163 Works

Curvature sensing of a soft robot based on conductive foam

Malte Grube & Robert Seifried
Soft material robots are an emerging and fast-growing field of research [1] with potential application in various technical fields. These applications include, but are not limited to medical applications and all sorts of human-machine-interaction. Due to the soft structure, conventional components and design methodologies are not applicable. For reliable control and positioning of soft robots in 3D space especially accurate knowledge about their current position and orientation is essential. In this contribution, a resistive curvature...

The inhomogeneous Cauchy-Riemann equation for weighted smooth vector-valued functions on strips with holes

Karsten Kruse
This paper is dedicated to the question of surjectivity of the Cauchy-Riemann operator ∂¯ on spaces EV(Ω, E) of C∞-smooth vector-valued functions whose growth on strips along the real axis with holes K is induced by a family of continuous weights V. Vector-valued means that these functions have values in a locally convex Hausdorff space E over C. We derive a counterpart of the Grothendieck-Köthe-Silva duality O(C\ K) / O(C) ≅ A(K) with non-empty compact...

A critical review with emphasis on recent pieces of evidence of Moringa oleifera biosorption in water and wastewater treatment

Asmaa Benettayeb, Muhammad Usman, Coffee Calvin Tinashe, Traore Adam & Boumediene Haddou
The increasing demand for using competent and inexpensive methods based on biomaterials, like adsorption and biosorption, has given rise to the low-priced alternative biosorbents. In the past few years, Moringa oleifera (MO) has emerged as a green and low-priced biosorbent for the treatment of contaminated waters with heavy metals and dyes, and given its availability, we can create another generation of effective biosorbents based on different parts of this plant. In this review paper, we...

Benchmark parts for the evaluation of optimized support structures in Laser Powder Bed Fusion of metals

Katharina Bartsch, Joost Ohrenberg & Claus Emmelmann
Laser powder bed fusion (PBF-LB/M) of metals belongs to the advanced additive manufacturing processes on the brink of industrialization. Successful manufacturing often requires the utilization of support structures to support overhangs, dissipate heat, and prevent distortion due to residual stresses. Since the support structures result in increased costs, research, as well as industry, aim at optimizing the application of those or the support structures themselves. New approaches are validated with individual use cases, though, preventing...

RAT-RS: a reporting standard for improving the documentation of data use in agent-based modelling

Sebastian Achter, Melania Borit, Edmund Chattoe-Brown & Peer-Olaf Siebers
This article describes and justifies a reporting standard to improve data use documentation in Agent-Based Modelling. Following the development of reporting standards for models themselves, empirical modelling has now developed to the point where these standards need to take equally effective account of data use (which previously has tended to be an afterthought to model description). It is particularly important that a standard should allow the reporting of the different uses to which data may...

Explant analysis and implant registries are both needed to further improve patient safety

Michael Morlock, Enrique Gomez-Barrena, Dieter Christian Wirtz, Alister Hart & Jan Philippe Kretzer
In the early days of total joint replacement, implant fracture, material problems and wear presented major problems for the long-term success of the operation. Today, failures directly related to the implant comprise only 2–3% of the reasons for revision surgeries, which is a result of the material and design improvements in combination with the standardization of pre-clinical testing methods and the post-market surveillance required by the legal regulation. Arthroplasty registers are very effective tools to...

Analysis phase of lean six sigma methodology with scaled-down laboratory experiments for an industrial-scale biogas plant

Samet Cinar, Senem Önen Cinar, She Ming Ng & Kerstin Kuchta
Although the benefits of the Lean Six Sigma (LSS) methodology have been proven for more than 20 years, it is still underutilized in environmental science, (e.g., in anaerobic digestion and biogas production). In order to obtain a structural and data-oriented perspective for process optimization in the renewable energy sector, LSS application must be considered one of the most valuable tools. To inform this paper, the LSS analysis phase was conducted in a scaled-down environment through...

Fast and artifact reducing joint multi-patch MPI reconstruction

Lena Zdun, Marija Boberg & Christina Brandt
The method of magnetic particle imaging (MPI) has a limited field of view due to physiological constraints. It is thus necessary to enlarge the field of view by a multi-patch approach in order to cover larger volumes. During reconstruction, truncation artifacts arise at the patches boundaries. We apply stochastic primal-dual hybrid gradient method to jointly reconstruct multi-patch magnetic particle images. We are thus able to apply a regularization taking into account neighborhood structures, not only...

Process intensification as game changer in enzyme catalysis

Bastien Oliver Burek, Ayad W. H. Dawood, Frank Hollmann, Andreas Liese & Dirk Holtmann
Enzyme catalysis, made tremendous progress over the last years in identification of new enzymes and new enzymatic reactivity’s as well as optimization of existing enzymes. However, the performance of the resulting processes is often still limited, e.g., in regard of productivity, realized product concentrations and the stability of the enzymes. Different topics (like limited specific activity, unfavourable kinetics or limited enzyme stability) can be addressed via enzyme engineering. On the other hand, there is also...

Spatial and temporal variability of bed exchange characteristics of fine sediments from the Weser estuary

Justus Patzke, Edgar Nehlsen, Peter Fröhle & Roland Hesse
Sedimentation of fine-grained sediments in estuaries is a natural physical phenomenon influenced by biogeochemical processes. In the estuarine turbidity maximum (ETM), enhanced net deposition of sediments is observed even in areas with higher hydrodynamic exposure, such as the navigational channel. Maintenance dredging is a common method to maintain the navigational channel, which requires large financial effort and has potential negative impacts on the environment. Research at the Institute for River and Coastal Engineering addresses the...

Information bottleneck signal processing and learning to maximize relevant information for communication receivers

Jan Lewandowsky, Gerhard Bauch & Maximilian Stark
Digital communication receivers extract information about the transmitted data from the received signal in subsequent processing steps, such as synchronization, demodulation and channel decoding. Technically, the receiver-side signal processing for conducting these tasks is complex and hence causes bottleneck situations in terms of power, delay and chip area. Typically, many bits per sample are required to represent and process the received signal in the digital receiver hardware accurately. In addition, demanding arithmetical operations are required...

Correlating granule surface structure morphology and process conditions in fluidized bed layering spray granulation

Maike Orth, Paul Kieckhefen, Swantje Pietsch & Stefan Heinrich
A workflow for developing a multidimensional, linear correlation between the process conditions during fluidized bed spray granulation and the surface morphology of the resulting granules is presented. Spray coating experiments with Cellets®500 particles and sodium benzoate solution were performed in a lab-scale fluidized bed varying liquid spray rate, fluidization air flow rate, fluidization air temperature, spray air temperature and spray atomization pressure. To characterize the surface structure, the surface roughness of the coated particles was...

Scaling laws for unmitigated pile driving: Dependence of underwater noise on strike energy, pile diameter, ram weight, and water depth

Jonas von Pein, Tristan Lippert, Stephan Lippert & Otto von Estorff
Sound produced by marine pile driving activities poses a possible risk to marine life. The assessment and mitigation of this risk requires a prediction of the expected sound levels. While different analytical models have been presented to estimate the decay characteristics of pile driving noise, the estimation of the source level still requires the use of numerical modelling in most cases. The paper at hand discusses the possibilities and limits of estimating approximate source or...

“Boiling water is not too hot for us!” : preferred living spaces of heat-loving microbes

Skander Elleuche, Carola Schröder, Nadine Stahlberg & Garabed Antranikian
Do you like to stay at the beach on a hot summer day? Sun bathing, chilling, and playing beach games? If it gets too hot, you can quickly cool off in the lukewarm ocean. Can you believe that there are living organisms on our planet that would still freeze on the hottest day of the year? These tiny creatures are called heat-loving microbes, and they do not grow at temperatures lower than 50°C, but they...

Design and optimization of a wave energy converter for drifting sensor platforms in realistic ocean waves

Julius Harms, Marten Hollm, Leo Dostal, Thorsten Alexander Kern & Robert Seifried
One of the biggest challenges in converting wave energy is to enable the use of low frequency waves, since the highest waves in typical sea states have low frequencies, as can be seen from the corresponding wave spectra, such as the Pierson–Moskowitz or JONSWAP spectra. In this paper, we show that this challenge is indeed achievable for the operation of small autonomous drifting sensor platforms. We present the design and optimization of a compact wave...

A modeling approach to predict the mechanical response of materials to irradiation damage from external sources: nanoindentation of Pb-implanted ZrSiO4

Norbert Huber & Tobias Beirau
Materials exposed to external irradiation undergo damage and detoriation of mechanical properties that decays with the distance from the surface. Finite element simulations are used to predict the hardness and Young´s mod- ulus as function of depth. The model incorporates the homogenized mechanical properties and the volumetric swelling, determined from micromechanical simulations, as function of the locally induced damage. Predicted Young’s modulus data showed a good agreement with nanoindentation results and confirmed the established mapping...

Fast strategies in waiter-client games

Dennis Clemens, Pranshu Gupta, Fabian Hamann, Alexander Haupt, Mirjana Mikalački & Yannick Mogge
Waiter-Client games are played on some hypergraph (X,𝓕), where 𝓕 denotes the family of winning sets. For some bias b, during each round of such a game Waiter offers to Client b+1 elements of X, of which Client claims one for himself while the rest go to Waiter. Proceeding like this Waiter wins the game if she forces Client to claim all the elements of any winning set from 𝓕. In this paper we study...

Influence of redox initiator component ratios on the emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester

Laurence Isabelle Jacob, Werner Pauer & Baldur Schröter

AHOI: Inexpensive, low-power communication and localization for underwater sensor networks and μAUVs

Bernd-Christian Renner, Jan Heitmann & Fabian Steinmetz
The recent development of small, cheap AUVs enables a plethora of underwater near- and inshore applications. Among these are monitoring of wind parks, detection of pollution sources, water-quality inspection, and the support of divers during disaster management. These tasks profit from online reporting, control, and AUV swarm interaction; yet they require underwater communication. Unfortunately, commercial devices are prohibitively expensive and typically closed-source, hampering their application in affordable products and research. Therefore, we developed the open-source1...

Nanoindentation of supercrystalline nanocomposites: linear relationship between elastic modulus and hardness

Cong Yan, Büsra Bor, Alexander Plunkett, Berta Domènech Garcia, Gerold A. Schneider & Diletta Giuntini
Supercrystalline nanocomposites (SCNCs) are a new category of nanostructured materials, with organically functionalized nanoparticles assembled into periodic structures, reminiscent of atomic crystals. Thanks to this nanoarchitecture, SCNCs show great promise for functional applications, and understanding and controlling their mechanical properties becomes key. Nanoindentation is a powerful tool to assess the mechanical behavior of virtually any material, and it is particularly suitable for studies on nanostructured materials. While investigating SCNCs in nanoindentation, a linear proportionality has...

Three dimensional flows beneath a thin layer of 2D turbulence induced by Faraday waves

Raffaele Colombi, Michael Schlüter & Alexandra von Kameke
Abstract: Faraday waves occur on a fluid being subject to vertical shaking. Although it is well known that form and shape of the wave pattern depend on driving amplitude and frequency, only recent studies discovered the existence of a horizontal velocity field at the surface, called Faraday flow. This flow exhibits attributes of two-dimensional turbulence and is replicated in this study. Despite the increasing attention towards the inverse energy flux in the Faraday flow and...

A novel p-harmonic descent approach applied to fluid dynamic shape optimization

Peter Marvin Müller, Niklas Kühl, Martin Siebenborn, Klaus Deckelnick, Michael Hinze & Thomas Rung
We introduce a novel method for the implementation of shape optimization for non-parameterized shapes in fluid dynamics applications, where we propose to use the shape derivative to determine deformation fields with the help of the p- Laplacian for p> 2. This approach is closely related to the computation of steepest descent directions of the shape functional in the W1,∞- topology and refers to the recent publication Deckelnick et al. (A novel W1,∞ approach to shape...

Extension of vector-valued functions and weak-strong principles for differentiable functions of finite order

Karsten Kruse
In this paper we study the problem of extending functions with values in a locally convex Hausdorff space E over a field K, which has weak extensions in a weighted Banach space Fν(Ω,K) of scalar-valued functions on a set Ω, to functions in a vector-valued counterpart Fν(Ω,E) of Fν(Ω,K). Our findings rely on a description of vector-valued functions as continuous linear operators and extend results of Frerick, Jordá and Wengenroth. As an application we derive...

Performance increase of wave energy harvesting of a guided point absorber

Marten Hollm, Leo Dostal, Daniil Yurchenko & Robert Seifried
The dynamics of a novel wave energy converter based on a guided inclined point absorber are investigated. Thereby, it is studied through simulations and experiments whether different inclination angles of the guided point absorber lead to larger motion amplitudes and velocities in regular and irregular waves, from which energy can be harvested. For that, different simulations and experimental setups are analyzed in the presence of wave forcing. In the case of irregular waves a random...

Topology-based initialization for the optimization-based design of heteroazeotropic distillation processes

Kai Kruber & Mirko Skiborowski
Distillation-based separation processes, such as extractive or heteroazeotropic distillation, present important processes for separating azeotropic mixtures in the chemical and biochemical industry. However, heteroazeotropic distillation has received much less attention than extractive distillation, which can be attributed to multiple reasons. The phase equilibrium calculations require a correct evaluation of phase stability, while the topology of the heterogeneous mixtures is generally more complex, comprising multiple azeotropes and distillation regions, resulting in an increased modeling complexity. Due...

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