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Miniature Testing Device to Study the Effect of External Load, and Irrigation Rate and Direction on the Capillary Collapse of Unsaturated Soil
No full textThe capillary collapse is an irreversible volumetric deformation of partially saturated soils induced by an increase in the water content. While extensively studied by several authors, there remain factors yet to be explored. Based on preliminary laboratory tests, this paper proposes an experimental device to study how changes in irrigation rate, direction, and total stress on the soil specimen affect collapse behavior. This device will be used in future collapse tests during with parallel X-ray computed tomography (CT) imaging to understand the phenomenon from a microscopic approach
Einfluss von Hochdruck auf die Synthese von N-Acetylneuraminsäure in einem Festbettreaktor
No full textDie kontinuierliche Anwendung von Hochdruck (bis 1300 bar) in der Biotechnologie wurde am Beispiel der Produktion von Neu5Ac beginnend mit GlcNAc und Pyr gezeigt. Hierfür wurden zwei immobilisierte Enzyme verwendet. Die Reaktionskinetik wurde mit einem Festbettreaktor und die Lage des Gleichgewichts mit einem eigens entwickelten Hochdruckumlaufreaktor untersucht. Die Lage des Gleichgewichts konnte positiv durch Anwendung von Druck verschoben werden. Einige Reaktanten zeigten durch Druck erhöhte Affinität zu den Enzymen. Insbesondere der Hochdruckumlaufreaktor ermöglicht durch zwei verschiedene Druckbereiche (Hochdruck und Umgebungsdruck) eine leichte Probenentnahme während im Reaktor Hochdruck herrscht.The continuous application of high pressure in biotechnology was shown for the production of Neu5Ac starting from GlcNac and Pyr. Two immobilized enzymes were used. For the investigation of the reaction kinetic a fixed bed reactor and for the position of equilibrium a circular reactor was used. By using up to 1,300 bar the equilibrium was positively influenced by pressure. Pressure caused an increase in affinity for some reactants towards the enzymes. The high-pressure circular reactor in particular showed great potential due to two different pressure regimes (high pressure and ambient pressure) enabling an easy taking of samples while the reaction is at high pressure.Federal Ministry of Education and Researc
Memory-Assisted Quantized LDPC Decoding
No full textWe enhance coarsely quantized LDPC decoding by reusing computed check node messages from previous iterations. Typically, variable and check nodes update and replace old messages every iteration. We show that, under coarse quantization, discarding old messages entails a significant loss of mutual information. The loss is avoided with additional memory, improving performance by up to 0.23 dB. We optimize quantization with a modified information bottleneck algorithm that considers the statistics of old messages. A simple merge operation reduces memory requirements. Depending on channel conditions and code rate, memory assistance enables up to 32% better area efficiency for 2-bit decoding
Communicating tokenomics and monetary policy : a comparative analysis of real and virtual economies
No full textThis article investigates the economic governance of blockchain-based virtual economies in the context of monetary policy. Focusing on tokenomics communication, we employ deductive and inductive approaches, applying real-world monetary policy metrics and text mining frameworks. Our comparative analysis reveals that the tokenomics communication in blockchain-based virtual economies primarily functions as a fundraising tool, lacking policy discussions, with divergences from real-world economies in policy goals and numerical targets. Furthermore, our research highlights similarities between blockchain-based virtual economies and early-stage low-income developing countries in communication dynamics
Systematic Investigation of Heart Sound Propagation using Continuous Wave Radar
No full textMonitoring the propagation of mechanical cardiac signals throughout the body is crucial for assessing cardiovascular health. A common drawback of current gold standard methods for vital sign monitoring is the necessity for continuous skin contact. Radar-based sensing offers a promising alternative by enabling contactless measurement of cardiac activity, including heart sound signals. As previous research has primarily focused on deriving signals from proximal body regions, insights into heart sound propagation to peripheral areas are lacking. To address this, we systematically investigated whether radar-based heart sound detection and propagation measurement is feasible across the whole body. We recorded heart sounds in N=22 participants sequentially at eleven locations using a custom-built continuous-wave radar system and phonocardiogram as heart sound gold standard. Additionally, an electrocardiogram was acquired as reference for overall heart activity. After synchronization and preprocessing, we manually segmented the heart sounds and extracted temporal characteristics from ensemble-averaged signals. Our findings show that heart sounds can be detected across the entire body with the radar-based as well as the gold standard system. Furthermore, the heart sounds’ temporal characteristics vary between measurement locations. As the distance to the heart increases, we observed significantly increased propagation time intervals. This finding is consistent across both systems, exhibiting a strong agreement for the first heart sound (r = 0.73, p < 0.001) and a moderate agreement for the second heart sound (r = 0.56, p < 0.001). In conclusion, our work is the first to demonstrate that radar-based systems are feasible for contactless evaluation of heart sound propagation, offering new possibilities for research and health monitoring
Integrated modelling of riverine levee breaches and subsequent inundation of protected areas
No full textLevees are earthen embankments, often constructed from locally available soil material, used to contain floodwaters in rivers. Levee design standards have improved over time, contributing to their reliability in providing flood protection. However, levees never provide absolute flood protection. The preparation of flood hazard maps for areas behind levees is therefore indispensable. Flood hazard maps can be produced using hydrodynamic numerical models that simulate flood inundation. The modelling of flood inundation due to levee breaching involves the modelling of two processes: i) the breaching of the levee and ii) the propagation of the flood through the resulting opening into the hinterland.
This thesis proposes the modelling of flood inundation due to levee breach with a 2D hydrodynamic numerical model with an integrated parametric levee breach model. To model levee breaching, a parametric levee breach model is developed, which is based on analyses of physical levee breaching experiments and of real levee breaches. The breach model is then integrated into the hydrodynamic numerical model Telemac-2D, a publicly available code for modelling flood propagation.
The thesis also developed methods for estimating the parameters of the parametric breach model based on historical (available) levee breach data. Regression fitting for the final breach width is performed using multiple linear regression, multiple non-linear regression and artificial neural networks. In addition, an approach is developed to estimate a possible breach location based on flood characteristics (water level and flood duration), geometric and geological characteristics of the levee in question and its foundation, the cause of the breach, and information from historical levee breaches on their breach location.
By re-modelling physical laboratory tests simulating levee breaching, this work has demonstrated that the hydrodynamic numerical model, Telemac-2D, is a suitable tool for modelling flood inundation due to levee breaching. The flood inundation caused by the levee breach on the Awash River at Wonji, Ethiopia in August 1996 could be reproduced using the proposed integrated approach. Furthermore, the determination of the breach location for this levee breach case using the approach proposed in this thesis resulted in the same location as the actual breach location, demonstrating the general applicability of the approach.
The uncertainties associated with the models used are also discussed. To demonstrate the uncertainty associated with the breach model, the sensitivity of flood inundation depth and breach discharge to variation of the levee breach parameters is systematically analysed using the August 1996 Awash River levee breach flood event at Wonji, Ethiopia.Deiche sind Erddämme, die häufig aus lokal verfügbarem Bodenmaterial errichtet werden und dazu dienen, Hochwasser von Flüssen zurückzuhalten. Die Baunormen für Deiche haben sich im Laufe der Zeit verbessert, was zu ihrer Zuverlässigkeit beim Hochwasserschutz beigetragen hat. Deiche bieten jedoch keinen absoluten Hochwasserschutz. Die Erstellung von Hochwassergefahrenkarten für Gebiete hinter Deichen ist daher unerlässlich. Hochwassergefahrenkarten können mit Hilfe von hydrodynamischen numerischen Modellen erstellt werden, die die Überflutung simulieren. Bei der Modellierung von Überflutungen infolge eines Deichbruchs werden zwei Prozesse modelliert: (i) der Deichbruch und (ii) die Ausbreitung des Hochwassers durch die entstandene Öffnung ins Hinterland.
In dieser Arbeit wird die Modellierung von Überflutungen infolge von Deichbrüchen mit einem 2D-hydrodynamischen numerischen Modell mit einem integrierten parametrischen Deichbruchmodell vorgeschlagen. Für die Modellierung von Deichbrüchen wird ein parametrisches Deichbruchmodell entwickelt, das auf der Analyse von physikalischen Deichbruchexperimenten und realen Deichbrüchen basiert. Das Bruchmodell wird dann in das hydrodynamische numerische Modell Telemac-2D integriert. Telemac-2D ist ein frei verfügbarer Code zur Modellierung der Hochwasserausbreitung.
Im Rahmen dieser Arbeit wurden auch Methoden zur Schätzung der Parameter des parametrischen Bruchmodells auf der Grundlage historischer (verfügbarer) Deichbruchdaten entwickelt. Insbesondere wurde eine Regressionsanpassung für die finale Durchbruchsbreite mittels multipler linearer Regression, multipler nichtlinearer Regression und künstlicher neuronaler Netze durchgeführt. Darüber hinaus wird ein Ansatz entwickelt, um eine mögliche Bruchstelle auf der Grundlage von Hochwassereigenschaften (Wasserstand und Hochwasserdauer), geometrischen und geologischen Eigenschaften des betroffenen Deichs und seines Fundaments, der Ursache des Bruchs und Informationen aus historischen Deichbrüchen über deren Bruchstelle zu schätzen.
Durch die Nachbildung physikalischer Laborexperimente, in denen ein Deichbruch simuliert wurde, konnte in dieser Arbeit gezeigt werden, dass das hydrodynamische numerische Modell Telemac-2D ein geeignetes Modell für die Modellierung von Überflutungen infolge von Deichbrüchen ist. Die durch den Deichbruch am Awash River in Wonji, Äthiopien, im August 1996 verursachte Überschwemmung konnte mit dem vorgeschlagenen integrierten Ansatz reproduziert werden. Darüber hinaus wurde mit dem in dieser Arbeit vorgeschlagenen Ansatz zur Bestimmung der Bruchstelle die tatsächliche Bruchstelle am Awash River bestimmt, was die allgemeine Anwendbarkeit des Ansatzes untermauert.
Die mit den verwendeten Modellen verbundenen Unsicherheiten werden ebenfalls diskutiert. Um die Unsicherheiten des Durchbruchmodells zu demonstrieren, wird die Sensitivität der Deichdurchbruchparameter auf die Berechnung der Überflutungstiefe und des Durchbruchabflusses anhand des Hochwasserereignisses vom August 1996 am Awash River in Wonji, Äthiopien, systematisch analysiert.Bundesministerium für Bildung und Forschung (BMBF
A modified Wagner stem design Increases the primary stability in cementless revision hip arthroplasty
No full textBackground: Primary stability is of great importance for the longevity of the implant in cementless revision total hip arthroplasty, since instability is a major cause of rerevision. The purpose of this study was to evaluate the effect of an additional set of less prominent, wider splines added to an established conical stem design with sharp splines on axial stability in a model with significant proximal bone defects. Methods: Twenty fresh-frozen human femurs were implanted with either the established or the additional spline design, dynamically loaded and tested in a load-to-failure configuration. Cortical contact in the femoral canal after implantation was evaluated by superimposing computed tomography scans and 3-dimensional laser scans. Stem subsidence and micromotion were evaluated to assess primary stability. Results: Stems remained stable during cyclic loading of up to 200% body weight, except in bones with cortical bone mineral density below 1000 mgHA/mL. A significant reduction of more than 85% in stem subsidence (P =.040), axial micromotion (P =.007), and rotational micromotion (P =.010) was achieved with the new spline design. Load-to-failure testing exceeded 400% body weight. Conclusions: The new spline design increased the cortical contact which resulted in increased axial primary stability in this in vitro experiment. Bone mineral density as a measure of bone quality proved to be a decisive factor for achieving immediate postoperative stability. Further variations of the established stem designs could further improve the longevity of artificial joint replacements
Anticipating customer substitution: a data-driven, distance-based approach for out-of-stock product configurations
No full textPurpose: When facing capacity bottlenecks, manufacturers of configurable, multi-variant products may adjust the product mix to uphold the scheduled output. However, maintaining market attractiveness by choosing the right product configurations as substitutes is a non-trivial task as it involves anticipating the substitution behaviour of customers. Substitution behaviour models currently used in quantitative production planning models for configurable products are either based on domain knowledge of experts, which makes them bias-prone, or they require extensive market research. The purpose of this study is to present a data-driven approach. Design/methodology/approach: Based on data science concepts, distance measures are applied to derive distances between different product configurations from historical order data. Different design options for such a distance measure are discussed regarding configurable products and tested with automotive industry data. Furthermore, the study shows ways to validate the distance results. Findings: The experiments show that the presented distance measure represents the expected customer substitution behaviour quite well. A context-sensitive distance measure including rank information of ordinal product features is most suitable for the automotive data sets. Originality/value: This study presents a new approach to model the substitution behaviour of customers. The attractiveness of a potential substitute is represented by a distance from the customer’s first-choice configuration. The presented distance measure provides an inexpensive tool using existing data instead of expensive market research. Thus, it supports the integration of substitution into quantitative production planning models that deal with a large variety of configurable products
Automated model discovery for tensional homeostasis: Constitutive machine learning in growth and remodeling
No full textWe present a built-in physics neural network architecture, known as inelastic Constitutive Artificial Neural Network (iCANN), to discover the inelastic phenomenon of tensional homeostasis. In this course, identifying the optimal model and material parameters to accurately capture the macroscopic behavior of inelastic materials can only be accomplished with significant expertise, is often time-consuming, and prone to error, regardless of the specific inelastic phenomenon. To address this challenge, built-in physics machine learning algorithms offer significant potential. We introduce the incorporation of kinematic growth and homeostatic surfaces into the iCANN to discover the Helmholtz free energy and the pseudo potential. The latter describes the state of homeostasis in a smeared sense. To this end, we additionally propose a novel design of the corresponding feed-forward network in terms of principal stresses. We evaluate the ability of the proposed network to learn from experimentally obtained tissue equivalent data at the material point level, assess its predictive accuracy beyond the training regime, and discuss its current limitations when applied at the structural level. Our source code, data, examples, and an implementation of the corresponding material subroutine are made accessible to the public at https://doi.org/10.5281/zenodo.13946282
High-pressure reactor technology for aerated biotransformations
No full textUtilizing pressure as a process parameter can make biotechnological processes more efficient and attractive compared to established ones. This paper presents a high-pressure reactor setup for enzymatically catalyzed gas–liquid reactions, which can be operated up to 15.0 MPa. The reactor is equipped with optical measurement technology for inline and in situ monitoring of the oxygen concentration under high-pressure conditions. The setup is characterized by assessing the influence of the process parameter pressure on the conversion of the glucose oxidation to d-glucono-δ-lactone by immobilized glucose oxidase. The study demonstrates that the increased oxygen availability due to higher solubility reduces the reaction time in a batch reactor from 270 to 90 min