60419 research outputs found
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Process fault diagnosis with model- and knowledge-based approaches: Advances and opportunities
No full textFault diagnosis plays a vital role in ensuring safe and efficient operation of modern process plants. Despite the encouraging progress in its research, developing a reliable and interpretable diagnostic system remains a challenge. There is a consensus among many researchers that an appropriate modelling, representation and use of fundamental process knowledge might be the key to addressing this problem. Over the past four decades, different techniques have been proposed for this purpose. They use process knowledge from different sources, in different forms and on different details, and are also named model-based methods in some literature. This paper first briefly introduces the problem of fault detection and diagnosis, its research status and challenges. It then gives a review of widely used model- and knowledge-based diagnostic methods, including their general ideas, properties, and important developments. Afterwards, it summarises studies that evaluate their performance in real processes in process industry, including the process types, scales, considered faults, and performance. Finally, perspectives on challenges and potential opportunities are highlighted for future work
Preliminary Investigations of an Opposed Rotary Piston Compressor for the Air Feeding of a Polymer Electrolyte Membrane Fuel Cell System
No full textAutomotive polymer electrolyte membrane fuel cell systems are attracting much attention, driven by the requirements of low automotive exhaust emissions and energy consumption. A polymer electrolyte membrane fuel cell system provides opportunities for the developments in different types of air compressors. This paper proposed an opposed rotary piston compressor, which had the merits of more compact structures, less movement components, and a high pressure ratio, meeting the requirements of polymer electrolyte membrane fuel cell systems. Preliminary performance evaluations of the opposed rotary piston compressor were conducted under various scenarios. This will make a foundation for optimizations of outlet pipe layouts of the compressor. A three-dimensional numerical simulation approach was used; further, in-cylinder pressure evolutions, fluid mass flow rates, and P–V diagrams were analyzed. It indicated that the cyclic period of the opposed rotary piston compressor was half of reciprocating piston compressors. The specific mass flow rate of the compressor is in the range of 0.094–0.113 kg·(s·L)−1 for the given scenarios. Outlet ports 1 and 2 dominated the mass flow in the discharge process under scenarios 1, 3, and 4. In-cylinder pressure profiles show multipeaks for all of these scenarios. In-cylinder pressure increased rapidly in the compression process and part of the discharge process, which led to high energy consumption and low adiabatic efficiency. The maximum adiabatic efficiency is approximately 43.96% among the given scenarios
Linearising Longitudinal Vehicle Dynamics through Adaptive Control Techniques for Platooning Applications
No full textVehicle platooning provides avenues to improve road transportation byreducingenergyconsumptionandpollutantemissionswhileincreasingsafety androadusage.However,tosafelyoperateasequenceofconnectedautonomous vehicles(CAVs)as a platoon, stringent conditions, such as string stability, on the closed-loop platoon dynamics must be guaranteed. To meet such platoon control specifications, linear longitudinal vehicle dynamics are usually assumed for the design of platoon control algorithms, and are imposed to each vehicle in the platoon by using mid-level control systems. However, disturbances and model mismatches can limit the compensation of the nonlinear vehicle dynamics, and thus jeopardise the tracking of the reference linear behaviour. To systematically impose the linear behaviour to the vehicles in a platoon despite model uncertainties and disturbances, in this paper two adaptive solutions are proposed and compared: (i) an adaptive solution for systems in Brunovsky form; and (ii) the Enhanced Model Reference Adaptive Control. Numerical results confirm that both adaptive techniques are effective in imposing the linear dynamics to the longitudinal vehicle motion, also when integrated within a platoon control architecture. The closed-loop platoon performance is assessed via a set of performance indicators for different platoon lengths
Who can I turn to? Social networks and the housing, care and support preferences of older lesbian and gay people in the UK
No full textWhat happens when lesbian and gay people, who are more likely to be childless and single than their heterosexual peers, get older and need support and care? Who can they turn to? In addressing this question, this article draws on data collected as part of a wider project concerning the housing preferences, experiences and concerns of older LGBT people in the United Kingdom. The article explores the social networks that older lesbian and gay people expect to utilise later in life if they require different forms of care. It uses social capital theory and considers the role of ‘families of choice’ in older lesbian and gay people’s lives, questioning whether such bonds may or may not be useful for different forms of care and support older lesbian and gay people may require late in life
Liminality And Festivals - Insights From The East
No full textThis research extends our knowledge of liminality through investigating how the liminal
experiences of festival-goers are constructed in a Chinese music festival context. The
research employs a multi-site data collection approach undertaking field observations and 68
in-depth semi-structured interviews at seven music festivals across three years. The study
contributes to the theoretical development of a liminality framework by providing empirical
evidence of the nature of liminality. It extends our understanding of event tourist
experiences by highlighting the development and role of three types of communitas and
identifying six stages within a rite of passage. The resulting multifaceted coexistence of
liminal behaviours and identity with everyday routine life provides a new approach to the
critical understanding of the role of liminality
A framework to explore the functioning and sustainability of business models
No full textThis paper presents a framework to enable case study analysis of sustainable development from
business models innovation. Increasing economic development can give rise to trade-offs between
economic growth and environmental degradation. Business model innovation can help address such
trade-offs by refocusing value creation and capture towards less environmentally damaging activities.
Business models therefore provide a critical tool in the move towards sustainable development. In this
paper a literature review of existing business model frameworks is conducted and gaps found in the
definition and conceptualisation of value, alignment with sustainable development, and assessment of
social and environmental impacts and goals. More generally, there is a lack of in depth case studies in
the sustainable business model literature. A framework is developed to address these gaps and to allow
in depth analysis and understanding of the functioning of business models for sustainable development.
Development and piloting of the framework made use of literature and co-operative enquiry. The
framework of the paper is applied in depth with a unique energy company case study. Application
shows economies of scope to be critical to the delivery of sustainable development. The business
model framework addresses equity and distributional issues that are key to sustainable development,
but missed by current frameworks
Offshore oil production planning optimization: An MINLP model considering well operation and flow assurance
No full textWith the increasing energy requirement and decreasing onshore reserves, offshore oil production has attracted increasing attention. A major challenge in offshore oil production is to minimize both the operational costs and risks; one of the major risks is anomalies in the flows. However, optimization methods to simultaneously consider well operation and flow assurance in operation planning have not been explored. In this paper, an integrated planning problem both considering well operation and flow assurance is reported. In particular, a multi-period mixed integer nonlinear programming (MINLP) model was proposed to minimize the total operation cost, taking into account of well production state, polymer flooding, energy consumption, platform inventory and flow assurance. By solving this integrated model, each well's working state, flow rates and chemicals injection rates can be optimally determined. The proposed model was applied to a case originated from a real-world offshore oil site and the results illustrate the effectiveness
Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*
No full textWe present the serendipitous discovery of the fastest main-sequence hyper-velocity star (HVS) by the Southern Stellar Stream Spectroscopic Survey (S5). The star S5-HVS1 is a ∼2.35 M⊙ A-type star located at a distance of ∼9 kpc from the Sun and has a heliocentric radial velocity of 1017 ± 2.7 kms−1 without any signature of velocity variability. The current 3D velocity of the star in the Galactic frame is 1755 ± 50 kms−1. When integrated backwards in time, the orbit of the star points unambiguously to the Galactic Centre, implying that S5-HVS1 was kicked away from Sgr A* with a velocity of ∼1800 kms−1 and travelled for 4.8 Myr to its current location. This is so far the only HVS confidently associated with the Galactic Centre. S5-HVS1 is also the first hyper-velocity star to provide constraints on the geometry and kinematics of the Galaxy, such as the Solar motion Vy,⊙ = 246.1 ± 5.3 kms−1 or position R0 = 8.12 ± 0.23 kpc. The ejection trajectory and transit time of S5-HVS1 coincide with the orbital plane and age of the annular disc of young stars at the Galactic Centre, and thus may be linked to its formation. With the S5-HVS1 ejection velocity being almost twice the velocity of other hyper-velocity stars previously associated with the Galactic Centre, we question whether they have been generated by the same mechanism or whether the ejection velocity distribution has been constant over time
Measurement uncertainty in nonlinear behavioural models of microwave and millimetre-wave amplifiers
No full textTo support the responsible implementation of next-generation wireless communications networks such as 5G, the efficiency of power amplifiers located in both base-stations and mobile handsets must be improved. This improvement will also benefit other areas of wireless innovation such as satellite communications, military and civilian short-range radar (automotive and gesture tracking), and future submillimetre-wave communications. Significant efficiency gains can be obtained by using nonlinear amplifier techniques, however these cause undesired distortion to the signal. Methods used to mitigate these effects rely on accurate models extracted from the internal transistors, which circuit simulators interrogate to predict the performance of new amplifier designs. This thesis presents the first evaluation of measurement uncertainty propagated into a nonlinear
behavioural model, X-parameters, and used within a circuit simulator to provide confidence in the results. This uncertainty evaluation can also reveal the relative uncertainty contributions from different aspects of the measurement setup, the knowledge of which can be used to
make informed improvements in manufacturing test laboratories. The evaluation was tested on a millimetre-wave amplifier designed for communications use, which showed encouraging results when simulated in a test circuit to provide figures for gain and PAE. During development of this uncertainty evaluation, a standard guidance document was reviewed and found to contain
ambiguities which significantly affect scattering-parameter measurements commonly used in RF laboratories. This ambiguity is highlighted to inform those working on revisions that is must be addressed. Finally, traditional uncertainty evaluation techniques for vector network analyser measurements in coaxial transmission lines are applied to rectangular metallic waveguide setups to investigate their success. Waveguide concerning frequencies up to 750 GHz are considered, covering E-band and higher which are being developed for future high-bandwidth communications. Although the uncertainty evaluation techniques work well for most waveguides tested, mechanical issues in WR-1.5 prohibits the feasibility of the technique
Thinking up, writing down:the artistic creativity, phenomenology and neurobiology of the creative writing process
No full textWhat happens in a writer’s head before the writing begins and while the writing is taking place? What are the internal processes involved in the thinking up and writing down of imaginative fiction? Cognitive science offers explanations based on scientific observation and measurement that are imminently rational, logical and readily depicted in neatly ordered models. However, none adequately reflect the descriptions contained in writers’ accounts of their lived experience of the creative writing process. These experiential and phenomenological accounts depict a complex, multi-layered process, that is often chaotic, uncertain and unpredictable; the descriptions peppered with references to non-cognitive factors such as intuition, inspiration, felt sense, incubation and the imagination. The two approaches, positivist and phenomenological, express themselves in different languages and thus seldom speak to each other.
This thesis seeks to address this gap by facilitating a bridge between them. It proposes a neurophenomenological model of the creative writing process that allows lived experience to sit comfortably alongside contemporary neurobiological research findings, so that each enriches and informs the other. The model, therefore, provides a clear, systemic account of the creative writing process that embraces both its cognitive and non-cognitive aspects within a single, coherent framework that combines third-hand objective research with first-hand subjective accounts of lived experience, thereby yielding deeper insights into, and fresh conceptualisations of, the creative writing process. It thus constitutes an original contribution to the discourse on Creative Writing as a field of study that also has the potential to impact the discourse in a range of related disciplines, such as the visual and performing arts, cognitive science, cognitive psychology, philosophy, phenomenology and neuroscience. The greatest impact of this contribution, however, lies in the scope it provides for cross-disciplinary conversations, particularly those that bridge the long-standing gap between the science and the arts
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