Analysis of additional leakage resulting from the feeding motion of a vacuum-compatible air bearing stage

A rise in pressure is generated when a vacuum-compatible air bearing stage moves in a vacuum condition. This study analyzed this pressure rise phenomenon theoretically and verified it experimentally. Results indicate that the pressure rise was caused by additional leakage resulting from stage velocity, along with adsorption and outgassing of gas molecules from the guide rail surface. Tilting of the stage had a negligible effect because the tilting time was very short. Additional leakage caused by stage velocity was inevitable if the stage incorporated mechanical movements, but rises in pressure caused by adsorption and outgassing could be suppressed by coating the guide rail surface with titanium nitride, to which gas molecules are less likely to adhere. The results also indicate that the pressure rise ratio increased when the air bearing stage operated under high-vacuum conditions.     

光刻设备中工件台激光测长原理

通过对双频激光干涉仪的原理、结构、双频产生机理进行分析,阐述激光干涉仪在光刻设备中的实际应用,探讨激光干涉仪技术。     

PLC在音乐厅舞台控制系统中的应用

本文论述了舞台控制系统的设计与实现。通过智能化控制实现舞台的升降、伸缩、伸缩升降等运动。应用CX—ONE软件设计系统的人、机界面。实践证明该PLC控制系统具有控制精度高,可靠性好,使用简便等优点,在舞台建设中得到广泛应用。     

重庆彭水地区茅口阶顶部牙形刺及古生态的初步探讨

重庆在二叠纪茅口晚期处于川鄂局限台地的中部 ,本文以重庆彭水县方石隧道旁茅口阶剖面为基础 ,对其沉积相及沉积环境进行了探讨 ,并对灰岩样品进行处理 ,将所得的牙形刺划分成 2个带 ,分别为Mesogodolellaxuanhanensis和Mesogodolellagranti带。在此基础上对牙形刺的古生态进行了初步的探讨。     

光刻机模拟工作台的精密隔振系统方案设计研究

提出了高精密设备光刻机模拟工作平台隔振系统的设计方法和系统结构;根据国内外现行的减振方法,建立了整个模拟工作台的结构模型;根据减振要求,选择了适当的减振器.由于光刻机所处激励环境的复杂性和系统内部存在的非线性,采用了主动控制方法BP神经网络 PID控制的主动控制方法来控制整个减振系统.     

Influence of axial clearance on solid particle erosion and efficiency of governing stage in ultra-supercritical steam turbine based on rebound effect

Based on the steam-solid two-phase flow model combined with rebound effect, the influence of axial clearance on the solid particle erosion (SPE) characteristics and efficiency in ultra-supercritical steam turbine governing stage was analyzed. The results show that the erosion damage degree caused by rebound is less than that caused by the particle first impact. With the increase of axial clearance, the number of particles rebounding back to the trailing edge of the suction surface(SS) in nozzle decreases. When the axial clearance increases, the large size particle impact velocity and impact angle move towards the leading edge of rotor blade, and the erosion area extends to the middle and front of the pressure surface (PS), resulting in the increase of erosion area. However, the particle impact angle deviates from the serious erosion angle, and the erosion degree decreases. The axial clearance has different influence trends on SPE and stage efficiency. With the increase of axial clearance, the erosion rate density decreases continuously, about 59.2%, but the stage efficiency increases first and then decreases. So the influence of SPE and stage efficiency should be comprehensively considered for the selection of axial clearance.     

垫筑伞芈施工阶段壬程造价动态拉制．

将灰色模糊预测理论引入施工阶段工程造价预测中,得到工程造价灰色模糊预测模型,运用预测模型估算未完成工程造价,进行优化、调整计划工作预算成本;设计了实施阶段工程造价缓冲管理控制机制,运用该机制可以及时进行工程造价动态控制预警;结合灰色模糊预测模型和缓冲管理控制机制可以在工程项目实施全过程中进行动态预警和控制,确保工程造价自始至终处于有效控制之下,达到成本控制总目标。工程造价灰色模糊预测模型和缓冲管理控制机制为施工单位造价管理工作提供重要的实践指导意义。     

当前中国城市建设现代化转型及发展趋势

对中国城市建设现代化进程概括了四个发展阶段,分析了当前中国城市现代化转型五个方面的表现,展望了中国城市建设在新世纪的八大发展趋势,同时指出要总结历史经验,走出城市建设误区,创造具有中国特色的现代化城市与建筑。     

委内瑞拉ANACO区块气井固井难点及对策

委内瑞拉ANACO区块地层破裂压力梯度低,有高压水层和低压气层,环空容易发生气窜,并含有H₂S和CO₂,呈泥质砂岩。基于以上认识,ANACO区块固井的复杂性主要源于水泥基材料固有的缺陷和地层条件的多变性,正确认识地质条件对固井的影响和选择合适的固井材料、工艺措施是解决固井难题的基本出发点。针对该地区地质因素,从分级注水泥、双密度或多密度水泥浆体系工艺上、水泥浆及外加剂选择等方面进行了研究;同时结合现场固井状况进行了对策方案归纳,并对腐蚀深度和防气窜性能进行实验探索。结果表明,研发的防窜防腐蚀水泥浆最低密度为1.2 g/cm3,且上下密度差低于0.03 g/cm3,游离液接近0,抗压强度高,渗透率低;通过引入防腐蚀材料BCE-750S后,硅酸盐水泥石在7、30和60 d的腐蚀深度大大降低,能够解决当地环空气窜、含有H₂S和CO₂酸性气体等问题。