Experimental Study on the Ventiduct Embankment in Permafrost Regions of the Qinghai-Tibet Railroad

This technical note presents an experimental study on the ventiduct embankment in permafrost regions of the Qinghai-Tibet Railroad. Two experiments were conducted in a test box and they were designed with similarity theory. Some preliminary results are given to describe the temperature regime properties of the embankment, and the temperature differences between the ventiduct embankment and the normal embankment are compared. Results showed that the ventiduct embankment has a good cooling effect; it has a faster cooling rate than the normal embankment; the range of influence of a single duct can reach one duct diameter; the temperature distribution of the ventiduct embankment is asymmetric along the wind direction.     

Effect of electric charge accumulation on low energy ion implantation in insulators

Charge accumulation at the surface of insulators during low energy ion implantation is related to two processes: ion impinging on the sample and secondary electron emission. Samples composed of a piece of Si (having the size of the ion beam) fixed on the centre of polyethylene (PE) coupons have been implanted with 2.2 keV H₂ ions to a fluence of 2 × 10¹⁶ H/cm². ERD (Elastic Recoil Detection) depth profiles of the implanted ions are shallower with an increase of the PE coupon size. The relative critical Si/PE size to repel all the incident ions is around 1.1 × 1.1 cm²/2.5 × 2.5 cm². The potential of the secondary electron suppressor has been varied from −500 V to +500 V. It changes the secondary electron distribution around the implanted area and, consequently, affects the accumulation of charges at the sample surface. When the potential is 0 V, a uniform ion implantation with little effect of charge accumulation for all sizes of PE coupons is obtained. A two-dimension model has been performed and gives a good explanation for the mechanism of the electric charge neutralisation.     

表征PAN纤维和炭纤维微细结构的HRTEM样品制备方法

为用高分辨透射电子显微术(HRTEM)表征聚丙烯腈(PAN)纤维和炭纤维的微细结构，从纤维性能出发，探讨研碎、离子束减薄和超薄生物切片三种制备方法及其工艺步骤，结合实验结果，对比了三种制备方法的原理、优缺点，提出了制备方法的适用范围和选择原则，并推断适于表征预氧化纤维微细结构的样品制备方法。与生物样品的制备方法类似，把超薄生物切片法引入到纤维材料HRTEM样品制备领域，为系统研究炭纤维微细结构的演变提供了线索。     

离子选择电极法测定氟化物过程中的质量控制

文章从氟离子选择电极的维护及其性能的判断、相应极限、空白电位值、参比电极的维护及其对电位值的影响、滤纸的使用以及溶液的pH值、温度、搅拌、电极浸入深度与位置、测定顺序等影响离子选择电极法测定氟化物的有关因素进行了研究和探讨，并提出对较复杂样品的测定易采用标准加入法以提高测定准确度和精密度。     

Ultraflat indium tin oxide films prepared by ion beam sputtering

Indium tin oxide (ITO) films with a smooth surface (root-mean-square roughness; R_rms=0.40 nm) were made using a combination of the deposition conditions in the ion beam-sputtering method. Sheet resistance was 13.8 Ω/sq for a 150-nm-thick film grown at 150 °C. Oxygen was fed into the growth chamber during film growth up to 15 nm, after which, the oxygen was turned off throughout the rest of the deposition. The surface of the films became smooth with the addition of ambient oxygen but electrical resistance increased. In films grown at 150 °C with no oxygen present, a rough surface (R_rms=2.1 nm) and low sheet resistance (14.4 Ω/sq) were observed. A flat surface (R_rms=0.5 nm) with high sheet resistance (41 Ω/sq) was obtained in the films grown with ambient oxygen throughout the film growth. Surface morphology and microstructure of the films were determined by the deposition conditions at the beginning of the growth. Therefore, fabrication of ITO films with a smooth surface and high electrical conductivity was possible by combining experimental conditions.     

氮离子注入铝的结构研究

采用掠射X射线衍射和AES方法分析了氮离子注入铝的结构和成分,采用TRIM?8程序对注入过程中氮浓度随深度的分布进行了模拟。结果表明:当温度低于300℃,能量为60 keV,用71017 /cm2和1?018 /cm2注量的氮离子注入铝时,在铝的表面生成了六方结构的AlN而不是立方结构的AlN;同时碰撞扩散作用在氮离子注入过程中居主导地位,热扩散作用和辐照增强扩散作用均不明显。     

离子束辅助沉积立方氮化硼的试验研究

运用离子束辅助沉积(IBAD)法在硅片上制备了立方氮化硼(c—BN)薄膜，研究了辅助能量、辅助束流及辅助束中氮气含量等参数对膜中c—BN含量的影响。用红外光谱(FTIR)及X射线光电子能谱(XPS)分析技术对得到的c—BN膜进行了分析。结果表明：合适的离子辅助能量能够获得c—BN含量高的薄膜；膜中c—BN的含量随辅助气体中N2含量的提高而增加；辅助束流对薄膜的形成影响不明显。     

飞行时间质谱峰形分析

从离子运动方程出发，用峰形分析方法离子的质谱峰进行数据再处理，首次从飞行时间质谱峰峰形中获得离子产生时的空间分布信息。这种峰形分析方法可以广泛应用于分析飞行时间质谱的各种离子源中离子的分布。     

二丙酮醇生产工艺的改进

探讨了用强碱性阴离子交换树脂催化下合成了二丙酮醇的适宜工艺，选择了合适的工艺条件，反应周期短，催化剂寿命长，如，反应从催化剂上端进行，反应温度２０～２５℃。单程反应的最短时间为４ｈ，收率９２％，比重０．９３，折光率１．４２４０～１．４２４２产品质量与文献值相符，催化剂寿命大于１５０ｈ。     

关于辅助沉积霍尔离子源的几个问题

本文目的在于改进霍尔源的设计,实现宽能、大束流、低气耗、低污染、能自动化控制的新一代霍尔源.