对ENVISAT ASAR level2算法固有误差的分析   总被引：1，自引：0，他引：1  

王贺  杨劲松  黄韦艮  王隽 《海洋学报》2008,30(3):72-76

欧洲空间局的ENVISAT ASAR level 2算法是从合成孔径雷达(SAR)单视复图像反演涌浪方向谱的算法.该算法假设双峰海浪谱的SAR图像交叉谱是涌浪的图像交叉谱和风浪的图像交叉谱之和.实际上双峰海浪谱的SAR图像交叉谱中还有一个混合项,正是该混合项导致ENVI-SAT ASAR level 2算法有固有误差.利用遥感仿真的方法分析了不同海况条件下该算法的这一固有误差,结果表明,只有在有效波高较小、或风浪的成分较少、或双峰海浪的传播方向较靠近SAR距离向、或波长较长时固有误差才较小,ENVISAT ASAR level 2算法对海浪谱的反演才较为适用.  相似文献   

Stochastically based review of site-dependent response spectra parameters adopted in the seismic design code of Albania     

B. Myslimaj  Y. Matsushima 《Soil Dynamics and Earthquake Engineering》2000,20(5-8):263-271

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Simulation of Random Waves and Associated Laminar Bottom Shear Stresses     

Mao-Lin SHEN  Ching-Jer HUANG 《中国海洋工程》2008,22(3):477-490

This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundaiy conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves axe determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the nanlerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug＇ s model （1995）. The transfer function method is also employed to determine the maximum shear stress, and is proved accurate.  相似文献   

Bubble Size Distribution for Waves Propagating over A Submerged Breakwater     

TIEN Tsung-mo HUANG Ching-jer HSU Tai-wen LEE Chien-hsun HSU Shi-sheng 《中国海洋工程》2008,22(2):227-240

Experiments are carried out to study the characteristics of active bubbles entrained by breaking waves as these propagate over an abruptly topographical change or a submerged breakwater. Underwater sounds generated by the entrained air bubbles are detected by a hydrophone connected to a charge amplifier and a data acquisition system. The size distribution of the bubbles is then determined inversely from the received sound frequencies. The sound signals are converted from time domain to time-frequency domain by applying Gabor transform. The number of bubbles with different sizes are counted from the signal peaks in the time-frequency domain. The characteristics of the bubbles are in terms of bubble size spectra, which account for the variation in bubble probability density related to the bubble radius r. The experimental data demonstrate that the bubble probability density function shows a - 2.39 power-law sealing with radius for r 〉 0. 8 mm, and a- 1.11 power law for r 〈0.8 mm.  相似文献   

基于ASTER 和ETM+数据的蚀变信息提取 比较研究———以西藏泽当矿田为例   总被引：1，自引：1，他引：0  

黄照强 《地质与勘探》2009,45(5):606-611

利用ASTER和ETM+数据分别对西藏泽当矿田试验区进行了遥感数据矿物蚀变信息提取。根据研究区岩石矿物光谱特征,采用主成分分析法,提取了含三价Fe离子和粘土矿化蚀变信息,通过对两者提取的结果进行比较之后认为,ASTER数据比ETM+数据在矿化蚀变信息提取中能进一步识别不同类型的含羟基蚀变矿物,并且也能很好的提取含三价Fe离子蚀变信息,未来具有较大的优势。  相似文献   

Spectral characteristics of the nearshore waves off Paradip,India during monsoon and extreme events     

V. M. Aboobacker  P. Vethamony  K. Sudheesh  S. P. Rupali 《Natural Hazards》2009,49(2):311-323

Spectral and statistical wave parameters obtained from the measured time series wave data off Paradip, east coast of India during May 1996–January 1997 were analysed along with MIKE 21 spectral wave model (SW) results. Statistical wave parameters and directional wave energy spectra distinctly separate out the wave conditions that prevailed off Paradip in the monsoon, fair weather and extreme weather events during the above period. Frequency-energy spectra during extreme events are single peaked, and the maximum energy distribution is in a narrow frequency band with an average directional spreading of 20°. Spectra for other seasons are multi-peaked, and energy is distributed over a wide range of frequencies and directions. The NCEP re-analysis winds were used in the model, and the results clearly bring out the wave features during depressions. The simulated wave parameters reasonably show good match with the measurements. For example, the correlation coefficient between the measured and modelled significant wave height is 0.87 and the bias −0.25.  相似文献   

巴基斯坦祖母绿的红外光谱和包裹体特征研究     

郭鸿舒  余晓艳 《岩石矿物学杂志》2019,38(5):724-732

通过宝石显微镜、显微红外、电子探针和拉曼光谱等测试方法对巴基斯坦祖母绿的孔道水和包裹体进行了研究。红外光谱测试可知,巴基斯坦祖母绿中存在Ⅰ型和Ⅱ型水,且Ⅱ型水(5 270、3 600、1 632 cm~(-1))吸收强度远大于Ⅰ型水(1 600 cm~(-1))。流体包裹体以气液两相包裹体为主,常呈拉长状或"卡脖子"状形态,且定向排列,气相包裹体主要成分为CO_2+N_2+CH_4的混合气体,液相主要为水溶液;矿物包裹体主要有菱镁矿、白云石、白云母、石英等。特征包裹体和红外光谱特征有助于鉴定巴基斯坦祖母绿的产地来源。  相似文献   

高原地区云对地闪电首次回击的光谱研究   总被引：7，自引：1，他引：6       下载免费PDF全文

袁萍  刘欣生  张义军  郄秀书  张广庶  王怀斌 《地球物理学报》2004,47(1):42-46

用无狭缝光栅摄谱仪,获得了青海西宁地区云对地闪电首次回击过程400～700nm波 长范围的光谱,并首次在闪电的单次回击光谱中记录到了波长为604.6nm和619.4nm的谱线. 将原子结构的理论应用于闪电光谱的研究,用多组态Dirac Fock方法,计算了有关光谱线 的 波长、振子强度以及相应的激发态能量等参数,理论与试验观测资料进行比较分析后发现, 高原地区闪电首次回击光谱的结构及跃迁特性与其他地区有明显的区别,除NII离子n=3 的低 激发态产生的跃迁谱线外,激发能量为13～14eV左右的中性NI和OI的跃迁增多,但很难观测 到OII离子的跃迁谱线.  相似文献   

工程结构等延性地震抗力谱研究   总被引：28，自引：7，他引：21  

翟长海  公茂盛  张茂花  谢礼立  张敏政 《地震工程与工程振动》2004,24(1):22-29

研究结构的非弹性反应谱对改进现有的结构抗震设计、发展基于性态的抗震设计以及了解复杂地面运动特性与结构动力特性之间的关系具有重要的意义。利用大量的单自由度在强震记录作用下的弹塑性动力时程分析,对等延性地震抗力谱这一重要的非弹性反应谱进行了较为详尽的研究,给出了四类场地条件(基岩、硬土、一般土和软土)下的平均等延性地震抗力谱,总结了对工程结构的抗震设计和研究具有实际意义的规律和特征,并分析了场地条件、结构的延性系数以及周期等对等延性地震抗力谱的影响,提出了新的拟合公式,其成果可供抗震研究和设计直接应用。  相似文献   

在线监测环境下土木结构的模态识别研究   总被引：4，自引：0，他引：4  

淡丹辉  孙利民 《地震工程与工程振动》2004,24(3):82-88

建立在线监测环境下结构考虑时效的模态识别计算方案。采用基于各测点加速度响应互功率谱的频域多参考点模态识别法来实现结构模态参数的抽取,从而绕过了监测环境下激励监测的技术难题;并用频域的平均法使识别参数的拟合曲线平滑和发现参数的变化趋势。通过对美国结构健康监测研究小组公布的Benchmark问题的第一阶段解析模型模拟加速度响应数据的识别,表明本文采用的算法有较好的识别精度和识别速度,是一个可行的在线监测环境下的模态识别计算方案。  相似文献