5 research outputs found
Biogenic crust dynamics on sand dunes
Sand dunes are often covered by vegetation and biogenic crusts. Despite their
significant role in dune stabilization, biogenic crusts have rarely been
considered in studies of dune dynamics. Using a simple model, we study the
existence and stability ranges of different dune-cover states along gradients
of rainfall and wind power. Two ranges of alternative stable states are
identified: fixed crusted dunes and fixed vegetated dunes at low wind power,
and fixed vegetated dunes and active dunes at high wind power. These results
suggest a cross-over between two different forms of desertification
EXTENSION OF XENON OSCILLATIONS SAFETY MARGINS USING WEAKLY NONLINEAR STABILITY ANALYSIS
Weakly nonlinear stability analysis is applied to study xenon oscillations in nuclear reactors using the approach of multiple time-scales method. This approach allows to characterize the dynamics of the system beyond the Hopf instability point. It provides important insight on the characteristics of the oscillations, namely if they diverge with time, or converge into a bounded limit cycle. Detailed derivation of the amplitude equation is presented. This equation is used to identify parameter ranges of bounded periodic oscillations, which may be allowed for safe operation. The influence of neutron generation time and the power feedback coefficients on the amplitude of limit cycles, as well as on convergence times, is discussed. The described method may be used to extend the safety margins required to prevent xenon unstable oscillations in reactor cores
EXTENSION OF XENON OSCILLATIONS SAFETY MARGINS USING WEAKLY NONLINEAR STABILITY ANALYSIS
Weakly nonlinear stability analysis is applied to study xenon oscillations in nuclear reactors using the approach of multiple time-scales method. This approach allows to characterize the dynamics of the system beyond the Hopf instability point. It provides important insight on the characteristics of the oscillations, namely if they diverge with time, or converge into a bounded limit cycle. Detailed derivation of the amplitude equation is presented. This equation is used to identify parameter ranges of bounded periodic oscillations, which may be allowed for safe operation. The influence of neutron generation time and the power feedback coefficients on the amplitude of limit cycles, as well as on convergence times, is discussed. The described method may be used to extend the safety margins required to prevent xenon unstable oscillations in reactor cores