平面波经小圆环衍射轴上光强特性分析

从标量衍射理论出发,采用瑞利-索末菲衍射边界条件,通过求解第一类瑞利-索末菲衍射积分得到平面波经圆环衍射后轴上的波函数,进而分析轴上的光强特性以及光强极值数量、位置和大小与衍射圆环内外孔径的关系.比较用传统的光强定义和精确定义得到的光强公式的偏差,以及偏差与内外半径的关系.并将圆环衍射向内半径为零和外半径为无穷大两个方向进行推广,即对圆孔和圆形障碍物两种情况下的衍射情况进行讨论.     

双天线对消弹射式干扰中的相位估计

在对抗对合成孔径雷达的弹射式干扰中,双路对消技术取得了较好的结果,但是对消的前提是知道两路中的干扰信号相位差.本文提供了一种有效的估计干扰信号相位差的方法.以两路对消后的能量最小为准则,采用以黄金分割法为基础的自动搜索算法,得到相位差.同时通过仿真实验验证了方法的正确性.     

入侵检测系统中基于变量相似性特征选择

ReliefF是一种在很多场合经常使用的filter式的特征选择方法．然而该方法的一大缺点是不能辨别冗余特征。基于ReliefF算法提出一种混合的有监督的特征选择算法。该算法首先利用ReliefF算法去除与分类无关的以及权重低于一定阈值的特征，然后采用一种变量相似性准则来去除冗余特征。在实际的数据集KDDCUP＇99上进行的实验结果表明该混合特征选择方法较单独使用ReliefF方法在分类精度上有一定的提高。     

Valence band studies of the formation of ultrathin pure silicon nitride films on Si(1 0 0)

The growth of ultrathin films of Si₃N₄ directly on Si surfaces is studied with valence band photoemission. The information from these studies about the growth mechanism and the changes of the electronic structure is enhanced by the use of various photon energies with synchrotron radiation. The silicon nitride films are grown isothermally on the Si(1 0 0) and Si(1 1 1) surfaces by reactions with atomic N. The atomic nitrogen is produced by using a remote, microwave excited nitrogen plasma. The growth under these conditions was earlier shown to be self limiting. The details in the valence band spectra are identified and resolved with numerical methods, and followed systematically during the growth. Thus the identification of Si surface states, Si-nitride interface states and bulk nitride states becomes possible. The previously obtained separation between amorphous and crystalline growth occurring around 500 °C is further supported in the present studies.     

The Hilbert Kernel Regression Estimate

Let (X, Y) be an ^d× -valued regression pair, whereXhas a density andYis bounded. Ifni.i.d. samples are drawn from this distribution, the Nadaraya–Watson kernel regression estimate in ^dwith Hilbert kernelK(x)=1/x^dis shown to converge weakly for all such regression pairs. We also show that strong convergence cannot be obtained. This is particularly interesting as this regression estimate does not have a smoothing parameter.     

Selection of response measurement locations to improve inverse force determination

The forces obtained by inverse methods are prone to errors. These arise due to a combination of errors in the measurements and high condition numbers in the matrix of transfer functions to be inverted. Ill-conditioning of the frequency response function matrix causes measurement errors to be magnified significantly. When the condition numbers are small, the measurement errors simply propagate without much amplification. Due to modal behaviour of the structure, the condition numbers can vary significantly over the frequency range and with the spatial location of the response measurements. The spatial variation can be quite considerable across the structure. The potential for using this characteristic to improve force determination is explored in this paper as an alternative to matrix regularization methods. The aim is to reduce error magnification in inverse methods by an ‘optimal’ spatial distribution of response locations. A method is proposed which is based on the minimization of the average condition number across the frequency range. If many possible locations are available, however, this can involve excessive calculation. An approximate method is therefore proposed which results in consistently good location selection for use in inverse force determination but involves much less computational effort. The error reduction in reconstructed forces is found to be significant in numerical simulations on a simply supported plate and in validation experiments.     

超小碳纳米管的高效率光致可见发光

镶嵌在分子筛骨架中的4A直径的单壁碳纳米管可发出高效的、位于可见光区的光致发光．发光谱呈较宽的线形，其效率约为1％—5％．无论是对激发光的响应，还是发光强度都有很强的偏振依赖特性．结合其吸收光谱、拉曼光谱以及电子能带结构的理论计算，作者讨论了4A碳纳米管的发光机制，并给出了合理的解释．     

Spatial and Temporal Variations of the Indoor Wireless EHF Channel

This paper reports line-of-sight propagation measurements performed at 37.2GHz between two terminals in an empty room in order to investigate the spatialand temporal fadings in terms of antenna directivity and human motion,respectively. The empirical data base consists of recordings of CW envelopefading waveforms with a fixed transmitter and either moving or stationaryreceiver. The reported results include amplitude fading distributions,propagation loss gradients, level crossing rates and fade durationsstatistics. These results can be used in the modeling, design reliableoperation of local multi-point communication systems.     

固体反射光谱的挖孔机制——红外吸波材料机理探讨之三

深入研究了固体反射光谱红外活性模剩余反射带短波边对介电常数变化的敏感性，并在此基础上研究了强弱振子介电耦合对反射光谱的影响，发现在一定条件下可以在强振子的剩余反射带内形成局部的低反射率频域     

IR spectra of tellurium germanate glasses and their structure

We have used IR spectroscopy to study the structure of tellurium germanate glasses synthesized in the system TeO₂-GeO₂-B₂O₃-PbO. The structure of the glasses consists of [BO₃], [BO₄], [GeO₄], [GeO₆], [TeO₃], and [PbO₆] groups. Changes in the coordination of boron and germanium ions occur when the PbO and GeO₂ contents in the glasses increase. The glasses are attractive for designing optical and laser devices. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 78–81, January–February, 2007.