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111.
Lingyong Huang Zhiping Lu Guojun Zhai Yongzhong Ouyang Motao Huang Xiuping Lu Taiqi Wu Kaifeng Li 《GPS Solutions》2016,20(4):761-769
Triple-frequency global navigation satellite systems allow the introduction of additional linear observation combinations. We define two geometry-free phase combinations and one geometry-free pseudorange minus phase linear combination to detect and correct cycle slip in real time. At first, the optimal BDS (BeiDou System) triple-frequency geometry-free phase combinations are selected for cycle slip detection. Then, a detailed analysis of the cycle slip detection is performed by examining whether some special cycle slip groups cannot be discovered by the selected combinations. Since there still remain some cycle slip groups undetectable by the two geometry-free phase combinations, we add a pseudorange minus phase linear combination which is linearly independent with these two phase combinations, to be sure that all the cycle slips can be detected. After that, an effective decorrelation search based on LAMBDA and least squares minimum principle is applied to calculate and determine the cycle slips. The method has been tested on triple-frequency undifferenced BDS data coming from a benign observation environment. Results show that the proposed method is able to detect and repair all the small cycle slips in the three carriers. 相似文献
112.
牛栏江—滇池补水工程是滇池流域及周边地区的水资源综合利用工程,是增加滇池生态环境水量,改善滇池水资源质量的重要工程,对于保障现代新昆明建设和云南省经济社会可持续发展具有重大战略意义。然而近年的监测结果表明,牛栏江流域水资源质量有下降趋势。在以往的研究中曾提出面源污染是主要污染源。通过研究,发现牛栏江水污染物以总磷(TP)为主,且主要集中在七星桥断面以上;总磷(TP)污染主要来自于工业排放。并据此提出水污染治理的水资源保护对策。水环境治理措施和水质监测结果验证了结果的可靠性。 相似文献
113.
In order to determine the genesis and the factors that control the low-porosity and low- permeability sandstone reservoirs in the eastern Sulige Gas Field in the Ordos Basin, systematic studies on the sedimentary facies and diagenesis were conducted by means of analysis of cores, thin sections, fluid inclusions, X-ray diffraction, cathode luminescence and scanning electron microscope. It was found that the sand bodies of the major gas reservoirs in the Shan1 section (P1S1) and the He8 section (P2H8) were formed during the Permian as sedimentary facies such as braided-channel bars, braided-river channels and point bars of a meandering river. Four types of diagenetic facies developed subsequently: in order from the best to the poorest properties these are type A (weak compaction, early calcite cement-chlorite film facies), type B (moderate compaction, quartz overgrowth-feldspar corrosion-kaolinite filling facies), type C (strong compaction, late calcite cement-quartz corrosion facies) and type D (matrix filling and strong compaction facies). This diagenesis is undoubtedly the main reason for the poor reservoir properties of sandstone reservoirs, but the sedimentary facies are the underlying factors that greatly affect the diagenesis and thus the reservoir performance. Favorable diagenetic facies developed mainly in relatively small lithofacies such as braided-river channels, channel bars and point bars. The vertical distribution of the physical properties and the diagenetic facies of the reservoirs are related to the stratigraphic succession. Most of the sandstones between mudstones and thin beds of sandstone are unfavorable diagenetic facies. Analyses indicate that siliceous cementation can hardly be stopped by hydrocarbon filling. Authigenic chlorite could hardly protect the primary porosity. It not only occupies pore space, but also blocks pathways through sandstone reservoirs, so that it has significant influence on the permeability. Authigenic chlorite cannot be used as a marker for a 相似文献
114.
大气环流模式在松花江流域的适用性评价 总被引:2,自引:1,他引:1
不同GCMs的输出变量在区域上的表现差异较大。以11个统计特征量为基础,构建了基于秩评分的评价方法,分别对比分析了21个GCMs的17个输出变量在松花江流域与ERA-40再分析资料的吻合程度,以秩评分进行了定量评价。结果显示:不同GCMs对高空气象变量的模拟表现与地面气候要素的模拟表现并不一致,IPSL:CM4、GISS:ER、HadCM3和CSIRO:MK30在松花江流域高空气象变量模拟方面表现相对较好,而CSIRO:MK30、CGCM3.1_T63、GFDL:CM21和BCCR:BCM20在地面气候要素的模拟方面表现相对较好。综合评分结果显示,IPSL:CM4、CSIRO:MK30、GISS:ER和BCCR:CM20在松花江流域的综合表现相对较好。 相似文献
116.
117.
甘肃武都万象洞方解石现代沉积控制因素分析 总被引:1,自引:0,他引:1
对洞穴次生碳酸盐沉积机理的认识是解释洞穴石笋气候环境指示意义的关键.近两个水文年的洞穴现代过程监测结果显示,万象洞内温湿度全年基本保持恒定;洞穴滴水的pH值夏季偏低、冬季偏高,呈现出一定的季节变化特征,电导率和HCO3-浓度及主要阴阳离子含量年内变化不显著;洞内CO2分压夏季偏高,冬季降低接近于当地大气的CO2分压水平.对不同滴水点的对比研究表明,滴水中Ca2+达到一定浓度是方解石沉积的必要条件.此外,万象洞夏季CO2分压的升高对方解石形成产生明显的抑制作用.万象洞石笋沉积的主要受控于滴水饱和度以及洞穴CO2分压. 相似文献
118.
119.
Carbon storage capacity of different plantation types under sandstorm source control program in Hebei Province,China 总被引:2,自引:1,他引:1
Huitao Shen Wanjun Zhang Xue Yang Xiuping Liu Jiansheng Cao Xinhua Zeng Xin Zhao Xuexun Chen Wenxi Zhang 《中国地理科学(英文版)》2014,24(4):454-460
Afforestation and reforestation are effective and ecological ways of mitigating elevated atmospheric carbon dioxide(CO2) concentration and increasing carbon(C) storage in terrestrial ecosystems. In this study, we measured the above-ground(tree, herbaceous plants and litter) and below-ground(root and soil) C storage in an aspen plantation(Populus davidiana) monoculture(PD), a larch plantation(Larix pincipis-rupprechtii) monoculture(LP), a pine plantation(Pinus tabulaeformis) monoculture(PT), a larch and birch mixed plantation(L. pincipis-rupprechtii and Betula platyphlla mixed)(MLB), and an apricot plantation(Armeniaca sibirica) monoculture(AS) under the Desertification Combating Program in Hebei Province, the northern China. The objective was to assess the effect of afforestation species on ecosystem C pools of different plantation types. Results showed that C storage of LP stand(258.0 Mg/ha) and MLB(163.4 Mg/ha) were significantly higher than the C storage in PD(45.5 Mg/ha), PT(58.9 Mg/ha) and AS(49.4 Mg/ha), respectively. Soil C was the main carbon pool of the ecosystem C storage in the five plantation stands, ranging from 31.4 Mg/ha to 232.5 Mg/ha, which accounted for 69.0%–90.1% of the total ecosystem C storage. The C storage in tree layer was about 5.2%–23.2% of ecosystem C storage. The herbaceous plants and litter layers contained 1.0%–6.0% and 1.5%–3.3% of ecosystem C storage, respectively. Our results suggest that tree species should be incorporated to accurately develop regional C budget of afforestation program, and also imply that substantial differences in ecosystem C stocks among plantation types can facilitate decision making on C management. 相似文献
120.
Jiali Xin Xiaoyu Sun Liu Liu Hao Li Xingcai Liu Xiuping Li Lei Cheng Zongxue Xu 《水文研究》2021,35(3):e14069
Climate variability and underlying surface changes are strongly associated with runoff alterations. The Yarlung Zangbo River Basin (YZRB) is a typical alpine region located in the southeast Qinghai–Tibet Plateau, where runoff is particularly sensitive and vulnerable to climate and environmental changes. Here, we conducted a quantitative assessment of the contributions of climate variability and underlying surface changes to runoff alterations from 1966 to 2015 in the upper, middle, and lower regions of the YZRB. The year 1997 was identified as the runoff breakpoint in all three sub-regions, which divided the runoff time series into the baseline period (1966–1997) and change period (1998–2015). An adjusted Budyko framework accounting for glacier runoff was developed to conduct a runoff alteration attribution analysis. The results indicated that the increase in runoff in the upper region was dominated by changes in the underlying surface and glacier runoff, whose contribution accounted for 59.61 and 49.18%, respectively. The runoff increase in the middle and lower regions was mainly attributed to the increase in precipitation, accounting for 39.36 and 129.21% of the total runoff alteration, respectively. Moreover, due to the little variation in vegetation and degradation of permafrost in the upper region, increases in runoff might be largely attributed to increases in subsurface runoff caused by the melting of permafrost. In the middle region, in addition to increased precipitation, vegetation degradation had positive effects on runoff increases. The lower region exhibited far higher water consumption rates due to its extensive and dense vegetation coverage accompanied by rising temperature, which resulted in a negative contribution (−58.74%) to runoff alteration. Our findings may therefore have important implications for water resource security and sustainable development in alpine regions. 相似文献