White Rose Research Online
Este es el repositorio institucional de tres universidades del Reino Unido (York, Leeds y Sheffield), creado con el apoyo de SHERPA. Proporciona acceso a los artículos de investigación de las instituciones.
Status = In Press
Mostrando recursos 1 - 20 de 681
Arabic Learner Corpus: Texts Transcription and Files Format - Alfaifi, AYG; Atwell, ES
This paper introduces standards used for transcribing texts of the Arabic Learner Corpus (ALC) from the hand-written sheets into an electronic format. It describes the transcription process which was performed by three transcribers, and the measurement conducted for keeping consistency in transcription. The paper concludes with a description of the corpus file produced based on the electronic format.
Fracture aperture and fill characterization in a limestone quarry using GPR thin-layer AVA analysis - Kana, AA; West, LJ; Clark, RA
Detection and characterization of fractures is important in many engineering practices e.g. rock fall assessment, quarry rock quality determination, mine roof and tunnel stability. Fractures may provide suitable contrasts in electrical properties for detection by GPR instruments. Their ability to reflect radar waves and the dependence of this reflectivity on fracture properties (aperture and fill) makes the GPR method a promising tool for rock fracture characterization. Doing so successfully requires quantification of the reflectivity, reflection coefficient, R of individual fractures, and it’s variation with incidence angle (AVA) or in practice, offset. Measuring the full AVA response using Common Mid Point...
Terahertz quantum cascade lasers with thin resonant-phonon depopulation active regions and surface-plasmon waveguides - Salih, M; Dean, P; Valavanis, A; Khanna, SP; Li, LH; Cunningham, JE; Davies, AG; Linfield, EH
We report three-well, resonant-phonon depopulation terahertz quantum cascade lasers with semi-insulating surface-plasmon waveguides and reduced active region (AR) thicknesses. Devices with thicknesses of 10, 7.5, 6, and 5 μm are compared in terms of threshold current density, maximum operating temperature, output power and AR temperature. Thinner ARs are technologically less demanding for epitaxial growth and result in reduced electrical heating of devices. However, it is found that 7.5-μm-thick devices give the lowest electrical power densities at threshold, as they represent the optimal trade-off between low electrical resistance and low threshold gain.
'Dare voce alle vite marginali: plurilinguismo di genere nella narrativa di Laura Pariani' - Sulis, G
This article analyses the literary work of Laura Pariani (1951-), a writer who, over the last twenty years, has gained a niche position in the contemporary canon. After situating Pariani in the context of Italian fiction in the years 1990s-2010s, the analysis focuses on the ‘centrality of margins’ as the inspiring principle underpinning her production. In Pariani’s writings marginality – geographical, gender-based, generational, linguistic – becomes a privileged point of view from which to assess the world. The protagonists of her works are women, but also children, immigrants, the socially marginalised, often dialect speakers, or those caught in situations of...
Transient Analysis of THz-QCL Pulses Using NbN and YBCO Superconducting Detectors - Scheuring, A; Dean, P; Valavanis, A; Stockhausen, A; Thoma, P; Salih, M; Khanna, SP; Chowdhury, S; Cooper, JD; Grier, A; Wuensch, S; Il in, K; Linfield, EH; Davies, AG; Siegel, M
We report the time-domain analysis of fast pulses emitted by a quantum cascade laser (QCL) operating at ~3.1 THz using superconducting THz detectors made from either NbN or YBa2Cu3O7- (YBCO) thin films. The ultra-fast response from these detectors allows resolution of emission features occurring on a nanosecond time-scale, which is not possible with commercially available Ge or InSb bolometers owing to their much larger time constants. We demonstrate that the time-dependent emission can be strongly affected by relatively small variations in the driving pulse. The QCL output power–current relationship was determined, based on correlation of the time-dependent emission of radiation...
Characterization and evaluation of Ni/SiO catalysts for hydrogen production and tar reduction from catalytic steam pyrolysis-reforming of refuse derived fuel - Blanco, PH; Wu, C; Onwudili, JA; Williams, PT
A series of Ni/SiO catalysts have been prepared and investigated for their suitability for hydrogen production and tar reduction in a two-stage pyrolysis-reforming system, using refuse derived fuel (RDF) as the raw material. Experiments were conducted at a pyrolysis temperature of 600°C, and a reforming temperature of 800°C. The product gases were analysed by gas chromatography (GC) and the condensed fraction was collected and quantified using gas chromatography-mass spectrometry (GC-MS). The effects of the catalyst preparation method, nickel content and the addition of metal promoters (Ce, Mg, Al), were investigated. Catalysts were characterised using BET surface area analysis, temperature programmed...
Improved Nonlinear Solvers in BOUT++ - Dudson, Benjamin Daniel; Farley, Sean; Curfman McInnes, Lois
Challenging aspects of large-scale turbulent edge simulations in plasma physics include robust nonlinear solvers and efficient preconditioners. This paper presents recent advances in the scalable solution of nonlinear partial differential equations in BOUT++, with emphasis on simulations of edge localized modes in tokamaks. A six-field, nonlinear, reduced magnetohydrodynamics model containing the fast shear Alfven wave and electron and ion heat conduction along magnetic fields is solved by using Jacobian-free Newton-Krylov (JFNK) methods and nonlinear GMRES (NGMRES). Physics-based preconditioning based on analytic Schur factorization of a simplified Jacobian is found to result in an order of magnitude reduction in runtime over...
Using web-based reflection with video to enhance high fidelity undergraduate nursing clinical skills education. (In Press) - Shortridge, A; McPherson, MA; Loving, G
The United States is currently facing a crisis in health care and health professions education. Various studies (Committee on Quality of Health Care in America 2000; 2001; General Accounting Office, 2001) have documented astonishing death rates from medical errors as well as nursing and physician shortages. Thus it is obvious that the traditional “hands on” model historically used to teach and assess clinical judgment competence is or has become inadequate. New advances in simulation and web-based technologies can, if leveraged well, help educators address these challenges. Thus far, high fidelity simulation (HFS) clinical skills education sessions have been primarily conducted...
Creep curve measurement to support wear and adhesion modelling, using a continuously variable creep twin disc machine - Fletcher, D. I.; Lewis, S.
Predictive modelling of wear and adhesion at rolling-sliding contacts such as a railway rail and wheel depends on understanding the relationship between slip and shear force at the contact surface, i.e. the creep verses force curve. This paper describes a new approach to creep curve measurement using a twin disc machine running with a continuous programmed variation of creep, enabling an entire creep curve to be defined in a single experiment. The work focuses on very low levels of creep, ranging from zero to 1%, and shows clear correlation between the creep curve gradient and the full slip friction coefficient...
A new two-dimensional model of rolling-sliding contact creep curves for a range of lubrication types - Fletcher, D. I.
Experimentally determined creep curves for rolling-sliding contact in lubricated conditions are found to deviate greatly from the standard theory for two body contact. This paper presents a new model to represent coefficient of adhesion (also known as traction coefficient) and creep based on experimental data gathered for a range of railway rail-wheel contact conditions. The model developed is based on a 2D elastic foundation representation of a twin disc contact. This is used to quantify the creep curves in a similar manner to existing 3D models of real rail-wheel contacts undergoing partial slip for a range of lubrication conditions.
How to measure quality of life for cost effectiveness analyses in personality disorders? A systematic review. - Papaioannou, D.; Brazier, J.; Parry, G.
Objective: To assess the construct validity and responsiveness of four generic health related quality of life (HRQL) measures in personality disorders (PDs).
Methods: A systematic review was undertaken. Ten databases were searched and reference lists scrutinised to identify relevant studies. Relevant data were extracted accordingly. A narrative synthesis was performed of the evidence on construct validity including known groups validity (detecting differences in HRQL scores between two different groups), convergent validity (strength of association between generic HRQL and other measures (e.g. symptom) and responsiveness (differences in generic HRQL measure scores in responders/non-responders or correlation with changes in other measures).
Enhancing microbial iron reduction in hyperalkaline, chromium contaminated sediments by pH amendment - Whittleston, RA; Stewart, DI; Mortimer, RJG; Burke, IT
Soil collected from beneath a chromite ore processing residue (COPR) disposal site contained a diverse population of anaerobic alkaliphiles, despite receiving a continuous influx of a Cr(VI) contaminated, hyperalkaline leachate (pH 12.2). Chromium was found to have accumulated in this soil as a result of an abiotic reaction of Cr(VI) with Fe(II) present in the soil. This sediment associated Fe(II) was therefore acting as a natural reactive zone beneath the COPR and thereby preventing the spread of Cr(VI). In anaerobic microcosm experiments soil microorganisms were able to reduce nitrate at pH 11.2 coupled to the oxidation of electron donors derived...
Towards an agenda for post-carbon cities: Lessons from LILAC, the UK's first ecological, affordable, cohousing community - Chatterton, P
This paper explores an agenda towards post-carbon cities, extending and deepening established debates around low-carbon, sustainable cities in the process. The label post-carbon builds upon issues beyond those of greenhouse gas (GHG) emissions, energy conservation and climate change, adding a broader set of concerns including economic justice, behaviour change, wellbeing, land ownership, the role of capital and the state, and community self management. The paper draws upon a case-study of an embryonic post-carbon initiative due for completion in 2013 called Lilac. Based in Leeds, Lilac stands for Low Impact Living Affordable Community and is the first attempt to build an...
The stewardship of things: Property and responsibility in the management of manufactured goods - Lane, R.; Watson, M.
In the context of broad-based concerns about the need to move towards a more sustainable materials economy, particularly as they are expressed in debates around ecological modernisation (EM), we argue that product stewardship has radical potential as a means to promote significant change in the relationship between society and the material world. We focus on two important dimensions that have been neglected in approaches to product stewardship to date. Firstly, we argue that immanent within the basic concept of stewardship is a problematisation of dominant understandings of property ownership in neoliberal market economies. In the space opened up by notions...
On the Willingness to Pay for Rural Rail Service Level Changes - Johnson, DH; Nash, C; Jackson, J
In the context of current plans for public sector expenditure, cuts in the provision of regional and rural rail services may be under consideration. We show how it is possible to assess the values of different aspects of rural rail services to aid quantitative appraisal and management decision-making. To this end we conduct an SP experiment which values the provision of different levels of rural rail services and compares them with the values held for a replacement bus or coach service. While a number of studies have examined the field of rural rail services in the UK, and other studies...
Modelling of segmentation-driven vibration in machining - Taylor, C M; Turner, S; Papatheou, E; Sims, N D
Excessive vibration, such as chatter, is a common problem in machining processes. Meanwhile, numerous hard, brittle metals have been shown
to form segmented chips, also known as sawtooth chips, during machining.
In the literature, a cyclic cutting force has been demonstrated where
segmented chips are formed, with the force cycle corresponding to
the formation of segments. Segmented chip formation has been shown
to be linked to high vibration levels in turning and milling processes.
Additionally, it has been proposed that the amplitude of chatter
vibrations can be limited by interference between the tool flank
and wavy workpiece surface, a phenomenon known as tool-flank process
damping. In this contribution, a model...
A finite element method for active vibration control of uncertain structures - Morales, A.L.; Rongong, J.A.; Sims, N.D.
This work introduces a fuzzy design method using the finite element procedure to simulate and analyze active vibration control of structures subjected to uncertain parameters. The purpose of this work is to provide a tool for studying the influence of uncertainty propagation on both stability and performance of a vibration control system, whilst avoiding the need for computationally expensive probabilistic methods or complex robust control techniques. The proposed procedure applies a general and efficient strategy for computing fuzzy results to a sequence of finite element calculations. Finally, the applicability of the methodology is illustrated through some realistic case studies related...
Density matrix modelling of Ge/GeSi quantum cascade terahertz lasers - Dinh, TV; Ivanov, P; Valavanis, A; Lever, LJM; Ikonic, Z; Kelsall, RW
The prospect of making silicon-based quantum cascade lasers (QCLs) has attracted considerable research interest in recent years, due to their significant potential advantages including a mature Si processing technology, the prospect of integration with Si microelectronics, and superior thermal performance to that of III–V devices. Amongst various proposed designs, with different material compositions and substrate orientations, (001)-oriented n-type Ge/GeSi structures utilising L-valley intersubband transitions appear to be the most promising due to a small quantisation effective mass, and hence large optical matrix elements, and practically realisable layer widths. While all the previous simulations for group IV-based QCLs used the rate...