一种抗压缩的等高线数据盲水印算法     

牛莉婷  王明孝  曾端阳  高晨  黄定军 《测绘与空间地理信息》2013,(12):31-33

根据等高线数据的特点,提出了一种抗压缩的等高线数据盲水印算法。首先采用逐点前进法对等高线数据进行数据压缩,提取特征点,然后基于量化思想将水印信息嵌入在特征点的小数部分。实验结果表明,该算法具有较好的抗压缩效果。  相似文献   

    

Jihong Jia  Wenzhi Zhao  Shoubo Li 《水文研究》2013,27(24):3409-3414

The surface energy balance algorithm for land method was used in this study to calculate the evapotranspiration (ET) rate for the middle reaches of the Heihe River Basin, Gansu Province, China, to analyse ET distribution within the oasis and the surrounding desert and, especially, on the edge zone of the oasis. Five profile graphs were created vertical to the river. Because of the inverse humidity phenomenon, the least amount of evapotranspiration occurred on the desert close to the oasis. The average evapotranspiration rate was roughly proportioned from the edge of the oasis to inside and outside its boundary. Two meteorological ground stations located close to the oasis edge showed a notable difference in net radiation flux that led to the difference found in ET. The primary reason for the significant differences observed in net radiation may be largely the result of differences in flux reflectivity and surface temperature. Meteorological data show that water supply also played an important role. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

An application of a new method in permafrost environment assessment of Muli mining area in Qinghai-Tibet Plateau,China   总被引：1，自引：2，他引：1  

Wei Cao  Yu Sheng  Yinghong Qin  Jing Li  Jichun Wu 《Environmental Earth Sciences》2011,63(3):609-616

The permafrost environment in the Muli mining area, an opencast mining site in the Qinghai-Tibet Plateau, China, is now undergoing significant degradation because of the ongoing mining activities. The permafrost environment in this mining site had already been evaluated by previous study, in which analytic hierarchy process was applied. Although this method can roughly characterize the permafrost environment of this mining site, it has limitations by being easily affected by man-made factors. In view of this limitation, this study attempts to employ a new method, the catastrophe progression method, to estimate the current stage of the permafrost environment in this mining area. The results show that, by catastrophe progression method, currently the calculated indexes of the permafrost freezing–thawing disintegration, permafrost thermal stability, permafrost ecological fragility, and the permafrost environment are 0.43 (general situation), 0.77 (general situation), 0.71 (bad situation) and 0.83 (general situation), respectively. These values imply that the permafrost environment has been damaged by anthropologic activities to a certain degree and potentially may be further degenerated. However, at this degree, a new equilibrium stage of permafrost environment could be achieved if the current state of environmental degradation is stabilized and treatments are constructed against further damages.  相似文献   

兰州城市建筑的空间分布   总被引：1，自引：0，他引：1  

杨永春 《世界地理研究》2008,17(1):39-46

利用高精度卫星影象和大规模实地调查方法获取数据,采用GIS手段、景观生态学和数理统计等方法,利用建筑占地面积和建筑面积等指标分别研究了兰州市各区、功能区、各组团、各圈层现状建筑的空间分布与组合,以及城市资产、土地强度的空间变化规律。结果表明：住宅、工业、商务三类建筑是兰州市建筑的绝对核心类型,空间分布均衡而广泛,且工业建筑向外围迁移过程中存在全域分散化特征：兰州市各区建筑用途复杂程度、多样性和均匀性由中心到外围大致逐步降低,优势度逐渐增加,组团分布特征显著而强烈;建筑更新具有明显的全域化和快速推进特征;建筑用途空间组合、建筑容积率由中心到外围的空间波动性较为显著：建筑用途多样性、建筑容积率等指标高或低的“插花”分布现象相当显著;住宅、工业建筑更新与空间分化是城市建筑更新、建筑用途空间分化与组合及其变迁的核心动力因素,单位制模式的影响依旧强烈和深刻。  相似文献   

Seasonal variations of organic carbon and nitrogen in the upper basins of Yangtze and Yellow Rivers     

Xiang-ying Li  Yong-jian Ding  Tian-ding Han  Jian-zhong Xu  Shi-chang Kang  Qing-bai Wu  Mika Sillanpää  Zhong-bo Yu  Cong-rong Yu 《山地科学学报》2017,14(8):1577-1590

The profound impacts exerted by climate warming on the Tibetan Plateau have been documented extensively, but the biogeochemical responses remain poorly understood. This study was aimed at seasonal variations of total organic carbon (TOC) and total organic nitrogen (TON) in stream water at two gauging sections (TTH, ZMD) in the upper basin of Yangtze River (UBYA) and at four gauging sections (HHY, JM, JG, TNH) in the upper basin of Yellow River (UBYE) in 2013. Results showed that concentrations of TON exhibit higher values in spring and winter and lower values in summer. TOC exhibits higher concentrations in spring or early summer and lower concentrations in autumn or winter. Seasonal variations of TOC and TON fluxes are dominated by water flux. In total, the UBYE and UBYA delivers 55,435 tons C of organic carbon and 9,872 tons N of organic nitrogen to downstream ecosystems in 2013. Although the combined flux of TOC from UBYA and UBYE is far lower than those from large rivers, their combined yields is higher than, or comparable with, those from some large rivers (e.g. Nile, Orange, Columbia), implying that organic carbon from the Tibetan Plateau may exert a potentially influence on regional and/or global carbon cycles in future warming climate.  相似文献   

中国公众对全球气候变化认知与支持减缓气候变化政策研究——基于全球调查数据和与美国比较视角     

常跟应  黄夫朋  李曼  李国敬 《地理科学》2012,(12):1481-1487

公众对气候变化的认知影响个人和家庭限制温室气体排放、支持减缓气候变化的政策措施等。基于5次全球调查数据和与美国的对比,分析了中国公众对气候变化的认知、减缓气候变化支付意愿和对气候政策的支持。分析表明中国大部分公众听说过气候变化,认为人类活动是气候变化的重要原因,但对气候变化深层原因了解不够;大部分公众认为气候变化对自然灾害的发生、降水和水资源、食物种类等带来了很大不利影响,进而担忧气候变化,认为气候变化问题很严重;大部分公众认为限制温室气体排放是国际社会共同的责任,应该立即采取行动限制温室气体排放,包括改变生活方式、接受较高的能源价格、保护森林、取消政府对私家车的补贴、提高机动车的能效等。最后讨论了进一步需要研究的问题。  相似文献   

Luminescence study of the initial,pre-casting firing temperatures of clay mould and core used for bronze casting at Yinxu (13c. BC∼11c. BC)     

《Quaternary Geochronology》2015

During the Anyang period in Shang dynasty (13c.BC ∼ 11c.BC), the bronze manufacture of Ancient China reached its maximum glory and splendor, as evidenced by the casting moulds and cores unearthed in the Yinxu. The pre-casting firing temperature of the moulds, one of the key technologies in the casting system, is still a controversial issue. In this article, the firing temperature of the mould and the core, unearthed at the Xiaomintun Site, Yin ruins, is estimated to be 600°C–700 °C, analyzed by luminescence techniques. This study can settle down the dispute in the results of the thermal expansion analysis.  相似文献   

Geological evaluation of Halfway–Doig–Montney hybrid gas shale–tight gas reservoir,northeastern British Columbia     

《Marine and Petroleum Geology》2013,39(1):53-72

Evaluation of the reservoir quality of the Triassic Halfway–Montney–Doig hybrid gas shale/tight gas reservoir in the Groundbirch field in northeastern British Colombia requires an integration of unconventional and conventional methodologies. Reservoir evaluation includes reservoir thickness and structure, total porosity, TOC content, organic maturity, pore size distribution (micro- to macro-pore size fractions), surface area, mineralogy and pulse-decay permeability. Quartz (10–74%), carbonate (13–73%) and feldspar (0–42%) dominate the mineralogy of all formations with illite (0–32%) being locally important. The T_max values range between 443 and 478 °C placing the reservoirs beyond the oil window. Pore size distribution by low-pressure gas adsorption analysis identifies a large variation between the contributions from the micro-, meso- and macro-pore size fractions. Matrix permeabilities range between 1.0E-3 and 6.5E-7 mD at an effective stress between 2400 and 3300 PSI (16.5–22.8 MPa).Changes in depositional environments and diagenetic processes manifest as differences in lithology and mineralogy within the Montney and Doig reservoirs which subsequently affect the fabric, texture and pore size distribution. Fabric, texture and pore size distribution contribute to the variation in the permeability and the proportions of free to sorbed gas within the reservoir. Quartz-rich, coarser-grained intervals (upper portions of Doig C, B and Halfway Formation) have lower surface area, greater porosities and a higher volume of macropores compared to the carbonate- and clay-rich finer-grained intervals (Doig A). Permeabilities do not vary according to lithology with higher permeabilities found within both fine-grained (Doig A) and coarser-grained (Halfway Formation) units. Permeability is controlled by pore size distribution. Higher permeability samples contain a balanced ratio between micro-, meso- and macro-porosity. The finer-grained intervals have higher sorbed gas capacity due to higher surface areas because of the higher volumes of finer mesopores and micropores than the coarser-grained units. However, porosity and permeability are low in some parts of the Doig A and fracture stimulation is necessary to achieve economic flow rates.  相似文献   

    

Yu Huang  Zhidan Zhao  Jiangang Jiao  Bibo Qiu  Zhen Ma  Di-Cheng Zhu 《Geological Journal》2021,56(4):1987-2007

Voluminous Early Cretaceous volcanic rocks in the central Lhasa subterrane provide an ideal opportunity for understanding the mantle–crust interaction and tectonic-magmatic evolution of the Lhasa Terrane. Here, we report zircon U–Pb ages, geochemical and Sr–Nd–Pb–Hf isotopic data for the Early Cretaceous volcanic rocks, including high-silica rhyolites (117.2 ± 1.1 Ma) and contemporaneous andesites (114.1 ± 0.8 Ma) in the Sailipu area, central Lhasa subterrane. All these rocks show enriched light rare earth elements (LREE), and radioactive heat-generating elements (e.g., Th, U, K, and Pb) but depleted high-field-strength elements (HFSEs, e.g., Nb, Ta, P, and Ti). The different bulk-rock Sr–Nd–Pb and zircon Hf isotopic compositions of the rhyolites and andesites suggest that these rocks have distinct magma sources and petrogenetic history rather than an identical source involving assimilation-fractional crystallization process. The Sailipu high-silica rhyolites exhibit the characteristics of fractional crystallization and have varying zircon ε_Hf(t) values (−12.2 to +5.2), negative ε_Nd(t) values (−9.5 to −1.6), high and variable initial Sr isotopic compositions ([⁸⁷Sr/⁸⁶Sr]_i = 0.7047–0.7116) and radiogenic Pb isotopic signatures (²⁰⁶Pb/²⁰⁴Pb = 18.784–18.802, ²⁰⁷Pb/²⁰⁴Pb = 15.722–15.737, and ²⁰⁸Pb/²⁰⁴Pb = 39.382–39.492). A combined process of magma mixing (involving crustal-derived felsic melts and mantle-derived mafic melts) and subsequent fractional crystallization were mainly responsible for the formation of these high-silica rhyolites. The Sailipu andesites show more enriched Sr–Nd isotopic compositions [(⁸⁷Sr/⁸⁶Sr)_i = 0.7088–0.7154, ε_Nd(t) = −9.9 to −6.7] relative to rhyolites, and less radiogenic Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.632–18.669, ²⁰⁷Pb/²⁰⁴Pb = 15.686–15.689, ²⁰⁸Pb/²⁰⁴Pb = 39.140–39.201). They were likely derived from partial melting of an enriched mantle wedge previously metasomatized by melts derived from subducted sediments. We interprete these Early Cretaceous volcanic rocks as the product of slab break-off during the southward subduction of the Bangong-Nujiang Tethyan oceanic seafloor. The dominantly positive ε_Hf(t) and ancient T_DM^C ages (0.85–1.90 Ga) of Sailipu high-silica rhyolites further imply that, under the stress relaxation regime, the mantle-derived melts locally reworked the ancient basement of the central Lhasa subterrane.  相似文献   

Parameter estimation for a karst aquifer with unknown thickness using the genetic algorithm method   总被引：3，自引：2，他引：3  

Chengpeng Lu  Longcang Shu  Xunhong Chen  Cheng Cheng 《Environmental Earth Sciences》2011,62(4):797-807

The combination of ecological fragility and agricultural activity in the loess hilly–gully regions of western China has received broad environmental concerns. In this region, rainfall and soil moisture can fatally influence crop production under dry land farming. In this study, field experiments were conducted, from March 2001 to September 2005, to demonstrate the variation of soil moisture and fertilizer contents at different depths in slope and terraced lands, and to evaluate the ecological impacts and economic benefits in the terraced land of Loess Plateau. The results of both field test and Grey model (GM) calculation show that the terraced land, as compared to the sloping land, in the agricultural area of the Loess Plateau tends to store and retain much water, promoting more favorable interactions between water and fertilizer. During the months from March to June of the year with less rainfall, the water supply for crop growth is mainly derived from the deep storage of soil moisture accumulated from July to September of the previous year. The field experiments indicate that the crop yield of the 3-year-old terraced lands was 27% higher than that of the sloping lands with slopes greater than 10°, and that the crop yield can increase by 27.07 to 52.78% in the following cultivation years. In particular, potato was found to be more drought-resistant than winter wheat, thus it is more suitable for the arid and semi-arid Loess Plateau regions.  相似文献