Role of market agents in mitigating the climate change effects on food economy

Natural Hazards - Agriculture’s ability to adapt to the impacts of climate change is critical for agricultural households as well as the general public and policymakers. Economic agents can...     

Physicochemistry and Mineralogy of Storm Dust and Dust Sediment in Northern China

Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites.     

新疆和田河流域柽柳沙堆的生物地貌发育过程

Tamarix nabkha is one of the most widespread nabkhas,distributing in the arid region of China.Based on the observations outdoors and the simulation experiments in laboratories,analysis in this paper refers to the biological geomorphologic features and growth process of Tamarix nabkhas in the middle and lower reaches of the Hotan River,Xin- jiang.And the results indicate that the ecological type of Tamarix in the study area is a kind of Tugaic soil habitat based on the deep soil of the Populus Diversifolia f...     

长江三峡GPS处理结果和应变背景场

采用Bernese GPS Software 4.2对长江三峡工程诱发地震监测系统GPS监测网络1998~2003年的6期观测数据进行了处理,结果表明,三峡库区与华南块体的水平相对运动在0~3mm/a(±0.1~±2.0mm/a);蓄水导致的垂直形变区域主要集中在茅坪香溪巴东库段,近岸点垂直沉降的量级在10~35mm左右,最大峰值区域香溪约35mm(±8.6mm),垂直形变沿远离库中心方向迅速衰减。采用贝塞尔双三次样条函数模型拟合该地区的应变率,推算各类水平应变场,结果表明,蓄水前各种应变背景在10^-9/a~10^-10/a量级。作为构造稳定地区,三峡库区近期因蓄水导致大规模形变,从而诱发中强地震的可能性不大。     

我国国家大地网的地壳形变改正探讨

以2000网为例,根据1991~2001年累积的GPS重复观测资料,利用GIPSY软件建立具有1115个测点的地壳运动模型。在此基础上,采用双三次样条函数数值拟合法,模拟出2000网网点相对西安基准站的地壳形变改正值,并给出了效果图。     

Landsat 8全色影像阴影的扁平冰山出水高度提取

冰山出水高度是测量冰山厚度进而估算冰山体积的一个重要几何参数,是定量评估冰山对海洋的淡水输入量的基础。冬季冰山在海冰上成影且阴影较长,本文提出利用阴影测高模型高精度测量冰山出水高度的方法。试验选择2016年8月29日、9月7日和9月16日中心太阳高度角分别为5.43°、7.49°和11.01°的3期Landsat 8全色15 m影像,以独立扁平冰山为例,自动提取冰山在海冰上的阴影长度计算冰山出水高度,并利用不同时相同名成影点进行交叉验证评估测量精度。结果显示：阴影长度测量误差优于1个像元,在太阳高度角低于11.01°时,全色15 m影像提取的冰山出水高度均方根误差（RMSE）低于2.0 m,平均绝对误差（MAE）低于1.5 m。由此表明：在冬季低太阳高度角下,Landsat 8全色15 m影像可用于高精度测量冰山出水高度,具有大范围测量南极冰山出水高度的潜力。     

Experimental Analysis of Various Types of Road Intersections for Interchange Detection

Road interchanges are a major pattern type in road networks. Recognition of road interchanges benefits automated road network generalization, car navigation and traffic flow analysis. This study first investigated several existing approaches to automatically detecting interchanges in a road network, and determined that the recognition of characteristic road intersections is essential for the effective detection of interchanges. Several experiments were carried out to investigate nine types of road intersections for interchange detection and to analyze characteristic ones. Furthermore, an approach to the detection of both intersections and segments of interchanges was proposed and validated. The road networks across different scales were tested and results show that: (1) the T‐shaped and Cross‐shaped junctions are very common in road networks, but they are not the most characteristic ones for interchange detection; (2) the y‐shaped, Y‐shaped types, X‐shaped, Fork‐shaped and Multi‐leg may be the characteristic types for interchange detection; (3) the proposed approach to detecting interchanges is effective, and most of the intersections and segments of interchanges can be detected. In addition, taking multiple characteristic types into consideration for interchange detection is suggested.     

Comparative Study of Approaches to Delineating Built‐Up Areas Using Road Network Data

Delineated built‐up areas may be used for applications such as navigation, database enrichment and the identification of urban sprawl. As more road network data have become available, many studies have considered using road network data to delineate built‐up areas. This study investigated the three existing approaches to delineating built‐up areas on a map: the grid‐based approach, kernel density analysis and an approach based on street blocks. These approaches are evaluated and compared from three angles. First, two measures were proposed to quantitatively evaluate the land area of the delineated built‐up areas; second, a questionnaire was designed to visually compare the representations of the delineated built‐up areas; and, third, the time complexity of using each approach was tested. The three approaches were applied to different sets of road network data for New Zealand; data from buildings and residential areas were used as benchmarks. The results showed that: (1) in a quantitative assessment, both the grid‐based approach and kernel density analysis can usually detect more built‐up areas than the approach based on street blocks; (2) on visual inspection, most of the students who completed the questionnaire performed the representations using the approach based on street blocks; and (3) in time complexity, the approach based on street blocks always takes the least time.     

基于Google软件的农地区高程获取及精度评价

相比于传统大比例尺测绘,高分遥感和雷达技术可以快速高效地获取农地地形边界和特征点位高程,因而可为农地整理和机械化前期研究提供决策依据。本研究基于Google Maps高分辨率遥感影像数字化农地特征点位和边界,开发了在Google Earth(谷歌地球)软件上获取坐标点位高程的程序,实现了农地特征点位数字化和高程获取;使用国家1:1万数字地形图对该方法进行了精度评估,并且与直接基于SRTM3和ASTER数字高程模型插值方法进行了比较。结果表明,本研究实现了高分辨率遥感影像和数字地形模型的整合应用,在农地边界和特征点位获取、影像校正方面比直接通过SRTM3数据插值获取高程有优势,有较好的应用潜力。