COOH ion implantation-modified indium tin oxide electrode for the direct electrochemistry of cytochrome c

A COOH⁺ ion implantation-modified indium tin oxide (COOH/ITO) electrode was prepared and the existence of carboxyl group on the electrode was verified by X-ray photoelectron spectroscopy analysis. The field emission-scanning electron microscope result showed that the ion implantation formed many active centers on the ITO surface. The COOH/ITO electrode was applied for cytochrome c (cyt c) immobilization and the electrochemical behaviors of cyt c were evaluated by cyclic voltammetric techniques. The results demonstrated that the immobilized cyt c retained its electrocatalytic activity to the reduction of H₂O₂. This ion implantation-modified electrode might be used in development of new biosensors and biofuel cells.     

纤维体积率对聚丙烯粗纤维混凝土力学性能的影响研究

通过试验对比研究不同体积率的聚丙烯粗纤维对混凝土力学性能的影响。研究结果显示:聚丙烯粗纤维对混凝土的抗压性能无增强效果;对混凝土的劈裂抗拉、抗折及抗冲击性能有显著增强效果,当聚丙烯粗纤维体积率为0.50%~0.65%时,聚丙烯粗纤维对混凝土的劈裂抗拉和抗折性能增强效果最优,且纤维混凝土的抗冲击强度在试验范围内随聚丙烯粗纤维体积率的增加而增强,最高可提高2.8倍。     

TiC颗粒强化型马氏体耐磨钢的性能研究

采用模铸、连铸两种工艺工业化试制一种TiC颗粒强化型马氏体耐磨钢,分析了TiC颗粒的析出规律,对比研究了试验钢与传统马氏体耐磨钢的组织、力学性能及耐磨性能。试验结果表明:凝固速度越大,TiC析出相越细;轧制压缩比越大,颗粒分布越均匀;TiC颗粒强化马氏体钢强度与传统马氏体钢相当,韧性有所降低;微米级的TiC可以有效提高材料的磨粒磨损性能,试验钢磨损失重仅为同等硬度传统马氏体钢的70%;耐磨性能的提高主要是因为在磨粒磨损条件下,微米级TiC硬质点可以破碎磨砺、钝化尖角、阻断磨痕。     

A comparative study of Mg-Gd-Y-Zr alloy cast by metal mould and sand mould

The differences of the microstructure and mechanical property between metal mould and sand mould cast Mg-10Gd-3Y-Zr alloy were investigated both under as-cast condition and after solution heat treatment.In the as-cast specimens,the microstructure is similar and composed of α-Mg solid solution and eutectic compound of α-Mg+ Mg24(Gd,Y) 5;whereas the grain size using metal mould and sand mould is 27 μm and 71 μm,respectively.The eutectic compound of metal mould cast alloy was completely dissolved after solution treated at 500℃ for 8 h,however it needs higher temperature(525 ℃) and longer time(12 h) to achieve the absolute dissolving under sand mould condition.In contrast to metal mould,the peak time of sand mould alloy aged at 225 ℃ and 250 ℃ of was advanced by 4 h and 6 h,respectively.The precipitation reaction sequence in sand mould cast Mg-10Gd-3Y-Zr alloy during isothermal ageing at 250 ℃ follows S.S.S.S.→β″(D019) →β'(cboc) →β1(fcc) →β(fcc) ,which is similar to that in the alloy cast using metal mould.     

取向硅钢中铜硫化物结构稳定性的赝势平面波法研究

基于密度泛函理论的第一性原理赝势平面波方法计算研究了取向硅钢中可能存在的两种铜硫化物抑制剂Cu2S和CuS的能量和电子结构,并从形成能和结合能两方面分析了这两种铜硫化物的相结构稳定性.结果表明:Cu2S具有较强的形成能力和更稳定的结构.计算电子态密度(DOS)的结果为:Cu2S和CuS费米能级处的态密度分别为1.65/eV和2.28/eV;Cu2S的赝能隙比CuS更宽些.这些结论也证明了Cu2S具有更稳定的结构.     

Effects of TMP Structure and Material on Cryogenic Target Temperature Field

The ice layers in the deuterium-tritium capsule must be uniform and smooth enough, and the maximum temperature difference of the target surface is not higher than 0.1 mK for high quality cryogenic target. However, there are many factors affecting the cryogenic target temperature field. In this paper, the effects of sleeve wall thicknesses (0.2, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 mm), materials (AL5052, SS304 and high-purity copper) and hohlraum structures (single convex and double convex) on the cryogenic target temperature field were studied with FLUENT software. The results show that the temperature difference of target surface is small when hohlraum structure is double convex ring. With the increase of sleeve wall thickness, the natural convection intensity of the hohlraum and the temperature difference on the surface of the target decrease. There is a lower temperature and more uniform temperature field around target surface when copper is used as sleeve material, because of its high heat conduction and specific heat. Considering the wall thicknesses, materials and hohlraum structures, the surface temperature field of the target is best when the sleeve adopts high-purity copper with thickness of 1 mm, and the hohlraum structure is double convex ring.     

CO2气体保护焊短路过渡液相桥自由液面分析

针对短路过渡液相桥在焊丝回抽至不同高度时的液面形态，进行了二维数值的分析和三维有限元分析。试验验证并考察了不同焊丝直径，表面张力系数及焊缝堆高对液相桥失效高度的。为焊线停送，回抽促进液相桥平稳拉断的控制方法奠定了理论基础。     

稀溶体中第二相质点的Ostwald熟化—Ⅱ.解析解

本文根据稀溶体中第二相质点的Ostwald熟化过程的普适微分方程,得出各种不同情况下第二相质点的似稳态尺寸分布函数及其平均尺寸随熟化时间而变化的解析解,并由此分析比较了不同情况下第二相质点的粗化规律及相互关系。     

铌微合金钢中碳氮化铌化学组成的计算与分析

采用由热力学计算方法导出的二元微合金碳氮化物化学组成的理论计算公式,对一系列铌微合金钢中在奥氏体中沉淀析出的碳氮化铌的化学组成进行了实际计算,计算结果与有关文献给出的实验结果基本吻合。计算结果表明,碳氮化铌中碳化铌的摩尔分数x随温度的变化曲线一般为具有一极大值的连续上凸曲线;钢的化学成分中C量升高将使x增大,N量升高将使x减小,Nb量升高将使x增大;C、N量升高将使x取极大值的温度升高,而Nb量升高将使该极值温度降低。     

Remote sensing of evapotranspiration and carbon uptake at Harvard Forest

A land surface vegetation index, defined as the difference of microwave land surface emissivity at 19 and 37 GHz, was calculated for a heavily forested area in north central Massachusetts. The microwave emissivity difference vegetation index (EDVI) was estimated from satellite SSM/I measurements at the defined wavelengths and used to estimate land surface turbulent fluxes. Narrowband visible and infrared measurements and broadband solar radiation observations were used in the EDVI retrievals and turbulent flux estimations. The EDVI values represent physical properties of crown vegetation such as vegetation water content of crown canopies. The collocated land surface turbulent and radiative fluxes were empirically linked together by the EDVI values. The EDVI values are statistically sensitive to evapotranspiration fractions (EF) with a correlation coefficient (R) greater than 0.79 under all-sky conditions. For clear skies, EDVI estimates exhibit a stronger relationship with EF than normalized difference vegetation index (NDVI). Furthermore, the products of EDVI and input energy (solar and photosynthetically active radiation) are statistically significantly correlated to evapotranspiration (R = 0.95) and CO₂ uptake flux (R = 0.74), respectively.