用改进的线性近似方法研究单模激光损失模型随机共振

采用周期信号、具有实虚部关联的量子噪声和抽运噪声作用下的单模激光损失模型,运用改进的线性化近似方法计算得到了模型输出光强的相关函数、功率谱及信噪比.分析了激光的净增益系数、噪声强度和输入信号对信噪比(SNR)随量子噪声实虚部关联系数(λ)变化曲线的影响.研究发现了信噪比随量子噪声实虚部系数的变化出现了新的随机共振现象.     

关联噪声驱动下单模激光损失模型的输出功率

运用线性化近似方法分析具有实虚部关联的量子噪声和泵噪声驱动的单模激光损失模型的动力学性质，计算了光强的关联函数、功率谱及输出功率，讨论了量子噪声实虚部关联系数λq，量子噪声强度P和净增益系数a0对输出功率的不同影响，并发现输出功率S随λq，的关系曲线在a0改变时出现了类似于概率分布中的“重复相变”等新现象．     

亚硝酸钠光学性质的第一性原理研究

为了更好地理解亚硝酸钠在铁电相和顺电相间光学性质的差异，计算了它的介电虚部ε2(ω)、光吸收系数I(ω)及反射系数R(ω)．ε2(ω)、I(ω)和R(ω)的计算结果表明，亚硝酸钠是一种各向异性比较明显的材料，并且其光学性质在铁电相中要比在顺电相中具有更高的各向异性．     

基于FFT的正弦信号频率估算新方法

介绍一种新的基于FFT的正弦信号频率估计的插值方法。该方法利用了DFT最大值谱线及与其相邻两根谱线系数的实部(或虚部)进行插值得到频率估计值。与传统的算法不同,在本方法中不需要判断第二大峰值谱线的位置,避免了找该谱线时可能会出错,从而使频率估算值出错的问题。另外,插值时算法中先对几根谱线DFT系数的实部和虚部的大小进行比较,实部大于虚部时用利用实部进行插值,反过来则利用虚部进行插值,从而减少了噪声的影响并提高了估算精度。数值模拟结果表明利用该方法可以得到良好的插值效果,能取得很小的频率估算偏差。     

用有效介质理论模拟Ag/AAO纳米有序阵列复合结构光学常数

运用Maxwell—Garnett有效介质理论，计算了Ag／阳极氧化铝（AAO）纳米有序阵列复合结构的光学常数（250～2000nm波段），探讨了Ag组分的体积分数对Ag／AAO光学常数的调制作用和Ag纳米粒子的长径比对其表面等离子共振吸收的影响．模拟结果表明，随着Ag组分体积分数的增加，在小于450nm波段，Ag／AAO复合结构的介电函数实部和折射率均逐渐减小，而介电函数虚部和消光系数逐渐增大；在大于450nm波段，Ag／AAO复合结构的介电函数实部、介电函数虚部及折射率均逐渐增大，消光系数则变化较小．模拟结果显示出Ag纳米粒子的长径比与复合结构表面等离子共振吸收峰位有较强的相关性．另外，理论模拟预期透射谱也与实验透射谱变化趋势一致．     

等离子体噻吩聚合膜紫外吸收的讨论

从等离子体噻吩聚合膜的反射谱和透射谱,运用传递距阵方法计算得到膜的光学常数:折射率n_f和消光系数k_f(受测量仪器限制,反射谱和透射谱以能量(?)ω表示的频率宽度为0.4～4.0 eV)。等离子体噻吩聚合膜在这个频率宽度内,没有显示出对光的强吸收。由膜的折射率谱及塞尔迈耶公式,可推断在大于4.0 eV紫外区,等离子体噻吩聚合膜存在一定强度的吸收。并进一步利用复数介电函数的实部与虚部之间的 k-k关系,以振子模型进行外推,对等离子体噻吩聚合膜的紫外吸收进行讨论。     

电子计算机在防振油锯设计中的应用

<正>本文从油据系统的频响函数H(ω)出发,较全面地论述了油锯系统的力学模型的确定和简化,用傅氏变换的方法求解油锯系统的常系数微分方程,应用电子计算机,对油锯系统的质量、刚度及其分布进行优化设计,使得对人体最敏感的振动带内的|H(ω)|1。     

量子噪声实虚部关联对饱和激光模型光强涨落的影响

文章基于实、虚部关联的量子噪声及泵噪声驱动的饱和激光模型，推导了近似福克—普郎克方程、激光强度定态概率分布函数，通过计算机进行数据计算及作图，得到了定态情况下光强概率分布函数图形，讨论了量子噪声实、虚部的互关联对光强关联函数的影响。结果表明：量子噪声实、虚部互关联会增大激光强度的涨落。     

修正条纹调节的圆谐联合变换相关器作旋转不变的目标检测

提出一种修正条纹调节的圆谐联合变换相关器作旋转不变的目标检测的方法．在这种方法中,参考图像（即圆谐展开分量的实部和虚部）、圆盘状的局部偏置函数以及目标图像同时显示于输入面．这一方法对联合功率谱作了修正,先将联合功率谱减去纯输入景物（含局部偏置函数）的功率谱和参考图象（含局部偏置函数）的功率谱,再加上局部偏置函数的功率谱,然后将所得修正的联合功率谱乘以条纹调节滤波函数．它能产生比普通的圆谐联合变换相关器更好的相关输出．给出计算机模拟结果．     

实虚部间关联泵噪声对激光动力学性质的影响

在损失模型中引入平方色泵噪声,并考虑泵噪声实虚部间关联λp,推导了一个新的含有λp的光强朗之万方程.用线性化近似的方法从理论上对具有实虚部间关联的泵噪声驱动的单模激光的动力学性质进行分析,计算了光强的关联函数、功率谱及输出功率S.讨论了泵噪声实虚部间的关联强度λp、泵噪声强度p'、净增益系数a和关联时间τ对S的影响,发现λp对光强的输出功率影响显著.当λp=±0.5时,输出功率S最大,|λp|=1或λp=0时,输出功率S最小.     

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.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。