Directional spectrum analysis and statistics obtained from ERS-1 SAR wave images     

Yi-Yu Kuo  Li-Guang Leu  I Lang Kao 《Ocean Engineering》1999,26(11):1303

This work examines ERS-1 (the first European Remote Sensing Satellite) SAR (Synthetic Aperture Radar) water surface wave images over Hualien of Taiwan, indicating that the variation of SAR signals in space domain is similar to in situ wave data's in time domain. Some statistical properties of SAR data are investigated. The Rayleigh distribution function closely corresponds with the histogram of wave heights, but the Gaussian one cannot for water surface displacements. Evidence reveals that SAR wave signals do not respond well to actual ocean waves effectively. As wave spectral analysis of available SAR data reveals, the appropriate sample size of SAR wave image, sampling average, and moving average should be taken carefully to accurately confirm directional power spectra. Moreover, SAR spectra are compared with in situ ones, confirming that peak frequencies correlate well and wave directions approximately agree with each other. Some differences between both spectral shapes remain somewhat unclear and require further study. Nevertheless, in this study, ERS-1 SAR power spectra verified the feasibility of deriving an appropriate dominant wave direction and peak frequency.  相似文献   

Spatial distribution of grossly visible diseases and parasites in flounder (Platichthys flesus) from the Baltic Sea: a synoptic survey     

Lang  T.; Mellergaard  S.; Wosniok  W.; Kadakas  V.; Neumann  K. 《ICES Journal of Marine Science》1999,56(2):138-147

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Contrasting responses of oligochaetes (Annelida) and chironomids (Diptera) to the abatement of eutrophication in Lake Neuchâtel   总被引：1，自引：0，他引：1  

Claude Lang 《Aquatic Sciences - Research Across Boundaries》1999,61(3):206-214

: Lake Neuchâtel (Switzerland) has been recovering from human-induced eutrophication since 1982. Oligochaetes and chironomid larvae were used to monitor the recovery of sediment at a depth of 40 m. In oligochaete communities, the mean proportion of individuals belonging to species indicative of oligotrophic conditions (mostly Spirosperma velutinus and Stylodrilus heringianus) increased from 16 % in 1984 to 33 % in 1992, but decreased to 11 % in 1997. Based on oligochaetes, benthic conditions deteriorated in 1997 whereas, based on the increase of oligotrophic chironomids (mostly Micropsectra), they improved. This difference was attributed to the impact of large planktonic algae whose sedimentation had altered oxygen concentrations at the water-sediment interface. Oligochaetes were more affected than chironomids because they are less mobile and they depend more on the inner sediment for their food and reproduction than the latter. However, based on the combined response of oligochaetes and chironomids, benthic recovery was stalled in 1997 but was not reversed.  相似文献   

Environmental genotoxicity and cytotoxicity in the offshore zones of the Baltic and the North Seas     

Aleksandras Rybakovas  Janina Bar&#x;ien&#x;  Thomas Lang 《Marine environmental research》2009,68(5):246-256

Micronuclei (MN), nuclear buds (NB) and fragmented-apoptotic cells (FA) were analyzed in mature peripheral blood and immature cephalic kidney erythrocytes of flounder (Platichthys flesus), dab (Limanda limanda) and cod (Gadus morhua) from 12 offshore sites in the Baltic Sea (479 specimens) and 11 sites in the North Sea (291 specimens), which were collected during three research vessel cruises in December 2002, 2003 and in September 2004. The highest levels of environmental genotoxicity (frequencies of MN up to 0.5‰, NB – up to 0.75‰) and cytotoxicity (FA – up to 0.53‰) were observed in flatfishes from areas close to oil and gas platforms in the North Sea and in zones related to the extensive shipping and potentially influenced by contamination from large European Rivers (Elbe, Vistula, Oder). In dab from the offshore zones of the North Sea, the levels of nuclear abnormalities were higher as compared to those in dab from the Baltic Sea. Responses in immature kidney erythrocytes were higher than in mature erythrocytes from peripheral blood. MN frequency lower than 0.05‰ (the Baltic Sea) and lower than 0.1‰ (the North Sea) could be suspected as a reference level in the peripheral blood erythrocytes of flatfish.  相似文献   

单位四元数、罗德里格转换模型与欧拉角的映射关系     

程烺  俞家勇  马龙称  周茂伦  曹岳飞 《北京测绘》2020,(1):44-50

在大角度姿态运动场景中,运动状态通常采用单位四元数或罗德里格转换模型,但转换参数并不具有直观性和几何意义,因此研究单位四元数、罗德里格转换模型与欧拉角的映射关系十分必要。然而,单位四元数、罗德里格参数与欧拉角相互之间并不存在一一对应的关系。结合三种转换模型的特点及欧拉角、罗德里格参数存在奇异问题,本文对可能出现的情况进行推导分析,建立各模型间转换参数的映射关系,实现单位四元数、罗德里格转换模型与欧拉角大角度范围的转换。  相似文献   

Complementing the European earth observation and geographic information body of knowledge with a business‐oriented perspective     

Barbara Hofer  Sven Casteleyn  Estefanía Aguilar‐Moreno  Eva‐Maria Missoni‐Steinbacher  Florian Albrecht  Rob Lemmens  Stefan Lang  Jochen Albrecht  Martyna Stelmaszczuk‐Grska  Glenn Vancauwenberghe  Aida Monfort‐Muriach 《Transactions in GIS》2020,24(3):587-601

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Protoraphis Simonsen,a newly recorded marine epizoic diatom genus for China     

李朗  陈长平  孙琳  张家卫  梁君荣  高亚辉 《海洋学报(英文版)》2020,39(4):120-126

Epizoic diatoms on marine copepods are common in nature and may have a special ecological relationship with their hosts.However,this special ecological group is not well known,and it has only rarely been studied in the China seas.To address this knowledge gap,the species diversity and classification of epizoic diatoms on planktonic copepods were studied with samples collected from the East China Sea.In the present study,a marine araphid diatom genus Protoraphis and its type species,Pr.hustedtiana,were observed and identified by light and electron microscopy,thus representing the first record of this genus and its type species in China.This genus is characterized by a median sternum strongly bent to opposite sides and terminate in two transapical grooves at the valve ends.Protoraphis hustedtiana was found to be epizoic on the posterior body appendages and segments of the marine calanoid copepod Candacia bradyi.An internal view shows a complex,ear-shaped process that is close to the apical slit field.The ecological habitats and geographical distributions of Protoraphis were also discussed,and,together with complementary morphological studies,our results have increased the number of records for marine epizoic diatoms to three genera with three species in China,including Pseudohimantidium and Pseudofalcula.  相似文献   

站点气温格点化方法在贵州区域的研究与应用          下载免费PDF全文

李刚  汤天然  杨秀庄  姚浪  万超 《中低纬山地气象》2023,47(1):63-69

利用2019年1—12月国家气象信息中心实况格点资料、贵州地面观测站资料以及ECMWF 2 m气温起报场资料,讨论了相同插值方案下站点数对空间分布的反演效果以及相同测站数下不同插值方案的表现,同时对国家气象信息中心实况格点场进行检验,并对本地建立的气温格点分析场进行初步评估。结果表明：相同的插值方案下,站数越多越能反映要素场的实际分布状态;基于贵州特殊地形,在相同站数下双线性插值法优于邻域法;通过对国家气象信息中心实况格点分析场评估,日最高、最低气温在贵州区域均存在明显误差,其平均绝对误差分别为1.6℃与1.1℃左右,平均RMSE分别达2.2℃与1.6℃。采用Cressman方案对离散观测资料重建的本地化气温格点分析场进行评估,其最高、最低气温平均绝对误差降至0.2℃与0.1℃左右,大幅度降低了与测站观测值的差异,基本可以代替国家气象信息中心下发的气温格点分析场,并将为今后贵州省业务或研究工作中格点预报的客观订正提供新的更符合实际的参考。  相似文献   

Presence of Antibiotics in Shallow Groundwater in the Northern and Southwestern Regions of China   总被引：1，自引：0，他引：1       下载免费PDF全文

Liang Chen  Hang Lang  Fei Liu  Song Jin  Tao Yan 《Ground water》2018,56(3):451-457

Antibiotics are widely used, and there is a serious concern about its adverse impacts on the environment and human health. To our knowledge, prior to this work, there was no evidence of the potential presence of antibiotics in groundwater in China, despite populous speculations. This study reported the detection of 35 target antibiotics of 6 groups (chloramphenicois, lincosamides, marcrolides, quinolones, sulfonamides, and tetracyclines), in shallow groundwater samples collected in northern and southwestern China. Thirty‐four of thirty‐five target antibiotics were detected in the groundwater samples; 73 of 74 monitoring wells contained at least one antibiotic; and at least two antibiotics were detected in 72 of the 74 wells. Ofloxacin (1199.7 ng/L), lincomycin (860.7 ng/L), and norfloxacin (441.9 ng/L) as well as antibiotics with the highest detection frequency such as sulfapyridine (70%), norfloxacin (69%), and lincomycin (64%) were detected at elevated concentrations. The highest detection frequency and concentration of lincosamides were observed in those groundwater samples, but no clear distribution patterns were observed for the six antibiotic groups. Moreover, shallow groundwater in southwestern China seemed to contain most antibiotics, likely due to the high antibiotics discharge and frequent exchange of groundwater with surface matrices. The findings from this work suggest that groundwater in China has been widely contaminated by antibiotics, and presumably other pharmaceutical compounds that have not been investigated to date.  相似文献   

Geomorphological investigations and luminescence dating in the southern part of the Khangay and the Valley of the Gobi Lakes (Central Mongolia)     

Frank Lehmkuhl  Andreas Lang 《第四纪科学杂志》2001,16(1):69-87

Geomorphological investigations in the catchment area of the Baydragiyn river along the southern slope of the Khangay and in the Valley of the Gobi Lakes in western Mongolia provide evidence for Late Quaternary glaciations and lake‐level changes. Thermoluminescence (TL) and infrared optically stimulated luminescence (IRSL) dating of aeolian and colluvial sediments from the central Khangay place the sediments that overlie fluvial and glaciofluvial terraces in the Holocene. An age of 21 ka is determined for a sand deposit overlying the terrace that is related to the last glacial ice‐margin. Lacustrine sediments from higher beach lines in the Valley of the Gobi Lakes provide evidence for a slightly more humid period around 1.5 ka, and a larger extent of the lakes in the Early Holocene at about 8.5 ka, as also reported from other parts of Central Asia. Remnants of lacustrine sediments buried by alluvial gravel, and indicating a huge palaeolake in the basin of the Orog Nuur, however, date to the early stage of the last glaciation around 70 ka. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献