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  5. Multi-principal element alloys (MPEAs) with remarkable performances possess great potential as structural, functional, and smart materials. However, their efficient performance-orientated design in a wide range of compositions and types is an extremely challenging issue, because of properties strongly dependent upon the composition and composition-dominated microstructure. Here, we propose a multistage-design approach integrating machine learning, physical laws and a mathematical model for developing the desired-property MPEAs in a very time-efficient way. Compared to the existing physical model- or machine-learning-assisted material development, the forward-and-inverse problems, including identifying the target property and unearthing the optimal composition, can be tackled with better efficiency andmore »higher accuracy using our proposed avenue, which defeats the one-step component-performance design strategy by multistage-design coupling constraints. Furthermore, we developed a new multi-phase MPEA at the minimal time and cost, whose high strength-ductility synergy exceeded those of its system and subsystem reported so far by searching for the optimal combination of phase fraction and composition. The present work suggests that the property-guided composition and microstructure are precisely tailored through the newly built approach with significant reductions of the development period and cost, which is readily extendable to other multi-principal element materials.« less
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  7. How does the physical and chemical structure of the Critical Zone (CZ), defined as the zone from treetops to the bottom of groundwater, govern its hydro-biogeochemical functioning? Multiple lines of evidence from past and newly emerging research have prompted the shallow and deep partitioning concentration-discharge (C-Q) hypothesis. The hypothesis states that in-stream C-Q relationships are shaped by distinct source waters from flow paths at different depths. Base flows are often dominated by deep groundwater and mostly reflect groundwater chemistry, whereas high flows are often dominated by shallow soil water and thus mostly reflect soil water chemistry. The contrasts between shallowmore »soil water versus deeper groundwater chemistry shape stream solute export patterns. In this context, the vertical connectivity that regulates the shallow and deep flow partitioning is essential in determining chemical contrasts, biogeochemical reaction rates in soils and parent rocks, and ultimately solute export patterns. This talk will highlight insights gleaned from multiple lines of recent studies that include collation of water chemistry data from soils, rocks, and streams in intensively monitored watersheds, meta-analysis of stream chemistry data at the continental scale, and integrated reactive transport modeling at the hillslope and watershed scales. The hypothesis underscores the importance of subsurface vertical structure and connectivity relative to the extensively studied horizontal connectivity. It also alludes to the potential of using streams as mirrors for subsurface water chemistry, and the potential of using C-Q relationships to infer flow paths and biogeochemical reaction rates and the response of earth’s subsurface to climate and human perturbations. Broadly, this simple conceptual framework links CZ subsurface structure to its functioning under diverse climate, geology, and land cover conditions.« less
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