The dynamics of a kink driven by noise is analyzed using the two collective variables of the Rice ansatz: position and width. Starting from a stochastic partial differential equation, with the phi(4) potential in the overdamped limit, the pair of stochastic differential equations for the collective variables are derived without approximation other than the ansatz itself. From the steady state p...

The theory of optimal control for distributed parameters systems is adjusted for solving the problems of determining the con-troled temperature fields of hidrotehnical construction with the aim of appointment of the tehnical and technological operations, which assure their integrity. The problem is simulated with the help of the conduction equation with initial and boundary condition. The contr...

The Fisher-Kolmogorov-Petrovskii-Piskunov equation with a variable growth rate and advection by an incompressible velocity field is considered as a model for plankton dispersed by ocean currents. If the average growth rate is negative then the model has a survival-extinction transition; the location of this transition in the parameter space is constrained using variational arguments and delimit...

Communicated by D.B. Spalding) A model equation for the scalar dissipation rate, based on the Two Scale Direct Interaction Approximation (TSDIA) of Yoshizawa [1J was solved and applied to a turbulent round jet in conjunction with turbulence modelling based on the eddy viscosity and diffusivity. The model coefficients were adjusted by using a similarity analysis for the round jet. This led to an...

The charge transport equation is affected by thermal and concentration gradients as well as any applied electric field. In the charge transport equation the electrical conductivity, the electrical diffusivity and the electrical thermophoresis coefficient are all dependent on the electrical mobility which in turn is dependent on the collision time. When a time varying electric field is applied t...

We consider the linear dissipative Boltzmann equation describing inelastic interactions of particles with a fixed background. For the simplified model of Maxwell molecules first, we give a complete spectral analysis, and deduce from it the optimal rate of exponential convergence to equilibrium. Moreover we show the convergence to the heat equation in the diffusive limit and compute explicitely ...

On the basis of data constructed with large-eddy simulation (LES), an attempt is made to improve the Mellor–Yamada (M–Y) turbulence closure model. Firstly, stably-stratified and convective planetary boundary layers without moisture are simulated by a LES model to obtain a database for the improvement. Secondly, based on the LES data, closure constants are re-evaluated and a new diagnostic equat...

high moisture levels in fresh dairy manure provide a suitable environment for growth of pathogens and cause environmental pollution. dry manure can be used for different purposes in agriculture and in livestock industry. such heat properties of manure as specific heat, thermal conductivity and thermal diffusivity are important needed factors for the design and development of a suitable efficien...