衬底温度对氧化锌薄膜微结构及光学性能的影响

衬底温度是磁控溅射法制备氧化锌薄膜中一个非常重要的工艺指标,探索衬底温度对氧化锌薄膜微结构及光学性能的影响对制备环保型高质量氧化锌紫外屏蔽材料具有重要意义。以质量分数99.99%的氧化锌陶瓷靶为溅射源,利用射频磁控溅射技术在石英衬底上沉积了氧化锌紫外屏蔽薄膜,通过X射线衍射仪、薄膜测厚仪、紫外-可见分光光度计、荧光分光光度计进行测试和表征,研究了不同衬底温度对ZnO薄膜微结构及光学性能的影响。实验结果表明:制备所得薄膜均为六角纤锌矿结构,具有沿(002)晶面择优取向生长的特点,其晶格常数、晶粒尺寸、透过率、光学能隙、可见荧光、结晶质量等都与衬底温度密切相关,当衬底温度为250 ℃,溅射功率160 W,氩气压强0.5 Pa,氩气流速8.3 mL/min,沉积时间60 min时,所得氧化锌薄膜样品取向性最好,晶粒尺寸最大,薄膜结构致密,具有良好的光学性能和结晶质量。     

基于平均法的旋转薄壁圆柱壳非线性行波振动研究

应用Donnell's简化壳理论,在考虑阻尼和几何非线性的情况下,基于平均法对旋转的薄壁悬臂圆柱壳在法向激振力作用下的非线性行波振动进行了研究.在分析过程中,首先,引入考虑阻尼及几何非线性的薄壁圆柱壳非线性波动方程,进行降阶处理后,得到模态坐标下的振动方程;其次,对模态方程进行平均化处理,确定转换矩阵,进行变量的幅值相角化,从而得到自治的标准化方程组;最后,由系统谐波共振周期解对应平均方程稳态解的原理,得到幅频特性方程.根据上述所得结果,进行了系统参数振动及稳定性研究,并进一步将结果与谐波平衡法及数值解作了比较.     

南海峡谷慕斯地层的近底声学探测

为测量南海深海表层沉积物反射特性,在探索一号TS12航次中,使用高频浅地层剖面仪搭载深海勇士号载人潜水器,潜水器下潜深度1578 m,高频浅地层剖面仪(110 kHz)近底作业高度约2 m,在南海北部琼东南盆地大陆坡峡谷进行了近底浅表沉积物反射测量。浅地层剖面图像表明峡谷海底表层2 m内沉积物存在5分层结构的慕斯地层。慕斯地层水-沉积物界面反射强度平均值-11.86 dB,标准差2.51 dB,原位取样结果测量得沉积物颗粒平均粒径7.2μm,反射系数与沉积物粒径结果均表明慕斯地层表面为泥质沉积物。慕斯地层处于大陆坡峡谷折弯处,其中的沉积物大量来自浊流输运,特殊的地理环境使不同时期经浊流输运而来的沉积物通过沉降形成了具有典型分层结构的慕斯地层。首次获得了慕斯地层的高分辨声学剖面图像,为研究海底表层沉积物的细致分层和声学特性提供了依据,同时由于慕斯地层汇聚了大量输运而来的沉积物,对海底沉积历史特性具有重要的研究价值。     

NSD误差下线性模型LAD估计的线性表示

考虑了NSD误差下的线性模型并建立回归参数LAD估计的线性表示.这些结果将独立误差的情形推广和改进到NSD误差的情形.作为一个应用,获得了LAD估计量的收敛率.     

凸肩叶片的非线性振动特性与运动分岔

以凸肩叶片作为研究模型, 建立了考虑凸肩摩擦力, 几何大变形与阻尼的非线性振动方程.采用Galerkin法对振动方程离散化, 应用平均法对离散后模态方程组的非线性响应进行解析分析, 得到了非线性幅频特性曲线, 与数值解比较验证了解析解, 并讨论了系统周期解的稳定性. 用非线性振动理论详细研究了平均方程组的运动分岔现象, 揭示了平均方程组周期解的变化过程及其具有的非线性动力学性质. 解析结果表明, 凸肩之间的摩擦对系统第二阶非线性振动特性影响很大. 由于凸肩之间摩擦力方向的不断改变, 系统第二阶非线性幅频特性曲线不连续, 出现两个共振频域. 随着时间的推移, 系统振动的幅值会以$T/ 4$为周期在两个频域的幅频曲线上来回跳动, 这会使叶片的振动响应大幅降低.      

Identification of Antioxidant and Anti-α-amylase Components in Lotus (Nelumbo nucifera,Gaertn.) Seed Epicarp

Nano-sized Fe₃O₄ was synthesized by chemical co-precipitation and subsequently modified with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde to introduce aldehyde group on its surface. With the help of “interface activation” by adding sucrose esters-11 as surfactant, lipase from Rhizopus oryzae was successfully immobilized onto the carrier with great enhancement of activity. The hydrolysis activity of immobilized enzyme were 9.16 times and 31.6 times of free enzyme when p-nitrophenol butyrate and p-nitrophenol palmitate were used as substrates. The thermo-stability of immobilized enzyme was also enhanced compared to free enzyme. The immobilized enzyme was successfully applied in synthesis of 1,3-diacyglycerols (1,3-DAG). The specific esterification activity of immobilized enzyme was about 1.5 times of the free enzyme. The immobilized enzyme showed good region-selectivity towards 1,3-diacyglycerols and retained nearly 80% of its activity after reused for 60 times, revealing a good industrial application prospect.

     

Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia synthesis

Photocatalytic N₂ fixation to NH₃via defect creation on TiO₂ to activate ultra-stable N N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N₂ preferentially adsorbs on phase-selective defect sites on TiO₂ in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (A_d) preferentially exhibit higher N₂ adsorption ability with a reduced energy barrier for a potential-determining-step (*N₂ to NNH*) than the disordered rutile (R_d) phase of TiO₂. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO₂ photocatalyst (Na-A_d/R_o) by sodium-amine treatment of P25-TiO₂ under ambient conditions, which exhibits an efficient NH₃ formation rate of 432 μmol g⁻¹ h⁻¹, which is superior to that of any other defect-rich disordered TiO₂ under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N₂ chemisorption on the defect sites of Na-A_d with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with R_o enable substantially enhanced N₂ fixation.

This work highlights the importance of a rational design for more energetically suitable nitrogen reduction reaction routes and mechanisms by regulating the electronic band structures with phase-selective defect sites.     

纳米压痕条件下MgB2超导块材的压入力学行为研究

本文采用纳米压痕技术对固相烧结法制备的 MgB2 超导块材进行压入力学实验, 对不同压深的载荷-位移曲线和纳米压痕数据的再现性进行了分析, 实验数据使用 Oliver-Pharr 方法计算得出 MgB2 的硬度值, 借助经验方程拟合纳米压痕蠕变曲线求得蠕变速率敏感指数(m ) . 结果表明, 微观结构不均匀性会对材料在压头压入过程中抵抗外力作用时产生影响, 使压痕数据再现性变差; MgB2 的硬度表现出尺寸效应, 即随着压入深度的增加硬度逐渐下降;m 值随压入深度增加而增加是位错滑移速度加快的结果.     

稀土提高碳钢耐蚀性的行为研究研究

通过实验室干湿周浸加速腐蚀试验,研究了稀土对碳钢耐腐蚀性能的影响,利用X射线荧光光谱仪和场发射扫描电镜对含稀土钢锈层进行分析。结果表明：稀土元素的添加能大幅度提高碳钢的耐蚀性,在加速腐蚀试验条件下,在含稀土钢的锈层中发现了稀土元素的存在,稀土元素不均匀分布于内锈层中,在锈层中稀土元素部分以稀土化合物颗粒形式存在,并且还有少量的稀土化合物颗粒含有Si和Al等合金元素。     

Multi-objective global optimal parafoil homing trajectory optimization via Gauss pseudospectral method

Based on a simplified parafoil model, this paper designs multi-objective global optimal homing trajectory of a parafoil by the Gauss pseudospectral method. Connecting with all constraint conditions, homing trajectories at different initial positions and heading angles are simulated. Simulation results show that the terminal error and flaredlanding angle error are small and that the control quantity is global optimal. The planned trajectory in horizontal plane is composed of arc and straight line, which accords with the features of parafoil completely.