Compared with the traditional converter transformer,the new-type converter transformer has particular connection scheme,for which the remnant conversion method is proposed to calculate its short-circuit faults.

In order to explore the method to calculate the short-circuit faults of a new-type converter transformer,which can provide the theoretical foundation for the setting of relay protection and design of automatic control device in the new-type converter transformer,This paper studied the residual voltage transformation method which is an effective method to calculate short circuit fault.

Under the background of DATIAN doub- le-arch tunnel in construction of the Tonghuang Highway,cyclic variable method is used to optimize the parameters of SVM based on SVM algorithm in order to present the nonlinear relation between the data,meanwhile the nonlinear model for displacement is established.

Compared to other widely used direct search method,random search methods and cyclic variable method have the advantages of simpleness and clear,easily programmed and smple implementation,especially when the gradient is burdensome or impossible to calculate.

The cyclic variable method is used to optimize parameters of SVM so as to establish the nonlinear time series model.

With proper method of variable substitution, the soluble method to two kinds of inegrable equation of Riccati form is found, and the general integral expressions are given.

It is offered Euler differential equations depending on a parameter λ,and given the general solution formula express of them by method of variation replacement,method of variation position transformation,method of linearization,and method of reduction of order.

Two types of new Abel differential equation are structured by method of variation replacement, variation position transformation and compound function derivation law.

Application of "variable substitution" in higher mathematics;