Validation of the Decomposition Method for Fast MIMO Over-the-Air Measurements

Over-the-air (OTA) throughput tests of wireless Multiple-Input Multiple-Output (MIMO) devices are an important tool for network operators and manufacturers. The user equipment (UE) is placed in an anechoic chamber and a random fading process is emulated by a base-station emulator (BSE). The antenna characteristic of the UE is taken into account by sampling the sphere around the UE with the BSE test antenna at a large number of positions. For low-variance throughput results, long measurement intervals over many fading realizations are required, leading to long and expensive measurement periods in an anechoic chamber. To speed up the OTA test, we analyze the Decomposition Method (DM). The DM splits the throughput measurement into two parts: (1) a receiver algorithm performance tests taking the fading process into account and (2) an antenna performance test without fading process emulation. Both results are combined into a single throughput estimate. The DM allows for a measurement time reduction of more than one order of magnitude. We provide an analytic and numerical analysis as well as measurements. Our detailed results show the validity of the DM in all practical settings

Internal oxidation and formation of Si/Al-enriched oxide bands in the scale of electrical steel grades

Oxidation during steel hot rolling is responsible for various surface defects. Local enrichments of oxygen-affine alloying elements such as silicon or aluminium can cause such defects by complicating oxide scale removal. In this paper, correlations between the temperature profile during oxidation and enrichment formation in electrical steels are investigated. Diffusion and reaction simulations using the numerical Crank-Nicolson-scheme are evaluated by comparing them to laboratory-scale oxidized samples. Furthermore, analytical approximations (spectral methods) are investigated as an alternative approach, focusing on trade-offs between accuracy and calculation times. A link between heating periods during oxidation and Si/Al-rich bands in the scale was established

Grain boundary oxidation in iron-based alloys, investigated by 18O enriched water vapour : the effect of mixed oxides in binary and ternary Fe-{Al, Cr, Mn, Si} systems

Selective oxidation experiments at 700C in binary and ternary iron-based model alloys containing Al, Cr, Mn, and Si were carried out. The internal oxidation behaviour along grain boundaries and inside ferrite grains was analyzed by LOM, SEM and ToF-SIMS. Oxygen isotope exchange revealed the location of fast diffusion pathways in the alloy. Numerical calculations of oxide distributions were compared to experimental findings, revealing that oxygen transport within ferrite grains is significantly lower than reported from literature. Discrepancies between simulations and experiments were discussed. The presented hypothesis of oxygen trapping represents an important viewpoint to explain internal oxidation in metallic alloys

Broadband Modeling and Simulation Strategy for Conducted Emissions of Power Electronic Systems Up to 400 MHz

Energy efficiency is becoming one of the most important topics in electronics. Among others, wide band-gap semiconductors can raise efficiency and lead to shrinking volumes in power conversion systems. As different markets have regulations that require different designs, it is necessary to cope with a large variety of similar designs. By using effective modeling and simulation strategies, the efforts of building these variants can be diminished, and re-designs can be avoided. In this paper, we present a universally valid way to come to reasonable simulation results for conducted emissions of a power electronic system in the frequency range from 150 kHz up to 400 MHz. After giving an overview of the state-of-the-art, the authors show how to implement and set up a simulation environment for a gallium-nitride (GaN) power converter. It shows how to differentiate between important and not that important components for Electromagnetic Compatibility (EMC), how to model these components, the printed circuit board, the load, and the setup, including the Line Impedance Stabilization Networks (LISNs), etc. Multiport S-parameter strategies as well as vector fitting methods are employed. Computational costs are kept low, and all simulations are verified with measurements; thus, this model is valid up to 400 MHz

Entwicklung von Simulationsmethoden für die Bestimmung der Schirmdämpfung von realen Gerätegehäusen

Aufgrund der Untersuchungen konnte festgestellt werden, dass es in vielen Bereichen eine gute Übereinstimmung von Messung und Simulation gibt, in einigen Frequenzbereichen gibt es jedoch größere Abweichungen. Der Grund für diese Differenzen muss in weiteren Untersuchungen bestimmt werden. Trotzdem kann das Simulationsmodell verwendet werden, um den Einfluss von verschiedenen Veränderungen des Gehäuses auf die Emission zu untersuchen. Bei niedrigen Frequenzen gibt es sowohl in der Messung als auch in der Simulation noch Verbesserungsbedarf. Es können am Messaufbau noch Veränderungen vorgenommen werden (Empfangsantenne, Messempfänger), um die Messdynamik bei niedrigen Frequenzen zu erhöhen. Auch in der Simulation können noch Parameter verändert werden (z.B. die räumliche Auflösung des Modells), um die Ergebnisse bei niedrigen Frequenzen zu verbessern. Im nächsten Schritt muss ein passendes Simulationsmodell der Leistungselektronik entwickelt werden. Dazu werden die für die Emission wichtigsten Strompfade der Leistungselektronik identifiziert und in der Simulation modelliert. Ein vollständiges Modell der Leistungselektronik wäre für die Simulation zu komplex, somit müssen Vereinfachungen vorgenommen werden. Die Emission der Leistungselektronik wird durch einige solcher Strompfade nachgebildet, wobei jeder Strompfad über einen Strom mit einem anderen Spektrum verfügt. Das Spektrum des Stromes wird aus Schaltungssimulationen (z.B. mit LT-Spice) der Leistungselektronik gewonnen. In die Quelle des Strompfades kann entweder ein Signal im Zeitbereich eingespeist werden oder es wird ein breitbandiges Signal verwendet, welches nach der Berechnung mit dem Spektrum des Stromes multipliziert wird. Die Methodik der Modellierung der Emission der Leistungselektronik muss jedoch noch durch Vergleich mit entsprechenden Messungen validiert werden

Crowdsourced analysis of clinical trial data to predict amyotrophic lateral sclerosis progression

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with substantial heterogeneity in its clinical presentation. This makes diagnosis and effective treatment difficult, so better tools for estimating disease progression are needed. Here, we report results from the DREAM-Phil Bowen ALS Prediction Prize4Life challenge. In this crowdsourcing competition, competitors developed algorithms for the prediction of disease progression of 1,822 ALS patients from standardized, anonymized phase 2/3 clinical trials. The two best algorithms outperformed a method designed by the challenge organizers as well as predictions by ALS clinicians. We estimate that using both winning algorithms in future trial designs could reduce the required number of patients by at least 20%. The DREAM-Phil Bowen ALS Prediction Prize4Life challenge also identified several potential nonstandard predictors of disease progression including uric acid, creatinine and surprisingly, blood pressure, shedding light on ALS pathobiology. This analysis reveals the potential of a crowdsourcing competition that uses clinical trial data for accelerating ALS research and development