The construction industry is a significant source of waste generation in any economy, producing various greenhouse gases, releasing harmful substances into the natural environment, and requiring large areas of land for processing, treatment, and landfilling. The emerging field of off-site prefabrication and assembly is perceived as a viable method to reduce waste and improve sustainability. However, there is a lack of quantifiable research into the difference between off-site prefabrication and on-site, conventional construction for numerous sustainability criteria. This paper focuses on modular construction as an off-site production system, where a framework to compare waste generation of modular and conventional, in-situ construction methods is proposed. This paper aims to quantify these differences. The framework relies on a comprehensive literature review to estimate the waste rates of building materials, which are then applied to realistic case studies in order to determine the differences in waste generation. Overall, modular construction reduces the overall weight of waste by up to 83.2%, for the cases considered. This corresponds to a 47.9% decrease in the cost of waste for large structures. Care must be taken to keep modular wastage as low as possible for a reduced cost of waste to be also present in smaller structures. This reduces the research gap of quantifying the waste differences between conventional and modular construction, and provides thoroughly researched waste rates for future research, while also improving the knowledge of industry stakeholders, informing them of the benefits of modular construction. This allows stakeholders to make more informed decisions when selecting an appropriate construction method.

This paper provides a comparative study on the impulse breakdown performance of SF 6 and 20% C 3 F 7 CN / 80% CO 2 gas mixture under weak non-uniform electric fields. Two geometrically distinct electrode configurations, with similar field utilization factor, were subjected to standard lightning impulse waveform (1.2/50 μs) and the effects of pressure, gap distance and impulse polarity on breakdown characteristics were studied. The results show that SF 6 has a higher breakdown voltage than the C 3 F 7 CN/CO 2 mixture and the positive 1.2/50 µs breakdown voltages were found to be higher than the negative counterparts. These results show that the effect of polarity on breakdown voltage does not exclusively depend on electrode geometry but also on pressure and gas type. The results of this paper identify the weaker polarity for 20% C 3 F 7 CN / 80% CO 2 tested with hemispherical rod-plane and coaxial electrode configurations and the results contribute to the design of SF 6-free gas insulated equipment. Index Terms-heptafluoro-iso-butyronitrile (C 3 F 7 CN), sulphur hexafluoride (SF 6), lightning impulse, non-uniform field, polarity effect, breakdown, gas insulation

Sulphur hexafluoride (SF6), the most popular dielectric medium adopted in compressed gas insulated equipment, has been identified as a highly potent greenhouse gas. This has led to increased interest in finding a more environmentally friendly replacement candidate. In this paper, the technical viability of C3F7CN/CO2 gas mixtures was assessed as a potential retro-fill solution for existing SF6-filled gas insulated lines (GIL) and busbars (GIB). A reduced-scale coaxial prototype was developed to establish the breakdown strength of 20% C3F7CN / 80% CO2 and 16% C3F7CN / 84% CO2 gas mixtures in direct comparison with pure SF6 under the standard lightning impulse (1.2/50 μs). Breakdown results demonstrate that a mixture of 20% C3F7CN / 80% CO2 exhibits comparable insulation capability to pure SF6 in coaxial geometries with similar field uniformity to GIL / GIB. This initial finding has led to the construction of a full-scale GIB demonstrator rated for 420/550 kV. Type tests according to IEC 62271-204 showed that the 20% C3F7CN / 80 % CO2 gas mixture has passed all the required voltage levels as SF6. The research findings in this paper are an encouraging step towards a technically viable SF6-free retro-fill solution for existing GIL / GIB installed for the 400 kV transmission network in the UK.

A compact, planar antenna operating at 433 MHz is proposed for wireless smart systems with dimensions of 51 × 28 mm 2 including a ground plane, and printed on a low-cost FR4 material. Significant size reduction is achieved using the variation of an inverted-F antenna configuration with a square-spiral section and rectangular patch element. Fine-tuning of the antenna's resonant frequency is possible using a small capacitive stub. Sensor and radio transceiver electronics can be accommodated above the ground plane. The measured results indicate a 10 dB return loss bandwidth of 4.5 MHz, and a peak realised gain of −13 dBi with omnidirectional radiation characteristics.Introduction: In recent years, wireless smart systems have rapidly emerged in areas such as healthcare and activity monitoring with applications in outpatient monitoring and the provision of in-home lifelines for the elderly [1, 2]. Wireless sensor motes operating in the 433 MHz industrial scientific and medical (ISM) band are a popular choice for low data rate applications and provide a good communication range due to reduced body absorption when compared to higher frequencies.Small and lightweight sensor realisations are key constraints for unobtrusive monitoring and an example of a 433 MHz sensor device is presented in [3] measuring 25 mm 2 in size excluding the antenna. A λ 0 /4 resonant antenna at 433 MHz would require dimensions of ∼170 mm excluding a ground plane. For the intended application, the goal is to realise a wrist-worn sensor with an area of 51 × 28 mm 2 . This size constraint means that a λ 0 /4 antenna is impractical and significant reduction of antenna dimensions is therefore necessary. It is well known however that decreasing the antenna size can negatively affect the efficiency, gain and bandwidth of the antenna [4]. Several small-sized 433 MHz antennas have been reported in the literature [5][6][7], but these antennas are too large in size for this application. A dual-band loop antenna configuration with dimensions very similar to those required is presented in [8] with a reported gain figure of −20 dBi at 433 MHz. In this Letter, an antenna structure is proposed that meets the required size constraints while also providing an acceptable figure for a peak realised gain of −13 dBi. The Letter discusses the design of the proposed antenna structure as well as size reduction methods. In addition, the simulated and measured results for the antenna impedance and radiation characteristics are presented and discussed.

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