Integrating CART algorithm and multi-source remote sensing data to estimate sub-pixel impervious surface coverage: a case study from Beijing Municipality,China

The sub-pixel impervious surface percentage(SPIS) is the fraction of impervious surface area in one pixel,and it is an important indicator of urbanization.Using remote sensing data,the spatial distribution of SPIS values over large areas can be extracted,and these data are significant for studies of urban climate,environment and hydrology.To develop a stabilized,multi-temporal SPIS estimation method suitable for typical temperate semi-arid climate zones with distinct seasons,an optimal model for estimating SPIS values within Beijing Municipality was built that is based on the classification and regression tree(CART) algorithm.First,models with different input variables for SPIS estimation were built by integrating multi-source remote sensing data with other auxiliary data.The optimal model was selected through the analysis and comparison of the assessed accuracy of these models.Subsequently,multi-temporal SPIS mapping was carried out based on the optimal model.The results are as follows:1) multi-seasonal images and nighttime light(NTL) data are the optimal input variables for SPIS estimation within Beijing Municipality,where the intra-annual variability in vegetation is distinct.The different spectral characteristics in the cultivated land caused by the different farming characteristics and vegetation phenology can be detected by the multi-seasonal images effectively.NLT data can effectively reduce the misestimation caused by the spectral similarity between bare land and impervious surfaces.After testing,the SPIS modeling correlation coefficient(r) is approximately 0.86,the average error(AE) is approximately 12.8%,and the relative error(RE) is approximately 0.39.2) The SPIS results have been divided into areas with high-density impervious cover(70%–100%),medium-density impervious cover(40%–70%),low-density impervious cover(10%–40%) and natural cover(0%–10%).The SPIS model performed better in estimating values for high-density urban areas than other categories.3) Multi-temporal SPIS mapping(1991–2016) was conducted based on the optimized SPIS results for 2005.After testing,AE ranges from 12.7% to 15.2%,RE ranges from 0.39 to 0.46,and r ranges from 0.81 to 0.86.It is demonstrated that the proposed approach for estimating sub-pixel level impervious surface by integrating the CART algorithm and multi-source remote sensing data is feasible and suitable for multi-temporal SPIS mapping of areas with distinct intra-annual variability in vegetation.     

从欧州一体化看泛北部湾经济合作途径

区域经济一体化是当前世界发展的重要趋势。回顾欧洲一体化走过的道路给了我们很多启示:必须树立合作理念,确立核心力量,建立有效的制度约束,适时选择利益切合点,深入推进泛北部湾经济合作。当务之急是要把泛北部湾经济合作上升为国家战略,解决经济合作中主体对等问题。同时,把能源合作问题作为泛北部湾经济合作的重点,这不仅可以有效阻止第三方势力进入,而且还可以有助于提高我国能源通道的安全性,并与国家在北部湾地区布局重大石化项目的战略形成呼应。     

澜沧江上游某水电站坝肩岩体倾倒变形的成因控制条件研究

该变形体是一个较独特的倾倒变形问题,它与澜沧江上游河谷其他地段倾倒变形问题的形成控制因素有着较大的不同。通过深入研究该倾倒变形岩体的分布情况、基本形式及变形特征、发展过程及力学机制等方面,本文从地形临空条件、岩体结构、特殊的侧向切割结构面等3个方面阐述了该倾倒变形体特殊的控制条件,并进一步分析了该倾倒变形体的形成发展演化全过程。     

地基GNSS遥感探测气象应用

全球导航卫星系统（GNSS）给定位、导航和授时服务带来了革命性变化,同时其L波段（1160～1610MHz）微波信号可用于全球覆盖、高时间分辨率的大气、海洋和陆表参数遥感探测。基于信号类型,GNSS遥感可分为折射信号遥感和反射信号遥感两大类;基于探测平台,GNSS遥感可分为地基GNSS遥感、空基GNSS遥感和天基GNSS遥感三大类。随着我国自主建设的北斗卫星导航系统全面建成,GNSS遥感将迎来新的发展机遇和挑战。本文回顾近20年地基GNSS遥感探测在气象领域的应用进展,展望其在气象领域下一步可能的应用。     

Seismicity simulation with a rate- and state-dependent friction law

The dynamic motions and stabilities of a single-degree-of-freedom elastic system controlled by different friction laws are compared. The system consists of a sliding block connected to an elastic spring, driven at a constant velocity. The friction laws are a laboratory-inferred friction law called the rate-and-state-dependent friction law, proposed by Dieterich and Ruina, and a simple friction law described by dynamic and static frictions. We further extend the solution to a one-dimensional mass-spring model which is an analog of a fault controlled by the rate-and-state-dependent friction law. This model predicts non uniform slip and stress drop along the rupture length of a heterogeneous fault. This result is very different from some earlier modelings based on the simple friction law and a slip weakening friction law. In those earlier modelings the stress and slip functions become smoother with time along the length of the fault rupture, owing to the interactions between fault segments during slip. Because of this smoothing process the number of small events will decrease with time, and the universilly observed stationary magnitude-frequency relation cannot be explained. The interaction between a fault segment and its neighboring segments can be measured when the post-slip stress on this segment is compared with the stress on an identical segment (represented by a block in this modeling) without neighboring segments. If the post-slip stress of the former is much higher than that of the latter, strong interaction exists; if the two are close, only weak interaction exists. The interaction is determined by the relative motion between fault segments and the time duration of interaction. Our new modeling with the rate-and-state-dependent friction law appears to show no such smoothing effect and provides a physical mechanism for the roughening process in the difference between the fault strength and stress that is necessary to explain the observed stationary magnitude-frequency relation. The noninstantaneous healing predicted by the rate-and-state-dependent friction law may be repsonsible for the recurring nonuniform slip and stress drop, and may be explained by the reduction of interaction among fault segments due to the low frictional strength during the fault stopping. The very low friction during slip stopping allows much longer times than does the higher friction due to instantaneous healing for the fault segments to adjust their motions from an upper-limit slip velocity to almost rest. According to newton's second law, a process with fixed masses and constant velocity changes involves low forces and weak interactions if it is accomplished in a long time period, and vice versa. Our modeling also indicates that the existence of strong patches with higher effective stress on a fault is needed for the occurrence of major events. The creeping section of a fault, such as the one along the San Andreas fault in central California, on the other hand, can be simulated with the rate-and-state-dependent friction law by certain model parameters, which, however, must not include strong patches. In this case small earthquakes and aseismic creep relieve the accumulating strain without any large events.     

东营凹陷盐家地区沙四上亚段砂砾岩储层岩相与物性关系

依据岩性、粒度、沉积构造等特征,将东营凹陷盐家地区沙四上亚段近岸水下扇砂砾岩体划分为10种岩相类型和13种在一次沉积事件中形成的岩相组合类型,并将其岩相组合类型划分为3大类6小类。针对砂砾岩储层在任一深度物性范围变化较大的问题,遵循"岩相组合类型-岩相类型-距砂泥接触面距离"的研究思路,采用逐步分解的方法,建立"岩相组合类型-岩相类型-距砂泥接触面距离"约束下的物性纵向演化图,结果显示任一深度物性参数变化范围相对较小,各岩相类型储层孔隙度的变化一般为±2%,渗透率的变化一般在一个数量级以内。对比分析各岩相类型物性图可知:随埋深增加,各岩相类型远泥岩部位储层物性整体变差;同一深度,由Ⅰ型岩相类型到Ⅱ型岩相类型物性变好。与远泥岩的各岩相组合底部岩相类型相比,扇中比扇根部位各级别孔隙度和渗透率的深度上限增加了800~1 200 m;与远泥岩的各岩相组合中上部岩相类型相比,扇中比扇根部位各级别孔隙度和渗透率的深度上限增加了1 100~1 650 m。扇中近泥岩部位和扇缘薄层砂因发生强烈胶结作用而使物性变差,在3 400 m以下基本为超低孔超低渗储层。     

Functional characterization of a Δ6 fatty acid desaturase gene and its 5′-upstream region cloned from the arachidonic acidrich microalga Myrmecia incisa Reisigl (Chlorophyta)

Journal of Oceanology and Limnology - It is suggested that Δ6 fatty acid desaturase (FAD) plays a critical role in the biosynthesis of polyunsaturated fatty acids in plants and microalgae. But...     

“东北寨式”金矿床中雄黄的成因矿物学研究

本文较系统地探讨了“东北寨式”金矿床中雄黄的产状、化学成分、物理性质、晶胞参数、红外光谱与硫同位素组成等特征。雄黄富As亏S、含Sb和微量Au、Ag、Tl、Hg、Bi、Se、Te(Se/Te=29—58);晶胞体积>800;红外吸收340,370cm~(-1);显微硬度平均达57kg/mm~2,δ~(34)S≈-5‰。这些可作为研究区金矿化的标型特征。将其用于对比其它雄黄矿(床)点的研究,预测和评价深部金矿化已获得初步成效。     

气候变暖有益于中国的社会和谐

中国传统农业的产量受气候控制,气候表现为冷暖和干湿交替的循环,因此农业产量也出现循环演变的规律,在冷期中生活资源的短缺所造成的生存压力,加剧了矛盾,促进了战争。而气候变暖可以缓解这些矛盾,因此,气候变暖有益于中国的社会和谐。