PurposeIn recent years, there have been many concerns about issues surrounding building maintenance, which are continually increasing. However, there is a lack of comprehensive studies on building maintenance issues, their effects and the way forward. Therefore, the purpose of this paper is to carry out a comprehensive review of building maintenance issues, their effects and the way forward. It also aims to develop a conceptual model that can support future research.Design/methodology/approachA systematic review of the literature published from 2009 to 2019 was carried out. Five relevant databases were searched, based on this study's search terms, and a narrative synthesis of the results from the included studies was carried out. Studies were eligible for inclusion if they fulfilled the inclusion criteria of this systematic review.FindingsThis study has identified and classified building maintenance issues, their effects and the way forward, and also developed a conceptual model that demonstrates the association between issues, their effects and the way forward. The way forward of the conceptual model focuses on effective management, technical capability, development of human resources and cost optimisation.Originality/valueThis paper addresses an important topic: the aspect in which it differs from existing studies is that, in the latter, the researchers studied a single sub-issue, whereas this systematic review includes a comprehensive study of building maintenance issues. Furthermore, this review has demonstrated how the way forward can moderate issues and their effects.

No abstract

In this article, a new multiband frequency reconfigurable substrate integrated waveguide cavity slot antenna was designed using Computer Simulation Technology software tool for addressing the specific design challenges posed by the internet of things (IoT) based cognitive radio networks. Reconfiguration of frequency bands is achieved using PIN diodes. The antenna resonated at 2.624, 2. 664, 2.720, 2.752, 4.304, 4.532, 4.556, 5.236, 5.304, 5.368, 5.332, and 5.392 GHz. The resonant frequency capability and radiation performance are demonstrated by both simulations and measurements. The simulated and measured results were in agreement. The higher efficiency, gain and average bandwidth obtained are 90%, 8.2 dBi and 65 MHz, respectively. The compactness, integrity, reliability, and performance at various operating frequencies make the proposed antenna a good candidate for IoT applications.cognitive radio, frequency reconfigurable, internet of things, multiband, PIN diodes, SIW

In this research, a reconfigurable metamaterial (MM) structure was designed using a millimeter-wave (MMW) band with two configurations that exhibit different refractive indices. These two MM configurations are used to guide the antenna’s main beam in the desired direction in the 5th generation (5G) band of 28 GHz. The different refractive indices of the two MM configurations created phase change for the electromagnetic (EM) wave of the antenna, which deflected the main beam. A contiguous squares resonator (CSR) is proposed as an MM structure to operate at MMW band. The CSR is reconfigured using three switches to achieve two MM configurations with different refractive indices. The simulation results of the proposed antenna loaded by MM unit cells demonstrate that the radiation beam is deflected by angles of +30° and −27° in the E-plane, depending on the arrangement of the two MM configurations on the antenna substrate. Furthermore, these deflections are accompanied by gain enhancements of 1.9 dB (26.7%) and 1.5 dB (22.4%) for the positive and negative deflections, respectively. The reflection coefficients of the MM antenna are kept below −10 dB for both deflection angles at 28 GHz. The MM antennas are manufactured and measured to validate the simulated results.

No abstract