Improvement of Thermal Characteristics of Refractory Castable by Addition of Gel-Route Spinel Nanoparticles

Selected physical and thermal properties of conventional spinel-alumina castables were compared with those of castables produced using spinel fines prepared from a prepared gel. Limited numbers of hydroxyl groups created around the spinel precursor helped to improve thermal shock resistance. Micrographic examination confirmed that retained nanodimensional spinels firmly connected the hibonite and corundum grains in the castable, developing multiple interfaces after densification. Castable-containing spinel with excess alumina powder was found to have the best combination of bulk density, apparent porosity, and hot modulus of rupture. The reactive magnesia fine used to prepare in situ spinel-bonded castable was not found to give satisfactory results, owing to progressive disintegration of brucite-type compounds and abnormally grown spinels. Thermal characteristics of castables were assessed by differential thermal analysis (DTA), measurement of porosity, and percent linear change (PLC). Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS) analysis of the gel-derived spinel and castable confirmed their differences, particularly with commercial spinel having comparable chemistry but lacking nanocrystalline structure.     

Influence of organoclay dispersion on air retention and fatigue resistance of tyre inner liner compound

In a pneumatic tire, the contained air carries the load of the vehicle and also augments performance for other functional requirements, such as, rolling resistance, ride and handling, durability, and so on. The inner liner of the tire is responsible to ensure air retention by virtue of its high air impermeability. The present study focused on developing inner-liner compounds of improved air impermeability by utilizing platelet filler (layered silicate). The obtained organoclay was subjected to a pre-treatment process called exfoliation to increase the d spacing between the clay layers that further improved the morphological aspect of the compound. The inner-liner compound has been modified by partial replacement of carbon black with organically modified bentonite clay in 1:1 and 2.5:1 ratio. Air impermeability of rubber compounds was tested in a gas permeability tester. Field emission scanning electron microscope, transmission electron microscope, atomic force microscope, and x-ray diffraction were utilized to understand the distribution and dispersion of clay in the rubber compounds. Fatigue crack growth analysis was carried out to measure the fatigue life of the materials. The modified compounds exhibited air impermeability improvement from 7% to 30% vs the reference carbon-black filled compound with improved mechanical properties and filler dispersion.     

Energy efficient fault-tolerant multipath routing scheme for wireless sensor networks

In wireless sensor network （MSN）, reliability is the main issue to design any routing technique. To design a comprehensive reliable wireless sensor network, it is essential to consider node failure and energy constrain as inevitable phenomena. In this paper we present energy efficient node fault diagnosis and recovery for wireless sensor networks referred as energy efficient fault tolerant multipath routing scheme for wireless sensor network. The scheme is based on multipath data routing. One shortest path is used for main data routing in our scheme and other two backup paths are used as alternative path for faulty network and to handle the overloaded traffic on main channel. Shortest pat data routing ensures energy efficient data routing. Extensive simulation results have revealed that the performance of the proposed scheme is energy efficient and can tolerates more than 60% of fault.     

Systematic approach to treat chronic osteomyelitis through ceftriaxone-sulbactam impregnated porous β-tri calcium phosphate localized delivery system

Present investigation deals with in vitro and in vivo experimentation to treat chronic osteomyelitis, using pure β-tri calcium phosphate porous scaffolds. A novel approach was given to treat such infections using the scaffolds and drug combinations consisting of ideal antibiotics. In vitro studies include variation of porosity with interconnectivity, pore-drug interfacial studies by SEM-EDAX and drug elution studies both in contact with PBS and SBF at ca. 37 °C. In vivo trials were based on experimental osteomyelitis in rabbit model in tibia by Staphylococcus aureus. Characterizations included histopathology, radiology and estimation of drug in both bone and serum for 42 days by HPLC and subsequent bone-biomaterial interface by SEM. Samples having 60-65% porosity with average pore size ca. 55 μm and higher interconnectivity (22-113 μm), high adsorption efficiency (ca. 79%) of drug showed prolonged, sustained release of the drugs considered being sufficient to treat chronic osteomyelitis with desirable bone formation.     

Comparative Evaluations and Microstructure: Mechanical Property Relations of Sintered Silicon Carbide Consolidated by Various Techniques

A comparative evaluation between pressureless or self-sintered silicon carbide (SSiC), hot-pressed silicon carbide (HP-SiC), and spark plasma-sintered silicon carbide (SPS-SiC) has been carried out with emphasis on examination of their microstructures and mechanical properties. The effect of sample dimensions on density and properties of SPS-SiC has been also examined. Elastic modulus, flexural strength, and fracture toughness measured by indentation or testing of single-edge notched beam specimens have been found to follow the following trend, HP-SiC > SSiC > SPS-SiC. The SPS-SiC samples have shown size-dependent densification and mechanical properties, with the smaller sample exhibiting superior properties. The mechanical properties of sintered SiC samples appear to be influenced by relative density, grain size, and morphology, as well as the existence of intergranular glassy phase. Studies of fracture surface morphologies have revealed the mechanism of failure to be transgranular in SSiC or HP-SiC, and intergranular in case of SPS-SiC, indicating the dominating influence of grain size and α-SiC formation with high aspect ratio.     

Isolation and characterization of biosurfactant producing microorganisms from petroleum contaminated soil samples for EOR and bioremediation

Using of biosurfactant producing microorganisms for pipeline cleaning, bioremediation, enhanced oil recovery, etc. is a much soughed approach of petroleum industry. Although, many alternatives are available to serve these purposes, being ecofriendly and economic, microbial application is considered superior than most of the alternatives. This paper presents a comprehensive study on effectiveness of bacterial strain isolated from oil contaminated soil sample of Lakwa oilfield for required purposes. Its temperature sustainability and surfactant production capability was studied. Further characteristics of the produced biosurfactant were assessed through Emulsification Index measurement, Fourier Transform Infrared Spectra, Drop Collapse Test, Contact Angle and Viscosity measurement.     

Predictions of High Strain Rate Failure Modes in Layered Aluminum Composites

A dislocation density-based crystalline plasticity formulation, specialized finite-element techniques, and rational crystallographic orientation relations were used to predict and characterize the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary distributions. Different layer arrangements were investigated for high strain rate applications and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-bonded interface and the potential delamination of the layers. Shear strain localization, dynamic cracking, and delamination are the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be used to optimize behavior for high strain rate applications.     

Efficient computation of cross-sections from human brain model by geometric processing

In this paper, an efficient method for computing the cross-sections of the internal structure from a 3D human brain model has been proposed. It can extract image slices from the brain model in sagittal, coronal, and axial views used for computed tomography and ultrasonography. A doubly connected edge list (DCEL) has been used for speeding up the computation during geometric processing, since the DCEL captures the topological relationship among vertices, edges, and faces of the triangulated surface. For a sectional plane, image slices are computed quite efficiently using the information of geometric coherence from the previous sectional plane with the help of DCEL. The optimal distance between two successive sectional planes is determined from the frequency distribution (Poisson distribution) of the edge lengths in the model. It reduces computational overhead without compromising on the quality of output, as demonstrated by experimental results.     

Seasonal variability in aerosol optical depth over India: a spatio-temporal analysis using the MODIS aerosol product

Aerosols are one of the key components of climate systems. They absorb and scatter both solar and terrestrial radiation and produce strong surface as well as atmospheric radiative forcing effects. Aerosol climatology includes the measurement of light extinction by aerosol scattering and absorption, by procedures such as aerosol optical depth (AOD), angstrom exponent (α), single-scattering albedo (ω), and size distribution. This article analyses the dynamics of seasonal AOD over the Indian subcontinent from 2001 to 2009 using the MODIS level 2 data set. The analysis carried out for winter, pre-monsoon, monsoon, and post-monsoon seasons is based on 8 days’ composite AOD data for selected months representative of each season. The spatial variability of AOD has been shown to be 0.47 μm and 0.66 μm for fine- and coarse-mode aerosols, respectively, which illustrates the principle of relative difference. The dynamics of seasonally averaged AOD over the period under study represent an increasing tendency from 0.20 to 0.37 at 0.47 μm and from 0.16 to 0.26 at 0.66 μm during winter (2003–2009), whereas AOD in the pre-monsoon season ranged from 0.24 to 0.16 at 0.47 μm and from 0.24 to 0.16 at 0.66 μm (2005–2009). The monsoon season yielded an AOD of less than 0.15 throughout the study period, and the post-monsoon season recorded an increasing tendency from 0.18 to 0.29 at 0.47 μm and from 0.16 to 0.19 at 0.66 μm (2005–2009), reflecting a similar trend to that of the winter AOD curve. The spatial distribution of AOD shows that the northern part of India – especially the Indo-Gangetic plain – remains most affected by high AOD throughout the year. Such high AOD can be attributed to increasing anthropogenic emission due to an ever-increasing population, and urban, industrial, and other economic activities causing high concentrations of fine-mode organic and inorganic aerosol particles, along with coarse soil and mineral dust over the Indo-Gangetic plain.     

Offset error analysis of ball-end mill for cutter-path generation from point-based surfaces

Moulds and dies with sculptured surfaces are usually finished using a three-axis computer numerically controlled milling machine with a ball-end mill. In this paper, the surface shapes are defined by a rectangular grid of surface points and the inverse offset method (IOM) is used to generate the cutter paths. The error of the offset (cutter path) points generated by the IOM due to spacing of surface points is determined. The error analysis enables an appropriately dense set of points to be chosen so that the offset surface can be generated within a specified tolerance.