• An Analytical and Numerical Study of Magnetic Spring Suspension with Energy Recovery Capabilities

      Jia, Yu; Li, Shasha; Shi, Yu; University of Chester; China National Intellectual Property Administration (MDPI, 2018-11-12)
      As the automotive paradigm shifts towards electric, limited range remains a key challenge. Increasing the battery size adds weight, which yields diminishing returns in range per kilowatt-hour. Therefore, energy recovery systems, such as regenerative braking and photovoltaic cells, are desirable to recharge the onboard batteries in between hub charge cycles. While some reports of regenerative suspension do exist, they all harvest energy in a parasitic manner, and the predicted power output is extremely low, since the majority of the energy is still dissipated to the environment by the suspension. This paper proposes a fundamental suspension redesign using a magnetically-levitated spring mechanism and aims to increase the recoverable energy significantly by directly coupling an electromagnetic transducer as the main damper. Furthermore, the highly nonlinear magnetic restoring force can also potentially enhance rider comfort. Analytical and numerical models have been constructed. Road roughness data from an Australian road were used to numerically simulate a representative environment response. Simulation suggests that 10’s of kW to >100 kW can theoretically be generated by a medium-sized car travelling on a typical paved road (about 2–3 orders of magnitude higher than literature reports on parasitic regenerative suspension schemes), while still maintaining well below the discomfort threshold for passengers (<0.315 m/s2 on average).
    • Analytical and numerical treatment of oscillatory mixed differential equations with differentiable delays and advances

      Ferreira, José M.; Ford, Neville J.; Malique, Md A.; Pinelas, Sandra; Yan, Yubin; Instituto Superior Técnico, Lisbon : University of Chester : University of Chester : Universidade dos Açores : University of Chester (Elsevier, 2011-04-12)
      This article discusses the oscillatory behaviour of the differential equation of mixed type.
    • Angus I. Kirkland and Sarah J. Haigh (Eds.): Nanocharacterization, 2nd ed.

      Smith, Graham C.; Department of Natural Sciences, University of Chester (Springer, 2016-01-29)
      Book review of NanoCharacterisation, second edition, Editors Angus I. Kirkland and Sarah J. Haigh. Published by Royal Society of Chemistry ISBN: 978-1-84973-805-7
    • Anodic stripping voltammetry with graphite felt electrodes for the trace analysis of silver

      Davies, Trevor J.; University of Chester (Royal Society of Chemistry, 2016-05-31)
      Graphite felt (GF) is a mass produced porous carbon electrode material commonly used in redox flow batteries. Previous studies have suggested GF may have valuable applications in electroanalysis as a low cost disposable carbon electrode material, although most GF sensors have used flow cell arrangements. In this work, an elegant wetting technique is employed that allows GF electrodes to be used in quiescent solution to detect trace levels of silver in water via anodic stripping voltammetry. GF electrodes display good repeatability and a limit of detection of 25 nM of Ag+ in 0.1 M HNO3, with a linear range spanning two orders of magnitude. This compares to a value of around 140 nM when using conventional carbon electrodes. Combined with their low cost and disposable nature, the results suggest GF electrodes can make a valuable contribution to electroanalysis.
    • Appearance Modeling of Living Human Tissues

      Maciel, Anderson; Meyer, Gary W.; John, Nigel W.; Walter, Marcelo; Nunes, Augusto L. P.; Baranoski, Gladimir V. G.; Federal Institute of Paraná, Londrina; Universidade Federal do Rio Grande do Sul; University of Minnesota; University of Chester; University of Waterloo (Wiley, 2019-02-27)
      The visual fidelity of realistic renderings in Computer Graphics depends fundamentally upon how we model the appearance of objects resulting from the interaction between light and matter reaching the eye. In this paper, we survey the research addressing appearance modeling of living human tissue. Among the many classes of natural materials already researched in Computer Graphics, living human tissues such as blood and skin have recently seen an increase in attention from graphics research. There is already an incipient but substantial body of literature on this topic, but we also lack a structured review as presented here. We introduce a classification for the approaches using the four types of human tissues as classifiers. We show a growing trend of solutions that use first principles from Physics and Biology as fundamental knowledge upon which the models are built. The organic quality of visual results provided by these Biophysical approaches is mainly determined by the optical properties of biophysical components interacting with light. Beyond just picture making, these models can be used in predictive simulations, with the potential for impact in many other areas.
    • Application of Virtual Reality and Electrodermal Activity for the Detection of Cognitive Impairments

      Patient, Rebecca; Ghali, Fawaz; Kolivand, Hoshang; Hurst, William; John, Nigel W.; Liverpool John Moores; Wageningen University; University of Chester (IEEE, 2022-03-01)
      Mild Cognitive Impairment (MCI) is a definition of the diagnosis of early memory loss and disorientation. This study aims to identify people’s symptoms through technology. However, machine learning (ML) can classify Cognitive Normal (CN) and Mild Cognitive Impairment (MCI) and Early Mild Cognitive Impairment (EMCI) using standard assessments from the Alzheimer’s Disease Neuroimaging Initiative (ADNI); Montreal Cognitive (MoCA), Mini-Mental State Examination (MMSE), Functional Activities Questionnaire (FAQ). Consequently, a Multilayer Perceptron (MLP) model was assembled into tables; MCI vs CN, MCI vs EMCI, and CN vs MCI. Additionally, an MLP model was developed for CN vs MCI vs EMCI. As a result, of advanced model performance, a cascade 3-path categorisation approach was created. Similarly, the exploitation of meta-analysis indicated a combination of MLP models (MCI vs CN, MCI vs EMCI, and CN vs MCI) with an overall accuracy within an acceptable limit. In addition, better results were found when assessments were combined rather than individually. Furthermore, applying class weights and probability thresholds could improve the MLP framework by performance achieving a balanced specificity and sensitivity ratio. Altering class weights and probability thresholds when training the MLP neuro network model, the sensitivity and Accuracy could be progressed further. In conclusion, ML, VR and electrodermal activity are constrained. Introducing the possibility of activity-based applications to enhance innovative solutions for cognitive impairment diagnosis and treatment.
    • An approach to construct higher order time discretisation schemes for time fractional partial differential equations with nonsmooth data

      Ford, Neville J.; Yan, Yubin; University of Chester (De Gruyter, 2017-10-31)
      In this paper, we shall review an approach by which we can seek higher order time discretisation schemes for solving time fractional partial differential equations with nonsmooth data. The low regularity of the solutions of time fractional partial differential equations implies standard time discretisation schemes only yield first order accuracy. To obtain higher order time discretisation schemes when the solutions of time fractional partial differential equations have low regularities, one may correct the starting steps of the standard time discretisation schemes to capture the singularities of the solutions. We will consider these corrections of some higher order time discretisation schemes obtained by using Lubich's fractional multistep methods, L1 scheme and its modification, discontinuous Galerkin methods, etc. Numerical examples are given to show that the theoretical results are consistent with the numerical results.
    • Assessment of Multi-Domain Energy Systems Modelling Methods

      Stewart, M.; Counsell, John M.; Al-Khaykan, A.; University of Chester (World Academy of Science, Engineering and Technology, 2017-06-06)
      Emissions are a consequence of electricity generation. A major option for low carbon generation, local energy systems featuring Combined Heat and Power with solar PV (CHPV) has significant potential to increase energy performance, increase resilience, and offer greater control of local energy prices while complementing the UK’s emissions standards and targets. Recent advances in dynamic modelling and simulation of buildings and clusters of buildings using the IDEAS framework have successfully validated a novel multi-vector (simultaneous) control of both heat and electricity approach to integrating the wide range of primary and secondary plant typical of local energy systems designs including CHP, solar PV, gas boilers, absorption chillers and thermal energy storage, and associated electrical and hot water networks, all operating under a single unified control strategy. Results from this work indicate through simulation that integrated control of thermal storage can have a pivotal role in optimizing system performance well beyond the present expectations. Environmental impact analysis and reporting of all energy systems including CHPV LES presently employ a static annual average carbon emissions intensity for grid supplied electricity. This paper focuses on establishing and validating CHPV environmental performance against conventional emissions values and assessment benchmarks to analyze emissions performance without and with an active thermal store in a notional group of non-domestic buildings. Results of this analysis are presented and discussed in context of performance validation and quantifying the reduced environmental impact of CHPV systems with active energy storage in comparison with conventional LES designs.
    • Assisting Serious Games Level Design with an Augmented Reality Application and Workflow

      Beever, Lee; John, Nigel W.; Pop, Serban R.; University of Chester (Eurographics Proceedings, 2019-09-13)
      With the rise in popularity of serious games there is an increasing demand for virtual environments based on real-world locations. Emergency evacuation or fire safety training are prime examples of serious games that would benefit from accurate location depiction together with any application involving personal space. However, creating digital indoor models of real-world spaces is a difficult task and the results obtained by applying current techniques are often not suitable for use in real-time virtual environments. To address this problem, we have developed an application called LevelEd AR that makes indoor modelling accessible by utilizing consumer grade technology in the form of Apple’s ARKit and a smartphone. We compared our system to that of a tape measure and a system based on an infra-red depth sensor and application. We evaluated the accuracy and efficiency of each system over four different measuring tasks of increasing complexity. Our results suggest that our application is more accurate than the depth sensor system and as accurate and more time efficient as the tape measure over several tasks. Participants also showed a preference to our LevelEd AR application over the depth sensor system regarding usability. Finally, we carried out a preliminary case study that demonstrates how LevelEd AR can be successfully used as part of current industry workflows for serious games level design.
    • Associating Colours with Emotions Detected in Social Media Tweets

      Harvey, Robert; Muncey, Andrew; Vaughan, Neil; University of Chester (The Society for the Study of Artificial Intelligence and Simulation for Behaviour (AISB), 2018-04-06)
      This project involves two major areas of work, the detection of emotions in text from Twitter posts (tweets), and the association of that emotion with colour. Emotion mining is the field of natural language processing which is concerned with the detection and classification. It is a subfield of semantic analysis which contains both emotion and opinion mining. Both tasks depend on an emotion model to classify detected emotions and to associate a colour depending on the location of the emotion in the model. This research paper demonstrates preliminary results from classification of tweets to assign emotion labels. Also designs are presented for a prototype web interface for displaying the assigned colour and emotion associated with tweets.
    • Atomic and vibrational origins of mechanical toughness in bioactive cement during setting

      Tian, Kun V.; Yang, Bin; Yue, Yuan-Zheng; Bowron, Daniel T.; Mayers, Jerry; Donnan, Robert S.; Dobo-Nagy, Csaba; Nicholson, John W.; Greer, A. Lindsay; Chass, Gregory A.; et al. (Nature Publishing Group, 2015-11-09)
      Bioactive glass ionomer cements (GICs) have been in widespread use for ~40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of calorimetry, terahertz (THz) spectroscopy and neutron scattering, how GIC’s developing fracture toughness during setting is related to interfacial THz dynamics, changing atomic cohesion and fluctuating interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass–polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces. Subsequently, toughness declines asymptotically to long-term fracture test values. We expect the insight afforded by these in situ non-destructive techniques will assist in raising understanding of the setting mechanisms and associated dynamics of cementitious materials.
    • Atomic-layer-deposited aluminum and zirconium oxides for surface passivation of TiO 2 in High-Efficiency Organic Photovoltaics

      Vasilopoulou, Maria; Georgiadou, Dimitra G.; Soultati, Anastasia; Boukos, Nikos; Gardelis, Spyros; Palilis, Leonidas C.; Fakis, Mihalis; Skoulatakis, Georgios; Kennou, Stella; Botzakaki, Martha A.; et al. (Wiley, 2014-06-23)
      The reduction in electronic recombination losses by the passivation of surfaces is a key factor enabling high-efficiency solar cells. Here we investigate a strategy to passivate surface trap states of TiO 2 films used as cathode interlayers in organic photovoltaics (OPVs) through applying alumina (Al2O3) or zirconia (ZrO2) insulating nanolayers by thermal atomic layer deposition (ALD). Our results suggest that the surface traps in TiO 2 are oxygen vacancies, which cause undesirable recombination and high electron extraction barrier, reducing the open-circuit voltage and the short-circuit current of the complete OPV device. It was found that the ALD metal oxides enable excellent passivation of the TiO2 surface followed by a downward shift of the conduction band minimum. OPV devices based on different photoactive layers and using the passivated TiO2 electron extraction layers exhibited a significant enhancement of more than 30% in their power conversion efficiencies (PCEs) as compared to their reference devices without the insulating metal oxide nanolayers as a result of significant suppression of charge recombination and enhanced electron extraction rates at the TiO2/ALD metal-oxide/organic interface.
    • An Augmented Reality Tool to aid Radiotherapy Set Up implemented on a Tablet Device

      Cosentino, Francesco; Vaarkamp, Japp; John, Nigel W.; University of Chester, North Wales Cancer Treatment Centre (International Conference on the use of Computers in Radiation Therapy, 2016-06)
      The accurate daily set up of patients for radiotherapy treatment remains a challenge for which the development of new strategies and solutions continues to be an area of active research. We have developed an augmented reality tool to view the real world scene, i.e. the patient on a treatment couch, combined with computer graphics content, such as planning image data and any defined outlines of organ structures. We have built this on widely available hand held consumer tablet devices and describe here the implementation and initial experience. We suggest that, in contrast to other augmented reality tools explored for radiotherapy[1], due to the wide availability and low cost of the hardware platform the application has further potential as a tool for patients to visualize their treatment and demonstrate to patients e.g. the importance of compliance with instructions around bladder filling and rectal suppositories.
    • Avoiding ambient air and light induced degradation in high-efficiency polymer solar cells by the use of hydrogen-doped zinc oxide as electron extraction material

      Polydorou, Ermioni; Sakelis, Elias; Soultati, Anastasia; Kaltzoglou, Andreas; Papadopoulos, Theodoros A.; Briscoe, Joe; Tsikritzis, Dimitris; Fakis, Mihalis; Palilis, Leonidas C.; Kennou, Stella; et al. (Elsevier, 2017-02-24)
      Polymer solar cells have undergone rapid development in recent years. Their limited stability to environmental influence and during illumination, however, still remains a major stumbling block to the commercial application of this technology. Several attempts have been made to address the instability issue, mostly concentrated on the insertion of charge transport interlayers in the device stack. Although zinc oxide (ZnO) is one of the most common electron transport materials in those cells, the presence of defects at the surface and grain boundaries significantly affects the efficiency and stability of the working devices. To address these issues, we herein employ hydrogen-doping of ZnO electron extraction material. It is found that devices based on photoactive layers composed of blends of poly(3-hexylthiophene) (P3HT) with electron acceptors possessing different energy levels, such as [6,6]-phenyl-C70butyric acid methyl ester (PC70BM) or indene-C60 bisadduct (IC60BA) essentially enhanced their photovoltaic performance when using the hydrogen-doped ZnO with maximum power conversion efficiency (PCE) reaching values of 4.62% and 6.65%, respectively, which are much higher than those of the cells with the pristine ZnO (3.08% and 4.51%). Most significantly, the degradation of non-encapsulated solar cells when exposed to ambient or under prolonged illumination is studied and it is found that devices based on un-doped ZnO showed poor environmental stability and significant photo-degradation while those using hydrogen-doped ZnO interlayers exhibited high long-term ambient stability and maintained nearly 80–90% of their initial PCE values after 40 h of 1.5 AM illumination. All mechanisms responsible for this enhanced stability are elucidated and corresponding models are proposed. This work successfully addresses and tackles the instability problem of polymer solar cells and the key findings pave the way for the upscaling of these and, perhaps, of related devices such as perovskite solar cells.
    • Bacillus Spores and Their Relevant Chemicals Studied by Terahertz Time Domain Spectroscopy

      Tang, Jianhua; Yang, Bin; Llewellyn, Ian; Cutler, Ronald R.; Donnan, Robert S.; Queen Mary University of London; University of Bolton (Elsevier, 2013-12-28)
      Terahertz Time Domain Spectroscopy has been used to investigate 0.2 to 2.2 terahertz (THz) transmission responses of Bacillus spores and their related chemical components. Whilst no THz signatures could be clearly associated with either sporulated cells or their chief chemical components, differing degrees of signal attenuation and frequency-dependent light scattering were observed depending on spore composition and culture media. The observed monotonic increase in absorption by spores over this THz spectral domain is mainly from Mie scattering and also from remnant water bound to the spores.
    • A barrier and techno-economic analysis of small-scale bCHP (biomass combined heat and power) schemes in the UK.

      Wright, Daniel G.; Dey, Prasanta K.; Brammer, John G.; Aston University (Elsevier, 2014-05-17)
      bCHP (Biomass combined heat and power) systems are highly efficient at smaller-scales when a significant proportion of the heat produced can be effectively utilised for hot water, space heating or industrial heating purposes. However, there are many barriers to project development and this has greatly inhibited deployment in the UK. Project viability is highly subjective to changes in policy, regulation, the finance market and the low cost fossil fuel incumbent. The paper reviews the barriers to small-scale bCHP project development in the UK along with a case study of a failed 1.5 MWel bCHP scheme. The paper offers possible explanations for the project’s failure and suggests adaptations to improve the project resilience. Analysis of the project’s: capital structuring; contract length and bankability; feedstock type and price uncertainty, and; plant oversizing highlight the negative impact of the existing project barriers on project development. The research paper concludes with a discussion on the effects of these barriers on the case study project and this industry more generally. A greater understanding of the techno-economic effects of some barriers for small-scale bCHP schemes is demonstrated within this paper, along with some methods for improving the attractiveness and resilience of projects of this kind.
    • Benchmarking of a micro gas turbine model integrated with post-combustion CO2 capture

      Usman, Ali; Font Palma, Carolina; Nikpey Somehsaraei, Homam; Mansouri Majoumerd, Mohammad; Akram, Muhammad; Finney, Karen N.; Best, Thom; Mohd Said, Nassya B.; Assadi, Mohsen; Pourkashanian, Mohamed; et al. (Elsevier, 2017-03-19)
      The deployment of post-combustion CO2 capture on large-scale gas-fired power plants is currently progressing, hence the integration of the power and capture plants requires a good understanding of operational requirements and limitations to support this effort. This article aims to assist research in this area, by studying a micro gas turbine (MGT) integrated with an amine-based post-combustion CO2 capture unit. Both processes were simulated using two different software tools –IPSEpro and Aspen Hysys, and validated against experimental tests. The two MGT models were benchmarked at the nominal condition, and then extended to part-loads (50 and 80 kWe), prior to their integration with the capture plant at flue gas CO2 concentrations between 5 and 10 mol%. Further, the performance of the MGT and capture plant when gas turbine exhaust gases were recirculated was assessed. Exhaust gas recirculation increases the CO2 concentration, and reduces the exhaust gas flowrate and specific reboiler duty. The benchmarking of the two models revealed that the IPSEpro model can be easily adapted to new MGT cycle modifications since turbine temperatures and rotational speeds respond to reaching temperature limits; whilst a detailed rate-based approach for the capture plant in Hysys resulted in closely aligned simulation results with experimental data.
    • Bifurcations in approximate solutions of stochastic delay differential equations

      Baker, Christopher T. H.; Ford, Judith M.; Ford, Neville J.; University College Chester/UMIST ; UMIST; University College Chester (World Scientific Publishing Company, 2004)
    • Bifurcations in numerical methods for volterra integro-differential equations

      Edwards, John T.; Ford, Neville J.; Roberts, Jason A. (World Scientific Publishing Company, 2003)
      This article discusses changes in bifurcations in the solutions. It extends the work of Brunner and Lambert and Matthys to consider other bifurcations.
    • Binary self-dual and LCD codes from generator matrices constructed from two group ring elements by a heuristic search scheme

      Dougherty, Steven; Korban, Adrian; Șahinkaya, Serap; Ustun, Deniz (American Institute of Mathematical Sciences (AIMS), 2022)
      &lt;p style='text-indent:20px;'&gt;We present a generator matrix of the form &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$ [ \sigma(v_1) \ | \ \sigma(v_2)] $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;, where &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ v_1 \in RG $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; and &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ v_2\in RH $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;, for finite groups &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ G $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; and &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}$ H $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; of order &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ n $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; for constructing self-dual codes and linear complementary dual codes over the finite Frobenius ring &lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$ R $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;. In general, many of the constructions to produce self-dual codes forces the code to be an ideal in a group ring which implies that the code has a rich automorphism group. Unlike the traditional cases, codes constructed from the generator matrix presented here are not ideals in a group ring, which enables us to find self-dual and linear complementary dual codes that are not found using more traditional techniques. In addition to that, by using this construction, we improve &lt;inline-formula&gt;&lt;tex-math id="M8"&gt;\begin{document}$ 10 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; of the previously known lower bounds on the largest minimum weights of binary linear complementary dual codes for some lengths and dimensions. We also obtain &lt;inline-formula&gt;&lt;tex-math id="M9"&gt;\begin{document}$ 82 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; new binary linear complementary dual codes, &lt;inline-formula&gt;&lt;tex-math id="M10"&gt;\begin{document}$ 50 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; of which are either optimal or near optimal of lengths &lt;inline-formula&gt;&lt;tex-math id="M11"&gt;\begin{document}$ 41 \leq n \leq 61 $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; which are new to the literature.&lt;/p&gt;