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Calculation of optical gain in AlGaN quantum wells for ultraviolet emission
(2020-09-03)
Stimulated emission from AlGaN based quantum wells (QWs) emitting at ultraviolet wavelengths is investigated theoretically. Maxwell–Bloch equations in the second Born approximation are solved self-consistently with the Poisson equation. The valence band dispersion is obtained from a 6-band kp-model. For a QW emitting at around 270 nm with a thickness of 2.2 nm, an estimated FWHM of 10 meV for homogeneous broadening and an excitonic red shift of 100 meV are extracted under typical laser conditions. From a comparison ...
Aufsatz
Potentials and Limitations of WorldView-3 Data for the Detection of Invasive Lupinus polyphyllus Lindl. in Semi-Natural Grasslands
(2021-10-28)
Semi-natural grasslands contribute highly to biodiversity and other ecosystem services, but they are at risk by the spread of invasive plant species, which alter their habitat structure. Large area grassland monitoring can be a powerful tool to manage invaded ecosystems. Therefore, WorldView-3 multispectral sensor data was utilized to train multiple machine learning algorithms in an automatic machine learning workflow called ‘H2O AutoML’ to detect L. polyphyllus in a nature protection grassland ecosystem. Different ...
Aufsatz
Sugar Beet Damage Detection during Harvesting Using Different Convolutional Neural Network Models
(2021-11-09)
Mechanical damages of sugar beet during harvesting affects the quality of the final products and sugar yield. The mechanical damage of sugar beet is assessed randomly by operators of harvesters and can depend on the subjective opinion and experience of the operator due to the complexity of the harvester machines. Thus, the main aim of this study was to determine whether a digital two-dimensional imaging system coupled with convolutional neural network (CNN) techniques could be utilized to detect visible mechanical ...
Aufsatz
Mirau-Based CSI with Oscillating Reference Mirror for Vibration Compensation in In-Process Applications
(2021-10-15)
We present a Mirau-type coherence scanning interferometer (CSI) with an oscillating reference mirror and an integrated interferometric distance sensor (IDS) sharing the optical path with the CSI. The IDS works simultaneously with the CSI and measures the distance changes during the depth scanning process with high temporal resolution. The additional information acquired by the IDS is used to correct the CSI data disturbed by unwanted distance changes due to environmental vibrations subsequent to the measurement. Due ...
Aufsatz
Microstructural and mechanical properties of dissimilar nitinol and stainless steel wire joints produced by micro electron beam welding without filler material
(2020-09-18)
Nitinol is a shape memory and superelastic alloy, respectively, and stainless steels are widely used materials in medical engineering, e.g., for implants and medical instruments. However, due to its high price and poor machinability, there is a high demand for dissimilar welding of nitinol components to stainless steel. During welding of titanium-containing alloys, like nitinol, to ferrous metals like stainless steel, intermetallic phases between titanium and iron may form. These phases are brittle and lead to rapid ...
Aufsatz
3D printed dielectric lens for the gain enhancement of a broadband antenna
(2020-01-13)
A novel 3D printed dielectric lens to enhance antenna gain parameters is presented. The lens is fabricated using a fused deposition method (FDM) which is a cost‐effective and an efficient 3D printing technique. Poly‐methyl methacrylate (PMMA) is used as a dielectric material due to its good RF properties. The thickness of the dielectric lens is 14 mm and provides a gain enhancement of up to 6.9 dBi over a wide frequency range. The dielectric lens is designed and computationally analyzed to demonstrate refractive index ...
Aufsatz
Augmented-Reality-basierte Assistenz für das Anlernen manueller und roboterunterstützter Montageprozesse
(2021-10-14)
Durch eine zunehmend flexibilisierte Produktion und relativ hohe Personalfluktuation bei einfachen Tätigkeiten wird das Anlernen neuer Mitarbeitender bzw. für neue oder geänderte Produktionsprozesse zunehmend relevanter. Konventionelle Anlernmethoden, bspw. durch Demonstration oder Arbeitspläne, haben Schwächen (bspw. binden sie zusätzliche Arbeitskraft oder sind kognitiv anspruchsvoll), die durch ein Augmented-Reality-(AR-)basiertes Assistenzsystem kompensiert werden können. Ein AR-Assistenzsystem zum Anlernen eines ...
Aufsatz
Iterative feature detection of a coded checkerboard target for the geometric calibration of infrared cameras
(2021-08-11)
The geometric calibration of cameras becomes necessary when images should be undistorted, geometric image information is needed or data from more than one camera have to be fused. This process is often done using a target with a checkerboard or circular pattern and a given geometry. In this work, a coded checkerboard target for thermal imaging cameras and the corresponding image processing algorithm for iterative feature detection are presented. It is shown that, due in particular to the resulting better feature ...
Aufsatz
Efficiency and agility of a liquid CO2 cooling system for molten metal systems
(2021-09-24)
In this study investigations on the efficiency and agility of a liquid CO2 cooling system, using expansion bores fed with liquid CO2 by capillary tubes, to form a thermal seal in a magnesium hot runner channel are performed in a test rig. Via temperature measurements the performance of different sets of cooling parameters is tested and cooling rates are identified depended on a varying nozzle geometry. To validate the measurements, the tests are modelled in a thermal simulation study. The applicability of the liquid ...
Aufsatz
Wine quality under integrated, organic and biodynamic management using image-forming methods and sensory analysis
(2021-12-24)
Background and aims
The image-forming methods copper chloride crystallization, capillary dynamolysis and circular chromatography are presented as an instrument for assessing wine quality. Wine quality of samples from a long-term field trial comparing integrated, organic and biodynamic management were investigated by using image-forming methods and sensory analysis.
Methods and results
Concerning the image-forming methods copper chloride crystallization, capillary dynamolysis and circular chromatography, the images ...