CO_2激光器腔外吸收室4.3μm荧光稳频技术

介绍了腔外吸收室４．３μｍ荧光稳频方法。对利用低压 ＣＯ２气休的 ４.３μｍ荧光饱和共振吸收来稳定ＣＯ２激光频率的原理和装置进行了较详细的描述．测量了４. ３ μｍ荧光兰姆凹陷的相对深度及其宽度；利用三次微分信号确定了最佳调制电压范围．稳频激光输出功率为６Ｗ；利用鉴频曲线估算出锁定后频率稳定度为１０－１０量级。     

单频外腔半导体激光器的主动稳频

采用鉴频反馈电路控制外腔长，对长外腔单纵模半导体激光器进行主动稳频，获得线宽小于２００ｋＨｚ的稳定单频输出，在２ｈ内频率漂移小于２ＭＨｚ     

全球定位系统在频率及其稳定度测量中的应用

在测量信号源的频率及其稳定度时，以前普遍采用稳定度很高的晶振作为基准进行测量，但是测量精度不够理想，而其他的改善办法又使得费用过高。鉴于此，文中提出了一种新的方法，该方法以全球定位系统（GPS）的秒脉冲作为基准，利用高密度可编程逻辑器件（HDPLD）设计相应的电路，再用示波器进行观察测量。全球定位系统中采用了精度高、稳定性好的原子钏作为时间基准，而且它的接收设备价格便宜，因此，用这种方法开发的系统经济实用。实验结果证明，该方法可以使测量结果得到较大的改善。     

正交解调Pound-Drever-Hall激光稳频技术实验研究

为了提高激光器的频率稳定度,设计了基于正交解调原理的Pound-Drever-Hall(PDH)稳频系统。该系统采用直接数字频率合成器同步产生三路同频正弦和余弦信号,其中一路正弦信号用作电光相位调制器的驱动信号,另两路正弦和余弦信号同时用作相位解调的参考信号。解调所得PDH稳频系统的误差信号用于反馈调节激光器腔长,使得激光器频率自动稳定到Fabry-Perot(F-P)参考腔的谐振频率上。建立了正交解调PDH稳频实验系统,实验结果表明,在1.5 h稳频时间内,激光器的频率漂移不超过±0.13 MHz,根据Allan方差计算得到其频率稳定度优于1.2×10^-11。这种稳频激光器可用作合成波绝对距离干涉测量系统的理想光源。     

晶体管参数对高稳晶振频率稳定度的影响

本文利用晶体管混合π型等效电路和振荡器的相位平衡条件，计算出晶体管参数对振荡器频率稳定度的影响，计算结果表明，晶体管发射结电容对频率稳定影响最大，为了减轻这些影响，本文提出了一行之有效的办法。     

Pound-Drever-Hall激光稳频系统线性化复频域建模及分析研究

Pound-Drever-Hall(PDH)稳频系统利用了调制光谱技术和外差探测技术,将激光频率锁定在F-P参考腔的中心频率上以实现稳频。鉴频曲线的线性区为PDH系统的频率快速捕获区。在此区域内,PDH误差信号与激光频率差成正比。本文建立了该频率快速捕获区的PDH稳频系统线性化复频域模型,研究了系统的稳定性和稳态误差。F-P参考腔作为稳频基准,其干扰对系统稳频性能影响极大。将F-P参考腔干扰作为噪声源,分析了系统的扰动误差。分析了系统动态性能,研究了频率锁定的暂态响应过程,给出了系统参数设计依据。     

连续波腔衰荡技术测量系统的参数选择

连续波腔衰荡技术是一种非常规、高精度的腔损测量技术。考虑入射光线宽和谐振腔失调等情况，本文依照多光束干涉理论对连续波腔衰荡法的腔出射光强公式进行了推导，并围绕腔出射光强，就测量系统各部分参数的选择对测量精度和稳定度的影响进行了数值模拟和分析，这将为该技术应用时的参数选择提供理论指导。     

机械谐振式热声制冷机模态频率研究

研究了一种机械谐振式热声制冷机结构,建立了装置机械谐振系统的二维模型,从振动方程中分析获得了系统的模态频率关系,同时研究了振动质量、机械和气体弹簧、腔体尺寸以及工作压力等参数对模态频率的影响.研究结果显示系统存在两个模态频率,且频率随谐振参数的变化出现分岔.通过对谐振参数的设计和调节,装置可以获得所需的特性和谐振频率.     

石英晶体振荡器

石英谐振器是较新型的电子元件。石英振荡器的频率稳定度可达10^-6-10^-11,Q值在10^5以上，且振荡频率可以做得很高，在对频率稳定度要求较高的各种通讯及其他电子设备中有广泛的应用。     

谐振隔离式频率编码轨道电路解码研究

研究UM2000谐振隔离式频率编码轨道电路的解码问题,提出了一种先进行鉴频,然后进行低频频率提取的解码方法,并对该方法进行了仿真,仿真结果表明采用本文提出的解码方法仅需要1.36s的采样数据即可完成解码.     

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