Kinetic and Hydrodynamic Aspects of Polymer Flocculation

This article highlights the kinetic and hydrodynamic aspects of polymer-induced flocculation, as well as some of the common applications of flocculation in mineral processing. Rate equations for polymer adsorption, floe formation, floe growth and break up are summarized and analyzed. Similarly, hydro-dynamic functions relevant to the various aspects of flocculation are summarized and analyzed. Experimental results on the effects of hydrodynamic conditions on the flocculation process arc presented.     

Vibration analysis of a rotating flexible shaft–disk system

Free vibrations of a spinning disk–shaft system are analysed using the finite-element method. The spinning disk is described by the Kirchhoff plate theory. The shaft is modelled by a rotating beam. Using Lagrange’s principle and including the rigid-body translation and tilting motion, equations of motion of the spinning flexible disk and shaft are derived consistently to satisfying the geometric compatibility conditions on the internal boundaries among the substructures. The finite-element method is then used to discretize the derived governing equations. The method is applied to the shaft–disk spinning system. The sensitivity to the running speed as well as the effect of both disk flexibility and boundary condition on the natural frequencies of the spinning system are numerically investigated.     

Experimental evaluation of dynamic resource orchestration in multi-layer (packet over flexi-grid optical) networks

Network services in 5G will be rolled out as pools of virtual network functions (VNFs) exploiting the advantages of both software-defined networking and network function virtualization. In this context, 5G network services are envisaged as ordered sequences of VNFs resulting in the so-called VNF Forwarding Graphs (VNFFGs). Such VNFs can be allocated over a number of distributed but interconnected data centers (DCs). In this work, a cloud/network orchestrator is discussed to dynamically process and accommodate VNFFG requests over a pool of DCs interconnected by a multi-layer (packet/flexi-grid optical) transport network infrastructure. Two different cloud and network resource allocation algorithms are proposed aiming at: (1) minimizing the distance between the selected DCs and (2) minimizing the load (i.e., consumed cloud resources) of the chosen DCs. In the performance evaluation, the proposed algorithms are experimentally validated and compared on the CTTC ADRENALINE testbed.

     

Shaft misalignment effect on bearings dynamical behavior

The inherent problems of the rotating machine dysfunction are often caused by shaft misalignment. This defect generates some important loads and vibrations, and can lead to a premature failure of the bearing, the shaft, or the coupling. This work deals with the development of a theoretical model describing this phenomenon. This allows obtaining and analysing the vibration response as well as the reaction in bearings.     

Extraction and Refining of High Purity Terbium Metal From Rare Earth Resources

Terbium metal finds applications in the phosphor industry such as in fluorescent lighting and television tubes, and in the electronic industry for the production of magneto-optical recording media for computer storage discs, and in the production of specialty alloys. There are no direct high grade ores of terbium, rather it occurs as a very minor constituent in ores of the rare-earth minerals. For example, terbium oxide constitutes only 0.01% of California's bastnaesite. 0.05-0.16% of Florida' s monazite. and in the order of 1.00% in the Malaysian xenotime. Currently, the chief rare-earth bearing minerals of commercial importance are bastnaesite (California), monazite (Florida, Australia. India and China) and xenotime( Malaysia).

Extraction of high purity terbium metal involves several major steps. These are

(1) Recovery of rare earth minerals from ores into (REO)concentrates

(2)Leaching of rare earth metals (REM) into leach solutions. This step is often preceded by a roasting step and a mild leaching to remove associated carbonates

(3)Separation or concentration of the rare earth metals into groups or individual metal solutions by either solvent extraction and/ or ion-exchange. Terbium is precipitated out from the solvent extraction solution as oxalate or carbonate compounds, which are converted to terbium oxide upon heating in air

(4)Production and refining of terbium from terbium oxide. These involve conversion of terbium oxide to terbium fluoride, followed by a metallothermic reduction step to the terbium metal, using calcium metal reductant. 3N (99.9%) and 4N (99.99%) purity terbium metal can be obtained by vacuum remelting and sublimation (distillation) of the crude metal, respectively.

In this article, modern practices for extraction and refining of high purity terbium metal is reviewed and reported.     

Shaft misalignment effect on bearings dynamical behavior

The inherent problems of the rotating machine dysfunction are often caused by shaft misalignment. This defect generates some important loads and vibrations, and can lead to a premature failure of the bearing, the shaft, or the coupling. This work deals with the development of a theoretical model describing this phenomenon. This allows obtaining and analysing the vibration response as well as the reaction in bearings.     

Reinforcement of polyolefins‐based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (PP) and ethylene propylene copolymer (EPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated‐Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO₂ systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high‐shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization‐process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties. POLYM. ENG. SCI., 55:2328–2338, 2015. © 2015 Society of Plastics Engineers     

HYDRODYNAMIC AND ELASTOHYDRODYNAMIC STUDIES OF A CYLINDRICAL JOURNAL BEARING

In this article, the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is analyzed. The variety of simulation models covers hydrodynamic (HD) and elastohydrodynamic (EHD) lubrication theories. The Reynolds equations governing the flow in the clearance space of the journal bearing are obtained by considering the effect of mass transfer across the fluid film. The finite element method with an iteration scheme was employed to solve both the Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell. The converged solutions for the lubricant flow and elastic deformation vector are obtained. Dynamic characteristics of the journal bearing are computed for HD and EHD theories. Numerical simulation results show that the flexibility of bearing liner has a significant influence on the performance of a cylindrical journal bearing. Indeed, the elastic deformations of the bearing liner extend the pressure area in the bearing and increase the minimum film thickness. Although, dynamic coefficient, load capacity and attitude angle decrease.     

Storage stability of traditional Tunisian butter oil produced from spontaneous fermentation of cow's milk

Physicochemical characteristics of traditional Tunisian butter (TTB) and thermal stability of the butter oil were studied. Thermal stability of samples was estimated by using the accelerated shelf life testing method. Effect of heating on some quality characteristics of traditional Tunisian butter oil (TTBO) was investigated and compared at different temperatures (60°C, 100°C and 130°C). Induction period of sample heated at 60°C was important compared to that at 100°C and 130°C. This result may indicate the sensitivity of TTBO to elevated temperature. Absorption at 232 and 270 nm, acidity and PV increased rapidly after reaching the oxidation induction time. The temperature had a significant effect on the formation of oxidation products in traditional butter oil (TTBO). Fatty acid composition of TTBO was also changed after heating. This may explain the observed modification on some quality characteristics of TTBO such as viscosity, hardness, cohesiveness and colour. As a consequence, heat treatment produced alterations in the oxidative status of the butter oil that could affect the shelf life.