Observation of Andreev Surface Bound States in the 3-K phase Region of Sr_2RuO_4

The tunneling spectrum of the superconducting phase with T_c ~ 3.0 K has been measured in the Ru-embedded region of Sr_2RuO_4 using cleaved junctions. A sharp zero-bias conductance peak (ZBCP) has been observed below 3 K. All characteristics of this ZBCP suggest that it originates from Andreev surface bound states, indicating that the pairing in the 3-K phase is also non-s-wave. Below the bulk T_c of Sr_2RuO_4 (~1.5 K), a bell-shaped ZBCP was found. This supports that there is a phase transition in the 3-K phase region near the bulk T_c.Comment: 4 pages, to appear in Phys. Rev. Lett. 87 (2001

Life cycle environmental and economic assessment of alumina recovery from secondary aluminum dross in China

Secondary aluminum dross is regarded as a hazardous solid waste in many countries. A coupled life cycle assessment and life cycle costing method was used to evaluate the environmental impact and economic cost of two processes for producing alumina from bauxite and secondary aluminum dross. The results showed that the total normalized midpoint value of the dross process is 32.16% lower than that of the bauxite process. The cost of producing 1 t alumina by dross process is 130.01 $, accounting for only 49.54$. These findings could be attributed to the decrease in energy and raw material consumption (i.e., steam, sodium hydroxide, electricity) and the relatively low cost of secondary aluminum dross. Adjusting raw materials for steam production and optimizing electricity structure could reduce the overall environmental impact of secondary aluminum dross recovery. Based on the forecast of environmental impact and policy adjustment in the future, inter-provincial dross transportation and southwest aluminum industry migration in China could be feasible solutions

Subcritical Propagation and Coalescence of Oil-Filled Cracks: Getting the Oil Out of Low-Permeability Source Rocks

We use a fracture mechanics model to study subcritical propagation and coalescence of single and collinear oil-filled cracks during conversion of kerogen to oil. The subcritical propagation distance, propagation duration, crack coalescence and excess oil pressure in the crack are determined using the fracture mechanics model together with the kinetics of kerogen-oil transformation. The propagation duration for the single crack is governed by the transformation kinetics whereas the propagation duration for the multiple collinear cracks may vary by two orders of magnitude depending on initial crack spacing. A large amount of kerogen (\u3e90%) remains unconverted when the collinear cracks coalesce and the new, larger cracks resulting from coalescence will continue to propagate with continued kerogen-oil conversion. The excess oil pressure on the crack surfaces drops precipitously when the collinear cracks are about to coalesce, and crack propagation duration and oil pressure on the crack surfaces are strongly dependent on temperature. Citation: Jin, Z.-H., S. E. Johnson, and Z. Q. Fan (2010), Subcritical propagation and coalescence of oil-filled cracks: Getting the oil out of low-permeability source rocks, Geophys. Res. Lett., 37, L01305, doi:10.1029/2009GL041576