An algorithm for the kinetics of tire pyrolysis under different heating rates

Tires exhibit different kinetic behaviors when pyrolyzed under different heating rates. A new algorithm has been developed to investigate pyrolysis behavior of scrap tires. The algorithm includes heat and mass transfer equations to account for the different extents of thermal lag as the tire is heated at different heating rates. The algorithm uses an iterative approach to fit model equations to experimental data to obtain quantitative values of kinetic parameters. These parameters describe the pyrolysis process well, with good agreement (r² > 0.96) between the model and experimental data when the model is applied to three different brands of automobile tires heated under five different heating rates in a pure nitrogen atmosphere. The model agrees with other researchers’ results that frequencies factors increased and time constants decreased with increasing heating rates. The model also shows the change in the behavior of individual tire components when the heating rates are increased above 30 K min⁻¹. This result indicates that heating rates, rather than temperature, can significantly affect pyrolysis reactions. This algorithm is simple in structure and yet accurate in describing tire pyrolysis under a wide range of heating rates (10–50 K min⁻¹). It improves our understanding of the tire pyrolysis process by showing the relationship between the heating rate and the many components in a tire that depolymerize as parallel reactions.     

Control of dynamic overvoltages due to load rejection by static shunt compensation

A digital computer method used to evaluate the performance of a static shunt compensator as a device for controlling dynamic overvoltages caused by load rejection is presented. A typical system of a generating station connected to a load centre through an EHV transmission line with a static compensator at the load end is considered, and the envelopes of dynamic overvoltages following load rejection are evaluated. Detailed mathematical models incorporating the dynamics of a synchronous machine, transmission network and static shunt compensator are employed in the analysis. The static shunt compensator is shown to be an effective tool for controlling dynamic overvoltages. The application of this analysis for choosing an economic voltage rating of the surge arrestor is highlighted.     

A test of metabolically efficient coding in the retina

We tested the hypothesis that aspects of the neural code of retinal ganglion cells are optimized to transmit visual information at minimal metabolic cost. Under a broad ensemble of light patterns, ganglion cell spike trains consisted of sparse, precise bursts of spikes. These bursts were viewed as independent neural symbols. The noise in each burst was measured via repeated presentation of the visual stimulus, and the energy cost was estimated from the total charge flow during ganglion cell spiking. Given these costs and noise, the theory of efficient codes predicts an optimal distribution of symbol usage. Symbols that are either noisy or costly occur less frequently in this optimal code. We found good qualitative and quantitative agreement with the measured distribution of burst sizes for ganglion cells in the tiger salamander retina.     

Extrusion of alumina fibre using sol-gel precursor

Alumina fibres were prepared by extrusion using boehmite sol as binder. The microstructure and mechanical properties of the fibres were studied. The fibres sintered at 1400 oC have relatively dense microstructure and the highest strength.     

Glutathione modulates lipid composition of human colon derived HT-29 cells

Glutathione (GSH) is important in maintaining intracellular thiol status. The present study looked at the effect of GSH depletion on lipid composition of colon-derived HT-29 cells. GSH was depleted in HT-29 cells by incubation either with buthionine-S, R-sulfoximine (BSO) or diethylmaleate (DEM). GSH was restored during early periods of cells growth by supplementation of growth medium with either GSH ester or N-acetyl cysteine (NAC). Lipids were analysed following GSH depletion and supplementation. Among the neutral lipids, an increase in free cholesterol and diacylglycerol and decrease in cholesteryl ester and triacylglycerol were seen in GSH-depleted cells as compared to control cells. There were no detectable free fatty acids either in control or GSH-depleted cells. Among the phospholipids, a decrease in phosphatidylcholine and phosphatidylinositol and an increase in phosphatidylethanolamine were observed. These changes were a completely reversed by supplementation of BSO-treated cells with GSH ester and partially reversed by N-acetyl cysteine. These results suggest that the GSH status of the cell plays an important role in the lipid composition of the cells.     

Electrical conduction of erbium fluoride thin films

Thin-film capacitors of erbium fluoride were fabricated by electron beam gun deposition. The current-voltage characteristics of the erbium fluoride films were studied in the temperature range 323 to 396 K. For sufficiently high electric fields (>10⁴ V cm^–1), the leakage current increases exponentially with the square root of the applied field. Analysis of the data suggests an electrode-limited mechanism such as that suggested by Schottky. It is seen that the conduction mechanism is an activated process with the activation energy decreasing with increasing field.     

Multimodal behaviour of nonlinear systems with narrowband Gaussian inputs

A method for predicting multimodal behaviour in nonlinear systems with narrowband Gaussian inputs is described. The technique is applicable when the nonlinearity is a function of the input and its derivatives.