Output Dead-Time in Point Processes

When events of temporal point processes are too close to each other they can be erased by dead-time effects. Among various possible mechanisms of dead-time, the output dead-time is the most important. Dead-time effects modify the statistical properties of point processes and some of these modifications are analyzed in this article. To do so, we note that a point process is defined by the distance between its successive points called life-time which constitutes a discrete time positive signal. The dead-time mechanism is a system which transforms such a signal into another discrete time positive signal. Except in very specific cases this transformation cannot be expressed in closed form. We show, however, that it can be written in a recursive form analogous to the state representation of systems. By using this recursion, various statistical properties of point processes with dead-time are analyzed in computer experiments. In this study, we focus on the probability distribution of the intervals between points and the coincidence function which describes the second-order properties of the point process. For the rare processes where theoretical calculations are possible there is an excellent agreement between experiment and theory.     

组合约束下单一产品信号消费者决策贡献率

信号是制造商面对消费者逆向选择问题所采取的重要手段。只有了解消费者在组合约束下产品属性及其水平的重要性排序,制造商才能针对性运用产品属性对消费者实施信号传递。正交设计实验结果显示,具有信号作用的产品属性在不同产品之间具有相似性,而组合约束下单一产品信号消费者决策贡献率具有较大差异,产品属性水平对消费者效用也会产生不同程度的影响。     

WLAN环境下移动点切换时机选择算法

大型无线局域网环境中移动点在不同AP间进行高速移动时需要进行切换,切换过程产生的延迟会影响无线局域网的服务质量,尤其对于多媒体应用,减小移动点在AP之间的切换延迟是提高无线局域网服务质量的关键。该文提出了确定下一个AP的确认、认证与连接过程开始的最佳距离和最佳接收信号强度的算法,算法结合移动点的移动速度、移动偏移角度等因素来确定最佳切换时机,提高切换成功率,减少切换延迟。算法已在地铁信号系统国产化预研项目中得到应用。     

Adaptive threshold method for peak detection of surface electromyography signal from around shoulder muscles

This paper illustrates the accurate identification of the surface electromyography signal obtained from the shoulder muscles (Teres, Trapezius and Pectoralis) of amputee subjects with three different arm motions (elevation, protraction and retraction). During the acquisition of the signal, a variety of variations (amplitude, frequency and noise) were introduced into the acquired signal which will misguide in the prediction of motion of the shoulder. Therefore, a novel approach has been aimed to adaptively adjust the threshold of Teager energy operator in order to filter the unwanted peaks in the pre-processing stage of the surface electromyography (SEMG) signal. Results show that the proposed approach is accurate and effective in the analysis of biomedical signal where peaks are important to detect without the knowledge of the shape of the waveform. As clinical research continues, these algorithms helps us to process SEMG signal and the identified signal would be used to design more accurate and efficient controllers for the upper-limb amputee.     

Fitting spatial regressions to large datasets using unilateral approximations

Maximum likelihood estimation of a spatial model typically requires a sizeable computational capacity, even in relatively small samples, and becomes unfeasible in very large datasets. The unilateral approximation approach to spatial model estimation (suggested in Besag 1974 Besag, J. E. 1974. Spatial interaction and the statistical analysis of lattice systems. Journal of the Royal Statistical Society. Series B (Methodological) 36 (2):192–236.[Crossref], [Web of Science ®] , [Google Scholar]) provides a viable alternative to maximum likelihood estimation that reduces substantially the computing time and the storage required. In this article, we extend the method, originally proposed for conditionally specified processes, to simultaneous and to general bilateral spatial processes over rectangular lattices. We prove the estimators’ consistency and study their finite-sample properties via Monte Carlo simulations.     

Some factors affecting statistical power of approximate tests in the linear mixed model for longitudinal data

Different longitudinal study designs require different statistical analysis methods and different methods of sample size determination. Statistical power analysis is a flexible approach to sample size determination for longitudinal studies. However, different power analyses are required for different statistical tests which arises from the difference between different statistical methods. In this paper, the simulation-based power calculations of F-tests with Containment, Kenward-Roger or Satterthwaite approximation of degrees of freedom are examined for sample size determination in the context of a special case of linear mixed models (LMMs), which is frequently used in the analysis of longitudinal data. Essentially, the roles of some factors, such as variance–covariance structure of random effects [unstructured UN or factor analytic FA0], autocorrelation structure among errors over time [independent IND, first-order autoregressive AR1 or first-order moving average MA1], parameter estimation methods [maximum likelihood ML and restricted maximum likelihood REML] and iterative algorithms [ridge-stabilized Newton-Raphson and Quasi-Newton] on statistical power of approximate F-tests in the LMM are examined together, which has not been considered previously. The greatest factor affecting statistical power is found to be the variance–covariance structure of random effects in the LMM. It appears that the simulation-based analysis in this study gives an interesting insight into statistical power of approximate F-tests for fixed effects in LMMs for longitudinal data.     

基于线性正则变换的时频信号分离方法

时频信号分析是当今信号处理领域研究的一个热点问题,各种时频分布函数得到了广泛的研究和应用。线性正则变换是一种重要的时频分析工具。文中研究了线性正则变换与传统时频分布函数的关系;并基于这些关系,提出了一种新的时频信号分离方法,能够把在时频面上互不重叠、但在时域和频域均存在较强耦合的多分量合成信号有效地分离。仿真实例表明了该方法的正确性和实用性。     

基于环境信息和金融市场不对称博弈模型分析

由于金融市场存在信息不对称使得投资决策者缺乏必要的环境信息,从而导致了投资决策信息不完全、金融资金分配不合理等问题。本文在Nikolaou,Chymis和Evangelinos^[5]提出的环境信息、金融市场不对称博弈模型的基础上,引入政府局中人行为策略,构建了政府、企业与金融市场之间的博弈模型。通过设置相关参数发现,该博弈模型能够覆盖Nikolaou,Chymis和Evangelinos^[5]提出的模型,并证明了在政府局中人参与并满足一定条件的情况下,由环境信息缺失引起的信息不对称问题可以通过引入第三方国际环境审计来解决,从而为我国环境污染问题的化解机制提供新的研究角度。