溶胶-凝胶法制备TiO2-C纳米复合材料的研究

采用溶胶-凝胶法制备了TiO2-C纳米复合材料,利用XRD、SEM和TEM等方法对样品进行分析表征。实验结果表明:网络诱导剂的加入有利于样品在室温下静置后更快凝胶,经600℃焙烧3 h后样品中二氧化钛晶粒有不同程度长大,其特征峰更加明显,且其中二氧化钛晶粒为锐钛矿型;乙酰乙酸乙酯的加入有利于溶胶-凝胶的形成,且随着乙酰乙酸乙酯加入量的增加,TiO2-C纳米复合材料的孔容和孔径均增加。     

轧辊用高钒高速钢的滚-滑动磨损性能及失效行为研究

在高应力滚-滑动(滑动率约10%)条件下,利用自制的磨损试验机研究了高钒高速钢的磨损性能,并利用电子显微镜分析了失效行为.结果表明:高钒高速钢的相对耐磨性是高铬铸铁(Cr20)的2倍以上.磨损失效形式为显微切削与疲劳剥落的复合,兼有碳化物碎裂.碳化物对磨损失效有重要作用,高铬铸铁中的杆状M7C3型碳化物易于弯曲、碎裂而在其内部形成大量裂纹,促进磨损表面产生大块的疲劳剥落;高钒高速钢中团块状VC硬度高、形态好、具有精细亚结构、不易碎裂,可有效地抵御显微切削和疲劳剥落,是高钒高速钢耐磨性优良的原因.     

舞台音乐反射罩的声学参量分析

利用有限元技术对不同形状舞台音乐反射罩所产生的声场及其建筑声学参量进行了数值分析,并与无音乐罩时的声场情况进行了对比。结果表明音乐罩对舞台及观众席的音质改善有明显效果。此方法对音乐罩设计有实际指导意义。     

大型海湾水交换计算中随机游动方法的应用研究

水交换矩阵是反映大型海湾不同子区域之间水交换关系的有效工具,该文对随机游动方法在水交换矩阵计算中的应用进行了研究．通过与对流扩散模型的对比,指出用随机游动方法计算水交换矩阵比用对流扩散方程求解更快更灵活．同时,为了对不同区域之间的水交换特性进行长期快速预测,采用了Thompson提出的预测矩阵方法．通过理论分析得出,影响该矩阵预测效果的因素主要有:粒子数目、分区数和预测矩阵取值时间．以一个矩形海湾为例,将数值模拟结果和预测矩阵预测结果进行对比,分析了以上各因素对预测效果的影响．结果表明,粒子数目越多,预测矩阵取值时间越长,预测矩阵的预测效果越好．在粒子数目足够多的情形下,分区数越多,预测效果越好．相反,粒子数目如果较少,过多的分区数将可能导致预测矩阵效果太差而不可用．     

Hes1调控 AKT-MDM2-p53-PTEN通路的一种物理机制

基于Hill动力学与Michaelis-Menten方程,建立理论模型研究发状分裂相关增强子1(hairy and enhancer of split 1,Hes1)调控蛋白激酶B (Protein Kinase B,AKT)-鼠双微体2 (Murine Double Minute2,MDM2)-抗癌基因p53(p53)-第10号染色体缺失的磷酸酶及张力蛋白同源的基因(Phosphatase and tensin homolog deleted on chromosome ten,PTEN)通路的一种物理机制.研究发现,Hes1通过与PTEN结合抑制PTEN表达,并调控AKT信号.表明了Hes1蛋白的合成,以及Hes1与PTEN相互作用调控AKTMDM2-p53-PTEN通路信号,将会有效地控制细胞结果 . Hes1作为AKT-MDM2-p53-PTEN信号通路中上游调节的重要因素,还可以在一定程度上通过影响p53蛋白功能,改变p53对肿瘤的抑制性.理论结果可用于预测Notch通路信号异常诱导的致癌性,并进一步揭示了Notch信号通路影响细胞AKT-MDM2-p53-PTEN通路的激活...     

A method of beam combination of high- power incoherent fiber laser

Diffraction efficiency of grating plays an important role in output power of incoherent fiber laser beam combination. Through theoretic analysis and numerical simulations it has been proved that the diffraction efficiency would increase with the decrease of grating frequency and wavelength bandwidth. On the condition that the width of a fiber array is fixed at W=10 cm, an optimum grating frequency were numerically simulated as f=230 mm-1. Also an unequal interval method was proposed to improve the system efficiency of diffraction into 0.4293, which is higher than 0.3824 under the equal interval condition.     

Stereoisomeric Tris-BINOL-Menthol Bulky Monophosphites: Synthesis,Characterisation and Application in Rhodium-Catalysed Hydroformylation

Four stereoisomeric monoether derivatives, based on axially chiral (R)- or (S)-BINOL bearing a chiral (+)- or (−)-neomenthyloxy group were synthesised and fully characterised by NMR spectroscopy and X-ray crystallography. The respective tris-monophosphites were thereof prepared and fully characterised. The coordination ability of the new bulky phosphites with Rh(CO)₂(acac), was attested by ³¹P NMR, which presented a doublet in the range of δ = 120 ppm, with a ¹J(¹⁰³Rh-³¹P) coupling constant of 290 Hz. The new tris-binaphthyl phosphite ligands were further characterised by DFT computational methods, which allowed us to calculate an electronic (CEP) parameter of 2083.2 cm⁻¹ and an extremely large cone angle of 345°, decreasing to 265° upon coordination with a metal atom. Furthermore, the monophosphites were applied as ligands in rhodium-catalysed hydroformylation of styrene, leading to complete conversions in 4 h, 100% chemoselectivity for aldehydes and up to 98% iso-regioselectivity. The Rh(I)/phosphite catalytic system was also highly active and selective in the hydroformylation of disubstituted olefins, including (E)-prop-1-en-1-ylbenzene and prop-1-en-2-ylbenzene.     

(Mo + N) codoped TiO2 for enhanced visible-light photoactivity

A series of Ti_1−xMo_xO_2−yN_y samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti_1−xMo_xO_2−yN_y samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO₂, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO₂ is promising for a photocatalyst with high photocalystic activity under visible light.