基于理论仿真和实验的两端固定梁模态测试方法

基于欧拉-伯努利梁理论,得到两端固定梁自由振动的振型函数。通过数值计算得出实验用的两端固定梁前五阶振型的节点位置及其与梁长的比值。考虑传感器对两端固定梁固有频率的影响,建立梁-传感器模型进行仿真分析并得出两端固定梁前五阶固有频率。基于节点位置和测点位置,在实验中选择参考点。将具体实验的结果与梁-传感器仿真模型结果进行对比,通过前五阶固有频率的误差分析,发现仿真分析结果与实验结果误差最高为2.92%。研究完整地叙述了两端固定梁的模态测试流程,可为工程技术人员的模态测试起一定的指导作用。     

基于理论、仿真和实验的两端固定梁的模态测试方法

基于欧拉-伯努利梁理论,得到两端固定梁自由振动的振型函数。通过数值计算得出实验用的两端固定梁前五阶振型的节点位置及其与梁长的比值。考虑传感器对两端固定梁固有频率的影响,建立梁-传感器模型进行仿真分析并得出两端固定梁前五阶固有频率。基于节点位置和测点位置,在实验中选择参考点。将具体实验的结果与梁-传感器仿真模型结果进行对比,通过前五阶固有频率的误差分析,发现仿真分析结果与实验结果误差最高为2.92%。研究完整地叙述了两端固定梁的模态测试流程,可为工程技术人员的模态测试起一定的指导作用。     

基于随机子空间法的异步实测桥梁模态识别

针对工程结构模态参数测试时，多个测点之间的时间不同步采样导致识别出的振型结果不准确问题，文章提出基于随机子空间法的异步实测桥梁模态识别方法，通过误差函数值表征不同步数据在分析过程中产生的数值误差程度，以误差函数为最小值时所对应的时间作为估计的时间延迟，并以此延迟修正异步实测响应数据；利用随机子空间法对修正数据进行模态参数识别，通过有限元模拟和实验验证分别讨论模态识别时，桥梁不同测点异步采样对振型识别的影响，验证所提出的时间延迟识别方法的准确性和可行性。     

叠层板型元件模型干模态固有频率与振型分析

本文对一个叠层板型堆芯元件实验模型的干模态固有频率和振型进行了理论、数值分析，作者将该结构视为多层平行梁与整体单梁的对接问题，根据各梁的振型方程及对接处的连续性条件和平衡条件，建立了确定固有频率与振型系数的特征方程，并采用隐式选代法对其进行数值求解．文中给出了部分固有频率与振型曲线的计算结果，其固有频率与实验测试结果相当吻合．     

一种获取结构实模态振型的方法

为获取结构真实而精确的实模态振型,提出将复振型向量构建的特征方程应用于基于参考点的数据驱动子空间方法中进行结构模态参数识别的方法.为验证该方法识别结构模态参数的可行性和精确性,对一矩形截面悬臂梁端部突加一集中荷载,进行有限元时程分析,得到梁上一系列节点的加速度响应数据,进而利用提出方法识别了悬臂梁的频率、实模态振型及阻尼比.识别结果与悬臂梁模态参数的理论值吻合较好,表明利用复振型向量构建的特征方程结合基于参考点的数据驱动子空间方法进行结构模态参数识别是可行和精确的,该方法可以得到结构可靠的实模态振型.     

主塔刚度对斜拉桥固有特性的影响分析

文章以一类单塔斜拉桥为例,研究了主塔刚度对斜拉桥的固有频率和模态的影响,以欧拉-伯努利梁模型描述桥面和塔的运动,并同时考虑斜拉索的横向和纵向运动,建立斜拉桥的动力学方程、边界条件及子结构间的相容条件,推导出斜拉桥的固有频率方程和振型函数。数值结果表明:将塔视为柔性构件时,塔的刚度对斜拉桥的固有频率和模态影响并不显著;若将塔视为刚性构件,则所求解出的固有频率和模态与柔性塔的情况相差很大,并会丢失某些模态;斜拉桥存在密集固有频率、模态跃迁及频率曲线偏转现象。研究结果可为斜拉桥结构设计及振动分析提供理论依据。     

环境激励下湘潭莲城大桥模态参数识别研究

对环境激励下结构模态参数识别进行了理论分析和试验研究.基于随机振动理论阐述了峰值拾取法的基本原理和方法,并提出了虚拟响应的概念.从湘潭莲城大桥在环境激励下的加速度测试信号中提取高信噪比的虚拟响应信号,根据峰值拾取法对虚拟响应信号进行频域分析,识别了该桥主跨结构的固有频率、阻尼比和振型等模态参数.试验模态参数与理论模态参数基本吻合,验证了识别结果的可靠性.模态置信矩阵表明,结构的线性响应特性明显,竖向振动具有良好的正交特性.     

基于影像及小波变换的桥梁损伤识别

桥梁损伤定位和定量分析是桥梁健康监测的难点，为提高桥梁结构损伤位置识别的精度及准确性，本文利用位移模态对结构局部损伤的敏感特性，提出基于影像和小波变换的桥梁损伤识别新方法，通过工业相机获取悬臂梁振动形态，利用模版匹配方法提取结构动态位移响应及模态参数，对位移模态进行小波变换，建立小波系数平方差的损伤指标识别结构损伤位置。通过室内悬臂竖梁振动实验，对全域测点的振动衰减信号快速傅里叶变换成功获取了结构的模态振型，与数值模拟结果比较表明试验获得一阶固有频率最大误差为2.202%，二阶固有频率最大误差为3.182%，表明本文方法用于结构位移测量的可行性以及测量精度的可靠性；在此基础上利用小波系数平方差的明显突峰特性可准确识别结构单损伤、多损伤的存在，并能准确定位损伤位置。研究表明，该方法可以准确识别不同位置、不同程度的单损伤和多损伤，具有远距离、非接触、高精度、高效快捷、可多点监测提升振型空间分辨率等优点，为桥梁结构全域损伤识别提供了一种新方法。     

基于不完备模态测试信息的结构损伤识别方法研究

测试信息不完备、测量噪声等因素是制约结构损伤识别方法应用的主要难点.为此首先采用部分测点的实测模态振型数据和未测点的有限元模型模态振型数据构造出完整的模态振型.其次,建立了一种适合梁系和杆系结构的基于不完备测试信息的损伤识别方程,并采用Levenberg-Marquardt非线性最小二乘算法进行了方程的求解.由于采用的是标量损伤模型,该方法可以同时进行结构的损伤定位和定量研究.最后,用一个平面桁架模型进行了数值模拟,重点考查了实测自由度数、模态数、测试噪声对损伤识别结果的影响.研究表明,在测试数据不完备及一定噪声水平条件下,该方法仍有较好的损伤识别能力.     

模态参数识别方法

本文对模态阻尼比、模态质量、模态刚度的识别做了介绍,并探讨了模态参数识别、修改的方法。模态参数识别的主要任务是从测试所得的数据中,确定振动系统的模态参数,其中包括模态固有频率,模态阻尼比,模态质量,模态刚度及振型等。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.