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网络安全伴侣SAFEmate
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《计算机安全》 2004年第6期49-49,共1页
关键词 网络安全伴侣 safemate 网络系统安全性 扫描分析 网络入侵监测
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钢轨垂直振动模态的导波频散曲线、波结构及应用 被引量:14
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作者 卢超 刘芮辰 常俊杰 《振动工程学报》 EI CSCD 北大核心 2014年第4期598-604,共7页
频散曲线和波结构是钢轨导波检测时设计检测方法和分析回波波形的基础。首先介绍了半解析有限元计算任意截面弹性波导中导波传播的频散曲线和波结构的基本方法。然后应用该方法求解了U60型钢轨中垂直振动模态的导波频散曲线和波结构,并... 频散曲线和波结构是钢轨导波检测时设计检测方法和分析回波波形的基础。首先介绍了半解析有限元计算任意截面弹性波导中导波传播的频散曲线和波结构的基本方法。然后应用该方法求解了U60型钢轨中垂直振动模态的导波频散曲线和波结构,并讨论了频散曲线和波结构在钢轨轨头缺陷导波检测中的应用。最后采用模态力锤实验及时频联合分析的方法验证了频散曲线数值计算结果。钢轨轨头横向裂纹垂直振动模态导波检测的有限元数值模拟和实验表明该模式导波是检测钢轨轨头缺陷的有效检测模式波型。 展开更多
关键词 钢轨检测 导波 频散曲线 波结构 半解析有限元方法
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半航空频率域电磁探测三分量线圈传感器设计 被引量:1
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作者 滕飞 王鹏飞 +2 位作者 王宇 张铭 林君 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2023年第1期430-441,共12页
半航空频率域电磁探测方法(semi-airborne frequency domain electromagnetic method,简称SAFEM)通常借助水平线圈传感器观测垂直分量磁场信号.然而,在实际探测过程中,观测单一分量磁场信号不仅缺失水平分量磁场信息,并且在磁场响应畸... 半航空频率域电磁探测方法(semi-airborne frequency domain electromagnetic method,简称SAFEM)通常借助水平线圈传感器观测垂直分量磁场信号.然而,在实际探测过程中,观测单一分量磁场信号不仅缺失水平分量磁场信息,并且在磁场响应畸变区域难以校正,造成视电阻率解释结果精度低、误差大等问题.为此,本文设计并研制了一种能够用于SAFEM探测的三分量空心线圈传感器,采用三组相互垂直的接收线圈分别接收三个分量的磁场信号.首先,为满足旋翼机载重要求,设计0.5 m直径的小尺寸圆形线圈用于接收垂直方向磁场,两个0.01 m边长的方形线圈用于接收水平方向磁场,并对三组线圈的互耦情况进行分析,确定了线圈的最佳相对位置.其次,针对线圈传感器的物理结构特点,综合线圈的寄生电阻、电感和电容值大小的分析结果,确定最终的物理结构参数.进一步地,通过分析不同阻尼状态下的传感器及前置放大电路的频率响应特性,确定了最佳的阻尼系数调节范围.在此基础上,设计了带有阻尼状态调节的低噪声差分前置放大器电路作为SAFEM信号调理模块.最后,开展屏蔽室测试实验和野外探测实验验证三分量线圈传感器的可靠性.屏蔽室内对比测试结果表明,小尺寸的三分量线圈传感器带宽能够满足探测需求,能够提供与商用传感器相当的灵敏度和测量准确性.在野外探测实验中,使用该三分量线圈传感器获得了实验场地的三分量磁场响应信号,进一步证明了该三分量传感器的有效性. 展开更多
关键词 半航空电磁探测 三分量传感器 线圈互耦分析 阻尼电路设计
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Application of semi-analytical finite element method to analyze asphalt pavement response under heavy traffic loads 被引量:4
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作者 Pengfei Liu Dawei Wang Markus Oeser 《Journal of Traffic and Transportation Engineering(English Edition)》 2017年第2期206-214,共9页
Accurate assessment of the impact of heavy traffic loads on asphalt pavements requires a computational model which is able to calculate the response of the pavement fast and precisely. Currently the most finite elemen... Accurate assessment of the impact of heavy traffic loads on asphalt pavements requires a computational model which is able to calculate the response of the pavement fast and precisely. Currently the most finite element analysis programs based on traditional methods have various limitations. A specific program SAFEM was developed based on a semi-analytical finite element method to overcome the problems. It is a three-dimensional FE program that requires only a two-dimensional mesh by incorporating the semi- analytical method using Fourier series in the third dimension. The computational accuracy and efficiency of the program was verified by analytical verification previously. The experimental verification is carried out in this paper and the results show that the SAFEM is able to predict the mechanical responses of the asphalt pavement. Using the program SAFEM, the impact of heavy traffic loads was analyzed in terms of stress and strain dis- tribution, surface deflection and fatigue life. The results indicate that if the asphalt pave- ment is subjected to the heavy traffic load more, the thicknesses and stiffness of the pavement structural layers should be increased adequately in order to support the surface deflection, The compressive stress in asphalt binder course is relatively large and increases more significantly compared with that in the other asphalt layers when the axle load becomes larger. With comparison of the predicted fatigue life, the increase of the axle load will lead to the destruction of the asphalt pavement extremely easily. 展开更多
关键词 Asphalt pavement response Heavy traffic loads safem Deflection Stress Fatigue
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