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Articles 1 - 30 of 67
Full-Text Articles in Engineering
Optimisation Of Multicast Routing In Wireless Mesh Networks, Brian Keegan, Karol Kowalik, Mark Davis
Optimisation Of Multicast Routing In Wireless Mesh Networks, Brian Keegan, Karol Kowalik, Mark Davis
Conference papers
In recent years Wireless Mesh Networks have been deployed and grown in popularity in many metropolitan areas. The deployment of such networks has allowed clients to gain access to publicly available broadband networks. The implementation of wireless mesh networks requires that backhaul services (traditionally carried by wired networks) be maintained via wireless mesh points. Because of their structure, wireless mesh networks provide an excellent means for targeting a large group of end users or simply to relay data. This may be achieved by means of broadcasting or more specifically multicasting. The lack of standards and support for multicasting over wireless …
Investigation Of Across-Layer Modification To The Dsr Routing Protocol In Wireless Mesh Networks, Mustafa Ramadhan, Mark Davis
Investigation Of Across-Layer Modification To The Dsr Routing Protocol In Wireless Mesh Networks, Mustafa Ramadhan, Mark Davis
Conference papers
This work introduces a cross-layer modification to the DSR protocol that increases the global throughput in wireless mesh networks. In our modified DSR protocol we have introduced the Access Efficiency metric as an alternative to the hop-count metric in order to improve the route selection mechanism. The selected path in the route selection mechanism is identified by choosing the path with the highest minimum Access Efficiency value. We have employed the OPNET modeller as a simulator to examine two different patterns of traffic for a series of randomly generated network topologies. Each topology was simulated twice. One simulation used the …
Effects Of Lline Rate On Vvideo Qos Over Wireless Networks: An Experimental Approach, Stuart Wallace, Mark Davis
Effects Of Lline Rate On Vvideo Qos Over Wireless Networks: An Experimental Approach, Stuart Wallace, Mark Davis
Conference papers
Video streaming over Wireless Local Area Networks (WLANS) is becoming an increasingly popular service. However, end user OoS is highly influenced by many factors. These include the video codec used, the packetization scheme, error concealment and correction techniques, the complexity of the video, propagation losses, and the line rate. In this paper the effect of the line rate on the capacity of the network when streaming multimedia content is analyzed experimentally. It is shown that as the line rate decreases the bandwidth load of the video stream dramatically increases leading to poor QoS at the client side. As automatic line …
An Investigation Of The Correlation Between Passive Monitoring And Activie Probing Techniques Used In Wlan Mesh Networks, Chenzhe Zhang, Mark Davis
An Investigation Of The Correlation Between Passive Monitoring And Activie Probing Techniques Used In Wlan Mesh Networks, Chenzhe Zhang, Mark Davis
Conference papers
In recent years, Wireless Mesh Networks (WMNs) have emerged as a promising solution to provide low cost networks that extend Internet access and other networking services. Mesh routers form the backbone connectivity through cooperative routing in an often unstable wireless medium. Therefore, the techniques used to monitor and manage the performance metrics to help optimize the link performance in WMNs. This paper presents an assessment of the correlation between passive monitoring and active probing techniques used for link performance measurement in WMNs. This paper presents an assessment of the correlation between passive monitoring and active probing techniques used for link …
Hand-Held Flyback Driven Coaxial Dielectric Barrier Discharge: Development And Characterization, Victor J. Law, Vladimir Milosavljevic, Neil O’Connor, James F. Lalor, Steven Daniels
Hand-Held Flyback Driven Coaxial Dielectric Barrier Discharge: Development And Characterization, Victor J. Law, Vladimir Milosavljevic, Neil O’Connor, James F. Lalor, Steven Daniels
Articles
The development of a handheld single and triple chamber atmospheric pressure coaxial dielectric barrier discharge driven by Flyback circuitry for helium and argon discharges is described. The Flyback uses external metal-oxide-semiconductor field-effect transistor power switching technology and the transformer operates in the continuous current mode to convert a continuous dc power of 10–33 W to generate a 1.2–1.6 kV 3.5 μs pulse. An argon discharge breakdown voltage of ∼768 V is measured. With a 50 kHz, pulse repetition rate and an argon flow rate of 0.5–10 argon slm (slm denotes standard liters per minute), the electrical power density deposited in …
Control Of Double Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions, Joseph Kearney, Michael Conlon
Control Of Double Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions, Joseph Kearney, Michael Conlon
Conference papers
The behaviour of Double-Fed Induction Generators to supply network voltage unbalance is investigated. The paper describes a method to control the rotor-side converter in a DFIG when subjected to the effects of network voltage unbalance conditions. A parallel control scheme is implemented to control the positive and negative sequence components independently. A DFIG model is implemented in Matlab/Simulink and simulations show the reduction in power and torque oscillations and a reduction in the high unbalanced currents generated as a result of the applied voltage unbalance.
The Role Of Micro Wind Generation In Ireland’S Energy Future, Keith Sunderland, Michael Conlon
The Role Of Micro Wind Generation In Ireland’S Energy Future, Keith Sunderland, Michael Conlon
Conference papers
This paper defines the current position for micro-generation, with particular reference to the potential for micro-wind units, in the Irish electricity supply system. A network model is developed using the Distflow method of load flow analysis and is applied to consider the appropriate level of micro-generation penetration.
An Evaluation Of A Conservative Transmit Power Control Mechanism On An Indoor 802.11 Wireless Mesh Testbed, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
An Evaluation Of A Conservative Transmit Power Control Mechanism On An Indoor 802.11 Wireless Mesh Testbed, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Conference papers
Power control techniques for IEEE 802.11 wireless networks have already gained considerable attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operation such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. In this paper we propose a novel delivery ration based Conservative Transmit Power Control (ConTPC) mechanism. Our implementation is conservative when it comes to deciding if the transmit power should be reduced for a given link. This is because we do not want poor quality wireless links to further reduce their quality and be overwhelmed by …
Practical Issues Of Power Control In Ieee 802.11 Wireless Devices, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Practical Issues Of Power Control In Ieee 802.11 Wireless Devices, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Conference papers
Power control techniques for IEEE 802.11 wireless networks have already gained much attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operations such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. However, until recently implementing such advanced power control using off-the-shelf wireless devices was not considered possible. For example, Abdesslem et al. [1] stated that “many novel power control solutions cannot be efficiently implemented over existing IEEE 802.11 cards”. However, in this paper we demonstrate that power control is now feasible and can be implemented in current …
A Real-Time Framework For Video Time And Pitch Scale Modification, Ivan Damnjanovic, Dan Barry, David Dorran, Josh Reiss
A Real-Time Framework For Video Time And Pitch Scale Modification, Ivan Damnjanovic, Dan Barry, David Dorran, Josh Reiss
Conference papers
A framework is presented which addresses the issues related to the real-time implementation of synchronised video and audio time-scale and pitch-scale modification algorithms. It allows for seamless real-time transition between continually varying, independent time-scale and pitch-scale parameters arising as a result of manual or automatic intervention. We illuminate the problems which arise in a real-time context as well as provide novel solutions to prevent artefacts, minimise latency, and improve synchronisation. The time and pitch scaling approach is based on a modified phase vocoder with optional phase locking and an integrated transient detector which enables high quality transient preservation in real-time. …
Analysis Of Mimo Communications Systems Based On Experimentally Observed Channels, Pat Chambers
Analysis Of Mimo Communications Systems Based On Experimentally Observed Channels, Pat Chambers
Doctoral
This thesis presents an analysis of multiple-input/multiple-output (MIMO) communications systems where the objective is to provide a unified solution to the problems of (i) crosstalk coupling in transmission line channels (ii) multi-path fading in the time variant high frequency wireless channel. In the case of transmission line channels, a comparative analysis is presented of the performance of MIMO communications systems based on balanced CAT 5 twisted-pair transmission lines, balanced twisted-pair telephone transmission lines scheme as well as unbalanced flat-pair transmission lines. The unbalanced flat-pair transmission lines are viewed as a model for digital subscriber lines (DSLs) which may be deemed …
Real-Time Plasma Controlled Chemistry In A Two-Frequency, Confined Plasma Etcher, Vladimir Milosavljevic, Albert R. Ellingboe, Cezar Gaman, John V. Ringwood
Real-Time Plasma Controlled Chemistry In A Two-Frequency, Confined Plasma Etcher, Vladimir Milosavljevic, Albert R. Ellingboe, Cezar Gaman, John V. Ringwood
Articles
The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O2flow). A phenomenological physics model of the nonlinear coupling between the independent controls and the dependent variables of the plasma is presented. By using a design of experiment, the functional dependencies of the response surface are determined. In conjunction with the physical model, the dependencies are used to deconvolve the sensor …
Extended Nonnegative Tensor Factorisation Models For Musical Sound Source Separation, Derry Fitzgerald, Matt Cranitch, Eugene Coyle
Extended Nonnegative Tensor Factorisation Models For Musical Sound Source Separation, Derry Fitzgerald, Matt Cranitch, Eugene Coyle
Articles
Recently, shift-invariant tensor factorisation algorithms have been proposed for the purposes of sound source separation of pitched musical instruments. However, in practice, existing algorithms require the use of log-frequency spectrograms to allow shift invariance in frequency which causes problems when attempting to resynthesise the separated sources. Further, it is difficult to impose harmonicity constraints on the recovered basis functions. This paper proposes a new additive synthesis-based approach which allows the use of linear-frequency spectrograms as well as imposing strict harmonic constraints, resulting in an improved model. Further, these additional constraints allow the addition of a source filter model to the …
Unified Power Quality Conditioner: Protection And Performance Enhancement, Iurie Axente
Unified Power Quality Conditioner: Protection And Performance Enhancement, Iurie Axente
Doctoral
The proliferation of power electronics-based equipment has produced a significant impact on the quality of electric power supply. Nowadays, much of the equipment is based on power electronic devices, often leading to problems of power quality. At the same time this equipment is typically equipped with microprocessor-based controllers which are quite sensitive to deviations from the ideal sinusoidal line voltage. Conventional power quality mitigation equipment is proving to be inadequate for an increasing number of applications, and this fact has attracted the attention of power engineers to develop dynamic and adjustable solutions to power quality problems. One modern and very …
Linear Prediction: The Problem, Its Solution And Application To Speech, Alan O'Cinneide, David Dorran, Mikel Gainza
Linear Prediction: The Problem, Its Solution And Application To Speech, Alan O'Cinneide, David Dorran, Mikel Gainza
Conference papers
Linear prediction is a signal processing technique that is used extensively in the analysis of speech signals and, as it is so heavily referred to in speech processing literature, a certain level of familiarity with the topic is typically required by all speech processing engineers. This paper aims to provide a well-rounded introduction to linear prediction, and so doing, facilitate the understanding of the technique. Linear prediction and its mathematical derivation will be described, with a specific focus on applying the technique to speech signals. It is noted, however, that although progress in linear prediction has been driven primarily by …
A Low Polarization Sensitivity All-Fiber Wavelength Measurement System, Ginu Rajan, Yuliya Semenova, Gerald Farrell, Qian Wang, Pengfei Wang
A Low Polarization Sensitivity All-Fiber Wavelength Measurement System, Ginu Rajan, Yuliya Semenova, Gerald Farrell, Qian Wang, Pengfei Wang
Articles
A low polarization-sensitive all-fiber wavelength measurement system using a twisted macro-bend fiber edge filter together with polarization-insensitive (PI) 3-dB coupler is presented. Eliminating the polarization-dependent loss (PDL) is essential when macro-bending single-mode fiber is utilized as an edge filter. A new bending configuration to eliminate the PDL of a fiber edge filter is proposed in this letter by twisting the fiber by 90deg between two bending sections with equal length. The PDL of this configuration retains a low value even while the bending length is increased to achieve a steeper response for the edge filter. This configuration together with a …
Investigation On Singlemode-Multimode-Singlemode Fiber Structure, Qian Wang, Gerald Farrell, W. Yan
Investigation On Singlemode-Multimode-Singlemode Fiber Structure, Qian Wang, Gerald Farrell, W. Yan
Articles
This paper presents an investigation on a single-mode-multimode-single-mode fiber structure. A one-way guided-mode propagation analysis for the circular symmetry waveguide is employed to model the light propagation and the approximated formulations are derived and evaluated concerning the accuracy. Phase conjunction of the multimode interference within the fiber structure is revealed. A simple way to predict and analyze the spectral response of the structure is presented through the space to wavelength mapping with the derived approximated formulations. The prediction of spectral response is verified numerically and experimentally.
Group Velocity Dispersion Reduction In Fibre-Based Slow-Light Systems Via Stimulated Brillouin Scattering, Ronny Henker, A. Wiatrek, K. U. Lauterbach, Max Ammann, Andreas Schwarzbacher, Thomas Schneider
Group Velocity Dispersion Reduction In Fibre-Based Slow-Light Systems Via Stimulated Brillouin Scattering, Ronny Henker, A. Wiatrek, K. U. Lauterbach, Max Ammann, Andreas Schwarzbacher, Thomas Schneider
Articles
Presented are theoretical investigations and simulations of a reduction of the group velocity dispersion (GVD) in slow-light systems by an optimisation of the gain spectrum of the stimulated Brillouin scattering (SBS). A comparison between a natural Brillouin gain spectrum and a broadened Brillouin gain spectrum with and without two additional losses at its wings is demonstrated. The focus of the theoretical examination was set on the superposition of a gain and two losses with an equal magnitude. Therefore, a low GVD and a high group index change could be achieved and hence, a small pulse distortion and a high time …
Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed By Microstrip Line, Xiulong Bao, Max Ammann
Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed By Microstrip Line, Xiulong Bao, Max Ammann
Articles
A new design of a dual-frequency dual circularly-polarized slot antenna is presented. The dual-frequency is achieved using a single-layer microstrip-fed configuration coupled to a modified annular-slot antenna. The dual sense circular-polarization is obtained by four unequal linear slots which augment the annular slot. Experimental results show the proposed antenna has good circular polarization characteristics for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). The 10 dB return loss impedance bandwidths for the lower (RHCP) and higher (LHCP) bands are 26.7% and 11.3%, respectively. The 3 dB axial-ratio bandwidths are 6.1% and 6.0% with respect to 1.5 GHz (RHCP) …
Dual Frequency Dual Circularly-Polarised Patch Antenna With Wide Beamwidth, Xiulong Bao, Max Ammann
Dual Frequency Dual Circularly-Polarised Patch Antenna With Wide Beamwidth, Xiulong Bao, Max Ammann
Articles
A dual-frequency dual-circularly polarised patch antenna with wide beamwidth is proposed. The two-layer structure comprises circular patches with offset circular slots connected to rectangular slots. They provide orthogonal perturbations realising RHCP and LHCP for the lower and upper bands, respectively. The wide beamwidth is realised by extending the substrate beyond the groundplane. Measurements show a maximum beamwidth of 180deg and gains of 3.9 and 0.5 dBic for zenith and 10deg elevation, respectively, for the upper band. The measured beamwidth for the low band is 130deg with a maximum gain of 3.9 and -0.7 dBic for zenith and 10deg elevation, respectively. …
Influence Of Fiber Manufacturing Tolerances On The Spectral Response Of A Bend Loss Based All-Fiber Edge Filter, Pengfei Wang, Gerald Farrell, Yuliya Semenova, Ginu Rajan
Influence Of Fiber Manufacturing Tolerances On The Spectral Response Of A Bend Loss Based All-Fiber Edge Filter, Pengfei Wang, Gerald Farrell, Yuliya Semenova, Ginu Rajan
Articles
It is shown that manufacturing tolerances of the fiber parameters bend radius and NA significantly influence the fiber bend loss performance and spectral response of a fiber-based edge filter. A theoretical model, validated by experimental results, is used to determine the changes in key spectral parameters for an edge filter, resulting from changes within their manufacturing tolerance range, for both the bend radius and NA. Finally is shown that bend-radius tuning during fabrication of such filters is a means of mitigating the effect of manufacturing variations.
Ratiometric Wavelength Monitor Based On Singlemode-Multimode-Singlemode Fiber Structure, Agus Hatta, Gerald Farrell, Qian Wang, Ginu Rajan, Pengfei Wang, Yuliya Semenova
Ratiometric Wavelength Monitor Based On Singlemode-Multimode-Singlemode Fiber Structure, Agus Hatta, Gerald Farrell, Qian Wang, Ginu Rajan, Pengfei Wang, Yuliya Semenova
Articles
An all-fiber ratiometric wavelength monitor for optical wavelength measurement is proposed and is investigated theoretically and experimentally. Two edge filters with opposite slope spectral responses based on singlemode-multimode-singlemode (SMS) fiber structures are developed. A ratiometric wavelength measurement system employing the developed SMS edge filters demonstrates a high discrimination range of 20.41 dB and a potential wavelength measurement resolution of 10 pm over a wavelength range from 1530 to 1560 nm.
Throughput Enhancement Through Combined Fragmentation And Rate Method In Ieee 802.11b Wlans, Marek Bykowski, Karol Kowalik, Brian Keegan, Mark Davis
Throughput Enhancement Through Combined Fragmentation And Rate Method In Ieee 802.11b Wlans, Marek Bykowski, Karol Kowalik, Brian Keegan, Mark Davis
Conference papers
IEEE 802.11 allows for fragmentation tuning and rate selection. Their combined usage is referred sometimes to link adaptation. However, the algorithms of link adaptation are beyond the 802.11 standards. In this paper we investigate the benefits arising from proper use of link adaptation. Particularly, we develop a mathematical model describing the fragmented transmission in 802.11b. We examine potential benefits of it over AWGN and fading channels. More significantly we combine fragmentation tuning with bit-rate selection to yield the highest achievable throughput performance for any given channel conditions. Finally, we propose an algorithm that performs the optimal link adaptation.
Interaction Of Rf-Hyperthermia Applicator With High Fidelity Human Body Model, Sergio Curto, T.S. P. See, Z. N. Chen, Patrick Mcevoy, Max Ammann
Interaction Of Rf-Hyperthermia Applicator With High Fidelity Human Body Model, Sergio Curto, T.S. P. See, Z. N. Chen, Patrick Mcevoy, Max Ammann
Conference papers
A compact patch antenna working at the 434 MHz ISM frequency band is proposed as an RF-Hyperthermia applicator. The electromagnetic interaction in terms of S11, SAR and E-Field distribution of the antenna with a High Fidelity human body model is investigated. This analysis provides useful information for engineers and clinical staff to develop more efficient and smaller antennas for medical applications, in particular for RF-Hyperthermia cancer therapy, where the size of the antenna determines tumor accessibility.
High Performance Zno Varistors Prepared From Nanocrystalline Precursors For Miniaturised Electronic Devices, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh
High Performance Zno Varistors Prepared From Nanocrystalline Precursors For Miniaturised Electronic Devices, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh
Articles
An industrially viable solution-based processing route using minimal amounts of solvent has been used to prepare bulk quantity nanopowders (average particle size 15.3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterised. The preparation of varistors from nanopowders has been optimised by studying the effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 C for 2 hours, a temperature that is significantly lower than that used in the current industrial process. Highly dense varistor discs prepared from the sintered material produce devices, with …
Pitch Tracking And Voiced/Unvoiced Detection In Noisy Environment Using Optimat Sequence Estimation, Moshe Wasserblat, Mikel Gainza, David Dorran, Yuval Domb
Pitch Tracking And Voiced/Unvoiced Detection In Noisy Environment Using Optimat Sequence Estimation, Moshe Wasserblat, Mikel Gainza, David Dorran, Yuval Domb
Conference papers
This paper addresses the problem of pitch tracking and voiced/unvoiced detection in noisy speech environments. An algorithm is presented which uses a number of variable thresholds to track pitch contour with minimal error. This is achieved by modeling the pitch tracking problem in such a way that allows the use of optimal estimation methods, such MLSE. The performance of the algorithm is evaluated using the Keele pitch detection database with realistic background noise. Results show best performance in comparison to other state of the art pitch detector and successful pitch tracking is possible in low signal to noise conditions.
Structural Segmentation Using Set Accented Tones, Cillian Kelly, Mikel Gainza, David Dorran, Eugene Coyle
Structural Segmentation Using Set Accented Tones, Cillian Kelly, Mikel Gainza, David Dorran, Eugene Coyle
Conference papers
An approach which efficiently segments Irish Traditional Music into its constituent structural segments is presented. The complexity of the segmentation process is greatly increased due to melodic variation existent within this music type. In order to deal with these variations, a novel method using ‘set accented tones’ is introduced. The premise is that these tones are less susceptible to variation than all other tones. Thus, the location of the accented tones is estimated and pitch information is extracted at these specific locations. Following this, a vector containing the pitch values is used to extract similar patterns using heuristics specific to …
Thermodynamic Modelling And Ray-Trace Modelling Of Luminescent Solar Concentrators: A Comparison Of The Two Approaches, Manus Kennedy, Amanda Chatten, Daniel Farrell, Rahul Bose, Andreas Büchtemann, Sarah Mccormack, John Doran, Brian Norton, Keith Barnham
Thermodynamic Modelling And Ray-Trace Modelling Of Luminescent Solar Concentrators: A Comparison Of The Two Approaches, Manus Kennedy, Amanda Chatten, Daniel Farrell, Rahul Bose, Andreas Büchtemann, Sarah Mccormack, John Doran, Brian Norton, Keith Barnham
Conference Papers
The electrical and spectral output from luminescent solar concentrator (LSC) devices is predicted using thermodynamic modelling and ray-trace modelling techniques. Predicted output from four LSCs of varying dimensions, containing different luminescent dyes, are found to be in good agreement with measured output taken from fabricated LSCs. Despite the many different processes involved in the two modelling approach, predicted short circuit current densities from both approaches are found to be in excellent agreement.
Investigation On The Performance Of Upqc-Q For Voltage Sag Mitigation And Pq Improvement At A Critical Load Point, Malabika Basu, S. P. Das, Gopal Dubey
Investigation On The Performance Of Upqc-Q For Voltage Sag Mitigation And Pq Improvement At A Critical Load Point, Malabika Basu, S. P. Das, Gopal Dubey
Articles
The unified power quality conditioner (UPQC) is one of the major custom power solutions, which is capable of mitigating the effect of supply voltage sag at the load end or at the point of common coupling (PCC) in a distributed network. It also prevents the propagation of the load current harmonics to the utility and improves the input power factor of the load. The control of series compensator (SERC) of the UPQC is such that it injects voltage in quadrature advance to the supply current. Thus, the SERC consumes no active power at steady state. The other advantage of the …
Audio Data Verification And Authentication Using Frequency Modulation Based Watermarking, Jonathan Blackledge, Omar Farooq
Audio Data Verification And Authentication Using Frequency Modulation Based Watermarking, Jonathan Blackledge, Omar Farooq
Articles
An approach to watermarking digital signals using frequency modulation - ‘Chirp Coding’ - is considered. The principles underlying this approach are based on the use of a matched filter to reconstruct a ‘chirp stream’ code that is uniquely robust. The method is generic in the sense that it can, in principle, be used for a variety of different signal (the authentication of speech and biomedical signals, for example). Further, by generating a bit stream that is signal dependent, chirp coding provides a method of self-authentication, which has a wide range of applications including copyright protection and digital rights management. However, …