超磁致伸缩微位移致动器碟簧特征分析与设计

在传统的超磁致伸缩微位移致动器碟簧设计中，以预压力大小作为唯一设计指标．首先定性分析了微位移致动器的结构形式、传力机理；然后定量分析了超磁致伸缩致动器的输出特征，指出引入软性碟簧的可行性和必要性，使超磁致伸缩材料在阶跃段可获得更大的位移输出．针对不同预压应力及相关条件设计碟簧参数，通过试验证明了采用软性碟簧可以有效降低阶跃段系统等效刚度，从而改善换能系统输出．     

考虑温变时超磁致伸缩微致动器的动力学分析

建立了考虑温度变化时的超磁致伸缩微致动器的动态振动微分方程,得到了微致动器振动响应的非共振解析解.在已知磁化强度情况下,讨论了温度和预应力对振动响应的影响,并得到了位移响应随温度变化的系数;解出由于超磁致伸缩材料非线性而产生的亚谐共振解,讨论了温度对共振因子的影响.仿真结果表明,超磁致伸缩材料的磁-力-热耦合非线性对微...     

基于实验的超磁致伸缩微致动器动力学特性分析

基于超磁致伸缩微致动器实验所得的激励电流-磁致伸缩材料轴向位置-磁场强度三者之间的关系式,修正了厚壁线圈轴向电流-磁场理论公式.利用修正公式对超磁致伸缩微致动器动力学模型进行理论分析,得到了微致动器的振动响应;分析了修正系数、偏置磁场及预压应力对微致动器的影响.结果表明:修正系数对微致动器动力学特性影响十分明显,当修正系数K′=1.24时,基于实验拟合函数与基于厚壁线圈电流-磁场理论公式所得到的微致动器的输出位移与输入激励电流之间的滞回环完全吻合;微致动器振动响应具有明显的非线性特性,而且修正系数对其影响很大.偏置磁场与预压应力对微致动器的幅频特性影响也十分明显.     

超磁致伸缩微致动器车削系统的动力学分析

考虑温度及预应力的影响,建立了应用于车削加工系统的超磁致伸缩微致动器动力学模型,并讨论了温度及预应力对其振动响应的影响.预应力对磁滞及理想磁化模型的超磁致伸缩微致动器模型输出位移的影响变化趋势相同,都出现"翻转"现象,在激励磁场小幅值范围内,系统的输出位移随着预应力的增加而减小,随着激励幅值的增加而增加;当激励磁场幅值较小时,温度对输出位移的影响较小,但是当激励磁场幅值较大时,输出位移随着温度的升高而明显减小.该结果对如何处理预应力、温度、超磁致伸缩材料的滞回的影响提供了理论依据.     

高精度快速刀具伺服系统中的超磁致伸缩致动器结构设计与控制研究

本文介绍了超磁致伸缩致动器的结构设计与位移精密控制方法,给出了致动器的结构原理图,并对位移的PID控制及模糊PID控制两种控制方法进行了仿真研究。仿真结果表明,模糊PID控制具有较好的控制精度。     

国内外超磁致伸缩材料及作动器的研究

超磁致伸缩作动器具有推力强、反应快和分辨率高等特点,在精密定位、精密驱动、机器人、微型阀等领域展现了广阔的应用前景本文在介绍超磁致伸缩材料及其应用的基础上,分析了国内外超磁致伸缩作动器的研究动态、应用状况等,并对几类超磁致伸缩作动器的原理、结构进行了阐述,最后提出了超磁致伸缩作动器的四个研究方向。     

超磁致伸缩微位移执行器控制系统研究

以单片机和上位PC微机为控制核心,设计并构建了利用超磁致伸缩棒开发的超磁致伸缩执行器的计算机闭环控制系统,完成了相应的软硬件设计．结合所开发的超磁致伸缩微位移执行器的结构建立了传递函数模型,针对微位移执行器控制系统进行了数字PID控制器设计,通过实验得出,在不降低其相对稳定性情况下数字控制系统的精度提高,为进一步提高超磁致伸缩执行器的精度、改善整个系统的动态特性奠定了基础．     

超磁致伸缩驱动微泵的磁场优化分析与实验验证

为使超磁致伸缩驱动微泵中超磁致伸缩材料(GMM)棒获得最佳的磁致伸缩性能,在ANSYS Maxwell软件中建立双线圈式驱动磁场、外线圈内永磁体式驱动磁场、内线圈外永磁体式驱动磁场模型,进行仿真分析,得到三种情况下微泵轴线上平均磁场强度和磁场均匀度,并通过试验验证优选结构的磁场强度和均匀度。结果表明:外线圈长度L_(q1)=104 mm,厚度d_(q1)=12.5 mm;内线圈长度L_(q2)=104 mm,厚度d_(q2)=12.5 mm的双线圈式驱动磁场相对于外线圈内永磁体式和内线圈外永磁体式平均磁场强度提高了117%和8.6%,磁场均匀度下降4%。试验结果与仿真结果基本吻合,验证了仿真模型的正确性。     

基于超磁致伸缩材料的驱动器设计及磁场仿真

基于超磁致伸缩材料的工作原理,设计了具有微位移可控特性的驱动器。为了探究驱动器内部磁场设计的合理性以及超磁致伸缩驱动器的磁感应强度与激励电流之间的关系,应用ANSYS有限元分析软件对超磁致伸缩驱动器的内部磁场进行仿真。研究结果表明,超磁致伸缩驱动器磁场设计合理;随着电流的增大,超磁致伸缩材料中的磁感应强度也随之增加并且磁感应强度逐渐趋于饱和。     

微振动控制中超磁致伸缩作动器的设计与分析

针对微振动控制中对作动器的要求,基于超磁致伸缩材料的特性对作动器进行了优化设计,通过对其进行磁路分析、热效应分析,验证了设计的合理性;针对超磁致伸缩材料的非线性性能,利用实验测量的主迟滞回线和一阶折返曲线数据点建立Preisach模型,采用输入校正迭代算法对非线性进行补偿,然后对作动器进行精密定位控制实验.实验结果表明...     

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

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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