7,638 research outputs found

    Artificial neural network prediction of weld distortion rectification using a travelling induction coil

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    An experimental investigation has been carried out to determine the applicability of an induction heating process with a travelling induction coil for the rectification of angular welding distortion. The results obtained from experimentation have been used to create artificial neural network models with the ability to predict the welding induced distortion and the distortion rectification achieved using a travelling induction coil. The experimental results have shown the ability to reduce the angular distortion for 8 mm and 10 mm thick DH36 steel plate and effectively eliminate the distortion on 6 mm thick plate. Results for 6 mm plate also show the existence of a critical induction coil travel speed at which maximum corrective bending occurs. Artificial neural networks have demonstrated the ability to predict the final distortion of the plate after both welding and induction heating. The models have also been used as a tool to determine the optimum speed to minimise the resulting distortion of steel plate after being subjected to both welding and induction heating processes

    Techno-economic evaluation of reducing shielding gas consumption in GMAW whilst maintaining weld quality

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    A new method of supplying shielding gases in an alternating manner has been developed to enhance the efficiency of conventional gas metal arc welding (GMAW). However, the available literature on this advanced joining process is very sparse and no cost evaluation has been reported to date. In simple terms, the new method involves discretely supplying two different shielding gases to the weld pool at predetermined frequencies which creates a dynamic action within the liquid pool. In order to assess the potential benefits of this new method from a technical and cost perspective, a comparison has been drawn between the standard shielding gas composition of Ar/20%CO2, which is commonly used in UK and European shipbuilding industries for carbon steels, and a range of four different frequencies alternating between Ar/20%CO2 and helium. The beneficial effects of supplying the weld shielding gases in an alternating manner were found to provide attractive benefits for the manufacturing community. For example, the present study showed that compared with conventional GMAW, a 17 per cent reduction in total welding cost was achieved in the case of the alternating gas method and savings associated with a reduction in the extent of post-weld straightening following plate distortion were also identified. Also, the mechanical properties of the alternating case highlighted some marginal improvements in strength and Charpy impact toughness which were attributed to a more refined weld microstructure

    Limitation of Life-Sustaining Care in the Critically Ill: A Systematic Review of the Literature

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    When life-sustaining treatments (LST) are no longer effective or consistent with patient preferences, limitations may be set so that LSTs are withdrawn or withheld from the patient. Many studies have examined the frequency of limitations of LST in intensive care unit (ICU) settings in the past 30 years. This systematic review describes variation and patient characteristics associated with limitations of LST in critically ill patients in all types of ICUs in the United States. A comprehensive search of the literature was performed by a medical librarian between December 2014 and April 2017. A total of 1,882 unique titles and abstracts were reviewed, 113 were selected for article review, and 36 studies were fully reviewed. Patient factors associated with an increased likelihood of limiting LST included white race, older age, female sex, poor preadmission functional status, multiple comorbidities, and worse illness severity score. Based on several large, multicenter studies, there was a trend toward a higher frequency of limitation of LST over time. However, there is large variability between ICUs in the proportion of patients with limitations and on the proportion of deaths preceded by a limitation. Increases in the frequency of limitations of LST over time suggests changing attitudes about aggressive end-of-life-care. Limitations are more common for patients with worse premorbid health and greater ICU illness severity. While some differences in the frequency of limitations of LST may be explained by personal factors such as race, there is unexplained wide variability between units

    Columnar and lamellar phases in attractive colloidal systems

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    In colloidal suspensions, the competition between attractive and repulsive interactions gives rise to a rich and complex phenomenology. Here, we study the equilibrium phase diagram of a model system using a DLVO interaction potential by means of molecular dynamics simulations and a thermodynamical approach. As a result, we find tubular and lamellar phases at low volume fraction. Such phases, extremely relevant for designing new materials, may be not easily observed in the experiments because of the long relaxation times and the presence of defects.Comment: 5 pages, 5 figure

    Light scattering and phase behavior of Lysozyme-PEG mixtures

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    Measurements of liquid-liquid phase transition temperatures (cloud points) of mixtures of a protein (lysozyme) and a polymer, poly(ethylene glycol) (PEG) show that the addition of low molecular weight PEG stabilizes the mixture whereas high molecular weight PEG was destabilizing. We demonstrate that this behavior is inconsistent with an entropic depletion interaction between lysozyme and PEG and suggest that an energetic attraction between lysozyme and PEG is responsible. In order to independently characterize the lysozyme/PEG interactions, light scattering experiments on the same mixtures were performed to measure second and third virial coefficients. These measurements indicate that PEG induces repulsion between lysozyme molecules, contrary to the depletion prediction. Furthermore, it is shown that third virial terms must be included in the mixture's free energy in order to qualitatively capture our cloud point and light scattering data. The light scattering results were consistent with the cloud point measurements and indicate that attractions do exist between lysozyme and PEG.Comment: 5 pages, 2 figures, 1 tabl

    An assessment of the Hua Oranga outcome instrument and comparison to other outcome measures in an intervention study with Maori and Pacific people following stroke

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    The Hua Oranga instrument, developed for Maori people with mental illness, showed good responsiveness and adequate psychometric properties in Maori and Pacific people after stroke. Its simplicity, relative brevity, minimal cost and adequate psychometric properties should favour its use in future studies with both Maori and Pacific people. Suggestions are made for refinements to the measure. These should be tested in a new population before Hua Oranga is recommended for general use in a clinical setting. Abstract Aim Health outcomes research for Maori has been hampered by the lack of adequately validated instruments that directly address outcomes of importance to Maori, framed by a Maori perspective of health. Hua Oranga is an outcome instrument developed for Maori with mental illness that uses a holistic view of Maori health to determine improvements in physical, mental, spiritual and family domains of health. Basic psychometric work for Hua Oranga is lacking. We sought to explore the psychometric properties of the instrument and compare its responsiveness alongside other, more established tools in an intervention study involving Maori and Pacific people following acute stroke. Method Randomised 2x2 controlled trial of Maori and Pacific people following acute stroke with two interventions aimed at facilitating self-directed rehabilitation, and with follow-up at 12 months after randomisation. Primary outcome measures were the Physical Component Summary (PCS) and Mental Component Summary (MCS) of the Short Form 36 (SF36) at 12 months. Hua Oranga was used as a secondary outcome measure for participants at 12 months and for carers and whanau (extended family). Psychometric properties of Hua Oranga were explored using plots and correlation coefficients, principal factors analysis and scree plots. Results 172 participants were randomised, of whom 139 (80.8%) completed follow-up. Of these, 135 (97%) completed the Hua Oranga and 117 (84.2%) completed the PCS and MCS of the SF36. Eighty-nine carers completed the Hua Oranga. Total Hua Oranga scores and PCS improved significantly for one intervention group but not the other. Total Hua Oranga scores for carers improved significantly for both interventions. Total Hua Oranga score correlated moderately with the PCS (correlation coefficient 0.55, p<0.001). Factor analysis suggested that Hua Oranga measures two and not four factors; one 'physical-mental' and one 'spiritual-family'. Conclusion The Hua Oranga instrument, developed for Maori people with mental illness, showed good responsiveness and adequate psychometric properties in Maori and Pacific people after stroke. Its simplicity, relative brevity, minimal cost and adequate psychometric properties should favour its use in future studies with both Maori and Pacific people. Suggestions are made for refinements to the measure. These should be tested in a new population before Hua Oranga is recommended for general use in a clinical setting
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