113 Matching Results

Search Results

Advanced search parameters have been applied.

Mapping the evolution of scientific ideas

Description: Despite the apparent conceptual boundaries of scientific fields, a formal description for their evolution is lacking. Here we describe a novel approach to study the dynamics and evolution of scientific fields using a network-based analysis. We build an idea network consisting of American Physical Society PACS numbers as nodes representing scientific concepts. Two PACS numbers are linked if there exist publications that reference them simultaneously. We locate scientific fields using Cfinder, an overlapping community finding algorithm, and describe the time evolution of these fields using a community evolution method over the course of 1985-2006. The communities we identify map to known scientific fields, and their age strongly depends on t.heir size, impact and activity. Our analysis further suggests that communities that redefine themselves by merging and creating new groups of ideas tend to have more fitness as measured by the impact per paper, and hence communities with a higher fitness tend to be short-lived. The described approach to quantify the evolution of ideas may be relevant in making predictions about the future of science and how to guide its development.
Date: January 1, 2009
Creator: Roberts, David; Herrera, Mark & Gulbahce, Natali
Partner: UNT Libraries Government Documents Department

Analysis of community structure in networks of correlated data

Description: We present a reformulation of modularity that allows the analysis of the community structure in networks of correlated data. The new modularity preserves the probabilistic semantics of the original definition even when the network is directed, weighted, signed, and has self-loops. This is the most general condition one can find in the study of any network, in particular those defined from correlated data. We apply our results to a real network of correlated data between stores in the city of Lyon (France).
Date: December 25, 2008
Creator: Gomez, S.; Jensen, P. & Arenas, A.
Partner: UNT Libraries Government Documents Department

Compact Graph Representations and Parallel Connectivity Algorithms for Massive Dynamic Network Analysis

Description: Graph-theoretic abstractions are extensively used to analyze massive data sets. Temporal data streams from socioeconomic interactions, social networking web sites, communication traffic, and scientific computing can be intuitively modeled as graphs. We present the first study of novel high-performance combinatorial techniques for analyzing large-scale information networks, encapsulating dynamic interaction data in the order of billions of entities. We present new data structures to represent dynamic interaction networks, and discuss algorithms for processing parallel insertions and deletions of edges in small-world networks. With these new approaches, we achieve an average performance rate of 25 million structural updates per second and a parallel speedup of nearly28 on a 64-way Sun UltraSPARC T2 multicore processor, for insertions and deletions to a small-world network of 33.5 million vertices and 268 million edges. We also design parallel implementations of fundamental dynamic graph kernels related to connectivity and centrality queries. Our implementations are freely distributed as part of the open-source SNAP (Small-world Network Analysis and Partitioning) complex network analysis framework.
Date: February 15, 2009
Creator: Madduri, Kamesh & Bader, David A.
Partner: UNT Libraries Government Documents Department

Network and adaptive system of systems modeling and analysis.

Description: This report documents the results of an LDRD program entitled ''Network and Adaptive System of Systems Modeling and Analysis'' that was conducted during FY 2005 and FY 2006. The purpose of this study was to determine and implement ways to incorporate network communications modeling into existing System of Systems (SoS) modeling capabilities. Current SoS modeling, particularly for the Future Combat Systems (FCS) program, is conducted under the assumption that communication between the various systems is always possible and occurs instantaneously. A more realistic representation of these communications allows for better, more accurate simulation results. The current approach to meeting this objective has been to use existing capabilities to model network hardware reliability and adding capabilities to use that information to model the impact on the sustainment supply chain and operational availability.
Date: May 1, 2007
Creator: Lawton, Craig R.; Campbell, James E.; Anderson, Dennis James & Eddy, John P.
Partner: UNT Libraries Government Documents Department

Behavior, a Balanced Network of Chemical Transformations(Biokinetics)

Description: While the concept of a biological system as a balanced network of chemical transformations is not a new one, experimental definition of specific systems has been lacking. This paper defines theoretically and experimentally a number of such networks and their behavior and response to some limited environmental changes.
Date: January 13, 1954
Creator: Bradley, D.F. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Distributed sensor networks with collective computation

Description: Simulations of a network of N sensors have been performed. The simulation space contains a number of sound sources and a large number of sensors. Each sensor is equipped with an omni-directional microphone and is capable of measuring only the time of arrival of a signal. Sensors are able to wirelessly transmit and receive packets of information, and have some computing power. The sensors were programmed to merge all information (received packets as well as local measurements) into a 'world view' for that node. This world view is then transmitted. In this way, information can slowly diffuse across the network. One node was monitored in the network as a proxy for when information had diffused across the network. Simulations demonstrated that the energy expended per sensor per time step was approximately independent of N.
Date: January 1, 2001
Creator: Lanman, D. R. (Douglas R.)
Partner: UNT Libraries Government Documents Department

Analyzing the effect of routing protocols on media access control protocols in radio networks

Description: We study the effect of routing protocols on the performance of media access control (MAC) protocols in wireless radio networks. Three well known MAC protocols: 802.11, CSMA, and MACA are considered. Similarly three recently proposed routing protocols: AODV, DSR and LAR scheme 1 are considered. The experimental analysis was carried out using GloMoSim: a tool for simulating wireless networks. The main focus of our experiments was to study how the routing protocols affect the performance of the MAC protocols when the underlying network and traffic parameters are varied. The performance of the protocols was measured w.r.t. five important parameters: (i) number of received packets, (ii) average latency of each packet, (iii) throughput (iv) long term fairness and (v) number of control packets at the MAC layer level. Our results show that combinations of routing and MAC protocols yield varying performance under varying network topology and traffic situations. The result has an important implication; no combination of routing protocol and MAC protocol is the best over all situations. Also, the performance analysis of protocols at a given level in the protocol stack needs to be studied not locally in isolation but as a part of the complete protocol stack. A novel aspect of our work is the use of statistical technique, ANOVA (Analysis of Variance) to characterize the effect of routing protocols on MAC protocols. This technique is of independent interest and can be utilized in several other simulation and empirical studies.
Date: January 1, 2002
Creator: Barrett, C. L. (Christopher L.); Drozda, M. (Martin); Marathe, A. (Achla) & Marathe, M. V. (Madhav V.)
Partner: UNT Libraries Government Documents Department

Network Theory

Description: This book chapter discusses network theory, defined as the proposed processes and mechanisms that relate network properties to outcomes of interest.
Date: 2011
Creator: Borgatti, Stephen P. & Lopez-Kidwell, Virginie
Partner: UNT College of Business

Bonding and Bridging Forms of Social Capital in Wildlife Tourism Microentrepreneurship: An Application of Social Network Analysis

Description: This article examines a network of wildlife tourism microentrepreneurs for bonding and bridging forms of social capital using a social network analysis approach.
Date: December 29, 2017
Creator: KC, Birendra; Morais, Duarte B.; Seekamp, Erin; Smith, Jordan W. & Peterson, M. Nils
Partner: UNT College of Merchandising, Hospitality and Tourism

The value of auxiliary stations and the need for network calibration

Description: To address the question of the value of auxiliary stations placed before the GSE by the Ad Hoc Committee on Nuclear Test Ban, we examined the published location error estimates given by both the NEIS and the IDC. The results of our analysis demonstrate the well-known principle that the uncertainty in the location for a given event decreases as the number of defining phases (or stations) increases and as the azimuthal coverage increases. More importantly, however, the results also show that the location uncertainty dramatically decreases as the distance to the nearest station decreases. We also show that the empirically observed rate of overlap of corresponding IDC and NEIS error ellipses is inconsistent with expectation as determined by statistically modeling the performance of each. To overcome this shortcoming the IMS must be calibrated.
Date: February 1, 1996
Creator: Denny, M.
Partner: UNT Libraries Government Documents Department

A Faster Parallel Algorithm and Efficient Multithreaded Implementations for Evaluating Betweenness Centrality on Massive Datasets

Description: We present a new lock-free parallel algorithm for computing betweenness centralityof massive small-world networks. With minor changes to the data structures, ouralgorithm also achieves better spatial cache locality compared to previous approaches. Betweenness centrality is a key algorithm kernel in HPCS SSCA#2, a benchmark extensively used to evaluate the performance of emerging high-performance computing architectures for graph-theoretic computations. We design optimized implementations of betweenness centrality and the SSCA#2 benchmark for two hardware multithreaded systems: a Cray XMT system with the Threadstorm processor, and a single-socket Sun multicore server with the UltraSPARC T2 processor. For a small-world network of 134 million vertices and 1.073 billion edges, the 16-processor XMT system and the 8-core Sun Fire T5120 server achieve TEPS scores (an algorithmic performance count for the SSCA#2 benchmark) of 160 million and 90 million respectively, which corresponds to more than a 2X performance improvement over the previous parallel implementations. To better characterize the performance of these multithreaded systems, we correlate the SSCA#2 performance results with data from the memory-intensive STREAM and RandomAccess benchmarks. Finally, we demonstrate the applicability of our implementation to analyze massive real-world datasets by computing approximate betweenness centrality for a large-scale IMDb movie-actor network.
Date: February 15, 2009
Creator: Madduri, Kamesh; Ediger, David; Jiang, Karl; Bader, David A. & Chavarria-Miranda, Daniel
Partner: UNT Libraries Government Documents Department

Journalist as Information Provider: Examining the One-Voice Model of a Corporate Sports Account

Description: While journalists were once viewed as gatekeepers, dispensing news and information via one-way communication channels, their role as information provider has evolved. Nowhere is this more apparent than on the social networking site Twitter, where information seekers have unprecedented access to information providers. The two-way communication that these information seekers have come to expect can be challenging for organizations such as ESPN who have multiple Twitter accounts and millions of followers. By designating one team of people as responsible for the organization's largest Twitter account, SportsCenter, ESPN has sought to establish manageable methods of interacting with this account's followers, while furthering the goals of the organization and providing sports news around the clock. This study provides a better understanding of the group responsible for ESPN's SportsCenter Twitter account: the motivation and strategies behind the group's Twitter use as well as the dynamics of this network, such as information flow and collaboration. Relying on the Information Seeking and Communication Model, this study also provides a better understanding of information exchanges with those outside the network, specifically a selection of the account's Twitter followers. Additionally, the role of journalist as information provider and certain themes that emerged from the content of the tweets are discussed. The research employed social network analysis and exploratory, descriptive case study methods. The results of this study contribute to social network and information theory as well as to journalistic and information science practice.
Date: August 2016
Creator: Norris, Tiffany D.
Partner: UNT Libraries

C%2B%2B tensor toolbox user manual.

Description: The C++ Tensor Toolbox is a software package for computing tensor decompositions. It is based on the Matlab Tensor Toolbox, and is particularly optimized for sparse data sets. This user manual briefly overviews tensor decomposition mathematics, software capabilities, and installation of the package. Tensors (also known as multidimensional arrays or N-way arrays) are used in a variety of applications ranging from chemometrics to network analysis. The Tensor Toolbox provides classes for manipulating dense, sparse, and structured tensors in C++. The Toolbox compiles into libraries and is intended for use with custom applications written by users.
Date: April 1, 2012
Creator: Plantenga, Todd D. & Kolda, Tamara Gibson
Partner: UNT Libraries Government Documents Department

Investigating the effectiveness of many-core network processors for high performance cyber protection systems. Part I, FY2011.

Description: This report documents our first year efforts to address the use of many-core processors for high performance cyber protection. As the demands grow for higher bandwidth (beyond 1 Gbits/sec) on network connections, the need to provide faster and more efficient solution to cyber security grows. Fortunately, in recent years, the development of many-core network processors have seen increased interest. Prior working experiences with many-core processors have led us to investigate its effectiveness for cyber protection tools, with particular emphasis on high performance firewalls. Although advanced algorithms for smarter cyber protection of high-speed network traffic are being developed, these advanced analysis techniques require significantly more computational capabilities than static techniques. Moreover, many locations where cyber protections are deployed have limited power, space and cooling resources. This makes the use of traditionally large computing systems impractical for the front-end systems that process large network streams; hence, the drive for this study which could potentially yield a highly reconfigurable and rapidly scalable solution.
Date: September 1, 2011
Creator: Wheeler, Kyle Bruce; Naegle, John Hunt; Wright, Brian J.; Benner, Robert E., Jr.; Shelburg, Jeffrey Scott; Pearson, David Benjamin et al.
Partner: UNT Libraries Government Documents Department

Modeling Temporal Behavior in Large Networks: A Dynamic Mixed-Membership Model

Description: Given a large time-evolving network, how can we model and characterize the temporal behaviors of individual nodes (and network states)? How can we model the behavioral transition patterns of nodes? We propose a temporal behavior model that captures the 'roles' of nodes in the graph and how they evolve over time. The proposed dynamic behavioral mixed-membership model (DBMM) is scalable, fully automatic (no user-defined parameters), non-parametric/data-driven (no specific functional form or parameterization), interpretable (identifies explainable patterns), and flexible (applicable to dynamic and streaming networks). Moreover, the interpretable behavioral roles are generalizable, computationally efficient, and natively supports attributes. We applied our model for (a) identifying patterns and trends of nodes and network states based on the temporal behavior, (b) predicting future structural changes, and (c) detecting unusual temporal behavior transitions. We use eight large real-world datasets from different time-evolving settings (dynamic and streaming). In particular, we model the evolving mixed-memberships and the corresponding behavioral transitions of Twitter, Facebook, IP-Traces, Email (University), Internet AS, Enron, Reality, and IMDB. The experiments demonstrate the scalability, flexibility, and effectiveness of our model for identifying interesting patterns, detecting unusual structural transitions, and predicting the future structural changes of the network and individual nodes.
Date: November 11, 2011
Creator: Rossi, R; Gallagher, B; Neville, J & Henderson, K
Partner: UNT Libraries Government Documents Department

EFFECT OF MOBILITY ON PERFORMANCE OF WIRELESS AD-HOC NETWORK PROTOCOLS.

Description: We empirically study the effect of mobility on the performance of protocols designed for wireless adhoc networks. An important ohjective is to study the interaction of the Routing and MAC layer protocols under different mobility parameters. We use three basic mobility models: grid mobility model, random waypoint model, and exponential correlated random model. The performance of protocols was measured in terms of (i) latency, (ii) throughput, (iii) number of packels received, (iv) long term fairness and (v) number of control packets at the MAC layer level. Three different commonly studied routing protocols were used: AODV, DSR and LAR1. Similarly three well known MAC protocols were used: MACA, 802.1 1 and CSMA. The inair1 conclusion of our study include the following: 1. 'I'he performance of the: network varies widely with varying mobility models, packet injection rates and speeds; and can ba in fact characterized as fair to poor depending on the specific situation. Nevertheless, in general, it appears that the combination of AODV and 802.1 I is far better than other combination of routing and MAC protocols. 2. MAC layer protocols interact with routing layer protocols. This concept which is formalized using statistics implies that in general it is not meaningful to speak about a MAC or a routing protocol in isolation. Such an interaction leads to trade-offs between the amount of control packets generated by each layer. More interestingly, the results wise the possibility of improving the performance of a particular MAC layer protocol by using a cleverly designed routing protocol or vice-versa. 3. Routing prolocols with distributed knowledge about routes are more suitable for networks with mobility. This is seen by comparing the performance of AODV with DSR or LAR scheme 1. In DSli and IAR scheme 1, information about a computed path is being stored in the route ...
Date: January 1, 2001
Creator: Barrett, C. L. (Christopher L.); Drozda, M. (Martin); Marathe, M. V. (Madhav V.) & Marathe, A. (Achla)
Partner: UNT Libraries Government Documents Department

Characterizing the Interaction Between Routing and MAC Protocols in Ad-Hoc Networks

Description: We empirically study the effect of mobility on the performance of protocols designed for wireless ad-hoc networks. An important objective is to study the interaction of the Routing and MAC layer protocols under different mobility parameters. We use three basic mobility models: grid mobility model, random waypoint model, and exponential correlated random model. The performance of protocols is measured in terms of (i) latency, (ii) throughput, (iii) number of packets received, (iv) long term fairness and (v) number of control packets at the MAC and routing layer level. Three different commonly studied routing protocols are used: AODV, DSR and LAR1. Similarly three well known MAC protocols are used: MACA, 802.1 1 and CSMA. Our main contribution is simulation based experiments coupled with rigorous statistical analysis to characterize the interaction of MAC layer protocols with routing layer protocols in ad-hoc networks. From the results, we can conclude the following: e No single MAC or Routing protocol dominated the other protocols in their class. Probably more interestingly, no MAURouting protocol combination was better than other combinations over all scenarios and response variables. 0 In general, it is not meaningful to speak about a MAC or a routing protocol in isolation. Presence of interaction leads to trade-offs between the amount of control packets generated by each layer. The results raise the possibility of improving the performance of a particular MAC layer protocol by using a cleverly designed routing protocol or vice-versa. Thus in order to improve the performanceof a communication network, it is important to study the entire protocol stack as a single algorithmic construct; optimizing individual layers in the seven layer OS1 stack will not yield performance improvements beyond a point. A methodological contribution of this paper is the use of statistical methods such as analysis of variance (ANOVA), to characterize the ...
Date: January 1, 2002
Creator: Barrett, C. L. (Christopher L.); Drozda, M. (Martin); Marathe, A. (Achla) & Marathe, M. V. (Madhav V.)
Partner: UNT Libraries Government Documents Department

Packet spacing : an enabling mechanism for delivering multimedia content in computational grids /

Description: Streaming multimedia with UDP has become increasingly popular over distributed systems like the Internet. Scientific applications that stream multimedia include remote computational steering of visualization data and video-on-demand teleconferencing over the Access Grid. However, UDP does not possess a self-regulating, congestion-control mechanism; and most best-efort traflc is served by congestion-controlled TCF! Consequently, UDP steals bandwidth from TCP such that TCP$ows starve for network resources. With the volume of Internet traffic continuing to increase, the perpetuation of UDP-based streaming will cause the Internet to collapse as it did in the mid-1980's due to the use of non-congestion-controlled TCP. To address this problem, we introduce the counterintuitive notion of inter-packet spacing with control feedback to enable UDP-based applications to perform well in the next-generation Internet and computational grids. When compared with traditional UDP-based streaming, we illustrate that our approach can reduce packet loss over SO% without adversely afecting delivered throughput. Keywords: network protocol, multimedia, packet spacing, streaming, TCI: UDlq rate-adjusting congestion control, computational grid, Access Grid.
Date: January 1, 2001
Creator: Feng, A. C. (Annette C.); Feng, W. C. (Wu-Chun) & Belford, Geneva G.
Partner: UNT Libraries Government Documents Department

ROUTING IN TIME-DEPENDENT AND LABELED NETWORKS

Description: We study routing problems in time-dependent and edge and/or vertex-labeled transportation networks. Labels allow one to express a number of discrete properties of the edges and nodes. The main focus is a unified algorithm that efficiently solves a number of seemingly unrelated problems in transportation science. Experimental data gained from modeling practical situations suggest that the formalism allows interesting compromises between the conflicting goals of generality and efficiency. 1. We use edge/vertex labels in the framework of Formal Language Constrained Path Problems to handle discrete choice constraints. The label set is usually small and does not depend on the graph. Edge labels induct! path labels, which allows us to impose feasibility constraints on the set of paths considered as shortest path candidates. Second, we propose monotonic piecewise-linear traversal functions to represent the time-dependent aspect of link delays. The applications that can be modeled include scheduled transit and time-windows. 3. Third, we combine the above models and capture a variety of natural problems in transportatiou science such as time-window constrained trip-chaining. The results demonstrate the robustness of the proposed formalisms. As evidence for our claims of practical efficiency in a realistic setting, we report preliminary computational experience from TRANSIMS case studies of Portland, Oregon.
Date: January 1, 2001
Creator: Barrett, C. L. (Christopher L.); Bisset, K. R. (Keith R.); Jacob, R. (Riko); Konjevod, G. (Goran) & Marathe, M. V. (Madhav V.)
Partner: UNT Libraries Government Documents Department

MAGNeT : Monitor for Application-Generated Network Traffic /

Description: Over the laqt decade, network practitioners have focused on monitoring, measuring, and characterizing traffic in the network to gain insight into building critical network components (from the protocol stack to routers and switches to network interface cards). Recent research shows that additional insight can be obtained by monitoring traffic at the application level (Le,, before application-sent traffic is modulated by the protocol stack) rather than in the network (i-e., after it is modulated by the protocol stack). Consequently, this paper describes a Monitor for Application-Generated Network Traffic (MAGNeT) that captures traffic generated by the application rather than traffic in the network. MAGNeT consists of application programs as well as modifications to the standard Linux kernel. Together, these tools provide the capability of monitoring an application's network behavior and protocol state information in production systems. The use of MAGNeT will enable the research community to construct a library of real traces of application-generated traffic from which researchers can more realistically test network protocol designs and theory. MAGNeT can also be used to verify the correct operation of protocol enhancements and to troubleshoot and tune protocol implementations.
Date: January 1, 2001
Creator: Feng, W. C. (Wu-Chun); Hay, J. R. (Jeffrey R.) & Gardner, M. K. (Mark K.)
Partner: UNT Libraries Government Documents Department