Labor Bauphysik
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Die Klosterkirche St. Georg zu Weltenburg an der Donau, spätbarockes Hauptwerk der Brüder Asam und bayerische Welterbestätte, musste sich aufgrund ihrer topographisch, geologisch und klimatisch exponierten Lage in der Vergangenheit tiefgreifenden Instandsetzungsmaßnahmen unterziehen. Um der hygrischen Problematik im Inneren des Kirchenraumes zu begegnen, wurde ein außergewöhnlicher Sanierungsansatz verfolgt, dessen bauphysikalische und raumklimatische Verifizierung im Rahmen dieses Forschungsprojektes durchgeführt wird. Dabei steht die Optimierung des Raumklimas im Zentrum der Untersuchungen. Ganzheitlich betrachtet stellt sich die Frage: Welche Maßnahmen dürfen – bei Bewahrung der denkmalgeschützten Bausubstanz – ergriffen werden, um eine nachhaltige Nutzung historischer Bauwerke zu ermöglichen und dabei die Anforderungen der heutigen Zeit zu erfüllen?
Magnetoresistance measurements and theoretical calculations for two-dimensional electron systems under a perpendicular magnetic field are presented which illuminate transport effects due to a periodic electrostatic potential modulation. We focus on features arising from the resolution of the magnetic miniband structure which are beyond the perturbative regime governed by the dispersion of Landau bands. Our non-perturbative quantum-mechanical calculations reveal that the dispersion of individual minibands is responsible for the complicated behaviour of the magnetoresistance in the regime of intermediate modulation strength. In particular, the interplay between miniband and scattering contributions to the conductivity leads to an almost structureless magnetoresistance in this regime followed by the formation of antidot peaks due to the miniband conductivity.
We review ground-state properties and collective excitations of semiconductor quantum dots in a magnetic field obtained from current-spin density-functional theory. Due to exchange-correlation, a generalized Hund’s rule in magnetic field can be established which leads to spin alignment in partially occupied energy shells at the Fermi energy. This results, in distinct spin structures in single-electron addition spectra. Current-dependent exchange-correlation modifies the magnetic-field dependence of the ground state configuration and leads to deviations from plain spin-density calculations. Moreover it gives rise to spontaneous current textures at zero magnetic field. Collective excitation spectra, explicitly calculated for inelastic light scattering, exhibit novel features in their magnetic field dependence due to a finite ground-state spin density.
High-power packages show a characteristic three-dimensional heat flow resulting in large lateral changes in chip and case surface temperature. This paper proposes an unambiguous definition for the R/sub thJC/ junction-to-case thermal resistance as a key parameter of such packages based on a transient measurement technique ensuring high repeatability even at very low R/sub th/ values. The technique is illustrated on thermal transient measurements of high-power MOSFET devices. It is also presented how the same measurement results can be used for die attach quality analysis. Finally, a comparative method is shown for measuring the differences of R/sub th/ values among samples with many times higher resolution compared with a direct R/sub thJC/ measurement.
RENARHIS - Nachhaltige energetische Modernisierung und Restaurierung historischer Stadtquartiere
(2016)
Die Lebensqualität in einem Stadtquartier lässt sich steigern, wenn Baukunst, Energieeffizienz, regenerative Energieversorgung und kostengünstiges Wohnen zusammenkommen. All das braucht umfassendes Know-how von Architekten, Planern und Betreibern. Forscher der Ostbayerischen Technischen Hochschule Regensburg (OTH) zeigen, wie ein historisches Stadtquartier behutsam modernisiert werden kann und gleichzeitig die Mieten bezahlbar bleiben. Das Bundesinstitut für Bau-, Stadt- und Raumforschung (BBSR) hat die Forschungsarbeit kostenlos herausgegeben. Die Handlungsempfehlungen des Leitfadens richten sich an Planer, Architekten und Eigentümer.
Wie lässt sich eine Gebäudesanierung erfolgreich zum Zwecke des Klimaschutzes und der nachhaltigen Wohnqualität umsetzen? Strategien hierfür entwickelten Professor Oliver Steffens und sein Forschungsteam der OTH am Beispiel des Plato-Wild-Ensembles, einem genossenschaftlichen Wohnquartier aus den 1920er-Jahren im Regensburger Osten. Das Besondere an dem Sanierungskonzept ist sein fachübergreifender Ansatz: 30 Projektbeteiligte aus den technischen sowie wirtschafts- und sozialwissenschaftlichen Disziplinen erarbeiteten für das Plato-Wild-Ensemble mehrere Lösungsansätze: Das Projektteam verfolgte nach einer eingehenden Bestandsaufnahme das Konzept der Nachverdichtung sowie der energetischen Ertüchtigung der Gebäudehülle. Ziel war dabei, die historische Fassade zu bewahren. Das Projektteam unterlegte die Ansätze der architektonischen Modernisierung sowie der regenerativen Energieversorgung mit zahlreichen Entwürfen, Berechnungen und Simulationen. Bauphysikalische Betrachtungen zum Wärme-, Feuchte- und Schallschutz waren ein weiterer wichtiger Baustein.
A semiconductor die typically undergoes a variety of assembly processes, each of them influencing the mechanical stress environment of the chip. We report on a stress-sensitive testchip and its application to measure and characterize the respective stress distributions across the die. Particularly in the field of MEMS and sensor devices, even low stresses might deteriorate the electrical performance of a device significantly, while higher stress levels may even cause cracks and irreversible damage. This is why the present methodology has a high potential to develop into a useful tool in the field of sensor package development. After a brief introduction to the sensing principle, we investigate the stress distribution in various sample assemblies – all of them targeting pressure sensors. Typical low stress packages use silicone based soft elastic encapsulations. Changing to a harder material with a young’s modulus comparable to standard mold compounds, we demonstrate an increase of the average stress level by more than one order of magnitude.
We present ground-state calculations for laterally coupled quantum dots containing 2, 4, and 8 electrons. As our emphasis is on spin effects our results are obtained by applying spin-density functional theory (SDFT). By varying the distance between the centers of the coupled quantum dots, the transition from weak to strong coupling situation is realized. For the 2-electron system we also apply the Heitler-London approximation and analytical concepts to check the reliability of SDFT calculations in this case. In addition we discuss the features of the Coulomb staircase of laterally coupled quantum dots in the weak and strong coupling regimes in comparison to that of a circular parabolic quantum dot.
The reduction of the energy demand of existing buildings is the main objective of building refurbishment. Managing the heat radiation properties of the wall construction is a possible way to develop highly effective and resource efficient insulation materials and concepts. The application of infrared reflective wall paints and coatings has been studied since the latter half of the 20th century. A brief review of the literature gives an account of the current research status. One has to realise that the conclusions are not uniformly consistent but depend strongly on the specific boundary conditions and investigated parameters. The study presented here discusses the usage of infrared reflective wall paint in conjunction with heat insulation for historic brick masonry. The possible energy savings are linked to the resulting thermal comfort. We identify critical parameters that must be taken into account when using infrared reflective wall paint and derive recommended design rules for the refurbishment of such building types. The findings prove that infrared reflective wall paint can decrease heat losses by 18% and up to 22% if comfort conditions are considered. Increasing energy savings can also cause the negative effect of high radiative asymmetry. Thus, each configuration must be observed in detail.
This paper presents a convolutional neural network (CNN)which can be used for forecasting electricity load profiles 36 hours intothe future. In contrast to well established CNN architectures, the inputdata is one-dimensional. A parameter scanning of network parameters isconducted in order to gain information about the influence of the kernelsize, number of filters, and dense size. The results show that a goodforecast quality can already be achieved with basic CNN architectures.The method works not only for smooth sum loads of many hundredconsumers, but also for the load of apartment buildings