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有关钢结构地震作用的讨论 总被引：2，自引：0，他引：2
简要介绍了6本国内标准(TJ11-74、TJ11-78、GB J11-89、GB50011-2001、JG J99-98、CECS160:2004)有关钢结构地震作用的计算方法,包括荷载组合方法和底部剪力法。通过归一化后的结果比较,评价了各本标准地震作用的大小。分析表明,除JG J99-98和GB50011-2001 2本标准由于考虑钢结构的阻尼比为0.02或0.035后,其地震作用有显著增大外,其它4本标准的地震作用处于接近的水平。考虑到钢筋混凝土和砖石结构等的地震作用水平在新旧抗震规范中并无多大变化,过分提高抗震性能较优的钢结构的地震作用水平显然是不合理的。 相似文献
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基于VTK的医学图像系统研究 总被引：6，自引：0，他引：6
医学三维数据场可视化是当前科学计算可视化应用的重点。本文论述了可视化工具包VisualizationToolkit(VTK)的主要特点,介绍了三维医学可视化系统实现的原理和方法。根据一系列人体断面图像,应用VTK实现了三维医学图像重构,对重构后的三维图像进行解剖分析;并实现对人体的二维图像逐帧浏览及柱状统计。实验结果表明,VTK具有使用灵活,功能强大的优点,是医学三维数据场可视化的有力工具。 相似文献
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Occurrence of water ponding on soil surfaces depending on infiltration rates on Mongolian rangeland 
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下载免费PDF全文 Katori Miyasaka Sho Shiozawa Kazuhiro Nishida Siilegmaa Batsukh Shuichiro Yoshida Undarmaa Jamsran 《水文研究》2017,31(22):3996-4005
The occurrence of water ponding on soil surfaces during and after heavy rainfall produces surface run‐off or surface water accumulation in low‐lying areas, which might reduce the water supply to soils and result in a reduction of the soil water that plants can use, especially in arid climates. On Mongolian rangeland, we observed ponded water on the surface of a specific soil condition subjected to a heavy rainfall of 30 mm/hr. By contrast, ponded water was not observed for the same type of soil where livestock grazing had been removed for 6–8 years via a fence or for nearby soil containing less clay. We measured the infiltration rate (the saturated hydraulic conductivity of the surface soil, Ks) of the three sites by applying ponded water on the soil surface (an intake rate test). The results showed that Ks in the rangeland was lower than the rainfall intensity in the site where water ponded on the soil surface; however, Ks of the soil inside of the fence has recovered to 3 times that of the soil outside of the fence to exceed the rainfall intensity. Heavy rainfall that exceeds the infiltration rate occurs several times a year at the livestock grazing site where we observed ponded water. Slight water repellency of the soil reduces rain infiltration to increase the possibility of surface ponding for the soil. 相似文献
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基于地震动参数的建筑物震害研究 总被引：15，自引：3，他引：12
本文介绍了多步简化的push—over(MSP)方法,引导出求解单体建筑物易损性指数和群体建筑物易损性指数的办法,并通过建筑物平均易损性指数曲线,来评价城市的总体抗震性能。本文不采用过去以烈度为地震输入的易损性评定方法,采用地震动参数作为城市建筑物易损性的评定标准。给出的易损性指数曲线,可用来查找不同地震动参数下各类建筑物的易损性结果,比较城市各类建筑物的抗震性能。本文研究可望在城市建筑物震害评估中有好的应用前景。 相似文献
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断层错动对隧道的影响分析 总被引：1，自引：0，他引：1
隧道通过潜在地震地区时.存在活动断层的错动形成的重大工程地质问题的威胁.基于断裂儿何学和震源的运动学特征,以广州地区活动断裂为研究背景,通过在断层左右盘施加一定的速度荷载,模拟了断层错动达到0.28 m时对隧道的影响.得出隧道结构在断层错动影响下的位移和应力的变化规律.分别建立隧道结构距离断层50 m、100 m、150 m三个模型,比较了三种情况下的位移和应力状况.归纳出隧道与断层之间的安全距离. 相似文献
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MEMS加速度计的噪声和线性指标是地震监测应用领域的关键问题,采用闭环力反馈是提高这些性能的有效途径。然而,由于对质量块不需要额外的电极来施加电静力,并且其残余位移会给闭环传递函数带来显著的非线性,从而影响该方法的有效性。因此,本文提出一种基于离散时间反馈的闭环MEMS加速度计,分时完成电容变化检测及静电力反馈,最大程度的减小了反馈信号对检测信号的馈通及耦合。利用开关电容电路中的相关双采样电路噪声消除技术,及电路参数噪声优化,可实现噪声谱密度小于0.5μg/Hz1/2的微加速度计。 相似文献
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介绍了ArcIMS的体系结构、特点及技术优势。构建了基于ArcIMS的地震目录等信息的发布系统,提出了系统设计的思想、功能、特点及实现的方法,并通过实例操作演示了基于WebGIS的地震目录数据发布系统。 相似文献
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基于结构振动信息的损伤识别研究综述 总被引：6，自引：1，他引：6
随着传感技术、信号采集与处理和系统建模等技术的发展,基于结构振动信息的损伤识别已经成为土木工程结构健康监测与损伤检测领域的研究热点。本文系统地综述了近20年来国内外基于振动信息的结构损伤识别的研究和应用现状,评述了各类方法的优缺点,并针对土木工程结构损伤识别的特点,对有待于进一步研究的问题进行了展望。 相似文献
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基于FTP协议的地震数据共享技术研究 总被引：1，自引：0，他引：1
随着互联网技术的广泛应用, 为地震数据共享提供了必要的外部条件, 但是怎样提供优质的地震数据共享方案一直是地震观测技术的一个研究课题。 文中研究了一种基于FTP协议的地震数据共享方案, 该方案不仅可以提供传统的数据下载、 上载功能, 而且还可以根据用户需求, 提供采样率变换、 数据格式转换等服务, 可以方便地为地震数据用户提供服务, 从而使地震数据得到更加广泛的共享应用。 该文重点介绍了该基于FTP协议的数据共享技术的模型设计和实现。 相似文献
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从与历史地震数据的时间衔接考虑,合理选择初始地震危险性模式。借鉴美国地震危险性图编制的思路,并基于GIS的思想和技术,使用历史地震数对初始模式进行多次叠加改造,获得当今中国地震危险性模式。与实际地震灾害的对照结果,验证了该方法的有效性。可见,基于GIS的中国地震危险性模式研究具有一定的现实意义。 相似文献
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为了分析高速公路对场地微振动的影响,在高速公路旁边选择了几块环境相似的场地,进行间隔50 m布点多测线测量,对测量得到的数据进行RMS值计算和功率谱密度分析后,得出微振动的能量主要集中在5～15 Hz之内,卓越周期为0.2～0.1 s.并得出了几块场地的微振动速度及位移的RMS值分布情况,还得出了该值随测点与高速公路的距离增加而衰减的简单关系以及该值在普通路基和高架桥路基高速公路影响下的不同衰减关系. 相似文献
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常规滤波方法对浅海多次波压制不能取得理想效果.通过改变模型表面边界条件，求解波动方程实现多情景地震数值模拟.利用自由边界条件模拟时获得含海平面强反射多次波地震记录，而利用吸收边界条件时得到理想条件下无多次波地震记录.对比分析多次波对有效地震信号的影响得到海平面强反射多次波改变了有效地震信号的振幅、频率和相位.利用归一化方法计算得到压制多次波滤波器算子，并作用于含海平面强反射多次波地震记录.叠加地震剖面对比分析表明，归一化滤波器算子较好的压制了地震记录中的多次波，提高地震资料分辨率.最后，根据多次波产生条件，给出了利用实际区域简化地质模型的地震数值模拟结果计算归一化滤波器算子的方法，从而利用该方法压制实际地震数据中多次波. 相似文献
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为应对地震观测数据量激增以及发报时间要求日趋紧张的情况,作者开发了一个基于Ftp,具有较高效率的上报数据自动传输程序.本文就程序的开发目的、实现方法和实际应用效果进行阐述. 相似文献
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Introduction With rapid development of national economy, urbanization has been speeded up in China, and several city groups or city belts with extra-large cities as their centers have been formed. For example, Pearl River Delta urbanized area surrounds Guangzhou City, Shenzhen City, Zhuhai City; Yangtze River Delta urbanized area surrounds Shanghai City, Suzhou City, Wuxi City, Nanjing City, Hangzhou City; Beijing-Tianjin-Tangshan urbanized area surrounds Beijing City, Tianjin City… 相似文献
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The goal of cathodic protection is to prevent corrosion by maintaining buried pipelines at a constant potential with respect to the surrounding soil. In practice, however, the implementation is very complicated since many factors can contribute to the current flowing off the pipe. Design requires characterization of the parameters impacting the corrosion process, such as soil resistivity, size of the pipe and quality of the coating.In the present paper, we have studied the effect of geomagnetic fields on the pipe-induced currents considering it as an additional cause of corrosion. A theoretical method implemented to model the induced currents was tested in a previous work and the effect during disturbed days was quantified. This theoretical model indicated that the intensity of the current induced in a pipeline by the varying geomagnetic field depends on the intensity and rate of change of the field and the electrical resistivity of the soil. This induced current is in equilibrium with the host current and there is no current drainage between the pipeline and the host until, along the length of the pipeline, the host resistivity becomes different. At that point, current must flow between the pipe and host in order to establish a new equilibrium. It is this drainage current, flowing between the pipeline and the host, which causes corrosion problems.Following these results, experimental tests were performed in Tierra del Fuego. In this zone, a geophysical study was made to determine the discontinuities in soil resistivities and simultaneous measurements of the geomagnetic field and the drainage of current were recorded at different sites. The results obtained from the correlation of the data are consistent with the theoretical predictions. 相似文献
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本文介绍了一种建立在磁弹效应原理基础上的可用来测量钢索轴向拉力的传感器。文中详细阐述了其基本原理,设计了单路磁循环的磁路结构,进行了磁路分析并提出一种电脉冲磁化法的实验装置,给出实验结果。实验结果与理论设计相符,系统稳定可靠。该装置具有可由电池供电、体积小、造价低廉、便于携带的特点。 相似文献
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Humans are exposed to ionizing radiation all the time, and it is known that it can induce a variety of harmful biological
effects. Consequently, it is necessary to quantitatively assess the level of exposure to this radiation as the basis for estimating
risks due to ionization radiation. During the Work Package 2400 of the COST-724/WG-2 action, a number of spacecraft and aircraft
experiments have been performed with both active and passive detectors. A large data base has been created.
In this contribution we would like to stress the results obtained and their importance in three particular directions: (i)
Simultaneous investigation of galactic cosmic rays on aircraft and on the International Space Station (ISS); (ii) Onboard
spacecraft neutron contribution as estimated on the basis of the comparison of results measured with MDU/Liulin equipment
onboard ISS, foton capsule and a commercial aircraft flying at subsonic altitudes; (iii) Complex analysis of the results of
long term measurements onboard a Czech Airlines aircraft. The results obtained are presented, analyzed, and discussed, and
their complementary nature is underlined. The contribution represents a version of the Final Report of the Work Package 2400
of the COST-724/WG-2: Radiation Environment of the Earth. 相似文献