A stochastic equivalence approach for an Ornstein-Uhlenbeck process driven power system dynamics

This paper develops a stochastic equivalence approach for an Ornstein-Uhlenbeck process-driven power system. The concept of stochastic equivalence coupled with stochastic differential rule plays the important role to develop the stochastic equivalence approach of this paper. This paper also develops the prediction theory of power system dynamics with the OU process as well.

Superoscillations and Analytic Extension in Schur Analysis

We give applications of the theory of superoscillations to various questions, namely extension of positive definite functions, interpolation of polynomials and also of R-functions; we also discuss possible applications to signal theory and prediction theory of stationary stochastic processes. In all cases, we give a constructive procedure, by way of a limiting process, to get the required results.

Assessment and Prediction for China’s Regional Agricultural Sustainability

This paper proposes a sustainable agricultural development index (SADI) and a hybrid grey model for measuring the changes in agricultural sustainability over time. Firstly, a comprehensive indicator system for co-evaluating the level of agricultural economy, resource, environment, ecology, technology and rural society is presented based on a holistic understanding of agricultural sustainability. Then, the entropy-based TOPSIS model, grey prediction theory and genetic algorithm are combined to build a synthesis method for evaluating and predicting agricultural sustainability and detecting its regional heterogeneity. Furthermore, an empirical study at a provincial scale is conducted by collecting panel data from 2003 to 2017. The result shows that regional agricultural sustainability in China will continue to improve, with different rates in the different provinces from 2020 to 2030. And the regional heterogeneity of agricultural sustainability will increase significantly.

Prevention of Nanoscale Fines in Open-Hole Horizontal Coalbed Methane Wells During the Drainage Process

Because coal is quite weak compared with conventional sandstone, shear failure downhole will produce a large amount of nanoscale coal fines during the drainage process. Since the size of pores in coal is on the nanoscale range, these fines will sometimes cause serious damage problems downhole. The origin of coal fines cannot be explained by conventional sand prediction theory, which was previously designed for conventional sandstone. During the drainage process, the in situ stress change in coal was caused by the combination of the poroelastic effect, methane desorption and compression around the borehole. To prevent nanoscale coal fines, the critical pressure drawdown can be predicted by the comprehensive stress model. A special test was also designed to determine the key model parameters, making the model easy to use. It was proven that the induced stress due to methane desorption can exaggerate the shear failure, which is different from conventional sand prediction theory. Based on the stress model, the safe window of bottom hole pressure was applied for open-hole horizontal wells to prevent the origin of nanoscale coal fines.