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Vipul Kumar Gupta,Pradeep Kumar Jha,Pramod Kumar Jain 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
In continuous casting, the molten metal quality in the mold is affected by flow pattern, temperature distribution and inclusiontransport in the multistrand tundish. Natural convection due to thermal buoyancy directly influences these parameters andwith gas bubbling, further improvisation can be made. In the present work, numerical investigation of the effect of thermalbuoyancy is carried out to examine the flow field, temperature distribution and inclusion trajectories. Further, gas bubblingcurtain modeling using the Euler-Euler approach is performed for the different locations on the bottom wall of the tundishand quantitative analysis of tundish performance is presented using residence time distribution (RTD) curves. The resultsshow that big circulation loop generated due to thermal buoyancy assists in inclusion removal and mixing at each outlet. Gas bubbling increases the molten metal flow velocity in the central region of tundish, leading to a decrease in the dimensionlessnumber Gr/Re2 near the outlets which are far away from the inlet of the tundish i.e. outlet 2 and outlet 3. Hence, thedominance of natural convection decreases. The inclusion removal rate is found to increase significantly as the circulationloop formed at each side of the curtain forces them upward direction. However, the reported inclusion removal rate in gasbubbling cases is found to be independent of particle size and curtain location.
Ajay Kumar Goel,Meenu Jain,Pramod Kumar,Pennagaram Sarguna,Meera Bai,Neha Ghosh,Natrajan Gopalan 한국미생물학회 2011 The journal of microbiology Vol.49 No.2
Thirty-four Vibrio cholerae isolates collected from a cholera outbreak in Hyderabad, South India were found to belong to serogroup O1 biotype El Tor serotype Ogawa. The genotype of all the isolates was confirmed by PCR assays. All the isolates were found PCR positive for ctxAB, ompW, rfbO1, rtxC, and tcpA genes. All the isolates but one harboured rstR^(El Tor) allele. However, one isolate carried both rstR^(El Tor) as well as rstR^(Classical) alleles. Cholera toxin (ctxB) genotyping of the isolates confirmed the presence of altered cholera toxin B of classical biotype in all the isolates. All the isolates except VCH35 harboured an RS1-CTX prophage array on the large chromosome. The isolate VCH35 contained a tandem repeat of classical CTX prophage on the small chromosome. The clonal relationship among the V. cholerae isolates as carried out by enterobacterial repetitive intergenic consensus sequences PCR, BOX PCR and randomly amplified polymorphic DNA, uniformly showed a genetic relationship among the outbreak isolates. The results of this study suggest that altered El Tor biotype V. cholerae with the classical cholera toxin gene are involved in cholera outbreaks in India.