Optimization of the polycondensation stage of poly(ethylene terephthalate) reactors

A general kinetic scheme for the polycondensation step of the PET formation has been used to establish the mole balance equations of various functional groups in batch reactors. An objective function has been defined which aims to attain a desired degree of polymerization in the shortest time, has a specified level of diethylene glycol group content, and minimizes the other side products. Using the control vector iteration procedure, an optimum temperature profile has been calculated. The computations suggest that a high temperature should be used initially which must be lowered as the time of reaction increases for limiting the formation of side products.     

A method for generation and transmission planning

This paper presents a method for the optimal expansion planning of generation and transmission facilities in a power system for a given future demand. The planning problem is defined as to minimize the cost associated with the installation of generating stations, transmission lines and the operating costs of the system subject to constraints associated with the security of the transmission system and the limits on the capacities available for expansion at each power plant site and the maximum number of lines permitted in each right of way available for new construction.     

On the entropy function of degree β

Kamiński and Mikusiński (1974) formed a functional equation H(x,y,z) = H(x + y,0,z) + H(x,y,0), x ? 0, y ? 0, z ? 0, xy + yz + zx > 0, and determined its continuous and symmetric solution which is homogeneous of degree 1. This approach simplifies Fadeev's well-known characterization of Shannon's entropy. In this paper we obtain this functional equation from a generalized set of axioms and solve it under continuity and homogeneity of degree β (β ≠ 1, β > 0). This extends Kamiński and Mikusiński's approach of characterizing to degree β the measure of entropy, which has been studied by a number of workers with considerable interest.     

Effect of liquid zinc on Armco iron with relevance to pots used in galvanizing

The present investigation deals with the comparative study of liquid zinc attack on Armco iron and Tisco A grade iron within a temperature range of 450°C to 550°C. The effect of variables, e.g. time of contact, temperature, on weight loss of iron for a similar geometry of specimens has been studied and discussed. The maximum weight loss of iron has been found at 500°C for both the irons. It has been observed that even a slight variation in silicon content (on increase) appreciably increases the rate of attack on iron.     

Effect of small concentrations of zirconium on high temperature oxidation behaviour of Fe-15 Cr-4 Al

Effect of 1% Zr on oxidation behaviour of Fe-15 Cr-4 Al alloy under isothermal conditions in air, O₂ and O₂-10% H₂O environments in the temperature range 1000–1150°C was investigated. The effect of zirconium concentration was studied at 1 200°C in air. Oxidation rate increases with increase in zirconium concentration. Parabolic rate of oxidation was observed. Limited study on cyclic oxidation was carried out at 1150°C in air. The cycle consisted of one hour holding at isothermal temperature followed by half an hour air cooling. The oxidised samples were examined by X-Ray diffractometry, SEM, EDAX. Extensive spalling was observed in the base alloy, Fe-15 Cr-4 Al in all environments. Zirconium additions eliminated the spalling of the scale. The EDAX analysis of a spalled region shows the presence of iron and chromium while the unspalled region is aluminium rich. A common structural feature, localised formation of granules/nodules was observed in the scale of zirconium containing alloys in all the environments. The number of granules increased with increase in zirconium concentration and was observed to be a maximum in 1% Zr and also increases with increasing temperature. The observations reveal that 1% Zr alloy shows lower oxidation rate in O₂-H₂O environment under isothermal conditions. X-Ray diffraction analysis shows the additional presence of Fe₂O₃ and Cr₂O₃ in α-Al₂O₃ scale which have not been detected in the α-Al₂O₃ scale formed in other environments, air and O₂. 0.2% Zr is most effective in increasing oxidation resistance of Fe-15 Cr-4 Al alloy both under isothermal and cyclic oxidation conditions.     

An Empirical Evaluation of the “Entrapment” Procedure for Scheduling Jobs on Identical Machines

This work empirically evaluates the “entrapment” procedure used by Barnes and Brennan's branch-and-bound algorithm to minimize total cost of tardy jobs to be processed on identical machines. Using 25 problems taken from various known sources, it is shown that entrapment does not necessarily decrease computational time required to optimally solve such a problem.     

Development of cadmium-free silver metal-oxide contact materials

A cadmium-free silver-base alloy has been developed to substitute the standard Ag-12% CdO contact alloy which is widely used in electrical and electronics industries. Substitution of cadmium was attempted through the addition of zinc as the basic and major alloying element and with minor additions of tin and copper. The developed alloy, after internal oxidation, possesses better electrical contact characteristics than the standard alloy.     

The regulation of AMPA receptor-binding sites

A wide variety of mechanisms have been identified that can regulate the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-receptor complex. Modulation has been shown to occur at the nucleic acid level via RNA editing and alternative splicing. At the posttranslational level, processes such as phosphorylation, glycosylation, chemical modification of reactive groups on the receptor proteins, interaction with a putative receptor-associated modulatory protein, and changes in the lipid environment have been reported to regulate receptor binding and function. In this review, we discuss general aspects of the cell biology, pharmacology, and function of AMPA receptors. In particular, we focus on some factors shown to modulate agonist binding and discuss possible molecular mechanisms underlying the regulation observed.