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Appropriate consideration of interfaces in product development
No full textThe development of modular product families depends on correctly implementing appropriate interfaces. They exert a significant impact on the configurability of products, the interchangeability of modules, and the production processes and respective equipment. This paper analyses interfaces of modular product architectures from a strategic perspective and discusses the impact of these interfaces on sustainability and module-wise product modification of modular product families. In this context, it presents an enhancement of the module interface graph (MIG) for more effective treatment of interfaces in product development, based on two case studies in different fields of application
Bias-corrected high-resolution temperature and precipitation projections for Canada
No full textHigh-resolution precipitation and temperature projections are indispensable for informed decision-making, risk assessment, and planning. Here, we have developed an extensive database (SPQM-CMIP6-CAN) of high-resolution (0.1°) precipitation and temperature projections extending till 2100 at a daily scale for Canada. We employed a novel Semi-Parametric Quantile Mapping (SPQM) methodology to bias-correct the Coupled Model Intercomparison Project, Phase-6 (CMIP6) projections for four Shared Socio-economic Pathways. SPQM is simple, yet robust, in reproducing the observed marginal properties, trends, and variability according to future scenarios, while maintaining a smooth transition from observations to projected simulations. The SPQM-CMIP6-CAN database encompasses 693 simulations derived from 34 diverse climate models for precipitation. Similarly, for temperature projections, our database comprises 581 simulations from 27 climate models. These projections are valuable for hydrological, environmental, and ecological studies, offering a comprehensive resource for analyses within these domains. Furthermore, these projections serve as a vital tool for the quantification of uncertainties arising from climate models, their variant configurations, and future scenarios
A comprehensive framework for computational modeling of growth and remodeling in tissue-engineered soft collagenous materials
No full textDeveloping clinically viable tissue-engineered structural cardiovascular implants—such as vascular grafts and heart valves—remains a formidable challenge. Achieving reliable and durable outcomes requires a deeper understanding of the fundamental mechanisms driving tissue evolution during in vitro maturation. Although considerable progress has been made in modeling soft tissue growth and remodeling, studies focused on the early stages of tissue engineering remain limited. Here, we present a general, thermodynamically consistent model to predict tissue evolution and mechanical response throughout the in vitro maturation of passive, load-bearing soft collagenous constructs. The formulation utilizes a stress-driven homeostatic surface to capture volumetric growth, coupled with an energy-based approach to describe collagen densification via the strain energy of the fibers. We further employ a co-rotated intermediate configuration to ensure the model’s consistency and generality. The framework is demonstrated with two numerical examples: a uniaxially constrained tissue strip validated against experimental data and a cruciform-shaped biaxially constrained specimen subjected to load perturbation. These results highlight the potential of the proposed model to advance the design and optimization of tissue-engineered structural cardiovascular implants with clinically relevant performance
Misconceptions about control flow in introductory programming courses and their remedy
No full textI investigate the identification, explanation and treatment of common conceptual problems of students in introductory programming courses about control flow while reading code. In previous work I have identified and quantified several difficulties with control flow structures. The ultimate goal for my thesis is to develop a taxonomy, a concept inventory and effective educational methods for control flow concepts using methods of active learning and threshold concepts. These then can help more students to master the fundamental concepts of CS0 and CS1
The ground truth effect: investigating SZZ variants in Just-in-Time vulnerability prediction
No full textJust-in-Time (JIT) vulnerability prediction is critical for proactively securing software, yet its effectiveness heavily relies on the quality of the ground truth used for training models. This ground truth is commonly established using variants of the SZZ algorithm to identify vulnerability-contributing commits (VCCs). However, the impact of choosing a specific SZZ variant on model performance remains largely unexplored. In this study, we systematically investigate the effect of eight SZZ variants on JIT vulnerability prediction across seven open-source Java projects. Our findings reveal that the choice of the SZZ variant is a non-trivial factor. Models trained with datasets labeled by variants like B-SZZ, V-SZZ, and VCC-SZZ achieve strong and stable predictive performance, with median MCC scores often exceeding 0.50. In contrast, variants such as L-SZZ and R-SZZ produce models that perform no better than random chance, with median MCC scores close to 0.0. This performance gap demonstrates that an inappropriate SZZ variant can invalidate prediction models, underscoring the necessity of a principled approach to defining ground truth
Electrochemo-mechanical coupling in electrocatalytic oxidation of methanol on platinum
No full textThis study investigates the impact of elastic strain on platinum electrode surfaces and its effects on both the adsorption of reactants and the electrocatalytic oxidation of methanol in alkaline solutions. By exploring the coupling between external mechanical modulation and electrocatalytic activity, the research aims to uncover how strain influences both the reaction currents (Faraday currents) and the adsorption enthalpy of methanol and its intermediates.
To explore this coupling effect, two experimental approaches are employed. First, the impact of surface strain on adsorption enthalpy is assessed through surface stress variations, measured via cantilever bending experiments. Second, the strain effect on the overall reaction current is examined using Dynamic Electro-Chemo-Mechanical Analysis (DECMA). Here, a lock-in technique is utilized to capture strain-modulated reaction currents, quantifying them as functions of the applied potential. The study also discusses the role of uncompensated resistance in parameter adjustments, which is crucial for accurately interpreting the intrinsic coupling between externally applied strain and reaction currents on platinum thin film electrode surfaces.
Methanol oxidation reaction (MOR) is selected as the model system due to its importance in various industrial applications, including fuel cells and chemical production. To gain a deeper understanding of the complex electrocatalytic processes involved in MOR, classical electrochemical characterization techniques are employed, such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). These techniques are applied under different parameters and methanol concentrations to capture a comprehensive view of the reaction mechanisms.
The findings reveal that external strain significantly influences the methanol oxidation current. Tensile strain enhances reactivity at low overpotentials, while compressive strain becomes more effective at higher overpotentials, a condition more typical in practical applications. However, the adsorption enthalpy of methanol exhibits negligible dependence on strain, suggesting that the observed changes in electrocatalytic activity are not primarily driven by alterations in methanol adsorption strength. These insights underscore the importance of considering strain effects in the design of high-performance electrocatalysts. Understanding and quantifying how mechanical strain impacts overall reaction rates provides valuable guidance for developing more efficient catalytic materials.Diese Studie untersucht den Einfluss elastischer Dehnung auf Platin-Elektrodenoberflächen sowie deren Auswirkungen sowohl auf die Adsorption von Reaktanden als auch auf die elektrokatalytische Oxidation von Methanol in alkalischen Lösungen. Durch die Analyse der Kopplung zwischen äußerer mechanischer Modulation und elektrokatalytischer Aktivität soll aufgeklärt werden, wie Dehnung sowohl die Reaktionsströme (Faraday-Ströme) als auch die Adsorptionsenthalpie von Methanol und seinen Zwischenprodukten beeinflusst.
Zur Untersuchung dieses Kopplungseffekts werden zwei experimentelle Ansätze verfolgt. Erstens wird der Einfluss der Oberflächendehnung auf die Adsorptionsenthalpie anhand von Änderungen der Oberflächenspannung ermittelt, die mittels Cantilever-Biegeversuchen gemessen werden. Zweitens wird der Dehnungseffekt auf den Gesamtreaktionsstrom mithilfe der Dynamic Electro-Chemo-Mechanical Analysis (DECMA) untersucht. Dabei kommt eine Lock-in-Technik zum Einsatz, um dehnungsmodulierte Reaktionsströme zu erfassen und diese als Funktionen des angelegten Potentials zu quantifizieren. Zudem wird die Rolle des nichtkompensierten Widerstands bei der Parametereinstellung diskutiert, die entscheidend für eine präzise Interpretation der intrinsischen Kopplung zwischen äußerer Dehnung und Reaktionsströmen auf Platin-Dünnfilm-Elektrodenoberflächen ist.
Die Methanoloxidationsreaktion (MOR) wird als Modellsystem ausgewählt, da sie in verschiedenen industriellen Anwendungen, einschließlich Brennstoffzellen und chemischer Produktion, von großer Bedeutung ist. Um ein tieferes Verständnis der komplexen elektrokatalytischen Prozesse in der MOR zu erlangen, werden klassische elektrochemische Charakterisierungsmethoden wie Zyklovoltammetrie (CV) und elektrochemische Impedanzspektroskopie (EIS) eingesetzt. Diese Techniken werden unter variierenden Parametern und Methanolkonzentrationen angewandt, um ein umfassendes Bild der Reaktionsmechanismen zu gewinnen.
Die Ergebnisse zeigen, dass äußere Dehnung den Methanoloxidationsstrom erheblich beeinflusst. Zugdehnung steigert die Reaktivität bei niedrigen Überspannungen, während Druckdehnung bei höheren Überspannungen, wie sie in praktischen Anwendungen häufiger auftreten, effektiver ist. Die Adsorptionsenthalpie von Methanol weist hingegen kaum Abhängigkeit von der Dehnung auf, was darauf hindeutet, dass die beobachteten Veränderungen in der elektrokatalytischen Aktivität nicht primär durch Modifikationen der Methanol-Adsorptionsstärke verursacht werden. Diese Erkenntnisse unterstreichen die Bedeutung der Berücksichtigung von Dehnungseffekten beim Design leistungsfähiger Elektrokatalysatoren. Das Verständnis und die Quantifizierung der Auswirkungen mechanischer Dehnung auf die Gesamtreaktionsraten liefern wertvolle Hinweise für die Entwicklung effizienterer Katalysatormaterialien
Kalkulation des durch Propulsionssysteme mit Rudern oder Flossenkappen emittierten Unterwasser-Schalls; Akronym: KRaWall; im Verbundvorhaben: Reduktion der hydroakustischen Emission von Propulsionssystemen; Akronym: Red-Emi
No full textDas Verbundvorhaben beschäftigt sich mit der Vorhersage von Schallemissionen durch Schiffsantriebsanlagen. Signifikante Schallquellen stellen dabei die Propellerdruckfelder, fluktuierende Schicht- und Wirbelkavitation sowie der Körperschall dar. Diese Effekte sollen in diesem Vorhaben numerisch modelliert werden, um eine effiziente numerische Prognose zu ermöglichen. Die Wechselwirkung der erstgenannten physikalischen Phänomene soll dabei ebenfalls berücksichtigt werden. In diesem Teilvorhaben liegt der Schwerpunkt auf der Simulation der Umströmung und hydrodynamischen Wechselwirkung zwischen Propeller und Schiffsanhängen wie Rudern oder anderen Flossen sowie ihrer resultierenden akustischen Emissionen. Um entsprechende Prognosen in einem Entwurfsprozess innerhalb kurzer Zeit zu ermöglichen, sollen diese Interaktionen in einem zeiteffizienten Simulationsverfahren implementiert werden. Zu diesem Zweck werden zunächst mit Unterstützung von detaillierten Simulationen entsprechende Modelle für die realistische Abbildung dieser Wechselwirkungen in einem vereinfachenden Verfahren entwickelt. Mit diesem Verfahren sollen anschließend Ruderpropeller in Zug-Konfiguration sowie Propeller mit Flossenkappen hinsichtlich ihrer hydroakustischen Emission bewertet werden. Auf Basis der Ergebnisse wird ein künstliches neuronales Netz entworfen und trainiert, das die Schallemissionen solcher Konfigurationen vorhersagen kann. Die Zuströmung zum Propeller wird in allen Fällen mittels eines weiterentwickelten, Datenbank-gestützten Ersatzmodells bestimmt. Die zu untersuchenden Teilbereiche in diesem Teilvorhaben sind damit die effiziente Prognose der Schichtkavitation auf dem Propeller, die Wirbelkavitation in Spitzen- und Nabenwirbel sowie die Deformation und Interaktion der freien Wirbel mit weiteren Auftriebsflächen. Hinzu kommen die Vorhersage des Nachstromfelds bei unbekannter Schiffsgeometrie bis auf Hauptabmessungen sowie die Entwicklung eines neuronalen Netz.Bundesministerium für Wirtschaft und Energie (BMWE
Development of an anthropomorphic phantom of the lower extremities for feasibility studies and verification of total-body irradiation
No full textBackground: Total-body irradiation (TBI) is a specialised radiotherapy treatment used alongside chemotherapy to prepare leukaemia patients for stem cell transplants. For commissioning and validation of conformal irradiation techniques, anatomically detailed phantoms of the whole body play an important role. This study aimed to create a cost-effective modular phantom of the lower extremities that can be combined with a commercial torso phantom, thus enabling the optimisation of TBI treatment planning and dose delivery. Methods: We designed a modular leg phantom consisting of five key components: foot, calf, knee, thigh, and hip. Variants of knee and hip allow for both straight and angled leg positions. Inserts for dosimeters are integrated into the knee and hip joints, as well as within femur and fibula. To assess the phantom functionality in TBI, we analysed a currently used static-field technique and studied the feasibility of an intensity-modulated sweeping-beam technique. Results: We employed 3D printing to create hollow structures of bones, pelvis, and legs, which we filled with surrogate materials representing soft tissue and bone marrow. We simulated cortical bone with a gypsum coating. The CT numbers of soft tissue and bone surrogates align accurately with literature data. The material properties remained stable even one-year post-manufacturing, ensuring long-term use of the phantom. First dose verification measurements for the static-field technique show an agreement with the prescribed dose within less than ±10 %. Conclusion: The cost-effective modular phantom can be combined with a commercial torso phantom, allowing for the optimization and verification of various CT-based TBI techniques.Technische Universität Hambur
Identification of factors limiting the efficiency of transplanting extracellular electron transfer chains in Escherichia coli
No full textResearch in electro-microbiology provides unique opportunities to study and exploit microbial physiology. Several efforts have been made to transplant the extracellular electron transport chain from the native exoelectrogenic model organism Shewanella oneidensis into Escherichia coli. However, systematic comparisons between donor and recipient strain configurations are largely missing. Hence, the proposed minimal protein set, consisting of the c-type cytochromes cytoplasmic membrane protein A (CymA), small tetraheme cytochrome (STC), MtrA, and MtrC, as well as the β-barrel protein MtrB, was heterologously expressed in E. coli in different expansion stages. These stages were compared to corresponding S. oneidensis strains in terms of anthraquinone-2,6-disulfonate (AQDS) and ferric citrate reduction rates. This revealed that transplantation of heterologous extracellular electron transfer (EET) chains is associated with a tremendous decrease in electron transfer rates. As the acquired electron transfer rates were not competitive to S. oneidensis, it was hypothesized that protein localization and maturation might be affected by heterologous expression. Hence, the type II secretion system from S. oneidensis was also transplanted into an E. coli strain. The latter allowed the secretion of the terminal reductase MtrC onto the cell surface of E. coli for the first time. This was correlated with significantly increased but still insufficient extracellular electron transfer rates. Further experiments suggest that the correct folding of MtrB might be a further bottleneck
Sustainability Nexus AID: storms
No full textStorms include a range of weather events resulting in heavy liquid and solid precipitation and high winds. These events critically impact crops and natural resources and, in turn, health, economy, and infrastructure safety. The intensity and frequency of the physical mechanisms triggering storms will most likely increase under global warming due to the changing flows of water and energy in the atmosphere. Addressing storm threats holistically requires a nexus approach that links climate change, infrastructure, and human prosperity and well-being, contributing to achieving the UN’s Sustainable Development Goals. This work introduces the Storms Module of the United Nations University (UNU) Sustainability Nexus Analytics, Informatics, and Data (AID) Programme. The paper aims to emphasize the importance of AID tools in addressing storm impacts through a data-driven nexus approach that recognizes the connections between storm hazards, policy, and society. Today, AID tools are instrumental in understanding storms and making informed decisions to manage them. AID tools contribute to archiving and monitoring storm data, employing predictive models and early warning systems, estimating storm risk, conducting post-storm analysis, and aiding preparedness, response, and recovery efforts. The Storms Module lists freely available AID tools, including large databases, simulation and precipitation tools, and resources for storm preparedness. Over the next years, new Artificial Intelligence (AI) technologies, are expected to revolutionize storm understanding, forecasting, and adaptive planning. However, especially for the operational use of new AI tools, caution is advised due to potential limitations regarding data quality, ethical concerns, cybersecurity risks, and the need for legal frameworks