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Subjectsfractional differential equations (20)XPS (20)Energy harvesting (18)numerical methods (16)Ageing (10)stability (10)Error estimates (9)atmospheric chemistry (8)Virtual Reality (8)delay differential equations (7)View MoreJournalJournal of Computational and Applied Mathematics (11)Applied Numerical Mathematics (8)Journal of Physics: Conference Series (8)Applied Surface Science (5)Atmospheric Chemistry and Physics (5)View MoreAuthorsFord, Neville J. (75)Smith, Graham C. (46)Yan, Yubin (33)Mc Auley, Mark T. (24)Lawrence, Jonathan (23)Waugh, David G. (23)Baker, Christopher T. H. (22)Jia, Yu (20)John, Nigel W. (20)Banks, Craig E. (17)View MoreTypesArticle (355)Meetings and Proceedings (30)Book chapter (23)Technical Report (20)Doctoral (18)View More

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Computational methods for a mathematical model of propagation of nerve impulses in myelinated axons

Lima, Pedro M.; Ford, Neville J.; Lumb, Patricia M. (Elsevier, 2014-07-07)

This paper is concerned with the approximate solution of a nonlinear mixed type functional differential equation (MTFDE) arising from nerve conduction theory. The equation considered describes conduction in a myelinated nerve axon. We search for a monotone solution of the equation defined in the whole real axis, which tends to given values at ±∞. We introduce new numerical methods for the solution of the equation, analyse their performance, and present and discuss the results of the numerical simulations.

Halanay-type theory in the context of evolutionary equations with time-lag

Baker, Christopher T. H. (University of Chester, 2009)

We consider extensions and modifications of a theory due to Halanay, and the context in which such results may be applied. Our emphasis is on a mathematical framework for Halanay-type analysis of problems with time lag and simulations using discrete versions or numerical formulae. We present selected (linear and nonlinear, discrete and continuous) results of Halanay type that can be used in the study of systems of evolutionary equations with various types of delayed argument, and the relevance and application of our results is illustrated, by reference to delay-differential equations, difference equations, and methods.

An algorithm for the numerical solution of two-sided space-fractional partial differential equations.

Ford, Neville J.; Pal, Kamal; Yan, Yubin (de Gruyter, 2015-08-20)

We introduce an algorithm for solving two-sided space-fractional partial differential equations. The space-fractional derivatives we consider here are left-handed and right-handed Riemann–Liouville fractional derivatives which are expressed by using Hadamard finite-part integrals. We approximate the Hadamard finite-part integrals by using piecewise quadratic interpolation polynomials and obtain a numerical approximation of the space-fractional derivative with convergence order

Higher order numerical methods for solving fractional differential equations

Yan, Yubin; Pal, Kamal; Ford, Neville J. (Springer, 2013-10-05)

In this paper we introduce higher order numerical methods for solving fractional differential equations. We use two approaches to this problem. The first approach is based on a direct discretisation of the fractional differential operator: we obtain a numerical method for solving a linear fractional differential equation with order 0 < α < 1. The order of convergence of the numerical method is O(h^(3−α)). Our second approach is based on discretisation of the integral form of the fractional differential equation and we obtain a fractional Adams-type method for a nonlinear fractional differential equation of any order α >0. The order of convergence of the numerical method is O(h^3) for α ≥ 1 and O(h^(1+2α)) for 0 < α ≤ 1 for sufficiently smooth solutions. Numerical examples are given to show that the numerical results are consistent with the theoretical results.

Real-Time Guidance and Anatomical Information by Image Projection onto Patients

Edwards, Marc R.; Pop, Serban R.; John, Nigel W.; Ritsos, Panagiotis D.; Avis, Nick J. (Eurographics Association, 2016-09)

The Image Projection onto Patients (IPoP) system is work in progress intended to assist medical practitioners perform procedures such as biopsies, or provide a novel anatomical education tool, by projecting anatomy and other relevant information from the operating room directly onto a patient’s skin. This approach is not currently used widely in hospitals but has the benefit of providing effective procedure guidance without the practitioner having to look away from the patient. Developmental work towards the alpha-phase of IPoP is presented including tracking methods for tools such as biopsy needles, patient tracking, image registration and problems encountered with the multi-mirror effect.

Flicker mitigation strategy for a doubly fed induction generator by torque control

Zhang, Yunqian Q.; Hu, Weihao; Chen, Zhe; Cheng, Ming; Hu, Yanting (IET, 2014-03)

Owing to the rotational sampling of turbulence, wind shear and tower shadow effects grid connected variable speed wind turbines could lead to the power fluctuations which may produce flicker during continuous operation. A model of an megawatt (MW)-level variable speed wind turbine with a doubly fed induction generator is presented to investigate the flicker mitigation. Taking advantage of the large inertia of the wind turbine rotor, a generator torque control (GTC) strategy is proposed, so that the power oscillation is stored as the kinetic energy of the wind turbine rotor, thus the flicker emission could be reduced. The GTC scheme is proposed and designed according to the generator rotational speed. The simulations are performed on the national renewable energy laboratory 1.5 MW upwind reference wind turbine model. Simulation results show that damping the generator active power by GTC is an effective means for flicker mitigation of variable speed wind turbines during continuous operation. keywords: {asynchronous generators;oscillations;power generation control;torque control;wind power plants;wind turbines;GTC strategy;continuous operation;doubly fed induction generator;flicker emission;flicker mitigation strategy;generator active power;generator torque control;kinetic energy;megawatt-level variable speed wind turbine;power oscillation;tower shadow effects grid connected variable speed wind turbines;turbulence;upwind reference wind turbine model;variable speed wind turbines;wind shear;wind turbine rotor

Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz

Wu, Bian; Tuncer, Hatice M.; Naeem, Majid; Yang, Bin; Cole, Matthew T.; Milne, William I.; Hao, Yang (Nature Publishing Group, 2014-02-19)

The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers’ operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

Micromachined Thick Mesh Filters for Millimeter-Wave and Terahertz Applications

Wang, Yi; Yang, Bin; Tian, Yingtao; Donnan, Robert S.; Lancaster, Michael J. (IEEE, 2014-03-01)

This paper presents several freestanding bandpass mesh filters fabricated using an SU-8 based micromachining technique. The important geometric feature of the filters, which SU8 is able to increase, is the thickness of the cross-shaped micromachined slots. This is 5 times its width. This thickness offers an extra degree of control over the resonance characteristics. The large thickness not only strengthens the structures, but also enhances the resonance quality factor (Q-factor). A 0.3 mm thick, single layer, mesh filter resonant at 300 GHz has been designed, fabricated and its performance verified. The measured Q-factor is 16.3 and the insertion loss is 0.98 dB. Two multi-layer filter structures have also been demonstrated. The first one is a stacked structure of two single mesh filters producing a double thickness, which achieved a further increased Q-factor of 27. This is over six times higher than a thin mesh filter. The second multi-layer filter is an electromagnetically coupled structure forming a two-pole filter. The coupling characteristics are discussed based on experimental and simulation results. These thick mesh filters can potentially be used for sensing and material characterization at millimeter-wave and terahertz frequencies.

Data aggregation in wireless sensor networks with minimum delay and minimum use of energy: A comparative study

Qayyum, Bushra; Saeed, Mohammed; Roberts, Jason A. (British Computer Society, 2015)

The prime objective of deploying large- scale wireless sensor networks is to collect information from to control systems associated with these networks. Wireless sensor networks are widely used in application domains such as security and inspection, environmental monitoring, warfare, and other situations especially where immediate responses are required such as disasters and medical emergency. Whenever there is a growth there are challenges and to cope with these challenges strategies and solutions must be developed. This paper discusses the recently addressed issues of data aggregation through presenting a comparative study of different research work done on minimizing delay in different structures of wireless sensor networks. Finally we introduce our proposed method to minimize both delay and power consumption using a tree based clustering scheme with partial data aggregation.

On integral equation formulation of a class of evolutionary equations with time-lag

Baker, Christopher T. H.; Lumb, Patricia M. (Rocky Mountain Mathematics Consortium, 2006)

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