陶瓷材料放射性衰变时间及最佳平衡周期研究

简述了有关放射性样品衰变平衡及平衡时间的基本理论,运用碘化钠γ谱仪对衰变时间介于0～27 d区间内的三组陶瓷样品进行放射性比活度测定,采取t检验法分析了同一样品在0d～7d、7d～12d、15 d、21 d等不同衰变时间条件下,放射性核素226Ra、232Th、40K比活度测试结果之间的差异程度,通过实验验证陶瓷样品衰变时间对其放射性测定结果准确性的影响.研究表明,当每组检测结果数据的显著性差异水平为5％,若兼顾科学性和经济性,则陶瓷样品的最佳放射性衰变时间应为至少21 d.     

深圳大气PM2.5中水溶性有机物的来源特征

对2017年9月～2018年8月深圳市北部大气PM_2.5中水溶性有机物(WSOM)的质量浓度、质谱及来源结构进行测量和分析.结果表明:PM_2.5的质量浓度为(32.3±18.4)μg/m³,WSOM的质量浓度为(9.4±5.7)μg/m³,占颗粒物总有机物的(77.6%±14.0%).质谱分析显示,WSOM的氧碳比(O/C)平均值达到(0.57±0.09),属于二次有机物的O/C值范围,且生物质燃烧排放的离子碎片C₂H₄O₂⁺的丰度显著,说明WSOM的来源中有显著的生物质燃烧排放的有机气溶胶.为了明确WSOM的来源结构,利用正矩阵因子分解法(PMF)模型进行来源解析,发现3个合理因子:高氧化态有机气溶胶(MO-OOA),低氧化态有机气溶胶(LO-OOA)和生物质燃烧(BBOA),贡献比例分别为51.7%,31.8%和16.5%.MO-OOA和BBOA贡献浓度均呈现秋冬高、春夏低的季节变化特征,反向轨迹分析显示其与...     

Warm forming die design,Part II: Parting surface temperature response characterization of a novel thermal finite element modeling code

The majority of the research activities in the area of warm forming are concentrated on demonstrating or simulating the improved formability associated with forming lightweight materials such as aluminum alloys at elevated temperatures. However, the ability to design the proper thermal management system within the forming tool is a critical aspect to delivering this technology as a viable, stable production alternative to traditional stamping. This work begins to address the thermal stability issues of this process by examining the impact of process cycle time on the parting surface temperature response. Cycle times of 10, 15, 30, and 300 s were evaluated using a reciprocating surface and a self-heated experimental block of 1020 steel fitted with resistance cartridge heaters. The presented results indicate that cycle time does not significantly impact the steady-state temperature response at the parting surface for a well-insulated die that has proper thermal management. Parting surface experimental results were compared to values obtained numerically and through the use of the novel thermal finite element analysis software PASSAGE/Forming^®.     

火旋风的模拟实验研究

模拟火旋风的实验研究，应用热成像方法获得了火旋风温度场的结构，测量得到火旋风火焰特有的大高度直径比的物理现象；火焰高度比相同燃料，油液面积的油池火高度高，趱戏比油池火直径小。火旋风的切向速度比油池火大，卷吸效果好，可用这一特点来研究熄灭火旋风的火灾。对火旋风火灾机理的研究提出了一种有效的实验方法。     

PWM变频驱动电机轴电压与轴电流的测试方法

PWM变频器的广泛应用大大改善了电机调速性能,但是,由于PWM变频器共模电压在电机内部耦合电容作用下,形成轴电压和轴电流,会引起轴承早期失效危及系统安全运行。轴电流问题的研究包括对轴电流的分析、预测和抑制。然而这些过程需要轴电压和轴电流的准确测量进行验证和比对分析。设计合理而有效的测量装置和测量方法是非常重要的一环。在分析轴电流产生机理的基础上,对现有的各种轴电流测量方法和轴承阻抗特性测试方法进行介绍,总结对比这几种方法的优缺点,为轴电流的测试平台的新设计提供参考。     

西山白家庄矿8煤可排放硫含量的测定

针对西山白家庄矿8煤的实际情况，初步尝试了测定其硫的实际排放状况，探索了温度及添加剂对可排放 硫含量的影响。结果表明该煤的自身固硫率不高； 添加9％的CaO可排放硫含量可以达到城市窑（锅）炉对硫分的要求；同时试验表明MgO对可排放硫影响不大。     

污水处理系统臭气污染问题的研究

通过对污水处理系统中臭气来源和特征的分析 ,系统地阐述臭气产生的原因和测定、处理方法 ,指出对臭气控制是今后污水处理系统发展的方向之一。     

微波、毫米波电磁材料特性及参数宽频带测试方法

讨论一种微波、毫米波电磁材料特性和参数宽频带测量方法——自由空间法。给出了该测量方法的测试原理和基于国产AV3630幅相接收机为基础的测试系统构成及系统扩频方法,论述了自由空间测试法需注意的关键技术问题。     

低水平放射性废水中钚的分析方法研究进展

钚是重要的核燃料,也是一种极毒的放射性核素,在核燃料循环和放射性废物处置过程中占有重要地位.近些年来,钚在自然水体中的含量、分布引起人们的关注.科研工作者针对低水平放射性废水,核设施周围自然水体,核试验、核事故情况下可能污染的自然水体等,建立了一些钚的分析方法.作者在对这些方法进行了比较的基础上,提出了一种在盐酸体系中用TEVA树脂负压微色谱柱液闪法将水溶液中钚与其他锕系元素及金属离子分离并测量的新方法.该方法有望在日常和应急监测中的得到应用.     

The potential implementation of green infrastructure assessment using high-resolution National Agriculture Imagery Program data for sustainable hazard mitigation

As green infrastructure gets its attention in hazard mitigation, it is necessary to improve general understanding on what makes green infrastructure important for hazard and resiliency research. To better understand how green infrastructure fits with more traditional notions of structural and nonstructural mitigation, this study examines the relationship between green infrastructure and ‘structural and nonstructural’ mitigation approaches for hazard mitigation. Also, this study discusses a new measurement of locational aspects and spatial patterns of green infrastructure by utilizing high-resolution data in urban areas, and its potential implementation in hazard mitigation. Compared to previous research using land-use land-cover datasets, the normalized difference vegetation index (NDVI) utilizing National Agriculture Imagery Program dataset provides an ability to capture green infrastructure in greater detail. A visual comparison suggests that the NDVI data are able to capture and identify more types of ‘green’ land uses in Harris County. The total green infrastructure percentages for Harris County, Texas, based on 1-m high resolution were found to be 61.5% of the area, compared to the 51.5% based on the National Land Cover Database. This study provides support for utilizing high-resolution data to establish guidelines for green infrastructure’s spatial characteristics and sustainable hazard mitigation. The outcomes of this study will be helpful in the strategic planning and implementation of green infrastructure in urban areas with hazard issues.