Correlation Analysis of Influencing Factors and the Monthly Displacement Increment of a Hydrodynamic Landslide Using a Pseudo-Maximum-Likelihood-Estimation-Mixed-Copula Approach

Heavy rainfall and changes in the water levels of reservoirs directly affect the degree of landslide disasters in major hydropower project reservoir areas. Correlation analyses of rainfall- and water-level fluctuations with landslide displacement changes can provide a scientific basis for the prevention and early warning of landslide disasters in reservoir areas. Because of the shortcomings of the traditional correlation analysis based on linear assumptions, this study proposed the use of a pseudo-maximum-likelihood-estimation-mixed-Copula (MLE-M-Copula) method instead of linear assumptions. We used the Bazimen landslide in the Three Gorges Reservoir Area as a case study to carry out the correlation analysis of the rainfall, water-level fluctuations, and landslide displacement. First, we selected several appropriate influencing factors to construct four candidate Copula models and estimated the parameters using the pseudo-MLE method. After the goodness-of-fit test, we selected the M-Copula model as the optimal model and used this model to study correlations between the monthly displacement increment of the landslide and influencing factors. We then established the joint distribution functions of these correlations. We computed and analyzed the overall and tail correlations between the displacement increment and the influencing factors, and we constructed the conditional probability distribution of the monthly displacement increment for different given conditions. The results showed that the pseudo-MLE-M-Copula method effectively quantified the correlation between the rainfall, reservoir-level fluctuations, and landslide displacement changes, and we obtained the return periods and value at risk of the influencing factors of the Bazimen landslide under different rainfall conditions and reservoir-level changes. Furthermore, the tail correlations between the monthly displacement increment of the landslide and the rainfall- and reservoir-level changes were higher than the overall correlations.

Analysis for Feasibility of the Method for Bars Driving the Ball Tensegrity Robot

In tensegrity robots, the ball tensegrity robot attracts the most attention. The method of driving the ball tensegrity robot is analyzed here. At first, the ball tensegrity structure is described, and its mathematical model is setup. Through analysis, the method for driving bars to make the robot deform and roll is selected. A method for analyzing the deformation of the tensegrity robot is studied. In the method, the nodes are regarded as the objects and displacement increment of the nodes is the product of displacement mode of the robot structure and unbalanced forces on the nodes. The method is applied to analyze deformation of the robot driven by the bars. The methods of driving the robot on two ground-touching triangles are studied. Then, through experiments with the physical model, the methods are verified. A continuous movement of the model is done further to prove the correctness of the analysis. The method for driving bars to make the ball tensegrity robot deform and roll is obtained finally.