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181.
Few approaches exist that explicitly use the uncertainty associated with the spread of climate model simulations in assessing climate change impacts. An approach that does so is second-order approximation (SOA). This incorporates quantification of uncertainty to ascertain its impact on the derived response using a Taylor series expansion of the model. This study uses SOA in a statistical downscaling model of monthly streamflow, with a focus on the influence of dependence in the uncertainty of multiple atmospheric variables. Uncertainty is quantified using the square root error variance concept with a new extension that allows the inter-dependence terms among the atmospheric variable uncertainty to be specified. Applying the model to selected point locations in Australia, it is noted that the downscaling results differ considerably from downscaling that ignores uncertainty. However, when the effects of dependence in uncertainty are incorporated, the results differ according to the regional variations in dependence structure. 相似文献
182.
针对海域重力场变化特征和远程飞行器机动发射保障应用需求,本文分析研究了地球外部空间扰动引力三类传统计算模型的技术特点及其适用性,指出了采用表层法作为海域流动点扰动引力计算模型的合理性及需要解决的关键问题,分析论证了空中扰动引力计算对地面观测数据的分辨率和精度要求,提出通过引入局部积分域恒等式变换、局域泰勒级数展开和非网格点内插方法,消除表层法计算模型积分奇异性固有缺陷的研究思路,进而推出了适合于海域流动点应用的扰动引力无奇异计算模型,较好地满足了全海域和全高度段对局部扰动重力场快速赋值的实际需求.以超高阶全球位模型EGM2008作为标准场,通过数值计算验证了无奇异计算模型的可行性和有效性,在重力场变化比较剧烈的海沟区,该模型的计算精度优于2×10-5m·s-2. 相似文献
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184.
A semi-analytical approach to free dry and wet vibration of a trapezoidal, 2-way tapered, pivoted hollow spade rudder is presented. The rudder is modeled as a hollow Kirchhoff’s plate, with a NACA0018 profile chord section. The rudder pivot is modeled as a combination of a translational spring and a rotational spring. The span-wise and chord-wise non-uniform beam vibration is first analyzed by the Rayleigh-Ritz method, to establish the non-uniform beam modeshapes, which act as admissible functions to the Galerkin’s method for plate vibration. Eigenvalue analysis generates the plate natural frequencies and the plate modeshapes. Alternately, uniform beam modeshapes themselves are used as admissible functions into the Galerkin’s method. Frequencies are analyzed for various pivot positions, taper ratios, and NACA sections. For the wet vibration, constant strength source distribution technique is used to generate the added mass of a 2D aerofoil. Also, 3D panel method is used to generate the modal added masses, and hence the wet natural frequencies. The added mass coefficient is generated for various aerofoil fineness ratios, pivot fixities, taper ratios, aspect ratios. 相似文献
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186.
针对目前建立区域地磁场模型截断阶数受限,地磁图精度偏低等缺陷,研究了运用Taylor多项式拟合法建立区域地磁场模型所存在的边界效应问题.从理论上深入分析了产生边界效应误差的根源,提出了采用边界插值约束的Taylor多项式拟合法,在改善区域地磁模型边界效应的同时,提高了模型拟合的截断阶数,进而绘制出较高精度的区域地磁场图,同时对该技术和现有补充国际地磁参考场值方法进行了比较分析,最后进行了仿真试验.试验证明,该技术具有优于补充国际地磁参考值的方法,能克服现有区域地磁场模型的边界效应问题,提高了区域地磁场模型的拟合精度. 相似文献
187.
分析温度场中桥面矩形板受横向均布简谐激励作用的动力稳定性问题。应用弹性力学理论建立其动力学方程,应用Galerkin方法将其转化为非线性振动方程。利用稳定性理论分析其运动稳定性,给出系统随控制参数变化运动稳定性规律。利用非线性振动的多尺度分析方法求得系统主共振的近似解,系统主共振幅频响应曲线具有跳跃现象和明显的硬刚度特性。 相似文献
188.
基于整体最小二乘(TLS)数据处理理论以及TLS迭代算法,利用泰勒公式确定非线性模型一阶偏导数,推导了其误差量级。并将该方法应用于TLS精度评定,提出了检验结果可靠性的方法,最后通过实验验证了该方法的可行性。 相似文献
189.
A simple structure under earthquake excitation is modeled as a single‐degree‐of‐freedom system with nonlinear stiffness subject to modulated Kanai–Tajimi excitation. The nonstationary responses including the nonstationary probability densities of the system responses and the statistical moments are obtained in semi‐analytical form. By applying the stochastic averaging method based on the generalized harmonic functions, the averaged Fokker–Planck–Kolmogorov(FPK) equation governing the nonstationary probability density of the amplitude is derived. Then, the solution of the FPK equation is approximately expressed by a series expansion in terms of a set of properly selected basis functions with time‐dependent coefficients. According to the Galerkin method, the time‐dependent coefficients are solved from a set of linear first‐order differential equations. Thus, the nonstationary probability densities of the amplitude and the state responses as well as the statistic moments of the amplitude are obtained. Finally, two types of the modulating functions, i.e. constant function and exponential function, are considered to give some semi‐analytical formulae. The proposed procedures are checked against the Monte Carlo simulation. The effects of the structure natural frequency and the intensity of the excitation as well as the ground stiffness on the system responses are discussed. It should be pointed out that the proposed method is good for broadband excitation and light damping. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
190.