HF激光脉冲与水柱表面相互作用产生电信号(英文)

研究了脉冲HF激光与水柱表面相互作用下电信号的产生过程。电信号显示了与激光能量线性相关的峰值间有时间间隔的两峰结构,且第二个尖峰在水柱底部的蒸汽腔塌缩后出现。实验还显示电信号的幅值和激光脉冲照射过程中是否存在膨胀和挤压的薄水层密切相关。如果在电池上边缘和石英平板(石英板紧邻电池,并与水柱上表面相接)之间存在一薄水层,电信号强度会增加10倍。     

ON THE STABILITY OF FORCED DISSIPATIVE NONLINEAR SYSTE

ＯＮＴＨＥＳＴＡＢＩＬＩＴＹＯＦＦＯＲＣＥＤＤＩＳＳＩＰＡＴＩＶＥＮＯＮＬＩＮＥＡＲＳＹＳＴＥＭ￥ＣｈｅｎＤａｄｕａｎ（陈达段）ＬｉｕＸｉａｏｍｉｎｇ（刘晓明）ＳｈｉＷｅｉｈｕｉ（施惟慧）（ＳｈａｎｇｈａｉＵｎｉｖｅｒｓｉｔｙ．Ｓｈａｎｇｈａｉ２００...     

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.     

摩托车正时链和传动链磨损特性的研究

研究油润滑条件下摩托车发动机正时链的磨损特性,发现疲劳磨损,裂纹的形成和扩展是影响疲劳寿命的主要因素;定期刷油或滴油润滑条件下,摩托车传动链的磨损机制是磨粒磨损,并伴有疲劳磨损,销轴和套筒零件的渗层及心部组织等是影响链条磨损特性的重要因素,因为中碳调质钢经碳氮共渗后可获得弥散分布的颗粒状碳化物的表层组织及回火屈氏体的心部组织,从而显示出表层耐磨、心部强韧性好及抗塑变能力高的综合机械性能。     

Formation and elasticity of layer networks

Layer network formation of poly(styrene‐alt‐n‐octadecylmaleimide) in dodecane is investigated. It is shown that the polymer in the bulk exhibits lamellar structures of alternated alkane side‐chain and main‐chain layers. Adding dodecane into the polymer separates the polymer layers, increases the mean distance between the layers, and results in a less orderly layered structure. Crystallization of the alkane side chains introduces linkages to staple the layers together and builds up a layer network. Dimensional analysis predicts that the modulus (G) of the layer network is simply related to the long period (L) of the layer network through a cubic power law, i.e., G ∼ L⁻³. This prediction is indeed observed experimentally. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 667–677, 1999     

超细钼丝亚硫酸盐脉冲镀金实验研究

 超细钼丝是Z-pinch物理实验常用的材料之一。采用亚硫酸脉冲镀金技术,在超细钼丝上镀制一层均匀致密的金层来改善钼丝性能。实验研究和优化了影响镀层质量和沉积效率的主要工艺条件,优化后的阴极电流密度2 mA/cm²,溶液pH值8.5,溶液温度40°。用扫描电镜观察镀金钼丝的表面形貌及镀层质量;用划痕法测试了镀层与钼丝表面的结合力。实验结果表明,采用经过优化的镀金工艺能够在直径小于15 μm的钼丝上镀制厚度0.6~2.5 μm的致密金层,且能够有效地降低钼丝表面的粗糙度和提高抗氧化能力,满足Z-pinch实验的需要。     

About the Dominance of Mesopores in Physisorption in Amorphous Materials

Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including meso- and macropores. Within such a pore network, material moisture plays a crucial role in almost all transport processes. In the hygroscopic range, the pores are partially saturated and liquid water is only located at the pore fringe due to physisorption. Therefore, material parameters such as porosity or median pore diameter are inadequate to predict material moisture and moisture transport. To quantify the spatial distribution of material moisture, Hillerborg’s adsorption theory is used to predict the water layer thickness for different pore geometries. This is done for all pore sizes, including those in the lower nanometre range. Based on this approach, it is shown that the material moisture is almost completely located in mesopores, although the pore network is highly dominated by macropores. Thus, mesopores are mainly responsible for the moisture storage capacity, while macropores determine the moisture transport capacity, of an amorphous material. Finally, an electrical analogical circuit is used as a model to predict the diffusion coefficient based on the pore-size distribution, including physisorption.     

Al纳米颗粒表面等离激元对ZnO光致发光增强的研究

基于聚苯乙烯球自组装法,在P型氮化镓(P-GaN)衬底上制备了有序致密的掩模板;采用热蒸发法在该模板上沉积金属Al薄膜,通过甲苯溶液去除聚苯乙烯球,得到了金属Al纳米颗粒阵列;采用原子层沉积法,在Al纳米颗粒阵列表面依次沉积氧化铝(Al_2O_3)和氧化锌(ZnO).通过测试Al纳米颗粒阵列的消光谱以及ZnO薄膜的光致发光谱,研究了Al纳米颗粒表面等离激元与ZnO薄膜激子之间的耦合效应.实验结果表明:引入Al纳米颗粒后,在约380 nm位置附近的ZnO近带边发光峰积分强度增强了1.91倍.对Al纳米颗粒表面等离激元增强ZnO光致发光的机理进行探讨.     

无限展长后掠翼边界层定常横流不稳定转捩分析

采用γ-Re_θt横流转捩拓展模型对NLF （2）-0415无限展长后掠机翼进行数值模拟,重点分析来流雷诺数、机翼表面粗糙度及后掠角对边界层横流不稳定性的影响.研究发现γ-Re_θt横流转捩拓展模型能够准确预测边界层定常横流不稳定转捩,计算结果与试验数据吻合较好.结果表明来流雷诺数越大、机翼表面越粗糙,横流转捩位置越靠前;随着机翼后掠角的增加,转捩位置先前移随后逐渐靠后.     

基于高光谱分析的玉米叶片氮含量分层诊断研究

为了明确不同生育时期进行玉米氮素营养诊断的叶片层位,建立准确稳健的玉米氮素营养诊断模型,以达到合理追施氮肥,提高氮肥利用率的目的。试验采用单因素盆栽试验设计,以玉米（郑单958）为研究对象,应用高光谱技术,分析了不同氮营养水平下不同生育时期不同层位玉米叶片的氮含量分布和变化规律及光谱响应特征;并依据叶片氮含量与光谱反射率的相关关系,叶片氮含量与全波段(400～2 000 nm)任意两两波段组合构建的比值光谱指数(RSI)的回归关系,初步确定了不同生育时期进行氮素营养高光谱诊断的目标叶片,筛选出最优的比值光谱指数,建立了叶片氮素含量估算模型。结果表明：玉米叶片氮含量：上层>中层>下层;随着玉米的生长,在低氮条件下上层叶片氮含量呈先减少后增加（追肥）再减少趋势,在高氮条件下呈减少趋势,中下层叶片氮含量呈递减趋势。六叶期下层玉米叶片光谱反射率敏感范围较大,相关性较强;九叶期和灌浆期上层玉米叶片的光谱反射率敏感范围较广,相关性较强;开花吐丝期中层叶片的光谱反射率敏感范围较大,相关性较强。六叶期选取下层叶作为诊断目标叶,选取最佳比值光谱指数RSI(1 811, 1 842)建立线性估算模型,九叶期和灌浆期选取上层叶片作为诊断目标叶,选取的最佳比值光谱指数分别为RSI(720, 557),RSI(600, 511)建立线性估算模型,开花吐丝期选取中层叶片作为诊断目标叶,选取比值光谱指数RSI(688, 644)建立线性估算模型。研究结果可为快速准确地利用光谱技术进行玉米叶片氮素营养诊断提供理论依据。