Passenger exposure to respiratory aerosols in a train cabin: Effects of window, injection source, output flow location

Nowadays the use of public transportation (PT) has been identified as high risk as due to the transfer of particles carrying the coronavirus from an infected passenger to others. This study puts forward a new computational framework for predicting the spread of droplets produced while the infected passenger talking inside the cabin of a train during various scenarios, including the changes in the outflows\u27 location and the infected passenger\u27s position. CFD was used to conduct the study, using the Euler-Lagrange approach to capture the transmission of particles, and Reynolds-averaged Navier–Stokes equations (RANS) to compute the airflow field. The results revealed that opening the window reduces the duration of particles inside the domain. So that when the window is open, the particle\u27s shelf time can decrease to 25 percent comparing with closed mode. It was found that the passenger sitting next to the infected passenger encountered the highest infection risk. The conclusions made in this work show that the most desirable situation is obtained when the infected passenger is sitting next to the exits, whether the window is closed or open. The results of this paper offer comprehensive insights into how to keep indoor environments safe against infection aerosols

Multi-objective optimization of a double tapered flow field Proton Exchange Membrane Fuel cell

Flow fields are essential in Proton Exchange Membrane Fuel Cell (PEMFC) performance. Appropriate in-plane tapering in the main channels width of parallel flow fields enhances flow distribution uniformity, increasing performance. To the best of the authors, there is no literature discussing the through-plane inclination in a parallel flow field with in-plane tapered main channels. This study develops a surrogate model based on a data set to study double tapering in the flow field. The three-dimensional multiphase Computational Fluid Dynamics (CFD) generates the data set. Decision variables are the angle of depth tapering, operating pressure, temperature, stoichiometries, and voltage. Also, the objectives are power density and efficiency. Proper depth tapering increases mass transfer, decreasing the concentration loss. The increment of 19.6% in maximum power is captured by tapering. Depth tapering in the parallel flow field improves efficiency, especially at a higher temperature and lower pressure. Furthermore, a multi-layer multi-objective optimization methods are utilized. A reference depth tapering angle θ is defined. Optimum characteristics are the tapering angle of 0.13θ, the temperature of 329.9 K, the operating pressure of 4 atm, the operating voltage of 0.465 V, and the unit stoichiometry of both sides. Optimum characteristics bring the best performance, an efficiency of 21.55%, and a power density of 0.75 W cm−2

Cathode Side Transport Phenomena Investigation and Multi-Objective Optimization of a Tapered Parallel Flow Field PEMFC

A Proton Exchange Membrane Fuel Cell (PEMFC) provides stable, emission-free, high-efficiency power. Water management and durability of PEMFCs are directly affected by transport phenomena at the cathode side. In the present study, transport phenomena are investigated and optimized in a tapered parallel flow field. Main channels in the flow field are tapered, which increases limiting current density by 41%. Two objectives, i.e. water saturation and transport resistance, are considered metrics for transport phenomena in a tapered parallel flow field PEMFC. Operating pressure, temperature, stoichiometries at both sides, and the porosity of gas diffusion layers are selected as parameters to be optimized. Two functions are generated for objectives by integrating 3D multiphase-flow computational fluid dynamics and Response Surface Methodology. Multi-Objective Optimization (MOO) is carried out with two different methods. Multi-Objective Particle Swarm Optimization (MOPSO) and Non-dominated Sorting Genetic Algorithm II (NSGA-II) are employed to produce two challenging Pareto fronts. The results demonstrate that MOPSO performs better than NSGA-II. MOPSO recognized quite the same Pareto front with lower runtime. In the last step, the Technique of Order Preference Similarity to the Ideal Solution (TOPSIS) is used to select an optimum point from the Pareto front. The results are compared against experimental data, and good correspondence is observed. The optimum features are temperature 323, pressure 1 atm, anode stoichiometry 3, cathode stoichiometry 2.62, and porosity 0.68. The porosity and pressure played the most significant roles in determining water saturation and resistance

Cathode Side Transport Phenomena Investigation and Multi-Objective Optimization of a Tapered Parallel Flow Field PEMFC

A Proton Exchange Membrane Fuel Cell (PEMFC) provides stable, emission-free, high-efficiency power. Water management and durability of PEMFCs are directly affected by transport phenomena at the cathode side. In the present study, transport phenomena are investigated and optimized in a tapered parallel flow field. Main channels in the flow field are tapered, which increases limiting current density by 41%. Two objectives, i.e. water saturation and transport resistance, are considered metrics for transport phenomena in a tapered parallel flow field PEMFC. Operating pressure, temperature, stoichiometries at both sides, and the porosity of gas diffusion layers are selected as parameters to be optimized. Two functions are generated for objectives by integrating 3D multiphase-flow computational fluid dynamics and Response Surface Methodology. Multi-Objective Optimization (MOO) is carried out with two different methods. Multi-Objective Particle Swarm Optimization (MOPSO) and Non-dominated Sorting Genetic Algorithm II (NSGA-II) are employed to produce two challenging Pareto fronts. The results demonstrate that MOPSO performs better than NSGA-II. MOPSO recognized quite the same Pareto front with lower runtime. In the last step, the Technique of Order Preference Similarity to the Ideal Solution (TOPSIS) is used to select an optimum point from the Pareto front. The results are compared against experimental data, and good correspondence is observed. The optimum features are temperature 323, pressure 1 atm, anode stoichiometry 3, cathode stoichiometry 2.62, and porosity 0.68. The porosity and pressure played the most significant roles in determining water saturation and resistance

Investigation of MexAB-OprM Efflux Pump Expression Level in Pseudomonas aeruginosa Strains Isolated from Patients Hospitalized in Shahid Motahari Hospital in Tehran City using Real-Time PCR method (Iran)

Background and Objectives: Drug resistance in Pseudomonas aeruginosa strains has become a worldwide problem, and efflux pumps are one of the major resistance mechanisms in this bacterium. The aim of this study was to identify the mutation in mexA and mexB pumps and to investigate the expression level of mexA pump in the isolates from burn patients.   Methods: This study was conducted as a descriptive study on 100 isolates of P. aeruginosa isolated from patients hospitalized in Shahid Motahari Hospital during 2014-2015. Antibiogram tests were performed using disc diffusion (according to CLSI guidelines). The inhibitory effect of carbonyl cyanide 3-chlorophenylhydrazone (CCCP), was assessed by broth microdilution method. Mutation in mexA and mexB genes, was detected by PCR and sequencing, and the expression level of mexA gene, was evaluated by real-time PCR and 2−ΔΔCT formula.   Results: Ninety-five out of 100 isolates of P. aeruginosa, were resistant to imipenem. Sixteen isolates had response to the inhibitory effect, and a 4-fold reduction was observed in MIC results at the presence of this inhibitor. In one isolate, glycine was replaced by aspartic acid at position 257 of mexB protein sequence, but no change was seen in MexA. All isolates had mexA and mexB genes. Twenty percent of the isolates showed overexpression in mexA gene.   Conclusion: According to the results of this study, the antibiotic resistance as a result of overexpression of efflux pump, is of great concern. Hence, infection control by accurate management of drug prescription and identification of resistant isolates, is essential to prevent the spread of resistance.   &nbsp