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991.
The effect of ambient currents on nearshore nonlinear wave–wave energy transfer in random waves is studied with the use of a nonlinear frequency domain wave–current interaction model. We focus on the phenomenon of wave recurrence as a classical nonlinear phenomenon whose characteristics are well established for systems truncated to small numbers of frequency modes. The model used for this study is first extended to enhance accuracy; comparisons of permanent form solutions to analytical forms confirm the model accuracy. Application of the model to a highly truncated system confirmed the model’s consistency with published results for both positive (following) and negative (adverse) currents. Propagation of random wave spectra over a flat bottom was performed with the model, with the intent of determining the prevalence of recurrence between the spectral peak and its harmonics. For spectra of moderate Ursell number, it was found that positive currents extended the length scale of recurrence relative to the case with no currents; conversely, negative currents reduced the recurrence lengths. However, beyond a propagation distance of ≈40 wavelengths of the spectral peak, recurrence becomes almost completely damped as the spectra becomes broad and the spectral energies equilibrate. For spectra of high Ursell number, in contrast, recurrence is almost immediately damped, suggesting that the nonlinearity is sufficient to allow immediate spectral broadening and equilibration and overwhelming any preferential interactions among the spectral peak and its harmonics, regardless of current magnitude or direction. 相似文献
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995.
北黄海典型水域春夏季浮游植物的昼夜变化 总被引:1,自引:0,他引:1
根据黄海西北部2006年夏季3个连续站和2007年春季1个连续站垂直分层拖网的调查资料,研究了黄海西北部典型海区浮游植物的昼夜垂直变化.夏季共检出浮游植物79种,主要优势种为旋链角毛藻Chaetoceros curvisetus、梭角藻Ceratium fusus、三角角藻Ceratium tripos和具槽帕拉藻Paralia sulcata;春季检出51种,主要优势种为浮动弯角藻Eucampia zodiacus、具槽帕拉藻和尖刺伪菱形藻Pseudo-nitzschia pungens.夏季L01站受潮汐的影响各水层低潮期浮游植物细胞丰度高于高潮期,垂直分布趋势为表层细胞丰度最高,底层最低.而由于底栖硅藻的细胞再悬浮作用夏季L02、L03站和春季L02站底层细胞丰度高于表层,但各水层细胞丰度的昼夜变化相对较平缓. 相似文献
996.
实时动态(Real Time Kinematic)测量技术,简称RTK技术已风靡全球,它具有全球、全天候工作、定位精度高等优点,在当今测绘界已经得到广泛应用。RTK技术在南阳市全国土地二次调查中起到了关键的作用,大大提高了工程进度,降低了成本。 相似文献
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998.
针对多个县(市)、区土地调查文字材料将1:100万图号中的行、列号用错而产生严重缺陷的事实,本人认真学习了"国家基本比例尺地形图分幅和编号"的基础知识,并总结归纳出简易的快速判断正误的方法,以杜绝类似差错的发生. 相似文献
999.
This paper presents soft computing approach for estimation of missing wave heights at a particular location on a real-time basis using wave heights at other locations. Six such buoy networks are developed in Eastern Gulf of Mexico using soft computing techniques of Artificial Neural Networks (ANN) and Genetic Programming (GP). Wave heights at five stations are used to estimate wave height at the sixth station. Though ANN is now an established tool in time series analysis, use of GP in the field of time series forecasting/analysis particularly in the area of Ocean Engineering is relatively new and needs to be explored further. Both ANN and GP approach perform well in terms of accuracy of estimation as evident from values of various statistical parameters employed. The GP models work better in case of extreme events. Results of both approaches are also compared with the performance of large-scale continuous wave modeling/forecasting system WAVEWATCH III. The models are also applied on real time basis for 3 months in the year 2007. A software is developed using evolved GP codes (C++) as back end with Visual Basic as the Front End tool for real-time application of wave estimation model. 相似文献
1000.
A systematic assessment of Planctomycetales diversity in a South China Sea, deep‐sea sediment (1657 m) was conducted using the 16S rRNA gene analysis approach. PCR amplification of the samples from seven sediment layers (0.1, 1, 3, 5, 7, 9 and 11 m below the surface sediment) using the primer set Pla‐46‐F/1392‐R showed that the Planctomycetales existed within a limited range of sediment depths (≤ 5 m), and had a decreasing trend in diversity with increasing depth. The majority of the retrieved Pla‐46‐F/1392‐R sequences belonged to Pirellula‐related Planctomycetales, and two sequences retrieved from the 0.1‐m layer (GenBank accession numbers: DQ996944 and DQ996945 ) shared the same anammox‐related signature oligonucleotides and were closely related to commonly recognized anammox organisms. To identify new anammox‐related biomarkers, three primer sets were designed for amplifying the fragments of hydroxylamine oxidoreductase and S‐adenosylmethionine radical enzyme genes, but no related sequences were found. Our multiple 16S rRNA gene primer sets (Journal of Rapid Methods and Automation in Microbiology, 2008, in press) revealed even an higher diversity of Planctomycetales in the 0.1‐m layer of the sediment, especially at genus level. Our data profiled the distribution pattern of Planctomycetales diversity along sediment depths, and provided molecular evidence for the existence of anammox‐related bacteria in a new location, which broadens our understanding of Planctomycetales diversity in deep sea sediments. 相似文献