4242 research outputs found
Sort by
Entwicklungspfade intelligenter Transportsysteme für den Straßengüterverkehr
Get PDFToday's road network has reached its limits in most major cities and at certain times. Similarly, the capacity of the road network is largely exhausted. In addition, the change in delivery cycles in the food industry from a regular delivery structure to just-in-time deliveries leads to an increased delivery volume. But also E-commerce, the share economy and the customer's demand for faster delivery (same-day delivery) are leading to an additional rise in the supply sector. With the road infrastructure remaining the same, it is therefore not surprising that more and more slow-moving traffic and congestion are occurring. Intelligent transport systems (ITS) offer the possibility to improve the road capacity without excessive structural measures. The aim of this dissertation project is to provide insights of research achieved so far in the field of ITS for road freight transport and to estimate further developments by means of scenario generation. In addition to the presentation of ITS for road freight transport and the creation of environmental scenarios, action implications for the individual areas of ITS in road freight transport are presented. If the first scenario occured, this would have many positive effects on the transport process, but it would be of little importance, as the favourable factors are present in this scenario. If the second scenario occured, this would have many effects and a medium significance for ITS. In the case of the third scenario, this would be of medium to high significance, since in this scenario there are few ITS factors favouring road freight transport. The effects on the intelligent transport sector would be correspondingly small because these systems would not exist. This work provides first future oriented analysis in ITS related research
Finite and Infinite Rotation Sequences and Beyond
Get PDFThe encoding of orbits attained from rigid rotations are investigated from different perspectives. In the first part of the thesis regularity conditions for irrational rotations will be studied in terms of their continued fraction expansions and a categorisation is achieved for continued fraction expansions which do not grow too fast. The second part focuses on the spectral properties of beta-transformations for beta sqrt(2). Here an explicit representation for the Bochner transform of autocorrelations stemming from Dirac combs derived from beta-transformations is achieved, which consists of a Lebesgue absolutely continuous part and a discrete part. The last part focuses on vague limits of these autocorrelations where beta tends to 1. Here a link to subshifts derived from rigid rotations will be established. The Bochner transform of these vague limits can be given explicitly in some cases and is shown to be either discrete, non-discrete singular to Lebesgue, or a mixture of both
Logistik, eine technologisch-ökonomische Revolution? - Eine historisch-konzeptionelle Studie aus innovationswissenschaftlicher Perspektive
Get PDFIt s all about the base : Marine biofilms in the plastic age
Get PDFPlastic litter is entering and accumulating in our oceans and can be found in the marine environment all over the globe. When entering marine waters, plastics as any other surface, is rapidly colonized by a plethora of organisms, which form dense biofilms on the plastic surface, the so-called a Plastispherea . Despite growing concerns about the ecological impact of plastics on the marine environment during the last decade, the number of studies addressing Plastisphere-related questions remains limited. This thesis aimed to tackle this knowledge gap by comprehensively describing and analysing specificities of Plastisphere communities attached to chemically distinct plastic types. The specificity of mature Plastisphere communities was investigated on nine chemically different plastic types, and compared to the inert control substrate glass. The Plastisphere communities attached to diverse plastic types were found to be distinct from glass-associated communities. A more general marine biofilm core community serves as shared core among all tested plastic types and glass, rather than specific Plastisphere communities. The general heterogeneity of eukaryotic communities was much higher, indicating that the term Plastisphere is valid for mature prokaryotic biofilm communities, but may not be for eukaryotic ones. This work also showed that the prokaryotic shared core of the various mature Plastisphere communities are rather substrate unspecific, pointing towards the importance of rather rare species in plastic associated marine biofilms. A high-pressure water Jet treatment technique was developed to remove the cohesive layer of mature biofilms, while the adhesive layer remains on the plastics surface . It was shown that tightly attached microorganisms might account rather to the rare biosphere in mature Plastisphere communities, which suggests the presence of plastic a specifica microorganisms/assemblages. Due to their longevity, plastics could be transported over long distances in marine environments, and therefore may function as a vector for the dispersal of pathogenic species. To test this, plastic particles were collected in the North Sea and the Baltic Sea and screened for the presence of pathogens. Potentially pathogenic Vibrio parahaemolyticus were discovered on a number of microplastic particles, e.g. polyethylene, polypropylene and polystyrene. Mostly, this species co-occurred also in surrounding seawater, suggesting that seawater serves as a possible source for Vibrio colonization on microplastics. The confirmed occurrence of potentially pathogenic bacteria on marine microplastics highlights the urgent need for detailed biogeographical analyses of marine microplastics. The results from this thesis substantially increase our understanding of the diversity and specificity of Plastisphere communities. This thesis comprises a detailed and descriptive approach, which provides a fundamental knowledge basis for future research on Plastisphere questions related to e.g. potential biodegradation of marine plastics and the vector function for alien and potentially pathogenic species
The implications of automation for economic growth when investment decisions are irreversible
Get PDFThis paper discusses automation embedded into a standard growth model without exogenous growth when investment decisions for physical and automation capital are irreversible. The imposed nonnegativity constraints on physical and automation capital induces an imbalance effect between the growth rate of output and the fraction between physical and automation capital. The paper shows that this imbalance effect leads (i) to transitional dynamics off the steady state while (ii) retaining perpetual growth of the AK style in the steady state without exogenous technological progress. We also show that the resulting transition path does not have to be on the saddle path of the system without the nonnegativity constraints
Polysaccharide utilization loci and associated genes in marine Bacteroidetes - compositional diversity and ecological relevance
Get PDFThe synthesis of marine organic carbon compounds by photosynthetic macroalgae, microalgae (phytoplankton) and bacteria provide a basis for life in the ocean. In marine surface waters this primary production is largely dominated by microalgae and is especially pronounced during spring phytoplankton blooms. During and after these often diatom-dominated blooms, increased amounts of organic matter are released into the surrounding waters. Here, the organic matter, rich in polysaccharides, can trigger blooms of heterotrophic bacteria. Marine members of the Bacteroidetes are consistently found related to such bloom events. These bacteria are regularly detected as the first responders to thrive after phytoplankton spring blooms in temperate coastal regions and are often equipped with a variety of polysaccharide utilization gene clusters. These gene clusters, termed polysaccharide utilization loci (PULs), encode enzymes for the extracellular hydrolysis of polysaccharides and the subsequent uptake of oligosaccharides into the periplasm, where they are shielded from competing bacteria. This mechanism allows for rapid uptake and substrate hoarding, and thus could be one reason why Bacteroidetes are often seen as the first responders of the bacterioplankton community. The investigation of the so far largely unknown diversity and the ecological relevance of PULs in marine Bacteroidetes was the major goal of the work presented here. We could show that genomes of Bacteroidetes isolates from the North Sea, with free-living to micro- and macro-algae associated lifestyles, harboured a variety of these loci predicted to target in total 18 different substrate classes. Overall PUL repertoires of these isolates showed considerable intra-genus and inter-genus, variations suggesting that Bacteroidetes species harbour distinct glycan niches, independent of their phylogenetic relationships. By investigating the PUL repertoires of uncultured free-living Bacteroidetes during three consecutive years of spring phytoplankton blooms at the North Sea island of Helgoland, I could further reveal that the set of targeted substrates during these bloom events was dominated by only five of the substrate classes targeted by the isolates. These were the diatom storage polysaccharide laminarin, alpha-glucans, alginates, as well as substrates rich in alpha-mannans and sulfated xylans. In addition to this constrained set of substrate classes targeted by the free-living Bacteroidetes community, I could show that the species diversity during these blooms was limited and dominated by only 27 abundant and recurrent species that carried a limited number of abundant PULs. The majority of these PULs were targeting laminarin and alpha-glucan substrates, which were likely targeted during the entire time of the blooms. The less frequent PULs, targeting alpha-mannans and sulfated xylans, were predominantly detected during mid- and late- bloom phases, suggesting a relevance of these two substrate classes in the later phases of phytoplankton blooms. Overall these findings highlight the recurrence of a few specialized Bacteroidetes species and the environmental relevance of specific polysaccharide substrate classes during spring phytoplankton blooms. However, for some of these substrate classes the origin, structural details and their abundance during blooms are as yet largely unknown. To further shed light on the polysaccharide niches of abundant key-players, these findings can serve as a guide for future laboratory studies
Round Table Discussion on Nation(alism), Identity and Video Gaming with Megan Condis, Marijam Didzgalvyt , Georg Hobmeier and Souvik Mukherjee
No full textQuestions of nation and identity not only concern multiple aspects of video games, their production, and their consumption, but also require further and manifold discussion from different perspectives. In an effort to bring together voices from different fields that engage with video games and gaming practices from various perspectives, this virtual round table discussion attempts to open up the conversation beyond the realms of academia. Kathrin Trattner and Lisa Kienzl talked to Megan Condis, Marijam Didzgalvyt , Georg Hobmeier and Souvik Mukherjee about how concepts such as nation(alism) and identity impact video game representations, the gaming industry, and online gaming cultures in numerous ways
Natural resources and technology - on the mitigating effect of green tech
Get PDFThis paper deals with the question as to whether technology can lessen the problem of scarce resources. Focusing on fossil and biomass materials as important resources for production and consumption, the paper empirically investigates whether environmental innovations reduce the material usage in European economies. A dynamic panel model is employed to estimate the effect of environmental innovations on the use of fossil and biomass materials. It shows that there is no continuously mitigating effect of green technology. For biomass, no significant technology effects are found. Fossil materials are saved by innovations in recycling as well as by new production and processing technologies, but not by all categories of relevant green technology
Modular and Analytical Methods for Solving Kinematics and Dynamics of Series-Parallel Hybrid Robots
Get PDFWhile serial robots are known for their versatility in applications, larger workspace, simpler modeling and control, they have certain disadvantages like limited precision, lower stiffness and poor dynamic characteristics in general. A parallel robot can offer higher stiffness, speed, accuracy and payload capacity, at the downside of a reduced workspace and a more complex geometry that needs careful analysis and control. To bring the best of the two worlds, parallel submechanism modules can be connected in series to achieve a series-parallel hybrid robot with better dynamic characteristics and larger workspace. Such a design philosophy is being used in several robots not only at DFKI (for e.g., Mantis, Charlie, Recupera Exoskeleton, RH5 humanoid etc.) but also around the world, for e.g. Lola (TUM), Valkyrie (NASA), THOR (Virginia Tech.) etc.These robots inherit the complexity of both serial and parallel architectures. Hence, solving their kinematics and dynamics is challenging because they are subjected to additional geometric loop closure constraints. Most approaches in multi-body dynamics adopt numerical resolution of these constraints for the sake of generality but may suffer from inaccuracy and performance issues. They also do not exploit the modularity in robot design. Further, closed loop systems can have variable mobility, different assembly modes and can impose redundant constraints on the equations of motion which deteriorates the quality of many multi-body dynamics solvers. Very often only a local view to the system behavior is possible. Hence, it is interesting for geometers or kinematics researchers, to study the analytical solutions to geometric problems associated with a specific type of parallel mechanism and their importance over numerical solutions is irrefutable. Techniques such as screw theory, computational algebraic geometry, elimination and continuation methods are popular in this domain. But this domain specific knowledge is often underrepresented in the design of model based kinematics and dynamics software frameworks. The contributions of this thesis are two-fold. Firstly, a rigorous and comprehensive kinematic analysis is performed for the novel parallel mechanisms invented recently at DFKI-RIC such as RH5 ankle mechanism and Active Ankle using approaches from computational algebraic geometry and screw theory. Secondly, the general idea of a modular software framework called Hybrid Robot Dynamics (HyRoDyn) is presented which can be used to solve the geometry, kinematics and dynamics of series-parallel hybrid robotic systems with the help of a software database which stores the analytical solutions for parallel submechanism modules in a configurable and unit testable manner. HyRoDyn approach is suitable for both high fidelity simulations and real-time control of complex series-parallel hybrid robots. The results from this thesis has been applied to two robotic systems namely Recupera-Reha exoskeleton and RH5 humanoid. The aim of this software tool is to assist both designers and control engineers in developing complex robotic systems of the future. Efficient kinematic and dynamic modeling can lead to more compliant behavior, better whole body control, walking and manipulating capabilities etc. which are highly desired in the present day and future robotic applications
Modellierung des Tribosystems beim trockenen Vollvorwärtsfließpressen mithilfe eines erweiterten Reibmodells
Get PDFWerkzeuge in der Kaltmassivumformung sind hohen Prozessbelastungen ausgesetzt. Zur Reduzierung dieser Prozessbelastung werden Fest- und Flüssigschmierstoffe eingesetzt. Der Einsatz von Schmierstoffen ist jedoch aus ökologischen, ökonomischen und gesetzlichen Gründen nachteilig. Neuartige Ansätze in der Kaltmassivumformung zielen auf die Verwendung von ökologisch unbedenklichen Schmierstoffen oder die vollständige Vermeidung des Einsatzes von Schmierstoffen ab. Dieser Beitrag konzentriert sich auf die Substitution von Schmierstoffen beim Kaltfließpressen durch Oberflächentexturen auf den Halbzeugen und einer selbstschmierenden Beschichtung auf dem Werkzeug. Das Potenzial von Oberflächenstrukturen an Halbzeugen und selbstschmierenden Werkzeugbeschichtungen zur Reduzierung von Reibung und Verschleiß beim trockenen Vollvorwärtsfließpressen wurde in Vorarbeiten durch Analogieuntersuchungen nachgewiesen. Analogieuntersuchungen unter trockenen tribologischen Randbedingungen haben positive Ergebnisse in Vorarbeiten erbracht und im Zuge dieses Beitrags wurden trockene Vollvorwärtsfließpressversuche durchgeführt. Hierbei lag der Schwerpunkt der Untersuchungen auf der Machbarkeit sowie in der Selektion der potenziell besten Kombination aus Oberflächentextur der Halbzeuge und Werkzeugbeschichtung in Bezug auf Reibung und Verschleiß. Zur Untersuchung wurde neben der Presskraft auch die Oberfläche der Fließpresswerkzeuge mittels REM analysiert. Parallel wurde der Prozess durch eine validierte numerische FE-Prozesssimulation mit der Simulationssoftware Forge NxT 2.1 unterstützt. Hierbei wurde ein Ansatz mithilfe eines erweiterten Reibmodells gewählt, um den Kraftverlauf quantitativ genauer ab-zubilden. Der Vollvorwärtsfließpressprozess konnte ohne Schmierstoff durchgeführt werden und die Proben ohne Schädigung ausgeworfen werden. Es wurde beobachtet, dass der höchste Verschleiß der Matrizen nicht in dem Bereich mit der höchsten Werkzeugbelastung, sondern in dem Bereich mit relativ geringer Belastung auftrat. Darüber hinaus wurde gezeigt, dass es bisher kein für das Kaltfließpressen geeignetes Verschleißmodell gibt