火车车钩舌面仿形自动堆焊机仿形系统设计

火车车钩舌面经常需要进行焊补，传统的手工堆焊工效低且质量差，为配合仿形自动堆焊机的研制，本文设计了自动堆焊机的控制系统，该系统采用眦控制技术，两个伺服电机、一个步进电机驱动和三维精密工作台机械传动，实现三坐标、多道自动堆焊，保证S面精确成型。经过调试及模拟运行后表明，该控制系统能使焊枪运动轨迹为要求的S形，并使Z向工作台在规定的时间内上下运动，保证了自动堆焊机的仿形精度和工作效率，达到其技术要求。     

考虑误差影响的力学参数反分析神经网络方法研究

通过求偏导技术将反分析的参数误差分别表示为模型误差与测量误差的函数，利用这些函数研究了模型误差与测量误差在力学参数反分析神经网络方法中的传递过程以及影响反分析结果的影响因素．研究结果说明：输入变量的选择严重影响力学参数反分析的精度，选取力学参数灵敏度大的测点位移作为神经网络的输入变量，可以减小模型误差与测量误差对反分析结果的影响．这对提高力学参数反分析的实用性与可信性有重要意义．     

一种基于SPIHT的分层图像压缩方法

提出一种利用SPIHT算法进行图像分层压缩的编码方法,该方法首先利用图像平滑技术将图像分解为平滑部分和轮廓部分,然后以一定的编码率分别对它们进行编码.实验结果表明,合理分配各层的编码率,能够获得视觉效果比单独采用SPIHT编码更好的编码图像.     

基于粗糙集理论的模糊信息分类方法

介绍了属性约简的概念,并用模糊语义距离矩阵解决了含有模糊数据的相互依赖的数据库的信息分类问题。     

使用IEEE802.1X技术优化校园网计费管理

通过对IEEE 80 2 .1X技术的认证计费系统的分析 ,论述如何用其解决校园网计费管理中现存的问题 ,优化校园网的计费管理     

Efficient expression of human factor Ⅸ cDNA in liver mediated by hydrodynamics-based plasmid administration

The transfection of plasmid DNA into mammalian cells is an indispensable tool in the study of gene transfer and gene function. Since the original report in 1990 on the successful expression of a reporter gene in muscle[1], plasmid DNA injection has been widely used to mediate gene transfer study. As a gene transfer vector, naked DNA has many obvious advantages. It is easy and cheap to be prepared and more safe after transfection. But the plasmid mediated gene expression is low because of t…     

Shift visual cryptography scheme of two secret images

A new visual cryptography scheme of two secret images, which is named the shift visual cryptography of two secret images, is given. The compound function family of a general construction model is also introduced. The uniqueness and validity of this model are proved, and the minimum rows and columns for realizing the scheme are obtained. Compared with visual cryptography of one secret image, the shift visual cryptography scheme can share two secret images with the same size of pixels expansion without losing the contrast. It has randomness and various forms, and furthermore, we can also visually recover two secret images even if the two shares are different in form and color.     

Rapid cold hardening process of insects and its ecologically adaptive significance

In contrast to overwintering cold hardening, a rapid cold hardening process has recently been described in insects. This process can rapidly enhance cold tolerance of insects in several hours or even minutes. The characteristics of rapid cold hardening include inducing conditions, cold hardening effects, and fitness costs. Physiological and biochemical mechanisms of rapid cold hardening include rapid changes in the phospholipid composition and the increase in hemolymph osmolalities, polyols production, proline and cold-induced proteins. Moreover, there are different views about the ecologically adaptive significance of rapid cold hardening in insects. This paper reviews research results about rapid cold hardening of insects since 1987, focusing on forms of cold injury, strategies of cold tolerance, and definitions, characteristics, physiological and biochemical mechanisms and adaptive significance of rapid cold hardening.     

井下掺液抽稠油泵研究

通过对常规泵进行串联、改造 ,研制出了井下掺液抽稠油泵。对泵结构的可行性进行了论证 ,阐述了泵的工作原理 ,并对泵的工作参数进行了分析。该泵是通过从油管掺入液、从油套环空产出液 ,在上冲程时吸入产出液 ,在下冲程时举升混合液 ,从而实现了在柱塞下方掺液 ,避免了出现砂磨柱塞的现象 ,减少了稠油对柱塞运动的阻力 ,克服了泵上掺液不能降低进泵原油粘度的缺点 ,解决了在井筒降粘和稠油抽汲中存在的问题。该泵使用了连动式凡尔与弹簧 ,保证了底阀与顶阀打开与关闭的同步性 ,能够达到吸入产出液、加入掺入液以及举升混合液同时进行的目的。该泵的设计原理可行 ,工艺容易实现 ,是一种理想的新型抽稠油泵。     

Building of hFⅨ transgenic mice by spermatogenic cells

Human FⅨ expression vector pCMVⅨ was packaged by effectene^TM reagent and injected into mice seminiferous tubules with glass pipettes.The expressional frame of pCMVⅨ was examined by PCR and Southern blotting among 41 progenies.There were 2(4%) mice being integrated with hFⅨ gene into chromosomes.4.6ng/mL of hFⅨ protein was expressed in plasma of one mouse,which was tested by ELISA.We demonstrated that building of transgenic animals by spermatogonial stem cells is an efficient method.Meanwhile,it has also been proved to be an alternative choice for mammary gland bioreactor.