MODELING, IDENTIFICATION AND ADAPTIVE CONTROL OF A NONLINEAR SYSTEM

Mathematical or physical models offer a possibility to solve problems like to control un- known state variables. These models are often described by physical parameters. Some of these parameters can be determined beforehand, some of them can only be identified in the running process. In this paper an algorithm to identify physical parameters is presented in the state space. The mathematical model of a nonlinear thermal system is developed and together with the identification algorithm the adaptive feedback control of not measurable state variables is shown. A simple and robust feedback controller is presented based on the power balance. A brief discussion of the results of the control and - at the same time - the estimation of unknown parameters is closing the paper

Alte Photoreaktionen in neuem Licht

The scope of the work presented is the investigation of photochemical reactions by means of ultrafast spectroscopy. Naturally these reactions start off in an optically bright excited state. Femtosecond time-resolved fluorescence spectroscopy is thus the method of choice to track the spectral and temporal dynamics of these emissive states. Here, an ultrafast fluorescence spectrometer based on the optical Kerr-effect serves as the appropriate tool to pursue this task. Additional information on dark states and ground states is provided by Uv-Vis transient absorption experiments. The first part of the thesis deals with a fundamental concept of mechanistic chemistry – the pericyclic reactions. The spectroscopic consequences implied within this theoretical framework are investigated by means of emission and absorption spectroscopy. The molecular probe is an indolyl-substituted fulgimide which undergoes a light-induced cyclization or cycloreversion, respectively. Both reactions feature a bi-phasic emission decay (cyclization: 0.06 ps, 0.4 ps, cycloreversion: 0.09 ps, 2.4 ps) whereas the slower component goes along with the product formation. The large difference in the slower time constants as well as the spectral properties of the corresponding emission point to the existence of different excited state pathways for both reactions. These results challenge the basic one-dimensional reaction scheme commonly used to describe pericyclic reactions. Referring to theoretical investigations, a two-dimensional reactive space is proposed to hold responsible for the different behaviour of the two isomers. The second part of the studies focuses on the dynamics of a certain type of photolabile protecting groups. These molecules are intramolecularly sensitised by a triplet energy donor, namely thioxanthone, and feature an ortho-substituted nitroaromatic as the reactive core. Investigations on the closely related energy donor xanthone reveal that photo-excitation is followed by a rapid (~ 1 ps) equilibration between the emissive singlet and a triplet state. This equilibrium holds responsible for a delayed fluorescence with a lifetime of ~ 0.1 − 1 ns and is ”switched off” by an internal conversion within the triplet manifold. These results can be directly transferred to thioxanthone and the sensitised protecting groups. The energy transfer in the latter molecules features a fast component from the initially populated triplet state (~ 100 ps) and a further slower contribution from the relaxed triplet state. Finally, the photo-reactive ortho-nitrobenzaldehyde (o-NBA) is compared with its non-reactive isomers m- and p-NBA as model systems to obtain information on the reactive core of the protecting groups. These first fluorescence experiments on monocyclic nitrated aromatics feature bi-phasic emission decays in all three cases – each with time constants of 1npi* relaxation

European standardization efforts from FAIR toward explainable-AI-ready data documentation in materials modelling

Security critical AI applications require a standardized and interoperable data and metadata documentation that makes the source data explainable-AI ready (XAIR). Within the domain of materials modelling and characterization, European initiatives have proposed a series of metadata standards and procedural recommendations that were accepted as CEN workshop agreements (CWAs): CWA 17284 MODA, CWA 17815 CHADA, and CWA 17960 ModGra. It is discussed how these standards have been ontologized, and gaps are identified as regards the epistemic grounding metadata, i.e., an annotation of data and claims by something that substantiates whether, why, and to what extent they are indeed knowledge and can be relied upon.European standardization efforts from FAIR toward explainable-AI-ready data documentation in materials modellingsubmittedVersio

Glass Studio

p. 843-847The Institute for Lightweight Structures and Conceptual Design has for many years been actively engaged in the research and development of advanced glass structures and systems, including long-span glass arches, adhesively-constructed glass domes, switchable glazing elements, and reinforced glass. In the summer semester of 2008 the institute held an interdisciplinary workshop for students from the faculties of Civil Engineering and Architecture, with technical guidance provided by the glass fabrication shop at the Stuttgart State Academy of Art and Design. During the workshop new possibilities were explored in the use of glass as a material. The students gained insight into the theoretical foundations of glass while simultaneously accumulating practical experience working with the material. Different fabrication approaches and technologies were used to create glass objects which reveal new design qualities beyond the aspect of transparency. During the studio, lamination techniques were used to embed optical fibres between two glass panes, generating three-dimensional light images; glass rod structures were created with smooth, pure glass joints achieved through local heating; horizontal slats of glass were layered vertically to achieve a visual superposition of direct and reflected views; glass shards were fused at different temperatures to generate sharp-edged and fragile, or smoothedged and sturdy objects; different thermal treatments were applied to produce flexible glass hybrid materials combining metal wires and glass shards, or slumped glass panes which recall the design vocabulary of lightweight structures. A detailed description of the different techniques employed and the various objects created follows in this article.Puller, K.; Heinz, P.; Frettlöhr, B.; Sobek, W. (2010). Glass Studio. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/695

Saharan dust and ice nuclei over Central Europe

Surface measurements of aerosol and ice nuclei (IN) at a Central European mountain site during an episode of dust transport from the Sahara are presented. Ice nuclei were sampled by electrostatic precipitation on silicon wafers and were analyzed in an isothermal static vapor diffusion chamber. The transport of mineral dust is simulated by the Eulerian regional dust model DREAM. Ice nuclei and mineral dust are significantly correlated, in particular IN number concentration and aerosol surface area. The ice nucleating characteristics of the aerosol as analyzed with respect to temperature and supersaturation are similar during the dust episode than during the course of the year. This suggests that dust may be a main constituent of ice nucleating aerosols in Central Europe

Learning from Recent Work on Innovation Processes and the Co-evolution of Technology, Economy and Society

CrESSI Deliverable D4.1, part 2

A passive GHz frequency-division multiplexer/demultiplexer based on anisotropic magnon transport in magnetic nanosheets

The emerging field of magnonics employs spin waves and their quanta, magnons, to implement wave-based computing on the micro- and nanoscale. Multi-frequency magnon networks allow for parallel data processing within single logic elements whereas this is not the case with conventional transistor-based electronic logic. However, a lack of experimentally proven solutions to efficiently combine and separate magnons of different frequencies has impeded the intensive use of this concept. In this Letter, we demonstrate the experimental realization of a spin-wave demultiplexer enabling frequency-dependent separation of GHz signals. The device is based on two-dimensional magnon transport in the form of spin-wave beams in unpatterned magnetic nanosheets. The intrinsic frequency-dependence of the beam direction is exploited to realize a passive functioning obviating an external control and additional power consumption. This approach paves the way to magnonic multiplexing circuits enabling simultaneous information transport and processing.Comment: 16 pages, 3 figure

Atmospheric ice nuclei in the Eyjafjallajökull volcanic ash plume

We have sampled atmospheric ice nuclei (IN) and aerosol in Germany and in Israel during spring 2010. IN were analyzed by the static vapor diffusion chamber FRIDGE, as well as by electron microscopy. During the Eyjafjallajökull volcanic eruption of April 2010 we have measured the highest ice nucleus number concentrations (>600 l−1) in our record of 2 yr of daily IN measurements in central Germany. Even in Israel, located about 5000 km away from Iceland, IN were as high as otherwise only during desert dust storms. The fraction of aerosol activated as ice nuclei at −18 °C and 119% rhice and the corresponding area density of ice-active sites per aerosol surface were considerably higher than what we observed during an intense outbreak of Saharan dust over Europe in May 2008. Pure volcanic ash accounts for at least 53–68% of the 239 individual ice nucleating particles that we collected in aerosol samples from the event and analyzed by electron microscopy. Volcanic ash samples that had been collected close to the eruption site were aerosolized in the laboratory and measured by FRIDGE. Our analysis confirms the relatively poor ice nucleating efficiency (at −18 °C and 119% ice-saturation) of such "fresh" volcanic ash, as it had recently been found by other workers. We find that both the fraction of the aerosol that is active as ice nuclei as well as the density of ice-active sites on the aerosol surface are three orders of magnitude larger in the samples collected from ambient air during the volcanic peaks than in the aerosolized samples from the ash collected close to the eruption site. From this we conclude that the ice-nucleating properties of volcanic ash may be altered substantially by aging and processing during long-range transport in the atmosphere, and that global volcanism deserves further attention as a potential source of atmospheric ice nuclei

Principal Stratum Strategy: Potential Role in Drug Development

A randomized trial allows estimation of the causal effect of an intervention compared to a control in the overall population and in subpopulations defined by baseline characteristics. Often, however, clinical questions also arise regarding the treatment effect in subpopulations of patients, which would experience clinical or disease related events post-randomization. Events that occur after treatment initiation and potentially affect the interpretation or the existence of the measurements are called {\it intercurrent events} in the ICH E9(R1) guideline. If the intercurrent event is a consequence of treatment, randomization alone is no longer sufficient to meaningfully estimate the treatment effect. Analyses comparing the subgroups of patients without the intercurrent events for intervention and control will not estimate a causal effect. This is well known, but post-hoc analyses of this kind are commonly performed in drug development. An alternative approach is the principal stratum strategy, which classifies subjects according to their potential occurrence of an intercurrent event on both study arms. We illustrate with examples that questions formulated through principal strata occur naturally in drug development and argue that approaching these questions with the ICH E9(R1) estimand framework has the potential to lead to more transparent assumptions as well as more adequate analyses and conclusions. In addition, we provide an overview of assumptions required for estimation of effects in principal strata. Most of these assumptions are unverifiable and should hence be based on solid scientific understanding. Sensitivity analyses are needed to assess robustness of conclusions