厚壁管道内部缺陷的超声柔性探头仿真分析

根据超声柔性探头的原理,介绍了柔性探头的成像模型3针对核电站等领域广泛使用的不锈钢厚壁管道,基于CIVA无损检测仿真软件,建立了厚达72.3 mm的厚壁管道模型,分别仿真了柔性探头及刚性探头在检测裂纹、分层及夹杂3种管道常见缺陷时的缺陷响应,定性及定量的比较了2种探头检测结果的区别.结果表明:柔性探头在检测厚壁管道等曲面形工件的10 mm×2mm、倾斜的横向裂纹,5 mm×5 mm的分层缺陷和直径4 mm、内部为铝的夹杂缺陷时具有较大的优势.     

板式橡胶支座在缺陷状态下的力学性能分析

对板式橡胶支座在带缺陷状况下的抗压、抗剪力学性能进行分析,将支座的竖向变形及横向剪切变形结果与相同规格的合格支座比较,分析支座在带缺陷状态下受压变形及剪切变形值的变化规律,可为橡胶支座的设计及使用提供参考.     

Estimating arterial link speed using conventional road detectors

Abstract

In response to an initiative to develop an advanced traffic information system in Bangkok, this paper explores practical guidelines for the optimal location of road sensors, such that the data collected on spot speeds reflect an entire link's average speed. In particular, the authors use microsimulation software to investigate optimal detector locations, using the sum of squared errors and root mean squared errors. The analysis hypothesizes that road segments are 0.4, 0.6, 0.8, 1.0, 2.0 and 3.0 km in length and are specially designed to replicate typical arterial streets in Bangkok. The results show that a single detector location can produce good estimates of link speed only for segments that are shorter than 1.0 km. For distances of 1.0 km or more, the results suggest that two detectors be used for good link speed estimates under all traffic conditions.     

路面平整度检测技术现状与发展分析

路面平整度是衡量路面质量的重要标准,也是运输经济的一个重要指标。 综合当前路面平整度状况,对现有路面平整度的检测方法和相关问题进行了总结,以促进相应方法在路面质量检测中的合理使用与推广。     

混凝土桩基础超声波探缺原理及典型缺陷对比验证分析

超声波无损检测是混凝土桩基础完整性检测中最常采用的方法之一,由于钢筋混凝土材料组成的复杂性和超声波声学参数的敏感性,对检测人员掌握仪器的工作原理和工程经验提出越来越高的要求。详细阐述混凝土桩基础超声波检测的原理,并结合工程实践,对经过钻芯验证过的典型缺陷的波形及其声学特征做了详细的对比分析,可为检测人员和检测仪器的进一步智能化提供可靠的经验参考。     

超声波再生颗粒活性炭的试验研究*

利用超声波吸附对氯苯酚颗粒状活性炭进行再生,探讨超声波功率、作用时间、再生液温度、再生次数等对再生过程的影响．实验结果表明：在超声波频率50 kHz、功率110 W、再生温度30℃、再生液为含饱和氩气去离子水,作用时间20 min的条件下,活性炭再生效率为64．5％．再生两次所得活性炭再生效率为67．8％,换水超过两次再生效率增加不明显．超声波再生活性炭效率较高,炭损失率很低．     

基于 LaBr3探测器和数字化多道的便携式γ谱仪研制

连续监控燃料元件的完整性是保证反应堆安全运行和人员辐射安全的重要措施之一。介绍一种便携式γ谱仪的研制情况,用于主冷却剂中放射性核素的现场识别及其活度浓度的监测分析。采用铝合金材料包裹1″×1″的 LaBr3晶体、CR173型光电倍增管和前置放大器作为探测器。脉冲信号经线性放大器和 AD变换后进入以FP-GA为核心的数字化多道系统,再用 ARM嵌入式系统完成能谱数据的读取、分析处理和人机交互。测试结果表明,该便携式谱仪的主要指标能够初步满足一回路水现场监测的需求。     

Using stop bar detector information to determine turning movement proportions in shared lanes

Turning vehicle volumes at signalized intersections are critical inputs for various transportation studies such as level of service, signal timing, and traffic safety analysis. There are various types of detectors installed at signalized intersections for control and operation. These detectors have the potential of producing volume estimates. However, it is quite a challenge to use such detectors for conducting turning movement counts in shared lanes. The purpose of this paper was to provide three methods to estimate turning movement proportions in shared lanes. These methods are characterized as flow characteristics (FC), volume and queue (VQ) length, and network equilibrium (NE). FC and VQ methods are based on the geometry of an intersection and behavior of drivers. The NE method does not depend on these factors and is purely based on detector counts from the study intersection and the downstream intersection. These methods were tested using regression and genetic programming (GP). It was found that the hourly average error ranged between 4 and 27% using linear regression and 1 to 15% using GP. A general conclusion was that the proposed methods have the potential of being applied to locations where appropriate detectors are installed for obtaining the required data. Copyright © 2016 John Wiley & Sons, Ltd.     

Isocyanic acid and ammonia in vehicle emissions

Vehicles are considered to be an important source of ammonia (NH₃) and isocyanic acid (HNCO). HNCO and NH₃ have been shown to be toxic compounds. Moreover, NH₃ is also a precursor in the formation of atmospheric secondary aerosols. For that reason, real-time vehicular emissions from a series of Euro 5 and Euro 6 light-duty vehicles, including spark ignition (gasoline and flex-fuel), compression ignition (diesel) and a plug-in electric hybrid, were investigated at 23 and −7 °C over the new World harmonized Light-duty vehicle Test Cycle (WLTC) in the Vehicle Emission Laboratory at the European Commission Joint Research Centre Ispra, Italy. The median HNCO emissions obtained for the studied fleet over the WLTC were 1.4 mg km⁻¹ at 23 °C and 6 mg km⁻¹ at −7 °C. The fleet median NH₃ emission factors were 10 mg km⁻¹ and 21 mg km⁻¹ at 23 and −7 °C, respectively. The obtained results show that even though three-way catalyst (TWC), selective catalytic reduction (SCR), and NOx storage catalyst (NSC) are effective systems to reduce NOx vehicular emissions, they also lead to considerable emissions of the byproducts NH₃ and/or HNCO. It is also shown that diesel light-duty vehicles equipped with SCR can present NH₃ emission factors as high as gasoline light-duty vehicles at both, 23 and −7 °C over the WLTC. Therefore, with the introduction in the market of this DeNOx technology, vehicular NH₃ emissions will increase further.     

基于超声导波的钢桥面板纵肋对接焊缝疲劳裂纹检测方法

纵肋对接焊缝疲劳开裂作为钢桥面板结构的重要失效模式之一,严重危害桥梁结构耐久和安全运营。通过引入超声导波技术,结合对接焊缝的几何特点与疲劳失效特征,建立了基于超声导波的钢桥面板纵肋对接焊缝疲劳裂纹检测方法。首先搭建了超声导波裂纹检测试验系统,并结合钢桥面板纵肋对接焊缝疲劳试验,对超声导波检测纵肋对接焊缝裂纹的适用性和准确性进行了验证。在此基础上,通过数值分析方法探究了超声导波在纵肋对接焊缝局部区域的传播机制,并进一步分析了不同焊缝与裂纹参数对超声导波传播的影响规律。研究结果表明:采用超声导波方法能够有效检测钢桥面板纵肋对接焊缝的疲劳裂纹,并确定疲劳开裂的位置;超声导波有限元理论分析与试验测试结果符合较好,验证了有限元模型的正确性;采用单面激励的方式在纵肋中形成的超声导波包括A₀和S₀模态,其中A₀模态占主要部分,超声导波传递至焊缝形成的反射波以A₀模态为主,而较深裂纹形成的反射波以S₀模态为主;不同焊缝和裂纹参数对超声导波的反射波和透射波表现为差异性的影响。所采用的基于超声导波的对接焊缝疲劳裂纹检测方法,可为钢结构桥梁疲劳损伤的检测与监测提供科学依据。