157 Works

Determination of flow parameters of a water flow around an AUV body

Julian Hoth & Wojciech Kowalczyk
Autonomous underwater vehicles (AUVs) have changed the way marine environment is surveyed, monitored and mapped. Autonomous underwater vehicles have a wide range of applications in research, military, and commercial settings. AUVs not only perform a given task but also adapt to changes in the environment, e.g., sudden side currents, downdrafts, and other effects which are extremely unpredictable. To navigate properly and allow simultaneous localisation and mapping (SLAM) algorithms to be used, these effects need to...

Theoretical and practical issues that are relevant when scaling up hMSC microcarrier production orocesses

Valentin Jossen, Cedric Schirmer, Dolman Mostafa Sindi, Regine Eibl, Matthias Kraume, Ralf Pörtner & Dieter Eibl
The potential of human mesenchymal stem cells (hMSCs) for allogeneic cell therapies has created a large amount of interest. However, this presupposes the availability of efficient scale-up procedures. Promising results have been reported for stirred bioreactors that operate with microcarriers. Recent publications focusing on microcarrier-based stirred bioreactors have demonstrated the successful use of Computational Fluid Dynamics (CFD) and suspension criteria (N S1u , N S1) for rapidly scaling up hMSC expansions from mL- to pilot...

Capturing rogue waves by multi-point statistics

Ali Hadjihosseini, Matthias Wächter, Norbert P. Hoffmann & Joachim Peinke
As an example of a complex system with extreme events, we investigate ocean wave states exhibiting rogue waves. We present a statistical method of data analysis based on multi-point statistics which for the first time allows the grasping of extreme rogue wave events in a highly satisfactory statistical manner. The key to the success of the approach is mapping the complexity of multi-point data onto the statistics of hierarchically ordered height increments for different time...

Photocrosslinkable polysaccharide hydrogel composites based on dextran or pullulan-amylose blends with cytokines for a human co-culture model of human osteoblasts and endothelial cells

Ulrike Ritz, Peter Kögler, Isabel Höfer, Petra Frank, Sven Klees, Sören Gebhard, Christian Brendel, Kerstin Kaufmann, Alexander Hofmann, Pol Maria Rommens & Ulrich Jonas
Although a large body of research has been devoted to biomaterial development for bone tissue engineering and related medical disciplines in the last few years, novel and optimized materials especially for bone fractures of critical sizes demand continued development. In this respect, polysaccharide-based hydrogels demonstrate beneficial properties and fulfill the main requirements for a bone tissue scaffold as they are hydrophilic, biocompatible, and biodegradable. The aim of the present study was the development of a...

Maximizing the fixation strength of modular components by impaction without tissue damage

Annika Krull, Michael M. Morlock & Nicholas E. Bishop
Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted...

On notch and crack size effects in fatigue, Paris’ law and implications for Wöhler curves

Michele Ciavarella & Antonio Papangelo
As often done in design practice, the Wöhler curve of a specimen, in the absence of more direct information, can be crudely retrieved by interpolating with a power-law curve between static strength at a given conventional low number of cycles N0(of the order of 10-103), and the fatigue limit at a “infinite life”, also conventional, typically N∞=2·106or N∞=107cycles. These assumptions introduce some uncertainty, but otherwise both the static regime and the infinite life are relatively...

Regelungsverfahren für dieselelektrische Schiffsantriebe für hohe dynamische Anforderungen

Robert Benjamin Banek
On ships with diesel electric drive trains the power consumption of the prolusion motors has to be limited to prevent overloading of the diesel generators. As an alternative to the state-of-the-art limitation of the change rate of propulsion speed a dynamic limitation is developed that takes the current load acceptance capability into account. In this case the current load acceptance capability is computed using Hammerstein-Models that require only little computation work. Such dynamic limitation of...

Synthetic pathways and processes for effective production of 5-hydroxytryptophan and serotonin from glucose in Escherichia coli

José Aníbal Mora-Villalobos & An-Ping Zeng
Tryptophan derivatives such as 5-hydroxytryptophan (5HTP) and serotonin are valuable molecules with pharmaceutical interest. 5HTP is presently mainly obtained by extraction from the plant Griffonia simplicifolia and serotonin is produced by chemical synthesis. A simple biotechnological method for the production of these compounds is desired.

Dataset of ptychographic X-ray computed tomography of inverse opal photonic crystals produced by atomic layer deposition

Kaline P. Furlan, Emanuel Larsson, Ana Diaz, Mirko Holler, Tobias Krekeler, Martin Ritter, Alexander Yu. Petrov, Manfred Eich, Robert Blick, Gerold A. Schneider, Imke Greving, Robert Zierold & Rolf Janßen
This data article describes the detailed parameters for synthesizing mullite inverse opal photonic crystals via Atomic Layer Deposition (ALD), as well as the detailed image analysis routine used to interpret the data obtained by the measurement of such photonic crystals, before and after the heat treatment, via Ptychographic X-ray Computed Tomography (PXCT). The data presented in this article are related to the research article by Furlan and co-authors entitled "Photonic materials for high-temperature applications: Synthesis...

Understanding and control of biopolymer fouling in ultrafiltration of different water types

Xing Zheng, Frederik Zietzschmann, Stephan Plume, Hendrik Paar, Mathias Ernst, Martin Jekel & Zi Wang
The present work focuses on understanding and control of biopolymer fouling in ultrafiltration of a typical surface water and nearby secondary effluent for direct and indirect portable use. Characterization results show that both kinds of biopolymers are of similar molecular weight. Longer than one year water quality monitoring results show that the C/N ratio in the secondary effluent biopolymers was relatively constant at around 4.8, while that in the surface water macromolecules fluctuated at around...

Analysis of the influence of burst-mode laser ablation by modern quality tools

Claus Emmelmann & Juan Pablo Calderón Urbina
The development of lasers in terms of pulse length and ablation quality has made wider the perspective of material processing. Ablation using picosecond lasers offers an almost "cold material removal", which causes minimal heat affected zones and enables sublimation without melt formation. Moreover, burst-mode intensifies these effects by the partition of pulses into groups of micro-pulses. Therefore, removal rate and surface quality are improved with an appropriate combination of burst-mode and other relevant process parameters....

Flue gas concentrations and efficiencies of a coal-fired Oxyfuel power plant with circulating fluidised bed combustion

Matthias Weng, Claas Günther & Alfons Kather
In contrast to an Oxyfuel process with pulverised coal (PC) firing, possible advantages of a circulating fluidised bed combustion (CFBC) are the in-furnace sulphur dioxide removal - no additional sulphur dioxide removal downstream the steam generator might be necessary - And the feasibility for concepts with a reduced flue gas recirculation. In [1] design conditions for the overall process of an Oxyfuel CFBC with highest flue gas recirculation up to 75 % are compared to...

Modeling of delamination during milling of unidirectional CFRP

Wolfgang Hintze & Dirk Hartmann
The production of CFRP needs edge trimming in order to remove burrs as well as undefined orientated fibres and to shape the final part contour. Edge trimming is usually done by contour milling. The quality of machined edges may be affected by fibre protrusions and delaminated fibres which cause manual repair or may even lead to scrap. Delamination of fibres is often initiated by stresses applied during engagement of the cutting edge. Based on measured...

Continuing education and personalization of design methods to improve their acceptance in practice : an explorative study

Selin Üreten, Gregor Beckmann, Eilika Schwenke, Dieter Krause & Shi Cao
One possibility to establish and foster efficient method transfer from academia to industry is via the heads of professional designers and design students. The transfer and use of design methods in a sustainable way is related to the methods' acceptance by the user which is accompanied by many challenges. Educational concepts and design method adaptions have been chosen as decisive control parameters among many others in order to understand and evaluate how these can influence...

Carbon nanoparticles’ impact on processability and physical properties of epoxy resins : a comprehensive study covering rheological, electrical, thermo-mechanical, and fracture properties (mode I and II)

Hauke Meeuw, Johann Körbelin, Valea Kim Wisniewski, Ali Shaygan Nia, Adrián Romaní Vázquez, Martin Rudolf Lohe, Xinliang Feng & Bodo Fiedler
A trade-off between enhancement of physical properties of the final part and the processability during manufacturing always exists for the application of nanocarbon materials in thermoset-based composites. For different epoxy resins, this study elaborates the impact of nanocarbon particle type, functionalization, and filler loading on the resulting properties, i.e., rheological, electrical, thermo-mechanical, as well as the fracture toughness in mode I and mode II loading. Therefore, a comprehensive set of carbon nanoparticles, consisting of carbon...

Porous starch materials via supercritical- and freeze-drying

Victor Baudron, Pavel Gurikov, Irina Smirnova & Steve Whitehouse
The production of porous materials based on starch has been explored with supercritical drying—yielding aerogel—and freeze-drying. The two drying procedures were applied on the same gelling solution of amylomaize starch pasted at 140 °C and for two concentrations (5 and 10 wt.%). After gelation and retrogradation, water from the samples to be supercritically dried was exchanged to ethanol. The resulting starch aerogel presented high specific surface area (197 m2/g). Freeze-drying was assessed by investigating the...

Scope of cooperation between India & Germany in renewables with a focus on opportunities in the wind sector in India

Sadhana Tiwari & Rajnish Tiwari
In 2015, India set itself a very ambitious task of expanding its installed base of renewable energies by more than five times to 175 gigawatt (GW) within seven years (by 2022). It was envisioned that 60 GW would be contributed by wind power. In 2018, the objective was revised upwards to 227 GW in total and 67 GW for wind power. The country needed such challenging goals to ensure an early, universal, and 24x7 access...

Residue - and by-product based bioresources - characterization, properties and pathways

Ina Körner, Saskia Hertel, Moses Ogun, Steffen Walk, Jessica Schermuly, Phillipp Lüssenhop & Stefan Deegener

The generation and application of biogas and digestates

Ina Körner & Deegener

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  • 2019
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