verlag g mainz (737 risultati)

Condizione: very good. Gut/Very good: Buch bzw. Schutzumschlag mit wenigen Gebrauchsspuren an Einband, Schutzumschlag oder Seiten. / Describes a book or dust jacket that does show some signs of wear on either the binding, dust jacket or pages.

Condizione: very good. Gut/Very good: Buch bzw. Schutzumschlag mit wenigen Gebrauchsspuren an Einband, Schutzumschlag oder Seiten. / Describes a book or dust jacket that does show some signs of wear on either the binding, dust jacket or pages.

Engl. Broschur. 40 S. mit Abb. - 23,5 x 15,5. Einband etwas berieben, sonst gut erhalten. Sprache: Deutsch Gewicht in Gramm: 124.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: New. The need for artificial intelligence systems that are not only capable of mastering complicated tasks but also of explaining their decisions has massively gained attention over the last years. This also seems to offer opportunities for further interconnecting different approaches to artificial intelligence, such as machine learning and knowledge representation.This work considers the task of learning knowledge bases from agent behavior, with a focus on human-readability, comprehensibility and applications in games. In this context, it will be presented how knowledge can be organized and processed on multiple levels of abstraction, allowing for efficient reasoning and revision. It will be investigated how learning agents can benefit from incorporating the approaches into their learning processes.Examples and applications are provided, e.g., in the context of general video game playing. The most essential approaches are implemented in the InteKRator toolbox and show potential for being applied in other domains (e.g., in medical informatics).

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. 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 of energy systems. Regarding model generation, the presented data-driven methods solve the trade-off between accuracy and computational efficiency of the energy system model by weighting each component model by its role in the overall system. Thereby, the methods automatically generate energy system models that allow for accurate and computationally efficient optimization.To accelerate the operational optimization of energy systems, we present two methods that decompose the complex operational optimization problem into smaller subproblems. The methods provide high-quality solutions. The first method employs expert knowledge about the individual energy system to significantly accelerate the operational optimization while retaining an excellent solution quality.The second method applies artificial neural nets to solve the operational optimization in a reliably short time while offering a high solution quality. Overall, the methods presented in this thesis enable a broader application of mathematical optimization for energy systems. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. Thermal energy storage (TES) helps to reduce energy consumption and peak demands by balancing heat supply and demand on all time scales from short-term to seasonal. Thus, TES is an important technology to improve flexibility and efficiency of energy systems. In particular, adsorption TES systems, which exploit the enthalpy of adsorption, provide high energy storage density and high efficiency.The present thesis therefore analyzes an adsorption TES unit for residential and industrial applications. Industrial energy supply can be made more efficient by integrating waste heat into the process heat supply and by using energy-efficient technologies. Adsorption TES contributes to both approaches: waste heat can be integrated via the heat pump effect and TES allows for energy-efficient cogeneration heat supply for batch processes.We evaluate the energy efficiency of the heat supply for an industrial batch process by adsorption TES and cogeneration. To evaluate the performance, a dynamic model of an adsorption TES unit is developed. Measurements from earlier experimental investigations of an adsorption TES unit are used to calibrate the storage model. As benchmark, a peak boiler and TES based on a phase-change material are considered. Our comparison demonstrates the significance of the process conditions for the choice of the appropriate technology. The study shows that adsorption TES offers significant potential to increase the energy efficiency: primary energy consumption can be reduced by up to 25%. The key is the availability of low-grade heat at times of discharging and of a low-grade heat demand when charging the storage unit.The study reveals that a comprehensive evaluation of the storage performance requires dynamic models that precisely describe the storage performance and the heat losses in particular. The present thesis provides the basis with a new experimental setup to precisely characterize the adsorption TES unit. In an experimental analysis of the TES performance, we quantify the heat losses, the energy recovery ratio (6991%) and the energy storage density (20.4 kWh/m3) of the adsorption TES unit for varying charging temperatures and storage times ranging from continuous operation to seasonal storage.The extensive experimental study provides the basis to improve our model of the adsorption TES unit. The model is calibrated to heat-loss measurements and a storagecycle measurement. We quantify the simulation accuracy and validate the model with measurements at various process conditions. The model achieves a higher prediction accuracy than other models from literature. The thesis thus provides a basis for future investigations of energy systems to exploit the advantages of adsorption TES. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

Paperback. Condizione: new. Paperback. 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) in IEEE 802.11p network is analyzed for highway scenarios using the developed analytical models. The study reveals that in a hidden station scenario the reliability performance of the CAM broadcast communication deteriorates with increased topological distance between the transmitter and the receiver. This study provides quantitative analysis of this performance with respect to network density, frame length, traffic load and settings of the IEEE 802.11p MAC protocol. Analysis of the mean update interval of CAM at a receiver vehicle discovers though in general the performance degrades with increased network density, the update interval of CAM frames from a particular vehicle in the vicinity of the receiver, e.g. with a topological distance less than 8 between the transmitter and the receiver, can be easily maintained below 1 second by using control mechanisms like transmit power control, transmit rate control and link control. The analytical models developed in this work provide quantitative guidance on optimizing protocol parameters and utilization of these control mechanisms. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. 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 implement the WiMAX protocol stack, also known as WiMAC, into the openWNS simulator. The approach is based on atomic protocol functions that are bound to so called FU and interconnected in a network of functional units (FUs) and thereby implement the WiMAX protocol bit-by-bit. Besides the performance evaluation of VoIP services based on the ITU-R scenarios and channel model, this work also determines the optimal radio resource configuration for up- and downlink and furthermore investigates the impact of RS location on system capacity. Core functions of the simulator are being validated by comparison of equivalent results of other simulators.Cumulative distribution functions of the end-to-end delay of VoIP user data packets, determined by simulation show that relays double the carried VoIP traffic load compared to a scenario without relay stations (RSs) due to the improved prediction of the uplink channel state that is the bottleneck of the system.The performance enhancement is a surprise since relays increase the end-to-end packet delay and packet error due to an additional transmission compared to conventional single-hop operation. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

Paperback. Condizione: new. Paperback. During the last 25 years, most of the communication systems have been converted to purely digital technology, although the transmitted content mostly is analog by nature. The principal advantages of digital communication are compression by source encoding, bit error protection by channel coding and robust transmission over noisy channels by appropriate modulation. Digital systems are usually designed for worst case channel conditions. However, often the channel quality is much better, which is not reflected in an improved end-to-end transmission quality due to inevitable quantization noise produced by the source encoder.In this thesis, the focus is set on systems which: are not purely digital anymore benefit from increasing channel qualities and avoid the saturation effect using discrete-time, continuous-amplitude techniques.In the first part, purely analog, i.e., discrete-time and continuous-amplitude transmission systems are considered with linear or nonlinear components. Theoretical performance limits are discussed and a new rate-distortion upper bound is derived which can be evaluated semi-analytically. The performance of linear transmission systems is derived analytically while simulations assess several nonlinear systems including the famous Archimedes spiral. A new class of nonlinear discrete-time analog coding systems, i.e., the Analog Modulo Block Codes (AMBCs) is developed. One important observation is that nonlinear discrete-time, continuous-amplitude systems can be decomposed into a discrete and a continuous-amplitudes part. The considered systems exhibit a considerable gap to capacity but they all circumvent the saturation effect due to the continuous-amplitude components.In the main part of the thesis, these findings are turned into a design principle. Hybrid Digital-Analog (HDA) transmission systems consist of separate digital and analog branches while each is constructed independently. By combining both worlds digital and continuous-amplitude transmission new concepts emerge which fuse their advantages: capacity achieving performance in the digital branch with a huge variety of conventional digital codes plus avoiding the saturation effect in the analog branch. The performance of HDA systems is assessed theoretically as well as by simulations. These Hybrid Digital-Analog (HDA) transmission systems outperform both purely digital and continuous-amplitude concepts. HDA transmission is an attractive solution for wireless systems such as microphones, loudspeakers or distributed sensors. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. 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 hydrogen is supplied by fossil-based steam reforming, formic acid reduces global warming and fossil depletion impacts. All other CO2-based C1-chemicals require hydrogen from electrolysis using renewable electricity.In the following, the supply of hydrogen by electrolysis is analyzed in more detail. The CO2-based processes for carbon monoxide and methane required about 60 % and 88 % renewable electricity (in 2020 in the EU-27) to reduce global warming impacts compared to the fossil-based processes.If 100 % renewable electricity is used, all CO2-based C1-chemicals reduce global warming and fossil depletion impacts compared to the fossil-based processes. For the assessment of these reductions, also alternative utilization options for renewable electricity (Power-to-X) are analyzed such as electricity storage systems, battery electric vehicles and heat pumps. The highest reductions per electricity used are achieved for heat pumps followed by battery electric vehicles and electricity storage systems. Then, the CO2-based C1-chemicals follow.Since renewable electricity is used more efficiently outside the chemical industry, also biomass-based methane and methanol are analyzed. The utilization of biomass achieves the highest reductions if coal-fired power plants are substituted followed by the production of methanol. For methanol and methane, the yield per biomass can be increased if additional hydrogen is used. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. Smoking chimneys are a symbol for environmental impacts of industrial processes. Indeed, industrial processes are major contributors to environmental problems such as global warming. Beyond emission-related problems, industrial processes deplete limited resources because they require raw materials. Raw materials are directly linked to costs, emission-related impacts cause indirect expenditures, e.g., through the European emissions trading scheme (EU-ETS) for greenhouse gas emissions. Therefore, industrial enterprises seek to reduce costs by reducing environmental impacts of their processes.Two well-known strategies for reducing environmental impacts of industrial processes are process integration and recycling. Process integration establishes interconnections between formerly separate processes by utilizing co-products. Process integration thereby relies on unit processes with multiple products, so-called multi-product processes. Similarly, recycling uses waste as raw material for new products. But neither process integration for recycling guarantee reduced environmental impacts. E.g., recycling may cause more impacts than waste disposal. Decision makers thus need a holistic method for comparing environmental impacts from multi-product processes.This work investigates methods for comparisons of industrial multi-product processes. The environmental impacts of multi-product processes can be analyzed using life cycle assessment (LCA). LCA studies all environmental impacts of all processes involved in a procucts entire life cycle. Due to ist holistic approach, LCA identifies shifting of environmental problems between processes and between different types of environmental impacts. Results of LCA-studies can thus help avoiding such problem shifting. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.

PAP. Condizione: New. New Book. Shipped from UK. Established seller since 2000.

Paperback. Condizione: new. Paperback. In recent years, spectroscopy has developed into an increasingly valuable tool to determine the composition of mixtures; for scientific questions as well as for the industry. The increasing use of spectroscopy raises the question how to best use the obtained data. For the analysis of spectral data, the method of Indirect Hard Modeling (IHM) has been established besides statistical methods like PLS. IHM is a nonlinear method that can therefore efficiently treat nonlinear effects such as peak-shifts. In the present work, the IHM method is expanded to increase its applicability.IHM treats nonlinear effects in the spectral evaluation. Therefore, the direct proportionality between the concentration and the Raman signal of a component can be used for calibration. The resulting linear calibration model allows for reliable extrapolation. Thus, IHM can be used to study reactive systems, even if only binary subsystems can be used for calibration. However, thermodynamic systems with intermediates can so far only be calibrated by using thermodynamic models. In this work, a method is established that calibrates a reactive system with intermediates only based on the reaction mechanism as well as stoichiometry and electroneutrality.Spectral backgrounds, e.g., fluorescence, can be treated by a spectral pretreatment or via background models. However, spectral backgrounds are still a common source of error in IHM. Derivatives have long been used very effectively in statistical methods. Therefore, IHM is adapted so that it becomes possible to evaluate the first derivative of spectra.The calibration of IHM is mostly limited to the relative spectral intensities of the involved components. In the present work, a method is presented that uses the information in the calibration spectra more thoroughly. For this purpose, nonlinear effects are parametrized as a function of concentration.The commonly used peak profiles do not reflect the physical reality at a detector very well. As a result, narrow modelled peaks may change their apparent intensity if they are shifted. To correct these shortcomings, a new peak model is proposed in this work that is more closely aligned to the physical reality of a detector. Shipping may be from multiple locations in the US or from the UK, depending on stock availability.