Dual quaternion-based moving target trajectory tracking adaptive sliding mode control for robotic manipulator

This article focuses on the moving target trajectory tracking control problem for robotic manipulator. The dynamics models of the rigid-body moving target and the manipulator end-effector based on the unit dual quaternion are firstly established. Then, the relative motion dynamics equation is deduced according to the arithmetic rules of dual quaternion. Further, an adaptive sliding mode controller is put forward to guarantee that the error between the pose of the rigidbody moving target and the pose of manipulator end-effector asymptotically converges to zero, where the upper bound on the norm of the uncertainty in the second-order differential error dynamics equation is estimated online by adaptive law. It is ensured via the Lyapunov theory that the asymptotic stability of the closed-loop system. Numerical simulation validates the theoretical consequences.</p

Practical Asymmetric Hydrogenation-Based Synthesis of a Class-Selective Histone Deacetylase Inhibitor

Two syntheses of the class-selective histone deacetylase inhibitor <b>1</b> are reported. In the first, eight-step entailing synthesis, the key transformations were a highly efficient [3 + 2] dipolar cycloaddition affording <i>trans</i>-<i>rac</i>-<b>5</b> and its resolution. In the second, asymmetric approach, the key steps were a highly selective asymmetric hydrogenation to produce the <i>cis</i>-(<i>S,S</i>)-3,4-disubstituted pyrrolidine <b>18</b> followed by an amide formation with simultaneous chiral inversion of the carboxy stereocenter to generate the key intermediate <i>trans</i>-(<i>R,S</i>)-3,4-disubstituted pyrrolidine <b>19</b>. The overall yield increased from ∼6% for the resolution approach to ∼26% for the enantioselective approach

Mechanistic Study of the Direct Hydrodeoxygenation of <i>m</i>‑Cresol over WO_<i>x</i>‑Decorated Pt/C Catalysts

Hydrodeoxygenation (HDO) of <i>m</i>-cresol to produce toluene over carbon-supported Pt and Pt-WO_<i>x</i> catalysts was studied. In stark contrast to Pt/C that exhibits only modest selectivity and low stability for this reaction, Pt-WO_<i>x</i>/C was found to be unusually active and selective to toluene with greater than 94% selectivity to this product while exhibiting little to no deactivation under a wide range of reaction conditions. Reactivity studies in combination with density functional theory (DFT) calculations for the adsorption and reaction of <i>m</i>-cresol on structurally optimized WO_<i>x</i>-decorated Pt(111) structures indicate that the HDO reaction on Pt-WO_<i>x</i>/C proceeds via a direct hydrogenolysis of the C–O bond in <i>m</i>-cresol adsorbed on oxygen vacancy (or redox) sites on WO_<i>x</i> species. The DFT results also indicate that Pt helps stabilize the WO_<i>x</i> film while facilitating oxygen vacancy formation