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A grey-box approach based on Johnson-Cook constitutive model to improve predictions of mechanical loads of cutting simulations for normalized AISI 1045
No full textIn machining, high temperatures and strain rates impact the flow stress of the workpiece material, making it essential to understand the materials behaviour in these process conditions for meaningful finite element analysis (FEA) of the cutting process. The Johnson-Cook constitutive model, despite being the most widely applied, is reported to struggle in capturing the material behaviour outside of the reference conditions it was calibrated on. However determining these parameters in conventional material tests is challenging. To solve this issue, this study proposes a grey-box approach which aims to increase the accuracy of process force prediction of FEA, employing a Johnson-Cook model determined by experiments conducted on a Split-Hopkins Pressure Bar and compression tests at elevated temperatures on a Gleeble 3800c for AISI 1045, over a variety of cutting parameters. In total 110 cutting experiments and their corresponding simulations were carried out in a fully factorial experimental design with eleven cutting speeds and ten uncut chip thicknesses. Succeeding the white-box model, a black box model is trained to capture the non-linear behaviour between the simulation and the cutting experiments. Among the tested algorithms, XGBoost and Support Vector Regression outperformed Random Forests and Neural Network for predicting cutting force and feed force. The proposed grey-box approach showed an improved capability of predicting cutting force and feed force, reducing the mean absolute error and mean squared error compared to the white-box model by 97.9 % and 99.9 % for cutting force and by 94.9 % and 99.7 % for feed force, respectively. The grey-box model achieved a mean error of 1.3 % with a standard deviation of 0.1 in process force prediction
Unique microphysical properties of small boundary layer ice particles under pristine conditions on Dome C, Antarctica
No full textThe Antarctic plateau, one of the coldest and cleanest regions of our planet, experiences almost exclusively frozen precipitation. Understanding the microphysical properties of inland Antarctic boundary layer ice particles with sizes below a few hundred micrometers is essential to improve atmospheric models and accurately validate remote sensing data for this region. Currently, only a small number of in situ atmospheric measurements exist for particle sizes smaller than 100 µm on the Antarctic plateau, performed over short measurement times. We present the first multi-week study of optical in situ measurements of boundary layer ice particle size, shape and morphological complexity for sizes down to 11 µm with a temporal resolution in the order of minutes, including a multi-day ice fog event. Classifying ice fog events with a lidar system, we found mean particle sizes smaller than 11 µm for ice fog events and of about 70 µm for cirrus precipitation and diamond dust events. The mean particle concentration of the ice fog at Dome C (3.9 L) is found to be lower than in parametrisations of Arctic ice fog and lower than the concentration of anthropogenically influenced urban ice fog measured at Fairbanks, Alaska during a three-year study with the same instrument (90 L). Moreover, ice fog particles at Dome C are found to be more pristine than at Fairbanks. Our findings show that Antarctic boundary layer ice particles may need to be parametrised differently than their Arctic counterparts due to distinct conditions on the Antarctic plateau
Thermal Insulation, Lasting Consequences: Forecasting ETICS Waste and Its Sustainability Challenges
No full textThis study quantifies post-demolition External Thermal Insulation Composite Systems (ETICS), with a focus on Expanded Polystyrene (EPS) as insulation material in Germany. Using a top-down approach, it estimates mass distribution at the NUTS-3 level and predicts future EPS waste volumes. Residential and non-residential buildings are categorized by type and construction age, with insulation rates determined through database queries. Waste projections incorporate ETICS lifetimes survey data, and probabilistic single-house sampling. Findings indicate a fourfold increase in annual EPS waste from ETICS by 2050, with 80% originating from residential buildings and 20% from non-residential structures, predominantly in urban areas. ETICS pose recycling challenges due to their composite nature, combining organic and inorganic materials, and the presence of HBCD, a toxic flame retardant banned by the EU in 2015. Currently, most ETICS waste is incinerated, a linear approach that fails to address the anticipated surge in waste volumes. Given these projections, sustainable alternatives for ETICS waste management are urgently needed. The study provides insights into waste distribution across building types and administrative regions, offering a basis for informed policy decisions. The building typology used in this approach is available for other European countries, supporting the development of comprehensive waste management strategies across Europe
Production-Optimized Automotive Software Architecture: Theory and Applications
No full textThe automotive software architecture is struggling with production stability and efficiency, as frequent and regular software updates incur side effects on software-related processes in the end assembly. To close the gap, this article refines and formalizes the concept of production-oriented software partitioning (POSP), a novel architecture for in-car software which physically decouples software used within production from production-irrelevant software. Experimental evaluation using a developed prototype confirms the feasibility of the proposed architecture. The prototype further showcases the potential of POSP, achieving a 16% reduction in software size for production use. Moreover, the article contributes a generic model for analyzing automotive software systems at the software component level, a formal workflow for refactoring legacy systems toward POSP, and a redundancy-based method for partitioning software systems following the generic model. These contributions are demonstrated on an industry-grade AUTOSAR Classic platform, highlighting the potential of production-oriented software partitioning (POSP) for short-term industrial adoption and enhanced stability and efficiency in large-scale automotive production
NovaCrate v1.7.0
No full textWebbasierter interaktiver Editor für die Erstellung, Bearbeitung, Validierung und Visualisierung von Research Object Crates
Evaluating Time-Series Foundation Models for Cooling Demand Forecasting with Little Data
No full textModern buildings increasingly integrate local energy generation, consumption, and storage, often involving multiple energy carriers such as electricity and thermal energy. This complexity creates opportunities for cost-efficient operation based on accurate forecasts of key energy parameters such as the cooling demand. However, generating such forecasts on a building-level can be challenging, as individual buildings likely exhibit highly specific consumption patterns and often offer only limited historical data.
Time Series Foundation Models (TSFMs) offer a promising solution to this problem due to their ability to generalise across forecasting tasks and adapt to new domains with minimal data via fine-tuning. This study evaluates three state-of-the-art TSFMs (MOIRAI, MOIRAI-MoE and Chronos) in both zero-shot and fine-tuned settings. The models are tested on real-world energy consumption data from a split-type cooling unit used in a server room, spanning a period of less than four months. Outdoor air temperature is included as a covariate to assess its impact on prediction accuracy. Results are compared to two baseline
models.
Our findings show that Chronos, when incorporating outdoor air temperature, achieves a substantial improvement in forecasting accuracy for three-day ahead forecasts, reducing the Mean Absolute Percentage Error (MAPE) to as low as 2.57 %. In contrast, MOIRAI and MOIRAI-MoE show no significant benefit from the inclusion of temperature information. Overall, the study demonstrates that TSFMs represent a promising alternative for cooling demand forecasting in Section 5. Section 6 summarises the findings and outlines future research directions
Sprachlos? Technische Innovationen im Mittelalter
No full textDie Vermutung, das Mittelalter sei innovationsfeindlich gewesen, ist seit Jahrzehnten widerlegt. Unzählige Befunde aus Disziplinen von der Mittelalterarchäologie bis zur Umweltgeschichte zeigen, dass sich das technische Inventar europäischer Gesellschaften zum Ausgang des Mittelalters deutlich von dem der Spätantike unterschied. Wie mittelalterliche Zeitgenossen selbst technische Kreativität in Text und Bild thematisierten, ist allerdings noch immer nicht systematisch erforscht.
Wie geeignet sind vor diesem Hintergrund moderne Schlagworte wie „Innovation“, um Veränderungen der materiellen Kultur des Mittelalters auf den Punkt zu bringen? Welche Narrative sind der technischen Kreativität dieser Epoche angemessen, gerade auch aus globalhistorischer Perspektive oder im Vergleich zur Moderne? Der Vortrag argumentiert, dass solche Fragen für die historische Forschung ebenso relevant sind wie für eine breiter angelegte Wissenschaftskommunikation
