A simulation study of reduction kinetics for sponge iron production in a rotary hearth furnace

ABSTRACT

A mathematical model has been developed by coupling genetic algorithm (GA) with heat and material balance equations to estimate rate parameters and solid-phase evolution related to the reduction of iron ore-coal composite pellets in a multi-layer bed Rotary hearth Furnace (RHF). The present process involves treating iron ore-coal composite pellets in a crucible over the hearth in RHF. The various solid phases evolved at the end of the process are estimated experimentally, and are used in conjunction with the model to estimate rate parameters. The predicted apparent activation energy for the wustite reduction step is found to be lower than those of the reduction of higher oxides. The thermal efficiency is found to decrease significantly with an increase in the carbon content of the pellet. Thermal efficiency was also found to increase mildly up to three layers. Multilayer bed remains as a potential design parameter to increase thermal efficiency.     

Key-dependent side-channel cube attack on CRAFT

CRAFT is a tweakable block cipher introduced in 2019 that aims to provide strong protection against differential fault analysis. In this paper, we show that CRAFT is vulnerable to side-channel cube attacks. We apply side-channel cube attacks to CRAFT with the Hamming weight leakage assumption. We found that the first half of the secret key can be recovered from the Hamming weight leakage after the first round. Next, using the recovered key bits, we continue our attack to recover the second half of the secret key. We show that the set of equations that are solvable varies depending on the value of the key bits. Our result shows that 99.90% of the key space can be fully recovered within a practical time.     

Thermal and hydraulic performance of a modified two-stage evaporative cooler

The thermal and hydraulic performance of a modified two-stage evaporative cooler is evaluated. Variables considered are the mode of operation, packing thickness, mass flow rate of the water flowing to the precooler, and the mass flux of water flowing over the packing media. The effectiveness of the system increased with the increase of the mass flow rate of water flowing to the precooler, decreasing the mass flux of water flowing to the packing, and with the increase of the packing thickness. The effectiveness of the system with structured packing was higher than that with sheathy leaf base or natural fiber packing.The air-side pressure drop per unit length in the direction of air flow was nearly constant when the structured packing was used. For the sheathy leaf and natural fiber packings, the air pressure drop increased at a uniform rate as the mass flux of water flowing over the packing increased. The air pressure drop was lowest for the setup with the structured packing.     

Electromagnetic Resistive Drift Instability in Current Carrying Low Temperature Tokamak Edges

It is shown that the purely growing electrostatic rippling mode can couple with the shear Alfven wave to give rise to an oscillatory electromagnetic instability in tokamak edge regions. This mechanism can be one of the causes of electromagnetic fluctuations observed near plasma edges. This instability can occur only in the very low temperature regions where resistivity fluctuations can become important due to large electron-ion collision frequency.     

Mechanisms of resistance in a human cell line exposed to sequential topoisomerase poisoning

Camptothecins are a new class of anticancer drugs that target DNA topoisomerase I; current efforts are directed toward elucidating optimal combinations of these drugs with other antineoplastic agents. A rationale for the use of sequential therapy involving the combination of camptothecins with topoisomerase II-targeting drugs, such as etoposide, has arisen from observations of increased topoisomerase II protein levels in cell lines resistant to camptothecin. In an effort to understand potential mechanisms of resistance to this strategy, we developed a U-937 cell subline, denoted RERC, that is capable of surviving exposure to sequential topoisomerase poisoning. The RERC cells are 200-fold resistant to camptothecin, 8-fold resistant to etoposide, and 10-fold hypersensitive to cisplatin compared to the parental U-937 cells. Biochemical analyses indicate that the resistant phenotype involves alterations in both topoisomerase I and topoisomerase IIalpha. Topoisomerase I catalytic activity in the resistant cells is similar to that of the parental line but is resistant to camptothecin. Moreover, the resistant cells express a single mRNA species of topoisomerase I that codes for a mutation in codon 533. In addition, topoisomerase IIalpha protein levels are decreased 10-fold in the resistant line, coincident with a two-fold decrease in the expression of topoisomerase IIalpha mRNA. Collectively, these results indicate that resistance to sequential topoisomerase poisoning may involve a reduction in total cellular topoisomerase activity.     

Fecal bile acid excretion and composition in response to changes in dietary wheat bran,fat and calcium in the rat

The effect and possible interactive influence of different dietary amounts of wheat bran, fat and calcium on the fecal excretion, concentration and composition of bile acids was studied in Fischer-344 rats. The fecal bile acids were analyzed using gas-liquid chromatography. Dietary wheat bran increased both total bile acid excretion and fecal weight without changes in fecal bile acid concentration. The proportion of fecal hyodeoxycholic acid decreased with increasing dietary fiber, whereas that of lithocholic and deoxycholic acids increased significantly with fiber intake. The percent content of fecal chenodeoxycholic acid did not change. Increasing dietary fat led to an increase in bile acid excretion without changes in either fecal weight or bile acid concentration. In contrast, the level of dietary calcium did not affect the total excretion of bile acids. However, since calcium increased the fecal weight, it consequently diluted bile acids and decreased their fecal concentration. Dietary fat and calcium had no influence on fecal bile acid composition. There were no interactive effects of wheat bran, fat and calcium on fecal bile acids. The finding in this study that dietary fiber, fat and calcium induce significant changes in fecal bile acids may be of relevance to the potential of bile acids to promote carcinogenesis.     

Optimization Models for Layout and Pipe Design for Storm Sewer Systems

Optimization models are developed for simultaneously determining the pipe layout and the pipe design for storm sewer systems. The pipe design process includes computation of commercial diameters, slopes, and crown elevations for the storm sewer pipes. The optimization models aim to minimize the total costs of the layout and the pipe design for most of system elements. The optimization models are formulated as a 0–1 Integer Nonlinear Programming problem and solved using the General Algebraic Modeling System without the use of heuristic models which were characteristic of all previous models for the simultaneous determine of the pipe layout and pipe design of sewer networks. The models are based upon two different optimization approaches: (1) considers one or more commercial diameters of pipe connecting two manholes and (2) considers only one commercial diameter in a pipe connecting two manholes. The commercial diameters, pipe slopes, crown elevations, and total costs of the storm sewer system were compared for the two approaches using an example that illustrates the savings in cost by allowing multiple pipe sizes. The two new optimization modeling approaches developed herein can simultaneously determine the minimum cost pipe design (commercial diameters, slopes, and crown elevations) and pipe layout of storm sewer systems and satisfy all design constraints.

     

Hyperspectral imaging-based unsupervised adulterated red chili content transformation for classification: Identification of red chili adulterants

Neural Computing and Applications - Preserving red-chili quality is of utmost importance in which the authorities demand quality techniques to detect, classify, and prevent it from impurities. For...