区域性CORS系统监测地表形变的可行性     

黄兵杰  郑凤娇  白洁  王勇 《测绘学院学报》2011,(3)

连续运行卫星定位服务系统(简称为CORS)已经在国内外广泛建立,CORS在维护区域大地测量基准和城市测绘工作中得到了非常广泛的应用。但在城市地面沉降监测方面,仍存在基准站的稳定性、测量精度对平面及高程形变影响等问题。这里提出了一套完整的基于CORS系统变形监测网的稳定性分析的方法和流程。采用秩亏自由网平差,以位移向量一次性范数最小原则求取监测网点最合理的位移量及权阵。采用正态分布函数对监测点的位移显著性进行检验。结合武汉市地面沉降监测项目,分析评价了武汉市连续运行卫星定位服务系统(简称为WHCORS)用于城市地表形变监测的可行性。  相似文献   

2010年早春浙江罕见连阴雨天气环流特征及成因分析   总被引：4，自引：0，他引：4  

张建海  曹艳艳 《高原气象》2011,30(6):1543-1553

利用客观分析资料分析了2010年早春浙江连阴雨天气的环流特征和热力、动力条件,并与历史同期天气状况进行了对比,结果表明：（1）乌拉尔山地区长波脊前偏北气流为连阴雨天气提供了冷空气条件,西太平洋副热带高压偏北偏西有利于其西北侧建立持久、稳定的水汽通道。（2）南北温差分布的变化导致高空西风急流出现分支,浙江位于北支急流南侧...  相似文献   

Long-term plankton studies at the lower Rhine/Germany     

Günther Friedrich  Marlies Pohlmann 《Limnologica》2009,39(1):14-39

The river Rhine has lain under considerable anthropogenic stress of its water quality for 100 years. As early as 1905 the first results of studies of the plankton in the Rhine were published. Due to the long residence time of the water a real potamoplankton can develop and at the end of the Lower Rhine it reaches its highest density. The paper consists of two parts. At first an overview is given about the history of plankton studies in the Rhine. The second part is the presentation of results from a monitoring at the Lower Rhine from 1979 to 2004.First systematic studies started at the beginning of the 20th century at the beginning of pollution. Our studies started during a phase of recreation from extreme pollution and eutrophication. Samples were taken at four stations: Bad Honnef, km 640, entrance to North Rhine-Westphalia, Düsseldorf, km 732, Duisburg, km 792 downstream large industrial effluents and big cities, Kleve-Bimmen, km 865 at the border to the Netherlands.In the 1970s nutrients were high, especially phosphate 0.65 mg PO₄-P L⁻¹ in 1979. After 1980 phosphate dropped to 0.11 mg PO₄-P L⁻¹ in 2004 (mean values of the growing season). Ammonia was reduced from about 0.52 (1979) to 0.02 (2004) mg NH₄-N L⁻¹. Nitrate remained between 3.72 (1989) and 2.26 (2004) mg NO₃-N L⁻¹ at a relatively high level. Oxygen concentrations were very low during the 1960s and 1970s, sometimes only 4 mg L⁻¹ O₂. During our studies the oxygen increased up to 9 mg L⁻¹ O₂ with a tendency to 11 mg L⁻¹ O₂ in the last years. Chlorophyll a was estimated to be between 59 (1979) and 31μg L⁻¹ (1986) with short peaks up to 170 μg L⁻¹ (1989). Since 1992 the mean values have varied between 30 (1993) and 21 μg L⁻¹ (2004).The floristic phytoplankton composition is characterised by the dominance of the centric diatom Stephanodiscus hantzschii. Other diatoms like Skeletonema subsalsum, Skeletonema potamos and Asterionella formosa were regularly present in smaller quantities. The second dominant group was coccale green algae. During the 1980s they formed up to 35% of the biomass. Since the 1990s their contribution to the phytoplankton became much smaller. This change corresponds with the increase of wastewater treatment and the diminution of nutrients. All the other groups of algae were present in minor quantities. During the time of higher trophy in the 1970s and 1980s the phytoplankton formed two peaks, in recent years only one peak has developed, depending on different flow conditions during the growing season and lower trophic state in the upstream parts of the river.Excellent correspondence exists between cell number, biovolume and chlorophyll a content and the results of delayed fluorescence (DF) measurement. The trophic status in the Lower Rhine may be estimated as (moderate) eutrophic. The ecological status of the phytoplankton is good based on the requirements of the European Water Framework Directive (WFD).The zooplankton consists mainly of rotatoria and larvs of Dreissena polymorpha. Grazing on phytoplankton seems to be mainly due to the large quantities of benthic Dreissena and the newly introduced mussel Corbicula.  相似文献   

利用GPS连续观测资料进行强震危险性预测的探讨   总被引：1，自引：0，他引：1  

杨国华  张风霜  武艳强  韩月萍  沈午春  杨博 《地震》2008,28(1):33-39

中国地壳运动观测网络基准站自1999运行以来已经积累了8年多的观测资料,目前针对地震预测、观测对象和数据处理方法,广义地提出了"点、线、面"的分析方法。实际应用表明,利用"线"的分析方法可能是比较好的方法,它最大的优点是在恰当的空间范围内不但可降低噪声,而且可突出异态信息。在目前较低测控能力的基础上,可通过全空间扫描与现象分析发现:①距昆仑山口西地震震中最近的德令哈观测站相对于拉萨观测站在震前较早的时间,其EW向就出现了缓慢变化,乃至闭锁(或无差异变化),直至地震发生为止,持续时间超过2年,闭锁数值10 mm以上,震后恢复正常;②云南地区数次强震震前下关观测站相对于泸州观测站EW向出现了闭锁或低于正常的变化,2003年强震之后恢复正常;最近的普洱强震自2006年初EW与SN向均出现了相对闭锁,两个方向的数值分别接近和达到10 mm;此外,每阶段异常的持续时间均超过1年;③塔什—乌什间EW向在新疆巴楚地震前出现了闭锁性活动,时间2年以上,数值约10 mm,震后恢复正常;目前SN向有相对闭锁迹象,并正在趋于明朗;④鼎新—西宁间EW方向有相对闭锁的迹象,但时间尚短;⑤通过寻找相对"闭锁"区段有可能成为判定强震危险性存在与否的主要方法。由此推测,若普洱6.4级地震后闭锁不解除,川滇菱形块体的西边界构造带及周围地区仍是近期强震最有可能发生的地区,其次是新疆的西天山地区,目前青藏高原东北缘尚不明朗。  相似文献   

In situ heavy metals (copper, lead and cadmium) in different plankton compartments and suspended particulate matter in two coupled Mediterranean coastal ecosystems (Toulon Bay, France)     

Rossi N  Jamet JL 《Marine pollution bulletin》2008,56(11):1862-1870

We monitored the concentrations of copper, lead and cadmium in seawater, in suspended particulate matter (SPM) and in bacteria, phyto- and zooplankton communities separated from abiogenic particles, over a one year cycle in two coupled Mediterranean coastal ecosystems (Little Bay (LiB) and Large Bay (LaB)). Metals were present in seawater in the order Cu > Pb > Cd in both bays and showed important variations within the same month than among months. In LiB, their concentrations were between 0.62 and 2.82 μg Cu l⁻¹, 0.16 and 19 μg Pb l⁻¹ and 0.007 and 0.14 μg Cd l⁻¹, respectively, whereas in LaB, they were between 0.23 and 2.11 μg Cu l⁻¹, 0.09 and 0.76 μg Pb l⁻¹ and not detected and 0.65 μg Cd l⁻¹. SPM play an important role on metal adsorption, especially for copper. Bioaccumulation factors showed that bacteria and phytoplankton accumulate metals whereas zooplankton tends to biodiminish them in the plankton food web.  相似文献   

A positive definite continuous FEM model for advection     

Pablo Ortiz 《Advances in water resources》2009

This work introduces a continuous and sign-preserving finite element model (FEM) for advection problems. The model is formulated by integrating flux corrected transport technique (FCT) with the characteristic based (CB) FEM. Low order solution for the FCT has the form of element contribution and derives from an upwind monotone scheme with the minimum necessary diffusion for positivity. Selected numerical experiments illustrate the efficacy of the method by comparing results with some successful models, by demonstrating an approximate conservation of the accuracy of original CB algorithm once the complete procedure is operating, and by testing the model for severe time dependent advective flows.  相似文献   

Calanus finmarchicus in the North Atlantic: the year of Calanus in the context of interdecadal change   总被引：1，自引：0，他引：1  

Planque  B.; Batten  S. D. 《ICES Journal of Marine Science》2000,57(6):1528-1535

  相似文献   

2018年冬季浙江连续阴雨天气东亚高空急流特征分析     

王洪勋 《沙漠与绿洲气象(新疆气象)》2021,15(1):19-27

利用欧洲中心ERA 5月平均资料和日资料分析2018年冬季浙江罕见连续阴雨寡照期间东亚高空副热带急流和温带急流的位置和强度特征,分析连阴雨异常天气期间东亚高空急流在位置和强度上的部分异常特征.结果表明:东亚高空急流活动区域以青藏高原上空为分界线,分为南北两支,南支副热带急流活动区域沿青藏高原南侧呈准纬向分布,北支温带急...  相似文献   

Auswirkung von Schwermetallgemischen auf die biologische Behandlung naphthalinsulfonsäurehaltiger Abwässer     

H. Pack  D. C. Hempel 《洁净——土壤、空气、水》1997,25(6):306-310

Effect of Mixtures of Heavy Metals on the Biological Treatment of Sewages Containing Naphthalenesulfonic Acid Biological wastewater treatment processes can be destabilized considerably by heavy metals. In this investigation, the effect of loadings of heavy metals on the degradation of naphthalene-2-sulfonic acid (2NS) by immobilized bacteria in continuously operated airlift-loop reactors was studied. Shock loadings with mixtures of cadmium and nickel, or cadmium and zinc, respectively, resulted in increases in inhibition compared to those observed with the single metals. In contrast, the 2NS-degradation was less inhibited by shock loadings with mixtures of nickel and zinc than by the single metal ions. Repeated shock loadings up to 100 mg L^?1 nickel and 1000 mg L^?1 zinc effected an adaptation of the microorganisms. Continuous loadings with up to 10 mg L^?1 cadmium and nickel each, or with 50 mg L^?1 nickel and 210 mg L^?1 zinc, respectively, did not inhibit the degradation of 2NS. The permanent loadings led to an adaptation of the bacteria with an increased biosynthesis of proteins from 0.2 to 0.5 g g^?1 cell dry weight. However, if the immobilized cells were incubated with mixtures of cadmium and nickel, the specific polysaccharide content decreased to less than 0.2 g g^?1 cell dry weight, resulting in a detachment of the biofilms.  相似文献   

连续流动化学发光法测定地质样品中痕量金   总被引：2，自引：0，他引：2  

唐良保  李振涛 《铀矿地质》1990,6(3):179-182

根据Au(Ⅲ)离子催化过氧化氢氧化鲁米诺原理,研究成功了连续流动化学发光法测定地质样品中痕量金的方法。样品用盐酸、过氧化氢及溴水分解后,在巯基棉柱中进行了分离和预富集。方法检出限为2×10~(-10)gAu/ml,工作曲线线性范围为2×10~(-10)—1×10~(-5)gAu/ml。对于2×10~(-9)gAu/ml和2×10~(-8)gAu/ml的变异系数分别为5.7％和3.0％。  相似文献