Pyrolysis characteristics and thermal kinetics of expanded polystyrene(EPS) and styrene-methyl methacrylate(St-MMA) copolymer in LFC process

The pyrolysis behaviors of foam patterns have critical influences on fluid morphology and defect formation in Lost Foam Casting(LFC). The pyrolysis behaviors of expanded polystyrene(EPS) and styrenemethyl methacrylate(St-MMA) foams were compared using synchronous thermal analysis(STA), which was performed under argon atmosphere at different heating rates(from 10 to 40 K·min^(^(-1))). The degradation heat was calculated by integrating DSC curves. Results show that the calculated degradation heat of St-MMA(605.28 J·g^(-1)) was significantly lower than that of EPS(706.71 J·g^(-1)). Furthermore, the non-isothermal iso-conversional method was used to determine the pyrolysis apparent activation energies of EPS and St-MMA, and results show that the activation energy of St-MMA(200.36 kJ·mol^(-1)) was apparently higher than that of EPS(167.92 kJ·mol^(-1)). These calculated results indicate that the weight loss rate of EPS is greater than St-MMA in the pyrolysis process. In addition, the apparent activation energies at various pyrolysis stages demonstrate that the pyrolysis reactions of EPS and St-MMA may involve physical and chemical changes in the decomposition layer of the LFC process.

Construction and analysis of dynamic solidification curves for non-equilibrium solidification process in lost-foam casting hypoeutectic gray cast iron

Most lost-foam casting processes involve non-equilibrium solidification dominated by kinetic factors, while construction of a common dynamic solidification curve is based on pure thermodynamics, not applicable for analyses and research of non-equilibrium macro-solidification processes, and the construction mode can not be applied to nonequilibrium solidification process. In this study, the construction of the dynamic solidification curve(DSC) for the nonequilibrium macro-solidification process included: a modified method to determine the start temperature of primary austenite precipitation(T_(AL)) and the start temperature of eutectic solidification(T_(ES)); double curves method to determine the temperature of the dendrite coherency point of primary austenite(T-(AC)) and the temperature of eutectic cells collision point(T_(EC)); the "technical solidus" method to determine the end temperature of eutectic reaction(T_(EN)). For this purpose, a comparative testing of the non-equilibrium solidification temperature fields in lost-foam casting and green sand mold casting hypoeutectic gray iron was carried out. The thermal analysis results were used to construct the DSCs of both these casting methods under non-equilibrium solidification conditions. The results show that the transformation rate of non-equilibrium solidification in hypoeutectic gray cast iron is greater than that of equilibrium solidification. The eutectic solidification region presents a typical mushy solidification mode. The results also indicate that the primary austenite precipitation zone of lost-foam casting is slightly larger than that of green sand casting. At the same time, the solid fraction(f_s) of the dendrite coherency points in lost-foam casting is greater than that in the green sand casting. Therefore, from these two points, lost-foam casting is more preferable for reduction of shrinkage and mechanical burntin sand tendency of the hypoeutectic gray cast iron. Due to the fact that the solidification process(from the surface to center) at primary austenite growth area in the lost-foam cylinder sample lags behind that in the green sand casting, the mushy solidification tendency of lost-foam casting is greater and the solidification time is longer.

Update report on the quality of gliomas radiomics:An integration of bibliometric and radiomics quality score

BACKGROUND Despite the increasing number of publications on glioma radiomics,challenges persist in clinical translation.AIM To assess the development and reporting quality of radiomics in brain gliomas since 2019.METHODS A bibliometric analysis was conducted to reveal trends in brain glioma radiomics research.The Radiomics Quality Score(RQS),a metric for evaluating the quality of radiomics studies,was applied to assess the quality of adult-type diffuse glioma studies published since 2019.The total RQS score and the basic adherence rate for each item were calculated.Subgroup analysis by journal type and research objective was performed,correlating the total RQS score with journal impact factors.RESULTS The radiomics research in glioma was initiated in 2011 and has witnessed a surge since 2019.Among the 260 original studies,the median RQS score was 11,correlating with a basic compliance rate of 46.8%.Subgroup analysis revealed significant differences in domain 1 and its subitems(multiple segmentations)across journal types(P=0.039 and P=0.03,respectively).The Spearman correlation coefficients indicated that the total RQS score had a negative correlation with the Journal Citation Report category(-0.69)and a positive correlation with the five-year impact factors(0.318)of journals.CONCLUSION Glioma radiomics research quality has improved since 2019 but necessitates further advancement with higher publication standards.