485 Works

Computation of backwater effects in surface waters of lowland catchments including control structures – an efficient and re-usable method implemented in the hydrological open-source model Kalypso-NA (4.0)

Sandra Hellmers & Peter Fröhle
Backwater effects in surface water streams and on adjacent lowland areas caused by mostly complex drainage and flow control structures are not directly computed with hydrological approaches yet. A solution to this weakness in hydrological modelling is presented in this article. The developed method enables transfer of discharges into water levels and calculation of backwater volume routing along streams and adjacent lowland areas by balancing water level slopes. The implemented and evaluated method extends the...

Reliable IoT-based monitoring and control of hydroponic systems

Konstantinos Tatas, Ahmad Al-Zoubi, Nicholas Christofides, Chrysostomos Zannettis, Michael Chrysostomou, Stavros Panteli & Anthony Antoniou
This paper presents the design and implementation of iPONICS: an intelligent, low-cost IoT-based control and monitoring system for hydroponics greenhouses. The system is based on three types of sensor nodes. The main (master) node is responsible for controlling the pump, monitoring the quality of the water in the greenhouse and aggregating and transmitting the data from the slave nodes. Environment sensing slave nodes monitor the ambient conditions in the greenhouse and transmit the data to...

Fragmentation of beaded fibres in a composite

Carol Winnifred Rodricks, Israel Greenfeld, Bodo Fiedler & Hanoch Daniel Wagner
The fibre–matrix interface plays an important role in the overall mechanical behaviour of a fibre-reinforced composite, but the classical approach to improving the interface through chemical sizing is bounded by the materials’ properties. By contrast, structural and/or geometrical modification of the interface may provide mechanical interlocking and have wider possibilities and benefits. Here we investigate the introduction of polymer beads along the interface of a fibre and validate their contribution by a single fibre fragmentation...

Statistical analysis of sub-zero temperature effects on fatigue strength of welded joints

Moritz Braun
Ships and offshore structures in Arctic environments are exposed to severe environmental actions and sub-zero temperatures. Thus, the design of such structures has to account for the Arctic environment and must be cost-efficient at the same time. A vital part of the design process is to ensure that fatigue-induced failure does not occur in the lifetime of the structure. While effects of high temperatures on material behavior are well covered in international standards and guidelines,...

Towards adaptive asset management in flood risk management : a policy framework

Paul Sayers, Berry Gersonius, Frank den Heijer, Wouter Jan Klerk, Peter Fröhle, Philipp Jordan, Ulf Radu Ciocan, Jeroen Rijke, Bart Vonk & Richard M. Ashley
EU Member States invest some €2.5 billion per year in flood protection, yet flood damages continue to increase. A new approach to the planning, design and management of flood protection assets is needed to ensure risks are better managed and asset management is aligned with broader socio-economic policies and supporting governance systems. This paper sets out a policy framework to enable this transition. The framework results from a collaboration of researchers and practitioners from around...

Estimating Weibull parameters using Mabchour’s method (MMab) for wind power at RAWA City, Iraq

Amani I. Altmimi, Safaa J. Al-Swaiedi & Oday Ibraheem Abdullah
Wind power is one of the most important sources of renewable energy. In this research paper, we developed an approach to select the optimum site among four different locations in Iraq (Talafar, Nasiriyah, Baghdad and RAWA) according to wind power density. Based on the optimization process, it was found that the RAWA city is the optimal site. We adopted Mabchour’s Method (MMab) to estimate the Weibull distribution parameters (c, k) for RAWA city at two...

Dynamic stability analysis of a ship at high forward speed in calm water

Hendrik Simonis, Patrick Marleaux, Moustafa Abdel-Maksoud & Norbert Stuntz
The dynamic stability of a ship can become more and more of an issue as the ship speed increases. While many different forms of dynamic instability are known, often very little is known about their cause and only a limited amount of research exists. Therefore, an incident of dynamic instability observed during model tests of a semi-displacement vessel in calm water is investigated. The incident occurred at a very high Froude number of Fn =...

Variability in femoral preparation and implantation between surgeons using manual and powered impaction in total hip arthroplasty

Tobias Konow, Johanna Bätz, David E. Beverland, Tim N. Board, Frank Lampe, Klaus Püschel & Michael Morlock
Background: The influence of the surgical process on implant loosening and periprosthetic fractures (PPF) as major complications in uncemented total hip arthroplasty (THA) has rarely been studied because of the difficulty in quantification. Meanwhile, registry analyses have clearly shown a decrease in complications with increasing experience. The goal of this study was to determine the extent of variability in THA stem implantation between highly experienced surgeons with respect to implant size, position, press-fit, contact area,...

Open-Access-Publikationskosten 2022-2024: Beschreibung des Vorhabens ohne Anhänge

Andreas Timm-Giel & Inken Feldsien-Sudhaus
DFG-Projektantrag im Bereich„Wissenschaftliche Literaturversorgungs- und Informationssysteme“ (LIS) Förderprogramm: "Open-Access-Publikationskosten"

A computational framework for conceptual blending

Manfred Eppe, Ewen Maclean, Roberto Confalonieri, Oliver Kutz, Marco Schorlemmer, Enric Plaza & Kai-Uwe Kühnberger
We present a computational framework for conceptual blending, a concept invention method that is advocated in cognitive science as a fundamental and uniquely human engine for creative thinking. Our framework treats a crucial part of the blending process, namely the generalisation of input concepts, as a search problem that is solved by means of modern answer set programming methods to find commonalities among input concepts. We also address the problem of pruning the space of...

Development of combined load spectra for offshore structures subjected to wind, wave, and ice loading

Moritz Braun, Alfons Dörner, Kane F. ter Veer, Tom Willems, Marc Seidel, Hayo Hendrikse, Knut V. Høyland, Claas Fischer & Sören Ehlers
Fixed offshore wind turbines continue to be developed for high latitude areas where not only wind and wave loads need to be considered but also moving sea ice. Current rules and regulations for the design of fixed offshore structures in ice-covered waters do not adequately consider the effects of ice loading and its stochastic nature on the fatigue life of the structure. Ice crushing on such structures results in ice-induced vibrations, which can be represented...

Entwicklung einer chemoenzymatischen Reaktionssequenz zur Synthese von Fettalkoholen

Kim Elisabeth Naße
Fettalkohole sind wichtige chemische Zwischenprodukte und werden insbesondere als Emulgatoren, Tenside und Schmierstoffe eingesetzt. Somit werden effiziente und nachhaltige Synthesen dieser benötigt. In dieser Arbeit wurde ein chemoenzymatischer Ansatz für eine lösungsmittelfreie und nahezu vollständig atomökonomische Reaktionssequenz entwickelt. Bestehend aus der Veresterung eines Fettalkohols mit der korrespondierenden Fettsäure und der anschließenden Hydrierung des intermediär gebildeten Waxesters werden neben den Katalysatoren keine weiteren Hilfsstoffe benötigt. Basierend auf dieser Idee konnten zwei Prozessvarianten realisiert werden. Darüber hinaus...

Analyzing the complexity of ice with explainable machine learning for the development of an ice material model

Leon Kellner
Meeresregionen, die nur saisonal oder teilweise mit Eis bedeckt sind, sind für viele Interessengruppen von Bedeutung. Schiffe und Strukturen, die in diesen Regionen eingesetzt werden, müssen gegen Eislasten ausgelegt werden. Dies wird mit empirischen Ansätzen oder Modelleisversuchen gemacht, jedoch haben beide Ansätze mehrere Nachteile. Numerische Simulationen sind wünschenswert, aber deren Genauigkeit ist durch aktuelle Eismaterialmodelle begrenzt, da diese nur teilweise Eisverhalten abbilden können. Verbesserte Materialmodelle zu entwickeln ist durch Lücken, was Messungen in vollmaßstäblichen Versuchen...

Towards semi automated pre-assembly for aircraft interior production

Florian Kalscheuer, Henrik Eschen & Thorsten Schüppstuhl
The growing aviation market puts first tier suppliers of aircraft interior under great pressure. Cabin monuments, not only consist of various assemblies with a wide range of parts, they are also highly customized by the airliners. Historically grown, poorly optimized manual processes offer the required flexibility, but limit the production rate of the individual products. The aviation industry responds with an increased use of automation technology. Recent standardization and automation approaches for efficient manufacturing, lead...

Report on results for household food waste collection and decentralised shredding in the “Lübeck-case” : DECISIVE Deliverable D3.6 : a decentralised management scheme for innovative valorisation of urban biowaste

Jessica Schermuly, Steffen Walk, Victor Oyedele, Antonio Ernesto Arroyo Cuara, Ina Körner & Stefan Deegener
This study focuses on the collection and characterisation of bio-waste and in particular food waste (FW) as the core-substrate of DECISIVE. These issues are investigated in a case-study performed at the eco-settlement Lübeck-Flintenbreite (LF), which is part of the City of Lübeck (LC). Within the study, the locations are characterised, whereby LF specifically includes explanations on the settlement structures and LC focuses on the current applied collection and treatment procedures for bio-waste including source-separated bio-waste...

Enrichment of phosphate-accumulating organisms (PAOs) in a microfluidic model biofilm system by mimicking a typical aerobic granular sludge feast/famine regime

Edina Klein, Janek Weiler, Michael Wagner, Minja Čelikić, Christof M. Niemeyer, Harald Horn & Johannes Gescher
Wastewater treatment using aerobic granular sludge has gained increasing interest due to its advantages compared to conventional activated sludge. The technology allows simultaneous removal of organic carbon, nitrogen, and phosphorus in a single reactor system and is independent of space-intensive settling tanks. However, due to the microscale, an analysis of processes and microbial population along the radius of granules is challenging. Here, we introduce a model system for aerobic granular sludge on a small scale...

Ordinary differential equations

Christian Seifert, Sascha Trostorff & Marcus Waurick
In this chapter, we discuss a first application of the time derivative operator constructed in the previous chapter. More precisely, we analyse well-posedness of ordinary differential equations and will at the same time provide a Hilbert space proof of the classical Picard–Lindelöf theorem (There are different notions for this theorem. It is also called existence and uniqueness theorem for initial value problems for ordinary differential equations as well as Cauchy–Lipschitz theorem). We shall furthermore see...

Causality and a Theorem of paley and wiener

Christian Seifert, Sascha Trostorff & Marcus Waurick
In this chapter we turn our focus back to causal operators. In Chap. 5 we found out that material laws provide a class of causal and autonomous bounded operators. In this chapter we will present another proof of this fact, which rests on a result which characterises functions in L2(ℝ; H) with support contained in the non-negative reals; the celebrated Theorem of Paley and Wiener. With the help of this theorem, which is interesting in...

Initial value problems and extrapolation spaces

Christian Seifert, Sascha Trostorff & Marcus Waurick
Up until now we have dealt with evolutionary equations of the form (∂t,νM(∂t,ν)+A¯)U=F (∂ t,ν M(∂ t,ν )+A)U=F for some given F∈ L2,ν(ℝ; H) for some Hilbert space H, a skew-selfadjoint operator A in H and a material law M defined on a suitable half-plane satisfying an appropriate positive definiteness condition with ν∈ ℝ chosen suitably large. Under these conditions, we established that the solution operator,, is eventually independent of ν and causal; that is,...

Zum Versagen von Unterwasserböschungen im Seegang

Julian Bubel
Die Analyse des Einflusses der Lagerungsdichte, der Bodensättigung und der Seegangsparameter auf die Stabilität von Unterwasserböschungen in sandigem Boden führt zu einer Eingrenzung der relevanten Parameter. Verflüssigungsversagen von Unterwasserböschungen können in locker gelagerten Böden bei dimensionslosen Lastamplituden p* > 0,05 auftreten. Mindestens mitteldicht gelagerte Böden versagen unter den betrachte-ten Randbedingungen hingegen nicht.

Partial least squares structural equation modeling (PLS-SEM) using R : a workbook

Joseph F. Hair, G. Tomas M. Hult, Christian M. Ringle, Marko Sarstedt, Nicholas Patrick Danks & Soumya Ray

Risk management for green transport corridors

Meike Schröder & Gunnar Prause
The Green Corridor concept represents a cornerstone in the development and implementation of integrated and sustainable transport solutions based on trans-nationality, multi-modality and a high involvement of public and private stakeholders, including the political level. Hence, the implementation and management of a Green Transport Corridor is connected with a variety of risks due to the high level of complexity and the strong frame conditions of the concept. E.g. stakeholders' violation of ecological and sustainable obligations...

Primary and recurrent repair of incisional hernia based on biomechanical considerations to avoid mesh-related complications

Regine Nessel, Thorsten Löffler, Johannes Rinn, Philipp Lösel, Samuel Voß, Vincent Heuveline, Matthias Vollmer, Johannes Görich, Yannique Ludwig, Luai Al-Hileh & Friedrich Kallinowski
Aim: Mechanical principles successfully guide the construction of polymer material composites in engineering. Since the abdominal wall is a polymer composite augmented with a textile during incisional hernia repair we ask: can incisional hernia be repaired safely and durably based on biomechanical principles? Material and Methods: Repair materials were assessed on a self-built bench test using pulse loads to elude influences on the reconstruction of the abdominal wall. Tissue elasticity was analyzed preoperatively as needed...

Utility-based operation management for low voltage distribution grids using online optimization

Hanko Ipach, Leonard Fisser, Christian Becker & Andreas Timm-Giel
Wir stellen einen Betriebsführungsregler für Niederspannungsnetze vor, der eine Vielzahl dezentraler Energieanlagen (DEA) in Echtzeit koordiniert, um die Nutzung der erneuerbaren Energieerzeugung zu maximieren. Der Regler verwendet ein LTE-Funknetzwerk, das die DEA mit dem Verteilnetzbetreiber verbindet. In unserem Ansatz werden den DEA Nutzenfunktionen zugewiesen und die Nutzenmaximierung wird als Optimierungsproblem formuliert. Das Optimierungsproblem wird durch einen iterativen Algorithmus gelöst, der inkrementelle Anpassungen der Leistungssollwerte der DEA in Richtung des Optimums vornimmt. Um den Netzzustand im...

New insights from locally resolved hydrodynamics in stirred cell culture reactors

Fabian Freiberger, Jens Budde, Eda Ateş, Michael Schlüter, Ralf Pörtner & Johannes Möller
The link between hydrodynamics and biological process behavior of antibody-producing mammalian cell cultures is still not fully understood. Common methods to describe dependencies refer mostly to averaged hydrodynamic parameters obtained for individual cultivation systems. In this study, cellular effects and locally resolved hydrodynamics were investigated for impellers with different spatial hydrodynamics. Therefore, the hydrodynamics, mainly flow velocity, shear rate and power input, in a single- and a three-impeller bioreactor setup were analyzed by means of...

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