Simplified Method of Stability Analysis of Nonlinear Systems without Using of Lyapunov Concept

In this paper a new simplified method of stability study of dynamical nonlinear systems is proposed as an alternative to using Lyapunov’s method. Like the Lyapunov theorem, the new concept describes a sufficient condition for the systems to be globally stable. The proposed method is based on the assumption that, not only the state matrix contains information on the stability of the systems, but also the eigenvectors. So, first we will write the model of nonlinear systems in the state-space representation, then we use the eigenvectors of the state matrix as system stability indicators.

A sludge volume index (SVI) model based on the multivariate local quadratic polynomial regression method

In this study, a multivariate local quadratic polynomial regression(MLQPR) method is proposed to design a model for the sludge volume index(SVI). In MLQPR, a quadratic polynomial regression function is established to describe the relationship between SVI and the relative variables, and the important terms of the quadratic polynomial regression function are determined by the significant test of the corresponding coefficients. Moreover, a local estimation method is introduced to adjust the weights of the quadratic polynomial regression function to improve the model accuracy. Finally, the proposed method is applied to predict the SVI values in a real wastewater treatment process(WWTP). The experimental results demonstrate that the proposed MLQPR method has faster testing speed and more accurate results than some existing methods.

Simplified Optimization Routine for Tuning Robust Fractional Order Controllers

Fractional order controllers have been used intensively over the last decades in controlling different types of processes. The main methods for tuning such controllers are based on a frequency domain approach followed by optimization routine, generally in the form of the Matlab fminsearch, but also evolving to more complex routines, such as the genetic algorithms. An alternative to these time consuming optimization routines, a simple graphical method has been proposed. However, these graphical methods are not suitable for all combinations of the imposed performance specifications. To preserve their simplicity, but also to make these graphical methods generally applicable, a modified graphical method using a very straightforward and simple optimization routine is proposed within the paper. Two case studies are presented, for tuning fractional order PI and PD controllers.

Production of electrical energy from living plants in microbial fuel cells

Growing energy demand is a current problem with greater incidence in the future.The research objective is to establish seed bases to give a leading role to plants used in anthropogenic production activities and consumption,and even plants belonging to wildlife in terms of energy production.The use of living plants to obtain electrical energy through a microbial-vegetable fuel cell is proposed as a mech-anism to supply the energy demand with easy access worldwide,especially in areas far from urban centres.In this work,the voltage produced by microbial-vegetable fuel cells was measured using graphite electrodes and plants belonging to the species of aloe(Aloe vera),corn(Zea mays),black beans(Phaseolus vulgaris),tomato(Solanum lycopersicum)and moss(Dicranidae).They were selected for their presence in everyday life and their great commercial and agricultural value,reaching a maximum voltage of 884 mV from moss.There is evidence that all plants can be a source of energy to a greater or lesser extent and that their performance is given by the plant root interactions at the electrodes.However,an extensive root system can favour the accumulation of substrate after the hydrolysis of dead roots,provided that their presence does not interfere with microbial activity on the anodic surface.For this,using plants with low resistance to thermal stress can lead to a substrate richer in substances that can be decomposed.Therefore,it is recommended to use plants according to their life cycle and the morphology of their roots,and plants that can grow in waterlogged conditions or without direct contact with the Sun.

A transformation algorithm for incompatible information systems based on variable precision values

The variable precision rough set （VPRS） model extends the basic rough set （RS） theory with finite uni- verses and finite evaluative measures. VPRS is concerned with the equivalence and the contained relationship between two sets. In incompatible information systems, the inclusion degree and/3 upper （lower） approximation of the inconsistent equivalence class to the decision equivalence classes may be affected by the variable precision. The analysis of an example of incompatible decision table shows that there is a critical point in fl available-values region. In the new/3 range limited at the critical point, the incompatible decision table can be converted to the coordination decision table reliably. The method and its algorithm implement are introduced for the critical value search. The examples of the inconsistent equivalence class transformation are exhibited. The results illustrate that this algorithm is rational and precise.

Modelling of phosphorus accumulation in an aeroponic coriander crop

A model was developed for phosphorus(P)concentration over time in a closed aeroponic coriander culture.In addition,the setting and starting up of the soilless culture is described,and the measurements of electrical conductivity(EC),pH and concentration of major ions in the mixing tank are provided.By using mass balance principles,the dynamics of the nutrient concentration in the mixing tank and in the drainage solution are stated.Two series of continuous stirred tank reactors are considered for the flow structure,using a power law relationship to represent the rate of nutrient removal,considering water volume changes.Phosphorus concentration measurements were used for model fitting,and the resulting simulation is in good agreement with data.