openHSU (HSU Hamburg)
Not a member yet
7291 research outputs found
Sort by
Analysis of flow rates in cracked reinforced concrete
No full textAccording to Eurocode 2, part 3, autogenous self‐healing of separation cracks with a width ≤0.20 mm can be considered under certain hydraulic conditions. However, practical experience shows that healing does not always reliably occur even when this crack width is maintained. This study examines the flow rates of centrally cracked and water‐permeated concrete using Edvardsen's method. An analytical approach following Hagen–Poiseuille is developed to estimate the flow rate immediately after the start of the water flow Q₀, which is particularly relevant for tightness class TC0. In addition to the water pressure, Q₀ is influenced by the crack width distribution across the cross‐section, the roughness of the crack flanks, and the tortuosity of the crack path. Therefore, a reliable estimation of the flow rate necessitates the introduction of a correction factor ξ, which is proposed with 0.52 due to the high variability of the experimental data.Vo
Second harmonic generation into the near ultraviolet in Zr-diffusion-doped lithium tantalate ridge waveguides
No full textWe report on the efficient second harmonic generation at a near-UV wavelength of 399.7 nm in periodically poled Zr-doped LiTaO3 waveguides. High-temperature in-diffusion of ZrO2 layers into congruent LiTaO3 substrates with simultaneous improvement of crystal stoichiometry by vapor transport equilibration in a Li-rich atmosphere was performed for the fabrication of planar waveguides. This new method enables very high photorefractive damage thresholds and allows us to avoid the known disadvantages of, e.g., proton exchange or titanium in-diffusion waveguide fabrication methods, which lower resistance to photorefractive damage. Low-loss ridge waveguides were then fabricated using a diamond blade saw. At a maximum available coupled power of 540 mW of the near-infrared pump laser, 49 mW of second harmonic light was generated in a 22 mm long sample with a normalized conversion efficiency of 3.5%·W-1·cm-2, exceeding the previously reported powers for LiTaO3 waveguides in this wavelength range. Furthermore, by heating the sample, a temperature tuning coefficient of 32 pm/°C was measured for the generated second harmonic wave.Vo
Europe's reinforced concrete structures
No full textThe long-term deterioration of reinforced concrete (RC) structures poses a significant challenge to their strength and serviceability, with steel reinforcement corrosion being the primary degradation mechanism. Corrosion is a complex process highly influenced by climatic conditions, making the prediction of corrosion rates under changing climate scenarios crucial for reliable service life assessments of ageing RC structures. In particular, increasing global temperatures due to climate change are expected to accelerate deterioration, promoting steel corrosion and increasing its rate. This study presents a predictive analysis of corrosion rate variations using a multi-model ensemble of daily climate projections under different future scenarios, incorporating existing knowledge on temperature dependency in corrosion models. A European-scale map illustrating the impact of climate change on corrosion rates is developed and analyzed, highlighting a significant increase in corrosion rates that will critically affect the durability and serviceability of RC structures and infrastructure.Vo
Informationen und Empfehlungen des Arbeitskreises 1.6 „Numerik in der Geotechnik“ zur Berechnung von Grundwasserströmungen und deren Auswirkung auf die Standsicherheit mit der FEM
No full textInformation and recommendations of the working group 1.6 ‘Numerics in Geotechnics’ on the calculation of groundwater flow and its effect on stability using the FEM. In this article, DGGT Working Group 1.6 ‘Numerics in Geotechnics’ provides information and recommendations on the calculation of groundwater flow and its effect on the overall stability using numerical methods, with special attention to the finite element method. These supplement the existing general recommendations of Working Group 1.6 and the recommendations for numerical analysis of the overall stability using the FEM. Important principles for the numerical analysis of saturated as well as partially saturated groundwater flow are topics of this article. The associated initial and boundary conditions as well as simplified calculation models are also discussed. Furthermore, physical properties of boundary value problems, such as their time dependency and the type of coupling between the mechanical behavior of the grain structure and the groundwater flow, are used for classification into analysis types. Finally, recommendations are given to support the selection of an analysis type and to find an adequate strategy for the calculation. Some further recommendations deal with the selection which of the numerous influences from groundwater flow on the results of FEM calculations should be taken into account, particularly for determining the overall stability. To conclude, guidelines for plausibility checking of the calculation results are provided.Vo
Portierung eines Raytracing-Verfahrens zur Ermittlung des Zielmaßes (TES) von Unterwasserobjekten auf GPUs - ein Erfahrungsbericht
No full textInvestigations of a test implementation of the “simple” Kirchhoff approximation method (KIA) for GPU graphics adapters (using OpenCL) have shown that, depending on the GPU hardware available, significant performance improvements can be achieved. Therefore, as part of the “Computational Acoustics” research project, the BEAM ray tracing method, originally implemented in C++, was ported to address the required acoustic problems (bistatic, monostatic calculations and their combination).
This article discusses the challenges encountered during this process, shares the practical experiences implementing the complex parallelized algorithm in OpenCL and shows the results achieved. It also highlights the speed advantages compared to conventional high-performance PC workstations using examples of underwater objects.Vo
Effectiveness of an integrated platform-based intervention for promoting psychosocial safety climate and mental health in nursing staff
No full textThis is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)Background: Organisational and individual factors cause strain in the daily lives of nurses and other healthcare professionals, who have a high prevalence of stress-related disorders. Accordingly, there is a strong need for integrated occupational health promotion interventions that include both work-directed and person-directed interventions. The psychosocial safety climate is seen as an overarching occupational health objective and can potentially be improved by implementing integrated mental health interventions. Objective: Following an integrated approach, we developed an occupational e-mental health platform, Care4Care, which integrates both work- and person-directed interventions for promoting mental health in nurses. We evaluated the effects of the platform compared with those of an extended care-as-usual control condition. Design: Clustered randomised controlled trial. Setting: Healthcare service facilities in Germany nationwide. Participants: 347 nursing staff members (intervention: 211, control: 136) from 33 healthcare service facilities. Methods: The participants received either immediate access to the platform or access to two short subcomponents of the platform plus routine occupational health promotion offerings as well as delayed access to the whole platform after 6 months. The primary outcome was improvement in the psychosocial safety climate after 6 months. The secondary outcomes included perceived stress, depressive symptoms, and other strain-related indicators. Results: Bayesian multilevel analyses revealed an improvement of approximately 2 points (Cohen's d = 0.25) in the psychosocial safety climate in the intervention group compared with the control group. Applying a 95 % credible interval, this effect contained zero (− 0.32, 4.44), which indicated uncertainty about the effectiveness of the intervention on the psychosocial safety climate. The analyses of the secondary outcomes revealed effects in the expected direction with high credibility for a decreasing effect on perceived stress and considerable uncertainty with regard to all other secondary and tertiary outcomes. A total of 85 (40 %) participants in the intervention group used Care4Care, whereas 37 (27 %) participants in the control group used the two subcomponents of the platform. Conclusions: This study highlights the potential of an occupational e-mental health platform that combines work- and person-directed interventions with face-to-face components for nursing staff. The findings emphasise the necessity of conducting more in-depth implementation studies to identify the factors that facilitate the successful implementation and uptake of occupational e-mental health platforms. Registration: German Clinical Trials Register – DRKS (DRKS00027869). Registration date: February 23, 2022. Start of recruitment: June 21, 2022.Vo
Using autoencoders and automatic differentiation to reconstruct missing variables in a set of time series
No full textExisting black box modeling approaches in machine learning suffer from a fixed input and output feature combination. In this paper, a new approach to reconstruct missing variables in a set of time series is presented. An autoencoder is trained as usual with every feature on both sides and the neural network parameters are fixed after this training. Then, the searched variables are defined as missing variables at the autoencoder input and optimized via automatic differentiation. This optimization is performed with respect to the available features loss calculation. With this method, different input and output feature combinations of the trained model can be realized by defining the searched variables as missing variables and reconstructing them. The combination can be changed without training the autoencoder again. Furthermore, fully missing feature data in a set of time series can be reconstructed from the available data. Possible applications are for example large production systems, inaccessible feature data in a running application, reduced datasets due to limited data processing capabilities or perhaps the reconstruction of dead pixels in a video. The approach is evaluated on the base of a strongly nonlinear electrical component and on a door frame production system. It is working well for single features missing and generally even for multiple missing features. But a coupling between the features inside a dataset is required for reconstruction of a feature.Vo