Investigating the Mechanical Properties and Durability of Asphalt Mixture Modified with Epoxidized Natural Rubber (ENR) under Short and Long-Term Aging Conditions.

Modifiers such as fibers, fillers, natural and synthetic polymer extenders, oxidants and anti-oxidants, and anti-stripping agents are added to produce modified asphalt. However, polymers are the most widely utilized modifiers to enhance the function of asphalt mixtures. The objective of this research was to evaluate the mechanical properties and durability of epoxidized natural rubber (ENR)-modified asphalt mix under short- and long-term aging conditions. The physical and rheological characteristics of the base asphalt and ENR-modified asphalt (ENRMA) were tested. In order to evaluate the mechanical properties and durability of the modified mixtures, the resilient modulus of the ENR-asphalt mixtures under unaged, and short- and long-term aging conditions at various temperatures and frequencies was obtained. Furthermore, the resistance to moisture damage of asphalt mixtures was investigated. The findings showed that the stiffness of the ENR-asphalt mixes increased because of the mutual influence of short- and long-term aging on the mixes. In addition, ENR reduced the susceptibility to moisture damage. The stiffness of the mixes was influenced by the temperature and frequencies. By using mathematical modelling via the multivariable power least squares method, it was found that temperature was the dominant factor among all other factors. The results suggested that the durability of asphalt pavements is improved by using ENR.

Effects of medical staff's turning movement on dispersion of airborne particles under large air supply diffuser during operative surgeries.

The present study examines the effect of medical staff's turning movements on particle concentration in the surgical zone and settlement on the patient under single large diffuser (SLD) ventilation. A computational domain representing the operating room (OR) was constructed using computer-aided design (CAD) software. The airflow and particle models were validated against the published data before conducting the case studies. The airflow in the OR was simulated using an RNG k-ε turbulence model, while the dispersion of the particles was simulated using a discrete phase model based on the Lagrangian approach. A user-defined function (UDF) code was written and compiled in the simulation software to describe the medical staff member's turning movements. In this study, three cases were examined: baseline, SLD 1, and SLD 2, with the air supply areas of 4.3 m2, 5.7 m2, and 15.9 m2, respectively. Results show that SLD ventilations in an OR can reduce the number of dispersed particles in the surgical zone. The particles that settled on the patient were reduced by 41% and 39% when using the SLD 1 and SLD 2 ventilations, respectively. The use of the larger air supply area of SLD 2 ventilation in the present study does not significantly reduce the particles that settle on a patient. Likewise, the use of SLD 2 ventilation may increase operating and maintenance costs.