A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River.Among the strata,there are two confined aquifers,between which lies an aquiclude that is partially missing.T...A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River.Among the strata,there are two confined aquifers,between which lies an aquiclude that is partially missing.To guarantee the safety of pit excavation,the piezometric head of the upper confined aquifer,where the pit bottom is located,should be 1 m below the pit bottom,while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem.The Yangtze River levee is notably close to the pit,and its deformation caused by dewatering should be controlled.A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer.The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d,which is larger than the values from numerical simulation(horizontal hydraulic conductivity K_H=16 m/d and vertical hydraulic conductivity K_V=S m/d).The difference between K_H and K_V indicates the anisotropy of the aquifer.Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes.The results show that though the first scheme could meet the dewatering requirements,the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰,respectively,greatly exceeding the limited values.Meanwhile,the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level,and 27 recharge wells are set along the levee,can control the deformation of the levee significantly.展开更多
在GNSS边坡监测中,基准站与监测站间的大高差会增加相对对流层延迟误差,严重制约实时动态差分(real time kinematic,RTK)垂向定位精度.为此,本文构建了一种顾及大高差改进的区域对流层模型.该模型基于基准站与监测站高精度天顶对流层延...在GNSS边坡监测中,基准站与监测站间的大高差会增加相对对流层延迟误差,严重制约实时动态差分(real time kinematic,RTK)垂向定位精度.为此,本文构建了一种顾及大高差改进的区域对流层模型.该模型基于基准站与监测站高精度天顶对流层延迟(zenith tropospheric delay,ZTD)模型数据,采用三次多项式函数建立ZTD与站间高程之间的函数关系,同时考虑了ZTD的季节变化特征,建立了区域对流层模型.为验证模型的有效性,以滨海某大高差边坡为研究对象,实验结果表明,本文提出的该模型有效提升了U方向的定位精度,较Saastamoinen模型、第三代全球气压和气温(Global Pressure and Temperature 3,GPT3)模型分别提升了约15%、8%.该模型有效提升站间大高差对流层误差改正效果,为GNSS大高差边坡监测提供了方案.展开更多
随着移动互联网和通讯技术的发展,多媒体通信技术成为国家信息产业发展的重大需求,广泛地应用在视频会议、各类直播应用、远程医疗、远程监控和远程教育等方面。然而,大容量多媒体通信业务面临着网络带宽的压力。本文将媒体计算引入通...随着移动互联网和通讯技术的发展,多媒体通信技术成为国家信息产业发展的重大需求,广泛地应用在视频会议、各类直播应用、远程医疗、远程监控和远程教育等方面。然而,大容量多媒体通信业务面临着网络带宽的压力。本文将媒体计算引入通信系统,建立新的多媒体通信研究范式,从提升体验质量(quality of experience,QoE)的角度,形成新的多媒体编码与传输方法,从根本上降低网络带宽需求的压力。体验质量即信息接收者结合自身期望对客观信息载体的有关性能给出的主观评价,是区别于服务质量(quality of service,QoS)的通信质量评价准则。本文介绍了QoE的评价准则,分为基于用户的评价方法和基于客观参数的评价方法,通过用户主观评分或对用户的相关生理、心理指标进行测量进而分析、推测用户的感受;或者通过对业务客观指标的主观化修正实现体验质量的评价。本文综述了多媒体编码方法,主要包括基于波形的编码和基于内容的编码方法。前者对任意视频信号进行有效编码而不需要分析视频内容,如一系列视频编码标准;后者识别视频序列中的物体和相关区域并对它们进行编码。本文阐述了5G+AI(artificial intelligence)时代的新型视频传输方法,如多视点视频编码、4 K、8 K视频编码,3D立体视频,点云、光场、AR(augmented reality)、VR(virtual reality)等视频业务。展开更多
基金financially supported by the doctoral fund of the Ministry of Education of Chinathe Nature Science Foundation of Jiangsu Province,China(Grant Nos.20130091110020 and BE2015675)
文摘A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River.Among the strata,there are two confined aquifers,between which lies an aquiclude that is partially missing.To guarantee the safety of pit excavation,the piezometric head of the upper confined aquifer,where the pit bottom is located,should be 1 m below the pit bottom,while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem.The Yangtze River levee is notably close to the pit,and its deformation caused by dewatering should be controlled.A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer.The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d,which is larger than the values from numerical simulation(horizontal hydraulic conductivity K_H=16 m/d and vertical hydraulic conductivity K_V=S m/d).The difference between K_H and K_V indicates the anisotropy of the aquifer.Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes.The results show that though the first scheme could meet the dewatering requirements,the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰,respectively,greatly exceeding the limited values.Meanwhile,the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level,and 27 recharge wells are set along the levee,can control the deformation of the levee significantly.
文摘在GNSS边坡监测中,基准站与监测站间的大高差会增加相对对流层延迟误差,严重制约实时动态差分(real time kinematic,RTK)垂向定位精度.为此,本文构建了一种顾及大高差改进的区域对流层模型.该模型基于基准站与监测站高精度天顶对流层延迟(zenith tropospheric delay,ZTD)模型数据,采用三次多项式函数建立ZTD与站间高程之间的函数关系,同时考虑了ZTD的季节变化特征,建立了区域对流层模型.为验证模型的有效性,以滨海某大高差边坡为研究对象,实验结果表明,本文提出的该模型有效提升了U方向的定位精度,较Saastamoinen模型、第三代全球气压和气温(Global Pressure and Temperature 3,GPT3)模型分别提升了约15%、8%.该模型有效提升站间大高差对流层误差改正效果,为GNSS大高差边坡监测提供了方案.
文摘随着移动互联网和通讯技术的发展,多媒体通信技术成为国家信息产业发展的重大需求,广泛地应用在视频会议、各类直播应用、远程医疗、远程监控和远程教育等方面。然而,大容量多媒体通信业务面临着网络带宽的压力。本文将媒体计算引入通信系统,建立新的多媒体通信研究范式,从提升体验质量(quality of experience,QoE)的角度,形成新的多媒体编码与传输方法,从根本上降低网络带宽需求的压力。体验质量即信息接收者结合自身期望对客观信息载体的有关性能给出的主观评价,是区别于服务质量(quality of service,QoS)的通信质量评价准则。本文介绍了QoE的评价准则,分为基于用户的评价方法和基于客观参数的评价方法,通过用户主观评分或对用户的相关生理、心理指标进行测量进而分析、推测用户的感受;或者通过对业务客观指标的主观化修正实现体验质量的评价。本文综述了多媒体编码方法,主要包括基于波形的编码和基于内容的编码方法。前者对任意视频信号进行有效编码而不需要分析视频内容,如一系列视频编码标准;后者识别视频序列中的物体和相关区域并对它们进行编码。本文阐述了5G+AI(artificial intelligence)时代的新型视频传输方法,如多视点视频编码、4 K、8 K视频编码,3D立体视频,点云、光场、AR(augmented reality)、VR(virtual reality)等视频业务。
