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2007

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Articles 4621 - 4650 of 6758

Full-Text Articles in Physical Sciences and Mathematics

Small Area Estimation For Spatially Correlated Populations - A Comparison Of Direct And Indirect Model-Based Methods, Hukum Chandra, Nicola Salvati, Ray Chambers Jan 2007

Small Area Estimation For Spatially Correlated Populations - A Comparison Of Direct And Indirect Model-Based Methods, Hukum Chandra, Nicola Salvati, Ray Chambers

Faculty of Informatics - Papers (Archive)

Linear mixed models underpin many small areas estimation (SAE) methods. In this paper with investigate SAE based on linear models with spatially correlated small area effects where the neighbourhood structure is described by a contiguity matrix. Such models allow efficient use of spatial auxiliary information in SAE.

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Optimal Receiver For Space Time Spreading Across A Time Hopping Ppm Over Ultra Wideband Saleh-Valenzuela Mimo Channel, Peter James Vial, Beata J. Wysocki, Tadeusz A. Wysocki Jan 2007

Optimal Receiver For Space Time Spreading Across A Time Hopping Ppm Over Ultra Wideband Saleh-Valenzuela Mimo Channel, Peter James Vial, Beata J. Wysocki, Tadeusz A. Wysocki

Faculty of Informatics - Papers (Archive)

This paper outlines a technique which can use multiple transmit antennas to send more than one binary bit using the same number of transmit antennas over a single transmission. It uses Ultra Wideband orthogonal pulse position modulation to achieve this, with the receiver employing a Rake receiver and a Maximum Ratio Combiner optimal detector. This is done over a Space Time Spreading Time Hopping Ultra Wideband Pulse Position Modulation system assuming a rich multipath Saleh-Valenzuela MIMO channel model. Simulation results indicate that a significant gain can be achieved compared with other proposed schemes utilising multiple transmit antennas for Ultra Wide …

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Community Domain Name Policy Development, Alison Norris, Mark B. Freeman Jan 2007

Community Domain Name Policy Development, Alison Norris, Mark B. Freeman

Faculty of Informatics - Papers (Archive)

In August 2006, auDA launched a new domain name space designed specifically for community groups to develop community websites for the benefit of the local community. This paper presents an overview of the scheme, and identifies the changes made to the governing policies since they were initially proposed. A comparison of the proposed and implemented policies is presented, and the potential effects of these changes on a ‘world first’ community website scheme are considered. The changes made by the administrators to the scheme were in the following areas: local focus; sale of geographic .com.au and .net.au domains; management and licensing; …

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A Distributed Time-Fair Scheduling Algorithm For Multi-Rate Wlans, Kwan-Wu Chin Jan 2007

A Distributed Time-Fair Scheduling Algorithm For Multi-Rate Wlans, Kwan-Wu Chin

Faculty of Informatics - Papers (Archive)

The performance anomaly experienced by nodes in multi-rate wireless local area networks (WLANs) leads to low throughput and unfairness. To this end, we propose a distributed, token-based approach that allows applications to control nodes channel occupancy time via a single tuning knob. Our approach makes use of local information extensively and does not require any modifications to the IEEE 802.11 MAC nor require explicit signaling. Simulation results show our approach to be effective in ensuring fairness, and isolating high and low rate flows.

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A Peirce-Style Calculus For Alc, Frithjof Dau, Peter Eklund Jan 2007

A Peirce-Style Calculus For Alc, Frithjof Dau, Peter Eklund

Faculty of Informatics - Papers (Archive)

Description logics (DLs) are a well-understood family of knowledge representation (KR) languages. The notation of DLs has the flavour of a variable-free first order predicate logic. In this paper, a diagrammatic representation of the DL ALC, based on Peirce’s existential graphs, is presented, and a set of transformation rules on these graphs is provided. It is proven that these rules form a sound and complete diagrammatic calculus for ALC.

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A Diagrammatic Reasoning System For Alc, Frithjof Dau, Peter Eklund Jan 2007

A Diagrammatic Reasoning System For Alc, Frithjof Dau, Peter Eklund

Faculty of Informatics - Papers (Archive)

Description logics (DLs) are a well-known family of knowledge representation (KR) languages. The notation of DLs has the style of a variable-free first order predicate logic. In this paper a diagrammatic representation of the DL ALC– based on Peirce’s existential graphs – is presented and a set of transformation rules on these graphs provided. As the transformation rules modify the diagrammatic representation of ALC this produces a diagrammatic calculus. Some examples present in the paper illustrate the use and properties of this calculus.

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Closed-Form Derivations Of Isi And Mui For Time-Reversed Ultra Wideband, Keni Popovski, Tadeusz A. Wysocki, Beata J. Wysocki Jan 2007

Closed-Form Derivations Of Isi And Mui For Time-Reversed Ultra Wideband, Keni Popovski, Tadeusz A. Wysocki, Beata J. Wysocki

Faculty of Informatics - Papers (Archive)

Through transmitter pre-filtering, a time reversed UWB system is capable if harnessing a multipath channel to achieve temporal and spatial focusing. Unfortunately, large RMS channel delay spread leads to significant intersymbol and multiuser interference. This paper presents closed-form expressions for self and multi-user interference for a UWB system utilizing a time-reversed approach. The influence of user multiplexing codes is taken to account through incorporation of a ‘separation probability’, which characterizes a family of hopping sequences. The standardized IEEE 802.15.3a channel model is applied, and the derived performances are compared with that of a simulated time hopped time-reversed UWB system.

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Fast Rsvp: A Cross Layer Resource Reservation Scheme For Mobile Ipv6 Networks, Yi Sun, Bin Feng, Yucheng Zhang, Gengfa Fang, Jinglin Shi, E. Dutkiewicz Jan 2007

Fast Rsvp: A Cross Layer Resource Reservation Scheme For Mobile Ipv6 Networks, Yi Sun, Bin Feng, Yucheng Zhang, Gengfa Fang, Jinglin Shi, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

This paper proposes a new cross layer scheme (Fast (Fast RSVP) RSVP) to reserve resources in mobile IPv6 networks. networks. Through the cooperation of mobile IP and RSVP modules, The organ Fast RSVP includes a number of mechanisms such as ad- introduces re vanced resource reservation on neighbor tunnels, resource RSVP schem reservation on optimized routes, resource reservation for results; Secti handover sessions, path merge etc. Network simulation re- conclusions. sults show that our scheme, compared with other traditional ways to reserve resources in mobile environments, has the 2. Related following advantages: (1) it allows a mobile node to realize …

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Toward Automatic Measurement Of The Linewidth-Enhancement Factor Using Optical Feedback Self-Mixing Interferometry With Weak Optical Feedback, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch Jan 2007

Toward Automatic Measurement Of The Linewidth-Enhancement Factor Using Optical Feedback Self-Mixing Interferometry With Weak Optical Feedback, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch

Faculty of Informatics - Papers (Archive)

This paper proposes an approach for automatically measuring the linewidth-enhancement factor (LEF) of semiconductor lasers using optical feedback self-mixing interferometry (OFSMI), which works in weak optical feedback regime and where the external target is subject to simple harmonic vibration with unknown vibration frequency and magnitude. According to well-known Lang–Kobayashi theory the waveform of the modulated optical output power from the OFSMI system is influenced by multiple parameters, including the LEF, the optical feedback level factor, and the parameters related to the movement of external target. In order to estimate LEF, other parameters must also be considered and, hence, a multiple …

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Beyond Videoconference: Increased Functionality To Enhance Media-Rich Interactions In Teaching And Learning, Elahe Aminifar, R. Caladine, Anne Porter, Mark I. Nelson Jan 2007

Beyond Videoconference: Increased Functionality To Enhance Media-Rich Interactions In Teaching And Learning, Elahe Aminifar, R. Caladine, Anne Porter, Mark I. Nelson

Faculty of Informatics - Papers (Archive)

Modern technologies provide new approaches to tertiary education and will be an increasing component of the educational experience in the future. Their use poses a significant challenge to the design and delivery of teaching and learning as many teachers and students are unfamiliar with them in this context. Over the last decade there has been a very rapid expansion in the capability and usage of Information and Communication Technologies (ICTs) in teaching and learning. To use them effectively there is a need to understand how different ICTs can be applied to learning and teaching. Videoconference, Access Grid and Web Conference …

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Blind Colour Isolation For Colour-Channel-Based Fringe Pattern Profilometry Using Digital Projection, Y. Hu, Jiangtao Xi, Joe F. Chicharo, Zongkai Yang Jan 2007

Blind Colour Isolation For Colour-Channel-Based Fringe Pattern Profilometry Using Digital Projection, Y. Hu, Jiangtao Xi, Joe F. Chicharo, Zongkai Yang

Faculty of Informatics - Papers (Archive)

We present an algorithm for estimating the color demixing matrix based on the color fringe patterns captured from the reference plane or the surface of the object. The advantage of this algorithm is that it is a blind approach to calculating the demixing matrix in the sense that no extra images are required for color calibration before performing profile measurement. Simulation and experimental results convince us that the proposed algorithm can significantly reduce the influence of the color cross talk and at the same time improve the measurement accuracy of the color-channel-based phase-shifting profilometry.

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Optimizing Initial Ranging Region Allocation In Ieee 802.16 Ofdma Systems, Jihua Zhou, E. Dutkiewicz, Di Pang, Jinlong Hu, Jinglin Shi Jan 2007

Optimizing Initial Ranging Region Allocation In Ieee 802.16 Ofdma Systems, Jihua Zhou, E. Dutkiewicz, Di Pang, Jinlong Hu, Jinglin Shi

Faculty of Informatics - Papers (Archive)

The IEEE 802.16 standard has been developed for metropolitan broadband wireless access systems. As part of the standard, the random access scheme is used for initial ranging. The ratio between the numbers of initial ranging slots and data slots in the uplink subframe decides the contention throughput, access delay and data throughput. However, no specific ratio is standardized in the protocol, so it is still necessary to determine the optimal number of initial ranging slots which is the decisive factor of the ratio. In this paper, we analyze the three parameters above, contention throughput, access delay and data throughput, each …

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Energy Efficient Integrated Scheduling Of Unicast And Multicast Traffic In 802.16e Wmans, Lin Tian, Yubo Yang, Jinglin Shi, E. Dutkiewicz, Gengfa Fang Jan 2007

Energy Efficient Integrated Scheduling Of Unicast And Multicast Traffic In 802.16e Wmans, Lin Tian, Yubo Yang, Jinglin Shi, E. Dutkiewicz, Gengfa Fang

Faculty of Informatics - Papers (Archive)

In this paper we address a new problem that has not been addressed in the past: how to improve energy efficiency for both unicast and multicast services without violating QoS requirements of mobile stations in 802.16e wireless networks. We propose a scheduling set based integrated scheduling (SSBIS) algorithm to solve the problem. SSBIS partitions all the mobile stations into multicast Scheduling Sets and a unicast Scheduling Set on the principle of minimizing mobile stations' energy consumptions by making use of the multicast transmission scheme and it adopts different scheduling policies based on the attributes of the Scheduling Sets to improve …

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Prediction Of Partners' Behaviors In Agent Negotiation Under Open And Dynamic Environments, Fenghui Ren, Minjie Zhang Jan 2007

Prediction Of Partners' Behaviors In Agent Negotiation Under Open And Dynamic Environments, Fenghui Ren, Minjie Zhang

Faculty of Informatics - Papers (Archive)

Prediction of partners' behaviors in negotiation has been an active research direction in recent years in the area of multi-agent and agent system. So by employing the prediction results, agents can modify their own negotiation strategies in order to achieve an agreement much quicker or to look after much higher benefits. Even though some of prediction strategies have been proposed by researchers, most of them are based on machine learning mechanisms which require a training process in advance. However, in most circumstances, the machine learning approaches might not work well for some kinds of agents whose behaviors are excluded in …

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How To Find The Sufficient Collision Conditions For Haval-128 Pass 3 By Backward Analysis, Pairat Thorncharoensri, Tianbing Xia, Yi Mu Jan 2007

How To Find The Sufficient Collision Conditions For Haval-128 Pass 3 By Backward Analysis, Pairat Thorncharoensri, Tianbing Xia, Yi Mu

Faculty of Informatics - Papers (Archive)

Wang et al. recently found several collisions in some hash functions, such as MD4, MD5, Haval-128 and RIPEMD. These findings have significantly changed our views about the security of existing hash functions. Unfortunately, al- though it is easy for us to verify the correctness of the collisions published by Wang et al., the sufficient condi- tions for collisions are not clear. In this paper, we present our methodology for constructing the sufficient conditions of collision tables by using Haval-128 Pass 3 as an ex- ample. We propose a backward analysis method of com- pression functions for constructing the sufficient condition …

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Enhanced Random Testing For Programs With High Dimensional Input Domains, Fei-Ching Kuo, K. Y. Sim, Chang-Ai Sun, S.-F. Tang, Zhiquan Zhou Jan 2007

Enhanced Random Testing For Programs With High Dimensional Input Domains, Fei-Ching Kuo, K. Y. Sim, Chang-Ai Sun, S.-F. Tang, Zhiquan Zhou

Faculty of Informatics - Papers (Archive)

Random Testing (RT) is a fundamental technique of software testing. Adaptive Random Testing (ART) has recently been developed as an enhancement of RT that has better fault detection effectiveness. Several methods (algorithms) have been developed to implement ART. In most ART algorithms, however, the above enhancement diminishes when the dimensionality of the input domain increases. In this paper, we investigate the nature of failure regions in high dimensional input domains and propose enhanced random testing algorithms that improve the fault detection effectiveness of RT in high dimensional input domains.

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The Impact Of Avatar Mobility On Distributed Server Assignment For Delivering Mobile Immersive Communication Environment, Ying Peng Que, Farzad Safaei, P. Boustead Jan 2007

The Impact Of Avatar Mobility On Distributed Server Assignment For Delivering Mobile Immersive Communication Environment, Ying Peng Que, Farzad Safaei, P. Boustead

Faculty of Informatics - Papers (Archive)

In our previous work, we proposed a distributed server architecture to deliver multi-party immersive voice communication service to mobile clients (e.g. Sony PSP) accessing a distributed virtual environment (DVE). We refer to such immersive voice communication service as mobile immersive communication environment (MICE). We also proposed solutions to assign server to create the auditory scene for each avatar. In this work, we ascertain the necessary update period of server reassignment in order to cope with avatar mobility in the virtual world. In our simulations, we measure the percentage differences in delay deviation and bandwidth cost between the case of no …

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An Immersive Voice Over Ip Service To Wireless Gaming: User Study And Impact Of Virtual World Mobility, Ying Peng Que, Farzad Safaei, P. Boustead Jan 2007

An Immersive Voice Over Ip Service To Wireless Gaming: User Study And Impact Of Virtual World Mobility, Ying Peng Que, Farzad Safaei, P. Boustead

Faculty of Informatics - Papers (Archive)

The current generation of VoIP services offer only single channel (mono) party-mix of voices. Thus when added to a network game engine, mono VoIP service can not really contribute to the gamers’ sense of virtual world immersion. As a future development, the Immersive VoIP service delivers to each gamer an Auditory Scene, mixing the live voices of surrounding gamers which are all directionally placed and distance attenuated according to the appropriate virtual world positions. In previous work, we have proposed the Wireless Immersive Communication Environment (WICE) which is special type of Immersive VoIP service tailored to the scarce resources of …

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Auto-Id And Location-Based Services In National Security: Social Implications, Holly Tootell Jan 2007

Auto-Id And Location-Based Services In National Security: Social Implications, Holly Tootell

Faculty of Informatics - Papers (Archive)

This paper provides an overview of auto-ID and location-based service technologies that are currently being used for the purposes of national security. The paper addresses the social dimensions of technology which have a bearing on their acceptance by individuals. This overview from both a technology and social perspective allows for an understanding to be created as increasingly decisions regarding adoption need to be made by different sectors in society.

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Reconfigurable Media Coding: A New Specification Model For Multimedia Coders, Christophe Lucarz, Marco Mattavelli, Joseph Thomas-Kerr, Jorn Janneck Jan 2007

Reconfigurable Media Coding: A New Specification Model For Multimedia Coders, Christophe Lucarz, Marco Mattavelli, Joseph Thomas-Kerr, Jorn Janneck

Faculty of Informatics - Papers (Archive)

Multimedia coding technology, after about 20 years of active research, has delivered a rich variety of different and complex coding algorithms. Selecting an appropriate subset of these algorithms would, in principle, enable a designer to produce the codec supporting any desired functionality as well as any desired trade-off between compression performance and implementation complexity. Currently, interoperability demands that this selection process be hard-wired into the normative descriptions of the codec, or at a lower level, into a predefined number of choices, known as profiles, codified within each standard specification. This paper presents an alternative paradigm for codec deployment that is …

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Subquadratic Binary Field Multiplier In Double Polynomial System, Pascal Giorgi, Christophe Negre, Thomas Plantard Jan 2007

Subquadratic Binary Field Multiplier In Double Polynomial System, Pascal Giorgi, Christophe Negre, Thomas Plantard

Faculty of Informatics - Papers (Archive)

We propose a new space efficient operator to multiply elements lying in a binary field F2k . Our approach is based on a novel system of representation called Double Polynomial System which set elements as a bivariate polynomials over F2. Thanks to this system of representation, we are able to use a Lagrange representation of the polynomials and then get a logarithmic time multiplier with a space complexity of O(k1:31) improving previous best known method.

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Business And It Alignment With Seam For Enterprise Architecture, Alain Wegmann, Gil Regev, Irina Rychkova, Lam-Son Le, Jose Diego De La Cruz, Philippe Julia Jan 2007

Business And It Alignment With Seam For Enterprise Architecture, Alain Wegmann, Gil Regev, Irina Rychkova, Lam-Son Le, Jose Diego De La Cruz, Philippe Julia

Faculty of Informatics - Papers (Archive)

To align an IT system with an organization's needs, it is necessary to understand the organization 's position within its environment as well as its internal configuration. In SEAM for enterprise architecture the organization is considered as a hierarchy of systems that span from business down to IT. The alignment process addresses the complete hierarchy. We illustrate the use of SEAM for enterprise architecture with an example in which a new hiring process and an IT system are developed. With this approach it is possible to train new engineers in the design of business and IT alignment. It is also …

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Spin-Polarized Transport In Dilute Magnetic Semiconductor Tunnel Junctions, J E. Bunder Jan 2007

Spin-Polarized Transport In Dilute Magnetic Semiconductor Tunnel Junctions, J E. Bunder

Faculty of Informatics - Papers (Archive)

No abstract provided.

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Adaptive Self-Organisation Of Wireless Ad-Hoc Control Networks, Fazel Naghdy, Nathan Simiana Jan 2007

Adaptive Self-Organisation Of Wireless Ad-Hoc Control Networks, Fazel Naghdy, Nathan Simiana

Faculty of Informatics - Papers (Archive)

A novel concept called Wireless ad-hoc Control Networks (WACNets), exploring an ad-hoc approach to networked distributed control, has been under study for the last five years in the research group. Such systems represent a new stage in the evolution of distributed control and monitoring. The work carried out in developing an adaptive self-organisation algorithm for WACNet is reported. The algorithm deploys a distance measure technique while satisfying the rules and assumptions developed for WACNet framework. The effectiveness of the algorithm is verified through computer simulation under a number of given scenarios. The results obtained show that the algorithm effectively drives …

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Empirical Modelling Of Human Gaits For Bipedal Robots, Matthew Field, David A. Stirling, Fazel Naghdy, Zengxi Pan Jan 2007

Empirical Modelling Of Human Gaits For Bipedal Robots, Matthew Field, David A. Stirling, Fazel Naghdy, Zengxi Pan

Faculty of Informatics - Papers (Archive)

Modelling of human motion through a discrete sequence of motion primitives, retaining elements of skillful or unique motion of an individual is addressed. Using wireless inertial motion sensors, a skeletal model of the fluid human gait was gathered. The posture of the human model is described by nine sets of euler angles for each sample. An intrinsic classification algorithm known as Minimum Message Length encoding (MML) is deployed to segment the stream of data and subsequently formulate certain Gaussian Mixture Models (GMM) that contain a plausible range of motion primitives. The removal of certain less seemingly important modes has been …

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Dynamical Symmetry Enlargement In Metallic Zigzag Carbon Nanotubes, J E. Bunder, Hsiu-Hau Lin Jan 2007

Dynamical Symmetry Enlargement In Metallic Zigzag Carbon Nanotubes, J E. Bunder, Hsiu-Hau Lin

Faculty of Informatics - Papers (Archive)

No abstract provided.

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Oscillating Carbon Nanotori Along Carbon Nanotubes, Tamsyn A. Hilder, James M. Hill Jan 2007

Oscillating Carbon Nanotori Along Carbon Nanotubes, Tamsyn A. Hilder, James M. Hill

Faculty of Informatics - Papers (Archive)

The discovery of carbon nanostructures, such as nanotubes and C60 fullerenes, has given rise to a number of potential nanoscale devices. One such device is the gigahertz oscillator, comprising an inner shell sliding inside an outer shell of a multiwalled carbon nanotube, and which, at least theoretically, generates oscillatory frequencies in the gigahertz range. Following the concept of these gigahertz oscillators and the recent discovery of “fullerene crop circles,” here we propose the notion of a nanotorus-nanotube oscillator comprising a carbon nanotorus which is sucked by the van der Waals force onto the carbon nanotube, and subsequently oscillates along the …

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Continuum Modelling For Carbon And Boron Nitride Nanostructures, James M. Hill, Ngamta Thamwattana Jan 2007

Continuum Modelling For Carbon And Boron Nitride Nanostructures, James M. Hill, Ngamta Thamwattana

Faculty of Informatics - Papers (Archive)

Continmuum based models are presented here for certain boron nitride and carbon nanostructures.

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On The Characteristics Of Bgp Multiple Origin As Conflicts, Kwan-Wu Chin Jan 2007

On The Characteristics Of Bgp Multiple Origin As Conflicts, Kwan-Wu Chin

Faculty of Informatics - Papers (Archive)

The Internet has thousands of autonomous systems (ASs), each advertising one or more prefixes it owns. According to RFC 1930, each prefix should originate from a single AS. However, routing updates involving multiple ASs advertising reachability to a given prefix, so called multiple origin AS conflict (MOAS), are becoming prevalent. To this end, this paper analyzes and quantifies MOAS conflicts observed in routing updates collected over 21 days in January 2007, and presents ten reasons that explain why they occur.

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Real-Time Facial Feature Point Extraction, Ce Zhan, Wanqing Li, Philip Ogunbona, Farzad Safaei Jan 2007

Real-Time Facial Feature Point Extraction, Ce Zhan, Wanqing Li, Philip Ogunbona, Farzad Safaei

Faculty of Informatics - Papers (Archive)

Localization of facial feature points is an important step for many subsequent facial image analysis tasks. In this paper, we proposed a new coarse-to-fine method for extracting 20 facial feature points from image sequences. In particular, the Viola-Jones face detection method is extended to detect small-scale facial components with wide shape variations, and linear Kalman filters are used to smoothly track the feature points by handling detection errors and head rotations. The proposed method achieved higher than 90% detection rate when tested on the BioID face database and the FG-NET facial expression database. Moreover, our method shows robust performance against …

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