A high‐order element based adaptive mesh refinement strategy for three‐dimensional unstructured grid

Adaptive mesh refinement (AMR) shows attractive properties in automatically refining the flow region of interest, and with AMR, better prediction can be obtained with much less labor work and cost compared to manually remeshing or the global mesh refinement. Cartesian AMR is well established; however, AMR on hybrid unstructured mesh, which is heavily used in the high‐Reynolds number flow simulation, is less matured and existing methods may result in degraded mesh quality, which mostly happens in the boundary layer or near the sharp geometric features. User intervention or additional constraints, such as freezing all boundary layer elements or refining the whole boundary layer, are required to assist the refinement process. In this work, a novel AMR strategy is developed to handle existing difficulties. In the new method, high‐order unstructured elements are first generated based on the baseline mesh; then the refinement is conducted in the parametric space; at last, the mesh suitable for the solver is output. Generating refined elements in the parametric space with high‐order elements is the key of this method and this helps to guarantee both the accuracy and robustness. With the current method, 3‐dimensional hybrid unstructured mesh of huge size and complex geometry can be automatically refined, without user intervention nor additional constraints. With test cases including the 2‐dimensional airfoil and 3‐dimensional full aircraft, the current AMR method proves to be accurate, simple, and robust.     

KMnO4-mediated direct selective radical cross-coupling: An effective strategy for C2 arylation of quinoline N-oxide with arylboronic acids

Direct C—H functionalization of quinoline N-oxides with arylboronic acids is achieved using KMnO_4 as the sole and efficient oxidative system.This method provides an efficient protocol to construct regioselectively 2-arylquinoline N-oxides via radical cross-coupling reaction in moderated to good yields under mild conditions.     

A finite volume scheme preserving extremum principle for convection–diffusion equations on polygonal meshes

We propose a nonlinear finite volume scheme for convection–diffusion equation on polygonal meshes and prove that the discrete solution of the scheme satisfies the discrete extremum principle. The approximation of diffusive flux is based on an adaptive approach of choosing stencil in the construction of discrete normal flux, and the approximation of convection flux is based on the second‐order upwind method with proper slope limiter. Our scheme is locally conservative and has only cell‐centered unknowns. Numerical results show that our scheme can preserve discrete extremum principle and has almost second‐order accuracy. Copyright © 2017 John Wiley & Sons, Ltd.     

The Structural Fate of Individual Multicomponent Metal‐Oxide Nanoparticles in Polymer Nanoreactors

Multicomponent nanoparticles can be synthesized with either homogeneous or phase‐segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal‐oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co‐Ni‐O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu‐Ni‐O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher‐ordered structure, Co‐Ni‐Cu‐O, was found to follow the behavior of lower ordered systems.     

Short syntheses of (−)-clavaminol A and deacetyl (+)-clavaminol H

Concise stereoselective syntheses of (?)-clavaminol A and deacetyl (+)-clavaminol H have been achieved from simple starting materials. Highlights of the synthesis for (?)-clavaminol A include a highly diastereoselective chelation-controlled hydride reduction of an amino ketone to give the anti amino alcohol directly, and NaBH₄-mediated dehalogenation. The main synthetic approach for deacetyl (+)-clavaminol H features a highly diastereoselective chelation-controlled hydride reduction of the amino ketone to construct the anti amino alcohol and a palladium catalyzed hydrogenation reaction at the final step.     

Cu(OAc)2-catalyzed direct radical C2 arylation of quinoline N-oxide with arylamines

A Cu(OAc)₂-catalyzed synthesis of 2-arylquinoline N-oxides with easily available arylamines is described. The main features of this reaction are mild reaction conditions, high functional-group tolerance, excellent regioselectivity, and good to excellent yields. This procedure is mild, operationally simple, and constitutes a greener approach to the arylation of quinoline N-oxides.     

Interfacial passivation mechanism of sulfide towards quantum dot-sensitized nanocrystalline thin films

Journal of Solid State Electrochemistry - We report on the interfacial passivation mechanism in CdSe quantum dot-sensitized ZnO nanocrystalline thin film, where different sulfide semiconductors...     

Existence results for second-order system with impulse effects via variational methods

In this paper, we investigate the positive solutions of a second-order system with impulse effects. By using critical point theory the existence result of positive solutions is obtained.