Two-stage identification of interlayer contact loss for CRTS Ⅲ prefabricated slab track based on multi-index fusion

To accurately identify the potential contact loss of the China railway track system(CRTS)III prefabricated slab track,a finite element model with contact loss of self-compacting concrete(SCC)under transient impact was established.Then the vertical accelerations near impact points on the track slab surface were extracted to obtain damage-sensitive indices in the time and frequency domains.The indices were initially normalized to obtain independent items of evidence before the Dempster-Shafer(D-S)evidence theory was used to fuse these into one.Finally,a two-stage identification was performed to identify the damaged SCC area,comprising a rough identification(Stage I)and a precise identification(Stage II).The research results show that the damage indices extracted based on the transient impact response change abruptly at the damage location,and that can be used for damage identification.However,the use of a single index to determine the damage of the impact point may be misjudged.In Stage I,five damage indices of acceleration were fused to magnify the difference between the damaged point and undamaged point,thereby improving the accuracy of finding damage.In Stage II,in the area where more impact points were added,a fusion of three indices of acceleration response,that is,the absolute mean of the time domain,the maximum amplitude of the frequency domain,and the power density ratio,further narrowed down the area where damage exists.As a result,when the contact loss of SCC is greater than 50%along the thickness direction,the identification accuracy can be as high as 70%to 80%.The two-stage identification method proposed in this study can greatly improve the efficiency of interlayer damage detection of slab tracks and is expected to provide effective technical support for damage identification of track structures in the future.

内嵌对称扇形金属谐振腔的MIM可调谐等离子体滤波器

采用有限元方法设计了一种基于金属-电介质-金属(MIM)的内嵌对称扇形金属块的纳米圆形谐振腔滤波器。研究发现,通过改变扇形共振角度、圆形谐振腔半径、耦合距离、共振腔内的介质折射率等主要参数可有效调节该结构的透射特性。该滤波器同时出现两个显著的共振峰,透射率最高可达76%,品质因子最高可达40,能高效实现可调谐双通道带通滤波功能。对结构参量进行调整和优化,相应的谐振波长可分布在近红外波段光纤通信的850 nm和1310 nm通信窗口。该结构为设计光通信领域下一代高性能微纳等离子体滤波器提供了重要的理论依据。

Design theories and maintenance technologies of slab tracks for high-speed railways in China:a review

The durability and reliability of slab track structures are essential for the long-term safety and stable operation of high-speed railways.In order to provide a solid theoretical basis and technical reference for the advancement of high-speed railway quality,this paper comprehensively discusses design theories of slab track structures,service performance evolution and maintenance technologies,and reviews the innovation happening in the industry.On top of that,the damage evolution,fatigue features and durability of slab tracks,which are highly relevant to serviceability,are summarized,and the future research trend of slab track service behaviours is pointed out.In addition,this paper summarizes the rules of establishing standards for damage maintenance,typical solutions for repairing damage and methods of evaluating the maintenance outcomes that combine field tests and numerical simulations.It also envisions a future direction where advanced testing technologies would assist the evaluation of maintenance effects.

A Low-Cost, Portable Optical Sensing System With Wireless Communication Compatible of Real-Time and Remote Detection of Dissolved Ammonia

一个便宜、便携式的光化学传感器基于察觉到能够检测溶解的氨直到 5 ppm 的系统的氨被介绍。在系统，一个光化学传感器为察觉到溶解的氨集中被设计并且制作。传感器把曙红用作被气体可渗透的保护层在玻璃底层上使不能调动的荧光染料。一个紧缩的模块被开发保持光部件，和一节电池动力的微控制器系统被设计读出并且处理测量的数据。没有实验室的要求，系统操作使它合算、高度便携式的仪器。而且，在系统的计算结果能无线被传给 PC，它允许遥远、即时溶解的氨监视。