通用交流伺服驱动器的功耗与效率估算

近年来随着永磁同步电机的发展和全球对能源问题的关注增加，交流伺服驱动器与永磁同步电机组成的伺服系统的应用就越来越广泛。由于现阶段IGBT的开关频率高和额定电流大特性，使之成为主流通用交流伺服驱动器的功率开关元件，但是现阶段主流变流方式是控制IGBT的脉宽的进行PWM的调制，这样调制方法决定着IGBT的开关损耗成为驱动器的已经成为主要能量损耗和发热来源，本论文将利用IGBT的官方参数特性和主流的SPWM的调整方式的原理，对主流的交流伺服驱动器的功率损耗和效率进行估算。     

MnZn功率铁氧体的损耗特性研究

研究了MnZn功率铁氧体在不同温度、频率和磁感应强度情况下的损耗特性，分析了磁滞损耗、涡流损耗和剩余损耗的机理，及这三种损耗与温度、频率和磁感应强度的关系．结果表明，频率不高于100kHz时，MnZn功率铁氧体的损耗是由磁滞损耗、涡流损耗组成，其中磁滞损耗在低温时占主要成分；随着频率的升高，即使在磁感应强度较低时，涡流损耗和剩余损耗的影响不容忽视，且两者都随温度的升高而升高．     

高频域工程结构减振降噪方法的研究

从分析受高频随机激励结构单元贮存的统计平均能量入手，讨论了通过改变输入功率大小，损耗因子和耦合损耗因子来降低贮存能量的途径．提出了降低结构响应和降噪的方法，分析了结构质量和刚度的改变对减振降噪的影响．     

闭域空间中泄漏同轴电缆耦合损耗的研究

从泄漏同轴电缆的辐射理论出发，以屏蔽良好的室内空间为例分析了其中的辐射场，再根据耦合损耗的定义，利用接收功率和电缆传输功率得出了漏缆的耦合损耗，同时讨论了室内墙壁的材质对耦合损耗的影响，并通过仿真对结果进行了验证．该理论和结果可以扩展到其他场所，对于进一步研究闭域空间中的无线通信问题具有较强的参考价值．     

矿用隔爆水冷变频器散热路径与传热模型研究

隔爆水冷变频器的主电路损耗是比较大的,这些功率损耗全部通过热量的形式释放,导致功率元件的温度升高,而IGBT模块、整流二极管和晶闸管的最高工作温度受到最高温度不大于150℃的限制．因此．功率元件损耗所释放出来的热量是不容忽视的,必须采取有效的散热措施．保证功率元件工作在最高结温以下。     

电力电子器件损耗的测试与计算研究

电力电子器件是功率变换装置系统的主要组成部分,在工作中会产生功率损耗,降低了能量转换效率,损耗过大还会影响到器件自身安全和系统的性能指标。以Buck电路为对象作为器件IGBT损耗测试的实验平台,设定了几种器件损耗的主要影响因素,并建立基准值。通过这些影响因素的不同取值对IGBT反复测试,测出示波器中IGBT工作时的电压和电流波形后,转化成数据的方式来保存输出结果到计算机,利用算法编程来计算出相应损耗功率值。最后,对影响损耗的相关因素进行分析和总结。     

开关稳压电源的热功率与散热

对开关稳压电源的热损耗功率进行了深入分析，给出了降低开关电源热损耗功率，提高效率的途径，并论证了开关电源无风扇改进的可能性．     

电动潜油离心泵保护器性能测试装置

介绍了电动潜油离心泵保护器试验装置的结构组成，测试原理及其特点．利用该装置可以检测保护器的功率损耗和密封性能是否满足要求．该装置测试原理简单可靠，无中间环节，测量结果精确度高     

充电功率在输电线路中导致损耗的分摊

为了合理计算电源对输电线路的利用份额，正确计及输电线路中由充电功率所导致损耗的分摊问题，在电流追踪法的基础上，结合电力网络本身的特性，提出了在求取充电功率所导致网络损耗时，可将充电功率按无功电源进行处理，国输电线路中，一个电源所应承担的由充电功率民导致损耗的比例应与其对该输电线路的利用份额相同。数字仿真结果表明，该方法是可行的。     

光纤接续损耗分析、测量与处理

通过对单模光纤损耗特性的分析,阐述了单模光产生接续损耗的原因及用背向散射法和“四功率法”测量接续损耗的方法以及对接续损耗的处理。     

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