Oxidation of Silicon Carbide in Environments Containing Potassium Salt Vapor

At high temperatures in clean oxidizing environments, SiC forms a very protective SiO₂ film, but, in environments containing low levels of gaseous alkali salt contaminants or where condensed salts may deposit on the surface, the resistance of the film is significantly reduced. Oxidation kinetics of SiC were measured by continuous thermogravimetric analysis in a controlled environment containing CO₂, H₂O, and O₂ plus low levels of potassium-containing salts. Potassium was found to be incorporated into the SiO₂ scale and to significantly change its transport properties and its morphology. The rate of scale formation was found to increase directly in proportion to K in the scale. A change in mechanism was observed when water vapor was added to the reacting gas stream.     

Effects of Hall current and two temperatures in transversely isotropic magnetothermoelastic with and without energy dissipation due to ramp-type heat

The present article is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of type-II and type-III. Laplace and Fourier transform techniques are applied to solve the problem. The analytical expressions of displacements, stress components, temperature change, and current density components are obtained in the transformed domain. A numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of Hall current and two temperatures on resulting quantities. Some special cases are also deduced from the present investigation.     

Deformation due to expanding ring load in modified couple stress thermoelastic diffusion in time and frequency domain

The two-dimensional problem of expanding ring load in a modified couple stress theory of thermoelastic diffusion with heat sources in time and frequency domains is investigated. The mathematical formulation prepared for thermoelastic diffusion solids with one and two relaxation times using Laplace and Hankel transforms. The displacements, stress components, temperature change, and chemical potential are obtained in a transformed domain. Numerical computation is performed for these quantities and the resulting quantities are shown graphically for the time and frequency domains. Comparisons are made with the results predicted by the two theories and different values of time and frequency. Particular cases of interest are also deduced.     

Viscous effect at an orthotropic micropolar boundary surface

Steady state responses at viscous fluid/ orthotropic micropolar solid interfaces to moving point loads have been studied. An eigenvalue approach using the Fourier transform has been employed to solve the problem. The displacement, microrotation and stress components for the orthotropic micropolar solids so obtained in the physical domain are computed numerically by applying numerical inversion technique. Viscosity and anisotropy effects on normal displacement, normal force stress and tangential couple stress have been shown graphically for a particular model. Some special cases of interest have been presented.     

Interaction dynamics of a spherical particle with a suspended liquid film

Hydrodynamics of collision interactions between a particle and gas‐liquid interface such as droplet/film is of keen interest in many engineering applications. The collision interaction between a suspended liquid (water) film of thickness 3.41 ± 0.04 mm and an impacting hydrophilic particle (glass ballotini) of different diameters (1.1–3.0 mm) in low particle impact Weber number ( ) range (1.4–33) is reported. Two distinct outcomes were observed—particle retention in the film at lower Weber number and complete penetration of the film toward higher Weber number cases. A collision parameter was defined based on energy balance approach to demarcate these two interaction regimes which agreed reasonably well with the experimental outcomes. It was shown that the liquid ligament forming in the complete penetration cases breaks up purely by “dripping/end pinch‐off” mechanism and not due to capillary wave instability. An analytical model based on energy balance approach was proposed to determine the liquid mass entrainment associated with the ligament which compared well with the experimental measurements. A good correlation between the %film mass entrained and the particle Bond number ( ) was obtained which indicated a dependency of Bo^1.72. Computationally, a three‐dimensional CFD model was developed to simulate these interactions using different contact angle boundary conditions which in general showed reasonable agreement with experiment but also indicated deficiency of a constant contact angle value to depict the interaction physics in entirety. The computed force profiles from computational fluid dynamics (CFD) model suggest dominance of the pressure force over the viscous force almost by an order of magnitude in all the Weber number cases studied. © 2015 American Institute of Chemical Engineers AIChE J, 62: 295–314, 2016     

Numerical investigation of heat transfer and friction factor in ribbed triangular duct solar air heater using Computational fluid dynamics (CFD)

Journal of Mechanical Science and Technology - The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened...     

Thermal modeling of drilling process in titanium alloy (Ti-6Al-4V)

Abstract

In drilling in titanium alloys, heat trapped in a hole adversely affects tool life, hole surface quality and integrity. Therefore, modeling temperature distribution in drilling is vital for effective heat dissipation and improving quality of drilled surfaces. The existing numerical and finite element models consider only frictional heat, whereas the effect of shear heat generation and tertiary heat generation is neglected. In the present work, a comprehensive thermal model of the drilling process is developed by considering all heat generated in shear, friction and tertiary zones. The drill cutting edges are divided into a series of independent elementary cutting tools (ECT). The calculated heat flux loads are applied on an individual ECT in the finite element model to determine the temperature distribution and the maximum temperature around the cutting edge. The temperature in the drill was also measured experimentally with the help of an Infrared (IR) camera. The results of numerical simulations lie within the error of ～8.75% when compared to the prior studies, and ～5.41% when compared to our experimental work. The thermal model gives the temperature distribution, and the maximum temperature observed at the corner of cutting edge was 604.2°C at a cutting speed of 35?m/min.     

Intracavernous Injection of Platelet-Rich Plasma Therapy Enhances Erectile Function and Decreases the Mortality Rate in Streptozotocin-Induced Diabetic Rats

Erectile dysfunction (ED) is an agonizing complication of diabetes mellitus (DM) and it is challenging to treat ED in DM patients. Platelet-rich plasma (PRP) is a unique therapeutic strategy comprising intrinsic growth factors. An attempt was made to explore the potentiality of the PRP treatment in DM-induced ED rats in various groups (control, DM-non-ED, DM-ED, and DM-ED treated with PRP). Streptozotocin (STZ) was used to induce DM in rats. The blood glucose levels of the DM rats were maintained at >300 mg/dl. In the 18-week experiment, survival rate, body weight, intracavernous pressure (ICP) variations, and arterial blood pressure were analyzed. The tissue restoration results were validated by histological, immunofluorescence, and transmission electron microscopic analysis. PRP treatment of DM-ED rats significantly increased all parameters of erectile function compared to pre-treatment of PRP and DM-ED treated with vehicle. The histological results revealed that PRP treatment substantially enhanced the regeneration of myelinated nerves and decreased the atrophy of corporal smooth muscle. Notably, the PRP treatment immensely enhanced the survival rate in post-surgery DM-ED rats. These results indicated certain benefits of PRP treatment in delaying damage and preventing post-surgery complications in DM patients. Hence, PRP treatment is a novel multifactorial strategy for DM-ED patients.     

Internalization of Escherichia coli O157:H7 following biological and mechanical disruption of growing spinach plants

The internalization and persistence of a bioluminescent Escherichia coli O157:H7 Ph1 was investigated in growing spinach plants that had been either biologically or mechanically damaged. In control (undamaged) plants cultivated in soil microcosms inoculated with E. coli O157:H7 Phl, the bacterium was recovered from surface-sterilized root tissue but not from leaves. Mechanical disruption of the seminal root and root hairs of the plants did not result in the internalization of the pathogen into the aerial leaf tissue. When imprints of the root tissue were made on plates of tryptic soy agar plus ampicillin, no colonies of E. coli O157:H7 were observed around damaged tissue. The roots of growing plants were exposed to the northern root-knot nematode, Meloidogyne hapla, in the presence of E. coli O157:H7. Although this treatment caused knot formation on the roots, it did not enhance the internalization of the bacterium into the plant vascular system. Coinoculation of intact leaves with E. coli O157:H7 and the phytopathogen Pseudomonas syringae DC3000 resulted in localized necrosis, but the persistence of the human pathogen was not affected. The mechanical disruption of roots does not result in the internalization of E. coli O157:H7 into the aerial tissue of spinach, and there does not appear to be any effect of P. syringae in terms of enhancing the persistence of E. coli O157:H7 in spinach leaves.     

Electro-dissolution of 30Nb–Ti alloys in methanolic sulfuric acid—Optimal conditions for electropolishing

The electro-dissolution behaviour of a (30 at.%) Niobium–Titanium (NbTi) alloy in non-aqueous methanolic sulfuric acid solution using the rotating disc electrode (RDE) was ascertained. The optimal condition for electropolishing and the mechanism were proposed. The influence of the rotation rate, process temperature and sulfuric acid concentration on the dissolution kinetics was investigated. The dissolution rate (limiting current) increases linearly with increase in rotation rate and follows a Levich behaviour confirming a mass transport controlled process. The temperature dependence in terms of Arrhenius plot renders an activation energy value of E_a = 16.1 kJ mol⁻¹ for the process. The dissolution rate shows a strong dependence on the sulfuric acid concentration (1 M, 3 M and 5 M). Higher sulfuric acid concentrations lead to decreased dissolution rates (limiting current). The dissolution process is mass transport controlled in all concentrations of sulfuric acid. From an electrochemical perspective, a 3 M sulfuric acid was chosen as optimum owing to better controllability of the material removal rate. The dissolving ions are the probable rate limiting species, indicating a compact salt-film mechanism. The average root mean square (RMS) roughness value for an electropolished surface was approximately 10 nm, which is significantly lower than a mechanically polished surface.