Refine
Year of publication
Institute
- Fachbereich Energietechnik (604) (remove)
Language
- English (357)
- German (245)
- Multiple languages (1)
- Dutch (1)
Document Type
- Article (604) (remove)
Keywords
- Earthquake (4)
- Blitzschutz (3)
- Lightning protection (2)
- Algal Turf Scrubber (1)
- Algal–bacterial bioflm (1)
- Alternative Energiequelle (1)
- Antibias (1)
- Artificial intelligence (1)
- BIM (1)
- Basisisolierung (1)
- Bauwerksüberwachung (1)
- Behaviour factor q (1)
- Bemessung (1)
- Biogas (1)
- Cardiovascular MRI (1)
- Circular bioeconomy (1)
- Civil engineering (1)
- DAC (1)
- DIN EN 1996 (1)
- Decoupling (1)
- Diversity Management (1)
- Dynamic simulation (1)
- Emilia-Romagna earthquake (1)
- Empirical consequence curves (1)
- Empirical fragility functions (1)
- Energietechnische Anlage (1)
- Engineering Habitus (1)
- Erdbebeneinwirkung (1)
- Fracture classification (1)
- Frame structure (1)
- Genetic algorithm (1)
- Germany (1)
- INODIS (1)
- INSYSME (1)
- Imaging (1)
- In-plane performance, isolation (1)
- Infill wall design (1)
- Left ventriular function (1)
- Linear elastic analysis (1)
- MR-stethoscope (1)
- Magnetic field strength (1)
- Magnetic resonance imaging (MRI) (1)
- Masonry infill (1)
- Masonry partition walls (1)
- Mauerwerksbauten (1)
- Mauerwerksgebäude (1)
- Methane (1)
- Modern constructions (1)
- Molten salt receiver system (1)
- Molten salt solar tower (1)
- Momentenverteilung (1)
- Monitoring (1)
- Monte Carlo Tree Search (1)
- Morphing (1)
- Multi-storey (1)
- Numerical modelling (1)
- Organizational Culture (1)
- Out-of-plane capacity (1)
- PBEE (1)
- Piping (1)
- Precast buildings (1)
- Probability distribution mapping (1)
- PushoverAnalysen (1)
- Rahmentragwirkung (1)
- Regenerative Energieanlagen (1)
- Reinforced concrete frame (1)
- Risikoabschätzung (1)
- Risikomanagement (1)
- Risk assessment (1)
- Risk management (1)
- Seismic design (1)
- Seismic loading (1)
- Sensor (1)
- Shoulder (1)
- Slab deflection (1)
- Structural design (1)
- Tank (1)
- Transient flux distribution (1)
- Two-phase modelling (1)
- Unreinforced masonry buildings (1)
- Verhaltensbeiwerte (1)
- Wand-Decken-Interaktion (1)
- bio-methane (1)
- body limbs (1)
- bubble column (1)
- carbon dioxide removal (1)
- cardiac gating (1)
- cardiovascular MR imaging (1)
- change management (1)
- churches (1)
- climate neutrality (1)
- concentrating collector (1)
- deserts (1)
- direct air capture (1)
- distribution grid simulation (1)
- diversity management (1)
- e-mobility (1)
- earthquake engineering (1)
- economics (1)
- electrocardiogram (1)
- engineering (1)
- equivalent stiffness (1)
- granular silo (1)
- high field MR imaging (1)
- hypoplasticity (1)
- impulsive effects (1)
- in-plane behaviour (1)
- innovation management (1)
- lightning protection (1)
- liquid-storage tank (1)
- liquid-structure interaction (1)
- lizards (1)
- macro-element (1)
- magnetic resonance imaging (1)
- masonry infill (1)
- methanation (1)
- negative emissions (1)
- nonlinear transient analyses (1)
- out-of-plane behaviour (1)
- phonocardiogram (1)
- plug flow reactor (1)
- point-focussing system (1)
- power-to-gas (1)
- raytracing (1)
- renewable energy (1)
- research association (1)
- rollout (1)
- seismic (1)
- seismic response (1)
- smart-charging (1)
- solar process heat (1)
- structure-soil-structure interaction (1)
- swimming (1)
- truss (1)
- vault (1)
Heat production in the windings of the stators of electric machines under stationary condition
(2014)
In electric machines due to high currents and resistive losses (joule heating) heat is produced. To avoid damages by overheating the design of effective cooling systems is required. Therefore the knowledge of heat sources and heat transfer processes is necessary. The purpose of this paper is to illustrate a good and effective calculation method for the temperature analysis based on homogenization techniques. These methods have been applied for the stator windings in a slot of an electric machine consisting of copper wires and resin. The key quantity here is an effective thermal conductivity, which characterizes the heterogeneous wire resin-arrangement inside the stator slot. To illustrate the applicability of the method, the analysis of a simplified, homogenized model is compared with the detailed analysis of temperature behavior inside a slot of an electric machine according to the heat generation. We considered here only the stationary situation. The achieved numerical results are accurate and show that the applied homogenization technique works in practice. Finally the results of simulations for the two cases, the original model of the slot and the homogenized model chosen for the slot (unit cell), are compared to experimental results.
Since the 80s power production with solar thermal power plants has been a way to substitute fossil fuels. By concentrating direct solar radiation from heliostats very high temperatures of a thermal fluid can be reached. The resulting heat is converted to mechanical energy in a steam cycle which generates electricity.
High efficiencies and fast start-up are reached by using air as a heat medium, as well as using porous ceramic materials as solar receiver of the concentrated sunlight.
In Germany the construction of a 1.5 MWe solar tower power plant began in 2008. It is operational since December 2008 and started production of electricity in the spring of 2009.
In Greece and Cyprus, countries with high solar potential, the development of this competitive solar thermal technology is imperative, since it has already been implemented in other Mediterranean countries.
Numerische Simulation des Gefrierprozesses bei der Baugrundvereisung im durchströmten Untergrund
(2008)
The sandfish (Scincus scincus) is a lizard having the remarkable ability to move through desert sand for significant distances. It is well adapted to living in loose sand by virtue of a combination of morphological and behavioural specializations. We investigated the bodyform of the sandfish using 3D-laserscanning and explored its locomotion in loose desert sand using fast nuclear magnetic resonance (NMR) imaging. The sandfish exhibits an in-plane meandering motion with a frequency of about 3 Hz and an amplitude of about half its body length accompanied by swimming-like (or trotting) movements of its limbs. No torsion of the body was observed, a movement required for a digging-behaviour. Simple calculations based on the Janssen model for granular material related to our findings on bodyform and locomotor behaviour render a local decompaction of the sand surrounding the moving sandfish very likely. Thus the sand locally behaves as a viscous fluid and not as a solid material. In this fluidised sand the sandfish is able to “swim” using its limbs.
Objective: As high-field cardiac MRI (CMR) becomes more widespread the propensity of ECG to interference from electromagnetic fields (EMF) and to magneto-hydrodynamic (MHD) effects increases and with it the motivation for a CMR triggering alternative. This study explores the suitability of acoustic cardiac triggering (ACT) for left ventricular (LV) function assessment in healthy subjects (n=14). Methods: Quantitative analysis of 2D CINE steady-state free precession (SSFP) images was conducted to compare ACT’s performance with vector ECG (VCG). Endocardial border sharpness (EBS) was examined paralleled by quantitative LV function assessment. Results: Unlike VCG, ACT provided signal traces free of interference from EMF or MHD effects. In the case of correct Rwave recognition, VCG-triggered 2D CINE SSFP was immune to cardiac motion effects—even at 3.0 T. However, VCG-triggered 2D SSFP CINE imaging was prone to cardiac motion and EBS degradation if R-wave misregistration occurred. ACT-triggered acquisitions yielded LV parameters (end-diastolic volume (EDV), endsystolic volume (ESV), stroke volume (SV), ejection fraction (EF) and left ventricular mass (LVM)) comparable with those derived fromVCG-triggered acquisitions (1.5 T: ESVVCG=(56± 17) ml, EDVVCG=(151±32)ml, LVMVCG=(97±27) g, SVVCG=(94± 19)ml, EFVCG=(63±5)% cf. ESVACT= (56±18) ml, EDVACT=(147±36) ml, LVMACT=(102±29) g, SVACT=(91± 22) ml, EFACT=(62±6)%; 3.0 T: ESVVCG=(55±21) ml, EDVVCG=(151±32) ml, LVMVCG=(101±27) g, SVVCG=(96±15) ml, EFVCG=(65±7)% cf. ESVACT=(54±20) ml, EDVACT=(146±35) ml, LVMACT= (101±30) g, SVACT=(92±17) ml, EFACT=(64±6)%). Conclusions: ACT’s intrinsic insensitivity to interference from electromagnetic fields renders
Antibias training is increasingly demanded and practiced in academia and industry to increase employees’ sensitivity to discrimination, racism, and diversity. Under the heading of “Diversity Management,” antibias trainings are mainly offered as one-off workshops intending to raise awareness of unconscious biases, create a diversity-affirming corporate culture, promote awareness of the potential of
diversity, and ultimately enable the reflection of diversity in development processes. However, coming from childhood education, research and scientific articles on the sustainable effectiveness of antibias in adulthood, especially in academia, are very scarce. In order to fill this research gap, the article aims to explore how sustainable the effects of individual antibias trainings on participants’ behavior are. In order to investigate this, participant observation in a qualitative pre–post setting was conducted, analyzing antibias training in an academic context. Two observers actively participated in the training sessions and documented the activities and reflection processes of the participants. Overall, the results question the effectiveness of single antibias trainings and show that a target-group adaptive approach is mandatory owing to the background of the approach in early childhood education. Therefore, antibias work needs to be adapted to the target group’s needs and realities of life. Furthermore, the study reveals that single antibias trainings must be embedded in a holistic diversity management approach to stimulate sustainable reflection processes among the target group. This article is one of the first to scientifically evaluate antibias training effectiveness, especially in engineering sciences and the university context.
Extrem hohe Blitzströme
(2018)
Blitze sind nach wie vor eine enorme Schadensquelle für Personenschäden, Brände, mechanische Zerstörungen und insbesondere auch Überspannungen. Das zeigen nicht zuletzt aktuelle Statistiken der Schadensversicherer. Immer wieder gibt es Meldungen über extrem hohe Blitzströme, die natürlich auch zu großen Schäden und Zerstörungen führen können. Dabei werden Scheitelwerte von teilweise deutlich über 300 kA genannt. Dies wirft Fragen auf, da die „klassische“ Blitzstatistik (z. B. nach CIGRE und IEC [8][10]) bisher solche Werte nicht kennt. Diese extremen Blitzströme werden meist aus den Daten von Blitzortungssystemen ermittelt.
Previous studies optimized the dimensions of coaxial heat exchangers using constant mass fow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar fow types. In contrast, in this study, fow conditions in the circular ring are kept constant (a set of fxed Reynolds numbers) during optimization. This approach ensures fxed fow conditions and prevents inappropriately high or low mass fow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic efort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass fow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefcients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy diference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy fux and hydraulic efort. The Reynolds number in the circular ring is instead of the mass fow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar fow and 60% for turbulent fow scenarios. Net-exergetic optimization shows a predominant infuence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the fow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.
Direct air capture (DAC) combined with subsequent storage (DACCS) is discussed as one promising carbon dioxide removal option. The aim of this paper is to analyse and comparatively classify the resource consumption (land use, renewable energy and water) and costs of possible DAC implementation pathways for Germany. The paths are based on a selected, existing climate neutrality scenario that requires the removal of 20 Mt of carbon dioxide (CO2) per year by DACCS from 2045. The analysis focuses on the so-called “low-temperature” DAC process, which might be more advantageous for Germany than the “high-temperature” one. In four case studies, we examine potential sites in northern, central and southern Germany, thereby using the most suitable renewable energies for electricity and heat generation. We show that the deployment of DAC results in large-scale land use and high energy needs. The land use in the range of 167–353 km2 results mainly from the area required for renewable energy generation. The total electrical energy demand of 14.4 TWh per year, of which 46% is needed to operate heat pumps to supply the heat demand of the DAC process, corresponds to around 1.4% of Germany's envisaged electricity demand in 2045. 20 Mt of water are provided yearly, corresponding to 40% of the city of Cologne‘s water demand (1.1 million inhabitants). The capture of CO2 (DAC) incurs levelised costs of 125–138 EUR per tonne of CO2, whereby the provision of the required energy via photovoltaics in southern Germany represents the lowest value of the four case studies. This does not include the costs associated with balancing its volatility. Taking into account transporting the CO2 via pipeline to the port of Wilhelmshaven, followed by transporting and sequestering the CO2 in geological storage sites in the Norwegian North Sea (DACCS), the levelised costs increase to 161–176 EUR/tCO2. Due to the longer transport distances from southern and central Germany, a northern German site using wind turbines would be the most favourable.
In diesem Artikel werden zunächst einleitend der Gasmarkt Deutschland und der sich daraus ergebende Speicherbedarf skizziert. Folgend wird auf verschiedene Speichernutzen aus betriebswirtschaftlicher Perspektive eingegangen und die in diesem Artikel vorgestellten Bewertungsverfahren einleitend beschrieben. In diesem Artikel werden stochastische Optimierungsmethoden aufgegriffen, die sowohl eine Bewertung der Speicher gegenüber einem Spotpreis, als auch gegenüber einer gesamten Forwardcurve ermöglichen. Hierzu werden zunächst Modelle zur Beschreibung der Marktpreise vorgestellt und anhand empirischer Daten kalibriert. Dann wird eine beispielhafte Speicherscheibe zunächst auf Basis der LeastSquareMonteCarloTechnik gegenüber dem stochastischen mehrfaktoriellen Spotpreismodell bewertet. Hieran schließt sich die Vorstellung der Bewertung sowie des Hedgings gegenüber der Forwardcurve an. Abschließend erfolgt eine vergleichende Gegenüberstellung beider Verfahren.
Einfluß von Temperaturschwankungen auf das Verformungsverhalten von Rohren bei hohen Temperaturen
(1992)