1,744 Works

Author Correction: Reflection from a free carrier front via an intraband indirect photonic transition

Mahmoud A. Gaafar, Dirk Jalas, Liam O'Faolain, Juntao Li, Thomas F. Krauss, Alexander Yu. Petrov & Manfred Eich
The original version of this article contained an error in first sentence of the Acknowledgements ...

Unconventional electron states in δ-doped SmTiO3

Frank Lechermann
The Mott-insulating distorted perovskite SmTiO3, doped with a single SrO layer in a quantum-well architecture is studied by the combination of density functional theory with dynamical mean-field theory. A rich correlated electronic structure in line with recent experimental investigations is revealed by the given realistic many-body approach to a large-unit-cell oxide heterostructure. Coexistence of conducting and Mott-insulating TiO2 layers prone to magnetic order gives rise to multi-orbital electronic transport beyond standard Fermi-liquid theory. First hints...

Hierarchical aerographite 3D flexible networks hybridized by InP micro/nanostructures for strain sensor applications

Irina Plesco, Julian Strobel, Fabian Schütt, Cameliu Himcinschi, Nabiha Ben Sedrine, Teresa Monteiro, Maria Rosário Correia, Leonid Gorceac, Boris Cinic, Veaceslav Ursaki, Janik Marx, Bodo Fiedler, Yogendra Kumar Mishra, Lorenz Kienle, Rainer Adelung & Ion Tiginyanu
In the present work, we report on development of three-dimensional flexible architectures consisting of an extremely porous three-dimensional Aerographite (AG) backbone decorated by InP micro/nanocrystallites grown by a single step hydride vapor phase epitaxy process. The systematic investigation of the hybrid materials by scanning electron microscopy demonstrates a rather uniform spatial distribution of InP crystallites without agglomeration on the surface of Aerographite microtubular structures. X-ray diffraction, transmission electron microscopy and Raman scattering analysis demonstrate that...

Modeling, simulation and optimization of general solar updraft towers

Hannes Von Allwörden, Ingenuin Gasser & Muhammad Junaid Kamboh
A model to describe a solar chimney power plant with a generally sloped collector field and for the general situation of humid air is presented. This is a significant development of existing simple models for solar updraft towers with planar collector fields for the sit- uation of purely dry air. The model describing the gas dynamics in the collector and in the chimney includes a turbine model, friction and heat transfer losses, evaporation and condensation...

Modeling and simulation of a desiccant assisted solar and geothermal air conditioning system

Arne Speerforck, Jiazhen Ling, Vikrant Aute, Reinhard Radermacher & Gerhard Schmitz
In this study we investigated a disiccant assited air conditioning system ...

Analysis of the influence of imaging-related uncertainties on cerebral aneurysm deformation quantification using a no-deformation physical flow phantom

Daniel Schetelig, Jan Sedlacik, Jens Fiehler, Andreas Frölich, Tobias Knopp, Thilo Sothmann, Jonathan Waschkewitz & René Werner
Cardiac-cycle related pulsatile aneurysm motion and deformation is assumed to provide valuable information for assessing cerebral aneurysm rupture risk. Accordingly, numerous studies addressed quantification of cerebral aneurysm wall motion and deformation. Most of them utilized in vivo imaging data, but image-based aneurysm deformation quantification is subject to pronounced uncertainties: unknown ground-truth deformation; image resolution in the order of the expected deformation; direct interplay between contrast agent inflow and image intensity. To analyze the impact of...

An analytical model for wireless mesh networks with collision-free TDMA and finite queues

Florian Kauer & Volker Turau
Wireless mesh networks are a promising technology for connecting sensors and actuators with high flexibility and low investment costs. In industrial applications, however, reliability is essential. Therefore, two time-slotted medium access methods, DSME and TSCH, were added to the IEEE 802.15.4 standard. They allow collision-free communication in multi-hop networks and provide channel hopping for mitigating external interferences. The slot schedule used in these networks is of high importance for the network performance. This paper supports...

Dielectric breakdown toughness from filament induced dielectric breakdown in borosilicate glass

Pia-Kristina Fischer & Gerold A. Schneider
The dielectric breakdown strength of borosilicate glass was measured as a function of the length of a conducting filament in order to determine the critical energy release for the growth of a breakdown channel. The concept is similar to the experimental determination of the toughness in fracture mechanics and based on a Griffith type model for the electrical energy release rate in dielectric materials with space charge limited conductivity. By Focused-Ion-Beam-milling and Pt-deposition, up to...

Wissenschaft und Offenheit : Reflexion über Wissenschaft als Teil der Lehre zum wissenschaftlichen Arbeiten und Schreiben

Thomas Hapke
Fostering academic research and writing is more and more part of the services of university libraries within their activities to promote information literacy. The actual challenge and trend to openness, to topics like Open Access and Open Science, emphasizes especially questions of scientificality and the quality of science. A debate on this can enrich learning and teaching academic research and writing. As a holistic view on information literacy includes reflection about the production of information...

Aspekte wissenschaftlichen Arbeitens in den Ingenieurwissenschaften : erste Thesen und Literaturüberblick

Thomas Hapke
Dieser Text, entstanden im Jahre 2008 als Internes Arbeitspapier zum Projekt StudIPort 2.0 der TUHH, will auf Basis eines Literaturüberblicks Aspekte ingenieurwissenschaftlichen Arbeiten bzw. des wissenschaftlichen Arbeiten von Ingenieuren thesenartig unterscheiden.

Correlating Synthesis Parameters to Morphological Entities: Predictive Modeling of Biopolymer Aerogels

Ameya Rege, Imke Preibisch, Maria Schestakow, Kathirvel Ganesan, Pavel Gurikov, Barbara Milow, Irina Smirnova & Mikhail Itskov
In the past decade, biopolymer aerogels have gained significant research attention due to their typical properties, such as low density and thermal insulation, which are reinforced with excellent biocompatibility, biodegradability, and ease of functionalization. Mechanical properties of these aerogels play an important role in several applications and should be evaluated based on synthesis parameters. To this end, preparation and characterization of polysaccharide-based aerogels, such as pectin, cellulose and k-carrageenan, is first discussed. An interrelationship between...

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...

Measuring and modeling energy consumption of embedded systems for optimizing compilers

Mikko Roth, Arno Luppold & Heiko Falk
Estimating energy consumption already during development as precisely as possible is crucial for many embedded system designs. These energy estimates should be expressed such that they can be used by subsequent automated optimizations during the compilation phase in order to minimize the expected energy consumption. In this paper we present our current approach on measuring and modeling, and subsequently using the derived energy estimates. Our model is implemented within an optimizing compiler, allowing for future...

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...

Jahresbericht 2017 des Präsidiums der Technischen Universität Hamburg

Technische Universität Hamburg & Garabed Antranikian
Jahresbericht des Präsidiums der TU Hamburg 2017

The influence of pressure on crude oil biodegradation in shallow and deep Gulf of Mexico sediments

Uyen T. Nguyen, Sara A. Lincoln, Ana Gabriela Valladares Juárez, Martina Schedler, Jennifer L. Macalady, Rudolf Müller & Katherine H. Freeman
A significant portion of oil released during the Deepwater Horizon disaster reached the Gulf of Mexico (GOM) seafloor. Predicting the long-term fate of this oil is hindered by a lack of data about the combined influences of pressure, temperature, and sediment composition on microbial hydrocarbon remineralization in deep-sea sediments. To investigate crude oil biodegradation by native GOM microbial communities, we incubated core-top sediments from 13 GOM sites at water depths from 60-1500 m with crude...

Viscosity quantification using multi-contrast magnetic particle imaging

Martin Möddel, Christian Meins, Jan Dieckhoff & Tobias Knopp
Magnetic particle imaging (MPI) is a relatively new tomographic imaging technique using static and oscillatingmagnetic fields to image the spatial distribution ofmagnetic nanoparticles.The latter being the contrastMPI has been initially designed for. However, recently it has been shown thatMPIcan be extended to amulti-contrast method that allows one to simultaneously image the signals of differentMPI tracer materials. Additionally, it has been shown that changes in the particles environment, e.g. the viscosity have an impact on theMPI...

Compiler-based extraction of event arrival functions for real-time systems analysis

Dominic Oehlert, Selma Saidi & Heiko Falk
Event arrival functions are commonly required in real-time systems analysis. Yet, event arrival functions are often either modeled based on specifications or generated by using potentially unsafe captured traces. To overcome this shortcoming, we present a compiler-based approach to safely extract event arrival functions. The extraction takes place at the code-level considering a complete coverage of all possible paths in the program and resulting in a cycle accurate event arrival curve. In order to reduce...

Reaction systems for bubbly flows

Melanie Paul, Florian Strassl, Alexander Hoffmann, Marko Hoffmann, Michael Schlüter & Sonja Herres-Pawlis
Reactive bubbly flows are at the heart of multiphase flows which are a major topic in chemical engineering since many bulk chemicals are produced in bubbly flows. However, the factors determining product yield and selectivity are often subject of complicated mass transfer effects. Herein, we describe the latest developments in the detection of mass transfer effects in bubbly flows. Coordination chemistry has given new impulses to this topic due to the possibility to synthesise tailored...

Relevanz und Potenziale frugaler Innovationen für Österreich

Rajnish Tiwari, Stephan Buse, Katharina Kalogerakis, Jakob Scheitza & Cornelius Herstatt
This qualitative-explorative study set out to investigate potentials and relevance of frugal innovations, as enablers of “affordable excellence”, for Austria. Employing a multi-method approach combining literature review, case studies and expert interviews it sought to generate preliminary insights about the strategic imperative of frugal innovations for Austrian firms. The generated insights were analyzed with experts in a focus group to identify the resulting implications for Austria’s research and innovation system. The study discovered that some...

Energy efficient operation of variable speed submersible pumps : simulation of a ground water well field

Alexander Sperlich, Dino Pfeiffer, Jens Burgschweiger, Enrique Campbell, Marcus Beck, Regina Gnirß & Mathias Ernst
Due to their lower energy consumption, permanent magnet synchronous motor (PMSM) submersible pumps have been introduced in ground water well field operation. Besides direct savings of energy, the introduction of PMSM pumps together with the required variable frequency converters offers new operational scenarios to meet the seasonally varying water demand. In this work, potential energy savings of variable speed submersible pumps were investigated. A ground water well field consisting of 13 wells and their transport...

Electro-conductive composite gold-polyethersulfone-ultrafiltration-membrane : characterization of membrane and natural organic matter (NOM) filtration performance at different in-stiu applied surface potentials

Tomi Mantel, Paul Benne, Stanislav Parsin & Mathias Ernst
Next to the pore size distribution, surface charge is considered to be one main factor in the separation performance of ultrafiltration (UF) membranes. By applying an external surface potential onto an electro-conductive UF membrane, electrostatic induced rejection was investigated. This study introduces in a first part a relatively simple but yet not reported technology of membrane modification with direct current sputter deposition of ultrathin (15 nm) highly conductive gold layers. In a second part, characterization...

Modeling of surface effects in crystalline materials within the framework of gradient crystal plasticity

Xiang-Long Peng, Edgar Husser, Gan-Yun Huang & Swantje Bargmann
A finite-deformation gradient crystal plasticity theory is developed, which takes into ac- count the interaction between dislocations and surfaces. The model captures both ener- getic and dissipative effects for surfaces penetrable by dislocations. By taking advantage of the principle of virtual power, the surface microscopic boundary equations are obtained naturally. Surface equations govern surface yielding and hardening. A thin film under shear deformation serves as a benchmark problem for validation of the proposed model. It...

Comparison of different approaches tracking a wing-tip vortex

Dag-Frederik Feder, Mahesh Dhone, Nikolai Kornev & Moustafa Abdel-Maksoud
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...

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

Giulio Barth
Multiple studies validated effects of institutions on the diffusion of scientific innovations, but there is a lack in explaining emergence and change of institutions. The institutional entrepreneurship approach faces this limitations and models, how institutional entrepreneurs diffuse an institutional logic to then create institutions in order to facilitate diffusion of innovations. In this thesis, three studies endeavor to validate this end-to-end process beginning from institutional entrepreneurs diffusing a logic to the impact of created institutions...

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