Numerical analysis for the mixed Navier–Stokes and Darcy Problem with the Beavers–Joseph interface condition

In this article, we consider the coupled Navier–Stokes and Darcy problem with the Beavers–Joseph interface condition. With suitable restrictions of physical parameters α and ν, we prove the existence and local uniqueness of a weak solution. Then we propose a coupled finite element scheme and a decoupled and linearized scheme based on two‐grid finite element. Under suitable further restrictions, their optimal error estimates are obtained. Finally numerical experiments indicate the validity of the theoretical results as well as the efficiency and effectiveness of the decoupled and linearized two‐grid algorithm. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1009–1030, 2015     

Ni/SAPO-11催化剂上棕榈油加氢脱氧制异构烃燃料(英)

采用水热法合成了小粒径、具有介孔结构的SAPO-11分子筛.采用浸渍法制备了不同Ni负载量的Ni/SAPO-11催化剂.并采用X射线衍射,扫描电镜,N₂物理吸附-脱附,NH₃程序升温脱附,热重和H₂化学吸附技术对该类催化剂的物理化学性质进行了详细表征.结果表明,SAPO-11较大表面积和介孔结构可分散Ni,使得Ni粒子尺寸较小.在棕榈油加氢脱氧制备液体烃类燃料反应中,液体烷烃产物由相关脂肪酸中间产物的直接加氢脱氧和脱羰-加氢脱氧两种途径产生.Ni/SAPO-11催化剂的弱/中强酸性质及其匹配的金属-酸双功能可显著抑制积炭反应,提高催化剂的寿命,液体烷烃收率高达70%,异构烷烃选择性超过80%.     

An E1-Catalyzed Chemoenzymatic Strategy to Isopeptide-N-Ethylated Deubiquitylase-Resistant Ubiquitin Probes

Triazole-based deubiquitylase (DUB)-resistant ubiquitin (Ub) probes have recently emerged as effective tools for the discovery of Ub chain-specific interactors in proteomic studies, but their structural diversity is limited. A new family of DUB-resistant Ub probes is reported based on isopeptide-N-ethylated dimeric or polymeric Ub chains, which can be efficiently prepared by a one-pot, ubiquitin-activating enzyme (E1)-catalyzed condensation reaction of recombinant Ub precursors to give various homotypic and even branched Ub probes at multi-milligram scale. Proteomic studies using label-free quantitative (LFQ) MS indicated that the isopeptide-N-ethylated Ub probes may complement the triazole-based probes in the study of Ub interactome. Our study highlights the utility of modern protein synthetic chemistry to develop structurally and new families of tool molecules needed for proteomic studies.     

Highly Regio-, Diastereo-, and Enantioselective Synthesis of Tetrahydroazepines and Benzo[b]oxepines through Palladium-Catalyzed [4+3] Cycloaddition Reactions

A novel Pd⁰-catalyzed asymmetric [4+3] annulation reaction of two readily accessible starting materials has been developed for building seven-membered heterocyclic architectures. The potential [3+2] side pathway could be suppressed though fine tuning of the conditions. A broad scope of cycloaddition donors and acceptors participated in the transformation with excellent chemo-, regio-, diastereo-, and enantioselectivtities, leading to valuable tetrahydroazepines and benzo[b]oxepines.     

Hybrid Copolymerization via the Combination of Proton Transfer and Ring-opening Polymerization

Phosphazene base,t-BuP2,was employed to catalyze the proton transfer polymerization(PTP)of 2-hydroxyethyl acrylate(HEA),and PTP was further combined with ring-opening polymerization(ROP)to exploit a new type of hybrid copolymerization.The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature,giving an excellent monomer conversion.Throughout the polymerization,transesterification reactions were unavoidable,which increased the randomness in the structures of the resulting polymers.The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25°C.During copolymerization,HEA not only provided hydroxyl groups to initiate the ROP ofε-caprolactone(CL)but also participated in the polymerization as a monomer for PTP.The copolymer composition was approximately equal to the feed ratio,demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio.This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials.Hence,it is important not only in polymer chemistry but also in environmental and biomedical engineering.     

Nonlinear free vibrations of porous composite microplates incorporating various microstructural-dependent strain gradient tensors

The main objective of the present numerical analysis is to predict the nonlinear frequency ratios associated with the nonlinear free vibration response of porous composite plates at microscale in the presence of different microstructural gradient tensors. To achieve this end, by taking cubic-type elements into account, isogeometric models of porous composite microplates are obtained with and without a central cutout and relevant to various porosity patterns of distribution along the plate thickness. The established unconventional models have the capability to capture the effects of various unconventional gradient tensors continuity on the basis of a refined shear deformable plate formulation. For the simply supported microsized uniform porous functionally graded material (U-PFGM) plate having the oscillation amplitude equal to the plate thickness, it is revealed that the rotation gradient tensor causes to reduce the frequency ratio about 0.73%, the dilatation gradient tensor causes to reduce it about 1.93%, and the deviatoric stretch gradient tensor leads to a decrease of it about 5.19%. On the other hand, for the clamped microsized U-PFGM plate having the oscillation amplitude equal to the plate thickness, these percentages are equal to 0.62%, 1.64%, and 4.40%, respectively. Accordingly, it is found that by changing the boundary conditions from clamped to simply supported, the effect of microsize on the reduction of frequency ratio decreases a bit.

     

Evolution of concentration fluctuation during phase separation of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica

The influence of nanosilica on the concentration fluctuation of polystyrene/poly (vinyl methyl ether) (PS/PVME) mixtures was investigated during phase separation. The amplitude of concentration fluctuation was quantified by dielectric spectrums based on the idea of Lodge–Mcleish model and the linearized Cahn–Hilliard theory could describe the amplitude evolution of concentration fluctuation at the early stage of phase separation. Hydrophilic nanosilica A200 dispersed in PVME‐rich phase behaved an obvious inhibition effect on the concentration fluctuation of blend matrix, while hydrophobic nanosilica R974 dispersed in PS‐rich phase had little effect on the concentration fluctuation. The kinetics and amplitude evolution of concentration fluctuation during phase separation for PS/PVME/A200 nanocomposites were remarkably restrained due to the surface adsorption of PVME on A200. As the segmental dynamics of PVME and PS in homogeneous matrix was hardly influenced by A200 and R974, the enhanced miscibility and the significantly constrained flow relaxation of PVME chains might contribute to the retarded concentration fluctuation of PS/PVME/A200 nanocomposites. While the weak interaction between R974 and components of blend matrix and little effect of R974 on the molecular dynamics of PS chains may result in the weak retardation of concentration fluctuation for blend matrix. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1337–1349