Search results for " mathematical model"
showing 10 items of 59 documents
Donnan phenomena in membranes with charge due to ion adsorption. Effects of the interaction between adsorbed charged groups
1993
A physical model for the modified Donnan phenomenon associated with ion adsorption on localized membrane sites is presented. This model accounts for the dependence of the concentration of adsorbed ions on electrolyte concentration and pH as it is influenced by the electrostatic interaction between adsorbed ions. The equilibrium thermodynamic concepts employed are based on the Donnan formalism for the ion equilibria between membrane and solution, and the Bragg–Williams approximation for an adsorption isotherm that incorported interaction between adsorbed ions. Our results include the concentration of charged groups in the membrane, the pH of the membrane phase solution, and the Donnan potent…
A commentary on the Special Issue “Innovations in measuring and fostering mathematical modelling competencies”
2021
This is a commentary on the ESM 2021 Special Issue on Innovations in Measuring and Fostering Mathematical Modelling Competencies. We have grouped the ten studies into three themes: competencies, fostering, and measuring. The first theme and the papers therein provide a platform to discuss the cognitivist backgrounds to the different conceptualizations of mathematical modelling competencies, based on the modelling cycle. We suggest theoretical widening through a competence continuum and enriching of the modelling cycle with overarching, analytic dimensions for creativity, tool use, metacognition, and so forth. The second theme and the papers therein showcase innovative ideas on fostering an…
Mathematical and numerical modeling of an airlift perfusion bioreactor for tissue engineering applications
2022
The Tissue Engineering (TE) strategy is widely focused on the development of perfusion bioreactors to promote the production of three-dimensional (3D) functional tissues. To optimize tissue production, it is worth investigating the engineering parameters of a bioreactor system for identifying a beneficial range of operation variables. Mathematical and numerical modeling of a perfusion bioreactor is capable to provide relevant insights into the fluid flow and nutrients transport while predicting experimental data and exploring the impact of changing operating parameters, such as fluid velocities. In this work, the hydrodynamic parameters and oxygen transport were investigated using mathemati…
Cost analysis of a vaccination strategy for respiratory syncytial virus (RSV) in a network model
2010
[EN] In this paper an age-structured mathematical model for respiratory syncytial virus (RSV) is proposed where children younger than one year old, who are the most affected by this illness, are specially considered. Real data of hospitalized children in the Spanish region of Valencia are used in order to determine some seasonal parameters of the model. Once the parameters are determined, we propose a complete stochastic network model to study the seasonal evolution of the respiratory syncytial virus (RSV) epidemics. In this model every susceptible individual can acquire the disease after a random encounter with any infected individual in the social network. The edges of a complete graph co…
Decoupled control scheme of grid-connected split-source inverters
2017
Grid-connected power conversion systems for renewable energy sources must fulfill several requirements, e.g., the high efficiency, the reduced cost and complexity, and, quite often, the boost capabilities that is usually achieved using a front-end dc–dc boost converter before the inversion stage, leading to a two-stage architecture. Meanwhile, single-stage power conversion systems, which perform the boosting operation within the inversion one, offer some potential advantages, in terms of reducing the complexity and the volume of the whole system. Among several proposed options, the split-source inverter (SSI) has been recently proposed by Abdelhakim et al. as an alternative option with some…
Application of the General Model "Biological Nutrient Removal Model No.1" to upgrade two full-scale WWTPs
2012
In this paper, two practical case studies for upgrading two wastewater treatment plants (WWTPs) using the general model BNRM1 (Biological Nutrient Removal Model No. 1) are presented. In the first case study, the Tarragona WWTP was upgraded by reducing the phosphorus load to the anaerobic digester in order to minimize the precipitation problems. Phosphorus load reduction was accomplished by mixing the primary sludge and the secondary sludge and by elutriating the mixed sludge. In the second case study, the Alcantarilla WWTP, the nutrient removal was enhanced by maintaining a relatively low dissolved oxygen concentration in Stage A to maintain the acidogenic bacteria activity. The VFA produce…
Mathematical Model of a PM Brushless Motor with Different Stator-Rotor Pole Pairs Number
2013
The paper presents a mathematical model of Permanent Magnet AC brushless machines (PMSM) having a number of stator poles-obtained via the distribution of the three-phase winding- different from the rotor one, realized by the displacement of the permanent magnets. For these so- called ‘Fractional-Slot’ motors (where few total slots generate high equivalent number of poles) the available mathematical models appear partial and/or incomplete, despite of numerous designing considerations made in literature. In this paper an analytical approach is developed to point out an instantaneous- values mathematical model with concentrated parameters, that can be suitable for control architecture systems …
Rainwater Reuse in Urban Areas: A Mathematical Model and a Long-Term Modelling Approach
2018
Natural water resources are becoming increasingly limited due to global-scale climate change and water availability issues have become so severe that they must be addressed. Given these issues, reuse of wastewater and rainwater provides a promising way to cope with water shortages. This paper describes an investigation into the efficiency of rainwater usage systems. A conceptual model was built to assess the behaviour of rainwater tanks and their effectiveness in coping with water shortages. The study is based on a long-term simulation (12 years) of different rainwater reuse tank schemes. The associated reductions in residential freshwater demand (water reuse efficiency) and wet-weather run…
Evaluation of biogas production and usage potential
2016
The aim of the research is the development of theoretical and methodical bases for determining the feasibility of plant raw materials growing for its further bioconversion into energy resources and tec hnological materials to maximize profit from business activities. Monograph, statistics, modelling and abstract logical methods have been used during the research. Directions of biogas usage have been examined. Biogas yields from different crops have been analyzed. It has been determined that high methane yields can be provided from root crops, grain crops, and several green forage plants. So, forage beet and maize can provide more than 5,500 m3 of biogas per hectare. Attention is paid to the…