Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show ...Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modem compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region .The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^-8 to 7.0×10^-10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.展开更多
喷射3D打印喷口与受喷面的间距空间可解决3D打印和钢筋协同建造的问题。本工作基于协同连续布筋和喷射3D打印混凝土工艺,提出喷射3D打印微筋混凝土的设计方法,研究了不同微筋直径(0.6、0.8、1.0 mm)和根数(1—4)对喷射3D打印微筋混凝土...喷射3D打印喷口与受喷面的间距空间可解决3D打印和钢筋协同建造的问题。本工作基于协同连续布筋和喷射3D打印混凝土工艺,提出喷射3D打印微筋混凝土的设计方法,研究了不同微筋直径(0.6、0.8、1.0 mm)和根数(1—4)对喷射3D打印微筋混凝土抗弯性能的影响规律。试验结果表明,微筋可显著提升打印混凝土的抗弯强度和韧性,对比未增强组(D0试样),喷射3D打印微筋混凝土的抗弯强度和弯曲位移分别最高提升了800%和2 076.47%。此外,基于喷射3D打印的高速喷压和逐层打印特性,微筋与喷射混凝土界面粘结密实,进一步保证了喷射3D打印微筋混凝土的抗弯性能和结构整体性。本工作打印了尺寸为1 300 mm (Z)×800 mm (X)×86 mm (Y)的异形火炬结构,验证了喷射3D打印微筋混凝土系统的实用性,为3D打印钢筋混凝土结构的制备及在大尺寸结构中的应用提供了一定的参考。展开更多
为评估交通管控策略的环境效益,提出有效融合微观交通仿真模型和微观车辆排放模型的方法。利用VISSIM平台构建案例微观交通仿真模型,提出基于轨迹数据的不同速度区间的加减速特征,应用K-means聚类方法划分4种驾驶行为,通过驾驶特性标定...为评估交通管控策略的环境效益,提出有效融合微观交通仿真模型和微观车辆排放模型的方法。利用VISSIM平台构建案例微观交通仿真模型,提出基于轨迹数据的不同速度区间的加减速特征,应用K-means聚类方法划分4种驾驶行为,通过驾驶特性标定仿真模型全局参数,描述了参数总敏感度以及参数之间相互作用的敏感度。利用DBSCAN(density-based spatial clustering of applications with noise)聚类分析并标定局部参数值,优化了参数标定流程。计算仿真轨迹工况,本地化MOVES(motor vehicle emission simulator)微观排放模型,得到交叉口不同流向和不同驾驶行为下的HC、CO、NO_(x)、CO_(2)排放。研究表明:仿真模型优化效果显著,所提方法可精确识别高排放的空间位置,解析排放与驾驶行为之间的联系。应用DBSCAN聚类分析参数寻优值有助于实现自动化标定流程,全局参数标定将速度分布χ^(2)误差由0.6327降至0.1306,加速度分布χ^(2)误差由0.1441降至0.0528,对于环境视角下仿真模型构建至关重要。展开更多
基金National Natural Science Foundation of China (40074024).
文摘Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modem compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region .The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^-8 to 7.0×10^-10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.
文摘作为热结构材料,陶瓷基复合材料(ceramic matrix composites,CMC)在航空航天领域应用潜力巨大。连续纤维的引入解决了陶瓷脆性大的问题,而纤维与基体间微小区域——界面层的设计是保证CMC具有高韧性的关键。一直以来相关研究主要集中于界面层与CMC宏观力学性能之间的关系,受限于表征难以深入研究界面层微区力学行为的困难。随着微纳力学测试与聚焦离子束(focused ion beam,FIB)技术的发展,近些年来对于CMC界面层结合强度以及其失效行为的表征逐渐增多。在此基础上,本文综述CMC中界面层的作用以及界面剪切强度的影响因素与调控机制,同时汇总当下通过直接或间接手段测试界面剪切强度的方法,重点总结微纳力学手段下纤维push-out/push-in以及微柱压缩等方法的适用条件以及差异,报道这些方法在界面区失效机制研究方面的进展,并指明尚存在的一些问题。其中,纤维pushout/push-in可以反映基体应力作用对界面剪切强度的影响,但测试结果可能受到外部因素的影响;而微柱压缩测试则更多地反映界面层本征特性,无法反映基体应力对界面剪切强度的影响,也无法反映纤维拔出过程。最后展望未来的研究方向:进一步拓展界面微区力学行为的表征方法,同时确定微区力学与宏观力学性能间的影响机制并建立模型,最终实现CMC的界面层优化。
文摘喷射3D打印喷口与受喷面的间距空间可解决3D打印和钢筋协同建造的问题。本工作基于协同连续布筋和喷射3D打印混凝土工艺,提出喷射3D打印微筋混凝土的设计方法,研究了不同微筋直径(0.6、0.8、1.0 mm)和根数(1—4)对喷射3D打印微筋混凝土抗弯性能的影响规律。试验结果表明,微筋可显著提升打印混凝土的抗弯强度和韧性,对比未增强组(D0试样),喷射3D打印微筋混凝土的抗弯强度和弯曲位移分别最高提升了800%和2 076.47%。此外,基于喷射3D打印的高速喷压和逐层打印特性,微筋与喷射混凝土界面粘结密实,进一步保证了喷射3D打印微筋混凝土的抗弯性能和结构整体性。本工作打印了尺寸为1 300 mm (Z)×800 mm (X)×86 mm (Y)的异形火炬结构,验证了喷射3D打印微筋混凝土系统的实用性,为3D打印钢筋混凝土结构的制备及在大尺寸结构中的应用提供了一定的参考。
文摘为评估交通管控策略的环境效益,提出有效融合微观交通仿真模型和微观车辆排放模型的方法。利用VISSIM平台构建案例微观交通仿真模型,提出基于轨迹数据的不同速度区间的加减速特征,应用K-means聚类方法划分4种驾驶行为,通过驾驶特性标定仿真模型全局参数,描述了参数总敏感度以及参数之间相互作用的敏感度。利用DBSCAN(density-based spatial clustering of applications with noise)聚类分析并标定局部参数值,优化了参数标定流程。计算仿真轨迹工况,本地化MOVES(motor vehicle emission simulator)微观排放模型,得到交叉口不同流向和不同驾驶行为下的HC、CO、NO_(x)、CO_(2)排放。研究表明:仿真模型优化效果显著,所提方法可精确识别高排放的空间位置,解析排放与驾驶行为之间的联系。应用DBSCAN聚类分析参数寻优值有助于实现自动化标定流程,全局参数标定将速度分布χ^(2)误差由0.6327降至0.1306,加速度分布χ^(2)误差由0.1441降至0.0528,对于环境视角下仿真模型构建至关重要。
