1,425 Works

Self-stabilizing algorithms in wireless sensor networks

Gerry Siegemund
The presented dissertation focuses on the applicability of self-stabilizing algorithms in systems using wireless communication. Especially wireless sensor networks (WSN) which use low power radios that are prone to message loss and corruption. Furthermore, temporary node failures (e.g., due to exhausted batteries) are common sources of nonconformances. Thus, distributed algorithms, middleware systems, and applications have to respond to these faults. A typical approach is to foresee such error situations and program routines to react to...

Bibliothek in Zukunft?! Texte von Studierenden zum Wandel von Bibliotheken : aus dem Bachelor-Seminar „Wissenschaftliches Arbeiten“ an der TU Hamburg

Thomas Hapke
Die in diesem Werk vorgestellten Texte von Studierenden zum Wandel von Bibliotheken, insbesondere von Universitätsbibliotheken, sind Ergebnisse einer Hausaufgabe, die während des Bachelor-Seminars „Wissenschaftliches Arbeiten“ erarbeitet wurden. Das Seminar wird federführend von der Universitätsbibliothek der Technischen Universität Hamburg (tub.) organisiert und ist Teil des Komplementärstudiums (Nichttechnisches Angebot NTA) der TUHH.

Fretting-Korrosion modularer Hüftendoprothesen

Dennis Bünte
Early failure of total hip replacements can be caused by the release of wear products from modular junctions due to fretting-corrosion. The aim was to identify design factors that make the analyzed tapers susceptible to wear and corrosion. A quantitative analysis of wear from circular and flat taper designs for a mixed metal coupling (CoCr-TMZF) was performed. Based on the reconstruction of explanted taper geometries, individual engagement properties are determined, providing an estimate of the...

Jahresbericht 2016 des Präsidiums der Technischen Universität Hamburg

Technische Universität Hamburg & Garabed Antranikian
Annual report by the president of the TUHH 2016

A conceptual modeling approach to health-related urban well-being

Malte Von Szombathely, Myriam Albrecht, Dejan Antanaskovic, Jobst Augustin, Matthias Augustin, Benjamin Bechtel, Thomas Bürk, Jana Fischereit, David Grawe, Peter Hoffmann, Giedrius Kaveckis, Anne Caroline Krefis, Jürgen Oßenbrügge, Jürgen Scheffran & Katharina Heinke Schlünzen
In cities, social well-being faces obstacles posed by globalization, demographic and climate change, new forms of social organization, and the fragmentation of lifestyles. These changes affect the vulnerability of city societies and impact their health-related urban well-being (UrbWellth). The conceptual model introduced in this paper systematizes the relevant variables while considering previous research, and establishes the target value UrbWellth. The model differs from existing approaches mainly in the analytical distinctions it suggests. These allow us...

Enhancement of alkaline protease activity and stability via covalent immobilization onto hollow core-mesoporous shell silica nanospheres

Abdelnasser S. S. Ibrahim, Ali A. Al-Salamah, Ahmed Mohamed El-Toni, Khalid S. Almaary, Mohamed A. El-Tayeb, Yahya B. Elbadawi & Garabed Antranikian
The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS–NH2 nanospheres showed...

A novel cyclodextrin glycosyltransferase from alkaliphilic amphibacillus sp. NPST-10 : purification and properties

Abdelnasser S. S. Ibrahim, Ali A. Al-Salamah, Mohamed A. El-Tayeb, Yahya B. Elbadawi & Garabed Antranikian
Screening for cyclodextrin glycosyltransferase (CGTase)-producing alkaliphilic bacteria from samples collected from hyper saline soda lakes (Wadi Natrun Valley, Egypt), resulted in isolation of potent CGTase producing alkaliphilic bacterium, termed NPST-10. 16S rDNA sequence analysis identified the isolate as Amphibacillus sp. CGTase was purified to homogeneity up to 22.1 fold by starch adsorption and anion exchange chromatography with a yield of 44.7%. The purified enzyme was a monomeric protein with an estimated molecular weight of 92...

Use of novel composite coagulants for arsenic removal from waters : experimental insight for the application of polyferric sulfate (PFS)

Ioannis A. Katsoyiannis, Nikolaos M. Tzollas, Athanasia K. Tolkou, Manassis Mitrakas, Mathias Ernst & Anastasios I. Zouboulis
In the present study, several pre-polymerized coagulants of iron and aluminum were tested for their efficiency towards As(V) and As(III) removal from water sources. The results showed that the pre-polymerized coagulants of iron, such as poly-ferric sulfate and poly-ferric silicate chloride, were very efficient for As(V) removal. With regard to As(III) removal, among all examined coagulants, including the conventional ferric chloride, only the poly-ferric sulfate (PFS) was able to reduce As(III) to concentrations below the...

Correction: Raman Subrahmanyam, et al. On the road to biopolymer aerogels—dealing with the solvent. Gels 2015, 1, 291–313

Subrahmanyam Raman, Pavel Gurikov, Paul Dieringer, Miaotian Sun & Irina Smirnova
The authors wish to make the following correction to their paper [1].[...]

What exactly is the Nusselt Number in convective heat transfer problems and are there alternatives?

Heinz Herwig
The often used Nusselt number is critically questioned with respect to its physical meaning. Based on a rigorous dimensional analysis, alternative assessment numbers are found that in a systematic way separately account for the quantitative and qualitative aspect of a heat transfer process. The qualitative aspect is related to the entropy generated in the temperature field of a real, irreversible heat transfer. The irreversibility can be quantified by referring it to the so-called entropic potential...

Towards online visualization and interactive monitoring of real-time CFD simulations on commodity hardware

Nils Koliha, Christian F. Janßen & Thomas Rung
Real-time rendering in the realm of computational fluid dynamics (CFD) in particular and scientific high performance computing (HPC) in general is a comparably young field of research, as the complexity of most problems with practical relevance is too high for a real-time numerical simulation. However, recent advances in HPC and the development of very efficient numerical techniques allow running first optimized numerical simulations in or near real-time, which in return requires integrated and optimized visualization...

Impact of powdered activated carbon structural properties on removal of organic foulants in combined adsorption-ultrafiltration

Martin Schulz, Sönke Bünting & Mathias Ernst
The impact of structural properties of three commercial PACs as well as two mechanically ground PACs on their efficiency in NOM removal and fouling reduction in combined adsorption-ultrafiltration (PAC-UF) of northern German groundwater was investigated. All PACs showed highest adsorption affinity for medium molecular weight NOM fractions. The meso-pore surface area rather than the total surface area (B.E.T.) mainly governed the extent of NOM removal. However, adsorption of macromolecular NOM fractions, which were found to...

Using an interactive lattice Boltzmann solver in fluid mechanics instruction

Mirjam Sophia Glessmer & Christian F. Janßen
This article gives an overview of the diverse range of teaching applications that can be realized using an interactive lattice Boltzmann simulation tool in fluid mechanics instruction and outreach. In an inquiry-based learning framework, examples are given of learning scenarios that address instruction on scientific results, scientific methods or the scientific process at varying levels of student activity, from consuming to applying to researching. Interactive live demonstrations on portable hardware enable new and innovative teaching...

Online monitoring of surface cracks and delaminations in carbon fiber/epoxy composites using silver nanoparticle based ink

Till Augustin, Danny Grunert, Hauke H. Langner, Vico Haverkamp & Bodo Fiedler
In this study, we present an online-monitoring approach using silver nanoparticle based ink on carbon fiber reinforced plastics (CFRP). After production of CFRP plates in a prepreg autoclave process and printing conductive paths on the material, we investigate the conductive paths of printed silver nanoparticle-based ink on CFRP by light microscopy. Mechanical tests with simultaneous electrical resistance measurements demonstrate the possibility to detect particular modes of failure with samples specifically designed to promote inter-fiber failures...

Characterization of the microstructure evolution in IF-Steel and AA6016 during plane-strain tension and Simple Shear

Gregory Gerstein, Benjamin Klusemann, Swantje Bargmann & Mirko Schaper
In the current work, the evolutions of grain and dislocation microstructures are investigated on the basis of plane strain tension and simple shear tests for an interstitial free steel (DC06) and a 6000 series aluminum alloy (AA6016-T4). Both materials are commonly-used materials in the automobile industry. The focus of this contribution is on the characterization and comparison of the microstructure formation in DC06 and AA6016-T4. Our observations shed light on the active mechanisms at the...

How to determine losses in a flow field: A paradigm shift towards the second law analysis

Heinz Herwig & Bastian Schmandt
Assuming that CFD solutions will be more and more used to characterize losses in terms of drag for external flows and head loss for internal flows, we suggest to replace single-valued data, like the drag force or a pressure drop, by field information about the losses. These information are gained when the entropy generation in the flow field is analyzed, an approach that often is called second law analysis (SLA), referring to the second law...

The entropic potential concept: a new way to look at energy transfer operations

Tammo Wenterodt & Heinz Herwig
Energy transfer operations or processes are systematically analyzed with respect to the way they can be assessed. It turns out that the energy transfer should not only be characterized by the operation or process itself but that it should be seen in a wider context. This context is introduced as the entropic potential of the energy that is transferred. It takes into account the overall transfer from the energy in its initial and finite states,...

Diffuser and nozzle design optimization by entropy generation minimization

Bastian Schmandt & Heinz Herwig
Diffusers and nozzles within a flow system are optimized with respect to their wall shapes for a given change in cross sections. The optimization target is a low value of the head loss coefficient K, which can be linked to the overall entropy generation due to the conduit component. First, a polynomial shape of the wall with two degrees of freedom is assumed. As a second approach six equally spaced diameters in a diffuser are...

Extension of the contour integral method for stochastic modeling of waveguiding structures

Jan Preibisch
Elektromagnetische Felder innerhalb von Leiterplatten, substratintegrierten Wellenleitern, sowie orthogonal gestreute Felder unendlich ausgedehnter Strukturen breiten sich in Ebenen aus. In dieser Arbeit wird die Kontourintergralmethode (CIM) erweitert, um Leiterplatten und planare Hochfrequenzbauelemente, sowie optische Bauelementen in TE und TM Polarisation zu simulieren. Das Einkoppeln in die planaren Strukturen wird mittels physikalisch motivierter Ersatzschaltungsmodelle modelliert. Zur Handhabung stochastischer Formulierungen dieser Modelle wurde die polynomielle Chaos Zerlegung (PCE) verwendet. Algorithmen und Methoden zur schnellen und aussagekräftigen Analyse...

Complete genome sequence of Thermus brockianus GE-1 reveals key enzymes of xylan/xylose metabolism

Christian Schäfers, Saskia Blank, Sigrid Wiebusch, Skander Elleuche & Garabed Antranikian
Thermus brockianus strain GE-1 is a thermophilic, Gram-negative, rod-shaped and non-motile bacterium that was isolated from the Geysir geothermal area, Iceland. Like other thermophiles, Thermus species are often used as model organisms to understand the mechanism of action of extremozymes, especially focusing on their heat-activity and thermostability. Genome-specific features of T. brockianus GE-1 and their properties further help to explain processes of the adaption of extremophiles at elevated temperatures. Here we analyze the first whole...

A concept for multi-criteria environmental assessment of aircraft trajectories

Sigrun Matthes, Volker Grewe, Katrin Dahlmann, Christine Frömming, Emma Irvine, Ling Lim, Florian Linke, Benjamin Lührs, Bethan Owen, Keith Shine, Stavros Stromatas, Hiroshi Yamashita & Feijia Yin
Comprehensive assessment of the environmental aspects of flight movements is of increasing interest to the aviation sector as a potential input for developing sustainable aviation strategies that consider climate impact, air quality and noise issues simultaneously. However, comprehensive assessments of all three environmental aspects do not yet exist and are in particular not yet operational practice in flight planning. The purpose of this study is to present a methodology which allows to establish a multi-criteria...

Laser beam welding of high-alloyed aluminium-zinc alloys

Josephin Enz
The automotive industry is currently facing major challenges. In the course of the enacting of comprehensive environmental regulations for the fuel consumption and CO2 emission of passenger vehicles in Europe and the world, the weight of future vehicles need to be considerably reduced. A weight reduction for automotive structures can be achieved by the substitution of heavy materials by lighter and stronger materials, the implementation of new designs and manufacturing technologies or ideally by a...

Metabolic and proteomic analyses of product selectivity and redox regulation in Clostridium pasteurianum grown on glycerol under varied iron availability

Christin Groeger, Wei Wang, Wael Sabra, Tyll Utesch & An-Ping Zeng
Background: Clostridium pasteurianum as an emerging new microbial cell factory can produce both n-butanol (BuOH) and 1,3-propanediol (1,3-PDO), and the pattern of product formation changes significantly with the composition of the culture medium. Among others iron content in the medium was shown to strongly affect the products selectivity. However, the mechanism behind this metabolic regulation is still unclear. For a better understanding of such metabolic regulation and for process optimization, we carried out fermentation experiments...

Innovation pathways and trajectories in India’s auto component industry

Rajnish Tiwari & Katharina Kalogerakis
India’s automotive sector has grown tremendously in the post-liberalization period. The growing domestic market, increased export opportunities and greater emphasis of vehicle manufacturers on high-quality, innovative solutions have created a context for component suppliers to ramp up their innovation capabilities as well. For about past 20 years the auto component industry has consistently acted as a key enabler of various frugal vehicles launched in India. Our multi-level and multi-approach study, making use of firm and...

Kapazitätsplanung und -steuerung in der Instandhaltungsproduktion von Investitionsgütern

Nico Koppold
With the proposed applications, uncertainty of work order times can be taken into account for capacity planning, coordination and control to reduce or avoid the consequences of uncertainty. The method adds ranges to work load planning and defines the occurrence pro-bability for this range of work load. This enables capacity flexibility to be adjusted to existing uncertainties to save costs and avoid a deficit in flexibility. Real work orders of maintenance and repair production for...

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