PN codes versus chaotic codes: Performance comparison in a Gaussian approximated wideband CDMA system over Weibull fading channels

The performance of a Wideband Code Division Multiple Access (W-CDMA) system using Pseudo Noise (PN) codes and chaotic codes in the presence of a Weibull fading channel is studied in this paper. The W-CDMA system modeled using Gaussian Approximation is analyzed on a Weibull fading channel which fades the amplitude of the transmitted signal randomly according to the Weibull distribution. Closed-form expressions for Bit Error Rate (BER) are derived and expressed in terms of Meijer?s-G function. Performance measures in terms of BER are plotted versus Signal-to-Noise Ratio (SNR) for various values of fading severity, average fading power, and channel memory using PN and chaotic codes. Performance comparison between PN codes and chaotic codes are also analyzed.     

基于最可几值的学科期刊影响因子的讨论

在分析多学科期刊影响因子分布特征的基础上,引入学科期刊最可几影响因子表征学科期刊整体的影响因子水平,并使用对数正态分布函数表征学科期刊影响因子的分布形状,利用对数正态分布函数的特征参数表达学科期刊平均影响因子水平与分布宽度。最后,提出学科最可几期刊影响因子加上相应对数正态分布函数的特征参数可以表征学科期刊整体影响因子水平的观点。     

A unified approach to average LCR and AFD performance of SC diversity in generalized fading environments

The average level crossing rate (LCR) and average fading duration (AFD) criterions are applied to analyze the selection combining (SC) diversity for wireless communication systems over correlated-Rayleigh and correlated-Rice fading in this paper. The scenarios of the fading channel models are characterized as 4 generalized and experimental distributions, e.g., Rayleigh, Rice, Nakagami-m, and Weibull distributed statistics. Moreover, both of independent and correlated proprieties between branches are also involved for consideration. For purpose of unifying and clarifying the average LCR and AFD performance formulas results from the evaluation for SC diversity, it is not only the results from our research presented, but some of the published results are also cited and illustrated by numerical evaluation again in this study.     

我国股市收益率非线性下的随机游走检验

在对中国股市收益率的分布和独立性进行检验后,我们发现该收益率序列不独立、不服从正态分布且存在显著的非线性关系。随后我们运用乘积过程模型对中国股市收益率在非线性模型下的随机游走假设进行了检验,认为中国股市收益率服从随机游走假设。     

Geometrical attacks resilient statistical watermark decoder using polar harmonic Fourier moments

This paper presents a new robust multiplicative watermark detector. Due to the strong robustness against various attacks, polar harmonic Fourier moment (PHFM) magnitudes are used as the employed watermark carrier. The distribution of PHFM magnitudes is highly non-Gaussian and can be properly modeled by a heavy-tailed probability density function (PDF). In this paper, we proved that Weibull distribution can suitably fit the distribution of PHFM magnitudes, and based on this, we presented a statistics-based watermark decoder by using the Weibull as a prior for the PHFM magnitudes. In watermark embedding, a multiplicative manner was used to embed watermark information in PHFM magnitudes of the highest entropy blocks to achieve better robustness and imperceptibility. In watermark detection, we developed a Weibull distribution-based statistical watermark decoder, which uses the maximum likelihood (ML) decision rule. Compared with Bessel K form (BKF), Cauchy, and generalized Gaussian (GG)-based decoders, the Weibull-based decoder demonstrates stronger robustness. In addition, the proposed watermark decoder is more robust against geometrical and common image processing attacks than existing statistical watermark decoders.     

Explicit expressions for the Leimkuhler curve in parametric families

In this paper we obtain the Leimkuhler curve in the case of some important statistical distributions proposed in the informetrics and econometrics literature. In this way, we complete the previous work of Burrell [Burrell, Q. L. (2005). Symmetry and other transformation features of Lorenz/Leimkuhler representations of informetric data. Information Processing and Management, 41, 1317–1329], where several open problems were stated. To do this, we use a recent and general definition of the Leimkuhler curve proposed by Sarabia [Sarabia, J. M. (2008a). A general definition of the Leimkuhler curve. Journal of Informetrics, 2, 156-163], and a new representation of the Leimkuhler curve in terms of the first-moment distribution of the population. Specifically, we obtain the Leimkuhler curve of the following distributions: classical and exponentiated Pareto distributions; three-parameter lognormal distribution; generalized gamma distribution, which includes to the exponential and classical gamma distributions among others; generalized beta distribution of the first kind and generalized beta distribution of the second kind, which includes as particular or limiting cases next important families like beta distribution of the second kind, Singh–Maddala, Dagum, Fisk or Lomax distributions. All the obtained Leimkuhler curves can be computed easily.     

关于学科期刊引文密度的讨论

在针对基础学科、工程技术、社会科学领域的多学科期刊引文密度进行分析的基础上,引入学科期刊平均引文密度与学科期刊最可几引文密度表征学科期刊的引文密度水平。使用对数正态分布函数拟合学科期刊引文密度的频数分布显示,拟合峰值接近学科期刊最可几引文密度。最后,提出对数正态分布函数的特征参数可以表征学科期刊引文密度水平的观点。     

Simultaneous H∞ stabilization for large-scale systems within distributed wireless networked control framework over fading channels

In this paper, the simultaneous H_∞ stabilization problem is investigated for a physically interconnected large-scale system which works in multiple operation modes. A distributed wireless networked control framework is introduced, in which the distributed dynamic output feedback controllers not only use the local measurements, but also receive the neighboring controllers’ broadcasts via wireless networks. The channel fading in wireless communications is described as the Rice fading model. Our focus is on the design of the distributed controllers such that the large-scale system is mean-square stable in each operation mode and achieves a prescribed H_∞ disturbance attenuation level. By employing the Lyapunov functional method and related stochastic analysis techniques, a sufficient condition on the existence of desired controllers is presented, and the parameterization of the controller gains is derived. Finally, a numerical example is utilized to illustrate the feasibility of the proposed scheme.     

Moments generating function of the harmonic mean of two non-identical gamma random variables and its applications in wireless communications

In this paper, a closed-form expression for the moments generating function of the half-harmonic mean of two independent, not necessarily identically distributed gamma random variables with arbitrary parameters is presented. This statistical result is useful to the performance analysis of dual-hop wireless communication systems with amplify-and-forward relays in a Nakagami-m fading environment. The proposed mathematical analysis is substantiated by various numerically evaluated and computer simulation results.     

基于高校门户网站的有向网络模型

通过对广西师范大学门户网站的网页进行分层搜索,本文组建了一个以网页为节点、超链为边的有向网络,发现它的出八度分布均呈现良好的幂律分布特性,出度分布在开始部分出现弯曲.根据这些特性,本文提出了一种含有增长,择优和重连机制的有向网络演化模型,模型的演化机制较好的反应了广西师范大学网的这些特性.     

State estimation for jump markov nonlinear systems of unknown measurement data covariance

For state estimation of high accuracy, prior knowledge of measurement noise is necessary. In this paper, a method for solving the joint state estimation problem of jump Markov nonlinear systems (JMNSs) without knowing the measurement noise covariance is developed. By using the Inverse-Gamma distribution to describe the dynamics of measurement noise covariance, the joint conditional posterior distribution of the state variable and measurement noise covariance is approximated by a product of separable variational Bayesian (VB) marginals. In the newly constructed approach, the interacting multiple model (IMM) algorithm, as well as the particle-based approximation strategy, is employed to handle the computationally intractable problem and the nonlinear characteristics of systems, respectively. An interesting feature of the proposed method is that the distribution of states is spanned by a set of particles with weights, while the counterpart of measurement noise covariance is obtained analytically. Moreover, the number of particles is fixed under each mode, indicating a reasonable computational cost. Simulation results based on a numerical example and a tunnel diode circuit (TDC) system are presented to demonstrate that the proposed method can estimate the measurement noise covariance well and provide satisfied state estimation when the statistics of the measurement are unavailable.     

浅析期刊影响因子及其扩展研究

根据期刊影响因子的定义,分析了影响期刊影响因子的相关因素。然后基于时间和专业因素对影响因子的影响,利用新兴学科的期刊文献引用量在一段较长时间内呈现短期内快速增长并到达一个顶峰、之后呈现逐年下降趋势的特点,建立了期刊发行期内基于W eibu ll分布的扩展影响因子模型。最后结合R因子和两年期刊影响因子对JCR中的8种生物类期刊进行了实证研究。     

Distributed Kalman filtering over sensor networks with fading measurements and random link failures

This paper investigates the distributed state estimation problem for a linear time-invariant system characterized by fading measurements and random link failures. We assume that the fading effect of the measurements occurs slowly. Additionally, communication failures between sensors can affect the state estimation performance. To this end, we propose a Kalman filtering algorithm composed of a structural data fusion stage and a signal date fusion stage. The number of communications can be decreased by executing signal data fusion when a global estimate is required. Then, we investigate the stability conditions for the proposed distributed approach. Furthermore, we analyze the mismatch between the estimation generated by the proposed distributed algorithm and that obtained by the centralized Kalman filter. Lastly, numerical results verify the feasibility of the proposed distributed method.     

Minimal-order observer-based distributed fault detection and isolation for stochastic multi-agent systems

In this paper, the problem of distributed fault detection and isolation (FDI) is investigated for a class of linear discrete-time stochastic multi-agent systems (MASs) with additive Gaussian white noises. By using the information received from the generalized neighbor agents, a set of residual generators are designed for one agent based on the minimal-order observers. After dividing the MAS into several first-order components, the residuals are designed to be robust to the faults in some designated components and sensitive to the faults in all the other components. Combining with FDI strategies, multiple concurrent faults in the generalized neighbor agents can be detected and isolated simultaneously. In addition, a necessary condition is established for the observer to have the minimum order. By means of the statistical method, a set of hypothesis tests are derived to detect and isolate the faults. Finally, a simulation example is presented to show the feasibility and effectiveness of the proposed methods.     

The Kumaraswamy Weibull distribution with application to failure data

For the first time, we introduce and study some mathematical properties of the Kumaraswamy Weibull distribution that is a quite flexible model in analyzing positive data. It contains as special sub-models the exponentiated Weibull, exponentiated Rayleigh, exponentiated exponential, Weibull and also the new Kumaraswamy exponential distribution. We provide explicit expressions for the moments and moment generating function. We examine the asymptotic distributions of the extreme values. Explicit expressions are derived for the mean deviations, Bonferroni and Lorenz curves, reliability and Rényi entropy. The moments of the order statistics are calculated. We also discuss the estimation of the parameters by maximum likelihood. We obtain the expected information matrix. We provide applications involving two real data sets on failure times. Finally, some multivariate generalizations of the Kumaraswamy Weibull distribution are discussed.     

中国省际煤炭资源流动的集中程度与位序-规模变化

本文首先运用基尼系数研究我国1985-2010年省际煤炭资源流动集中程度的变化,结论显示：1985-2010年我国煤炭资源的输出和输入都稍有分散,但煤炭输出相对于输入较集中,从各个年份上看,这与我国煤炭资源生产区和消费区分布不平衡的情形是一致的。然后,运用齐夫定律,进一步探讨其位序-规模分布规律,结论显示：各时点煤炭资源流动的位序-规模分布均满足齐夫法则。煤炭资源输出的均衡程度略有增大,规模分布形态是单分形,齐夫参数q值始终大于1且逐年减小,说明煤炭资源输出体系整体规模差异正在减小,规模分布逐渐均衡,无标度区向西北部地区移动。煤炭资源输入的均衡程度也略有增大,但规模分布形态由双分形演化为单分形,之后,q值逐渐减小,表明高位序节点发展缓慢,中低位序节点较为发育,规模分布逐渐均衡,无标度区向东南地区移动。这种变化主要与各地煤矿煤炭资源情况、煤炭流通体制、经济水平、产业结构有关。     

期权-博弈方法在产学研协同创新利益分配中的应用

将期权和博弈作为整体方法研究产学研协同创新的多方利益分配问题。根据各投资阶段的期权种类并基于实物期权的复合性,采用三叉树期权定价模型评估不同合作方式下项目的复合实物期权收益,运用合作博弈理论研究期权收益如何在各主体间进行分配。采用初等无穷小量阶数估计以及随机分析法求解得到的三叉树期权定价模型,考虑战略决策和管理柔性的价值,与Shapley值法结合并改进该方法在分配合作剩余时忽略风险的不足,并确保按各方贡献程度划分收益。     

Spectral efficiency for selection combining RAKE receivers over Weibull fading channels

Novel closed-form expressions for the probability density function and the average output signal-to-noise ratio at the output of a selection combiner in Weibull fading are derived. Using these expressions, the spectral efficiency of a direct sequence code division multiple access system is analytically obtained and performance evaluation results are presented.     

复值型数据Improper线性回归模型的估计(英文)

复随机变量称为"improper"随机变量,若它的"伪"协方差阵不为0,否则称为"proper"随机变量.研究了误差服从独立同分布的improper复高斯分布的线性回归模型.利用极大似然方法和2阶段最小二乘方法来估计回归系数.模拟表明,这2种方法与经典复版本的最小二乘法有不同之处,并将该方法用于实际风信号数据的处理.     

考虑使用环境差异的产品可靠性监控

在统计过程控制的研究中,产品的可靠性与产品的使用环境息息相关。当对多产品同时监控时,少有研究将各产品的不同使用环境加以考虑。传统控制图通常假设各产品的故障率服从相同参数,但现实生活中,不同的使用环境使得相同故障率的假设很难成立。本文基于似然比统计量提出了一种新的控制图。该统计量考虑了使用环境差异造成的产品故障率的个异性,用于产品总体的可靠性监控。仿真结果表明,本文提出的控制图在不同样本量及环境差异程度下均有很好的检测能力。