Durch die enge Verknüpfung von Konstruktion, Berechnung und Versuch in Verbindung mit einem mathematischen Ersatzmodell ist es möglich den optimalen Einlasskanal für einen bestimmten Zylinderkopf zu entwerfen.

Seit 2015 gibt es Doppler-LIDAR-Messungen der Windgeschwindigkeit über Leipzig. Diese Messungen werden zum einen vom HALO Photonics Streamline Doppler-LIDAR am Leipziger Institut für Troposphärenforschung (TROPOS) sowie vom Leosphere Windcube 8 Doppler-LIDAR am Leipziger Institut für Meteorologie (LIM) aufgenommen. In dieser Arbeit werden insbesondere die Daten des Windcubes bezüglich der horizontalen Windgeschwindigkeit, der Windrichtung und der Turbulenzintensität bis in eine Höhe von ca. 500 m ausgewertet. Der Vergleich mit dem HALO Photonics Streamline Doppler-LIDAR zeigt gute Korrelationen zwischen beiden Geräten. Die Ergebnisse beinhalten unter anderem eine gute Übereinstimmung mit der Ekman-Theorie. Auch die erhöhte Rauhigkeit der Stadtfläche gegenüber dem ländlichen Raum wird in der Auswertung deutlich. Es wurde ein Verfahren getestet, das es erlaubt, den turbulenten Diffusionskoeffizienten und die aerodynamische Rauhigkeitslänge aus den Messwerten abzuleiten und erste Abschätzungen dieser Größen vorzunehmen. Diese Arbeit legt nahe, den Einsatz der Fernerkundungsmessung zur Bestimmung der urbanen Grenzschichtdynamik fortzusetzen und wenn möglich zu erweitern. / Since 2015 Doppler-LIDAR measurements above Leipzig are available. The Leibniz Institute for Tropospheric Research (TROPOS) operates a HALO Photonics Streamline Doppler-LIDAR while the Institute of Meteorology Leipzig uses a Leosphere Windcube 8 Doppler-LIDAR. In this study mainly meausrements of the Windcube for horizontal wind velocity, wind direction and turbulence intensity below 500 m are evaluated. The comparison to the HALO Photonics Streamline LIDAR shows good correlations between both devices. Among others, the results include good agreements with the Ekman theory. Additionally the increased roughness of the city surface compared to rural areas becomes apparent. A way to determine characteristic quantities like the turbulent diffusion coefficient and the aerodynamic roughness length is described and initial estimations were conducted. This study suggests to continue and if possible expand such remote sensing measurements for analyses of urban boundary layer dynamics.

The present thesis is devoted to the investigation of the magnetocaloric effect (MCE) by direct measurements in pulsed and quasi-static magnetic fields as well as by analyzing specific-heat data taken in static magnetic fields. The emphasis is on the direct measurement of the adiabatic temperature change Tad in pulsed magnetic fields, because the pulsed-field data allow for an analysis of the sample-temperature response to the magnetic field on a time scale of 10 to 100 ms, which is on the order of typical operation frequencies (10 - 100 Hz) of magnetocaloric cooling devices. Besides extending the accessible magneticfield range to beyond 70 T, the short pulse duration provides nearly adiabatic conditions during the measurement. In this work, the magnetocaloric properties of various types of solids are investigated: Gadolinium (Gd) with a second-order transition, Ni50Mn35In15 with multiple magnetic transitions, and La(Fe,Si,Co)13 compounds with first and second-order transitions, depending on the Co concentration. The adiabatic temperature change of a polycrystalline Gd sample has been measured in pulsed magnetic fields up to 70 T and also in quasi-static fields up to 2 T. A very large adiabatic temperature change of Tad 60 K is observed near the Curie temperature (TC = 294 K) for a field change of 70 T. In addition, we find that this maximum temperature change grows with H2=3. We have studied the MCE in the shape-memory Heusler alloy Ni50Mn35In15 by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results obtained for 6 T pulses are compared with data extracted from specific-heat experiments. We find a saturation of the inverse MCE, related to the firstorder martensitic transition, with a maximum adiabatic temperature change of Tad = 7 K at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. Our results disclose that in shape-memory alloys the different contributions to the MCE and hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications. Finally, a comparative study of the magnetic and magnetocaloric properties of La(Fe,Si,Co)13 alloys is presented by discussing magnetization, Tad, specificheat, and magnetostriction measurements. The nature of the transition can be changed from first to second order as well as the temperature of the transition can be tuned by varying the Co concentration. The MCE of two samples with nominal compositions of LaFe11:74Co0:13Si1:13 and LaFe11:21Co0:65Si1:11 have been measured in pulsed magnetic fields up to 50 T. We find that LaFe11:74Co0:13Si1:13 with a first-order transition (TC = 198 K) shows half of the net MCE already at low fields (2-10 T). Whereas the MCE of LaFe11:21Co0:65Si1:11 with secondorder transition (TC = 257 K) grows gradually. The MCE in both compounds reaches almost similar values at a field of 50 T. The MCE results obtained in pulsed magnetic fields of 2 T are in good agreement with data from quasistatic field measurements. The pulsed-field magnetization of both compounds has been measured in fields up to 60 T under nearly adiabatic conditions and compared to steady-field isothermal measurements. The differences between the magnetization curves obtained under isothermal and adiabatic conditions give the MCE via the crossing points of the adiabatic curve with the set of isothermal curves. For LaFe11:74Co0:13Si1:13, a S - T diagram has been constructed from specific-heat measurements in static fields, which is used to extract the MCE indirectly. Magnetostriction measurements are carried out for two compounds in both static and pulsed magnetic fields. For LaFe11:74Co0:13Si1:13, the strain shows a sharp increase. However, due to cracks appearing in the sample an irreversible magneto-volume effect of about 1% is observed in pulsed magnetic fields. Whereas for LaFe11:21Co0:65Si1:11 the data show a smooth increase of the sample length up to 60 T, and a 1.3% volume increase is obtained. We also find that magnetizing the latter sample in the paramagnetic state is tightly bound to the volume increase and this, likewise for the former sample, gives the main contribution to the entropy change.

The present thesis is devoted to the investigation of the magnetocaloric effect (MCE) by direct measurements in pulsed and quasi-static magnetic fields as well as by analyzing specific-heat data taken in static magnetic fields. The emphasis is on the direct measurement of the adiabatic temperature change Tad in pulsed magnetic fields, because the pulsed-field data allow for an analysis of the sample-temperature response to the magnetic field on a time scale of 10 to 100 ms, which is on the order of typical operation frequencies (10 - 100 Hz) of magnetocaloric cooling devices. Besides extending the accessible magneticfield range to beyond 70 T, the short pulse duration provides nearly adiabatic conditions during the measurement. In this work, the magnetocaloric properties of various types of solids are investigated: Gadolinium (Gd) with a second-order transition, Ni50Mn35In15 with multiple magnetic transitions, and La(Fe,Si,Co)13 compounds with first and second-order transitions, depending on the Co concentration. The adiabatic temperature change of a polycrystalline Gd sample has been measured in pulsed magnetic fields up to 70 T and also in quasi-static fields up to 2 T. A very large adiabatic temperature change of Tad 60 K is observed near the Curie temperature (TC = 294 K) for a field change of 70 T. In addition, we find that this maximum temperature change grows with H2=3. We have studied the MCE in the shape-memory Heusler alloy Ni50Mn35In15 by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results obtained for 6 T pulses are compared with data extracted from specific-heat experiments. We find a saturation of the inverse MCE, related to the firstorder martensitic transition, with a maximum adiabatic temperature change of Tad = 7 K at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. Our results disclose that in shape-memory alloys the different contributions to the MCE and hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications. Finally, a comparative study of the magnetic and magnetocaloric properties of La(Fe,Si,Co)13 alloys is presented by discussing magnetization, Tad, specificheat, and magnetostriction measurements. The nature of the transition can be changed from first to second order as well as the temperature of the transition can be tuned by varying the Co concentration. The MCE of two samples with nominal compositions of LaFe11:74Co0:13Si1:13 and LaFe11:21Co0:65Si1:11 have been measured in pulsed magnetic fields up to 50 T. We find that LaFe11:74Co0:13Si1:13 with a first-order transition (TC = 198 K) shows half of the net MCE already at low fields (2-10 T). Whereas the MCE of LaFe11:21Co0:65Si1:11 with secondorder transition (TC = 257 K) grows gradually. The MCE in both compounds reaches almost similar values at a field of 50 T. The MCE results obtained in pulsed magnetic fields of 2 T are in good agreement with data from quasistatic field measurements. The pulsed-field magnetization of both compounds has been measured in fields up to 60 T under nearly adiabatic conditions and compared to steady-field isothermal measurements. The differences between the magnetization curves obtained under isothermal and adiabatic conditions give the MCE via the crossing points of the adiabatic curve with the set of isothermal curves. For LaFe11:74Co0:13Si1:13, a S - T diagram has been constructed from specific-heat measurements in static fields, which is used to extract the MCE indirectly. Magnetostriction measurements are carried out for two compounds in both static and pulsed magnetic fields. For LaFe11:74Co0:13Si1:13, the strain shows a sharp increase. However, due to cracks appearing in the sample an irreversible magneto-volume effect of about 1% is observed in pulsed magnetic fields. Whereas for LaFe11:21Co0:65Si1:11 the data show a smooth increase of the sample length up to 60 T, and a 1.3% volume increase is obtained. We also find that magnetizing the latter sample in the paramagnetic state is tightly bound to the volume increase and this, likewise for the former sample, gives the main contribution to the entropy change.

Durch die enge Verknüpfung von Konstruktion, Berechnung und Versuch in Verbindung mit einem mathematischen Ersatzmodell ist es möglich den optimalen Einlasskanal für einen bestimmten Zylinderkopf zu entwerfen.

Spectral reflectivity and albedo are obtained from airborne measurements of spectral irradiance and radiance during two field campaigns in Leipzig, Germany and Zhongshan, China. The data measured above urban and rural areas have been investigated with respect to the heterogeneity and anisotropy of the surface. Furthermore the spectral albedo and reflectivity measured above the same surface but at different flight altitudes have been analyzed. These data is used to estimate the impact of multiple scattering processes by aerosol particles and gas molecules.

Several years of my experiences in the use of real-time experiments are now upgraded in order to enhance also the teaching of mathematics. The motion sensor device enables us to get real time x(t) and v(t) graphs of a moving object or person. We can productively use these graphs to introduce differentiation on visual level as well as to show the integration procedure. The students are fully involved in the teaching as they are invited to walk in front of the sensor. This approach motivates them by the realistic aspects of mathematical structures. The method could help to fulfill the credo of teaching: comprehension before computation. The steps of such an approach are explained and discussed in further detail below.

Die Arbeit untersucht das Orientierungsverhalten von niedermolekularen thermotropen nematischen Flüssigkristallen in externen elektrischen und magnetischen Feldern. Mit einer Kombination von Protonen- und Fluor-NMR-Experimenten und Orientierungsexperimenten in elektrischen Feldern wird eine Vielzahl von dynamischen Prozessen in einem Zeitbereich von 100 ms bis 100 us untersucht. Der erste Teil der Arbeit enthält eine Beschreibung des experimentellen Aufbaus für eine elektrische Steuerung von Orientierungsexperimenten im Magnetfeld eines NMR-Spektrometers. Die verschiedenen Komponenten zur Erzeugung von Hochspannungsimpulsen, zur Automatisierung des Meßablaufs und zur Synchronisation mit dem NMR-Spektrometer werden vorgestellt. Dabei wird auf die Schwierigkeiten bei NMR-Messungen an dünnen Kondensatorproben eingegangen. Im zweiten Teil der Arbeit folgt eine Untersuchung verschiedener dynamischer Prozesse in nematischen Flüssigkristallen. Durch die Kombination von elektrisch induzierten Prozessen mit unterschiedlichen Spannungsimpulsen kann ein sehr weiter Zeitbereich, der sich bis zu minimalen Orientierungszeiten von etwa 50 us erstreckt, erfaßt werden. Eine Analyse dieser Experimente erlaubt Rückschlüsse auf die Natur des dynamischen Prozesses wie z. B. den Übergang von homogenen zu inhomogenen Prozessen und ergibt eine Reihe von Materialparametern. Die zeitaufgelöste Messung der Orientierungsprozesse erfolgt mit verschiedenen, speziell für die Anwendung in elektrischen Feldern entwickelten NMR-Techniken. In einer Reihe von Protonen- und Fluor-Messungen werden die dipolare Dublettaufspaltung und die chemische Verschiebung als Funktionen des Winkels zwischen dem nematischen Direktor und dem Magnetfeld untersucht. Dabei nimmt die Linienbreite der Protonen-Spektren von ca. 30 kHz auf unter 300 Hz ab, und die Position der Fluor chemischen Verschiebung variiert in einem Bereich von etwa 10 kHz. / Electrically Induced Dynamic Processes in Liquid Crystals Investigated by Means of NMR --------------------------------------------------------- Within the thesis reorientation processes of thermotropic low molar mass nematic liquid crystals are described. Dynamic processes in external electric and magnetic fields are investigated by means of proton and fluorine NMR. A combination of different reorientation experiments with NMR methods allows the direct observation of the director dynamics on a timescale from 100 milliseconds to 100 microseconds. The first part provides a detailed description of the experimental setup. The reorientation experiments in the magnetic field of the NMR spectrometer are induced by high voltage pulses. The different parts of the high voltage supply are specified together with the synchronisation with the NMR experiment and several automation techniques. Some difficulties related to the usage of thin capacitor cells as NMR samples are discussed. The second part deals with different types of dynamic processes in nematic liquid crystals. The reorientation dynamics can be changed in a wide range by varying the electric excitation. Reorientation times down to 50 us are possible. Special time resolved NMR techniques provide the dipolar splitting and the chemical shift as a function of the orientational state. The proton linewidth changes in such an experiment from approx. 30 kHz to less than 300 Hz, the position of the fluorine chemical shift varies within a range of 10 kHz. These results yield a multitude of material parameters and provide information about the underlying dynamic process which may be e.g. homogeneous or inhomogeneous.

Recently, the fundamental and nanoscale understanding of complex phenomena in materials research and the life sciences, witnessed considerable progress. However, elucidating the underlying mechanisms, governed by entangled degrees of freedom such as lattice, spin, orbit, and charge for solids or conformation, electric potentials, and ligands for proteins, has remained challenging. Techniques that allow for distinguishing between different contributions to these processes are hence urgently required. In this paper we demonstrate the application of scattering-type scanning near-field optical microscopy (s-SNOM) as a novel type of nano-probe for tracking transient states of matter. We introduce a sideband-demodulation technique that allows for probing exclusively the stimuli-induced change of near-field optical properties. We exemplify this development by inspecting the decay of an electron-hole plasma generated in SiGe thin films through near-infrared laser pulses. Our approach can universally be applied to optically track ultrafast/-slow processes over the whole spectral range from UV to THz frequencies.

Das Projekt OEKO-ID hat zum Ziel. problematische Bauteilanschlüsse, insbesondere Balkenköpfe von Holzdecken, im Zusammenhang mit "ökologischen" Innendämmsystemen messtechnisch zu untersuchen. Des Weiteren sollen Möglichkeiten und Grenzen der hygrothermischen Simulation aufgezeigt werden. Ferner wurde eine neue Methode molekularbiologischer und baubiologischer Untersuchungen, hier zur Detektierung von Schimmelpilzen, entwickelt und optimiert.