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81.
M. Liess R. Hua K. Elsenaar 《The International Journal of Advanced Manufacturing Technology》2002,20(1):58-62
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability
owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional
forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers
and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial
off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce
standing-wave effects is also discussed. 相似文献
82.
分子印迹技术及其应用 总被引:3,自引:0,他引:3
分子印迹技术是将高分子科学、材料科学、生物学、化学工程等有机集成。基于分子印迹技术所制备的分子印迹聚合物具有选择性高、稳定性好、应用范围广等特点 ,近年来得到了日益广泛和深入的研究。介绍了分子印迹技术的原理、分子印迹聚合物的制备方法、分子印迹技术的应用场合和实例 ,并简要预测了分子印迹技术领域未来的发展趋势。 相似文献
83.
聚合物降解产物伤害与糖甙键特异酶破胶技术 总被引:22,自引:1,他引:21
综述了钻井,完井,尤其是水力压裂作业中产生的多糖类聚合物伤害和应用糖甙键特异酶破胶,解除多糖类聚合物伤害的技术。第一节报道了聚合物降解产物造成的伤害,指出冻胶破胶液粘度低并不代表压裂液已从充填裂缝中充分返排,氧化破胶剂和普通酶破胶剂不能使多糖类聚合物充分降解,产生的大分子量,水不溶的降解产物可对地层造成伤害,消除伤害的办法是采用对糖甙键有特异性的各种水解酶作压裂液破胶剂或伤害地层处理剂。第二节报道了各种聚合物(纤维素,瓜尔胶,淀粉)糖甙键特异酶降解聚合物的机理。第三节报道了糖甙键特异酶(主要针对瓜尔胶)的应用性能测试及结果,包括岩心流动实验,含糖量和分子量测定,传导性测试。第四节介绍了糖甙键特异酶消除聚合物伤害和用作压裂液破胶剂的现场应用,包括选井原则,实施工艺要点及3个典型井例。 相似文献
84.
A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the HF/6-31G* level with molecular models for the polymers. Coordination by one to six oxygens was considered. In addition, higher level calculations were carried out using G3(MP2) theory for coordination of Li+ by one oxygen. For coordination of lithium by one oxygen, the binding energy ordering is PTMO>PPO>PEO, with PTMO having the largest lithium cation affinity. The same ordering is found for larger coordination numbers with the exception of coordination by six oxygens, where the ordering changes due to the steric interactions. 相似文献
85.
Banded textures produced in a thermotropic liquid crystal polymer by shearing between glass slides are examined by using both transmission electron and polarized light microscopy. The periodic variation in director orientation about the shear axis, as measured by light microscopy, is shown to be distinctly different from that indicated by electron diffraction. Measurements of birefringence and observation of Zernicke phase contrast indicate periodic variations in optical properties of the polymer, in step with the bands. Such effects are accounted for in terms of a synchronous rotation of the planar aromatic groups about the molecular chain axes. Evidence for an out-of-plane component of molecular orientation is also presented. 相似文献
86.
大庆长垣外围油田的开发问题 总被引:1,自引:0,他引:1
方凌云 《大庆石油地质与开发》1989,(3)
本文在对大庆长垣外围油田的地质情况、油藏类型综合分析评价的基础上,论述了开发这些油田的一系列有关问题。 相似文献
87.
Cheul-Ro Lee 《Journal of Electronic Materials》2002,31(4):327-331
We have investigated the growth characteristics of n-Al0.15Ga0.85N:Si/GaN and the electronic properties of Au/n-Al0.15Ga0.85N:Si diode structures grown by metal-organic chemical vapor deposition (MOCVD) with various Si incorporations. The Al0.15Ga0.85N:Si layers were grown on undoped GaN/sapphire (0001) epitaxial layers in a horizontal MOCVD reactor at the reduced pressure
of 300 torr. The mirrorlike surface, free of defects, such as cracks or hillocks, can be seen in the undoped Al0.15Ga0.85N epilayer, which was grown without any intentional flow of SiH4. However, many cracks are observed in the n-Al0.15Ga0.85N:Si, which was grown with Si incorporation above 1.0 nmol/min. While Au/n-Al0.15Ga0.85N:Si diodes having low incorporation of Si showed retively good rectifying behavior, the samples having high Si incorporation
exhibited leaky current-voltage (I-V) behavior. Particularly, the Au/n-Al0.15Ga0.85N:Si structure grown with Si incorporation above 1.0 nmol/min cannot be used for electrical rectification. Both added tunneling
components and thermionic emission influence the current transport at the Au/n-Al0.15Ga0.85N:Si barrier when Si incorporation becomes higher. 相似文献
88.
Frédéric Gaschet 《Papers in Regional Science》2002,81(1):63-81
This article examines the relationships between the employment suburbanisation from central cities towards their suburbs,
and the process of intra-urban specialisation that occurred simultaneously in the fifty largest French metropolitan areas.
A methodology is proposed to identify urban subcentres and to analyse the effects of the intra-urban specialisations on suburbanisation
patterns. We conclude that the specialisation of both subcentres and central cities has a significant effect on suburbanisation
rates. Lastly, an intra-metropolitan shift/share analysis provides additional insights into the employment dynamics of central
cities and suburbs during the last twenty years.
Received: 25 July 2000 / Accepted: 29 May 2001 相似文献
89.
90.
用辐射功率200W微波(2450MHz)处理6~16,明显促进离体黄瓜子叶生根.根长和根鲜重增加。不同辐射强度和辐服时间对离体黄瓜子叶生根有不同影响。用TTC法测定,微波处理后与根活力相关的OD值比对照体增加了。用温箱模拟FISO微波炉功率为200W的温度,不同处理时间处理离体黄瓜子叶,没有发现促进生根。说明在一定条件下,微波辐射处理离体黄瓜子叶促进生根.主要是微波的辐射效应。 相似文献