Detecting damage to offshore platform structures using the time-domain data

A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first constructed using the time-domain of noise data. A sensitivity matrix consisting of the first differential of the autoregressive coefficients of the time series models with respect to the stiffness of structural elements was then obtained based on time-domain response data. Locations and severity of damage may then be estimated by solving the damage vector whose components express the degrees of damage to the structural elements. A unique aspect of this detection method is that it requires acceleration history data from only one or a few sensors. This makes it feasible for a limited array of sensors to obtain sufficient data. The efficiency and reliability of the proposed method was demonstrated by applying it to a simplified offshore platform with damage to one element. Numerical simulations show that the use of a few sensors＇ acceleration history data, when compared with recorded levels of noise, is capable of detecting damage efficiently. An increase in the number of sensors helps improve the diagnosis success rate.     

美国舰载电子战系统的发展

介绍美国舰载电子战系统的发展历程以及装备的研制、改进情况,指出在现代战争中发展舰载电子战系统的优势和重要性,探讨几种电子战装备的性能及其特点,论述美国舰电子战系统的发展分析.     

Prenatal assessment of normal fetal pulmonary grey-scale and lung volume by three-dimensional ultrasonography

Objective To quantitatively analyze the fetal lung echo and right lung volume in the third trimester by real-time three-dimensional ultrasound (3-D US) and evaluate the feasibility of fetal lung maturity. Methods A total of 732 women with normal singleton pregnancies between 28 and 42 weeks of gestation underwent ultrasound examination. The 3-D US equipment with a 3.5-5MHz transabdominal transducer was used for the fetal biometric measurement. The echogenicity ratio between fetal lung and liver was compared. The fetal lung volume was calculated by the rotational multiplanar technique for volume measurement (VOCAL). Results The right fetal lung volume increased with the increase of gestational age with a linear positive correlation (r=0.884, P<0.01). After 34 weeks, the echogenicity ratio of fetal lung to liver was more than 1.1. Conclusion The echogenicity of lung/liver and fetal lung volume could be used as normal fetal predictable indicators for fetal lung maturity.     

基于FEKO的球体电磁散射分析

使用电磁场仿真软件进行雷达目标的电磁散射分析已成为重要的手段之一.利用FEKO软件的EditFEKO界面强大的图形编辑和数值分析功能,实现电磁场偏微分方程的有限元解法.与参考资料上的实验结果进行比较,得出运算速度快,误差小,便于进一步工程实践等优点.     

铁路建设标准化管理的实践与思考

介绍我国铁路建设形势、铁路建设标准化管理的基本框架要求,叙述上海铁路局推行标准化管理的基本特点,重点阐述贯彻标准化管理实践中的突出做法以及对有关问题的思考。     

传感器组故障自诊断自修正方法

提出用RBF神经网络对传感器组中的各个输出进行预测,若预测值与输出值发生较大的偏差,可能是传感器故障或设备故障,运用传感器之间的冗余率,进一步判断传感器是否发生故障,进而采用对应的诊断策略。     

L18型粮食漏斗车研制

阐述了L18型粮食漏斗车的研制过程、技术参数、特点、结构，介绍了该车的优化设计、试验、效益和运用情况。     

锰的心血管毒性

体内外实验表明，锰能迅速富集在动物心脏，引起心脏收缩功能降低和血压下降，这可能与心肌线粒体受损和Ca^2 通道受阻有关。迄今为止，锰的心血管毒性实验研究主要局限于体外试验、急性和亚急性毒性试验，尚缺乏慢性毒性试验的资料，其毒作用性质及其转归过程尚未完全明了，有必要深入探讨。     

通过微气泡控制湍流边界层减阻的研究与进展

本文介绍了微气泡减阻的研究现状，阐述了湍流状态下微气泡减阻机理，对平板、轴对称体和船模等典型微气泡减阻试验做了简述后，总结了微气泡减阻理论研究的成果及相关的数学模型，最后介绍了微气泡减阻在实船上应用的现状和前景。     

企业铁路调度集中系统的研究与实现

针对企业铁路运输作业的特点，提出了企业铁路调度集中系统中联锁控制、通信等方面的设计原则与方法，并对企业调度集中系统的权限设置、安全与风险控制方案进行了讨论，最后介绍了一个应用实例。