河南“米”字形高铁网构建对可达性及城市空间格局影响

从可达性的视角采用平均旅行时间、经济潜力、日常可达性等指标对河南“米”字形高速铁路网构建对各地市省内和省际可达性及城市空间格局的影响进行分析发现,① “米”字形高速铁路网有助于各地市省内和省际可达性水平提升,郑州的极化与集聚效应进一步增强,边界城市的交通边缘化状况明显改善,“米”字形城镇发展轴带正在形成;② 各地市省内和省际经济潜力大幅度提升,位置居中的高铁沿线城市省内区位优势显著,边界高铁沿线城市在省际联系中的门户区位优势显现;③ 以郑州中心的0.5 h核心圈、1 h紧密圈正在形成,“同城效应”显现,各地市省际2 h交流圈大幅度拓展,以郑州为中心的1.5 h省际合作圈即将形成。高铁网的构建将成为河南城市空间格局演变的重要推动因素和空间结构优化的基础支撑条件。     

Integrating spatial and temporal contexts into a factorization model for POI recommendation

Matrix factorization is one of the most popular methods in recommendation systems. However, it faces two challenges related to the check-in data in point of interest (POI) recommendation: data scarcity and implicit feedback. To solve these problems, we propose a Feature-Space Separated Factorization Model (FSS-FM) in this paper. The model represents the POI feature spaces as separate slices, each of which represents a type of feature. Thus, spatial and temporal information and other contexts can be easily added to compensate for scarce data. Moreover, two commonly used objective functions for the factorization model, the weighted least squares and pairwise ranking functions, are combined to construct a hybrid optimization function. Extensive experiments are conducted on two real-life data sets: Gowalla and Foursquare, and the results are compared with those of baseline methods to evaluate the model. The results suggest that the FSS-FM performs better than state-of-the-art methods in terms of precision and recall on both data sets. The model with separate feature spaces can improve the performance of recommendation. The inclusion of spatial and temporal contexts further leverages the performance, and the spatial context is more influential than the temporal context. In addition, the capacity of hybrid optimization in improving POI recommendation is demonstrated.     

Relationships between Genetic Diversity of Vascular Plant Species and Climate Factors

Genetic diversity is crucial for plants to respond to global climate change, and exploring relationships between genetic diversity and climatic factors may help predict how global climate change will shape the genetic diversity of plants in the future. So far, however, the extent and magnitude of the impact of climatic factors on the genetic diversity of plants has not been clarified. We collected data from 68 published papers on two widely used measures of genetic diversity of populations (average expected heterozygosity (He) and average observed heterozygosity (Ho)) and on localities of populations of 79 vascular plants, and extracted data on 19 climatic factors from WorldClim. We then explored the relationships between measures of genetic diversity and climatic factors using linear regressions. He of plant populations was significantly correlated with climatic factors in 58.7% (44) of the 75 species that used He as a measure of genetic diversity, and Ho was correlated with climatic factors in 65.1% (41) of the 63 species that used this genetic diversity measure. In general, Mean Temperature of Wettest Quarter, Precipitation Seasonality, Precipitation of Driest Quarter and Temperature Seasonality played a vital role in shaping He, and Ho was mostly correlated with Precipitation of Warmest Quarter, Mean Temperature of Wettest Quarter, Precipitation of Driest Quarter and Precipitation of Driest Month. Also, the proportion of the significant correlations between genetic diversity of populations and climatic factors was higher for woody than for herbaceous species, and different climatic factors played different roles in shaping genetic diversity of these two growth forms. Our results suggest that climate may play an important role in shaping genetic diversity of plant populations, that climatic change in the future may alter genetic diversity of plants, and that genetic diversity of different plant forms may respond to climatic change differently.     

一次华南超级单体风暴的S波段偏振雷达观测分析

利用珠海与澳门共建的中国首部S波段业务双偏振雷达探测资料、风廓线资料和地面加密观测资料,对2015年4月20日发生在珠海附近的一次典型华南春季冷锋触发的超级单体风暴的偏振观测特征进行了分析。天气分析表明,风暴发生于地面冷锋和低空切变线附近,中等对流不稳定（对流有效位能为1300 J/kg）和较强风垂直切变（0-6 km风矢量差为20 m/s）环境中。环境总理查逊数为18,与中纬度典型超级单体的生成环境接近,风暴相对螺旋度为2.9 s-1。偏振观测分析表明,大雹粒子的翻滚使冰雹区具有水平反射率因子高（>50 dBz）、差分反射率低（-1-0.5 dB）的特点;雨和冰相粒子的混合导致了相关系数的下降（小于0.9）;比差分相位观测对冰雹并不敏感（比差分相位与水平反射率因子的线性拟合率仅为0.05）。在混合相粒子和液相粒子的共同作用下,融化层附近存在差分反射率增大、相关系数减小的现象。风暴侧前方下沉气流偏东侧边界（水平反射率因子梯度高值区）存在一条“差分反射率弧”（差分反射率高值区）,主要由大雨滴构成,粒子分选机制合理解释了其形成原因。同时,相对较大的环境风使差分反射率弧更加远离（相对北美观测事实）风暴主体。风暴水平反射率因子中心附近存在“差分反射率柱”,与大雨滴被上升气流（连续分布的正径向风）带入高层冻结且失去取向稳定而导致差分反射率值迅速减小有关。      

武汉城市区域水陆风环流的形成与转化特征研究

大气细颗粒物PM_2.5污染引起的雾霾天气既与本地污染物排放密切有关,也受局地特殊的风场影响.本文以武汉城市区域为研究对象,分别研究了长江沿岸的江陆风环流、东湖沿岸湖陆风环流的形成与转化特征,发现江风、湖风开始时间均为07：00-08：00,一年中最大风速均能达到2 m/s左右,而春夏季江风的持续时间高于秋冬季,夏季湖风的持续时间高于春季.同时发现区域附近温度和相对湿度之间有明显的相关性,湿度变化趋势大体上跟温度变化趋势相反,且温度对相对湿度的影响存在一定的滞后性,延迟时间大约为1 h.     

Extraction of basic trends of urban expansion in China over past 40 years from satellite images

If urban sprawl is to be avoided in China in the next ten years, it is not only crucial to understand the overall history, current status, and future trends of urban expansion there, but also these differences, and this is presently lacking. In this study, remotely sensed images with approximately 30 m spatial resolution were used to quantitatively assess the spatial and temporal patterns of urban expansion of 60 Chinese cities(1973–2013). Urban-expansion-process curves of the cities studied were drawn using annual expansion area as an indicator. Curve similarity analysis generated four basic process modes of urban expansion in China. These included cities that: 1) peaked around 2004 and then decelerated; 2) peaked around 2010 and then decelerated; 3) showed sustained acceleration, and 4) showed continued deceleration. Four basic process modes represented cities under different levels of development stage. Geographic location was found to be the most related characteristic to urban expansion process. Regional development policies at the national level in each region also showed highly temporal consistency with fluctuation characteristics of urban expansion process. Urban characteristic such as population size and administrative level were not found to be significantly related to urban expansion-process modes. Understanding the basic process-mode categories well is extremely important for future regional-balance planning and development of macroeconomic policies.     

空间目标信息系统的访问控制方案设计

空间目标信息系统(STIS)是基于空间信息实现重要目标信息采集、管理、显示、查询、分析等功能的一种面向多部门、多应用的分布式地理信息系统,不同用户具有不同的操作权限。引入基于角色的访问控制技术,从访问控制体系结构、RBAC数据库、用户访问控制流程3个不同的角度对STIS访问控制方案设计进行了详细阐述。该方案对于保证系统的安全性和明确用户职责具有非常重要的意义。     

基于e-Learning的测绘专业教学训练系统的设计与实现

介绍了e-Learning的概念及体系结构,结合测绘专业教育的实际需求,在e-Learning三层体系结构的基础上,给出e-Learning环境下测绘专业教学训练的系统设计及实现方案。     

依巴谷星表和第谷星表的特征和意义

主要论述依巴谷星表和第谷星表的观测特征和天体测量特征,依巴谷卫星在短期内同时测定大量高精度的恒星位置,自行和视差等五个天体测量参数以及星等和色指数,依巴谷星表和第谷星表为建立高精度的光学参考系,为研究恒星的起源,演化,分布,质量,大小和光度等,为研究双星和聚星的分布和运动,为研究星系运动和星系动力学提供了大量的高精度资料,具有重要的科学意义。     

探矿权公告数据库设计初探

在参考相关探矿权数据库的基础上,针对地质立项工作的实际需要,设计了含有综合查询和坐标范围查询等项的探矿权公告数据库。有效解决了地质人员在信息不全面时产生的查询困难,弥补了国土资源部网《探矿权信息查询系统》的不足之处。