基于情景分析的天津市滨海新区地面沉降预测

鉴于地面沉降演化的地质系统渐变性特征,从主要致灾因子考虑建立地面沉降数值模型。设计3种地下水开采情景,编译计算机程序预测地下水位动态变化过程中的地面沉降值。至2020年,在最不利、适中和最理想3种情景下天津市滨海新区最大累计沉降量分别达640 mm、520 mm和150mm;全区平均累计沉降量分别达268 mm、177 mm和95 mm。     

Denudation rates of crystalline rock in the Huangling anticline of the Three Gorges of the Yangtze River in China since the Eocene

The processes and rates of the weathering denudation of the bare crystalline rock are important problems in the field of geosciences[1—6]. Essentially, the weathering denudation process is the process of rock destruction and transportation. In different …     

Trajectory Analysis and Design for A Jupiter Exploration Mission

The trajectory design for a Jupiter exploration mission is investigated in this paper. The differences between the Jupiter exploration trajectory and the Mars or Venus exploration trajectory are mainly concerned about. Firstly, the selection of the Jupiter-centered orbit is analyzed based on the Galileo Jupiter mission. As for the Earth-Jupiter transfer orbit, the fuel consumption of the direct transfer is too large. So the energy-saving technologies such as the planetary gravity assist should be used for the trajectory to the Jupiter. The different sequences of planetary gravity assists are examined by applying the Particle Swarm Optimization (PSO). According to the searched result, the Venus-Earth-Earth sequence (VEEGA) is the most effective one for the Jupiter mission. During the Jupiter mission, the spacecraft will pass though the main asteroid belt between the orbits of Mars and Jupiter, and may encounter multiple asteroids. Therefore the Jupiter mission is able to combine with the main-belt asteroid flyby mission. The design method of the intermediate asteroid flyby trajectory is also considered. At last, an entire trajectory for the Jupiter mission launched in 2023 is presented.     

利用空间测地技术结果估计地球平均下地幔粘性(英)

基于IEC－4G冰期后地壳反弹模型,和地球上Laurentia,Fennoscandia,Antarctica,andGreenland四大冰盖最近21000年以来的冰融参数,计算了对地球最大主转动惯量的影响△I33,并进而由现代空间测地技术观测资料分析得到的地球自转非潮汐加速项为约束,估计了地球平均下地幔（670km以下）粘性vLM为（0．9～2．5）·1022Pas,这个结果表明了vLM应具有1022Pas量级．     

异地异构天文数据资源的统一访问

天文观测数据资源具有时间跨度大,数据量大,存储、管理分散,管理工具驳杂等特点.如何提供给天文学家一个统一访问这些异地存放的异构数据资源的方案,是虚拟天文台的一个重要研究课题.本文提出了一种基于网格的解决方案.我们基于OGSA-DAI技术实现了对天文星表数据,图像数据和光谱数据的封装(DataNode).我们设计的虚拟天文台数据访问服务(VO-DAS)实现了对DataNode的自动资源发现以及异地异构数据库的联合访问.这将使天体的多波段交叉证认成为可能.VO-DAS支持国际虚拟天文台联盟(IVOA)的各项相关标准,使得它具有良好的互操作性.它的对外接口简单实用,可以针对不同需求的天文数据用户发展出多种网格应用产品.通过在两个科学范例中应用VO-DAS服务,证明了它的可行性.     

长三角经济高速发展地区土壤pH时空变化及其影响因素

通过调查和分析长三角地区张家港市2004年和第二次土壤普查时(1980)的土壤pH,探讨了该市近20年来基于经济高速发展影响下的土壤pH变化及影响因素。结果表明,自第二次土壤普查以来,该市土壤pH变化明显。南部人为土地区绝大部分土壤pH值都下降了一个单位,平均值由7.39降至6.33;北部雏形土区,两个时期的土壤pH值分别为7.92和7.98。土壤pH的降低可能同该地区长期施用化学肥料、酸雨及工业酸性“三废”排放的增加有关。此外,土地利用和田间管理也对土壤pH变化起着较为重要的作用,而土壤地球化学性质差异则是导致南北地区土壤pH变化不同的内在因素。     

Combining AHP and genetic algorithms approaches to modify DRASTIC model to assess groundwater vulnerability: a case study from Jianghan Plain,China

Accurate identification of vulnerability areas is critical for groundwater resources protection and management. The present study employed the modified DRASTIC model to assess the groundwater vulnerability of Jianghan Plain, a major farming area in central China. DRASTICL model was developed by incorporating the land use factor to the original model. The ratings and weightings of the selected parameters were optimized by analytic hierarchy process (AHP) method and genetic algorithms (GAs) method, respectively. A combined AHP–GAs method was proposed to further develop this methodology. The unity-based normalization process was employed to categorize the vulnerability maps into four types, such as very high (>0.75), high (0.5–0.75), low (0.25–0.5), and very low (<0.25). The accuracy of vulnerability mapping was validated by Pearson’s correlation coefficient between vulnerability index and the nitrate concentration in groundwater and analysis of variance F statistic. The results revealed that the modified DRASTIC model had a large improvement over the conventional model. The correlation coefficient increased significantly from 41.07 to 75.31% after modification. Sensitivity analysis indicated that the depth to groundwater with 39.28% of mean effective weight was the most critical factor affecting the groundwater vulnerability. The developed vulnerability model proposed in this study could provide important objective information for groundwater and environmental management at local level and innovation for international researchers.     

Effects of agricultural practices on nitrogen distribution in unsaturated soils

Nitrogen fertilizer consumption is very common in the agricultural practices. Nitrogen application could be an important source of groundwater N pollution. Normally, nitrogen can pass through the unsaturated zone to pollute the groundwater. Different agricultural practices have different cultivation methods, accordingly different fertilization and irrigation techniques. Hence, the agricultural practice determines the environment of the unsaturated zone, which subsequently determines the extent of groundwater N pollution. To verify the pollution modes and transformation mechanisms of nitrogen, both in situ and laboratory tests were conducted at four different sites to study the effects of agricultural practices on nitrogen distribution in unsaturated zones. The inorganic nitrogen in soil is extracted by potassium chloride solution, and the soil utilization form and pollution type are identified by δ¹⁵N by comparing with the known standard values. The experimental results indicate that continual fertilization and sewage irrigation in these agricultural regions were the primary sources of nitrogen in the unsaturated zone. In the soils planted with rice, δ¹⁵N–NH₄ ⁺ was relatively elevated due to ammonium volatilization. In the unsaturated zone of rice–wheat rotation fields, NO₃ ^?–N and δ¹⁵N were both elevated because of manure fertilizer. Meanwhile, denitrification also occurred in the hypoxic environment due to the high soil water content.     

Catalytic ozonation of dimethyl phthalate by Ce-substituted goethite

Dimethyl phthalate (DMP) is ubiquitous in aquatic environments due to extensively used as plasticizer, which has received increasing attention in recent years. In this study, the catalytic ozonation of dimethyl phthalate was performed using Ce-substituted goethite as a novel catalyst, which was prepared by isomorphous substitution method. The specific surface area, pHpzc and surface hydroxyl density of the catalyst were determined. The catalyst was characterized using X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy. The removal efficiency of DMP was almost 100% after 30 min, and about 40% DMP was mineralized after 60 min, which was nearly four times higher than single ozonation. During catalytic ozonation process, anions (PO₄ ^3?, SO₄ ^2?, Cl^?) affected DMP degradation, indicating that surface hydroxyl groups on the surface of catalyst were main active sites. The electron transfer process by redox reaction between Ce³⁺/Ce⁴⁺, Fe²⁺/Fe³⁺ was proposed, and their interaction could also promote the formation of hydroxyl radicals. Ce-substituted goethite was an efficient catalyst for degradation of DMP by catalytic ozonation.     

BIM技术在深基坑工程中的应用探讨

BIM技术是一种新型的设计方法,它实现了设计从二维空间向三维空间变革,从静态的信息向动态的信息发展。在大量查阅国内外有关基坑支护设计研究文献的基础上,综述了基坑支护设计方法,分析了不同设计软件优缺点和设计方法需解决的关键性理论问题,提出了基于BIM技术在深基坑工程中的应用设想,分析了BIM技术应用在深基坑工程中需解决的关键性技术问题,为相关研究提供参考借鉴。