Effect of printing parameters on mechanical properties of extrusion-based additively manufactured ceramic parts

The purpose of this study is to investigate the effect of printing parameters on the physical and mechanical properties of additively manufactured ceramics (alumina and zirconia). Sample parts were obtained by extrusion-based additive manufacturing of a ceramic-binder mixture and subsequent post-processing (debinding and sintering). Their mechanical properties (microhardness, flexural strength, toughness) were measured and correlated with the printing parameters. Part orientation is the most significant factor for microhardness and flexural strength in both ceramic materials. Parts with vertical orientation show higher hardness while horizontal samples show higher flexural strength compared to their respective counterparts. Extrusion velocity was found to be insignificant for hardness and flexural strength. However, a marginal increase in fracture toughness with the increase in the extrusion velocity was observed. The fracture toughness of additively manufactured ceramics shows an increasing trend with elastic modulus and flexural strength and a decreasing trend with hardness and sintered density.     

Nonsimilar solutions for mixed convection of water at 4°C over a vertical surface with a convection boundary condition in a porous medium

A boundary layer analysis has been presented for the mixed convection of water at 4°C over a vertical plate embedded in a porous medium. The Robin or convective boundary condition at the surface has been considered where the heat lost from the surface is the product of a heat transfer coefficient and the temperature difference between the surface and the free stream. The governing non‐similar boundary layer equations for both the forced and free convection dominated regimes were solved numerically by means of an implicit finite difference method. The friction factor and dimensionless heat transfer rate (Nusselt number) are presented for several values of the dimensionless heat transfer coefficient and buoyancy parameter. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21022     

On stochastic methods for surface reconstruction

In this article, we present and discuss three statistical methods for surface reconstruction. A typical input to a surface reconstruction technique consists of a large set of points that has been sampled from a smooth surface and contains uncertain data in the form of noise and outliers. We first present a method that filters out uncertain and redundant information yielding a more accurate and economical surface representation. Then we present two methods, each of which converts the input point data to a standard shape representation; the first produces an implicit representation while the second yields a triangle mesh.     

An investigation of LPCVD and PECVD of in situ doped polycrystalline silicon for VLSI

In general, high-temperature processes cause thermal stresses and diffusion of dopants, resulting in reduced device yields. It is thus desirable to reduce the number of high-temperature steps and the use of an in situ doping technique eliminates one such step. In this investigation, low-pressure chemical vapour deposition (LPCVD) and plasma-enhanced chemical vapour deposition (PECVD) have been utilised to deposit in situ doped polycrystalline silicon films. The process characteristics and properties such as spreading resistance, grain structure, etch rate using a plasma and dopant concentrations of these films have been investigated and explained using a simple model for dopant activation and grain growth. It is shown that good-quality films suitable for VLSI can be produced.     

Characterization of Pb-doped Sr-Ferrites at Room Temperature

We report the magnetic characteristics of Pb-doped Sr-ferrites at room temperature. The polycrystalline samples of the series Sr_0.5Pb_0.5^{2 +} Fe_{12 - x}Pb_x^{3 +} O₁₉\mathrm{Sr}_{0.5}\mathrm{Pb}_{0.5}^{2 +} \mathrm{Fe}_{12 - x}\mathrm{Pb}_{x}^{3 +} \mathrm{O}_{19} (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) have been prepared by the standard ceramic technique with the aim to study the magnetic properties including coercivity, remanence, and energy at room temperature. The measurements show decreasing trends in coercivity and remanence from 4682 Oe to 1783 Oe and from 1833 G to 1511 G for the sample with x-content of 0.0 to 1.0, respectively. A minute addition of Pb affects the behavior of the materials by decreasing its energy product.     

Numerical Study of Heat and Mass Transfer MHD Viscous Flow Over a Moving Wedge in the Presence of Viscous Dissipation and Heat Source/Sink with Convective Boundary Condition

In this article, the effects of viscous dissipation and internal heat generation/absorption on combined heat and mass transfer MHD viscous fluid flow over a moving wedge in the presence of mass suction/injection with the convective boundary condition are carried out numerically for the various values of dimensionless parameters. With the help of similarity transformation, the momentum, energy, and concentration equations are reduced to a set of dimensionless non‐linear ordinary differential equations. The significance of the dimensionless velocity, temperature, mass profiles, and their gradients are presented in graphical form. Three types of flows—particularly the flat plate, vertical wedge, and stagnation point flows—in favorable and unfavorable regimes are analyzed. The obtained results confirm that the flow field is substantially influenced by the magnetic, stretching/shrinking, pressure, Prandtl number, heat generation/dissipation, and mass suction/injection parameters. Current results indicate that stretching a wall boundary causes an increase in velocity, temperature, shear stress, temperature, and mass gradients while shrinking causes a decreasing trend with these profiles. The special modified form of the current problem is found to be in good agreement with the other published data. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(1): 17–38, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21063     

Locality-aware process placement for parallel and distributed simulation in cloud data centers

The Journal of Supercomputing - Cloud is a multi-tenant paradigm providing resources as a service. With its easily available computing infrastructure, researchers are adopting cloud for...     

Stochastic production phase design for an open pit mining complex with multiple processing streams

In a mining complex, the mine is a source of supply of valuable material (ore) to a number of processes that convert the raw ore to a saleable product or a metal concentrate for production of the refined metal. In this context, expected variation in metal content throughout the extent of the orebody defines the inherent uncertainty in the supply of ore, which impacts the subsequent ore and metal production targets. Traditional optimization methods for designing production phases and ultimate pit limit of an open pit mine not only ignore the uncertainty in metal content, but, in addition, commonly assume that the mine delivers ore to a single processing facility. A stochastic network flow approach is proposed that jointly integrates uncertainty in supply of ore and multiple ore destinations into the development of production phase design and ultimate pit limit. An application at a copper mine demonstrates the intricacies of the new approach. The case study shows a 14% higher discounted cash flow when compared to the traditional approach.