Effects of Composite Sintering Additives: Al(OH)3+Y2O3+CaF2 on the Performance of Porous Mullite Oxide-Bonded SiC Ceramics

A composite sintering additive system: Al(OH)3+Y2O3+CaF2 was proposed for porous mullite oxide-bonded SiC ceramics. Small variations of sintering additives have significant influences on the phase composition, pore shape/size, density and flexural strength. Samples sintered at 1550 ℃ for 4 h in the air atmosphere realized both good mullite densification and no detectable cristobalite phase, which was difficult to be achieved at the same time. Besides, the composite sintering additive system also promoted the formation of columnar shape mullite, which acts as a reinforcement. Flexural strength as high as 108 MPa was achieved at an apparent porosity of 40.3 vol%, which is higher than that sintered by SPS technique. Moreover, those additives also act as pore formers determining the shape and size of pores. Around 8.9 µm strip-like, 11.8 µm continuous channel-like and 4.1 µm irregular pores were obtained for Al(OH)3, Al(OH)3-Y2O3 and Al(OH)3-Y2O3-CaF2 added samples, respectively. Corresponding phase evolution, sintering mechanisms and pore formation models were established. This work provides a simple way to modify the phase, pore size/shape, and strength of mullite oxide-bonded porous SiC ceramics by properly selecting sintering additives without any additional pore formers.

Hybrid model for ecological vulnerability assessment in Benin

Identifying ecologically fragile areas by assessing ecosystem vulnerability is an essential task in environmental conservation and management. Benin is considered a vulnerable area, and its coastal zone, which is subject to erosion and flooding effects, is particularly vulnerable. This study assessed terrestrial ecosystems in Benin by establishing a hybrid ecological vulnerability index (EVI) for 2016 that combined a composite model based on principal component analysis (PCA) with an additive model based on exposure, sensitivity and adaptation. Using inverse distance weighted (IDW) interpolation, point data were spatially distributed by their geographic significance. The results revealed that the composite system identified more stable and vulnerable areas than the additive system; the two systems identified 48,600 km2 and 36,450 km2 of stable areas, respectively, for a difference of 12,150 km2, and 3,729 km2 and 3,007 km2 of vulnerable areas, for a difference of 722 km2. Using Moran’s I and automatic linear modeling, we improved the accuracy of the established systems. In the composite system, increases of 11,669 km2 in the potentially vulnerable area and 1,083 km2 in the highly vulnerable area were noted in addition to a decrease of 4331 km2 in the potential area; while in the additive system, an increase of 3,970 km2 in the highly vulnerable area was observed. Finally, southern Benin was identified as vulnerable in the composite system, and both northern and southern Benin were identified as vulnerable in the additive system. However, regardless of the system, Littoral Province in southern Benin, was consistently identified as vulnerable, while Donga Province was stable.

Developing Additive Systems of Biomass Equations for Robinia pseudoacacia L. in the Region of Loess Plateau of Western Shanxi Province, China

The accurate estimation of forest biomass is important to evaluate the structure and function of forest ecosystems, estimate carbon sinks in forests, and study matter cycle, energy flow, and the effects of climate change on forest ecosystems. Biomass additivity is a desirable characteristic to predict each component and the total biomass since it ensures consistency between the sum of the predicted values of components such as roots, stems, leaves, pods, and branches and the prediction for the total tree. In this study, 45 Robinia pseudoacacia L. trees were harvested to determine each component and the total biomass in the Loess Plateau of western Shanxi Province, China. Three additive systems of biomass equations of R. pseudoacacia L., based on the diameter at breast height (D) only and on the combination of D and tree height (H) with D2H and DbHc, were established. To ensure biomass model additivity, the additive system of biomass equations considers the correlation among different components using simultaneous equations and establishes constraints on the parameters of the equation. Seemingly uncorrelated regression (SUR) was used to estimate the parameters of the additive system of biomass equations, and the jackknifing technique was used to verify the accuracy of prediction of the additive system of biomass equations. The results showed that (1) the stem biomass contributed the most to the total biomass, comprising 51.82% of the total biomass, followed by the root biomass (24.63%) and by the pod and leaf biomass, which accounted for the smallest share, comprising 1.82% and 2.22%, respectively; (2) the three additive systems of biomass equations of R. pseudoacacia L. fit well with the models and were effective at making predictions, particularly for the root, stem, above-ground, and total biomass (R2adj > 0.812; root mean square error (RMSE) < 0.151). The mean absolute error (MAE) was less than 0.124, and the mean prediction error (MPE) was less than 0.037. (3) When the biomass model added the tree height predictor, the goodness of fit R2adj increased, RMSE decreased, and the accuracy of prediction was much improved. In particular, the additive system, which was developed based on DbHc combination prediction factors, was the most accurate. The additive system of biomass equations established in this study can provide a reliable and accurate estimation of the individual biomass of R. pseudoacacia L. in the Loess region of western Shanxi Province, China.

Aristotle on the Differences in Material Organisation Between Spoken and Written Language: An Inquiry into Part-Whole Relations

In this paper I aim at showing that, in Aristotle’s view, spoken and written language differ in their material organisation, in particular in their respective part-whole relations. I argue that, according to Aristotle, written language is an additive system (i.e. a system whose parts exist and are produced prior to what they are parts of), whereas spoken language is a non-additive system (i.e. a system whose parts cannot exist and be produced prior to what they are parts of), and that, in his view, spoken language, qua non-additive system, is analogous to organisms. Further, I outline two possible implications of this hypothesis. The first concerns the relevance of Aristotle’s conception of spoken language as a non-additive system to his account of human language’s power to signify. I set out some reasons for thinking that Aristotle endorses the view that the form of human language (i.e. its power to signify) is matter-involving. The second implication concerns the syllable analogy that Aristotle employs in Metaphysics Ζ 17. I argue that the syllable Aristotle refers to is a spoken one, and I develop some consequences of this hypothesis for the meaning of the analogy and, more generally, of the chapter.