Understanding surface discharge activity with epoxy silicon carbide nanocomposites

Surface discharge inception voltage (SDIV) with epoxy silicon carbide nanocomposite material in LN₂ medium is about three times higher than that in air. Under AC voltage that SDIV increases with increase in wt% of silicon carbide (SIC) material in epoxy nanocomposites. Dielectric measurements indicates an increase in temperature of the specimen and the weight percentage of SIC filler in epoxy resin increases the permittivity of the material. Also, irrespective of percentage of SiC in epoxy resin, the tan(δ) reduces with increase in frequency and the converse at room temperature. The UHF signal measured during surface discharge activity in air/LN₂ medium has frequency content in the range of 0.5–1.5 GHz. The charge decay characteristics of epoxy SiC nanocomposites indicate the deposited charge is less and the charge decay time reduces with increase in wt% of SiC in epoxy resin. The surface roughness caused due to surface discharge activity is high under negative DC voltage compared with positive DC/AC voltage. The phase resolved partial discharge (PRPD) analysis indicates discharges occur at the near peak of the AC voltage on inception of surface discharge and at higher stress it appears at the rising portion of AC voltage. POLYM. ENG. SCI., 57:1349–1355, 2017. © 2017 Society of Plastics Engineers     

The alkali roasting of complex oxide minerals for high purity chemicals-beyond the Le Chatelier era into the 21st century

A discussion of a 19th century process of solubilizing alumina from bauxite by Louise Le Chatelier is made here to see whether their contributions to the industrial chemistry is worthy of revisiting for developing “cleaner and greener” processing of minerals and industrial inorganic chemicals. The high-temperature process reduces waste by producing co-products such ilmenite, magnetite, and sodium silicate. The CO₂ generated from alkali decomposition is recycled in the process for regenerating NaHCO₃.     

Effect of CeO2 on the sintering behaviour of zirconia–alumina composite

Precursor for a composite containing equimolar proportion of ZrO₂ and Al₂O₃ having higher reactivity has been synthesized by the wet interaction of inorganic salts in aqueous phase. Sintering of the compact body indicated that the densification rate increased from 1500 °C. The role of CeO₂ as a dopant was positive with respect to densification and retention of t-ZrO₂.     

Software diversity: state of the art and perspectives

Diversity is prevalent in modern software systems to facilitate adapting the software to customer requirements or the execution environment. Diversity has an impact on all phases of the software development process. Appropriate means and organizational structures are required to deal with the additional complexity introduced by software variability. This introductory article to the special section “Software Diversity—Modeling, Analysis and Evolution” provides an overview of the current state of the art in diverse systems development and discusses challenges and potential solutions. The article covers requirements analysis, design, implementation, verification and validation, maintenance and evolution as well as organizational aspects. It also provides an overview of the articles which are part of this special section and addresses particular issues of diverse systems development.     

A review of the current knowledge and challenges of hydrothermal carbonization for biomass conversion

Greenhouse gases emitted from the excessive use of fossil fuels are threatening the environment, and thus alternative resources like biomass are being considered as a replacement. Biomass with high moisture content is better treated by hydrothermal carbonization method than any other process to generate biofuel. Research on this method on a lab scale has progressed recently. However, due to the complex reaction mechanisms and operational barriers, more improvements are required to make it a commercial technology. This paper aims to review the development of hydrothermal carbonization with a focus on the practical aspects of the process. Many references have been reviewed critically to provide a well-structured source for improving this process. After providing information about the biomass structure and general knowledge of hydrothermal carbonization, the challenges faced in attempts to improve the process have been identified as lack of valid kinetic and heat transfer models and insufficient data on continuous and large-scale reactors. Useful and practical suggestions have been presented to tackle all these challenges.     

Effect of Convection Heat Transfer on Performance of Waste Heat Thermoelectric Generator

Efficiency of energy conversion processes can be improved if waste heat is converted to electricity. A thermoelectric generator (TEG) can directly convert waste heat to electricity. The TEG typically suffers from low efficiency due to various reasons, such as ohmic heating, surface-to-surrounding convection losses, and unfavorable material properties. In this work, the effect of surface-to-surrounding convection heat transfer losses on the performance of TEG is studied analytically and numerically. A one-dimensional (1-D) analytical model is developed that includes surface convection, conduction, ohmic heating, and Peltier, Seebeck, and Thomson effects with top and bottom surfaces of TEG exposed to convective boundary conditions. Using the analytical solutions, different performance parameters (e.g., heat input, power output, and efficiency) are calculated and expressed graphically as functions of thermal source and sink temperatures and convection heat transfer coefficient. Finally, a two-dimensional (2-D) mathematical model is solved numerically to observe qualitative results of thermal and electric fields inside the TEG. For all calculations, temperature-dependent thermal/electric properties are considered. Increase in thermal source temperature results in an increase in the power output with adiabatic side wall conditions. A change in boundary condition to convection heat transfer from adiabatic boundary has a large impact on thermal efficiency.     

Effect of MgO Grain Size on Thermal Expansion Behavior of Alumina–Magnesia–Carbon Refractory

The effect of MgO grain size on the permanent linear change behavior of resin bonded alumina–magnesia–carbon refractory has been studied in relation to the formation of spinel phase in these refractories as a function of firing time and temperature. From scanning electron microscopic studies, spinelization at the interface of Al₂O₃ and MgO grains has also been studied to determine the reaction kinetics for gaining insight into the process.     

Tribological Behavior of AZ31 Alloy Against Si3N4 Using In-vitro and In-silico Submodeling Approach for Human Hip Prosthesis

Silicon - The use of magnesium alloy (AZ31) has profound applications in biomedical field as a substitute for joint replacements. The present study aims at analyzing the tribological behavior of...     

Learning latent actions to control assistive robots

Autonomous Robots - Assistive robot arms enable people with disabilities to conduct everyday tasks on their own. These arms are dexterous and high-dimensional; however, the interfaces people must...     

A family of thioxanthato ruthenium and osmium aryls

The title complexes of type M(RL²)(PPh₃)₂(CO)(S₂CSEt) ( 2a : M = Ru; 2b : M = Os) have been synthesized in excellent yields by reacting M(RL¹)(PPh₃)₂(CO)X ( 1a : M = Ru, × = Cl; 1b : M = Os, × = Br) with potassium ethyl thioxanthate and have been characterized with the help of spectral and electrochemical data. The RL² ligand in 2 is the imine-phenol tautomer of N-C₆H₄R(p)-4-methylsalicylaldimine (R = Me, MeO, Cl) coordinated at the carbanionic-C2 atom only while RL¹ in 1 is the iminium-phenolato tautomer chelated via carbanionic-C2 and phenolato-O atoms. The synthetic reaction is thus attended with tautomerization of the Schiff base ligand. It is also associated with a rotation of the ligand by ˜180° around the M–C bond in order to exclude steric repulsion. These features have been revealed by structure determination of 2a (R = Me). The metallated aldimine ring is found to be highly noncoplanar (dihedral angle ˜40°) with the thioxanthate chelate ring due to steric repulsion originating from the relatively large size of the sulfur atom. This phenomenon, which is absent in both the precursor 1 (R = Me) and in the carboxylate analogue Ru(MeL²)(PPh₃)₂(CO)(O₂CMe), 7 , has distinctive effects on bond parameters of 2a (R = Me). Thus the two Ru–P bonds in 2a (R = Me) differ in length by as much as 0.06 Å. The thioxanthate 2 is thermodynamically more stable than the precursor 1 as well as the carboxylate 7 . Accordingly, both of these are irreversibly transformed to 2a (R = Me) upon treatment with thioxanthate.