Eng C.H.,Singapore Technologies Kinetics Ltd |
Jenn D.C.,Naval Postgraduate School, Monterey |
Broadston R.,Naval Postgraduate School, Monterey
IEEE Antennas and Propagation Magazine | Year: 2010
Many commercial demodulator boards have an inherent problem of dc offset, due to their direct down-conversion architecture. It is necessary to measure the dc offsets and to compensate for them when the demodulators are used in a system such as a digital phased array. An automated calibration station is described, which uses a combination of commercial off-the-shelf hardware and software to generate RF signals that are used to plot the demodulator I and Q circle and to determine the offset. This automated station has improvements over a manual calibration, such as ease of use, shorter calibration time, accuracy, and repeatability. © 2006 IEEE.
Cizek J.,Brno University of Technology |
Man O.,Brno University of Technology |
Roupcova P.,Brno University of Technology |
Loke K.,Singapore Technologies Kinetics Ltd |
Dlouhy I.,Brno University of Technology
Surface and Coatings Technology | Year: 2015
Four blends of Al powder containing different amounts of Ti were deposited onto Ti-46Al-7Nb substrates as oxidation-protection layers using low-pressure cold spray. The coating morphology and chemical composition were assessed. Optimized heat treatment in protective atmosphere was carried out in order to induce formation of intermetallic phases within the deposits. The specimens were then subjected to 950. °C exposure for 100, 250, and 500. h and their oxidation performance was monitored using the gravimetric method. It was found that the oxidation rate of the coating-protected specimens was substantially reduced (an increase in the weight gain of 1.37mg·cm-2 after 500h of specimen with Al coating) as compared to their uncoated counterparts (1.21 mg ·cm-2 after 50h at 900 °C). The oxidation rates increased with increasing content of Ti in the coatings. Substantial changes of the coating integrity were recorded after the long-term oxidation testing. © 2014 Elsevier B.V.
Koh P.K.,SIM University Singapore |
Cheang P.,SIM University Singapore |
Loke K.,Singapore Technologies Kinetics Ltd |
Yu S.C.M.,Nanyang Technological University |
Ang S.M.,Swinburne University of Technology
Proceedings of the International Thermal Spray Conference | Year: 2012
Deposition of amorphous aluminium powder using cold spray technology as a corrosion prevention measure was studied. Amorphous aluminium (Al-Ni-Ce) powder was successfully deposited on 7000-series aluminium substrates using cold spray parameters of 1.7 MPa under compressed air and temperature of 450°C. The coatings were subjected to tensile bond strength measurement and comparative studies with cold sprayed pure Al6061 coatings were conducted. The results obtained showed that the amorphous aluminium coatings exhibited better adhesive strength. In addition, salt-water immersion test was conducted. The Al-Ni-Ce coating not only demonstrated better corrosion resistance but also exhibited evidence of passivation of surface imperfections such as scratches in the coatings.
Ji X.,Nanyang Technological University |
Khatri A.M.,Nanyang Technological University |
Chia E.S.,DSO National Laboratories |
Cha R.K.,Singapore Technologies Kinetics Ltd |
And 2 more authors.
Journal of Composite Materials | Year: 2014
This article deals with the computation of effective elastic properties of braided textile composites assisted by finite element analysis. In this approach, dynamic representative unit cells are first constructed to model typical geometry of braided textile preform. After establishing the elastic properties of braiding yarns, the effective Young's moduli, shear moduli and Poisson's ratios corresponding to varying braiding angles are obtained by analysing these geometric models of preform with the help of the commercial finite element analysis code Abaqus. Effects of fibre volume fraction on the elastic properties of both biaxial and triaxial composite unit cells are also examined. Finally, the bending behaviour of a simply supported beam with braided composite skin is evaluated via the finite element analysis assisted multi-scale modelling, which is further verified experimentally. The predicted results were compared favourably with the experiment, backing the accuracy of the proposed modelling approach. © The Author(s) 2013.
Tan S.C.,National University of Singapore |
Tan S.C.,Singapore Technologies Kinetics Ltd |
Kwok R.W.O.,Singapore Technologies Kinetics Ltd |
Chan J.K.W.,Singapore Technologies Kinetics Ltd |
Loh K.P.,National University of Singapore
Composites Part B: Engineering | Year: 2016
We demonstrate a facile and general technique for the orientation of nanoplatelet fillers dispersed in adhesives for tensile strength enhancement of compressed fibre-reinforced plastic (FRP) composites. Polyurethane adhesives filled with a selected exfoliated graphite nanoplatelet (MexGnP-8) powder at concentration range of 0-0.75 wt% were prepared. The same adhesives were used to fabricate compressed FRP composites in which the mechanical properties were assessed and found to be inconsistent with the findings from the tests conducted on uncompressed FRP composites and the filled adhesives. Only the polyurethane adhesive filled with 0.25 wt% MexGnP-8 had tensile strength higher than that of the neat adhesive, and the uncompressed FRP composites have similar results. However, all the compressed FRP composites fabricated with the polyurethane adhesive filled with MexGnP-8 between the concentration range of 0-0.75 wt% had greater tensile strengths than the compressed FRP fabricated with the neat adhesive. Compression has been found to induce orientation of MexGnP-8 and resulted in tensile strength enhancement in the FRP. © 2016 Elsevier Ltd. All rights reserved.