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2007

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Articles 751 - 780 of 6758

Full-Text Articles in Physical Sciences and Mathematics

Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, B. Allen, R. Amin, S. B. Anderson, W. G. Anderson, M. Arain, M. Araya, H. Armandula, M. Ashley, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, K. Bayer, K. Belczynski, S. J. Berukoff, J. Betzwieser, P. T. Beyersdorf, B. Bhawal, Tiffany Z. Summerscales Oct 2007

Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, B. Allen, R. Amin, S. B. Anderson, W. G. Anderson, M. Arain, M. Araya, H. Armandula, M. Ashley, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, K. Bayer, K. Belczynski, S. J. Berukoff, J. Betzwieser, P. T. Beyersdorf, B. Bhawal, Tiffany Z. Summerscales

Faculty Publications

We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. Both searches exploit fully coherent matched filtering and cover wide areas of parameter space, an innovation over previous analyses which requires considerable algorithm development and computational power. The first search is targeted at isolated, previously unknown neutron stars, covers the entire sky in the frequency band 160-728.8 Hz, and assumes a frequency derivative of less than 4×10-10Hz/s. The second search targets the accreting neutron star in the low-mass x-ray binary Scorpius X-1 and covers the frequency bands …

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Error Sensor Placement For Active Control Of An Axial Cooling Fan, Benjamin M. Shafer Oct 2007

Error Sensor Placement For Active Control Of An Axial Cooling Fan, Benjamin M. Shafer

Theses and Dissertations

Recent experimental achievements in active noise control (ANC) for cooling fans have used near-field error sensors whose locations are determined according to a theoretical condition of minimized sound power. A theoretical point source model, based on the condition previously stated, reveals the location of near-field pressure nulls that may be used to optimize error sensor placement. The actual locations of these near-field pressure nulls for both an axial cooling fan and a monopole loudspeaker were measured over a two-dimensional grid with a linear array of microphones. The achieved global attenuation for each case is measured over a hemisphere located in …

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Fept Nanodot Arrays With Perpendicular Easy Axis, Large Coercivity, And Extremely High Density, Chaehyun Kim, Thomas Loedding, Seongjin Jang, Hao Zeng, Zhen Li, Yucheng Sui, David J. Sellmyer Oct 2007

Fept Nanodot Arrays With Perpendicular Easy Axis, Large Coercivity, And Extremely High Density, Chaehyun Kim, Thomas Loedding, Seongjin Jang, Hao Zeng, Zhen Li, Yucheng Sui, David J. Sellmyer

David Sellmyer Publications

Ordered FePt nanodot arrays with extremely high density have been developed by physical vapor deposition using porous alumina templates as evaporation masks. Nanodot diameter of 18 nm and periodicity of 25 nm have been achieved, resulting in an areal density exceeding 1 x1012 dots/in2. Rapid thermal annealing converts the disordered fcc to L10 phase, resulting in (001)-oriented FePt nanodot arrays with perpendicular anisotropy and large coercivity, without the need of epitaxy. High anisotropy and coercivity, perpendicular easy axis orientation and extremely high density are desirable features for future magnetic data storage media applications.

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Nonparametric And Semiparametric Group Sequential Methods For Comparing Accuracy Of Diagnostic Tests, Liansheng Tang, Scott S. Emerson, Xiao-Hua Zhou Oct 2007

Nonparametric And Semiparametric Group Sequential Methods For Comparing Accuracy Of Diagnostic Tests, Liansheng Tang, Scott S. Emerson, Xiao-Hua Zhou

UW Biostatistics Working Paper Series

Comparison of the accuracy of two diagnostic tests using the receiver operating characteristic (ROC) curves from two diagnostic tests has been typically conducted using fixed sample designs. On the other hand, the human experimentation inherent in a comparison of diagnostic modalities argues for periodic monitoring of the accruing data to address many issues related to the ethics and efficiency of the medical study. To date, very little research has been done in the use of sequential sampling plans for comparative ROC studies, even when these studies may use expensive and unsafe diagnostic procedures. In this paper, we propose a nonparametric …

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A Bayesian Image Analysis Of The Change In Tumor/Brain Contrast Uptake Induced By Radiation Via Reversible Jump Markov Chain Monte Carlo, Xiaoxi Zhang, Tim Johnson, Roderick J.A. Little Oct 2007

A Bayesian Image Analysis Of The Change In Tumor/Brain Contrast Uptake Induced By Radiation Via Reversible Jump Markov Chain Monte Carlo, Xiaoxi Zhang, Tim Johnson, Roderick J.A. Little

The University of Michigan Department of Biostatistics Working Paper Series

This work is motivated by a pilot study on the change in tumor/brain contrast uptake induced by radiation via quantitative Magnetic Resonance Imaging. The results inform the optimal timing of administering chemotherapy in the context of radiotherapy. A noticeable feature of the data is spatial heterogeneity. The tumor is physiologically and pathologically distinct from surrounding healthy tissue. Also, the tumor itself is usually highly heterogeneous. We employ a Gaussian Hidden Markov Random Field model that respects the above features. The model introduces a latent layer of discrete labels from an Markov Random Field (MRF) governed by a spatial regularization parameter. …

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Incorporating Geostatistical Constraints In Nonlinear Inverse Problems, T. C. Johnson, Partha S. Routh, Tom Clemo, Warren Barrash, William P. Clement Oct 2007

Incorporating Geostatistical Constraints In Nonlinear Inverse Problems, T. C. Johnson, Partha S. Routh, Tom Clemo, Warren Barrash, William P. Clement

CGISS Publications and Presentations

In this paper we present a method of incorporating semivariogram constraints into nonlinear inversion problems. That is, we describe a method of sampling the space of inverse solutions that honor a specified semivariogram or set of semivariograms and also explain a set of state data. The approach can be considered a method of conditional simulation where model conditioning is based upon state data (as opposed to parameter data). The difference between this approach and other simulation approaches is that the simulation is posed as an optimization problem with the joint objective of matching the semivariograms and honoring the state data. …

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80-Channel Multiplexer-Demultiplexer Module For Dwdm Communications Using Hybrid Awg -- Interleaver Technology, Corneliu Rablau, Lance Bredthauer Oct 2007

80-Channel Multiplexer-Demultiplexer Module For Dwdm Communications Using Hybrid Awg -- Interleaver Technology, Corneliu Rablau, Lance Bredthauer

Physics Presentations And Conference Materials

Aside from the more traditional data, voice and e-mail communications, new bandwidth intensive applications in the larger consumer markets, such as music, digital pictures and movies, have led to an explosive increase in the demand for transmission capacity for optical communications networks. This has resulted in a widespread deployment of Dense Wavelength Division Multiplexing (DWDM) as a means of increasing the communications capacity by multiplexing and transmitting signals of different wavelengths (establishing multiple communication channels) through a single strand of fiber. We report on the design, assembly and characterization of a 50-GHz, 80-channel Mux-Demux module for DWDM systems. The module …

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1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das Oct 2007

1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das

Andrzej Rajca Publications

Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for throughbond and through-space intramolecular exchange couplings.

Includes Supplemental Data (27 pages).

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Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison Oct 2007

Investigating The Photoyield Of Spacecraft Materials, Jennifer Albretsen, Ryan Hoffmann, Jr Dennison

Presentations

No abstract provided.

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Resistivity Of Kapton E At Intermediate Time Scales Following High-Energy Electron Irradiation, S Hart, Jr Dennison, J Brunson, Jodie C. Gillespie Oct 2007

Resistivity Of Kapton E At Intermediate Time Scales Following High-Energy Electron Irradiation, S Hart, Jr Dennison, J Brunson, Jodie C. Gillespie

Presentations

No abstract provided.

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Evidence For A Dinuclear Active Site In The Metallo-Β-Lactamase Bcii With Substoichiometric Co(Ii): A New Model For Uptake, Leticia L. Llarrull, Mariana F. Tioni, Jason M. Kowalski, Brian Bennett, Alejandro J. Vila Oct 2007

Evidence For A Dinuclear Active Site In The Metallo-Β-Lactamase Bcii With Substoichiometric Co(Ii): A New Model For Uptake, Leticia L. Llarrull, Mariana F. Tioni, Jason M. Kowalski, Brian Bennett, Alejandro J. Vila

Physics Faculty Research and Publications

Metallo-β-lactamases are zinc-dependent enzymes that constitute one of the main resistance mechanisms to β-lactam antibiotics. Metallo-β-lactamases have been characterized both in mono- and dimetallic forms. Despite many studies, the role of each metal binding site in substrate binding and catalysis is still unclear. This is mostly due to the difficulties in assessing the metal content and site occupancy in solution. For this reason, Co(II) has been utilized as a useful probe of the active site structure. We have employed UV-visible, EPR, and NMR spectroscopy to study Co(II) binding to the metallo-β-lactamase BcII from Bacillus cereus. The spectroscopic features were …

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A Note On Targeted Maximum Likelihood And Right Censored Data, Mark J. Van Der Laan, Daniel Rubin Oct 2007

A Note On Targeted Maximum Likelihood And Right Censored Data, Mark J. Van Der Laan, Daniel Rubin

U.C. Berkeley Division of Biostatistics Working Paper Series

A popular way to estimate an unknown parameter is with substitution, or evaluating the parameter at a likelihood based fit of the data generating density. In many cases, such estimators have substantial bias and can fail to converge at the parametric rate. van der Laan and Rubin (2006) introduced targeted maximum likelihood learning, removing these shackles from substitution estimators, which were made in full agreement with the locally efficient estimating equation procedures as presented in Robins and Rotnitzsky (1992) and van der Laan and Robins (2003). This note illustrates how targeted maximum likelihood can be applied in right censored data …

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High-Spin States In 191, 193Au And 192Pt: Evidence For Oblate Deformation And Triaxial Shapes, Y. Oktem, D. L. Balabanski, B. Akkus, C. W. Beausang, M. Bostan, R. Cakirli, R. F. Casten, M. Danchev, M. Djongolov, M. N. Erduran, S. Erturk, K. A. Gladniski, G. Gurdal, J. Tm. Goon, D. J. Hartley, A. A. Hecht, R. Krucken, N. Nikolov, J. R. Novak, G. Rainovski, L. L. Riedinger, I. Yigitoglu, N. V. Zamfir, O. Zeidan Oct 2007

High-Spin States In 191, 193Au And 192Pt: Evidence For Oblate Deformation And Triaxial Shapes, Y. Oktem, D. L. Balabanski, B. Akkus, C. W. Beausang, M. Bostan, R. Cakirli, R. F. Casten, M. Danchev, M. Djongolov, M. N. Erduran, S. Erturk, K. A. Gladniski, G. Gurdal, J. Tm. Goon, D. J. Hartley, A. A. Hecht, R. Krucken, N. Nikolov, J. R. Novak, G. Rainovski, L. L. Riedinger, I. Yigitoglu, N. V. Zamfir, O. Zeidan

Physics Faculty Publications

High-spin states of 191, 193Au and 192Pt have been populated in the 186W(11B, xn) and 186W(11B, p4n) reactions, respectively, at a beam energy of 68 MeV and their γ decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory at Yale University. The level scheme of 193Au has been extended up to Iπ = 55/2+. New transitions were observed also in 191Au and 192Pt. Particle-plus-Triaxial-Rotor (PTR) and Total Routhian Surface (TRS) calculations were performed to determine the equilibrium deformations of the …

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The Structure Of Games, David Michael Kaiser Oct 2007

The Structure Of Games, David Michael Kaiser

FIU Electronic Theses and Dissertations

Computer Game Playing has been an active area of research since Samuel’s first Checkers player (Samuel 1959). Recently interest beyond the classic games of Chess and Checkers has led to competitions such as the General Game Playing competition, in which players have no beforehand knowledge of the games they are to play, and the Computer Poker Competition which force players to reason about imperfect information under conditions of uncertainty. The purpose of this dissertation is to explore the area of General Game Playing both specifically and generally. On the specific side, we describe the design and implementation of our General …

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Comparing Three Methods For Teaching Newton’S Third Law, Trevor I. Smith, Michael C. Wittmann Oct 2007

Comparing Three Methods For Teaching Newton’S Third Law, Trevor I. Smith, Michael C. Wittmann

College of Science & Mathematics Departmental Research

Although guided-inquiry methods for teaching introductory physics have been individually shown to be more effective at improving conceptual understanding than traditional lecture-style instruction, researchers in physics education have not studied differences among reform-based curricula in much detail. Several researchers have developed University of Washington–style tutorial materials, but the different curricula have not been compared against each other. Our study examines three tutorials designed to improve student understanding of Newton’s third law: the University of Washington’s Tutorials in Introductory Physics (TIP), the University of Maryland’s Activity-Based Tutorials (ABT), and the Open Source Tutorials (OST) also developed at the University of Maryland. …

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Effects Of Coyote Population Reduction On Swift Fox Demographics In Southeastern Colorado, Seija M. Karki, Eric M. Gese, Mead L. Klavetter Oct 2007

Effects Of Coyote Population Reduction On Swift Fox Demographics In Southeastern Colorado, Seija M. Karki, Eric M. Gese, Mead L. Klavetter

United States Department of Agriculture Wildlife Services: Staff Publications

The distribution and abundance of swift foxes (Vulpes velox) has declined from historic levels. Causes for the decline include habitat loss and fragmentation, incidental poisoning, changing land use practices, trapping, and predation by other carnivores. Coyotes (Canis latrans) overlap the geographical distribution of swift foxes, compete for similar resources, and are a significant source of mortality amongst many swift fox populations. Current swift fox conservation and management plans to bolster declining or recovering fox populations may include coyote population reduction to decrease predation. However, the role of coyote predation in swift fox population dynamics is not …

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Ecology And Management Of Rodents In No-Till Agriculture In Washington, Usa, Gary W. Witmer, Rodney Sayler, David Huggins, Jason Capelli Oct 2007

Ecology And Management Of Rodents In No-Till Agriculture In Washington, Usa, Gary W. Witmer, Rodney Sayler, David Huggins, Jason Capelli

United States Department of Agriculture Wildlife Services: Staff Publications

No-till farming is an important approach to sustainable agriculture because it can conserve soil and water resources. Unfortunately, rodent populations can thrive under no-till conditions because burrow systems are not disrupted by annual plowing and plant residues build-up on the surface, providing cover and insulation. This can result in substantial crop damage. We assessed rodent populations, habitat use, food habits, and crop damage in a no-till cropping system in Washington, USA. We also conducted preliminary trials of methods to reduce rodent populations and crop damage. In the fall, many more rodents were captured in fields with unharvested crops than in …

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Electric Power: Cyber And Electromagnetic Security Issues, George H. Baker Oct 2007

Electric Power: Cyber And Electromagnetic Security Issues, George H. Baker

George H Baker

Electric power is essential to the functioning of U.S. society. The electric power system increasingly operates at or near its reliability limits. The geographic scale of the tightly coupled networks involved makes the system susceptible to large-scale outages. More frequent natural and accidental failures portend possible catastrophes from intentional disruption. Deregulation has been a major factor to the lack of investment in system upgrades. Techniques to prevent attacks and reduce vulnerabilities are available and affordable.

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Should Wildlife Trapping Have A Place In A Christian Environmental Ethic?, Stephen Vantassel Oct 2007

Should Wildlife Trapping Have A Place In A Christian Environmental Ethic?, Stephen Vantassel

Other Publications in Wildlife Management

Animal protectionist groups lobby for the banning of wildlife trapping because of its perceived cruelty and harm to the environment. This paper evaluates those claims and suggests that Christians carefully consider all the data before adopting an anti-trapping stance.

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Improving Inventory Control In A Small-To-Medium Retailer Using Rfid., D. Hamilton Oct 2007

Improving Inventory Control In A Small-To-Medium Retailer Using Rfid., D. Hamilton

Faculty of Informatics - Papers (Archive)

Small-to-medium retailers are organizations that have traditionally had problems with inaccurate inventory control systems. This paper documents a research project that is currently in progress, aiming to explore the use of RFID for improving inventory control in a small-to-medium retailer. The aim of this paper is to review literature related to the project to emphasise its significance. In the initial part of this paper, the purpose of inventory control and the basic principles of RFID technology will be outlined. The latter part of this paper examines literature that has been published in relation to RFID and inventory control, highlighting areas …

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The Mpeg-7 Query Format: A New Standard In Progress For Multimedia Query By Content, Kevin Adistambha, M. Doeller, R. Tous, M. Gruhne, M. Sano, C. Tsinaraki, S. Christodoulakis, Kyoungro Yoon, C. H. Ritz, I. S. Burnett Oct 2007

The Mpeg-7 Query Format: A New Standard In Progress For Multimedia Query By Content, Kevin Adistambha, M. Doeller, R. Tous, M. Gruhne, M. Sano, C. Tsinaraki, S. Christodoulakis, Kyoungro Yoon, C. H. Ritz, I. S. Burnett

Faculty of Informatics - Papers (Archive)

ln recent years, the amount of Internet accessible digital audiovisual media files has vastly increased. Therefore the need to describe the media (by way of metadata) has also increased significantly. MPEG-7 (finalized in 2001) provides a comprehensive and rich metadata standard for the descr iption of multimedia content. Unfortunately, a standardized query format does not exist for MPEG-7, or other multimedia metadata. Such a standard would provide for communications between quer ying clients and databases, suppor ting cross-modal and cross-media retrieval. The ISO/IEC SC29WG11 committee decided therefore to contribute to this application space by adding such functionality as a new …

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Reconfigurable Media Coding: Self-Describing Multimedia Bitstreams, Joseph Thomas-Kerr, J. Janneck, M. Mattavelli, I. Burnett, C. Ritz Oct 2007

Reconfigurable Media Coding: Self-Describing Multimedia Bitstreams, Joseph Thomas-Kerr, J. Janneck, M. Mattavelli, I. Burnett, C. Ritz

Faculty of Informatics - Papers (Archive)

The development of MP3 and JPEG sparked an explosion in digital content on the internet. These early encoding formats have since been joined by many others, including Quicktime, Ogg, MPEG-2 and MPEG-4, which poses an escalating challenge to vendors wishing to develop devices that interoperate with as much content as possible. This paper presents aspects of Reconfigurable Media Coding (RMC), a project currently mat. In other words, an RMC bitstream contains metadata to assemble a decoder from a fundamental building-blocks, as well as a schema that describes the syntax of the content data, and how it may be parsed. RMC …

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Diversity Performance Of Interleaved Spread Spectrum Ofdm Signals Over Frequency Selective Multipath Fading Channels, P. Tu, Xiaojing Huang, E. Dutkiewicz Oct 2007

Diversity Performance Of Interleaved Spread Spectrum Ofdm Signals Over Frequency Selective Multipath Fading Channels, P. Tu, Xiaojing Huang, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) system for achieving both frequency diversity and time diversity and investigate the system performance over frequency selective fading channels. The purpose is to exploit the diversity capability of OFDM systems, develop efficienct spectrum spreading technique and improve the system performance against frequency selective channel fading. At the transmitter, the ISS-OFDM signal is generated by employing spread spectrum modulation and interleaving techniques. At the receiver, the received signals are combined by using maximum ratio combining (MRC) technique. The simulation indicates that the ISS-OFDM system has improved performance …

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Logistics Service Recovery And The Role Of Technology, A. Brinsmead Oct 2007

Logistics Service Recovery And The Role Of Technology, A. Brinsmead

Faculty of Informatics - Papers (Archive)

The logistics industry is becoming increasingly competitive, and supply chains becoming increasingly complex. Service failures are inevitable and part of the logistics landscape. Service recovery is relevant given the logistic industry’s trend toward a proactive approach to service failures. Furthermore, service recovery has the potential to become a source of organisational differentiation. Service failure management needs to be an integral part of the greater customer service program, rather than a reactive ad hoc process. Technology, already underpinning much of the industries capabilities, is seen as a likely enabler of sophisticated service recovery processes. The service recovery process is broken down …

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Intelligent Multimedia Delivery? It’S A Question Of Semantics, Joseph Thomas-Kerr, I. Burnett, C. Ritz Oct 2007

Intelligent Multimedia Delivery? It’S A Question Of Semantics, Joseph Thomas-Kerr, I. Burnett, C. Ritz

Faculty of Informatics - Papers (Archive)

Intelligent multimedia delivery uses semantic information about content to enhance the delivery process. This paper proposes a model for intelligent multimedia delivery that advances the state of the art by incorporating a concept of semantic distortion into the delivery optimization process. Furthermore, the model combines format-independence with rate-distortion optimization to provide a flexible framework for intelligent delivery of multimedia in existing and future formats. The paper provides a review of the existing work covering components of the model: scalable coding formats, rate-distortion optimization, format-independent adaptation, and semantic adaptation. It then details the model, and identifies open problems and opportunities for …

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Dynamic Bandwidth Mcids - A Cognitive Solution For Mcids Based Uwb Communications, J. Zhao, Xiaojing Huang, E. Dutkiewicz Oct 2007

Dynamic Bandwidth Mcids - A Cognitive Solution For Mcids Based Uwb Communications, J. Zhao, Xiaojing Huang, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

Dynamic bandwidth multicode interleaved direct sequence (MCIDS), an enhanced MCIDS based Ultra-wideband (UWB) application is proposed in this paper, featuring a cognitive transmission bandwidth adaptation without any adverse effect on the data rate. By introducing a specific lowpass filtering and down-sampling into the traditional MCIDS algorithm, this system can decrease the transmission bandwidth into part of its original bandwidth but still be able to recover all the transmitted data from the reduced bandwidth. This solution can efficiently improve the coexistence ability of UWB devices in a cognitive manner without increasing hardware complexity.

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On The Accuracy Of Rfid Tag Estimation Functions, Dheeraj Klair, K. Chin, R. Raad Oct 2007

On The Accuracy Of Rfid Tag Estimation Functions, Dheeraj Klair, K. Chin, R. Raad

Faculty of Informatics - Papers (Archive)

Dynamic Framed Slotted Aloha (DFSA) based tag reading protocols rely on a tag estimation function to calculate the best frame size to use for a given tag set. An inaccurate estimate results in high identification delays and unnecessary energy wastage. This is particularly serious when DFSA based tag reading protocols are used in RFID-enhanced wireless sensor networks (WSNs), where nodes are battery constrained. To this end, this paper presents qualitative and quantitative analysis of five tag estimation functions using Monte Carlo simulations. We iteratively estimate a given set of tags and evaluate the mean error, variability, skew and Kurtosis of …

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Peak-To-Average Power Ratio Performance Of Interleaved Spread Spectrum Ofdm Signals, P. Tu, Xiaojing Huang, E. Dutkiewicz Oct 2007

Peak-To-Average Power Ratio Performance Of Interleaved Spread Spectrum Ofdm Signals, P. Tu, Xiaojing Huang, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) transmission scheme and demonstrate its reduced peak-toaverage power ratio (PAR). The proposed ISS-OFDM signal is realized by two steps. The first step is to modulate the data symbol by complex exponential spreading and the second is to use an interleaving technique to spread the signal spectrum as well as reduce the signal peak-to-average power ratio. The distinctive features of the proposed method are that in the frequency domain the same data information is carried by a number of subbands to effectively spread the signal spectrum and …

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Viability Of Concurrent Transmission And Reception For Uwb Radios Over Multipath Channels, Ricardo Gandia Sanchez, Xiaojing Huang, K. Chin Oct 2007

Viability Of Concurrent Transmission And Reception For Uwb Radios Over Multipath Channels, Ricardo Gandia Sanchez, Xiaojing Huang, K. Chin

Faculty of Informatics - Papers (Archive)

Multihop transmissions over wireless mesh networks present limited end-to-end (E2E) data rates, as every hop waits for an entire packet to arrive before starting retransmission. That is, the E2E data rate drops when every hop stores and then forwards packets, thus making such transmissions unsuitable for multimedia applications. In this work, in order to increase data rates, we present an ultra-wideband (UWB) radio transceiver capable of concurrently transmit and receive (cTxRx) packets. However, concurrently receiving and transmitting comes at the cost of a channel model with increased interference level. Herein, we explain a new interference model and propose a transceiver …

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On The Characteristics Of Bgp Routes, J. Clement, K. Chin Oct 2007

On The Characteristics Of Bgp Routes, J. Clement, K. Chin

Faculty of Informatics - Papers (Archive)

This paper studies the characteristics of Border Gateway Protocol (BGP) routes. In particular, it identifies autonomous systems (ASs) that appear frequently in path vectors. In addition, it analyzes path vector lengths. Finally, it investigates the prevalence of inflated paths, commonly used by ASs for traffic engineering purposes.

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