Now showing items 1-20 of 1128

    • Coherent generation of nonclassical light on chip via detuned photon blockade

      Müller, K; Rundquist, A; Fischer, KA; Sarmiento, T; Lagoudakis, KG; Kelaita, YA; Sánchez Muñoz, C; Del Valle, E; Laussy, FP; Vučković, J; et al. (American Physical Society (APS), 2015-06-08)
      © 2015 American Physical Society. The on-chip generation of nonclassical states of light is a key requirement for future optical quantum hardware. In solid-state cavity quantum electrodynamics, such nonclassical light can be generated from self-assembled quantum dots strongly coupled to photonic crystal cavities. Their anharmonic strong light-matter interaction results in large optical nonlinearities at the single photon level, where the admission of a single photon into the cavity may enhance (photon tunneling) or diminish (photon blockade) the probability for a second photon to enter the cavity. Here, we demonstrate that detuning the cavity and quantum-dot resonances enables the generation of high-purity nonclassical light from strongly coupled systems. For specific detunings we show that not only the purity but also the efficiency of single-photon generation increases significantly, making high-quality single-photon generation by photon blockade possible with current state-of-the-art samples.
    • Biased perceptions and personality traits attribution: cognitive aspects in future interventions for organizations

      Riva, Silvia; Chinyio, Ezekiel; Hampton, Paul (Frontiers Media, 2019-01-15)
      In most European countries, the proportion of females and males pursuing a career in Technology and Engineering is quite different. The under-representation of women in these jobs may be attributable to a variety of factors, one of which could be the negative and stereotyped perception of these work sectors as unsuitable for women. The purpose of this study was to determine whether stereotyped perceptions impact the job representation of males and females in the Construction Industry, which is a particularly male-dominated work sector. Three construction organizations in the West Midlands (United Kingdom) were studied by means of ethnographic interviews and observations. Three (6.7%) of the 45 research participants (mean age 44.3) were women (focusing only in people working in Construction sites). There was a high differentiation of activities between the males and females. Biased perceptions and personality traits attribution played a fundamental role in such a differentiation. Despite some main limitations (low generalisability, lack of longitudinal findings), this study focused on some important practical implications for current work policies: changing the mindsets of people (starting from school age), using new flexible strategies and creating the role of internal advocates. The findings provide definitive evidence of the need to increase the promotion of social communication and public campaigns on gender equalities in male-dominated work sectors, taking into account the cognitive processes behind gender differences. The findings also give new hints on re-thinking the contribution of Psychology, particularly Cognitive Psychology, in fields with allegedly wide gender gaps.
    • Emitters of N-photon bundles

      Muñoz, CS; Del Valle, E; Tudela, AG; Müller, K; Lichtmannecker, S; Kaniber, M; Tejedor, C; Finley, JJ; Laussy, FP; Condensed Matter Physics Center (IFIMAC), Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain. (Springer Science and Business Media LLC, 2014-06-01)
      Controlling the output of a light emitter is one of the basic tasks in photonics, with landmarks such as the development of the laser and single-photon sources. The ever growing range of quantum applications is making it increasingly important to diversify the available quantum sources. Here, we propose a cavity quantum electrodynamics scheme to realize emitters that release their energy in groups (or 'bundles') of N photons (where N is an integer). Close to 100% of two-photon emission and 90% of three-photon emission is shown to be within reach of state-of-the-art samples. The emission can be tuned with the system parameters so that the device behaves as a laser or as an N-photon gun. Here, we develop the theoretical formalism to characterize such emitters, with the bundle statistics arising as an extension of the fundamental correlation functions of quantum optics. These emitters will be useful for quantum information processing and for medical applications. © 2014 Macmillan Publishers Limited.
    • Knowledge integration challenges and critical success factors within construction traditional procurement system

      Takhtravanchi, Mohammad; Pathirage, Chaminda (LLC CPC Business Perspectives, 2018-10-11)
      <jats:p>The purpose of this study is to explore and identify the challenges and Critical Success Factors (CSFs) of Knowledge Integration (KI) in terms of capturing, sharing and transferring knowledge within construction projects based on the Traditional Procurement System (TPS). On the basis of available studies on KI and TPS within the industry investigated, multiple case studies were developed to reach the aforementioned objective, involving two case studies to reflect the building sector within construction industry. Furthermore, an Interpretive Structural Modelling (ISM) approach was used to summarize and identify the relationships between the identified challenges. ‘Culture of Organization, ‘Contractual Boundaries’ and ‘Knowledge Management System’ (policies and strategies of organization) are identified as the main challenges. Having an ‘open environment’ and ‘clear liability of project members for sharing knowledge at different phases of project’ are two of identified CSFs, which will assist project managers to enhance the KI process within construction projects undertaken through the TPS.</jats:p>
    • Farmers perceptions of climate change related events in Shendam and Riyom, Nigeria

      Goyol, S; Pathirage, C (MDPI AG, 2018-12-19)
      © 2018 by the authors. Although agriculture in Nigeria is the major source of income for about 70% of the active population, the impact of agrarian infrastructure on boosting productivity and supporting livelihoods has increased. Climate change and the increasing trend of climate-related events in Nigeria challenge both the stability of agrarian infrastructure and livelihood systems. Based on case studies of two local communities in Plateau state in Nigeria, this paper utilizes a range of perceptions to examine the impacts of climate-related events on agrarian infrastructures and how agrarian livelihood systems are, in turn, affected. Data are obtained from a questionnaire survey (n = 175 farmers) and semi-structured interviews (n = 14 key informants). The study identifies local indicators of climate change, high risks climate events and the components of agrarian infrastructures that are at risk from climate events. Findings reveal that, changes in rainfall and temperature patterns increase the probability of floods and droughts. They also reveal that, although locational differences account for the high impact of floods on road transport systems and droughts on irrigation infrastructures, both have a chain of negative effects on agricultural activities, economic activities and livelihood systems. A binomial logistic regression model is used to predict the perceived impact levels of floods and droughts, while an in-depth analysis is utilized to corroborate the quantitative results. The paper further stresses the need to strengthen the institutional capacity for risk reduction through the provision of resilient infrastructures, as the poor conditions of agrarian infrastructure were identified as dominant factors on the high impact levels.
    • Analysis and optimization of sandwich tubes energy absorbers under lateral loading

      Baroutaji, A; Gilchrist, MD; Smyth, D; Olabi, AG (Elsevier BV, 2015-02-07)
      © 2015 Elsevier Ltd. All rights reserved. In this paper, the sandwich tubes, which consist of thin-walled circular tubes with aluminium foam core, were proposed as energy absorption devices. The sandwich tubes were laterally crushed under quasi-static loading conditions. Detailed finite element model, validated against existing experimental results, was developed using the explicit code (ANSYS-LSDYNA) to assess the energy absorption responses and deformation modes. Response surface methodology (RSM) was employed in parallel with the finite element models to perform both parametric studies and multi-objective optimization in order to establish the optimal configuration of the sandwich tube. Sampling designs of the sandwich tubes were constructed based on a D - optimal design of experiment (DOE) method. Factorial analysis was performed using the DOE results to investigate the influences of the geometric parameters on the responses of sandwich tubes. In addition, multi-objective optimization design (MOD) of the sandwich tubes is carried out by adopting a desirability approach. It was found that the tube with a minimum diameter of the inner layer and a maximum foam thickness are more suitable for use as energy absorbing components.
    • Lateral collapse of short-length sandwich tubes compressed by different indenters and exposed to external constraints

      Baroutaji, A; Olabi, AG (Wiley, 2014-05-02)
      In this paper, sandwich tube components which consist of thin-walled circular tubes with aluminium foam core are proposed as energy absorption systems. The sandwich tubes were laterally crushed under quasi-static loading conditions. The sandwich tubes were crushed under two types of indenters and exposed to three different types of external constraints. The collapsing behaviour and the energy absorption responses of these systems were investigated by nonlinear finite element analysis through ANSYS-LS-DYNA. Various indicators which describe the effectiveness of energy absorbing systems were used as a marker to compare the various systems. It was found that the sandwich tube systems compressed by cylindrical indenters particularly the unconstrained system and the system with inclined constraints offered a very desirable force-deflection in which the force is almost constant in the post collapse stage. The employing of external constraints was noticed as a feasible method of increasing the SEA particularly when cylindrical indenter is used. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    • Microstructural analysis of TRISO particles using multi-scale X-ray computed tomography

      Lowe, T; Bradley, RS; Yue, S; Barii, K; Gelb, J; Rohbeck, N; Turner, J; Withers, PJ (Elsevier BV, 2015-02-28)
      TRISO particles, a composite nuclear fuel built up by ceramic and graphitic layers, have outstanding high temperature resistance. TRISO fuel is the key technology for High Temperature Reactors (HTRs) and the Generation IV Very High Temperature Reactor (VHTR) variant. TRISO offers unparalleled containment of fission products and is extremely robust during accident conditions. An understanding of the thermal performance and mechanical properties of TRISO fuel requires a detailed knowledge of pore sizes, their distribution and interconnectivity. Here 50 nm, nano-, and 1 μm resolution, micro-computed tomography (CT), have been used to quantify non-destructively porosity of a surrogate TRISO particle at the 0.3–10 μm and 3–100 μm scales respectively. This indicates that pore distributions can reliably be measured down to a size approximately 3 times the pixel size which is consistent with the segmentation process. Direct comparison with Scanning Electron Microscopy (SEM) sections indicates that destructive sectioning can introduce significant levels of coarse damage, especially in the pyrolytic carbon layers. Further comparative work is required to identify means of minimizing such damage for SEM studies. Finally since it is non-destructive, multi-scale time-lapse X-ray CT opens the possibility of intermittently tracking the degradation of TRISO structure under thermal cycles or radiation conditions in order to validate models of degradation such as kernel movement. X-ray CT in-situ experimentation of TRISO particles under load and temperature could also be used to understand the internal changes that occur in the particles under accident conditions.
    • Designing an app for managing stress in the construction industry

      Riva, Silvia; Chinyio, Ezekiel; Hampton, Paul (Association of Researchers in Construction Management, 2018-09-05)
      High levels of stress at work, great responsibilities, hazards and lack of balance between tasks and deadlines are common in the daily lives of many construction workers. Changing the patterns of thinking and behaviours is not an easy mission, and it requires constant support, learning and determination. E-health applications can contribute to this change through their ability to foster continuous interaction with the user. Mobile phone apps have shown promising results in the field of ‘e-health and wellbeing’. Accordingly, an App is being designed as a self-help system for stress management which will enable construction workers to 1) detect the onset of stress quite early, 2) track their stress status, 3) empower persons to cope with stressful and/or demanding situations in an adaptive way, 4) improve and streamline the operability of job tasks, and 5) optimise efficient solutions for the construction industry. The development of this innovative app, known as Streblo, is part of a wider research that is studying stress management in the construction industry. Streblo’s blueprint will match personality traits with coping strategies in real-life situations. Its inputs are being generated from a field study that has commenced, where structured interviews have been used to collect data from construction workers on their 1) personality and 2) behaviours while experiencing stress. Results of the data collection and analysis are being used to develop Streblo (an App) with IT experts. The paper reports the detail development and performance of Streblo’s prototype. Ultimately, users will be able to engage Streblo on electronic devices (mobile phones, tablets, computers) through both text and image-based communication to obtain real-time solutions and feedbacks on their stress status. Streblo will enhance and support attitude and behavioural changes in people who suffer from stress symptoms in the construction industry.
    • Can the impact of grey literature be assessed? An investigation of UK government publications cited by articles and books

      Bickley, Matthew; Kousha, Kayvan; Thelwall, Michael (International Society for Scientometrics and Informetrics, 2019-08-06)
      Grey literature encompasses a range of relatively informal textual outputs that are not indexed in citation databases. Although they are usually ignored in research evaluations, it is important to develop methods to assess their impact so that their contributions can be recognised, and successful types of grey literature can be encouraged. This article investigates the extent to which 97,150 UK government publications were cited by Scopus articles and Google Books during 2013-2017 in eleven broad subject areas. A method was used to semi-automatically extract citations to the UK government publications from articles and books with high recall and precision. The results showed that Scopus citations are more common than Google Books citations to UK government publications, especially for older documents, and for those in Healthcare, Education and Science. Since the difference is not huge, both may provide useful grey literature impact data.
    • Quasi-static, impact and energy absorption of internally nested tubes subjected to lateral loading

      Baroutaji, A; Gilchrist, MD; Olabi, AG (Elsevier BV, 2015-10-20)
      © 2015 Published by Elsevier Ltd. This paper presents the responses of nested tube systems under quasi-static and dynamic lateral loading. Nested systems in the form of short internally stacked tubes were proposed as energy absorbing structures for applications that have limited crush zones. Three configurations of nested tube systems were experimentally analysed in this paper. The crush behaviour and energy absorbing responses of these systems under various loading conditions were presented and discussed. It was found that the quasi-static and dynamic responses of the nested systems were comparable under an experimental velocity of v=4.5 m/sec. This is due to insignificant strain rate and inertia effects of the nested systems under the applied velocity. The performance indicators, which describe the effectiveness of energy absorbing systems, were calculated to compare the various nested systems and the best system was identified. Furthermore, the effects of geometrical and loading parameters on the responses of the best nested tube system were explored via performing parametric analysis. The parametric study was performed using validated finite element models. The outcome of this parametric study was full detailed design guidelines for such nested tube energy absorbing structures.
    • Briefing: US environmental science women are high impact team players

      Thelwall, Mike A (Thomas Telford Ltd., 2019-08-23)
      In the context of continuing gender inequality in environmental science, this briefing investigates the evolution of the share of female first-authored journal articles in US environmental science specialisms in 1996–2018 and whether there are gender differences in average citation impact. The proportion of female first authors has increased by at least 16% in all 11 Scopus environmental science categories in the USA, with none achieving a female majority by 2018. Female last authors were rarer and increased less during the same period. There is a citation (ratio) advantage for female first-authored research of 2–10% that could be partly accounted for by females tending to lead larger teams (up to 8% if team size is factored out). Irrespective of the main author’s gender, extra authors produce expected citation rate increases of between 6% for an ecology second author and 70% for at least five waste management and disposal authors. The female citation advantage in one field might be substantial enough to boost female careers, although collaboration is a much stronger indicator of greater impact.
    • Data stream ensemble in a new health application for stress management at work: the case of Streblo

      Chinyio, Ezekiel; Riva, Silvia (International Conference on Digital Health, 2019-04-25)
      The negative effects of stress at work in terms of emotional disorders and organisational difficulties have pressed the need for new solutions and especially direct-to-user tools such as mobile applications. While new technology can support the architecture of such tools, adaptive coping behaviours have also been identified as an important factor for promoting new strategies for coping effectively with stress at work. A study being reported in this paper investigates how technology can be used to influence adaptive coping behaviours. The study is synthesizing the key aspects of personality and behavior into a conceptual model for creating a new mobile application. The overall goal of this application (aka Streblo) is to detect: 1) Early signs of stress; that is the mental (personality) and physical state resulting when the resources of the individual are inadequate to cope with the demands and pressures of the situation, 2) Stress consequences that can undermine the achievement of goals; and 3) Propose innovative solutions to cope with stress. A literature review concerning coping behaviours and use of technology was conducted to gather evidence for the foundation of the conceptual model. Primary data is being collected and the empirical findings of the research will be tested and verified using the WEKA software (fig. 1) against the theoretical framework consisting of the ‘Big 5 Theory of Personality, ‘Stress & Coping Theory’ and the concept of ‘Gamification’. Particularly, the following aspects of the theoretical framework are being used to design Streblo: customization to the user, use of relevant and tailored information and feedback and, uses of positive reinforcement and indirect suggestions. Meanwhile, the conceptual model provides further knowledge of key aspects to be considered when developing persuasive tools that aim to encourage more efficient ways of coping with stressful events.
    • A new algorithm for zero-modified models applied to citation counts

      Shahmandi Hounejani, Marzieh; Wilson, Paul; Thelwall, Michael (International Society for Scientometrics and Informetrics, 2019-08-31)
      Finding statistical models for citation count data is important for those seeking to understand the citing process or when using regression to identify factors that associate with citation rates. As sets of citation counts often include more or less zeros (uncited articles) than would be expected under the base distribution, it is essential to deal appropriately with them. This article proposes a new algorithm to fit zero-modified versions of discretised log-normal, hooked power-law and Weibull models to citation count data from 23 different Scopus categories from 2012. The new algorithm allows the standard errors of all parameter estimates to be calculated, and hence also confidence intervals and p-values. This algorithm can also estimate negative zero-modification parameters corresponding to zero-deflation (fewer uncited articles than expected). The results find no universal best model for the 23 categories and a given dataset may be zero-inflated relative to one model, but zero-deflated relative to another
    • Performance-driven 3D printing of continuous curved carbon fibre reinforced polymer composites: A preliminary numerical study

      Zhang, H; Yang, D; Sheng, Y (Elsevier BV, 2018-06-19)
      © 2018 Elsevier Ltd This paper presents a new concept to place continuous curved fibres for carbon fibre reinforced polymer (CFRP) composites, which can be fulfilled by potential additive or hybrid manufacturing technology. Based on the loading condition, principal stress trajectories are generated through finite element analysis (FEA) and used as the guidance for the placement paths of carbon fibres. Three numerical cases including an open-hole single ply lamina under uniaxial tension and open-hole cross-ply laminate under biaxial tension and normal pressure are studied and compared with traditional reinforced composites with unidirectional fibres. The modelling results show that the stress concentration in both fibre and matrix are reduced significantly by the curved fibre placement and the stiffness of CFRP composites have been improved. This concept of performance-driven optimization method could lead to a useful tool for the design of future 3D printing process for fibre reinforced composites.
    • The interaction of a cold atomised spray with a circular cylinder

      Aroussi, A; Lad, N; Muhamad Said, MF; Adebayo, D; Al-Atabi, M (Taylor's University, 2010-09-01)
      The development of non-intrusive diagnostic techniques has significantly increased with the introduction of lasers. Laser based anemometry, such as Laser Doppler (LDA), Phase Doppler (PDA), and Particle Image Velocimetery (PIV) can provide an accurate description of flows without interference. This study determines experimentally the fluid motion resulting from the interaction of a liquid spray with a circular cylinder. Two experimental settings were examined: the first is a discharging spray into free air and the second is a spray impinging on a circular cylinder placed 25 cylinder diameters downstream of the nozzle. These sprays were quantified using PIV. A non-intrusive droplet sizing technique was used to characterise the spray. This has shown that, within the spray, the average droplet diameter increases when the circular cylinder is introduced and so does the frequency of occurrence of these large droplets. In the wake behind the cylinder, the smaller droplets were quickly entrained and recirculated, while the larger droplets continued in the general direction of the spray cone. © School of Engineering, Taylor's University College.
    • PIV study of the flow across the meridional plane of rotating cylinders with wide gap

      Adebayo, DS; Rona, A (Praise Worthy Prize, 2015-02-28)
      This study investigates by Particle Image Velocimetry (PIV) the wavy Taylor vortex flow that develops in the gap between concentric rotating cylinders of low aspect ratio and low radius ratio, which is a configuration relevant to oil bearing chambers in turbomachinery. The configuration is characterised by a larger annular gap width than in classical journal bearing and by a Taylor number (Ta) of 2.47 × 106, which is 1000 times higher than the first critical Taylor number. It is found that the non-uniform axial spacing of the vortex cores induces an asymmetric radial velocity profile and an inflected axial velocity profile close to the cylindrical walls. The outflow at the centre of each pair of Taylor vortices that make up a vortex cell is strong and it is characterised by a sharp radial velocity peak. The inflow between pairs of Taylor vortex cells is unconventional in that it is characterised by pairs of confluent streams from the outer cylinder that merge towards the inner cylinder. These results form a body of experimental evidence on the flow features that may occur in engineering practice in oil bearing chamber flows, with relevance to lubrication and wear.
    • Dr. Inventor, promoting scientific creativity by utilising web-based research objects, FP7

      Dong, Feng; O'Donoghue, DiarmuidP; Ersotelos, Nikolaos; Wu, Shaopeng; Saggion, Horacio; Ronzano, Francesco; Corcho, Oscar; Hurley, Donny; Abgaz, Yalemisew; Zhang, JianJ; et al. (Science Impact, Ltd., 2017-02-07)
      Scientific creativity and innovation represent the beating heart of European growth at a time of rapid technological change. Dr Inventor is built on the vision that technologies have great potential to supplement human ingenuity in science by overcoming the limitations that people suffer in pursuing scientific discovery. It presents an original system that will provide inspiration for scientific creativity by utilising the rich presence of web-based research resources. Dr Inventor will act as a personal research assistant, utilising machine-empowered search and computation to bring researchers extended perspectives for scientific innovation by informing them of a broad spectrum of relevant research concepts and approaches, by assessing the novelty of research ideas, and by offering suggestions of new concepts and workflows with unexpected features for new scientific discovery. Dr Inventor is an attempt to understand the potential of technology in the scientific creative process within current technology limitations. It represents a sound balance between scientific insight into individual scientific creative processes and technical implementation using innovative technologies in information extraction, document summarization, semantics and visual analytics. The outcomes will be integrated into a web-based system that will allow evaluation in a selected research area under real-world settings with carefully designed metrics, benchmarks and baseline for creative performance, leading to tangible measurements on the performance of the technologies in enhancing human creativity and a blueprint for future technologies in computational creativity. Dr Inventor has huge implications for scientific innovation in Europe, as it has the potential to change the way in which scientific research is undertaken. The acceptance of the system by general research communities will open opportunities for many industrial sectors, leading to reinforced leadership of European industry.
    • A hybrid RANS model of wing-body junction flow

      Rona, Aldo; El-Dosoky, M. F. F.; Adebayo, David (Elsevier, 2019-09-26)
      The three-dimensional flow separation over the Rood wing-body junction is an exemplar application of separation affecting many important flows in turbomachinery and aerodynamics. Conventional Reynolds Averaged Navier Stokes (RANS) methods struggle to reproduce the complexity of this flow. In this paper, an unconventional use is made of a hybrid Reynolds Averaged Navier Stokes (RANS) model to tackle this challenge. The hybridization technique combines the Menter 𝑘 − 𝜔 − 𝑆𝑆𝑇 model with the one equation sub-grid-scale (SGS) model by Yoshizawa through a blending function, based on the wall-normal distance. The hybrid RANS turbulence closure captured most of the flow features reported in past experiments with reasonable accuracy. The model captured also the small secondary vortex at the corner ahead of the wing nose and at the trailing edge. This feature is scarcely documented in the literature. The study highlights the importance of the spatial resolution near the wing leading edge, where this localised secondary recirculation was observed by the hybrid RANS model. It also provides evidence on the applicability of the hybrid Menter and Yoshizawa turbulence closure to the wing-body junction flows in aircraft and turbomachines, where the flows are characterised by a substantially time-invariant three-dimensional separation.
    • Numerical investigation of the three-dimensional pressure distribution in Taylor Couette flow

      Adebayo, DS; Rona, A (ASME International, 2017-08-08)
      Copyright © 2017 by ASME. An investigation is conducted on the flow in a moderately wide gap between an inner rotating shaft and an outer coaxial fixed tube, with stationary end-walls, by threedimensional Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD), using the realizable k - ϵ model. This approach provides three-dimensional spatial distributions of static and dynamic pressures that are not directly measurable in experiment by conventional nonintrusive optics-based techniques. The nonuniform pressure main features on the axial and meridional planes appear to be driven by the radial momentum equilibrium of the flow, which is characterized by axisymmetric Taylor vortices over the Taylor number range 2.35 × 106 ≤ Ta ≤ 6.47 × 106. Regularly spaced static and dynamic pressure maxima on the stationary cylinder wall follow the axial stacking of the Taylor vortices and line up with the vortex-induced radial outflow documented in previous work. This new detailed understanding has potential for application to the design of a vertical turbine pump head. Aligning the location where the gauge static pressure (GSP) maximum occurs with the central axis of the delivery pipe could improve the head delivery, the pump mechanical efficiency, the system operation, and control costs.