激波在带扩容室的变截面管中传播和消波效果的数值分析

在利用实验结果验证程序的基础上，对激波在具有复杂结构管道内的传播特性进行了数值模拟，比较了不同入射激波条件和特征尺寸对扩容室消波效应的影响，并考虑了二维(轴对称、平面)模型和三维模型的影响。计算结果表明，同一尺寸的扩容室对不同马赫数人射激波的消波效果是相近的，扩容室特征尺寸不同则消波效果差别很大。

Ocean currents-induced pipeline lateral stability on sandy seabed

Unlike previous mechanical actuator loading methods, in this study, a hydrodynamic loading method was employed in a flow flume for simulating ocean currents induced submarine pipeline stability on a sandy seabed. It has been observed that, in the process of pipeline losing lateral stability in currents, there usually exist three characteristic times: (1) onset of sand scour; (2) slight lateral displacement of pipeline; and (3) breakout of pipeline. An empirical linear relationship is established between the dimensionless submerged weight of pipeline and Froude number for describing pipeline lateral stability in currents, in which the current-pipe-soil coupling effects are reflected. Scale effects are examined with the method of "modeling of models," and the sand particle size effects on pipeline stability are also discussed. Moreover, the pipeline stability in currents is compared with that in waves, which indicates that the pipeline laid directly upon the sandy seabed is more laterally stable in currents than in waves.

星系密度波的维持问题以及Waser机制的进一步数值研究

本文着眼于星系螺旋结构的维持问题,采用一种简化的星系模型,以数值解方法研究了密度波的各种有关的动力学特性。结果还进一步证实了作者用渐近分析方法所得到的Waser开关特性和共转圈势垒上的隧道效应。

不同烧蚀条件下飞秒激光脉冲诱导ZnO纳米结构研究

烧蚀条件对飞秒激光脉冲诱导氧化锌纳米结构有重要影响。研究了800nm,150fs,250kHz的飞秒激光脉冲分别在空气中,去离子水中以及无水乙醇中垂直聚焦于氧化锌晶体表面,诱导形成不同形态的纳米结构。实验结果表明,在空气中利用飞秒激光脉冲辐照样品表面,形成了周期为180nm的纳米线;在去离子水中辐照诱导形成了由氧化锌纳米线聚集而成的"纳米球";在无水乙醇中形成出现分叉结构的纳米线。拉曼光谱分析辐照前后晶体晶相结果表明,形成的纳米结构相对于辐照前特征峰437cm-1强度有所下降,在570cm-1处的峰值则显著增强。分析了在各种烧蚀条件下诱导形成纳米结构的演化过程以及物理机理。

Yb：YAG透明陶瓷的制备和激光输出

制备了高质量的Yb：YAG透明陶瓷．Yb：YAG透明陶瓷的晶粒尺寸为10μm左右且分布均匀，晶界处和晶粒中没有杂质、气孔的存在．Yb：YAG样品中所有元素分布均匀，不同的晶粒间，晶粒和晶界间成分是一致的，没有出现成分的偏析．4mm厚样品的透过率为80％．LD泵浦获得了波长为1030nm，最大功率为268mW的连续激光输出．

建立猕猴Go/NoGo视觉分辨任务的方法

在认知神经科学研究中,Go/NoGo模型是一种非常有效的研究方法。在本试验中,以两只猕猴为研究对象,采用Go/NoGo模型,以不同的视觉线索作为刺激来研究相关认知行为。结果表明猕猴能够很快学会Go/NoGo视觉分辨任务,而且对NoGo任务的完成要优于对Go任务的完成。本实验建立了一种有效的猕猴Go/NoGo视觉分辨实验的方法及计算机控制系统,为进一步记录神经元活动建立了良好的基础。

藻类生物膜技术脱氮除磷效果研究

利用藻类生物膜去除水体氮磷为富营养化的防治提供了1种新途径,实验室条件下研究了以巨颤藻(Oscillatoria princeps)占优势的藻类生物膜对人工合成污水、污水处理厂二级污水和富营养化湖水氮(N)、磷(P)的去除效果.结果表明,通过5 d的处理,藻类生物膜对人工合成污水、污水处理厂二级污水和富营养化湖水总氮(TN)去除率分别为57.1%、94.5%和93.8%,对总磷(TP)去除率分别为93%、73%和79%.藻类产量达到3.7~7.2 g.(m2.d)-1;收获藻体总凯氏氮(TKN)达5.7%

Characteristics of oxide-free InGaAlAs layers grown by narrow stripe selective MOVPE

Narrow stripe selective MOVPE has been used to grow high quality oxide-free InGaAlAs layers on an InP substrate patterned with SiO2 masks at optimized growth conditions. Mirror-like surface morphologies and abrupt cross sections are obtained in all samples without spike growth at the mask edge. For the narrow stripe selectively grown InGaAlAs layers with a mesa width of about 1.2 mu m, a bandgap wavelength shift of 70 nm, a photoluminescence (PL) intensity of more than 80% and a PL full width at half maximum (FWHM) of less than 60 meV are obtained simultaneously with a small mask width variation from 0 to 40 mu m. The characteristics of the thickness enhancement ratio and the PL spectrum dependence on the mask width are presented and explained by considering both the migration effect from a masked region and the lateral vapour diffusion effect.

Effect of cryoprotectants on hatching rate of red seabream (Pagrus major) embryos

The objectives were to investigate the effect of cryoprotectants on the hatching rate of red seabream embryos. Heart-beat embryos were immersed in: five permeable cryoprotectants, dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), 1,2-propylene glycol (PG), and ethylene glycol (EG). in concentrations of 5-30% for 10, 30, or 60 min; and two non-permeable cryoprotectants: polyvinylpyrrolidone (PVP), and sucrose (in concentrations of 5-20% for 10 or 30 min). The embryos were then washed and incubated in filtered seawater until hatching occurred. The hatching rate of the embryos treated with permeable cryoprotectants decreased (P < 0.05) with increased concentration and duration of exposure. In addition, PG was the least toxic permeable cryoprotectant, followed by DMSO and EG, whereas Gly and MeOH were the most toxic. At a concentration of 15% and 30 min exposure, the hatching rate of the embryos immersed in PG was 93.3 +/- 7.0% (mean +/- S.D.), however. in DMSO. EG, Gly. and MeOH, it was 82.7 +/- 10.4, 22.0 +/- 5.7, 0.0 +/- 0.0, and 0.0 +/- 0.0%, respectively. Hatching rate of embryos treated with PVP decreased (P < 0.05) with the increase of concentration and exposure time, whereas for embryos treated with sucrose, there was no significant decrease in comparison with the control at the concentrations used. (C) 2008 Elsevier Inc. All rights reserved.