Volume 1 Issue 1
Authors: Robiah Adnan; Xiaojian Xu; Seyed Ehsan Saffari; Adeleh Hashemi Fard
Abstract: A Poisson regression model is well-known for modeling the data with response variable in form of counts. However, one often encounters the situation with excess zeros occurred in the observed responses. Therefore, Poisson model is not suitable any more for this kind of data. Thus, we propose to use a hurdle negative binomial model. Furthermore, the response variable in such cases is truncated for some values. So, a truncated hurdle negative binomial model is introduced on count data with many zeros. In this model, we consider a response variable and one or more than one explanatory variables. The estimates using the maximum likelihood method are discussed and the goodness-of-fit for the regression model is examined. We study the effects of right truncation in terms of parameters estimation and their standard errors via an example and a simulation.
Keywords: Hurdle Negative Binomial Regression; Truncated Data; Maximum Likelihood Method; Goodness-of-fit
Authors: Z. Kalateh Bojdi; S. Ahmadi-Asl; A. Aminataei
Abstract: In this manuscript, we deal with a spectral method for the numerical approximation of boundary value problems associated with a high order linear differential-difference equation with polynomial coefficients. The basic idea is to reduce the analysis of the problem to the solution of a system of linear equations satisfied by the coefficients of the Jacobi projection. This is the main result stated and proved. Further, several numerical experiments are analyzed in order to illustrate this approach. In addition, the basic tool of the manuscript is the description of an operational matrix approach to the shift, the derivative, and the linearization formula for Jacobi polynomials.
Keywords: General Jacobi Matrix Method, Differential-Difference Equations, Coefficients of the Jacobi Projection, Polynomial Coefficients
Authors: Andres Feijoo; Jos′e Luis Pazos; Daniel Villanueva
Abstract: Asynchronous wind turbines (WT) have been among the most used type of converters in wind energy plants. Conventional asynchronous WTs were installed during the first years of wind energy research, but doubly-fed induction generator (DFIG) WTs and other types have also been added for current and future use. So, the massive presence of such machines in electrical networks means it is important to develop dynamic and steady-state models to describe their behaviour. This paper presents a review of steady-state models of asynchronous WTs for the load flow analysis (LF) that have been presented in recent years. A large number of conventional asynchronous WTs can still be found in electrical systems in many different countries all over the world. This fact constitutes a reason for the authors not to overlook them when studying the operation of such systems. In addition, there has been some discussions about these models over the last few years.
Keywords: Asynchronous Wind Turbine; Load Flow Analysis; Newton-Raphson