无人机航摄相片倾角对立体高程扭曲的影响分析     

连镇华 《地理空间信息》2010,8(1):20-22

通过对相片倾角对航测高程误差影响的理论分析,结合无人机低空摄影实际生产出现的问题,提出无人机低空摄影飞行姿态控制的指导性建议。  相似文献   

Plastic litter in sediments from the Croatian marine protected area of the natural park of Telaščica bay (Adriatic Sea)     

Andrea Blašković  Paolo Fastelli  Hrvoje Čižmek  Cristiana Guerranti  Monia Renzi 《Marine pollution bulletin》2017,114(1):583-586

This paper reports baseline levels of litter (macro, meso and microplastics) in sediments collected from different areas of the Croatian MPA of the Natural Park of Tela??ica bay (Adriatic Sea, GSA n. 17). The distribution of total abundance according to size, for all analysed locations evidences that microplastics are the dominant fraction concerning item's numbers. In all analysed samples no macroplastics were found, while microplastics are 88.71% and mesoplastics are 11.29% of the total.  相似文献   

Consumption,growth and survival of the endemic stream shredder Limnephilus atlanticus (Trichoptera,Limnephilidae) fed with distinct leaf species     

《Limnologica》2017

Oceanic freshwater communities tend to be species poor but rich in endemism due to their physical isolation. The ecology of endemic freshwater species is, however, poorly known. This study assessed allometric relationships, feeding preferences, growth and survival of larvae of the endemic stream insect Limnephilus atlanticus (Trichoptera, Limnephilidae) exposed to four leaf species differing in their physical and chemical characteristics (Ilex perado, Morella faya, Alnus glutinosa and Clethra arborea), in laboratory trials. All regression models used to estimate L. atlanticus dry mass from body and case dimensions and wet mass were significant, but wet mass and body length were the best predictors. Limnephilus atlanticus consumed all the four leaf species offered, but when given a choice, shredders significantly preferred A. glutinosa over the other three leaf species. Relative larval growth rate was significantly higher when L. atlanticus fed on A. glutinosa and I. perado leaves in comparison with the other leaf species. Survival of 95% was found when individuals fed on A. glutinosa leaves while it decreased to 75% when they fed on the other leaf species. Our results suggest that L. atlanticus can be an active shredder and that it exhibits the same basic patterns of food exploitation as its continental counterparts. The lack of an effect of shredders on litter decomposition in Azorean streams revealed by previous studies may thus be due to low densities or to a preference for food resources other than the low quality native litter species.  相似文献   

Effect of riparian land use on environmental conditions and riparian vegetation in the east African highland streams     

《Limnologica》2017

Agricultural land use is expanding and at an accelerated rate. In Ethiopia, most of this expansion has occurred in highland areas and involve deforestation of natural riparian vegetation. However, the impacts on the water quality of streams are poorly understood, especially with regard to the influence of land use patterns on highland streams. In this study, we investigated the effects of land use modifications on the water quality and riparian condition of highland streams and examined whether the preservation of riparian vegetation would help mitigate the negative impacts of intensive agriculture practices. Our results show significant differences in the water quality of streams with different land use. Several parameters commonly used to indicate water quality, such as the concentrations of orthophosphate, turbidity, and suspended solids were significantly higher in the agricultural streams than in the forest stream. The preservation of riparian vegetation in the surrounding highland streams was associated with overall better riparian condition, floristic quality, and water quality such as lower turbidity, total suspended solids, orthophosphate, and higher dissolved oxygen. We conclude, that increases in vegetation cover improved riparian condition and water quality relative to other non-vegetated areas. Therefore, we strongly recommend the preservation of riparian vegetation in tropical highland streams surrounded by intensive agriculture. More studies on the effects of best management practices in areas dominated by agriculture can greatly improve our capacity to prevent the degradation of water quality in tropical highland streams of Africa.  相似文献   

无网格局部Petrov-Galerkin法大地电磁场二维正演模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

卢杰  李予国 《地球物理学报》2017,60(3):1189-1200

有限差分法和有限单元法在大地电磁场数值模拟中已经得到了广泛的应用,但其数值结果的精度在很大程度上依赖于网格的离散程度.当模拟起伏地形、弯曲界面等复杂地电模型大地电磁场响应时,常常需要花费大量的时间以便得到较合理的离散网格.无网格局部Petrov-Galerkin法(MLPG)不同于有限差分法和有限元法,其形函数和权函数脱离了网格的束缚.本文详细推导了二维大地电磁场边值问题的弱式形式,并将其离散为局部积分域内的表达形式.通过模拟二维海洋地电模型大地电磁场响应,并与结构网格有限元结果进行对比,验证了本文算法和程序的正确性及精度.设计了一个含有弯曲界面的二维地电模型,讨论了不同离散网格对MLPG无网格法模拟结果的影响,并与结构有限元法结果进行了比较,结果表明MLPG无网格法模拟结果受离散网格影响较小.最后利用MLPG无网格法计算了两个海洋起伏地形模型的大地电磁响应,讨论了海底起伏地形对大地电磁响应的影响.  相似文献   

Holocene river and slope activity in the Visoko Basin,Bosnia‐Herzegovina – climate and land‐use effects     

S. DREIBRODT  C. LUBOS  R. HOFMANN  N. MÜLLER‐SCHEEßEL  I. RICHLING  O. NELLE  M. FUCHS  K. RASSMANN  Z. KUJUNDŽIĆ‐VEJZAGIĆ  H.‐R. BORK  J. MÜLLER 《第四纪科学杂志》2013,28(6):559-570

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Nitrous oxide production and denitrification rates in estuarine intertidal saltmarsh and managed realignment zones     

Martin S.A. Blackwell  Sirwan Yamulki  Roland Bol 《Estuarine, Coastal and Shelf Science》2010

Increasing concerns over habitat loss and rising costs of sea defence maintenance due to rising sea levels, has seen increases in the practice of managed realignment and reflooding of former reclaimed areas of intertidal saltmarsh and mudflat around the world. These practices are taking place with little knowledge of their impact on soil biogeochemical processes. Rates of denitrification (using the acetylene inhibition technique) and nitrous oxide (N₂O) production were measured from a long-established saltmarsh (SM) and an adjacent, recently re-flooded managed realignment (MR) site comprising former arable land in the estuary of the River Torridge, Devon, UK. Incubations were carried out in closed chambers in which patterns of tidal flooding were simulated automatically. Measurements were made during periods of flood and non-flood over a total of four tidal inundations with estuarine water. During the latter two flooding episodes floodwater was amended with nitrate (NO₃⁻). Nitrous oxide production in the SM soil generally was lower than in the MR soil, with mean values and standard errors over the whole incubation of 0.27 ± 0.16 mg N₂O-N m⁻² h⁻¹ and 0.65 ± 0.15 mg N₂O-N m⁻² h⁻¹ respectively. Denitrification rates demonstrated a similar trend although generally were an order of magnitude higher than N₂O production, with mean rates and standard errors of 2.88 ± 1.12 mg N₂O-N m⁻² h⁻¹ in the SM soil and 3.39 ± 1.16 mg N₂O-N m⁻² h⁻¹ in the MR soil. The data suggest that both soils are net sinks for NO₃⁻ and net sources for N₂O. Both patterns of tidal inundation and floodwater chemistry affect the process rates in each soil differently. The impact of flooding with NO₃⁻ – amended water was greater on the SM soil than the MR soil, and it is likely that decomposing vegetation buried in the accreting sediments following reflooding at the MR site were supplying a source of N in the soil, and so process rates were less dependent upon external supplies. The act of managed realignment in intertidal zones could therefore result in an increase in mean production of N₂O in intertidal zones, at least in the short term.  相似文献   

两种体色三疣梭子蟹线粒体DNA 部分片段序列的比较分析     

迟大利  高焕  沈颂东  阎斌伦 《海洋科学》2010,34(11):27-34

三疣梭子蟹(Portunus trituberculatus)作为重要的海洋经济动物,其常见体色(头胸甲)为茶绿色。近年来在我国沿海海域海捕三疣梭子蟹中开始出现体色为紫色的一类梭子蟹,除体色不同外,二者表型特征并无显著差异。对两种体色三疣梭子蟹不同个体的线粒体COI和16S rRNA基因进行了序列比对分析以判定二者之间的亲缘关系。结果发现COI和16S rRNA基因在两种体色三疣梭子蟹群体中的核苷酸序列一致性分别为99.87%和99.88%,表明紫色三疣梭子蟹并未发生亚种的分化,即紫色和茶绿色群体属于同一个种。并利用GenBank数据库检索了梭子蟹科其他15种海产蟹的16S rRNA序列,进行了序列同源性比对分析和分子系统学方面的探讨,为梭子蟹种属分类学研究提供分子依据。  相似文献   

厦门同安湾鳄鱼屿海岸侵蚀与防护对策     

林河山  廖连招  庄孔造  朱嘉  蔡晓琼  蔡鹭春 《台湾海峡》2010,29(4):566-570

在2009年3月对鳄鱼海岸线测量的基础上,利用ArcGIS软件分析比较了现有海岸线与厦门市集美区地形图（1988年版,图号：7-50-129甲-）中鳄鱼屿海岸线位置的变化.结果表明21a来,鳄鱼屿海岸最大侵蚀率为2.0 m/a,东南侧最大侵蚀宽度达42 m,侵蚀总面积达14 000 m2;其东北侧海岸侵蚀后退约35 m,侵蚀总面积达4 100 m2;其西北侧海岸最大侵蚀宽度达30 m,侵蚀面积达12 000 m2.文中就厦门市鳄鱼屿海岸侵蚀的成因进行了分析,提出了工程防护、人工补沙、红树林修复以及加强海岛及其周边海域资源综合管理等方面的防护对策.这可为我国其他无居民海岛的海岸侵蚀防护提供经验借鉴.  相似文献   

有机农药六六六对胶州湾海域水质的影响Ⅰ.含量的年份变化   总被引：1，自引：1，他引：0  

杨东方  陈豫  吴绍渊  丁咨汝  石强 《海洋科学》2010,34(12):52-56

根据1979～1984年(缺少1980年)的胶州湾水域调查资料,分析有机农药六六六(HCH)在胶州湾水域的含量大小、年份变化和季节变化。研究结果表明:在1979～1984年(缺1980年)期间,在胶州湾水体中HCH的含量逐年都在减少。在1983年,中国禁止HCH的使用,在禁用后,水体中HCH的含量全部低于一类海水的水质标准。在禁用后,水体中HCH的含量很低,几乎没有季节变化。因此,中国禁止HCH的使用对环境的改善取得显著的成效。  相似文献