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891.
892.
在低放射性环境样品进行测量时,要求测量仪器具有较好的稳定性。仪器在工作一段时间后,要了解所作的测量数据是否具有统计重复性,仪器指标发生的变化是否在统计基础上,仪器工作是否正常,绘制仪器质量控制图是一种有效方法。通过绘制质量控制图表的方法,可随时了解仪器的稳定性和仪器的技术指标,直观地展示出测量过程是否处于统计控制中。以确保仪器的测量精度。 相似文献
893.
The degradation of nonylphenol (NP) in aqueous solution with UV, H2O2/UV, and Fenton/photo-Fenton processes was studied. The efficacy of direct and hydrogen peroxide photolysis proved to be dependent on the pH value. The addition of H2O2 to UV treatment improved NP degradation. The application of UV photolysis and the H2O2/UV system at pH 7 resulted in low pseudo first-order rate constants at 10-4 sec-1. In the experiments at elevated pH values the pseudo-first order rate constants increased to 10-3 sec-1. The efficacy of the Fenton process was lower in comparison with UV and hydrogen peroxide photolysis. The addition of UV irradiation to the H2O2/Fe2+ system substantially improved NP degradation efficacy. In terms of performance, the photo-Fenton process was similar to the H2O2/UV process. The most favourable process for complete nonylphenol degradation considering both operational cost and treatment efficacy was H2O2/UV at pH 11 and 250 mol/L H2O2. 相似文献
894.
Satoru Isoda 《环境科学学报(英文版)》2013,(S1):S172-S179
Power conversion efficiency of p-i-n type microcrystalline silicon (c-Si:H) solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. The effect of the excitonic state on the charged carrier generation has been studied compared to a conventional scheme in which only charged carriers are taken into account for the operation of the solar cells. A numerical model has been developed to calculate current-voltage characteristics of solar cells on the basis of two types of charged carrier generation processes (exciton process and charged carrier process). The light trapping effect due to a textured back surface reflector (BSR) was embedded in the numerical model by using the effective medium theory in combination with the matrix method in the field of the electromagnetic theory of light. As an application of this modeling, it was found that the reported data of the power conversion efficiency were not explained by the conventional charged carrier process model and that the combined model of the charged carrier process with the exciton process well explains the performance of the p-i-n type c-Si:H solar cells. In this way, the typical power conversion efficiencies were estimated to be 10.5% for the device (i-layer thickness: 1.8 m) with the BSR (period: 600 nm; height: 250 nm) and 8.6% for the device with the flat reflector under the condition that the fractions of the exciton process and charged carrier process were 60% and 40%, respectively. 相似文献
895.
Power conversion efficiency of p-i-n type macrocrystalline silicon (µc-Si:H) solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. The effect of the excitonic state on the charged carrier generation has been studied compared to a conventional scheme in which only charged carriers are taken into account for the operation of the solar cells. A numerical model has been developed to calculate current-voltage characteristics of solar cells on the basis of two types of charged carrier generation processes (exciton process and charged carrier process). The light trapping effect due to a textured back surface reflector (BSR) was embedded in the numerical model by using the effective medium theory in combination with the matrix method in the field of the electromagnetic theory of light. As an application of this modeling, it was found that the reported data of the power conversion efficiency were not explained by the conventional charged carrier process model and that the combined model of the charged carrier process with the exciton process well explains the performance of the p-i-n type μc-Si:H solar cells. In this way, the typical power conversion efficiencies were estimated to be 10.5% for the device (i-layer thickness: 1.8 μm) with the BSR (period: 600 nm; height: 250 nm) and 8.6% for the device with the flat reflector under the condition that the fractions of the exciton process and charged carrier process were 60% and 40%, respectively. 相似文献
896.
人工渗滤系统以其建设费用低、管理运行方便、脱氮效果好等优势受到人们的普遍关注。该实验以海水养殖废水为处理对象,对人工渗滤系统的运行条件和氮素去除情况进行了研究。结果表明,水力负荷、水力运行周期和保水段高度对氮素的去除均有影响但影响各不相同。当水力负荷为20 cm3/(cm3/(cm2·d),运行周期为6 h/6 h时,总氮和氨氮的去除率较高,分别达到54.88%和89.69%,而硝态氮和亚硝态氮浓度保持稳定。提高保水段高度后,厌氧段得到扩充,在此条件下,氨氮的去除率基本保持不变,而总氮、硝态氮和亚硝态氮去除率明显升高。 相似文献
897.
美人蕉生态护坡对径流污染净化作用的初步研究 总被引:1,自引:0,他引:1
2010-04-10月,研究了合肥市南淝河美人蕉生态护坡对河道的水质改善作用。试验用水取自南淝河,TSS、TN、NH4+-N、TP和COD的平均浓度分别是94.1,5.42,2.98,0.202和55.5 mg/L,河水经流生态护坡后,相应的平均去除率分别为:76.4%,45.6%,57.5%,40.1%和29.0%。另外,考察了植物对土壤微生物(细菌、真菌、放线菌)数量的影响,美人蕉护坡微生物的数量显著多于无植物坡岸(p<0.01),微生物总数分别为:3.17×107和0.830×107cfu/g。由此,植物护坡兼具净化和生态景观效应。 相似文献
898.
899.
采用固体核径迹法和热释光剂量计,对成都市不同建造年代、建筑类型、建筑结构、建筑材料以及楼层的100间居室进行了室内环境氡浓度和辐射水平的测量.调查结果表明:成都市居室环境中氡浓度范围为(8.4~177.1)Bq/m3,算术平均值为(39.5±22.9)Bq/m3,低于世界平均水平;辐射水平的范围为(74.7~164.7)nSv/h,算术平均值为(122.0±16.2)nSv/h,与室内氡浓度无相关性.不同建筑年代、建筑类型、建筑楼层和建筑材料的房屋室内环境氡浓度水平有显著差异.室内环境氡及其子体和辐射照射所致公众的平均年有效剂量分别为0.99mSv和0.85mSv. 相似文献
900.
我国化肥施用量持续增长的原因分解及趋势预测 总被引:20,自引:0,他引:20
我国化肥大量使用在提高农业生产的同时也对环境产生了严重的负面影响。目前国内外学术界对我国化肥施用量持续增长的原因以及未来我国化肥使用的发展趋势还存在较大争议。论文利用过去20 a 间我国化肥施用量的相关数据, 对化肥施用量持续增长的成因进行了分解。研究结果表明:化肥使用强度的增长是我国化肥施用总量增长的主因, 但从2007 年以来, 使用强度的贡献不断下降, 播种面积调整的贡献有所提高。根据分解结果并利用“中国农业可持续发展决策支持系统”(CHINAGRO) 预测了2020 年全国和各省化肥使用量情况。模型分析结果表明如果不采取措施, 我国未来化肥的使用总量和单位播种面积化肥施用量将依然呈现增长趋势, 且单位面积化肥用量将长期高于225 kg/hm2的国际上限标准。预计到2020年我国化肥总施用量和单位播种面积化肥施用量比2010 年分别提高2%和4.3%。东部地区单位播种面积化肥施用量较高, 2020 年广东、福建、天津、北京等省(市) 化肥单位面积施用量将接近或超过600 kg/hm2, 这将对当地环境造成巨大压力。 相似文献