allowed us to conclusively identify trends in the overall increase in KS, the incredible growth of specific review types, and possible relationships between librarian collaboration on a KS and the journal impact factor of the published research.
Pulling from these two information sources, this presentation will provide an overview of KS research output at RFHS and outline supports available to KS researchers. This session will be valuable for anyone involved in KS research within the RFHS – whether as summer research students or longtime KS investigators
Association between high-density lipoprotein cholesterol and lumbar bone mineral density in Chinese: a large cross-sectional study
No full textBackground
The association between lipid and bone metabolism, particularly the role of high-density lipoprotein cholesterol (HDL-C) in regulating bone mineral density (BMD), is of significant interest. Despite numerous studies, findings on this relationship remain inconclusive, especially since evidence from large, sexually diverse Chinese populations is sparse. This study, therefore, investigates the correlation between HDL-C and lumbar BMD in people of different genders using extensive population-based data from physical examinations conducted in China.
Methods
Data from a cross-sectional survey involving 20,351 individuals aged > = 20 years drawn from medical records of health check-ups at the Health Management Centre of the Henan Provincial People’s Hospital formed the basis of this study. The primary objective was to determine the correlation between HDL-C levels and lumbar BMD across genders. The analysis methodology included demographic data analysis, one-way ANOVA, subgroup analyses, multifactorial regression equations, smoothed curve fitting, and threshold and saturation effect analyses.
Results
Multifactorial regression analysis revealed a significant inverse relationship between HDL-C levels and lumbar BMD in both sexes, controlling for potential confounders (Male: β = -8.77, 95% CI -11.65 to -5.88, P 28 kg/m2 and HDL-C > 1.45 mmol/L and in females with a BMI between 24 and 28 kg/m2.
Conclusion
Elevated HDL-C is associated with decreased bone mass, particularly in obese males. These findings indicate that individuals with high HDL-C levels should receive careful clinical monitoring to mitigate osteoporosis risk.
Trial registration
The research protocol received ethics approval from the Ethics Committee at Beijing Jishuitan Hospital, in conformity with the Declaration of Helsinki guidelines (No. 2015-12-02). These data are a contribution of the China Health Quantitative CT Big Data Research team, registered at clinicaltrials.gov (code: NCT03699228)
Characterizing range of motion, strength and performance outcomes in patients with femoroacetabular impingement syndrome prior to hip arthroscopy
Get PDFHip arthroscopy has historically focused on patient-reported outcome measures with limited evaluation of range of motion (ROM), strength, and dynamic performance to determine a successful outcome. The purpose of this study was to characterize active ROM, strength, and dynamic performance of participants who have elected to undergo hip arthroscopy for femoroacetabular impingement. It was hypothesized that measurements isolated to the hip (active ROM and strength) will be lower in the affected limb with less limitation in multi-joint, dynamic outcomes. Participants were included if they were 16-50 years of age, had a confirmed diagnosis of Femoroacetabular impingement syndrome (FAIS) based on the Warwick Agreement, had no improvement with conservative management, had symptomatic relief with an intra-articular injection, and required unilateral surgical intervention. Participants completed an assessment including active hip ROM, clinical special tests, isometric hip abduction and extension strength, isokinetic hip flexion and extension strength, and dynamic performance measures including change of direction, hopping and jump tests. Clinical special tests were evaluated with the Χ2 test and between limb performance was compared with paired T-Tests except for SL-CMJ vGRFS (ANOVA, p<0.05). Range of motion was greater on the unaffected limb across all movements in our participants. Isokinetic hip flexion (mean difference 0.15 nm/kg, p = 0.01) and extension (mean difference 0.28 nm/kg, p < 0.001) were reduced in the affected limb; However, the only statistically significant finding was for abduction (p < 0.001). A between-limb difference in performance occurred in the single leg countermovement jump (mean difference 0.93 cm, p = 0.018). Measures isolated to the hip joint itself, including active ROM of abduction and isokinetic flexion and extension strength, were lower in the affected limb, while multi-joint performance measures that required the lower extremity to function in multiple planes of motion were unable to objectively confirm the subjective reports of performance impairments in people diagnosed with FAIS.October 202
Canadian Society of Allergy and Clinical Immunology position statement: panel testing for food allergies
Get PDFAbstract This position statement addresses the critical concerns and recommended practices surrounding the use of panel food testing for diagnosing food allergies. Food allergies are a significant public health concern, and the misdiagnosis of food allergies remains a prevalent concern, made worse by the ongoing use of panel food testing. The practice of screening patients for multiple food allergens, regardless of clinical relevance, is commonly referred to as “panel food testing.” Fundamentally, a panel food test is not simply a single test; a panel food test is a series of several distinct tests for multiple foods, each with its own variable predictive value. These tests have not been adequately validated as screening tests and carry a considerable false positive rate. The resulting false diagnoses lead to unnecessary dietary restrictions, increased healthcare costs, and significant psychosocial distress for patients and their families
The association of Chronic Kidney Disease with sarcopenia: a population wide study
Get PDFSarcopenia, defined as the loss of muscle mass, is a growing public health concern, and is an underrecognized problem in adults with Chronic Kidney Disease (CKD). The clinical diagnosis of sarcopenia can be made via measurement of appendicular lean mass index (ALMi, indexed to height by m2), traditionally obtained through whole-body dual-energy X-ray absorptiometry (DXA) scans, however these are not frequently performed. As a result, large population studies examining the relationship between CKD and sarcopenia are lacking.
Using databases held at the Manitoba Centre for Health Policy, we identified adults who had at least one DXA scan linkable to serum creatinine values within 365 days, between 2007 and 2022. Serum creatinine was used to calculate estimated glomerular filtration rate, and estimated ALMi (eALMi) was calculated through central DXA scans via a previously developed algorithm. We constructed Linear, logistic, and Cox proportional hazards models to examine the relationship between CKD, sarcopenia, and adverse clinical outcomes.
Our CKD cohort contained 24,660 individuals (64.4 ± 12.5 years, 84.4% female), with 3,204 individuals (13.0%) having eALMi indicating sarcopenia. 22,648 individuals (91.8%) had eGFR <= 60, and 2,012 (8.2%) had eGFR < 60. After adjustment for age, sex, estimated central mass index, and comorbid conditions, both sarcopenia and declining eALMi were also associated with adverse clinical outcomes including hospitalization and emergency room visits, home care use, long-term care use, and all-cause mortality. Additionally, the presence of eGFR < 60 was associated with higher odds of sarcopenia (OR: 1.39; 95% CI: 1.16–1.67), and lower eALMi (-0.057; 95% CI: -0.081, -0.034). In individuals with two DXA scans (n=2,985), eGFR < 60 at baseline was associated with a larger decline in eALMi compared to individuals with preserved eGFR (OR: 1.61; 95% CI: 1.05–2.45).
Our results show that CKD is associated with sarcopenia and leads to more rapid declines in appendicular lean mass over time. Furthermore, we demonstrate that eALMi as derived from routine central DXA scanning is associated with long-term downstream adverse clinical outcomes. These findings validate our central DXA based measurement of eALMi and sarcopenia and highlight the importance preservation of muscle mass in individuals with CKD.October 202
Improved aggregation techniques for electromagnetic transient simulation of wind farms considering windspeed variability
Get PDFA foreseeable relatively high wind power penetration of global electricity demand will be reached in the near future. This research aims to improve aggregation modeling techniques for large wind farms considering the effect of local windspeed variations.
A new structurally complete dynamic model of a doubly-fed induction generator (DFIG) consisting of an induction machine, a back to back converter, and a step-up transformer are developed in a compact state-space form. A structure-preserving aggregation method to select the model’s parameters so that the major collective dynamic characteristics of a group of DFIGs is closely approximated. The proposed aggregation method maintains the same steady-state results compared with the original unreduced model. It also preserves the major collective dynamic responses of the clustered DFIGs. A particular three-winding transformer model with current magnifying functions is developed to realize the DFIGs aggregation for Electromagnetic Transient (EMT) simulations.
Furthermore, the impact of the wake effect and varying wind speed within a wind farm on the aggregated model is investigated. Although complex models can estimate and simulate wind interaction with high accuracy, a simpler model is needed for system level simulations. First, Jensen’s model is used to estimate the local windspeeds at each generator location from the ambient windspeed. Next, the aggregation algorithm generates a single representative windspeed for a cluster of generators for use in the DFIG dynamic model.
The mechanism responsible for loss of synchronization following ac faults for a DFIG is identified in the thesis. A dq frame theoretical model for the DFIG and its phase locked loop (PLL) is developed which identifies positive and negative feedback mechanisms involved in synchronization. This is combined with a large signal plot of the synchronizing signal (proportional to measured q axis voltage Vmq) and a signal dependent on the PLL’s output phase angle. The plot shows the largest allowable swing for Vmq before a point of no-return is reached. A ‘stability indicator index’ is introduced to indicate the likelihood of the system to experience synchronization failure.
Next, a detailed more realistic model of the DFIG is simulated on an EMT simulator (PSCAD) to show the impacts of PLL parameters and DFIG rotor speed on the grid synchronizing stability of DFIG for a remote and 3-phase fault applied to the point of common coupling (PCC). It is shown that decreasing the rotor side converter PLL integration gain or increasing/decreasing rotor speed can help increase the stability degree of wind turbine.October 202
A field study comparing soil profile N2O concentration with surface flux under different farming practices
Get PDFExisting research has consistently demonstrated a significant increase in N2O emissions during the spring thaw period. However, understanding the precise influence of farming practices such as cover crops and enhanced efficiency nitrogen fertilizers (EENFs) on N2O dynamics—production, diffusion, consumption in the soil profile, and surface emissions—remains limited, particularly in clay soil in Manitoba. A two-year field study was conducted in 2022 and 2023 on clay soil at the TGAS-MAN research station in Manitoba to investigate the impact of different farming practices [cover crop and enhanced efficient nitrogen fertilizers (EENFs)] on soil profile N2O concentrations at 5, 15, 30 and 60 cm of soil profile in relation to surface flux. The research site was divided into four 4-hectare fields, each measuring 200 meters by 200 meters. Six modified silicone diffusive equilibrium samplers were installed in each field to collect soil profile gas samples from different depths. The micrometeorological method was used to measure N2O surface flux rates. The results indicated that growing winter rye as a cover crop significantly (p<0.01) decreased soil profile N2O concentrations across all depths from September to December. Compared to non-cover crop, the cover crop treatment decreased the median N2O concentrations at 5, 15, 30, and 60 cm. With the increasing temperature and soil moisture at spring–thaw, profile N2O concentrations at all depths increased significantly. In contrast, no significant difference was observed between the non-cover and cover crop treatments during spring–thaw. While different fertilizer sources did not significantly affect N2O concentrations, EENF demonstrated a capacity to reduce N2O concentration in the 5 cm depth but did not have a discernible effect at deeper depths during the growing season 2023. The lowest N2O concentrations were consistently observed at shallow depths (5 cm) throughout the study period, while peak N2O concentrations were observed at deeper soil depths (30-60 cm). The peak N2O concentration during spring–thaw 2022 and 2023 occurred at 30 cm of soil profile likely due to higher microbial activity, confirming that de novo production is the main mechanism driving N2O peak emission during spring–thaw.October 202
Optimization of geometric measures of sets of moving objects
Get PDFGiven a set S of objects, each moving with linear motion in R^d, consider the diameter D(S, t) of S at time t. In this thesis we explore optimization of extent and proximity measures of S. For instance, one possibility is to identify minimum
diameter D(S, t) of S over the domain of time t. D(S, t) is an example of a measure of extent of S. On the basis of this model, other geometric measures could also be explored to be optimized for sets of objects in motion. Let n be the cardinality of S and let M(S, t) be a geometric measure of extent or proximity at time t. Given an integer k, select a subset Q ⊂ S such that |Q| = k and Q has extreme measure M(Q, t) over all possible subsets Q of cardinality k. The present thesis focuses on minimizing and maximizing M(Q, t), in one and two dimensions (d = 1 or d = 2), for which the measure corresponds to set diameter, set width, minimum axis-aligned bounding box, and minimum enclosing disk. For each measure, exact polynomial-time algorithms are proposed for selecting an optimal subset of S and finding the time t of which the subset optimizes the measure.October 202