共查询到12条相似文献，搜索用时 156 毫秒
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为了有效地考虑浮体慢漂运动对钢悬链线立管疲劳损伤的影响,提出了波频和慢漂运动组合作用下钢悬链线立管疲劳损伤简化计算的位置组合叠加法。其核心是:基于浮体慢漂运动概率分布选取若干典型慢漂位置,进行波频运动作用下钢悬链线立管动力响应分析;根据钢悬链线立管运动位置变化特征,截取若干慢漂位置对应的波频应力时程叠加到慢漂应力时程上,得到波频和慢漂运动的组合应力时程;编写基于雨流计数法的MATLAB程序处理立管各节点应力,采用海水环境下Do E.E型S-N曲线和Palmgren-Miner累积损伤准则计算立管各节点疲劳损伤。应用位置组合叠加法对某海域500 m水深的立管进行了疲劳分析,并与全耦合法、权重组合叠加法以及波频和慢漂疲劳损伤简单相加法的结果进行了对比,结果表明该方法具有较高的精度和效率。此外,进行了区域设定系数、波浪高度、波浪周期和土壤表面剪切强度等参数对组合作用下立管疲劳损伤的敏感性分析。 相似文献
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复杂海洋环境中，顶张力立管顶部平台受到不同分量叠加的波浪作用，导致其轴向张力与多个频率相关，系统产生多频参激与涡激的联合振动，其动力学行为变得更为复杂，尤其是分岔和混沌等非线性振动特性有待进一步分析。首先，基于欧拉—伯努利梁理论，引入范德波尔尾流振子，建立和推导受多频参激—涡激联合作用下立管的动力学模型及其运动微分方程；接着，利用伽辽金法得到离散后的常微分方程组，采用多尺度法得到系统共振响应的调谐方程；最后，通过数值算例探究系统在多源和多频载荷联合作用下的共振响应。结果表明：对于多频参数激励，其中一个参数激励幅值在立管振动中起主导作用，而另一个会引起分岔的位置、数量和性质发生改变；随质量—阻尼参数增大，系统共振响应幅值整体先增大后减小，各分岔点出现的位置整体先向泄涡频率较大处移动，随后向泄涡频率较小处移动；质量—阻尼参数的变化还可能诱使系统发生倍周期分岔和混沌现象，危害结构安全。此外，采用直接数值积分求解微分方程组，验证近似分析结果，两者吻合较好。 相似文献
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探讨了壳寡糖及全乙酰壳寡糖的制备方法,通过正交实验考察了原料、温度、时间对降解产物的影响.制备了八种寡糖（八乙酰壳二糖、十一乙酰壳三糖、十四乙酰壳四糖和十七乙酰壳五糖,以及N,N′-二乙酰壳二糖、N,N′,N″-三乙酰壳三糖、N,N′,N″,N′′′四乙酰壳四糖和N,N′,N″,N′′′,N′′′′-五乙酰壳五糖）,并通过IR、NMR及MS等确定了其化学结构. 相似文献
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Coastal and estuarine habitat mapping, using LIDAR height and intensity and multi-spectral imagery 总被引：3，自引：1，他引：2
Guillem Chust Ibon Galparsoro ngel Borja Javier Franco Adolfo Uriarte 《Estuarine, Coastal and Shelf Science》2008,78(4):633-643
The airborne laser scanning LIDAR (LIght Detection And Ranging) provides high-resolution Digital Terrain Models (DTM) that have been applied recently to the characterization, quantification and monitoring of coastal environments. This study assesses the contribution of LIDAR altimetry and intensity data, topographically-derived features (slope and aspect), and multi-spectral imagery (three visible and a near-infrared band), to map coastal habitats in the Bidasoa estuary and its adjacent coastal area (Basque Country, northern Spain). The performance of high-resolution data sources was individually and jointly tested, with the maximum likelihood algorithm classifier in a rocky shore and a wetland zone; thus, including some of the most extended Cantabrian Sea littoral habitats, within the Bay of Biscay. The results show that reliability of coastal habitat classification was more enhanced with LIDAR-based DTM, compared with the other data sources: slope, aspect, intensity or near-infrared band. The addition of the DTM, to the three visible bands, produced gains of between 10% and 27% in the agreement measures, between the mapped and validation data (i.e. mean producer's and user's accuracy) for the two test sites. Raw LIDAR intensity images are only of limited value here, since they appeared heterogeneous and speckled. However, the enhanced Lee smoothing filter, applied to the LIDAR intensity, improved the overall accuracy measurements of the habitat classification, especially in the wetland zone; here, there were gains up to 7.9% in mean producer's and 11.6% in mean user's accuracy. This suggests that LIDAR can be useful for habitat mapping, when few data sources are available. The synergy between the LIDAR data, with multi-spectral bands, produced high accurate classifications (mean producer's accuracy: 92% for the 16 rocky habitats and 88% for the 11 wetland habitats). Fusion of the data enabled discrimination of intertidal communities, such as Corallina elongata, barnacles (Chthamalus spp.), and stands of Spartina alterniflora and Phragmites australis, which presented misclassification when conventional visible bands were used alone. All of these results were corroborated by the kappa coefficient of agreement. The high classification accuracy found here, selecting data sources, highlights the value of integrating LIDAR data with multi-spectral imagery for habitat mapping in the intertidal complex fringe. 相似文献
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