1,097 research outputs found

    Direct processing of structural thermoplastic composites using rapid isothermal stamp forming

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    A novel rapid isothermal stamp forming process is proposed which enables the rapid manufacture of structural thermoplastic composite laminate parts directly from multilayer hybrid fabrics comprising stitched unidirectional carbon fibre-thermoplastic polymer veil. The process employs rapid-response variothermal tooling, allowing macro-scale (fabric forming/draping) and micro-scale (fibre wetting/laminate consolidation) composite material transformation processes to occur isothermally above the constituent polymer matrix melt temperature (Tm), thus manufacturing a composite component directly from a hybrid dry fabric in a single press cycle in a relatively short overall cycle time. The proposed rapid isothermal stamp forming (RISF) concept is presented, and details of the process are given along with some considerations made throughout the formulation of the process. As a result of the RISF process development work, candidate manufacturing parameters were derived, delivering parts that exhibit acceptable composite laminate microstructure and mechanical performance within a press station cycle time of 330 s

    Strain mapping and nanocrystallite size determination by neutron diffraction in an aluminum alloy (AA5083) severely plastically deformed through equal channel angular pressing

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    Six specimens of an aluminum alloy (AA-5083) extruded by Equal Channel Angular Pressing following two different routes plus a blank sample were examined with a neutron radiation of 1.5448 Å. Macrostrain maps from the (311) reflection were obtained. A clear difference about accumulated macrostrain with the extrusion cycles between the two routes is shown. The diffraction data of annealed specimens did permit to estimate crystallite sizes that range between 89 nm and 115 nm depending on the routes

    Enhancement of reliability in condition monitoring techniques in wind turbines

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    The majority of electrical failures in wind turbines occur in the semiconductor components (IGBTs) of converters. To increase reliability and decrease the maintenance costs associated with this component, several health-monitoring methods have been proposed in the literature. Many laboratory-based tests have been conducted to detect the failure mechanisms of the IGBT in their early stages through monitoring the variations of thermo-sensitive electrical parameters. The methods are generally proposed and validated with a single-phase converter with an air-cored inductive or resistive load. However, limited work has been carried out considering limitations associated with measurement and processing of these parameters in a three-phase converter. Furthermore, looking at just variations of the module junction temperature will most likely lead to unreliable health monitoring as different failure mechanisms have their own individual effects on temperature variations of some, or all, of the electrical parameters. A reliable health monitoring system is necessary to determine whether the temperature variations are due to the presence of a premature failure or from normal converter operation. To address this issue, a temperature measurement approach should be independent from the failure mechanisms. In this paper, temperature is estimated by monitoring an electrical parameter particularly affected by different failure types. Early bond wire lift-off is detected by another electrical parameter that is sensitive to the progress of the failure. Considering two separate electrical parameters, one for estimation of temperature (switching off time) and another to detect the premature bond wire lift-off (collector emitter on-state voltage) enhance the reliability of an IGBT could increase the accuracy of the temperature estimation as well as premature failure detection

    Inkjet printed TiO2 nanoparticles from aqueous solutions for dye sensitized solar cells (DSSCs)

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    This is the accepted version of the following article: Cherrington, R., Hughes, D. J., Senthilarasu, S. and Goodship, V. (2015), Inkjet-Printed TiO2 Nanoparticles from Aqueous Solutions for Dye-Sensitized Solar Cells (DSSCs). Energy Technology., which has been published in final form at http://dx.doi.org/10.1002/ente.201500096This work reports on the formulation of suitable ink for inkjet printing of TiO2 by investigating the critical parame- ters of particle size, pH, viscosity, and stability. Aqueous sus- pensions of TiO2 nanoparticles (Degussa, P25) were pre- pared with the addition of 25 wt % polyethylene glycol 400 as a humectant to minimize drying at the printer nozzles and reduce the likelihood of nozzle blockage. The inkjet-printed TiO2 layers were assembled into dye-sensitized solar cells. The current–voltage (I–V) characteristics were measured under one sun (air mass 1.5, 100 mW cm 2) using a source meter (Model 2400, Keithley Instrument, Inc.), and the active area of the cell was 0.25 cm2. The inkjet-printed TiO2 photoanode produced a device with a short-circuit current (Isc) of 9.42 mA cm 2, an open-circuit voltage (Voc) of 0.76 V, and a fill factor (FF) of 0.49, resulting in a power conversion efficiency (PCE) of 3.50 %.Engineering and Physical Sciences Research Council (EPSRC

    The influence of cultivar, environment and nutrition management onwheat quality in the high rainfall zone of south west, Western Australia

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    The high rainfall zone (HRZ) of south west Western Australian (WA) has traditionally been dominated by livestock industries. However, a reduction in wool price throughout the 1990’s has stimulated a transition to farm systems that contain an increasing proportion of annual cropping enterprises. The HRZ, compared to traditional wheat belt areas of WA, has higher rainfall and a longer, cooler growing season. Potential grain yields as determined by seasonal rainfall are not often achieved because of inadequate nutrition and other constraints such as water-logging and disease. Substantial research has been conducted in the HRZ focusing on increasing grain yield to limits set by seasonal rainfall. Research on wheat grain quality characteristics, however, has been limited. The aim of this research was to examine the influence of cultivar, environment and nutrition management on wheat quality characteristics in the HRZ of south west WA and to examine the stability of cultivar performance in relation to site and season.A series of experiments was grown at Moora and Williams in 2005, 2006 and 2007. Sites were chosen to represent contrasting environments within the HRZ. Moora, the more northern site typically has higher temperatures and lower rainfall compared to Williams. Eight cultivars were selected, two that are accepted into each of the commercial quality grades (Australian Prime Hard APH, Australian Hard AH, Australian Premium White APW and Durum). Three levels of nutrition management were applied ‘control’, ‘grower’ and ‘researcher’ and were chosen to simulate low, medium and high fertiliser rates likely to be used by growers in the HRZ. Treatments effects were measured for grain yield, physical grain quality characteristics and grain protein quality charactertics as determined by a mixograph.Environment was responsible for almost 90% of the variation for grain yield, screenings, Hagberg falling number and milling yield. Management of crop nutrition was the principal source of variation for grain protein quantity (48%), dough strength as measured by mixograph area below the curve (52%) and water absorption (46%-52%). It was often the second greatest source of variation for other characteristics measured in this study. Cultivar was the predominant source of variation for dough strength as measured by mixograph initial build-up (46%) and dough stability (47%), but it had only a small affect on grain yield and grain protein quantity (2%).The increase in nutrition resulted in a significant increase in water absorption and dough strength and a trend towards increasing dough stability. An increase in gliadin and glutenin proteins is thought to be responsible for this result. The low nutritional status of soils in the HRZ not only restricts grain yield but grain protein quantity and quality. The impact of nutrition management on grain yield and quality characteristics as shown in these experiments should be considered by breeders, agronomists and marketers when interpreting experimental results. Furthermore, the results indicate that the nutritional management of breeding experiments should be based on a sound methodical approach, incorporating a combination of soil test results, grain yield potential and seasonal monitoring for the environment in question and not be simply based on levels that are either ‘district practice’ or ‘non-limiting’.This study has also identified statistically significant differences between cultivars for stability of grain yield and grain protein quality. Four cultivars (three bread wheat and one durum wheat) were characterised as having dynamic stability, which is described as the ability to respond to an environment in a predictable way. In addition, three cultivars were assessed as having static stability, unchanged performance regardless of any variation in environment for water absorption. This information indicates that assessment of stability of cultivars during the early stages of testing can assist commercial buyers in sourcing suitable grain quality and even that there may be potential to breed cultivars with improved static or dynamic stability.If it is assumed that the Australian wheat industry cannot compete in a global wheat market based on the relatively small level of production. Then the future of the industry lies in producing the qualities required by specific markets. Realizing the impact of nutrition management on quality characteristics in the HRZ of WA will be a positive step towards a sustainable industry

    The formation of a nanohybrid shish-kebab (NHSK) structure in melt-processed composites of poly (ethylene terephthalate) (PET) and multi-walled carbon nanotubes (MWCNTs)

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    The combination of synchrotron Small- and Wide-Angle X-ray scattering (SAXS/WAXS), and thermal analysis was used to follow the evolution of crystalline morphology and crystallization kinetics in a series of melt-processed composites of poly(ethylene terephthalate) (PET) and multiwall carbon nanotubes (MWCNT). The as-extruded PET-MWCNT composites underwent both hot and cold isothermal crystallizations where a final oriented nanohybrid shish-kebab (NHSK) crystalline structure was observed. An oriented NHSK structure was seen to persist even after melting and recrystallization of the composites. From the scattering data, we propose a model whereby the oriented MWCNTs act as heterogeneous nucleation surfaces (shish) and the polymer chains wrap around them and the crystallites (kebabs) grow epitaxially outwards during crystallization. However, depending on crystallization temperature, unoriented crystallites also grow in the polymer matrix, resulting in a combination of a NHSK and lamellar morphology. In contrast, the neat PET homopolymer showed the sporadic nucleation of a classic unoriented lamellar structure under the same isothermal crystallization conditions. These results provide a valuable insight into the distinctive modification of the crystalline morphology of melt-processed polymer-MWCNT composites prior to any secondary processing, having a significant impact on the use of MWCNTs as fillers in the processing and modification of the physical and mechanical properties of engineering polymers

    Strengths-based Programming for First Nations Youth in Schools: Building Engagement Through Healthy Relationships and Leadership Skills

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    FirstNationsyouthinCanadademonstratedisproportionatelyhighratesofnegative behaviors such as violence, substance abuse, and leaving school early. An understanding of historical context and current environment helps explain these patterns. Providing culturally relevant opportunities for youth to build healthy relationships and leadership skills has the potential to increase youth engagement. Over the past four years our multidisciplinary team of researchers, educators, program developers, and community leaders have worked together to develop a number of school-based initiatives that focus on increasing youth engagement through building on strengths and the promotion of healthy relationships. Specific strategies include peer mentoring, a credit-based academic course, and transition conferences for grade 8 students. This article describes these initiatives and some of the early successes and challenges we have faced in the design and implementation of them. Preliminary evidence is presented to support the contention that these initiatives increase youth engagement

    Novel class of Bi(iii) hydroxamato complexes: synthesis, urease inhibitory activity and activity against H. pylori.

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    Reaction of Bi(NO3)3 with benzohydroxamic acid (Bha) and salicylhydroxamic acid (Sha) gives the novel Bi(iii) complexes [Bi2(Bha-1H)2(μ-Bha-1H)2(η(2)-NO3)2] () and [Bi6(CH3OH)2(η(1)-NO3)2(η(2)-NO3)(OH2)2(Sha-1H)12](NO3)2 (). X-ray crystal structure of reveals two hydroxamato coordination modes; bidentate bridging (O, O\u27) and bidentate non-bridging (O, O\u27) and of reveals one coordination mode; bidentate bridging (O, O\u27). , specifically designed to and demonstrated to inhibit the activity of urease, exhibits excellent antibacterial activity against three strains of Helicobacter pylori with MIC ≥ 16 μg mL(-1)

    Optimisation and Management of Energy Generated by a Multifunctional MFC-Integrated Composite Chassis for Rail Vehicles

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    With the advancing trend towards lighter and faster rail transport, there is an increasing interest in integrating composite and advanced multifunctional materials in order to infuse smart sensing and monitoring, energy harvesting and wireless capabilities within the otherwise purely mechanical rail structures and the infrastructure. This paper presents a holistic multiphysics numerical study, across both mechanical and electrical domains, that describes an innovative technique of harvesting energy from a piezoelectric micro fiber composites (MFC) built-in composite rail chassis structure. Representative environmental vibration data measured from a rail cabin have been critically leveraged here to help predict the actual vibratory and power output behaviour under service. Time domain mean stress distribution data from the Finite Element simulation were used to predict the raw AC voltage output of the MFCs. Conditioned power output was then calculated using circuit simulation of several state-of-the-art power conditioning circuits. A peak instantaneous rectified power of 181.9 mW was obtained when eight-stage Synchronised Switch Harvesting Capacitors (SSHC) from eight embedded MFCs were located. The results showed that the harvested energy could be sufficient to sustain a self-powered structural health monitoring system with wireless communication capabilities. This study serves as a theoretical foundation of scavenging for vibrational power from the ambient state in a rail environment as well as to pointing to design principles to develop regenerative and power neutral smart vehicles
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