双ZBS2型酒杯塔输电线路雷电绕击特性研究

通过建立缩小比例为25:1的双ZBS2型酒杯塔输电线路模型,对其进行长间隙放电,研究了塔头、避雷线保护角、地面倾斜度等因素对雷击绕击率的影响。结果表明:杆塔对雷电先导具有吸引作用,雷击杆塔附近时,线路绕击率较低,从杆塔到档距中央,绕击率呈现一种先增大后减小的趋势;随着避雷线保护角由正到负变化,绕击概率随之降低;线路绕击概率随地面倾斜角增大,而呈现先增大后减小的趋势。本研究结果可指导企业输配电线路的雷电防护工作,为线路绕击防护装置的研发提供数据支持。     

A Two‐Decade Watershed Approach to Stream Restoration Log Jam Design and Stream Recovery Monitoring: Finney Creek,Washington

A federal, state, and private partnership leveraged resources and employed a long‐term, systematic approach to improve aquatic habitat degraded by decades of intensive forest management in Finney Creek, a tributary to the Skagit River of Northwest Washington State. After more than a decade of work to reduce sediment sources and the risk of landslides within the watershed, log jam installation commenced in 1999 and progressed downstream through 2010. Log jam design was adapted as experience was gained. A total of 181 log jams, including 60 floating log ballasted jams, were constructed along 12 km of channel. The goal was to alter hydraulic processes that affect aquatic habitat formation along 39 km of stream with emphasis on 18.5 km of lower Finney Creek. Aquatic habitat surveys over a five‐year period show an increase in the area of large pools and an accompanying increase in residual and maximum pool depth in the lower river reach. Channel cross sections show a generally deeper channel at the log jams, better channel definition in the gravel deposits at the head of the log jams, and improved riffle and thalweg development below the log jams. Stream temperature in the upper river decreased by 1.0°F in the first three years, and 1.1°F in the lowest treated reach over nine years. There is a trend of less stream heating over the restoration time period. Photo points show that riparian vegetation is recolonizing gravel bars.     

2024-T62铝合金薄板长裂纹腐蚀扩展研究

通过变化应力比、预腐蚀时间、试验环境,开展2024-T62铝合金薄板长裂纹扩展试验。对试验结果进行处理与分析,给出腐蚀环境下2024-T62铝合金裂纹扩展Paris公式或Walker公式的材料常数,确定上述变化因素对2024-T62铝合金薄板长裂纹扩展速率的影响规律。     

雪冰中持久性有机污染物的研究进展

雪冰是温带和极地生态系统中最重要的环境组份,它们不仅影响了能量平衡和水循环,而且也能直接影响当地、区域以及全球环境范围内的化学行为。降雪能很有效地从大气中清除颗粒和气相的POPs。本文简要介绍了雪冰环境中持久性有机污染物研究的科学意义,着重综述了POPs在极地和高海拔地区雪冰中的环境化学行为和雪冰中POPs的历史环境记录,并讨论了雪冰中POPs浓度的不确定性。持久性有机污染物从大气到冰川的过程并不容易理解,半挥发性有机化合物在沉积后的浓度存在不确定性。有机物沉积在积雪中后,随着积雪的老化和变形,它们能够随着融水迁移或者又挥发到大气中。全文最后对未来雪冰中POPs的研究需要进行了展望,并提出四点今后需加强研究的内容。由于青藏高原位于人类居住的低纬度高海拔地区,可能在POPs全球输送过程中起到重要的作用,今后需加强青藏高原地区雪冰中持久性有机污染物的研究;有机污染物在雪冰中主要是通过光化学反应进行转化,雪冰中有机污染物的光化学反应机理研究必须引起重视;随着雪冰样品前处理和分析测试技术的提高,将会推动雪冰中痕量POPs的环境变化记录研究的发展;通过建立模型模拟预算和评价POPs在积雪中的物理化学行为,也可以利用模型模拟POPs在老雪中的命运,确定其在融水中成比例蒸发和渗浸的速率。     

嗜热地芽孢杆菌DM-2烃降解特性研究

从油田地层水中分离到1株嗜热解烃菌(地芽孢杆菌DM-2),通过研究该菌株在不同条件下降解原油的性能以及在最适条件下降解烃的特性发现：地芽孢杆菌DM-2可在45～70℃、pH 4.0～10.0、 0.2%～3.0%的盐离子浓度缺氧条件下降解原油烃类,其降解原油烃的最适温度和pH值分别为60℃和7.0.在此条件下,该菌可乳化液体石蜡作为碳源进行生长;气相色谱和红外光谱进一步分析表明,其能降解原油中的C14～C30的直链烷烃、支链烷烃和芳香烃类,并能降解C16～C36的长链单烷烃,其中对C28的降解量最高,达88.95%.DM-2菌株代谢烷烃的产物之一为脂肪酸,经液相色谱和质谱分析代谢十六烷产生的脂肪酸为乙酸,5 d产量达0.312 g/L,说明其采用次末端氧化途径氧化烷烃,之后进入β-氧化途径代谢.DM-2菌株在高温缺氧的极端环境下对烃的乳化、降解和产酸特性使其在高温石油污水的生物处理和开采重质原油方面具有潜在的应用价值.     

油气长输管道工程风险评价发展及现状

介绍了油气长输管道工程风险评价的国内外研究概况、进展、主要评价方法及存在的问题.     

Towards a natural disaster intervention and recovery framework

Contemporary responses to facilitate long‐term recovery from large‐scale natural disasters juxtapose between those of humanitarian agencies and governments and those of the affected community. The extent to which these mechanisms articulate is crucial to the recovery propensity of the affected communities. This research examines such action by exploring the relationship between the scale of post‐disaster response interventions, the extent of community participation in them, and their impact on community recovery, using a community wealth capital framework. The investigation was applied to a study of the longer‐term community recovery of the island of Vilufushi, Republic of Maldives, which was almost completely destroyed by the Indian Ocean tsunami of 26 December 2004. Data were analysed through the employment of a pattern match technique and a holistic recovery network analysis. The research framework, informed by the case‐study results, other long‐term recovery evaluations, and existing resilience theory, is reconfigured as a testable roadmap for future post‐disaster interventions.     

HDPE土工膜长期性能稳定性的研究进展

垃圾填埋场底部高密度聚乙烯(HDPE)土工膜会因氧化降解而使防渗性能降低,对环境带来二次污染风险,因此,HDPE膜的长期稳定性是值得关注的问题,但国内相关研究甚少。HDPE膜的降解过程可分为3个阶段,主要受自身性质、温度、接触介质和衬垫结构等因素的影响。文章重点综述了国外研究HDPE膜长期稳定性的试验方法,归纳了相关的数学模型,并根据存在的问题提出了建议。室内试验一般采用老化试验,包括浸泡试验和模拟试验,二者均能加快HDPE膜的老化进程。前者一般将试样完全浸泡于研究介质中试验,试验值较为保守;后者将样品置于模拟的衬垫构造中试验,结果更接近实际。数学模型采用Arrhenius模型,精度和所需参数取决于老化试验,现阶段大部分计算结果较片面,完善试验是后续工作的重点。     

基于CNN_LSTM模型的复杂支路故障电弧检测*

在低压交流配电系统中,当多支路并联的复杂系统的某1支路中出现串联电弧故障时,识别难度大幅提升。为了预防此类情况引发的电气火灾,提出1种卷积神经网络(CNN)与长短时记忆网络(LSTM)结合的串联故障电弧检测方法。首先,搭建实验平台用以采集不同负载在不同支路下发生故障时和正常工作时的干路电流数据;然后,构建CNN_LSTM模型并做出相应改进,将电流数据直接输入到模型中,由模型自主提取波形特征并进行分类。研究结果表明:该方法可以快速、准确地识别出电弧故障,准确率达99.04%以上,且能够较为准确地检测出是哪类负载所在的支路发生电弧故障,准确率达97.90%,可为复杂支路下的电弧故障识别研究提供参考。     

狼尾草根系对阿特拉津长期胁迫的氧化应激响应

通过盆栽实验研究了抗性植物狼尾草根部丙二醛(MDA)、脯氨酸(Pro)、抗坏血酸(As A)含量及超氧化物歧化酶(SOD)、谷胱甘肽还原酶(GR)等氧化应激生理指标对不同浓度阿特拉津长期(48 d)胁迫的响应规律。结果表明:当阿特拉津胁迫浓度分别高于20 mg·kg~(-1)和50 mg·kg~(-1)时,狼尾草根系的MDA与Pro含量较对照组显著升高(P0.05);随着阿特拉津胁迫浓度的增加,狼尾草根部SOD和GR活性呈先升高后降低的趋势,其中当阿特拉津胁迫浓度为20 mg·kg~(-1)时,SOD和GR活性达到最大值;供试植物根系中As A含量与阿特拉津胁迫浓度呈正相关。综上,中低浓度(≤20 mg·kg~(-1))阿特拉津处理没有对狼尾草的根系产生明显的氧化胁迫效应,狼尾草根系的上述抗氧化应激生理指标对于发挥阿特拉津抗性起着重要的作用。