20005 research outputs found
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Efficient treatment of long-range electrostatics in charge equilibration approaches
No full textA charge equilibration method based on real-space Gaussians as charge densities is presented. The implementation is part of the Electrode package available in the Large-scale Atomic/Molecular Massively Parallel Simulator and benefits from its efficient particle-mesh Ewald approach. A simple strategy required to switch from the previously used Slater-type orbital (STO) shielding to Gaussians is provided by fitting the Coulomb energy of two Gaussian charge distributions to the repulsion between two STOs. Their widths were optimized for O, Si, and Ti species, obtaining results consistent with previous studies using STOs in the case of SiO2 polymorphs. In the limit of sufficiently narrow Gaussians, it is shown that the implementation converges to electronegativity equalization method results for the case of Ti/TiOx interfaces. The method presented is implemented in a way that is potentially beneficial for the application of modern machine-learning force fields that include long-range electrostatic interactions
Specification mining facing generative AI
No full textSpecifications for complex designs and their consistency are always a headache. Automated specification mining - including but not limited to generative AI - offers attractive solutions, but there are also various unmet needs
Accounting for environmental impact: the impact of estimation methods on errors in carbon accounting systems
No full textThis study aims to evaluate the accuracy and uncertainty of corporate carbon accounting methods in the absence of known “true” emissions. We address this limitation by creating a simulated, idealized carbon accounting system – based on real industry data. By comparing commonly used methods, namely spend-based, activity-based, and hybrid approaches, against this benchmark, we can systematically analyze where and how errors arise. This numeric simulation-based approach provides a controlled environment to identify typical biases, uncertainty ranges, and reliability issues
A Pd–Pt-based bulk nanoporous alloy with continuous solubility for hydrogen
No full textMetal hydrides that enable reversible solute exchange with a reservoir often exhibit a miscibility gap at room temperature. Misfit strain during two-phase coexistence may then lead to degradation on repeated charging/discharging cycles. Furthermore, the miscibility gap impairs continuous and uniform composition tuning for functional applications. We explore electrochemical dealloying as a pathway to macroscopic monolithic samples of nanoporous Pd–Pt with continuous solubility for H at room temperature. The ligament size is tunable in the range of 4–40 nm, and sorption isotherms suggest a miscibility-gap critical point marginally below room temperature. With a maximum hydrogen fraction of 0.5, we demonstrate a reversible actuation strain of 3.3 % and a high cycle stability
Towards a socio-ecological system understanding of urban flood risk and barriers to climate change adaptation using causal loop diagrams
No full textWhile cities are facing increasing challenges of flood risk due to combined effects of climate change and socioeconomic development, understanding of the complexity of urban flood risk is still limited, hampering decision-making and urban adaptation planning. This study presents a qualitative system dynamics modelling framework to investigate urban flood risk and adaptation under climate change in a coupled socio-ecological system, the city of Hamburg. The developed integrated conceptual model provides a holistic understanding of key physical and socio-economic processes and the role of feedback loops underlying the urban system, and contributes to the understanding of vicious cycles of barriers that perpetuate and hinder adaptation processes within cities. The qualitative approach can help to break down silo-thinking in urban flood risk assessments. Decision-makers could use the framework to understand the complexity of interactions among multiple drivers of flood risk to overcome barriers and lock-in effects to adaptation in cities
Advancements in Application of a 3T Vertical MRI System for Analyzing Hydrodynamics in Stirred Tank Reactors
No full textMagnetic Resonance Imaging (MRI) is a powerful tool that provides deep insights into the human body by determining the distribution of various components and visualizing dynamic processes such as cardiac blood flow. Similarly, in the field of process engineering, understanding flow parameters and component distribution is critical, particularly in the study of stirred tank reactors (STRs). Traditional medical MRI scanners, which are typically designed for horizontal orientation, present certain limitations for investigating STRs. The non-intrusive nature of MRI, combined with its ability to analyse opaque and complex mixtures offers detailed, three-dimensional insights into STRs. These insights help tackling the significant challenge of understanding the complex hydrodynamics of STRs, thus fasten optimization and ease scale-up efforts [1].
In this study we use MRI to investigate liquid flow in an STR model of an inner diameter of 188 mm and a height of 1000 mm. All measurements were performed on a vertical 3T MRI system, optimized for process imaging. The open radiofrequency shielding design and the vertical orientation of the MRI system, allow to accurately control the stirrer speed with an electric motor. Different impeller types and rotational speeds and their effects on the fluid hydrodynamics are studied. In the future we are planning to investigate realistic industrial conditions and complex multi-phase material systems.
We anticipate these measurements to enhance our understanding of the complex hydrodynamics within STRs. Moreover, the measurements can be used to test and improve the accuracy of computational fluid dynamics (CFD) models for process design and optimization.
References:
[1] Stitt, H., Chemical Engineering Journal (2002), 47-6
Challenges and opportunities for increase sustainability and energy efficiency in ceramic tile industry
No full textThe ceramic tile has an estimated global warming potential of 14.4 kg CO2 equivalent per square meter, with CO2 emissions contributing to approximately 92.1% of the overall impact. The total emissions amount to 19 million tons of CO2 annually, representing approximately 1% of Europe's industrial emissions that are regulated by the EU Emissions Trading System. As a result, the ceramic industry is under growing pressure to decrease carbon emissions and improve energy efficiency in accordance with Europe's new climate and energy objectives. However, this process holds a clear challenge. This work addresses the challenges and opportunities facing the ceramic tile industry in reducing carbon emissions and improving energy efficiency in line with new climate and energy goals worldwide. It highlights the importance of adopting innovative strategies across product, process efficiency, and market and supply chain aspects
Vibration reduction of lightweight structures through adjustable damping and stiffness properties at their interfaces
No full textThis paper presents the vibration reduction of lightweight components by adjusting the mechanical properties of their boundary conditions in vibration test rigs. The variable boundary conditions are achieved by adjustable impedance elements, which are mechanical elements that can change their stiffness and damping behavior separately and are designed for use in vibration testing. A new generation of an adjustable impedance element is presented in this publication and its use in a large component test environment. The influence of the adjustable mechanical properties of the interfaces on an aircraft partition is shown. A holistic finite element model is presented to predict the interactions between the adjustable interfaces and the test object. A vibration reduction of about 65% compared to current rigidly designed joints is achieved. The influence of vibration on the partition is investigated experimentally for different stiffness and damping ranges and the corresponding simulation model is validated
Tailored enzyme expression modifies Shewanella oneidensis biofilms and increases current density
No full textBiofilm formation is the most effective pathway for electron transfer to anodes in bioelectrochemical systems. However, the mechanisms triggering biofilm formation under anoxic conditions, as well as the architectural and compositional factors that positively influence current generation, are not well understood. Recent findings have shown that riboflavin can function similarly to a quorum sensing molecule in the γ-proteobacterium Shewanella oneidensis. Enhanced biofilm formation induced by riboflavin correlates with increased current densities. Only a limited number of candidate proteins were found to have altered concentrations due to this quorum sensing mechanism. This study demonstrates that the catalytic functions of the UDP-N-acetylglucosamine C4 epimerase WbpP and UDP-N-acetyl-D-glucosamine 6-dehydrogenase WbpA affect biofilm formation and lead to increased current density. Using optical coherence tomography, we found that the expression of each protein individually causes specific, quantifiable changes in biofilm architecture, including biovolume, height, and porosity. However, the current density did not significantly differ when these proteins were expressed alone compared to the control. In contrast, co-expression of WbpP and WbpA resulted in a doubling of current density, closely resembling the increases observed with riboflavin-mediated quorum sensing. We hypothesize that riboflavin-based quorum sensing may lead, through several intermediary steps, to the overproduction of WbpA and WbpP, resulting in better attachment to graphite anodes and thus higher current densities
Aktuelle und zukünftige Anwendungsgebiete des 3D-Druck in der Medizin und der Stellenwert der Radiologie
No full textDer Einsatz von dreidimensionalen (3D) Druckmodellen in der Patientenversorgung bietet eine Vielzahl von Möglichkeiten sowohl in Hinblick auf personalisierte Therapieansätze als auch bei der Aus- und Weiterbildung von medizinischem Fachpersonal. Als Grundlage für die Mehrzahl der 3D-Modelle in der Medizin dienen DICOM-Dateien aus bildgebenden Verfahren wie der CT und MRT. Die Erhebung, Bearbeitung und Interpretation dieser obliegt vorwiegend der Radiologie, der somit eine Schlüsselrolle in der Ausübung und Weiterentwicklung des 3D-Drucks zukommt. Diese Übersichtsarbeit soll einen Überblick über die Grundlagen des 3D-Drucks in der Medizin geben und seine wichtigsten Anwendungsgebiete zusammenfassen. Hierbei soll die Rolle der Radiologie als Knotenpunkt bei der Entstehung und Verwaltung von 3D-Modellen im klinischen Alltag beleuchtet werden.Medical three-dimensional (3D) printing is playing an increasingly important role in clinical practice. The use of 3D printed models in patient care offers a wide range of possibilities in terms of personalized medicine, training and education of medical professionals, and communication with patients. DICOM files from imaging modalities such as CT and MRI provide the basis for the majority of the 3D models in medicine. The image acquisition, processing, and interpretation of these lies within the responsibility of radiology, which can therefore play a key role in the application and further development of 3D printing. The purpose of this review article is to provide an overview of the principles of 3D printing in medicine and summarize its most important clinical applications. It highlights the role of radiology as central to developing and administering 3D models in everyday clinical practice