Cross Dehydrogenation Coupling Reaction of Purine Derivatives with Thioethers

A metal-free cross-dehydrogenation coupling method was established to synthesize N9 alkylated purine derivatives. Using PhI(OAc)2 as oxidants, versatile thioethers were successfully employed as alkylation reagents, Under optimized conditions, a variety...

Electrochemical Dehydrogenative C-N Coupling of Hydrazones for the Synthesis of 1H-Indazoles

An electrochemical dehydrogenative C-N coupling method has been developed for the synthesis of 1H-Indazoles from easily available hydrazones. Various functional groups are compatible with this metal and oxidant free protocol...

Study on Numerical Simulation Methods for Hypervelocity Impact on Large-Scale Complex Spacecraft Structures

This paper aims to study the difference of results in breakup state judgment, debris cloud and fragment characteristic parameter during hypervelocity impact (HVI) on large-scale complex spacecraft structures by various numerical simulation methods. We compared the results of the test of aluminum projectile impact on an aluminum plate with the simulation results of the smooth particle hydrodynamics (SPH), finite element method (FEM)-smoothed particle Galerkin (SPG) fixed coupling method, node separation method, and finite element method-smooth particle hydrodynamics adaptive coupling method under varying mesh/particle sizes. Then based on the test of the complex simulated satellite under hypervelocity impact of space debris, the most applicable algorithm was selected and used to verify the accuracy of the calculation results. It was found that the finite element method-smooth particle hydrodynamics adaptive coupling method has lower mesh sensitivity in displaying the contour of the debris cloud and calculating its characteristic parameters, making it more suitable for the full-scale numerical simulation of hypervelocity impact. Moreover, this algorithm can simulate the macro breakup state of the full-scale model with complex structure and output debris fragments with clear boundaries and accurate shapes. This study provides numerical simulation method options for the follow-up research on breakup conditions, damage effects, debris clouds, and fragment characteristics of large-scale complex spacecraft.