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141.
Cheng-Bang An Shi-Chen Tao Jiaju Zhao Fa-Hu Chen Yanbin Lv Weimiao Dong Hu Li Yongtao Zhao Ming Jin Zongli Wang 《Journal of Paleolimnology》2013,49(2):145-154
Surface and fossil pollen samples were collected to reconstruct the vegetation and environment since 30.7 cal ka BP in the Lake Balikun Basin, northwest China. This record demonstrates that the region was occupied by four vegetation communities during the interval 30.7–9.0 cal ka BP, including desert steppe (30.7–25.1 cal ka BP), Amaranthaceae-Asteraceae desert (25.1–17.7 cal ka BP), Amaranthaceae-Artemisia-Asteraceae desert (17.7–12.8 cal ka BP) and Amaranthaceae desert (12.8–9.0 cal ka BP), corresponding to relatively humid, the coldest and driest, cold and dry, and colder and drier conditions, respectively. The reconstructions of vegetation and environmental changes around Lake Balikun do not support the interpretation of an extremely humid LGM in Central Asia, challenging the cold-moist (glacial), warm-dry (interglacial) pattern of late Quaternary environmental change in Central Asia. The Last Glacial Maximum was cold and dry, and similarly harsh conditions continued into the early Holocene. 相似文献
142.
143.
The Tianjin coastal area is a typical soft soil region,where the soil is a marine deposit of the late Quaternary.The soil dynamic parameters from seismic risk assessment reports are collected,and drilling of 15 holes was carried out to sample the soils and measure their dynamic characteristics.The data was divided into 7 types based on lithology,namely,muddy clay,muddy silty clay,silt,silty clay,clay,silty sand and fine sand.Statistics of the dynamic parameters of these soils are collected to obtain the mea... 相似文献
144.
考虑震源破裂过程的青海玉树地震震动图研究 总被引:4,自引:0,他引:4
为了在缺少实时台站数据的情况下,研究震后地表地震动分布,本文尝试通过对震源做出某些约束,以提高震动图的精度.由于青海玉树地震的发震断层近似直立(倾向83°),震源破裂过程在时间和空间上呈明显的分区特征,分别考虑了地表破裂的线源发生模型和主震震级分解方法,用考虑了场地效应的震动图快速生成方法生成震动图.将两种方法生成的震动图与调查烈度比较.结果表明,基于震源破裂过程对主震震级进行分解,综合考虑各子事件生成震动图的方法,对震后的应急决策和灾情的快速评估是可行的. 相似文献
145.
根据所掌握的仪器映震能力、震前(后)大震特殊捕捉现象,以及对相同地震不同仪器映震的对比,可以看出,VP型宽频带垂直摆倾斜仪具备前兆仪器捕捉(反映)地震孕育及地震发生的相关作用,能够正确、客观的作用于地震前兆数据产出,对地震预测研究具有深远影响. 相似文献
146.
为确定适合广州市地下排水管道的修复方法,对广州老城区近100kin2地区进行调查。调查采用管道潜望镜(Quick View,QV)、管道闭路电视(closed—Circuit Television,CCTV)、管道声纳(Sonar)进行综合探测,结果表明,调查区域内的地下排水管道存在的主要问题是破损断裂、错位、路基下沉、管道淤塞现象,其中小直径管道的损坏情况较为严重,尤其是300mm的管道将近报废。针对地下排水管道的调查情况,结合现有修复技术的特点,经过对修复成本及施工的难易性的研究讨论,得出适合多种管道和缺陷类型的翻转内衬法(Cured In Place Pipe,CIPP)和施工要求相对简单的U型折叠法(U-fold)满足要求,并能够产生较高经济社会效益。 相似文献
147.
Slope reliability analysis by updated support vector machine and Monte Carlo simulation 总被引:1,自引:0,他引:1
This paper presents a new methodology for slope reliability analysis by integrating the technologies of updated support vector machine (SVM) and Monte Carlo simulation (MCS). MCS is a powerful tool that may be used to solve a broad range of reliability problems and has therefore become widely used in slope reliability analysis. However, MCS often involves a great number of slope stability analysis computations, a process that requires excessive time consumption. The updated SVM is introduced in order to build the relationship between factor of safety and random variables of slope, contributing to reducing a large number of normal computing tasks and enlarging the problem scale and sample size of MCS. In the algorithm of the updated SVM, the particle swarm optimization method is adopted in order to seek the optimal SVM parameters, enhancing the performance of SVM for solving complex problems in slope stability analysis. Finally, the integrating method is applied to a classic slope for addressing the problem of reliability analysis. The results of this study indicate that the new methodology is capable of obtaining positive results that are consistent with the results of classic solutions; therefore, the methodology is proven to be a powerful and effective tool in slope reliability analysis. 相似文献
148.
Xiaosi Su Hang Lv Wenjing Zhang Yuling Zhang Xun Jiao 《Environmental Earth Sciences》2013,69(6):2091-2101
Biodegradation is one of the main natural attenuation processes in groundwater contaminated with petroleum hydrocarbons. In this work, preliminary studies have been carried out by analyzing the concentrations of total petroleum hydrocarbons (TPH), dissolved inorganic carbon (DIC), dominant terminal electron accepters or donors, as well as δ 13CDIC and δ 34SSO4, to reveal the biodegradation mechanism of petroleum hydrocarbons in a contaminated site. The results show that along groundwater flow in the central line of the plume, the concentrations of electron acceptors, pH, and E h increased but TPH and DIC decreased. The δ 13CDIC values of the contaminated groundwater were in the range of ?14.02 to ?22.28 ‰PDB and ?7.71 to 8.36 ‰PDB, which reflected a significant depletion and enrichment of 13C, respectively. The increase of DIC is believed to result from the non-methanogenic and methanogenic biodegradation of petroleum hydrocarbon in groundwater. Meanwhile, from the contaminated source to the downgradient of the plume, the 34S in the contaminated groundwater became more depleted. The Rayleigh model calculation confirmed the occurrence of bacterial sulfate reduction as a biodegradation pathway of the petroleum hydrocarbon in the contaminated aquifers. It was concluded that stable isotope measurements, combined with other biogeochemical measurements, can be a useful tool to prove the occurrence of the biodegradation process and to identify the dominant terminal electron-accepting process in contaminated aquifers. 相似文献
149.
作为一个中长期地震预测方法,基于复杂系统统计物理的图象信息学PI算法近年来广受关注.针对7级以上强震成组和突发交替的川滇地区,考虑将与其构造和地震活动关系密切,且强震频发的安达曼-苏门答腊地区作为统一的强震预测研究区,使用PI算法进行MW7.0及以上预测ldquo;目标震级rdquo;的地震危险性分析.计算中使用了1973年以来的NEIC目录,采用10年尺度的地震活动ldquo;异常学习rdquo;时段和3年尺度ldquo;预测时间窗rdquo;,对预测效果进行了ROC检验.回溯性研究显示,PI预测效果较好,表明将川滇-安达曼-苏门答腊地区作为统一的7以上强震PI预测研究区在统计上具有合理性.从统计物理角度,研究区组合前后的各态遍历性曲线显示,组合后的研究区对PI的适用程度虽不优于单独考虑川滇地区,但优于安达曼-苏门答腊地区.PI图象显示,2008震前可能存在中长期尺度的ldquo;前兆性rdquo;地震活动异常. 相似文献
150.