A method of inducing specific polymorph transformations is exemplified with two single-component systems, whereby a given crystal form undergoes conversion when subjected to solid state grinding in the presence of a minor quantity of a certain solvent.

Vegetation can reduce pore water pressure in soil by root water uptake. The reduction of pore water pressure results in higher shear strength but lower water permeability of soil, affecting slope stability and rainfall infiltration, respectively. Effects of different root architectures on root water uptake and hence pore water pressure distributions are not well understood. In this study, new analytical solutions for calculating pore water pressure in an infinite unsaturated vegetated slope are derived for different root architectures, namely the uniform, triangular, exponential and parabolic root architectures. Using the newly developed solutions, four series of analytical parametric analyses are carried out to improve understanding of the factors affecting root water uptake and hence that influence pore water pressure distributions. In the dry season, different root architectures can lead to large variations in pore water pressure distributions. It is found that the exponential root architecture induces the highest negative pore water pressure in the soil, followed by the triangular, uniform and parabolic root architectures. The maximum pore water pressure induced by the parabolic root architecture is about 77% of that induced by the exponential root architecture at the steady state. For a given root architecture, vegetation in completely decomposed granite (CDG, classified as silty sand) induces the highest negative pore water pressure than that in fine sand and silt. The zone influenced by vegetation can be about three to six times the root depth. In wet season, after a ten-year return period rainfall with a duration of 24 hours, different root architectures show similar pore water pressure distributions.

In this paper, we present a mesoscale simulation method for heavy petroleum combing structural unit (SU) and dissipative particle dynamics (DPD). We proposed 16 basic SUs, which represent the basic structural fragments for heavy petroleum molecules. The SUs were then used as beads in DPD simulation. The process for bead partition and DPD parameter calculation were described. The presented method links the molecular compositional modeling with mesoscale modeling via a chemical-defined mapping process. The equilibrium state of aromatic hydrocarbons with different ring numbers was simulated by the SU−DPD method, proving that the self-assembly behavior of polycyclic aromatic hydrocarbon systems can be properly revealed. On this basis, we built the SU−DPD model for heavy petroleum in terms of averaged four-components molecules. Various heavy petroleum systems were simulated at a coarse-grained level, including pure asphaltene system, asphaltene− toluene system, heavy petroleum system, and heavy petroleum−water system. The simulation results were consistent with the Yen−Mullins model and experimental results.

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