川藏公路中段地质灾害现象的航空遥感研究   总被引：2，自引：0，他引：2  

李志中  赵长英 《国土资源遥感》1998,9(3):14-18

川藏公路巴塘至林芝段位于我国青藏高原东南部,该地区是现今地壳运动十分强烈的地区之一,地形起伏强烈,气候变化多样,因此地质灾害十分发育,川藏公路就穿过这样一个复杂的地区。为查明公路沿线的地质灾害分布情况,90年代初,地矿部航空物探遥感中心沿川藏公路进行了彩色红外航空摄影,比例尺为1∶6万。通过彩色红外航片的解译及野外实地观测,圈定出滑坡、泥石流及崩塌等灾害现象,并对这些灾害的强度、活动性及其对公路的影响进行分析,最后对灾害成因及治理方法提出了建议。  相似文献   

基于GF-3的不同极化方式SAR图像海面油膜识别的比较 ——以"桑吉"轮事故为例          下载免费PDF全文

付弘涛  秦平 《海洋开发与管理》2019,36(3):54-56

基于我国自主研发的首颗分辨率达到1m的C频段多极化合成孔径雷达高分三号卫星(GF-3),通过典型溢油案例定性和定量地比较了双极化与单极化图像预处理性能,分析了不同的极化组合对海面油膜识别结果的影响。得出结论:同向极化与异向极化成像差异明显,VV极化明显比VH极化回波强度高,并且油膜识别度较高;相反,双极化VHVV方式与单极化VH方式图像效果区别不大,双极化方式并不能绝对性地提高地物识别度。  相似文献   

基于分数阶Fourier变换的高性能SAR成像算法     

王振力  王群  陈先意  马如坡  刘晓迁 《地球信息科学学报》2020,22(11):2247-2255

传统距离多普勒算法（RD）较低精度的SAR成像质量越来越不能满足当前实际应用的需要。为解决传统距离多普勒算法成像性能低的问题,本文提出基于分数阶Fourier变换的高性能SAR成像算法（FrFT-RD）。本文详细推导SAR距离向信号运用分数阶Fourier变换时最佳阶数的计算表达式,同时给出方位向相应的计算式。理论分析表明距离（方位）向最佳阶数均取决于SAR成像参数并具有唯一性,无须迭代运算,可极大提高FrFT-RD算法的工程实用性。根据计算得到的距离向和方位向上最优阶数,在分数阶Fourier变换域完成FrFT-RD算法的构建。机载SAR模拟数据和星载SAR实测数据测试表明,FrFT-RD算法在分辨率、峰值旁瓣比（PSLR）成像性能方面比传统RD算法均得到显著提高,其中距离向和方位向分辨率提高比值分别为45.92%和48.06%;距离向PSLR和ISLR降低幅度为1.45 dB和2.59 dB,而FrFT-RD算法在方位向PSLR和ISLR成像性能方面与传统RD算法相当。  相似文献   

Characterizing geographical preferences of international tourists and the local influential factors in China using geo-tagged photos on social media     

《Applied geography (Sevenoaks, England)》2016

Understanding the geographical preferences of international tourists is critical for the tourism planning and marketing. However, it is not an easy endeavor to gather the corresponding information, given the absence of city-level tourism statistical data and high costs of participant survey. This paper characterizes the geographical preferences of international tourists using geo-tagged photos on social media (the Flickr in particular). Data are harvested for 333 prefecture-level cities in China from 2008 to 2013, and the intensity of photo sharing (IPS: the ratio between total number of uploaded photos and total area of the city/region) is used an indicator of tourist geographical preferences. IPS visualization shows the geography that tourism hotpots generally concentrate in regional capital cities and economically developed megaregions. More specifically, the East Asia and Oceania tourists exhibit more preferences towards the eastern coastal cities, while the Europe and North America visitors show increasing interest in exploring the western and northern places. Spatial regression is employed to quantify the local influential factors of tourists’ geographical preferences. It is found that international tourists usually consider the local economy, accessibility, infrastructure and cultural attractions when they choose their destinations in China. East Asia and Oceania visitors particularly appreciate the local economy and cultural attractions. Europe and North America tourists especially value the cultural attractions and local openness. The demonstrated methodological framework is not restricted to Flickr data, and it can be applicable to social media offer geo-tagging service. This paper is therefore believed to advance the applications of social media into geographical research.  相似文献   

Phytoplankton response to short-term temperature and nutrient changes     

《Limnologica》2016

Meteorological extreme events (heavy rainfall, heat waves) may lead to fast changes in nutrient load and water temperature in temperate lakes. We conducted laboratory experiments with an artificial phytoplankton community to mimic a rapid temperature increase (from 21 °C to 29 °C) at low nutrient levels (‘heat wave scenario’), respectively temperature decrease (from 21 °C to 16 °C) and increased nutrient load (‘heavy rainfall scenario’). We hypothesised that there is a taxon specific nutrient x temperature interaction, leading to significant shifts in the phytoplankton community composition when both variables change. To separate the temperature effect from the nutrient effect, we performed another experimental series at a reduced temperature but without addition of nutrients. As expected, the nutrient effect was overall more important than temperature and significantly affected all five taxa tested that represented different algal classes. However, temperature also played an important role for community composition, because the cryptophyte Cryptomonas sp. and the dinoflagellate Peridinium sp. reached significantly higher biovolumes at lower temperatures. The nutrient x temperature interaction was significant in the green alga Scenedesmus obliquus. These findings suggest that our experimental results cannot be interpreted primarily by species competition for nutrients. Heterotrophic bacteria were present in all experiments. Bacterial biomass was significantly positively related to temperature and nutrients. However, relative to phytoplankton biovolume, bacterial biovolume decreased under nutrient replete conditions. In conclusion, our results demonstrate that short-term environmental change may significantly affect both the phytoplankton community (in terms of species dominance and total biomass) and the ratio between autotrophs and heterotrophs in temperate lakes.  相似文献   

华南前汛期广东暴雨分区动力特征及特大暴雨分析   总被引：5，自引：0，他引：5  

王坚红  徐碧裕  刘刚  徐安高 《气象与环境学报》2014,30(6):43-51

依据2009－2013 年华南地区72 测站逐日降水资料,利用 REOF方法、合成分析等方法,分析华南前汛期（4-6 月）暴雨时空特征。结果表明：暴雨降水量占总降水量34.6%,年暴雨日数170天以上。REOF方法分析获得华南前汛期5个暴雨模态区, 其中广东两模态区中心荷载强于其余3个区,降雨更多,雨强更大。合成分析显示,广东北部暴雨区受西风带系统影响为主, 暴雨中尺度系统为气旋及变形场锋生。沿海暴雨区受副热带系统控制为主,中尺度系统主要为低空急流,输送气旋式切变和旋转涡度,及低空速度辐合, 并提供自海上来的充沛水汽,造成沿海区暴雨远强于北部区。 近5 a前汛期广东24 h累积降雨量大于200mm的大暴雨有14次,均发生在沿海暴雨模态区。两区暴雨机制分别为西风带中尺度低值系统锋生降水,和副热带系统暖区登陆地形作用降水。海温SST方面沿海暴雨区环境较北部暴雨区具有更大平均水汽潜热量,含更充沛水汽。而感热场反映沿海暴雨区从下垫面吸收更多热能量,更有利于不稳定暴雨过程维持与加强。对2010 年6 月9 -12 日广东沿海上川岛持续性特大暴雨分析显示,东北阻塞高压强盛与副热带高压西伸北进势均力敌配置,水汽通道和水汽通量散度輻合异常强盛, 湿位涡湿正压项和湿斜压项均构成有利于垂直涡度增长环境, 这些因子维持了特大暴雨过程。  相似文献   

Speleothems from Mawsmai and Krem Phyllut caves,Meghalaya, India: some evidences on biogenic activities     

Sushmitha Baskar  R. Baskar  Natuschka Lee  P. K. Theophilus 《Environmental Geology》2009,57(5):1169-1186

The Mawsmai cave and Krem Phyllut caves, East Khasi hills, Meghalaya, India has so far not yet attracted the attention of geomicrobiologists. Observations and hypotheses on the possible influence of identified microorganisms for speleothem formations in Meghalaya are reported for the first time. XRD studies identified calcite in speleothems and gypsum in cave wall deposits as the dominant minerals. SEM-EDAX showed interesting microfabric features showing strong resemblance with fossilised bacteria, calcified filaments, needle calcite and numerous nano scale calcite crystals, highly weathered and disintegrated crystals of calcite, that point towards a significant microbial influence in its genesis. Thin section petrography showed laminated stromatolitic features. The microorganisms identified by conventional isolation and further evaluation of isolates by molecular techniques include Bacillus cereus, Bacillus mycoides, Bacillus licheniformis, Micrococcus luteus, and Actinomycetes. Microscopic observations also showed unidentifiable cocci and four unidentifiable strains of CaSO₄ (gypsum) precipitating bacteria. Experimental studies confirmed that these bacteria are able to precipitate calcium minerals (calcite, gypsum, minor amounts of dolomite) in the laboratory. These results allow us to postulate that species like these may contribute to active biogenic influence in the cave formations at Meghalaya.  相似文献   

泥蚶(Tegillarca granosa)血红蛋白基因(Tg-HbIIA)克隆、分析及免疫表达研究   总被引：1，自引：0，他引：1  

汪青  林志华  包永波  霍礼辉  顾海龙 《海洋与湖沼》2012,43(1):88-94

通过已构建的泥蚶血液cDNA文库,克隆得到泥蚶Tg-HbIIA基因全长cDNA序列,对其进行生物信息学、组织表达及免疫相关分析。结果表明,泥蚶Tg-HbIIA cDNA全长731bp,包含63bp5′非编码区(5′-UTR),246bp3′非编码区(3′-UTR),开放阅读框450bp,编码150个氨基酸;其氨基酸序列与毛蚶(Scapharca kagoshimensis)和不等壳毛蚶(Scapharca inaequivalvis)的序列有较高的同源性,分别达到89%和88%;对其结构预测显示该蛋白具有血红蛋白功能域,含有10个潜在血红素结合位点。qRT-PCR检测结果显示:泥蚶不同组织部位中,Tg-HbIIA mRNA在血液表达量最大,其次为外套膜和鳃,表达量最低的是肝胰脏;在副溶血弧菌(Vibrio parahaemolyticu)、脂多糖、肽聚糖刺激后,泥蚶血液Tg-HbIIA mRNA表达量显著上调,表明Tg-HbIIA在贝类抗菌免疫防御中可能起重要作用,而Tg-HbIIA对不同致病因子免疫反应的灵敏度和表达时序存在一定差异。  相似文献   

Degradation of Reactive Dyes Using Advanced Oxidation Method          下载免费PDF全文

Özgen Ercan  Sabahattin Deniz  Ece Kök Yetimoğlu  Adnan Aydın 《洁净——土壤、空气、水》2015,43(7):1031-1036

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Microbial Decolorization of Reactive Dye Solutions          下载免费PDF全文

Neha Parmar  Sanjeev R. Shukla 《洁净——土壤、空气、水》2015,43(10):1426-1432

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