In this paper, we study the dynamical behavior of a stochastic food chain chemostat model, in which the white noise is proportional to the variables. Firstly, we prove the existence and uniqueness of the global positive solution. Then by constructing suitable Lyapunov functions, we show the system has a unique ergodic stationary distribution. Furthermore, the extinction of microorganisms is discussed in two cases. In one case, both the prey and the predator species are extinct, and in the other case, the prey species is surviving and the predator species is extinct. Finally, numerical experiments are performed for supporting the theoretical results. 相似文献
This paper generalizes the analysis of four magnetohydrodynamic (MHD) flow problems of an Oldroyd-B fluid discussed by Asghar
et al. [Int. J. Non-linear Mech. 40, 589–601 (2005)] into three directions: (i) to discuss the problems in a porous medium using modified Darcy’s law (ii) to
see the influence of Hall current (iii) to determine the effect of rheological parameter of Burgers’ fluid. Analytical solutions
of velocity distribution valid at large and small times are given in each problem. Comparison has been provided for Oldroyd-B
and Burgers’ fluids through graphs. The physical interpretation is also included. 相似文献
The solution for the flow of a third grade fluid bounded by two parallel porous plates is given using homotopy analysis method (HAM). A comparison is made with the exact numerical solution for the various values of the physical parameters. It is found that a proper choice of the auxiliary parameter occurring in HAM solution gives very close results. 相似文献
The steady-state solutions for three types of unsteady oscillating flows of generalized Burgers fluids are determined by means of the Fourier sine transforms. These solutions are also presented in equivalent forms in terms of elementary functions exp, sine, cosine, hyperbolic sine and hyperbolic cosine. The similar solutions for Burgers, Oldroyd-B, Maxwell, Second grade and Navier-Stokes fluids can be also obtained as limiting cases of our solutions. 相似文献
In the present investigation the exact analytical solutions for three fundamental flows namely the Couette, Poiseuille and generalized Couette are obtained. The resulting problems involve nonlinear equations and nonlinear boundary conditions. Finally the influence of the emerging parameters is discussed by plotting graphs. 相似文献
The mineral extraction activities may disturb the natural radioactivity, therefore current study aims to generate baseline data of natural radionuclides and anthropogenic 137Cs before the start of industrial activities. Gamma spectrometry and gross alpha and beta counting systems were used for activity measurement in environmental samples. In soil, the mean activity of 232Th, 226Ra, 40K and 137Cs were determined as 79 (66–117), 47 (34–80), 823 (602–1159) and 1.3 (1.1–4.5) Bq kg?1, respectively. The average annual effective dose rate (128.7 µSv h?1) in the study area was twice higher than world’s average value. Indoor hazard index was greater than unity at two places; therefore, proper ventilation is proposed during construction.
Darcy–Forchheimer three-dimensional rotating flow of nanoliquid in the presence of activation energy and heat generation/absorption is examined. Heat and mass transport via convective process is considered. Buongiorno model has been employed to illustrate thermophoresis and Brownian diffusion effects. Adequate transformation procedure gives rise to system in terms of nonlinear ODE’s. An efficient numerical technique namely NDsolve is used to tackle the governing nonlinear system. The graphical illustrations examine the outcomes of various sundry variables. Heat and mass transfer rates are also computed and examined. Our results indicate that the temperature and concentration distributions are enhanced for larger values of porosity parameter and Forchheimer number.
This paper reports numerical study for peristalsis of Carreau–Yasuda nanofluid in a symmetric channel. Constant magnetic field is applied. Modified Darcy’s law and nonlinear thermal radiation effects are considered. Viscous dissipation and Ohmic heating effects are also present. Long wavelength and small Reynolds number are considered. Resulting nonlinear problems are solved numerically. Graphical illustrations depict that temperature increases for larger Hartmann number and it decays for thermophoresis parameter.