储能飞轮永磁卸载设计及试验

为解决大功率立式高速储能飞轮下支承高负荷高损耗问题,采用在飞轮上端轴向永磁轴承卸载的技术方案.以尺寸最小、卸载力达到飞轮重力(1 kN)的80%为目标,磁路估算与有限元精算相结合,设计了一种磁路漏磁微小的内外双永磁静环与合金钢导磁转环组合的新型轴向卸载磁轴承.磁轴承的转动部件使用合金钢导磁材料,可适应500 r/s、 200℃工况需要.建立了永磁轴承卸载力测试装置,测量结果与有限元计算结果相吻合,在工作间隙1.5 mm时,磁轴承卸载力达860 N, 轴承径向刚度为3.07 kN/m.该卸载方案在旋转试验中收效良好, 280 r/s升降速过程中下支承温升始终处于正常范围.     

电流响应速度及力响应速度对磁轴承系统性能的影响

为了同时实现磁悬浮磨床电主轴系统高刚度和高转速这两个主要性能指标 ,通过理论分析、计算机仿真和实验 ,研究了功率放大器环节的电流响应速度、电磁铁的力响应速度对磁轴承系统性能的影响。结果表明 ,功放的电流响应速度、电磁铁的力响应速度直接影响系统的闭环控制性能。通过提高功放的电流响应速度、电磁铁的力响应速度 ,实现了磁轴承系统在刚度为 39.3N /μm ,转速为 46 .32 0 kr/min情况下的稳定运转。研究结果对于磁悬浮系统的设计具有参考价值     

新型混合径向磁轴承结构及其磁力特性

针对当前永磁偏置径向磁轴承的永磁磁路的磁通密度低,磁力小,缺乏自稳定的问题,提出一种应用于立式轴流泵的新型混合径向磁轴承结构.应用分子电流法及虚位移定理建立新型混合径向磁轴承承载力的非线性模型及其线性化方程,分析得出新型径向混合磁悬浮轴承在径向某个自由度上具有自稳定的特点,且永磁轴承可以减小系统总的位移负刚度.研究结果表明,采用Halbach阵列结构后,混合磁轴承气隙的磁通密得到很大提高.电流刚度和位移刚度与平衡点的初始电流及初始间隙密切相关,在平衡位置附近电流刚度和位移刚度呈线性变化,当气隙增大时仍保持较好的线性度,而当气隙减小时呈现一定的非线性特性.     

磁悬浮主被动飞轮和被动磁轴承轴向力设计分析

针对现有商业卫星用磁悬浮飞轮存在发射成本高、体积大、重量大、功耗大、结构复杂和控制难度大等缺陷,提出了采用三自由度自稳定被动磁轴承代替原有磁轴承方案的磁悬浮主被动飞轮。分别介绍了飞轮和被动磁轴承结构、工作原理;通过等效磁荷法对被动磁轴承轴向力和轴向力刚度进行了数学建模;采用数值分析法,对被动磁轴承不同高宽比和气隙宽度的轴向力—位移曲线进行分析比较,并基于工程实际,选用高宽比为2和气隙宽度为1mm的被动磁轴承模型;采用有限元法,对飞轮在仅轴向偏移、径向偏移扰动、径向扭转扰动和同时发生径向偏移扰动与径向扭转扰动四种工作状态下轴向力自稳定性进行了分析。研究结果表明,轴向自稳定性满足性能需求,该自稳定被动磁轴承为商业航天卫星的磁悬浮飞轮的性能提升与成本降低提供了新的思路。     

飞轮电池磁轴承系统结构及控制

文章提出了一种由径向永磁轴承与推力电磁轴承组成的单轴主动控制的飞轮电池磁轴承系统结构,径向永磁轴承提供径向恢复力和轴向悬浮力,推力电磁轴承提供轴向恢复力,在磁轴承系统数学模型的基础上,采用状态反馈控制的设计方法建立闭环控制系统,并进行计算机仿真。仿真结果表明,闭环系统在较短时间内达到稳定,具有良好的动态特性。     

飞轮电池转子偏移对磁轴承性能的影响

由于飞轮电池转子在高速运转时避免不了会产生一定的偏移,偏移会对飞轮电池磁轴承的刚度产生影响,为了更加清楚地知道其具体影响,本文介绍了自归位轴承的模型和磁力计算理论,同时借助有限元法,描述了转子在不同方向偏移下,磁轴承产生自归位磁力和磁轴承刚度的变化,最终得:随着转子偏移量的增大,磁轴承所受到自归位磁力也随之增大,其自归位效果良好;在转子刚刚发生偏移时,磁轴承刚度变化较大,随着转子偏移量增大磁轴承刚度逐步趋向稳定;转子产生径向位移时磁轴承刚度远小于产生轴向位移时的磁轴承刚度.     

可控磁悬浮轴承刚度与阻尼特性研究

可控磁悬浮轴承的刚度与阻尼特性主要取决于系统的电器控制环节,可根据实际需要设计,以满足不同的应用要求,但如何设计和调整则是一个实际问题。因此,从刚度和阻尼的角度研究了基于独立式控制原则并采用ＰＩＤ校正方法的磁轴承—转子系统。结果表明,由调节器中比例和微分环节决定磁轴承的刚度、阻尼的同时,其它滤波环节的引入改变了轴承刚度、阻尼在低频和高频段内的频率特性,在共振区域,刚度和阻尼仍保持原设计值。因此,通过电控系统的设计得到不同的转子动态特性,并且兼顾稳定性和高性能是完全可行的。同时,还可以得到一种简便的ＰＩＤ参数设计方法。     

抗磁性磁悬浮轴承装置的研究

对运用抗磁材料的磁性轴承,一般通过实验装置来研究其轴承的静态平衡和负载能力及其动态特性。本文所设计研究的实验装置由1个1.010 5 g的NdFeB柱形永磁转子,NdFeB偏置磁体和抗磁材料石墨构成,并对其进行了抗磁轴承负载的有限元计算,计算结果表明与解析式所计算的结果是一致的。     

五自由度磁轴承系统的α阶逆系统解耦控制

采用α阶逆系统理论对五自由度磁轴承系统进行解耦控制.在建立磁轴承系统状态方程的基础上,对该系统进行了基于逆系统理论的线性解耦,并根据时间乘以误差绝对值积分(integral of time-weighted absolute error,ITAE)最小评价准则设计了闭环控制器.仿真和试验表明,α阶逆系统解耦后系统各自由度之间不存在耦合,解耦控制器与PID控制器相比,具有更好的动态特性和静态特性.     

转台轴承静刚度建模及其影响因素分析

为了改善转台的动静特性,分析了三排圆柱滚子转台轴承静刚度与轴承结构型式、装配工艺和外载荷的关系。结合轴承游隙、螺钉拧紧力矩、径向与轴向滚子间的相互作用和外载荷等因素,将轴向滚子与轴圈间的接触看作理想平面接触,考虑径向滚子压力沿轴向的分布,并利用Boussinesq力与变形关系式求解实际的压力值,通过求解轴承的整体静力平衡方程,得到了三排圆柱滚子转台轴承5个方向的静刚度值。分析结果表明:转台固有频率测试与理论值误差不超过3.0%,验证了刚度理论模型的准确性;轴向滚子与径向滚子载荷间的相互作用很小;螺钉拧紧力矩、径向游隙和外载荷对转台轴承刚度有重要影响,随着螺钉拧紧力矩和径向预压量的增大,外载荷对刚度的影响减弱。     

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