RETRACTED: A Hybrid Nonlinear Active Noise Control Method Using Chebyshev Nonlinear Filter

Investigations into active noise control (ANC) technique have been conducted with the aim of effective control of the low-frequency noise. In practice, however, the performance of currently available ANC systems degrades due to the effects of nonlinearity in the primary and secondary paths, primary noise and louder speaker. This paper proposes a hybrid control structure of nonlinear ANC system to control the non-stationary noise produced by the rotating machinery on the nonlinear primary path. A fast version of ensemble empirical mode decomposition is used to decompose the non-stationary primary noise into intrinsic mode functions, which are expanded using the second-order Chebyshev nonlinear filter and then individually controlled. The convergence of the nonlinear ANC system is also discussed. Simulation results demonstrate that proposed method outperforms the FSLMS and VFXLMS algorithms with respect to noise reduction and convergence rate.     

非平稳随机激励下结构体系动力可靠度时域解法

将结构动力方程写成状态方程形式,采用精细积分法对其进行数值求解,导出了非平稳激励下结构随机响应的时域显式表达式,该过程的计算量仅相当于两次确定性时程分析的计算量. 基于该显式表达式,结合首次超越失效准则,提出了非平稳随机激励下结构体系动力可靠度的数值模拟算法. 与功率谱方法相比,该方法无需同时在时频域内进行大量数值积分,也无需引入关于响应过程跨越界限次数概率分布, 以及各失效模式相关性等方面的假定. 通过数值算例, 对比了该方法与泊松过程法、马尔可夫过程法、传统蒙特卡罗法的计算精度和计算效率,结果显示该方法具有理想的精度和相当高的效率.      

Fluctuations and pseudo long range dependence in network flows: A non-stationary Poisson process model

In the study of complex networks (systems), the scaling phenomenon of flow fluctuations refers to a certain power-law between the mean flux (activity) < F_i> of the i-th node and its variance σ_i as F_{i ∝ <Fi^α. Such scaling laws are found to be prevalent both in natural and man-made network systems, but the understanding of their origins still remains limited. This paper proposes a non-stationary Poisson process model to give an analytical explanation of the non-universal scaling phenomenon: the exponent α varies between 1/2 and 1 depending on the size of sampling time window and the relative strength of the external/internal driven forces of the systems. The crossover behaviour and the relation of fluctuation scaling with pseudo long range dependence are also accounted for by the model. Numerical experiments show that the proposed model can recover the multi-scaling phenomenon.}     

Hawking Radiation of Dirac Particles in a Variable-Mass Kerr Space-Time

The Hawking effect of Dirac particles in a variable-mass Kerr space-time is investigated by using a method called as the generalized tortoise coordinate transformation. The location and the temperature of the event horizon of the non-stationary Kerr black hole are derived. It is shown that the temperature and the shape of the event horizon depend not only on the time but also on the angle. However, the Fermi–Dirac spectrum displays a residual term which is absent from that of Bose–Einstein distribution.     

多点非均匀调制演变随机激励下结构地震的响应

针对大跨度结构在非均匀调制演变随机激励作用下,考虑行波效应时的非平衡随机地震响应问题,应用虚拟激励法进行了分析,由于虚拟激励法自动计及了参振振型的互相关项以及激励之间的互相关项,理论上是精确解,时变功率谱的计算采用精细逐步积分格式,使计算效率进一步得到提高。     

Solution of sector plate by Fourier-Bessel series

In this paper a solution of deflection in the form of Fourier-Bessel double series with supplementary terms is proposed to analyse bending and vibration problems of thin elastic sector plate with various edge conditions. This solution is suitable to a wider range, convenient for calculation and it is in an analytical form. As computational examples, the distribution curves of deflection and bending moment of plates with various sector angles, simply supported or clamped along the radial edges under uniform or concentrated load are obtained and the result are compared with the numerical results of related references. Thus the range of application of the Fourier series method with supplementary terms is extended. Frequencies and nodal lines in free vibration of plates with various sector angles simply supported along the radial edges are also given in this paper.Communicated by Hsueh Dai-wei.     

Non Stationary Multi-Armed Bandit: Empirical Evaluation of a New Concept Drift-Aware Algorithm

The Multi-Armed Bandit (MAB) problem has been extensively studied in order to address real-world challenges related to sequential decision making. In this setting, an agent selects the best action to be performed at time-step t, based on the past rewards received by the environment. This formulation implicitly assumes that the expected payoff for each action is kept stationary by the environment through time. Nevertheless, in many real-world applications this assumption does not hold and the agent has to face a non-stationary environment, that is, with a changing reward distribution. Thus, we present a new MAB algorithm, named f-Discounted-Sliding-Window Thompson Sampling (f-dsw TS), for non-stationary environments, that is, when the data streaming is affected by concept drift. The f-dsw TS algorithm is based on Thompson Sampling (TS) and exploits a discount factor on the reward history and an arm-related sliding window to contrast concept drift in non-stationary environments. We investigate how to combine these two sources of information, namely the discount factor and the sliding window, by means of an aggregation function f(.). In particular, we proposed a pessimistic (f=min), an optimistic (f=max), as well as an averaged (f=mean) version of the f-dsw TS algorithm. A rich set of numerical experiments is performed to evaluate the f-dsw TS algorithm compared to both stationary and non-stationary state-of-the-art TS baselines. We exploited synthetic environments (both randomly-generated and controlled) to test the MAB algorithms under different types of drift, that is, sudden/abrupt, incremental, gradual and increasing/decreasing drift. Furthermore, we adapt four real-world active learning tasks to our framework—a prediction task on crimes in the city of Baltimore, a classification task on insects species, a recommendation task on local web-news, and a time-series analysis on microbial organisms in the tropical air ecosystem. The f-dsw TS approach emerges as the best performing MAB algorithm. At least one of the versions of f-dsw TS performs better than the baselines in synthetic environments, proving the robustness of f-dsw TS under different concept drift types. Moreover, the pessimistic version (f=min) results as the most effective in all real-world tasks.     

The maxima and sums of multivariate non-stationary Gaussian sequences

Let {Xk1, ···, Xkp, k ≥ 1} be a p-dimensional standard(zero-means, unit-variances)non-stationary Gaussian vector sequenceIn this work, the joint limit distribution of the maxima of {Xk1, ···, Xkp, k ≥ 1}, the incomplete maxima of those sequences subject to random failure and the partial sums of those sequences are obtained.     

我国房地产财富效应分析——基于非平稳面板计量

90年代住房商品化改革以来,我国房地产市场迅速发展.十二五规划明确提出要提高我国居民消费率.研究房地产市场的财富效应为我国房地产市场政策调控提供有效的参考,具有重要的现实意义.在对我国房地产财富效应传导机制进行研究的基础上,利用2003-2011年我国3个省市自治区的季度面板数据,采用非平稳面板计量方法对我国房地产市场财富效应进行了分析.研究结果表明:我国房地产财富效应存在明显的地区性差异.房地产市场调控政策应当实行有针对性的差异化调控.     

线性随机结构的非平稳随机响应变异性分析

对于具有随机参数的结构受到非平稳随机激励的问题，给出了结构随机响应变异系数的虚拟激励摄动算法。它应用虚拟激励法先将随机荷载转化为确定性荷载，以使随机问题精确地转化为仅结构参数具有随机性的问题，从而将问题归结为应用随机摄动法求解单随机问题。求解过程简单高效，且有较高的精度。