EPR studies on H-abstraction from methylbenzenes by “magic blue” reagent

After mixing a methylbenzene 4 with “magic blue” solution in F113 (CClF₂CCl₂F) containing bis{perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl}nitroxide 2 and perfluoro-1-nitroso-1-[1-(2-fluorosulfonyl)ethoxy]ethane 3 at room temperature, benzylic H-atom of 4 could be selectively abstracted by 2, and benzyl radical 5 thus generated was immediately trapped by 3. Based on hyper-fine splitting constants (hfsc), the structure of the spin adducts perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl benzyl nitroxides 6 derived from seven methylbenzenes have been identified. The mechanism of the H-abstraction/spin trapping process is also discussed.     

Photocatalytic and antifouling properties of TiO2-based photocatalytic membranes

Photocatalysis has been extensively studied due to its potential ability to avoid the excessive use of chemical reagents and reduce the energy consumption by employing solar energy. Moreover, to alleviate the reduction in the membrane permeation selectivity, separation efficiency, and membrane service life caused by the emerging micro-pollutants and membrane fouling, membrane technology is often coupled with microbial, electrochemical, and catalytic processes. However, although physical/chemical cleaning and membrane module replacement can overcome the inherent limitations caused by membrane fouling and other membrane separation processes, high operating costs limit their practical applications. In this review, common preparation methods for TiO₂ photocatalytic membranes are described in detail, and the main approaches to enhancing their photocatalytic performance are discussed. More importantly, the mechanism of the TiO₂ photocatalytic membrane antifouling process is elucidated, and some applications of photocatalytic membranes in other areas are described. This review systematically outlines future research directions in the field of photocatalytic membrane modification, including metal and non-metal doping, fabrication of heterojunction structures, control over reaction conditions, increase in hydrophilicity, and increase in membrane porosity.     

Conjugated polymers containing B←N unit as electron acceptors for all-polymer solar cells

Polymer electron acceptors are the key materials in all-polymer solar cells(all-PSCs).In this review,we focused on introducing the principle of boron-nitrogen coordination bond(B←N),and summarizing our recent research on polymer electron acceptors containing B←N unit for efficient all-PSC devices.Two approaches have been reported to design polymer electron acceptors using B←N unit.One is to replace a C-C unit by a B←N unit in conjugated polymers to transform a polymer electron donor to a polymer electron acceptor.The other approach is to construct novel electron-deficient building block based on B←N unit for polymer electron acceptors.The polymer electron acceptors containing B←N unit showed tunable lowest unoccupied molecular orbital(LUMO) energy levels and exhibited excellent all-PSC device performance with power conversion efficiency of exceeding6%.These results indicate that organic boron chemistry is a new toolbox to develop functional polymer materials for optoelectronic device applications.     

Synthesis and properties of a thiophene-substituted diaza[7]helicene for application as a blue emitter in organic light-emitting diodes

Carbazole-based diaza[7]helicene substituted by thiophene groups, 2,12-dithiophene-5,15-dihexyl-5,15-diaza[7]helicene (6), was synthesised successfully and confirmed by ¹H NMR, ¹³C NMR, High Resolution Mass Spectrometry, Time of Flight Mass Spectrometry. Compound 6 exhibited good solubility and excellent thermal stability with no melting point and a high decomposition temperature of 453.64 °C. A doped device with a structure of ITO/NPB (50 nm)/CBP: 10% 6 (30 nm)/Bphen (20 nm)/Mg:Ag (150 nm)/Ag (50 nm) emitted the blue light at 460 nm with Commission Internationale de LEclairage (CIE) coordinate of (0.176, 0.26). The maximum brightness and external quantum efficiency (EQE) were 2306 cd m^?2 and 0.41%, respectively.     

An Alternating Polymer of Two Building Blocks Based on B←N Unit:Non-fullerene Acceptor for Organic Photovoltaics

B←N coordination bond can be used to develop polymer electron acceptors for efficient all-polymer solar cells(all-PSCs). Here, we report a new alternating conjugated polymer containing two building blocks based on B←N unit. The polymer exhibits strong light absorption in the visible range, low-lying LUMO/HOMO energy levels and moderate electron mobility. The resulting all-PSC devices exhibit power conversion efficiencies of 1.50%–2.47%.     

Asymptotic stability of viscous shock wave profiles for viscous conservation laws

This paper is concerned with the asymptotic stability of travelling wave solution to the two-dimensional steady isentropic irrotational flow with artificial viscosity. We prove that there exists a unique travelling wave solution up to a shift to the system if the end states satisfy both the Rankine–Hugoniot condition and Lax's shock condition, and that the travelling wave solution is stable if the initial disturbance is small.     

Development of efficient and accurate skeletal mechanisms for hydrocarbon fuels and kerosene surrogate

In this paper,the methodology of the directed relation graph with error propagation and sensitivity analysis(DRGEPSA),proposed by Niemeyer et al.(Combust Flame 157:1760-1770.2010).and its differences to the original directed relation graph method are described.Using DRGEPSA,the detailed mechanism of ethylene containing 71 species and 395 reaction steps is reduced to several skeletal mechanisms with different error thresholds.The 25-species and 131-step mechanism and the 24-species and115-step mechanism are found to be accurate for the predictions of ignition delay time and laminar flame speed.Although further reduction leads to a smaller skeletal mechanism with 19 species and 68 steps,it is no longer able to represent the correct reaction processes.With the DRGEPSA method,a detailed mechanism for n-dodecane considering low-temperature chemistry and containing 2115 species and8157 steps is reduced to a much smaller mechanism with249 species and 910 steps while retaining good accuracy.If considering only high-temperature(higher than 1000 K)applications,the detailed mechanism can be simplified to even smaller mechanisms with 65 species and 340 steps or48 species and 220 steps.Furthermore,a detailed mechanism for a kerosene surrogate having 207 species and 1592 steps is reduced with various error thresholds and the results show that the 72-species and 429-step mechanism and the66-species and 392-step mechanism are capable of predicting correct combustion properties compared to those of the detailed mechanism.It is well recognized that kinetic mechanisms can be effectively used in computations only after they are reduced to an acceptable size level for computation capacity and at the same time retaining accuracy.Thus,the skeletal mechanisms generated from the present work are expected to be useful for the application of kinetic mechanisms of hydrocarbons to numerical simulations of turbulent or supersonic combustion.     

求一阶数值微分的L-广义解方法cTSVD

<正>1引言数值微分也就是给定一个函数在一个区间或某些离散点上的扰动数据来求函数的导数,它产生于很多实际问题当中,比如,图象处理中的边界识别问题;Abel积分方程的求解问题;化学中波谱的波峰识别问题.以及一些数学物理反问题当中.数值微