Study of effect on tensile stress test from distortion of fibre laser welded Ti6Al4V using FEA

Distortion is one type of defect in the weld, which is troublesome for some reasons, especially in thin plate welding. Distortion was found in fibre laser welding processing for 0.7mm thickness Ti6Al4V plate. The purpose of this paper is to understand and evaluate the effect of distortion on stress level by FEA and tensile test. A group of 0.7mm Ti6Al4V plates welded using continuous wave fibre laser. FEA models were established for fibre laser welded Ti6Al4V in abaqus 6.7. © (2011) Trans Tech Publications.

A micro gas turbines for UK domestic combined heat and power

Various micro-radial compressor configurations were investigated using one-dimensional meanline and computational fluid dynamics (CFD) techniques for use in a micro gas turbine (MGT) domestic combined heat and power (DCHP) application. Blade backsweep, shaft speed, and blade height were varied at a constant pressure ratio. Shaft speeds were limited to 220 000 r/min, to enable the use of a turbocharger bearing platform. Off-design compressor performance was established and used to determine the MGT performance envelope; this in turn was used to assess potential cost and environmental savings in a heat-led DCHP operating scenario within the target market of a detached family home. A low target-stage pressure ratio provided an opportunity to reduce diffusion within the impeller. Critically for DCHP, this produced very regular flow, which improved impeller performance for a wider operating envelope. The best performing impeller was a low-speed, 170 000 r/min, low-backsweep, 15° configuration producing 71.76 per cent stage efficiency at a pressure ratio of 2.20. This produced an MGT design point system efficiency of 14.85 per cent at 993 W, matching prime movers in the latest commercial DCHP units. Cost and CO2 savings were 10.7 per cent and 6.3 per cent, respectively, for annual power demands of 17.4 MWht and 6.1 MWhe compared to a standard condensing boiler (with grid) installation. The maximum cost saving (on design point) was 14.2 per cent for annual power demands of 22.62 MWht and 6.1 MWhe corresponding to an 8.1 per cent CO2 saving. When sizing, maximum savings were found with larger heat demands. When sized, maximum savings could be made by encouraging more electricity export either by reducing household electricity consumption or by increasing machine efficiency.

An evaluation of the effectiveness of intervention strategies for the promotion of health and safety performance in small firms

Recognition of the contribution of small firms to the UK economy has grown considerably since 1995 when this research first began. The poor record of small firms in managing health and safety effectively has caused concern, and efforts made to improve knowledge and awareness of the target group through various initiatives have had some success. This research thesis attempts to identify the range of intervention routes and methods available to reach the target group, and to consider ways of evaluating the outcome of such efforts. Various interventions were tested with small firms, including a Workshop; use of Questionnaires; short postal Reply Slip survey; leading to a closer evaluation of a specific industry- the Licensed Trade. Attitudes and beliefs of the sample were identified, and observations carried out to consider actions taken by workers and others in the workplace. These empirical research findings were used to develop the theme of Primary and Secondary interventions intended to change behaviours, and to confirm assumptions about what small firms currently do to manage health and safety risks. Guidance for small firms was developed as a Secondary intervention tool to support Primary interventions, such as inspection or insurance provision.

Development and psychometric tests of the Chinese-version low vision quality of life questionnaire

Background/Aims: To develop and assess the psychometric validity of a Chinese language Vision Health related quality-of-life (VRQoL) measurement instrument for the Chinese visually impaired. Methods: The Low Vision Quality of Life Questionnaire (LVQOL) was translated and adapted into the Chinese-version Low Vision Quality of Life Questionnaire (CLVQOL). The CLVQOL was completed by 100 randomly selected people with low vision (primary group) and 100 people with normal vision (control group). Ninety-four participants from the primary group completed the CLVQOL a second time 2 weeks later (test-retest group). The internal consistency reliability, test-retest reliability, item-internal consistency, item-discrimination validity, construct validity and discriminatory power of the CLVQOL were calculated. Results: The review committee agreed that the CLVQOL replicated the meaning of the LVQOL and was sensitive to cultural differences. The Cronbach's α coefficient and the split-half coefficient for the four scales and total CLVQOL scales were 0.75-0.97. The test-retest reliability as estimated by the intraclass correlations coefficient was 0.69-0.95. Item-internal consistency was >0.4 and item-discrimination validity was generally <0.40. The Varimax rotation factor analysis of the CLVQOL identified four principal factors. the quality-of-life rating of four subscales and the total score of the CLVQOL of the primary group were lower than those of the Control group, both in hospital-based subjects and community-based subjects. Conclusion: The CLVQOL Chinese is a culturally specific vision-related quality-of-life measure instrument. It satisfies conventional psychometric criteria, discriminates visually healthy populations from low vision patients and may be valuable in screening the local community as well as for use in clinical practice or research. © Springer 2005.

The macular mapping test:a reliability study

Background: Age-related macular degeneration (ARMD) is the leading cause of visual disability in people over 60 years of age in the developed world. The success of treatment deteriorates with increased latency of diagnosis. The purpose of this study was to determine the reliability of the macular mapping test (MMT), and to investigate its potential as a screening tool. Methods: The study population comprised of 31 healthy eyes of 31 participants. To assess reliability, four macular mapping test (MMT) measurements were taken in two sessions separated by one hour by two practitioners, with reversal of order in the second session. MMT readings were also taken from 17 age-related maculopathy (ARM), and 12 AMD affected eyes. Results: For the normal cohort, average MMT scores ranged from 85.5 to 100.0 MMT points. Scores ranged from 79.0 to 99.0 for the ARM group and from 9.0 to 92.0 for the AMD group. MMT scores were reliable to within ± 7.0 points. The difference between AMD affected eyes and controls (z = 3.761, p = < 0.001) was significant. The difference between ARM affected eyes and controls was not significant (z = -0.216, p = 0.829). Conclusion: The reliability data shows that a change of 14 points or more is required to indicate a clinically significant change. This value is required for use of the MMT as an outcome measure in clinical trials. Although there was no difference between MMT scores from ARM affected eyes and controls, the MMT has the advantage over the Amsler grid in that it uses a letter target, has a peripheral fixation aid, and it provides a numerical score. This score could be beneficial in office and home monitoring of AMD progression, as well as an outcome measure in clinical research. © 2005 Bartlett et al; licensee BioMed Central Ltd.

Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and cost-effectiveness

OBJECTIVE: To determine the accuracy, acceptability and cost-effectiveness of polymerase chain reaction (PCR) and optical immunoassay (OIA) rapid tests for maternal group B streptococcal (GBS) colonisation at labour. DESIGN: A test accuracy study was used to determine the accuracy of rapid tests for GBS colonisation of women in labour. Acceptability of testing to participants was evaluated through a questionnaire administered after delivery, and acceptability to staff through focus groups. A decision-analytic model was constructed to assess the cost-effectiveness of various screening strategies. SETTING: Two large obstetric units in the UK. PARTICIPANTS: Women booked for delivery at the participating units other than those electing for a Caesarean delivery. INTERVENTIONS: Vaginal and rectal swabs were obtained at the onset of labour and the results of vaginal and rectal PCR and OIA (index) tests were compared with the reference standard of enriched culture of combined vaginal and rectal swabs. MAIN OUTCOME MEASURES: The accuracy of the index tests, the relative accuracies of tests on vaginal and rectal swabs and whether test accuracy varied according to the presence or absence of maternal risk factors. RESULTS: PCR was significantly more accurate than OIA for the detection of maternal GBS colonisation. Combined vaginal or rectal swab index tests were more sensitive than either test considered individually [combined swab sensitivity for PCR 84% (95% CI 79-88%); vaginal swab 58% (52-64%); rectal swab 71% (66-76%)]. The highest sensitivity for PCR came at the cost of lower specificity [combined specificity 87% (95% CI 85-89%); vaginal swab 92% (90-94%); rectal swab 92% (90-93%)]. The sensitivity and specificity of rapid tests varied according to the presence or absence of maternal risk factors, but not consistently. PCR results were determinants of neonatal GBS colonisation, but maternal risk factors were not. Overall levels of acceptability for rapid testing amongst participants were high. Vaginal swabs were more acceptable than rectal swabs. South Asian women were least likely to have participated in the study and were less happy with the sampling procedure and with the prospect of rapid testing as part of routine care. Midwives were generally positive towards rapid testing but had concerns that it might lead to overtreatment and unnecessary interference in births. Modelling analysis revealed that the most cost-effective strategy was to provide routine intravenous antibiotic prophylaxis (IAP) to all women without screening. Removing this strategy, which is unlikely to be acceptable to most women and midwives, resulted in screening, based on a culture test at 35-37 weeks' gestation, with the provision of antibiotics to all women who screened positive being most cost-effective, assuming that all women in premature labour would receive IAP. The results were sensitive to very small increases in costs and changes in other assumptions. Screening using a rapid test was not cost-effective based on its current sensitivity, specificity and cost. CONCLUSIONS: Neither rapid test was sufficiently accurate to recommend it for routine use in clinical practice. IAP directed by screening with enriched culture at 35-37 weeks' gestation is likely to be the most acceptable cost-effective strategy, although it is premature to suggest the implementation of this strategy at present.

Overall justice, work group identification and work outcomes:test of moderated mediation process

This study examined an integrated model of the antecedents and outcomes of organisational and overall justice using a sample of Indian Call Centre employees (n = 458). Results of structural equation modelling (SEM) revealed that the four organisational justice dimensions relate to overall justice. Further, work group identification mediated the influence of overall justice on counterproductive work behaviors, such as presenteeism and social loafing, while conscientiousness was a significant moderator between work group identification and presenteeism and social loafing. Theoretical and practical implications are discussed.

Uncovering the root cause of ethnic difference in ability testing:differential test functioning, test familiarity and trait optimism as explanations of ethnic group differences

The present research represents a coherent approach to understanding the root causes of ethnic group differences in ability test performance. Two studies were conducted, each of which was designed to address a key knowledge gap in the ethnic bias literature. In Study 1, both the LR Method of Differential Item Functioning (DIF) detection and Mixture Latent Variable Modelling were used to investigate the degree to which Differential Test Functioning (DTF) could explain ethnic group test performance differences in a large, previously unpublished dataset. Though mean test score differences were observed between a number of ethnic groups, neither technique was able to identify ethnic DTF. This calls into question the practical application of DTF to understanding these group differences. Study 2 investigated whether a number of non-cognitive factors might explain ethnic group test performance differences on a variety of ability tests. Two factors – test familiarity and trait optimism – were able to explain a large proportion of ethnic group test score differences. Furthermore, test familiarity was found to mediate the relationship between socio-economic factors – particularly participant educational level and familial social status – and test performance, suggesting that test familiarity develops over time through the mechanism of exposure to ability testing in other contexts. These findings represent a substantial contribution to the field’s understanding of two key issues surrounding ethnic test performance differences. The author calls for a new line of research into these performance facilitating and debilitating factors, before recommendations are offered for practitioners to ensure fairer deployment of ability testing in high-stakes selection processes.