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41.
介绍了一种新型带放大器的压杆式压电压力传感器。该传感器采用压电陶瓷作为敏感元件;为提高其响应速率,采用带声吸收杆式的结构;并充分考虑到测试专用设备的特殊构造,放置放大器及电池的需要,采用了特殊的外观及内腔结构;为提高传感器及其测试系统的响应速率,采用具有高输入阻抗及50Ω输出阻抗的电压放大器,同时也采用SYV- 50- 7- 1较粗的射频传输电缆,减少了爆炸与冲击模拟信号的传输畸变。该传感器经过爆炸洞及爆炸罐压力测试的反复试验,证明性能的确优异 相似文献
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水位变动下三峡库区消落带植物群落特征 总被引:6,自引:0,他引:6
水位变动是湿地的基本特征之一,对湿地生态系统意义重大。为了解水位变动对三峡库区消落带植物群落的影响,于2010年8月对白夹溪消落带植物群落进行调查,采用TWINSPAN分类法对植物群落进行分类。结果表明:共发现维管植物85种,隶属34科70属;植物群落可划分为18个类型,狗牙根等5种群落为白夹溪消落带代表性植物群落;随着淹水程度的加深,群落组成呈现出由旱生植物到湿生植物的过渡趋势;植物群落香农指数、均匀度指数、丰富度指数和生物量指数随水位梯度呈“∧”型变化趋势,辛普森指数呈“∨”型变化趋势。与156 m蓄水周期相比,植物物种数量、群落类型及组成、多样性均发生改变。水位变动是消落带新生湿地植物群落变化的主要驱动因子 相似文献
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Moti L. Rijal Erwin Appel Ulrich Blaha 《Environmental pollution (Barking, Essex : 1987)》2010,158(5):1756-1762
Sediments affected by fluctuations of hydrocarbon contaminated groundwater were studied at a former military site. Due to remediation, groundwater table fluctuation (GWTF) extends over approximately one meter. Three cores were collected, penetrating through the GWTF zone. Magnetic parameters, sediment properties and hydrocarbon content were measured. We discovered that magnetic concentration parameters increased towards the top of the GWTF zone. Magnetite is responsible for this enhancement; rock magnetic parameters indicate that the newly formed magnetite is in a single domain rather than a superparamagnetic state. The presence of hydrocarbons is apparently essential for magnetite to form, as there is clearly less magnetic enhancement in the core, which is outside of the strongly contaminated area. From our results we conclude that the top of the fluctuation zone has the most intensive geomicrobiological activity probably responsible for magnetite formation. This finding could be relevant for developing methods for simply and quickly detecting oil spills. 相似文献
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Light nonaqueous-phase liquids (LNAPLs) such as gasoline and diesel fuel are among the most common causes of soil and groundwater contamination. Dissolution and subsequent advective transport of LNAPL components can negatively impact water supplies, while biodegradation is thought to be an important sink for this class of contaminants. We present a laboratory investigation of the effect of a water-table fluctuation on dissolution and biodegradation of a multi-component LNAPL (85% hexadecane, 5% toluene, 5% ethylbenzene, and 5% 2-methylnapthalene on a molar basis) in a pair of similar model aquifers (80 cm x 50 cm x 3 cm), one of which was subjected to a water-table fluctuation. Water-table fluctuation resulted in LNAPL and air entrapment below the water table, an increase in the vertical extent of the LNAPL source zone (by factor 6.7), and an increase in the volume of water passing through the source zone (by factor ~18). Effluent concentrations of dissolved LNAPL components were substantially higher and those of dissolved nitrate lower in the model aquifer where a fluctuation had been induced. Thus, water-table fluctuation led to enhanced biodegradation activity (28.3 mmol of nitrate consumed compared to 16.3 mmol in the model without fluctuation) as well as enhanced dissolution of LNAPL components. Despite the increased biodegradation, fluctuation led to increased elution of dissolved LNAPL components from the system (by factors 10-20). Hence, water-table fluctuations in LNAPL-contaminated aquifers might be expected to result in increased exposure of downgradient receptors to LNAPL components. Accordingly, water-table fluctuations in contaminated aquifers are probably undesirable unless the LNAPL is of minimal solubility or the dissolved-phase plume is not expected to reach a receptor due to distance or the presence of some form of containment. 相似文献
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在分析电网电压波动、闪变的定义和各国对电压波动、闪变研究现状的基础上,介绍了几种测量和分析电压波动及闪变的设备及其对电压波动和闪变的测量和评估方法。 相似文献
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为探索浅层地下水氮浓度及水位波动对土壤剖面中氮转化功能基因丰度的影响,以洱海近岸农田原状土壤剖面为对象,研究了模拟常规氮浓度的浅层地下水进行水位波动(SND)和持续淹水(SNF),以及无氮浓度的浅层地下水位波动(0ND)后土壤剖面氮浓度和氮转化功能基因丰度的变化,探讨了土壤因子与功能基因丰度的关系。结果表明:SNF、SND和0ND处理较试验前土壤剖面中溶解性总氮(TDN)浓度分别降低了44%、21%和30%,NO3−-N浓度分别降低了55%、28%和38%。同时,0ND和SNF处理较SND处理土壤剖面中反硝化功能基因丰度分别降低20%和1%,厌氧氨氧化功能基因丰度则分别增加68%和7%,硝化功能基因丰度分别降低34%和增加23%,土壤含水率(MC)、NH4+-N、NO3−-N和TDN均为功能基因丰度变化的重要驱动因子。土壤剖面持续淹水会显著降低溶解性氮浓度,浅层地下水波动及水中氮浓度引起的土壤剖面干湿交替和氮浓度变化是氮转化功能基因丰度变化的主要驱动力。 相似文献