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Date palm rachis fibers are rich in cellulose, relatively inexpensive, and readily available in Algeria. The aim of this study is to investigate the morphology, structure, mechanical and physicochemical characteristics of both vascular bundles and fiber strands extracted from date palm rachis. The difficulties encountered are associated to the extraction of the fibers without damaging them. The study focuses on the morphological and surface roughness analysis using optical and scanning electron microscopies (SEM), and a non-contact 3D profiler. The chemical, physical and thermal properties have been studied using Fouriertransform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The mechanical properties were accessed by tensile tests and they were analyzed using two-parameter Weibull distribution.

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This paper presents a comparative study of both the surface roughness (Ra and Rz) and the tangential cutting force (Fz) achieved during the machining of EN-GJL-250 cast iron by uncoated and coated silicon nitride ceramics (Si 3 N 4). Experimental tests were planned according to a L 27 Taguchi design. Both the surfaces of response (RSM) and analysis of variance (ANOVA) methods were applied to determine and classify the cutting parameters affecting the surface roughness and cutting forces and for deriving the mathematical models to be used in the optimization stage when implementing the desirability function. Moreover, in order to localize the surface defects in the machined profiles, 2D and 3D topographic analysis based on the Abbott-Firestone curve was employed. The results obtained show that the surface roughness is largely influenced by both the feed rate and the cutting speed, while the depth of cut is the factor that most influenced the cutting force followed by the feed rate. Furthermore, the coated ceramic tool demonstrates a better surface quality and lower cutting force than those obtained by uncoated ceramic. The 3D topographic analysis indicates the generated surfaces as constituted by numerous interrupted ridges. The wear tests show that the CC1690 ceramics are more efficient than the CC6090 ceramics in terms of cutting force, surface roughness and wear resistance.

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Steady state and dynamic solutions to the problem of isothermal elastohydrodynamic lubrication of single-layered journal bearings are derived and presented. The mathematical problem comprises two parts: fluid and elasticity. The elasticity problem is governed by the elastostatic equations which are solved by application of a complex variable approach using the complex Kolosov-Muskhelishvili potentials. The fluid problem is described by the two-dimensional Reynolds equation which is discretized using a finite difference approach and solved by application of the Gauss-Seidel scheme with the Swift-Stieber boundary conditions. The fluid-structure coupling is achieved by an iterative procedure with an under-relaxation algorithm. The dynamic coefficients are obtained by use of a first-order perturbation approach. The results obtained show that the proposed elasticity model permits a fast solution of the problem, particularly under dynamic conditions. They also show that, under the effect of coating elastic deformation, the contact geometry is modified and the load-carrying capacity decreases while the stability margin of the journal bearing system increases.