Homogeneous Desulfurization of Thiols and Sulfides by Yb[N(SiMe3)2]2.2 THF. Relevance to Heterogeneous and Biological Desulfurizations and the Synthesis of Lanthanide(II) Sulfides

Yb[N(SiMe₃)₂]₂·2THF was found to desulfurize thiols (RSH) and dibenzyl sulfide. With thiols, the extent of desulfurization was a function of the relative stability of the corresponding radical, R·. Radicals were also involved in the desulfurization of dibenzyl sulfide. A unified mechanism involving a series of one-electron redox steps leading to the generation of organic radical intermediates has been proposed.     

Design and experimental validation of a two-stage superplastic forming die

The conventional superplastic forming (SPF) of complex and deep geometries can result in excessive thinning and necking. To address these issues, a two-stage SPF process has been developed and demonstrated in forming trials using a superplastic aluminum sheet alloy. Within a single die, gas pressure is used to form the blank into a preform die cavity prior to the pressure being reversed to form the sheet into the final component cavity. The preforming of the blank creates length of line, while preserving metal thickness in certain regions to improve the thickness profile of the final part. In this work, a preform has been designed to improve the forming of a complex component by providing a superior thickness profile as compared to a conventional single stage forming cycle. Finite element analysis was used to guide the design of the preform cavity since the preforming surface was not intuitive and could cause wrinkling in the final part.     

Duality-based robust polynomial matrix controller

Summary Complex dynamic processes partly contain unknown parameters (in the controller) and known parameters (in the process). The latter are frequently deteriorated by uncertainties. The inverse problem results from the challenge to find the unknown system parameters such that the over-all input output behaviour turns out close to some given performance. As the index of performance the stability margin is selected. In this paper, a computer-assisted gradient approach is presented which improves the stability margin of a multivariable control system in the presence of spherical uncertainties. Following the appropriate gradient and observing a heuristic stopping condition from the viewpoint of design engineering, the method provides a unified approach both for controller design and robustification.      

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