新型钢-砼组合简支桁梁桥自振频率研究

建立了钢-砼组合简支桁梁桥振动性能的力学分析模型,并推导了基于自由界面模态综合法计算结构自振频率的基本原理和公式,以西平铁路80m钢-砼组合桁梁桥的实桥模型为基础,应用有限元软件Midas建立了钢-砼组合桁梁桥模型并对其进行了模态分析,通过脉动试验的自振频率测试结果和有限元分析结果验证了自由界面模态综合法计算桥梁自振频率的准确性和高效性,采用有限元数值计算的方法研究了桥面宽度、腹杆和横撑刚度、槽型梁及上弦杆截面尺寸对钢-砼组合桁梁桥自振频率的影响.     

60Co集装箱检测车悬臂振动分析

在分析振动对集装箱检测车系统性能影响的基础上 ,提出了 6 0 Co集装箱检测车悬臂的振动指标。为了验证悬臂结构的强度和刚度条件 ,采用动力学分析软件 AL GOR计算了 6 0 Co集装箱检测车悬臂的静态变形、振形和固有频率。悬臂在启动加速过程中振动最大 ,通过给悬臂施加一个与启动加速度相当的惯性力的方法 ,非常简单地模拟了启动加速过程 ,数值计算结果与实际测试结果较吻合 ,说明了该有限元模型能够正确分析出悬臂结构的力学特性     

仿人机器人路径规划研究

针舛仿人机器人机械连杆控制结构的动力学、运动学等特点,建立了25自由度仿人机器人家谱树彤结构,提供了连杆数据列表,分析了步态规划约束、步行倒立摆、奇异位姿控制、落地步态方向控制等特性,构建了行走步态模型,并采用链接图法对环境空间建模,引入种群规模自调整遗传算法实现路径规划。潋仿人机器人NAO为实验平台,采用链接图法进行全局建模,实验表明,改进的遗传算法在仿人机器人路径规划中具有更快的收敛速度与更好的适应性。     

机器人步态算法仿真研究

以仿人机器人双足步行为研究重点,实现了线性倒立摆步行规划和正逆运动学算法。推导出机器人机械结构对线性倒立摆步行参数的约束条件,并采用遗传算法探索参数空间以得到可行、稳定、快速的步行模式。最后,在该仿真平台上验证了步态生成算法的有效性。     

某航空发动机高压压气机盘的振动特性分析

基于含预应力结构模态分析的有限元理论,对某典型航空发动机压气机盘进行振动特性分析。根据初始设计参数,在通用有限元软件中建立起盘的三维有限元模型。首先计算了盘在不旋转时的频率和振型,然后计算了盘在常用转速下存在预应力时的频率和振型,并分析了离心负荷对盘固有振动特性的影响。最后分析了盘的行波振动特性,计算了节径振动的行波频率,考虑盘外缘叶片受到的周期性气体力对盘的激振影响,画出共振特性曲线,为后续结构分析和排故提供依据;同时发现盘的驻波临界转速高于盘的最大工作转速,表明该盘不会发生驻波共振,对保证该发动机的可靠工作具有重要意义。     

基于二阶锥方法的仿人机器人稳定性控制

步行环境复杂,外力干扰等因素都会影响仿人机器人的步行稳定性.为了提高仿人机器人的稳定性,在7连杆仿人机器人模型的基础上,提出了用二阶锥方法控制仿人机器人运动的稳定性.首先介绍了二阶锥规划的原理;其次利用摩擦力、ZMP和运动能量3个约束条件构建二阶锥,从而进行求解;最后通过仿真实验证明,该方法与LMS和微粒群在多方面对比有明显优势,提高了仿人机器人运动的稳定性.     

刚架桥动力特性测试分析与研究

桥梁结构的动力特性能够很好地表现桥梁的健康状况和损伤状态,分别通过环境随机激振技术和定点跳车激振方法对一座刚架桥的动力特性进行了测试,给出了利用随机振动理论和响应传递函数识别结构的频率、振型和阻尼比的方法,并对两种测试方法进行了比较.通过ANSYS建立空间有限元模型,对桥梁结构的无载和有载动力特性进行了仿真分析.实测与理论分析表明:按本方案测试获得的试验结果较为理想,环境激励测试能获得更多阶的振型和自振频率;而跳车激振方法只能很好地激发结构的基本弯曲振动模态.通过试验研究结果验证了有限元动力分析模型的正确性,可为同类桥梁的测试和分析提供参考.     

整体叶盘结构模态特性分析及应力分布规律

为了研究整体叶盘结构的模态特性及应力分布规律,基于有限元分析方法建立了整体叶盘结构有限元仿真模型,对自由状态及离心力载荷下的整体叶盘进行模态及振动特性分析;并探究实心与空心整体叶盘的应力分布差异及不同叶片间隙的整体叶盘应力分布规律。为了验证仿真结果的准确性,基于多点激励单点响应方法开展了整体叶盘结构模型的模态试验,并在多功能转子实验台上开展不同转速下应力测试试验。结果表明,该结构模态频率的仿真结果与试验测试结果误差在4%以内,验证了所建立的有限元仿真模型的正确性;应力测试试验验证了其不同转速下的应力分布规律;离心力载荷对整体叶盘二节径振动下固有频率影响最为显著;空心叶盘较实心叶盘应力集中现象更为突出,且叶片根部应力值会随着叶片间隙的增大而有明显提高。     

简支梁桥的振动测试与动力特性分析

以某座钢筋混凝土梁桥为例,在简要介绍该桥梁概况及桥梁振动测试试验过程的基础上,结合试验结果建立了符合测试桥梁当前状态的有限元模型,通过测试桥梁实测结果和有限元模拟计算结果的比较,较为详细地分析了该钢筋混凝土梁桥的动力特性。结果表明:桥梁实测、计算频率和振型基本吻合;建立合适有限元模型可作为测试桥梁今后的动力特性变化的参考,对桥梁评价和养护有一定的指导意义。     

四缸柴油发动机机体有限元模态仿真及其测试

为了研究某四缸柴油发动机机体结构的动力学特性,建立了机体的三维有限元模型,运用ANSYS有限元软件对其进行了模态分析.为了验证有限元数值计算的合理性,根据实验模态分析理论,对自由状态下的发动机机体进行了模态测试.测试结果和有限元计算结果一致,说明计算方法正确、合理,所建有限元模型具有较高的精度,有效反映了机体的振动特性,该实验方法具有工程指导和应用价值.     

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.     

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.     

A computer generator for randomly layered structures

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

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

<正>~~     

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。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

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