464 Works

Constant depth scoring of fibre reinforced plastic structures to prevent delamination

Tobias Geis, Christian Klingelhöller & Wolfgang Hintze
Scoring of the outer layers of a workpiece with small engagement (ae) using circular saws is a well known method to avoid unwanted delamination of these layers, such as coatings of wooden particle boards. In edge milling fibre reinforced plastics (FRP), delamination also occurs in the top or bottom layer of the component and requires time intensive rework or scrapping of material. A combined process of scoring and milling is presented in this paper as...

Ultrasonic joining of through-the-thickness reinforced metal-composite hybrid structures

Eduardo Etzberger Feistauer
Verbindungskonzepte, die traditionell für den Verbinden von Metall-Verbundstoff-Strukturen verwendet werden, weisen mehrere Beschränkungen in Bezug auf den Lasttransfer zwischen den Materialien. Die vorliegende Doktorarbeit zielt auf die Einführung von Ultrasonic Joining (U-Joining) ab, einem neuen Fügeverfahren zur Herstellung von throught-the-thickness verstärkten Hybridverbindungen aus Metall und Faserverbundwerkstoff mit verbesserter out-of-plane Festigkeit. Um die Machbarkeit des Fügeprozesses zu demonstrieren und die Korrelation zwischen Prozess- und Fügeeigenschaften zu beschreiben, wurde ein Fallstudienansatz gewählt, der kommerziell erhältliches glasfaserverstärktes Polyetherimid...

Using tutorials in introductory physics on circuits in a German university course: observations and experiences

Peter Riegler, Andreas Simon, Marcus Prochaska, Christian H. Kautz, Rebekka Bierwirth, Susan Hagendorf & Gerd Kortemeyer
We describe the implementation of Tutorials in Introductory Physics in a German university course. In particular, we investigate if the conceptual challenges that gave rise to the development of Tutorials are also found among German students, which hurdles to the implementation of Tutorials are encountered in a German context, and how Tutorials are perceived in this different context. To that end, video recordings from workgroup sessions and guided group discussions with students and teaching assistants,...

The temperatures distributions of a single-disc clutches using heat partitioning and total heat generated approaches

Oday Ibraheem Abdullah, Josef Schlattmann, Mahir H. Majeed & Laith Abed Sabri
An accurate estimation of temperature distribution is considered necessary to avoid the premature failure of friction clutches. In this work, different approaches were used to compute the surface temperatures of the friction clutch disc. The results presented the maximum surface temperature when the contact occurs between the rubbing surfaces during a single engagement and repeated engagements. Two approaches were used to simulate the thermal models of the automotive clutches to obtain the temperature field are...

Wertstromanalyse und -design für Auftragsfertiger

Christoph Koch
Die vorliegende Arbeit entwickelt eine Wertstrommethode für Auftragsfertiger zur Analyse und Verbesserung der logistischen Zielgrößen. Die Vor-Ort-Aufnahme von Termintreue, Durchlaufzeit und Bestand ist das zentrale Element der Analysephase, die zusätzlich die Erfassung der aktuellen Konfiguration der Fertigungssteuerung beinhaltet. Die Wertstromanalyse schließt mit der Darstellung der Wertstromkarte. Das anschließende Wertstromdesign wendet erprobte und für Auftragsfertiger relevante Verfahren der Produktionsplanung und -steuerung an. Es umfasst neben der Terminierung die Aufgaben der Fertigungssteuerung Auftragsfreigabe, Reihenfolgebildung und Kapazitätssteuerung.

Hysteresis analysis and control of a metal-polymer hybrid soft actuator

Manuel Schimmack, Eduardo Etzberger Feistauer, Sergio Amancio & Paolo Mercorelli
The number of applications of stimulus-responsive polymers is growing at an impressive rate. The motivation of this contribution is to use a commercially available low-budget silver-coated polyamide (PA6) as a thermo-responsive metal-polymer hybrid soft actuator. Polyamide is a hygroscopic polymer; therefore, its mechanical and physical-chemical properties are affected by exposition to humidity or immersion in water. The effect of water absorption content on the PA6 and silver-coated PA6 monofilament properties, such as mass change and...

Konzept OER Referatorium, TUHH

Axel Dürkop
Das Konzeptpapier umreißt die Idee eines OER-Referatoriums. Dabei steht keine zentrale Instanz im Mittelpunkt, vielmehr werden dezentrale Instanzen miteinander vernetzt und aggregieren die referenzierten Bildungsresourcen.

Protein-protein-interaction network organization of the hypusine modification system

Henning Sievert, Simone Venz, Oscar Platas Barradas, Vishnu Mukund Dhople, Martin Schaletzky, Claus-Henning Nagel, Melanie Braig, Michael Preukschas, Nora Pällmann, Carsten Bokemeyer, Tim H. Brümmendorf, Ralf Pörtner, Reinhard Walther, Kent E. Duncan, Joachim Hauber & Stefan Balabanov
Hypusine modification of eukaryotic initiation factor 5A (eIF-5A) represents a unique and highly specific post-translational modification with regulatory functions in cancer, diabetes, and infectious diseases. However, the specific cellular pathways that are influenced by the hypusine modification remain largely unknown. To globally characterize eIF-5A and hypusine-dependent pathways, we used an approach that combines large-scale bioreactor cell culture with tandem affinity purification and mass spectrometry: "bioreactor-TAP-MS/MS." By applying this approach systematically to all four components of...

Alternating the twin rotor damper between two modes of operation to eliminate small vibrations

Richard Bäumer, Richard Terrill & Uwe Starossek
In previous research, the twin rotor damper (TRD), an active mass damper, was presented. In a preferred, energy-efficient mode of operation, the continuous rotation mode, two eccentric control masses rotate with constant angular velocities about two parallel axes in opposite directions. The resulting centrifugal forces combine into a directed harmonic control force that can be used for the control of structural vibrations. In another, more power-demanding mode of operation, the swinging mode, both control masses...

3DScapeCS : application of three dimensional, parallel, dynamic network visualization in Cytoscape

Qi Wang, Biao Tang, Lifu Song, Biao Ren, Qun Liang, Feng Xie, Ying Zhuo, Xueting Liu & Lixin Zhang
Background: The exponential growth of gigantic biological data from various sources, such as protein-protein interaction (PPI), genome sequences scaffolding, Mass spectrometry (MS) molecular networking and metabolic flux, demands an efficient way for better visualization and interpretation beyond the conventional, two-dimensional visualization tools.Results: We developed a 3D Cytoscape Client/Server (3DScapeCS) plugin, which adopted Cytoscape in interpreting different types of data, and UbiGraph for three-dimensional visualization. The extra dimension is useful in accommodating, visualizing, and distinguishing large-scale...

Bioprozessentwicklung der AMDase katalysierten Synthese von Arylpropionsäure Derivaten

Miriam Aßmann
Die biokatalytische Prozessführung für enantiomerenreine Produkte stellt eine vielversprechende und umweltfreundliche Alternative zu herkömmlichen chemischen Synthesewegen dar und findet vermehrt Anwendung. Im Fokus der vorliegenden Arbeit lag die Bioprozessentwicklung für die enzymkatalysierte Synthese von Arylpropionsäuren, wie Ibuprofen oder Naproxen. Der enantioselektive Syntheseschritt wird durch die Arylmalonat Decarboxylase (AMDase) realisiert, welche die Decarboxylierung von aromatischen Dicarbonsäure Derivaten in einer einfachen einstufigen Reaktion katalysiert. Eine Herausforderung war hierbei, die sehr geringe enzymatische Stabilität zu verbessern. Durch Immobilisierung...

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Brett D. Crist, Ferris M. Pfeiffer, Michael S. Khazzam, Rebecca A. Kueny, Gregory J. Della Rocca & William L. Carson
Background: Pelvic ringecomminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of boneeimplant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacralerami fractures and screws relative to bone was measured with...

X-ray studies of nanoporous gold : powder diffraction by large crystals with small holes

Matthias Graf, Dinh Bao Nam Ngo, Jörg Weissmüller & Jürgen Markmann
X-ray diffraction studies of nanoporous gold face the poorly understood diffraction scenario where large coherent crystals are riddled with nanoscale holes. Theoretical considerations derived in this study show that the ligament size of the porous network influences the scattering despite being quasi single crystalline. Virtual diffraction of artificially generated samples confirms the results but also shows a loss of long-range coherency and the appearance of microstrain due to thermal relaxation. Subsequently, a large set of...

Realistic many-body approaches to materials with strong nonlocal correlations

Frank Lechermann, Alexander I. Lichtenstein & Michael Potthoff
Many of the fascinating and unconventional properties of several transition-metal compounds with partially filled d-shells are due to strong electronic correlations. While local correlations are in principle treated exactly within the frame of the dynamical mean-field theory, there are two major and interlinked routes for important further methodical advances: On the one hand, there is a strong need for methods being able to describe material-specific aspects, i.e., methods combining the DMFT with modern band-structure theory,...

Backscattering design for a focusing grating coupler with fully etched slots for transverse magnetic modes

Jahn Hoffmann, Kai Marvin Schulz, Giampaolo Pitruzzello, Lena Simone Fohrmann, Alexander Yu Petrov & Manfred Eich
Grating couplers are a fundamental building block of integrated optics as they allow light to be coupled from free-space to on-chip components and vice versa. A challenging task in designing any grating coupler is represented by the need for reducing back reflections at the waveguide-grating interface, which introduce additional losses and undesirable interference fringes. Here, we present a design approach for focusing TM grating couplers that minimizes these unwanted reflections by introducing a modified slot...

Quantitative magnetic particle imaging monitors the transplantation, biodistribution, and clearance of stem cells in vivo

Bo Zheng, Marc Philip von See, Elaine Yu, Beliz Gunel, Kuan Lu, Tandis Vazin, David V. Schaffer, Patrick W. Goodwill & Steven M. Conolly
Stem cell therapies have enormous potential for treating many debilitating diseases, including heart failure, stroke and traumatic brain injury. For maximal efficacy, these therapies require targeted cell delivery to specific tissues followed by successful cell engraftment. However, targeted delivery remains an open challenge. As one example, it is common for intravenous deliveries of mesenchymal stem cells (MSCs) to become entrapped in lung microvasculature instead of the target tissue. Hence, a robust, quantitative imaging method would...

Integration of value stream map and strategic layout planning into DMAIC approach to improve carpeting process

Ayman Nagi & Safwan Altarazi
This paper presents an implementation of the Six Sigma DMAIC approach implementing lean tools and facilities layout techniques to reduce the occurrence of different types of nonconformities in the carpeting process. Such carpeting process can be found in several industries including construction, aviation, and automotive. Design/methodology/approach: The improvement process was built through a sequential implementation of appropriate interconnected tools at each phase of the DMAIC approach. Utilized tools included: Pareto analysis, control charts, Ishikawa chart,...

My smartphone tattles: considering popularity of messages in opportunistic data dissemination

Asanga Udugama, Jens Dede, Anna Förster, Vishnupriya Kuppusamy, Koojana Kuladinithi, Andreas Timm-Giel & Zeynep Vatandas
Opportunistic networks have recently seen increasing interest in the networking community. They can serve a range of application scenarios, most of them being destination-less, i.e., without a-priori knowledge of who is the final destination of a message. In this paper, we explore the usage of data popularity for improving the efficiency of data forwarding in opportunistic networks. Whether a message will become popular or not is not known before disseminating it to users. Thus, popularity...

Damage due to rolling in total knee replacement : the influence of tractive force

Markus A. Wimmer, Lars Birken, Kay Sellenschloh & Erich Schneider
© 2013, The author(s). The femoral condyles of a knee prosthesis articulate with a combination of rolling and sliding on the tibial polyethylene plateau. Little is known about potential polyethylene damage due to rolling motion. Since rolling does not exclude the presence of tangential surface loads, this study sought to investigate the influence of tractive rolling on the wear of polyethylene. A “wheel-on-flat” apparatus, consisting of a metal wheel and a polyethylene flat, mimicked contact...

Near-field radiative heat transfer with hyperbolic metamaterials

Slawa Lang
Max Plancks bedeutende Schwarzkörper Theorie kann den Anstieg der strahlenden Wärmeübertragung zwischen eng aneinanderliegenden Körpern, bekannt als Nahfeld Wärmeübertragung, nicht erklären. Wir demonstrieren diesen Effekt mit Hilfe einer neuen, dynamischen Messmethode und messen Wärmeströme bis zu 16-mal größer als die Schwarzkörper Grenze. Wir zeigen, dass thermische Strahlung in hyperbolischen Metamaterialien (HMMs) – äußerst anisotropen Nanostrukturen – sehr stark ist und ihre Eigenschaften sich von Schwarzkörper Strahlung deutlich unterscheiden. Schließlich erweisen sich Nahfeld Wärmeströme zwischen HMMs...

Thermal behavior of friction clutch disc based on uniform pressure and uniform wear assumptions

Oday Ibraheem Abdullah & Josef Schlattmann
High temperatures appear in the contacting surfaces of a single-disc clutch system (friction clutch disc, flywheel and pressure plate) due to the relative motion between these parts during the sliding period. These high temperatures are responsible for several disadvantages such as increasing wear rate, surface cracks and permanent distortions. In some cases, these disadvantages may lead the contacting surfaces to failure before the expected lifetime. In this work, mathematical models of the friction clutch system...

Thy-1 deficiency augments bone loss in obesity by affecting bone formation and resorption

Ann-Kristin Picke, Graeme Michael Campbell, Felix N. Schmidt, Björn Busse, Martina Rauner, Jan C. Simon, Ulf Anderegg, Lorenz C. Hofbauer & Anja Saalbach
Healthy bone remodeling results from a balanced bone formation and bone resorption realized by bone-forming osteoblasts and bone-resorbing osteoclasts, respectively. Recently, Thy-1 (CD90) was identified as positive regulator of osteoblast differentiation and activation, thus, promoting bone formation while concurrently inhibiting adipogenesis and obesity in mice. Additionally, Thy-1 did not affect bone resorption. An obesity-related co-morbidity that is increasing in prevalence is a disturbed bone formation resulting in an increased fracture risk. The underlying mechanisms of...

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....

Smart control for functional electrical stimulation with optimal pulse intensity

Aljoscha Reinert, Jan C. Loitz, Fanny Quandt, Dietmar Schröder & Wolfgang H. Krautschneider
Transcutaneous electrical stimulation is a common treatment option for patients suffering from spinal cord injury or stroke. Two major difficulties arise when employing electrical stimulation in patients: Accurate stimulation electrode placement and configuration of optimal stimulation parameters. Optimizing the stimulation parameters has the advantage to reduce muscle fatigue after repetitive stimulation. Here we present a newly developed system which is able to automatically find the optimal individual stimulation intensity by varying the pulse length. The...

Geometrical effects on the concentrated behavior of heat flux in metamaterials thermal harvesting devices

Guoqiang Xu, Haochun Zhang, Ming Xie & Yan Jin
Thermal harvesting devices based on transformation optics, which can manipulate the heat flux concentration significantly through rational arrangements of the conductivities, have attracted considerable interest owing to several great potential applications of the technique for high-efficiency thermal conversion and collection. However, quantitative studies on the geometrical effects, particularly wedge angles, on the harvesting behaviors are rare. In this paper, we adopt wedge structure-based thermal harvesting schemes, and focus on the effects of the geometrical parameters...

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  • 2019
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