374 Works

Reliable data streams in the presence of external interference

Florian Meyer
Vermaschte Netzwerke, als ein Mittel zur drahtlosen Kommunikation in großen industriellen Anwendungen, haben über die letzten Jahre mehr und mehr an Popularität gewonnen. Dabei stellen diese Anwendungen neue Anforderungen an die konventionellen drahtlosen Lösungen bezüglich ihrer Zuverlässigkeit und Voraussagbarkeit unter dem Einfluss externer Störungen, besonders bei der Kontrolle und Überwachen von sicherheitskritischen Systemen. Viele Anwendungen verlangen gar eine vollständig verlustfreie Datenübertragung, in dem Sinne, dass jedes auf der Anwendungsschicht versendete Paket schlussendlich beim Empfänger ankommt....

Combined FEM-SPH simulations for ice in compression

Niklas Düchting
Within this chapter the outcome of the numerical investigation on a combined FEM-SPH simulation is summed up. The practical approach of this project allows only a rather sim-ple assessment and there are aspects that need to be investigated further. An outlook in-dicates possible aspects for future research. Regarding the correlation of the contact forces the results of the final simulations pre-sented in section 3.3.1 are satisfying. The ability to model the transformation of the ma-terial...

Nanomechanics of individual aerographite tetrapods

Raimonds Meija, Stefano Signetti, Arnim Schuchardt, Kerstin Meurisch, Daria Smazna, Matthias Mecklenburg, Karl Schulte, Donats Erts, Oleg Lupan, Bodo Fiedler, Yogendra Kumar Mishra, Rainer Adelung & Nicola M. Pugno
Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of their individual building blocks. Here we characterize the mechanical response of single aerographite tetrapods via in situ scanning electron and atomic force microscopy measurements. To understand the acquired results, which show that...

COLIBRI MODULE O17 : documentation of project results : final report

Jens Myrup Pedersen
During 2014 and 2017 the project COLIBRI (Collaboration and Innovation for Better, Personalised and IT-Supported Teaching) was carried out between seven European Universities, two companies, and a national documentation center. The aim was to develop and try out new and innovative teaching methods. You can read more about the project at www.erasmus-colibri.eu . The purpose of this document is to share the experiences we had during the three years, in a way that is useful...

Hydrogen supply chains for mobility : environmental and economic assessment

Christina Wulf & Martin Kaltschmitt
Hydrogen mobility is one option for reducing local emissions, avoiding greenhouse gas (GHG) emissions, and moving away from a mainly oil-based transport system towards a diversification of energy sources. As hydrogen production can be based on a broad variety of technologies already existing or under development, a comprehensive assessment of the different supply chains is necessary regarding not only costs but also diverse environmental impacts. Therefore, in this paper, a broad variety of hydrogen production...

Bioengineering of a full-thickness skin equivalent in a 96-well insert format for substance permeation studies and organ-on-a-chip applications

Katharina Schimek, Hao-Hsiang Hsu, Moritz Boehme, Jacob Jan Kornet, Uwe Marx, Roland Lauster, Ralf Pörtner & Gerd Lindner
The human skin is involved in protecting the inner body from constant exposure to outer environmental stimuli. There is an evident need to screen for toxicity and the efficacy of drugs and cosmetics applied to the skin. To date, animal studies are still the standard method for substance testing, although they are currently controversially discussed Therefore, the multi-organ chip is an attractive alternative to replace animal testing. The two-organ chip is designed to hold 96-well...

Lurie solution for spherical particle and spring layer model of interphases : its application in analysis of effective properties of composites

Lidiia V. Nazarenko, Swantje Bargmann & Henryk K. Stolarski
A new approach to the determination of equivalent inhomogeneity for spherical particles and the spring layer model of their interphases with the matrix material is developed. To validate this approach the effective properties of random composites containing spherical inhomogeneities surrounded by an interphase material of constant thickness are evaluated. The properties of equivalent inhomogeneity, incorporating only properties of the original inhomogeneity and its interphase, are determined employing a new approach based on the exact Lurie's...

Design of cylindrical shells using the single perturbation load approach : potentials and application limits

Benedikt Kriegesmann, Eelco Luc Jansen & Raimund Rolfes
The Single Perturbation Load Approach (SPLA) is a promising deterministic procedure on the basis of mechanical considerations to determine reasonable design loads for cylindrical shells in axial compression. In this paper, two main issues are identified that should be understood better in order to appreciate the potential and the limits of application of the SPLA. Firstly, the question whether a single perturbation load in general represents a “worst case” imperfection is addressed. Secondly, the influence...

Computability theory

Karl-Heinz Zimmermann
Die Veröffentlichung gibt eine Einführung in die Theorie der Berechenbarkeit.

LWE-based encryption schemes and their applications in privacy-friendly data aggregation

Daniela Becker
Wir konstruieren neue Verschlüsselungssysteme basierend auf dem Learning With Errors Problem and lösen die folgenden Probleme: Durch datenschutzfreundliche Aggregation lassen sich Daten von mehreren Nutzern unter Wahrung ihrer Privatsphäre aggregieren ohne dem Aggregator zu vertrauen. Unsere Systeme verbessern sowohl Laufzeit als auch Bandbreite der Verschlüsselung, insbesondere die Entschlüsselung ist ca. 150 Mal schneller als zuvor. Überdies stellen wir die erste Lösung für datenschutzfreundliche Werbung auf sozialen Medien vor - unsere Architektur hat hohe Sicherheits- und...

Development of a colored GFRP with antistatic properties

Hauke Meeuw, Markus Radek & Bodo Fiedler
This study shows that a modification with ultralow filler content of novel single wall carbon nanotubes (SWCNT) converts an intrinsic insulating GFRP into one with antistatic properties. These properties remain even by adding pigments for customizing without affecting the wanted bright coloring (e.g. signal color). We developed a bright colored and antistatic glass fiber reinforced polymer (GFRP) by addition of carbon nanoparticle and pigments. Novel, in industrial scale available SWCNT dispersed in polyester resin with...

Driving diffusion of scientific innovation - the role of institutional entrepreneurship and open science in synthetic biology

Giulio Barth
Effekte von Institutionen auf die Diffusion von wissenschaftlichen Innovationen wurden in mehreren Studien belegt, ohne auf die Schaffung von Institutionen einzugehen. Die Theorie von institutionellen Entrepreneuren thematisiert diese Lücke und erklärt, wie Schlüsselfiguren eine institutionelle Logik verbreiten und auf dieser aufbauende Institutionen schaffen, um die Diffusion von Innovationen zu beeinflussen. In meiner Dissertation validiere ich den vollständigen Prozess ausgehend vom Entrepreneur, der eine Logik verbreitet, bis hin zu Effekten von frei verfügbaren Forschungsmethoden. Basierend auf...

Comparison of different approaches tracking a wing-tip vortex

Dag-Frederik Feder, Mahesh Dhone, Nikolai Kornev & Moustafa Abdel-Maksoud Gomaa
This paper compares the performance of different grid based and grid free modelling approaches to predict the tip vortex evolution in both near and far wing wake fields. The grid based methods cover different turbulence modelling approaches, adaptive mesh refinement and the adaptive vorticity confinement (VC) method using the OpenFOAM code. Computational vortex method (CVM) coupled with the OpenFOAM simulation of the near field is utilised to properly predict the tip vortex behaviour in the...

Influence of furfuryl alcohol fiber pre-treatment on the moisture absorption and mechanical properties of flax fiber composites

Yunlong Jia & Bodo Fiedler
Poor moisture resistance of natural fiber reinforced bio-composites is a major concern in structural applications. Many efforts have been devoted to alleviate degradation of bio-composites caused by moisture absorption. Among them, fiber pre-treatment has been proven to be effective. This paper proposes an alternative “green” fiber pretreatment with furfuryl alcohol. Pre-treatments with different parameters were performed and the influence on the mechanical properties of fiber bundles and composites was investigated. Moisture resistance of composites was...

Experimental investigation of a ground-coupled desiccant assisted air conditioning system

Arne Speerforck & Gerhard Schmitz
In a pilot installation at Hamburg University of Technology the coupled operation of an open cycle desiccant assisted air conditioning system with borehole heat exchangers is investigated. The paper presents experimental data recorded during the cooling period 2014. Results show that the electricity demand of the system can be reduced to the parasitic consumption of the fans, wheels and pumps. An electric energy efficiency ratio of 6.63 is achieved, enabling electricity savings of more than...

Numerical computation of lightning transfer functions for layered, anisotropically conducting shielding structures by the method of moments

Fabian Happ, Heinz-Dietrich Brüns, Gazmend Mavraj & Frank Gronwald
A formalism for the computation of lightning transfer functions by the method of moments, which involves shielding structures that may consist of layered, anisotropically conducting composite materials, is presented in this contribution. The composite materials, being of a type that is widely used in space- and aircraft design, are electrically characterized by an equivalent conductivity. As basis for the quantitative analysis the method of moments is used where shielding surfaces can be treated by a...

Design and analysis of ultra-wideband antennas for transient field excitations

Miroslav A. Kotzev, Matthias Kreitlow & Frank Gronwald
This work addresses the design of two ultrawideband antennas for the application of transient field measurements that are characterized by frequency spectra that typically range from a few MHz to several GHz. The motivation for their design is the excitation of high power transient pulses, such as double exponential or damped sinusoidal pulses, within highly resonant metallic enclosures. The antenna design is based on two independent numerical full-wave solvers and it is aimed to achieve...

Remote sensing in humanitarian logistics : an integrative approach

Christian Hein, Henning Hünemohr & Rainer Lasch
Remote sensing is becoming increasingly important for the acquisition of information in humanitarian logistics. While different platforms (e.g. satellites, drones) with their own characteristics and advantages exist, the literature often refers to just one of them. This paper aims at integrating platforms, making full use of their specific advantages. The work is conceptual, comparing different remote sensing platforms according to their advantages and limitations as well as evaluating the potentials of their combination drawing on...

Supplier Integration in Industry 4.0 – Requirements and Strategies

Julian Müller, Johannes Veile & Kai-Ingo Voigt
Cross-company networking is essential to successfully implement Industry 4.0. In this context, numerous new demands on suppliers arise leading to integration challenges that require specific integration strategies. While these topics are important in business practice, an aggregated holistic overview is still missing. Therefore, this article examines new demands on suppliers, challenges in the implementation process, and integration strategies for supplier integration in the context of Industry 4.0. Expert interviews with 15 different industrial companies from...

Running the machine faster : acceleration, humans and warehousing

Tony Cragg, Thierry Sauvage, Mohammed Haouari, Sarrah Chraibi & Oussama El Khalil Houssaini
To reduce the lead-time, modern logistics seeks to respond faster by accelerating physical and information flows. However, what are the impacts on logistics workers of an ever-faster logic? The purpose of this paper is to examine the relationship between process acceleration and the autonomy of order pickers. The method is to use exploratory qualitative research, based on fifteen visits to different regional distribution centers (RDCs) in the retail supermarket sector. The contribution of this paper...

About the future role of software in the product

Henning Skirde & Robert Steinert
Product development is shifting towards realizing an extended scope of product functions in software. This leads to new challenges in terms of a methodological integration and synchronization of different development disciplines. This paper provides insights on how to systematically manage the harmonization of traditional development disciplines with agile software development based on an integrated data model. To achieve this, the traditional product data model is extended to a seamless system data model that covers –...

Towards picogram detection of superparamagnetic iron-oxide particles using a gradiometric receive coil

Matthias Gräser, Tobias Knopp, Patryk Szwargulski, Thomas Friedrich, Anselm von Gladiß, Michael Kaul, Kannan M. Krishnan, Harald Ittrich, Gerhard Adam & Thorsten M. Buzug
Superparamagnetic iron-oxide nanoparticles can be used in medical applications like vascular or targeted imaging. Magnetic particle imaging (MPI) is a promising tomographic imaging technique that allows visualizing the 3D nanoparticle distribution concentration in a non-invasive manner. The two main strengths of MPI are high temporal resolution and high sensitivity. While the first has been proven in the assessment of dynamic processes like cardiac imaging, it is unknown how far the detection limit of MPI can...

Clean technologies and energy efficiency in SMEs

Maria Ines Jatib, Juan Ignacio Somoza, Javier Parysow, Horacio Repetto & Agustina Cerullo
A strategic association has been made between the National University of Tres de Febrero (UNTREF) and the Municipality of Tres de Febrero. These institutions jointly analyzed SMEs (small and medium-sized enterprises) located in the mentioned district, with the aim of designing and analyzing the implementation of clean technologies. Firstly, based on the information provided by the Industry Department, the SME sector was surveyed. Three manufacturing companies from different industries were selected, in order to carry...

Exploring congestion impact beyond the bulk cargo terminal gate

Mihai Neagoe, Mohammad Sadegh Taskhiri, Hong-Oanh Nguyen, Hans-Henrik Hvolby & Paul A. Turner
Bulk cargo terminal congestion management, approaches have tended to be almost exclusively focused on the sea side of bulk terminals. To-date there has been very limited work on land-side approaches to mitigate congestion in bulk terminals. This research aims to address these gaps by considering the effectiveness of multiple congestion management methods across a range of throughput scenarios. This paper develops a discrete event simulation model based on data collected from an Australian bulk wood...

Alternative Development Paths for Supply Chains in 2030

Denis Daus, Ana Cristina Barros, Dimitra Kalaitzi, Victoria Muerza & Irene Marchiori
Many different megatrends such as digitalization, are posing specific challenges and opportunities for supply chains creating the urgent need to adapt and rethink the way they are organized. This paper aims to define development paths (DPs), which constitute projections into the future. The DPs are based on the analysis of megatrends, which might have an impact on the design of supply chains until the year 2030. The results are 51 possible DPs, which are derived...

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