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Item Open Access Eignung von metallorganischen Gerüstverbindungen als stationäre Phase in der Hochleistungsflüssigchromatographie (HPLC)(2017) Lieder, Christian; Klemm, Elias (Prof. Dr.-Ing.)Anwendung von metallorganischen Gerüstverbindungen als stationäre Phase in der HPLC, Vergleich mit klassischen Silika-Materialien. Synthese der metallorganischen Gerüstverbindungen, Modifizierung. Befüllung chromatographischer Säulen und Gegenüberstellung der Füllmethoden. Methodenentwicklung, Einflüsse auf chromatographische Ergebnisse. Chirale Erkennung, Untersuchung der Wechselwirkungen. Theoretisch chemische Berechnungen der Wechselwirkungen.Item Open Access Optical and magneto-optical investigations on 3D Dirac- and Weyl-semimetals(2017) Neubauer, David; Dressel, Martin (Prof. Dr.)This work concentrates on optical investigations on 3D Dirac- and Weyl-semimetals with and without applied magnetic fields. Four compounds are extensively discussed, namely the 3D Dirac semimetal Cd3As2, the Weyl semimetals TaAs and NbP, and finally evidence is found for 2D Dirac states in the iron based superconductor FeSe. For the measurements in magnetic fields a novel magneto-optical installation is designed and implemented in the lab. The design principle and characterization of this setup is presented.Item Open Access Beendigung von Kontraktlogistikbeziehungen : Häufigkeiten, Treiber, Gründe und Phasen der Beendigung kontraktlogistischer Beziehungen(2017) Drodofsky, Michael; Large, Rudolf (Prof. Dr.)Item Open Access Active electronic loads for radiometric calibration(2017) Weissbrodt, Ernst; Kallfass, Ingmar (Prof. Dr.)Although radiometer systems are widely applied in very different fields, they all have one important requirement in common: They require a thorough radiometric calibration. Various conventional calibration references are well established, but their bulkiness, high power consumption, and complexity are limiting the expanding fields of application. Since novel industrial applications such as passive millimeter-wave imaging emerge, the requirements for calibration references have increased drastically. But also in scientific fields like radio astronomy, cosmology or environmental monitoring, modern remote sensing radiometers do not rely only on conventional references anymore. In this work, millimeter-wave monolithic integrated circuits (MMICs) based on metamorphic high electron mobility transistors (mHEMT) were designed to be used as active electronic loads for radiometric calibration. These novel references have not only the outstanding property, that they can be directly integrated on chip-level into the radiometer front-end, but also, that they can exhibit cold as well as hot reference noise temperatures. Since this is achieved without any physical cooling or heating, the power consumption is notably reduced. By monolithic integration of field effect transistor (FET) switches, theses multiple references can internally be routed to the receiver input without any mechanical wear. As a result, laborious external references can be omitted and the repetition rate of the calibration procedure increased, which results in a higher radiometric accuracy and allows a more compact and cost-effective design of modern radiometer systems. This work presents the first radiometric calibration front-end that allows to internally switch between active electronic cold and active electronic hot loads, as well as a passive ambient load. All components are integrated on a single MMIC, and a patent was granted for this innovation. To predict the achievable noise temperatures of active cold loads (ACLs), different simulation approaches were previously published. This work evaluates and adapts these existing approaches to design and manufacture several W-band loads. But the required design-flow was found to be very time-consuming because multiple iterations are necessary to successively design and optimize the input- and output matching networks, and to finally achieve the desired low noise temperature. Therefore, a novel simulation approach is introduced that makes efficiently use of modern optimization algorithms and the very accurate model library of the mHEMT technology and the passive structures. With this novel simulation method, the first active hot loads (AHLs) were designed as well as state-of-the-art ACLs up to 140 GHz. However, the characterization of low-noise one-port devices is particularly challenging, especially at such high frequencies. Hence, a substantial part of this work is to investigate the reliability of different noise measurement setups and the repeatability of noise temperature results. Dedicated setups in W- and D-band are used to characterize all manufactured active loads and some selected results are cross-checked by measuring the same circuits with independently designed measurement systems of other research facilities. The discrepant results are discussed, concluding that high variations in measured one-port noise temperature do not allow to rely on one single measurement setup. At the same time, this thorough investigation and comparison permits to establish an accuracy range within which the results of the manufactured active electronic loads are reliable, whereas other previously published ACLs are typically only measured with one measurement setup.Item Open Access Simultaneous optimization of office building facades in terms of both energy consumption and transparency in hot arid climates, analysed on the example of Cairo(2017) Mohamed, Tamer Awny Abd Elkader; Moro, José Luis (Prof. Dipl.-Ing.)Since the early days, buildings forms, types of construction, and development were closely responding to the local climatic conditions. However, the technical innovations during the last 150 years and the calls of modern architecture to transparency drove the building sector towards the extensive usage of glazed facades in commercial buildings and to the adoption of the international style buildings. Those building models can only function through the extensive intervention of technical equipment to guarantee the desired internal comfort conditions at any place of the world with the corresponding massive energy input, owing to the poor thermal performance of glazing and its selective property with respect to radiation permeability (greenhouse effect). Unfortunately, this situation is very apparent in Cairo. Contemporary commercial buildings are being increasingly designed and constructed based upon highly glazed building models originally conceived in, and for, countries with moderate climates. Such architecture is totally maladapted to the hot-arid climate, especially with the extensive solar radiation and the relatively high summer temperatures. However, on the other hand, transparency provides crucial psychological values and benefits to the occupants. It affects their comfort, sense of well-being, and affords them view and natural light. View provides the occupants with visual amenity, access to environmental information, relief from claustrophobia and monotony, and recovery from daily stress. While natural lighting has a direct influence on mood and cognition, and influences the production of hormones, it also regulates motivation, and improves productivity in the workplace. In addition, the proper use of natural day-light decreases the energy used for lighting and improves the environmental quality indoors. The research work aims to elaborate a scientific methodology in order to optimize the office facades configurations in hot-arid climates, analyzed on the example of Cairo. The research methodology is based on investigating the adequate balance between two critical, and at the same time conflicting requirements or tasks, which are: First: To provide the required level of transparency that provides the occupants with their psychological sense of satisfaction and general well-being. Second: To reduce the total energy consumption of the building through an energy-efficient concept based on a proposed solar protection strategy. Through a series of parametric analysis processes of the energetic performance of the selected solar protection variants (represented by their total annual energy consumption per square meter) with their corresponding visual quality (represented by their view index measures), the research provides an optimized definition for the configuration of office facades. The optimized façade designs achieved the required balancing ratio that gives the occupants psychological satisfaction and general well-being. The research proposes an Energy-Transparency Balancing Factor (ETBF) in order to compare and differentiate between the findings of these optimized configurations.Item Open Access Transformation von B. subtilis 168 : Optimierung und Regulation des Transkriptionsfaktors ComK(2017) Franzen, Regine; Mattes, Ralf (Prof. Dr. rer. nat.)Item Open Access Nonlinear optical microspectroscopy with few-cycle laser pulses(2017) Wan, Hui; Wrachtrup, Jörg (Prof. Dr.)Nonlinear optical (NLO) microscopy is a powerful tool in physics, chemistry, and material science it probes intrinsic optical properties of the sample without the need of labeling. In order to investigate the ultrafast processes in nonlinear materials with high spatial resolution, we need to combine both ultrashort pulses and techniques focusing them to the diffraction limit. Previously, few-cycle laser pulses have often been tightly focused using conventional microscope objectives. However, the propagation of an ultrashort pulse in optical materials, particularly in the glass of a high numerical aperture (N.A.) microscope objective, results in spatial and temporal distortions of the pulse electric field, which can severely affect its quality in the focus. By purely passive group delay dispersion (GDD) and third-order dispersion (TOD) management, in this thesis, we experimentally demonstrate in-focus diffraction-limited and bandwidth-limited few-cycle pulses by using high N.A. objectives. Based on these achievements, the performance of a novel few-cycle NLO microscope for both second-harmonic generation (SHG) imaging and microspectroscopy in the frequency- and time-domains was characterized. The inverse linear dependence of SHG intensity on the in-focus pulse duration was demonstrated down to 7.1 fs for the first time. The application of shorter in-focus pulses for the enhancement of SHG image contrast was successfully demonstrated on a single collagen (type-I) fibril as a biological model system for studying protein assemblies under physiological conditions. Beyond imaging, a collagen fibril has been found to act as a purely non-resonant χ(2) soft matter under the present excitation conditions, and its ratio of forward- to epi-detected SHG intensities allowed for the estimation of the fibril thickness, which corresponds well with atomic force microscopy (AFM) measurements. The ultrafast dephasing of the localized surface plasmon resonance (LSPR) in the metallic nanoparticles, that only occurs on a time scale of a few femtoseconds, has gained a lot of attraction in the field of nanoplasmonics. This thesis is the first systematic experimental demonstration of time-resolving ultrashort plasmon dephasing in single gold nanoparticles by using interferometric SHG spectroscopy with in-focus 7.3 fs excitation pulses in combination with linear scattering spectroscopy performed on the same nanoparticle. For nanorods, nanodisks, and nanorectangles, strong plasmon resonance enhanced SHG is observed, where the SHG intensity strongly depends on the spectral overlap between the LSPR band and the excitation laser spectrum. For single nanorods and nanorectangles, the polarization dependence of the SHG intensity was found to follow second-order dipole scattering, and the effect of size and shape on the LSPR properties was directly observed in the time-domain. Good agreement between experimental and simulated values of dephasing times and resonance wavelengths is obtained, which confirms that a common driven damped harmonic oscillator model for the LSPR in the nanoparticle can qualitatively explain both the linear scattering spectra in the frequency-domain and the SHG response in the time-domain. Resonance bands in linear transmission and scattering spectra have also been observed for nanoholes with sizes smaller than the wavelength of the incident light in a metal film, which are assigned to LSPR modes of the electric field distribution around the nanohole with qualitatively similar resonance properties as a nanoparticle. The polarization-resolved nonlinear optical properties of the single nanoholes with different shapes and symmetries were also reported. The objective of this thesis has been systematic SHG studies of the size effect in the LSPR of single nanoholes in metal films and of their ultrafast dephasing dynamics. Although, enhancement of both the forward- and epi-detected SHG emissions from single rectangular nanoholes are observed,however,no ultrafast dephasing dynamics of LSPRs in rectangular nanoholes could be time-resolved with our in-focus 7.3 fs excitation laser pulses, which indicates that contributions from LSPR enhanced SHG to the detected SHG signal are negligible. More work needs to be done in order to overcome the current experimental limitations. However, in this thesis, the polarization dependence of the forward- and epi-detected SHG intensity from the single rectangular nanohole was found to follow that of a second-order dipole pattern. While the SHG dipole pattern observed for rectangular nanoparticles is oriented parallel to its long-axis, the SHG dipole pattern of its complementary rectangular nanohole is oriented perpendicular to its long-axis. This observation represents the first experimental demonstration of Babinet’s principle in second-order nonlinear scattering of a single rectangular nanohole in a gold film.Item Open Access An approach for automated detection and classification of pavement cracks(2017) Al-Mistarehi, Bara'; Schwieger, Volker (Prof. Dr.-Ing. habil.)Item Open Access Investigating superconductivity by tunneling spectroscopy using oxide heterostructures(2017) Fillis-Tsirakis, Evangelos; Mannhart, Jochen (Prof. Dr.)Item Open Access Shape derivatives and shock capturing for the Navier-Stokes equations in discontinuous Galerkin methods(2017) Sonntag, Matthias; Munz, Claus-Dieter (Prof. Dr.)This work addresses two different topics, the shape derivatives for the compressible Navier-Stokes equations on the one hand and, on the other hand, the treatment of shocks or other flow discontinuities in Discontinuous Galerkin methods. There is a strong demand for very efficient methods for shape optimization in the aerospace industry, for example drag reduction or lift maximization of an aircraft. The use of gradient based optimization schemes requires derivatives of the cost function with respect to the shape of an object. With the shape derivatives presented in this work, these derivatives can be calculated independent of the parametrization of the object's shape, and, since the derivation takes place in the continuous space, they can be applied to almost any discretization. Nevertheless, one has to take the numerical scheme, which is later applied, into account. For methods based on the variational formulation a difference in the shape derivative, compared to the pointwise approach, arises, which cannot be neglected. Hence, one objective of this work is to derive the shape derivatives of the drag- and lift-coefficient for the Navier-Stokes equations in variational formulation and compare it with the pointwise approach both analytically and numerically. A discrepancy has to be expected, especially for flow phenomena with high gradients or discontinuities which do not fulfill the strong form of the governing equations. These flow phenomena require a special treatment in numerical methods of high order. In the second part of this work, a shock capturing for the Discontinuous Galerkin method is developed which prevents the oscillations originating from the approximation of discontinuities with high order polynomials. Therefore a hybrid approach is presented, where the original DG scheme is coupled with a second order Finite Volume method. In all elements containing shocks or discontinuities the operator of the DG method is replaced by the Finite Volume scheme. This scheme is, due to the use of slope limiters, well known for its strengths in handling shocks. However, in regions where the flow is smooth the Finite Volume method requires a finer resolution for the same accuracy than the Discontinuous Galerkin scheme. Using the same mesh for the FV method as for the DG scheme would lead to a big reduction in resolution. Hence, to compensate this loss the original elements of the mesh are divided into logical sub-cells. By associating exactly one Finite Volume sub-cell to each degree of freedom of a DG element, the same data structures can be used. This enables an efficient implementation of the outlined shock capturing designated for high performance computations. Therefore, not only the basic properties of this hybrid DG/FV sub-cell approach are investigated with several examples, but also studies regarding the parallel efficiency are performed.