Heat-transfer characteristics of a water-to- cryogenic-hydrogen heat exchanger

Heat transfer characteristics of water/cryogenic hydrogen heat exchanger for nuclear rocket reacto

Lepton flavor violation in low-scale seesaw models: SUSY and non-SUSY contributions

Taking the supersymmetric inverse seesaw mechanism as the explanation for neutrino oscillation data, we investigate charged lepton flavor violation in radiative and 3-body lepton decays as well as in neutrinoless $\mu-e$ conversion in muonic atoms. In contrast to former studies, we take into account all possible contributions: supersymmetric as well as non-supersymmetric. We take CMSSM-like boundary conditions for the soft supersymmetry breaking parameters. We find several regions where cancellations between various contributions exist, reducing the lepton flavor violating rates by an order of magnitude compared to the case where only the dominant contribution is taken into account. This is in particular important for the correct interpretation of existing data as well as for estimating the reach of near future experiments where the sensitivity will be improved by one to two orders of magnitude. Moreover, we demonstrate that ratios like BR($\tau\to 3 \mu$)/BR($\tau\to \mu e^+ e^-$) can be used to determine whether the supersymmetric contributions dominate over the $W^\pm$ and $H^\pm$ contributions or vice versa.Comment: 75 pages, 7 figures. v3: references and comments added. Matches published versio

Equilibrium-Independent Control of Continuous-Time Nonlinear Systems via the LPV Framework -- Extended Version

In this paper, we consider the analysis and control of continuous-time nonlinear systems to ensure universal shifted stability and performance, i.e., stability and performance w.r.t. each forced equilibrium point of the system. This "equilibrium-free" concept is especially beneficial for control problems that require the tracking of setpoints and rejection of persistent disturbances, such as input loads. In this paper, we show how the velocity form, i.e., the time-differentiated dynamics of the system, plays a crucial role in characterizing these properties and how the analysis of it can be solved by the application of Linear Parameter-Varying (LPV) methods in a computationally efficient manner. Furthermore, by leveraging the properties of the velocity form and the LPV framework, a novel controller synthesis method is presented which ensures closed-loop universal shifted stability and performance. The proposed controller design is verified in a simulation study and also experimentally on a real system. Additionally, we compare the proposed method to a standard LPV control design, demonstrating the improved stability and performance guarantees of the new approach.Comment: Non-extended version submitted to IEEE Transactions on Automatic Contro

Convex Equilibrium-Free Stability and Performance Analysis of Discrete-Time Nonlinear Systems

This paper considers the equilibrium-free stability and performance analysis of discrete-time nonlinear systems. We consider two types of equilibrium-free notions. Namely, the universal shifted concept, which considers stability and performance w.r.t. all equilibrium points of the system, and the incremental concept, which considers stability and performance between trajectories of the system. In this paper, we show how universal shifted stability and performance of discrete-time systems can be analyzed by making use of the time-difference dynamics. Moreover, we extend the existing results for incremental dissipativity for discrete-time systems based on dissipativity analysis of the differential dynamics to more general state-dependent storage functions for less conservative results. Finally, we show how both these equilibrium-free notions can be cast as a convex analysis problem by making use of the linear parameter-varying framework, which is also demonstrated by means of an example.Comment: Submitted to IET Control Theory & Application

Interpretation of transverse tune spectra in a heavy-ion synchrotron at high intensities

Two different tune measurement systems have been installed in the GSI heavy-ion synchrotron SIS-18. Tune spectra are obtained with high accuracy using these fast and sensitive systems. Besides the machine tune, the spectra contain information about the intensity dependent coherent tune shift and the incoherent space charge tune shift. The space charge tune shift is derived from a fit of the observed shifted positions of the synchrotron satellites to an analytic expression for the head-tail eigenmodes with space charge. Furthermore, the chromaticity is extracted from the measured head-tail mode structure. The results of the measurements provide experimental evidence of the importance of space charge effects and head-tail modes for the interpretation of transverse beam signals at high intensity