2,228 Works

Development of hydrogen storage systems using Sodium alanate

Gustavo Adolfo Lozano Martinez
Hydrogen storage systems based on sodium alanate are studied, modelled, and optimised, on the basis of both experimental and theoretical approaches. The experimental hydrogen sorption behaviour (kinetics, heat transfer and cycling) of small cells up to kg-scale storage tanks is compared and analysed. In particular the effect of the size of the system, powder compaction, and addition of expanded graphite on the sorption behaviour is investigated and characterized. In order to implement simulations and further...

Windkanalversuche mit gewölben Plattensegeln an einem rahgetakelten elliptischen Mast neuer freitragender Konstruktion

Bernd Wagner
Windkanalversuche mit gewölben Plattensegeln an einem rahgetakelten elliptischen Mast neuer freitragender Konstruktion

A local restart procedure for iterative projection methods for nonlinear symmetric eigenproblems

Heinrich Voß & Marta Betcke
For nonlinear eigenvalue problems $T(lambda)x = 0$ satisfying a minmax characterization of its eigenvalues iterative projection methods combined with safeguarded iteration are suitable for computing all eigenvalues in a given interval. Such methods hit their limitation if a large number of eigenvalues (in the interior of the spectrum) are required. In this paper we propose a localized version of safeguarded iteration which is able to cope with this problem.

Die Windkräfte am Schiff

Werner Blendermann
Die Windkräfte am Schiff

Neutron activation as a routine method for the determination of trace elements in water

Karl Heinrich Lieser, Wolfgang Calmano, E. Heuss & Volker Neitzert
By freeze-drying the following elements can be determined in natural water except sea water: Au, Ba, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Mo, Na, Sb, Sc, Se, U, Zn. Some problems may arise with respect to As and Hg. Cu, Cd and Ni can only be determined if present in high concentrations. Separation by adsorption on charcoal in presence of complexing agents gives yields between 75 and 100% for the following elements...

Business model innovation : a case of the offshore lifting equipment supplier

Mikhail Shlopak, Richard Myhre & Gabriele Hofinger Jünge
The purpose of this paper is to present the background for and the process of development of an Internet of Things (IoT) business model (BM) for a Norwegian offshore lifting equipment supplier. The paper presents both challenges and new opportunities connected to the case company’s transition towards IoT, servicebased BM. The research methodology is a single case study research. The research approach involves four steps: theoretical discussion; a case study; analysis of the case study,...

Thickness-dependence of the breakdown strength: analysis of the dielectric and mechanical failure

Claudia Neusel, Hans Jelitto, Dieter Schmidt, Rolf Janßen, Frank Felten & Gerold A. Schneider
The breakdown strength as well as the mechanical strength of ceramic materials decreases with increasing volume. The volume-effect of the mechanical strength can be explained by the Weibull theory. For the breakdown strength the same explanation has been often assumed. In order to validate this assumption breakdown strength and mechanical strength of alumina samples with defined porosities were compared. Differences in the Weibull moduli of breakdown and mechanical strength distributions indicate that the volume-effect cannot...

Advances in porous biomaterials for dental and orthopaedic applications

Meenakshi Mour, Debarun Das, Thomas Winkler, Elisa Hoenig, Gabriela Mielke, Michael Morlock & Arndt Schilling
The connective hard tissues bone and teeth are highly porous on a micrometer scale, but show high values of compression strength at a relatively low weight. The fabrication of porous materials has been actively researched and different processes have been developed that vary in preparation complexity and also in the type of porous material that they produce. Methodologies are available for determination of pore properties. The purpose of the paper is to give an overview...

Zur Geschichte der Schiffbauforschung in Hamburg

Odo Krappinger
Zur Geschichte der Schiffbauforschung in Hamburg

Performance evaluation of a sensor concept for solving the direct kinematics problem of general planar 3-RPR parallel mechanisms by using solely the linear actuators’ orientations

Stefan Schulz
In this paper, we experimentally evaluate the performance of a sensor concept for solving the direct kinematics problem of a general planar 3-RPR parallel mechanism by using solely the linear actuators’ orientations. At first, we review classical methods for solving the direct kinematics problem of parallel mechanisms and discuss their disadvantages on the example of the general planar 3-RPR parallel mechanism, a planar parallel robot with two translational and one rotational degrees of freedom, where...

Recycling-oriented design in soft robotics

Anh Minh Nguyen & Arthur Seibel
Soft robotics is a novel approach in the field of robotics. Soft robots or soft actuators are typically polymer-based and are characterized by their flexibility and adaptability, which brings new far-reaching applications. Soft robotics is currently at the peak of its research. One circumstance that is also present in this age is constant climate change; there is a demand for sustainability. This goes hand in hand with the design of products that are suitable for...

Desiccant-assisted air conditioning system relying on solar and geothermal energy during summer and winter

Peter Niemann, Finn Richter, Arne Speerforck & Gerhard Schmitz
At Hamburg University of Technology the combination of an open cycle desiccant-assisted air conditioning system and a geothermal system is investigated in the framework of different research projects for several years. The objective of this study is to investigate the energy efficiency of the overall system and to evaluate the geothermal system during summer and winter mode, based on data measured for a temperate climate region. Monitoring results of the performance for dehumidification and remoistening...

Theoretische Ausgangspositionen in der Sequenzanalyse Andrew Abbotts

Jan-Philipp Alexander Fleck
Ziel der hier wiedergegebenen, perspektivgebundenen Durchsicht der Literatur Abbotts ist es zunächst, die bei Abbott zugrunde gelegten theoretischen Annahmen entlang ihrer wesentlichen „Fluchtlinien“ darzustellen. Es geht also darum, den theoretischen Rahmen zu skizzieren, innerhalb dessen Abbott seine methodologisch spezifischen Vorstöße zu den sozialen Sequenzen unternimmt. Diese Beschäftigung mit den bei Abbott anzutreffenden theoretischen Grundan-nahmen erfolgt voreingenommen, also: perspektivgebunden. Uns interessiert, inwiefern die bei Abbott aufzufindenden Konzeptionen seines methodologisch-theoretischen Inventars geeignet sind, um als Bezugspunkte einer...

Schrägschleppversuche für einen Seglerrumpf mit und ohne Balkenkiel und für den "Mariner"

Bernd Wagner
Schrägschleppversuche für einen Seglerrumpf mit und ohne Balkenkiel und für den "Mariner"

Jahresbericht des Präsidiums 2005

Edwin Kreuzer & Technische Universität Hamburg-Harburg

Strain-gauge-based measurements of ice loads on ships

Till Zorn
Design loads are a central element of ship construction, because they influence plate and frame thickness. For the construction of ships that are destined to navigate in cold areas, it is extremely important to take into account the loads of ice impacts and their location on the hull. But ice is a particularly inconsistent material. To measure ice-induced loads, a lot of measurement has been undertaken, many of them used strain gauges. However, long-term strain...

Zur Diskussion um den Informationsbegriff - eine Rezension

Thomas Hapke
In dieser Rezension zum Buch von Sascha Ott: Information : zur Genese und Anwendung eines Begriffs (Konstanz : UVK Verl.-Ges., 2004) werden Begriffe wie Information, Kommunikation, Medien und Wissen als vielfältig verwendete Schlüsselbegriffe unserer Zeit angesehen, die immer wieder philosophisch-theoretische Reflexionen herausfordern. Charakteristisch für das Konzept Information ist, dass seine Realität plausibel und nützlich in Abhängigkeit von der Fachdisziplin in vielfältiger, oft widersprüchlicher Art und Weise bestimmt werden kann. Information kann für den Rezensenten nie...

Supplier Integration in Industry 4.0 – Requirements and Strategies

Julian Marius 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...

Process and mechanical properties: Applicability of a scandium modified Al-alloy for laser additive manufacturing

K. Schmidtke, F. Palm, A. Hawkins & Claus Emmelmann
The applicability of an aluminium alloy containing scandium for laser additive manufacturing (LAM) is considered. Modified aluminium alloys with a scandium content beyond the eutectic point offer great potential to become a high prioritized aerospace material. Depending on other alloying elements like magnesium or zirconium, strongly required weight reduction, corrosion resistance and improved strength properties of metallic light weight alloys can be achieved. The development, production and testing of parts built up by a laser...

Frequency or amplitude? : Rheo-electrical characterization of carbon nanoparticle filled epoxy systems

Hauke Meeuw, Valea Kim Wisniewski & Bodo Fiedler
Dispersion of carbon nanoparticles in epoxy resin is the key factor to adjust the resulting electrical and mechanical properties of the nanocomposite. A profound understanding of the driving forces of standard methods like ultrasonic and mechanical dispersion is necessary. To derive the impact of applied frequency and strain on the resulting dispersion of multi-walled carbon nanotube (MWCNT)-filled epoxy resin, this work addresses the strain and frequency dependency of oscillatory shear flow-induced network changes. Strain- and...

Exploring the acceptance of ubiquitous computing-based Information services in brick and mortar retail environments : an integration of UTAUT2 and media system dependency theory

Sara Kheiravar
Stationäre Einzelhändler setzen zunehmend digitale Technologie ein, um ihren Kunden bei Informationssuche und -bewertung zu unterstützen. Die eingesetzten Technologien werden als In-Store Ubiquitous Computing basierende Informationstechnologien bezeichnet. Erkenntnisse zu Akzeptanz dieser Technologien durch Kunden stehen noch aus. In dieser Dissertation wird ein Kontext spezifisches Modell zur Technologieakzeptanz basierend auf UTAUT2 entwickelt und um Nutzer, Service und Technologie relevante Aspekte erweitert. Das abgeleitete Modell wird mit Hilfe eines Strukturgleichungsmodells (PLS) auf Basis einer auf Szenarien basierenden...

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...

An energy approach for the active vibration control of an oscillator with two translational degrees of freedom using two auxiliary rotating masses

Richard Bäumer, Richard Terrill & Uwe Starossek
An active mass damper implementing two auxiliary masses rotating about a single axis is presented. This device is used for the vibration control of an oscillator performing translational motion in a plane (two translational degrees of freedom). In a preferred mode of operation, both auxiliary masses rotate with the same constant angular velocity in opposite directions. The resultant of the produced harmonic centrifugal forces is used for the vibration control. The direction of this control...

Facing the challenge of sustainable bioenergy production : could halophytes be part of the solution?

Ahmed Debez, Ikram Belghith, Jan Friesen, Carsten Montzka & Skander Elleuche
Due to steadily growing population and economic transitions in the more populous countries, renewable sources of energy are needed more than ever. Plant biomass as a raw source of bioenergy and biofuel products may meet the demand for sustainable energy; however, such plants typically compete with food crops, which should not be wasted for producing energy and chemicals. Second-generation or advanced biofuels that are based on renewable and non-edible biomass resources are processed to produce...

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