李鸿章与晚清漕粮海运

晚清漕粮海运与李鸿章的关系密不可分.他通过恢复海运扩大漕粮海运的参与省份,调整海运规章、抚恤海运群体,扶植轮船招商局、促进漕粮运输工具近代化等方式,对漕粮海运的变革产生了全方位影响,成为推动中国社会走向近代的重要人物.     

元明清政府决策与淮河问题的产生

元明清时期,京杭大运河的开通,便利了北方政治中心与南方经济中心之间的联系。特别是在明清时期,大运河漕运事关国计。当时政府的诸多治河措施是为确保漕运畅通,加之明代保陵的需要,更使黄河、淮河、运河之间的关系复杂化。封建政府的决策行为使本自独流入海的淮河改道主要由长江入海,使淮河流域成为十年九灾之区。     

Grain‐scale permeabilities of faceted polycrystalline aggregates

Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg–clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10–50% faceted. The relationship of their permeability (k) to porosity (φ) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78–90% faceting. These materials showed much lower k for a given φ, with an apparent permeability threshold at φ_c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low φ with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.