Reliability optimization of a series system with active and standby redundancy

This paper presents a method of maximizing reliability of a series system subject to multiple constraints. The use of both active series parallel and standby redundancy is considered to increase the reliability of the system. A flexible tree search method has been used in this paper which is found to be an efficient method of solution, as it requires only simple mathematical computations. A three stage system is used for illustration.     

Role of clay as catalyst in Friedel–Craft alkylation

Solid acids have become increasingly important for many liquid-phase industrial reactions these days. Montmorillonite clays (2:1 clay mineral) have been used as efficient solid acid catalysts for a number of organic and liquid phase reactions and offer several advantages over classic acids. Tailor made catalysts can be prepared from clays by suitably adjusting their acidity and surface area by acid activation. In the present work, preparation, characterization and performance of Pt (II) clays, Cu (II) clays, acid clay, and sol–gel hybrids of Cu (II) clays as solid catalysts in a test Friedel–Craft alkylation reaction of benzyl chloride with toluene using differential scanning calorimeter (DSC) are reported. Product formation has been analysed by FTIR spectroscopy. The main objective of this work is to show how clay as a solid catalyst affects reaction rates and activation energies. Acidity and dispersion of solid catalysts are two main factors which govern a catalysis reaction. Kinetic parameter analysis and XRD studies confirm that acid Pt (II) clay and Pt (II) clay dispersed by natural dispersants are more effective catalysts. In contrast to the reactions using AlCl₃, the experimental conditions are non-polluting and the final work up does not require any aqueous treatment.     

Interface Reactions Between Metals and Ceramics: IV, Wetting of Sapphire by Liquid Copper-Oxygen Alloys

The wettability of sapphire single crystals by liquid copper which contained oxygen added as cupric oxide was investigated using the sessile drop technique in vacuum at 1230°C. Additions of cupric oxide to copper, varying from 1 to 72% of copper weight, resulted in rapid chemical reaction at the solid-liquid interface with a significant reduction of the contact angle, the final value being dependent on the oxygen in the system. In all cases the interfacial product was CuAlO₂. A linear relation between the fourth power of the basal radius of the molten drop and the amount of oxygen present was observed. The initial stage of the reaction could be explained by the formation of a Cu₂O layer at the interface, followed by reaction between Cu₂O and Al₂O₃ to form CuAlO₂.     

Effect of a Water Soluble Fraction Derived from Mycobacterium phlei on the Surface Characteristics and Flotation of Apatite and Dolomite

Abstract

When Mycobacterium phlei is subjected to sonication, a solid and a water soluble fraction are obtained. The water soluble material is highly surface-active and adsorbs onto both dolomite and apatite. In both cases the mineral becomes more hydrophobic with the effect being greater on dolomite than on apatite. The change in surface characteristics of the minerals was monitored by contact angle, zeta potential and micro flotation experimentation. The data obtained were compared to results obtained when whole cells of M.phlei were used in place of the soluble fraction. Implications on the effect of the addition of both M.phlei and its soluble fraction on the flotation separation of the two minerals are discussed.     

Studies on the interaction of p-phenylene diamine with phospholipids

In vitro studies on the interaction of phospholipids with p-phenylene diamine, a major component of hair dyes, were undertaken. Thin layer and molecular sieving chromatography along with phosphorus estimation and spectral characterization suggested the possibility of p-phenylene diamine and its biotransformation products combining with lipophilic biomolecules.     

Availability and failure frequency of repairable m-order systems

Availability and other related parameters, such as failure frequency, mean down Lima, otc, aro important reliability parameters to be considered at the design stage of a system; and this needs appropriate mathematical models for their assessment. This paper presents algorithms to assess quantitatively the above parameters of a repairable m-ordor system comprising units with unequal failuro and repair rates. The concepts of minimal cut sets and minimal tie sets have been employed. The modols developed here can be applied to series and parallol systems as well.