共查询到20条相似文献，搜索用时 62 毫秒
1.
2.
The results of studying physicochemical properties of bottom sediments in the Kuibyshev Reservoir are given. The evaluated characteristics include their porosity, specific surface area and density, and chemical state characteristics (pH, oil products, organic matter, phenols, and the mobile and total forms of heavy metals). Technogenic geochemical anomalies of bottom sediments are evaluated. The obtained results characterize the environmental state of bottom sediments in the study area. 相似文献
3.
4.
Assessing ecological security at the watershed scale based on RS/GIS: a case study from the Hanjiang River Basin 总被引：1，自引：0，他引：1
Guangming Yu Shu Zhang Qiwu Yu Yong Fan Qun Zeng Lei Wu RuiRui Zhou Na Nan Pengjie Zhao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(2):307-318
The purpose of this study is to develop an assessment framework of ecological security at the watershed scale to meet the need of watershed management, and to assess ecological security using this framework in the middle and lower reaches of Hanjiang River Basin (in Hubei Province, China). The states and their changes of ecological security in the study region are investigated with the support of ERDAS and ARC/INFO platform. The results show that the ecological security index (P) values in 1995 and 2000 were 0.685 and 0.699 respectively in the study region. While in 2005 and 2010, the P values were decreased to 0.657 and 0.624. In 1995, there were 5 counties with degree II state (the poor state) of ecological security, and 14 counties with degree III state (the common state). By 2000, the amount of counties with degree II decreased to 4 counties. And the number of counties with degree II is the same as 2000 in 2005. The result of 2010 shows there were 12 countries with degree III state as well as 7 counties with degree II state. The results of our case study of the Hanjiang River Basin reflect that the ES situation is very grim in the study area. The degree of ecological security developed in this study can be used as a useful tool for watershed managers and decision-makers. 相似文献
5.
The results of hydrological, ecological-hydrochemical, and hydrobiological studies, aimed at the protection and rational use of water resources of the Pavlovskoe Reservoir are considered. The results of experimental studies of the effect of submerged wood on water chemistry and the assessment of the ecological state of the reservoir based on phytoplankton data are given. 相似文献
6.
E. B. Fainberg 《Surveys in Geophysics》1980,4(1-2):157-171
The general state of global investigations of electromagnetic induction in the oceans and also some new results obtained in the past few years in the U.S.S.R. are considered. 相似文献
7.
8.
传统瞬变电磁法（TEM）认为临界阻尼匹配时传感器响应快、无振荡,为最佳匹配方式.本文通过建立基于标定环的TEM系统标定模型,理论证明当略欠阻尼匹配时传感器响应最快、时域畸变最小,为最佳匹配方式.本文采用基于实测数据的背景场剔除方法将一次场和大地响应剔除,通过对不同阻尼状态下标定环早期响应畸变的定量评价,实验证明传感器在略欠阻尼匹配状态下二次场响应畸变最小.本文理论和标定实验均证明,在纯二次场观测方式下,采用略欠阻尼匹配方式能够显著降低早期响应畸变、提高系统浅层探测能力,是浅层探测时传感器最佳匹配方式. 相似文献
9.
顺层岩质边坡的抗震性指标大部分都是非确定的,无法用固定阈值衡量。提出基于非确定性分析法的顺层边坡抗震性性能研究,将顺层岩质边坡看作若干个叠加的薄板;运用非确定性分析法计算各个薄板的动力安全系数和动力极限状态方程,并对顺层边坡动力极限状态方程进行求解,可得在地震作用力下顺层边坡动力可靠度指标与顺层边坡失效概率之间的关系;评估地震作用力下顺层边坡整体稳定性,同时综合考量顺岩边坡的最小平均安全系数以及平均失效概率,得出评估结果。实验结果显示,在地震作用力下,顺层边坡坡高、坡角、岩层倾角对顺岩边坡抗震性能影响显著,评估结果与实际结果一致。 相似文献
10.
受印度板块向欧亚板块持续北东向挤压作用,青藏高原腹地拉萨块体内新构造活动强烈,其地应力特征一直是工程规划建设、地球动力学和地壳稳定性研究的重要内容.2014至2015年,沿雅鲁藏布江断裂带,分别在西藏林芝县(LZ)、朗县(LX)和乃东县(ND)开展了水压致裂原地应力测量工作.本文通过测试结果分析,获得了拉萨块体现今地壳浅表层的应力状态及分布特征.LX及ND测点应力强度均高于LZ测点,且应力结构均为逆断型,表现为S_HS_hS_v,水平应力作用占主导.LZ测点在测试深度内揭穿了断裂,且应力结构不够明确.三个测点的应力状态显示出拉萨块体现今地壳强度处于破裂临界状态,结合各测点所处构造环境,应力的持续累积可能会打破这种平衡导致断裂活动.主应力比值K_(Hv)=S_H/S_v,K_(av)=(S_H+S_h)/2S_v和K_f=(S_H—S_h)/2也显示出该区强烈的水平构造运动.三测点揭示的最大水平主应力方向集中于近SN(LX)-NNE(LZ及ND)向,与该区背景应力场特征相一致,且与地壳运动场相耦合,反映出该区应力状态主要受控于印度板块北向欧亚大陆持续挤压碰撞的构造背景,同时各测点之间应力状态的差异性也体现了区域构造作用的差异影响. 相似文献
11.
许多研究人员利用GPS测量的速度资料计算了地应变率场，但其结果差异较大. 本文将地质统计学中的Kriging方法引入到GPS观测的速度场研究中, 通过Kriging插值得到青藏高原及邻区均匀网格节点上的速度值，然后运用有限单元中形函数(Lagrange插值函数)的求导方法，计算每个网格单元积分点处的地应变率分量，从而获得青藏高原及邻区的地应变率场的分布. 计算结果显示，青藏高原主体处在南北向受挤压、东西向被拉张的应变状态之中，但高原东部地区则正好相反，即南北向拉张、东西向出现挤压. 青藏高原及邻区主应变率的方位与震源机制解中P轴、T轴的方向基本一致；最大主压应变率的高值区分布在喜马拉雅主边界冲断带及附近地区，高原内部出现主张应变率大于压应变率的现象，且高原内部处在拉张应变状态. 面膨胀率结果也表明，喜马拉雅山及附近地区为面收缩区，而高原内部其他地区主要为膨胀区；最大剪应变率分布清晰地显示出青藏高原周边的主要断裂带轮廓. 文中的应变率计算结果预示青藏高原及周边地区现今的地应变与较长期的地质活动之间有一定的继承关系. 相似文献
12.
本文介绍了对岩石在不同应力途径下的体积变化进行的实验研究。主要的应力途径有三种,并且都是首先把岩石加载到破裂前一定的应力状态,再分别三种类型加载。实验用电阻应变片测量纵向和横向应变以计算体应变。实验表明:同一种岩石在不同应力途径下膨胀效应有显著的不同。文中用辉长岩的实验数据对过密量和超膨胀量进行了估算。研究表明,过密与膨胀是应力途径变化时岩石体积变化的滞后效应。研究了B型实验过密状态出现的条件。从强度80%左右开始减小最小主应力的B型实验明显表现经历过密状态。从低应力状态(强度50%左右)和高应力状态(强度92%以上)开始减小最小应力的B型实验,岩石均未经历过密状态。最后联系地震预报问题进行了简单的讨论 相似文献
13.
The results of investigations carried out in May, July, September, and November 2000 and 2001 are used to analyze the species composition and biomass structure of phytolankton of 13 tributaries of Lake Ladoga and the Neva River and assess the trophic state of the rivers and their saprobity. 相似文献
14.
15.
16.
In model-based sensitivity studies, the growth of model error over long-term integrations may lead to serious deviations between the simulated and actual states. To reduce these errors, we have developed a new modeling approach with application of the Newtonian relaxation technique, or nudging. In this approach, an identical artificial Newtonian relaxation term that reflects the difference between the model reference state and its analysis (available in many sensitivity studies) is added to the prognostic equations of the two simulated states, the reference state and the perturbed state (for which observations are nonexistent). We have conducted idealized sensitivity experiments with a shallow-water model to evaluate the benefits and viability of this approach and to test its sensitivity to changes in the nudging period and error in the analysis data. The experimental results confirm that this approach lead to more credible atmospheric responses to modified external forcing if the data error is within a reasonable range. The results also indicate that a 12-hour period is more favorable for nudging than a 24-hour period. 相似文献
17.
1970年以来中国大陆25次6.8级以上地震前态矢量异常特征研究 总被引：2，自引：0，他引：2
利用态矢量方法对中国大陆1970年以来25次6.8级以上地震进行了较为全面的分析研究, 结果表明, 19次地震前3年内态矢量出现明显异常, 其中10次地震发生前60天内态矢量有明显的变化, 只有6次地震前态矢量变化不明显。 由此认为态矢量方法对强震具有一定的中期和短临预测能力。 研究结果还表明, 相对于态矢量增量的模、 态矢量方向的改变等参量, 态矢量的模在震前的变化更为敏感, 此外, 对于相同震级的地震, 最佳扫描区域尺度大小不一, 并对这些现象进行了一定的解释。 相似文献
18.
利用小波变换分析方法提取沂沭断裂带及其分支断裂跨断层流动短水准和长水准趋势变化成分, 计算分析不同断裂的垂直形变速率和受力状态, 结果表明: 沂沭断裂带及其北西向分支断裂近期垂直形变速率均较小, 没有明显的速率异常和受力状态改变; 同一断裂具有分段和分时活动特征, 断裂活动性质与地质考察结果基本一致; 大部分水准观测场地在1995年苍山5.2级、 2011年日本9.0级地震前后断裂垂直形变速率和受力方式发生了变化; 山东近几年出现的跨断层水准异常基本结束, 仅存的冯家坊子水准异常存在一定干扰, 沂沭断裂带及附近地区近期发生强震的形变背景尚不明显。 相似文献
19.
A. N. Chetyrbotskii 《Water Resources》2006,33(3):264-273
Data of a sample from long-term observations (made with an interval of ten days) of ice cover state parameters in the Sea of Japan are analyzed. The results of analysis are used to formulate a model describing the evolution of ice floe distribution in terms of area and thickness. The obtained model is used to construct a model describing the evolution of ice thickness. Particular cases are studied analytically. A method for parametric identification of the model is considered and its adequacy is assessed against observed distributions. The model can be used to predict the state of the ice cover in the Sea of Japan. 相似文献
20.
汶川MS8.0地震的“孕育”、发生和发展是深部物质分异、调整和运移的产物.为此,在四川中西部地区（松潘—甘孜,龙门山断裂系和四川盆地）应用重力布格异常场资料并通过两条典型剖面的地壳厚度(Moho界面深度）分布与依据Airy均衡理论给出的理论均衡地壳厚度做对比分析,探讨四川盆地、龙门山造山带、邛崃山等川西地域的地壳均衡状态,得到龙门山及其以西地带的深部地壳结构.龙门山造山带恰处于很不均衡的状态,即与其西北和东南部相比差异明显,故地壳处于不稳定状态.为探讨该区重力场均衡与强烈地震活动之间的关系,还必须进行新一轮的高精度观测,以对该区深部精细结构、重力场效应和均衡补偿深入研究.此外,本文研究结果有益于震后确定城镇布局和为不同类型建筑物重建选址提供深部要素. 相似文献