基于抛物方程法的部分森林覆盖山区电波传播分析

基于Fourier分步步进法的抛物方程模型求解了山区不规则地形部分森林覆盖环境的电波传播,并分析了森林对电波传播的影响.模型中为了简化边界条件,地形用分段线性函数来近似.然后预测了一个山区部分针叶林覆盖环境的电波传播,得到的结果与实测数据进行对比,二者吻合很好.最后对算法的稳定性与误差进行了分析,本文的模型能处理不规则地形、森林等复杂环境且算法效率高.     

抛物方程法在森林环境电波传播特性预测中的应用

为提高大区域森林环境电波传播特性预测的准确性,研究抛物方程（PE）法在森林环境电波传播特性预测中的应用,提出了基于抛物方程的森林模型。该模型采用PE法实现准确快速求解,考虑森林在垂直方向上的非均匀性,引入森林分层模型,将森林分为树冠、树干两个均匀有耗介质层,并根据森林区域的特性参数确定各有耗介质层的等效介电常数,相比于传统将森林等效为一个给定介电常数的均匀有耗介质层,能够更准确地描述森林对电波传播的影响。将其应用于三种常见绿叶林的电波传播特性预测中,仿真结果表明,该模型能够反映不同区域、不同植被种类的森林对电波传播的影响差异,有效预测大区域森林环境电波传播特性。     

宽角抛物方程在阻抗边界条件下的应用

对抛物方程中的伪差分算子进行Feit-Fleck宽角近似处理,分析了这种近似所带来的误差;详细阐述了阻抗边界条件下求解这种宽角抛物方程的分步傅立叶变换方法,并以此计算了海平面上电波传播情况,与窄角抛物方程及几何光学双射线模型的计算结果进行比较,说明了这种宽角抛物方程在阻抗边界条件下计算较大仰角电波传播问题是可行的.     

多刃峰环境无线电波传播预测的双向抛物方程法

基于迭代双向抛物方程法求解了单刃峰和多刃峰环境下的前向和后向电波传播。对单刃峰,将双向与单向抛物方程法的数值结果做了比较,并分析了刃峰的位置和高度对后向反射场的影响。对多刃峰,采用迭代步进的双向抛物方程法计算相邻刃峰间的电波传播,并将数值结果与单向抛物方程法的结果进行对比。双向抛物方程法能计算出无线电波的前向传播场和后向传播场叠加的总场,比单向抛物方程法的预测结果更准确。     

抛物方程方法的非均匀网格技术研究

为了快速准确地求解大尺度区域环境中存在局部精细结构的电波传播问题,研究了抛物方程方法的非均匀网格技术.利用该技术求解了标准大气结构中不规则地形上的电波传播问题,研究了基于该技术计算传统抛物方程非整格点场值的方法.算例结果表明：非均匀网格抛物方程方法相较于均匀细网格结构,其网格空间下降达68%,计算时间减少了71%,而相对于均匀粗网格结构则具有更高的计算精度.因此,采用非均匀网格的抛物方程方法能在保证计算精度的同时,减少计算所占内存及所需时间,极大地提高了计算效率,适用于求解复杂环境中的电波传播问题.     

弯折谱估计在抛物型方程模型电波传播中的应用研究

射线追踪法求解入射余角时与电波频率无关,且存在部分区域多值或无值问题,此外平面波谱估计的平面波前假设违背了非均匀大气条件下的电波传播特性.针对上述问题,提出了一种基于弯折谱估计进行抛物方程模型海面电波传播的计算方法.通过对光滑表面条件下的抛物方程模型计算结果进行弯折谱估计得到入射余角,再将其用于粗糙海面的抛物方程模型求解.该方法可以唯一的估计任意距离上的入射余角,避免了计算当前值需要用到基于该值估计参数的悖论.对射线追踪法、平面波谱估计和弯折谱估计的估计特性进行了仿真分析,数值试验验证了该方法应用于粗糙海面抛物方程求解的可行性和性能.     

基于抛物方程法的粗糙海面电波传播分析

提出了一种改进阻抗边界条件的方法,并用格林函数法求解抛物方程的初始解:从而提高了抛物方程法的稳定性与精确度.最后基于抛物方程法分析了粗糙海面上的电波传播特性,得到的结果与Miller-Brown模型进行对比,结果吻合很好.     

海上蒸发波导条件下电波传播的分析

抛物方程方法已经被广泛地应用于电磁波传播的研究,并成为解决电磁波传播问题主要的工具。应用抛物方程和电波传播的基本理论,计算了电磁波在蒸发波导和标准大气中的传输损耗,得到了电波的空间传播损耗图,与射线理论的射线描迹技术得到的结论是一致的,但是抛物方程方法求解速度快,具有很好的实时计算特性,并且能弥补目前射线描迹技术尚不能精确描述空间场分布的缺点,因此更具有实用价值。     

部分森林覆盖山区电波传播特性预测的快速算法

为提高部分森林覆盖山区电波传播特性预测的时效性,提出了一种基于宽角抛物方程(PE)的快速预测算法。采用PE通过分步傅里叶变换(SSFT)求解;在SSFT步进迭代过程中,根据传播路径上森林的等效介电常数、地形的起伏情况,动态选择PE的水平步长。通过对部分森林覆盖的不规则地形条件下的电波传播特性进行仿真,探讨了该方法的可行性和有效性。结果表明：相比于均匀大步长算法,该方法更准确;而相比于均匀小步长算法,该方法能够保证抛物方程的计算精确度,同时极大地提高计算效率。     

预估城镇小区电波传播损耗的一种三维抛物方程算法

为城镇小区电波传播问题建立了一种三维抛物方程模型,并且用二维分部傅立叶变换方法求解。计算了几种不同地形上建筑物障碍分布的小区电波传播衰减因子,和UTD理论及数值积分方法计算出的结果吻合得比较好,从而验证该模型的有效性,同时也说明了三维抛物方程模型能更准确地反映出小区建筑物宽度对场的绕射作用,为城镇小区电波传播问题的估算提供了一种更为准确的算法模型。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks