Browsing by Author "Duffy, A. P."
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Item Open Access 3D Simulation of Partial Discharge in High Voltage Power Networks(IWCS Inc, 2019-10-01) Ragusa, Antonella; Sasse, Hugh G.; Duffy, A. P.Partial discharge (PD) events arise inside power cables due to defects of cable’s insulation material, characterized by a lower electrical breakdown strength than the surrounding dielectric material. These electrical discharges cause signals to propagate along the cable, manifesting as noise phenomena. More significantly, they contribute to insulation degradation and can produce a disruptive effect with a consequent interruption of power network operation. PD events are, therefore, one of the best ‘early warning’ indicators of insulation degradation and, for this reason, the modeling and studying of such phenomena, together with the development of on-line PDs location methods, are important topics for network integrity assessment, and to define methods to improve the power networks’ Electricity Security. This paper presents a 3D model of PD events inside a void in epoxy-resin insulation cables for High Voltage (HV) power networks. The 3D model has been developed using the High Frequency (HF) Solver of CST Studio Suite® software. PD events of a few µs duration have been modelled and analyzed. The PD behavior has been investigated using varying electrical stress. A first study of the PD signal propagation in a power network is described.Item Metadata only Accurate method for predicting return loss of communication channel.(IEEE, 2001) Al-Asadi, M. M.; Duffy, A. P.; Willis, A. J.; Hodge, K.Item Open Access Achieving Vertically-integrated Carbon-fibre Reinforcement Design and Manufacture Demonstrators for Structural Manufacturing and Construction 3-D Composites(2014-09-23) Kang, Parminder Singh; Sun, Yong; Silva, C.; Duffy, A. P.Item Open Access Analysing transient phenomena in the time domain using the Feature Selective Validation (FSV) Method(IEEE, 2013-02-04) Jauregui, R.; Zhang, Gang; Rojas-Mora, J.; Ventosa, O.; Silva, F.; Duffy, A. P.; Sasse, Hugh G.The increasing application of simulation tools to increasingly complex problems makes the use of validation tools essential to improve confidence in the veracity of those simulation results. IEEE Standard 1597.1 is the first true standard for validation of computational electromagnetic. This standard uses the Feature Selective Validation (FSV) method as the key quantification tool. However, despite its many advantages, there have been some interesting issues surrounding the validation of transients. This paper presents a new approach to the validation of a set of generally representative transient types using the Feature Selective Validation (FSV) method and shows how the previously experienced limitations can be overcome. In order to analyse the main parameters associated with transient comparison, a survey which included 20 experts was conducted. This information was used to identify the significant regions that need to be taken into account in the transient comparison. Finally, using the statistics obtained by the experts, a new solution was defined and its improvement over the existing approach demonstrated.Item Metadata only Analysis and modelling of structured wiring communication channels(IEEE, 2001-05-01) Al-Asadi, M. M.; Duffy, A. P.; Hodge, K.; Willis, A. J.The authors present equations for the calculation of the attenuation constant of both unshielded and shielded cables as a function of cable dimension, material parameters and frequency of operation. An analytical approach is given for calculating the return loss of a communication channel as a function of such parameters as impedance, length and propagation constant. A transmission-line matrix (TLM) method to assess the effects on attenuation and return loss of longitudinal variations along a structured wire cable is developed. Results are presented using both analytical and modelling approaches; these are validated against measurements.Item Metadata only Analysis of techniques to compare complex data sets.(Emerald, 2002) Coleby, D. E.; Duffy, A. P.Item Metadata only Analyzing Transient Phenomena in the Time Domain Using the Feature Selective Validation (FSV) Method(IEEE, 2013-05-24) Jauregui, R.; Zhang, G.; Rojas-Mora, J.; Ventosa, O.; Silva, F.; Duffy, A. P.; Sasse, Hugh G.The increasing application of simulation tools to increasingly complex problems makes the use of validation tools essential to improve confidence in the veracity of those simulation results. IEEE Standard 1597.1 is the first true standard for the validation of computational electromagnetics method. This standard uses the feature selective validation (FSV) method as the key quantification tool. However, despite its many advantages, there have been some interesting issues surrounding the validation of transients. This paper presents a new approach to the validation of a set of generally representative transient types using the FSV method and shows how the previously experienced limitations can be overcome. In order to analyze the main parameters associated with transient comparison, a survey which included 20 experts was conducted. This information was used to identify the significant regions that need to be taken into account in the transient comparison. Finally, using the statistics obtained by the experts, a new solution was defined and itsItem Metadata only Antenna efficiency measurements in a reverberation chamber without the need for a reference antenna.(Institute of Electrical and Electronics Engineers Inc., 2008) Lee, C. S.; Duffy, A. P.; Lee, C.Item Open Access Application of probabilistic models for multitone electromagnetic immunity analysis(IEEE, 2022-10-12) Devaraj, Lokesh; Khan, Qazi Mashaal; Ruddle, Alastair R.; Duffy, A. P.; Perdriau, Richard; Koohestani, MohsenThe operational environment of modern electronic systems may include multiple frequency electromagnetic dis- turbances. However, immunity measurements usually employ single frequency continuous waveforms (i.e. single-tones). The performance of two oscillator circuits with different topologies (one simulated and one measured) were used as case studies to in- vestigate immunity to simultaneous single-tone disturbances (i.e. multitones) using probabilistic Bayesian network models. For the multitone analysis, the noisy-OR model was first used to identify the type of causal interactions between simultaneously occurring single-tones. Probabilistic theories derived from the recursive noisy-OR model, which inherits the independence assumptions of the noisy-OR and any known causal dependence between simultaneously occurring single-tones, were then used to predict the probability of higher order multitone failures. For the two case studies, the probability of three-tone failures was estimated using the single-tone and two-tone failure probability values. An improved adaptive recursive noisy-OR model was also proposed to overcome the practical difficulties of obtaining multitone failure probabilities, from either simulations or measurements.Item Metadata only Applying a behavioural and operational diagnostic typology of competitive intelligence practice: Empirical evidence from the SME sector in Turkey.(Taylor and Francis, 2012) Wright, Sheila; Bisson, C.; Duffy, A. P.Item Metadata only A behavioural and operational typography of competitive intelligence practices in Turkish SMEs(2011) Wright, Sarah; Bisson, C.; Duffy, A. P.Item Metadata only Cable coupling measurements in a reverberation chamber.(Electronic Components Association, 2009) Duffy, A. P.; Sasse, Hugh G.; Coates, A.; Lee, C. S.; Hodge, K.Item Metadata only Challenges in developing a multidimensional feature Selective Validation implementation.(IEEE, 2010) Archambeault, B.; Duffy, A. P.; Sasse, Hugh G.; Li, X. K.; Scase, M. O.; Shafiullah, M.; Orlandi, A.; Di Febo, D.Item Metadata only Classification and Clustering Approaches to Understanding Customer Ordering by Customers of a Fresh Food Supplier(The 20th Annual Conference of The Chartered Institute of Logistics & Transport, Logistics Research Network (LRN), Derby, UK, 2015-09-11) Clement, Ross; Kang, Parminder Singh; Duffy, A. P.; Hopewell, AshleyPurpose: This paper looks at characterization of B2B customers of a fresh food wholesale company supplying SME clients in terms of their weekly orders of a variety of fresh products. Customers whose orders can be predicted (days of the week order is placed, size of order) can easily be supplied without risk of waste due to the wholesaler ordering stock that is not sold to customers before it must be disposed of. Greater understanding of customer order patterns is necessary to improve demand prediction and reduce waste. Research Approach: Extensive real-world data from a fresh food wholesaler has been analysed in bulk. Customers’ weekly orders have been classified into one of nine classes depending on how each week’s order compares to the previous week. Equal order amounts on the same day (or days) of the week as the previous week are the most predictable class. Varying order amounts for orders placed on different days of the week are a much less predictable class. Other classes represent customers who either cease ordering after having made previous orders, or who place an order after not ordering in previous weeks. K-means clustering has also been used to extract clusters of customers showing similar ordering patterns from the customer base. These functions have been integrated into a data visualization tool which displays the clusters in terms of the frequency of occurrence of order classes, and their standard deviation within the clusters.Item Metadata only Closing remarks: Standards as living documents(2012) Duffy, A. P.Item Open Access Comparison of 3-dimensional datasets by using the generalized n-dimensional (n-D) Feature Selective Validation (FSV) technique(IEEE, 2016-09-28) Zhang, Gang; Orlandi, A.; Duffy, A. P.; Wang, LixinAutomatic methods to evaluate the validity of computational electromagnetics computer modeling and simulations have widespread applications. The Feature Selective Validation method is a heuristic technique which has been shown to give broad agreement with visual assessment for 1-dimensional data. As a heuristic technique, extending the dimensionality is an important target for the improvement and development of FSV. One of the major challenges in the development of n-dimensional FSV is the difficulty of obtaining visual assessment results, since the visual comparison of three and higher dimensional data is difficult or even impossible. This paper formulates the comparison of 3-dimensional data based on an established generalized n-dimensional FSV approach. The performance of the approach is investigated by means of the LIVE Video Quality Database which provides subjective scores of 150 distorted videos. A statistical evaluation of the relative performance of FSV and other publicly available full-reference Video Quality Assessment algorithms is presented. Further, parameter tuning is performed to improve the agreement of 3-dimensional FSV results and subjective scores. The proposed approach is finally applied to the self-referenced validation of an electromagnetic simulation model to identify and locate the continuous variation of electric field within a region of space.Item Open Access Comparison of Data with Multiple Degrees of Freedom Utilizing the Feature Selective Validation (FSV) Method(IEEE, 2016-04-27) Zhang, Gang; Duffy, A. P.; Orlandi, A.; Di Febo, D.; Wang, Lixin; Sasse, Hugh G.The feature selective validation method has been shown to provide results that are in broad agreement with the visual assessment of a group of engineers for line, 1-D, data. An implementation using 2-D Fourier transforms and derivatives have been available for some years, but verification of the performance has been difficult to obtain. Further, that approach does not naturally scale well for 3-D and higher degrees of freedom, particularly if there are sizable differences in the number of points in the different directions. This paper describes an approach based on repeated 1-D FSV analyses that overcomes those challenges. The ability of the 2-D case to mirror user perceptions is demonstrated using the LIVE database. Its extension to n-dimensions is also described and includes a suggestion for weighting the algorithm based on the number of data points in a given “direction.”Item Metadata only Competitive Intelligence and Information Technology Adoption of SMEs in Turkey: Diagnosing Current Performance and Identifying Barriers(2013) Wright, Sheila; Bisson, C.; Duffy, A. P.The need for SMEs to behave in a more concise and coherent competitive fashion is well recognised. This study reports on an empirical study of SMEs in Turkey. Their responses were applied to a behavioural and information technology adoption framework which enabled the identification of areas where changes would be required for these firms to begin operating at a higher level of competence. The findings revealed significant scope for improvements on all strands of the diagnostic framework: attitude, gathering, location, technology support, IT systems support and finally, use of intelligence-based output by decision-makers. Through free form responses, it was also possible to identify barrier to higher level adoption and performance inhibiters, which were subsequently, categorised and assessed for significance.Item Metadata only Item Metadata only Crosstalk bandwidth of grating-assisted ring resonator add/drop filter(Springer, 2014) Mansoor, Riyadh; Sasse, Hugh G.; Ison, Stephen; Duffy, A. P.