扩孔螺栓连接型消能梁段的力学模型及参数研究          下载免费PDF全文

张波  胡淑军  熊进刚  王雪飞  曾思智 《世界地震工程》2019,35(3):073-82

当前国家对建筑结构的抗震性能和震后功能恢复能力提出了更高要求。基于短剪切型消能梁段的受剪屈服特性和剪切扩孔型螺栓连接的受剪滑移性能,提出一种新型扩孔螺栓连接型消能梁段,可有效增大消能梁段的延性和耗能能力并同时减小消能梁段的损伤,使带扩孔螺栓连接型消能梁段的新型Y形偏心支撑结构更好地适应当前要求。采用有限元方法详细分析扩孔螺栓连接型消能梁段的滞回性能、破坏模式和耗能机理,由此得到其骨架曲线和力学模型,并阐述其力学模型的影响参数,为相应偏心支撑结构的设计和分析提供理论依据。  相似文献   

机械连接预应力实心方桩承台节点抗震性能试验研究          下载免费PDF全文

孙传智  缪长青  李爱群    鲜铖  朱方之 《世界地震工程》2019,35(4):039-49

预应力管桩在高烈度抗震设防地区已禁用,而普通钢筋混凝土方桩成本较高。首先针对卡扣式机械连接预应力混凝土实心方桩、PHC管桩和普通钢筋混凝土方桩与承台处的节点进行拟静力试验,并利用试验数据针对Park-Ang损伤模型进行了修正,进行了损伤指数分析。研究结果表明:预应力方桩比普通钢筋混凝土方桩的抗裂性能明显好,而预应力混凝土实心方桩承台节点耗能能力和延性低于预应力管桩和普通钢筋混凝土方桩;截桩施工导致桩端部损失部分预应力,相比较未截桩试件屈服荷载和极限荷载均减小,节点裂缝开展较早,损伤较未截桩试件严重;增配普通钢筋试件的滞回曲线比较饱满,水平承载能力和位移延性得到提升,节点抗震性能得到提升与改善;预应力混凝土实心方桩损伤前期较小,而一旦发生损伤后,损伤指数发展较快。  相似文献   

Modeling spatiotemporal topological relationships between moving object trajectories along road networks based on region connection calculus     

Linbing Ma  Jing Wu  Qiliang Liu 《制图学和地理信息科学》2016,43(4):346-360

Considering the attempts to model spatiotemporal topological relationships between moving object trajectories, the conceptual and computational framework for moving objects along a road network has not received much attention. This paper aims to draw an improved model based on Region Connection Calculus (RCC) theory to represent the spatiotemporal topological relationships between moving object trajectories along road networks. This paper first uses a dimension reduction method based on a linear-reference transformation to model the moving object trajectories segments, and then defines new time–connection and space–connection relations between two trajectory segments. On this basis, the paper proposes an extension to the RCC-based spatiotemporal binary relationship set so that the combined semantics of the spatiotemporal predicates can be described completely. A case study was carried out using Floating Car Data in Guangzhou city. The computational results show that in a real application, the occurrence frequencies of the RCC-based binary relationships are distributed nonuniformly and the semantics of some binary relationships with the highest occurrence are coarse. Therefore, the partition of the spatiotemporal connection relations and the finer aspects of the spatiotemporal relationship model may require further research work.  相似文献   

Long-term fish and macro-crustacean community variation in a Mediterranean lagoon     

Gilles Poizat  Elizabeth Rosecchi  Philippe Chauvelon  Pascal Contournet  Alain J. Crivelli 《Estuarine, Coastal and Shelf Science》2004,59(4):615-624

The fish and macro-crustacean community of the Vaccarès lagoon (Rhône River delta, South France) was sampled monthly from 1993 to 2002. The lagoon salinity shifted from 15 in 1993 to 5 in 1994–1997 and went back to 15 in 1999–2002. Connections with the sea also varied during the study period with larger openings in 1996–1997. During the study period, the community changed to revert in 2002 to a state similar to 1993. These changes consisted of a sequence of increased and decreased patterns of freshwater species and some marine species. Typical lagoon species tended to resist to salinity changes. Freshwater species colonised the lagoon when the salinity was low. Marine species may have varied both in relation to connections with the sea and to indirect effects of freshwater outflow. This study shows that community changes following environmental variations can be delayed in time, and emphasises the need for long-term studies.  相似文献   

递归型多业务宽带GEO卫星网络跨层流量控制算法研究     

何宁  王磊 《武汉大学学报(信息科学版)》2010,(5)

提出了一种递归型多业务跨层流量控制算法。该算法首先将多业务输入的流量控制问题抽象为具有输入端速率控制机制的缓冲区门限优化问题,建立多输入递归型SFM单节点模型MRSFM;确定了反映用户应用层QoS丢包和延时性能要求的系统代价函数,建立了用于跨层流量控制优化模型。在跨层优化模型的基础上,以建立的MRSFM模型为基础,运用IPA方法推导了代价函数相对于优化参数(缓冲区门限)的IPA导数,并利用SA理论进行优化。仿真实验验证了宽带GEO卫星网络跨层流量控制算法的正确性。  相似文献   

MapGIS二次开发在绘制地震震中分布图中的应用   总被引：2，自引：0，他引：2  

李恒  姚运生  陈蜀俊 《大地测量与地球动力学》2007,27(Z1):129-132

MapGIS制图功能强大,但在绘制地震构造图过程中添加地震震中位置点时却极为繁琐.为此提出一种把记录地震信息的文本文件转换成MapGIS明码文件再生成图形文件,并通过属性连接达到动态标注的方法.按上述方法,以Microsoft VC 6.0为工具,二次开发MapGIS,实现了快速准确绘制地震震中分布图.  相似文献   

一种支持大规模连接数的状态检测防火墙     

李林  卢显良  李泽平  聂晓文  蒲汛  彭永祥 《中国海洋大学学报(自然科学版)》2008,(Z1)

状态检测防火墙,是目前最常见的防火墙,这种类型的防火墙,需要维护每个连接的状态信息。近年来随着P2P应用的深入发展,特别是随着BT下载、视频直播、点播的广泛应用,状态检测防火墙需要维护的连接数越来越多,造成防火墙空间使用量过大。针对这一问题,文中提出一种能够支持大规模连接数的状态检测防火墙SDBF(Stateful DetectingBloom Filter),与传统的状态检测防火墙不同,SDBF防火墙将每个连接的标识信息存储在Bloom filter内,并将Bloom filter放在片内SRAM中。理论分析和仿真实验表明:在使用6MBytes片内SRAM的情况下,SDBF防火墙能够支持100万连接数;其内存使用量,远小于支持100万连接数的传统状态检测防火墙。  相似文献   

A missing link of the Proto-Tethys Ocean between the Qinling and Qilian orogens,China:Insights from geochronology and structural geology     

《地学前缘(英文版)》2020,11(5):1495-1509

The Qinling-Qilian connection zone(QQCZ) is a key area to reveal the relationship and to make a link of the North Qinling and the North Qilian orogens,China.Here we present U-Pb dating data of detrital zircons from four sedimentary/metasedimentary rocks in the QQCZ and the southwestern North China Block(NCB) and detailed regional structural data.Three episodes of fold deformation(D_1,D_2 and D3) are distinguished in the QQCZ,with the former two occurred during the early Paleozoic.The D_1 deformation is mainly characterized by regionally penetrative schistosity and some residual rootless intrafolial folds due to the intensive superpositions by the subsequent D_2 and D3 deformations.The D_2 deformation characterized by tight folds,associated axial plane foliations and crenulation lineations indicates a stress field characterized by NNE-SSW-directed compression,which may be induced by the collision between the NCB and the southern blocks.The D3 deformation which might occur during the Mesozoic is marked by upright open folds and kink bands.The similarity of the detrital zircon age spectra of the Huluhe Group in the North Qilian Orogen and the Erlangping Group in the North Qinling Orogen suggests that the two groups have similar provenance,which may indicate that the North Qilian Orogen corresponded to the North Qinling Orogen in a regional tectonic framework.In addition,the remarkable age peak at～435 Ma of the detrital zircon age spectrum of the Duanjiaxia Formation in the southwestern NCB indicates that this formation obtained the provenance of the North Qilian and North Qinling orogens,which may be generated by the collage of the southwestern NCB and the QQCZ during the Late Ordovician-Early Silurian.Based on structural,detrital zircon and metamorphic data,we suggest that the North Qilian and North Qinling orogens underwent similar evolution during the early Paleozoic due to the closure of the North Qilian and the Kuanping oceans which located at the northern boundary of the Proto-Tethys Ocean.  相似文献   

完全残差连接与多尺度特征融合遥感图像分割     

张小娟  汪西莉 《遥感学报》2020,24(9):1120-1133

遥感图像数据规模大，光照、遮挡等情况复杂，目标密集、尺度不一以及缺乏大量带标注图像用于训练深度网络等特点对遥感图像分割的完整性和正确性造成了更大的挑战。针对深度卷积网络中因多次卷积造成分辨率显著下降，像素类别预测精度降低的问题，本文在深度卷积编码—解码网络的基础上设计了一个采用完全残差连接和多尺度特征融合的端到端遥感图像分割模型。该模型具有两方面优点：首先，长距离和短距离的完全残差连接既简化了深层网络的训练，又为本层末端融入了原始输入信息，增强了特征融合。其次，不同尺度和方式的特征融合使网络能够提取丰富的上下文信息，应对目标尺度变化，提升分割性能。本文通过对ISPRS Vaihingen和Road Detection数据集做数据扩充并进行实验，分别从平均IOU、平均F1值两方面对模型进行评价。通过与目前先进的模型以及文献中的研究成果进行比较，结果表明本文所提模型优于对比模型，在两个数据集上的平均IOU分别达到了85%和84%，平均F1值分别达到了92%和93%，能够有效提高遥感图像目标分割的完整性和正确性。  相似文献   

流域交通运输地理研究进展与展望     

吴威  梁双波  曹有挥 《地理科学进展》2019,38(8):1136-1149

流域交通运输地理在区域交通运输地理的理论框架下,以流域或流域的部分区域为研究区开展交通运输组织及其发展规律研究。论文从交通网络、运输联系及区域效应3个方面梳理了流域交通运输地理的研究进展。 ① 交通网络相关研究围绕综合交通发展水平与格局、网络连接特征与可达性、港口体系的空间结构与供应链等展开,多式联运正成为流域交通运输地理研究的新热点;② 运输联系主要研究客货运输联系规律和交通流,流域物流地理的研究重点正从物流产业布局与企业选址向物流网络与空间组织、物流供应链转移;③ 区域效应偏重于经济增长效应,资源环境生态效应研究较为薄弱。基于流域交通运输地理研究的侧重点,结合当前研究进展与流域发展需求,流域交通运输地理学未来应重视流域港口体系与水运发展,关注综合交通网络构建与运输组织以及多式联运,探究不同层级流域交通运输间的关联性,同时应加强流域交通运输的资源环境与生态效应研究。  相似文献