We have developed a mathematical model of the AT1 mediated pathways including activation of PLC, PKC, IPS, and channel mediated variation of the cytosolic Ca2+ level after Angiotensin II stimulation. Different Ca2+ re...
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We have developed a mathematical model of the AT1 mediated pathways including activation of PLC, PKC, IPS, and channel mediated variation of the cytosolic Ca2+ level after Angiotensin II stimulation. Different Ca2+ responses and the respective time courses of activated PKC and Ca2+ dependent proteins, e.g. CaMKII are described in the model. The obtained simulation results are in good agreement with the measurement data found in literature. For example, the model describes the state-dependent exposure to Angll: increase in Ca2+ at low baseline Ca2+ levels as well as the decrease in Ca2+ at high (chronic activated) baseline. Additionally, simulation studies revealed that variations in the Na-Ca-exchanger transport characteristics could account for the observed cell-to-cell variability. Additional pathways were included in the model, e.g. MAPK, thus enabling the description of relevant transcription factor patterns. Also a Hodgkin-Huxley model approach is used to investigate the function of cell signaling in altering the firing behavior of NTS neurons in response to various baroreceptor stimuli.
This work studies the issue of optimal output transition control for nonlinear flat differential systems with constraints. Of special interest here is to generate a state reference trajectory and a feedforward input c...
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This work studies the issue of optimal output transition control for nonlinear flat differential systems with constraints. Of special interest here is to generate a state reference trajectory and a feedforward input command, which are essential for the implementation of exact feedforward linearization. Our approach is to transfer the transition problem in the real output space into a trajectory planning issue in the flat output space. The new aspect of this idea in our approach is to involve the generation of a noncausal trajectory for the flat output. This novelty turns out to be considerably effective for the performance improvement. It is also remarkable that our methodology guarantees the planned trajectories feasible for all nonlocal transitions. This is a new contribution to noncausal output transition control of nonlinear systems. The proposed method is illustrated on a benchmark system, the ICSTR, although its applicability could be much more wider.
A novel concept of feedback loop design for modal test and model updating is proposed. This method uses the closed-loop frequency information for parameter modifications to overcome the problems associated with the co...
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Active queue management (AQM) is an attempt to find a delicate balance between two antagonistic Internet queuing requirements: first, buffer space should be maximized to accommodate the possibly huge transient bursts;...
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Active queue management (AQM) is an attempt to find a delicate balance between two antagonistic Internet queuing requirements: first, buffer space should be maximized to accommodate the possibly huge transient bursts; second, buffer occupation should be minimum so as not to introduce unnecessary end-to-end delays. Traditional AQM mechanisms have been built on heuristics to achieve this balance, and have mostly done so quite well, but often require manual tuning or have resulted in slow convergence. In contrast, the PURPLE approach predicts the impact of its own actions on the behavior of reactive protocols and thus on the short-term future traffic without keeping pre-flow state. PURPLE allows much faster convergence of the main AQM parameters, at least towards a local optimum, thereby smoothing and minimizing both congestion feedback and queue occupancy. To improve the quality of the prediction, we also passively monitor (using lightweight operations) information pertaining to the amount of congestion elsewhere in the network, for example, as seen by flows traversing this router.
A novel approach for the design of feedback boundary tracking control for parabolic infinite-dimensional systems is illustrated for two coupled nonlinear partial differential equations modelling a tubular reactor. The...
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A novel approach for the design of feedback boundary tracking control for parabolic infinite-dimensional systems is illustrated for two coupled nonlinear partial differential equations modelling a tubular reactor. The method is based on a re-interpretation of the flatness-based open-loop design approach using an infinite power series ansatz in the spatial coordinate. It is shown, that by truncating the power series solution, a finite-dimensional approximation of the PDEs can be derived, which is suitable for flatness-based design of feedback boundary control with observer.
The section-wise macroscopic modeling of traffic flow is considered. A section is supposed to be bounded by detectors and several kilometers long. To compute a section model without input from the adjacent sections, f...
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The section-wise macroscopic modeling of traffic flow is considered. A section is supposed to be bounded by detectors and several kilometers long. To compute a section model without input from the adjacent sections, feasible boundary conditions have to be specified and boundary variables have to be approximated by the detector measurements. These approximations lead to unknown disturbances in the section model, depending on the direction of propagation of information in the traffic flow. Various approximations of the boundary variables are described and a disturbance modeling approach is proposed. The application of section models in traffic state estimation and the effects on the estimation error are discussed. Simulation tests are showing the performance of the estimation, based on the various boundary approximations.
In this paper, by exploiting the intrinsic structure of system equations and uncertainties, we first establish a nonconservative PID stabilization criterion for driver support systems. We then show some interesting re...
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In this paper, by exploiting the intrinsic structure of system equations and uncertainties, we first establish a nonconservative PID stabilization criterion for driver support systems. We then show some interesting results on positivity and connections of PID controllers. Finally, some extreme point results on PID α-stabilization are obtained. These results give certain explanations and justifications for the simulation results performed at German Aerospace Research Center.
Robust low-complexity control laws design is the ultimate goal which Computer-Aided controlsystem Design (CACSD) aims for. We recognize seven classes of services CACSD tools and environments have to support w.r.t. th...
Robust low-complexity control laws design is the ultimate goal which Computer-Aided controlsystem Design (CACSD) aims for. We recognize seven classes of services CACSD tools and environments have to support w.r.t. this view: physical system modelling with modelling uncertainty descriptions; mathematical system modelling with suited uncertainty models; system model analysis in state space, time- and frequency domain; control law synthesis; multiobjective (multicriteria and multimodel) synthesis-parameter tuning; nonlinear assessment via simulation; control code generation. We deal with state of the art aspects of such services and their integration within an interactively controlled automatic design feedback loop. This is illustrated by experience gained during the two-years GARTEUR a design challenge project on Robust Aircraft Flight control, where 12 teams from 6 European countries demonstrated 11 different CACSD synthesis methods to design a landing-approach autopilot controller based on a Beluga-type aircraft model from Airbus Industries.
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