基于Web的虚拟数控系统的研究与开发

基于服务器／客户模式的的虚拟数控系统体系结构，讨论了虚拟数控系统的建模技术和基于VRML的实现方法，并指出虚拟数控机床的建模是虚拟数控加工过程仿真的实现关键．利用VRML语言、分布式对象技术和Java技术开发和建立了基于Web环境的虚拟数控系统原型。并对系统的开发平台进行了分析和介绍，同时给出了系统的运行实例．研究表明，所开发的系统是可行的和合理的．     

Molecular and Cellular Basis of Regeneration and Tissue Repair

The Xenopus tadpole is a favourable organism for regeneration research because it is suitable for a wide range of micromanipulative procedures and for a wide range of transgenic methods. Combination of these techniques enables genes to be activated or inhibited at specific times and in specific tissue types to a much higher degree than in any other organism capable of regeneration. Regenerating systems include the tail, the limb buds and the lens. The study of tail regeneration has shown that each tissue type supplies the cells for its own replacement: there is no detectable de-differentiation or metaplasia. Signalling systems needed for regeneration include the BMP and Notch signalling pathways, and perhaps also the Wnt and FGF pathways. The limb buds will regenerate completely at early stages, but not once they are fully differentiated. This provides a good opportunity to study the loss of regenerative ability using transgenic methods.     

Protein arginine deiminase 4: a target for an epigenetic cancer therapy

The recent approvals of anticancer therapeutic agents targeting the histone deacetylases and DNA methyltransferases have highlighted the important role that epigenetics plays in human diseases, and suggested that the factors controlling gene expression are novel drug targets. Protein arginine deiminase 4 (PAD4) is one such target because its effects on gene expression parallel those observed for the histone deacetylases. We demonstrated that F- and Cl-amidine, two potent PAD4 inhibitors, display micromolar cytotoxic effects towards several cancerous cell lines (HL-60, MCF7 and HT-29); no effect was observed in noncancerous lines (NIH 3T3 and HL-60 granulocytes). These compounds also induced the differentiation of HL-60 and HT29 cells. Finally, these compounds synergistically potentiated the cell killing effects of doxorubicin. Taken together, these findings suggest PAD4 inhibition as a novel epigenetic approach for the treatment of cancer, and suggest that F- and Cl-amidine are candidate therapeutic agents for this disease.     

Mesoderm induction in early Xenopus embryos by heparin-binding growth factors

In early embryonic development the basic body plan arises because cells in different regions become programmed to follow different developmental pathways. We have proposed that in the early amphibian embryo this process of regional specification arises from the action of three different inducing factors, or morphogens, but we have not until now had any idea of their chemical nature. In this paper we report that pure basic fibroblast growth factor (bFGF), at very low concentrations and with high specificity, closely mimics the effect of the ventrovegetal (VV) signal and that the transmission of the natural VV signal can be blocked by heparin, suggesting that it may be a heparin-binding factor such as bFGF.     

数控机床补偿误差的激光干涉仪识别技术

提出了基于数控机床的空间误差模型,用激光干涉仪测量机床工作空间中的对角线位移误差来识别机床空间误差的方法,解决了机床垂直轴roll误差的测量难题。结果表明所提出的方法测量精度高,缩短了测量时间,减少了对光学器件的需求量。     

ANALYSIS AND COMPUTATIONAL ALGORITHM FOR QUEUES WITH STATE-DEPENDENT VACATIONS Ⅱ:M(n)/G/1/K

We study a single-server queueing system with state-dependent arrivals and general service-distribution.or simply M(n)/G/1/K.where the server follows an N policy and takes multiple vacationswhen the system is empty.We provide a recursive algorithm using the supplementary variable tech-nique to munerically compute the stationary queue length distribution of the system.The only inputrequirements are the Laplace-Stieltjes transforms of the service time distribution and the vacation timedistribution.and the state-dependent arrival rate.The computational complexity of the algorithm isO(K~3).     

基于现场总线的开放式数控系统体系结构研究

结合现场总线的特点和开放式系统的要求，提出了一种基于现场总线的开放式CNC系统的体系结构，并把该体系划分为应用层，功能层和设备层三个层次，对每一层的功能进行了系统的分析和描述。在实现方法上，采用COM／DCOM技术的OPC规范的软件方法，实现了数控系统的软件 模块的重用与扩充；采用Profibus现场总线实现了数控系统的硬件模块的互操作与互换，从而满足了数控系统开放性的要求。