中国高速铁路网络的发展过程、格局及空间效应评价

高速铁路作为现代交通基础设施的重要组成部分,其建设产生时空收敛效果,并进一步对生产要素流动、城市空间扩张、区域空间结构重构产生重要影响。文章在分析中国高速铁路发展过程、模式的基础上,剖析了其空间格局特征及与区域人口和经济的耦合关系;同时,借助ArcGIS方法从空间服务水平、时空收敛效应和中心城市交通圈等角度,探讨高速铁路网络的空间效应。结果显示：高速铁路的空间扩展过程表现出独特的“核心―核心”至“核心―网络”模式,与城市群的空间分布具有较好的耦合性;高速铁路的空间格局与中国城市人口、工业分布表现基本一致,站点1 h范围内可覆盖全国50.07%的城镇人口、73.47%的GDP和98.17%的第二产业产值;中国高速铁路建设导致的时空收敛效果呈现出明显的廊道效应,中心城市枢纽地位得以强化,服务范围的拓展和生产要素的便捷流动为城市群的空间扩张和重构提供了条件。     

湖南洞庭湖地区土壤酸化特征及机理研究

湖南省洞庭湖地区是中国酸雨沉降和土壤酸化严重的地区之一,酸雨沉降具有明显的季节性和地域性差异,酸雨沉降与土壤酸化具有较好的空间对应性,但土壤酸化的程度还取决于土壤中盐基离子的含量。在土壤酸化较严重的地区,垂向上,土壤酸化深度已达50cm左右,土壤酸化伴随着大量的可溶性铝的溶出。在土壤pH值与盐基离子、氮和硫含量的关系曲线上,存在着pH值突变的临界点(临界点pH值为8),在碱性范围内,硅酸盐和铝硅酸盐矿物的水解使大量盐基离子溶出,中和了因SO42-和NO3-的输入而造成的土壤酸化,但当pH值下降到小于7·25的中酸性范围时,酸性物质和碱性物质组成的土壤缓冲体系失去缓冲作用,酸性物质略有增加,就会导致土壤迅速酸化。     

岩土工程勘察中土体取样合理子样数的探讨

合理子样数应随土的性质、指标特征、土样质量和工程要求而异。本文在分析了沿海平原各主要土层的物理力学性质指标变异性的基础上 ,运用概率统计方法 ,针对不同土层不同的物理力学性质指标提出了岩土工程勘察合理子样数确定原则。     

ECS-DBMS中的更新传播技术及其测试与分析

在标准的Client/Server结果中,数据库处理由Server来承担,Client运行用户接口程度,直接和用户交互,并向Seerver发送数据库请求,而在增强型Client/Server结构的DBMS（简写为ECS－DBMS）中,充分利用了可以利用的Client资料,包括长久存储器,对于数据库中经常使用数据,客户机可以将这些数据拷贝并存储到自己久存储器,对于数据库中经常使用数据,客户机可以将这些数据拷贝并存储到自己的磁盘中,以免下次使用这些数据时再去访问Server,另外,客户机的磁盘中,还可以存储该客户自己的专用数据,这样便可以提高系统的性能,由于公共数据都存放在Server中,数据一致性的维护也由Server来承担,当Server中出现更新时,Server要将更新的内容传递给需要该更新的Clients,以替换客户机磁盘中的旧数据,针对ECS－DBMS,介绍并提出几种Server更新传播策略,并通过计算机模拟试验分析这些策略的性能。     

强震前短临地震前兆时空分布非均匀性变化特征

给出一个描述前兆时空分布非均匀性的参数——CV值．研究了华北北部地区６级左右强震前水氡与电磁波观测值异常的时空分布非均匀性的变化特征．结果表明,在强震前,水氡与电磁波观测异常台站的空间分布非均匀性发生了显著变化,CV值有明显的升高过程．这说明,震前短临地震前兆异常在空间上分布的非均匀性增强,变得更加不均匀．这可能与地壳应力场的增强过程有关．如果这个结果得到进一步证实,不仅有助于认识地震孕育发生过程,还对地震预报具有现实意义,并将为充分利用现有前兆资料进行地震预测研究,开辟一条新的途径．      

Research on the Spatial Inhomogeneity Paramter C_v of Earthquake Precursory Group

A research method and parameter C_v which depicts the spatial inhomogeneity of earthquakeprecursory group, are developed in the paper. The influences of factors, such asinhomogeneous distribution of precursory observatory stations, the variety of observing itemnumber at each observatory station and the anomaly number of the same observing item atdifferent stations, etc., which cause the non-earthquake induced inhomogeneity, can beeliminated from C_v. The criteria of C_v to recognize particular spatial pattern of earthquakeprecursory group are also introduced. Based on the method, the spatial inhomogeneity ofradon precursory group and its relation to moderately strong earthquakes occurred in NorthChina during the same period are analyzed. The results show 5 strengthen processes of spatialinhomogeneity of radon precursory group before each of 5 earthquakes with M≥5. 0 in theregion during the period from Jan. 1, 1995 to Feb. 1, 1998. Among them 4 earthquakesoccurred within the time interval which the precu     

西巩驿—李店断裂晚第四纪活动特征——及对1352年会宁7级地震发震构造的初步探讨

西巩驿—李店断裂为陇中盆地内部发育的一条活动断裂,断裂活动性的认识对评估陇中盆地内部地震危险性,以及深入理解印度板块与欧亚板块碰撞的远程响应具有重要的科学意义。遥感解译和地震地质调查结果表明：(1)西巩驿—李店断裂位于陇中盆地中部,断裂长度约120 km、走向NWW、倾向NW、倾角75°～80°。(2)断裂活动的分段特征明显,断裂中部位于加里东期花岗岩隆起区,地表出露不明显,据此将断裂划分为东、西两段。(3)西段新活动现象明显,主要表现为线性陡崖、高约几米的陡坎地形、山梁和冲沟水系的左旋位错等;东段地表构造地貌人为改造严重且黄土区滑坡发育,断层断错晚第四纪的剖面出露较少,晚更新世有活动,性质为逆冲兼左旋,浅地表局部表现为视正断。(4)结合¹⁴C测年结果分析,初步认为西段存在全新世活动,且活动性质为逆冲兼左旋走滑,全新世以来的垂直滑动速率为0.342 mm/a±,晚更新世晚期以来的左旋滑动速率最大为1.60～1.67 mm/a。(5)西段在晚更新世晚期以来至少发生过两次地震事件,一次发生在(11 808～11 401) a B.P.之前;一次事件发生在(6 291～...     

Modelling bivariate extreme precipitation distribution for data‐scarce regions using Gumbel–Hougaard copula with maximum entropy estimation

A new method of parameter estimation in data scarce regions is valuable for bivariate hydrological extreme frequency analysis. This paper proposes a new method of parameter estimation (maximum entropy estimation, MEE) for both Gumbel and Gumbel–Hougaard copula in situations when insufficient data are available. MEE requires only the lower and upper bounds of two hydrological variables. To test our new method, two experiments to model the joint distribution of the maximum daily precipitation at two pairs of stations on the tributaries of Heihe and Jinghe River, respectively, were performed and compared with the method of moments, correlation index estimation, and maximum likelihood estimation, which require a large amount of data. Both experiments show that for the Ye Niugou and Qilian stations, the performance of MEE is nearly identical to those of the conventional methods. For the Xifeng and Huanxian stations, MEE can capture information indicating that the maximum daily precipitation at the Xifeng and Huanxian stations has an upper tail dependence, whereas the results generated by correlation index estimation and maximum likelihood estimation are unreasonable. Moreover, MEE is proved to be generally reliable and robust by many simulations under three different situations. The Gumbel–Hougaard copula with MEE can also be applied to the bivariate frequency analysis of other extreme events in data‐scarce regions.     

Comparison of Salix Genotypes for Co-Phytofiltration of Iron and Manganese from Simulated Contaminated Groundwater in a Floating Culture System

Groundwater contamination with iron (Fe) and manganese (Mn) is directly related to drink water safety. It remains challenging to simultaneously remove Fe and Mn from groundwater by conventional physical and chemical methods. Willows (Salix spp.) show promise for co-phytofiltration of Mn and Fe from groundwater. Here, a floating culture system was developed using willows for co-phytofiltration of Mn and Fe from simulated groundwater. Genotypic differences of willows were evaluated in terms of their tolerance to and accumulation of a mixture of Fe and Mn. The results showed that the growth responses of eight genotypes significantly differed to a mixture of Fe and Mn, ranging from growth inhibition to enhancement. Tolerance index analysis further indicated wide variation in the responses of willows. Tissue-specific analysis also revealed genotypic variation in the capacity of willows for translocation and accumulation of Fe and Mn. Compared with other genotypes, SB7 (Salix babylonica) and J842 (S. babylonica × Salix alba) demonstrated higher co-phytofiltration potentials for Fe and Mn based on tolerance, tissue metal concentrations, and shoot metal contents. Thus, both SB7 and J842 are candidates for co-phytofiltration of Fe and Mn from groundwater.     

中国东北的深源地震波形匹配检测及定位

中国东北珲春周边地区位于环太平洋地震带上,也是中国唯一存在的深源地震带.较大地震发生后常会有若干震级较小的余震发生,但在相同的地震震级情况下深源地震的余震一般比浅源地震的余震数量要少1~3个数量级,且在全球不同深震区的深震余震数量也存在显著差异.针对国际地震中心（ISC）2010年7月至2014年12月目录中给出的中国东北附近27次震源深度超过300 km的深源地震,我们首先利用区域固定地震台及NECsaids流动地震台阵的连续波形数据,选取已知地震事件作为模板,采用Match&Locate及Matched Filter方法进行波形互相关叠加分析来检测微小深震事件;然后对1966至2017年ISC目录中的东北地区深源地震进行双差重定位以提高震源位置的准确性,进一步分析深震活动与俯冲板片的关系.研究结果显示除ISC目录中给出的深震事件,我们未能检测出作为模板的深源地震的前震或余震活动,证明东北深源地震余震活动较少并不是由于台站分布有限而造成的漏检结果;重定位后震源延伸的角度与西太平洋板片在410~660 km地幔转换带内的俯冲角度较为一致,并且大部分深震震源位置位于俯冲板片中的亚稳态橄榄岩楔形区内部.结合双差定位结果、b值分析及前人研究成果,我们认为东北深源地震应不属于与俯冲非直接相关的"孤立地震",而是与西太平洋板块俯冲直接相关.