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共有20条相似文献,以下是第1-20项 搜索用时 164 毫秒

1.  INTERANNUAL VARIATION OF EARTH ROTATION,El Nio EVENTS AND ATMOSPHERIC ANGULAR MOMENTUM  
   郑大伟  罗时芳  宋国玄《中国科学B辑(英文版)》,1989年第6期
   In this paper the multi-stage digit filter is used to analyse the data of Earth rotation represented by the length of day, ΔLOD. The results show that the interannual variations of Earth rotation, which are in the time scale of several years but not quasi-periodic terms, exist in the long periodic fluctuations. They induce the relative variation in the length of day of 0.3×10~(-8).Comparing the series of length of day with the data of temperature departure of the sea surface in the equatorial area of the eastern Pacific, we found that the deceleration and acceleration of the interannual rate of Earth rotation are consistent with the warming up and down of sea temperature in the equatorial area very well. This means that every El Nio event always occurs after the turning of acceleration of the interannual rate of Earth rotation to deceleration.According to the strong interannual variation in the length of day and strong warming of the sea surface temperature in the equatorial area between 1982 and 1983    

2.  Theoretical analysis and experimental research on port/starboard discrimination in towed line array  
   《Chinese Journal of Acoustics》,2001年第1期
   1 IntroductionThe port/starboard (P/S) ambiguity is one of main drawbacks of a towed line array' Theship must maneuver one time at least to achieve port/starboard discrimination. It is endurablewhen the ship is spying on or tracking the target in long range, but it is unendurable in thecomplicated and varied situation of sea warfare, particularly when surface ship has an attacko f underwater weapons such as torpedoes. So, the research on P/S discrimination has beenriveted special attention.B…    

3.  Investigation of composite electromagnetic scattering from ship-like target on the randomly rough sea surface using FDTD method  被引次数:2
   李娟  郭立新  曾浩  韩旭彪《中国物理 B》,2009年第18卷第7期
   Composite electromagnetic scattering from a two-dimensional(2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain(FDTD) method.A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices.The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly.To validate the proposed numerical technique,a 2D infinitely long cylinder over the sea surface is taken into account first.The variation of angular distribution of the scattering changing with incident angle is calculated.The results show good agreement with the conventional moment method.Finally,the influence of the incident angle,the polarization,and the size of the ship-like target on the composite scattering coefficient is discussed in detail.    

4.  Numerical study of electromagnetic scattering from one-dimensional nonlinear fractal sea surface  
   谢涛  何超  William Perrie  旷海兰  邹光辉  陈伟《中国物理 B》,2010年第19卷第2期
   In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.    

5.  The periodic solution to a delayed sea-air oscillator coupling model for the El Nifio-Southern Oscillation (ENSO)  
   李晓静《中国物理》,2007年第16卷第10期
   A time-delay sea-air oscillator coupling model is studied. Using Mawhin's continuation theorem, the result on the existence of periodic solutions for the sea-air oscillator model is obtained.    

6.  Bistatic Reverberation in Shallow Water:Modelling and Data Comparison  
   李风华 刘建军《中国物理快报》,2002年第19卷第8期
   Bistatic and monostatic reverberation data were recorded in the 2001 Asian Sea International Acoustic Experiment (ASLIAEX).A model based on the normal mode theory has been developed to calculate bistatic bottom reverberation in shallow water and to explain the recorded data.The comparisons between the monostatic and bistatic reverberation data are discussed,and the comparisons between model predictions and measured bistatic reverberation data are also presented.The numerical and experimental results show that the numerical predictions from the bistatic reverberation model fit the experimental data well,and the long-range bistatic reverberation with a time delay can be approximately expressed by the monostatic reverberation data.    

7.  Time-Resolved Photoluminescence Spectra of Porous Si  
   FEI Hao-sheng  HAN Li   CHE Yan-long  NIE Rui-juan and LI Tie-jin《高等学校化学研究》,1995年第1期
   Time-ResolvedPhotoluminescenceSpectraofPorousSiFEIHao-sheng,HANLi,CHEYan-long,NIERui-juanandLITie-jin(DeparrmentofPhysicsandD...    

8.  SEDIMENTARY PROPERTIES AND ENVIRONMENTAL VARIATIONS FROM CONTINENTAL SLOPE TO DEEP SEA PLAIN IN THE NORTHERN SOUTH CHINA SEA SINCE LATE PLEISTOCENE  
   冯文科  杨达源  黎维锋《中国科学B辑(英文版)》,1989年第7期
   The South China Sea is the westernmost marginal sea in the west Pacific Ocean. On thebasis of the analyses of sedimentary components, biofossils, oxygen-carbon isotopes and theirdatings in four seafloor cores which were collected from the deep sea plain to continentalslope in the northern South China Sea, the environmental variations were basically similarto other tropical ocean areas, and their cycle changes in about the ages of 40 ka and 20 kawere more apparent since the late Pleistocene. During the warm climates, the depositionrate on the continental slope was about 2.6 times as rapid as on the deep sea plain margin.The seafloor in the deep sea plain was below the CaCO_3 compensation depth. During thecold periods, however, the deposition rate on the deep sea plain margin was slightly quickerthan on the continental slope due to the sea level reduction on a larger scale and moresupply of the terrigenous clastics.    

9.  Evolution of slowly modulated wave train on porous sea bed  
   Tang Ling  Liu Ying-zhong《应用数学和力学(英文版)》,1990年第11卷第1期
   In this paper, the problem of evolution of slowly modulated wave train on porous sea bed is investigated with the method of multiple scales. For the sea water in the upper region, the classical potential theory is used while the fluid motion in the porous sea bed is described by Darcy’s law. The equations of the first and second order modulations of wave amplitude are derived by using matching conditions on the sea bed. The corresponding solutions are found and seepage pressures are also given at the same time.    

10.  Numerical Study for the Role Playing of Atmospheric Dynamic Processes Caused by Seasonal and Non-seasonal Forcings in Formation of the Short-Term Anomalous Climate Change  
   倪允琪  王万秋  袁重光  张勤《中国科学B辑(英文版)》,1993年第5期
   In this paper, it has been pointed out that anomalous climate change can be found, which is similar to that caused by anomalous external forcing, in the 25-year simulations from the model without non-seasonal external forcings. It shows that the short-term anomalous climate change can be formed by dynamic processes in the atmosphere caused by seasonal and non-seasonal external forcings.In this research, two numerical experiments with different initial states and different time sub-series of the natural climate change have been done using the IAP atmospheric general circulation model with same sea surface temperature anomalies in the tropical Pacific. The results reveal that anomalous climate phenomena in the atmosphere can arise as a result of interaction between the inherent internal dynamic process (caused by seasonal external forcings) in the long-range climate natural change process of the atmosphere and the dynamic process caused by non-seasonal external forcings (external dynamic process); in the    

11.  Study of scattering from time-varying Gerstners sea surface using second-order small slope approximation  
   张彦敏  王运华  郭立新《中国物理 B》,2010年第19卷第5期
   Backscattered fields from one-dimensional time-varying Gerstners sea surface are calculated utilising the secondorder small slope approximation.It is well known that spectral properties of the backscattered echoes relate to the velocity of the small elementary scatterers on sea surface profiles.Therefore,modeling Doppler spectra from the ocean requires an accurate description of the sea surface motion.The profile of nonlinear Gerstners sea surface shows verticalskewness of sea waves,it is sharper at the crest and flatter at the trough than linear waves,and its maximum slope position is closer to the crest than to the trough.Furthermore,the horizontal component of the small elementary scatterers orbit velocity on the sea surface,which yields noticeable influence on Doppler spectra,can be obtained conveniently by Gerstners sea surface model.In this study,the characteristics of Doppler spectra of backscattered fields from time-varying Gerstners sea surface are investigated and the dependences of the Doppler frequency and the Doppler bandwidth on the parameters,such as the wind speed,the radar frequency,the incident angle,etc.are discussed.It is shown that the Doppler bandwidth of microwave scattered fields from Gerstners sea surface is considerably broadened.For the case of high frequency backscattered fields,the values of the higher-order spectrum peaks are larger than those obtained by linear sea surface.    

12.  Modeling ocean wave propagation under sea ice covers  
   Xin Zhao  Hayley H. Shen  Sukun Cheng《Acta Mechanica Sinica》,2015年第31卷第1期
   Operational ocean wave models need to work globally, yet current ocean wave models can only treat ice covered regions crudely. The purpose of this paper is to provide a brief overview of ice effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea ice can be classified as: landfast ice zone, shear zone, and the marginal ice zone. All ice covers attenuate wave energy. Only long swells can penetrate deep into an ice cover. Being closest to open water, wave propagation in the marginal ice zone is the most complex to model. The physical appearance of sea ice in the marginal ice zone varies. Grease ice, pancake ice,brash ice, floe aggregates, and continuous ice sheet may be found in this zone at different times and locations. These types of ice are formed under different thermal-mechanical forcing. There are three classic models that describe wave propagation through an idealized ice cover: mass loading,thin elastic plate, and viscous layer models. From physical arguments we may conjecture that mass loading model is suitable for disjoint aggregates of ice floes much smaller than the wavelength, thin elastic plate model is suitable for a continuous ice sheet, and the viscous layer model is suitable for grease ice. For different sea ice types we may need different wave ice interaction models. A recently proposed viscoelastic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various ice covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea ice types, previous wave ice interaction models, wave attenuation mechanisms,the methods to calculate wave reflection and transmission between different ice covers, and the effect of ice floe breaking on shaping the sea ice morphology. Laboratory experiments,field measurements and numerical simulations supporting the fundamental research in wave-ice interaction models are discussed. We conclude with some outlook of future research needs in this field.    

13.  THE HUANGHAI SEA IN THE LAST GLACIAL PERIOD——ACQUISITION AND STUDY OF SOME NEW DATA ON ITS PALEOGEOGRAPHY  
   徐家声  高建西  谢福缘《中国科学B辑(英文版)》,1982年第2期
   Based on the studies on the sediments of the Huanghai Sea (Yellow Sea) formed in thelast glacial period, the complicated palaeogeographic environments of the Huanghai Sea arefound. By the data newly found in the peat and shell layers, it is revealed that the HuanghaiSea is three times exposed and dried as a continent. And the marine sediments are foundfor the first time in the so-called "continental sediment" formed in the early of thelast glacial period. The evolutionary pattern and geological chronicle of natural environ-ments of the Huanghai Sea can primarily be established by the facts that the reversed polarevents of palaeomagnetic variations in the cores are determined and that the peat layer isdated by using ~(14)C.    

14.  LONG-TIME UNIFORM STABILITY OF SOLUTION TO MAGNETOHYDRODYNAMICS EQUATION  
   GuoBoling ZhangLinghai HuangHaiyang《高校应用数学学报(英文版)》,1999年第14卷第1期
   The long-time uniform stability of solutions to the initial value problems for 2-dimensional Magnetohydrodynamics equations is studied. The decay estimates are given.    

15.  LONG-RANGE REVERBERATION AND BOTTOM SCATTERING STRENGTH IN SHALLOW WATER  
   周纪浔  关定华  尚尔昌  罗恩生《Chinese Journal of Acoustics》,1982年第1期
   According to the method of angular power spectrum for averaged sound field in shallow water,the transformation relation between arbitrary angle dependence of hottom scattering and the rangedependence of long-range reverberation in shallow water homogeneous layer is established.Ascompared with the conventional model of boundary reverberation at short range in deep sea,a multipath correction factor is added.By using the transformation relation,the bottombackscattering strength for the frequency band of 0.8—4.0kHz and grazing angle range of 2—10°has been derived from shallow-water reverberation data at five locations in the Yellow Sea,theBobai Sea and the East China Sea.It is shown that the bottom scattering constant(μ)and theangle index(2n)for high speed sediment of the continental shelf depend not only on sea area andfrqucncy,but also on angle range.    

16.  Anomalous sound propagation due to the horizontal variation of seabed acoustic properties  
   LI Zhenglin  ZHANG Renhe  PENG Zhaohui & LI Xilu National Laboratory of Acoustics  Institute of Acoustics  Chinese Academy of Sciences  Beijing 100080  China《中国科学G辑(英文版)》,2004年第47卷第5期
   Sound speed profile and the bottom acoustic property are two of the most important factors, which influence the sound propagation in shallow water. The activities of the internal waves make the temperature of the sea-water varying with the time and space, and then affect the sound propagation in the sea. In 1991 Zhou and his colleagues postu-lated that unusually high transmission losses (TL) over a limited frequency range found in annual measurements taken in the Yellow Sea was due to the in…    

17.  Pattern recognition of acoustic sea-bed profiling records(part 1: a dynamic reasoning expert system)  
   《Chinese Journal of Acoustics》,2001年第2期
   1 IntroductionSince the acoustic sea-bed profiler can provide continuous and explicit sea-bed sedimentprofiles in real time, it has been widely used for seismic explorations in the area of sea) river,and lake. The fact that a certain inherent corresponding relationship exists between the patterncharacteristics of ASPRs and different geological categories of sediment layers, makes ASPRsbe able to classify marine sediment layers and recognize the geological categories of each layer.UP to now…    

18.  EVOLUTION OF SLOWLY MODULATED WAVE TRAIN ON POROUS SEA BED  
   唐苓  刘应中《应用数学和力学(英文版)》,1990年第1期
   In this paper,the problem of evolution of slowly,modulated wave train on porous seabed is investigated with the method of multiple scales.For the sea water in the upper region,the classical potential theory is used while the fluid motion in the porous sea bed is describedby Darcy’s law.The equations of the first and second order modulations of wave amplitudeare derived by using matching conditions on the sea bed.The corresponding solutions arefound and seepage pressures are also given at the same time.    

19.  Time-Domain Techniques for Transient Scattering from Dielectric Bodies and Sea Surface Governed by Jonswap~s Sea Spectra *  
   张民  朱蕾  周平  张向阳《中国物理快报》,2009年第8期
   A time-domain surface integral equation (TDCFIE) approach is utilized to calculate the transient scattering from arbitrarily shaped, three-dimensional dielectric bodies. In conjunction with the marching-on-in-time (MOT) method, the TDCFIE-MOT method is used to derive explicit expressions for the present-time current as a function of the incident field. Sample results showing various geometries are presented and are compared with other numerical techniques. Finally, by an incident Gaussian plane tapered wave, transient scattering from the sea surface governed by Jonswap's sea spectra is computed.    

20.  A two scale nonlinear fractal sea surface model in a one dimensional deep sea  
   谢涛  邹光辉  WilliamPerrie  旷海兰  陈伟《中国物理 B》,2010年第19卷第5期
   Using the theory of nonlinear interactions between long and short waves,a nonlinear fractal sea surface model is presented for a one dimensional deep sea.Numerical simulation results show that spectra intensity changes at different locations(in both the wave number domain and temporal-frequency domain),and the system obeys the energy conservation principle.Finally,a method to limit the fractal parameters is also presented to ensure that the model system does not become ill-posed.    

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