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  • 1
    Publication Date: 2018-08-21
    Description: It has been reported that backward surface waves of Tamm state can be supported by a multilayered metal–dielectric metamaterial with different partner materials, such as left-handed metamaterial or dissimilar metallic–dielectric metamaterial. In this paper, the transfer-matrix method is employed to reveal that transverse-magnetic (TM)-polarized backward surface waves can be realized by a multilayered metal–dielectric metamaterial in contact with a conventional homogenous dielectric medium. Owing to the strong optical nonlocality, the existence of such backward surface waves is proved to be dependent on the order of the metallic/dielectric layers. The relevant anomalous dispersion relations can also be dramatically engineered by varying the unit-cell thickness and the filling factor. Additionally, the distribution of the energy flow is presented to further unfold the physical mechanism of the backward surface waves. Finally, a numerical simulation of backward surface wave excited by a TM-polarized Gaussian beam based on a prism-coupled configuration is displayed.
    Electronic ISSN: 2076-3417
    Topics: Natural Sciences in General
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  • 2
    Publication Date: 2019-05-09
    Description: Rapid urbanisation and the associated infrastructure development are creating a deficit of conventional construction materials and straining the natural resources. On the other hand, municipal solid waste (MSW) disposal poses a serious environmental problem. Landfilling of MSW is both costly and polluting. Incineration of MSW to generate energy is a commonly adopted approach. However, there are concerns associated with micro pollutants emitted from the combustion process. The carbon footprint of the process and the environmental cost–benefit balancing are disputable. There is clearly a need to adopt cost-effective alternatives to treat MSW. This paper proposes the potential application of “treated” MSW as an ingredient for construction materials. The treatment process involves placing MSW in an autoclave at 150 °C with 5 bars (0.5 MPa), followed by the separation of metals, plastics and glass for recycling purposes. The end-product, which is a semi-organic mixture (referred to as ‘biomass’), is passed through a vortex-oscillation system, which makes it more uniform as a material. Compressive testing of Portland cement-based pastes containing 10% and 15% biomass shows consistency in the results, demonstrating the potential use of biomass in construction materials.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 3
    Publication Date: 2019-10-14
    Description: To address sustainability issues by facilitating the use of high-volume fly ash (HVFA) concrete in industry, this paper investigates the early age hydration properties of HVFA binders in concrete and the correlation between hydration properties and compressive strengths of the cement pastes. A new method of calculating the chemically bound water of HVFA binders was used and validated. Fly ash (FA) types used in this study were sourced from Indonesia and Australia for comparison. The water to binder (w/b) ratio was 0.4 and FA replacement levels were 40%, 50% and 60% by weight. Isothermal calorimetry tests were conducted to study the heat of hydration which was further converted to the adiabatic temperature rise. Thermo-gravimetric analysis (TGA) was employed to explore the chemically bound water (WB) of the binders. The results showed that Australian FA pastes had higher heat of hydration, adiabatic temperature rise, WB and compressive strength compared to Indonesian FA pastes. The new method of calculating chemically bound water can be successfully applied to HVFA binders. Linear correlation could be found between the WB and compressive strength.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
    Publication Date: 2020-11-27
    Description: The aircraft hydraulic system is very important for the actuation system and its failure has led to a number of catastrophic accidents in the past few years. The reasons for hydraulic loss can be leakage, blockage, and structural damage. Fortunately, the development of more electric aircraft (MEA) provides a new means of solving this difficult problem. This paper designs an active fault tolerant control (AFTC) method for MEA suffering from total hydraulic loss and actuation system failure. Two different kinds of scenarios are considered: leakage/blockage and vertical tail damage. With the application of the dissimilar redundant actuation system (DRAS) in MEA, a switching mechanism can be used to change the hydraulic actuation (HA) system into an electro-hydrostatic actuation (EHA) system when the whole hydraulic system fails. Taking account of the gap between HA and EHA, a degraded model is built. As for vertical tail damage, engine differential thrust control is adopted to help regain lateral-directional stability. The engine thrust dynamics are modeled and the mapping relationship between engine differential thrust and rudder deflection is formulated. Moreover, model reference control (MRC) and linear quadratic regulator (LQR) are used to design the AFTC method. Comparative simulation with the NASA generic transportation model (GTM) is carried out to prove the proposed strategy.
    Electronic ISSN: 2076-0825
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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