基于DC-DC升压和LC振荡的叠层压电陶瓷驱动电源研究

根据叠层压电陶瓷的大容性负载特性,在电路分析的基础上提出了基于DC-DC升压变换器和LC振荡的驱动控制电源,在驱动电路中加入偏置电压,使输出电压在-20 V到100 V之间,满足叠层压电陶瓷的驱动要求.将此驱动器用于压电直线电机,电机运转平稳,电路功耗小,通过匹配不同的电感实现了宽频率范围驱动.     

数字共焦显微仪压电陶瓷物镜驱动电源设计

采用模块化设计思想,设计一种数字共焦显微仪压电陶瓷物镜驱动电源,并进行测试。该电源以AT89S52单片机作为主控芯片,控制12位D/A转换器MAX538,再将D/A转换的输出电压用运算放大器HA17741构成的比例放大电路进行小电压放大,用来控制高压DC-DC转换器BYH12-200S01。电源测试时,输出电压能在16～200V内数控可调,并且精度达60mV,纹波电压小于20mV,能够满足压电陶瓷物镜驱动的电压设计要求。     

双驱动足压电直线电机驱动电源的设计

设计了一种基于可编程片上系统的新型驱动器。根据非共振压电直线电机的驱动要求,设计了四路相位差分别为90°的正弦信号发生器。采用嵌入式芯片作为主处理器,结合直接内存存取数据传输技术,增大了输出信号的频率范围,提高了嵌入式系统的效率。设计了运算缓冲和线性功率放大电路,并对该电路进行了幅频特性分析。将设计的驱动器应用于非共振压电直线电机,电机驱动足交替运行,驱动信号稳定。     

压电陶瓷动态驱动电源研究

采用分立元件设计了一种基于电压控制型的可动态应用压电陶瓷驱动电源.该驱动电源由高压放大电路、功率放大电路、过流保护电路和负反馈环节构成,克服了目前常用的压电陶瓷驱动电源所存在的成本高、驱动能力不足、静态纹波大等缺点.最后对实际电路的各项性能进行了测试和分析.结果表明:该电路具有良好的动态和静态性能,能够很好的满足驱动压电微位移平台的要求.     

基于单片机控制的压电陶瓷变压器驱动电源

以单片机及其控制电路为基础,设计了压电陶瓷变压器驱动电源,该电源为压电陶瓷变压器提供特定的振荡信号,根据压电陶瓷变压器的输出信号,适时调整输入频率,使其与压电陶瓷谐振频率一致,最大限度地保持了压电陶瓷的升压比,保证了压电陶瓷变压器的最大输出。实验数据表明,利用该驱动电源控制的压电陶瓷变压器,具有响应速度快,稳定性好,结构简单,调试方便,造价低廉,实用性强等特点,适用于压电陶瓷驱动器。     

一种基于率相关回滞的压电带载驱动建模方法

以压电驱动器为代表的智能材料驱动器,以其能实现微纳米级精密驱动的优势逐步在精密装备中得以应用,但其内部的回滞非线性在微纳米级驱动性能要求下成为限制精度提升的瓶颈.文中以压电驱动器为研究对象,在不同输入信号频率的条件下研究其带载输出特性,结合压电驱动器的机电特性,提出了一种压电驱动系统带载环境下的建模方法.该方法基于率相关Prandtl-Ishlinskii(RDPI)回滞模型,同时考虑工作频率增加时载荷对系统输出所造成的影响,以克服常规RDPI回滞模型无法表征带载条件下输出特性的局限.结合压电驱动系统带载2. 94 N工作条件,完成1～80 Hz驱动频率范围的实验验证.结果表明,文中提出的建模方法能有效地反映压电驱动器在带载环境下的输入-输出特性.     

高频热声制冷机中的压电驱动器

为了研究压电驱动器与热声谐振腔间的耦合特性,建立了压电驱动系统的网络模拟模型。根据压电片的简支和固定两种边界条件,对压电驱动器及(热)声谐振腔声负荷系统的频率和电压特性进行了模拟计算。研究结果显示在高频时系统元件间的耦合特性较低频时好,具有简支边界的压电片产生的声压级比固定边界的要大得多,声压级随输入电压的变化特性计算与实验是相一致的。该模型可用于热声制冷机中压电驱动系统的特性分析。     

基于刚架的压电驱动器驱动力试验研究

压电材料是一种新型智能材料,利用压电材料制成的压电驱动器具有良好的主动驱动效果.据此开展了基于刚架的压电驱动器驱动性能的试验研究.研究表明,压电驱动器的驱动力与输入电压大致呈线性关系,增加预紧力能在一定程度上提高驱动器的驱动力.在试验的基础上,应用数据分析软件,对压电驱动器的驱动力与输入电压之间的理论关系进行了数据拟合,建立了"驱动力一电压"控制方程.研究成果可为实现基于压电驱动器的智能结构主动控制提供基础数据.     

IR2110的功能及其在高频感应加热电源中的应用

对功率MOSFET的几种基本驱动电路与由IR2 110构成的驱动电路进行了分析比较 ,详尽地分析和研究了IR2 110的工作原理、功能及在高频感应加热电源中的应用技术。还通过实验结果说明了IR2 110在高频感应加热电源中用作电力半导体开关器件功率MOSFET的驱动器 ,既可以满足其驱动要求 ,又极大简化硬件 ,提高工作可靠性并弥补其它驱动电路的不足 ,具有良好的应用前景。     

基于PZT-Si的MEMS微驱动器的设计与仿真分析

设计了一种基于PZT和Si的蟹爪型MEMS微驱动器,该具有结构简单,响应速度快,输出位移大的特点。为了进一步优化结构、提高使用性能寿命,本文根据微驱动器的结构特征,建立了直流电压下PZT蟹爪梁的的力-电耦合数学模型,得到了驱动电压与变形量的关系曲线。采用数值模拟方法开展了压电层材料、厚度等等参数对微驱动器驱动性能的影响研究,研究表明：相对于压电层厚度和输入电压的影响,压电材料性能是系统稳定性的主要影响因素。以弹性柔顺系数相对较低的“硬陶瓷”PZT-4作为压电层时,微驱动器的稳定性增强但驱动响应有所降低;而当选用弹性柔顺系数相对较大的“软陶瓷”PZT-5和PZT-5H作为压电层时,微驱动器的驱动效应增强而稳定性降低。在此基础上,对微驱动器的结构参数进行了优化分析,确定了蟹爪梁结构参数的最优组合, 为微驱动器的设计和改进提供了理论指导。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

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.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the