激光与材料参数对瞬态SBS 诱导的激光超声破坏效果的影响

 通过数值求解一维瞬态受激布里渊散射（SBS）声光耦合波方程，从理论上分析了泵浦激光参数及光学材料参数对SBS过程发生阈值的影响。以SBS过程中建立起来的应力场抗拉（压）强度和散射场的反射率为判据，分析了激光脉宽及作用区域长度对激光超声破坏材料效果的影响，探讨了短脉冲激光（约ns）引起的激光超声对材料的破坏机理；讨论了通过参数配置有效遏制SBS过程激光超声对光学材料的破坏问题。     

Investigation the effects of the excess Pb content and annealing conditions on the microstructure and ferroelectric properties of PZT (52-48) films prepared by sol-gel method

The effects of the PbO volatilization, excess Pb content of PbZr_0.52Ti_0.48 (PZT) precursor, PbTiO₃ (PT) seeding layers and annealing condition on the microstructures, surface morphologies, preferred orientation and ferroelectric properties of PbZr_0.52Ti_0.48 films were systematically investigated. PZT films with a variety of excess Pb (0-20%) were spin-deposited on Si(1 0 0) and Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by sol-gel technique. The films composition, Pb/Zr/Ti/O atom rate and Pb loss were semiquantitative analyzed by X-ray photoelectron spectrometer (XPS). When the excess Pb of PZT precursor was 10%, the Pb/Zr/Ti/O atomic rate of the fabricated films was very close to the designed rate of 1:0.52:0.48:3. The XRD and AFM investigations confirmed that PT seeding layer promoted the PZT films perovskite phase transformation and grains growth with (1 1 0) plane preferred orientation, accordingly lowered perovskite phase crystallization temperature and reduced Pb loss. The PZT films annealed in O₂ flow demonstrated better microstructure and ferroelectric properties comparing with films annealed in air by double remnant polarization increase and 8% coercive field increase. The underlying mechanism was also investigated.     

Effect of seeded substrates on hydrothermally grown ZnO nanorods

We report a study on the effect of seeding on glass substrates with zinc oxide nanocrystallites towards the hydrothermal growth of ZnO nanorods from a zinc nitrate hexahydrate and hexamethylenetetramine solution at 95 °C. The seeding was done with pre-synthesized ZnO nanoparticles in isopropanol with diameters of about 6–7 nm as well as the direct growth of ZnO nanocrystallites on the substrates by the hydrolysis of pre-deposited zinc acetate film. The nanorods grown on ZnO nanoparticle seeds show uniform dimensions throughout the substrate but were not homogenously aligned vertically from the substrate and appeared like nanoflowers with nanorod petals. Nanorods grown from the crystallites formed in situ on the substrates displayed wide variations in dimension depending upon the preheating and annealing conditions. Annealing the seed crystals below 350 °C led to scattered growth directions whereupon preferential orientation of the nanorods perpendicular to the substrates was observed. High surface to volume ratio which is vital for gas sensing applications can be achieved by this simple hydrothermal growth of nanorods and the rod height and rod morphology can be controlled through the growth parameters.     

Effect of seeded surface area on crystal size distribution in glycine batch cooling crystallization: a seeding methodology

In batch cooling crystallization, if the seeding process is not carefully carried out, the crystal size distribution (CSD) is dispersed. The aim of this work is to determine the optimal conditions for seeding operations. Results show that the CSD is controlled if the seed surface area reaches a specific value called critical surface S_c. Nevertheless, S_c is not the only parameter to be considered. The mean crystal size of the product obtained actually depends on the size of the seeds used because of the growth rate distribution. In fact, seeds behave differently according to their crystal sizes, which accounts for the difference in crystal growth rates. Rules are proposed for seeding with the view to obtain a uni-modal CSD and a final product size predefined by the seed crystals.     

金纳米花的合成及其与人血清白蛋白相互作用的研究

采用晶种法合成了金纳米花（AuNFs）。利用紫外可见吸收光谱法和原子力显微镜方法对金纳米花进行了表征,结果表明制备的金纳米花呈蓝紫色,在549nm处有特征吸收峰,且形状为花状。借助紫外可见吸收光谱法和荧光光谱法研究了AuNFs与人血清白蛋白（HSA）的结合过程。当AuNFs与HSA相互作用时,随着AuNFs溶液浓度的增加,HSA的紫外吸收峰强度也随之增加,但荧光光谱强度则发生了猝灭。由变温荧光实验可以获得两者相互作用的热力学参数,如结合常数（K_a）、吉布斯自由能变（ΔG）、熵变（ΔS）、焓变（ΔH）。ΔG<0表明在溶液中AuNFs与HSA可以自发结合发生反应并形成复合物;ΔH<0、ΔS<0表明结合过程以范德华力和氢键为主。同步荧光和3D荧光实验均表明,AuNFs的存在使得HSA的构象以及周围的环境发生了改变。     

无有机模板剂体系水热合成Beta沸石中晶种的导向机理(英文)

在无有机模板剂体系中研究了不同硅铝比和晶粒度Beta沸石晶种的结构导向行为,采用X射线衍射、X射线荧光光谱、扫描电镜、透射电镜、紫外-拉曼光谱、红外光谱和N2物理吸附等方法对不同晶化时间固相产物和Beta沸石产物进行了表征.结果表明,不同Beta沸石晶种,包括全硅晶种,均能够导向合成Beta沸石,而且晶种在晶化诱导期都发生溶解.但是,晶种的硅铝比、晶粒度、预处理(焙烧)以及晶种加入的时间对晶种的溶解行为、Beta沸石晶化过程和产物都有重要影响.形貌研究还发现,含铝晶种不仅溶解后的残体通过提供晶核聚集的"固载化"表面导向了新生Beta沸石小晶体的密集生长,而且溶解下来的结构片段也提供了分散的晶核导向形成相对分散的Beta沸石小晶体;全硅晶种则仅通过溶解下来的结构片段提供分散的晶核.在无模板体系中,使用适当高硅铝比、小晶粒和经过焙烧处理的Beta沸石作为晶种有利于合成得到高结晶度的Beta沸石纯相.     

大尺寸熔融织构YBCO超导体的制备及磁浮性能

采用熔融织构生长工艺结合籽晶技术制备出大尺寸ＹＢＣＯ超导块格。微观结构观察表明，其结晶取向在一定程度上得了控制，而且晶畴尺寸比较大，测量了样品的磁浮性能，得到了超导样品和永久磁铁之间的作用力与距离的关系曲线。     

砂壤潮土有机质含量可见-近红外光谱预测

土壤有机质（SOM）是影响播量的土壤关键参数,根据SOM信息对播量进行实时调控,投入最优化的种子量,充分利用地力资源挖掘产量潜力,节约良种,实现种植收益最大化,是目前播种领域最前沿的研究方向。以玉米主产区之一的华北平原为研究区域,对该区域砂壤潮土进行了可见-近红外（300～2 500 nm）光谱采集。采用蒙特卡罗交叉验证剔除了异常样本,结合Savitzky-Golay卷积平滑法对光谱数据进行平滑去噪处理。分别通过竞争性自适应重加权算法（CARS）、连续投影算法（SPA）、竞争性自适应重加权-连续投影（CARS-SPA）、无信息变量消除（UVE）及变量组合集群分析法（VCPA）等波长筛选方法提取有效变量,并结合偏最小二乘回归（PLSR）分别建立了全波长和特征波长的SOM含量预测模型。结果表明,不同方法筛选的波长数目及波长位置存在显著差异,CARS和SPA算法选择的光谱特征在整个光谱范围都有分布,UVE和VCPA筛选的波段较为集中,且基于CARS-SPA方法可以进一步优选特征变量,其特征波长仅为全波长数量的15%。通过对比不同模型的建模及预测效果,除UVE和VCPA算法外,其余算法构建的模型均能实现SOM含量的有效预测,其RPD值均大于2.0。基于CARS-SPA构建的PLSR模型效果最好,其R2_P和RPD分别0.901和3.188,均高于其他方法,不仅降低了无效信息对预测效果的干扰,且模型的运算效率得到了明显的提高,可以很好地实现该地区SOM含量的可靠预测。该研究可以为SOM含量快速预测及仪器设计提供方法参考。     

Development of a dynamic simulation model of a towed seeding implement

As the size of western Canadian farms increase and the productivity demands on seeding equipment rise, improvement in the depth consistency performance of seeding implements at higher seeding speeds is a future focus of equipment designers. The objective of this work was to develop a dynamic simulation tool for predicting the motion of a hoe-opener style seeding implement with independent row units. The model was developed using simple low-order models available in the literature to compute the forces generated at soil-tire and soil-tool interfaces. By maintaining low computational cost, early-stage parameter sensitivity and design trade-off studies can assess the risk of a given design change. The amplitude of the power spectral density (PSD) of simulated row unit motion was typically lower with sharper peaks than measured results up to 3.3 m/s; these differences were due to both input amplitude differences, and the sensitivity of the model itself. Frequency agreement of major measured and simulated PSD peaks was acceptable considering the model simplifications. Row unit motion was dominated by two phenomena – a strong periodic input in the terrain surface, and feedback between the hoe-opener and packer wheel of the row unit.     

晶种法合成金溶胶过程中非球形粒子的抑制

羟胺晶种法制备金纳米粒子时会观察到少量的非球形粒子副产物.研究发现,反应试剂的比例以及试剂的加样顺序对非球形粒子的产生具有明显的影响.羟胺与金氯酸的摩尔比例([NH2OH]:[HAuCl4])较高时能够抑制非球形粒子的生成,较低时则生成较多的非球形粒子.不同的加样顺序使得加样过程中[NH2OH]:[HAuCl4]不同,也可以导致产物中非球形粒子含量的差异.基于以上发现,采用较大的NH2OH用量以维持反应过程中的[NH2OH]:[HAuCl4]比例在10～30左右,并采用适当的加样顺序(先将晶种同NH2OH混合,再加HAuCl4),从14 nm的晶种出发以逐步(step-by-step)的方式依次合成了平均粒径为26、57、81和130 nm的金纳米粒子,产物中基本不含非球形粒子,粒径可控，并具有良好的单分散性(RSD为～10％).