Multiple line arrays for the characterization of aeroacoustic sources using a time-reversal method

This letter investigates the use of multiple line arrays (LAs) in a Time-Reversal Mirror for localizing and characterizing multipole aeroacoustic sources in a uniform subsonic mean flow using a numerical Time-Reversal (TR) method. Regardless of the original source characteristics, accuracy of predicting the source location can be significantly improved using at least two LAs. Furthermore, it is impossible to determine the source characteristics using a single LA, rather a minimum of two are required to establish either the monopole or dipole source nature, while four LAs (fully surrounding the source) are required for characterizing a lateral quadrupole source.A. Mimani, C. J. Doolan, and P. R. Medwel

Exploring children's discourses of writing

This article reports on a study which was part of a two year writing project undertaken by a University in South East England with 17 primary schools. A survey sought the views of up to 565 children on the subject of writing. The analysis utilises Ivanič's (2004) discourses of writing framework as a heuristic and so provides a unique lens for a new understanding of children's ideological perspectives on writing and learning how to write. This study shows the development of learned or acquired skills and compliance discourses by the participating children within which accuracy and correctness overrides many other considerations for the use of the written word

Learners’ and teachers’ beliefs about learning tones and pinyin

This paper reports a study of the perceptions of English-speaking learners and teachers about the challenges and difficulties of Chinese as a Second Language (CSL) learning in England. The study involved a Likert-scale questionnaire and follow-up interviews with 37 university student learners, 443 school students and the 42 teachers of both groups. The questionnaires and interviews explored beliefs about language learning, about Chinese language learning and about language learning strategies. This paper focuses on the findings concerning the perceived challenges of speaking Chinese and of tones in learning Chinese. The findings of this study present a picture of teachers who are keen for their students to learn to speak and communicate in Chinese, and of students who are keen to take risks in speaking. However, in contrast to earlier findings about learners’ views about learning Chinese, the learners in this study claimed to be very tone aware and reported that they found listening and understanding Chinese more difficult than production. This is explored in relation to the pupils’ views about learning tones and pinyin and raises questions about the ways they address tones and pinyin learning in the context of their expressed aim of communicating and taking risks in speaking. The discussion raises issues about the possible effects of communicative teaching of languages in English schools. We ask whether an emphasis on communicative approaches may affect how learners address difficulties of the Chinese pronunciation system and the use of pinyin

Robot Guided ‘Pen Skill’ Training in Children with Motor Difficulties

Motor deficits are linked to a range of negative physical, social and academic consequences. Haptic robotic interventions, based on the principles of sensorimotor learning, have been shown previously to help children with motor problems learn new movements. We therefore examined whether the training benefits of a robotic system would generalise to a standardised test of ‘pen-skills’, assessed using objective kinematic measures [via the Clinical Kinematic Assessment Tool, CKAT]. A counterbalanced, cross-over design was used in a group of 51 children (37 male, aged 5-11 years) with manual control difficulties. Improved performance on a novel task using the robotic device could be attributed to the intervention but there was no evidence of generalisation to any of the CKAT tasks. The robotic system appears to have the potential to support motor learning, with the technology affording numerous advantages. However, the training regime may need to target particular manual skills (e.g. letter formation) in order to obtain clinically significant improvements in specific skills such as handwriting

Developing sports engineering education in Australia

This paper presents some examples of teaching material used in Australia's first sports engineering degree programme. In an Australian context, the field of sports engineering education is very young. Despite the growth of sports engineering degree programmes, there is no clear description outlining sports engineering as a discipline. Although sports engineering programmes typically incorporate aspects of existing courses in the broad fields of mechanical and electronic engineering, there are other skills that are specifically required for sports engineers to possess. Over many years, traditional engineering fields have developed a plethora of quality teaching textbooks and course syllabi. Due to the recent growth of sports engineering as a field, there is a distinct lack of such material. One approach of dealing with this issue is to adopt the use of blended learning, merging suitable refereed scientific publications with traditional engineering theory, to problems applicable to sports. A number of international journal and conference series are dedicated to sports engineering, and these offer a wide breadth of up-to-date material; however, the suitability of this literature for educational purposes is not clear. In light of this gap, sports engineering in the Australian education system requires a clearer definition, and also some examples of suitable teaching material. These issues will be explored in this paper, and some solutions will be addressed. Although the paper is focussed on the Australian system, the broad findings are applicable world-wide. © 2012 Published by Elsevier Ltd.Paul R. Medwell, Paul N. Grimshaw, Will S. Robertson and Richard M. Kels

Enhancing the focal-resolution of aeroacoustic time-reversal using a point sponge-layer damping technique

Abstract not availableA. Mimani, C. J. Doolan, and P. R. Medwel

Automated determination of size and morphology information from soot transmission electron microscope (TEM) generated images

The thermophoretic sampling of particulates from hot media, coupled with transmission electron microscope (TEM) imaging, is a combined approach that is widely used to derive morphological information. The identification and the measurement of the particulates, however, can be complex when the TEM images are of low contrast, noisy, and have non-uniform background signal level. The image processing method can also be challenging and time consuming, when the samples collected have large variability in shape and size, or have some degree of overlapping. In this work, a three-stage image processing sequence is presented to facilitate time-efficient automated identification and measurement of particulates from the TEM grids. The proposed processing sequence is first applied to soot samples that were thermophoretically sampled from a laminar non-premixed ethylene-air flame. The parameter values that are required to be set to facilitate the automated process are identified, and sensitivity of the results to these parameters is assessed. The same analysis process is also applied to soot samples that were acquired from an externally irradiated laminar non-premixed ethylene-air flame, which have different geometrical characteristics, to assess the morphological dependence of the proposed image processing sequence. Using the optimized parameter values, statistical assessments of the automated results reveal that the largest discrepancies that are associated with the estimated values of primary particle diameter, fractal dimension, and prefactor values of the aggregates for the tested cases, are approximately 3, 1, and 10 %, respectively, when compared with the manual measurements.Cheng Wang, Qing N. Chan, Renlin Zhang, Sanghoon Kook, Evatt R. Hawkes, Guan H. Yeoh, Paul R. Medwel

On the burning of sawdust in a MILD combustion furnace

The purpose of this work is to extend the applicability of moderate or intense low oxygen dilution (MILD) combustion to solid biomass fuels. A laboratory-scale furnace fitted with a parallel jet burner was operated in conventional nonpremixed flame mode, and in MILD combustion mode, using either natural gas or pine sawdust particles. Sawdust with particle sizes in the range of 212-355 μ were injected into the furnace using either air, CO2, or N2 as a carrier gas. Measurements of in-furnace wall temperatures and exhaust gas emissions of O2, CO, NOx, and ash are presented, together with visual observations at the burner exit region. It was found, through detailed comparisons, that MILD combustion was established without air preheat for both gaseous and solid fuels, suggesting that the parallel jet burner system is suitable for MILD combustion. A 3-fold reduction in NOx emissions and an increase in CO were recorded during the transition from conventional to MILD combustion using natural gas. The optimal equivalence ratio (φ) to reduce both CO and NOx emissions, when burning sawdust, was determined to be in the range of φ = 0.71-0.75, with CO2 as the carrier gas, and at φ ≈ 0.75, with N2 as the carrier gas. Ash content analysis showed that the extent of carbon burnout was low, which is thought to be due to the relatively short furnace residence times. © 2010 American Chemical Society.Bassam. B. Dally, Sung Hoon Shim, Richard. A. Craig, Peter J. Ashman and George G. Szeg