VHF频段10万跳/秒跳频器的研制

本讨论了一种高速跳频器的设计与实现．通过DSP与DDS相结合，该跳频器已经在VHF频段成功实现了10万跳／秒的跳速。     

高阶有源锁相环路滤波器的设计与仿真

基于频率响应的设计方法,本文对四阶电荷泵锁相环滤波器进行了设计和仿真,利用时间常数与滤波器组件的关系,推导和分析了环路滤波器的传递函数,并在Matlab环境下仿真得到了理想的相位裕度和环路带宽.实验表明,该高阶有源锁相环路滤波器可以在保证相同的鉴相杂散抑制的同时,可允许更宽的环路带宽和更高的鉴相频率,从而改善了锁相环的带内相位噪声性能.     

4mm速调管数字锁相稳频源

本文对一种采用数字鉴相鉴频器的毫米波锁相环路进行了理论分析，给出三阶环路的基本关系式和稳定性判据．计算出４ｍｍ速调管振荡器锁相环路的参数并讨论了数字鉴相鉴频器的特性．实验表明该环路容易入锁且很稳定可靠．     

快速锁定的低功耗电荷泵锁相环

为了加快锁相环的启动速度,提出了一种初始化电路,启动完成后,初始化电路停止工作,几乎不消耗功耗。提出了动态饱和鉴相鉴频器,扩展了鉴相鉴频器的工作范围,消除了死区并且不受环境变化的影响。使用逻辑电路直接控制一个标准计数器,把脉冲吞咽计数器简化为单环路结构,节省了一个计数器,降低了功耗。采用0.18um 1.8V 1P6M N阱标准CMOS数字工艺完成设计,版图面积为0.09mm2。仿真结果表明,初始化电路和动态饱和鉴相鉴频器使得锁定时间减小了19%,而且初始频率差越大,锁定性能提高地越为显著。输出信号的相对抖动峰峰值小于1.5%,整个锁相环的功耗低于18mW。     

一种改进型高性能CMOS锁相环电荷泵的设计

设计了一种高性能锁相环电荷泵电路.该电路采用UMC 0.18μm Mix-Mode CMOS工艺实现.仿真结果表明,通过利用电荷共享加速电流镜的开启,该电荷泵开启时间仅为0.3 ns,不会产生鉴相死区,能较好地抑制时钟馈通、电荷注入等非理想特性的影响,并且适合于低电压工作.通过与传统型及参考型两种电荷泵电路的仿真对比,验证了所设计电荷泵的优越性.     

数字鉴频鉴相器的死区特性及改进方法

通过对数字式鉴频监相器工作原理的分析．提出了其鉴相特性中存在的死区问题及其产生的影响．并给出了减小死区特性的改进电路．该电路采用并行方式工作．减少了复位时间延迟．从而使鉴相器的性能得到改善．     

中国区域定位系统的定位精度分析

中国区域定位系统（CAPS）与GPS都是典型直接序列伪码扩频测距系统,此类导航信号能达到的定位精度取决于多种因素,主要包括伪码速率、信号信噪比、跟踪环处理方法等．详细介绍了CAPS链路预算、CAPS定位解算方法,并着重从C／A码信号的自相关函数特性入手,在软件处理方法下,研究CAPS信号的测量精度问题,对其距离分辨率做了理论分析;针对传统DLL环路易受噪声影响,提出窄相关以及多相关器的环路结构及相应的鉴相方法,使跟踪环路更加稳健,码相位的测量分辨率也可以提高1倍左右,表明改进DLL环路结构以及鉴相方法是提高测距分辨率的一种重要手段．理论分析及定位实验表明利用3颗导航星并有高程辅助的CAPS接收机达到了20m左右的定位精度．     

棉花精量穴播器晃动频幅与充种性能的关系

低空穴率、低双粒率、低种子损伤等是棉花精量播种中的关键指标,而棉种的起拱、相互占位则是造成空穴、双粒以及种子损伤的主要原因之一。为探讨棉花精量排种器的设计、优化的理论依据和方法,本文以一种型孔式棉花精量穴播器为研究对象,基于虚拟样机技术对棉种在该穴播器沿进给方向上的不同晃动频率和幅度下的运动过程进行了仿真分析,得出了棉花精量穴播器晃动频幅对充种性能的影响趋势,结果表明高频小幅晃动可以提高穴播器充种性能。     

基于Kay加权的高动态载波跟踪环路初始频差估计方法

在高动态环境下,过大的载波跟踪环路初始频差会导致环路失锁或误锁。针对该情况已有学者通过增强环路跟踪稳定性和鉴频能力来解决,但仍存在鉴频范围小,精度低和运算量大等问题。为解决上述问题,提出了一种基于Kay加权的载波跟踪环路初始频差估计方法,该算法首先对跟踪环路中I、Q两路的短时积分结果进行二倍角处理,然后,再对其使用四象限反正切鉴频器鉴频,最后借鉴Kay算法对鉴频结果加权得到频差估计值。通过与传统方法做计算机仿真对比,结果表明：在信噪比为-26 dB及以上时,在相同运算采样点数的前提下,本文方法估计精度相较于最大似然估计和三阶锁频辅助四阶锁相环路方法分别提升8.72 dB和19.59 dB或更高。在达到相同估计精度情况下,本文算法运算采样点数为最大似然估计方法的6.25%,算法运算量中加法与乘法次数仅为其1.7%和5.6%,计算时长为其1.56%。     

非稳态多谐振荡器式压频转换器的设计

设计了一种可能在低电压、低电流（5V/1.5mA)的单双电源下工作，并且可心驱动高电压，高电流负载（36V/20mA)的非稳态多谐振荡器式压频转换器。该转换器的高输入阻抗和低失调电压漂移输入增益级可以保证芯片在微弱电压信号下正常工作，仿真结果表明：设计电路的线性度好，输出满度频带宽，输入信号功能范围宽。     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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