It is well-known that if the steady-state gain G(0) of a stable lumped system, with transfer function G(s), is positive, then compensating the system by an integral controller k=s, where k is a gain parameter, leads to a stable closed-loop system which achieves tracking of arbitrary constant reference signals, provided that the gain parameter k is positive and su ciently small. It is also well-...

In this paper we develop a globally stabilizing stability-based switching controller for a three-state lumped parameter centrifugal compressor surge model. The proposed model involves pressure and mass flow compression system dynamics as well as spool dynamics to account for the influence of speed transients on the compression surge dynamics. The proposed nonlinear switching controller architec...

OBJECTIVE Quantitative description of left ventricular diastolic filling and mitral valve function remains difficult despite advances in echocardiography. The purpose of the present study was to develop a lumped parameter model of left ventricular filling and validate it in porcine trials under physiological conditions and after valve replacement. METHODS Six animals were instrumented with ao...

In this paper, a lumped parameter mathematical model for hot water geothermal reservoirs is developed and applied to the Cerro Prieto geothermal field in Mexico. The production and pressure histories of Cerro Prieto were assembled from field data. A computer program was then used to perform sensitivity studies on reservoir size, porosity, aquifer recharge, and temperature of recharge fluid. Two...

Situs-specific organogenesis in the mouse results from leftward fluid flow in the node cavity and subsequent left-sided expression of Nodal in the lateral plate mesoderm (LPM). Nodal expression at the node is essential for the subsequent asymmetric Nodal expression in the left LPM, but the precise role of Nodal produced at the node has remained unknown. We have now investigated how the Nodal si...

In this paper a new 3 degree-of-freedom lumped-parameter model for machine tool vibrations is developed and analyzed. One mode is shown to be stable and decoupled from the other two, and thus the stability of the system can be determined by analyzing these two modes. It is shown that this mode-coupled nonconservative cutting tool model including the regenerative e¤ect (time delay) can produce a...