步进程控放大器的CPLD实现

ispLSI1032是Lattice公司生产的在系统复杂可编程逻辑器件。本文介绍利用可编程逻辑器件ispLSI1032和AD7520实现1000倍步进增益可调的程控放大器的设计方法。     

可编程增益放大器在惯性姿态测量系统中的应用

介绍了可编程增益放大器的概念、特点以及作用,给出了一个基于PC104型总线的宽动态范围高速数据采集卡,利用AD526实现的可编程增益放大器与A/D模块以及CPLD之间的接口电路,并给出了相应的软件设计流程.该采集卡可对动态小信号进行采集处理,测量精度高,通用性强.     

AD526在土壤电导测量过程中的应用

在土壤电导的测量中,由于土壤电导变化范围大,一般的放大器的测量结果误差很大。采用程序可编程增益放大器AD526,与单片机构成自动调整放大倍数的测量系统。该系统提高了土壤电导的测量精度,通用性更强。     

一种程控放大滤波器设计

利用AD620仪表运放、TL084、DAC转换器MAX527、可编程有源开关电容滤波器LMF100及DDS集成芯片AD9854等,设计了以单片机为控制核心的交流小信号程控放大和程控滤波器,程控滤波可实现四阶高通、低通以及带通滤波,放大器增益和低通、高通截止频率均可实时键盘调整,并介绍了设计的详细方法和原理.     

精确程控级联宽带放大器的设计

以STC89C52单片机为控制核心、两级AD603可控增益芯片为放大核心设计了一种程控级联宽带放大器,其主要由三个部分组成:前置级放大部分、程控增益部分及后级功率放大部分。利用十位的DAC芯片TLC5615输出模拟电压来控制两片AD603芯片的控制端电压,实现0~60 d B增益步进可调。此放大器具有宽频带、低噪声、高增益、性能稳定的特点。     

数模转换器构成的可编程放大器

介绍了一种实用的数模转换器构成的可编程放大器。该放大器利用外接参考电源及无放大器类的DA转换器,以参考电压端为输入信号端,外加入大器反馈电阻产生较大的电压增益,从而完成了大的动态范围多级增益的可编程放大器。     

基于DSP的宽带直流放大器的设计与研究

文章介绍了一种基于DSP的宽带直流放大器,该装置的信号放大由可控增益运算放大器AD603来完成。同时还采用DSP和AD558增益控制电路实现增益预置并显示,带宽达50MHz,并且增益在0~60 DB连续可调。     

一种用于便携式超声接收机的模拟AGC设计

传统模拟AGC电路由分立元件完成检波及反馈,使得系统稳定性及可靠性不高。本文提出了一种以可变增益放大器AD603、对数放大器AD8307和集成运放为核心实现的模拟AGC电路,以提高系统的稳定性。讨论了电路的工作原理和设计特点,并给出了电路原理图。     

基于AD8304对数放大器的高精度光功率计的设计

为了避免传统光功率计测量误差较大、测量范围较窄等缺点,文中对光功率计的测量精度及范围进行了优化设计。设计中使用PIN光电二极管将光电流转化为电压值,并采用AD8304对数放大器进行对数放大,避免了使用线性放大器时显示转换误差和烦琐的对数运算。给出了光功率计的设计思路,重点讨论了AD8304对数放大器的特性及在光功率计中的应用,并通过软件对本设计的计算精确性进行了验证。     

集成运放参数测试仪

该集成运放参数测试系统参照GB3442-82标准,采用辅助放大器测试集成运算放大器主要参数的方法,以单片机（AT89S52）为控制核心,结合可编程逻辑器件FPGA,使用多量程自动切换的方式,实现了对通用集成运放VIO（输入失调电压）、IIO（输入失调电流）、AVD（交流差模开环电压增益）、KCMR（交流共模抑制比）和BWG（单位增益带宽）的高精度自动测量。整个系统集成度高,具有友好人机交互界面。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-