Numerical Simulation On Blasting Cavity And Experimental Study Of Grouting For Supporting In Soil

This paper analyzes the efficiency of WTI crude oil markets based on detrended fluctuation analysis (DFA).First, we study the monofractal of spot and futures markets of WTI crude oil employing detrended fluctuation analysis. Empirical results show that the crude oil markets were anti-persistent in the short-term while weakly persistent in the long-term. That is to say, the oil markets were not efficient in the short-term but almost efficient in the long-term. Employing the technique of rolling windows, combining the method of multiscale analysis, we find that the crude oil market were overall more and more efficient over time under different time scale intervals. But the dynamics of efficiency for different time scale intervals were not consistent. Additionally, market external events could affect the short-term scaling behaviors while market internal factors and economics cycling could influence the long-term scaling behaviors of crude oil markets.Second, employing multifractal detrended fluctuation analysis (MF-DFA), we investigate the multifractality of two markets. Our evidence shows that the two markets were multifractal in the short-term while mono-fractal in the long-term. The short-term multifractality presented an about half-yearly cycling period. The markets were not efficient in the short-term and were almost to be weak-form efficient in the long-term. In other words, the oil markets were unpredictable in the long-term. Employing the method of shuffling and phase randomization, we analyze the contribution of short-term multifractality. Empirical results show that the main source of short-term multifractality was fat-tail distribution of returns, not the long-range correlations of large and small fluctuations. Using the method of rolling windows, we investigate the dynamics of short-term fractal structure of oil markets. Evidence showed that crude oil markets were more and more efficient over time. However, some essential events such as the Gulf War and could make important effects on the market structure.At last, as an innovation, we analyze the cross-correlations between oil spot and futures markets based on detrended cross-correlation analysis. Our evidence indicates that the short-term cross-correlations were nonlinear, multifractal specifically. Small fluctuations were strong positively correlated while large fluctuations were strong negatively correlated in the short-term. Two markets were almost not cross-correlated in the long-term.