虚拟激光柔性加工的完整过程仿真模型研究——覆盖件模具的激光硬化

提出了虚拟激光柔性加工系统的体系结构，运用IGRIP建立包括虚拟场景和虚拟加工设备的虚拟激光柔性加工平台；以覆盖件模具表面激光硬化加工为例，综合分析其过程中各影响因素（几何、激光、材料等方面的因素），建立了基于神经网络的工艺力学模型，并嵌入到虚拟加工平台中，以实现包括几何仿真与物理仿真的完整仿真过程，预测加工效果，为真实加工提供有效依据。

Hydrothermal Wave in a Shallow Liquid Layer

The oscillatory thermocapillary convection and hydrothermal wave in a shallow liquid layer, where a temperature difference is applied between two parallel sidewalls, have been numerically investigated in a two-dimensional model. The oscillatory thermocapillary convection and hydrothermal wave appear if the Marangoni number is larger than a critical value. The critical phase speed and critical wave number of the hydrothermal wave agree with the ones given analytically by Smith and Davis in the microgravity environment, and it travels in the direction opposed to the surface flow. Another wave traveled downstream in addition to the hydrothermal wave traveled upstream was observed in the case of earth gravity condition.

Research on Q-Switched Nd : YAG laser engraving

IN this paper, the engraving process with Q-Switched Nd:YAG laser is investigated. High power density is the pre- requisition to vapor materials, and high repetition rate makes the engraving process highly efficient. An acousto- optic Q-Switch is applied in the cavity of CW 200 W Nd:YAG laser to achieve the high peak power density and the high pulse repetition rate. Different shape craters are formed in a patterned structure on the material surface when the laser beam irradiates on it by controlling power density, pulse repetition rate, pulse quantity and pulse interval. In addition, assisting oxygen gas is used for not only improving combustion to deepen the craters but also removing the plasma that generated on the top of craters. Off-focus length classified as negative and positive has a substantial effect on crater diameters. According to the message of rotating angle positions from material to be engraved and the information of graph pixels from computer, a special graph is imparted to the material by integrating the Q- Switched Nd:YAG laser with the computer graph manipulation and the numerically controlled worktable. The crater diameter depends on laser beam divergence and laser focal length. The crater diameter changes from 50 micrometers to 300 micrometers , and the maximum of crater depth reaches one millimeter.

Numerical study on heavy rigid particle motion in a plane wake flow by spectral element method

Experimental particle dispersion patterns in a plane wake flow at a high Reynolds number have been predicted numerically by discrete vortex method (Phys. Fluids A 1992; 4:2244-2251; Int. J. Multiphase Flow 2000; 26:1583-1607). To address the particle motion at a moderate Reynolds number, spectral element method is employed to provide an instantaneous wake flow field for particle dynamics equations, which are solved to make a detail classification of the patterns in relation to the Stokes and Froude numbers. It is found that particle motion features only depend on the Stokes number at a high Froude number and depend on both numbers at a low Froude number. A ratio of the Stokes number to squared Froude number is introduced and threshold values of this parameter are evaluated that delineate the different regions of particle behavior. The parameter describes approximately the gravitational settling velocity divided by the characteristic velocity of wake flow. In order to present effects of particle density but preserve rigid sphere, hollow sphere particle dynamics in the plane wake flow is investigated. The evolution of hollow particle motion patterns for the increase of equivalent particle density corresponds to that of solid particle motion patterns for the decrease of particle size. Although the thresholds change a little, the parameter can still make a good qualitative classification of particle motion patterns as the inner diameter changes.

Fabrication and spectral properties of Nd3+-doped yttrium lanthanum oxide transparent ceramics

Transparent 1 at% Nd3+:Y1.9La0.1O3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H-2 atmosphere at 1550 degrees C for 30 h. The Nd3+:Y1.9La0.1O3 ceramics display uniform grains of about 50 mu m and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820 nm with absorption cross section of 2.48 x 10(-20) cm(2). The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 x 10(-20) cm(2) and broad full width at half maximum (FWHM) of about 6.3 nm. The strongest emission peak was centered at 1078 nm with large stimulated emission cross section of 9.63 x 10(-20) cm(2) and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd3+:y(1.9)La(0.1)O(3) transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively. (c) 2007 Elsevier B.V. All rights reserved.

中国西北地区蜜源植物花粉

我们采用光学显微镜和扫描电子显微镜观察了68种我国西北地区蜜源植物的花粉，并用透射电子显微镜观察了其中的5种。在文中，每种花粉的形态都有比较详细的描述。此外，作者还总结了蜜源植物花粉的形态特征，编制了这些花粉的形态检索表。 我们比较了虫媒植物和风媒植物的花粉。在形态上，它们有明显的不同之处。一般来说，虫媒植物的花粉粒较大，较重，表面纹饰较粗、具粘液;它们还常集结成块状。 紫草科花粉的异萌发孔、柳叶菜科柳兰花粉、伞形科芫荽花粉的极帽等形态均较特殊，文中作了详细的讨论。 花粉的大小和形状在醋酸酐分解前后多有变化。一般变化规律是：花粉粒大的，形态变化大;花粉粒小的，形态变化小。球形，具散孔花粉变化很小。 我们还对花粉形态研究中光镜、扫描电镜、透射电镜的使用进行了比较。

陕西铜川延安组植物群研究

在1991年和1992年秋天，笔者先后两次来到铜川采集标本200余块，进行古植物方面的研究。本文标本主要采集于崔家沟、下石节、焦坪三个矿区，其地层属于延安组宝塔山岩段。论文讨论了植物群落的特征和世代问题，论文引用了数学方法，并提供了该地区古植物特征的系统描述以及古环境问题。

云南鹅线粒体DNA多态及酶切图谱分析

用１８种限制性内切酶对７只云南鹅的线粒体ＤＮＡ（ｍｔＤＮＡ）进行了限制性片段长度多态（ＲＦＬＰ）分析。１７种酶在所有受试个体表现为一致的限制性态型（ｍｏｒｐｈ），一只灰羽鹅用ＰｖｕＩ消化时出现变异。用１４种限制性内切酶构建了云南鹅ｍｔＤＮＡ的酶切图谱。

内含子序列“三碱基组”的信息分析

在对编码序列的碱基分布作大量统计分析的基础上，对内含子序列中Ｇ、Ｃ的分布作了统计分析．发现内含子在“三碱基组”的意义下，第一位上（Ｇ＋Ｃ）含量占优势．如果将同一基因的外显子三联密码和内含子“三碱基组”做比较，发现在内含子中出现而外显子中没有的那些三碱基组，它们大多属于Ｌｉó所列出的“非偏爱”密码

Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules

Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, Delta GRT1 Delta GRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in Delta GRT1 Delta GRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from Delta GRT1 Delta GRT2 cells appear less adhesive than those from the wild type.