Papers by Keyword: Stationarity

Abstract: When analyzing time series an important issue is to decide whether the time series is stationary or nonstationary. Fixed sample statistical tests for that problem are well studies in the literature. In this paper we propose a moving variance ratio statistic to monitor the stationarity for normal sequence. Our Monte Carlo studies show that the proposed monitoring procedure has satisfactory test power and that the decision can often be made very early.

Abstract: Wheel diameter difference has great impact on the operation performance of vehicles which are traveling on the curved bridge. A simulation analysis model was built to analyze the influence of wheel diameter difference on safety and stationarity of vehicles on the curved bridge. The results demonstrate that along with the increase of wheel diameter difference, the security of vehicles on the curved bridge decreases and the vehicles run unsteadily. So the wheel diameter difference should be diminished as much as possible, especially strictly controlling the wheel diameter difference of high-speed vehicles.

Abstract: EEG (electroencephalography), as a noninvasive and inexpensive method, is widely used to measure brain function and make inferences about regional brain activity. The stationarity of EEG has been investigated by many researchers, while the stationarity of EEG segment with ERPs (Event-related Potentials) has hardly been concerned about. It is necessary to analyze the stationarity of this kind of EEG. In this paper, we concentrate on the stationarity of the EEG with ERPs by testing the stationarity of 500ms EEG segments with ERPs recorded from six subjects in two types of experiments. The results suggest that selected EEG segment whose length is larger than 190ms remains to be stationarity and all epochs duration less than 40ms is considered to be stationary, whichever channel the data is from and whatever type of cognitive task is performed in the experiment. This is an obvious difference between the stationarity of EEG with ERPs and that of EEG, which is reported to be stationary as long as its length is less than 12s.

Abstract: This paper takes a new-type 3-TPT 3-DOF parallel machine tool as the object of study, established the positive and negative solution of kinematic equations of the machine, and derived the Jacobian matrix and Jacobian inverse matrix of the machine tool. On this basis, the singularity and stationarity of the machine tool were researched by using Matlab and got the expression of the absolute value of Jacobian matrix determinant of the machine tool. The velocity distribution curves of telescopic driving rods of the machine tool were simulated, too. The results show that the machine tool has advantages such as good stationarity and no singularity and so on. The study provides certain theoretical basis for the structural optimum design and performance analysis of parallel machine tool.