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91.
延长测井电缆使用寿命的方法探讨 总被引:1,自引:0,他引:1
由于对测井电缆机械性能缺乏了解,使用不规范,使测井电缆使用寿命降低.通过对测井电缆结构、制造工艺进行分析,进一步掌握其性能,提出通过正确安装、使用前需进行稳定化处理、在使用中注意控制起下速度、日常清洁润滑、定期对电缆进行维护保养等方法维持铠装层正常状态,减少层间摩擦力,不扭曲,缆芯通断良好等方法,从而延长电缆的使用寿命. 相似文献
92.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
93.
无线局域网的安全解决方案 总被引:1,自引:1,他引:0
罗超 《信息安全与通信保密》2005,(7):271-276
本文描述了无线局城网中的认证和密钥管理协议,CCMP认证加密协议。IEEE 802.11依赖于IEEE 802.1x 来支持认证和密钥管理服务,更进一步的,四次握手协议用来建立分组传输的数据加密密钥。IEEE 802.11i也定义了认证者更新一个组暂时密钥(GTK)给请求者的组密钥握手,这样请求者可以接收广播消息。 相似文献
94.
95.
分析了BC-480支架在综采工作面使用中液压系统配置低的原因,提出了系统的改造原则和方案,比较了改制前后支架的动作速度. 相似文献
96.
Automated currency validation requires a decision to be made regarding the authenticity of a banknote presented to the validation system. This decision often has to be made with little or no information regarding the characteristics of possible counterfeits as is the case for issues of new currency. A method for automated currency validation is presented which segments the whole banknote into different regions, builds individual classifiers on each region and then combines a small subset of the region specific classifiers to provide an overall decision. The segmentation and combination of region specific classifiers to provide optimized false positive and false negative rates is achieved by employing a genetic algorithm. Experiments based on high value notes of Sterling currency were carried out to assess the effectiveness of the proposed solution. 相似文献
97.
98.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers. 相似文献
99.
首先对DTD和CSS的语法规则进行了简单介绍,然后给出了一个对DTD和CSS进行语法分析和编辑的设计思路,最后给出了编辑器的实现效果以及对下一步工作的展望。 相似文献
100.
In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional “chain-like objects” (CLO's) that are 1–2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm−1 whose width is 35–40 cm−1, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm−1 scattering) concentrations. The 490 and 35 cm−1 values are consistent with bond angle deviations approaching 0°, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH4), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H2 levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon. 相似文献