The efifect of wave breaking on surface wave imaging by Synthetic Aperture Radar     

孙建  管长龙  史剑 《中国海洋湖沼学报》2006,(1)

The effect of ocean wave breaking as a non-Bragg mechanism on backscattering cross-section and modulation transfer functions (MTF) of radar was investigated based on Bragg resonance theory and parametric method. The result showed that the additional effect of wave breaking on backscattering cross-section is not more than 20% except for the small incident angle of VV polarized electromagnetic (e.m.) wave but is significant for HH polarized e.m. wave. Breaking waves lead to increase in the modulus of tilt modulation MTF and the larger the wind speed, the faster the increase. For large incident angle, the modulus of tilt modulation MTF with wave breaking decreases quickly with incident angle for HH polarization and approach to that without wave breaking for VV polarization. The hydrodynamic MTF increases 30%-60% when considering wave breaking and the increase is larger for HH polarization than for VV polarization.  相似文献   

GPS中BOC调制的FPGA实现     

刘音华  卢晓春  边玉敬 《时间频率学报》2006,29(1):35-42

GPS系统中提出了一种新的信号形式,二进制偏移载波(BOC)调制是这种新的信号形式产生的技术关键。首先介绍了BOC调制的定义及其频谱特性,然后阐述了基于FPGA(现场可编程门阵列)硬件平台的BOC调制实现方法,并给出了仿真波形。结果表明,该实现方法是值得提倡的。  相似文献   

Periodic Intrusion of Cold Water from the Pacific Ocean into the Bottom Layer of the Bungo Channel in Japan     

Atsushi Kaneda  Hidetaka Takeoka  Eiji Nagaura  Yoshitsugu Koizumi 《Journal of Oceanography》2002,58(4):547-556

A cold-water intrusion, called a “bottom intrusion”, occurs in the lower layer of the Bungo Channel in Japan. It is an intrusion from the shelf slope region of the Pacific Ocean margin in the south of the channel. In order to reveal the fundamental characteristics of the bottom intrusion, we conducted long-term observations of water temperature at the surface and bottom layers of the channel and 15-day current observations at the bottom of the shelf-break region. The long-term water temperature data indicated that the bottom intrusion occurs repeatedly between early summer and late autumn, and its reiteration between early and mid-summer causes a local minimum of water temperature in the lower layer in mid-summer. Moreover, the data revealed that most of the bottom intrusions occurred in neap tidal periods. The current meter recorded a bottom intrusion with a speed of approximately 15 cm⋅s⁻¹. The current meter also revealed that the intruded cold water slowly retreated back to the shelf slope region after the intrusion. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A phase-averaged Boussinesq model with effective description of carrier wave group and associated long wave evolution     

K. Nadaoka  K. Raveenthiran 《Ocean Engineering》2002,29(1):21-37

From the phase-resolving improved Boussinesq equations (Beji and Nadaoka, Ocean Engineering 23 (1996) 691), a phase-averaged Boussinesq model for water waves is derived by more effectively describing carrier wave groups and accompanying long wave evolution with less CPU time. Linear shoaling characteristics of carrier wave equations are investigated and found to agree exactly with the analytical expression obtained from the constancy of energy flux for the improved Boussinesq equations themselves, showing that the present model equations are the results of a consistent derivation procedure regarding energy considerations. Numerical simulations of the derived equations for the single wave group and narrow-banded random waves show the validity of the present model and its high performance, especially on the CPU time.  相似文献   

旅游影响调适系统研究   总被引：2，自引：0，他引：2  

肖佑兴 《地理与地理信息科学》2006,22(5):81-85

旅游发展对目的地产生各种影响,如何调适旅游影响对目的地非常重要。该文从系统论的角度探讨旅游影响调适问题,分析旅游影响的形成机制,认为旅游影响是旅游影响动力因子模块、旅游影响应力因子模块及旅游影响规范因子模块在旅游影响场的作用下形成的。在此基础上探讨旅游影响调适机理及调适流程,指出旅游影响调适是旅游调适主体通过旅游制度创新系统对旅游利益相关者发生作用而进行的。根据调适机理和调适流程,建立旅游影响调适库,认为旅游影响调适的4个分目标(减量、扩容、治理和适应)通过旅游制度创新系统及其派生措施来实现。  相似文献   

付载波频偏的测量及其在遥测台网中的应用     

徐世林  张绍昌 《四川地震》1997,(3):23-25

付载波频偏测量对于保证调频系统传输质量具有重要的意义。本文介绍了我们设计制作的付载波频编测量仪。该仪器便于携带、使用方便、精度送±１０＾－３＊ｆ０＋１赫该精度满足模拟传输台网的需要。  相似文献   

应力调制在辽宁地区地震预报中的应用     

曹凤娟  张颖 《东北地震研究》2004,20(2):21-26

应用应力调制图像法对辽宁地区1970年以来的21次ML≥5．0地震进行了检验。结果显示，有18次地震的震前出现了S值异常单元，虚报地震11次，漏报3次，R值评分0．58。  相似文献   

Analytical methods Of assessing the image quality associated with digital and photographic imaging systems     

Grant H. Thomson 《The Photogrammetric Record》2004,19(107):237-249

The introduction of digital cameras for aerial survey photography and use of scanners with processed aerial film present a number of technical questions concerning the way photography is to be acquired in the future. Among the questions to be addressed are the comparative metric properties of images acquired by each system and the associated image quality characteristics. The new digital camera systems will require very careful appraisal, using well-established methods of assessing metric quality already available to survey organisations. The questions concerning image quality are more difficult to answer, as they require very specialised instrumentation if measurements are to be made directly in practice. Over the course of the past several decades a more analytical approach to assessing image quality has emerged, and one that may be used by individuals. The method is particularly effective where information on the micro-image characteristics of products is made available by the manufacturers concerned. An outline is given of some considerations that need to be taken into account when using an analytical approach, with references given for further reading.  相似文献   

Analysis of wave groups by wave envelope-phase and the Hilbert Huang transform methods     

《Applied Ocean Research》2016

The wave groups are studied by both conventional wave analysis methods and by the non-stationary Hilbert Huang Transform (HHT) method. Full-scale wave records containing abnormal waves are used. Instantaneous quantities, such as envelope, phase and frequency, are adopted to study the wave grouping. A refined definition of wave group is proposed considering that the wave process is simultaneously amplitude and frequency modulated. The validation of the proposed definition is conducted by analysis of numerical simulation data. Group parameters are proposed based on the time-frequency distribution of energy. An attempt is made to find the relationship between the characteristics of abnormal waves and the group characteristics.  相似文献   

黑潮延伸体上游中尺度涡场的年代际振荡及其相关机制   总被引：1，自引：1，他引：0  

王世红  刘志亮  庞重光  刘会庆 《海洋学报(英文版)》2016,35(5):9-17

黑潮延伸体上游区域的中尺度涡场的涡动能和涡特征尺度存在显著地年代际振荡,和黑潮延伸体路径的年代际变化有很好的相关性。当黑潮延伸体路径比较稳定时,其上游区域涡动能比较高,涡特征尺度比较大,反之相反。通过对黑潮延伸体上游区域的中尺度涡场进行集合分析发现:当黑潮延伸体处于稳定状态时,上游涡场几乎是各向均匀地,有轻微的径向伸长;而当黑潮延伸体处于不稳定状态时,上游的中尺度涡场有显著地纬向伸长。对与中尺度涡场的产生相关的线性斜压不稳定和正压不稳定进行了计算分析,结果显示,线性斜压不稳定不是控制中尺度涡场年代际变化的机制,而正压不稳定对中尺度涡场的年代际变化有积极的贡献。不稳定产生的中尺度涡之间存在非线性涡-涡相互作用。  相似文献