Search results for "mathematical model."
showing 10 items of 343 documents
A Simple Model for Ac Impedance Spectra in Bipolar Membranes
1996
A new model accounting for the ac impedance spectra of synthetic ion-exchange bipolar membranes is presented. The theoretical approach is based on the Nernst−Planck and Poisson equations and applies some of the concepts used in the semiconductor pn junctions to the case of a bipolar membrane. The results presented are the current−voltage curves and the impedance spectra at electric currents above the limiting current. It is shown that the model is able to identify the main contributions to the bipolar membrane impedance and gives valuable information about the bipolar junction structure and its influence on the characteristic parameters involved in the field-enhanced water dissociation phen…
Optimal control circuitry design for the digital p53 dynamics in cancer cell and apoptosis
2009
AbstractExperimental work and theoretical models deduce a "digital" response of the p53 transcription factor when genomic integrity is damaged. The mutual influence of p53 and its antagonist, the Mdm2 oncogene, is closed in feedback. This paper proposes an aerospace architecture for translating the p53/Mdm2/DNA damage network into a digital circuitry in which the optimal control theory is applied for obtaining the requested dynamic evolutions of some considered cell species for repairing a DNA damage. The purpose of this paper is not to improve the analysis of the actual mathematical models but to demonstrate the usefulness of such digital circuitry design capable to predict and detect the …
Further experiences on unsteady seepage flow
1973
The present paper describes the results of a study on the unsteady flow in a horizontal homogeneous filter, which is accomplished when the level of the reservoir that recharges the filter is instantly drawn up. This study was carried out at the University of Palermo Institute of Hydraulics as a part of a research program concerning artificial recharge of ground water and the geotechnical problems involving the stability of porous media subject to the variations of surrounding pressures. A numerical procedure, aiming at solving the equation of Boussinesq by a finite difference method, was adopted and an electronic computer was used. A Hele-Shaw filter model was used to carry out several expe…
An Iterative Method for Bifurcation-Free Resonant Inductive Power Transfer System Design
2021
The development of electric mobility makes the charging systems one of the main discussed topic. Among the different technologies, Resonant Inductive Power Transfer (RIPT) systems are in deep study. Several aspects, including the choice of coils, the compensation network and the bifurcation phenomenon are necessary for a proper design of the system. In this paper an iterative method for bifurcation-free RIPT system design is provided as a valid solution to the need of accurate models requiring low computational efforts.
Evaluation of Subgrade Resilient Modulus Predictive Model for Use in Mechanistic-Empirical Pavement Design Guide
2006
The characterization of unbound materials in the mechanistic–empirical pavement design guide (MEPDG), also known as the 2002 design guide, is reviewed, and this characterization is applied to Minnesota subgrades. The main emphasis is on the collection of k1-, k2-, and k3-parameters for Minnesota fine-grained soils and the procedure for the interpretation of the resilient modulus test to provide an input to the multilayer elastic theory (MLET) analysis (Level 2 input). This is an important aspect of adaptation of the MEPDG, because the guide recommends measurement of resilient moduli from laboratory testing, but the procedure does not specify how to interpret the test data to obtain an input …
Soft Sensor Transferability between Lines of a Sulfur Recovery Unit
2021
Abstract Soft Sensors (SSs) are mathematical models that allow real-time estimation of hard-to-measure variables as a function of easy-to-measure ones in an industrial process, emulating the behavior of existing sensors when they are, for instance, taken off for maintenance. The Sulfur Recovery Unit (SRU) from a refinery is taken in exam. Recurrent Neural Networks (RNN) can capture the nonlinearity of such process but present a high complexity training and a very time-consuming structure optimization. For this reason, strategies to use pre-existing models are here examined by testing the transferability of the SSs between two parallel lines of the process.
Search of a topological pattern to evaluate toxicity of heterogeneous compounds.
2001
Abstract Molecular connectivity has been applied to the search of mathematical models able to predict the carcinogenic and teratogenic activity of a wide group of structurally heterogeneous compounds. Through the linear discriminant analysis and the diagrams of distribution of pharmacological activity, the classification criteria that minimizes the percentage of error are established. The easiness and speed of the calculation of the descriptors used in this work make the models developed useful in data bases containing a huge number of compounds.
Drilling Systems: Stability and Hidden Oscillations
2013
There are many mathematical models of drilling systems Despite, huge efforts in constructing models that would allow for precise analysis, drilling systems, still experience breakdowns. Due to complexity of systems, engineers mostly use numerical analysis, which may lead to unreliable results. Nowadays, advances in computer engineering allow for simulations of complex dynamical systems in order to obtain information on the behavior of their trajectories. However, this simple approach based on construction of trajectories using numerical integration of differential equations describing dynamical systems turned out to be quite limited for investigation of stability and oscillations of these s…
The Influence of MSW Landfill Height in the Perched Leachate Formation
2012
During the last decades, the largest part of municipal solid waste (MSW) generated world wide has been disposed of in landfills without any pre-treatment. The main environmental impacts of such landfills, containing high amounts of biodegradable organic matter, are caused by emissions of liq-uid effluents and landfill gas. With no collection and treatment, leachates from landfills pollute groundwater and soils locally. Furthermore, besides the biological processes, many physical phe-nomena occur inside the landfill body which negatively affect landfill management. Indeed, the waste settlement inside the landfill body, with a consequent increase of its density, corresponds to a proportional …
Stopover strategies in birds: a review of methods for estimating stopover length
1999
This study categorizes and reviews methods used to estimate stopover length in migratory birds. Stopover length is an important variable in analysing migration strategies. The analysis of the stopover pattern of migratory birds typically attempts to investigate variability in the number of stopovers and in the length of time spent at stopover sites in relation to species, age, sex and body condition. Although the number of capture-recapture studies analysing stopover length has increased substantially, most are analysed using the simple last-first capture method which gives biased estimates. The use of mathematical models to calculate stopover length is uncommon. Most researchers assume hom…