鞍山-海城地区地震地下水地球化学研究

通过测量辽宁省鞍山-海城地区地震重点监测区地下水离子浓度和氢、氧同位素组成,讨论了该区地下水化学类型的时空变化及其成因。测量结果表明,取样点水温变化范围为11.0～97.0℃,水样的总固溶物（TDS）在197.89～829.99mg/L之间,水样分为8种化学类型。大部分水样的δD、δ¹⁸O值均沿中国东北地区大气降水线分布,少数有所偏离,表明该区的地下水主要接受大气降水的补给,并可能有深部水的供给。研究区Ca-HCO₃和Ca·Mg-HCO₃型水主要是岩石风化溶解和阳离子交换作用的结果;Ca-HCO₃·Cl和Ca·Na-Cl·SO₄型水主要受岩石风化溶解、阳离子交换作用、深部卤水混入或人类活动影响;Ca-HCO₃·SO₄和Ca-SO₄·HCO₃型水与岩石风化溶解以及深部流体混入有关;Na-SO₄·HCO₃和Na-HCO₃·SO₄型水主要是深部来源水体的混入造成的。采样期间研究区发生2次M_L≥3.0地震,采样点在地震发生月份出现了明显的离子浓度异常变化;Na⁺、Mg²⁺、Ca²⁺、Cl^-和SO₄^2-浓度变化明显,对地震活动响应较灵敏。     

Temporal and spatial changes of blue water and green water in the Taihang Mountain Region,China, in the past 60 years

ABSTRACT

Appropriate allocation of limited freshwater resources to humans and ecosystems is an important issue hampering sustainable development in mountainous regions. The Taihang Mountain Region (TMR), including the Yellow and Hai river basins, is an important water source area for the North China Plain. The distributed hydrological model Water and Energy transfer Processes in Large river basins (WEP-L) was used to simulate the water cycle processes and to summarize the temporal and spatial changes in the blue and green water in the TMR from 1956 to 2015. The results show that in the period 2011–2015 the annual average blue water decreased by 7.31 × 10⁹ m³, while the annual average green water increased by 13.60 × 10⁹ m³ compared to 1956–1960. At the inter-annual time scale, the blue water exhibited a downward trend while the green water exhibited an upward trend. The amount of seasonal blue water in the TMR is ranked in descending order: summer, autumn, spring and winter, while for green water, the rank is summer, spring, autumn and winter. The amounts of blue and green water are higher on the windward than on the leeward slopes. The blue water yield is generally higher in forests and grasslands than in farmland, while the green water exhibits the opposite response. A greater emphasis should be placed on the widening gap between blue water and green water due to climate warming, and on soil and water conservation measures.     

拱形与矩形断面地铁车站结构地震反应比较研究

采用动力时程法开展了拱形与矩形断面地铁车站结构地震反应的研究,分析了拱形断面和矩形断面地铁车站结构的关键截面在地震作用下的内力及变形的差异。结果表明:相比于矩形断面车站结构,拱形断面车站结构顶板边缘处和侧墙顶端的弯矩明显减小,车站侧墙顶端和顶板边缘处因承受弯矩过大而发生破坏的可能降低;内柱截面的轴压比明显减小,且与侧墙的轴压比差异显著减小,受力分配更为合理;拱形车站结构顶、底板的相对位移、内柱和侧墙的位移角相对较小。在已模拟的工况下拱形车站内力分布形式更为合理,水平变形相对较小,更有利于抗震。     

柱脚可更换的地下结构抗震截断柱技术性能分析

基于功能可快速恢复的抗震韧性设计目标,结合提升中柱水平变形能力的地下结构抗震截断柱技术,提出了可有效避免由于柱脚应力集中产生的破坏和震后可快速更换的地下结构中柱设计思路,其中复合截断中柱与顶、底纵梁采用剪力销栓连接,柱脚部采用局部增强或增韧可更换材料进一步替代。采用数值模型分析了复合柱的承载力、变形能力以及柱脚采用不同材料时对复合柱变形和承载力的影响规律,并与整体现浇柱进行了对比。结果表明:一般截断柱的承载能力明显低于整体现浇柱,但其变形能力远远优于整体现浇柱。随着中柱变形的增加,一般截断柱中柱柱脚位置出现明显的“应力集中”现象,局部增强或增韧材料的采用可有效避免复合截断柱脚部因应力集中而产生的破坏,提高了复合截断柱的水平变形能力。     

椭圆形柱体地震动水压力的简化分析方法

首先,文章基于辐射波浪理论,在椭圆坐标系下采用分离变量法推导了水中椭圆形柱体地震动水压力的解析解。之后,采用有限元方法建立了地震作用下水与结构相互作用的动力方程,方程中水体对结构的作用为一满阵的附加质量矩阵。满阵的附加质量矩阵难以在商业有限元中实现,因此提出了集中的附加质量矩阵方法,其中结构柔性引起的附加质量为集中附加质量矩阵和修正系数的乘积,该修正系数与无量纲参数宽深比和长短轴比相关。最后,通过曲线拟合,提出了刚性椭圆柱体动水力的均布附加量简化公式,该简化公式是无量纲参数宽深比和长短轴比的函数。     

城市更新对房地产市场的时空影响效应:基于杭州市的实证研究

以杭州市为例,采用双重差分法研究城市更新对房地产市场的时空影响效应。研究结果发现： 城市更新在不同阶段对周边住宅价格产生的影响效应不同,项目建设和运营期分别对周边房价产生28.6%和32.0%的推升作用; 城市更新对周边住房价格的影响在空间上存在显著差异,对城市边缘区的提升作用比核心区高23.0%; 城市更新对周边房价影响随着距离增加显著降低,距离城市更新项目中心2.0 km以内、2.0~3.5 km范围对房价的推升作用分别为41.9%、24.9%和9.1%。最后建议政府完善房地产市场微观调控,建立完善长效机制。     

车载测量系统教学试验设计

针对测绘学科从传统测绘到数字化测绘,再到信息化测绘的发展,分析了当前测绘教学模式中存在的一些不足,提出将车载测量系统新技术引入到本科生教学。分析了课堂进行车载测量系统学习的前沿性和可行性,并根据其原理进行课程和试验的模块化设计。结果表明,测绘新产品能够激发学生学习兴趣和创新能力,提高专业技能,符合测绘教育的现代化的要求。     

A simple assessment approach for winter wheat loss risk impacted by water stress

In this study, an empirical assessment approach for the risk of crop loss due to water stress was developed and used to evaluate the risk of winter wheat loss in China, the United States, Germany, France and the United Kingdom. We combined statistical and remote sensing data on crop yields with climate data and cropland distribution to model the effect of water stress from 1982 to 2011. The average value of winter wheat loss due to water stress for the three European countries was about ?931 kg/ha, which was higher than that in China (?570 kg/ha) and the United States (?367 kg/ha). Our study has important implications for the operational assessment of crop loss risk at a country or regional scale. Future studies should focus on using higher spatial resolution remote sensing data, combining actual evapotranspiration to estimate water stress, improving the method for downscaling of statistical crop yield data and establishing more sophisticated zoning methods.     

Modelling relational contexts in GEOBIA framework for improving urban land-cover mapping

In human cognition, both visual features (i.e., spectrum, geometry and texture) and relational contexts (i.e. spatial relations) are used to interpret very-high-resolution (VHR) images. However, most existing classification methods only consider visual features, thus classification performances are susceptible to the confusion of visual features and the complexity of geographic objects in VHR images. On the contrary, relational contexts between geographic objects are some kinds of spatial knowledge, thus they can help to correct initial classification errors in a classification post-processing. This study presents the models for formalizing relational contexts, including relative relations (like alongness, betweeness, among, and surrounding), direction relation (azimuth) and their combination. The formalized relational contexts were further used to define locally contextual regions to identify those objects that should be reclassified in a post-classification process and to improve the results of an initial classification. The experimental results demonstrate that the relational contexts can significantly improve the accuracies of buildings, water, trees, roads, other surfaces and shadows. The relational contexts as well as their combinations can be regarded as a contribution to post-processing classification techniques in GEOBIA framework, and help to recognize image objects that cannot be distinguished in an initial classification.     

Validation of Global Evapotranspiration Product (MOD16) Using Flux Tower Data from Panjin Coastal Wetland,Northeast China

Recent advances in remote sensing technology and methods have resulted in the development of an evapotranspiration(ET) product from the Moderate Resolution Imaging Spectrometer(MOD16). The accuracy of this product however has not been tested for coastal wetland ecosystems. The objective of this study therefore is to validate the MOD16 ET product using data from one eddy covariance flux tower situated in the Panjin coastal wetland ecosystem within the Liaohe River Delta, Northeast China. Cumulative ET data over an eight-day period in 2005 from the flux tower was calculated to coincide with the MOD16 products across the same period. Results showed that data from the flux tower were inconsistent with that gained form the MOD16 ET. In general, results from Panjin showed that there was an underestimation of MOD16 ET in the spring and fall, with Biases of -2.27 and -3.53 mm/8 d, respectively(–40.58% and -49.13% of the observed mean). Results for Bias during the summer had a range of 1.77 mm/8 d(7.82% of the observed mean), indicating an overestimation of MOD16 ET. According to the RMSE, summer(6.14 mm/8 d) achieved the lowest value, indicating low accuracy of the MOD16 ET product. However, RMSE(2.09 mm/8 d) in spring was the same as that in the fall. Relationship between ET and its relevant meteorological parameters were analyzed. Results indicated a very good relationship between surface air temperature and ET. Meanwhile a significant relationship between wind speed and ET also existed. The inconsistent comparison of MOD16 and flux tower-based ET are mainly attributed to the parameterization of the Penman-Monteith model, flux tower measurement errors, and flux tower footprint vs. MODIS pixels.