脉冲内拉曼散射所致啁啾的研究     

时延梅  王晶 《中国海洋大学学报(自然科学版)》2006,36(1):49-52

探究孤子自频移现象,从啁啾的角度来解释其产生的原因。运用数学求解及数值模拟方法,通过MATLAB编程画出了啁啾演变图,据此来研究自频移现象。研究结果表明,在高阶非线性效应中,脉冲内拉曼散射、色散和自相位调制共同所致的啁啾,与无拉曼散射效应时产生的啁啾相比,发生一系列新的变化:啁啾的中心发生漂移且图形的前后沿不对称,即负啁啾的峰值的绝对值大于正啁啾的峰值,这说明了脉冲频谱“红移”的谱峰变宽,或者说频谱移向了长波长方向—即人们所说的孤子自频移现象。  相似文献   

Free vibrations of three-dimensional extensible marine cables with specified top tension via a variational method   总被引：1，自引：0，他引：1  

Somchai Chucheepsakul  Narakorn Srinil 《Ocean Engineering》2002,29(9)

This paper presents a model formulation that can be used for analyzing the three-dimensional vibration behaviours of an inclined extensible marine cable. The virtual work-energy functional, which involves strain energy due to axial stretching of the cable and virtual work done by external hydrostatic forces is formulated. The coupled equations of motion in the Cartesian coordinates of global systems are obtained by taking into account the difference between Euler’s equations and equilibrium equations. The method of Galerkin finite element is used to obtain the mass and stiffness matrices which are transformed into the local coordinate systems. Then the eigenvalue problem is solved to determine its natural frequencies and corresponding mode shapes. The model formulation developed herein is conveniently applied for the cases of specified top tension. The numerical investigations are carried out to demonstrate the validity of the model and to explore in details the influence of various parameters on the behaviours of marine cables. Results for the frequency avoidance phenomenon, maximum dynamic tension and coupled transverse mode shapes are presented and discussed.  相似文献   

海上结构物的Ringing现象     

于定勇  徐德伦 《海岸工程》1997,16(3):6-11

介绍近年来新发现的海上结构物在高海况下遇到的一种现象－－ｒｉｎｇｉｎｇ高频共振响应现象及这一现象现有的研究成果，包括该现象的发现过程、特征、产生的机理及研究方法等。提出了研究ｒｉｎｇｉｎｇ现象的一种可能的新方法。  相似文献   

Variational iteration solving method for El Niño phenomenon atmospheric physics of nonlinear model     

MO Jiaqi  WANG Hui  LIN Wantao  LIN Yihua 《海洋学报(英文版)》2005,24(5):35-38

A class of E1 Niйo atmospheric physics oscillation model is considered. The E1 Niйo atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions. The conceptual oscillator model should consider the variations of both the eastern and western Pacific anomaly patterns. An E1 Niйo atmospheric physics model is proposed using a method for the variational iteration theory. Using the variational iteration method, the approximate expansions of the solution of corresponding problem are constructed. That is, firstly, introducing a set of functional and accounting their variationals, the Lagrange multiplicators are counted, and then the variational iteration is defined, finally, the approximate solution is obtained. From approximate expansions of the solution, the zonal sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the sea-air oscillation for E1 Niйo atmospheric physics model can be analyzed. E1 Niйo is a very complicated natural phenomenon. Hence basic models need to be reduced for the sea-air oscillator and are solved. The variational iteration is a simple and valid approximate method.  相似文献   

机场低能见度自动观测设备测量数据对比          下载免费PDF全文

明虎  陈丽杰  高联辉  王奇 《应用气象学报》2015,26(6):750-758

基于民航机场的实际应用,对比安装在陕西省西安咸阳国际机场跑道一端的大气透射仪和前向散射仪2013年1月—2014年8月测量的跑道视程数据,结果表明:整体上,当跑道视程R > 400 m时,前向散射仪测量数据大于大气透射仪数据的比例高;当跑道视程R≤400 m时,大气透射仪测量数据大于等于前向散射仪数据的比例更高。当跑道视程R≤600 m时,两种设备测量数据具有很好的相互替代性;当跑道视程R > 1000 m时,两种设备测量数据差距较大。在雾、冻雾、霾和暴雨天气时,两种设备测量数据在时间上具有很好的一致性,且在跑道视程R≤1000 m时,两种设备测量数据具有很好的相互替代性,而在雪、烟和扬沙天气时两种设备测量的数据差距较大。  相似文献   

地震地电方法在天祝—景泰6.2级地震前的预测预报     

余素荣  汪志亮 《地震》1993,(2)

本文通过对天祝—景泰6.2级地震监测预报工作全过程的研究,展示了地电方法监测预报地震的新进展。另外,对如何运用地电场的分布变化规律及地电阻率异常时间、幅度的特征进行监测预报作了探讨。  相似文献   

黑河实验(HEIFE)能量平衡和水汽输送研究进展   总被引：7，自引：1，他引：7  

胡隐樵 《地球科学进展》1994,9(4):30-34

It is a review about advance of research on energy budget and transportation of water vapour in the HEIFE area. A basic model, the cold island in oasis and the inverse humidity phenomenon in desert, about interaction of oasis with desert environment is established. The major disturbance of the oasis to observation in the desert is the latent heat flux that is an ignored value in the energy budget on ground surface in the desert. Consequently, it is representative of the arid region to have measured energy budget at the gobi station and desert station in the HEIFE area.  相似文献   

Simulation of the Urban Heat Island Phenomenon in Mediterranean Climates   总被引：2，自引：0，他引：2  

G.?MihalakakouEmail author  M.?Santamouris  N.?Papanikolaou  C.?Cartalis  A.?Tsangrassoulis 《Pure and Applied Geophysics》2004,161(2):429-451

An intelligent data-driven method is used in the present study for investigating, analyzing and quantifying the urban heat island phenomenon in the major Athens region where hourly ambient air-temperature data are recorded at twenty-three stations. The heat island phenomenon has a serious impact on the energy consumption of buildings, increases smog production, while contributing to an increasing emission of pollutants from power plants, including sulfur dioxide, carbon monoxide, nitrous oxides and suspended particulates. The intelligent method is an artificial neural network approach in which the urban heat island intensity at day and nighttime are estimated using as inputs several climatic parameters. Various neural network architectures are designed and trained for the output estimation, which is the daytime and nighttime urban heat island intensity at each station for a two-year time period. The results are tested with extensive sets of non-training measurements and it is found that they correspond well with the actual values. Furthermore, the influence of several input climatic parameters measured at each station, such as solar radiation, daytime and nighttime air temperature, and maximum daily air temperature, on the urban heat island intensity fluctuations is investigated and analyzed separately for the day and nighttime period. From this investigation it is shown that heat island intensity is mainly influenced by urbanization factors. A sensitivity investigation has been performed, based on neural network techniques, in order to adequately quantify the impact of the above input parameters on the urban heat island phenomenon.  相似文献   

高光谱中的Hughes现象与低通滤波器的运用   总被引：7，自引：0，他引：7  

杨哲海李之歆  韩建峰宫大鹏 《测绘学院学报》2004,21(4):253-255,258

由于高光谱图像具有很高的光谱分辨率，能够提供更为丰富的地面信息，正在受到国内外的广泛关注。针对高光谱分析过程中产生的Hughes现象，分析了其产生的原因，指出可以在图像预处理阶段对样本进行低通滤波，有效地削弱这种影响。  相似文献   

固结过程中孔隙水压力计算中的吉布斯(Gibbs)现象及其消除   总被引：1，自引：0，他引：1  

包太  刘新荣  朱凡  朱可善 《水文地质工程地质》2006,33(1):23-26

一维固结过程中，孔隙水压力的计算在整个计算中占有重要的位置，其计算结果的准确性对于固结度及固结系数的确定均有一定的影响。目前，孔隙水压力的计算均采用级数计算，而由于级数计算中Gibbs现象的存在，使得孔隙水压力的计算中会出现振荡。针对这种情况，本文以误差函数作为基础，对孔隙水压力的计算进行了分析，发现在一定的精度范围内，采用误差函数可以有效地消除由于Gibbs现象带来的振荡。  相似文献