Asymptotic methods are employed to revisit an earlier model for oscillation-mark formation in the continuous casting of steel. A systematic non-dimensionalization of the governing equations, which was not carried out previously, leads to a model with 12 dimensionless parameters. Analysis is provided in the same parameter regime as for the earlier model, and surprisingly simple analytical solutions are found for the oscillation-mark profiles; these are found to agree reasonably well with the numerical solution in the earlier model and very well with fold-type oscillation marks that have been obtained in more recent experimental work. The benefits of this approach, when compared with time-consuming numerical simulations, are discussed in the context of auxiliary models for macrosegregation and thermomechanical stresses and strains.

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The work presented here examines the surface cracks that can form during the continuous casting of near peritectic steels due to the volume changes during the peritectic reaction/transformation. The investigated samples were collected during plant trials from two different steel grades. The role and mode of the peritectic reaction/transformation are found to depend on the composition of the alloy, resulting in different types of surface cracks. The effect of the local variation in the cooling rate on the formation of the different types of cracks present in each steel grade, which can be due, for example, to the formation of oscillation marks, is demonstrated. The enhanced severity of the surface and internal oxidation, both of which depend on the alloy composition and consequent peritectic reaction, is highlighted. Experimental and theoretical studies show that different types of surface cracks can occur in peritectic steels depending upon the alloy composition and cooling rate, both of which define the fraction of the remaining liquid upon completion of the peritectic reaction/transformation.

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Background: Pakistan demographic and health survey (PDHS) estimated extensive ownership of cell phones in Pakistan with 94.7% in the urban population. Pakistan Advertiser Company reported 77 % of cell phone users aged between 21-30 years. Although, no research was conducted with university population for addiction and depression, so this study aims to find the link between Smartphone addiction and depression in SZABIST University students of Karachi, Pakistan.Methods: Cross-sectional study was conducted with self-assessment tools, comprised of three sections: socio-demographic information, smartphone addiction scale-short version (SAS-SV) and Beck’s depression inventory-II (BDI-II). Responses for SAS-SV were rated on a 6-point Likert scale and BDI-II was summated on range 0-60. Percentages mean score was commuted for SAS-SV; the mean score was computed and categorized for BDI-II. Descriptive statistics and regression analysis were used for data analysis. Statistical significance was set at p<0.01.Results: Total participants were N=225, of which 140 (62.2%) were males and 85 (35.8%) were females. The mean±SD of their ages were 20.9±2.9. Age was found insignificant with depression after applying multiple linear regressions. Mean score of SAS-SV was 54.8±17.2, and BDI-II was13.4±9.6, which showed a significant positive association (OR, 0.241; 95% CI, 0.2 to 0.3; p<0.001). Prior adjusting coefficient, males were speculated having a higher level of depression.Conclusions: A significant positive correlation was found between Smartphone addiction and depression, among University Students of SZABIST. Control smartphones usage is advised for undergraduate students as they are more prone to depression compared to postgraduate students.