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971.
用奇异谱分析(SSA)研究了136年(1856-1991年)全球平均海温季距平演变特征,并对各主分量作了最大熵谱分析。结果表明,海温演变除了具有81年周期外,还有一些非常明显的周期振动,这些周期主要是准10年和2.6-6年。从各主分量的方差贡献来看,前15个主分量的方差贡献之和是总方差的78%。从特征向量的分布函数来看,第1、2特征向量表示了海温序列的线性特征,它们的方差之和可以占到总方差的48% 相似文献
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974.
Laboratory studies of some environmental variables controlling sulfur emissions from plants 总被引:8,自引:0,他引:8
R. Fall D. L. Albritton F. C. Fehsenfeld W. C. Kuster P. D. Goldan 《Journal of Atmospheric Chemistry》1988,6(4):341-362
Several trace sulfur gases that can have a significant influence on atmospheric chemistry are emitted from biological systems. In order to begin to address biological questions on the mechnisms of production of such gases, laboratory-scale experiments have been developed that reproduce such emissions under controlled conditions. Using a flux chamber technique, flats containing soil, or soil plus plants were sampled for the net fluxes of sulfur gases. The major sulfur gas emitted from all the plants tested (corn, alfalfa, and wheat) was dimethyl sulfide (DMS). Alfalfa and wheat also emitted lesser amounts of methanethiol, variable amounls of hydrogen sulfide, and in some experiments wheat emitted carbon disulfide. The use of a plant incubator allowed a systematic study of the effects of variables such as temperature, photon flux, and carbon dioxide levels, on these emissions. Fluxes of all the emitted sulfur gases increased exponentially with increasing air temperature, and increased with increasing photon flux up to a saturation level of \~300 E/m–2 sec-1. Three to four-fold changes in DMS flux were observed during light to dark or dark to light transitions. By varying the CO2 content of the chamber flush gas, it was shown that the observed sulfur fluxes from corn and alfalfa were not related to the CO2 concentration. Growing these crop plants through holes in a Teflon soil-covering film allowed a separate determination of soil and foliage emissions and substantiation of the light dependent uptake of COS by growing vegetation observed in previous field studies. 相似文献
975.
本文运用Maslov渐近理论编写的二维横向非均匀介质中的理论地震图程序,与其它类型算法作了精确对比,结果表明,在层状介质模型中,本程序的结果无论振幅还是波形对比都与反射率法基本相同。对于二维横向非均匀模型,在射线理论的非奇点处,本算法与射线方法基本一致,在射线理论的奇异点处,Maslov方法消除了射线理论所固有奇点,提高了计算精度。 相似文献
976.
A low-order model of the unforced, inviscid barotropic model is examined as a dynamical system. Analytic solutions, consisting of linear and nonlinear oscillations (Rossby waves), are obtained in appropriate limiting initial conditions. These solutions are periodic. With less restrictive initial conditions the system shows quasi-periodic behaviour at low energies and chaotic behviour at high energies. This transition is accompanied by frequency-locking and period-doubling. Quasi-periodic and chaotic behaviour may coëxist in phase space for the same values of the model invariants. The results are interpreted in terms of perturbed integrable Hamiltonian systems. Considerations of the low-frequency variability of the atmosphere are also made. 相似文献
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通过对中纬区完全孢粉植被动态组合规律的分析,可以推导出某一地区沉积剖面中第四纪冷暖气候旋回的孢粉植被动态组合,其方式是:冷期孢粉动态组合,以比该区更北(平原)或更高位(山地)的孢粉植被为中间层,其上下依次对称出现比中间层更南(平原)或更低位(山地)的孢粉植被组合;暖期孢粉植被动态组合,以比该区更南(平原)或更低位(山地)的孢粉植被为中间层,其上下依次对称出现比中间层更北(平原)或更高位(山地)孢粉植被组合。 相似文献
979.
Josef Kallrath Johannes P. Schlöder Hans Georg Bock 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):353-371
A recent least squares algorithm, which is designed to adapt implicit models to given sets of data, especially models given by differential equations or dynamical systems, is reviewed and used to fit the Hénon-Heiles differential equations to chaotic data sets.This numerical approach for estimating parameters in differential equation models, called theboundary value problem approach, is based on discretizing the differential equations like a boundary value problem,e.g. by a multiple shooting or collocation method, and solving the resulting constrained least squares problem with a structure exploiting generalized Gauss-Newton-Method (Bock, 1981).Dynamical systems like the Hénon-Heiles system which can have initial values and parameters that lead to positive Lyapunov exponents or phase space filling Poincaré maps give rise to chaotic time series. Various scenarios representing ideal and noisy data generated from the Hénon-Heiles system in the chaotic region are analyzedw.r.t. initial conditions, parameters and Lyapunov exponents. The original initial conditions and parameters are recovered with a given accuracy. The Lyapunov spectrum is then computed directly from the identified differential equations and compared to the spectrum of the true dynamics.presently at IWR, Universität Heidelberg, Im Neuenheimer Feld 368, D-6900 Heidelberg, Germany 相似文献
980.
试论生态水——生态水在我们生活中的应用 总被引:1,自引:0,他引:1
从各个角度阐述了生态水的概念和作用机理,介绍了生态水在我们生活(饲养业、饮料业、美容业及医药业等)中的应用及在疾病防治中的作用。最后简单说明了生态水的优缺点。 相似文献