Rheo-processing of an alloy specifically designed for semi-solid metal processing on the Al-Mg-Si system

Semi-solid metal (SSM) processing is a promising technology for forming alloys and composites to near-net shaped products. Alloys currently used for SSM processing are mainly conventional aluminium cast alloys. This is an obstacle to the realisation of full potential of SSM processing, since these alloys were originally designed for liquid state processing and not for semi-solid state processing. Therefore, there is a significant need for designing new alloys specifically for semi-solid state processing to fulfil its potential. In this study, thermodynamic calculations have been carried out to design alloys based on the Al-Mg-Si system for SSM processing via the ‘Rheo-route’. The suitability of a selected alloy composition has been assessed in terms of the criteria considered by the thermodynamic design process, mechanical properties and heat treatability. The newly designed alloy showed good processability with rheo-processing in terms of good control of solid fraction during processing and a reasonably large processing window. The mechanical property variation was very small and the alloy showed good potential for age hardening by T5 temper heat treatment after rheo-processing

Does Mandatory IFRS Adoption Impact Audit Fees?: Theory and Evidence

Concurrent sessions 4C - Auditing / AuditThis study examines the impact of International Financial Reporting Standards (IFRS) adoption on audit fee. We first build an analytical audit fee model to analyze the impact on audit fee of the change in both audit complexity and financial reporting quality brought about by IFRS adoption. We then develop our hypotheses based on the model’s predictions, and test the hypotheses using audit fee data from European Union countries that mandated IFRS adoption in 2005. We find that mandatory IFRS adoption has led to an increase in audit fees. We also find that the IFRS-related audit fee premium increases with the increase in audit complexity brought about by IFRS adoption, and decreases with the improvement in financial reporting quality arising from IFRS adoption. Finally, we find some evidence that the IFRS-related audit fee premium is lower in countries with strong legal regimes. Our results are robust to a variety of sensitivity checks.published_or_final_versio

Single-machine scheduling with a time-dependent learning effect

Author name used in this publication: J.-B. WangAuthor name used in this publication: C. T. NgAuthor name used in this publication: T. C. E. Cheng2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Melt conditioning by advanced shear technology (MCAST) for refining solidification microstructures

MCAST (melt conditioning by advanced shear technology) is a novel processing technology developed recently by BCAST at Brunel University for conditioning liquid metal prior to solidification processing. The MCAST process uses a twin screw mechanism to impose a high shear rate and a high intensity of turbulence to the liquid metal, so that the conditioned liquid metal has uniform temperature, uniform chemical composition and well-dispersed and completely wetted oxide particles with a fine size and a narrow size distribution. The microstructural refinement is achieved through an enhanced heterogeneous nucleation rate and an increased nuclei survival rate during the subsequent solidification processing. In this paper we present the MCAST process and its applications for microstructural refinement in both shape casting and continuous casting of light alloys

Building a Socio-technical Perspective of Community Resilience with a Semiotic Approach

Situated in the diversity and adversity of real-life contexts facing crisis situations, this research aims at boosting the resilience process within communities supported by digital and social technology. In this paper, eight community leaders in different parts of the world are invited to express their issues and wishes regarding the support of technology to face social challenges. Methods and artefacts based on the Organisational Semiotics (OS) and the Socially-Aware computing have been applied to analyse and consolidate this data. By providing both a systemic view of the problem and also leading to the identification of requirements, the analysis evidences some benefits of the OS-based approach to consolidate perspectives from different real-life scenarios towards building a socio-technical solution

An economical fabrication technique for SIMOX using plasma immersion ion implantation

Buried oxide layers in Si were fabricated using non-mass analyzed plasma immersion ion implantation (PIII). The implantation was carried out by applying a large negative bias to a Si wafer immersed in an oxygen plasma and a dose of 3×1017 cm-2 of oxygen was implanted in about three minutes. Cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RES) were used to characterize the wafers. Our results indicate that a continuous buried oxide layer with a single crystal silicon overlayer was synthesizedpublished_or_final_versio

Summation of visual motion across eye movements reflects a nonspatial decision mechanism

Human vision remains perceptually stable even though retinal inputs change rapidly with each eye movement. Although the neural basis of visual stability remains unknown, a recent psychophysical study pointed to the existence of visual feature-representations anchored in environmental rather than retinal coordinates (e.g., "spatiotopic" receptive fields; Melcher and Morrone, 2003). In that study, sensitivity to a moving stimulus presented after a saccadic eye movement was enhanced when preceded by another moving stimulus at the same spatial location before the saccade. The finding is consistent with spatiotopic sensory integration, but it could also have arisen from a probabilistic improvement in performance due to the presence of more than one motion signal for the perceptual decision. Here we show that this statistical advantage accounts completely for summation effects in this task. We first demonstrate that measurements of summation are confounded by noise related to an observer's uncertainty about motion onset times. When this uncertainty is minimized, comparable summation is observed regardless of whether two motion signals occupy the same or different locations in space, and whether they contain the same or opposite directions of motion. These results are incompatible with the tuning properties of motion-sensitive sensory neurons and provide no evidence for a spatiotopic representation of visual motion. Instead, summation in this context reflects a decision mechanism that uses abstract representations of sensory events to optimize choice behavior. Copyright © 2010 the authors

The optical microscopy with virtual image breaks a record: 50-nm resolution imaging is demonstrated

We demonstrate a new 'microsphere nanoscope' that uses ordinary SiO2 microspheres as superlenses to create a virtual image of the object in near field. The magnified virtual image greatly overcomes the diffraction limit. We are able to resolve clearly 50-nm objects under a standard white light source in both transmission and reflection modes. The resolution achieved for white light opens a new opportunity to image viruses, DNA and molecules in real time

Macroscopic invisibility cloaking of visible light

Invisibility cloaks, which used to be confined to the realm of fiction, have now been turned into a scientific reality thanks to the enabling theoretical tools of transformation optics and conformal mapping. Inspired by those theoretical works, the experimental realization of electromagnetic invisibility cloaks has been reported at various electromagnetic frequencies. All the invisibility cloaks demonstrated thus far, however, have relied on nano- or micro-fabricated artificial composite materials with spatially varying electromagnetic properties, which limit the size of the cloaked region to a few wavelengths. Here, we report the first realization of a macroscopic volumetric invisibility cloak constructed from natural birefringent crystals. The cloak operates at visible frequencies and is capable of hiding, for a specific light polarization, three-dimensional objects of the scale of centimetres and millimetres. Our work opens avenues for future applications with macroscopic cloaking devices

Thylakoid-bound ascorbate peroxidase increases resistance to salt stress and drought in Brassica napus

Reactive oxygen species (ROS) are cellular indicators of stress. In plants, they function as secondary messengers in response to environmental stress. Ascorbate peroxidase (APX) is an important enzyme directly involved in the scavenging of ROS. In this study, we aimed at identifying the function of the Brassica napus thylakoid APX (tAPX). Germination efficiencies of seeds of B. napus plants over expressing tAPX were higher than those of the seeds of the control plants; this was true both on Murashige and Skoog medium with 300 mM mannitol and with 150 mM NaCl. Further experiments showed that 40-day-old seedlings of the control plants turned yellow, withered, and subsequently died, when treated with 150 mM NaCl for 12 days. In contrast, transgenic plants over expressing tAPX survived this treatment and had at least three green leaves at the end of the experiment. When 40-dayold seedlings were withheld water for 10 days, followed by a 2 day recovery, the control plants exhibited smaller leaves and shorter stems in comparison to tAPX-over expressing plants. In addition, compared with control plants, tAPX-overexpressing plants show reduced hydrogen peroxide accumulation and increased APX relative activity. Our results demonstrate that tAPX plays an important role in resistance to salt stress and drought in plants.Key words: tAPX, transgenic lines, Brassica napus, salt stress, water deficiency