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1
Vanderhyde, James. "Topology Control of Volumetric Data." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16215.
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Three-dimensional scans and other volumetric data sources often result in representations that are more complex topologically than the original model. The extraneous critical points, handles, and components are called topological noise. Many algorithms in computer graphics require simple topology in order to work optimally, including texture mapping, surface parameterization, flows on surfaces, and conformal mappings. The topological noise disrupts these procedures by requiring each small handle to be dealt with individually. Furthermore, topological descriptions of volumetric data are useful for visualization and data queries. One such description is the contour tree (or Reeb graph), which depicts when the isosurfaces split and merge as the isovalue changes. In the presence of topological noise, the contour tree can be too large to be useful. For these reasons, an important goal in computer graphics is simplification of the topology of volumetric data.
The key to this thesis is that the global topology of volumetric data sets is determined by local changes at individual points. Therefore, we march through the data one grid cell at a time, and for each cell, we use a local check to determine if the topology of an isosurface is changing. If so, we change the value of the cell so that the topology change is prevented.
In this thesis we describe variations on the local topology check for use in different settings. We use the topology simplification procedure to extract a single component with controlled topology from an isosurface in volume data sets and partially-defined volume data sets. We also use it to remove critical points from three-dimensional volumes, as well as time-varying volumes. We have applied the technique to two-dimensional (plus time) data sets and three dimensional (plus time) data sets.
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Barnett, Adam. "Topology based global crowd control." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9692.
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We propose a method to determine the flow of large crowds of agents in a scene such that it is filled to its capacity with a coordinated, dynamically moving crowd. Our approach provides a focus on cooperative control across the entire crowd. This is done with a view to providing a method which animators can use to easily populate and fill a scene. We solve this global planning problem by first finding the topology of the scene using a Reeb graph, which is computed from a Harmonic field of the environment. The Maximum flow can then be calculated across this graph detailing how the agents should move through the space. This information is converted back from the topological level to the geometric using a route planner and the Harmonic field. We provide evidence of the system’s effectiveness in creating dynamic motion through comparison to a recent method. We also demonstrate how this system allows the crowd to be controlled globally with a couple of simple intuitive controls and how it can be useful for the purpose of designing buildings and providing control in team sports.
3
Komali, Ramakant S. "Game-Theoretic Analysis of Topology Control." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28358.
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Ad hoc networks are emerging as a cost-effective, yet, powerful tool for communication.
These systems, where networks can emerge and converge on-the-fly, are guided by the
forward-looking goals of providing ubiquitous connectivity and constant access to information.
Due to power and bandwidth constraints, the vulnerability of the wireless medium, and
the multi-hop nature of ad hoc networks, these networks are becoming increasingly complex
dynamic systems. Besides, modern radios are empowered to be reconfigurable, which harbors
the temptation to exploit the system. To understand the implications of these issues, some
of which pose significant challenges to efficient network design, we study topology control
using game theory.
We develop a game-theoretic framework of topology control that broadly captures the radio
parameters, one or more of which can be tuned under the purview of topology control. In
this dissertation, we consider two parameters, viz. transmit power and channel, and study
the impact of controlling these on the emergent topologies.
We first examine the impact of node selfishness on the network connectivity and energy
efficiency under two levels of selfishness: (a) nodes cooperate and forward packets for one
another, but selfishly minimize transmit power levels and; (b) nodes selectively forward
packets and selfishly control transmit powers. In the former case, we characterize all the
Nash Equilibria of the game and evaluate the energy efficiency of the induced topologies.
We develop a better-response-based dynamic that guarantees convergence to the minimal
maximum power topology. We extend our analysis to dynamic networks where nodes have
limited knowledge about network connectivity, and examine the tradeoff between network
performance and the cost of obtaining knowledge. Due to the high cost of maintaining
knowledge in networks that are dynamic, mobility actually helps in information-constrained
networks. In the latter case, nodes selfishly adapt their transmit powers to minimize their
energy consumption, taking into account partial packet forwarding in the network. This
work quantifies the energy efficiency gains obtained by cooperation and corroborates the
need for incentivizing nodes to forward packets in decentralized, energy-limited networks.
We then examine the impact of selfish behavior on spectral efficiency and interference minimization
in multi-channel systems. We develop a distributed channel assignment algorithm
to minimize the spectral footprint of a network while establishing an interference-free connected
network. In spite of selfish channel selections, the network spectrum utilization is
shown to be within 12% of the minimum on average. We then extend the analysis to dynamic
networks where nodes have incomplete network state knowledge, and quantify the price of
ignorance. Under the limitations on the number of available channels and radio interfaces, we
analyze the channel assignment game with respect to interference minimization and network
connectivity goals. By quantifying the interference in multi-channel networks, we illuminate
the interference reduction that can be achieved by utilizing orthogonal channels and by distributing
interference over multiple channels. In spite of the non-cooperative behavior of
nodes, we observe that the selfish channel selection algorithm achieves load balancing.
Distributing the network control to autonomous agents leaves open the possibility that nodes
can act selfishly and the overall system is compromised. We advance the need for considering
selfish behavior from the outset, during protocol design. To overcome the effects of
selfishness, we show that the performance of a non-cooperative network can be enhanced by
appropriately incentivizing selfish nodes.Ph. D.
4
Wightman, Rojas Pedro Mario. "Topology Control in Wireless Sensor Networks." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1807.
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Wireless Sensor Networks (WSN) offer a flexible low-cost solution to the problem of event monitoring, especially in places with limited accessibility or that represent danger to humans. WSNs are made of resource-constrained wireless devices, which require energy efficient mechanisms, algorithms and protocols. One of these mechanisms is Topology Control (TC) composed of two mechanisms, Topology Construction and Topology Maintenance.
This dissertation expands the knowledge of TC in many ways. First, it introduces a comprehensive taxonomy for topology construction and maintenance algorithms for the first time. Second, it includes four new topology construction protocols: A3, A3Lite, A3Cov and A3LiteCov. These protocols reduce the number of active nodes by building a Connected Dominating Set (CDS) and then turning off unnecessary nodes. The A3 and A3-Lite protocols guarantee a connected reduced structure in a very energy efficient manner. The A3Cov and A3LiteCov protocols are extensions of their predecessors that increase the sensing coverage of the network. All these protocols are distributed -they do not require localization information, and present low message and computational complexity. Third, this dissertation also includes and evaluates the performance of four topology maintenance protocols: Recreation (DGTRec), Rotation (SGTRot), Rotation and Recreation (HGTRotRec), and Dynamic Local-DSR (DLDSR).
Finally, an event-driven simulation tool named Atarraya was developed for teaching, researching and evaluating topology control protocols, which fills a need in the area of topology control that other simulators cannot. Atarraya was used to implement all the topology construction and maintenance cited, and to evaluate their performance. The results show that A3Lite produces a similar number of active nodes when compared to A3, while spending less energy due to its lower message complexity. A3Cov and A3CovLite show better or similar coverage than the other distributed protocols discussed here, while preserving the connectivity and energy efficiency from A3 and A3Lite. In terms of network lifetime, depending on the scenarios, it is shown that there can be a substantial increase in the network lifetime of 450% when a topology construction method is applied, and of 3200% when both topology construction and maintenance are applied, compared to the case where no topology control is used.
5
Li, Xiaoyun. "Distributed topology-aware algorithms & topology control probabilistic analysis for wireless sensor networks." Thesis, University of Essex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446490.
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Zhao, Liang. "Topology control for mobile ad hoc networks." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 162 p, 2007. http://proquest.umi.com/pqdweb?did=1362541141&sid=26&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Hassan, Ahmed Mohamed Ali Omer. "Topology control in wireless ad hoc networks." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86709.
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Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Wireless ad hoc networks are increasingly used in today’s life in various areas ranging from environmental monitoring to the military. For technical reasons, they are severely limited in terms of battery power, communication capacity and computation capability. Research has been carried out to deal with these limitations using different approaches. A theoretical treatment of the subject is topology control whose basic task is to design network topologies with special properties that make them energy-efficient and interference-optimal. We study, implement and compare the XTC and CBTC algorithms in terms of interference reduction, length stretch factor and maximum degree. These two algorithms have two features that are absent in almost all competitive topology control algorithms which are practicality and maintaining connectivity. Both algorithms show good performance in terms of interference reduction and maintaining a good length stretch factor. Regarding CBTC, we prove that it is a power spanner. We show through extensive simulation that the degree distribution of wireless ad hoc networks modelled by the log-normal model is binomial if the average degree is not high. We find that there is no fixed threshold for the average degree at which the distribution is distorted and no longer binomial. We show through simulation that the node density which ensures the absence of isolated nodes is a tight lower bound for the node density which ensures connectivity. The implication of this result is that connectivity is ensured with high probability if the minimum node degree is equal to 1. Finally we show through simulation that the log-normal model is not a realistic representation of wireless ad hoc networks if the environmental parameter is at least 6. This result is important because there are no available measurements to determine the range of the environmental parameter for typical frequencies used in wireless ad hoc networks.
AFRIKAANSE OPSOMMING: Koordlose ad hoc netwerke word toenemend gebruik in vandag se lewe op verskillende gebiede wat wissel van die omgewing monitor tot militêregebruik. Vir tegniese redes is hulle ernstig beperk in terme van battery krag, kommunikasie kapasiteit en berekeningsvermoë. Navorsing vanuit verkillende benaderings word gedoen om met hierdie beperkings te deel. ’n Teoretiese benadering tot onderwerp is topologie beheer. Die basiese taak is om netwerktopologieë met spesiale eienskappe wat hulle energie-doeltreffend en interferensieoptimaal maak te ontwerp. Ons bestudeer, implementeer en vergelyk die XTC en CBTC algoritmes in terme van interferensie vermindering, lengte rek faktor en maksimum graad. Beide hierdie algoritmes het twee eienskappe wat afwesig is in byna al die mededingende topologie beheer algoritmes: hulle is prakties en handhaf verbindings. Beide algoritmes toon goeie prestasie in terme van interferensie verminder en die handhawing van ’n goeie lengte rek faktor. Ten opsigte van CBTC bewys ons dat dit ’n “power spanner” is. Ons wys deur middel van uitgebreide simulasie dat die graad verdeling van die koordlose ad hoc netwerke wat deur die log-normale model gemodelleer kan word binomiaal is as die gemiddelde graad nie hoog is nie. Ons vind dat daar geen vaste drempel is vir die gemiddelde graad waarby die verdeling vervorm en nie meer binomiaal is nie. Ons wys deur simulasie dat die node digtheid wat die afwesigheid van geïsoleerde nodusse verseker ’n streng ondergrens vir die node digtheid wat konnektiviteit verseker is. Die implikasie van hierdie resultaat is dat ‘n konneksie verseker word as die minimum node graad gelyk is aan 1. Ten slotte wys ons deur simulasie dat die log-normale model nie ’n realistiese voorstelling van koordlose ad hoc netwerke is wanneer die “environmental parameter” groter is as 6 nie. Hierdie resultaat is belangrik, want daar is geen beskikbare metings om die grense van hierdie parameter vir ’n tipiese frekwensie gebruik in koordlose ad hoc netwerke te bepaal nie.
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Liu, Yunhuai. "Probabilistic topology control in wireless sensor networks /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CSED%202008%20LIU.
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Javali, Nagesh. "Topology control for wireless ad-hoc networks." Click here for download, 2008. http://proquest.umi.com/pqdweb?did=1580780361&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.
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Thesis (M.S.)--Villanova University, 2008."This research work is funded in part by National Science Foundation (NSF), Computing and Communication Foundation (CCF) award 0728909"--P. iii. Computer Science Dept. Includes bibliographical references.
10
Volbert, Klaus. "Geometric spanners for topology control in wireless networks." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97580975X.
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Srivastava, Gaurav. "Efficient topology control algorithms for ad hoc networks." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080506.144718/index.html.
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Ozturk, Gozde. "Topology and Telechelic Functionality Control in Polyester Design." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28030.
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Research efforts have focused on synthesis of linear, long-chain branched, and novel crosslinked polyesters for applications spanning from pressure sensitive adhesives to biomedical applications. Altering polymer topology and functionality using different synthetic strategies was enabled tailoring the thermomechanical, rheological, and adhesive properties of polyesters. The synthesis and characterization of linear, long-chain branched, and crosslinked networks are described focusing on the structure-property relationships.
Aliphatic low-Tg polyesters with linear and long-chain branched topology were synthesized using melt polycondensation for pressure sensitive adhesive applications. Relationships between molecular weight, polymer composition, and adhesive performance were investigated. Melt rheological studies and the characterization of adhesive properties indicated that adhesive performance was enhanced with increasing molecular weight. Moreover, a series of long-chain branched low-Tg polyester were investigated to determine the influence of branching and molecular weight. Tailoring the degree of branching enabled the control of rheological and adhesive properties. Characterization of adhesive properties revealed that long-chain branched polymers displayed an enhanced cohesive strength. In addition, utilization of different comonomer compositions allowed tailoring thermal and adhesive properties of low-Tg polyesters over a wide range.
Biodegradable networks were synthesized for the first time using base-catalyzed Michael addition of acetoacetate functionalized polyesters with acrylates. Linear and star-shaped poly(caprolactone) (PCL) oligomers with different molecular weights were functionalized and crosslinked. Thermomechanical properties were evaluated as a function of precursor molecular weight and crosslink density. The glass transition temperature and the extent of crystallinity of the networks were dependent on the molecular weight of the PCL segment. Moreover, dynamic mechanical analysis (DMA) indicated that molecular weight of the oligomeric precursors influenced the plateau modulus of the networks as a result of the differences in crosslink density of the networks. In addition, covalently crosslinked networks were synthesized from Michael addition reaction of acetoacetate-functional oligomeric poly(trimethylene succinate)s and poly(trimethylene adipate)s with neopentylglycol diacrylate. The oligomeric polyesters with telechelic hydroxyl functionality were synthesized from renewable monomers, adipic acid, succinic acid, and 1,3-propanediol using melt polycondensation. The molecular weights of the precursors were varied systematically to probe the influence of molecular weight on thermomechanical properties of the networks. The extent of crystallinity and mechanical properties were dependent on the molecular weight of the oligomeric polyester precursors which also controlled crosslink density. Moreover, Michael addition chemistry was utilized to crosslink low-Tg polyesters to improve cohesive strength for PSA applications. In order to determine the influence of temperature and catalyst levels, crosslinking reactions were monitoring using measurement of loss and storage moduli during the reaction. Networks having different levels of gel fractions were investigated to elucidate the influence of degree of crosslinking on thermomechanical and adhesive properties of low-Tg polyesters.Ph. D.
13
Krajacich, Christopher A. "Designing a FORCEnet information topology." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FKrajacich.pdf.
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Casey, Michael J. "Self-organization and topology control of infrastructure sensor networks." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3183.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Civil Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
15
Shum, L. L. "Topology control and data handling in wireless sensor networks." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18577/.
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Our work in this thesis have provided two distinctive contributions to WSNs in the areas of data handling and topology control. In the area of data handling, we have demonstrated a solution to improve the power efficiency whilst preserving the important data features by data compression and the use of an adaptive sampling strategy, which are applicable to the specific application for oceanography monitoring required by the SECOAS project. Our work on oceanographic data analysis is important for the understanding of the data we are dealing with, such that suitable strategies can be deployed and system performance can be analysed. The Basic Adaptive Sampling Scheduler (BASS) algorithm uses the statistics of the data to adjust the sampling behaviour in a sensor node according to the environment in order to conserve energy and minimise detection delay. The motivation of topology control (TC) is to maintain the connectivity of the network, to reduce node degree to ease congestion in a collision-based medium access scheme; and to reduce power consumption in the sensor nodes. We have developed an algorithm Subgraph Topology Control (STC) that is distributed and does not require additional equipment to be implemented on the SECOAS nodes. STC uses a metric called subgraph number, which measures the 2-hops connectivity in the neighbourhood of a node. It is found that STC consistently forms topologies that have lower node degrees and higher probabilities of connectivity, as compared to k-Neighbours, an alternative algorithm that does not rely on special hardware on sensor node. Moreover, STC also gives better results in terms of the minimum degree in the network, which implies that the network structure is more robust to a single point of failure. As STC is an iterative algorithm, it is very scalable and adaptive and is well suited for the SECOAS applications.
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Hammarström, Emil. "Network optimisation and topology control of Free Space Optics." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-124546.
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In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskal’s minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.
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Shim, Yohan. "Topology control and pointing in free space optical networks." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7773.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Civil and Environmental Engineering . Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Nordkvist, Tobias. "Network optimisation and topology control of Free Space Optics." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-130003.
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In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics, FSO, is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskals minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.
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Foster, Justin M. "Control systems in power markets: demand response, transmission topology control, and renewable integration." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31554.
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Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
National directives emphasizing improved power grid sustainability, reliability, and economic performance motivate innovative research directions in demand response and renewable generation integration. In addition, advances in computing capabilities render feasible new techniques for long standing power market problems. This dissertation proposes and evaluates several novel decision support policies, balanced between improving existing power market operation and preparing for forthcoming technologies and capabilities. In particular, this dissertation considers (i) demand-side decision support and (ii) tractable transmission topology control. The first part of this dissertation uses dynamic programming and duality theory to develop a decision support framework for a load aggregator (LA) managing flexible loads sharing the same short-term capacity constraints -- and in particular -- plug-in electric vehicles (PEVs). The LA submits inflexible and flexible bids to a liberalized hour-ahead power market, while monitoring localized network constraints. Flexible bids are associated with a reservation price and the market clears these bids as a combination of energy demand and capacity reserve, as energy only, or rejects the bid entirely. By allowing the market operator to dispatch PEVs, this strategy provides an effective means for coordination with centralized renewable generation. In addition, the provision of voltage support in the presence of distributed solar arrays is considered. The second part of this dissertation develops sensitivity- or gradient-based algorithms aimed at reducing congestion costs by tractably including topology control in the economic dispatch. Currently, the economic dispatch minimizes generation costs subject to transmission constraints, where the status of each line, i.e., open or closed, is fixed. Recent research shows that by optimally dispatching the network topology along with generation resources, significant congestion costs may be avoided. Optimal transmission topology control requires the solution of a mixed integer program which is computationally intractable for real-sized power networks; however, it appears that much of the cost savings may be attained by changing the status of just a few appropriately selected lines. Therefore, this dissertation proposes tractable transmission topology control policies, which employ sensitivity information readily available from the economic dispatch to select candidate lines to change status.
2031-01-01
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He, Jing S. "Connected Dominating Set Based Topology Control in Wireless Sensor Networks." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/cs_diss/70.
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Wireless Sensor Networks (WSNs) are now widely used for monitoring and controlling of systems where human intervention is not desirable or possible. Connected Dominating Sets (CDSs) based topology control in WSNs is one kind of hierarchical method to ensure sufficient coverage while reducing redundant connections in a relatively crowded network. Moreover, Minimum-sized Connected Dominating Set (MCDS) has become a well-known approach for constructing a Virtual Backbone (VB) to alleviate the broadcasting storm for efficient routing in WSNs extensively. However, no work considers the load-balance factor of CDSsin WSNs. In this dissertation, we first propose a new concept — the Load-Balanced CDS (LBCDS) and a new problem — the Load-Balanced Allocate Dominatee (LBAD) problem. Consequently, we propose a two-phase method to solve LBCDS and LBAD one by one and a one-phase Genetic Algorithm (GA) to solve the problems simultaneously.
Secondly, since there is no performance ratio analysis in previously mentioned work, three problems are investigated and analyzed later. To be specific, the MinMax Degree Maximal Independent Set (MDMIS) problem, the Load-Balanced Virtual Backbone (LBVB) problem, and the MinMax Valid-Degree non Backbone node Allocation (MVBA) problem. Approximation algorithms and comprehensive theoretical analysis of the approximation factors are presented in the dissertation.
On the other hand, in the current related literature, networks are deterministic where two nodes are assumed either connected or disconnected. In most real applications, however, there are many intermittently connected wireless links called lossy links, which only provide probabilistic connectivity. For WSNs with lossy links, we propose a Stochastic Network Model (SNM). Under this model, we measure the quality of CDSs using CDS reliability. In this dissertation, we construct an MCDS while its reliability is above a preset applicationspecified threshold, called Reliable MCDS (RMCDS). We propose a novel Genetic Algorithm (GA) with immigrant schemes called RMCDS-GA to solve the RMCDS problem.
Finally, we apply the constructed LBCDS to a practical application under the realistic SNM model, namely data aggregation. To be specific, a new problem, Load-Balanced Data Aggregation Tree (LBDAT), is introduced finally. Our simulation results show that the proposed algorithms outperform the existing state-of-the-art approaches significantly.
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Deng, Songquan. "CONTROL AND TOPOLOGY IMPROVEMENTS IN HALF-BRIDGE DC-DC CONVERTERS." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2749.
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Efficiency and transient response are two key requirements for DC-DC converters. Topology and control are two key topics in this dissertation. A variety of techniques for DC-DC converter performance improvement are presented in this work. Focusing on the efficiency issue, a variety of clamping techniques including both active and passive methods are presented after the ringing issues in DC-DC converters are investigated. By presenting the clamping techniques, a big variety of energy management concepts are introduced. The active bridge-capacitor tank clamping and FET-diode-capacitor tank clamping are close ideas, which transfer the leakage inductor energy to clamping capacitor to prevent oscillation between leakage inductor and junction capacitor of MOSFETs. The two-FET-clamping tank employs two MOSFETs to freewheeling the leakage current when the main MOSFETs of the half-bridge are both off. Driving voltage variation on the secondary side Synchronous Rectifier (SR) MOSFETs in self-driven circuit due to input voltage variation in bus converter applications is also investigated. One solution with a variety of derivations is proposed using zerner-capacitor combination to clamping the voltage while maintaining reasonable power losses. Another efficiency improvement idea comes from phase-shift concept in DC-DC converters. By employing phase-shift scheme, the primary side and the secondary side two MOSFETs have complementary driving signals respectively, which allow the MOSFET to be turned on with Zero Voltage Switching (ZVS). Simulation verified the feasibility of the proposed phase-shifted DC-DC converter. From the control scheme point of view, a novel peak current mode control concept for half-bridge topologies is presented. Aiming at compensating the imbalanced voltage due to peak current mode control in symmetric half-bridge topologies, an additional voltage compensation loop is used to bring the half-bridge capacitor voltage back to balance. In the proposed solutions, one scheme is applied on symmetric half-bridge topology and the other one is applied on Duty-cycle-shifted (DCS) half-bridge topology. Both schemes employ simple circuitry and are suitable for integration. Loop stability issues are also investigated in this work. Modeling work shows the uncompensated half-bridge topology cannot be stabilized under all conditions and the additional compensation loop helps to prevent the voltage imbalance effectively.Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
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Nicholson, Mark. "Selecting a topology for safety-critical real-time control systems." Thesis, University of York, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263664.
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Wang, Baobing. "Topology control and channel assignment in wireless multi-hop networks /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-cs-b2375087xf.pdf.
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Thesis (M.Phil.)--City University of Hong Kong, 2009."Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references (leaves 60-64)
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Kashyap, Abhishek. "Profile based topology control and routing in wireless optical networks." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1440.
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Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lima, Coutinho Rodolfo Wanderson. "Topology Control and Opportunistic Routing in Underwater Acoustic Sensor Networks." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35957.
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Underwater wireless sensor networks (UWSNs) are the enabling technology for a new era of underwater monitoring and actuation applications. However, there still is a long road ahead until we reach a technological maturity capable of empowering high-density large deployment of UWSNs. To the date hereof, the scientific community is yet investigating the principles that will guide the design of networking protocols for UWSNs. This is because the principles that guide the design of protocols for terrestrial wireless sensor networks cannot be applied for an UWSN since it uses the acoustic channel instead of radio-frequency-based channel.
This thesis provides a general discussion for high-fidelity and energy-efficient data
collection in UWSNs. In the first part of this thesis, we propose and study the symbiotic design of topology control and opportunistic routing protocols for UWSNs. We propose the CTC and DTC topology control algorithms that rely on the depth adjustment of the underwater nodes to cope with the communication void region problem. In addition, we propose an analytical framework to study and evaluate our mobility-assisted approach in comparison to the classical bypassing and power control-based approaches. Moreover, we develop the GEDAR routing protocol for mobile UWSNs. GEDAR is the first OR protocol employing our innovative depth adjustment-based topology control methodology to re-actively cope with communication void regions. In the second part of this thesis, we study opportunistic routing (OR) underneath duty-cycling in UWSNs. We propose an analytical framework to investigate the joint design of opportunistic routing and duty cycle protocols for UWSNs. While duty-cycling conserves energy, it changes the effective UWSN density. Therefore, OR is proposed to guarantee a suitable one-hop density of awake neighbors to cope with the poor and time-varying link quality of the acoustic channel. In addition, we propose an analytical framework to study the impact of heterogeneous and on-the-fly sleep interval adjustment in OR underneath duty-cycling in UWSNs. The proposed model is aimed to provide insights for the future design of protocols towards a prolonged UWSN lifetime. The developed solutions have been extensively compared to related work either analytically or through simulations. The obtained results show the potentials of them in several scenarios of UWSNs. In turn, the devised analytical frameworks have been providing significant insights that will guide future developments of routing and duty-cycling protocols for several scenarios and setting of UWSNs.
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Mansouri, Seyed Akbar. "Circuit Topology Study of Grid-Connected Photovoltaic System." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308328627.
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Park, Seung-Jong. "Energy-Aware Topology Control and Data Delivery in Wireless Sensor Networks." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5065.
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The objective of this thesis is to address the problem of energy conservation in wireless sensor networks by tackling two fundamental problems: topology control and data delivery.
We first address energy-aware topology control taking into account throughput per unit energy as the primary metric of interest. Through both experimental observations and analysis, we show that the optimal topology is a function of traffic load in the network. We then propose a new topology control scheme, Adaptive Topology Control (ATC), which increases throughput per unit energy. Based on different coordinations among nodes, we proposed three ATC schemes: ATC-CP, ATC-IP, and ATC-MS. Through simulations, we show that three ATC schemes outperform static topology control schemes, and particularly the ATC-MS has the best performance under all environments.
Secondly, we explore an energy-aware data delivery problem consisting of two sub-problems: downstream (from a sink to sensors) and upstream (from sensors to a sink) data delivery. Although we address the problems as two independent ones, we eventually solve those problems with two approaches: GARUDA-DN and GARUDA-UP which share a common structure, the minimum dominating set.
For the downstream data delivery, we consider reliability as well as energy conservation since unreliable data delivery can increase energy consumption under high data loss rates. To reduce energy consumption and achieve robustness, we propose GARUDA-DN which is scalable to the network size, message characteristics, loss rate and the reliable delivery semantics. From ns2-based simulations, we show that GARUDA-DN performs significantly better than the basic schemes proposed thus far in terms of latency and energy consumption.
For the upstream data delivery, we address an energy efficient aggregation scheme to gather correlated data with theoretical solutions: the shortest path tree (SPT), the minimum spanning tree (MST) and the Steiner minimum tree (SMT). To approximate the optimal solution in case of perfect correlation among data, we propose GARUDA-UP which combines the minimum dominating set (MDS) with SPT in order to aggregate correlated data. From discrete event simulations, we show that GARUDA-UP outperforms the SPT and closely approximates the centralized optimal solution, SMT, with less amount of overhead and in a decentralized fashion.
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Kang, Intae. "Topology control for broadcasting over energy constrained wireless ad hoc networks /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6061.
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Hovareshti, Pedram. "Consensus problems and the effects of graph topology in collaborative control." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9304.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Leung, Ka-ho Andrew. "Localized topology control in wireless peer-to peer file sharing networks." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32048208.
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Leung, Ka-ho Andrew, and 梁嘉浩. "Localized topology control in wireless peer-to peer file sharing networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B32048208.
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Carey, Thomas. "Chemical control of thermal expansion in zeolites with the LTA topology." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4258/.
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Zeolites are microporous materials that have been commonly shown to exhibit remarkable negative thermal expansion (NTE) behaviour in their purely siliceous forms, with reported thermal expansion coefficients ranging from −3 x 10–\(_6\) K–\(_1\) to −26.1 x 10–\(_6\) K–\(_1\). In contrast, very little research has been reported on the aluminium-containing structures which are widely used for various commercial applications. Compounds exhibiting this property, which has only been observed in a small number of solids, are of considerable technological interest as their inclusion in devices or composite materials can counterbalance the more usual expansion on heating and contraction on cooling, thereby reducing the incidence of thermally induced failures. Here, we report an investigation into the effect that changing the chemical composition of the zeolite framework and intrapore species has on thermal expansion properties of zeolites with the LTA topology. Variable-temperature powder X−ray diffraction studies were used to determine the thermal expansion coefficients of the chemically modified zeolites over a sub-ambient temperature range and investigate the structural basis behind their thermal behaviour. Dramatic changes in the thermal expansion behaviour (from strong negative to weak positive) of the zeolites were observed as the structures were modified through ion-exchange, dehydration, varying the Al content in the framework and loading the pores with silver nitrate. The zeolitic pores contents have been shown to play a key role in the manner in which LTA-zeolites react to temperature variation, especially in the case of intra-porous water molecules. Detailed atomistic structural mechanisms behind the observed NTE behaviour have been produced for the more simplistic systems. Several key breakthroughs have also been achieved in understanding the formation of the superlattice when silver nitrate is incorporated into the zeolite pores and with regards to solving the unit cell structure.
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Savva, Andreas. "Modelling articulated figures on arbitrary meshes of control points." Thesis, London Metropolitan University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321713.
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Lindner, Brian Siegfried. "Exploiting process topology for optimal process monitoring." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95987.
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Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: Modern mineral processing plants are characterised by a large number of measured variables, interacting through numerous processing units, control loops and often recycle streams. Consequentially, faults in these plants propagate throughout the system, causing significant degradation in performance. Fault diagnosis therefore forms an essential part of performance monitoring in such processes. The use of feature extraction methods for fault diagnosis has been proven in literature to be useful in application to chemical or minerals processes. However, the ability of these methods to identify the causes of the faults is limited to identifying variables that display symptoms of the fault. Since faults propagate throughout the system, these results can be misleading and further fault identification has to be applied. Faults propagate through the system along material, energy or information flow paths, therefore process topology information can be used to aid fault identification. Topology information can be used to separate the process into multiple blocks to be analysed separately for fault diagnosis; the change in topology caused by fault conditions can be exploited to identify symptom variables; a topology map of the process can be used to trace faults back from their symptoms to possible root causes. The aim of this project, therefore, was to develop a process monitoring strategy that exploits process topology for fault detection and identification. Three methods for extracting topology from historical process data were compared: linear cross-correlation (LC), partial cross-correlation (PC) and transfer entropy (TE). The connectivity graphs obtained from these methods were used to divide process into multiple blocks. Two feature extraction methods were then applied for fault detection: principal components analysis (PCA), a linear method, was compared with kernel PCA (KPCA), a nonlinear method. In addition, three types of monitoring chart methods were compared: Shewhart charts; exponentially weighted moving average (EWMA) charts; and cumulative sum (CUSUM) monitoring charts. Two methods for identifying symptom variables for fault identification were then compared: using contributions of individual variables to the PCA SPE; and considering the change in connectivity. The topology graphs were then used to trace faults to their root causes. It was found that topology information was useful for fault identification in most of the fault scenarios considered. However, the performance was inconsistent, being dependent on the accuracy of the topology extraction. It was also concluded that blocking using topology information substantially improved fault detection and fault identification performance. A recommended fault diagnosis strategy was presented based on the results obtained from application of all the fault diagnosis methods considered.
AFRIKAANSE OPSOMMING: Moderne mineraalprosesseringsaanlegte word gekarakteriseer deur ʼn groot aantal gemete veranderlikes, wat in wisselwerking tree met mekaar deur verskeie proseseenhede, beheerlusse en hersirkulasiestrome. As gevolg hiervan kan foute in aanlegte deur die hele sisteem propageer, wat prosesprestasie kan laat afneem. Foutdiagnose vorm dus ʼn noodsaaklike deel van prestasiemonitering. Volgens literatuur is die gebruik van kenmerkekstraksie metodes vir foutdiagnose nuttig in chemiese en mineraalprosesseringsaanlegte. Die vermoë van hierdie metodes om die fout te kan identifiseer is egter beperk tot die identifikasie van veranderlikes wat simptome van die fout vertoon. Aangesien foute deur die sisteem propageer kan resultate misleidend wees, en moet verdere foutidentifikasie metodes dus toegepas word. Foute propageer deur die proses deur materiaal-, energie- of inligtingvloeipaaie, daarom kan prosestopologie inligting gebruik word om foutidentifikasie te steun. Topologie inligting kan gebruik word om die proses in veelvoudige blokke te skei om die blokke apart te ontleed. Die verandering in topologie veroorsaak deur fouttoestande kan dan analiseer word om simptoomveranderlikes te identifiseer. ʼn Topologiekaart van die proses kan ontleed word om moontlike hoofoorsake van foute op te spoor. Die doel van hierdie projek was dus om ʼn prosesmoniteringstrategie te ontwikkel wat prosestopologie benut vir fout-opspooring en foutidentifikasie. Drie metodes vir topologie-ekstraksie van historiese prosesdata is met mekaar vergelyk: liniêre kruiskorrelasie, parsiële kruiskorrelasie en oordrag-entropie. Konnektiwiteitsgrafieke verkry deur hierdie ekstraksie-metodes is gebruik om die proses in veelvoudige blokke te skei. Twee kenmerkekstraksiemetodes is hierna toegepas om foutdeteksie te bewerkstellig: hoofkomponentanalise (HKA), ʼn liniêre metode; en kernhoofkomponentanalise (KHKA), ʼn nie-lineêre metode. Boonop was drie tipes moniteringskaart metodes vergelyk: Shewhart kaarte, eksponensieel-geweegde bewegende gemiddelde kaarte en kumulatiewe som kaarte. Twee metodes om simptoom veranderlikes te identifiseer vir foutidentifikasie was daarna vergelyk: gebruik van individuele veranderlikes; en inagneming van die verandering in konnektiwiteit. Die konnektiwiteitgrafieke was daarna gebruik om hoofoorsake van foute op te spoor. Dit is gevind dat topologie informasie nuttig was vir foutidentifikasie vir meeste van die fouttoestande ondersoek. Nogtans was die prestasie onsamehangend, aangesien dit afhanklik is van die akkuraatheid waarmee topologie ekstraksie uitgevoer is. Daar was ook afgelei dat die gebruik van topologie blokke beduidend die fout-opspooring en foutidentifikasie prestasie verbeter het. ʼn Aanbevole foutdiagnose strategie is voorgestel.
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Zhang, Rui. "Sink localization and topology control in large scale heterogeneous wireless sensor networks." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002048.
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Qureshi, Hassaan Khaliq. "Graph-theoretic channel modeling and topology control protocols for wireless sensor networks." Thesis, City University London, 2011. http://openaccess.city.ac.uk/1168/.
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This report addresses two different research problems: (i) It presents a wireless channel model that reduces the complexity associated with high order Markov chains; and (ii) presents energy efficient topology control protocols which provide reliability while maintaining the topology in an energy efficient manner. For the above problems, real wireless sensor network traces were collected and extensive simulations were performed for evaluating the proposed protocols. Accurate simulation and analysis of wireless networks are inherently dependent on accurate models which are able to provide real-time channel characterization. High-order Markov chains are typically used to model errors and losses over wireless channels. However, complexity (i.e., the number of states) of a high-order Markov model increases exponentially with the memory-length of the underlying channel. In this report, a novel graph-theoretic methodology that uses Hamiltonian circuits to reduce the complexity of a high-order Markov model to a desired state budget is presented. The implication of unused states in complexity reduction of higher order Markov model is also explained. The trace-driven performance evaluations for real wireless local area network (WLAN) and wireless sensor network (WSN) channels demonstrate that the proposed Hamiltonian Model, while providing orders of magnitude reduction in complexity, renders an accuracy that is comparable to the Markov model and better than the existing reduced state models. Furthermore, a methodology to preserve energy is presented to increase the network lifetime by reducing the node degree forming an active backbone while considering network connectivity. However, in energy stringent wireless sensor networks, it is of utmost importance to construct the reduced topology with the minimal control overhead. Moreover, most wireless links in practice are lossy links with connectivity probability which desires that a routing protocol provides routing flexibility and reliability at a minimum energy consumption cost. For this purpose, distributed and semi-distributed novel graph-theoretic topology construction protocols are presented that exploit cliques and polygons in a WSN to achieve energy efficiency and reliability. The proposed protocols also facilitate load rotation under topology maintenance, thereby extending the network lifetime. In addition to the above, the report also evaluates why the backbone construction using connected dominating set (CDS) in certain cases remains unable to provide connected sensing coverage in the area covered. For this purpose, a novel protocol that reduces the topology while considering sensing area coverage is presented.
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Mudali, Pragasen. "Topology control for wireless mesh networks and its effect on network performance." Thesis, University of Zululand, 2017. http://hdl.handle.net/10530/1565.
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A thesis submitted to the Faculty of Science and Agriculture in fulfilment of the Degree of Doctor of Philosophy in the Department of Computer Science at the University of Zululand, 2017InfrastructureWireless Mesh Networks (I-WMNs) are increasingly used to provide network connectivity and Internet access to previously under-served areas in the developing world. It is common for some of these deployments to be battery-powered due to a lack of electrical infrastructure in the targeted areas. Thus, the energy-efficiency of these networks gains additional importance. Topology Control (TC) has been previously reported to improve the energy-efficiency and network performance of wireless ad-hoc networks, including I-WMNs. However,simulation-based studies have been relied upon to reach these conclusions and the study of TC prototypes applicable to I-WMNs has largely been limited to design issues. Thus, the study of the efficacy of TC prototypes as a mechanism for improving energy-fficiency and network performance remains an open issue. The thesis addresses this knowledge gap by studying the dynamic, run-time behaviours and the network topologies created by two standards-compatible TC prototypes. This study provides unique insight into how the prototypes consume computational resources, maintain network connectivity, produce cumulative transceiver power savings and affect the workings of the routing protocol being employed. This study also documents the topology instability caused by transceiver power oscillations produced by the PlainTC prototype. A context-based solution to reduce transceiver power oscillations and the subsequent topology instability is proposed. This solution applies the Principal Component Analysis statistical method to historical network data in order to derive the weights associated with each of the identified context variables. A threshold value is defined that only permits a node to adjust its transceiver power output if the observed change in a node’s context exceeds the threshold. The threshold mechanism is incorporated into the PlainTC+ prototype and is shown to reduce topology instability whilst improving network performance when compared to PlainTC.The results obtained in this study suggest that I-WMN topologies formed by TC are able to closely match the performance of networks that do not employ TC. However, this study shows that TC negatively affects the energy efficiency of the network despite achieving cumulative transceiver power savings.
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Johansson, Alexander. "Distributed PI Control in Multi-Agent Systems: From Anti-Windup to Topology." Thesis, KTH, Reglerteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206433.
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In this thesis, we study the impact of input saturation on multiagentsystems, which are controlled by the recently developed DAPI (DistributedAveraging Proportional Integral) control scheme. We are alsostudying modern anti-windup synthesis for these systems. Specically,we are constructing anti-windup compensators through a method thatminimizes an upper bound of the L2-gain globally for asymptotically stablecontrol systems. Both static and dynamic anti-windup compensatorsare constructed. Numerical examples of a water tank and a microgrid areconsidered. It is veried in simulations that the constructed compensatorssuccessfully prevent windup caused by actuator saturation, and that thedynamic compensator has better performance. The performance of thesecompensators are also compared with the classical anti-windup method,called back calculation.During our study of anti-windup compensators, we found a partiallyrelated problem, which is also included in the thesis. The problem is toarrange the edge weights in a multi-agent system such that the L2-gainis minimized. This problem does not include input saturation but theconnection is the minimization of an upper bound of the L2-gain and themulti-agent systems. For the considered class of multi-agent systems, weestablish a connection between the algebraic connectivity and an upperbound of the L2-gain.Denna uppsats är en studie om hur insignalsmättnad påverkar multiagentsystem som är reglerade med den nyutvecklade DAPI (DistributedAveraging Proportional Integral) regulatorn. Vi studerar också modernametoder för att dämpa effekten av insignalsmättnad. Mer specifikt,så konstruerar vi anti-uppvridningskompensatorer genom en metod somminimerar en övre gräns för L2-förstärkningen globalt för asymptotisktstabila reglersystem. Både statiska och dynamiska anti- uppvridningskompensatorerkonstrueras. Vi undersöker två numeriska exempel: det ena ärett vattentankexempel och det andra ett elektriskt mikronät. Vi verifierargenom simulationer att de konstruerade kompensatorerna framgångsriktdämpar effekten av insignalsmättnad och att den dynamiska kompensatornpresterar bättre. Prestandan är också jämförd med en klassiskanti-uppvridningskompensator.Under vår studie av anti-uppvridningskompensatorer så hittade vi ettintressant ödesnätverksproblem som också är inkluderat i uppsatsen.Detta problem inkluderar inte insignalsmättnad men kopplingen till restenav uppsatsen är minimering av en övre gräns av L2-förstärkningen ochmulti-agent system. För den studerade klassen av ödesnätverk härledervi en koppling mellan den algebraiska konnektiviteten hos ödesnätverketoch en övre gräns på L2-förstärkningen. Denna övre gräns är verifierad isimulationer.
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Kollipara, Nagasri. "Control and Optimization of Power in LLC Converter Using Phase Control." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1535402155288153.
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Park, Jaejong. "Advanced Topology Optimization Techniques for Engineering and Biomedical Problems." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534347400733419.
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Liu, Hui. "Topology Control, Routing Protocols and Performance Evaluation for Mobile Wireless Ad Hoc Networks." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/cs_diss/3.
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A mobile ad-hoc network (MANET) is a collection of wireless mobile nodes forming a temporary network without the support of any established infrastructure or centralized administration. There are many potential applications based the techniques of MANETs, such as disaster rescue, personal area networking, wireless conference, military applications, etc. MANETs face a number of challenges for designing a scalable routing protocol due to their natural characteristics. Guaranteeing delivery and the capability to handle dynamic connectivity are the most important issues for routing protocols in MANETs. In this dissertation, we will propose four algorithms that address different aspects of routing problems in MANETs. Firstly, in position based routing protocols to design a scalable location management scheme is inherently difficult. Enhanced Scalable Location management Service (EnSLS) is proposed to improve the scalability of existing location management services, and a mathematical model is proposed to compare the performance of the classical location service, GLS, and our protocol, EnSLS. The analytical model shows that EnSLS has better scalability compared with that of GLS. Secondly, virtual backbone routing can reduce communication overhead and speedup the routing process compared with many existing on-demand routing protocols for routing detection. In many studies, Minimum Connected Dominating Set (MCDS) is used to approximate virtual backbones in a unit-disk graph. However finding a MCDS is an NP-hard problem. In the dissertation, we develop two new pure localized protocols for calculating the CDS. One emphasizes forming a small size initial near-optimal CDS via marking process, and the other uses an iterative synchronized method to avoid illegal simultaneously removal of dominating nodes. Our new protocols largely reduce the number of nodes in CDS compared with existing methods. We show the efficiency of our approach through both theoretical analysis and simulation experiments. Finally, using multiple redundant paths for routing is a promising solution. However, selecting an optimal path set is an NP hard problem. We propose the Genetic Fuzzy Multi-path Routing Protocol (GFMRP), which is a multi-path routing protocol based on fuzzy set theory and evolutionary computing.
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Kamran, Farrukh. "A new UPS topology and deadbeat control techniques for improved utility interface compatibility." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15773.
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Yin, Bolian. "Adaptive clustering and transmission range adjustment for topology control in wireless sensor networks." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4485.
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Thesis (Ph. D.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2007) Vita. Includes bibliographical references.
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Mao, Hong. "Topology and control investigation for low-voltage high-current isolated DC-DC converters." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/4405.
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University of Central Florida College of Engineering ThesisHigh conversion efficiency and fast transient response at high switching frequency are the two main challenges for low-voltage high-current DC-DC converters, which are the motivations of the dissertation work. To reduce the switching power loss, soft switching is a desirable technique to keep power loss under control at high switching frequencies. A Duty-Cycle-Shift (DCS) concept is proposed for half-bridge DC-DC converters to reduce switching loss. The concept of this new control scheme is shifting one of the two symmetric PWM driving signals close to the other, such that ZVS can be achieved for the lagging switch due to the shortened resonant interval.
Ph.D.
Doctorate;
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical and Computer Engineering
216 p.
xviii, 216 leaves, bound : ill. ; 28 cm.
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Borman, Duncan James. "Mechatronic system topology and control for high-speed, high-reliability textile inkjet printing." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427769.
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Gong, Ning. "Resilient Control Strategy and Analysis for Power Systems using (n, k)-Star Topology." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/410406.
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Electrical EngineeringPh.D.
This research focuses on developing novel approaches in load balancing and restoration problems in electrical power distribution systems. The first approach introduces an inter-connected network topology, referred to as (n, k)-star topology. While power distribution systems can be constructed in different communication network topologies, the performance and fault assessment of the networked systems can be challenging to analyze. The (n, k)-star topologies have well defined performance and stability analysis metrics. Typically, these metrics are defined based on: i) degree, ii) diameter, and iii) conditional diagnosability of a faulty node. These parameters could be evaluated and assessed before a physical (n, k)-star topology power distribution system is constructed. Moreover, in the second approach, we evaluate load balancing problems by using a decentralized algorithm, i.e., the Multi-Agent System (MAS) based consensus algorithm on an (n, k)-star power topology. With aforementioned research approaches, an (n, k)-star power distribution system can be assessed with proposed metrics and assessed with encouraging results compared to other topology networked systems. Other encouraging results are found in efficiency and performance enhancement during information exchange using the decentralized algorithm. It has been proven that a load balance solution is convergent and asymptotically stable with a simple gain controller. The analysis can be achieved without constructing a physical network to help evaluate the design. Using the (n, k)-star topology and MAS, the load balancing/restoration problems can be solved much more quickly and accurately compared to other approaches shown in the literature.
Temple University--Theses
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Schmidt, Martin-Pierre. "Computational generation and optimization of mechanical structures On structural topology optimization using graded porosity control Structural topology optimization with smoothly varying fiber orientations." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR01.
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Cette thèse étudie et développe des méthodes de modélisation mathématique, analyse et optimisation numérique appliquées à la génération d’objets 3D. Les approches proposées sont utilisées pour la génération de structures lattices et de structure continue par optimisation topologiqueThis thesis studies and develops methods for mathematical modeling, numerical analysis and optimization applied to the generation of 3D objects. The proposed approaches are used to generate lattice structures and continuum structures with topology optimization
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Belhoul, Yacine. "Graph-based Ad Hoc Networks Topologies and Business Process Matching." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10202.
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Un réseau mobile ad hoc (Mobile Ad hoc Network, MANET) est un réseau sans fil, formé dynamiquement par un ensemble d'utilisateurs équipés de terminaux mobiles, sans l'utilisation d'une infrastructure préexistante, ou d'une administration centralisée. Les équipements utilisés dans les MANETs sont limités par la capacité de la batterie, la puissance de calcul et la bande passante. Les utilisateurs des MANETs sont libres de se déplacer, ce qui induit à des topologies dynamiques dans le temps. Toutes ces contraintes ajoutent plus de challenges aux protocoles et services de communications afin de fonctionner dans les MANETs. L'évolution des réseaux de 4ème génération (4G) est appelée à intégrer les MANETs avec les autres types de réseaux afin d'étendre leurs portées. Nous nous sommes intéressés dans la première partie de cette thèse à quelques challenges connus dans les MANETs en proposant des solutions novatrices utilisant des propriétés intéressantes des topologies de graphes. Dans un premier temps, nous avons effectué une étude sur la prédiction de la mobilité afin de maintenir une topologie d'ensemble dominant connecté dans les MANETs. Nous avons proposé dans un autre travail comment construire des topologies de graphes ayant des propriétés globales en se basant seulement sur des informations locales des nœuds mobiles. Ces topologies servent comme overlay aux MANETs. Nous avons proposé des algorithmes distribués pour construire des alliances offensives et défensives globales minimales. Nous avons aussi défini des heuristiques pour ces algorithmes afin de réduire les tailles des alliances obtenues. La première partie de cette thèse est achevée par la proposition d'un framework pour la conception et l'analyse des protocoles de contrôle de topologie dans les MANETs. Nous avons identifié les points communs des algorithmes de contrôle de topologie conçus pour les réseaux mobiles ad hoc et nous avons enrichi le simulateur NS-2 avec un ensemble d'extensions pour supporter le contrôle de topologieWe are interested in this thesis to graph-based approaches to deal with some challenges in networking, namely, graph topologies of mobile ad hoc networks (MANETs) and process model matchmaking in large scale web service. We propose in the first part: (1) a generic mechanism using mobility information of nodes to maintain a graph topology of the network. We show particularly, how to use the prediction of future emplacements of nodes to maintain a connected dominating set of a given MANET. (2) distributed algorithms to construct minimal global offensive alliance and global defensive alliance sets in MANETs. We also introduce several heuristics to get a better approximation of the cardinality of the alliance sets which is a desirable property for practical considerations. (3) a framework to facilitate the design and evaluation of topology control protocols in MANETs. We propose in the framework, a common schema for topology control based on NS-2 simulator and inspired from the commonalities between the components of the topology control algorithms in MANETs. In the second part, we focus on process model matchmaking. We propose two graph-based solutions for process model inexact matching to deal with high computational time of existing work in the literature. In the first solution, we decompose the process models into their possible execution sequences. After, we propose generic graph techniques using string comparator metrics for process model matchmaking based on this decomposition. In order to get better optimization of the execution time and to deal with process model matching in large scale web services, the second solution combines a spectral graph matching with structural and semantic proposed approaches. This solution uses an eigen-decomposition projection technique that makes the runtime faster
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Chiwewe, Tapiwa Moses. "A distributed topology control technique for low interference and energy efficiency in wireless sensor networks." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/22800.
Full textAbstract:
Wireless sensor networks are used in several multi-disciplinary areas covering a wide variety of applications. They provide distributed computing, sensing and communication in a powerful integration of capabilities. They have great long-term economic potential and have the ability to transform our lives. At the same time however, they pose several challenges – mostly as a result of their random deployment and non-renewable energy sources.Among the most important issues in wireless sensor networks are energy efficiency and radio interference. Topology control plays an important role in the design of wireless ad hoc and sensor networks; it is capable of constructing networks that have desirable characteristics such as sparser connectivity, lower transmission power and a smaller node degree.In this research a distributed topology control technique is presented that enhances energy efficiency and reduces radio interference in wireless sensor networks. Each node in the network makes local decisions about its transmission power and the culmination of these local decisions produces a network topology that preserves global connectivity. The topology that is produced consists of a planar graph that is a power spanner, it has lower node degrees and can be constructed using local information. The network lifetime is increased by reducing transmission power and the use of low node degrees reduces traffic interference. The approach to topology control that is presented in this document has an advantage over previously developed approaches in that it focuses not only on reducing either energy consumption or radio interference, but on reducing both of these obstacles. Results are presented of simulations that demonstrate improvements in performance. AFRIKAANS : Draadlose sensor netwerke word gebruik in verskeie multi-dissiplinêre areas wat 'n wye verskeidenheid toepassings dek. Hulle voorsien verspreide berekening, bespeuring en kommunikasie in 'n kragtige integrate van vermoëns. Hulle het goeie langtermyn ekonomiese potentiaal en die vermoë om ons lewens te herskep. Terselfdertyd lewer dit egter verskeie uitdagings op as gevolg van hul lukrake ontplooiing en nie-hernubare energie bronne. Van die belangrikste kwessies in draadlose sensor netwerke is energie-doeltreffendheid en radiosteuring. Topologie-beheer speel 'n belangrike rol in die ontwerp van draadlose informele netwerke en sensor netwerke en dit is geskik om netwerke aan te bring wat gewenste eienskappe het soos verspreide koppeling, laer transmissiekrag en kleiner nodus graad.In hierdie ondersoek word 'n verspreide topologie beheertegniek voorgelê wat energie-doeltreffendheid verhoog en radiosteuring verminder in draadlose sensor netwerke. Elke nodus in die netwerk maak lokale besluite oor sy transmissiekrag en die hoogtepunt van hierdie lokale besluite lewer 'n netwerk-topologie op wat globale verbintenis behou.Die topologie wat gelewer word is 'n tweedimensionele grafiek en 'n kragsleutel; dit het laer nodus grade en kan gebou word met lokale inligting. Die netwerk-leeftyd word vermeerder deur transmissiekrag te verminder en verkeer-steuring word verminder deur lae nodus grade. Die benadering tot topologie-beheer wat voorgelê word in hierdie skrif het 'n voordeel oor benaderings wat vroeër ontwikkel is omdat dit nie net op die vermindering van net energie verbruik of net radiosteuring fokus nie, maar op albei. Resultate van simulasies word voorgelê wat die verbetering in werkverrigting demonstreer.Dissertation (MEng)--University of Pretoria, 2011.
Electrical, Electronic and Computer Engineering
unrestricted
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Srivastava, Vivek. "Behavior-based Incentives for Node Cooperation in Wireless Ad Hoc Networks." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29172.
Full textAbstract:
A Mobile Ad Hoc Network (MANET) adopts a decentralized communication architecture which relies on cooperation among nodes at each layer of the protocol stack. Its reliance on cooperation for success and survival makes the ad hoc network particularly sensitive to variations in node behavior. Specifically, for functions such as routing, nodes which are limited in their resources may be unwilling to cooperate in forwarding for other nodes. Such selfish behavior leads to degradation in the performance of the network and possibly, in the extreme case, a complete cessation of operations. Consequently it is important to devise solutions to encourage resource-constrained nodes to cooperate.
Incentive schemes have been proposed to induce selfish nodes to cooperate. Though many of the proposed schemes in the literature are payment-based, nodes can be incentivized to cooperate by adopting policies which are non-monetary in nature, but rather are based on the threat of retaliation for non-cooperating nodes. These policies, for which there is little formal analysis in the existing literature on node cooperation, are based on observed node behavior. We refer to them as behavior-based incentives. In this work, we analyze the effectiveness of behavior-based incentives in inducing nodes to cooperate.
To determine whether an incentive scheme is effective in fostering cooperation we develop a game-theoretic model. Adopting a repeated game model, we show that nodes may agree to cooperate in sharing their resources and forward packets, even if they perceive a cost in doing so. This happens as the nodes recognize that refusing to cooperate will result in similar behavior by others, which ultimately would compromise the viability of the network as a whole.
A major shortcoming in the analysis done in past works is the lack of consideration of practical constraints imposed by an ad hoc environment. One such example is the assumption that a node, when making decisions about whether to cooperate, has perfect knowledge of every other node's actions. In a distributed setting this is impractical. In our work, we analyze behavior-based incentives by incorporating such practical considerations as imperfect monitoring into our game-theoretic models. In modeling the problem as a game of imperfect public monitoring (nodes observe a common public signal that reflects the actions of other nodes in the network) we show that, under the assumption of first order stochastic dominance of the public signal, the grim trigger strategy leads to an equilibrium for nodes to cooperate.
Even though a trigger-based strategy like grim-trigger is effective in deterring selfish behavior it is too harsh in its implementation. In addition, the availability of a common public signal in a distributed setting is rather limited. We, therefore, consider nodes that individually monitor the behavior of other nodes in the network and keep this information private. Note that this independent monitoring of behavior is error prone as a result of slow switching between transmit and promiscuous modes of operation, collisions and congestion due to the wireless medium, or incorrect feedback from peers. We propose a probability-based strategy that induces nodes to cooperate under such a setting. We analyze the strategy using repeated games with imperfect private monitoring and show it to be robust to errors in monitoring others" actions. Nodes achieve a near-optimal payoff at equilibrium when adopting this strategy.
This work also characterizes the effects of a behavior-based incentive, applied to induce cooperation, on topology control in ad hoc networks. Our work is among the first to consider selfish behavior in the context of topology control. We create topologies based on a holistic view of energy consumption " energy consumed in forwarding packets as well as in maintaining links. Our main results from this work are to show that: (a) a simple forwarding policy induces nodes to cooperate and leads to reliable paths in the generated topology, (b) the resulting topologies are well-connected, energy-efficient and exhibit characteristics similar to those in small-world networks.Ph. D.