混沌信号的相空间重构和预测方法研究

基于复杂非线性系统的相空间重构理论和神经网络本质为非线性映射关系的特点,提出利用混沌时间序列重构相空间和BP神经网络构建其预测模型的方法。利用该方法对典型的Lorenz混沌时间序列进行了空间重构,研究了预测模型的预测效果,结果表明单步预测效果理想,多步预测在50步以内也能取得较小的预测误差,证明了混沌信号不同于随机噪声,具有短期可预测、长期不可预测的特征。该方法为具有混沌特性的时间序列如心电信号、电力负荷等预测模型的建立提供了理论基础。     

应用混沌理论对煤矿瓦斯浓度预测

利用混沌时间序列短期可以预测的特点,构建煤矿瓦斯浓度预测模型,重构煤矿瓦斯浓度相空间,采用改进的C-C算法确定相空间时延t和相空间嵌入维数m。然后在重构相空间中,运用加权一阶局域法构建煤矿瓦斯浓度的预测模型,进行煤矿瓦斯浓度预测。     

基于相空间重构与最小二乘支持向量机的时延预测

针对网络控制系统的时延预测问题,提出一种基于相空间重构与最小二乘支持向量机的时延预测方法.首先利用0-1测试法确定时延序列具有混沌特性,引入相空间重构技术提高预测精度.对实际采集的时延序列进行Hurst指数分析,选择最小二乘支持向量机作为预测模型.然后利用C-C方法确定时延序列相空间重构参数,通过递归图确定时延序列的局部可预测性,利用遗传算法对最小二乘支持向量机的参数进行离线优化.最后通过优化后的最小二乘支持向量机并结合相空间重构对时延序列进行在线预测.与其它预测方法进行了仿真对比,结果表明本文方法具有更高的预测精度与更小的预测误差,同时并未降低预测算法的实时性.     

基于粒子滤波的混沌时间序列局域多步预测

对混沌时间序列进行预测研究具有重要的价值和实用性,例如,进行股票预测,降雨量预测,温度预测。混沌时间序列预测的难点在于其不确定性和多步预测的困难性。一般利用最小二乘法求解模型参数,从而对混沌时间序列进行局域预测,但是预测精度不是很高。为了提高局域线性预测的精度,提出基于粒子滤波(PF)的混沌时间序列局域多步预测法,利用粒子滤波进行参数优化得到更准确的优化模型进行多步预测。仿真实验结果表明,该方法的单步和多步预测效果明显得到了提升。     

新的混沌扩频序列抗多址性能的Simulink仿真

针对混沌扩频通信中提升混沌码性能的问题,通过重构Bernoulli映射相空间,得到一种改进的Bernoulli混沌映射,计算证明该映射具有弱结构特性,并在Simulink平台搭建了多用户混沌直接扩频通信系统的仿真模型,并与原Bernoulli混沌序列的抗多址性能做了比较。Simulink动态仿真结果表明,改进后的混沌扩频序列具有较好的抗多址干扰能力。     

混沌模拟信息转换——基于多射法的稀疏信号重构

混沌压缩采样是应用混沌系统实现非线性测量的压缩采样理论。该文研究模拟信号的混沌压缩采样-混沌模拟信息转换。该转换通过稀疏信号激励混沌系统,低速采样系统输出实现;信号重构则以混沌系统参数估计理论为基础,通过稀疏正则化的非线性最小二乘问题进行求解。该文将多射法(MS)与迭代再加权非线性最小二乘算法(IRNLS)结合,给出混沌模拟信息转换的MS-IRNLS信号重构算法。文中以Lorenz系统为例,仿真验证了MS-IRNLS算法的重构性能,结果表明方法的有效性。     

混沌时间序列预测的改进型加权一阶局域法

提出了一种用于混沌时间序列预测的改进型加权一阶局域法.用衰减系数对分维指数加权一阶局域法的向量距离公式进行修正,调节邻近点与中心点的相关性,也调节了同一邻近点的各个分量和中心点的最后一个分量的关联程度.利用该方法对Logistic混沌时间序列进行预测的结果表明,衰减系数取最佳值时,相对于现有算法,该方法可以更精确地预测...     

基于最小二乘支持向量机对称性的混沌时间序列预测

利用最小二乘支持向量机的对称性约束条件挖掘混沌时间序列的对称性,分析混沌系统固有的对称特性,提出一种对称性最小二乘支持向量机的混沌时间序列预测方法。该方法将混沌系统的对称性作为先验知识嵌入预测模型,Lorenz系统的仿真结果表明该方法不仅能够精确地预测混沌时间序列,而且扩展了混沌系统的预测空间,这一结论预示着最小二乘支持向量机是一种研究混沌时间序列的有效方法。     

基于混沌时间序列的短期电力负荷预测

针对电力系统负荷的复杂性及非线性,提出了结合混沌的思想,充分利用数据信息,在重构相空间的基础上对负荷进行预测.结合混沌理论,采用加权一阶局域法建立了电力负荷预测模型,并进行了实际预测,取得了满意的结果.     

基于连分式的混沌时间序列全局预测新方法

在混沌系统动力学方程未知的情形下,通过拓展多项式逼近到有理分式逼近理论,并借鉴混沌系统相空间重构思想,利用连分式法建立了混沌时间序列非线性全局预测模型,用此模型重构混沌系统的动力学方程,实现对其频率特性分析,达到预测目的.理论分析和仿真实验表明连分式法能够有效预测一些混沌时间序列,该方法预测精度高,并且能得到显式的预测表达式.     

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.     

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.     

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.     

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.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

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.