Green Density of a Powder Compact and Its Influence on the Steady-State Wave Velocity in Combustion Synthesis of Condensed Phase

Various experimental evidence indicates that the porosity of a compact has a pronounced effect on the steady-state velocity in combustion synthesis of condensed phases, hut no simple and explicit treatment for it is available in the literature. Utilizing an existing model of the effective thermal conductivity in a porous media, a simple model for the steady-state velocity of the combustion front has been developed. As ob- served in experiments, the model also predicts a decrease in combustion velocity with increasing porosity. The developed equation can be helpful in the analysis and interpretation of experimental results in self-propagating high-temperature synthesis of condensed phase.     

Processor preallocation and load balancing of DOALL loops

Load balance is important because it may affect the speedup attained through the concurrent execution of loop iterations on a parallel processor. We study loop load balance in the context of the well-known Perfect benchmarks. Several static and dynamic characteristics of the Perfect benchmark DOALL loops are observed and interpreted. Thelate arrival of processors is noted as a major source of load imbalance. This observation suggested the idea ofprocessor preallocation. An analytic cost model is presented and the advantages of processor preallocation are demonstrated by experimental evaluation on a CRAY Y-MP8 under the Unicos operating system.     

Comparative inhibitory properties of some Indian medicinal plant extracts against photosensitization-induced lipid damage

The protective activities of Emblica officinalis, Terminalia bellerica and Terminalia chebula ethanol extracts against photosensitization-induced oxidation of rat liver mitochondrial lipid were assessed. All the extracts could effectively prevent lipid peroxidation, as assessed by measuring thiobarbituric acid-reactive substrates, lipid hydroperoxide, conjugated diene and 4-hydroxynonenal. The E. officinalis extract was the most potent, revealing its superior ability to scavenge ¹O₂. The extracts also afforded excellent protection against iron-mediated lipid peroxidation that might also be useful in reducing photo-induced iron toxicity. The activities of the extracts were primarily due to their constituent phenolics.     

Some aspects of fluidized bed combustion of paddy husk

Some agricultural wastes—for example, bagasse, paddy husk, etc.—are frequently used as fuels, paddy husk appearing, in particular, to be quite suitable for fluidized bed combustion. The conventional method of combustion of paddy husk in grate-type furnaces is slow and inefficient.

This paper reports certain aspects of the fluidized bed combustion of paddy husk. Fluidized bed combustion was carried out by feeding husk in a bed of sand particles. The unexpanded bed height was 10 cm and the size of the sand particles, 351–420 μm. The superficial velocity of the ambient fluidization air through the bed ranged from 11·1 to 22·2 m/min.

A combustion intensity of about 530 kg/h/m² of distributor area could be achieved. This is about 7·5 times higher than the maximum combustion intensity possible in a grate-type furnace per unit grate area. The efficiency of combustion, which ranged from 81 to 98 per cent was found to increase with the air flow rate. There was significant carry-over of inert sand particles from the bed under conditions of high air flow rate.

Combustion intensity increased as the bed height rose from 10 cm to 15 cm, but increased sand entrainment also occurred.