Multistage treatment of high strength dye wastewater by coagulation and ozonation

Two types of wastewaters from the dye manufacturing process were treated by multistage chemical coagulation combined with ozonation. By using the coagulant iron(II) chloride and a commercial coagulant aid, the majority of COD was removed in advance of ozonation, a similar repeated treatment cycle was performed after settlement of the coagulant in each cycle. Results showed that the optimum concentrations to be used were 2·5% (v/v) iron(II) chloride and 35 mg dm⁻³ coagulant aid. The decolorization efficiency was >99% and the COD elimination was >90%. The multistage combined chemical coagulation ozonation treatment was found to be superior to the single-stage treatment. © 1998 SCI.     

Conductivities of polysilanes

Measurements of the electrical conductivities of three types of polysilanes were carried out over a range of dc fields and temperatures. These polymers are varied in substituents and structures with formulas of [C₆H₅SiCH₃]_n, [(C₆H₅SiCH₃)₇₀(CH₃SiH)₃₀]_n, and [(C₆H₅SiCH₃)₅₀(C₆H₅SiH)₃₀(CH₃Si)₂₀]_n. Undoped polysilanes behaved as insulators since their conductivities were observed in the range of 10⁻¹⁰ to 10⁻¹³ S cm⁻¹, while SbF₅-doped polysilanes of all kinds behaved as semiconductors with conductivities in the range of 10⁻² to 10⁻⁴ S cm⁻¹. No significant difference in conductivities was observed among three SbF₅-doped polysilanes although these polymers are very different in chemical properties. These experimental results suggest that electrical conductivities of polysilanes are associated with the Si Si main-chain backbone rather than with the side groups. It is evident that the dopant is able to diffuse throughout the bulk of the polymer and the conductivity of the doped polymer is a function of the dopant concentration from the result of in situ monitoring of the resistance of the silane homopolymer during SbF₅ doping at room temperature. The conductivities of polysilanes appeared to be temperature-dependent. The activation energy for the conduction of SbF₅-doped silane copolymer was found to change at its glass transition temperature. © 1996 John Wiley & Sons, Inc.     

Stabilized space–time computation of wind-turbine rotor aerodynamics

We show how we use the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) formulation for accurate 3D computation of the aerodynamics of a wind-turbine rotor. As the test case, we use the NREL 5MW offshore baseline wind-turbine rotor. This class of computational problems are rather challenging, because they involve large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. We compute the problem with both the original version of the DSD/SST formulation and a recently introduced version with an advanced turbulence model. The DSD/SST formulation with the advanced turbulence model is a space–time version of the residual-based variational multiscale method. We compare our results to those reported recently, which were obtained with the residual-based variational multiscale Arbitrary Lagrangian–Eulerian method using NURBS for spatial discretization and which we take as the reference solution. While the original DSD/SST formulation yields torque values not far from the reference solution, the DSD/SST formulation with the variational multiscale turbulence model yields torque values very close to the reference solution.