A High-gain and Low-scattering Waveguide Slot Antenna of Artificial Magnetic Conductor Octagonal Ring Arrangement

A novel design of high-gain and low-scattering waveguide slot antenna is proposed in this paper. Firstly the scattering pattern of artificial magnetic conductor (AMC) composite surface is estimated by array factor analysis method. The comparison between octagonal ring arrangement and chessboard arrangement proves that the former arrangement has the characteristic of diffuseness-like and expands the bandwidth of radar cross section (RCS) reduction. Secondly, the metal surface of waveguide slot antenna (WSA) is replaced by the octagonal ring arrangement composite surface (ORACS). The gain is improved because of spurious radiation units which are around the slot. At the same time using the phase cancellation principle, a backscatter null achieves RCS reduction in the vertical direction. Experimental results show that the novel antenna after loading with the ORACS, the gain is improved by 5dB; the bandwidth of RCS reduction (reduction greater than 10dB) is 5.24-5.92 GHz

Knowledge network modelling to support decision-making for strategic intervention in IT project-oriented change management

This is the Accepted Manuscript version of an article published by Taylor & Francis in Journal of Decision Systems on 20 March 2014, available online: http://www.tandfonline.com/doi/abs/10.1080/12460125.2014.886499.This paper focuses on knowledge management to enhance decision support systems for strategic intervention in information technology (IT) project-oriented change management. It proposes a model of change management knowledge networks (CMKNM) to support decision by tackling three existing issues: insufficient knowledge traceability based on the relationships between knowledge elements and key factors, lack of procedural knowledge to provide adequate policies to guide changes, and lack of ‘lessons learned’ documentation in knowledge bases. A qualitative method was used to investigate issues surrounding knowledge mobilisation and knowledge networks. Empirical study was undertaken with industries to test the CMKNM. Results are presented from the empirical study on the key factors influencing knowledge mobilisation in IT project-oriented change management, knowledge networks and connections. The CMKNM model allows key knowledge mobilisation factors to be aligned with each other; it also defines the connections between knowledge networks allowing knowledge to be mobilised by tracing knowledge channels to support decision.Peer reviewe

Tuning Fermi level within half-metallic gap in Co-based Heusler alloys

We systematically study the tuning of Fermi level in half-metal gap for Co-based full-Heusler alloys in the frame of first-principles calculations. It is found that the position of the Fermi level within whole gap can be specified in compounds Co2MnZ11-x Z2x (Z1 and Z2 are the III, IV or V main group element). As one of examples, Co2MnAl doped by As is further explored in detail, of which the Fermi level falls into the expectative position of the minority spin gap at proper concentration of As doping (0.5 < x < 0.75). This can effectively suppress the so-called spin-flip excitation and promise a good candidate for spintronics application

Numerical simulation of plate heat exchanger with improved mesh performance

A numerical and experimental study has been carried out on the heat transfer and fluid flow in a PHE. By means of a high-performance computing cluster, large-size and nosimplified plates can be simulated with 67 million computational cells. A new approach providing a proper clearance between two adjacent corrugated plates is proposed to improve the mesh quality around the contact points. The clearance value and the influence on the mesh quality and computational results are carefully studied. The results show that the ratio of clearance c to equivalent diameter De equals to 0.02 is proper. The CFD results agree with the experimental results with an error less than 10%. The proposed approach is proved to be effective and practical because it can increases the grid quality without losing the accurate of the results. This paper shows that CFD is a reliable tool for studying effect of various geometrical configurations on the optimum design of a PHE.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016