量子漂移扩散模型解的指数衰减

研究了量子漂移扩散模型解的指数衰减．该模型来自于量子流体动力学模型,是一个非线性四阶抛物型偏微分方程组,由于比较原理对于四阶偏微分方程不再成立,进而最大模估计成为本质困难．利用熵函数的方法,结合差分法,能量估计,梅造差分方程解的迭代．从而在时间增大时,得到解在L^1意义下以指数速度衰减到常定态．     

不确定时变时滞系统的指数稳定鲁棒H_∞可靠控制

针对一类含有时变时滞的参数不确定线性系统,研究了在执行器发生故障情况下系统指数稳定的鲁棒H∞可靠控制器设计问题.根据Lyapunov稳定性理论,给出了系统存在指数稳定鲁棒可靠控制器应满足的一个矩阵不等式;同时给出了系统具有H∞性能指标应满足的另一个矩阵不等式.论文将这两个矩阵不等式转化为两个线性矩阵不等式（LMIs）.利用论文方法设计的指数稳定鲁棒H∞可靠控制器能够使得时滞系统对于任意允许的不确定性以及任意执行器失效都保持鲁棒可靠指数稳定,并且使系统具有指定H∞范数的干扰抑制能力.仿真结果表明了该控制器设计方法的有效性.     

A new time-frequency analysis method based on single mode function decomposition for offshore wind turbines

The Hilbert-Huang transform (HHT) has been widely applied and recognised as a powerful time-frequency analysis method for nonlinear and non-stationary signals in numerous engineering fields. One of its major challenges is that the HHT is frequently subject to mode mixing in the processing of practical signals such as those of offshore wind turbines, as the frequencies of offshore wind turbines are typically close and contaminated by noise. To address this issue, this paper proposes a new time-frequency analysis method based on single mode function (SMF) decomposition to overcome the mode mixing problem in the structural health monitoring (SHM) of offshore wind turbines. In this approach, the structural vibration signal is first decomposed into a set of window components using complex exponential decomposition. A state-space model is introduced in the signal decomposition to improve the numerical stability of the decomposition, and then a novel window-alignment strategy, named energy gridding, is proposed and the signals are constructed in the corresponding gridding. Furthermore, energy recollection is implemented in each gridding, and the reassembling of these components yields an SMF that is comparable to the intrinsic mode function (IMF) of the HHT, but with a significant improvement in terms of mode mixing. Four case studies are conducted to evaluate the performance of the proposed method. The first case attempts to detect three different frequencies in a simulated time-invariant signal. The second case attempts to test a synthesised signal with segmental time-varying frequencies (each segment contains three different frequencies components). The analysis results in these two cases indicate that mode mixing can be reduced by the proposed method. Furthermore, a synthesised signal with slowly varying frequencies is used. These analysis results demonstrate the effective suppression of non-relevant frequency components using SMF decomposition. In the third case, the experimental data from vortex-induced vibration (VIV) experiments sponsored by the Norwegian Deepwater Programme (NDP) are used to evaluate the proposed SMF decomposition for vibration mode identification. In the final case, field data acquired from an offshore wind turbine foundation and offshore wind turbine are analysed. The mode identification results obtained using SMF decomposition are compared with those produced by the HHT. The comparison demonstrates superior performance of the proposed method in identifying the vibration modes of the VIV experimental and field data.     

接触式钢轨轮廓测量的数据处理

详细介绍基于接触式扫描测量的轮廓数据点的处理过程,包括噪声过滤、精简滤波,平滑处理,曲线分段等多个环节,并采用最小二乘法进行轮廓线拟合。通过工程实践应用表明,该数据处理效果较理想,能够获取满足精度要求的轮廓线。     

京津城际列车快通卡票额智能分配的研究与应用

通过对京津城际列车快通卡刷卡人数统计分析,挖掘出快通卡客流在非小长假期间具有以星期和列车始发时间为周期的规律,在小长假期间具有和去年同期相似的客流规律.依据此规律通过指数平滑法对京津城际列车快通卡客流进行了预测,研究开发了京津城际列车快通卡票额智能分配系统并成功应用于现场.     

单中心城市内部车流密度和行车速度模型研究

根据统计物理学的理论知识,将车辆自由出行活动看作粒子在一定空间(城市道路网)的自由活动;基于理想圆形城市和放射道路网的假设,借助玻耳兹曼统计方法推导出了城市内部车流密度空间分布的负指数理论模型,并借鉴交通阻抗的相关概念和算法用代表交通阻抗的最短出行时间代替垂直距离对模型做了修正.并根据Greenshields的速度-密...     

大众捷运不断电系统的可用度及可靠度分析

分析单一组件的历时可用度行为,探讨对数常态分布可靠度(中位数tmed以及误差因子EF)和指数分布维修度(平均维修时间MTTR)对其可用度的影响,得出数值分析结果:在固定稳态可用度ASS以及平均维修时间MTTR的情况下,中位数tmed越小(或是误差因子EF越大)的组件历时可用度越早单调下降且下降量越大,越晚回弹至其稳态可用度;在固定稳态可用度ASS以及误差因子EF的情况下,具有越大平均维修时间MTTR的组件历时可用度越晚单调下降但下降量不变,也越晚回弹至其稳态可用度.建立不断电系统可用度以及可靠度的分析模式,探讨正常供电、电池备援以及旁通供电3种不同模式对整体可用度以及可靠度的贡献程度,得出数值分析结果:正常供电模式贡献了绝大部分的整体不断电可用度;不考虑维修作业能力,整体不断电系统的可靠度参数MTTF为1184301h.     

指数平滑法在滑坡抢险工程中的应用

指数平滑技术是进行预测决策的有效方法,文章首先对指数平滑模型作了简单的介绍,然后根据某滑坡的实际情况,对部分监测点位移进行了建模和预测,预测结果表明,预测值与实际观测值之间的误差很小,说明此模型可很好地应用于滑坡位移预测,可为施工决策提供可靠的依据.     

二次指数平滑法中确定初始值的简便方法

在利用二次指数平滑法建立趋势预测模型时，必须合理确定初始平滑值．确定初始平滑值比较复杂繁琐，用初期指标值替代初始平滑值是一种简便的处理方法．通过推导，论证了这一方法的可行性，并给出了适用条件．     

公路枢纽项目客运量预测方法初探

公路客运量发展预测是公路客运枢纽站项目可行性研究中的主要内容 ,是确定一个项目建设规模的基础条件。探讨应用经济指标与公路客运量统计数据作为基础数据 ,在经济指标预测中采用增长系数法和三次指数平滑法进行预测 ,采用回归分析模型进行客运量预测 ,从而为公路客运枢纽项目确定规模提供依据