水中有限长纵向加肋圆柱壳体振动与声辐射

根据模态分析法,推导了水中有限长纵向加肋圆柱壳体的耦合振动方程.其中纵向肋骨的作用表现为在基本圆柱壳体流固耦合振动方程中增加相应的附加阻抗,因此壳体的振动和声辐射由壳体机械阻抗、辐射阻抗和纵向肋骨附加阻抗所决定.在此基础上通过算例对水中纵向加肋圆柱壳体振动与声辐射进行了研究.研究表明,纵向加肋对水中圆柱壳体的辐射声功率影响不大,但壳体表面平均振动速度明显降低,相应的辐射效率增加.     

单自由度刚性圆柱体绕流的不稳定性

基于Open FOAM开源软件,利用k-ωSST湍流模型与6自由度(DOF)动网格模型,对亚临界区单自由度运动刚性圆柱绕流进行了三维数值模拟,研究了在不同初始流场下圆柱的阻力系数、升力系数、运动轨迹以及流固耦合的形态,并利用C++面对对象的编程与试验结果及理论分析作对比,验证所用湍流模型与三维模型的可靠性.计算结果表明:分块化结构网格与k-ωSST湍流模型对于圆柱绕流问题的计算结果比较准确,圆柱体在垂直来流方向的运动具有不稳定性,且其稳定性的强弱、运动偏离的方向与初始流场状态相关;由于流固的耦合作用改变了圆柱体受力的频率,加快了圆柱的偏移.     

耦合超声振动系统的辐射特性

研究了一种用于液体中的由纵向夹心式换能器和纵径尺寸接近的金属圆柱辐射器构成的新型大功率超声振动系统。通过表观弹性法获得金属圆柱纵径耦合振动的机电等效电路及共振频率方程。对耦合振动系统的辐射特性进行了理论和数值分析,并通过实验进行验证。研究表明:该振动系统的圆柱辐射器的耦合振动可等效为一维径向振动和一维纵向振动的复合,其通过耦合系数相互作用;适当选择辐射圆柱的几何尺寸,振动系统产生强烈的纵径耦合振动,从而有效地辐射大功率超声波。     

基于辐射噪声线谱削峰的双层加肋圆柱壳结构声学设计

为降低水下航行器辐射噪声线谱,提出了一种弱辐射双层加肋圆柱壳结构. 采用机械阻抗理论分析了环肋圆柱壳模态响应幅值控制机理;引入圆截面内运动假设,利用模态展开法推导了环肋径向机械阻抗表达式;基于阻抗失配、波形转换原理,设计了阻抗加强环肋模型,并利用波动理论分析了其隔振性能;考虑壳间托板的强耦合作用,对托板进行了阻波设计. 将阻抗增强肋骨和复合阻波托板联合应用到双层壳结构声学设计中,数值分析了设计前后双层壳振动与声辐射性能. 结果表明:提出的新型双层加肋圆柱壳能有效实现辐射噪声线谱削峰,振动均方速度、辐射声功率和辐射声压大幅降低,具有显著的减振降噪效果.      

一种基于表面涡方法的流体诱导管束振动计算模型

为了研究热交换器中管束的流体诱导振动问题,提出了一种基于表面涡方法的圆柱绕流计算模型,包括分离点计算模型和流固耦合模型.利用这一模型,分别模拟了Re为2.67×104时单个刚性圆柱和弹性圆柱的流体诱导振动问题,并计算了圆柱的振动响应、流体力、振动频率和涡云图等.计算结果反映了流体绕刚性圆柱流动的主要特征,以及弹性圆柱流体诱导振动的限幅和非线性(共振区)特性,所得到的平均阻力系数、升力系数、斯德鲁哈尔频率和最大振动幅值与相关文献中的实验结果具有很好的一致性.该模型具有简便、快捷以及能够对亚临界雷诺数下的流体诱导振动问题进行计算等优点,为多圆柱流体诱导振动问题提供了一种新的计算模型.     

剪切来流作用下圆柱体结构物的双自由度流致振动

基于四步半隐式特征线分裂算子稳定化流体有限元方法,对二维线性剪切来流作用下弹性支撑圆柱体结构物双自由度流致振动问题进行了数值计算,着重研究雷诺数Re=150时,不同参数(频率比、剪切率与折减速度)对圆柱体结构物振动响应及其流场的影响.计算分析表明,随剪切率的增加,圆柱体结构物2个方向的频率锁定区间扩大,结构发生共振现象的范围亦增大;折减速度对圆柱钝体最大振动幅度的影响较大,在锁定区间内,圆柱振动位移较大,否则较小;在高频率比工况下圆柱运动轨迹呈‘8’字形;当频率较低时,圆柱运动轨迹随剪切率的增大由‘8’字形渐变为‘雨滴’形;在剪切来流作用下圆柱尾流模态为双单涡(2S)与涡对(P)+单涡(S)两种泄涡模式.     

水下环肋圆柱壳的振动耦合频率影响因素分析

在Flügge理论的基础上,考虑流体的影响,通过波动法推导出静水压力下环肋圆柱壳耦合振动特征方程,并利用牛顿迭代法求得耦合振动频率。将静水压力下圆柱壳与环肋圆柱壳的计算结果进行了对比,验证了本文方法的正确性和有效性。通过算例分析了在不同边界条件下,环肋形式、静水压力、圆柱壳尺寸、环肋尺寸和环肋数目等因素对静水压力下环肋圆柱壳耦合频率的影响。研究结果表明:在静水压力下,肋条的存在增强了圆柱壳的振动强度,耦合作用的存在降低了圆柱壳的振动强度。连续静水压力下,随着静水压力的增大,圆柱壳的振动强度不断减弱;圆柱壳尺寸、肋条尺寸和环肋数目的改变在不同程度上改变了圆柱壳的耦合频率。     

邻近效应对钢板阻抗的影响及其等效电路模型

为预测舰船系统的电磁兼容性和定量分析系统的共模干扰,研究了舰船接系统的阻抗特性。针对钢板两点之间阻抗特性与外部线路之间的关系,分析了邻近效应对钢板阻抗的影响机理,建立了系统之间共地耦合干扰的三阻抗等效电路模型,采用四端连接方法测量了两个共地系统之间的耦合阻抗。分析表明,在强邻近效应情况下磁场耦合不仅产生等效互感而且产生等效互电阻,实验测试表明邻近效应使钢板电阻在1MHz时比无邻近效应时大17倍。采用平面钢板简化模型和有限元计算方法分析了钢板的耦合电阻,与实测数据的误差小于17%,验证了等效电路模型的正确性。     

不可压缩柱形弹性动力学方程的解的定性分析

本文研究了轴对称变形假设下的不可压缩超弹性柱形结构的动力学稳定性问题.利用材料的不可压缩条件将描述圆柱形结构径向对称运动的弹性动力学方程约化为二阶非线性常微分方程.特别地,针对圆柱体、含有微孔的圆柱体、圆柱壳以及柱形薄膜等结构的径向对称运动问题,分别给出了一些具有共性的结论,如圆柱体轴线上空穴生成的条件、圆柱壳或薄膜产生非线性周期振动以及破裂的条件等.     

邻近效应对钢板阻抗的影响及其等效电路模型

为预测舰船系统的电磁兼容性和定量分析系统的共模干扰,研究了舰船接系统的阻抗特性。针对钢板2点之间阻抗特性与外部线路之间的关系,分析邻近效应对钢板阻抗的影响机理,建立了系统之间共地耦合干扰的三阻抗等效电路模型,采用四端连接方法测量了2个共地系统之间的耦合阻抗。分析表明,在强邻近效应情况下磁场耦合不仅产生等效互感而且产生等效互电阻,实验测试表明邻近效应使钢板电阻在1 MHz时比无邻近效应时大17倍。采用平面钢板简化模型和有限元计算方法分析钢板的耦合电阻,与实测数据的误差小于17%,验证了等效电路模型的正确性。     

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…     

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)

正~~     

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.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.