Lubricant Rheological Behavior Effect Analysis on the Performance of Finite Porous Self- Lubricating Journal Bearings

In this paper, the hydrodynamic lubrication of finite porous self-lubricating journal bearings is investigated taking into account the rheological lubricant behavior effect. The modified Reynolds equation is derived by considering both the fluid flow in the porous matrix and the lubricant rheological behavior where Darcy’s law and power- law model were used. Governing differential equations were solved numerically using the finite difference method. Static characteristics are obtained by considering three types of lubricants: pseudo-plastic, dilatant and Newtonian fluids. Obtained results showed that the power law index, n, has important effects on the performance of porous and non-porous bearings. An improvement in the fluid bearing characteristics (load capacity, pressure) is observed for dilatant fluids (n>1) while these characteristics decreased for pseudo-plastic fluids (n<1). The permeability of the porous structure has significant effects on the performance of porous journal bearings of finite length, particularly at higher eccentricity ratios. Good agreement is observed between the results obtained in this study and those of literature revue

Hydrodynamic self-lubricating journal bearings analysis using Rabinowitsch fluid lubricant

International audienc

Changes in bacterial populations in refrigerated raw milk collected from a semi-arid area of Algeria

Most of the studies on milk microbiota have been performed on cows’ milk from animals reared in temperate and humid areas. In this work, changes in the bacterial consortium of refrigerated raw milk collected from cows grazed in a semi-arid area of Algeria were studied during 21 days of refrigerated storage. Twenty bacterial morpho-physiotypes were selected among 150 isolates from milk at different times over storage and identified by partial 16S rRNA gene sequencing. The dominant bacterial populations were characterized by a few species. Stenotrophomonas rhizophila, S. maltophilia and Chryseobacterium indologenes were predominant during the first 7 days, Lactobacillus pentosus and L. plantarum were isolated only after the 10th day, while Acinetobacter spp. was isolated at the end of storage. Compared to the current literature on milk from temperate zones, sluggish and incomplete microbial growth was observed with a long incubation phase ranging from 6.7 to 10.5 days and a maximum growth not exceeding 5.3 log colony-forming units (CFU) · mL−1. The composition of milk microbiota and its evolution over refrigeration suggest a bio-geographical characterization due to environmental factors. In particular, the possible presence of antimicrobial molecules coming from plants grazed in the semi-arid zone around the farm may account for the presence of selected microbial species and the extended milk shelf-life. Despite this being a preliminary work, these results encourage the use of arid herbs in animal feed and motivate scientists to focus their efforts on the study of biochemical composition of plants from arid areas and their antimicrobial activity