纳米镍／铁对四氯乙烯快速脱氯试验   总被引：5，自引：0，他引：5  

黄园英　刘菲汤鸣皋  孙文超 《岩矿测试》2005,24(2):93-96101

实验室合成的纳米Ni/Fe(粒径20~60nm,比表面积为52. 61m2 /g),在固液比相对较低条件下(5. 4g/L),对四氯乙烯(PCE)能够快速并完全脱氯,在6h时,脱氯率为99. 70%,反应符合准一级反应动力学方程,标准化反应速率常数kSA为3. 04mL·m-2·h-1。反应过程中水样未检测到其他的氯代中间产物或最终产物,无毒的烃类乙烷(C2H6 )是主要产物,约占加入时PCE总碳质量的94% ~110%。试验结果说明加氢催化剂Ni的存在,通过原电池腐蚀作用提高了脱氯速率并同时增加了良性产物的产量(如CH )。  相似文献   

对大连历年汛期起止日期的客观判定   总被引：3，自引：1，他引：2  

王玲玲  邹耀仁  隋洪起 《气象》2000,26(3):12-16

根据大连市 195 1～ 1998年的逐日降水量资料 ,应用扫描 t检验方法对每年入汛期和出汛期进行了判定和分析 ,并与目前使用的经验方法划定的日期作了比较。结果表明 ,t检验方法能更客观、准确地判定汛期的开始日期和结束日期。  相似文献   

无裂栉江珧形态差异的比较研究     

余祥勇  王梅芳  李宏吾  蔡英亚 《热带海洋学报》2000,19(2):39-44

通过无裂栉江珧Atrinapectinata 4种类型 (青口 ,黄口 ,棘螺 ,沙螺 )的外壳测量、解剖观察 ,对其形态差异进行了比较研究 ,并对有关参数进行了显著性检验 ( t检验 )。结果表明 ,这 4种类型的贝壳形态和后闭壳肌的相对大小存在明显差异 ,其中沙螺与青口及黄口间的差异极为显著 ,棘螺的壳形及闭壳肌的大小变化幅度最大。由此提出 ,应对无裂栉江珧现定种作进一步研究。  相似文献   

宽甸火山群地质遗迹的地质特征与特殊性   总被引：1，自引：0，他引：1  

郑瑞伦  邹天人 《地质与资源》2006,15(1):75-77

宽甸地处营口-宽甸古隆起东部北缘,在距今0.12~8 Ma间,火山多次喷发留下了特殊的火山群地质遗迹.宽甸火山群的多期喷发,产生多种岩石组成的火山岩,火山岩中含有大量上地幔橄榄岩包体与丰富的巨晶矿物以及特殊的火山群地质地貌具有追溯地质历史的重大科学研究价值和观赏价值.  相似文献   

Response of streamflow to climate change and human activity in Xitiaoxi river basin in China          下载免费PDF全文

Canqiang Zhang  Biao Zhang  Wenhua Li  Moucheng Liu 《水文研究》2014,28(1):43-50

In recent years, the Xitiaoxi river basin in China has experienced intensified human activity, including city expansion and increased water demand. Climate change also has influenced streamflow. Assessing the impact of climate variability and human activity on hydrological processes is important for water resources planning and management and for the sustainable development of eco‐environmental systems. The non‐parametric Mann–Kendall test was employed to detect the trends of climatic and hydrological variables. The Mann–Kendall–Sneyers test and the moving <i>t</i>‐test were used to locate any abrupt change of annual streamflow. A runoff model, driven by precipitation and potential evapotranspiration, was employed to assess the impact of climate change on streamflow. A significant downward trend was detected for annual streamflow from 1975 to 2009, and an abrupt change occurred in 1999, which was consistent with the change detected by the double mass curve test between streamflow and precipitation. The annual precipitation decreased slightly, but upward trends of annual mean temperature and potential evapotranspiration were significant. The annual streamflow during the period 1999–2009 decreased by 26.19% compared with the reference stage, 1975–1998. Climate change was estimated to be responsible for 42.8% of the total reduction in annual streamflow, and human activity accounted for 57.2%. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Precipitation regional extreme mapping as a tool for ungauged areas and the assessment of climate changes          下载免费PDF全文

Jinhui Jeanne Huang  Yu Li  Junxian Yin  Edward Authur Mcbean 《水文研究》2016,30(12):1940-1954

The spatial‐temporal characteristics of mean annual daily maximum precipitation events in the upper Yangtze River basin in China are examined using a framework termed precipitation regional extreme mapping (PREM). The framework consists of regional analyses and mapping methods, which have the capability to assess the presence or absence of climate change. The findings confirm the homogeneous regions identified by Wang (2002) using a heterogeneity measure, where all three regions have heterogeneity less than 1.0. The Pearson type III (PE3) distribution was found to be acceptable for all three regions, while the generalized extreme‐value distribution performs better than PE3 for Region I (eastern portion of the upper Yangtze basin). Two indices, root mean square error and mean bias, were used to access the performance of the extreme map, and the results show that the map of extreme can predict precipitation for ungauged regions with acceptable accuracy. The regional frequency maps were used in conjunction with the Student's <i>t</i>‐test to identify the statistical significance of changes of extremes in precipitation. Results indicate that there have been no significant changes in maximum daily precipitation magnitudes over the past four decades, a finding that is valuable for the safe planning of major hydraulic projects and the management and planning of water resources in the upper Yangtze River basin. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

基于组合模型的建筑变形态势分析方法     

甘立蹇  吴栋  张东升 《现代测绘》2011,34(1)

传统的变形态势分析大都是基于单个模型进行的。虽然使用单个模型是经过一系列计算优选得到,但在实践中单个模型进行分析时,仍存在较大的局限性,其准确性亦不够高。本文对组合模型法的原理作了概述,并将其应用于高架桥墩监测进行了实例分析,不仅预测了变形量,也预测了变形速率,获得了变形终;变形态势分析结果验证了组合模型法较单模型法的优越性。  相似文献   

河西走廊沙尘暴50 a频率突变检测分析   总被引：2，自引：0，他引：2  

刘萱  张文煜  贾东于  张婕  王建州  赵伟刚 《中国沙漠》2011,31(6):1579-1584

 利用1958年至2007年民勤、敦煌、武威、张掖、景泰的沙尘暴春季发生频次资料,运用滑动t检验和滑动F检验进行突变检测分析,根据检验结果综合确定突变点及其突变强度,寻求沙尘暴发生频率突变规律及产生原因,为沙尘暴发生频率的变化趋势研究和预测提供参考。滑动t检测结果显示,5站点的沙尘暴春季频率突变数量呈现往东部递增的趋势;降低突变较多;升高突变年份集中在20世纪60年代末期和90年代末期,降低突变主要出现在1983年及2002年前后;均值降低突变强度大于升高突变。滑动Ｆ检验结果显示突变均是方差降低突变;河西走廊中东部的沙尘频率波动性差异较其他地区更为显著;方差突变出现在80年代中期及90年代初期,其余时间的波动性的差异维持在一个较低的水平。当对沙尘暴发生频率进行滑动t及滑动F检验时,两种情况下的降低突变检测结果存在一定的对应关系。河西走廊地区的沙尘暴发生频率突变与地面风速、大风日数、降水量及平均气温的突变存在密切联系,可作为沙尘暴频率突变的预测因子。  相似文献   

Fluid inclusion constraints on the uplift history of the metamorphosed massive sulphide deposits at Ducktown, Tennessee     

D. L. HALL  R. J. BODNAR  J. R. CRAIG 《Journal of Metamorphic Geology》1991,9(5):551-565

Abstract Standard petrographic, microthermometric and Raman spectroscopic analyses of fluid inclusions from the metamorphosed massive sulphide deposits at Ducktown, Tennessee, indicate that fluids with a wide range of compositions in the C–O–H–N–S–salt system were involved in the syn- to post-metamorphic history of these deposits. Primary fluid inclusions from peak metamorphic clinopyroxene contain low-salinity, H<sub>2</sub>O–CH<sub>4</sub> fluids and calcite, quartz and pyrrhotite daughter crystals. Many of these inclusions exhibit morphologies resembling those produced in laboratory experiments in which confining pressures significantly exceed the internal pressures of the inclusions. Secondary inclusions in metamorphic quartz from veins, pods, and host matrix record a complex uplift history involving a variety of fluids in the C–O–H–N–salt system. Early fluids were generated by local devolatilization reactions while later fluids were derived externally. Isochores calculated for secondary inclusions in addition to the chronology of trapping and morphological features of primary and secondary fluid inclusions suggest an uplift path which was concave toward the temperature axis over the <i>P–T</i> range 6–3 kbar and 550–225° C. Immiscible H<sub>2</sub>O–CH<sub>4</sub>–N<sub>2</sub>–NaCl fluids were trapped under lithostatic to hydrostatic pressure conditions at 3–0.5 kbar and 215 ± 20° C. Entrapment occurred during Alleghanian thrusting, and the fluids may have been derived by tectonically driven expulsion of pore fluids and thermal maturation of organic material in lower-plate sedimentary rocks which are thought to underlie the deposits. Episodic fracturing and concomitant pressure decreases in upper-plate rocks, which host the ore bodies, would have allowed these fluids to move upward and become immiscible. Post-Alleghanian uplift appears to have been temperature-convex. Uplift rates of 0.10–0.05 mm year<sup>?1</sup> from middle Ordovician to middle Silurian – late Devonian, and 0.07–0.12 mm year<sup>?1</sup> from middle Silurian – late Devonian to late Permian are suggested by our uplift path and available geochronological data.  相似文献   

Characteristics of turbulence over the semi-fixed desert area north of Xinjiang,China     

Ali Mamtimin  Yu Wang  Hajigul Sayit  Xing Hua Yang  Fan Yang  Wen Huo  Chenglong Zhou  Lili Jin 《地球表面变化过程与地形》2021,46(12):2365-2378

As the largest fixed and semi-fixed desert in China, the Gurbantünggüt Desert undergoes a long period of snow cover in the winter and the rapid growth of ephemeral plants in the spring, presenting obvious seasonal changes in the underlying desert surface type, which can lead to variation in the turbulence of the near-surface boundary layer turbulence over the desert. In this study, gradient tower data and eddy covariance data from 2017 were analysed to investigate the turbulence characteristics of the different surface boundary layers in the hinterland of the Gurbantünggüt Desert. The results indicate that stable atmospheric conditions in the desert occur exclusively during the early morning and at night in the desert, and the onset and duration of this stable state varies seasonally. Two regimes of intermittent turbulence occur during the night, a weak turbulent regime that occurs when the wind speed is less than the threshold and a strong turbulent regime when the wind speed exceeds the threshold, and different wind speed thresholds were observed at each level. These parameters follow a seasonal pattern of summer (July) > spring (April) > autumn (October) > winter (January) in terms of magnitude. The mean turbulence intensities of the along-wind, cross-wind and vertical wind are 0.5, 0.47 and 0.14, respectively, with <i>I</i><sub><i>u</i></sub> <i>> I</i><sub><i>v</i></sub> <i>> I</i><sub><i>w</i></sub>. The normalized standard deviation of the wind velocity components (<i>σ</i><sub><i>u</i></sub>, <i>σ</i><sub><i>v</i></sub> and <i>σ</i><sub><i>w</i></sub>) generally satisfies a 1/3 power-law relation. Our results show that the night-time turbulence regime classification for the Gurbantünggüt Desert strongly depends on meteorological and orographic features, and the intermittent turbulent events have the non-stationarity of the flow in common. The results can contribute to the study of land surface processes, climate change and desertification in inland arid desert areas.  相似文献