Dissertations / Theses on the topic 'Energy Packet'
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1
Nilsson, Samuel, and Joakim Eriksson. "Estimating Application Energy Consumption Through Packet Trace Analysis." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-110348.
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The advancement of mobile clients and applications makes it possible for people to always stayconnected, sending and receiving data constantly. The nature of the 3G technology widelyused, however, causes a high battery drain in cellular phones and because of that a lot of toolsfor measuring mobile phones energy consumption has been developed. In this report we lookinto the trace-driven tool EnergyBox and find out how we can use it to estimate the energyconsumption of 3G transmissions for an application we’ve developed ourselves. We beginwith identifying the types of traffic our application generates and identify which parts of itmake up our applications background traffic. Different combinations of the identified traffictypes are looked into in order to decide which ones that need to be present in the packet tracesfor an estimation of our applications energy footprint for 3G transmission. Further, answersare sought to how long the time span should be for which the packet traces are collected andhow many of them are needed in order to draw a conclusion about our application’s energyfootprint. We conclude that all traffic types responsible for our application’s backgroundtraffic need to be present in the analyzed packet traces, and data suggests that collectingmore than 10 one minute packet traces does not improve accuracy significantly (less than1%). Without user interaction, our application generates traffic, which transmitted over 3G,drains as much as an average of 930mW, meaning that a Samsung Galaxy S4 battery with acapacity of 9.88Wh would last for a maximum of 10 hours and 30 minutes (excluding otherenergy consuming sources inside the handset).
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Sanjuan, Joseba. "3G Energy-Efficient Packet Handling Kernel Module for Android." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84507.
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The use of mobile devices is increasing due to the constant development of more advanced and appealing applications and computing features. However, these new features are very power hungry leading to short battery lifetimes. Research shows that a major reason for fast battery depletion is the excessive and inefficient use of the wireless interfaces. This thesis studies how we can attempt to increase the battery lifetime of the devices without having to sacrifice the usage of these advanced features in some applications. The thesis focuses on adapting the traffic pattern characteristics of mobile communication using a widespread wireless communication technology like 3G. Traffic pattern adaptation is performed at packet level in kernel space in Android. The data transfers are scheduled with the knowledge of the energy consumption characteristics of 3G. The performed measurements indicate that our solution can provide energy savings ranging from 7% to 59%. This work confirms that 3G conscious scheduling of network traffic reduces energy consumption, and that, both applications and energy saving libraries are potential directions to be further studied.
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Oto, Mert Can. "Energy-efficient Packet Size Optimization For Cognitive Radio Sensor Networks." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613040/index.pdf.
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Cognitive Radio (CR) has emerged as the key technology to enable dynamic spectrum access. Capabilities of CR can meet the unique requirements of many wireless networks.
Hence, Cognitive Radio Sensor Networks (CRSN) is introduced as a promising solution to address the unique challenges of Wireless Sensor Networks (WSN) which have been widely used for reliable event detection for many applications. However, there exist many open research issues for the realization of CRSN. Among others, determination
of optimal packet size for CRSN is one of the most fundamental problems to be addressed. The existing optimal packet size solutions devised for CR networks as well as WSN are not applicable in CRSN regime and would cause a waste of energy resources. Hence, the objective of this thesis is to determine the optimal packet size for CRSN that maximizes energy-efficiency while maintaining acceptable interference
level for licensed primary users (PU) and remaining under the maximum allowed distortion level between tracked event signal and its estimation at sink. Energy-efficient packet size reduces energy consumption and increases the transmission efficiency for CRSN. In this thesis, the energy-efficient packet size optimization problem is analytically formulated. Then, sequential quadratic programming (SQP) method is used for solving the optimization problem. The variation of optimal packet size with respect to different parameters of CRSN network is observed through numerical analysis. Results
reveal that PU behavior and channel bit error rate (BER) are the most critical parameters in determining energy-efficient optimal packet size for CRSN.
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Mobin, Iftekharul. "Energy efficient packet size optimization for wireless ad hoc networks." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8769.
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Energy efficiency is crucial for ad hoc networks because of limited energy stored in the battery. Recharging the nodes frequently is sometimes not possible. Therefore, proper energy utilization is paramount. One possible solution of increasing energy efficiency is to optimize the transmitted packet size. But, we claim that only optimal packet size can not boost the energy efficiency in the noisy channel due to high packet loss rate and overhead. Hence, to reduce the overhead size and packet loss, compression and Forward Error Correction (FEC) code are used as remedy. However, every method has its own cost. For compression and FEC, the costs are computation energy cost and extra processing time. Therefore, to estimate the energy-optimize packet size with FEC or compression, processing energy cost and delay need to be considered for precise estimation. Otherwise, for delay sensitive real time applications (such as: VoIP, multimedia) over ad hoc network, energy efficient optimal packet size can be overestimated. We will investigate without degrading the Quality of Service (QoS) with these two different techniques FEC and compression, how much energy efficiency can be achieved by using the energy efficient optimal packet size for different scenarios such as: single hop, multi-hop, multiple source congested network etc. This thesis also shows the impact of time variable channel, packet fragmentation, packet collision on the optimal packet size and energy efficiency. Our results show that, for larger packets, error correction improves the energy efficiency in multi-hop networks only for delay tolerant applications. Whereas for smaller packets, compression is more energy efficient most of the cases. For real-time application like VoIP the scope of increasing the energy efficiency by optimizing packet after maintaining all the constraints is very limited. However, it is shown that, in many cases, optimal packet size improves energy efficiency significantly and also reduces the overall packet loss.
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Kassab, Hisham Ibrahim. "low-energy mobile packet radio networks : routing, scheduling, and architecture." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9121.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2000.Includes bibliographical references (leaves 171-176).
Packet Radio Networks (PRNETs), which are also called ad-hoc networks, have the capability of fast (and ad-hoc) deployment and set-up, and therefore potentially have several useful civilian and military applications. Building low-energy PRNETs is an important design goal, because the communication devices are typically powered by batteries, and therefore are useless when the batteries are depleted. We choose to look at low-energy PRNETs by focusing on the problem of minimum-energy communication over a PRNET, resolving any related issues or design decisions in a manner consistent with the overall goal of low-energy PRNETs. We conclude that the problem of minimum-energy communication over a PRNET is really a joint routing-scheduling-topological problem. We find the joint problem to be intractable, and therefore propose to solve it by decomposing it, solving each component separately. The resulting solution is not optimal but the degree of suboptimality depends on how the problem is decomposed. Therefore we compare different decomposition methods, and select the one that is likely to yield the best solution to the joint problem. After deciding how to decompose the joint problem, we study the separate components. For the topological problem we decide that nodes should communicate with a limited number of other nodes, referred to as neighbors. We also propose and analyze the performance of a procedure for managing the set of neighbors. For the scheduling problem, we propose a novel and practical class of scheduling algorithms. The routing problem is more complex than wireline routing because of interference and fading. When they are incorporated, routing becomes a non-convex problem; and we overcome this by a novel approach that is non-optimal, but is more robust than the optimal approach.
by Hisham Ibrahim Kassab.
Ph.D.
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Reza, C. M. F. S. "Design of Energy Mixer and Router for DC Power Packet Distribution System." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20137.
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Energy internet (EI) is introduced recently aiming to improve power system reliability, security and efficiency through advanced information and power electronic technologies. A power packet distribution system (PPDS) is a promising candidate for the EI implementation, as it transfers information alongside the distribution of electric power. The PPDS can be realized for both DC and AC power distribution. This thesis has made four key contributions to the DC-PPDS: (1) A revised PP structure is proposed, which has a reduced footer bit and hence reduction in power switching losses. A routing scheme which does not need footer bits like handshaking protocol is proposed to increase PP distribution efficiency. A new algorithm for PP generation is also proposed capable of generating the PP based on the load power requests and the source power availability. A systematic approach is given to select the energy buffer which is needed to sustain the load voltage. (2) An over-current protection (OCP) scheme based on a simple analog circuit and integrated with the PPDS is proposed to monitor and protect the system during the over-current scenario. The routing algorithm is also modified, which utilizes the information received from the OCP circuit to isolate the faulty loads without interrupting the PP delivery to the other loads. (3) A multiple- energy-source mixer based on a single-inductor, multiple-input and single-output converter structure is proposed to attain power conditioning and voltage regulation simultaneously to send power to various loads at distinct voltage levels. (4) A four-port converter-based mixer is also proposed, which can interface with battery to mitigate intermittency problem of RESs, hence ensure reliable power distribution in islanded mode. The proposed solutions have been verified through experimental results. The PPDS has the potential to be applied in systems where communication and power transfer occur simultaneously.
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Morfopoulou, Christina. "Queuing analysis and optimization techniques for energy efficiency in packet networks." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11681.
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Energy efficiency in all aspects of human life has become a major concern, due to its significant environmental impact as well as its economic importance. Information and Communication Technology (ICT) plays a dual role in this; not only does it constitute a major consumer itself (estimated 2-10% of the global consumption), but is also expected to enable global energy efficiency through new technologies tightly dependent on networks (smart grid, smart homes, cloud computing etc.). To this purpose, this work studies the problem of energy efficiency in wired networks. As this subject has recently become very active in the research community, there is parallel research towards several research directions. In this work, the problem is being examined from its foundations and a solid analytical approach is presented. Specifically, a network model based on G-network queuing theory is built, which can incorporate all the important parameters of power consumption together with traditional performance metrics and routing control capability. This generalized model can be applied for any network case to build optimization algorithms and estimate the performance of different policies and network designs. Composite optimization goals functions are proposed, comprising both power consumption and performance metrics. A gradient descent optimization algorithm that can run in O(N3) time complexity is built thereof. Using power consumption characteristics of current and future equipment, several case studies are presented and the optimization results are evaluated. Moreover, a faster gradient-descent based heuristic and a decentralized algorithm are proposed. Apart from the routing control analysis, the case of a harsher energy saving solution, namely turning o the networking equipment, is also experimentally explored. Applying a tradeoff study on a laboratory testbed, implementation challenges are identified and conclusions significant for future work are drawn. Finally, a novel admission control mechanism is proposed and experimentally evaluated, which can monitor and manage the power consumption and performance of a network.
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Eriksson, Daniel, and Axel Persson. "Energy Optimization of Scheduling and Packet Loss in Wireless Sensor Networks." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214699.
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We study the data aggregation of Wireless SensorNetworks (WSN). This is done by considering two problemformulations. The problems examine two different parts of thenetworks and their impact on its energy consumption. The firstproblem looks at the impact of packet loss and the secondproblem on the impact of network scheduling. The reason behindthis is that WSN usually operate on battery power and may beplaced in locations where they are hard to replace. Thus if itis possible to reduce the energy consumption of a WSN, thetotal lifespan of it will be increased. This led to the formulationof a NP-hard deadline constraint problem that is solved bysimulation. For simulation purposes a fixed tree topology wasused to investigate the impact of packet loss rate. The simulationsof the seven different scheduling policies use the same tree. Itcould be concluded from this that an increase in packet lossby only 12% percent leads to two times as long transmissiontime and therefore also twice the energy consumption. For thesecond problem the scheduling policies are evaluated by theirspeed, reliability and evenness and assigned an index based onthese parameters. Here we could see that clear improvementscould be done to a system depending on which parameters wereprioritized.
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Sachdeva, Gitanjali. "Measuring and Optimizing Energy Efficiency in Internet Communication : Implementing a Packet-Level Energy Model for Content Delivery Networks." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for telematikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22693.
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Green ICT (Information and Communication Technology) aims at reducing the environmental impacts of ICT operations, maximizing energy efficiency and promoting recyclability. The ICT industry is resource intensive with rapidly increasing demands for more infrastructure and power. It is heavily dependent on full-time network connectivity. Therefore, networks play a crucial role in the overall green ICT initiatives. Various research efforts are being made by network equipment manufacturers as well as researchers to promote energy efficiency in the networks. The target of this master thesis is to develop mechanisms that allow measuring the energy consumption in networks and using them to optimize network usage. The thesis implements a packet-level energy accounting model using NS-3 simulator. The main idea is that IP packets collect the information of energy they consume at each hop while traversing a network. This information is later processed to account for the overall network energy consumption.The thesis work analyzes a specific use case of selecting energy-efficient servers in Content Delivery Networks (CDNs) to deliver content to end users. The energy model is implemented and tested for different traffic scenarios and sample network topologies. Simulation results show that the model can prove highly useful in the CDN use case. The energy accounting scheme allows end users to choose energy-efficient server alternatives for accessing content over the internet. End users are made aware of their carbon footprint and are able to contribute to green networking.Additionally, there is also a possibility to integrate the model with other network performance metrics such as network throughput in order to increase its usability.
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Nawata, Shinya. "Design of Electrical Energy Network Based on Power Packetization." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225598.
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Baek, Seong Cheol. "Dynamical Analysis and Decentralized Control of Power Packet Network." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263664.
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Prevedi, Andrea. "Energy Communities in Italy." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21973/.
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Citizens are expected to have a great role in the future global energy transition toward a low-carbon economy and climate neutrality. The creation of energy communities can empower citizens, who become prosumers, providing flexibility and ancillary services, reducing losses and grid investment deferral. It also brings environmental and social benefits, activating virtuous circles in the local economy.
The purpose of this work is to analyze the current regulatory framework energy community; a deeper analysis is performed on renewable energy community whose regulation has been already transposed in the Italian regulation. Moreover, a realistic business-case is presented in order to verify the feasibility of a renewable energy community and a collective self-consumption schemes in the CAAB-FICO area.
The final part of the work seeks to present an overview of the possible future perspectives regarding energy community and their possible contribution to smart-cities development. Particular attention has been given to the role of the energy management system in an energy community and a how it can be designed to improve the community’s energy efficiency through the implementation of production and load forecasts.
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Mostowfi, Mehrgan. "Packet Coalescing and Server Substitution for Energy-Proportional Operation of Network Links and Data Servers." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4732.
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Electricity generation for Information and Communications Technology (ICT) contributes over 2% of the human-generated CO2 to the atmosphere. Energy costs are rapidly becoming the major operational expense for ICT and may soon dwarf capital expenses as software and hardware continue to drop in price. In this dissertation, three new approaches to achieving energy-proportional operation of network links and data servers are explored.
Ethernet is the dominant wireline communications technology for Internet connectivity. IEEE 802.3az Energy Efficient Ethernet (EEE) describes a Low Power Idle (LPI) mechanism for allowing Ethernet links to sleep. A method of coalescing packets to consolidate link idle periods is investigated. It is shown that packet coalescing can result in almost fully energy-proportional behavior of an Ethernet link. Simulation is done at both the queuing and protocol levels for a range of traffic models and system configurations. Analytical
modeling is used to gain a deeper general insight into packet coalescing.
The architecture of a hybrid web server based on two platforms - a low-power (ARM based) and a high-power (Pentium based) - can be used to achieve step-wise energy-proportional operation and maintain headroom for peak loads. A new method based on Gratuitous ARP for switching between two mirrored platforms is developed, prototyped, and evaluated. Experimental results show that for up to 50 requests per minute, a hybrid server where the Master platform is a 2012 server-grade desktop PC can sleep for 50% of time with no increase in response time.
HTTP can be used for redirection in space - a new method for precise redirection in time is proposed and used to schedule requests to a high-power server in a hybrid server. The scheduling method is modeled as a single server queue with vacations where the vacation duration is fixed and the service distribution is directly a function of the request load. This approach is well suited for delay tolerant applications such as application updates and file back-up. Energy-proportional operation is shown to be achievable in a prototype
system.
A first-order estimation with conservative assumptions on the adoption rate of the methods proposed and studied here shows that these methods can collectively enable energy savings in the order of hundreds of million dollars in the US annually.
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Erkal, Hakan. "Optimization Of Energy Harvesting Wireless Communication Systems." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613937/index.pdf.
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In an energy harvesting communication system, energy is derived from outside sources and becomes partially available at different points in time. The constraints induced by this property on energy consumption plays an active role in the design of efficient communication systems. This thesis focuses on the optimal design of transmission and networking schemes for energy harvesting wireless communication systems. In particular, an energy harvesting transmitter broadcasting data to two receivers in an AWGN broadcast channel assuming that energy harvests and data arrivals occur at known instants is considered. In this system, optimal
packet scheduling that achieves minimum delay is analyzed. An iterative algorithm, DuOpt, that achieves the same structural properties as the optimal schedule is proposed. DuOpt is proved to obtain the optimal solution when weaker user data is ready at the beginning. A dual problem is defined and shown to be strictly convex. Taking advantage of the dual problem, uniqueness of the solution of the main problem is proved. Finally, it is observed that DuOpt is almost two orders of magnitude faster than the SUMT (sequential unconstrained minimization technique) algorithm that solves the same problem.
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Ajibesin, Adeyemi Abel. "Novel approaches to performance evaluation and benchmarking for energy-efficient multicast: empirical study of coded packet wireless networks." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20323.
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With the advancement of communication networks, a great number of multicast applications such as multimedia, video and audio communications have emerged. As a result, energy efficient multicast in wireless networks is becoming increasingly important in the field of Information and Communications Technology (ICT). According to the study by Gartner and Environmental Protection Agency (EPA) report presented to United State Congress in 2007,energy consumption of ICT nodes accounts for 3% of the worldwide energy supply and is responsible for 2% of the global Carbon dioxide (CO2) emission. However, several initiatives are being put in place to reduce the energy consumption of the ICT sector in general. A review of related literature reveals that existing approaches to energy efficient multicast are largely evaluated using a single metric and while the single metric is appropriate for effective performance, it is unsuitable for measuring efficiency adequately. This thesis studied existing coded packet methods for energy efficiency in ad hoc wireless networks and investigates efficiency frontier, which is the expected minimum energy within the minimum energy multicast framework. The energy efficiency performance was based on effective evaluation and there was no way an inefficient network could reach a level of being an efficiency frontier. Hence, this work looked at the position of how true efficiency evaluation is obtained when the entire network under examination attains their efficiency frontiers using ratios of weighted outputs to weighted inputs with multiple variables. To address these challenges and assist network operators when formulating their network policies and performing network administrations, this thesis proposed novel approaches that are based on Data Envelopment Analysis (DEA) methodology to appropriately evaluate the efficiency of multicast energy and further minimizes energy transmission in ad hoc wireless networks without affecting the overall network performance. The DEA, which was used to study the relative efficiency and productivity of systems in Economic and Operational Research disciplines, is a non-parametric method that relies on linear programming technique for optimization of discrete units of observation called the decision making units (DMUs).
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Ozcelik, Fatih Mehmet. "Optimal And Implementable Transmission Schemes For Energy Harvesting Networks." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614636/index.pdf.
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Progress in energy harvesting technology and the increasing need for the energy efficient and environmentally friendly applications have called for reconsideration of communication systems. This reconsideration results in new problem formulations regarding the recent developments on energy harvesting systems. Recently, optimal strategies for various types of energy harvesting networks have been developed based on different harvesting models. This thesis reports the results of our research to develop the optimal scheduling structures on an energy harvesting broadcast and fading channels, and to devise online implementable algorithms for a
point-to-point communication system. Particularly, structural properties of an optimal offline schedule in, (1) an energy harvesting broadcast channel with one transmitter two receivers, (2) a single user communication system under fading conditions, are investigated. Moreover, an online algorithm is proposed for a single-user energy harvesting communication system considering the physical constraints and necessities regarding implementation. The proposed scheme is implemented through GNU Radio framework on a USRP device.
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Phan, V. V. (Vinh V. ). "Smart packet access and call admission control for efficient resource management in advanced wireless networks." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514276779.
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Abstract
Efficient management of rather limited resources, including radio spectrum and mobile-terminal battery power, has been the fundamental design challenge of wireless networks and one of the most widespread research problems over the years. MAC (Medium Access Control) for packet access and CAC (Call Admission Control) for connection-oriented service domains are commonly used as effective tools to manage radio resources, capacity and performance of wireless networks while providing adequate QoS (Quality of Service) to mobile users. Hence, analysis and synthesis of efficient MAC and CAC schemes for advanced wireless networks have significant academic and practical values. This dissertation addresses that topic and presents seven separate contributions of the author: four on adaptive MAC schemes for centralized PRN (Packet Radio Networks), referred to as SPA (Smart Packet Access) and three on CAC schemes for cellular networks, referred to as SCA (Smart Call Admission). These contributions are published in eighteen original papers by the author, which are listed and referred to as Papers I–XVIII in this thesis.
In SPA, the first contribution, reported in Papers II and IV, studies implementation losses of adaptive feedback-control MAC schemes for the uplink of DS-CDMA (Direct-Sequence Code Division Multiple Access) PRN in the presence of various system imperfections. The second contribution, reported in Papers XI, XII, XV and XVI, proposes a bit-rate adaptive MAC scheme for DS-CDMA PRN, referred to as SPR (Smart Packet Rate). The third contribution, reported in Papers III, XIII and XIV, develops two alternative MAC schemes with adaptive packet-length over correlated fading channels in DS-CDMA PRN, referred to as SPL (Smart Packet Length). The fourth contribution, reported in Papers XVII and XVIII, develops alternative adaptive MAC schemes for optimal trade-offs between throughput and energy consumption of TCP (Transmission Control Protocol) applications in advanced cellular networks. These include a so-called SPD (Smart Packet Dispatching) for HSPA (High Speed Packet Access) and, again, SPL for LSPA (Low Speed Packet Access).
Moving on to SCA, the first contribution, reported in Papers V and VII, provides a simple and accurate analytical method for performance evaluation of a class of fixed-assignment CAC schemes with generic guard-channel policy and queuing priority handoffs in cellular networks. The second contribution, reported in Papers VI, IX and X, proposes a simple and effective SCAC (Soft-decision CAC) scheme for CDMA cellular networks. This is evaluated against fixed-assignment and measurement-based CAC schemes with a simple and reliable method provided as a part of the contribution. The third contribution, reported in Papers I and VIII, incorporates alternative QoS differentiation paradigms and resource partitioning into CAC, defines GoS (Grade of Service) for multimedia cellular networks, and provides an in-hand tool for efficient capacity and GoS management.
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Bacinoglu, Tan Baran. "Finite-horizon Online Energy-efficient Transmissionscheduling Schemes Forcommunication Links." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615468/index.pdf.
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The proliferation of embedded systems, mobile devices, wireless sensor applications and in-
creasing global demand for energy directed research attention toward self-sustainable and
environmentally friendly systems. In the field of communications, this new trend pointed
out the need for study of energy constrained communication and networking. Particularly, in
the literature, energy efficient transmission schemes have been well studied for various cases.
However, fundamental results have been obtained mostly for offline problems which are not
applicable to practical implementations. In contrast, this thesis focuses on online counterparts
of offline transmission scheduling problems and provides a theoretical background for energy
efficient online transmission schemes. The proposed heuristics, Expected Threshold and Expected Water Level policies, promise an adequate solution which can adapt to short-time-scale
dynamics while being computationally efficient.
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Guegan, Loic. "Scalable end-to-end models for the time and energy performance of Fog infrastructures." Thesis, Rennes, École normale supérieure, 2021. http://www.theses.fr/2021ENSR0025.
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L'informatique géo-distribuée (Fog Computing) désigne la migration des ressources de calcul et de stockage du nuage (Cloud) vers les utilisateurs. Cette migration des ressources permet de réduire la latence des terminaux utilisateurs afin de répondre à l'évolution des usages de l'Internet. En parallèle, le nombre de terminaux ne cesse de croître avec le développement de l’Internet des objets. Cette croissance des infrastructures et du nombre d’objets connectés à Internet entraîne une hausse de la consommation électrique globale liée au numérique.Cependant, cette consommation est très distribuée et fait intervenir de multiples acteurs : objets connectés, réseaux locaux, fournisseurs d’accès à Internet, infrastructures de Fog et de Cloud. Il est ainsi difficile d’étudier l’impact de la croissance du nombre d’objets connectés sur la consommation électrique des infrastructures qui constituent l’Internet des objets.L’objectif de cette thèse est de proposer des modèles afin de permettre l’étude à grande échelle de la consommation énergétique des infrastructures Fog de manière efficace et reproductible. Les modèles proposés ont été intégrés à l’outil de simulation SimGrid afin d’être validés et diffusésFog Computing designates the migration of the computing and storage resources of the Cloud towards the edge of thenetwork. This resources migration allows to reduce the user’s nodes latency to answer to the evolution of the Internet usages. In parallel, the number of terminal is increasing with the development of the Internet Of Things. This infrastructures growth leads to an increase of the global energy consumption related to network infrastructures. However, this energy consumption is distributed and involved many actors such as: connected objects, local network, Internet Service Providers, Fog and Cloud infrastructures. Thus, it is difficult to study the impact of the connected objects growth on the infrastructures that composed the Internet of Things. The goal of this thesis is to propose models to study the energy consumption of large-scale Fog infrastructures in an efficient and reproducible manner. The proposed models have been integrated in the SimGrid simulation framework in order to be validated and spread
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Suciu, Ioana. "Energy aware optimization for low power radio technologies." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/668889.
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The explosive growth of IoT is pushing the market towards cheap, very low power devices with a strong focus on miniaturization, for applications such as in-body sensors, personal health monitoring and microrobots. Proposing procedures for energy efficiency in IoT is a difficult task, as it is a rapidly growing market comprised of many and very diverse product categories using technologies that are not stable, evolving at a high pace. The research in this field proposes solutions that go from physical layer optimization up to the network layer, and the sensor network designer has to select the techniques that are best for its application specific architecture and radio technology used. This work is focused on exploring new techniques for enhancing the energy efficiency and user experience of IoT networks. We divide the proposed techniques in frame and chip level optimization techniques, respectively. While the frame level techniques are meant to improve the performance of existing radio technologies, the chip level techniques aim at replacing them with crystal-free architectures.
The identified frame level techniques are the use of preamble authentication and packet fragmentation, advisable for Low Power Wide Area Networks (LPWANs), a technology that offers the lowest energy consumption per provided service, but is vulnerable in front of energy exhaustion attacks and does not perform well in dense networks. The use of authenticated preambles between the sensors and gateways becomes a defence mechanism against the battery draining intended by attackers. We show experimentally that this approach is able to reduce with 91% the effect of an exhaustion attack, increasing the device's lifetime from less than 0.24 years to 2.6 years. The experiments were conducted using Loadsensing sensor nodes, commercially used for critical infrastructure control and monitoring. Even if exemplified on LoRaWAN, the use of preamble authentication is extensible to any wireless protocol. The use of packet fragmentation despite the packet fits the frame, is shown to reduce the probability of collisions while the number of users in the duty-cycle restricted network increases. Using custom-made Matlab simulations, important goodput improvement was obtained with fragmentation, with higher impact in slower and denser networks. Using NS3 simulations, we showed that combining packet fragmentation with group NACK can increase the network reliability, while reducing the energy consumed for retransmissions, at the cost of adding small headers to each fragment. It is a strategy that proves to be effective in dense duty-cycle restricted networks only, where the headers overhead is negligible compared to the network traffic.
As a chip level technique, we consider using radios for communication that do not use external frequency references such as crystal oscillators. This would enable having all sensor's elements on a single piece of silicon, rendering it even ten times more energy efficient due to the compactness of the chip. The immediate consequence is the loss of communication accuracy and ability to easily switch communication channels. In this sense, we propose a sequence of frequency synchronization algorithms and phases that have to be respected by a crystal-free device so that it can be able to join a network by finding the beacon channel, synthesize all communication channels and then maintain their accuracy against temperature change. The proposed algorithms need no additional network overhead, as they are using the existing network signaling. The evaluation is made in simulations and experimentally on a prototype implementation of an IEEE802.15.4 crystal-free radio. While in simulations we are able to change to another communication channel with very good frequency accuracy, the results obtained experimentally show an initial accuracy slightly above 40ppm, which will be later corrected by the chip to be below 40 ppm.El crecimiento significativo de la IoT está empujando al mercado hacia el desarrollo de dispositivos de bajo coste, de muy bajo consumo energético y con un fuerte enfoque en la miniaturización, para aplicaciones que requieran sensores corporales, monitoreo de salud personal y micro-robots. La investigación en el campo de la eficiencia energética en la IoT propone soluciones que van desde la optimización de la capa física hasta la capa de red. Este trabajo se centra en explorar nuevas técnicas para mejorar la eficiencia energética y la experiencia del usuario de las redes IoT. Dividimos las técnicas propuestas en técnicas de optimización de nivel de trama de red y chip, respectivamente. Si bien las técnicas de nivel de trama están destinadas a mejorar el rendimiento de las tecnologías de radio existentes, las técnicas de nivel de chip tienen como objetivo reemplazarlas por arquitecturas que no requieren de cristales. Las técnicas de nivel de trama desarrolladas en este trabajo son el uso de autenticación de preámbulos y fragmentación de paquetes, aconsejables para redes LPWAN, una tecnología que ofrece un menor consumo de energía por servicio prestado, pero es vulnerable frente a los ataques de agotamiento de energía y no escalan frente la densificación. El uso de preámbulos autenticados entre los sensores y las pasarelas de enlace se convierte en un mecanismo de defensa contra el agotamiento del batería previsto por los atacantes. Demostramos experimentalmente que este enfoque puede reducir con un 91% el efecto de un ataque de agotamiento, aumentando la vida útil del dispositivo de menos de 0.24 años a 2.6 años. Los experimentos se llevaron a cabo utilizando nodos sensores de detección de carga, utilizados comercialmente para el control y monitoreo de infrastructura crítica. Aunque la técnica se ejemplifica en el estándar LoRaWAN, el uso de autenticación de preámbulo es extensible a cualquier protocolo inalámbrico. En esta tesis se muestra también que el uso de la fragmentación de paquetes a pesar de que el paquete se ajuste a la trama, reduce la probabilidad de colisiones mientras aumenta el número de usuarios en una red con restricciones de ciclos de transmisión. Mediante el uso de simulaciones en Matlab, se obtiene una mejora importante en el rendimiento de la red con la fragmentación, con un mayor impacto en redes más lentas y densas. Usando simulaciones NS3, demostramos que combinar la fragmentación de paquetes con el NACK en grupo se puede aumentar la confiabilidad de la red, al tiempo que se reduce la energía consumida para las retransmisiones, a costa de agregar pequeños encabezados a cada fragmento. Como técnica de nivel de chip, consideramos el uso de radios para la comunicación que no usan referencias de frecuencia externas como los osciladores basados en un cristal. Esto permitiría tener todos los elementos del sensor en una sola pieza de silicio, lo que lo hace incluso diez veces más eficiente energéticamente debido a la integración del chip. La consecuencia inmediata, en el uso de osciladores digitales en vez de cristales, es la pérdida de precisión de la comunicación y la capacidad de cambiar fácilmente los canales de comunicación. En este sentido, proponemos una secuencia de algoritmos y fases de sincronización de frecuencia que deben ser respetados por un dispositivo sin cristales para que pueda unirse a una red al encontrar el canal de baliza, sintetizar todos los canales de comunicación y luego mantener su precisión contra el cambio de temperatura. Los algoritmos propuestos no necesitan una sobrecarga de red adicional, ya que están utilizando la señalización de red existente. La evaluación se realiza en simulaciones y experimentalmente en una implementación prototipo de una radio sin cristal IEEE802.15.4. Los resultados obtenidos experimentalmente muestran una precisión inicial ligeramente superior a 40 ppm, que luego será corregida por el chip para que sea inferior a 40 ppm.
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Mostowfi, Mehrgan. "Improving the Energy Efficiency of IEEE 802.3az EEE and Periodically Paused Switched Ethernet." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3623.
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It is estimated that networked devices consumed about 150 TWh of electricity in 2006 in the
U.S. which has cost around $15 billion and contributed about 225 billion lbs of CO 2
to
greenhouse gas emissions. About 13.5% of this energy is consumed by network equipment such
as switches and routers.
This thesis addresses the energy consumption of Ethernet, and designs and evaluates
improvements on existing methods to reduce the energy consumption of Ethernet links and
switches.
Energy Efficient Ethernet (EEE) is an emerging IEEE 802.3 standard which allows Ethernet
links to sleep when idle. In this thesis, a performance evaluation of EEE is completed. This
evaluation replicates previous work by Reviriego et al. in an independent manner. The
performance evaluation shows that EEE overhead results in less energy savings than expected. A
new method based on Packet Coalescing is developed and evaluated to improve the energy
efficiency of EEE. Packet Coalescing bursts packets such that EEE overhead is minimized. The
results show that EEE with Packet Coalescing for 10 Gb/s Ethernet can achieve very close to
ideal (or energy proportional) performance at the expense of an insignificant added per
packet delay.
Periodically Paused Switched Ethernet (PPSE) was previously proposed and prototyped by
Blanquicet and Christensen in 2008. PPSE uses periodically sent notification packets to halt
packet transmission into a LAN Switch and thus allowing the switch to sleep periodically. In this
thesis, a first performance evaluation of PPSE is completed. The evaluation in this thesis shows
that a PPSE for 10 Gb/s Ethernet LAN Switches achieves either significant energy savings at the
expense of an excessive packet delay, or less than expected savings with a less than human
response time added per-packet delay. An improvement to PPSE (Adaptive PPSE) is proposed
and developed based on an adaptive policy. The adaptive policy considers past traffic load to
determine whether to put the switch to sleep or not. The evaluation shows that Adaptive PPSE
can achieve very close to ideal performance at the expense of an added average per packet delay
which is less than half of the human response time.
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Antepli, Mehmet Akif. "A Study On Certain Theoretical And Practical Problems In Wireless Networks." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612603/index.pdf.
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The aim of the thesis is to investigate the design of efficient wireless networks through practical as well as theoretical considerations.
We constructed a wireless sensor network (WSN) testbed with battery operated nodes capable of RF communication. The system is a centralized tree-based WSN to study challenges of target modeling, detection, and localization. The testbed employed magnetic sensors, on which relatively few results have been reported in the literature. A ferrous test target is modeled as magnetic dipole by validating experimentally. The problem of sensor sensitivity variation is addressed by including sensitivity estimates in model validation. After reliably detecting the target, maximum-likelihood and least-squares techniques are applied for localization. Practical considerations of constructing a WSN utilizing magnetic sensors addressed.
Maximum-lifetime operation of these networks requires joint consideration of sensing and communication. Energy harvesting is promising to overcome this major challenge for energy-constrained systems. In the second part of the thesis, we considered the minimization of transmission completion time for a given number of bits per user in an energy harvesting multiuser communication system, where the energy harvesting instants are known beforehand. The two-user case with achievable rate region having structural properties satisfied by the AWGN Broadcast Channel is studied. It is shown that the optimal scheduler ends transmission to both users at the same time while deferring a nonnegative amount of energy from each energy harvest for later use. The problem is formulated as an optimization problem and solved by exploiting its special structure.
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Haneberg-Diggs, Dominique Miguel. "Seismic attributes of the Clinton interval reservoir in the Dominion East Ohio Gabor gas storage field near North Canton, Ohio." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1418759184.
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Samoud, Wiem. "Analyse de performance d'un commutateur de paquets hybride opto-électronique." Thesis, Paris, ENST, 2016. http://www.theses.fr/2016ENST0058/document.
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La fibre optique demeure le support de transmission le plus utilisé, portant le trafic à une énergie par bit relativement faible. Cependant, à cause de l’absence de mémoire toutoptique pratique, la commutation de paquets est toujours exécutée électriquement. Les conversions Optiques Électriques Optiques (O-E-O) nécessaires font de la commutation l’un des domaines les plus consommateurs d’énergie. Ce problème est de plus en plus important spécialement avec la croissance exponentielle du trafic dans les réseaux optiques. Un défi majeur à prendre en considération dans la conception de futurs réseaux optiques est la restriction de leur consommation énergétique. De ce fait, dans le cadre de cette thèse, nous étudions un commutateur hybride opto-électronique qui consiste en une matrice de commutation optique complétée par une mémoire électronique partagée. L’analyse de performance prenant en compte différentes classes de service, distributions de paquets et méthodes de connectivité du commutateur (canaux WDMet/ou SDM), montre que, grâce aux stratégies de commutation établies, le commutateur hybride répond aux besoins de toutes les classes de service en termes de taux de perte de paquets, la charge durable du système et la latence. De plus, il réduit significativement les conversions O-E-O par rapport aux commutateurs électriques commercialisés, puisqu’ils n’auront lieu que pour les paquets mis en mémoire d’attente. Nous défendons que le commutateur de paquets hybride opto-électronique satisfait les exigences en qualité de service et pourrait être une solution prometteuse pour réduire la consommation d’énergie des réseaux optiquesMost transmission systems are based on optical fibers, carrying the traffic at a relatively low energy per bit. However, due to the lack of mature optical buffers, packet switching is still performed electrically. The required Optical-Electrical-Optical (O-E-O) conversions make the switching one of the areas with the fastest-growing energy consumption. A major challenge that must be met in designing future optical networks is curbing their energy consumption. Therefore, within this thesis, we investigate a hybrid optoelectronic switch which consists of an optical switching matrix supplemented with a shared electronic buffer. Performance analysis taking into account different classes of service, packet classifications and switch connectivity methods (WDM and/or SDM channels), shows that, thanks to the established switching strategies, the hybrid switch satisfies the requirements of all the different classes of service in terms of Packet Loss Rate, sustainable system load and latency. Moreover, it significantly reduces the O-E-O conversions compared to commercial off-the-shelf electrical switches, since they occur only for buffered packets. We defend that the hybrid opto-electronic packet switch meets the requirements on quality of service and could be a promising solution to reduce the energy consumption of optical networks
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Chibumba, Aubrey Muyeke. "Characterisation of thermal coefficients in packed beds." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303543.
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Hall, Stephen. "Optimisation of biogas production from percolating packed bed anaerobic digesters." Thesis, University of South Wales, 1986. https://pure.southwales.ac.uk/en/studentthesis/optimisation-of-biogas-production-from-percolating-packed-bed-anaerobic-digesters(6825c6bf-4ee7-439e-832a-28aa8b7cd4d3).html.
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Percolating packed bed digesters were operated successfully in a batch mode using a wheat straw - dairy manure substrate of between 21 and 27% total solids. The vessels used had a nominal 10 1 volume and were constructed of perspex. Temperatures of 25-35°C were used, recirculation rates of 0-15 litres.hr-1 (the digesters having a diameter of 0.18 metres thus corresponding to superficial flow rates of between O and 0.382 l/m2 /hr), solid : liquid ratios of 1:1 to 4:1 and bed heights of 0.26 to 2.05 metres. The optima found were a temperature of 35°C, recirculation rate of 3 litres.hr1-, a solid: liquid ratio of 2:1 and a bed height of 1.5 metres. Experiments were conducted for periods of up to 70 days, though operation beyond a 40 day period was found to produce little extra biogas. The performance compared favourably with other high solids waste digesters with gas yields of 0.305 m 3 /kg VS added and solids losses of 47% volatile solids and 64% cellulose being obtained over a 40 day period. No major problems of inhibition or blocking occurred. Linking of digesters in series via their recirculation systems was found to be advantageous. Gas yields were found to be increased by approximately 18% and solids losses increased by approximately 20% when the waste was treated in this semicontinuous manner. These increases were found to be a result of the rapid transfer of well-adapted bacteria to the fresh digester. Lag phase in the fresh digester was reduced by three days and potentially inhibitory levels of volatile fatty acids were not present. Concentrations of up to around 5000 ppm VFAs were found during the start-up of batch digesters causing some inhibition of gas production. During semi-continuous operation however concentrations of around 2000 ppm were developed when fresh digesters were linked in, no inhibition occurred and in fact this concentration proved stimulatory to gas production. Experimentation into the optimum retention time of a maximum of three digesters in series was conducted, with retention times of 90, 60 and 30 days being considered. A 30 day retention period was found to depress gas production due to unstable conditions when fresh digesters were added by up to 32% compared with Batch Operation. Gas production was increased at both 60 and 90 day retention times by amounts similar to those previously stated. A retention time of 60 days was found to be optimum as little extra gas was produced after this time, with volatile solids losses being increased by only 9.3% by operating for a further 30 days. Colonisation of the solid substrate was shown to be rapid, by the use of adenosine 51 triphosphate analysis, gas production rate and electron microscope analysis. In addition a dynamic bacterial population appeared to be present in the solid phase with the rates of growth and attachment being approximately equal to the rates of decay and detachment. When digesters were operating in their steady phase, methanogens were present in the liquor at concentrations of between 10 6 - 10 7 /ml and non-methanogens at between 10 7 - 108 /ml showing a large population of bacteria to be present for the inoculation of fresh digesters.
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Abou-Ziyan, H. Z. Z. "Heat and momentum transfer in porous material used for thermal energy storage." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233826.
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Edwards, Jacob N. "Thermal energy storage for nuclear power applications." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/36238.
Full textAbstract:
Master of ScienceDepartment of Mechanical and Nuclear Engineering
Hitesh Bindra
Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.
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Maidadi, Mohaman Bello. "Packed-bed rock thermal energy storage for concetrated solar power: enhancement of storage time and system efficiency." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020914.
Full textAbstract:
Solar thermal energy harvesting is a promising solution to offset the electricity demands of a growing population. The use of the technology is however still limited and this can most likely be attributed to the capital cost and also the intermittent nature of solar energy which requires incorporation of a storage system. To make the technology more attractive and effective, cheap means of harvesting solar energy and the development of efficient and inexpensive thermal energy storage devices will improve the performance of solar energy systems and the widespread use of solar energy. Heat storage in a packed-bed rock with air as the working fluid presents an attractive and simple solution for storing solar thermal energy and it is recommended for solar air heaters. A packed-bed rock storage system consists of rocks of good heat capacity packed in a storage tank. The working fluid (air) flows through the bed to transfer its energy. The major concern of the design for a packed-bed rock thermal storage system is to maximize the heat transfer and minimise the pressure drop across the storage tank and hence the pumping power. The time duration the stored energy can be preserved and the air flow wall effect through the bed are the common complications encountered in this system. This study presents an experimental and analytical analysis of a vacuum storage tank with the use of expanded perlite for high temperature thermal energy storage in a packed-bed of rocks. Dolerite rocks are used as the storage medium due to their high heat capacity and as they are locally available. To minimise the pressure drop across the tank, moderate rock sizes are used. The tank contains baffles, allowing an even spread of air to rock contact through the entire tank, therefore improving heat transfer. There is a good correlation between the predicted and the actual results (4 percent) which implies that the baffles incorporated inside the vacuum tank forces the air through the entire tank, thereby resulting in an even lateral temperature distribution across the tank. The investigation of heat loss showed that a vacuum with expanded perlite is a viable solution to high temperature heat storage for an extended period. The research also focuses on the investigation of a proposed low cost parabolic trough solar collector for an air heating system as shown in Figure (1.3). The use of a standard solar geyser evacuated tube (@R130 each) has cost benefits over the industry standard solar tubes normally used in concentrating solar power systems. A mathematical was developed to predict the thermal performance of proposed PTC and it was found that the measured results compared well with the predictions. The solar energy conversion efficiency of this collector is up to 70 percent. This research could impact positively on remote rural communities by providing a source of clean energy, especially for off-grid applications for schools, clinics and communication equipment. It could lead to a significant improvement in the cost performance, ease of installation and technical performance of storage systems for solar heating applications.
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Allen, Kenneth Guy. "Performance characteristics of packed bed thermal energy storage for solar thermal power plants." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4329.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Solar energy is by far the greatest energy resource available to generate power. One of the difficulties of using solar energy is that it is not available 24 hours per day - some form of storage is required if electricity generation at night or during cloudy periods is necessary. If a combined cycle power plant is used to obtain higher efficiencies, and reduce the cost of electricity, storage will allow the secondary cycle to operate independently of the primary cycle. This study focuses on the use of packed beds of rock or slag, with air as a heat transfer medium, to store thermal energy in a solar thermal power plant at temperatures sufficiently high for a Rankine steam cycle. Experimental tests were done in a packed bed test section to determine the validity of existing equations and models for predicting the pressure drop and fluid temperatures during charging and discharging. Three different sets of rocks were tested, and the average size, specific heat capacity and density of each set were measured. Rock and slag samples were also thermally cycled between average temperatures of 30 ºC and 510 ºC in an oven. The classical pressure drop equation significantly under-predicts the pressure drop at particle Reynolds numbers lower than 3500. It appears that the pressure drop through a packed bed is proportional to the 1.8th power of the air flow speed at particle Reynolds numbers above about 500. The Effectiveness-NTU model combined with a variety of heat transfer correlations is able to predict the air temperature trend over the bed within 15 % of the measured temperature drop over the packed bed. Dolerite and granite rocks were also thermally cycled 125 times in an oven without breaking apart, and may be suitable for use as thermal storage media at temperatures of approximately 500 ºC. The required volume of a packed bed of 0.1 m particles to store the thermal energy from the exhaust of a 100 MWe gas turbine operating for 8 hours is predicted to be 24 × 103 m3, which should be sufficient to run a 25-30 MWe steam cycle for over 10 hours. This storage volume is of a similar magnitude to existing molten salt thermal storage.
AFRIKAANSE OPSOMMING: Sonenergie is die grootste energiebron wat gebruik kan word vir krag opwekking. ‘n Probleem met die gebruik van sonenergie is dat die son nie 24 uur per dag skyn nie. Dit is dus nodig om die energie te stoor indien dit nodig sal wees om elektrisiteit te genereer wanneer die son nie skyn nie. ‘n Gekombineerde kringloop kan gebruik word om ‘n hoër benuttingsgraad te bereik en elektrisiteit goedkoper te maak. Dit sal dan moontlik wees om die termiese energie uit die primêre kringloop te stoor, wat die sekondêre kringloop onafhanklik van die primêre kringloop sal maak. Dié gevalle studie ondersoek die gebruik van ‘n slakof- klipbed met lug as hitteoordragmedium, om te bepaal of dit moontlik is om hitte te stoor teen ‘n temperatuur wat hoog genoeg is om ‘n Rankine stoom kringloop te bedryf. Eksperimentele toetse is in ‘n toets-bed gedoen en die drukverandering oor die bed en die lug temperatuur is gemeet en vergelyk met voorspelde waardes van vergelykings en modelle in die literatuur. Drie soorte klippe was getoets. Die gemiddelde grootte, spesifieke hitte-kapasiteit en digtheid van elke soort klip is gemeet. Klip en slak monsters is ook siklies tussen temperature van 30 ºC en 510 ºC verkoel en verhit. Die klassieke drukverlies vergelyking gee laer waardes as wat gemeet is vir Reynolds nommers minder as 3500. Dit blyk dat die drukverlies deur ‘n klipbed afhanklik is van die lug vloeispoed tot die mag 1.8 as die Reynolds nommer groter as omtrent 500 is. Die ‘Effectiveness-NTU’ model gekombineerd met ‘n verskeidenheid van hitteoordragskoeffisiënte voorspel temperature binne 15 % van die gemete temperatuur verskil oor die bed. Doloriet en graniet klippe het 125 sikliese toetse ondergaan sonder om te breek, en is miskien gepas vir gebruik in ‘n klipbed by temperature van sowat 500 ºC Die voorspelde volume van ‘n klipbed wat uit 0.1 m klippe bestaan wat die termiese energie vir 8 ure uit die uitlaat van ‘n 100 MWe gasturbiene kan stoor, is 24 × 103 m3. Dit behoort genoeg te wees om ‘n 25 – 30 MWe stoom kringloop vir ten minste 10 ure te bedryf. Die volume is min of meer gelyk aan dié van gesmelte sout store wat alreeds gebou is.
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Bang, Jang Young. "Generalized uncertainty principle and Gaussian wave packets in discrete quantum phase space." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3380062.
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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2009.Title from PDF t.p. (viewed on Jul 19, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7630. Adviser: Micheal S. Berger.
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Yeboah, Siegfried Kwame. "An integrated packed bed-oscillating heat pipe system for energy efficient isothermal adsorption processes." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/48342/.
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Energy use in buildings accounts for a large portion of global and regional energy demand and energy-related CO2 emissions. To steer the world towards a low carbon future, the development of new and more efficient technologies is required. In hot and humid climates, the high latent heat loads results in uncomfortable and unhealthy indoor environments, accounting for 30% to 50% of standard air conditioning energy requirements. Physical adsorption of water vapour on solid desiccants is found to offer an energy efficient alternative to conventional dehumidification process using standard air conditioning systems. However, the isosteric heat of adsorption released increases the surface vapour pressure of the solid desiccants resulting in a decreased adsorption capacity. In packed beds of solid desiccants, this heat of adsorption increases the bed temperature, exit air temperature and exit air humidity ratio subsequently imposing an increased cooling load requirement and high energy requirement in the regeneration of the solid desiccants. In literature, several approaches used in removing in situ the heat of adsorption released in packed bed systems were fraught with several limitations. To this end, an integrated packed bed-oscillating heat pipe (OHP) system was proposed. The concept was for the evaporator of the OHP to remove the heat of adsorption generated by the packed bed and reject at its condenser towards an energy efficient isothermal adsorption process. To achieve this, theoretical investigations of the individual systems and the integrated systems preceded experimental testing of a rig set up in the laboratory. For the theoretical studies, the OHP was helically coiled at both ends, filled with ethanol, methanol and water working fluids respectively at 50% volume fraction and numerically investigated using the Eulerian Volume of Fluid (VOF) model in ANSYS Fluent R15.0. The packed bed on the other hand was configured as a Heggs et al (1994) Z-type flow arrangement for enhanced radial flow using the Porous Media model in ANSYS Fluent R15.0 set up with the properties of Silica Gel. ANSYS Fluent R15.0 System Coupling limitations led to the development of mathematical models for the prediction of the integrated system performance. The experimental investigations were in line with the theoretical only in this case the optimum working fluid, deionized water, was used as the main working fluid in the helically coiled OHP (HCOHP). The results showed reasonable agreement between the performance of the numerical model and experimental prototype. The HCOHPs were capable of passively removing heat from the packed bed systems. Mean bed temperature reduction between the integrated packed bed-HCOHP system and corresponding individual packed bed configurations were about 5.61°C, 9.48°C and 10.14°C respectively for the large annulus (LAPB), medium annulus (MAPB) and small annulus (SAPB) packed bed configurations. Average packed bed outlet temperature reductions of about 6.61°C, 9.19°C and 6.29°C were also achieved for the respective configurations. A validation of the theoretical model showed average temperature difference of about 5.60°C between the experimental prototype of the integrated system and results predicted using experimental packed bed temperature data and HCOHP thermal resistance. Compared to other similar systems in literature, the integrated packed bed-HCOHP system showed capacity to passively remove significant amounts of the heat of adsorption released in silica gel packed beds towards isothermal adsorption.
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Grüner, Barbara, Martin Schlesinger, Philipp Heister, Walter T. Strunz, Frank Stienkemeier, and Marcel Mudrich. "Vibrational relaxation and dephasing of Rb2 attached to helium nanodroplets." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138750.
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The vibrational wave-packet dynamics of diatomic rubidium molecules (Rb2) in triplet states formed on the surface of superfluid helium nanodroplets is investigated both experimentally and theoretically. Detailed comparison of experimental femtosecond pump–probe spectra with dissipative quantum dynamics simulations reveals that vibrational relaxation is the main source of dephasing. The rate constant for vibrational relaxation in the first excited triplet state 13Σ+g is found to be constant γ ≈ 0.5 ns−1 for the lowest vibrational levels v [less, similar] 15 and to increase sharply when exciting to higher energiesDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Krist, Thomas. "Optimalizace zásobníku tepla typu "packed bed"." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417062.
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Tato diplomová práce se zabývá tématem výměny tepla v zásobníku tepla typu ”packed bed”. Cílem je popsat přenos tepla v zásobníku tepla obsahující kamínky malých průměrů, skrz který proudí horký vzduch. Toto je modelováno v prostředí MATLAB. Na začátku je krátký úvod do problematiky zahrnující ukládání tepla a jeho možné využití. Dále je uveden krátký přehled o základech přenosu tepla, typech přenosu tepla a termofyzikální vlastnosti systému vzduch-kámen. Ve třetí kapitole je představen zásobník tepla typu ”packed bed” a rozličné modely a dané podmínky jsou vysvětleny. Další kapitola se zabývá s numerickými metodami, převážně s metodou konečných diferencí použitou v této práci. Pátá kapitola se zaměřuje na obecnou optimalizaci daného problému přenosu tepla. Populačně založený metaheuristický optimalizační algoritmus zvaný Genetický algoritmus je popsán. Sestavení modelu je ukázáno v šesté kapitole, stejně jako prezentace výsledků získaných z programu MATLAB. V poslední kapitole je pak diskutován závěr a doporučení.
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Rohrdanz, Mary A. "Intermolecular communication via lattice phonons, probed by ultrafast spectroscopy /." view abstract or download file of text, 2005. http://wwwlib.umi.com/cr/uoregon/fullcit?p3190543.
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Thesis (Ph. D.)--University of Oregon, 2005.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 79-80). Also available for download via the World Wide Web; free to University of Oregon users.
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Gamble, Stephanie Nicole. "Conical Intersections and Avoided Crossings of Electronic Energy Levels." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/101899.
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We study the unique phenomena which occur in certain systems characterized by the crossing or avoided crossing of two electronic eigenvalues. First, an example problem will be investigated for a given Hamiltonian resulting in a codimension 1 crossing by implementing results by Hagedorn from 1994. Then we perturb the Hamiltonian to study the system for the corresponding avoided crossing by implementing results by Hagedorn and Joye from 1998. The results from these demonstrate the behavior which occurs at a codimension 1 crossing and avoided crossing and illustrates the differences. These solutions may also be used in further studies with Herman-Kluk propagation and more.
Secondly, we study codimension 2 crossings by considering a more general type of wave packet. We focus on the case of Schrödinger equation but our methods are general enough to be adapted to other systems with the geometric conditions therein. The motivation comes from the construction of surface hopping algorithms giving an approximation of the solution of a system of Schrödinger equations coupled by a potential admitting a conical intersection, in the spirit of Herman-Kluk approximation (in close relation with frozen/thawed approximations). Our main Theorem gives explicit transition formulas for the profiles when passing through a conical crossing point, including precise computation of the transformation of the phase and its proof is based on a normal form approach.Doctor of Philosophy
We study energies of molecular systems in which special circumstances occur. In particular, when these energies intersect, or come close to intersecting. These phenomena give rise to unique physics which allows special reactions to occur and are thus of interest to study. We study one example of a more specific type of energy level crossing and avoided crossing, and then consider another type of crossing in a more general setting. We find solutions for these systems to draw our results from.
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Grüner, Barbara, Martin Schlesinger, Philipp Heister, Walter T. Strunz, Frank Stienkemeier, and Marcel Mudrich. "Vibrational relaxation and dephasing of Rb2 attached to helium nanodroplets." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27778.
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The vibrational wave-packet dynamics of diatomic rubidium molecules (Rb2) in triplet states formed on the surface of superfluid helium nanodroplets is investigated both experimentally and theoretically. Detailed comparison of experimental femtosecond pump–probe spectra with dissipative quantum dynamics simulations reveals that vibrational relaxation is the main source of dephasing. The rate constant for vibrational relaxation in the first excited triplet state 13Σ+g is found to be constant γ ≈ 0.5 ns−1 for the lowest vibrational levels v [less, similar] 15 and to increase sharply when exciting to higher energies.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Al-Chalaby, K. A. J. "Heat transfer in a packed bed using a fluid near its critical point for solar energy applications." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377058.
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Alam, Tanvir E. "Experimental Investigation of Encapsulated Phase Change Materials for Thermal Energy Storage." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5632.
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Thermal energy storage (TES) is one of the most attractive and cost effective solutions to the intermittent generation systems like solar, wind and other renewable sources, compared to alternatives. It creates a bridge between the power supply and demand during peak hours or at times of emergency to ensure the continuous supply of energy. Among all the TES systems, latent heat thermal energy storage (LHTES) draws lots of interests as it has high energy density and can store or retrieve energy isothermally. Two major technical challenges associated with the LHTES are low thermal conductivity of the phase change materials (PCMs), and corrosion tendency of the containment vessel with the PCMs. Macro-encapsulation of the PCM is one of the techniques to encounter the low thermal conductivity issue as it will maximize the heat transfer area for the given volume of the PCM and restrict the PCMs to get in contact with the containment vessel. However, finding a suitable encapsulation technique that can address the volumetric expansion problem and compatible shell material are significant barriers of this approach.
In the present work, an innovative technique to encapsulate PCMs that melt in the 100-350 oC temperature range was developed for industrial and private applications. This technique did not require a sacrificial layer to accommodate the volumetric expansion of the PCMs on melting. The encapsulation consisted of coating a non-reactive polymer over the PCM pellet followed by deposition of a metal layer by a novel non-vacuum metal deposition technique. The fabricated spherical capsules were tested in different heat transfer fluid (HTF) environments like air, oil and molten salt (solar salt). Thermophysical properties of the PCMs were investigated by DSC/TGA, IR and weight change analysis before and after the thermal cycling. Also, the constrained melting and solidification of sodium nitrate PCM inside the spherical capsules of different sizes were compared to explore the charging and discharging time. To accomplish this, three thermocouples were installed vertically inside the capsule at three equidistant positions. Low-density graphene was dispersed in the PCM to increase its conductivity and compared with pure PCM capsules.
A laboratory scale packed-bed LHTES system was designed and built to investigate the performance of the capsules. Sodium nitrate (m.p. 306oC) was used as the PCM and air was used as the heat transfer fluid (HTF). The storage system was operated between 286oC and 326oC and the volumetric flow rate of the HTF was varied from 110 m3/h to 151 m3/h. The temperature distribution along the bed (radially and axially) and inside the capsules was monitored continuously during charging and discharging of the system. The effect of the HTF mass flow rate on the charging and discharging time and on the pressure drop across the bed was evaluated. Also, the energy and exergy efficiencies were calculated for three different flow rates.
Finally, a step-by-step trial manufacturing process was proposed to produce large number of spherical capsules.
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Rashidian, Babak. "Deflector effects in fixed bed (biomass) combustors and non-combusting packed beds." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1937.
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Combustion can be used to thermally process biomass fuels and yield both heat and power in a sustainable manner. At present, direct combustion of solid biomass is the primary approach for generating electricity and heat when these fuels are used at a commercial scale.
Deflectors have been used in the freeboard section of industrial combustors to reduce radiant heat loss through flue gases and for particle emissions abatement. Freeboard deflectors can also influence emissions and freeboard temperature distributions by changing the flow dynamics. Despite much research into laboratory scale biomass combustion and packed beds, there have been no systematic studies into the impact of deflectors (heat shields) on the axial and radial temperature profiles, test methodologies used or the emissions in laboratory scale fixed bed biomass combustors operated on pelletised fuels.
Through a combination of experiments and numerical simulations, this research has investigated such issues in both high temperature fixed bed biomass combustors as well as relatively lower temperature (non-combusting) packed beds subject to different heating modes.
Experiments have been carried out on a laboratory scale (continuous feed) fixed bed combustor featuring both primary air (supplied through the fuel bed) as well as secondary air (in the freeboard). A freeboard deflector was located at different axial locations during this testing. The aim was to characterize deflector effects on burning rate, temperature distribution (near-wall and near-centreline) and gaseous emissions (NO, CO, CO2) over a range of primary and secondary air flow rates. A systematic method has been developed to establish the steady state time period during the combustion process. In this regard, detailed analyses on the time series of thermocouples, emissions and fuel mass conversion data have been performed. The proposed method is based on calculating the percentile mean deviation of temperature and NO/CO emissions data which can provide a more effective means of resolving the stand of the steady state operating, compared to only using the time evolution of these variables. In addition, the significance of the thermocouple radiative corrections (losses) and its effect on the accuracy of measured temperatures has been investigated. The results concluded that NO, CO and CO2 emissions are affected by the presence of a deflector in the mid-range of combustion stoichiometry (λ=0.439-0.509). However, deflector effects were found to be most prominent for NO and CO emissions by reducing and rising their levels, respectively. Deflectors affect upstream near-wall temperatures, but their impact depends on relative (axial) position (H). Furthermore, results reveal that deflectors do not have significant effects on the burning rate and flow availability of the exhaust gases.
A CFD model of a porous media has been implanted to study the effects of freeboard deflectors on the heat transfer inside packed bed columns for the temperature range of 100°C to 400°C (which is typical for drying and volatile release in biomass combustion). Results show that the deflector do affect temperature profiles along the freeboard as well as wall temperatures but this is dependent on the mode of heating and emissivity of the deflector.
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Nyman, Johan, and Amy Rankka. "Energy Efficient, Electric-Hydraulic Power Pack." Thesis, Linköpings universitet, Fordonssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119477.
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Along with increased oil prices and rising environmental issues, a demand for alternatives to combustion engine driven hydraulic applications has risen. In the field of mobile hydraulics, the hydraulic applications have traditionally been driven by the combustion engine of the vehicle on which they are mounted. By instead using a battery driven power pack the hydraulic application is able to operate without the engine running, saving fuel costs and reducing sound levels. In this thesis, the concept of using an electric-hydraulic power pack with a variable-speed electric motor and a fixed-displacement hydraulic pump to provide power to a truck-mounted loader crane is investigated. This concept is compared to an electric-hydraulic system imitating the conventional combustion engine system by using a fixed-speed electric motor connected to a variable-displacement pump. The use of a variable speed motor where the speed can be controlled electrically by a control unit creates possibilities of using different control strategies to improve the efficiency and responsiveness of the application. The efficiencies of the two electric-hydraulic systems are compared by constructing a physical test rig and performing measurements in a test lab. The tests have shown an increased efficiency of about 20 \% when using the variable speed configuration. Three different control strategies are also investigated and tested on a simulated model. The simulations show that very good responsiveness and robustness can be achieved by using a hydraulic flow feed forward controller with a complementary pressure feedback controller. Furthermore, by controlling the hydraulic flow to the heaviest of the crane loads entirely with the flow from the hydraulic pump, the hydraulic pressure can be reduced and energy efficiency increased.
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Prenzel, Marco [Verfasser]. "Scale-up of horizontal packed bed thermal energy storage units: An in-depth experimental and numerical investigation / Marco Prenzel." Düren : Shaker, 2021. http://d-nb.info/1233548050/34.
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Diego, García Ramón Ignacio. "Análisis wavelet aplicado a la medida de armónicos, interarmónicos y subarmónicos en redes de distribución de energía eléctrica." Doctoral thesis, Universidad de Cantabria, 2006. http://hdl.handle.net/10803/10636.
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El análisis de Fourier es el método fundamental para la medida de armónicos e interarmónicos en señales eléctricas y es el principio de análisis que establece la International Electrotechnical Commission para los instrumentos de medida. Con el objetivo de superar las limitaciones que lo hacen poco efectivo en determinadas condiciones se han propuesto otras técnicas de análisis como las wavelets. En esta tesis doctoral se explora esta alternativa en el campo de la calidad del suministro de energía eléctrica.Como aportación principal se presenta un nuevo método de medida de armónicos e interarmónicos basado en la Transformada Wavelet Packet compatible con el estándar de medida IEC 61000-4-7 de 2002. El método propuesto utiliza un árbol de descomposición wavelet, que en sus distintos niveles suministra la medida de armónicos e interarmónicos de la señal, así como su contenido subarmónico e información de sus variaciones en el dominio temporal.Se exponen las características principales del método en cuanto a la elección de la función wavelet madre, el banco de filtros que implementa el árbol de descomposición wavelet y el postprocesado que posibilita la compatibilidad con el estándar de medida. Se analizan las prestaciones del método en la medida de armónicos e interarmónicos, tanto en condiciones estacionarias como en el caso de pérdida de sincronía por variación de la frecuencia fundamental o variación de la ventana de muestreo de la señal, presencia de componentes no síncronas con la frecuencia de la red o presencia de componentes de amplitud variable. Por último, se expone la información que aporta el método para la estimación temporal de las componentes frecuenciales medidas.El método desarrollado junto con el método de IEC, se ha implementado sobre un equipo electrónico para adquisición y procesado de señal utilizando técnicas de instrumentación virtual. Se expone la estructura y características del hardware utilizado y del software desarrollado así como los resultados obtenidos en la medida del espectro frecuencial de señales de diferente naturaleza.Por último se resumen las conclusiones obtenidas y se proponen futuras líneas de investigación motivadas por la realización de esta tesis doctoral.Fourier analysis is the fundamental method for the measurement of harmonics and interharmonics in electrical power systems and is the method proposed by the International Electrotechnical Commission (IEC) for standard measurement instruments. With the objective of overcoming the limitations in certain conditions, other techniques of analysis such as wavelets have been proposed. This doctoral thesis investigates alternatives in the field of the quality of the provision of electrical energy. The main contribution of this thesis is the proposal of a new method of measurement of harmonics and interharmonics based on the Wavelet Packet Transform compatible with the standard IEC 61000-4-7 of 2002. The method proposed simultaneously uses different levels of the same wavelet decomposition tree for the measurement of harmonic, interharmonic and subharmonic components in the input signal as well as their time evolution.The basic characteristics of the method in terms of the choice of the mother wavelet function, the bank of filters that implements the wavelet decomposition tree and the postprocessing to make the method compatible with the measurement standard are explained. The benefits of the method in the measurement of harmonics and interharmonics are analyzed, both in stationary conditions and in the case of loss of synchrony due to variation of the base frequency or variation of the sampling window of the signal, presence of nonsynchronous components with the frequency of the network or presence of components of variable amplitude. Finally, the information that the method provides about the temporal estimation of the measured frequencial components is described.The method developed and the IEC method have been implemented on a virtual instrument. The hardware used and the software developed are explained studying the performance of the instrument under different measurement conditions.Finally the conclusions obtained are summarized and future lines of investigation motivated by this doctoral thesis are proposed.
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Bäckebo, Markus. "The influence of particle size distribution on bio-coal gasification rate as related to packed beds of particles." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79084.
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This thesis is a part of a collaboration between Höganäs AB and Luleå University of Technology, aiming at replacing fossil process coal with bio-coal in their sponge iron process. The difference in gasification reactivity, i.e. reaction rate, between fossil coals and bio-coals is the major challenge in the endeavor to decrease the climate impact of the existing process. The goal of this thesis is to develop a model of reaction rate for bio-coals in relation to particle size distribution. Different particle size distributions were combined and tested to see how that affects the effective reaction rate. Within the scope of this work, gasification reactivities of different materials, including coal, cokes, and bio-coals, were determined. Three bio-coals were selected to study the effect of particle size distribution on reactivity. Kinetic parameters were determined by using thermogravimetric analysis in the temperature range of 770-850 °C while varying CO2 partial pressure between 0.1-0.4 atm. The effect of particle size on the reaction rate was investigated by using particles with diameter between 0.18 and 6.3 mm. The effect of particle size distribution on the reactivity of bio-coal in a packed bed was carried out in a macro thermogravimetric reactor with a constant bed volume of 6.5 cm3 at 980 °C and 40% (vol.) of CO2. The experimental investigation in three different rate-limiting steps was done for one bio-coal sample, i.e. Cortus Bark bio-coal. The activation energy of the bio-coal was 187 kJ mol-1, and the reaction order was 0.365. For the internal diffusion control regime, an increase in particle size resulted in low reaction rate. The effective diffusivity calculated from the Thiele modulus model was 1.41*10-5 m2 s-1. For the external diffusion control regime, an increase in particle size increased the reaction rate up to a certain point where it plateaued at >1 mm. By choosing two discrete particle size distributions, where a smaller average distribution can fit into a larger average distribution the reaction rate was lowered by 30% compared to only using a single narrow particle size distribution. This solution decreased the difference of apparent reaction rate in a packed bed between the bio-coal and anthracite from 6.5 times to 4.5 times. At the moment the model is not generalized for all bio-coals. However, the developed methodology can be routinely applied to assess the different bio-coal samples. One possible error can be that pyrolysis influences the gasification rate for bio-coal that is pyrolyzed below the temperature of the gasification test. There is a clear correlation between particle size distributions, bulk density, and apparent reactivity. By mixing two distributions the reaction rate of Cortus Bark was reduced from 6.5 times the reaction rate of anthracite to 4.5.
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Congiu, Brian Alexander. "Conversion of Carbon Dioxide and Hydrogen into Methane in Bench-scale Microcosms and Packed Column Reactors." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1292783980.
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Thomson, Sean Richard. "Methane Production by a Packed-Bed Anaerobic Digester Fed Dairy Barn Flush Water." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1329.
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Packed-bed digesters are an alternative to covered lagoon digesters for methane production and anaerobic treatment of dilute wastewaters such as dairy barn flush water. The physical media of packed-beds retain biofilms, often allowing increased treatment rates. Previous studies have evaluated several types of media for digestion of dilute wastewaters, but cost and media fouling have setback commercial development. A major operational cost has been effluent recirculation pumping.
In the present effort, a novel approach to anaerobic digestion of flush dairy water was developed at pilot-scale: broken walnut shells were used as a low-cost packed-bed medium and effluent recirculation was replaced by reciprocation mixing to decrease pumping costs and the risk of media clogging.
Three packed-bed digesters containing walnut shells as media were constructed at the on-campus dairy and studied for about six months. Over that time, several organic loading rates (OLRs), measured as both chemical oxygen demand (COD) and volatile solids (VS) were applied to the new packed-bed digesters to allow modeling of methane production. The influence of temperature on methane production was also investigated. Additionally, the study measured solids accumulation in the walnut shell packed-bed as well as the effectiveness and durability of walnut shells as packing media. Finally, a simple economic analysis was developed from the methane model to predict the financial feasibility of packed-bed digesters at flush water dairies under similar OLR conditions.
Three methane production models were developed from organic loading: saturation-type (following the form of the Monod equation), power and linear. The models were evaluated in terms of regression analysis and the linearity of experimental to predicted methane production. The best model was then chosen to develop the economic predictions. Economic predictions for packed-bed digesters were calculated as internal rate of return (IRR) using the methane models along with additional input variables. Comparisons of IRRs were made using electric retail rates of $0.10 to $0.20 per kilowatt-hour and capital cost subsidies from zero to 50%.
Sludge accumulation in the packed-bed was measured via change in porosity, and walnut shell durability was measured as the change in mass of representative walnut shells over the course of the study.
The linear-type model of methane production from volatile solids OLR best represented this data set. Digester temperature was not found to influence methane production in this study, likely due to the small daily average ambient temperature range experienced (14°C to 24°C) and the greater influence of organic loading. Porosity of the walnut shell packed-bed decreased from 0.70 at startup to 0.34±0.06 at the end of the six-month study, indicating considerable media fouling. Sludge accumulated in each digester from zero at startup to 281±46 liters at termination. Walnut shells in the packed-bed lost on average 31.4±6.3% mass during the study period which may be attributed to degradation of more readily bio-degradable cellulose and hemi-cellulose within the walnut shells.
Given the predicted methane production and media life, at present, the economic outlook for packed-bed digesters at commercial dairies is quite dependent on utility electrical rates, available subsidies and future improvements to packed-bed digester technology. The predicted IRRs ranged from below 0% (at 0% capital subsidy and $0.10/kWh) up to 25% (at 50% capital subsidy and $0.20/kWh) at large dairies (3000 milking cows). Increases in organic loading were not shown to necessarily increase IRR, particularly at OLRs above 10 g/Lliquid-d (as COD or VS). Ultimately, to better assess the value of packed-bed digesters for flush dairies, additional study is needed on topics such as sludge accumulation prevention, long-term walnut shell degradation, dairy barn flush water mixing, and more detailed economic analysis.
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Trahan, Jamie. "A Technical and Economic Comparative Analysis of Sensible and Latent Heat Packed Bed Storage Systems for Concentrating Solar Thermal Power Plants." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5598.
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Though economically favorable when compared to other renewable energy storage technologies, thermal energy storage systems for concentrating solar thermal power (CSP) plants require additional cost reduction measures to help transition CSP plants to the point of grid-parity. Thermocline packed bed storage is regarded as one potential low cost solution due to the single tank requirement and low cost storage media. Thus sensible heat storage (SHS) and latent heat storage (LHS) packed bed systems, which are two thermocline varieties, are frequently investigated. LHS systems can be further classified as single phase change material (PCM) systems or cascaded systems wherein multiple PCMs are employed.
This study compared the performance of SHS, single PCM, and cascaded PCM direct storage systems under the conditions that may be encountered in utility-scale molten salt CSP plants operating between 565°C and 288°C. A small-scale prototype SHS packed bed system was constructed and operated for use in validating a numerical model. The drawbacks of the latent heat storage process were discussed, and cascaded systems were investigated for their potential in mitigating the issues associated with adopting a single PCM. Several cascaded PCM configurations were evaluated. The study finds that the volume fraction of each PCM and the arrangement of latent heat in a 2-PCM and a 3-PCM system influences the output of the system, both in terms of quality and quantity of energy. In addition to studying systems of hypothetical PCMs, real salt PCM systems were examined and their selection process was discussed.
A preliminary economic assessment was conducted to compare the cost of SHS, single-PCM LHS, cascaded LHS, and state-of-the-art 2-tank systems. To the author's knowledge, this is the first study that compares the cost of all three thermocline packed bed systems with the 2-tank design. The SHS system is significantly lower in cost than the remaining systems, however the LHS system does show some economic benefit over the 2-tank design. If LHS systems are to be viable in the future, low cost storage media and encapsulation techniques are necessary.
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Rocco, Arthur Betti. "Processo decisório da União Europeia : um estudo sobre o Pacote Clima-Energia 2020." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/24230.
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Relações Internacionais, Programa de Pós-Graduação em Relações Internacionais, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-06-21T19:08:13Z No. of bitstreams: 1 2017_ArthurBettiRocco.pdf: 2452335 bytes, checksum: 5ec0124eea5fadc7b997a0b19f88ed8f (MD5)
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O objetivo geral desta dissertação é analisar como os diversos interesses no processo que formulou o Pacote Clima/Energia 2020 da União Europeia (UE) foram promovidos. As metas específicas são: identificar se houve ou não promoção dos interesses nacionais por meio da atuação dos comissários, descrever o processo decisório, analisar a atuação dos atores subnacionais e não estatais, e avaliar a consecução das metas postas para 2020. Este estudo concluiu que não há evidências, durante a elaboração do Pacote Clima/Energia 2020, da promoção de interesses nacionais pelos comissários. Observou-se uma dinâmica contínua de debates entre as instituições participes do processo de codecisão, fato que gera diversas janelas de oportunidades para promoção dos mais diversos interesses. Neste sentindo, o principal foco de promoção dos interesses foram os europarlamentares, relatores do Pacote Legislativo. Quanto à análise dos dados quantitativos da implementação das metas postas para 2020, inferiu-se que as metas de redução de 20% dos índices de emissão – tendo 1990 como ano base –, de inserção de 20% de fontes renováveis na matriz energética e de economia de 20% de energia por meio do incremento da eficiência energética poderiam ser mais audaciosas, uma vez que a crise internacional colaborou, em grande medida, para que essas fossem alcançadas. A forte contração das economias europeias, que se traduziu na redução do consumo, implicou na redução da produção e, consequentemente, reduziram-se o consumo de energia e os níveis de emissão de gases com efeito estufa.
This Master’s Thesis seeks to analyze how different interests were promoted during the process that led to the approval of the 2020 Climate & Energy Package in the European Union (EU). The specific aims of this thesis are to identify if national interests were pursued through the action of European commissaries, to describe the decision-making process, to analyze the performance by subnational and non-state actors and to examine the implementation of the targets set to 2020. This thesis concludes that there were no evidences that commissaries promoted national interests the conception of the 2020 Climate & Energy Package. There was observed a dynamic impetus of debates among the participant institutions of the co-decision process, which created several opportunity windows to the promotion of numerous interests. The main actors who promoted specific interests were the members of the European Parliament. Based on the quantitative analysis of the data regarding implementation of the 2020 targets, it is inferred that their three pillars – 20% cut in greenhouse gases emissions, based on 1990 levels, 20% European Union energy from renewables and 20% improvement in energy efficiency – could have been more ambitious, since the international economic crisis has been responsible, to a great extent, to the attainment of these goals. The decrease in consumption, caused by the strong recession of the European economies, led to a decrease in production, which, by its turn, provoked a slump in energy consumption levels as well as in greenhouse gases emission levels.
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Thiem, Stefanie. "Electronic and Photonic Properties of Metallic-Mean Quasiperiodic Systems." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-83831.
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Understanding the connection of the atomic structure and the physical properties of materials remains one of the elementary questions of condensed-matter physics. One research line in this quest started with the discovery of quasicrystals by Shechtman et al. in 1982. It soon became clear that these materials with their 5-, 8-, 10- or 12-fold rotational symmetries, which are forbidden according to classical crystallography, can be described in terms of mathematical models for nonperiodic tilings of a plane proposed by Penrose and Ammann in the 1970s. Due to the missing translational symmetry of quasicrystals, till today only finite, relatively small systems or periodic approximants have been investigated by means of numerical calculations and theoretical results have mainly been obtained for one-dimensional systems. In this thesis we study d-dimensional quasiperiodic models, so-called labyrinth tilings, with separable Hamiltonians in the tight-binding approach. This method paves the way to study higher-dimensional, quantum mechanical solutions, which can be directly derived from the one-dimensional results. This allows the investigation of very large systems in two and three dimensions with up to 10^10 sites. In particular, we contemplate the class of metallic-mean sequences. Based on this model we focus on the electronic properties of quasicrystals with a special interest on the connection of the spectral and dynamical properties of the Hamiltonian. Hence, we investigate the characteristics of the eigenstates and wave functions and compare these with the wave-packet dynamics in the labyrinth tilings by numerical calculations and by a renormalization group approach in connection with perturbation theory. It turns out that many properties show a qualitatively similar behavior in different dimensions or are even independent of the dimension as e.g. the scaling behavior of the participation numbers and the mean square displacement of a wave packet. Further, we show that the structure of the labyrinth tilings and their transport properties are connected and obtain that certain moments of the spectral dimensions are related to the wave-packet dynamics. Besides this also the photonic properties are studied for one-dimensional quasiperiodic multilayer systems for oblique incidence of light, and we show that the characteristics of the transmission bands are related to the quasiperiodic structureEine der elementaren Fragen der Physik kondensierter Materie beschäftigt sich mit dem Zusammenhang zwischen der atomaren Struktur und den physikalischen Eigenschaften von Materialien. Eine Forschungslinie in diesem Kontext begann mit der Entdeckung der Quasikristalle durch Shechtman et al. 1982. Es stellte sich bald heraus, dass diese Materialien mit ihren laut der klassischen Kristallographie verbotenen 5-, 8-, 10- oder 12-zähligen Rotationssymmetrien durch mathematische Modelle für die aperiodische Pflasterung der Ebene beschrieben werden können, die durch Penrose und Ammann in den 1970er Jahren vorgeschlagen wurden. Aufgrund der fehlenden Translationssymmetrie in Quasikristallen sind bis heute nur endliche, relativ kleine Systeme oder periodische Approximanten durch numerische Berechnungen untersucht worden und theoretische Ergebnisse wurden hauptsächlich für eindimensionale Systeme gewonnen. In dieser Arbeit werden d-dimensionale quasiperiodische Modelle, sogenannte Labyrinth-Pflasterungen, mit separablem Hamilton-Operator im Modell starker Bindung betrachtet. Diese Methode erlaubt es, quantenmechanische Lösungen in höheren Dimensionen direkt aus den eindimensionalen Ergebnissen abzuleiten und ermöglicht somit die Untersuchung von sehr großen Systemen in zwei und drei Dimensionen mit bis zu 10^10 Gitterpunkten. Insbesondere betrachten wir dabei quasiperiodische Folgen mit metallischem Schnitt. Basierend auf diesem Modell befassen wir uns im Speziellen mit den elektronischen Eigenschaften der Quasikristalle im Hinblick auf die Verbindung der spektralen und dynamischen Eigenschaften des Hamilton-Operators. Hierfür untersuchen wir die Eigenschaften der Eigenzustände und Wellenfunktionen und vergleichen diese mit der Dynamik von Wellenpaketen in den Labyrinth-Pflasterungen basierend auf numerischen Berechnungen und einem Renormierungsgruppen-Ansatz in Verbindung mit Störungstheorie. Dabei stellt sich heraus, dass viele Eigenschaften wie etwa das Skalenverhalten der Partizipationszahlen und der mittleren quadratischen Abweichung eines Wellenpakets für verschiedene Dimensionen ein qualitativ gleiches Verhalten zeigen oder sogar unabhängig von der Dimension sind. Zudem zeigen wir, dass die Struktur der Labyrinth-Pflasterungen und deren Transporteigenschaften sowie bestimmte Momente der spektralen Dimensionen und die Dynamik der Wellenpakete in Beziehung zueinander stehen. Darüber hinaus werden auch die photonischen Eigenschaften für eindimensionale quasiperiodische Mehrschichtsysteme für beliebige Einfallswinkel untersucht und der Verlauf der Transmissionsbänder mit der quasiperiodischen Struktur in Zusammenhang gebracht
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Falola, Bamidele Daniel. "TRANSITION METAL COATINGS FOR ENERGY CONVERSION AND STORAGE; ELECTROCHEMICAL AND HIGH TEMPERATURE APPLICATIONS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1354.
Full textAbstract:
Energy storage provides sustainability when coupled with renewable but intermittent energy sources such as solar, wave and wind power, and electrochemical supercapacitors represent a new storage technology with high power and energy density. For inclusion in supercapacitors, transition metal oxide and sulfide electrodes such as RuO2, IrO2, TiS2, and MoS2 exhibit rapid faradaic electron–transfer reactions combined with low resistance. The pseudocapacitance of RuO2 is about 720 F/g, and is 100 times greater than double-layer capacitance of activated carbon electrodes. Due to the two-dimensional layered structure of MoS2, it has proven to be an excellent electrode material for electrochemical supercapacitors. Cathodic electrodeposition of MoS2 onto glassy carbon electrodes is obtained from electrolytes containing (NH4)2MoS4 and KCl. Annealing the as-deposited Mo sulfide deposit improves the capacitance by a factor of 40x, with a maximum value of 360 F/g for 50 nm thick MoS2 films. The effects of different annealing conditions were investigated by XRD, AFM and charge storage measurements. The specific capacitance measured by cyclic voltammetry is highest for MoS2 thin films annealed at 500°C for 3h and much lower for films annealed at 700°C for 1 h. Inclusion of copper as a dopant element into electrodeposited MoS2 thin films for reducing iR drop during film charge/discharge is also studied. Thin films of Cu-doped MoS2 are deposited from aqueous electrolytes containing SCN-, which acts as a complexing agent to shift the cathodic Cu deposition potential, which is much more anodic than that of MoS2. Annealed, Cu-doped MoS2 films exhibit enhanced charge storage capability about 5x higher than undoped MoS2 films. Coal combustion is currently the largest single anthropogenic source of CO2 emissions, and due to the growing concerns about climate change, several new technologies have been developed to mitigate the problem, including oxyfuel coal combustion, which makes CO2 sequestration easier. One complication of oxyfuel coal combustion is that corrosion problems can be exacerbated due to flue gas recycling, which is employed to dilute the pure O2 feed and reduce the flame temperature. Refractory metal diffusion coatings of Ti and Zr atop P91 steel were created and tested for their ability to prevent corrosion in an oxidizing atmosphere at elevated temperature. Using pack cementation, diffusion coatings of thickness approximately 12 and 20 µm are obtained for Ti and Zr, respectively. The effects of heating to 950°C for 24 hr in 5% O2 in He are studied in situ by thermogravimetric analyses (TGA), and ex situ by SEM analyses and depth profiling by EDX. For Ti-coated, Zr-coated and uncoated P91 samples, extended heating in an oxidizing environment causes relatively thick oxide growth, but extensive oxygen penetration greater than 2.7 mm below the sample surface, and eventual oxide exfoliation, are observed only for the uncoated P91 sample. For the Ti- and Zr-coated samples, oxygen penetrates approximately 16 and 56 µm, respectively, below the surface. In situ TGA verifies that Ti-and Zr-coated P91 samples undergo far smaller mass changes during corrosion than uncoated samples, reaching close to steady state mass after approximately four hours.