基于扩展关系模型的整体空间数据管理

空间数据模型和数据管理是地理信息系统 (GIS)最重要的研究领域之一。该文介绍一体化的数据模型———扩展关系模型和以此为基础的 ,由作者设计的GIS软件原型系统———GEODBMS。GEODBMS使用统一的数据库管理系统 (DBMS)同时管理图形和属性数据 ;使用改进的四叉树———交叠四叉树索引空间目标 ;使用扩展的SQL语言进行空间查询 ;使用数据恢复和并发控制方法来加强分布式环境下数据的安全性和一致性维护     

砾卵石层中预制桩的承载性状研究

依据59根桩静载荷试验实测结果和桩侧相关土层的标贯试验成果,反算出砾卵石持力层中预制桩的极限桩端阻力,结合7根桩身埋设有应力计的预制桩桩端阻力的实测成果,分析了砾卵石层中的预制桩的桩端阻力、桩端荷载分担比例及端阻充分发挥所需的桩端位移。通过对121根以砾卵石为持力层的预制桩的静载试验成果与静压法施工终压力的比较,分析了砾卵石层中静压预制桩的施工终压力与极限承载力的关系。     

The impact of dredge-fill on Posidonia oceanica seagrass meadows: regression and patterns of recovery

Posidonia oceanica meadows can be severely damaged by dredge-fill operations. We report on the construction of gas pipelines that occurred between 1981 and 1993 in SW Sicily, Italy. A large portion of the meadow was mechanically removed, and the excavated trench was filled with a mosaic of substrates, ranging from sand to consolidated rock debris. Meadow loss and recovery were quantified over 7 years after the end of operations. We recorded an overall loss of 81.20 ha of meadow. Substrate strongly affected recovery as the percent cover by P. oceanica consistently increased on calcareous rubble, reaching values of 44.37 ± 3.05% in shallow sites after 7 years, whereas no significant increase occurred on other substrates. As in the Mediterranean Sea exploitation of coastal areas continues to grow with consequent impacts on P. oceanica meadows, this case study illustrates how artificial rubble-like materials could be employed to support the restoration of damaged meadows.     

Efficient GOCE satellite gravity field recovery based on least-squares using QR decomposition

We develop and apply an efficient strategy for Earth gravity field recovery from satellite gravity gradiometry data. Our approach is based upon the Paige-Saunders iterative least-squares method using QR decomposition (LSQR). We modify the original algorithm for space-geodetic applications: firstly, we investigate how convergence can be accelerated by means of both subspace and block-diagonal preconditioning. The efficiency of the latter dominates if the design matrix exhibits block-dominant structure. Secondly, we address Tikhonov-Phillips regularization in general. Thirdly, we demonstrate an effective implementation of the algorithm in a high-performance computing environment. In this context, an important issue is to avoid the twofold computation of the design matrix in each iteration. The computational platform is a 64-processor shared-memory supercomputer. The runtime results prove the successful parallelization of the LSQR solver. The numerical examples are chosen in view of the forthcoming satellite mission GOCE (Gravity field and steady-state Ocean Circulation Explorer). The closed-loop scenario covers 1 month of simulated data with 5 s sampling. We focus exclusively on the analysis of radial components of satellite accelerations and gravity gradients. Our extensions to the basic algorithm enable the method to be competitive with well-established inversion strategies in satellite geodesy, such as conjugate gradient methods or the brute-force approach. In its current development stage, the LSQR method appears ready to deal with real-data applications.     

基于TM遥感数据的汶川地震极重灾区生态恢复研究

本文以地震极重灾区2006、2008和2011年3期Landsat TM遥感影像为数据源,利用GIS提取灾区土地利用信息,结合坡度和高程等地形因子对灾区主要生态系统面积的变化进行综合分析.结果表明:2008年地震对灾区生态环境造成严重破坏,使研究区农田、森林和草地生态系统分别减少了124.6km2、461.6km2和9...     

保安湖沉水植被恢复及其渔业效益

通过消除对沉水植物生长有破坏作用的草食性鱼类和杂食性鱼类,在低水位的早春选择无风浪的天气移栽水草,于１９９年保安湖一个面积为３．３ｈｍ＾２网栏湖汊成功地恢复了绝迹８个月的水草群落,秋季水草覆盖盖达５０％,同时研究了在无鱼类摄食破坏的条件下苦草和黄丝草的生长动态。     

气举技术应用于深海无隔水管泥浆回收钻井工艺可行性分析

无隔水管泥浆回收钻井技术作为新兴钻井技术,具有安全环保、简化井身结构和降低钻探风险等优点。传统的无隔水管泥浆回收钻井技术依靠水下泵将海底井口泥浆举升至甲板面,该方式对水下泵的举升能力及可靠性要求极高。未来深海钻井领域,水下泵将会是限制无隔水管泥浆回收钻井技术应用的“瓶颈”。本文借鉴陆地气举反循环钻井原理,利用气举技术部分或完全替代水下泵,分别从设备技术现状、流量可调性、适用环境、井控安全等方面探究气举用于无隔水管泥浆回收技术的可行性。结果表明,气举反循环技术及相关设备性能满足无隔水管泥浆回收的使用要求,而且具有上返流量可调、安全等特点,有较高的研究应用价值。     

港口工程中非均质层状地基承载力计算方法

在深水码头、防浪堤等大型港口工程建设中常常会遇到构筑物下覆地基由非均质的层状土构成的情况。对于这类非均质层状地基,我国港口工程地基规范推荐采用Hansen 61公式、Hansen 69公式和Sokolovskii数值解法3种方法计算地基的极限承载能力。然而,工程实践中由这3种方法计算得出的地基极限承载力数值往往有较大的差别。考虑到规范的继承性,基于牛顿迭代法,针对3个理论计算公式编制了计算程序,根据长江口深水治理二期工程地质实测资料,运用该计算程序对该地区地基的极限承载能力进行了计算比较。计算结果表明,对于非均质层状地基,在相同地质条件、相同荷载条件下Sokolovskii数值解法得到的承载力数值最大,Hansen 69公式得到的承载力数值最小。     

毛细管气相色谱法测定矿坑水中的苯系物

以国家标准方法和EPA方法为基础, 进行了矿坑排水中苯系物的测定.在测定过程中进行了质量保证和质量控制实验, 用外标法定量.在水样测定的同时对用自动顶空进样器和吹扫捕集浓缩仪两种进样方式测定矿坑排水中苯系物的方法进行了比较, 对进样方式和影响测定的因素进行了讨论.结果表明, 自动顶空进样器的回收率为108.5 8%~116.38%, 方法检出限为5.00~10.00 μg/L; 吹扫捕集浓缩仪的回收率为94.87%~105.6 3%, 方法检出限为0.25~0.50 μg/L.      

Methodology and use of tensor invariants for satellite gravity gradiometry

Although its use is widespread in several other scientific disciplines, the theory of tensor invariants is only marginally adopted in gravity field modeling. We aim to close this gap by developing and applying the invariants approach for geopotential recovery. Gravitational tensor invariants are deduced from products of second-order derivatives of the gravitational potential. The benefit of the method presented arises from its independence of the gradiometer instrument’s orientation in space. Thus, we refrain from the classical methods for satellite gravity gradiometry analysis, i.e., in terms of individual gravity gradients, in favor of the alternative invariants approach. The invariants approach requires a tailored processing strategy. Firstly, the non-linear functionals with regard to the potential series expansion in spherical harmonics necessitates the linearization and iterative solution of the resulting least-squares problem. From the computational point of view, efficient linearization by means of perturbation theory has been adopted. It only requires the computation of reference gravity gradients. Secondly, the deduced pseudo-observations are composed of all the gravitational tensor elements, all of which require a comparable level of accuracy. Additionally, implementation of the invariants method for large data sets is a challenging task. We show the fundamentals of tensor invariants theory adapted to satellite gradiometry. With regard to the GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite gradiometry mission, we demonstrate that the iterative parameter estimation process converges within only two iterations. Additionally, for the GOCE configuration, we show the invariants approach to be insensitive to the synthesis of unobserved gravity gradients.