Mathematical modelling of a diesel common-rail system

In diesel common-rail systems, the exact knowledge of the injection pressure is important to accurately control the injected diesel mass and thus the combustion process. This paper focuses on the mathematical modelling of the hydraulic and mechanical components of a common-rail system in order to describe the dynamics of the diesel rail pressure. Based on this model, an average model is derived to reduce the model complexity and to allow for a fast calculation of the mass flow into the rail for different crank shaft revolution speeds and openings of the fuel metering unit. The main purpose of this average model is to serve as a basis for a model-based (non-linear) controller design. The stationary accuracy of the models is validated by means of measurement data.     

Stabilization of a reaction-diffusion system modelling a class of spatially structured epidemic systems via feedback control

A two-component reaction-diffusion system modelling a class of spatially structured epidemic systems is considered. The system describes the spatial spread of infectious diseases mediated by environmental pollution. A relevant problem, related to the possible eradication of the epidemic, is the so called zero stabilization. In a series of papers, necessary conditions, and sufficient conditions of stabilizability have been obtained. It has been proved that it is possible to diminish exponentially the epidemic process in the whole habitat, just by reducing the concentration of the pollutant in a nonempty and sufficiently large subset of the spatial domain. The stabilizability with a feedback control of the harvesting type is related to the magnitude of the principal eigenvalue of a certain operator which is not selfadjoint. In this paper, we have proposed an approximating method for this principal eigenvalue. Further, we have faced the problem of finding the optimal position (by translation) of the support of the feedback stabilizing control in order to minimize both the infected population and the pollutant at a certain finite time.     

Mathematical modelling of a first order sigma-delta modulator

In this paper an exact model for a basic, first order sigma-delta modulator is derived by means of a difference equation with discontinuous nonlinearity. An explicit solution is given in terms of the greatest integer function under certain boundedness and initial conditions of the input signal. Assumptions are made under which the explicit formula remains a solution of the difference equation although the suppositions of the main theorem are violated.     

Dynamic analysis of a non-conservative band-wheel system with a moving boundary Part 1: Mathematical modelling

The dynamic band/wheel system with a moving boundary is very different from that with a fixed length, it is a non-conservative mass system and the boundary position is not fixed. In this paper, the moving boundary is one unknown to be determined associated with the string displacement, and the partial differential equation of the transverse vibrations of the band and the transversality condition of the moving boundary are derived by the calculus of variation and Hamilton’s principle. In order to verify the dynamic formulation is correct, we reduce the governing equation and separation point to coincide with the previous studies. It is found that the physical properties of the moving boundary could be obtained from the geometric constraint of the band/wheel system.     

Mathematical modelling of nervous systems

An electrochemical theory of the action potential is described, which takes into account the electric field produced by the ions themselves in the Debye layer. It is shown that under suitable conditions oscillations can arise, involving relatively large fluctuations of the concentrations of sodium and calcium at the internal surface of the neural membrane. It is possible in this way to account quantitatively for the general character, amplitude and frequency of the action potential, without postulating large variations in the ionic conductances of the membrane. Formulas for the available energy and information associated with a neuron are derived by a variational method. Problems which arise in the modelling of extended nervous systems are discussed, and methods are applied to model the experimental behavior of a ganglion of the leech.     

Mathematical modelling of spark-ignition engines

The flow field, scavenging efficiency, power output, heat transfer losses, and unburned hydrocarbon emissions have been numerically studied by means of a two-equation model of turbulence in a four-stroke, homogeneous-charge, spark-ignition engine. The engine is equipped with an intake valve, an exhaust valve, and a constant rate heat source which simulates the spark plug. Combustion has been modelled by means of a one-step irreversible chemical reaction whose rate is controlled by an Arrhenius-type expression. The numerical results indicate that the intake stroke is characterized by the formation of two eddies which persist in the compression stroke. Turbulence is generated at the shear layers of the air jet drawn into the cylinder, but its level decreases in the compression stroke. Due to the heat released by the spark plug and the chemical reaction, a spherical flame kernel is formed. This kernel evolves into a cylindrical flame when the flame front reaches the piston. Fuel remains unburnt at the corner between the cylinder head and the cylinder wall due to heat transfer losses. The numerical results also indicate that despite uncertainties about the turbulence and heat transfer models, an engine model such as the one studied here can be used to understand the flow field, heat transfer losses, scavenging efficiency, and power output in conventional spark-ignition engines. Such capabilities are very helpful in the development and optimization stages of engines. For example, here the engine model thermal and scavenging efficiencies are 15.69% and 94%, respectively. The peak pressure is 33 atm and occurs at 6° ATDC. The unburnt hydrocarbon emissions are 7.41% of the total fuel admitted into the cylinder.     

Mathematical modelling of morphological analysis

A mathematical model of morphological analysis is given. A search of a morphological table is simulated by a nonhomogeneous Markov chain. This model was used in the developed computer program, which has been successfully applied in structural engineering for the generation of a number of innovative, patentable solutions.     

Mathematical modelling of heat transfer in a catalytic reformer

In this work we analyse heat transfer in a system of channelsconnected by thin conducting walls. The channels are packedwith catalytic pellets that promote exothermic catalytic combustionreactions and endothermic reforming reactions in adjacent channels.A model is developed in which the thermal conductivity and thethickness of the interconnecting wall can be used as controlparameters characterizing the heat exchange between the neighbouringchannels. The model is to be used as a mathematical tool toanalyse design alternatives and develop accurate numerical techniques.Our objective is to study how the heat is transferred acrossthe conducting walls and how this influences the temperaturedistribution in the channels. We use an asymptotic techniqueto do this. The structure of the walls is then examined in detail,focusing on the case when we have layered walls.     

Mathematical modelling of noise around a Y-shaped windy road

In this study, we investigated the sound radiation from vehicles moving on a road with a Y-shaped fork in windy conditions. First, we consider the problem for two point sound sources moving in opposite directions along a road with an arbitrary bend. The background of the road is modelled as an elastic half-space. The solution to this problem is obtained using the integral Fourier transforms over space variables and time, and the stationary phase method. Next, the solution to the general case for many sources moving along a Y-shaped road fork is obtained as the superposition of the partial solutions. We performed a numerical analysis of the traffic noise characteristics for a Y-shaped fork on a city road in the town of Lodz, Poland as an example.     

On the stochastic quasi-linear symmetric hyperbolic system

We establish the existence and uniqueness of a local smooth solution to the Cauchy problem for a quasi-linear symmetric hyperbolic system with random noise in Rd. When the noise is multiplicative satisfying some nondegenerate conditions and the initial data are sufficiently small, we show that the solution exists globally in time in probability, i.e., the probability of global existence can be made arbitrarily close to one if the initial date are small accordingly.     

Mathematical modelling: die cutting for a fresnel lens

The various stages in the mathematical modelling of real problems are first discussed briefly and then illustrated stepwise with the problem of cutting a die for the lenses of automobile stoplights. This requires the determination of the shape of a groove cut into a rotating metal blank as a function of the shape of a cross-section of a rotating cutting tool.