Material Length Research Articles

A gradient-based non-local GTN model: Explicit finite element simulation of ductile damage and fracture

Non-local models have over the years been established as an effective approach to solve the pathological mesh dependency problem observed in finite element simulation of strain-softening materials. This paper presents the formulation, implementation, and application of a gradient-based non-local Gurson–Tvergaard–Needleman (GTN) model for explicit finite element analysis. The porosity is taken as the non-local variable where the increment in porosity is averaged over the volume using an implicit gradient model. The gradient model is implemented in Abaqus/Explicit by utilising the coupled thermal–mechanical solver, which proves to be both a simple and computationally efficient approach. Due to the use of an explicit integration scheme, a transient term is introduced to the partial differential equation of the gradient formulation. The non-local GTN model is compared to the local counterpart for increasing mesh refinements using a plane strain shear band specimen, a plane strain tension specimen, and a plane strain compact tension specimen. The proposed approach can remedy the pathological mesh dependency problem. For the plane strain tension specimen, it is shown that the non-local GTN model will preserve the fracture mode (slant versus cup–cup fracture mode) when the mesh is refined. The non-local GTN model is also able to predict the same fracture mode as observed in ductile tearing experiments. However, non-local averaging can over-smooth the fields and exclude the slant fracture mode from occurring if the material length Lc is too large.

A non-local GTN model with two length scales – Application to ductile failure in a wide range of stress triaxiality

A non-local extension of the shear-modified Gurson model for porous plasticity is proposed, which is capable of preventing spurious strain localization and suitable for predicting crack initiation and growth under general loading conditions. In the extended model, the progression of shear failure is separated from flat dimple rupture by the assumption that these failure mechanisms are characterized by a deviatoric and a dilatational material length parameter, respectively. The two length parameters are introduced through a delocalization process based on the non-local integral approach evaluated on the current configuration. A comprehensive numerical investigation is conducted to disclose the influence of these length parameters. For this purpose, five different specimen geometries are considered covering a wide range of stress triaxiality including pure shear. It is observed that separation of the length parameters is essential for predicting crack branching driven by shear localization, e.g., the flat dimple-to-shear failure transition of a crack that approaches and penetrates a free surface.

Performance and Nutrient Content of Okra (Abelmoschus Esculentus L. Moench) Fruits as Influenced by Vermicompost, Nitrogen and Zinc Grown in Soil

This investigation aimed to assess the influence of soil-applied vermicompost, nitrogen and zinc on the vegetative growth parameters, yield, and mineral nutrient concentration of the fruits of okra (Abelmoschus esculentus L. Moench). The experiment was laid out in a Completely Randomized Design followed by three replications. Data were subjected to analysis of variance and mean values were compared using Tukey’s Range Test at p ≤ 0.05. Variation in mean values was compared among eight treatments: control (T1), 6 ton ha-1 vermicompost (T2), 60 kg ha-1 N (T3), 2 kg ha-1 Zn (T4), 6 ton ha-1 vermicompost + 60 kg ha-1 N (T5), 60 kg ha-1 N + 2 kg ha-1 Zn (T6), 6 ton ha-1 vermicompost + 2 kg ha-1 Zn (T7), and 6 ton ha-1 vermicompost + 60 kg ha-1 N + 2 kg ha-1 Zn (T8). The maximum growth performance and yield contributing properties of okra, viz. plant height (56 cm), leaf number (11 plant-1), leaf area (14.5 cm2), stem girth (3.5 cm), branch number (8 plant-1), and fruit number (6.50 plant-1), fruit diameter (5.50 cm), fruit length (13.50 cm), and weight of fresh (64.29 g) and dry plant materials (14.56 g), were found in T5. The control T1 performance showed reducing trends compared to other treatments. Although there was no significant difference with the application of vermicompost 6 t ha-1 + N 60 kg ha-1 + Zn 2 kg ha-1 (T8), the treated pot in vermicompost with 6 t ha-1 + N 60 kg ha-1 (T5) showed the best achievements of macro elements N (0.008%), P (6.70 ppm), K (0.08 cmol/kg), and S (18.22 ppm) of post-harvest soil compared to the control T1. Mineral nutrients of fruits N-1.64%, P-0.27%, K-0.30%, S-0.10%, and Fe-0.02% and protein content 10.23% were found to be highest in the identical T5 where Zn content was highest (0.28%) in T8. This study showed that the treatment of vermicompost with 6 t ha-1 + N 60 kg ha-1 (T5) contained and released quality nutrients is recommended for its overall best growth performance for okra. J. Biodivers. Conserv. Bioresour. Manag. 2023, 9(1): 101-108

Influence of ore size on the production of micro-sized ore particles by high-pressure gas rapid unloading

Comminution of ore is a critical and energy-intensive process in mineral resource utilization. High-pressure gas rapid unloading (GRU) has emerged as a promising ore grinding technique, wherein high-pressure gas is injected into the ore and is unloaded at high speed to induce tensile failure inside the ore. Although the GRU is capable to achieve more efficient ore comminution with lower energy consumption compared to conventional methods, it is still in the early stages of development. The pulverization effect of different size ores is a crucial question needing to be revealed before the GRU industrial application. This study explores the impact of ore size on ore pulverization by GRU, using kaolin as an experimental material. Specifically, we discuss the following: 1. the impact of ore size on high-pressure gas infiltration, 2. the effect of infiltration time on ore pulverization, and 3. the effect of ore size on GRU-pulverized ore. The results indicate that the GRU pulverization method is highly applicable to kaolin, and different ore sizes have minimal effects on ore pulverization. Finally, we explain the insignificant size effect of GRU-pulverized ore by discussing the ore material length scale, deformation scale, and ore size. The conclusion may provide a basis for extending the GRU method from the experimental lab scale to a larger one. It may also provide a reference for applying GRU in kaolin comminution.

Service-lines as major contributor to water quality deterioration at customer ends

Biofilm detachment contributes to water quality deterioration. However, the contributions of biofilm detachment from different pipes have not been quantified or compared. Following the introduction of partial reverse osmosis (RO) in drinking water production, this study analyzed particles at customers’ ends and tracked their origins to water distribution mains and service lines. For doing so, filter bags were installed in front of water meters to capture upstream detached particles, while biofilm from water main and service line were sampled by cutting pipe specimens. The results showed that elemental concentrations of the biofilm in mains were higher than those of service lines (54.3–268.5 vs. 27.1–44.4 μg/cm2), both dominated by Ca. Differently, filter bags were dominated by Fe/Mn (77.5–98.1%). After introducing RO, Ca significantly decreased in biofilms of mains but not service lines, but the released Fe/Mn rather than Ca arrived at customers’ ends. The ATP concentrations of service lines were higher than mains, which decreased on mains but increased in service lines after introducing RO. For the core ASVs, 13/24 were shared by service lines (17), mains (21), and filter bags (17), which were assigned mainly to Nitrospira spp., Methylomagnum spp., Methylocytis spp., and IheB2–23 spp. According to source tracking results, service lines contributed more than mains to the particulate material collected by filter bags (57.6 ± 13.2% vs. 13.0 ± 11.6%). To the best of our knowledge, the present study provides the first evidence of service lines’ direct and quantitative contributions to potential water quality deterioration at customers’ ends. This highlights the need for the appropriate management of long-neglected service line pipes, e.g., regarding material selection, length optimization, and proper regulation.

Heat pulse probe design optimization using numerical simulation

Heat pulse (HP) measurements are used as an alternative method for a variety of thermal and hydraulic properties critical for many scientific disciplines and engineering applications. This study investigated factors affecting heat pulse probe (HPP) measurements using COMSOL numerical simulations. We sought to understand the influence of rod support material (e.g., circuit board) and rod length on the measured temperature rise by comparing the parametric model-fitted thermal properties of ice and water with the known reference values. Temperature dynamics near the rod support were significantly impacted by the physical and thermal properties of the rod support material, while temperature changes further away from it were mostly affected by the properties of the surrounding media. In addition, comparing results for soil volumetric water contents of 0.00, 0.20, and 0.40 m3 m−3, thermal variations near the rod support material were greater at lower water contents. Results indicate the rod length should be 60 mm or longer, and the optimal thermistor location is at the midpoint of the rod, where more accurate temperature rise curves were obtained for both measurements and simulations.

Influence of Root Post Materials and Aging on Fracture Strength and Marginal Gap Quality of Ceramic Crowns-An In Vitro Study.

The design of and materials for prosthodontic abutments and posts have significant influences on the fracture resistance of restored teeth. This in vitro study compared the fracture strength and marginal quality of full-ceramic crowns as a function of the inserted root posts via simulation of a five-year period of use. Test specimens were prepared from 60 extracted maxillary incisors using titanium L9 (A), glass-fiber L9 (B), and glass-fiber L6 (C) root posts. The circular marginal gap behavior, linear loading capacity, and material fatigue after artificial aging were investigated. The marginal gap behavior and material fatigue were analyzed using electron microscopy. The linear loading capacity of the specimens was investigated using the Zwick Z005 universal testing machine. None of the tested root post materials showed statistically significant differences in marginal width values (p = 0.921), except in the case of marginal gap location. For Group A, there was a statistically significant difference from the labial to the distal (p = 0.012), mesial (p = 0.000), and palatinal (p = 0.005). Similarly, Group B showed a statistically significant difference from the labial to the distal (p = 0.003), mesial (p = 0.000), and palatinal (p = 0.003). Group C showed a statistically significant difference from the labial to the distal (p = 0.001) and mesial (p = 0.009). Linear load capacity reached mean values of 455.8-537.7 N, and micro-cracks occurred after artificial aging, predominantly in Groups B and C. Through the chosen experimental design, it was shown that the root post material and root post length had no influence on the fracture strength of the test teeth before or after artificial aging. However, the marginal gap location depends on the root post material and its length, which is wider mesially and distally and also tends to be greater palatinally than labially.

A gradient regularized model for shape memory alloys

In this work a transformation strain gradient enhancement is introduced into a phenomenological constitutive model for the pseudoelastic behavior of shape memory alloys. The constitutive model is able to capture several unique features of the constitutive response of these materials during the transformation between austenite and martensite during the pseudoelastic response. These features include the asymmetry in the initial transformation stresses in tension versus compression, the asymmetry in the transformation strains in tension and compression, and finally the asymmetry in the hardening behavior in tension and compression. In fact, experiments have shown that untrained NiTi exhibits hardening during its transformation in compression, but softening for tensile loading. It is this softening behavior that motivates the need for the introduction of the transformation strain gradient into the constitutive modeling. Transformation strain gradient effects are introduced via a phase variable that describes the extent of transformation. The free energy of the material then depends on gradients of the phase variable, which introduces a material length scale into the theory. The governing equation for the phase variable is developed from a microforce balance and continuum thermodynamics analysis. The model is implemented in the commercial finite element software Abaqus through user defined subroutines and several numerical simulations are performed to illustrate the model response and lack of numerical mesh-dependency of the results.

Response surface optimization and social impact evaluation of Houttuynia cordata Thunb solar drying technology for community enterprise in Chiangrai, Thailand

Drying has emerged as one of the most important ways of preserving high-quality and quantity food goods. A force convection solar drying is considered an ecologically and environmentally friendly alternative. This research presents parameter optimization of greenhouse tunnel dryer of Houttuynia cordata Thunb (H. cordata) using response surface methodology with the assessment of economic feasibility and social return on invesment. The influence parameters of the drying process were evaluated to obtain maximum efficiency. The individual parameters were temperature (40 – 60 °C), material length (10 – 30 cm), and relative humidity (30 – 50%). The individual parameters of drying temperature showed an extreme effect on the response of moisture content and color value change, while the relative humidity had only an influence on moisture content. On the other hand, the parameter of material length was not significance in both responses. When compared to open-air drying, solar drying reduced the drying time of H. cordata by 57.14%. The payback period of the dryer was found to be 2.5 years. Furthermore, the results reveal that the social return on investment ratio in 2021 was 2.18, then increasing to 2.52 in 2022 and 2.91 in 2023. According to the findings, solar drying technology has the potential to be an adequate product quality improvement technology for H. cordata. It is a feasible drying technology in terms of economic evaluation.

Nonlinear bending of FG metal/graphene sandwich microplates with metal foam core resting on nonlinear elastic foundations via a new plate theory

Nonlinear bending of functionally graded metal/graphene (FGMG) sandwich rectangular plate with metal foam core resting on nonlinear elastic foundations is elucidated in this article. A new shear deformation plate theory is presented to formulate the displacement field. The nonlinear partial differential equations considering the small size effect are established via the principle of virtual work. The nonlinearity is considered by using Von Karman’s strain-displacement relations. While, the size effect is captured by employing the modified couple stress theory. The upper and lower layers are made of aluminum as a matrix that reinforced with graphene platelets (GPLs). The GPLs are functionally graded through the thickness of the face layers according to a new cosine rule. Moreover, the metal foam core is also made of aluminum containing porosities that uniformly distributed or functionally graded through the core thickness. The governing equations are solved based on the Galerkin and Newton’s methods. The obtained results are examined by introducing some comparison examples. In addition, several parametric examples are discussed including the effects of the porosity type, GPLs distribution type, core-to-face thickness, elastic foundation stiffness, side-to-thickness ratio, plate aspect ratio and material length scale parameter on the nonlinear deflection and stresses of FGMG sandwich plate with metal foam core.

Temperature Dependence of Dynamic Properties of Poly(ethylene glycol) Molecules on a MHz-Oscillating Solid–Liquid Interface

The temperature dependence of resonant molecular weights and resonant lengths of soft materials was investigated at the nanoscale for a viscous penetration depth region and a physisorption region using a quartz crystal microbalance (QCM). Poly(ethylene glycol) (PEG) was used as a model for soft materials. The study revealed that, in the viscous penetration depth and physisorption regions, the logarithmic values of the resonant molecular weights decreased linearly with those of the QCM angular frequencies and converged to a single point of 1360 g/mol at 416 MHz independently of temperature. The convergence point was consistent with that of chemisorption. In addition, in the regions of the viscous penetration depth and physisorption at each temperature, the slopes of logarithms of the resonant lengths decreased linearly with the logarithms of the QCM angular frequencies and were equal to those of chemisorption. As a result, a convergence point of the resonant length appeared at 2.87 nm and 416 MHz, where its frequency was equivalent to that of the chemisorption. These results enabled us to quantitatively establish the behavior of the resonant molecular weight and resonant length as a function of temperature and frequency.

Nonlinear Finite Element Model for Bending Analysis of Functionally-Graded Porous Circular/Annular Micro-Plates under Thermomechanical Loads Using Quasi-3D Reddy Third-Order Plate Theory.

A nonlinear finite element model for axisymmetric bending of micro circular/annular plates under thermal and mechanical loading was developed using quasi-3D Reddy third-order shear deformation theory. The developed finite element model accounts for a variation of material constituents utilizing a power-law distribution of a two-constituent material, three different porosity distributions through plate thickness, and geometrical nonlinearity. The modified couple stress theory was utilized to account for the strain gradient effects using a single material length scale parameter. Three different types of porosity distributions that have the same overall volume fraction but different enhanced areas were considered as a form of cosine functions. The effects of the material and porosity distribution, microstructure-dependency, the geometric nonlinearity, and various boundary conditions on the bending response of functionally-graded porous axisymmetric microplates under thermomechanical loads were studied using the developed nonlinear finite element model.

Development of an ANC System with a Giant Magnetostrictive Actuator for Ultra-Compact Electric Vehicles: Thrust Force Characteristics Including Road Noise Range

Ultra-compact electric vehicles (EVs) have been recently sold as next-generation vehicles. However, they are yet to reach a notable phase of expansion and use. Ultra-compact EVs have compact and lightweight bodies. As the outer plate of an ultra-compact EV has low rigidity, the road noise generated by the tires and the wind noise generated from the vehicle’s projection shape are transmitted to the interior of the vehicle. Therefore, a new active noise control (ANC) system with a giant magnetostrictive actuator for ultra-compact EVs has been recently proposed. The giant magnetostrictive actuator is required to produce sufficient thrust, with less distortion, and delayed sound waves. In this work, we studied the thrust force characteristics of the giant magnetostrictive material, including in the road noise range. We considered the giant magnetostrictive thrust for output, including in the road noise range, using a finite element model of the giant magnetostrictive actuator by conducting an electromagnetic field analysis. The results showed that the effect of the thrust on the frequency changes depending on the length of the giant magnetostrictive material.

3D static bending analysis of functionally graded piezoelectric microplates resting on an elastic medium subjected to electro-mechanical loads using a size-dependent Hermitian C 2 finite layer method based on the consistent couple stress theory

Based on the consistent couple stress theory (CCST), we develop a size-dependent Hermitian C 2 finite layer method (FLM) for carrying out the three-dimensional (3D) static bending analysis of a simply-supported, functionally graded (FG) piezoelectric microplate which is placed under closed-circuit surface conditions. The microplate of interest is assumed to be resting on a Winkler-Pasternak foundation and subjected to either sinusoidal or uniformly distributed electro-mechanical loads. By setting the material length scale parameter at zero and ignoring the piezoelectric and flexoelectric effects, we reduce the formulation of the Hermitian C 2 FLM for analyzing FG piezoelectric microplates to that for analyzing FG piezoelectric macroplates and FG elastic microplates, respectively. The accuracy and the convergence rate of the Hermitian C 2 FLM are assessed by comparing the solutions it produces with the exact and approximate 3D solutions of FG piezoelectric macroplates and FG elastic microplates reported in the literature. Because the Hermitian C 2 FLM requires that the first-order and second-order derivatives of the primary variables must be continuous at each nodal plane, which in turn leads to their solutions converging rapidly and being able to obtain the accurate results of the electric and elastic variables induced in the microplates, especially for the transverse shear and normal stresses and the electric displacements. The effects of piezoelectricity, flexoelectricity, and the material length scale parameter on the deformations and stresses induced in the FG piezoelectric microplates are significant. Highlights A CCST-based Hermitian C 2 finite layer method (FLM) is developed for analyzing functionally graded (FG) piezoelectric microplates. The current FLM can be reduced to that for analyzing FG elastic microplates by ignoring the piezoelectric and flexoelectric effects. The current FLM can be reduced to that for analyzing FG piezoelectric macroplates by setting the material length scale parameter at zero. Implementing the current FLM reveals that its solutions converge rapidly and are in excellent agreement with those obtained using the exact 3D models. The effects of piezoelectricity, flexoelectricity, and the material length scale parameter on the static bending behavior of FG piezoelectric microplates are significant.

Effects of strain gradient on Moore-Gibson-Thompson generalized coupled non-fickian diffusion-thermoelasticity analysis in a Love-Bishop nanorod resonator: A size dependent meshless implementation

An effective meshless method based on the generalized finite difference (GFD) technique is developed to find the effects of strain gradient on the size-dependent Moore-Gibson-Thompson (MGT) generalized coupled non-Fickian diffusion-thermoelasticity analysis in a Love-Bishop nanorod resonator. A new MGT-based model with considering the strain gradient is proposed to obtain the shock-induced wave propagations in displacement, temperature and molar concentration fields in a Love-Bishop nanorod resonator for the first time. The transient governing equations of the size-dependent MGT generalized coupled non-Fickian diffusion-thermoelasticity are derived using the strain gradient equations of motion based on Love-Bishop theory, the size-dependent MGT-based energy balance equation and the size-dependent non-Fickian mass diffusion equation. The governing equations are transferred to Laplace domain and an effective GFD-based meshless method is employed to solve them. To obtain the temporal variation of fields’ variables, a proper Laplace inversion technique is employed in the problem. The small-scale effects in the MGT coupled non-Fickian diffusion-thermoelasticity analysis for the nano-sized Love-Bishop rods are taken into account using six small-scale parameters including three higher-order materials length parameters, the micro-length inertia, the micro-length thermal and the micro-length molar concentration parameters. The effects of small-scale parameters on wave propagations in all fields are discussed in detail.

Statistical analysis and Neural Network Modeling of functionally graded porous nanobeams vibration in an elastic medium by considering the surface effects

The natural frequency of a clamped–clamped functionally graded porous (FGP) nanobeam is predicted in this study. Material distribution is considered based on monotonous, symmetric, and non-symmetric patterns in the thickness direction. This paper deals with governing equations of nanobeams based on third-order shear deformation beam theory in conjunction with nonlocal strain gradient theory (NSGT) and surface effects. Artificial neural network (ANN) is utilized to predict the effect of eight parameters including temperature gradient, residual surface stress, porosity distribution pattern, porosity parameter, nonlocal and material length scale parameters, and elastic and shear coefficients of Pasternak foundation on the fundamental frequency of FGP nanobeam. Different training methods are selected to simulate input and output dependency. Results show that the dependency of the natural frequency is inverse to the temperature gradient and nonlocal parameter in the sense that increasing these factors will decrease the natural frequency. Also, increasing the material length scale parameter grows the effect of the nonlocal parameter. Residual surface stress, material length scale, and Pasternak foundation parameters have a direct effect on the output and among them; the material length scale parameter has a more noticeable effect. Finally, it was found that by increasing the porosity parameter value, the diversity of natural frequency levels up drastically

A study on the crack presence effect on dynamical behaviour of bi-directional compositionally imperfect material graded micro beams

This work uses the Quasi-3D (Q3D) shear and normal deformation beam concept in combination with the length scale capturing theory through the “Modified Couple Stress Theory” (MCST) and the novel computational approach namely, Differential Quadrature Finite Element Method (DQFEM) to investigate free vibratory conducts of an imperfect BD-FG microbeams with a crack. To obtain the relevant governing equations, the Lagrange's rule is utilized. “The differential quadrature” (DQ) and “Gauss-Lobatto quadrature” procedures for weighting coefficient matrices are used to easily construct the mass and stiffness matrices. The Gauss-Lobatto node scheme is used to determine the griding knots. In order to show the efficiency and exactness of the described numerical resolution method, the attained outcomes are authenticated with the similar results found in the literature. The effects of the crack position, crack depth, beam thickness by material length scale aspect, the volume fraction of material imperfection, edge supports state types, length through thickness factor, and the two-way material grading indexes on the nondimensional natural frequencies of 2D porous FG microbeams are inspected. This work will provide a numerical basis for the design of FG microstructures in the field of micromechanics. These findings can be used to construct porous FG microstructures in engineering.

Transient dynamic, energy absorption and out-phase/in-phase vibration response of coupled annular/circular SMA nanoplates assuming surface effects on frictional substrates

Shape and size are two important factors that affect the mechanical properties of nanostructures. Therefore, various forms of nano-scaled structures such as annular and circular ones have been applied in the engineering fields. Shape Memory Alloy (SMA), which can be used as the actuator because of its ability to change shapes, has potential applications in nano-electro mechanical system (NEMS). Dynamic behavior and the ability to absorb energy are two critical characteristics of advanced structures that are under static or various forms of dynamic loadings to be specific, this research numerically examined the in-phase/out-phase vibration, transient dynamic behavior under impulse load, and energy absorption in SMA annular/circular nanoplates with ferroelastic and pseudoelastic effects coupled together via damper and spring, placed between two frictional layers. In addition, an assumption of the Kuhn–Tucker phase transformation conditions was made. Moreover, the governing equations were derived based on Hyperbolic Higher Order Shear Deformation Theory (HHSDT) and solved using Differential Cubature Method (DCM). The constitutive equation of SMA proposed by Brinson was employed to model the pseudo-elastic behavior of SMA. Besides, Gurtin-Murdoch and modified couple stress theories were employed to calculate surface and micro-scale effects. As revealed by numerical achievements, under out-phase vibration mode, by increasing the surface effect coefficient to 0.4 when the annular nanoplate inner to outer radius ratio was 0.35, the natural frequency enhanced about 174%. As the material length scale parameter to thickness ratio was increased to 0.3 and the surface effects were considered, the energy absorption capacity was enhanced by nearly 28% and 23%, respectively.

Usability Testing of a Web-Based Empathy Training Portal: Mixed Methods Study.

The prepandemic period saw a rise in web-based teaching. However, web-based tools for teaching the essential clinical skill of cognitive empathy (also known as perspective taking) remain limited. More of these tools are needed and require testing for ease of use and understanding by students. This study aimed to evaluate the usability of the In Your Shoes web-based empathy training portal application for students using quantitative and qualitative methods. This 3-phase formative usability study used a mixed methods design. In mid-2021, we conducted a remote observation of student participants interacting with our portal application. Their qualitative reflections were captured, followed by data analysis and iterative design refinements of the application. Overall, 8 third- and fourth-year nursing students from an undergraduate baccalaureate program at a Canadian university, in the western province of Manitoba, were included in this study. Participants in phases 1 and 2 were remotely observed by 3 research personnel while engaged in predefined tasks. In phase 3, two student participants were asked to use the application as they liked in their own environments, after which a video-recorded exit interview with a think-aloud process was conducted as participants responded to the System Usability Scale. We calculated descriptive statistics and performed content analysis to analyze the results. This small study included 8 students with a range of technology skills. Usability themes were based on participants' comments on the application's appearance, content, navigation, and functionality. The biggest issues that participants experienced were with navigating the application's "tagging" features during video analysis and the length of educational material. We also observed variations in 2 participants' system usability scores in phase 3. This may be because of their different comfort levels with technology; however, additional research is required. We made iterative refinements to our prototype application (eg, added pop-up messages and provided a narrated video on the application's "tagging" function) based on participant feedback. With increasing engagement in web-based teaching, technology has become an essential medium for receiving health care education. We developed a novel prototype application as a supplemental classroom tool to foster students' self-directed learning of empathy. This study provided direction for refinements to optimize the usability of and satisfaction with this innovative application. Qualitative feedback revealed favorable input toward learning perspective taking place on the web and helpful recommendations for improving user experiences with the application. We could not fully assess the application's key functions owing to the COVID-19 protocols. Thus, our next step is to obtain feedback from a larger sample of student users, whose experiences performing "live" video capture, annotation, and analysis will be more authentic and wholesome with the refined application. We discuss our findings in relation to research on nursing education, perspective taking, and adaptive e-learning.

Reutilizing Single-Use Surgical Face Masks to Improve the Mechanical Properties of Concrete: A Feasibility Study

The coronavirus outbreak (COVID-19) has caused a sharp increase in the use of Single-Use Surgical Face Masks (SUSFMs) as personal protective equipment. These eventually end up in waste disposal facilities causing environmental pollution. Those that end up in the water bodies fragment into microplastics that affect marine life. Since the SUSFM materials are made from polypropylene, a thermoplastic polymer material that takes a long time to degrade, it is important to develop sustainable mitigation measures to remove them from the environment. This study investigated the feasibility of reutilizing SUSFMs in concrete. SUSFMs were shredded and added to C30/37 grade concrete in various percentages, 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, by mass of cement content. The specimens were cured for 28 days before being tested for compressive strength, splitting tensile strength, and ultrasonic pulse velocity. The compressive strength decreased with an increase in the length and dosage content. The least decrease of 10.4% was observed at 0.5% content of 30mm length of SUSFM material. The results showed that concrete improved regarding splitting tensile strength, with the highest increase of 15.2% at 0.5% content of 30mm SUSFM. In addition, the overall quality of concrete remains at UPV values of more than 4000m/s registering good quality concrete. The results underscore the use SUSFM material in concrete in order to improve its quality while at the same time reducing waste.