基于VCA822的正弦信号发生器程控放大器

DDS芯片产生的信号幅值不可控制,且随着频率改变,输出信号幅值在一定范围内改变,然而作为信号源常常需要信号幅值的精确控制。本文利用TI公司的可控增益放大器VCA822设计了增益自动调整电路和程控放大电路。实现将DDS芯片产生的不确定幅值的正弦波通过增益自动调整电路后,变化为固定幅值的正弦信号,再通过程控放大器完成输出正弦信号幅值0.5V～5V程控可调。     

Evaluation of ultimate bearing capacity of Y-shaped vibro-pile

Based on Mindlin stress solution, a numerical computational method was proposed to calculate the stresses in the ground induced by side friction and the resistance of Y-shaped vibro-pile. The improved Terzaghi’s and ЪерезанцевВГ’s methods for ultimate bearing capacity evaluation were proposed by considering the stress strength induced by friction resistance at pile head level of Y-pile. A new method to calculate the ultimate bearing capacity of Y-pile was also proposed based on the assumptions of soil failure mode at the tip of Y-pile and the use of Mohr-Coulomb soil yield criterion and Vesic compressive correction coefficient with the induced stresses in the ground. Based on the comparisons with the field static load test results, it is found that the improved Terzaghi’s method gives higher ultimate capacity, while the other two methods shows good agreement with the field results.     

新闻机构网络分析与防范

随着计算机设备和技术的日益更新,以及网络信息技术的发展,世界信息一体化已成为人类发展的现状。在这方面,新闻单位的计算机和网络利用率在各个机构里算是比较高的,在网络一体化中得到了很大的便利,非常便捷地实现了媒体信息资源的共享和提高媒体发布新闻资讯的工作效率。然而互联网络易受恶意病毒、木马、黑客等流氓软件的非法攻击。保障新闻单位计算机设备和内外网络的安全,成为一件非常重要的问题。     

Web安全技术与防火墙的功能

介绍几种用于解决Internet中的数据安全的方法。     

涩北二号气田高低压集输技术经济论证

通过对涩北二号气田内部4个集输方案的比选，以静态总费用（界定为工程固定资产投资和运行费用之和）、费用总现值（界定为工程固定投资现值和运行费用现值之和）为经济评价指标，论证了涩北二号气田采用高、低压集输系统的经济性和先进性；并从高、低压管网的水力和热力核算论证了该方案在技术上的可行性。本文在国内首次大胆提出了在涩北二号气田采用高、低压集输系统。对涩北二号气田地面工程建设具有重要的指导意义，为国内整装气田的地面工程设计提供了一种新的思路，具有一定的借鉴意义。     

Experimental Investigation of Lower Hybrid Wave Coupling in HT-7

Experiments on lower hybrid wave(LHW)coupling were investigated in the HT-7 tokamak.Good coupling of LHW plasma has been demonstrated at different conditions in the HT-7 tokamak.Relevant results have proved that LHW-plasma coupling is affected by the phase difference between adjacent waveguides.Furthermore,the edge density around the grill and relevant coupling can be adjusted by changing the plasma line average density or the gap value between the LH grill and the last closed flux surfaces(LCFS).It is found that the coupling of LHWs becomes poor when the edge density around the LH grill is large enough in the HT-7tokamak,and that coupling remains good with a proper edge density.With increasing LHW power,it is also found that the reflection coefficients(RCs)increase due to non-linear effects under conditions of low edge recycling,but can decrease under high edge recycling.The edge density depends mainly on the competition between the ponderomotive force(PMF)and the edge recycling intensity in the HT-7 tokamak.     

基于近义词分配的铁路接触网绝缘子识别与分类

为提高铁路接触网绝缘子检测中的图像识别精度并准确区分绝缘子类型,提出一种建立在"视觉词包模型"基础上,计算视觉单词语义距离并合理分配的绝缘子识别分类模型。首先应用潜在狄利克雷分布模型与相对熵计算视觉单词的语义相关性,然后根据底层特征与各单词的欧氏距离大小分配单词数目,最后采用支持向量机实现绝缘子的识别与分类。实验结果表明,该方法可以提高识别精度与分类效果。