Biot固结有限元方程组的病态规律分析

针对Biot固结有限元方程组的病态问题，采用正交试验和量纲分析法探讨病态性的变化规律及其影响因素。主要考虑单元平均尺寸、时间步长、压缩性和渗透性等4个因素的影响。分别提出2组相互独立的相似准则，在此基础上得到2个新的无量纲量，并将其用于分析Biot固结有限元方程组系数矩阵的条件数的变化规律。结合算例进行参数分析结果表明，对病态程度的敏感性由大到小依次为单元平均尺寸、时间步长、压缩性和渗透性；单元平均尺寸太小会使病态加剧；随着2个无量纲量的增大，病态程度呈现单调增加的趋势。其结果为深化对Biot固结数值分析病态问题的认识提供有益参考。     

关于酉矩阵的若干结果

在矩阵理论中,经常利用矩阵来描述变换。在实空间中正交变换保持度量不变,而正交变换中对应的变换矩阵就是正交矩阵,所以对正交矩阵的研究就显得格外重要。同样道理,想要得到复空间中保持度量不变的线性变换,就应该对正交变换进行推广,将其推广到复数域上,那对应的正交矩阵相应的也推广到复数域——酉矩阵。通过矩阵理论的深入研究,对正交矩阵与酉矩阵进行比较,得到了酉矩阵的若干结果。     

考虑岩土介质随机特性的工程场地地震动相干函数研究

将随机结构正交展开理论和随机振动分析的虚拟激励原理运用于场地波动有限元分析，形成了一种可以考虑岩土介质随机特性对工程场地地震动相干函数影响的分析方法。实例分析表明，非严格均匀分布的随机介质场地对场地表面的迟滞相干函数值有重要影响，这种影响可由场地的随机影响因子来衡量，在进行工程场地地震动随机场研究时应当考虑场地介质随机特性的影响。     

Spatial patterns from EOF analysis of soil moisture at a large scale and their dependence on soil,land-use,and topographic properties

We hypothesize that the spatial and temporal variation in large-scale soil moisture patterns can be described by a small number of spatial structures that are related to soil texture, land use, and topography. To test this hypothesis, an empirical orthogonal function (EOF) analysis is conducted using data from the 1997 Southern Great Plains field campaign. When considering the spatial soil moisture anomalies, one spatial structure (EOF) is identified that explains 61% of the variance, and three such structures explain 87% of the variance. The primary EOF is most highly correlated with the percent sand in the soil among the regional characteristics considered, but the correlation with percent clay is largest if only dry days are analyzed. When considering the temporal anomalies, one EOF explains 50% of the variance. This EOF is still most closely related to the percent sand, but the percent clay is unimportant. Characteristics related to land use and topography are less correlated with the spatial and temporal variation of soil moisture in the range of scales considered.     

基于正交试验和复合单元法的排水孔优化设计

排水孔是常用的工程渗控措施,其排水降压效果将直接影响工程的安全与稳定,因此,正确模拟排水孔进而优化设计尤为重要。由于影响排水效果的因素众多,优化设计需要针对多种排水孔方案进行渗流分析,计算量较大,采用正交设计法确定排水孔方案可以大大减少渗流分析次数;传统的数值模拟方法在排水孔方案改变时需要重新绘制计算网格,前处理难以实现,采用复合单元法,无需绘制排水孔网格,因而不同排水方案的渗流分析可共用一套网格,降低了前处理的工作量和难度。基于正交试验和复合单元法的排水孔优化设计的具体步骤为：确定试验指标、因素和水平;选择合适的正交表,确定渗流计算方案;对各方案依次采用复合单元法进行渗流分析;根据渗流计算结果进行极差分析和方案优选。该方法能够迅速有效地确定出“最优”的排水孔方案,具有一定的工程实用价值,实例分析表明了该方法的可行性和优越性。     

Volterra series-based system analysis of random wave interaction with a horizontal cylinder

The response of a long flexible cylinder excited by random waves in a large model basin was investigated. The linear and non-linear physical mechanisms associated with the wave–cylinder interaction were analysed using system identification and modelling techniques. A third-order frequency domain Volterra model and its orthogonalized counterpart were used to analyse the relationships between wave elevations at various locations in the vicinity of the cylinder and cylinder acceleration data at various cylinder longitudinal locations. It was found that linear mechanisms dominate, particularly at the frequency band where the majority of the wave energy is located. At higher frequencies, the cubic component of the Volterra model is the main contributor to the total model coherence, i.e. the fraction of the measured output power that can be approximated by the model output, whereas the quadratic component's contribution to the total model coherence was in general quite small. This process of identification and quantification of the non-linear mechanisms of the unknown physical system can lead to the design of improved parametric models for the cylinder response, which should by design simulate non-linearities such as the ones identified by the Volterra model. The estimated linear and non-linear Volterra transfer functions were also used to predict the cylinder acceleration under excitation inputs not used in the estimation of the model transfer functions. The good match between predicted and measured output auto-power spectra suggests that the estimated transfer functions are indeed true models of the underlying physical mechanisms of the interaction. However, the latter can only be achieved if a minimum number of data segments, as determined by an error analysis involving modelling and prediction errors, is used in the estimation of the Volterra transfer functions.     

水泥土挡墙整体稳定的敏感性分析

水泥土挡墙广泛应用于软土地区基坑支护。针对目前对于水泥土挡墙的整体稳定性与其影响因素之间相关性认识不足,引入正交设计方法分析水泥土挡墙整体稳定影响因素墙体厚度、嵌固深度、土体粘聚力、土体内摩擦角、土层重度、地下水位、地面超载的重要性和敏感性规律。分析结果表明,土的抗剪强度指标是影响水泥土挡墙的最重要因素,其变化对整体稳定有高度显著影响;而墙体厚度和嵌固深度对水泥土挡墙整体稳定无显著影响。     

区域气候模式对东亚气候时空演变特征的模拟研究

利用区域环境集成模式系统对东亚地区进行了1987年1月到1996年12月的长期积分试验,重点采用经验正交函数分析方法分析和比较模式模拟及观测气候主分量时空特征,从而考察区域气候模式对东亚地区的区域气候模拟能力.结果表明:(1) RIEMS能够较好地抓住地面气温年平均状况及其年变化和年际变率的主要特征;(2)尽管模式对降水的模拟能力没有对地面气温模拟的强,但RIEMS模式基本上能够模拟出降水的空间分布以及降水的季节变化特征,同时能够抓住降水的年际变率.       

一种改进的联合SRP-PHAT语音定位算法

提出了一种基于正交直线麦克风阵列的分级搜索SRP-PHAT(可控响应功率-相位加权)语音定位算法.利用正交直线麦克风阵列将二维搜索空间缩减为2个一维空间以减少计算量,并联合使用四叉树由粗到细的分级搜索(hierarchical search)策略分别在一维空间中搜索声源位置.通过Matlab对联合算法进行了仿真,实现了声源定位,并与传统的全搜索SRP-PHAT算法和改进前的基于正交直线麦克风阵列的加速SRP-PHAT算法进行比较分析.实验与仿真结果显示:该联合算法大大减少了计算量和定位时间,能准确定位声源位置.     

国家速滑馆动态高精度施工测量关键技术及应用

国家速滑馆建筑结构在空间上的不规则性、多样性、复杂性及超大规模给施工测量带来较大的难度,因此,加强对动态高精度测量技术的研究和应用,是实现施工过程各专业、各环节高精度搭接的重要基础。国家速滑馆动态高精度施工测量关键技术解决了不均匀作用力下大跨度马鞍形索网同步张拉困难的技术难题;突破了特大异形柔性结构屋顶预制、安装和调控精密测量关键技术,实现了精密工程测量从静态到动态、离散到连续的转变;形成了模型驱动的一测多用高密度网状排管表观形态高效测量新方法;解决了受阻或封闭环境长距离连续面超高精度地坪标高测量难题,有效指导了施工作业,为2022年冬奥会速滑项目的开展提供了保障。