拉削振动的数学分析和实验研究（I）

建立了新的拉削振动的动力学模型，推导出振动位移的数学表达式，得出了拉削振动的基本规律，为拉刀设计提供了理论依据。     

DDS在SIMULINK中的仿真设计

简单介绍了直接数字频率合成（DDS）技术和Simulink仿真系统的特点及背景，阐述了DDS的基本工作原理并对它的主要杂散进行了分析；在Simulink环境下建立了DDS的动态仿真模型，分析了DDS动态仿真模型各模块的功能和来源；对所建系统进行了仿真实验，在实验的基础上系统地分析了仿真结果，并给出了相位截断对DDS频谱分布的影响，为研究和设计直接数字频率合成系统提供了理论和实验基础。     

DDS原理及其应用

本文在深入分析了DDS波形产生原理，控制方式，频谱特性，对当前流行的主流DDS芯片做了详细的对比，并设计出一套基于MCS-51芯片和AD9851芯片的DDS波形发生系统，并总结了DDS目前的问题和未来的发展方向。     

基于FPGA的频率合成器的实现

本文介绍了直接数字频率合成器（DDS）的原理,并通过现场可编程门阵列FPGA以查找表的方式予以实现24位DDS的方案。相对于传统的专用的数字频率合成器芯片,用高性能的FPGA器件设计符合自己需要的数字频率合成电路具有方便的控制方式和快速的置频速率等等诸多优点。     

玻璃基质中稀土离子的多声子过程有效频率

多声子过程中的能量传递几率与无辐射驰豫几率具有相似的函数表达式，其中的指数参数却并不相同，从三个方面分析得出，差异的原因主要在于有效频率的不同。     

基于FPGA的直接数字频率合成器的设计

为了实现幅值和频率在一定范围连续可调,频率步进达到1Hz以下信号发生器的设计.采用直接数字频率合成技术(DDS),介绍根据直接数字频率合成技术组成及原理,给出了基于可编程逻辑器件FPGA及相应EDA软件QuartusⅡ实现DDS的具体设计方案及编程实现方法.通过改变设计参数可以调节所产生波形频率和幅度;通过改变ROM查找表中波形数据可以产生任意波形.利用FPGA器件设计DDS,大大简化了电路设计过程,缩短了调试时间,并为修改、添加DDS的功能提供了方便.     

电视机中频的最佳选择

从电视机中频的选择原则出发，研究了超外差式电视接收机的混频特性。导出了组合干扰频率的一般表达式，给出了组合干扰频率及其中心频率的计算公式，并将计算结果绘成图表，为合理地选择最佳中频提供了科学依据。     

四角点支撑的矩形板振动

本文给出了四角被点支撑的矩形板的振型函数，导出了求解自振频率的表达式，对该矩形板 的强迫振动也作了讨论，求出了强迫振动时挠曲面方程的一般解。     

直接数字频率合成器频谱性能分析

对直接数字频率合成器DDS(Direct Digital Frequency Synthesizer)的频谱性能进行了相关分析．在DDS频谱性能量化理论基础上,从相位噪声以及非线性余弦函数映射两个方面对DDS输出信号频谱纯度性能优化．对于硬件结构以及相关参数均确定的DDS而言,其频谱特性将随着频率调节字FFTW的变化而变化．研究结果表明,若字长M为32bit,只需要计算出FFTW为2^0,2^1,…,2^31时所对应的信噪比SSNR值即可,取其中最小值来衡量DDS的频谱特性．基于上述量化方法,可以通过调节DDS系统中不同参数值或结构,计算它们对应的SSNR,从而得到最佳性能的设计方案．分别对相位截尾误差以及非理想SCMF产生的误差进行优化．为进一步提高DDS的频谱纯度,可以对非理想SCMF误差进行优化．通常SCMF由只读存储器查找表和插值算法组合而成．ROM表可以很容易取到相应角度对应的正余弦函数精确值,但是插值算法总会带来一定的运算误差．文中提出一种自动调节算法能够实现对非理想SCMF误差的优化．     

注入锁定半导体激光器的调制特性

本文讨论了注入锁定半导体激光器的调制特性,给出了功罕响应和动态频率飘移的表达式。     

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-