Colour Centres and Energy Transfer in BaF2-xClx:Eu2+ Phosphors

The optical absorption spectra of BaF2-xClx:Eu2 after ultraviolet (UV) light excitation were investigated.The differences between the absorption spectra after and before excitation (DAS) were observed.The DAS increase at both the high and the low energy side of F band in BaF2-xClx:Eu2 after 245 nm UV light excitation.The bleach effect of UV light and the absorption of electrons in the valence band may account for the former and the formation of Fa centres (association of F(Cl-) centres), whose absorption band matches the HeNe laser better, may explain the latter.In the write-in process, the transfer of electrons is via tunneling.In the readout process, the transfer of electrons captured in F(F-) and Fa centres is more likely via tunneling, and that of F(Cl-) centres is more likely via conduction band.     

铣制三元流叶轮时产生误差的原因分析及解决方法

对在五坐标数控加工中心上铣制三元流叶轮时出现的叶轮附面尺寸误差问题，进行了详细分析，并提出了问题的解决方法，有效地避免了加工中产生的超差。     

数控超声加工的初步工艺试验

介绍在经过数控化改造的两坐标超声加工机床上所进行数控超声加工的初步工艺试验,并讨论试验结果。     

Triple tangent flank milling of ruled surfaces

This paper presents a positioning strategy for flank milling ruled surfaces. It is a modification of a positioning method developed by Bedi et al. [Comput Aided Des 35 (2003) 293]. A cylindrical cutting tool is initially positioned tangential to the two boundary curves on a ruled surface. Optimization is used to move these tangential points to different curves on the ruled surface to reduce the error. A second optimization step is used to additionally make the tool tangent to a rule line, further reducing the error and resulting in a tool position, where the tool is positioned tangential to two guiding rails and one rule line. The resulting surface has 88% less under cutting than the method of Bedi et al.     

Genetic synthesis of a fuzzy pulse discriminator in electrical discharge machining

In this paper, a sensor system, called a fuzzy pulse discriminator, is developed to classify various discharge pulses in electrical discharge machining (EDM). The fuzzy rules of the pulse discriminator are obtained based on the features of the gap voltage and gap current between the tool workpiece. The membership functions of the fuzzy pulse discriminator are automatically synthesized by using genetic algorithms. The effectiveness of this approach is verified under different cutting parameters.     

AHMED experiments on hygroscopic and inert aerosol behaviour in LWR containment conditions: experimental results

Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m³ total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compared to high RH. Thus at high RH (96–97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs. Experimental results were also compared with calculations obtained by severe accident computer codes. These calculated results will be presented in a later paper.     

钻杆接头螺纹退刀尺寸对接头寿命的影响

钻杆接头螺纹退刀尺寸是指外螺纹接头的台肩面到螺纹消失前第一个完整螺纹之间的距离。GB9253．1－88规定退刀尺寸应小于或等于12．7mm内螺纹，钻杆接头内螺纹的锤孔尺寸为16±2mm，以保证内、外螺纹啮合良好。经检测发现，从日本NKK公司进口的所有φ127mm钻杆接头外螺纹退刀尺寸都大于12．7mm，镗孔尺寸为16～18mm。而APISpec7K规定钻杆接头内螺纹最小镗孔尺寸为15．9mm。鉴于此，建议对我国的有关标准作相应修改，与API标准保持一致。     

数控加工的基本坐标系和对刀问题

数控加工中的对刀问题影响机械加工的各个方面。这里从介绍数控机床的基本坐标系出发，重点阐述了对刀的基本原理和方法以及常见数控机床对刀问题的处理。     

SSRF储存环预研制铝合金真空室的机械加工

上海同步辐射装置（SSRF）储存环铝合金超高真空室已研制成功，该机加真空室的尺寸大、尺寸精度、形位公差及粗糙度要求极高，不同于常规的大型超高真空室。在预研件加工中，成功地解决了一系列问题，如光洁度提高困难，加工成型后变形大；加工尺寸和精度受环境温度影响较大等。本文详细阐述了储存环真空室材料和热处理状态的选择依据，为了保证尺寸精度和形位公差所采取的工艺措施，分析了粗糙度的形成机理和影响因素，从刀具材料、几何角度、切削参数、冷却液选型等多方面提出了解决办法。     

LASER ENHANCED ELECTROCHEMICAL MACHINING PROCESS

An experimental apparatus was designed and built for the hybrid process of laser enhanced electrochemical machining (ECM). Comparison experiments had been done between solely ECM and laser enhanced ECM. The machining performance of hybrid process was investigated and compared with solely ECM. The principle of the hybrid process was exposed by analyzing the microstructure of machining surface. The results show that the hybrid process has advantages in machining accuracy, surface quality, and machining efficiency.