Basics: Current base oil quality and technological options for its improvement— an Overview

Recent technological developments have revolutionised the lubricant industry by spurring a widespread quality improvement in both base oils and additives, giving superior finished lubricants. The upgrading of base oils is being brought about by more demanding requirements from original equipment manufacturers (OEMs), by government regulations, and through consumer awareness, environmental concerns, decreasing supply of high‐quality lubricant‐bearing crudes, and expanding markets worldwide. Present‐day lubricant demand is for maximum oxidation stability, superior low‐temperature performance, low volatility, and improved additive response, which are difficult to achieve through conventional processing. Conventional solvent lubricant refining produces base oils with a viscosity index (VI) of 100 with a fair amount of sulphur and aromatics, i.e., Group I base oils only. The current requirements of high‐performance base oils can conveniently be met through the hydroprocessing route. Depending upon the severity level, hydroprocessing is able to produce base oils of VI 95–110, in addition to low sulphur and high saturates content (Group II and Group III) by transforming the undesirable molecules into more useful structures. In countries such as India, a hybrid approach offers a technical solution to meet current demands for lubricant quality. This approach can be implemented in existing lubricant refineries without entailing major changes in refinery configuration, besides being cost‐effective. This paper describes the current requirements of modern lubricants in relation to API Groups and trends in these, and describes a sequence of technologies involving solvent refining, a cost‐effective hybrid scheme, and more recent hydroprocessing that allows a cost‐effective upgrading of Group I refining process. A case study is given that discusses the adoption of the hybrid scheme in Indian refineries.     

Effect of Ca doping on the electrical conductivity of the high temperature proton conductor LaNbO4

The sintering properties, crystal structure and electrical conductivity of La_1−xCa_xNbO_4−δ (x = 0, 0.005, 0.01, 0.015, 0.02 and 0.025), prepared by a solid-state reaction, have been investigated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), and electrochemical impedance spectroscopy (EIS). In 2.5% Ca-doped samples, a small amount of impurities Ca₂Nb₂O₇ were observed from the XRD patterns. Impedance spectra show that the grain boundary resistance increases with increasing Ca content, while the bulk resistance remains essentially constant below 550 °C. Despite the higher degree of grain growth observed for higher Ca doping levels, the total conductivity of the La_1−xCa_xNbO_4−δ series decreases with increasing Ca content from 0.5 to 2.0 mol%. The activation energy for the total conductivity decreases with increasing Ca content from 0.71 eV (x = 0) to 0.54 eV (x = 0.01) for the high temperature tetragonal phase, then it increases to 0.60 eV for x = 0.02. For the monoclinic phase, the activation energy exhibits similar trend except La_0.995Ca_0.005NbO_4−δ shows the lowest value of 1.26 eV. The Ca and Nb content present at the grain boundaries for La_0.99Ca_0.01NbO_4−δ are much higher than that on the grain surface, as determined from the EDS analysis. These results imply that the solubility of CaO in LaNbO₄ is in the range from 0.5 to 1.0 mol%. By increasing the sintering temperature from 1500 °C to 1550 °C, the proton conductivity of the Ca-doped LaNbO₄ was improved with enlarged grain size due to a reduction in the resistive grain boundary contribution.     

Feasibility study of a solar chimney power plant in Jordan

A solar chimney power plant system is theoretically designed for future erection in Jordan. Analytical analysis of the system is simulated by mathematical software. The actual values of solar irradiation in Jordan are used in the simulation to predict the power output of the solar chimney power plant. The output results of the maximum (inlet) values of velocity, pressure, and mass flow rate of air versus the chimney height variation are obtained. Furthermore, the electrical power output and the efficiency of chimney versus chimney height variation were determined. For a solar collector diameter of 40 m and a chimney diameter of 3.5 m, the maximum power output (85 kW) was obtained for a chimney height of 210 m.     

A comparison of TiO2 nanoparticles and nanotubes for catalytic gas phase destruction of H2S gas at high temperatures

Reduction of H2S gas over Sulphur doped TiO2 nanoparticles and TiO2 nanotubes was studied in this work. Fixed bed catalytic system was used for the catalytic reduction of H2S gas at a high temperature of 450 degrees C under laboratory conditions. 99.97% reduction was achieved using S-doped TiO2. 2.89% Sulphur was adsorbed on S-doped TiO2 nanoparticles in the form of Ti(SO4)2, while 95.6% reduction was achieved in case of TiO2 nanotubes and the sulphur adsorption was 2.67%. The XRD, SEM, and EDX techniques were carried out to characterize the nanoparticles and nanotubes, while gas reduction analysis was carried out using GC-MS for gas samples.     

Structural and magnetic properties of Zn1-xcoxO nanorods prepared by microwave irradiation technique

We have successfully synthesized large-scale aggregative flowerlike Zn1-xCo(x)O (0.0 < or = x < or = 0.07) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100-150 nm (tip diameter approximately 50 nm) and length of approximately 1 microm. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magnetization measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice position of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn1-xCo(x)O nanorods exhibit room temperature ferromagnetism. This novel nanostructure could be a promising candidate for a variety of future spintronic applications.     

Selecting and prioritizing key factors for CAD/CAM software in small- and medium-sized enterprises using AHP

In today’s fast-paced world, computer-aided design/computer-aided manufacturing (CAD/CAM) systems have become a necessary element in manufacturing industries. Prior to investment in a CAD/CAM system, it is essential for investor to know how to maximize their benefits from buying a new or by changing an existing CAD/CAM system. The purpose of this study is to provide a methodology to assist small- and medium-sized manufacturing companies of Pakistan in selecting a CAD/CAM system. It will also facilitate the software providers in recognizing the current state of affairs as well as preceding problems regarding the application of CAD/CAM in manufacturing firms when assisting them in choosing the direction for future development simultaneously. To accomplish this purpose, data have been collected about current CAD/CAM systems. Important criteria for system selection and parameters for evaluation have also been identified and prioritized. Analytic hierarchy process (AHP) is used as a decision-making technique for identifying and prioritizing important factors for CAD/CAM software selection. Expert Choice (AHP-based software) has been used to validate the results.     

Analysis and assessment of an advanced hydrogen liquefaction system

In the present work, an advanced hydrogen liquefaction system with catalyst infused heat exchangers is proposed, analyzed and assessed energetically and exergetically. The analysis starts with exergetic considerations on hydrogen liquefaction using different alternatives of pre-cooling including the conversion from normal to parahydrogen. It further explains the fundamentals of a proposed liquefaction process. The goal is then to assess the proposed system, make modifications and improve the system. The present system covers all of these portions of a hydrogen liquefaction system with an ultimate goal of achieving a sustainable and environmentally harmless system. The proposed hydrogen liquefaction system is simulated in the Aspen Plus and the performance of the system is measured through energy and exergy efficiencies. The resulting energy efficiency of the system is calculated to be 15.4%, and the exergy efficiency of the system is found to be 11.5%.     

Lie symmetry analysis and numerical solutions for thermosolutal chemically reacting radiative micropolar flow from an inclined porous surface

Steady, laminar, incompressible thermosolutal natural convection flow of micropolar fluid from an inclined perforated surface with convective boundary conditions is studied. Thermal radiative flux and chemical reaction effects are included to represent phenomena encountered in high-temperature materials synthesis operations. Rosseland's diffusion approximation is used to describe the radiative heat flux in the energy equation. A Lie scaling group transformation is implemented to derive a self-similar form of the partial differential conservation equations. The resulting coupled nonlinear boundary value problem is solved with Runge-Kutta fourth order numerical quadrature (shooting technique). Validation of solutions with an optimized Adomian decomposition method algorithm is included. Verification of the accuracy of shooting is also conducted as a particular case of nonreactive micropolar flow from a vertical permeable surface. The evolution of velocity, angular velocity (microrotation component), temperature, and concentration are examined for a variety of parameters including coupling number, plate inclination angle, suction/injection parameter, radiation-conduction parameter, Biot number, and reaction parameter. Numerical results for steady-state skin friction coefficient, couple stress coefficient, Nusselt number, and Sherwood number are tabulated and discussed. Interesting features of the hydrodynamic, heat and mass transfer characteristics are examined.     

An approach to locational marginal price based zonal congestion management in deregulated electricity market

Congestion of transmission line is a vital issue and its management pose a technical challenge in power system deregulation. Congestion occurs in deregulated electricity market when transmission capacity is not sufficient to simultaneously accommodate all constraints of power transmission through a line. Therefore, to manage congestion, a locational marginal price (LMP) based zonal congestion management approach in a deregulated electricity market has been proposed in this paper. As LMP is an economic indicator and its difference between two buses across a transmission line provides the measure of the degree of congestion, therefore, it is efficiently and reliably used in deregulated electricity market for congestion management. This paper utilizes the difference of LMP across a transmission line to categorize various congestion zones in the system. After the identification of congestion zones, distributed generation is optimally placed in most congestion sensitive zones using LMP difference in order to manage congestion. The performance of the proposed methodology has been tested on the IEEE 14-bus system and IEEE 57-bus system.     

Analyzing combinations of circular birefringence,linear birefringence,and elliptical dichroism in magneto-optical rotators

We derive analytic expressions for the polarization characteristics of light emerging from a magneto-optical medium possessing arbitrary contributions from linear and circular birefringence as well as magnetic circular dichroism. The medium is placed inside a static magnetic field. The rotation of the plane of polarization and the ellipticity of the resultant light exhibit interesting characteristics that can be a useful guide in the design and analysis of new photonic devices. Furthermore, the Jones matrices are derived in all cases, including for elliptical dichroism, indicating the role of hyperbolic trigonometric functions in modeling the effects of dichroism. Finally, implications for experimental detection of the polarization state and the limits on the performance of optical isolators are discussed.