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- Genre: Academic theses
Description
Communication networks, both wired and wireless, are expected to have a certain level of fault-tolerance capability.These networks are also expected to ensure a graceful degradation in performance when some of the network components fail. Traditional studies on fault tolerance in communication networks, for the most part, make no assumptions regarding the location of node/link faults, i.e., the faulty nodes and links may be close to each other or far from each other. However, in many real life scenarios, there exists a strong spatial correlation among the faulty nodes and links. Such failures are often encountered in disaster situations, e.g., natural calamities or enemy attacks. In presence of such region-based faults, many of traditional network analysis and fault-tolerant metrics, that are valid under non-spatially correlated faults, are no longer applicable. To this effect, the main thrust of this research is design and analysis of robust networks in presence of such region-based faults. One important finding of this research is that if some prior knowledge is available on the maximum size of the region that might be affected due to a region-based fault, this piece of knowledge can be effectively utilized for resource efficient design of networks. It has been shown in this dissertation that in some scenarios, effective utilization of this knowledge may result in substantial saving is transmission power in wireless networks. In this dissertation, the impact of region-based faults on the connectivity of wireless networks has been studied and a new metric, region-based connectivity, is proposed to measure the fault-tolerance capability of a network. In addition, novel metrics, such as the region-based component decomposition number(RBCDN) and region-based largest component size(RBLCS) have been proposed to capture the network state, when a region-based fault disconnects the network. Finally, this dissertation presents efficient resource allocation techniques that ensure tolerance against region-based faults, in distributed file storage networks and data center networks.
ContributorsBanerjee, Sujogya (Author) / Sen, Arunabha (Thesis advisor) / Xue, Guoliang (Committee member) / Richa, Andrea (Committee member) / Hurlbert, Glenn (Committee member) / Arizona State University (Publisher)
Created2013
Description
Majority of the Sensor networks consist of low-cost autonomously powered devices, and are used to collect data in physical world. Today's sensor network deployments are mostly application specific & owned by a particular entity. Because of this application specific nature & the ownership boundaries, this modus operandi hinders large scale sensing & overall network operational capacity. The main goal of this research work is to create a mechanism to dynamically form personal area networks based on mote class devices spanning ownership boundaries. When coupled with an overlay based control system, this architecture can be conveniently used by a remote client to dynamically create sensor networks (personal area network based) even when the client does not own a network. The nodes here are "borrowed" from existing host networks & the application related to the newly formed network will co-exist with the native applications thanks to concurrency. The result allows users to embed a single collection tree onto spatially distant networks as if they were within communication range. This implementation consists of core operating system & various other external components that support injection maintenance & dissolution sensor network applications at client's request. A large object data dissemination protocol was designed for reliable application injection. The ability of this system to remotely reconfigure a network is useful given the high failure rate of real-world sensor network deployments. Collaborative sensing, various physical phenomenon monitoring also be considered as applications of this architecture.
ContributorsFernando, M. S. R (Author) / Dasgupta, Partha (Thesis advisor) / Bhattacharya, Amiya (Thesis advisor) / Gupta, Sandeep (Committee member) / Arizona State University (Publisher)
Created2013
Description
As networks are playing an increasingly prominent role in different aspects of our lives, there is a growing awareness that improving their performance is of significant importance. In order to enhance performance of networks, it is essential that scarce networking resources be allocated smartly to match the continuously changing network environment. This dissertation focuses on two different kinds of networks - communication and social, and studies resource allocation problems in these networks. The study on communication networks is further divided into different networking technologies - wired and wireless, optical and mobile, airborne and terrestrial. Since nodes in an airborne network (AN) are heterogeneous and mobile, the design of a reliable and robust AN is highly complex. The dissertation studies connectivity and fault-tolerance issues in ANs and proposes algorithms to compute the critical transmission range in fault free, faulty and delay tolerant scenarios. Just as in the case of ANs, power optimization and fault tolerance are important issues in wireless sensor networks (WSN). In a WSN, a tree structure is often used to deliver sensor data to a sink node. In a tree, failure of a node may disconnect the tree. The dissertation investigates the problem of enhancing the fault tolerance capability of data gathering trees in WSN. The advent of OFDM technology provides an opportunity for efficient resource utilization in optical networks and also introduces a set of novel problems, such as routing and spectrum allocation (RSA) problem. This dissertation proves that RSA problem is NP-complete even when the network topology is a chain, and proposes approximation algorithms. In the domain of social networks, the focus of this dissertation is study of influence propagation in presence of active adversaries. In a social network multiple vendors may attempt to influence the nodes in a competitive fashion. This dissertation investigates the scenario where the first vendor has already chosen a set of nodes and the second vendor, with the knowledge of the choice of the first, attempts to identify a smallest set of nodes so that after the influence propagation, the second vendor's market share is larger than the first.
ContributorsShirazipourazad, Shahrzad (Author) / Sen, Arunabha (Committee member) / Xue, Guoliang (Committee member) / Richa, Andrea (Committee member) / Saripalli, Srikanth (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation research analyzes the vernacular cosmopolitan praxis of Muslim women in transnational cyberspaces related to topical and collective action networks, in an effort to detangle cosmopolitanism from its Western biases and to move away from studies of online Muslim populations based on geographical locations or homogenous networks, linking individuals through their religious practices or consumption of religious knowledge. Through highlighting praxes rather than contexts, this dissertation disrupts the East/West binary and challenges stereotypes ascribed to Muslim women. One of the research questions related to the cosmopolitan praxis of Muslim women is the following: in what ways do Muslim women engage with "others" online and contribute to bridging dissimilar people? Findings suggest that the social media use of Muslim women contributes to their subtle resistance against communal norms and, although it can serve as an extension to their voices, some of their voices are more readily mediated than others. I employ a connective content analysis methodology to put various datasets associated with topics and collective actions related to Muslim women into conversation. The methodology not only highlights consistencies in the qualitative themes that were iteratively developed through the analyses of the datasets, but also more tangible connections related to social media users, topics, and content. Consequently, this thesis is as much concerned with recasting Western-oriented conceptualizations of cosmopolitanism as it is with how networks dynamics foster and constrain cosmopolitan praxis because digital networks have the extraordinary capacity to link dissimilar people beyond any other type of medium. One of the research questions related to the methodology is: how do network dynamics facilitate and constrain cosmopolitan praxis? The substantive chapters related to the datasets discuss various forms of cosmopolitan praxis that were identified in the analysis: social media use by Muslim women that expands the connective memory, which could contribute to dispelling stereotypes ascribed to them; activism that addresses universal concerns related to women's rights regardless of context; dialogically devising basic standards of social conduct and gender relations; and expressions of tolerance toward divergent views, including alternative interpretations of Islamic beliefs and practices.
ContributorsRobinson, Rebecca S (Author) / Lim, Merlyna (Thesis advisor) / Ali, Souad T. (Committee member) / Parmentier, Mary Jane C, (Committee member) / Arizona State University (Publisher)
Created2014
Description
As the number of devices with wireless capabilities and the proximity of these devices to each other increases, better ways to handle the interference they cause need to be explored. Also important is for these devices to keep up with the demand for data rates while not compromising on industry established expectations of power consumption and mobility. Current methods of distributing the spectrum among all participants are expected to not cope with the demand in a very near future. In this thesis, the effect of employing sophisticated multiple-input, multiple-output (MIMO) systems in this regard is explored. The efficacy of systems which can make intelligent decisions on the transmission mode usage and power allocation to these modes becomes relevant in the current scenario, where the need for performance far exceeds the cost expendable on hardware. The effect of adding multiple antennas at either ends will be examined, the capacity of such systems and of networks comprised of many such participants will be evaluated. Methods of simulating said networks, and ways to achieve better performance by making intelligent transmission decisions will be proposed. Finally, a way of access control closer to the physical layer (a 'statistical MAC') and a possible metric to be used for such a MAC is suggested.
ContributorsThontadarya, Niranjan (Author) / Bliss, Daniel W (Thesis advisor) / Berisha, Visar (Committee member) / Ying, Lei (Committee member) / Arizona State University (Publisher)
Created2014
Description
This thesis presents a model for the buying behavior of consumers in a technology market. In this model, a potential consumer is not perfectly rational, but exhibits bounded rationality following the axioms of prospect theory: reference dependence, diminishing returns and loss sensitivity. To evaluate the products on different criteria, the analytic hierarchy process is used, which allows for relative comparisons. The analytic hierarchy process proposes that when making a choice between several alternatives, one should measure the products by comparing them relative to each other. This allows the user to put numbers to subjective criteria. Additionally, evidence suggests that a consumer will often consider not only their own evaluation of a product, but also the choices of other consumers. Thus, the model in this paper applies prospect theory to products with multiple attributes using word of mouth as a criteria in the evaluation.
ContributorsElkholy, Alexander (Author) / Armbruster, Dieter (Thesis advisor) / Kempf, Karl (Committee member) / Li, Hongmin (Committee member) / Arizona State University (Publisher)
Created2014
Description
The rigidity of a material is the property that enables it to preserve its structure when deformed. In a rigid body, no internal motion is possible since the degrees of freedom of the system are limited to translations and rotations only. In the macroscopic scale, the rigidity and response of a material to external load can be studied using continuum elasticity theory. But when it comes to the microscopic scale, a simple yet powerful approach is to model the structure of the material and its interparticle interactions as a ball$-$and$-$spring network. This model allows a full description of rigidity in terms of the vibrational modes and the balance between degrees of freedom and constraints in the system.
In the present work, we aim to establish a microscopic description of rigidity in \emph{disordered} networks. The studied networks can be designed to have a specific number of degrees of freedom and/or elastic properties. We first look into the rigidity transition in three types of networks including randomly diluted triangular networks, stress diluted triangular networks and jammed networks. It appears that the rigidity and linear response of these three types of systems are significantly different. In particular, jammed networks display higher levels of self-organization and a non-zero bulk modulus near the transition point. This is a unique set of properties that have not been observed in any other types of disordered networks. We incorporate these properties into a new definition of jamming that requires a network to hold one extra constraint in excess of isostaticity and have a finite non-zero bulk modulus. We then follow this definition by using a tuning by pruning algorithm to build spring networks that have both these properties and show that they behave exactly like jammed networks. We finally step into designing new disordered materials with desired elastic properties and show how disordered auxetic materials with a fully convex geometry can be produced.
In the present work, we aim to establish a microscopic description of rigidity in \emph{disordered} networks. The studied networks can be designed to have a specific number of degrees of freedom and/or elastic properties. We first look into the rigidity transition in three types of networks including randomly diluted triangular networks, stress diluted triangular networks and jammed networks. It appears that the rigidity and linear response of these three types of systems are significantly different. In particular, jammed networks display higher levels of self-organization and a non-zero bulk modulus near the transition point. This is a unique set of properties that have not been observed in any other types of disordered networks. We incorporate these properties into a new definition of jamming that requires a network to hold one extra constraint in excess of isostaticity and have a finite non-zero bulk modulus. We then follow this definition by using a tuning by pruning algorithm to build spring networks that have both these properties and show that they behave exactly like jammed networks. We finally step into designing new disordered materials with desired elastic properties and show how disordered auxetic materials with a fully convex geometry can be produced.
ContributorsFaghir Hagh, Varda (Author) / Thorpe, Michael F. (Thesis advisor) / Beckstein, Oliver (Committee member) / Chamberlin, Ralph V. (Committee member) / Schmidt, kevin E. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Transportation network connectivity has been linked to positive urban outcomes, including increased rates of active transportation, reduced reliance on automobiles and other social and economic benefits. While many stakeholders in greenfield development processes have emphasized the positive benefits of connectivity and connectivity has increased in many U.S. metros in the past two decades, many street networks remain fragmented and local connectivity remains far below that of historic patterns. This paper explores barriers to and influences on connectivity outcomes in new community construction in the Phoenix metropolitan area, employing mixed qualitative and quantitative methods. Interviews were conducted with members from various stakeholder groups in the subdivision development process. Case studies were developed with space syntax and network analysis measurements to illustrate the influence of variables and stakeholders on the planning process. Participants illustrated a complex political and economic reality surrounding the concept of connectivity, with site conditions and development market dynamics playing the clearest roles in shaping connectivity. The result is subdivisions are achieving moderate levels of connectivity and improving from historic patterns of dendricity but remain entrenched in planning paradigms built around self-contained sites and the policy and market limitations for robust connectivity beyond individual developments.
ContributorsSchumerth, Noah John (Author) / King, David A (Thesis advisor) / Kuby, Michael (Committee member) / Lindsay, Lucas (Committee member) / Arizona State University (Publisher)
Created2022
Description
When does coercion succeed in international relations? Why do states resist coercion in some cases but concede in others? This dissertation adopts network analysis to investigate the network factors influencing the success and failure of economic and military coercion. The first chapter addresses the coercion target states’ information problem regarding how coercers would react to the targets’ resistances and concessions. By regarding resistances and concessions as network ties that can transmit information, it argues that past coercion outcomes endogenously influence targets’ current responses and coercion outcomes. Specifically, target states are more likely to concede to coercers who have been successful in gaining others’ compliance. Sender states are more likely to succeed in coercion when they had successful coercion in the past. The second chapter adds a condition to the first chapter’s argument. It argues that when being coerced by the same sender, a stronger sanction target’s compliance is likely to prompt a weaker target’s acquiescence, and that a weaker target’s resistance is likely to prompt a stronger target’s resistance. The third chapter explores how states’ positions in international security and economic networks influence the success and failure of military and trade coercion. States that occupy different network positions own different network power. I argue that when the coercion sender has relatively more network power than the target, the more likely coercion will be successful. I use interstate military alliances and arms transfer data to operationalize international security networks. International economic networks are operationalized by bilateral trade and regional trade agreements networks. Using military and trade coercion outcomes in the Military Compellent Threats (MCT) and the Threats and Imposition of Economic Sanctions (TIES) datasets as outcome variables, the statistical analysis partially supports my argument. Trade coercion is more likely to succeed when the sender has more network power. However, military coercion is less likely to succeed when the sender has more network power than the target.
ContributorsAi, Weining (Author) / Peterson, Timothy (Thesis advisor) / Thies, Cameron (Committee member) / Thomson, Henry (Committee member) / Chyzh, Olga (Committee member) / Arizona State University (Publisher)
Created2023
Description
The human transcriptional regulatory machine utilizes hundreds of transcription factors which bind to specific genic sites resulting in either activation or repression of targeted genes. Networks comprised of nodes and edges can be constructed to model the relationships of regulators and their targets. Within these biological networks small enriched structural patterns containing at least three nodes can be identified as potential building blocks from which a network is organized. A first iteration computational pipeline was designed to generate a disease specific gene regulatory network for motif detection using established computational tools. The first goal was to identify motifs that can express themselves in a state that results in differential patient survival in one of the 32 different cancer types studied. This study identified issues for detecting strongly correlated motifs that also effect patient survival, yielding preliminary results for possible driving cancer etiology. Second, a comparison was performed for the topology of network motifs across multiple different data types to identify possible divergence from a conserved enrichment pattern in network perturbing diseases. The topology of enriched motifs across all the datasets converged upon a single conserved pattern reported in a previous study which did not appear to diverge dependent upon the type of disease. This report highlights possible methods to improve detection of disease driving motifs that can aid in identifying possible treatment targets in cancer. Finally, networks where only minimally perturbed, suggesting that regulatory programs were run from evolved circuits into a cancer context.
ContributorsStriker, Shawn Scott (Author) / Plaisier, Christopher (Thesis advisor) / Brafman, David (Committee member) / Wang, Xiao (Committee member) / Arizona State University (Publisher)
Created2020