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901.
采用2013年西宁市城市居民周日和周一连续两天的活动日志调查数据,利用趋势面和路径缓冲区方法表征和测度西宁市城区单位、郊区单位、城区商品房、郊区商品房、城区混合5类居住区居民的活动空间,并进行比较研究,在行为层面上对西宁城市居民日常活动空间特征及成因进行解读,利用多元线性回归模型分析活动空间的影响因素。结果表明:(1)单位居住区居民形成了职住接近主导的近家工作活动空间,商品房和混合居住区居民形成了较为扩展的工作活动空间;(2)各类型居住区居民工作日非工作活动近家集聚;(3)休息日单位居住区居民活动空间较工作日扩展,郊区商品房居住区居民活动空间较工作日收缩,城区商品房与混合居住区与工作日几无差异;(4)郊区居民活动空间范围显著大于城区居民,居住区距离市中心的距离对西宁城市居民日常活动空间范围具有正向影响;(5)住房属性是影响居民日常活动空间的重要变量,工作日商品房居住区居民活动空间显著大于单位居住区居民,而休息日各类型居住区居民活动空间范围的差异缩小。 相似文献
902.
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904.
905.
Jun Tan Junhao Wei Shuiru Li Chunhua Zhang Yanjun Li Lingli Guo Yunfei Yan 《中国地球化学学报》2008,27(4):325-334
The time gap between diagenesis and mineralization (TGDM) for comagmatic gold deposits (CGD) plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the help of preciously published isotopic ages of some typical gold deposits and their related rocks in China, the authors have discussed and quantified the distribution characteristics and scope of the TGDM. Statistical analyses and Kolmogorov tests showed that mineralizing events are either contemporaneous with or slightly postdate their cognate magma. The TGDM conforms with normal distributions at a 0.05 confidence level and clusters between 0 and 16.0 Ma with a mean of 7.0 Ma. Thus, if the TGDM of CGD is less than 16.0 Ma, it is reasonable to consider, with the aid of other evidence, the possibility of its comagmatic genetic affiliation. The authors also emphasized that to get a precise time gap it is necessary to strengthen the diagenesis-mineralization geological background of the deposits studied, and to pay attention to the study of time gap in combination with trace elements and isotope tracing. 相似文献
906.
907.
Feng Gao Morisette J.T. Wolfe R.E. Ederer G. Pedelty J. Masuoka E. Myneni R. Bin Tan Nightingale J. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(1):60-64
Ecological and climate models require high-quality consistent biophysical parameters as inputs and validation sources. NASA's moderate resolution imaging spectroradiometer (MODIS) biophysical products provide such data and have been used to improve our understanding of climate and ecosystem changes. However, the MODIS time series contains occasional lower quality data, gaps from persistent clouds, cloud contamination, and other gaps. Many modeling efforts, such as those used in the North American Carbon Program, that use MODIS data as inputs require gap-free data. This letter presents the algorithm used within the MODIS production facility to produce temporally smoothed and spatially continuous biophysical data for such modeling applications. We demonstrate the algorithm with an example from the MODIS-leaf-area-index (LAI) product. Results show that the smoothed LAI agrees with high-quality MODIS LAI very well. Higher R-squares and better linear relationships have been observed when high-quality retrieval in each individual tile reaches 40% or more. These smoothed products show similar data quality to MODIS high-quality data and, therefore, can be substituted for low-quality retrievals or data gaps. 相似文献
908.
南极磷虾资源量大且营养丰富,是人类赖以生存的后备蛋白库,如何高效利用其资源已经成为当今科技的重点和难点。通过陆上实验,设定温度在120℃的恒定干燥条件下,对其进行热风干燥,来模拟船载南极海域条件下,南极磷虾的干燥曲线和干燥速率曲线。结果显示,在恒定干燥条件下,其干燥速率是0.497g·cm~(-2)·min~(-1),临界含水率为0.56 g水·g干物料~(-1);恒定干燥时间约占全部时间的三分之一。当低于临界含水率时,物料就进入了降速干燥阶段。此外,南极磷虾的干燥速率还与干燥温度和物料的烘干表面积有关;提高干燥温度和表面积都可加快干燥速率,这对于南极磷虾粉的设备设计、实际生产都有着重要的参考和指导意义。 相似文献
909.
Land circulation is an important measure that can be utilized to enable agricultural management at a moderate scale. It is therefore imperative to explore spatiotemporal changes in land circulation and the factors that drive these variations in order to maintain and increase the vitality of the land rental market. An initial analysis of spatiotemporal patterns in land circulation is presented in this study on the basis of data from 169,511 farm households between 2003 and 2013. The rural fixed observation point system advocated by the Chinese Ministry of Agriculture was utilized for this analysis, and Heckman two-stage models were developed and estimated in order to identify the drivers of regional differences in land circulation at the national scale and at the levels of different terrains. The results of this study show that the rate of land circulation in China rose from 15.09% to 25.1% over the course of the study period, an average rate of 0.8%. More specifically, data show that the rate of land circulation in the south of China has been higher than in the north, that the average land rental payment was 4256.13 yuan per ha, and that 55.05% of households did not pay such a fee during the land circulation process. In contrast, the average rent obtained was 3648.45 yuan per ha nationally even though 52.63% of households did not obtain any payments from their tenants. The results show that land quality, geographic location, transaction costs, and household characteristics have significantly affected land circulation in different regions of China. Specifically, the marginal effects of land quality and geographic location were larger in the plain regions, while transaction cost was the key factor influencing land circulation in the hilly and mountainous regions. The signal identified in this study, rent-free land circulation, is indicative of a mismatch that has led to the marginalization of mountainous regions and higher transaction costs that have reduced the potential value of land resources. Thus, as the opportunity cost of farming continues to rise across China, the depreciation of land assets will become irreversible and the phenomenon of land abandonment will become increasingly prevalent in hilly and mountainous regions in the future. The transaction costs associated with the land rental market should be reduced to mitigate these effects by establishing land circulation intermediaries at the township level, and the critical issues of land abandonment and poverty reduction in hilly and mountainous regions should arouse more attention. 相似文献
910.
兰新高铁烟墩大风区风沙地貌制图与风沙灾害成因 总被引:2,自引:1,他引:1
兰新高铁是中国首条穿越戈壁大风区和风沙区的高速铁路。哈密以东的烟墩大风区戈壁分布集中、地貌复杂,特殊的地貌和气候条件导致该区成为兰新高铁风沙灾害最严重的区域之一,风沙灾害影响路段占研究区路段全长的57%,其中K2810-K2817、K2820-K2840路段受灾最为严重,对高铁的安全运行造成威胁。研究表明:强劲风力和丰富沙源是造成兰新高铁风沙危害的主要原因,弃耕地、灌丛沙堆地、被破坏的戈壁地表和风蚀残丘是主要沙源。戈壁地表工程建设是高铁哈密东段地表疏松、沙害频发的另一成因。基于高分辨率遥感影像,结合实地调查,绘制了典型沙害形成模式下3个沙害路段的风沙地貌专题图,为今后建立科学合理的风沙灾害防治体系提供科学依据。 相似文献