小兴安岭五营林区近49a气候变化趋势及突变分析

利用1958～2006年五营林区的地面资料,采用气候倾向率、累积距平、信噪比等气候统计方法,研究了近49a五营气候的变化趋势、气候突变和异常年份等。结果表明:五营林区近49a气候明显变暖,雪季升温较雨季快。降水量异常的年份增加,年降水量呈显著减少的趋势,-22.44mm/10a。前后10a降水中心生了明显的时空变化。雨季降水日数、年平均气温分别在1974年、1987年发生了气候突变。     

Surface displacements due to batter piles driven in cross‐anisotropic media

This article derives the closed‐form solutions for estimating the vertical surface displacements of cross‐anisotropic media due to various loading types of batter piles. The loading types include an embedded point load for an end‐bearing pile, uniform skin friction, and linear variation of skin friction for a friction pile. The planes of cross‐anisotropy are assumed to be parallel to the horizontal ground surface. The proposed solutions are never mentioned in literature and can be developed from Wang and Liao's solutions for a horizontal and vertical point load embedded in the cross‐anisotropic half‐space. The present solutions are identical with Wang's solutions when batter angle equals to 0^°. In addition, the solutions indicate that the surface displacements in cross‐anisotropic media are influenced by the type and degree of material anisotropy, angle of inclination, and loading types. An illustrative example is given at the end of this article to investigate the effect of the type and degree of soil anisotropy (E/E′, G′/E′, and ν/ν′), pile inclination (α), and different loading types (a point load, a uniform skin friction, and a linear variation of skin friction) on vertical surface displacements. Results show that the displacements accounted for pile batter are quite different from those estimated from plumb piles, both driven in cross‐anisotropic media. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparison of spectral and time domain calibration methods for precipitation‐discharge processes

Hydrological model parameter estimation is an important aspect in hydrologic modelling. Usually, parameters are estimated through an objective function minimization, quantifying the mismatch between the model results and the observations. The objective function choice has a large impact on the sensitivity analysis and calibration outcomes. In this study, it is assessed whether spectral objective functions can compete with an objective function in the time domain for optimization of the Soil and Water Assessment Tool (SWAT). Three empirical spectral objective functions were applied, based on matching (i) Fourier amplitude spectra, (ii) periodograms and (iii) Fourier series of simulated and observed discharge time series. It is shown that most sensitive parameters and their optimal values are distinct for different objective functions. The best results were found through calibration with an objective function based on the square difference between the simulated and observed discharge Fourier series coefficients. The potential strengths and weaknesses of using a spectral objective function as compared to utilising a time domain objective function are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Water balance of the Salado–Juramento river basin (Argentina)

A lumped water balance model was used to derive a monthly water storage series in the Salado–Juramento southern basin, for the period 1954–1986. The evapotranspiration term was estimated using the Bouchet's complementary relationship. Different evapotranspiration formulas following the concepts of potential evapotranspiration and wet environmental evapotranspiration were used. The regional average groundwater levels and the specific yield were used to tune Bouchet's equation. The extrapolation of the water storage series to a secular period (1901–2002) was achieved using a synthetic annual discharge series. The water storage was deficient for most of the century, i.e. more than 60 years; nevertheless in the last 30 years, the system recovers half of the water previously lost. The singular spectral analysis showed that a significant low‐frequency signal is present in the water storage and precipitation series. The main cause of water storage variability would be given by precipitation, in spite of the vast anthropogenic changes on the basin. Anthropogenic effects would be reflected in the river discharges, where no significant signal is detected before 1970; however, an annual signal is insinuated after that year. The conclusions of this work could be different if we only looked at the 1954–1986 period. The results of that period suggest that the basin is primarily accumulating water instead of being mainly in deficit. Thus, here we demonstrated the importance of the secular analysis to illustrate the complete basin behaviour. Copyright © 2012 John Wiley & Sons, Ltd.     

The absorption of water color components and spectral modes in the Pearl River estuary

In-situ data from cruises in the Pearl River estuary and adjacent marine areas were collected during March to May 2001. The absorption coefficients of the water color components were studied in detail containing total suspended matter (TSM), chlorophyll-a (chl-a), colored dissolved organic matter (CDOM), and de-pigment particles. For absorption coefficient of TSM, ap, and that of de-pigment particles, ad, correlations of ap(440)-TSM, ad(440)-TSM, ap(440)-chl-a and ad-chl-a were done (the italicized term means the concentration). There was a good correlation between ap(440) and chl-a concentration. An empirical relationship model between aph(675) and chl-a was developed showing a strong correlation of 0.93. Based on the two models the chl-a and aph(λ) were correlated. The values of calculated empirical spectral slope for CDOM absorption coefficients and that of de-pigment particles, 0.017 0 and 0.011 6 respectively, both are within a relative standard error of 10.0%.     

非均匀各向异性弹性波场正演

推导了用于非均匀各向异性弹性波场正演的伪谱法基本公式，对特征值法边界修正方程进行了全面的理论推导，给出了二维和三维问题固体，流体的特征变量及各类边界修正方程，选用2个模型，模拟了2．5维弹性波场，对S波分裂的偏振图像和时间延迟作了较详细的分析。     

Probabilistic critical excitation for MDOF elastic–plastic structures on compliant ground

Earthquake ground motions and their effects on structural responses are very uncertain even with the present knowledge. It is therefore desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation method is proposed for MDOF elastic–plastic shear‐building structures on compliant ground. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except by laborious elastic–plastic time‐history response analysis. Statistical equivalent linearization is used to estimate the elastic–plastic stochastic peak responses approximately. The critical excitation responses are obtained for several examples and compared with those of the corresponding recorded earthquake ground motion. Copyright © 2001 John Wiley & Sons, Ltd.     

利用Landsat TM图像更新地形图

采用多项式纠正和直接线性变换两种数学模型 ,对TM图像进行几何纠正 ,获得的正射影像与地形图矢量数据配准。在Microstation 95系统下 ,进行地形图矢量数据的更新 ,并给出了相应的实验结果     

理论变异函数球状模型的加权线性规划法似合

对理论变异函数球状模型及其套合结构拟合这一问题作了探讨，提出了加权线性规划拟合法。同于该法在目标函数中既可考虑到对不同滞后h下所得实验变异函数值进行加权，又可保证拟合成功，同时还可进行人工干预，因此，方法综合了现有加权多项式拟合法及线性规划拟合法的各自优点，且在计算上较目标规划拟合法更为简单。