Browsing by Author "Weber, Gerhard Wilhelm"

Now showing 1 - 3 of 3

Citation - WoS: 9
Electricity Price Modelling for Turkey
(Springer-verlag Berlin, 2012) Yildirim, Miray Hanim; Yıldırım, Miray Hanım; Ozmen, Ayse; Bayrak, Ozlem Turker; Weber, Gerhard Wilhelm; 56416; Endüstri Mühendisliği
This paper presents customized models to predict next-day's electricity price in short-term periods for Turkey's electricity market. Turkey's electricity market is evolving from a centralized approach to a competitive market. Fluctuations in the electricity consumption show that there are three periods; day, peak, and night. The approach proposed here is based on robust and continuous optimization techniques, which ensures achieving the optimum electricity price to minimize error in periodic price prediction. Commonly, next-day's electricity prices are forecasted by using time series models, specifically dynamic regression model. Therefore electricity price prediction performance was compared with dynamic regression. Numerical results show that CMARS and RCMARS predicts the prices with 30% less error compared to dynamic regression.
Citation - WoS: 8
Citation - Scopus: 8
Modern tools for the time-discrete dynamics and optimization of gene-environment networks
(Elsevier, 2011) Defterli, Ozlem; Defterli, Özlem; Fuegenschuh, Armin; Weber, Gerhard Wilhelm; 31401; Matematik
In this study, we discuss the models of genetic regulatory systems, so-called gene-environment networks. The dynamics of such kind of systems are described by a class of time-continuous ordinary differential equations having a general form (E) over dot = M(E)E, where E is a vector of gene-expression levels and environmental factors and M(E) is the matrix having functional entries containing unknown parameters to be optimized. Accordingly, time-discrete versions of that model class are studied and improved by introducing 3rd-order Heun's method and 4th-order classical Runge-Kutta method. The corresponding iteration formulas are derived and their matrix algebras are obtained. After that, we use nonlinear mixed-integer programming for the parameter estimation in the considered model and present the solution of a constrained and regularized given mixed-integer problem as an example. By using this solution and applying both the new and existing discretization schemes, we generate corresponding time-series of gene-expressions for each method. The comparison of the experimental data and the calculated approximate results is additionally done with the help of the figures to exercise the performance of the numerical schemes on this example. (C) 2011 Elsevier B.V. All rights reserved.
Vester's sensitivity model for genetic networks with time-discrete dynamics
(Springer International Publishing, 2014) Defterli, Özlem; Defterli, Özlem; Fuegenschuh, Armin; Weber, Gerhard Wilhelm; Matematik
We propose a new method to explore the characteristics of genetic networks whose dynamics are described by a linear discrete dynamical model x(t+1) = Ax(t). The gene expression data x(t) is given for various time points and the matrix A of interactions among the genes is unknown. First we formulate and solve a parameter estimation problem by linear programming in order to obtain the entries of the matrix A. We then use ideas from Vester's Sensitivity Model, more precisely, the Impact Matrix, and the determination of the Systemic Roles, to understand the interactions among the genes and their role in the system. The method identifies prominent outliers, that is, the most active, reactive, buffering and critical genes in the network. Numerical examples for different datasets containing mRNA transcript levels during the cell cycle of budding yeast are presented