Sediment transport following water transfer from Yangtze River to Taihu Basin

AbstractTo meet the increasing need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration (SSC) of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course

Toward Achieving Highly Ordered Fluorinated Surfaces of Spin-Coated Polymer Thin Films by Optimizing the Air/Liquid Interfacial Structure of the Casting Solutions

Thin polymer films with well-assembled fluorinated groups on their surfaces are not easily achieved via spin-coating film-fabrication methods because the solution solidifies very rapidly during spin-coating, which hinders the fluorinated moieties from segregating and organizing on the film surface. In this contribution, we have proposed a comprehensive strategy toward achieving well-ordered fluorinated thin films surfaces by optimizing the molecular organization at air/liquid interface of the film-formation solutions. To validate such a route, poly­(methyl methacrylate) (PMMA) end-capped with several 2-perfluorooctylethyl methacrylate (FMA) units was employed as the model polymer for investigations. The air/solution interfacial structures were optimized by systematically changing the polymer chain structures and properties of the casting solvents. It was found that the polymers that form loosely associated aggregates (e.g., FMA₁-<i>ec</i>-PMMA₆₅-<i>ec</i>-FMA₁) and a solvent with better solubility to FMA while having not too low surface tension (i.e., toluene) can combine to produce solutions with well-assembled FMA at the interfaces. By spin-coating the solutions with well-organized interfaces, an ultrathin film with perfluorinated groups that were highly oriented toward the film surface was readily achieved, exhibiting surface energies as low as 7.2 mJ/m², which is among the lowest reported so far for the spin-coated thin films, and a very high F/C ratio (i.e., 0.98)

Sulfanilic Acid Pending on a Graphene Scaffold: Novel, Efficient Synthesis and Much Enhanced Polymer Solar Cell Efficiency and Stability Using It as a Hole Extraction Layer

In this contribution, we describe a novel, facile, and scalable methodology for high degree functionalization toward graphene by the reaction between bulk graphite fluoride and in situ generated amine anion. Using this, the rationally designed sulfanilic acid pending on a graphene scaffold (G-SO₃H), a two-dimensional (2D) π-conjugated counterpart of poly­(styrenesulfonate), is available. Combined reliable characterizations demonstrate that a very large quantity of sulfanilic blocks are linked to graphene through the foreseen substitution of carbon–fluorine units and an unexpected reductive defluorination simultaneously proceeds during the one-step reaction, endowing the resultant G-SO₃H with splendid dispersity in various solvents and film-forming property via the former, and with recovered 2D π-conjugation via the latter. Besides, the work function of G-SO₃H lies at −4.8 eV, well matched with the P3HT donor. Awarded with these fantastic merits, G-SO₃H behaves capable in hole collection and transport, indicated by the enhanced device efficiency and stability of polymer solar cells (PSCs) based on intensively studied P3HT:PCBM blends as an active layer. In particular, comparison with conventional poly­(3,4-ethylenedioxythiophene) doped with poly­(styrenesulfonate) and recently rising and shining graphene oxide, G-SO₃H outperforms above 17 and 24%, respectively, in efficiency. More impressively, when these three unencapsulated devices are placed in a N₂-filled glovebox at around 25 °C for 7 weeks, or subject to thermal treatment at 150 °C for 6 h also in N₂ atmosphere, or even rudely exposed to indoor air, G-SO₃H-based PSCs exhibit the best stability. These findings enable G-SO₃H to be a strongly competitive alternative of the existing hole extraction materials for PSC real-life applications