Engineering

Publication Search Results

Now showing 1 - 10 of 80
  • (2001) Diessel, Oliver; Milne, George
    Journal Article
    Reconfigurable computers based on field programmable gate array technology allow applications to be realised directly in digital logic. The inherent concurrency of hardware distinguishes such computers from microprocessor-based machines in which the concurrency of the underlying hardware is fixed and abstracted from the programmer by the software model. However, reconfigurable logic provides us with the potential to exploit `real` concurrency. It is therefore interesting to know how to exploit this concurrency, how to model concurrent computations, and which languages allow this dynamic hardware to be programmed most effectively. The purpose of this work is to describe an FPGA compiler for the Circal process algebra. In so doing, the authors demonstrate that behavioural descriptions expressed in a process algebraic language can be readily and intuitively compiled to reconfigurable logic and that this contributes to the goal of discovering appropriate high-level languages for run-time reconfiguration.

  • (2008) Song, Dengyuan; Cho, E.-C; Conibeer, Gavin; Huang, Yidan; Flynn, Christopher; Green, Martin
    Journal Article
    Amorphous Si1-xCx /SiC multilayer films were prepared by alternating deposition of Si-rich Si1-xCx and near-stoichiometric SiC layers by using magnetron sputtering. The as-deposited films were annealed at different temperatures Ta from 800 to 1100 oC. The influence of Ta and Si content in the Si-rich layer on the layered structural stability and on the formation of Si and/or SiC nanocrystals NCs is investigated by a variety of analytical techniques, including x-ray reflectivity XRR, x-ray diffraction XRD, transmission electron microscopy TEM, Raman spectroscopy, and Fourier transform infrared spectrometry FTIR. XRR showed that Si1-xCx /SiC multilayers annealed at temperatures of up to 800 oC retain their layered structure. XRD revealed that Si NCs were formed in samples with a high Si content in the Si-rich layer for Ta 800 oC. At annealing temperatures of 900 oC or greater, the formation of Si NCs was accompanied by the formation of -SiC NCs. Additionally, the formation of Si and SiC NCs was confirmed by TEM imaging and Raman spectroscopy. The Si-NC size obtained from the TEM micrographs is within the range of 3-5 nm. The -SiC NCs are smaller 2-3 nm than Si NCs. Raman analysis identified an 9 cm-1 Raman peak shift in the Si-NC peak to a lower energy with respect to that for bulk Si. FTIR Si-C bond absorption spectra exhibited narrowing of the full width at half maximum and a peak shift toward a higher wave number with increasing Ta. This behavior can be explained by an increase in order as well as an increase in the number of Si-C bonds.

  • (2007) Song, Dengyuan; Cho, E.-C; Conibeer, Gavin; Huang, Yidan; Green, Martin
    Journal Article
    Heterojunctions HJs were fabricated from p-type Si nanocrystals Si NCs embedded in a SiC matrix on an n-type crystalline Si substrate. Transmission electron microscopy revealed that Si NCs are clearly established, with sizes in the range of 3-5 nm. The HJ diodes showed a good rectification ratio of 1.0 104 at ±1.0 V at 298 K. The ideality factor, junction built-in potential, and open-circuit voltage are 1.24, 0.72 V, and 0.48 V, respectively. Measurement of temperature-dependent I-V curves in forward conduction suggests that, in the medium voltage range, junction interface recombination can be described as the dominant current transport mechanism.

  • (2007) Heiser, Gernot; Elphinstone, Kevin; Kuz, Ihor; Klein, Gerwin; Petters, Stefan
    Journal Article
    As computer systems become increasingly mission-critical, used in life-critical situations, and relied upon to protect intellectual property, operating-system reliability is becoming an ever growing concern. In the past, mission- and life-critical embedded systems consisted of simple microcontrollers running a small amount of software that could be validated using traditional and informal techniques. However, with the growth of software complexity, traditional techniques for ensuring software reliability have not been able to keep up, leading to an overall degradation of reliability. This paper argues that microkernels are the best approach for delivering truly trustworthy computer systems in the foreseeable future. It presents the NICTA operating-systems research vision, centred around the L4 microkernel and based on four core projects. The seL4 project is designing an improved API for a secure microkernel, L4, verified will produce a full formal verification of the microkernel, Potoroo combines execution-time measurements with static analysis to determine the worst case execution profiles of the kernel, and CAmkES provides a component architecture for building systems that use the microkernel. Through close collaboration with Open Kernel Labs (a NICTA spinoff) the research output of these projects will make its way into products over the next few years.

  • (2007) Kuz, Ihor; Liu, Yan; Gorton, Ian; Heiser, Gernot
    Journal Article
    Component-based software engineering promises to provide structure and reusability to embedded-systems software. At the same time, microkernel-based operating systems are being used to increase the reliability and trustworthiness of embedded systems. Since the microkernel approach to designing systems is partially based on the componentisation of system services, component-based software engineering is a particularly attractive approach to developing microkernel-based systems. While a number of widely used component architectures already exist, they are generally targeted at enterprise computing rather than embedded systems. Due to the unique characteristics of embedded systems, a component architecture for embedded systems must have low overhead, be able to address relevant non-functional issues, and be flexible to accommodate application specific requirements. In this paper we introduce a component architecture aimed at the development of microkernel-based embedded systems. The key characteristics of the architecture are that it has a minimal, low-overhead, core but is highly modular and therefore flexible and extensible. We have implemented a prototype of this architecture and confirm that it has very low overhead and is suitable for implementing both system-level and application level services.

  • (2001) Peters, G; Lundie, S
    Journal Article
    Biosolids are the reusable organic materials removed from sewage during treatment. Different options for biosolids handling in Sydney, Australia, are compared using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario one - local dewatering and lime-amendment; scenario two - a centralized drying system) and of technologies (thermal drying versus lime-amendment). The environmental issues addressed are energy consumption, global warming potential (GWP) and human toxicity potential (HTP). Scenario two would consume 24% more energy than scenario one. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the dryer. A centralized system using the same technologies as scenario one has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly. The assessment of technology choices showed significant differences. The ample supply of endogenous biogas at North Head Sewage Treatment Plant (STP) for the drying option for allows reductions, relative to the lime amendment option, of 68% in energy consumption, 45% in GWP and 23% in HTP. Technology choices have more significant influence on the environmental profile of biosolids processing than the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coal-sourced electrical energy, minimization of trucking distances and raising the solids content of biosolids products.

  • (2007) Zhu, Liming; Bui, N; Liu, Yan; Gorton, Ian
    Journal Article
    This paper describes an approach for generating customized benchmark suites from a software architecture description following a Model Driven Architecture (MDA) approach. The benchmark generation and performance data capture tool implementation (MDABench) is based on widely used open source MDA frameworks. The benchmark application is modeled in UML and generated by taking advantage of the existing community-maintained code generation `cartridges` so that current component technology can be exploited. We have also tailored the UML 2.0 Testing Profile so architects can model the performance testing and data collection architecture in a standards compatible way. We then extended the MDA framework to generate a load testing suite and automatic performance measurement infrastructure. This greatly reduces the effort and expertise needed for benchmarking with complex component and Web service technologies while being fully MDA standard compatible. The approach complements current model-based performance prediction and analysis methods by generating the benchmark application from the same application architecture that the performance models are derived from. We illustrate the approach using two case studies based on Enterprise JavaBean component technology and Web services.

  • (2005) Zhu, Liming; Aurum, Aybuke; Jeffery, David; Gorton, Ian
    Journal Article
    Software architecture evaluation involves evaluating different architecture design alternatives against multiple quality-attributes. These attributes typically have intrinsic conflicts and must be considered simultaneously in order to reach a final design decision. AHP (Analytic Hierarchy Process), an important decision making technique, has been leveraged to resolve such conflicts. AHP can help provide an overall ranking of design alternatives. However it lacks the capability to explicitly identify the exact tradeoffs being made and the relative size of these tradeoffs. Moreover, the ranking produced can be sensitive such that the smallest change in intermediate priority weights can alter the final order of design alternatives. In this paper, we propose several in-depth analysis techniques applicable to AHP to identify critical tradeoffs and sensitive points in the decision process. We apply our method to an example of a real-world distributed architecture presented in the literature. The results are promising in that they make important decision consequences explicit in terms of key design tradeoffs and the architecture`s capability to handle future quality attribute changes. These expose critical decisions which are otherwise too subtle to be detected in standard AHP results.

  • (2006) Ho, Minh; Allinson, G; Wiley, Dianne
    Journal Article
    The sequestration of CO2 as a greenhouse mitigation option is becoming an increasingly important priority for industry. Theoretically membrane based CO2 removal systems have the potential to provide a cost effective, low maintenance approach for removing CO2 from gas streams. This study examines the effect of membrane characteristics, operating parameters and system design on sequestration costs for any source-sink combination. The total sequestration cost per tonne of CO2 avoided for separation, transport and storage are compared for the separation of CO2 from a black coalfired power plant in Australia. The results show that the membranes currently available have a total sequestration cost of US$55-61/tonne CO2 avoided. Lower costs for CO2 avoided can be achieved using an MEA amine based absorption separation system. Gas separation membranes would require significant improvements in CO2 permeability and selectivity, together with reductions in the cost of membranes and changes to the process configurations and operating pressures to be competitive against MEA systems for the purposes of geo-sequestration.

  • (2007) Gaeta, Bruno; Malming, Harald R.; Jackson, Katherine J.L.; Bain, Michael E.; Wilson, Patrick; Collins, Andrew M.
    Journal Article
    Motivation: Immunoglobulin heavy chain (IGH) genes in mature B lymphocytes are the result of recombination of IGHV, IGHD and IGHJ germline genes, followed by somatic mutation. The correct identification of the germline genes that make up a variable VH domain is essential to our understanding of the process of antibody diversity generation as well as to clinical investigations of some leukaemias and lymphomas. Results: We have developed iHMMune-align, an alignment program that uses a hidden Markov model (HMM) to model the processes involved in human IGH gene rearrangement and maturation. The performance of iHMMune-align was compared to that of other immunoglobulin gene alignment utilities using both clonally related and randomly selected IGH sequences. This evaluation suggests that iHMMune-align provides a more accurate identification of component germline genes than other currently available IGH gene characterization programs.