Thrust bearings in time-dependent laminar flow

An analysis of thrust bearing characteristics in a motion generated by an accelerating slider is presented. Numerical solutions to the governing differential equations are obtained for the case of constant but arbitrary acceleration and for the case of acceleration proportional to time. It is found that the space inertia effect increases the pressure and consequently the loadcarrying capacity. However, drag also increases. The results indicated three classes of solutions depending on the magnitude of a dimensionless number which is the ratio of the time required for the fluid particle to traverse the length of the bearing to the time required for the slider to reach its terminal velocity.     

Studies on the composites of cellulose triacetate (prepared from sugar cane pulp) and gelatin

Sugarcane waste (bagasse) which is hitherto discarded as a waste at sugarcane parlors and jaggery units was recovered and cellulose triacetate (CTA) was prepared from the same, after isolation of cellulose. Using this CTA, CTA–gelatin composites were prepared. The materials prepared (i.e., sugarcane cellulose, CTA, CTA–gelatin composites) were characterized for their mechanical properties, water absorption capacity, infrared spectroscopy, and scanning electron microscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 847–853, 2001     

IONIC MASS TRANSFER IN THREE-PHASE FLUIDIZED BEDS IN THE PRESENCE OF DISC PROMOTERS

Three-phase fluidized beds have wide applications in process industries. The present investigation is carried out to identify the enhancement of ionic mass transfer coefficients due to the presence of a disc promoter in a three-phase fluidized bed. A diffusion-controlled electrode reaction—reduction of ferricyanide ion—was employed to obtain mass transfer coefficient data. The mass transfer coefficient data were obtained by varying the geometric variables of the disc promoter (disc diameter, disc spacing) and dynamic variables (superficial liquid velocity, superficial gas velocity). The effect of particle diameter was also investigated. The investigations revealed that the mass transfer coefficients were enhanced with decreased disc spacing, increased disc diameter, increased superficial gas velocity, increased superficial liquid velocity, and increased particle diameter.     

Using ball indentation to determine the mechanical properties of an Al-7475 alloy processed by high-pressure torsion

A commercial Al-7475 alloy with an initial grain size of ~40 μm was processed by high-pressure torsion (HPT) for up to 2 turns at room temperature under a pressure of 6.0 GPa. The mechanical properties of the processed materials were evaluated by the ball-indentation technique to give information on the yield strength and the ultimate tensile strength. Following HPT, microhardness measurements revealed a steady increase in the hardness values from the centers of the samples towards the edges. After 2 turns, the ultimate tensile strength was ~1050 MPa at the edge of the disk and the measured grain size was ~70 nm. The results demonstrate the potential for using HPT to achieve excellent grain refinement in the Al-7475 alloy.     

Effect of vibrating disc electrode on ionic mass transfer in an electrolytic cell

In the present investigation, a vertical disc electrode was vibrated in a rectangular electrolytic cell. The cell consisted of equimolal potassium ferricyanide and ferrocyanide electrolyte with excess indifferent electrolyte, sodium hydroxide. The mass transfer data were obtained on the disc electrode by varying the amplitude of vibration (0.033 to 0.089 m), frequency of vibration (2.93 to 16.16 Hz) and diameter (0.0125 to 0.0315 m) of the disc electrode. The mass transfer coefficient was increased with the decrease in the diameter of the disc electrode. The mass transfer coefficient was enhanced from 12 to 52 fold due to vibration.     

Optimal channel estimation and interference cancellation in MIMO-OFDM system using MN-based improved AMO model

In recent years, MIMO-OFDM plays a significant role due to its high-speed transmission rate. Various research studies have been carried out regarding the channel estimation to obtain optimal output without affecting the system performances. But due to increased bit error rate achieving optimal channel estimation is considered as a challenging task. Therefore, this paper proposes the modified Newton’s (MN)-based Improved Animal Migration Optimization (IAMO) algorithm in MIMO-OFDM system. The significant objective of this proposed approach involves the minimization of bit error rate and to enhance the system performance. In this paper, a modified Newton’s method is utilized to determine the discover capability and to speed up the convergence rate thereby obtaining the optimum search space positions. In addition to this, the proposed method is utilized to restrict the interference in the MIMO-OFDM systems. Finally, the performance of the proposed method is compared with other channel estimation methods to determine the effectiveness of the system. The experimental and comparative analyses are carried out, and the results demonstrate that the proposed approach provides better frequency-selective channels than other state-of-the-art methods.

     

Cu‐Al2O3/H2O hybrid nanofluid flow past a porous stretching sheet due to temperatue‐dependent viscosity and viscous dissipation

The resent development of research in the field of nano technology introduced hybrid nanofluids which are advanced classes of fluids with augmented thermal properties and it gives better results comparing to regular nanofluid. The aim of the present work is to study the significant effects of variable viscosity and viscous dissipation on a porous stretching sheet in the presence of hybrid nanofluid and radiative heating. In this model, two types of nanoparticles, namely copper (Cu) and alumina oxide (Al₂O₃), are suspended in the base fluid H₂O to form a hybrid nanoliquid. The novelty of this study is to introduce variable viscosity along with natural convection in the momentum equation and viscous dissipation in the energy equation. Mathematical modeling is employed in this study, whereby partial differential equations for the fluid flow are constructed and transformed to a set of ordinary differential equations, and hence resolved computationally by Runge‐Kutta‐Fehlberg method along with shooting scheme. The most important results for relevant parameters concerning the flow heat measure, surface drag, and heat transfer coefficients are thoroughly examined and presented graphically for both Cu‐Al₂O₃/water hybrid nanofluids. There is an increase in hybrid nanofluid velocity profile with mounting values of $\lambda$, and the Cu‐water nanofluid converges to the boundary more quickly than the hybrid nanofluid due to the occurrence of variable viscosity. The results concluded that the Nusselt number of the viscous fluid is lower than that of the nanofluid and hence the hybrid nanofluid (ie, heat transfer rate: normal fluid < nanofluid < hybrid nanofluid). The outcomes of present investigations are in close agreement with the viscous fluid as a particular case.     

Mass transport of cobalt and nickel in Incoloy-800

Lattice diffusion of cobalt and nickel in Incoloy-800 has been studied in the temperature range 1070 to 1500K by serial sectioning and residual activity techniques using radioactive tracers⁶⁰Co and⁶³Ni. The lattice diffusion coefficient can be expressed by the relation:

Dry Sliding Wear Properties of a 7075-T6 Aluminum Alloy Coated with Ni-P (h) in Different Pretreatment Conditions

Dry sliding wear behavior of electroless nickel-phosphorus (EN) coating of thickness ~35 μm deposited on a 7075-T6 aluminum alloy was studied. EN was deposited from a bath with sodium hypophosphite as a reducing agent. In as-deposited conditions, plating with 6-9 wt.% phosphorus has a mixture of amorphous and microcrystalline phase. Three pretreatments of Zn (zincate), Ni strike and absorbed hypophosphite layer were given to the substrate before EN coating to examine their wear performance. The surface morphology of the pretreatments was studied by a confocal laser scanning microscope. The performances of these pretreatments of EN were evaluated by dry sliding wear studies and followed by SEM studies. The results suggest that the wear behavior of EN mostly depends on the pretreatment conditions. Heat treatment at temperature of 400 °C can enhance the wear resistance properties for all types of pretreatment conditioned samples and in addition that the average coefficient of friction of 400 °C specimens (μ_av) had minimum value as compared to 200 °C specimens. Ni strike provided better interlocking adhesion between EN and Al and this pretreatment noticeably improved the wear, frictional and hardness behavior of the EN coatings on 7075 Al substrate and further enhanced it by heat treatment of 400 °C/h.