基于一种新型超腔的高亮度激光同步辐射分析

 提出了一种由一对抛物面构成的超腔的技术方案,计算了超腔汇聚点处的总光子密度。利用康普顿散射理论对基于抛物面超腔的激光同步辐射及其光子产额进行了讨论和计算。结果表明:当超腔镜面的反射率等于99.99%时,在超腔碰撞点处的总光子数密度大约是初始激光束在碰撞点处光子数密度的5 000倍,对应康普顿垂直散射的光子产额大约是电子束与初始激光束在碰撞点处发生康普顿垂直散射时的5 000倍。     

CeO2/RP-PSCFM@CoFe阳极材料用于质子导体乙烷燃料电池共生乙烯和电能

The continuous consumption and excessive use of fossil fuels promote the exploration of new energy conversion technologies. Meanwhile, the increase in the supply of ethane encourages the development of industrial technology for the production of ethylene chemical raw materials. Compared with traditional fossil fuel energy conversion equipment, solid oxide ethane cogeneration fuel cells are an efficient energy processing device. Through selective oxidation of fuel gas on the anode, the endothermic process of ethane dehydrogenation is converted into an exothermic oxidation reaction, which has a greater driving force for reaction thermodynamics, and simultaneously produces clean electricity and value-added chemicals without CO₂ emissions. The anode material used for the proton conductor ethane fuel cells needs to operate stably and efficiently under hydrocarbon fuel. Consequently, excellent catalytic activity, low polarization resistance, and anti-coking stability are essential. In this work, CeO₂ was uniformly impregnated into the surface of the porous cubic perovskite Pr_0.4Sr_0.6Co_0.2Fe_0.7Mo_0.1O_3−δ anode by wet impregnation, and then calcined and reduced to obtain a CeO₂/RP-PSCFM@CoFe composite anode embedded with nanoparticles, which was successfully used in electrolyte-supported proton conductor fuel cells. CeO₂ has a high ionic conductivity and transport capacity, which accelerates the transfer rate of protons on the anode and improves the catalytic reaction and transport process. Moreover, uniformly dispersed CeO₂ can effectively increase the three-phase interface of the anode reaction and increase the range of reaction activity. The peak power densities before and after wet impregnation reached 172 and 253 mW·cm⁻², respectively, at 750 ℃. When switching to ethane as the fuel, the peak power densities reached 136 and 183 mW·cm⁻², respectively. The polarization resistance of the impregnated single cell was significantly reduced, and the catalytic activity improved. Moreover, there was no attenuation for 10 h in the long-term test. Inversely, the current density increased with the continuous reduction of the composite anode. Product analysis revealed that the yield of ethylene increased from 23.52% at 650 ℃ to 34.09% at 750 ℃, and the ethylene selectivity exceeded 94%. These results clearly show that the impregnated anode exhibited excellent catalytic activity and anti-coking ability in hydrocarbon fuels at high temperatures. Combining CoFe nanoparticles with CeO₂ enhanced the electronic conductance and ionic conductance of the electrode, improved the transmission of electric energy and the efficient conversion of chemicals, thus successfully producing the cogeneration of electric energy and ethylene.     

A novel high-performance liquid chromatography-fluorescence analysis coupled with in situ degradation-derivatization technique for quantitation of organophosphorus thioester pesticide residues in tea

Analytical and Bioanalytical Chemistry - A novel high-performance liquid chromatography–fluorescence analysis in combination with in situ degradation–derivatization (ISD-D) technique...     

Synthesis of Porous Fe3C-Based Composite Beads as Heterogeneous Oxidation Catalysts

A series of multiscale cementite/iron/porous carbon (CIPC-T) composites with extremely low nitrogen content and millimeter-size spherical morphology were prepared by simple carbothermal pyrolysis of resin spheres exchanged with ferric oxalate anions. CIPC-T materials are composed of highly disperse core–shell-structured Fe₃C/Fe@graphitic carbon (CI@GC) nanoparticles embedded in a porous amorphous carbon framework. A mechanism for the formation of the composites is proposed on the basis of the results of XRD, SEM, TEM, and thermogravimetric analysis. The Fe₃C content can be easily controlled just by using different carbothermal temperatures. The CIPC-T materials proved to be active as heterogeneous catalysts for oxidation of ethylbenzene to acetophenone and Fenton-like oxidation of methylene blue. For the first time, the role of Fe₃C in catalytic oxidation was confirmed. The spherical morphology of the composites and magnetic property facilitate separation of the catalyst from the reaction solution. More importantly, no leaching of iron active sites occurs during the reactions and the catalyst can be reused in continuous runs without obvious loss of activity. Such high stability of iron sites in the composites is ascribed to the protecting outer graphitic carbon shell of CI@GC.     

Retroreflective projection gratings

A retroreflective projection grating technique has been investigated to inspect quasi flat and specular surfaces. The method introduces the flexibility to adjust the properties of the grating to a specific application or to move it as a whole, in order to use phase shifting technology. Three types of optical configuration have been demonstrated. The method has been tested with a quantified artifact. The experiment shows that it can successfully recover the contour and amplitude of the surface waviness on the artifact. The method can be developed for industrial application in nondestructive testing and evaluation (NDTE).     

钯铜纳米电催化剂的制备方法及应用

贵金属钯(Pd)基纳米材料是一类具有优异催化活性的电催化材料,其中钯-铜(Pd-Cu)二元材料由于具有低成本和高活性的优点,近年来备受瞩目。铜(Cu)的引入不但降低了Pd的用量,还带来了诸如配体效应、应力效应、聚集体效应等协同作用,这为优化材料的电催化性能带来了多种切入角度。特殊形貌及结构的构建可以使催化剂暴露更多的活性位点,增大电化学活性表面积,提高电催化性能。此外,对Pd-Cu组分的调整或构建复合结构可以实现对d带中心的调控,从而优化电极界面吸附能,最终实现增强活性和改善稳定性的目的。本文总结了具有球形、多面体、核壳、多孔、枝晶状以及单原子等结构的Pd-Cu二元材料的制备方法,并概述了它们在有机小分子(甲醇、乙醇、甲酸等)电氧化、无机小分子(氧、二氧化碳、氮、水等)电还原以及化学镀铜上的应用。最后展望了Pd-Cu电催化剂的发展前景。     

利用康普顿散射实现太赫兹皮秒脉冲的分析

 研究了利用微波与电子束团的康普顿散射实现太赫兹的方法、光子产额和辐射功率。推导出了单个电子产生的太赫兹的光子产额和辐射功率表达式,也推导出了电子束团产生的太赫兹的光子总产额和辐射总功率表达式。结果发现：利用微波与电子束团发生康普顿垂直散射,可以产生太赫兹皮秒脉冲;单个电子产生的太赫兹光子产额与微波功率、微波波长成正比,与微波束截面积成反比;单个电子产生的太赫兹辐射功率与微波功率、电子Lorentz因子的平方成正比,与微波束截面积成反比;电子束团产生的太赫兹光子总产额与微波功率的平方、微波波长的平方成正比,与微波束截面积的平方成反比;电子束团产生的太赫兹辐射总功率与微波功率的平方、微波波长以及电子Lorentz因子的平方成正比,与微波束截面积的平方成反比。     

LOCAL POLYNOMIAL DOUBLE-SMOOTHING ESTIMATION OF A CONDITIONAL DISTRIBUTION FUNCTION WITH DEPENDENT

Based on the idea of local polynomial double-smoother, we propose an estimator of a conditional cumulative distribution function with dependent and left-truncated data. It is assumed that the observations form a stationaryα-mixing sequence. Asymptotic normality of the estimator is established. The finite sample behavior of the estimator is investigated via simulations.     

Erratum on “Engineering of a universal polymeric nanoparticle platform to optimize the PEG density for photodynamic therapy”

Science China Chemistry - In a recent publication [1], these images in Figures 6(b, c) (NPEG-NPCe6 group), S7, S9 and S10 were inadvertently taken the incorrect images in the production. The...     

直接甲醇燃料电池质子膜研究进展

本文对直接甲醇燃料电池(DMFC)质子交换膜的要求及目前的研究状况作了简要的概述,特别是从基膜材料结构角度进行分类,较详细地介绍分析以Nafion膜为代表的全氟磺酸膜的各种改性研究及以PBI、PEEK、PSU等基膜材料为代表的聚芳环系列的DMFC质子交换膜的研究情况.总结了质子交换膜的一些研究方法,对直接甲醇燃料电池质子交换膜的发展前景进行了探讨。