单相双向变换器的仿真建模研究

区分了开关函数概念与开关状态变量概念,依据黑箱方法和功率变换器的实际,划分了电压开关函数与电流开关函数.提出了根据开关函数概念和黑箱方法用Matlab/Simulink对双向变换器建模的一般方法和步骤,给出了单相双向电压源变换器的仿真模型,该模型可仿真双向变换器的各种种运行方式及其转换,并与Matlab/Simulink内置的变换器模型作了仿真运行对比,结果验证了所建模型的有效性、准确性.     

直流变换器的建模仿真

针对燃料电池的应用条件和特点,分析和研究了直流变换器电路的电流和电压关系,通过引入参数变量,将Boost变换器开关过程表征为统一的状态方程,进而应用Matlab/Simulink的两种建模方法对变换器进行了仿真,得到了与理论相符的结果。     

相移控制型双向DC-DC变换器的建模与仿真

为了克服传统双向DC/DC变换器效率低、控制复杂的缺陷,以简化电路为基础,结合开关函数和状态空间平均的建模方法,对状态空间平均方程加以降阶,建立以移相角Φ和开关频率f为调节参数的简化模型.仿真结果表明:变压器两端电压与电流纹波较小,输出稳定.该模型仿真时间短,也适用于其他半桥双向DC/DC变换器的设计.     

一种CCM模式下非理想Boost变换器的建模方法

开关网络平均模型法广泛地应用于理想DC-DC变换器的建模,文章将其应用于连续导电模式下的非理想Boost变换器,并应用能量守恒原理和映射原则,将开关元件的寄生参数等效到电感支路中.用此方法,可以更便利地得到变换器的低频等效电路模型,用于变换器的直流特性和交流特性的分析,仿真结果证明了该建模方法的正确性.     

零电流开关电力电子变换器潜电路的布尔矩阵分析方法

提出了零电流开关电力电子变换器潜电路的布尔矩阵分析方法.通过建立电力电子变换器的开关布尔矩阵,并消去其中的无效开关向量,得到电路的最简布尔矩阵和与其相对应的有效开关状态.在此基础上将最简布尔矩阵与变换器设计的正常工作状态开关矩阵比较,判断变换器是否存在非设计要求的潜在开关路径.以Matlab7.0为平台设计了相应的算法程序,潜电路分析结果用模型文件的形式保存.最后,以零电流谐振开关电容变换器潜电路分析为例,验证了所提出方法的正确性和有效性.     

基于UC3854的Boost电路的仿真与应用

有源功率因数校正技术对解决电源污染问题有着重要意义。本文引入建模分析法和状态空间法研究一种平均电流控制模式的Boost型功率因数校正技术,分析Boost变换器各个环节的电压、电流的变化情况,推导其状态方程,建立了Boost变换器的MATLAB仿真模型,并利用UC3854控制芯片,设计出一个基于平均电流控制模式的功率因数校正实验装置。仿真与实验结果的一致性表明该模型是有效的。     

电力电子变换器开关拓扑的图论分析方法

提出了适用于电力电子变换器拓扑分析的广义连接矩阵,用于判别给定拓扑的电力电子变换器的开关路径,为分析变换器的开关模式提供了一种新的方法。同时,通过将变换器实际开关电路模态与电路设计的正常工作模态比较,可以判断变换器是否存在非设计要求的潜在开关路径,以便设计者及时对变换器的开关结构进行改进。最后,以三相PWM整流器和零电流谐振开关电容变换器为例,进行了详细的应用研究分析,验证实例证明了所提出方法是正确和有效的。     

Buck boost变换器的PWM滑模变结构控制方法

在Buck boost电路拓扑结构和工作原理分析的基础上,引入虚拟开关量构建Buck boost电路连续导电模式和断续导电模式的合并状态方程,在合并状态方程基础上采用等效控制法推导Buck boost变换器的PWM滑模变结构控制方程,将指数趋近率应用于控制方程,并将等效控制变量作为PWM控制的占空比,得到基于指数趋近率的PWM滑模变结构控制方法。仿真实验和实测验证结果表明:Buck boost变换器的PWM滑模变结构控制方法能使Buck boost变换器快速达到稳定状态,具有较好的动态特性和鲁棒性。     

基于非线性迭代的开关功率变换器仿真

开关功率变换器仿真的关键是精确确定开关元件换相的时刻，而一般开关函数为超越方程，很难求得其解析解。采用将超越方程转化为微分方程，然后利用微分方程的数值解法求取超越方程的零点，同时用精细历程积分法求取方程的指数矩阵。相对传统方法，非线性迭代法具有收敛范围宽、求解精度高、求解过程不需要使用导数，迭代效率高的优点。典型开关功率变换器仿真实例表明了该方法的正确性及迭代效率，是开关电路仿真的一种新思路。     

考虑寄生参数和电感电流纹波的CCM模式Boost变换器建模

在考虑电子器件寄生参数及电感电流纹波的情况下,运用三端开关器件模型法和能量守恒法对Boost变换器工作于CCM模式下的精确建模进行研究,推导了大信号等效电路模型、稳态等效电路模型和小信号等效电路模型,并在一个实际的Boost变换器上对存在寄生参数和电感电流纹波的情况进行仿真和稳态性能、动态特性分析。结果表明,此研究能够改善实际Boost变换器设计和系统性能。     

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)

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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.