排序方式： 共有49条查询结果，搜索用时 156 毫秒
41.
42.
According to theoretical analysis,a general characteristic of the ground vibration induced by high dam flood discharge is that the dominant frequency ranges over several narrow frequency bands,which is verified by observations from the Xiangjiaba Hydropower Station.Nonlinear base isolation is used to reduce the structure vibration under ground excitation and the advantage of the isolation application is that the low-frequency resonance problem does not need to be considered due to its excitation characteristics,which significantly facilitate the isolation design.In order to obtain the response probabilistic distribution of a nonlinear system,the state space split technique is modified.As only a few degrees of freedom are subjected to the random noise,the probabilistic distribution of the response without involving stochastic excitation is represented by theδfunction.Then,the sampling property of theδfunction is employed to reduce the dimension of the Fokker-PlanckKolmogorov(FPK)equation and the low-dimensional FPK equation is solvable with existing methods.Numerical results indicate that the proposed approach is effective and accurate.Moreover,the response probabilistic distributions are more reasonable and scientific than the peak responses calculated by conventional time and frequency domain methods. 相似文献
43.
南极中山站和企鹅岛变质岩类造岩矿物的矿物化学及其变质作用 总被引：1，自引：0，他引：1
本文利用电子探针分析了南极中山站和企鹅岛变质岩类岩石中主要造岩矿物(石榴石、斜长石、黑云母和角闪石)的化学组成,利用矿物地质温度计和各种成因判别图解,确定中山站变质岩类岩石的变质程度为高角闪岩相;企鹅岛变质岩类岩石的变质程度为低角闪岩相。 相似文献
44.
45.
Skewness of subsurface ocean temperature in the equatorial Pacific based on assimilated data 总被引：1，自引：0，他引：1
The skewness of subsurface temperature anomaly in the equatorial Pacific Ocean shows a significant asymmetry between the east and west.A positive temperature skewness appears in the equatorial eastern Pacific,while the temperature skewness in the western and central Pacific is primarily negative.There is also an asymmetry of the temperature skewness above and below the climatological mean thermocline in the central and western Pacific.A positive skewness appears below the thermocline,but the skewness is neg... 相似文献
46.
47.
全球海洋大气耦合环流模式中的ENSO特征对气候背景态改变的敏感性 总被引：3，自引：0，他引：3
文中利用一个高分辨率全球海-气耦合环流模式设计两组长期积分试验,揭示了在不同气候背景态下热带太平洋年际变化特征及模式ENSO循环控制机理的差异。通过分析海表温度、上层海洋热容量和低层风场异常的年际变化特征及其和赤道中东太平洋海表温度异常的关系,揭示了基于不同气候背景场的ENSO循环的不同演变过程。结果表明:ENSO年际变率特征(包括振幅、频率等)对气候背景态相当敏感,在不同的背景场下ENSO循环的控制模态可以明显不同。试验表明,当热带太平洋东冷西暖的背景热力梯度接近多年气候平均时,模式ENSO循环表现为所谓的“时滞振子”模态控制,而随着东西向背景热力梯度显著减小,ENSO循环则可以表现为驻波模态控制。研究结果为认识年代际背景变化影响年际ENSO循环的机理提供了一种启示。 相似文献
48.
利用雷达估算太行山降水对于海河流域水循环解析、变化预测及流域水资源管理具有重要意义。本文利用2013和2014年6—9月太行山东部中低山区多普勒天气雷达反射率(Z)产品和自动雨量站降水(I)数据,采用不同滑动时间窗(1~5h)估算Z-I关系,利用2013—2014年45次降水事件验证不同时间窗Z-I关系在小雨、中雨和暴雨情况下的精度,并针对2013年7月9日降水事件进行个例分析。结果表明:不同滑动时间窗Z-I关系反演降水精度不同,误差随滑动时间窗增大,呈现先下降后上升的趋势,其中2h滑动时间窗误差最小。对于不同量级降水的反演,2h滑动时间窗Z-I关系对中雨的改进最大。个例分析表明:滑动时间窗Z-I算法的主要优势在于改善其他算法对雨强较大降水的低估。 相似文献
49.
In this paper, the decadal predictability and forecast skill of the Sea Surface Temperature Anomalies (SSTA) in the North Pacific and North Atlantic Ocean were investigated by conducting three sets of perfect model forecast experiments using a global coupled general circulation model. The results show that the annual mean SSTA in the North Pacific is less predictable on decadal time scale, with the forecast skill notably weaker than that of the North Atlantic. By analyzing the predictability and forecast skill of seasonal mean SSTA, it is found that the decadal predictability and forecast skill of the winter mean (JFM) SSTA in the central and western North Pacific are significantly higher than those of other seasons, and the magnitude is comparable with that of the North Atlantic. The predictability and forecast skill of the North Atlantic SSTA also show seasonal variations. Further analysis indicates that the seasonal dependence of the SSTA decadal predictability and forecast skill in the North Pacific is due to the winter-to-winter reemergence mechanism of SSTA in the North Pacific, which results from the seasonal variation of the mixed layer depth of the North Pacific Ocean. While the seasonal dependence of the North Atlantic SSTA predictability and forecast skill might be related to seasonal variations of other processes, such as the Atlantic Decadal Oscillation. The results of this paper suggest that for decadal climate prediction, if the forecast skill of the seasonal mean is taken into account, we might obtain higher than annual mean forecast skill for some seasons. 相似文献