Pulse simulation, kinetic model

In this chapter we have reported on theoretical investigations of two different regimes of interaction between ultraintense EM radiation and plasmas, as examples of the application of the theoretical models developed in a previous chapter. First, we have studied the existence of localized spatial distributions of EM radiation, which appear in numerical simulations as a result of the injection of an ultrashort and intense laser pulse into an underdense plasma. Such solitonic structures originating from the equilibrium between the EM radiation pressure, the plasma pressure and the ambipolar field associated with the space charge have been described in the framework of both a relativistic kinetic model and a relativistic fluid approach. It has also been shown that... 

Figure 17 CO oxidation on Pd/alumina model catalysts. Top CO2 production versus time from a pulsed CO beam and a constant O2 beam. Xco is the equivalent CO pressure divided by the sum of the CO and O2 pressures. Down Simulation of the experimental data (on top) with a kinetic model. The inset is an enlargement of part of the figure showing the presence of a small dip after closing of the CO beam. (From J. Libuda et al. [203].)... 

A third example of the role of kinetic modelling in the analysis of practical combustion systems at high temperatures is in simulations of pulse combustion. Pulse combustors have been used for many years in propulsion, industrial processes such as drying, and in home furnaces, where they are valued for their thermal efficiency and low NOx production rates. However, until kinetic modelling was used to analyze the role of thermal ignition in these systems, it had been impossible to understand the principles of pulse combustion and the real reasons for their good performance. 

Theoretical models shed light on additional aspects of pulsatile cAMP signaling in Dictyostelium. First, like Ca + spikes, cAMP pulses are frequency encoded. Only pulses delivered at 5-min intervals are capable of accelerating slime mold development after starvation. Simulations indicate that frequency encoding is based on reversible receptor desensitization [76]. The kinetics of receptor resensitization dictates the interval between successive pulses required for a maximum relay response [78]. Second, cAMP oscillations in... 

The kinetic simulations of the pulse combustor ignition can be carried out under conditions which closely approximate those in a continuously stirred tank reactor (cstr). In those calculations, hot product gases are steadily mixed with cold, unbumed reactants until the mixtures ignite. The reaction mechanisms used are valid for high temperatures, and the most important, sensitive reaction is reaction (3), and the combined influences of chemical kinetics, acoustics, and fluid dynamics can all be incorporated into a coherent practical design model [20]. 

In this chapter two novel methods are presented which enable the direct and model independent determination of chain-length dependent termination rate coefficients. Both methods are based on single-pulse pulsed-laser polymerization. After a theoretical derivation, both kinetic approaches are validated by means of computer simulations. As will be demonstrated, these simulations prove that the essential assumptions needed to gain access to the chain-length dependent coefficients are valid and do not significantly undermine the accurate and reliable determination of the termination rate coefficients. 

---