混合方次的Waring——Goldbach问题

研究混合方次的Waring--Goldbach     

Improving Catalytic Stability and Coke Resistance of Ni/Al2O3 Catalysts with Ce Promoter for Relatively Low Temperature Dry Reforming of Methane Reaction

Aseries of Ni catalysts supported on alumina with different Ce contents(1.0%-6.0%, mass fraction) was prepared by the impregnation method and used for dry reforming of methane(DRM) at a relatively low temperature of 650 ^oC. The promotion effect of Ce with different loading amounts on the physicochemical properties of the catalysts was systematically characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), N₂ adsorption-desorption, thermo elemental IRIS Intrepid inductively coupled plasma atomic emission spectrometer (ICP-AES), UV-visible diffuse reflectance spectroscopy(UV-Vis DRS), Fourier transformation infrared(FTIR) spectra, H₂-temperature programmed reduction(H₂-TPR) analysis, H₂-temperature programmed desorption(H₂-TPD), and the X-ray photoelectron spectroscopy(XPS) techniques. The results indicate that all the catalysts mainly exist in the NiAl₂O₄ phase after being calcined at 750 ^oC with small Ni particle sizes due to the strong metal-support interaction derived from the reduction of the NiAl₂O₄ phase. The Ce-promoted catalysts show better catalytic performance as well as the resistance against sintering of Ni particles and deposition of carbon compared to the Ni/Al₂O₃ catalyst. The Ni-6Ce/Al₂O₃ exhibits the best catalytic stability and coke resistance among the four catalysts studied, which is due to its small Ni nanoparticles sizes, excellent reducibility as well as high amount of active oxygen species. In a 400 h stability test for DRM reaction at 650 ^oC, Ni-6Ce/Al₂O₃ exhibits less coke deposition and small growth of Ni nanoparticles. This work provides a simple way to preparing the Ni-Ce/Al₂O₃ catalyst with enhanced catalytic performance in DRM. The Ni-6Ce/Al₂O₃ catalyst has great potential for industrial application due to its anti-sintering ability and resistance to carbon deposition.     

广州大气细粒子中有机碳、元素碳和水溶性有机碳的分布特征

在广州市中山大学采样点进行了为期1年的大气细粒子(PM2.5)采样,监测分析得到PM2.5及有机碳(OC)、元素碳(EC)和水溶性有机碳(WSOC)等组分的质量浓度,并进行了比较和评价分析。结果表明广州市细粒子碳污染较严重。对OC、EC和WSOC质量浓度的月变化和季节变化特征进行了讨论,并分析了原因。OC、EC浓度相关性好,表明OC、EC来源大部分相同。根据OC/EC比值,估算二次有机碳(SOC)量,结果是SOC占OC的1/3。讨论了SOC和SOC/OC比值的季节分布,结果证明SOC夏季生成比冬季多。     

Ferritin as a Novel Catalyst for Selective Hydroxylation of Phenol

Ferritin molecule consists of a spherical polypeptide shell (apoferritin) surrounding a nanometeric inorganic core of iron oxide ferihydrite. It has the ability to sequester and store iron in a bio-available form by mobilizing or immobilizing iron through its narrow channels in the stable polypeptide quaternary structure^[1,2].Our original idea was to explore the catalytic activity of the inner nano-sized, iron oxide core. It was also hoped that the spherical hollow polypeptide shell with channels might act as a biological-molecular, sieve, displaying some kinds of shape and size selectivity.     

同位旋依赖的碎块判断方法对重离子碰撞观测量的影响(英文)

该工作提出了一个同位旋依赖碎块判断方法用以描述重离子碰撞过程中的碎块形成。利用该方法可以改善输运理论对于核子以及轻带电粒子产额的描写,其在计算中降低了发射核子产额、增加碎块(特别是丰中子碎块) 的产额。对于丰中子轻带电粒子的增强主要出现在中心快度区。研究表明,该方法对于同位旋敏感的观测量,如,n/p,t/3He,Rmidyield 和isoscaling parameters 等,以及系统的平衡度的量度都会产生影响。We introduce isospin dependence in the cluster recognition algorithms used in the Quantum Molecular Dynamics model to describe fragment formation in heavy ion collisions. This change reduces the yields of emitted nucleons and enhances the yields of fragments, especially for heavier fragments. The enhancement of neutron-rich lighter fragments mainly occurs at mid-rapidity. Consequently, isospin dependent observables, such as isotope distributions, yield ratios of n/p,t/3He, Rmid yield and isoscaling parameters are affected. We also investigate how equilibration in heavy ion collisions is affected by this change.     

Synthesis and Structure of Solvated Protons Incorporating Weakly Coordinating Anions. Precursors of Superacids

ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｕｎｉｖｅｒｓａｌｌｙｕｎｄｅｒｓｔｏｏｄｔｈａｔｗｒｉｔｉｎｇＨ+ ｉｓｓｈｏｒｔ ｈａｎｄｆｏｒａｓｏｌｖａｔｅｄｐｒｏｔｏｎ ,[Ｈ(ｓｏｌｖｅｎｔ) ｎ]+ ,ｔｈｅｖａｌｕｅｏｆｎａｎｄｔｈｅｄｅｔａｉｌｓｏｆｔｈｅｃｏｏｒｄｉｎａｔｉｏｎｅｎｖｉｒｏｎｍｅｎｔａｒｅｏｆｔｅｎｕｎｓｐｅｃｉｆｉｅｄ .Ｉｓｏｌａｔｉｏｎａｎｄｓｔｒｕｃｔｕｒａｌｃｈａｒａｃｔｅｒｉｚａｔｉｏｎｏｆｖａｒｉｏｕｓｓａｌｔｓｃｏｎｔａｉｎｉｎｇｒｅｐｒｅｓｅｎｔａｔｉｖｅ [Ｈ(ｓｏｌｖｅｎ…     

树脂型光刻胶薄膜中Eu~(3+)的辐射跃迁特性

合成了稀土配合物Eu(TTFA)3(TTFA,2-thenoyltfifluoroacetone)掺杂的树脂型光刻胶薄膜,测定了薄膜的激发光谱和发射光谱.根据Judd-Ofelt理论,由发射光谱获得了Eu3+在光刻胶薄膜中的J-O参数Ω2=24.4×10-20cm2,Ω4=2.8×10-20cm2.利用得到的J-O参数计算了光刻胶薄膜中5D0激发态的辐射跃迁概率(977 s-1)和辐射寿命(1.02 ms),同时导出了光刻胶薄膜中Eu3+的5D0→FJ(J=1,2,4)跃迁的受激发射截面σ和荧光分支比β.分析表明,Eu3+掺杂的光刻胶薄膜具有较长的亚稳态寿命以及较大的受激发射截面,是一种主动放大的光波导薄膜.其发射波长与光刻胶的低吸收损耗区很好地匹配,可用于研发聚合物光波导放大器和激光器.