Direct synthesis of propylene carbonate from propylene and carbon dioxide catalyzed by quaternary ammonium heteropolyphosphatotungstate–TBAB system

In this paper,we have developed a highly efficient method for the direct preparation of propylene carbonate from propylene and carbon dioxide(CO2) using quaternary ammonium heteropolyphosphatotungstate–quaternary ammonium halide catalytic system with anhydrous hydrogen peroxide as an oxidant through one-pot two-step process.The effects of the amount of tetrabutylammonium bromide(TBAB),the concentration of hydrogen peroxide and other reaction conditions were investigated.The catalyst system gave an optimum propylene oxide yield(91%) at75°C in oxidation step and the highest propylene carbonate yield(99%) at 140°C and 3.0 MPa in cycloaddition step.Based on the results,a reaction mechanism has been proposed.     

WKBJ近似保辛吗?

WKBJ短波近似是最常用的有效求解方法之一。保守体系的微分方程可用Hamilton体系的方法描述，其特点是保辛。保辛给出保守体系结构最重要的特性。但WKBJ短波近似却未曾考虑保辛的问题。本文给出验证近似解保辛的条件，并指出WKBJ近似难于保辛。然后给出正则变换的摄动保辛方法。数值例题展示了提出的保辛算法的有效性。     

受控结构风振响应分析的广义虚拟激励法

基于复模态分析和虚拟激励法．提出了用于具有密集频率和非经典阻尼受控结构风振响应分析的广义虚拟激励法。该法可以考虑任意风谱和空间相关性以及模态耦合效应，且计算效率很高。不同于SRSS法．该算法包含了全部参振模态之间和全部激励点之间的相关性．在理论上是精确解。     

结构设计中的混沌优化方法及其改进

在变尺度混沌优化方法研究中．结合结构优化问题的特点，提出了一种改进的混沌优化求解算法，用来解决带有多种约束条件的结构优化设计问题。在有限元分析和优化设计软件JEFIX中实现了上述算法．并通过数值算例讨论了变尺度混沌优化方法在结构优化中的可行性及存在的问题，得到了一些重要结论。     

低温等离子体物理进展

概述了低温等离子体物理研究现状、发展及其应用     

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen

Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis.In this study,vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V 2 O 5 and oxalic acid as sources of vanadium and reductant,respectively.The structures of samples,especially the oxidation state of vanadium,and the surface distribution of vanadium oxide species,have been thoroughly characterized using various techniques,including N 2-physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),UV-visible spectra(UV-Vis) and UV-visible-near infrared spectra(UV-Vis-NIR).It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium.By adjusting hydrothermal treatment time,the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites.These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant.The catalyst exhibits high selectivity for phenol(61%) at benzene conversion of 4.6%,which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.     

人血清Alpha-1-酸性糖蛋白的糖基化分析

获取真实准确的蛋白质糖基化信息是全面了解糖基化修饰生物学功能的前提.针对简单蛋白质的糖基化分析通常采用反相高效液相色谱-串联质谱技术在肽的水平上对糖基化信息进行采集和解析.本文以人血清Alpha-1-酸性糖蛋白(AGP)酶解液为对象,发展了一套简单有效的蛋白质糖基化分析方法.本方法分为三个步骤,第一步是建立糖肽的理论m/z值表;第二步是获取糖蛋白酶解液的LC-MS谱图,并将每一个色谱峰中所包含糖肽的实际m/z值与理论m/z值进行人工匹配;第三步是对每个色谱峰的糖肽结构归属进行LC-MS/MS验证.采用本方法,我们从AGP酶解液中共鉴定出172条糖肽.与单独采用Survey模式的方法相比,本方法能够显著提高糖肽的覆盖率.     

Synthesis and catalytic properties of hierarchical TS-1 in the presence of cationic organosilane surfactant

Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N₂ adsorption isotherm.The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20-30 nm.The BET surface area increases from 420 to 513 m²/g compared to conventional TS-1 zeolite.The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.     

Modelling of multi-bodies in close proximity under water waves——Fluid resonance in narrow gaps

Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the res...     

A novel simulation method to evaluate the collection performance of a monolithic active pixel sensor

A novel simulation method is presented in this paper to evaluate the collection performance of monolithic active pixel sensor (MAPS) devices for minimum ionizing particle tracking. A simplified 3D matrix pixel structure is built using the computer aided design software Sentaurus. The virtual device is then divided into hundreds of parts and an independent customized X photon model is involved in each part to simulate the conditions under ⁵⁵Fe radiation. After data processing and analysis, charge collection efficiency, collection time and diffusion conditions can be estimated in detail. In order to verify the reliability of the method, comparisons are made between the simulations and experiments. Although there are some defects, it can be concluded that the proposed idea is a feasible method for the evaluation of the MAPS collection performance.