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Medien unter Kontrolle
(2009)
Die vorliegende Online-Publikation fasst die Vorträge einer im WS 2007/08 gehaltenen Universitätsringvorlesung gleichen Titels an der Friedrich-Alexander-Universität Erlangen-Nürnberg zusammen und ergänzt sie durch nachträglich eingeworbene Beiträge. Die Ringvorlesung wie auch diese Publikation wurden organisiert vom Interdisziplinären Medienwissenschaftlichen Zentrum (IMZ), einem Forschungs- und Nachwuchsförderungsverbund der medienbezogenen Fächer an der Universität Erlangen-Nürnberg. Professorinnen und Professoren sowie NachwuchswissenschaftlerInnen der Fächer Buchwissenschaft, Christliche Publizistik, Christliche Archäologie, Klassische Archäologie, Kommunikationswissenschaft, Kunstgeschichte, Medienwissenschaft, Multimedia-Didaktik und Theaterwissenschaft forschen hierin selbstorganisiert an den Schnittstellen fächerübergreifend relevanter Fragestellungen der Medientheorie, -praxis, -ethik und -didaktik und führen auch den jeweiligen wissenschaftlichen Nachwuchs frühzeitig an entsprechende interdisziplinäre Arbeitsfelder heran. Der Zusammenschluss trägt dem Umstand Rechnung, dass Medien inzwischen ein primäres Bezugsfeld vieler Disziplinen darstellen, die aus je eigener Perspektive Fragen nach den Funktionen, Verwendungshinsichten, möglichen Wirkungen und Entwicklungstendenzen von Medien in einer sich immer stärker als Medien- und Kommunikationsgesellschaft verstehenden Gesellschaft generieren. Einen Überblick über Zusammensetzung und Aktivitäten des IMZ bietet die Homepage unter http://www.imz.uni-erlangen.de.
We present a new car-to-X communication protocol, Adaptive Traffic Beacon (ATB), which supports the exchange of delay-sensitive traffic information in a wide range of scenarios by flexibly adapting to the availability of infrastructure elements as well as to the network load. From previous work, we see that centralized solutions and flooding based approaches each show benefits and drawbacks depending on traffic density, penetration, network utilization, and other parameters. This observation is in line with findings about intelligent transportation systems that have been developed for specific settings. In order to overcome this limitation, we designed ATB to be adaptive in two dimensions: First, the beacon interval is adapted dynamically and, secondly, the protocol can dynamically make use of available infrastructure elements. We concentrate on a Traffic Information System (TIS) with a focus on congestion-aware communication. Simulation experiments clearly demonstrate that ATB performs well in a broad range of settings. It maintains a non-congested wireless channel to prevent collisions during TIS data exchange.
A Computationally Inexpensive Empirical Model of IEEE 802.11p Radio Shadowing in Urban Environments
(2010)
We present a realistic, yet computationally inexpensive simulation model for IEEE 802.11p radio shadowing in urban environments. Based on real world measurements using IEEE 802.11p/DSRC devices, we estimated the effect that buildings and other obstacles have on the radio communication between vehicles. Especially for evaluating safety applications in the field of Vehicular Ad Hoc Networks (VANETs), stochastic models are not sufficient for evaluating the radio communication in simulation. Motivated by similar work on WiFi measurements, we therefore created an empirical model for modeling buildings and their properties to accurately simulate the signal propagation. We validated our model using real world measurements in a city scenario for different types of obstacles. Our simulation results show a very high accuracy when compared with the measurement results, while only requiring a marginal overhead in terms of computational complexity.
The life cycle assessment of components is becoming increasingly important for planning and construction. In this paper, a novel storage technology for excess electricity consisting of a heat pump, a heat storage and an organic rankine cycle is investigated with regards to its environmental impact. Waste heat is exergetically upgraded, stored in a hot water storage unit and afterwards reconverted to electricity when needed. Such a pilot plant on a lab scale is currently built in Germany. The first part of this paper focuses on geothermal energy as a potential heat source for the storage system and its environmental impact. For a large scale application, geothermal hotspots in Germany are further investigated. The second part analyzes the storage technology itself and compares it to the impacts of commonly used battery storage technologies. Especially during the manufacturing process, significantly better global warming potential values are shown compared to lithium-ion and lead batteries. The least environmental impact while operating the system is with wind power, which suggests an implementation of the storage system into the grid in the northern part of Germany.
Storage of electricity from fluctuating renewable energy sources has become one of the predominant challenges in future energy systems. A novel system comprises the combination of a heat pump and an Organic Rankine Cycle (ORC) with a simple hot water storage tank. The heat pump upgrades low temperature heat with excess power. The upgraded heat can drive an Organic Rankine Process using the heat pump in reverse operation mode. This approach allows a comparably efficient storage of excess electricity. Waste heat sources usually do not qualify for electricity production even with ORC processes due to low temperatures. Upgrading the temperature of the waste heat by means of excess electricity makes the use of an ORC feasible in order to recover the electricity input. Thermodynamic cycle simulations with IPSEpro software outline that the process provides power-to-power efficiencies in a range of 50% for small-scale applications based on commercially available heat pump components. The isentropic efficiency of compressors/expanders plays a crucial role on the system performance. Applications of the proposed cycle in the megawatt range with more efficient turbines and dynamic compressors will therefore increase the power-to-power efficiency to above 70%.
In dieser Arbeit stellen wir eine durch Zeitautomaten modellierte Spezifikation des Mediumzugriffs im CAN-Protokoll vor sowie ihre Implementierung in UPPAAL. Zeitliche Anforderungen wurden dabei durch entsprechende Uhren-Nebenbedingungen erfasst. Dieses Zeitautomaten-Modell wurde anschließend automatisch verifiziert (Model Checking), wobei mehrere Anforderungen identifiziert wurden, die das CAN Protokoll erfüllen muß (wie Deadlock-Freiheit des Modells, Übertragungsrecht für die höchstpriore Nachricht, exklusives Übertragungsrecht für beliebigen CAN-Adapter nach der gewonnenen Arbitrage etc.). All diese Eigenschaften wurden in einer Variante der temporalen Logik CTL spezifiziert; die automatische Verifikation selbst wurde dabei mit UPPAAL durchgeführt, einem Model Checker für zeitautomaten-basierte Modelle.
The transportation industry is facing major challenges that come along with innovative trends like autonomous driving. Due to the growing amount of network participants, smart sensors, and mixed-critical data, scalability and interoperability have become key factors of cost-efficient vehicle engineering. One solution to overcome these challenges is the AUTOSAR Adaptive software platform. Its service-oriented communication methodology allows a standardized data exchange that is not bound to a specific middleware protocol. OPC UA is a communication standard that is well-established in modern industrial automation. In addition to its Client–Server communication pattern, the newly released Publish–Subscribe (PubSub) architecture promotes scalability. PubSub is designed to work in conjunction with Time-Sensitive Networking (TSN), a collection of standards that add real-time aspects to standard Ethernet networks. TSN allows services with different requirements to share a single physical network. In this paper, we specify an integration approach of AUTOSAR Adaptive, OPC UA, and TSN. It combines the benefits of these three technologies to provide deterministic high-speed communication. Our main contribution is the architecture for the binding between Adaptive Platform and OPC UA. With a prototypical implementation, we prove that a combination of OPC UA Client–Server and PubSub qualifies as a middleware solution for service-oriented communication in AUTOSAR.
Pumped Thermal Energy Storages (PTES) are suitable for bridging temporary energy shortages, which may occur due to the utilization of renewable energy sources. A combined heat pump (HP)-Organic Rankine Cycle (ORC) system with suitable thermal storage offers a favorable way to store energy for small to medium sized applications. To address the aspect of flexibility, the part load behavior of a combined HP-ORC system, both having R1233zd(E) (Trans-1-chloro-3,3,3-trifluoropropene) as working fluid and being connected through a water filled sensible thermal energy storage, is investigated using a MATLAB code with integration of the fluid database REFPROP. The influence on the isentropic efficiency of the working machines and therefore the power to power efficiency (P2P) of the complete system is shown by variation of the mass flow and a temperature drop in the thermal storage. Further machine-specific parameters such as volumetric efficiency and internal leakage efficiency are also considered. The results show the performance characteristics of the PTES as a function of the load. While the drop in storage temperature has only slight effects on the P2P efficiency, the reduction in mass flow contributes to the biggest decrease in the efficiency. Furthermore, a simulation for dynamic load analysis of a small energy grid in a settlement is conducted to show the course of energy demand, supplied energy by photovoltaic (PV) systems, as well as the PTES performance indicators throughout an entire year. It is shown that the use of PTES is particularly useful in the period between winter and summer time, when demand and supplied photovoltaic energy are approximately equal.
Besides the integration of renewable energies, electric vehicles pose an additional challenge to modern power grids. However, electric vehicles can also be a flexibility source and contribute to the power system stability. Today, the power system still heavily relies on conventional technologies to stay stable. In order to operate a future power system based on renewable energies only, we need to understand the flexibility potential of assets such as electric vehicles and become able to use their flexibility. In this paper, we analyzed how vast amounts of coordinated charging processes can be used to provide frequency containment reserve power, one of the most important ancillary services for system stability. Therefore, we used an extensive simulation model of a virtual power plant of millions of electric vehicles. The model considers not only technical components but also the stochastic behavior of electric vehicle drivers based on real data. Our results show that, in 2030, electric vehicles have the potential to serve the whole frequency containment reserve power market in Germany. We differentiate between using unidirectional and bidirectional chargers. Bidirectional chargers have a larger potential but also result in unwanted battery degradation. Unidirectional chargers are more constrained in terms of flexibility, but do not lead to additional battery degradation. We conclude that using a mix of both can combine the advantages of both worlds. Thereby, average private cars can provide the service without any notable additional battery degradation and achieve yearly earnings between EUR 200 and EUR 500, depending on the volatile market prices. Commercial vehicles have an even higher potential, as the results increase with vehicle utilization and consumption.