Synthesis and Physical Properties of Potential Biolubricants based on Ricinoleic Acid

The desire to replace petroleum-based materials with environmentally friendly and sustainable alternatives has stimulated the development of vegetable oil-based materials as biolubricants. Our studies have focused on molecules that might be produced by biosynthesis of genetically altered oilseed plants with limited post-harvest modification. Various ricinoleate and 12-hydroxystearate esters and estolides were synthesized and their melting points and viscosities were documented. The antifriction and antiwear properties of some esters were evaluated with a microtribometer. The purities of all the products were >98–99% by gas chromatography. Some of these compounds showed melting points, viscosities, and lubricity suitable for uses as biolubricants. Various ricinoleate esters acylated at the 12 positions with short-chain acids were particularly promising.     

Morphology and size dependent optical properties of CdS nanostructures

CdS nanoparticles with different sizes ranging from 2.5 nm to 300 nm and nanorods with aspect ratio -32 were synthesized by simple solvothermal process with a view to explore the effect of size and shape on the optical properties of these nanoforms. Solvent, temperature and the Cd source played important role in determining the morphologies and sizes of the nanocrystals. Comparative study of the optical properties of these nanoforms showed systematic changes in the optical absorption spectra with the reduction in particle size. Nanorods showed bulk like properties. Photoluminescence and Raman studies were carried out to explore the size and morphology dependent optical properties of the CdS nanoforms.     

Improving efficiency of CCS-enabled IGCC power plant through the use of recycle flue gas for coal gasification

Clean Technologies and Environmental Policy - CO2 capture from coal-fired power plants is necessary for continued use of coal as a fuel. Proven CO2 capture techniques such as amine absorption and...     

Solving general multi-class closed queuing networks using parametric decomposition

This paper presents a new approach to evaluate the performance of general multi-class closed queuing networks. The approach uses parametric characterization of the traffic processes to derive two-moment approximations for performance measures at individual nodes. Based on these approximations, linkage equations are derived to establish the relationships between the various nodes in the network. These relationships result in a system of non-linear equations that is solved using an iterative procedure. Numerical studies comparing the performance of the approach with detailed simulations suggest that the approach yields fairly accurate estimates of performance measures without significant computational complexity.     

Evolution of Texture and Microstructure in Commercially Pure Titanium with Change in Strain Path During Rolling

The evolution of microstructure and texture in commercially pure titanium has been studied as a function of strain path during rolling using experimental techniques and viscoplastic self-consistent simulations. Four different strain paths, namely unidirectional rolling, two-step cross rolling, multistep cross rolling, and reverse rolling, have been employed to decipher the effect of strain path change on the evolution of deformation texture and microstructure. The cross-rolled samples show higher hardness with lower microstrain and intragranular misorientation compared to the unidirectional rolled sample as determined from X-ray diffraction and electron backscatter diffraction, respectively. The higher hardness of the cross-rolled samples is attributed to orientation hardening due to the near basal texture. Viscoplastic self-consistent simulations are able to successfully predict the texture evolution of the differently rolled samples. Simulation results indicate the higher contribution of basal slip in the formation of near basal texture and as well as lower intragranular misorientation in the cross-rolled samples.     

Social embeddedness in an online weight management programme is linked to greater weight loss

The obesity epidemic is heightening chronic disease risk globally. Online weight management (OWM) communities could potentially promote weight loss among large numbers of people at low cost. Because little is known about the impact of these online communities, we examined the relationship between individual and social network variables, and weight loss in a large, international OWM programme. We studied the online activity and weight change of 22 419 members of an OWM system during a six-month period, focusing especially on the 2033 members with at least one friend within the community. Using Heckman''s sample-selection procedure to account for potential selection bias and data censoring, we found that initial body mass index, adherence to self-monitoring and social networking were significantly correlated with weight loss. Remarkably, greater embeddedness in the network was the variable with the highest statistical significance in our model for weight loss. Average per cent weight loss at six months increased in a graded manner from 4.1% for non-networked members, to 5.2% for those with a few (two to nine) friends, to 6.8% for those connected to the giant component of the network, to 8.3% for those with high social embeddedness. Social networking within an OWM community, and particularly when highly embedded, may offer a potent, scalable way to curb the obesity epidemic and other disorders that could benefit from behavioural changes.     

Evolution of crystallographic texture during equal channel angular extrusion of copper: The role of material variables

The evolution of crystallographic texture during equal channel angular extrusion (ECAE) using route A has been investigated experimentally as well as by simulations for three types of materials: pure, commercially pure, and impure (cast) copper. The ECAE texture of copper can be compared with simple shear textures. However, there are deviations in terms of location of the respective components. These differences can be nearly reproduced using a recent flow line approach for ECAE deformation (L.S. Tóth, R. Arruffat-Massion, L. Germain, S.C. Baik, and S. Suwas: Acta Mater., 2004, vol. 52, pp. 1885–98) with the help of the viscoplastic self-consistent polycrystal model. The main texture components common to all three materials are A_1E and B_E/B_E; the latter ones are significantly stronger in the cast material. The effect of further deformation on texture modification depends on material variables, such as purity, initial microstructure, and texture.     

Studies on buried layer resistors

Multilayer thick-film technology is one of the important technologies adopted in the miniaturization of electronic systems. Generally, only interconnections are made in the intermediate layers. The possibility of fabricating resistors along with interconnections in the buried layers/intermediate layers using conventional thick-film materials has been examined in this study. The fabrication has been carried out by processing layer after layer. It has been found that the buried layer resistors exhibited a sheet resistivity lower than those fabricated as open resistors. This change in sheet resistivity has been attributed to multiple firings that the resistors undergo during the fabrication. This reduction in sheet resistivity has been found to be due to segregation of active materials. A model has been proposed to explain this change in sheet resistivity through segregation of the active material. The work reported in the paper clearly indicates that buried resistors with consistent values (±10%) can be fabricated using conventional materials. However, the design of the resistors has to be carried out using modified sheet resistivities. The model that is proposed also indicates how one can make a paste that is likely to exhibit the same sheet resistivity for buried resistors and open resistors.