Image rotation method for identification of NPW signals in the localization of pipeline leakage

Gas and oil are mainly transported through long-distance pipelines on land. Pipeline leaks lead to severe hazards to the environment and economy and even imperil human lives. Negative pressure wave (NPW)-based methods are fast and effective for leak monitoring and localization. The key problem for an NPW-based method is to determine the NPW and its arrival time, which is characterized by the knee point in the time domain signal. In this paper, an image rotation method is proposed based on the shape characteristic of the time domain signal induced by an NPW. Through image rotation, the knee point turns into the highest point, which is easy to detect. To verify the performance of the proposed method, leakage experiments were conducted on liquid and gas pipeline models. Previously developed FBG pipe fixture sensors were used to detect an NPW. These sensors were equidistantly installed on the pipeline, forming a sensor array. Based on the sensing array, a novel leak localization algorithm was used to compute the leakage position. The experimental results indicated that the image rotation method has good performance for identifying an NPW, even though many noise- and pressure-induced fluctuations exist in the signals. This method enables automated real-time monitoring and has potential for practical application.     

The Thermodynamic Performance of a Double-Acting Traveling-Wave Thermoacoustic Engine with Liquid-Water Piston

A double-acting traveling-wave thermoacoustic engine with liquid-water piston (DTTELP) was proposed by the authors. This article conducted numerical simulation on its performance for the cases of with and without acoustical loads. The effects of mean working pressure and water-piston mass on its non-load performance were firstly discussed. Then, the output performance of this novel thermoacoustic engine under fixed heating temperature was analyzed. Also, influences of different heating temperatures on the performance of this engine were discussed. According to the simulation, the novel double-acting thermoacoustic heat engine (TTHE) is very efficient and a maximum thermal efficiency can reach about 51% when the heating temperature is 1500 K.     

天然橡胶减震垫减震性能研究分析

采用相同结构的两种天然橡胶减震垫,进行了三种条件下的冲击试验和一种条件的振动试验,研究了减震材料硬度、产品质量对减震性能的影响.承受60g以上冲击时,使用该减震垫的产品经受的冲击能量可衰减50%以上,谐振频率在20Hz～40Hz的产品不宜使用该减震垫.     

华北中北部地面运动衰减研究

使用河北省数字地震遥测台网25个台的259条波形记录资料,采用三段几何衰减模型,通过反演得到华北中北部地区剪切波的衰减模型和介质的品质固子Q(f)值,Q(f)=420.8f~(0.384)。研究发现,华北中北部地区的Q值与广东地区很接近,而与其它地区差异较大。     

用雨流计数法统计地震波的动力循环参数

引入雨流计数法统计地震波的动力循环参数。采用雨流计数法不仅可以统计地震动的振动幅度分布,而且可对地震波的动力循环的加载速度、加载顺序进行统计,也可为评估震后结构的损伤、砂土振动液化判别等与动力循环性质有关的研究提供必需载荷基础数据的一种新方法。     

直角拐弯通道中空气冲击波的传播及数值模拟

针对地下通道中空气冲击波的传播,通过试验研究,得到了空气冲击波在直角拐弯通道中传播的衰减系数.同时,应用流体网格法进行了数值模拟,获得了通道直角拐弯前后空气冲击波传播的波形图和流场图.并将两方面的研究成果进行了对比,证明了试验和数值研究方法及研究成果的一致性.     

1998年临猗5.0级地震前Q值的前兆异常

利用西安数字地震遥测台网记录的数字地震资料,采用P波初动半周期残差法求得了1998年7月临猗5.0级地震前后不同路径的Q值变化.发现在地震发生前Q在87(203之间,震后Q在67～164之间,震前震中区附近出现了明显的高Q值异常,表明地震前的高Q值异常可以作为地震预测的一种手段.     

Electrostatic hazards of charging of bedclothes and ignition in medical facilities

We investigated the charge generated on bedclothes (cotton and polyester) during bedding exchange with different humidities and the ignitability of an alcohol-based hand sanitizer (72.3 mass% ethanol) due to static spark with different temperatures to identify the hazards of electrostatic shocks and ignitions occurring previously in medical facilities. The results indicated that charging of the polyester bedclothes may induce a human body potential of over about 10?kV, resulting in shocks even at a relative humidity of 50%, and a human body potential of higher than about 8?kV can cause a risk for the ignition of the hand sanitizer. The grounding of human bodies via footwear and flooring, therefore, is essential to avoid such hazards (or to reduce such risks).     

智能防触电安全帽系统的设计

设计了一种智能防触电安全工作帽系统。在智能防触电安全帽外侧的不同方位上,加装若干感应探头,可探测各个方向场强,使佩戴者能实时了解头部周围电场强弱变化。根据设定,可以发出报警、提示信号。采用了zigbee芯片CC2430无线数据传输模块通讯,具有多点对多点的快速组网功能。每个安全帽都成为一个节点,可与后台安全监督基站通信。各个佩戴者之间可以相互提醒,后台安全监督基站能及时全面督查,为在高压环境下工作人员提供多重安全防护。     

Simulation analysis on structure safety of coal mine mobile refuge chamber under explosion load

In order to check structural strength of coal mine mobiles refuge chamber, and do security evaluation of the mobile refuge chamber, a refuge chamber model was established, then a finite element method was instituted for it to ensure the refuge chamber would not be severely damaged when gas or coal dust explosion suddenly happened. A triangle shock wave with 1.2 MPa over-pressure, 300 ms lasting time was settled. Explicit nonlinear dynamic analysis program was used to simulate response of the refuge chamber. The maximum stress was 244 MPa, located in central part of sides and tail end of the last capsule. The maximum displacement was 29.32 mm, located in central part of sides and tail end of the last capsule. The calculation indicated that the refuge chamber was not obviously damaged. It could reliable work to meet safety requirements. Compared with the reported experimental results, the simulation method was verified. Based on analysis, suggestions were put forward for further improving.