• Validation of the modified rule of mixtures using a combination of fibre orientation and fibre length measurements

      Hine, P.; Parveen, Bushra; Brands, D.; Caton-Rose, Philip D. (2014-09)
      The goal of this study was to investigate the fibre orientation distribution (FOD), and subsequent mechanical properties, of an injection moulded plate with two different number averaged fibre lengths, termed in this paper medium (1.35 mm) and long (2.40 mm). Fibre orientation measurements (FOD) were made using the 2D elliptical section method and an in-house developed image analyser. The samples were injected from a pin gate located at the centre and top of the plate. Expansion flow on the divergent flow front from this pin gate resulted in a core region with circumferential alignment, while through thickness shear resulted in the usual realignment of fibres in the flow direction either side of the core, termed the shell layers. Two interesting aspects were discovered from these measurements. First, and most importantly, the FOD was found to be independent of the two fibre lengths in this study, and so predominantly controlled by the mould shape and the interaction with the flow front. Second, the fibres in the core region were found to be much closer packed than those in the shell regions. The interaction between the flow front and the mould shape resulted in a range of FOD across the moulded plate, from equal in-plane orientation at the centre of the plate, to highly aligned at the plate edge. This gave a very useful set of samples from which to test out the well known modified rule of mixtures (MROM). Often the fibre orientation distribution cannot be measured directly, but indirectly using the modified rule of mixtures model in reverse. The samples from this moulding (at two different average fibre lengths) gave an excellent opportunity to validate this often used approach. Both the tensile modulus and strength (measured parallel to the injection direction) were found to show a strong correlation with the measured fibre orientation, with a significant increase in both measures between the centre and the edge of both plates. The increased length of the ‘long’ fibre plate was found to give only a small increase in tensile modulus but a much larger increase in tensile strength. The tensile modulus showed a linear dependence with the measured fourth order orientation tensor average, 〈cos4 θ〉, with respect to the injection direction of the plate, as predicted by the modified rule of mixtures. Excellent agreement was found between the measured modulus and the predictions from the modified rule of mixtures, based only on measured quantities (matrix modulus, fibre fraction and average fibre length) for both plates.
    • Validation of the Tranquillity Rating Prediction Tool (TRAPT): comparative studies in UK and Hong Kong

      Watts, Gregory R.; Marafa, L. (2017-08)
      The Tranquillity Rating Prediction Tool (TRAPT) has been used to make predictions of the quality of tranquility in outdoor urban areas using two significant factors i.e. the average level of anthropogenic noise and the percentage of natural features in view. The method has a number of applications including producing tranquillity contours that can inform decisions regarding the impact of new anthropogenic noise sources or developments causing visual intrusion. The methodwas intended for use in mainly outdoor areas and yet was developed using responses from UK volunteers to video clips indoors. Because the volunteers for this study were all UK residents it was important to calibrate responses for other ethnic groups who may respond differently depending on cultural background. To address these issues further studies were performed in Hong Kong using the same video recording played back under the same conditions as the study in the UK. The HK study involved recruiting three groups i.e. residents fromHong Kong, Mainland China and a diverse group from 16 different nations. There was good agreement between all these groups with average tranquillity ratings for the different locations differing by less than one scale point in most cases.
    • Velocity distribution and 3D turbulence characteristic analysis for flow over water-worked rough bed

      Pu, Jaan H.; Wei, J.; Huang, Y. (2017)
      To reproduce the natural flow topography in a laboratory environment, it is crucial to recapture its bed condition in order to ensure the accurate representation. Water-worked bed represents a state-of-the-art experimentally formed bed to imitate the natural-formed channel in most rivers or natural streams. Recently, this technique has been intensively studied through experimental and computational approaches; however, its actual influence towards the near-bed flow as compared to experimentally prepared rough bed in well-packed bedform order are still yet to be investigated deeply. This experimental study systematically investigated and compared the differences in velocity distribution and three-dimensional (3D) turbulence characteristics, including turbulence intensities and Reynolds stresses, between uniform smooth bed, laboratory-prepared rough bed and water-worked bed open channel flows. The flow comparisons were concentrated at near-bed region where clear flow behaviour change can be observed. Through these comparisons, the study inspected the characteristics of water-worked bedform thoroughly, in order to inform future experimental research that tries to reproduce natural stream behaviours.
    • Velocity Distribution in Open Channel Flows: Analytical Approach for the Outer Region

      Lassabatere, L.; Pu, Jaan H.; Bonakdari, H.; Joannis, C.; Larrarte, F. (2013-01-01)
      This paper presents an integration procedure for the Reynolds-averaged Navier-Stokes equations for the determination of the distribution of the streamwise velocity using the vertical component. This procedure is dedicated to the outer region and central part of channels. The proposed model is applicable to both rough and smooth flow regimes, provided the velocity at the inner-outer boundary has been properly defined. To generate a simplified expansion, a number of hypotheses are proposed, focusing in particular on the analytical modeling of the vertical component by adopting a negligible viscosity. The proposed hypotheses are validated by the experimental data existing in the literature. The proposed simplified expansion is studied through a sensitivity analysis and proved consistent in regards to model experimental data. The proposed model seems capable of demonstrating different kinds of flows, including dip phenomenon flow patterns.
    • Velocity Profile and Turbulence Structure Measurement Corrections for Sediment Transport-Induced Water-Worked Bed

      Pu, Jaan H. (MDPI, 2021)
      When using point measurement for environmental or sediment laden flows, there is well-recognised risk for not having aligned measurements that causes misinterpretation of the measured velocity data. In reality, these kinds of mismeasurement mainly happen due to the misinterpretation of bed orientation caused by the complexity of its determination in natural flows, especially in bedload laden or rough bed flows. This study proposes a novel bed realignment method to improve the measured data benchmarking by three-dimensional (3D) bed profile orientation and implemented it into different sets of experimental data. More specifically, the effects of realignment on velocity profile and streamwise turbulence structure measurements were investigated. The proposed technique was tested against experimental data collected over a water-worked and an experimentally arranged well-packed beds. Different from the well-packed rough bed, the water-worked bed has been generated after long sediment transport and settling and hence can be used to verify the proposed bed-alignment technique thoroughly. During the flow analysis, the corrected velocity, turbulence intensity and Reynolds stress profiles were compared to the theoretical logarithmic law, exponential law and linear gravity (universal Reynolds stress distribution) profiles, respectively. It has been observed that the proposed method has improved the agreement of the measured velocity and turbulence structure data with their actual theoretical profiles, particularly in the near-bed region (where the ratio of the flow measurement vertical distance to the total water depth, z/h, is limited to ≤0.4).
    • Venous hemodynamics in neurological disorders: an analytical review with hydrodynamic analysis

      Beggs, Clive B. (2013)
      Venous abnormalities contribute to the pathophysiology of several neurological conditions. This paper reviews the literature regarding venous abnormalities in multiple sclerosis (MS), leukoaraiosis, and normal-pressure hydrocephalus (NPH). The review is supplemented with hydrodynamic analysis to assess the effects on cerebrospinal fluid (CSF) dynamics and cerebral blood flow (CBF) of venous hypertension in general, and chronic cerebrospinal venous insufficiency (CCSVI) in particular.CCSVI-like venous anomalies seem unlikely to account for reduced CBF in patients with MS, thus other mechanisms must be at work, which increase the hydraulic resistance of the cerebral vascular bed in MS. Similarly, hydrodynamic changes appear to be responsible for reduced CBF in leukoaraiosis. The hydrodynamic properties of the periventricular veins make these vessels particularly vulnerable to ischemia and plaque formation.Venous hypertension in the dural sinuses can alter intracranial compliance. Consequently, venous hypertension may change the CSF dynamics, affecting the intracranial windkessel mechanism. MS and NPH appear to share some similar characteristics, with both conditions exhibiting increased CSF pulsatility in the aqueduct of Sylvius.CCSVI appears to be a real phenomenon associated with MS, which causes venous hypertension in the dural sinuses. However, the role of CCSVI in the pathophysiology of MS remains unclear.
    • A Versatile and Ubiquitous Secret Sharing: A cloud data repository secure access

      Adeka, Muhammad I.; Shepherd, Simon J.; Abd-Alhameed, Raed A.; Ahmed, N.A.S. (2015)
      The Versatile and Ubiquitous Secret Sharing System, a cloud data repository secure access and a web based authentication scheme. It is designed to implement the sharing, distribution and reconstruction of sensitive secret data that could compromise the functioning of an organisation, if leaked to unauthorised persons. This is carried out in a secure web environment, globally. It is a threshold secret sharing scheme, designed to extend the human trust security perimeter. The system could be adapted to serve as a cloud data repository and secure data communication scheme. A secret sharing scheme is a method by which a dealer distributes shares of a secret data to trustees, such that only authorised subsets of the trustees can reconstruct the secret. This paper gives a brief summary of the layout and functions of a 15-page secure server-based website prototype; the main focus of a PhD research effort titled ‘Cryptography and Computer Communications Security: Extending the Human Security Perimeter through a Web of Trust’. The prototype, which has been successfully tested, has globalised the distribution and reconstruction processes.
    • The versatile biomedical applications of bismuth-based nanoparticles and composites: therapeutic, diagnostic, biosensing, and regenerative properties

      Shahbazi, M-A.; Faghfouri, L.; Ferreira, M.P.A.; Figueiredo, P.; Maleki, H.; Sefat, Farshid; Hirvonen, J.; Santos, H.A. (2020-02)
      Studies of nanosized forms of bismuth (Bi)-containing materials have recently expanded from optical, chemical, electronic, and engineering fields towards biomedicine, as a result of their safety, cost-effective fabrication processes, large surface area, high stability, and high versatility in terms of shape, size, and porosity. Bi, as a nontoxic and inexpensive diamagnetic heavy metal, has been used for the fabrication of various nanoparticles (NPs) with unique structural, physicochemical, and compositional features to combine various properties, such as a favourably high X-ray attenuation coefficient and near-infrared (NIR) absorbance, excellent light-to-heat conversion efficiency, and a long circulation half-life. These features have rendered bismuth-containing nanoparticles (BiNPs) with desirable performance for combined cancer therapy, photothermal and radiation therapy (RT), multimodal imaging, theranostics, drug delivery, biosensing, and tissue engineering. Bismuth oxyhalides (BiOx, where X is Cl, Br or I) and bismuth chalcogenides, including bismuth oxide, bismuth sulfide, bismuth selenide, and bismuth telluride, have been heavily investigated for therapeutic purposes. The pharmacokinetics of these BiNPs can be easily improved via the facile modification of their surfaces with biocompatible polymers and proteins, resulting in enhanced colloidal stability, extended blood circulation, and reduced toxicity. Desirable antibacterial effects, bone regeneration potential, and tumor growth suppression under NIR laser radiation are the main biomedical research areas involving BiNPs that have opened up a new paradigm for their future clinical translation. This review emphasizes the synthesis and state-of-the-art progress related to the biomedical applications of BiNPs with different structures, sizes, and compositions. Furthermore, a comprehensive discussion focusing on challenges and future opportunities is presented.
    • Video extraction for fast content access to MPEG compressed videos

      Jiang, Jianmin; Weng, Y. (2009-06-09)
      As existing video processing technology is primarily developed in the pixel domain yet digital video is stored in compressed format, any application of those techniques to compressed videos would require decompression. For discrete cosine transform (DCT)-based MPEG compressed videos, the computing cost of standard row-by-row and column-by-column inverse DCT (IDCT) transforms for a block of 8 8 elements requires 4096 multiplications and 4032 additions, although practical implementation only requires 1024 multiplications and 896 additions. In this paper, we propose a new algorithm to extract videos directly from MPEG compressed domain (DCT domain) without full IDCT, which is described in three extraction schemes: 1) video extraction in 2 2 blocks with four coefficients; 2) video extraction in 4 4 blocks with four DCT coefficients; and 3) video extraction in 4 4 blocks with nine DCT coefficients. The computing cost incurred only requires 8 additions and no multiplication for the first scheme, 2 multiplication and 28 additions for the second scheme, and 47 additions (no multiplication) for the third scheme. Extensive experiments were carried out, and the results reveal that: 1) the extracted video maintains competitive quality in terms of visual perception and inspection and 2) the extracted videos preserve the content well in comparison with those fully decompressed ones in terms of histogram measurement. As a result, the proposed algorithm will provide useful tools in bridging the gap between pixel domain and compressed domain to facilitate content analysis with low latency and high efficiency such as those applications in surveillance videos, interactive multimedia, and image processing.
    • Video Indexing and Retrieval in Compressed Domain Using Fuzzy-Categorization.

      Fang, H.; Qahwaji, Rami S.R.; Jiang, Jianmin (2006)
      There has been an increased interest in video indexing and retrieval in recent years. In this work, indexing and retrieval system of the visual contents is based on feature extracted from the compressed domain. Direct possessing of the compressed domain spares the decoding time, which is extremely important when indexing large number of multimedia archives. A fuzzy-categorizing structure is designed in this paper to improve the retrieval performance. In our experiment, a database that consists of basketball videos has been constructed for our study. This database includes three categories: full-court match, penalty and close-up. First, spatial and temporal feature extraction is applied to train the fuzzy membership functions using the minimum entropy optimal algorithm. Then, the max composition operation is used to generate a new fuzzy feature to represent the content of the shots. Finally, the fuzzy-based representation becomes the indexing feature for the content-based video retrieval system. The experimental results show that the proposal algorithm is quite promising for semantic-based video retrieval.
    • VISINET: Collaborative 3D Visualization and Virtual Reality over Trans-European ATM Networks

      Lamotte, W.; Earnshaw, Rae A.; Van Reeth, F.; Flerackers, E.; Mena de Matos, J. (1997)
      Visinet is a trans-European 3D collaborative design project that brings together computer scientists, application developers, design specialists, and users in the context of shared environments supported by ATM networks. Experiments and trials have been conducted for the key application domains of architectural and industrial design. Different types of virtual representation and computer-supported collaborative work are applied to real-life projects between partners at different locations in Europe. Measurements of network requirements have enabled cost/benefits to be quantified. Measurements of user satisfaction and speed of completion of the design to product cycle have also been made, resulting in a greater understanding of the ways in which collaborative design environments linked by high-speed networks affect this cycle. Additional experiments are currently being conducted on the way in which an ATM backbone between principal partners in a project can be complemented with ISDN links to partners in a local area.
    • Vision and visual history in elite/near-elite level cricketers and rugby-league players

      Barrett, Brendan T.; Flavell, Jonathan C.; Bennett, S.J.; Cruickshank, Alice G.; Mankowska, Aleksandra M.; Harris, J.M.; Buckley, John G. (2017-11)
      Background: The importance of optimal and/or superior vision for participation in high-level sport remains the subject of considerable clinical research interest. Here we examine the vision and visual history of elite/near-elite cricketers and rugby-league players. Methods: Stereoacuity (TNO), colour vision, and distance (with/without pinhole) and near visual acuity (VA) were measured in two cricket squads (elite/international-level, female, n=16; near-elite, male, n=23) and one professional rugby-league squad (male, n=20). Refractive error was determined, and details of any correction worn and visual history were recorded. Results: Overall, 63% had their last eye-examination within 2 years. However, some had not had an eye examination for 5 years, or had never had one (near-elite-cricketers: 30%; rugby-league players: 15%; elite-cricketers: 6%). Comparing our results for all participants to published data for young, optimally-corrected, non-sporting adults, distance VA was ~1 line of letters worse than expected. Adopting α=0.01, the deficit in distance-VA deficit was significant, but only for elite-cricketers (p<0.001) (near-elite cricketers, p=0.02; rugby-league players, p=0.03). Near-VA did not differ between subgroups or relative to published norms for young adults (p>0.02 for all comparisons). On average, stereoacuity was better than in young adults, but only in elite-cricketers (p<0.001; p=0.03, near-elite-cricketers; p=0.47, rugby-league -players). On-field visual issues were present in 27% of participants, and mostly (in 75% of cases) comprised uncorrected ametropia. Some cricketers (near-elite: 17.4%; elite: 38%) wore refractive correction during play but no rugby-league player did. Some individuals with prescribed correction choose not to wear it when playing. Conclusion: Aside from near stereoacuity in elite-cricketers, these basic visual abilities were not better than equivalent, published data for optimally-corrected adults. 20-25% exhibited sub-optimal vision, suggesting that the clearest possible vision might not be critical for participation at the highest levels in the sports of cricket or rugby-league. Although vision could be improved in a sizeable proportion of our sample, the impact of correcting these, mostly subtle, refractive anomalies on playing performance is unknown.
    • Visual Representations and Interaction Technologies

      Earnshaw, Rae A. (2005)
      This chapter discusses important aspects of visual representations and interaction techniques necessary to support visual analytics. It covers five primary topics. First, it addresses the need for scientific principles for depicting information. Next, it focuses on methods for interacting with visualizations and considers the opportunities available given recent developments in input and display technologies. Third, it addresses the research and technology needed to develop new visual paradigms that support analytical reasoning. Then, it discusses the impact of scale issues on the creation of effective visual representations and interactions. Finally, it considers alternative ways to construct visualization systems more efficiently
    • Visualisation and analysis of interfacial instability in the co-extrusion of a LDPE melt

      Martyn, Michael T.; Coates, Philip D.; Spares, Robert; Zatloukal, M. (2004)
    • Visualising animal hard tissues

      O'Connor, Sonia A.; Sparrow, Thomas; Holland, Andrew D.; Kershaw, Rachael; Brown, Emma L.; Janaway, Robert C.; Ugail, Hassan; Wilson, Andrew S. (Springer Nature, 2022-04)
      This chapter summarises AHRC/EPSRC Science and Heritage Programme-funded research to develop a digital resource to disseminate knowledge of the identification of osseous and keratinous animal hard tissues. The choice of materials in the manufacture of individual artefacts or classes of objects can make a major contribution to understanding their cultural significance and questions of provenance or authenticity. This resource builds on understanding gained through a Fellowship to O’Connor in developing, evaluating and validating identification criteria for these materials in raw, worked and decayed states. The resource concentrates on the non-destructive visual methods of particular relevance to the examination of artworks, historic and archaeological artefacts. The chapter highlights the potential of various visualisation methods and digital technologies to capture and combine 2D images and 3D models and guide the viewer through the multi-scalar visual cues of each material to a reliable identification. By accessing a range of collections, the project has produced a comprehensive and accessible resource, disseminating these findings more widely than could be achieved by a physical reference collection. This resource supports the identification of cultural heritage objects for conservation scientists and heritage professionals and informs the fight against the illegal hunting and trafficking of rare and endangered species.
    • Visuomotor control of step descent: evidence of specialised role of the lower visual field

      Timmis, Matthew A.; Bennett, S.J.; Buckley, John G. (2009-05)
      We often complete step downs in the absence of visual feedback of the lower-limbs, and/or of the area on the ground where we intend to land (e.g. when descending a step whilst carrying a laundry basket). Therefore, the present study examined whether information from lower visual field (lvf) provides any advantage to the control of step descent. Ten healthy subjects (age 24.4 ± 9.4 years) completed repeated step downs over three-step heights with visual information available from either full or upper visual fields (lvf occluded), and for specific intervals relative to step initiation. Visuomotor control of step descent was assessed by determining pre-landing kinematic measures and landing mechanic variables for the initial landing period. Findings indicate that whilst there were only limited effects on pre-landing kinematic measures under lvf occlusion, individual’s ability to plan/control landing mechanics was significantly different in such conditions compared to when they had access to full field vision. These changes were consistent with participants being uncertain regarding precise floor height when access to lvf was restricted, and consequently led them to adapt their landing behaviour but without fundamentally altering their stepping strategy. Compared to when vision was available throughout, the occlusion of vision (full or upper visual field) from toe-off or mid-swing onwards caused very few differences in landing behaviour. This suggests that the contribution of information from lvf to the control of landing behaviour occurs predominantly prior to or during movement initiation and that ‘online’ vision is used only in the latter portion of the descent phase to subtly ‘fine tune’ landings.
    • Voltage Unbalance Mitigation in Low Voltage Distribution Networks using Time Series Three-Phase Optimal Power Flow

      Al-Ja'afreh, M.A.A.; Mokryani, Geev (IEEE, 2021)
      Due to high penetration of single-phase Photovoltaic (PV) cells into low voltage (LV) distribution networks, several impacts such as voltage unbalance, voltage rise, power losses, reverse power flow arise which leads to operational constraints violation in the network. In this paper, a time series Three Phase Optimal Power Flow (TPOPF) method is proposed to minimize the voltage unbalance in LV distribution networks with high penetration of residential PVs. TPOPF problem is formulated using the current injection method in which the PVs are modelled via a time-varying PV power profile with active and reactive power control. The proposed method is validated on a real LV distribution feeder. The results show that the reactive power management of the PVs helps mitigate the voltage unbalance significantly. Moreover, the voltage unbalance index reduced significantly compared to the case without voltage unbalance minimisation.
    • Vortices in Josephson arrays interacting with non-classical microwaves: The effect of dissipation.

      Konstadopoulou, Anastasia; Hollingworth, J.M.; Everitt, M.; Vourdas, Apostolos; Clark, T.D.; Ralph, J.F. (2003)
      Vortices circulating in a ring made from a Josephson array in the insulating phase are studied. The ring contains a `dual Josephson junction' through which the vortices tunnel. External non-classical microwaves are coupled to the device. The time evolution of this two-mode fully quantum mechanical system is studied, taking into account the dissipation in the system. The effect of the quantum statistics of the photons on the quantum statistics of the vortices is discussed. Entropic calculations quantify the entanglement between the two systems. Quantum phenomena in the system are also studied through Wigner functions. After a certain time (which depends on the dissipation parameters) these quantum phenomena are destroyed due to dissipation.
    • VPAStab: stabilised vector-Padé approximation with application to linear systems.

      Graves-Morris, Peter R. (2003)
      An algorithm called VPAStab is given for the acceleration of convergence of a sequence of vectors. It combines a method of vector-Padé approximation with a successful technique for stabilisation. More generally, this algorithm is designed to find the fixed point of the generating function of the given sequence of vectors, analogously to the way in which ordinary Padé approximants can accelerate the convergence of a given scalar sequence. VPAStab is justified in the context of its application to the solution of a large sparse system of linear equations. The possible breakdowns of the algorithm are listed. Numerical experiments indicate that these breakdowns can be classified either as pivot-type (type L) or as ghost-type (type D).