Gradient-echo imaging considerations for hyperpolarized 129Xe MR
No abstract available
NASA Discipline Environmental Health↗
Engineering topics
Williamson, D.
Publications and source records attributed to Williamson, D..
Periodic motion in a class of nth-order autonomous differential equations
Sufficient conditions are obtained for the existence of periodic motion in a class of autonomous nonlinear differential equations of order greater than two. The approach is based on the decomposition of an equation into a linear and a nonlinear part. The analysis relies on some basic ideas from linear analysis and geometry. Sufficient conditions for a periodic solution are derived by means of a general topological principle referred to as the torus principle. The existence of a periodic solution is concluded by an appropriate use of the Brouwer fixed-point theorem.
Williamson, D.↗
Periodic motion in nonlinear systems
In this paper it is shown how some basic ideas from system theory and differential geometry can be used to establish some new results on the existence of periodic motion in autonomous feedback systems. The conditions are expressed in terms of the frequency response characteristic of the open-loop system and certain general properties of the nonlinearities.
Williamson, D.↗
Oscillations in nonlinear feedback systems.
It is shown how some basic ideas from system theory and differential geometry can be used to establish new results concerning the existance of oscillations for autonomous feedback systems. The conditions obtained are expressed in terms of the frequency response characteristic of the open-loop system and certain general properties of the nonlinearity.
Williamson, D.↗