一类球面带形平移网络算子的逼近

借助于球调和多项式的de la Vallée Poussin和构造出了单位球面S^q上一类带形平移网络算子，并给出了其对L^p(S^q)中函数一致逼近的收敛速度.      

烷基苯磺酸盐表面活性剂对水合硅酸钙形貌和结构的影响

利用十二烷基苯磺酸钠(SDBS)为模板剂, 研究了SDBS的浓度、 Ca ²⁺和Si {\mathrm{O}}_3^{2-} 离子的浓度、 是否搅拌和反应时间等条件对水合硅酸钙(CSH)形貌特征和分散性能的影响, 并提出了不同CSH球壳形貌特征的形成机理. 结果显示, 溶液中Na₂SiO₃·9H₂O浓度增大、 SDBS浓度增大及反应时间延长均会使CSH的结晶度变好, 聚合度增大, Q ²结构的相对含量增加, 其中Na₂SiO₃·9H₂O和SDBS浓度是主要控制因素. SDBS在溶液中形成的球形胶束具有极强的模板作用, 能有效改变CSH的结晶生长方式; 通过调节SDBS浓度和钙硅比例, 并适当延长CSH的生长时间, 能够获得球壳完整、 分散性好且稳定性强的CSH.     

Preparation and characterization of spherical V2O3 nanopowder

V₂O₃ nanopowder with spherical particles was prepared by reducing pyrolysis of the precursor, (NH₄)₅[(VO)₆(CO₃)₄(OH)₉]·10H₂O, in H₂ atmosphere. The thermolysis process of the precursor in a H₂ flow was investigated by thermogravimetric analysis and differential thermal analysis. The results indicate that pure V₂O₃ forms at 620°C and crystallizes at 730°C. The effects of various reductive pyrolysis conditions on compositions of V₂O₃ products were studied. Scanning electron micrographs show that the particles of the V₂O₃ powder obtained at 650°C for 1 h are spherical about 30 nm in size with more homogeneous distribution. Experiments show that nanopowder has larger adsorption capacity to gases and is more easily reoxidized by air at room temperature than micropowder. Differential scanning calorimetry experiment indicates that the temperature of phase transition of nano-V₂O₃ powder is −119.5°C on cooling or −99.2°C on heating. The transition heats are −12.55 J g⁻¹ on cooling and 11.42 J g⁻¹ on heating, respectively.     

新型复合共沉淀法制备高能量/高功率型锂离子二次电池用5V正极材料LiNi_(0.5)Mn_(1.5)O_4及其电化学性能

在传统的固相法的基础上开发了新型复合共沉淀法制备LiNi0.5Mn1.5O4材料.新型复合共沉淀法采用(NH4)2CO3和(NH4)2C2O4共同作为沉淀剂,通过控制共沉淀反应条件,得到了具有均匀球形形貌的沉淀物颗粒.再通过与饱和氢氧化锂溶液的水热反应及高温反应,最终制备出具有球形次级形貌和纯相尖晶石结构的LiNi0.5Mn1.5O4材料.电化学测试表明,制备的LiNi0.5Mn1.5O4具有优异的电化学性能,其初始容量达到了141.4mAh·g-1.在0.3C、1C和3C倍率下经过200次循环后的容量分别为136.0 mAh·g-1(96.3%)、128.6 mAh·g-1(94.4%)和113.9 mAh·g-1(91.1%).通过高温反应及特殊的冷却处理,LiNi0.5Mn1.5O4在4.0 V低压区平台的容量损失得到了有效抑制.更重要的是,通过控制合成过程中的关键步骤,可实现半定量化控制材料结构中的原子有序排布程度,进而得到具有高能量密度和高功率密度的两种LiNi0.5Mn1.5O4材料,其能量密度和功率密度分别达到了648.6 mWh·g-1和7000 mW·g-1以上.     

球形木素基离子交换树脂的合成及其对Cr3+的吸附特性

以木素磺酸钙为原料,利用反相悬浮聚合技术在一种价廉无毒的介质相中制备出球状木质素基离子交换树脂,并讨论了它对Cr3 的吸附性能。结果表明,树脂对低浓度Cr3 的吸附效果好,前期吸附速度快,40min后吸附速率趋缓;升高温度能明显提高前期吸附速率,饱和吸附量约为60mgCr3 /g干树脂,而且树脂在较宽的弱酸性范围内表现出良好的吸附性能。     

Aqueous solutions of ionic liquids. Description of osmotic coefficients within the Binding Mean Spherical Approximation

The Binding Mean Spherical Approximation (BiMSA) is used to describe osmotic coefficients of aqueous solutions of salts containing imidazolium cations and bulky anions over the whole concentration range at temperature in the range (25 to 60) °C. A total of 13 salts have been considered altogether. The ion diameters, the permittivity of solution and the association constant were taken as adjustable parameters. Ionic liquids are described as being weakly associated in water, and association constants values obtained within the BiMSA model are in good agreement with those from the literature. Diameter values were assigned to 1-alkyl-3-methylimidazolium cations. The adjusted values obtained for the cation diameters increased with the number of carbons on the alkyl chain. For all systems studied, average relative deviations were found to be satisfactory.     

顺铂前药接枝修饰硫代DNA及其自组装靶向纳米药物研究

选用具有良好生物相容性的硫代修饰嵌段核酸为载体,将其非硫代修饰部分设计为靶向MUC-1蛋白的核酸适配体序列,同时在其硫代修饰部分通过硫代磷酸酯基团(Phosphorothioate, PS)接枝修饰四价顺铂前药,制备了两亲性核酸-顺铂前药缀合物MUC-1/^PODNA-b-(^PSDNA-g-Pt),并进一步自组装成类似球形核酸(Spherical nucleic acid, SNA)的含铂靶向纳米药物(MUC-1/Pt-SNAs).结果表明,该纳米药物递送体系载药率高、形貌稳定、分散性好,能够高效靶向MUC-1蛋白过表达的MCF-7乳腺癌细胞,并在体内外实验中表现出优异的抗肿瘤效果和极低的毒副作用.     

Burning velocity measurements of fluoropropanes by the spherical-vessel method

Burning velocity measurements of six types of fluoropropanes including structural isomers were carried out in order to understand the flammability of hydrofluorocarbons (HFC). The burning velocity (S_u) was determined by applying a spherical flame model to the pressure rise during combustion, which was measured at room temperature and at initial pressures of 80-107 kPa over a wide range of HFC/air concentrations. The maximum S_u of 1-fluoropropane (HFC-281fa), 2-fluoropropane (HFC-281ea), 1,3-difluoropropane (HFC-272fa), 2,2-difluoropropane (HFC-272ca), 1,2,3-trifluoropropane (HFC-263ea), and 1,1,1-trifluoropropane (HFC-263fb) was 35.0, 31.8, 31.9, 21.2, 25.7, and 14.5 cm s⁻¹, respectively. Note that the maximum S_u of HFC-263ea was appreciably higher than that of HFC-272ca, which shows the importance of the F-atom distribution, as well as of the F/H ratio in the HFC molecule. The results of equilibrium calculation for these HFCs showed that S_u is positively correlated with the flame temperature and the concentrations of the active chain carriers H and OH in the flame. We conducted a trial to interpret the magnitude of S_u by means of the effects of substituents for C₁-C₃ HFCs. As a result, it has been found that the order of inhibition efficiency for S_u decreases in the order of CF₃ > CF₂ > CF.     

On hydraulic permeability of random packs of monodisperse spheres: Direct flow simulations versus correlations

Hydraulic permeability is studied in porous media consisting of randomly distributed monodisperse spheres by means of computational fluid dynamics (CFD) simulations. The packing of spheres is generated by inserting a certain number of nonoverlapping spherical particles inside a cubic box at both low and high packing fractions using proper algorithms. Fluid flow simulations are performed within the interparticulate porous space by solving Navier-Stokes equations in a low-Reynolds laminar flow regime. The hydraulic permeability is calculated from the Darcy equation once the mean values of velocity and pressure gradient are calculated across the particle packing. The simulation results for the pressure drop across the packing are verified by the Ergun equation for the lower range of porosities (<0.75), and the Stokes equation for higher porosities (∼1). Using the results of simulations, the effects of porosity and particle diameters on the hydraulic permeability are investigated. Simulations precisely specified the range of applicability of empirical or semi-empirical correlations for hydraulic permeability, namely the Carman-Kozeny, Rumpf-Gupte, and Howells-Hinch formulas. The number of spheres in the model is gradually decreased from 2000 to 20 to discover the finite-size effect of pores on the hydraulic permeability of spherical packing, which has not been clearly addressed in the literature. In addition, the scale dependence of hydraulic permeability is studied via simulations of the packing of spheres shrunk to lower scales. The results of this work not only reveal the validity range of the aforementioned correlations, but also show the finite-size effect of pores and the scale-independence of direct CFD simulations for hydraulic permeability.     

More spherical large fullerenes and multi-layer fullerene cages

According to the experimental investigation, the carbon nano-particles have spherical multi-layer structure (also called onion-like carbon structure). Theoretically, the optimum structures of these large fullerenes contain highly faceted shapes with icosahedral symmetry. This discrepancy in structure may be attributed to the formation mechanism. Thus, a method is devised to construct spherical large fullerenes (C₂₄₀, C₅₄₀, C₉₆₀, C₂₁₆₀, C₂₉₄₀, C₃₈₄₀, C₄₈₆₀) by using the triangular motif. The 5–7–5–7 shape defect is applied in this method for assembling the large spherical fullerenes which could transform the graphene sheet to a spherical motif via SW rearrangement. The geometry-optimized structures of large spherical fullerenes have been generated by molecular mechanics calculation. Then, the average radius and standard deviation of these large fullerenes were obtained to verify the spherical shape. The multi-layer fullerene with spherical shape was confirmed by the TEM observation. According to the structure analysis, the distance between two neighboring encapsulating carbons is about 3.5 Å, which approximately coincides with the distance between two layers of graphite. The van der Waals force per carbon atom and of multi-layer fullerene with the spherical shape generated by force field calculation, predict their relative stability.