The effectiveness of iron-based shape memory alloy (Fe-SMA, ‘memory-steel’) reinforcements has been proven in several studies and site applications. Due to the novelty of ribbed memory-steel ...reinforcement bars, limited research has been performed on their application in structural engineering, however. In this study, the bond behaviour of memory-steel bars in a near-surface-mounted configuration designed for prestressed strengthening of concrete structures was investigated. Memory-steel bars were installed on concrete blocks and activated by resistive heating before being subjected to pull-out load. The effects of heating and hence prestressing, bar ductility, bond length and rigidity of the fixation were studied based on obtained prestress, crack development, slip and bar strain. During activation of the bars, a longitudinal splitting crack with insignificant crack width occured. Two failure modes were observed during subsequent external loading, including tensile rupture of the bar when less ductile material was used, or bond failure when material with higher ductility was under investigation. Initial prestressing did not result in a reduced bond capacity. Based on the differential equation of bond behaviour, an analytical calculation procedure was developed that enables prediction of bond shear stress, slip, bar strain, pull-out load, as well as the use of a non-linear material behaviour.
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•Heating of near-surface-mounted ribbed Fe-SMA bars bonded on one bar end led to successful prestress in the free bar length.•A longitudinal splitting crack with insignificant crack width was observed along the embedded length during heating.•Pull-out loading revealed that the heating and hence prestressing did not have a detrimental effect on the bond capacity.•Two materials with different ductility led to either rupture of the bar or bond failure.•Predicted distributed bond shear stress, slip, strain showed agreement with the data using a nonlinear material behaviour.
We introduce a parallel Wang-Landau method based on the replica-exchange framework for Monte Carlo simulations. To demonstrate its advantages and general applicability for simulations of complex ...systems, we apply it to different spin models including spin glasses, the Ising model, and the Potts model, lattice protein adsorption, and the self-assembly process in amphiphilic solutions. Without loss of accuracy, the method gives significant speed-up and potentially scales up to petaflop machines.
Many existing concrete buildings worldwide require improvement in structural integrity. Previous research has proven the effectiveness of iron-based shape memory alloy (Fe-SMA or memory-steel) ...reinforcements for the prestressed strengthening of structures. The unique function of the material, i.e., the so-called shape memory effect, enables cost-effectiveness and presents simple ways to prestress defective building components. Ribbed memory-steel bars have only been available recently. This study aimed to investigate their performance in a novel strengthening technique, named near-surface mounted (NSM) method. Bond experiments with short bond lengths were performed to investigate the feasibility of this configuration and to identify the effects of several design parameters including: groove dimensions, bar diameter, bar material, cover depth, mortar strength, and concrete strength. The use of a digital image correlation system enabled detailed measurements of slips, crack width, and surface strain.
An analytical procedure based on the differential equation of bond behaviour was developed, which enabled the calculation of slip, strain, bond shear stress, and load capacity. The results show that ribbed memory-steel bars can be used in an NSM configuration due to high bond capacity. The cover depth, substrate strength and elastic modulus had a significant effect on the failure mode and bond capacity.
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•Three pull-out failure modes were revealed: splitting, combined splitting and pull-out, splitting of the cube.•The failure modes mainly depend on cover depth, mortar and concrete strength, and bar diameter.•Longitudinal splitting cracks were observed with an image correlation system during experiments with low cover depth.•Stainless steel bars showed lower bond strength than memory-steel bars with non-linear stress-strain behaviour.•Analytical modelling reproduced bond stress, bar strain, and slip, as well as load capacity of the bonded joint.
The production of energy through nuclear fusion poses serious challenges related to the stability and performance of materials in extreme conditions. In particular, the constant bombardment of the ...walls of the reactor with high doses of He ions is known to lead to deleterious changes in their microstructures. These changes follow from the aggregation of He into bubbles that can grow and blister, potentially leading to the contamination of the plasma, or to the degradation of their mechanical properties. We computationally study the behavior of small clusters of He atoms in W in conditions relevant to fusion energy production. Using a wide range of techniques, we investigate the thermodynamics of the clusters and their kinetics in terms of diffusivity, growth, and breakup, as well as mutation into nanobubbles. Our study provides the essential ingredients to model the early stages of He exposure leading up to the nucleation of He bubbles.
In the absence of gravity, a capillary surface within a circular cylinder will have constant mean curvature and will make a constant contact angle with the cylinder. Two types of surfaces with these ...properties are Delaunay surfaces and cylinders (i.e., the free surface of the liquid is another circular cylinder). Stability and energy minimality of these capillary surfaces are investigated.
•This systematic review was conducted in 8 electronic databases.•53 articles meeting our inclusion criteria were considered in this review.•This review highlights the benefits of aerobic training ...(AT) on seniors’ health.•Physicians should encourage seniors to engage in AT to favour healthy ageing.
Aging is intrinsically associated with a progressive decline in muscle strength and mass, and aerobic capacity. This contributes to reduced mobility and impaired quality of life (QoL) among seniors. Regular physical activity, and more particularly aerobic training (AT), has demonstrated benefits on adults’ health. The aim of this review was to assess the current level of evidence regarding the health benefits of AT in the population aged 70 years and over. A comprehensive, systematic database search for manuscripts was performed. Two reviewers independently assessed interventional studies for potential inclusion. Cardiovascular, metabolic, functional, cognitive, and QoL outcomes were targeted. Fifty-three studies were included totalling 2051 seniors aged 70 years and over. Studies selected were divided into 5 categories according to their main outcomes: cardiovascular function (34 studies), metabolic outcomes (26 studies), functional fitness (19 studies), cognitive functions (8 studies), and QoL (3 studies). With a good level of evidence but a wide heterogeneity between study designs, a significant and beneficial effect of AT was measured on the 5 outcomes. For QoL results showed a significant but slighter improvement. This systematic review highlights the benefits of AT on seniors’ health outcome such as cardiovascular, functional, metabolic, cognitive, and QoL outcomes although the optimal program remains unclear. When more studies regarding this specific population are needed to determine the most favourable exercise program, clinicians should nevertheless encourage older adults over 70 to participate in AT programs to favour active and healthy ageing.
Analysis of convalescent plasma derived from individuals has shown that IgG3 has the most important role in binding to SARS-CoV-2 antigens; however, this has not yet been confirmed in large studies, ...and the link between binding and neutralization has not been confirmed. By analyzing plasma pools consisting of 247-567 individual convalescent donors, we demonstrated the binding of IgG3 and IgM to Spike-1 protein and the receptor-binding domain correlates strongly with viral neutralization in vitro. Furthermore, despite accounting for only approximately 12% of total immunoglobulin mass, collectively IgG3 and IgM account for approximately 80% of the total neutralization. This may have important implications for the development of potent therapies for COVID-19, as it indicates that hyperimmune globulins or convalescent plasma donations with high IgG3 concentrations may be a highly efficacious therapy.
Private groundwater wells can be unmonitored sources of contaminated water that can harm human health. Developing models that predict exposure could allow residents to take action to reduce risk. ...Machine learning models have been successful in predicting nitrate contamination using geospatial information such as proximity to nitrate sources, but previous models have not considered meteorological factors that change temporally. In this study, we test random forest (regression and classification) and linear regression models to predict nitrate contamination using rainfall, temperature, and readily available soil parameters. We trained and tested models for (1) all of North Carolina, (2) each geographic region in North Carolina, (3) a three‐county region with a high density of animal agriculture, and (4) a three‐county region with a low density of animal agriculture. All regression models had poor predictive performance (R2 < 0.09). The random forest classification model for the coastal plain showed fair agreement (Cohen's κ = 0.23) when trying to predict whether contamination occurred. All other classification models had slight or poor predictive performance. Our results show that temporal changes in rainfall and temperature, or in combination with soil data, are not enough to predict nitrate contamination in most areas of North Carolina. The low level of contamination (<25%) measured during the study could have contributed to the poor performance of the models.
•Exploration of the role of AI on student creative thinking.•Mixed method approach of AUT test: measured flexibility, fluency, elaboration, and originality.•Assessment of the impact of ChatGPT-3 on ...students’ divergent thinking.•While AI has the potential to significantly support creative thinking, there are also negative impacts on creativity and creative confidence.•The results advocate for a careful approach in integrating AI into creative education.
This study aimed to learn about the impact of generative artificial intelligence (AI) on student creative thinking skills and subsequently provide instructors with information on how to guide the use of AI for creative growth within classroom instruction. This mixed methods study used qualitative and quantitative data collected through an AUT test conducted in a college-level creativity course. The authors measured flexibility, fluency, elaboration, and originality of the data to assess the impact of ChatGPT-3 on students’ divergent thinking. The results advocate for a careful approach in integrating AI into creative education. While AI has the potential to significantly support creative thinking, there are also negative impacts on creativity and creative confidence. The authors of this study believe that creativity is central to learning, developing students’ ability to respond to challenges and find solutions within any field; thus the results of this study can be applicable to any classroom faced with the impact and/or integrating the use of AI on idea generation.
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