A 3-D finite-difference time-domain analysis of a photoconductive-semiconductor-switch-based terahertz (THz) source, integrated with a standard dipole and a large-aperture radiator, is presented. The simulation analysis is based on the coupling of semiconductor equations for charge transport with Maxwell electromagnetic equations. The simulation provides the transient field redistribution, carrier generation characteristics, and the field acceleration as a result of the bias voltage on the device, contributing to the nonlinear behavior of THz-pulse generation. A comparison of the radiation characteristics of the two antenna types shows that the large-aperture antenna produces approximately three times higher radiation amplitude and broader power spectrum than those produced by the dipole antenna.

This research focuses on the computational design, prototype development, and experimental validation of a compact microwave antenna for orthopaedic applications in biomedical regimes. The unique resonant structure comprises an embedded double negative (DNG) metamaterial (MTM)-inspired slotted stub, designed and simulated in the CST Microwave studio environment, as well as verified through simulation in Advanced Design Systems (ADS) software. This adaptation of the design technique improves the antenna’s performance, as demonstrated in the design and result analysis section of the research paper, which includes experimental comparison results from previously developed antenna prototypes. To make the design suitable for rapid industry prototyping, Rogers RT5880 substrates have been used with a standard substrate height of 0.79 mm (loss tangent of 0.009 and dielectric constant of 2.2). However, the antenna’s effectiveness was also compared with other commercially available variations of Rogers RT5880 substrate material (0.508 mm, 4.575 mm, and 3.175 mm) while transmitting the input power into the electromagnetic wave. Antenna performance for measuring bone tissue penetration was checked, and a gain of 3.5 dB and a distributed surface current value of 295 A/m were found to be satisfactory for the early stage bone fracture diagnosis application. The measured radiating efficiency was 97.5%. The far-field experiment measurements show an omnidirectional radiation pattern and a well-performed return loss well below -10 dB in the operating region of 3.8 GHz to 4.8 GHz. During simulation, the stacked bone phantom environment’s operational characteristics demonstrated satisfactory gain, directivity, and efficiency performance, which are also compared in this research analysis.

The rapid expansion of new metro systems in the last two decades shows a globally growing interest in urban rail transit infrastructure. Every time a new metro line is opened, it has the potential to change the existing modal split, which is usually dominated by private (car or motorcycle) transport users. For each new or expanding metro system, a feasibility study is conducted, which focusses mainly on existing mobility issues, travel demand, new infrastructure proposed, and environmental and financial aspects of a new metro project. In these documents, specific methodologies are applied, using local parameters and suitable software, for demand forecasting purposes. However, not much attention is usually dedicated to potential users, their modal choice characteristics, willingness to shift to metro and conditions under which such a shift would be encouraging. Therefore, it is often unclear what the actual public perception of a new service is and their interest in using it in the future. As a consequence of various shortcomings in feasibility studies, the actual demand for metro services is often much lower than originally predicted. Hence, a survey targeting a group of potential metro users located close to a planned metro line was designed to investigate people’s willingness to shift to metro and include soft factors that could facilitate such a change. Next, a case study of the Red Line whose final metro stop is at Salaya, Thailand, was selected, and a sample of 667 respondents, both staff and students based at a nearby university campus, was investigated. Results revealed that 90% of the sample is willing to shift to metro (easy and medium shifters) for a future 20-km trip between Salaya and Bangkok, while only 10% remains sceptic (difficult shifters). Moreover, there are some differences in shifters’ priorities, where easy shifters see factors such as reliable timetable, good mode connectivity and seamless station–campus connection as significantly more important than medium or difficult shifters do. Also, there is a significant association between a mode type currently used for Salaya and Salaya–Bangkok commutes, where private transport users (51% of staff and 43% of students) have already shifted to public transport. Based on the outcomes of the study, recommendations are addressed to stakeholders involved in the Red Line, as well as in other new metro projects in Thailand and internationally, and to those who aim to better understand the needs of potential customers in order to facilitate their shift to metro as a preferred mode of transport in the future.