Search results for ""Verlag G. Mainz""
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Verlag G. Mainz OptimizationBased Synthesis of LargeScale Energy Systems by TimeSeries Aggregation
Global greenhouse gas emissions significantly accelerate climate change and adversely affect life on earth. To mitigate these effects, greenhouse gas emissions need to be cut-down by significant reductions in primary energy consumption. Primary energy consumption can be reduced by increasing the efficiency of energy supply, which is mainly fixed during the synthesis of energy systems. Optimal synthesis of energy systems can be realized by mathematical optimization, however the solvable problem complexity is limited. In contrast, energy systems encompass highly complex energy conversion technologies and an increasing number of time-varying operation conditions. Thus, the synthesis of real-world energy systems usually result in large-scale optimization problems, which are computationally prohibitive.In this thesis, a solution framework is proposed to enable large-scale synthesis of energy systems. The framework exploits the two-stage character of synthesis problems: the decisio
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Verlag G. Mainz Lewis Acidic Alkali Metal and Aluminum Complexes
Most industrial processes for producing bulk and fine chemicals are transition metal catalyzed. Toxicity and high cost of platinum group metals are triggering the current search for sustainable catalysts. In this regard, nontoxic and earth-abundant alkali metals could become attractive alternatives. They are the most electropositive elements of the periodic table. With a single s electron in the valence shell and a low ionization enthalpy they easily form M+ ions. The vacant, low-energy orbital of the M+ ion is capable of accepting an electron pair. This Lewis acidic property can be utilized in molecular catalysis. Since alkali metal compounds easily dimerize, oligomerize or even polymerize (Scheme A.1-1), suitable ligands are crucial for the isolation of defined metal complexes in their monomeric form.
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Verlag G. Mainz Speech Signal Enhancement by Information Combining
Mobile phones as well as tablets are omnipresent and belong to everyday life. Today audiovisual communication takes place at different locations and in a large variety of acoustic environments. In consequence, the intelligibility as well as the quality of speech may significantly be degraded by ambient background noise. In order to improve speech intelligibility and to ensure a convenient communication with high audio quality, speech enhancement techniques are required. In this thesis all critical components contributing to the enhancement of the up-link signal are addressed: signal capturing at the acoustic front-end with a new near field beamformer new codebook based speech and noise estimation procedure generating and exploiting reliability information, and actual noise reduction exploiting spectral dependencies of human speech.For the acoustic front-end of the digital processing chain a novel concept for the filter optimization of a near field beamfor
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Verlag G. Mainz Integrated Design of Process and Working Fluids for Organic Rankine Cycles
This thesis presents systematic extensions of the continuous-molecular targeting framework for the integrated design of working fluids and ORC processes. In the first step of the proposed method, a simultaneous optimization of working fluid and process allows for the identification of an optimal hypothetical working fluid. The second step of the method is used to search for real working fluids that lead to similar performance.
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Verlag G. Mainz VoIP Performance of the Relayenhanced IEEE 802.16m Wireless Broadband System
In 2007 the International Telecommunication Union, Radiocommunication Sector (ITU-R) published evaluation guidelines for future mobile broadband radio networks including a minimal VoIP capacity that the IEEE 802.16m WiMAX system had to meet, proven by system level simulation. These evaluation guidelines are the foundation of this work that shows that relayenhanced 4G networks do not only meet the requirements but exceed them by far. The key-requirement for packet based VoIP services that has been set in the evaluation guidelines demands that the end-to-end packet delay of at least 98% of user data traffic stays below 50 ms.Since 2011 proposals of ComNets to implement relays into mobile radio networks to increase system capacity are part of all 4G systems (LTE and WiMAX). This work investigates the voice over IP (VoIP) capacity of the relay-enhanced WiMAX system by system simulation. The work presents a modular approach that has been developed by my colleagues and myself to im
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Verlag G. Mainz Automated OptimizationBased Synthesis of Distributed Energy Supply Systems
In this thesis, two novel synthesis methodologies are proposed to facilitate the use of optimization for efficient and reliable DESS synthesis, thus making optimization accessible for practitioners: The automated superstructure-based and the superstructurefree synthesis methodology. The proposed methodologies avoid both the a priori definition of a superstructure and the manual definition of many technology-specific replacement rules while accounting for the major characteristics inherent to DESS synthesis problems. The superstructure-based framework (chapter 4) relies on an algorithm for automated superstructure-generation. The method employs a successive superstructure expansion and optimization strategy that continuously increases the number of units included in the superstructure until the optimal solution is identified. The superstructure-free approach (chapter 5) combines evolutionary optimization and deterministic optimization for simultaneous alternatives generation and opti
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Verlag G. Mainz Immobilization of RutheniumTriphos Catalysts and their Application for the Hydrogenation of Polar Bonds in Batch and ContinuousFlow Systems
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Verlag G. Mainz Datadriven Modeling and Optimization of MultiEnergy Systems
Big data raises new opportunities for deep insights and supporting decision-making. To seize these opportunities, methods that derive useful knowledge from large amounts of data are needed. Such methods can help meet urgent challenges in many fields. An urgent challenge for energy systems is the necessary transformation towards sustainability to mitigate climate change. One crucial aspect of this challenge is a permanent optimal operation of energy systems. In principle, mathematical optimization can best determine the optimal operation of energy systems. However, manual model generation and operational optimization of energy systems are time-consuming and can thus prevent an application of mathematical optimization in practice. This thesis presents methods that use measured data to automatically generate mathematical models of energy systems to tackle the challenge of time-consuming model generations. Additionally, methods are presented that accelerate the operational optimization
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Verlag G. Mainz HD Telephony by Artificial Bandwidth Extension
The audio bandwidth of digital landline and mobile telephone networks is still mostly restricted to 200 Hz to 3.4 kHz. This is due to compatibility requirements during the transition phase from analogue to digital transmission technology. The resulting characteristic telephone speech is widely accepted, but the intelligibility of syllables is only 91%.Meanwhile, improved coding standards for so-called HD voice or Wideband Speech have been developed which are gradually being introduced into the networks. They support an audio frequency bandwidth of 50 Hz to 7.0 kHz with significantly increased audio quality and speech intelligibility. For a very long time however, new HD-telephones and old narrowband telephones have to co-exist. If an HD-terminal is connected over a narrowband link to an old telephone, the improved coding scheme cannot be used.In this thesis, signal processing concepts are developed for improving audio quality and intelligibility of narrowband speech by
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Verlag G. Mainz SystemWide Perspective for Life Cycle Assessment of CO based C1Chemicals
In recent years, the conversion of CO2 to basic chemicals with one carbon atom (C1-chemicals) such as methane and methanol has gained increasing interest. The major motivation for the utilization of CO2 is the reduction of global warming and fossil depletion impacts. However, these reductions are not guaranteed because all C1-chemicals require hydrogen besides the abundantly available CO2. Thus, the goal of this thesis is the life cycle assessment of CO2-based C1-chemicals (methane, methanol, carbon monoxide and formic acid). The assessment is based on a system-wide perspective, which means that for limited resources such as renewable electricity also the utilization of the limited resources is in other processes is considered.First of all, the CO2-based processes are compared to fossil-based processes for C1-chemicals. Formic acid has the highest potential to reduce global warming and fossil depletion impacts followed by carbon monoxide, methanol and methane. Even if hydroge
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Verlag G. Mainz HighCurrent Anode Phenomena in Vacuum Arcs
The emerging interest on the application of vacuum interrupter (VI) in medium and even high-voltage application has led to increase of comprehensive and fundamental research on VIs. Application of these interrupters is however hindered by limitation of interrupting capability, when high-current anode phenomena occur.The goal of the work is to investigate the high-current anode phenomena using spectroscopic methods se well as electrical measurements. Different current waveforms, i.e. AC and DC pulses are applied. Moreover, the impact of vacuum interrupter properties, e.g. electrode diameter and geometries, contact materials, opening time and opening speed on the formation of high-current anode phenomena are investigated.The results reveal that the threshold current of the high-current anode formation is dominated by the current in case of high-frequency pulsed, whereas in case of pulsed DC, it is controlled by transferred charge.Along with typical and already kno
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Verlag G. Mainz From LifeCycle Assessment towards LifeCycle Design of Carbon Dioxide Capture and Utilization
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Verlag G. Mainz Adaption of new strategies for parameterization of a microstructurebased flow stress model
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Verlag G. Mainz Analysis of CSMA Based Broadcast Communication in Vehicular Networks with Hidden Stations
This thesis studies the congestion problem at the Medium Access Control (MAC) layer of the IEEE 802.11p system in highway scenarios using an analytical approach. Using the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol, the IEEE 802.11p system suffers from the hidden station problem. This thesis provides formal definitions for the hidden station condition and the hidden station problem and develops an analytical methodology for CSMA protocols to investigate the interaction between stations in mutual channel sensing range and hidden to each other. Analytical models are developed for broadcast communication using the generic CSMA protocol and the IEEE 802.11p MAC protocol with a one-dimensional (1-D) homogeneous network topology. Simulation studies prove the accuracy of the models in analyzing the reliability performance and the efficiency performance of CSMA broadcast communication with hidden stations.The performance of Cooperative Awareness Message (CAM
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