为研究海洋桩基与附近土体的界面力学特性,进行了不同法向应力、土体含水率与压缩度下的混凝土-海洋黏土界面剪切试验,并通过PFC^(2D)离散元方法分析了海洋桩基附近土体剪切带随时间的变化情况。结果表明:压缩量-法向应力曲线符合“双...为研究海洋桩基与附近土体的界面力学特性,进行了不同法向应力、土体含水率与压缩度下的混凝土-海洋黏土界面剪切试验,并通过PFC^(2D)离散元方法分析了海洋桩基附近土体剪切带随时间的变化情况。结果表明:压缩量-法向应力曲线符合“双曲线”关系。土体的压缩度随含水率、法向应力的增大而增大,在达到相同的压缩度下,含水率越高或受法向应力越大的土体所用的压缩时间越短。峰值剪切应力随法向应力、压缩度的增大而增大,随含水率的增大而减小。降低土体压缩度或调整土体含水率至塑限附近可提高界面抗剪强度。含水率、法向应力越大,土体的剪缩特性越明显;压缩度越大,土体的剪胀特性越明显。土体剪切带面积随剪切时间先急剧增加,后逐渐减小至稳定值1.13 cm 2左右。压缩度越大,土体剪切带面积越大,但达到峰值剪切带面积所用时间基本相同。含水率越低,土体剪切带面积越大,峰值剪切带面积与剪切时间成正比例。展开更多
A new analog error correction （AEC） scheme based on the moving North Pacific index （MNPI） is designed in this study. This scheme shows obvious improvement in the prediction skill of the operational coupled general...A new analog error correction （AEC） scheme based on the moving North Pacific index （MNPI） is designed in this study. This scheme shows obvious improvement in the prediction skill of the operational coupled general circulation model （CGCM） of the National Climate Center of China for the rainy season rainfall （RSR） anomaly pattern correlation coefficient （ACC） over the mid-to-lower reaches of the Yangtze River （MLRYR）. A comparative analysis indicates that the effectiveness of the new scheme using the MNPI is better than the system error correction scheme using the North Pacific index （NPI）. A Euclidean distance- weighted mean rather than a traditional arithmetic mean, is applied to the integration of the analog year＇s prediction error fields. By using the MNPI AEC scheme, independent sample hindcasts of RSR during the period 2003-2009 are then evaluated. The results show that the new scheme exhibited a higher forecast skill during 2003-2009, with an average ACC of 0.47; while the ACC for the NPI case was only 0.19. Furthermore, the forecast skill of the RSR over the MLRYR is examined. In the MNPI case, empirical orthogonal function （EOF） was used in the degree compression of the prediction error fields from the CCCM, whereas the AEC scheme was applied only to its first several EOF components for which the accumulative explained variance accounted for 80% of the total variance. This further improved the ACC of the independent sample hindcasts to 0.55 during the 7-yr period.展开更多
目的比较经皮椎体成形术(PVP)术中使用高黏度骨水泥与经皮球囊扩张椎体后凸成形术(PKP)术中使用低黏度骨水泥治疗骨质疏松性胸腰椎Ⅲ度压缩性骨折的临床疗效及并发症。方法对87例患者的临床资料,进行回顾性分析,根据术式不同,将其分为PV...目的比较经皮椎体成形术(PVP)术中使用高黏度骨水泥与经皮球囊扩张椎体后凸成形术(PKP)术中使用低黏度骨水泥治疗骨质疏松性胸腰椎Ⅲ度压缩性骨折的临床疗效及并发症。方法对87例患者的临床资料,进行回顾性分析,根据术式不同,将其分为PVP组42例和PKP组45例。采用视觉模拟量表(VAS)进行疼痛评分,采用Oswestry功能障碍指数(ODI)进行胸腰椎功能评分,观察并比较两组患者手术前后VAS评分、ODI指数、病椎高度及Cobb角变化情况以及术后骨水泥渗漏情况。结果两组患者术后3 d VAS疼痛评分、ODI指数较术前均有明显改善(P<0.05)。术后测量PKP组病椎高度恢复及Cobb角改善较PVP组明显(P<0.05)。术后PVP组发生椎旁软组织渗漏、椎旁静脉渗漏、椎间盘渗漏分别为7例(16.66%)、9例(21.42%)、1例(2.38%),骨水泥椎管内硬膜外渗漏、椎间孔渗漏各1例(2.38%);术后PKP组发生椎旁软组织渗漏、椎旁静脉渗漏分别为1例(2.22%)、2例(4.44%),未发生骨水泥椎间盘渗漏、椎管内硬膜外渗漏及椎间孔渗漏。结论在治疗骨质疏松性胸腰椎Ⅲ度压缩性骨折中,PVP与PKP均能快速缓解疼痛,改善胸腰椎功能活动,但PKP较PVP能更好地降低骨水泥椎旁渗漏,有效恢复病椎高度,矫正脊椎后凸畸形。展开更多
文摘为研究海洋桩基与附近土体的界面力学特性,进行了不同法向应力、土体含水率与压缩度下的混凝土-海洋黏土界面剪切试验,并通过PFC^(2D)离散元方法分析了海洋桩基附近土体剪切带随时间的变化情况。结果表明:压缩量-法向应力曲线符合“双曲线”关系。土体的压缩度随含水率、法向应力的增大而增大,在达到相同的压缩度下,含水率越高或受法向应力越大的土体所用的压缩时间越短。峰值剪切应力随法向应力、压缩度的增大而增大,随含水率的增大而减小。降低土体压缩度或调整土体含水率至塑限附近可提高界面抗剪强度。含水率、法向应力越大,土体的剪缩特性越明显;压缩度越大,土体的剪胀特性越明显。土体剪切带面积随剪切时间先急剧增加,后逐渐减小至稳定值1.13 cm 2左右。压缩度越大,土体剪切带面积越大,但达到峰值剪切带面积所用时间基本相同。含水率越低,土体剪切带面积越大,峰值剪切带面积与剪切时间成正比例。
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2013CB430204)National Natural Science Foundation of China(41305100 and 41105055)China Meteorological Administration Special Public Welfare Research Fund(GYHY201306021)
文摘A new analog error correction （AEC） scheme based on the moving North Pacific index （MNPI） is designed in this study. This scheme shows obvious improvement in the prediction skill of the operational coupled general circulation model （CGCM） of the National Climate Center of China for the rainy season rainfall （RSR） anomaly pattern correlation coefficient （ACC） over the mid-to-lower reaches of the Yangtze River （MLRYR）. A comparative analysis indicates that the effectiveness of the new scheme using the MNPI is better than the system error correction scheme using the North Pacific index （NPI）. A Euclidean distance- weighted mean rather than a traditional arithmetic mean, is applied to the integration of the analog year＇s prediction error fields. By using the MNPI AEC scheme, independent sample hindcasts of RSR during the period 2003-2009 are then evaluated. The results show that the new scheme exhibited a higher forecast skill during 2003-2009, with an average ACC of 0.47; while the ACC for the NPI case was only 0.19. Furthermore, the forecast skill of the RSR over the MLRYR is examined. In the MNPI case, empirical orthogonal function （EOF） was used in the degree compression of the prediction error fields from the CCCM, whereas the AEC scheme was applied only to its first several EOF components for which the accumulative explained variance accounted for 80% of the total variance. This further improved the ACC of the independent sample hindcasts to 0.55 during the 7-yr period.
文摘目的比较经皮椎体成形术(PVP)术中使用高黏度骨水泥与经皮球囊扩张椎体后凸成形术(PKP)术中使用低黏度骨水泥治疗骨质疏松性胸腰椎Ⅲ度压缩性骨折的临床疗效及并发症。方法对87例患者的临床资料,进行回顾性分析,根据术式不同,将其分为PVP组42例和PKP组45例。采用视觉模拟量表(VAS)进行疼痛评分,采用Oswestry功能障碍指数(ODI)进行胸腰椎功能评分,观察并比较两组患者手术前后VAS评分、ODI指数、病椎高度及Cobb角变化情况以及术后骨水泥渗漏情况。结果两组患者术后3 d VAS疼痛评分、ODI指数较术前均有明显改善(P<0.05)。术后测量PKP组病椎高度恢复及Cobb角改善较PVP组明显(P<0.05)。术后PVP组发生椎旁软组织渗漏、椎旁静脉渗漏、椎间盘渗漏分别为7例(16.66%)、9例(21.42%)、1例(2.38%),骨水泥椎管内硬膜外渗漏、椎间孔渗漏各1例(2.38%);术后PKP组发生椎旁软组织渗漏、椎旁静脉渗漏分别为1例(2.22%)、2例(4.44%),未发生骨水泥椎间盘渗漏、椎管内硬膜外渗漏及椎间孔渗漏。结论在治疗骨质疏松性胸腰椎Ⅲ度压缩性骨折中,PVP与PKP均能快速缓解疼痛,改善胸腰椎功能活动,但PKP较PVP能更好地降低骨水泥椎旁渗漏,有效恢复病椎高度,矫正脊椎后凸畸形。
