8 research outputs found

    A new method to determine the elastopalstic properties of ductile materials by conical indentation

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    Based on load-displacement curves, indentation is widely used to extract the elastoplastic properties of materials. It is generally believed that such a measure is non-unique and a full stress-strain curve cannot be obtained using plural sharp and deep spherical indenters. In this paper we show that by introducing an additional dimensionless function of DA / A (the ratio of residual area to the area of an indenter profile) in the reverse analysis, the elastoplastic properties of several unknown materials that exhibit visually indistinguishable load-displacement curves can be uniquely determined with a sharp indentation

    Effects of calcination on mineralogical properties and reactivity of acidic aluminum sulfate residue

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    Acidic aluminum sulfate residue (AASR) is treated as a hazardous solid waste. However, it contains significant amounts of aluminosilicates which could be potentially utilized to produce geopolymers. The reactive activities of the aluminosilicate phases in AASR are generally low, which is a blockage of AASR-based activation to some extent. This paper aims to investigate the effect of calcination on mineralogical properties and reactivity of AASR at various temperatures ranging from 200 to 800 °C. It was demonstrated that AASR underwent substantial changes in its mineralogical, chemical, and dissolution properties after calcination. The specific surface area, pore-volume, pH, dissolution efficiency of Si and Al were increased with increasing of calcination temperature until 600 °C and then remained relatively stable at higher calcination temperatures. The results indicated that AASR is highly activated in a range of calcination temperatures between 600 and 800 °C, which verified the potential of using calcinated AASR to manufacture geopolymer products upon proper calcination process

    Are medical record front page data suitable for risk adjustment in hospital performance measurement? Development and validation of a risk model of in-hospital mortality after acute myocardial infarction

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    Objectives To develop a model of in-hospital mortality using medical record front page (MRFP) data and assess its validity in case-mix standardisation by comparison with a model developed using the complete medical record data.Design A nationally representative retrospective study.Setting Representative hospitals in China, covering 161 hospitals in modelling cohort and 156 hospitals in validation cohort.Participants Representative patients admitted for acute myocardial infarction. 8370 patients in modelling cohort and 9704 patients in validation cohort.Primary outcome measures In-hospital mortality, which was defined explicitly as death that occurred during hospitalisation, and the hospital-level risk standardised mortality rate (RSMR).Results A total of 14 variables were included in the model predicting in-hospital mortality based on MRFP data, with the area under receiver operating characteristic curve of 0.78 among modelling cohort and 0.79 among validation cohort. The median of absolute difference between the hospital RSMR predicted by hierarchical generalised linear models established based on MRFP data and complete medical record data, which was built as ‘reference model’, was 0.08% (10th and 90th percentiles: −1.8% and 1.6%). In the regression model comparing the RSMR between two models, the slope and intercept of the regression equation is 0.90 and 0.007 in modelling cohort, while 0.85 and 0.010 in validation cohort, which indicated that the evaluation capability from two models were very similar.Conclusions The models based on MRFP data showed good discrimination and calibration capability, as well as similar risk prediction effect in comparison with the model based on complete medical record data, which proved that MRFP data could be suitable for risk adjustment in hospital performance measurement
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