Effects of short flexible seagrass Zostera noltei on flow,erosion and deposition processes determined using flume experiments          下载免费PDF全文

Florian Ganthy  Laura Soissons  Pierre‐Guy Sauriau  Romaric Verney  Aldo Sottolichio 《Sedimentology》2015,62(4):997-1023

Innovative flume experiments were conducted in a recirculating straight flume. Zostera noltei meadows were sampled in their natural bed sediments in the field at contrasting stages of their seasonal growth. The aims of this study were: (i) to quantify the combined effects of leaf flexibility and development characteristics of Zostera noltei canopies on their interaction with hydrodynamics; and (ii) to quantify the role of Zostera noltei meadows in suspended sediment trapping and bed sediment resuspension related with changes in hydrodynamic forcing caused by the seasonal development of seagrasses. Velocity within the canopy was significantly damped. The attenuation in velocity ranged from 34 to 87% compared with bare sediments and was associated with a density threshold resulting from the flow‐induced canopy reconfiguration. The reduction in flow was higher in dense canopies at higher velocities than in less dense canopies, in which the reduction in flow was greater at low velocities. These contrasted results can be explained by competition between a rough‐wall boundary layer caused by the bed and a shear layer caused by the canopy. The velocity attenuation was associated with a two to three‐fold increase in bottom shear stress compared with unvegetated sediment. Despite the increase in near‐bed turbulence, protection of the sediment against erosion increased under a fully developed meadow, while sediment properties were found to be the main factor controlling erosion in a less developed meadow. Deposition fluxes were higher on the vegetated bed than on bare sediments, and these fluxes increased with leaf density. Fewer freshly deposited sediments were resuspended in vegetated beds, resulting in an increase in net sediment deposition with meadow growth. However, in the case of a very high leaf area index, sediment was mostly deposited on leaves, which facilitated subsequent resuspension and resulted in less efficient sediment trapping than in the less developed meadow.  相似文献   

采用倾斜摄影测量和几何造型方法的城市实景三维建模     

潘九宝  王玮  黄明伟  孙长奎 《测绘通报》2020,(6):121-124

近年来,数字城市在实景三维模型的基础上得到了广泛研究与应用。但是,传统三维建模手段难以满足现代数字城市更快速、更真实、更准确、更大规模的数据生产要求。本文以江苏省淮安市蒋坝古镇为例,开展快速构建城市精细化三维模型的研究,基于低空无人机倾斜摄影测量技术构建城市实景三维模型,利用几何造型方法对实景三维模型进行精细化加工。结果表明,采取的方案满足实景三维模型的应用需要,适合城市三维模型快速构建,对大规模三维模型数据生产具有一定的参考价值。  相似文献   

Energy‐compatible and spectrum‐compatible (ECSC) ground motion simulation using wavelet packets          下载免费PDF全文

Duruo Huang  Gang Wang 《地震工程与结构动力学》2017,46(11):1855-1873

A stochastic ground‐motion simulation and modification technique is developed to generate energy‐compatible and spectrum‐compatible (ECSC) synthetic motions through wavelet packet characterization and modification in both frequency and time domains. The ECSC method significantly advances traditional spectral matching approaches, because it generates ground motions that not only match the target spectral accelerations, but also match Arias intensity build‐up and significant durations. The great similarity between the ECSC simulated motions and the actual recorded motions is demonstrated through one‐to‐one comparison of a variety of intensity measures. Extensive numerical simulations were also performed to validate the performance of the ECSC ground motions through nonlinear analyses of elasto‐plastic oscillators. The ECSC method can be easily implemented in the generalized conditional intensity measure framework by directly simulating a set of motions following a targeted distribution of multiple intensity measures. Therefore, the ECSC method has great potential to be used in performance‐based earthquake design and analysis. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

一种修改建筑物底部DEM和DLG的实用方法     

李朝奎  刘文斌  路立娟  杨刚 《测绘工程》2010,19(6):4-8

三维快速建模在实现三维数字城市建设进程中起着举足轻重的作用。针对JX-4G数字摄影测量系统测得的数字高程模型（DEM）和数字线划图（DLG）,提出一种改进的方法,主要对建筑物底部的DEM和道路DEM处存在的不匹配问题进行修改,并对DLG数据中建筑物高度信息的缺失进行改进。改进后的DEM和数字正射影像图（DOM）能生成更高精度的数字表面模型（DSM）,为高效率、高精度地建立三维数字城市模型奠定基础。  相似文献   

内蒙古人工影响天气业务技术系统的建设与应用   总被引：1，自引：1，他引：0  

苏立娟  达布希拉图  邓晓东  卢士庆  闫宾  毕力格 《内蒙古气象》2010,(2):32-35

人工影响天气业务是涉及气象、航空等多领域多部门的一项综合性业务,依据此项业务的流程设计开发了内蒙古自治区级人工影响天气业务技术系统。该业务技术系统以1:25万地理信息为基础,包括综合监测、预报平台、决策平台、实时监控、效果评估和信息管理六部分。能够实现人影相关的观测资料显示、作业条件分析、航线设计、增雨飞机动态实时监控、效益评估及生成各种信息报表等功能,已经投入业务应用且在内蒙古自治区内推广应用。  相似文献   

硅烷偶联剂改性氢氧化镁的研究进展          下载免费PDF全文

王念贻  刘志启  李丽娟  朱黎霞  时东  宋雪雪  姬连敏  张波 《盐湖研究》2013,(4):53-59

氢氧化镁是一种重要的无卤阻燃剂,为了改善其阻燃效率低、与高分子材料相容性差等缺点,通常需要使用阻燃添加剂对其进行特殊处理,使之具备更好的阻燃性能。主要介绍了氢氧化镁作为阻燃剂的特性及其阻燃机理;硅烷偶联剂的结构特点及改性氢氧化镁的方法和机理;影响改性的因素以及改性效果的测评方法,并对硅烷偶联剂改性氢氧化镁的研究进展进行了概述。  相似文献   

市、县级人工影响天气轨道业务流程的研究   总被引：1，自引：0，他引：1  

王以琳 《干旱气象》2007,25(1):73-78

为推动气象业务技术体制改革,适应市、县级人工影响天气轨道建设,发挥市级指挥决策水平较高的优势,以提高作业指令的传达速度,减轻县级人影作业指挥的工作量,提出市级指挥中心直接指挥炮点作业等项新的市、县级人影轨道业务流程。该流程利用雷达指挥作业,使用GPRS技术传输作业指令,提高了地面增雨、防雹作业的科学性,保证了下达指令的实效和准确性,分工明确,减少了指挥环节,同时也加强了市级人影工作的管理功能。  相似文献   

CO_2改性水玻璃砂的热强度、高温强度和发气性     

许进 《广东海洋大学学报》2008,28(3)

研究了CO2改性水玻璃砂的热强度、高温强度和发气性,结果表明,随着粘结剂加入量的增加,热强度、高温强度和发气性增大;粘结剂种类不同,型砂的热强度、高温强度和发气性不同;其中,l#改性树脂改性水玻璃18#的热强度、高温强度均比普通水玻璃高,发气量则小于普通水玻璃;用扫描电镜分别观察了普通和改性水玻璃砂在加热温度为600℃、800℃、1000℃、1200℃时的高温炉内折断断口,解释了改性水玻璃砂比普通水玻璃砂高温强度高的原因。  相似文献   

拼合的准噶尔盆地基底: 基底火山岩Sr-Nd同位素证据   总被引：9，自引：2，他引：7       下载免费PDF全文

郑建平  吴晓智 《地球科学》2000,25(2):179-185

在详细岩相学、主元素和微量元素研究基础上, 报道了准噶尔盆地基底不同区块火山岩的Sr-Nd同位素和锆石颗粒年龄研究成果, 结合盆地周缘造山带古生代构造史、古生物、沉积建造、火山岩、侵入岩的综合研究成果, 表明准噶尔盆地基底可能由分属哈萨克斯坦板块、塔里木板块(?) 和西伯利亚板块刚性体外围的岛弧体系经构造软碰撞拼合而成, 它们又经历了块体拼合后的构造-岩浆热事件(如基性岩浆底侵作用) 的进一步改造和影响.   相似文献   

半导体多相光催化氧化技术在环境保护中的应用研究进展   总被引：2，自引：0，他引：2       下载免费PDF全文

罗菊仙  赵中一 《地球科学》2000,25(5):536-541

简单介绍了半导体多相光催化氧化的原理及其在降解污染物和环境保护中的应用和一些新型反应装置, 提出了提高光催化剂催化活性的方法, 讨论了影响光催化氧化反应速率的因素和提高光催化氧化反应速率的方法, 同时对光催化氧化技术今后的研究方向和工作重点提出了一些设想   相似文献