Polymer nanocomposites with cellulose nanocrystals made by co-precipitation

A premixing method to produce polymer nanocomposites with cellulose nanocrystals (CNCs) is reported. This method involves the dissolution and dispersion of a polymer and CNCs in an organic solvent, co-precipitation into water, drying of the resulting particles, and subsequent melt processing. The key aspect of the method is that it allows the kinetic trapping of well-dispersed CNCs in the polymer. Although the nanocomposite must be dried before subsequent melt-processing, the organic solvent can be removed by extraction in water and recycled, leaving only residual water in the composite, which is easily eliminated. This process presents numerous advantages compared with the time-consuming solvent casting process, which often suffers from incomplete organic solvent evaporation. As a testbed, polyurethane (PU) composites with up to 30% of CNCs were prepared. These materials were either melt-processed as produced or used as a masterbatch, i.e., they were diluted via melt-mixing with neat polymer toward nanocomposites with lower filler content. All nanocomposites prepared using this approach had a homogeneous appearance. They displayed similar mechanical properties as the corresponding reference materials made by solvent casting, and significantly better properties than materials prepared by direct melt mixing.Peer ReviewedPostprint (author's final draft

Deformation Modeling of Flexible Pavement in Expansive Subgrade in Texas

The tendency of expansive subgrade soil to undergo swelling and shrinkage with the change in moisture has a significant impact on the performance of the pavement. The repeated cycles of wet and dry periods throughout a year lead to considerable stress concentration in the pavement subgrade soil. Such stress concentrations leads to the formation of severe pavement cracks. The objective of the research is to develop a prediction model to estimate the deformation of pavement over expansive subgrade. Two pavement sites—one farm to market road and one state highway—were monitored regularly using moisture and temperature sensors along with rain gauges. Additionally, geophysical testing was performed to obtain a continuous profile of the subgrade soil over time. Topographical surveying and horizontal inclinometer readings were taken to determine pavement deformation. The field monitoring data resulted in a maximum movement up to 80 mm in the farm to market road, and almost 38 mm in the state highway. The field data were statistically evaluated to develop a deformation prediction model. The validation of the model indicated that only a fraction of the deformation was reflected by seasonal variation, while inclusion of rainfall events in the equation significantly improved the model. Furthermore, the prediction model also incorporated the effects of change in temperature and resistivity values. The generated model could find its application in predicting pavement deformation with respect to rainfall at any time of the year

Polymer nanocomposites with cellulose nanocrystals made by co‐precipitation

A premixing method to produce polymer nanocomposites with cellulose nanocrystals (CNCs) is reported. This method involves the dissolution and dispersion of a polymer and CNCs in an organic solvent, co-precipitation into water, drying of the resulting particles, and subsequent melt processing. The key aspect of the method is that it allows the kinetic trapping of well-dispersed CNCs in the polymer. Although the nanocomposite must be dried before subsequent melt-processing, the organic solvent can be removed by extraction in water and recycled, leaving only residual water in the composite, which is easily eliminated. This process presents numerous advantages compared with the time-consuming solvent casting process, which often suffers from incomplete organic solvent evaporation. As a testbed, polyurethane (PU) composites with up to 30% of CNCs were prepared. These materials were either melt-processed as produced or used as a masterbatch, i.e., they were diluted via melt-mixing with neat polymer toward nanocomposites with lower filler content. All nanocomposites prepared using this approach had a homogeneous appearance. They displayed similar mechanical properties as the corresponding reference materials made by solvent casting, and significantly better properties than materials prepared by direct melt mixing.Peer ReviewedPostprint (author's final draft

Shape Memory Composites Based on Electrospun Poly(vinyl alcohol) Fibers and a Thermoplastic Polyether Block Amide Elastomer

The present study aimed at developing new thermally responsive shape-memory composites, that were fabricated by compacting mats of electrospun poly­(vinyl alcohol) (PVA) fibers and sheets of a thermoplastic polyether block amide elastomer (PEBA). This design was based on the expectation that the combination of the rubber elasticity of the PEBA matrix and the mechanical switching exploitable through the reversible glass transition temperature (<i>T</i>_g) of the PVA filler could be combined to create materials that display shape memory characteristics as an emergent effect. Dynamic mechanical analyses (DMA) show that, upon introduction of 10–20% w/w PVA fibers, the room-temperature storage modulus (<i>E</i>′) increased by a factor of 4–5 in comparison to the neat PEBA, and they reveal a stepwise reduction of <i>E</i>′ around the <i>T</i>_g of PVA (85 °C). This transition could indeed be utilized to fix a temporary shape and recover the permanent shape. At low strain, the fixity was 66 ± 14% and the recovery was 98 ± 2%. Overall, the data validate a simple and practical strategy for the fabrication of shape memory composites that involves a melt compaction process and employs two commercially available polymers

A Study on the Effectiveness of Spatial Filters on Thermal Image Pre-Processing and Correlation Technique for Quantifying Defect Size

Thermal imaging plays a vital role in structural health monitoring of various materials and provides insight into the defect present due to aging, deterioration, and fault during construction. This study investigated the effectiveness of spatial filters during pre-processing of thermal images and a correlation technique in post-processing, as well as exploited its application in non-destructive testing and evaluation of defects in steel structures. Two linear filters (i.e., Gaussian and Window Averaging) and a non-linear filter (i.e., Median) were implemented during pre-processing of a pulsed thermography image sequence. The effectiveness of implemented filters was then assessed using signal to noise ratio as a quality metric. The result of pre-processing revealed that each implemented filter is capable of reducing impulse noise and producing high-quality images; additionally, when comparing the signal to noise ratio, the Gaussian filter dominated both Window Averaging and Median filters. Defect size was determined using a correlation technique on a sequence of pulsed thermography images that had been pre-processed with a Gaussian filter. Finally, it is concluded that the correlation technique could be applied to the fast measurement of defect size, even though the accuracy may depend on the detection limit of thermography and defect size to depth ratio

Triage practices for emergency care delivery: a qualitative study among febrile patients and healthcare workers in a tertiary care hospital in Nepal

Abstract Background Improving screening and triage practices is essential for early severity assessments at the first point of contact and ensuring timely attention by healthcare workers (HCWs). The main objective of this study was to explore the triage process among febrile patients and HCWs in the emergency department (ED) of a tertiary care hospital in a resource-constrained setting. Methods This qualitative study was conducted from March to May 2023 at the ED of Tribhuvan University Teaching Hospital (TUTH), Nepal. The study included in-depth interviews with febrile patients (n = 15) and HCWs (n = 15). Additionally, direct observation notes (n = 20) were collected to document the triage process and patients’ experiences in the ED. Data underwent thematic analysis using the Interpretative Phenomenological Analysis (IPA) approach. Results The ED of TUTH offered comprehensive triage services with clear delineation for the severity of febrile patients in line with the World Health Organization (WHO) guidelines. Nonetheless, challenges and constraints were identified. In the ED, evenings were generally the busiest period, and the triage process was not thorough during night shifts. Perception of triage was limited among patients and variable among HCWs. Digitalizing recordings of patient information including payment was deemed necessary for effective management of patients’ waiting times at the triage station. High patient throughput added pressure on HCWs and had a potential influence on the delivery of services. Availability of medical equipment and space were also identified as challenges, with patients sometimes compelled to share beds. There were constraints related to waste disposal, hygiene, cleanliness, and the availability and maintenance of washrooms. Febrile patients experienced delays in receiving timely consultations and laboratory investigation reports, which affected their rapid diagnosis and discharge; nonetheless, patients were satisfied with the overall healthcare services received in the ED. Conclusions Improving current triage management requires resource organization, including optimizing the waiting time of patients through a digitalized system. Urgent priorities involve upgrading visitor facilities, patient consultations, laboratory investigations, hygiene, and sanitation. HCWs’ recommendations to resource the ED with more equipment, space, and beds and a dedicated triage officer to ensure 24-hour service, together with training and incentives, warrant further attention

Additional file 1 of Triage practices for emergency care delivery: a qualitative study among febrile patients and healthcare workers in a tertiary care hospital in Nepal

Additional file 1. Word document; IDI Guide; interview guides used to interview patients and HCWs during the study