有源消声耳罩的设计研究

本文对有源消噪电路的设计进行了分析研究,并采用单通道有源消嗓电路,实现了320Hz—510Hz.频率范围内3dB以上的消声效果.根据理论上分析和实际模拟消声电路设计和实验,对有源消声提出了改进建议.     

一种新型模拟电感

在有源滤波器的设计中经常采用通用阻抗变换器（ＧＩＣ）模拟接地电感来实现有源滤波器,然而由于所采用的运放较多,存在消耗功率大和噪声问题,此外元件变化引起滤波器特性的变化大,其稳定性不如ＬＣ滤波器,由此提出了一种新型模拟电感电路。它只由一个运放和电阻电容组成,由这种新型模拟电感代替无源ＬＣ滤波器中的电感Ｌ组成亚音频有源高通滤波器,具有与无源ＬＣ滤波器相同的低灵敏度,并且电路简单经济、减少功率消耗和噪声     

一种基于电流传送器的电流模式N阶滤波器设计

提出了一种基于第2代电流传送器的电流模式N阶滤波电路.该电路由n个电流传送器(CCII+)、3n个无源元件构成,能实现N阶低通、带通、高通滤波功能.以2阶滤波器为例分析了电路的无源、有源灵敏度,分析数据表明无源、有源灵敏度都很低.最后对该电路用Pspice进行了仿真,仿真结果表明该电路设计正确.     

基于DDCC的互感耦合电路的有源模拟

 通过对互感耦合电路端口电压和电流关系的分析,提出了一种新的互感耦合电路有源模拟方法,并采用DDCC为有源器件实现了具体电路.提出的电路具有以下优点:① 控制不同开关组合可以实现正、负耦合电路;② 初、次级电感及互感可以通过调节外接电阻实现独立可调;③ 电路结构简单,仅由4个 DDCC器件,6个电阻和2个电容组成;④ 所有器件均接地,便于集成.将该电路应用到双调谐回路并进行PSPICE仿真分析,结果验证了该电路的正确性.     

数字有源电阻箱的设计

为解决传统电阻箱量程范围小、 阻值分辨度低、 装置体积大以及使用不便等问题, 设计了一种宽范围、 高阻值分辨度的数字化有源电阻箱。 该电阻箱采用模拟有源电阻硬件电路, 并应用 ARM7 系列微控制器 LPC2138 系统对其进行控制, 并使用矩阵键盘和 LCD(Liquid Crystal Display)液晶屏作为人机交互设备, 以便于 实现装置的电阻值数字化设定及同步显示。 实验数据表明, 该数字有源电阻箱的阻值范围为 10. 01Ω ~ 10. 01 MΩ, 精度为依0. 46%, 可广泛应用于电子电路中。     

单CCCS有源RC电流滤波器双二次实现

提出了一系列新的采用单一电流控制电流源的有源ＲＣ电流滤波器实现，这些电路是基于对偶变换由电压模式电路导出。生成了一系列新的电流模式有源高通、低通、带通、全通和带阻滤波器电路。这些电路不需要隔离级便可以级联起来实现多级有源电流滤波器。     

基于第3代电流传送器的电流模式有源滤波器的设计

 设计了一种有源滤波网络,提出了一种基于第3代电流传送器(Third-Generation Current Conveyor,CCⅢ)的电流模式二阶滤波器的系统设计方法,导出了该系统的设计公式,其电路由1个CCⅢ+和4个无源元件构成,可实现二阶低通、高通、带通滤波功能.各滤波电路具有很低的无源灵敏度和有源灵敏度,端口网络电路简单,电路结构固定,通过级联易生成高阶滤波电路.用PSPICE对电路进行了仿真,仿真结果表明,设计理论正确,设计方法可行.     

稳定电源用直流有源滤波器的检测纹波电压控制方法

对一种特殊的高精度、低纹波大功率直流稳定电源的直流有源滤波器的主电路结构和抑制纹波的原理进行了分析,提出了检测纹波电压的直流有源滤波器控制方法.该方法通过检测负载的纹波电压来控制有源滤波器的输出,从而降低了负载电流纹波.这种方法的显著优点是在对传感器和电路元件精度要求不高的情况下,非常容易实现大功率直流稳定电源的低纹波要求.对一台实际应用的工业装置的测试表明,其电流纹波系数达到了1×10-5.     

SAB电路的有源补偿及其灵敏度优化

单放大器双二次节电路(SAB)是RC有源滤波器中常见的电路,经过有源补偿,其有源灵敏度显著下降.本文提出了一个新的三运算放大器(简称运放)补偿的SAB电路,经同其他一些有源补偿SAB电路进行的分析和实验比较,说明它是有源和无源灵敏度性能较好的一种有源补偿SAB电路。本文还分析了有源补偿SAB电路的主极点位移和主极点有源灵敏度,并对现有的一些有源补偿SAB电路进行了有源灵敏度优化,给出了分析比较和性能上的评价.     

基于MOCCⅡ电流模式n阶滤波器综合设计

提出了一种新的基于MOCCⅡ的等电容和等电阻电流模式n阶滤波器综合设计方法.通过对n阶通用滤波传输函数进行分析,将其分解成一系列能用无损积分器实现的表达式,由低阶向高阶进行电路综合.该滤波电路包含n+2个有源器件和2n+4个接地无源元件.通过控制数字可编程开关在输出端可得到电流模式n阶低通、高通、带通、带阻和全通5种滤波功能.整个电路的部分无源元件灵敏度之和与全部无源元件灵敏度之和为0.对滤波器进行了PSPICE模拟验证.     

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-