Fracture behaviour assessment of high-performance fibre-reinforced concrete at high strain rates using interpretable modelling approaches.

High-performance fibre-reinforced concrete (HPFRC), a type of cementitious composite material known for its exceptional mechanical performance, has widespread applications in structures exposed to severe dynamic loading conditions. However, understanding nonlinear HPFRC fracture behaviour, particularly under high strain rates, remains challenging given the complexities of assessment procedures and cost-intensive nature of experiments. This study presents an interpretable framework for modelling and analysing HPFRC fracture strength at high strain rates. A wide range of machine learning methods, including ensemble techniques, were employed to capture multivariate effects of eight essential input features (e.g., mortar compressive strength, fibre physical and mechanical properties, cross-sectional area, and strain rate) on fracture strength response. To assess the derived models, a novel evaluation procedure was proposed involving a data-based analysis, employing established metrics (i.e., coefficient of determination, root mean squared error, and mean absolute error via K-fold cross-validation) and a domain experts-involved evaluation utilising global sensitivity analysis to discern first-order and higher-order interactions among input factors. The proposed approach efficiently yielded both quantitative and qualitative insights into crucial input factors governing HPFRC fracture strength with limited experimental data. The obtained findings highlight the significance of multivariate effects, such as the interaction between strain rate and fibre tensile strength, and between fibre volume and fibre diameter, on fracture behaviour. The proposed interpretable framework aims to provide a powerful tool for proactive material failure analysis by understanding fracture behaviour and identifying potential weak and strong interactions among input factors of HPFRC-based samples. Moreover, the utilisation of the proposed approach enables researchers and civil engineers to efficiently focus on the most critical input parameters during the early design stage and ensuring the structural integrity and safety of HPFRC-based constructions.

Production of 7,10-dihydroxy-8(E)-octadecenoic acid using cell-free supernatant of Pseudomonas aeruginosa.

Cell-free synthesis has been adopted in the bioconversion process due to its known advantages, such as fast production rate, high product content, and no substrate/product inhibition effect. In this study, the cell-free supernatant of Pseudomonas aeruginosa was used to improve the production of 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) from oleic acid. DOD production using cell-free supernatant demonstrated reduction in bioconversion duration and higher product concentration than conventional method using whole cell culture. The maximum DOD concentration (6.41 g/L) was obtained after 36 h of biotransformation using 1 % v/v oleic acid as a substrate with a productivity of 0.178 g/L/h and a yield of 74.8 %. DOD concentration, productivity, and yield using cell-free supernatant were 2.12, 7.12, and 2.22 times higher, respectively, than using the conventional whole cell culture method. Of the carbon and nitrogen sources used in pre-culture, galactose and sodium glutamate along with diammonium phosphate were found to be the most effective for DOD production. An incubation temperature of 27 °C and pH 8.0 were found to be most favorable for DOD production. In addition, sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis demonstrated the presence of enzymes related to DOD production in the cell-free supernatant, which was substantiated by performing DOD production experiment using the supernatant enzymes extracted from protein gel bands with oleic acid as a substrate. To the best of our knowledge, this is the first report on DOD production using a cell-free supernatant and verifying the existence of the relevant enzymes in the cell-free supernatant. Compared to whole cell process, cell-free DOD production holds several advantages, including higher DOD productivity which could be beneficial for large-scale production.

Microbial Conversion of Vegetable Oil to Hydroxy Fatty Acid and Its Application to Bio-Based Polyurethane Synthesis.

New polyurethanes were synthesized based on dihydroxy fatty acid obtained by the microbial conversion of olive oil. Monounsaturated 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced from olive oil by Pseudomonas aeruginosa PR3 and reacted with hexamethylene diisocyanate (HMDI) at different ratios to form polyurethanes. Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry confirmed the synthesis of DOD. The thermal and tensile properties of the polyurethanes were investigated by differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. At an isocyanate/hydroxyl ratio of 1.4, the polyurethane exhibited an elongation at break of 59.2% and a high tensile strength of 37.9 MPa. DOD was also mixed with polycaprolactone diol or polyethylene glycol at different weight ratios and then reacted with HMDI to produce new polyurethanes of various properties. These polyurethanes displayed higher elongation at break and good thermal stability. This is the first report on the synthesis of polyurethanes based on DOD produced by the microbial conversion of vegetable oil.