1. Senior Lecturer, School of Mathematical and Computer Sciences, Maxwell Institute for Mathematical Sciences, Heriot-Watt Univ., Edinburgh EH14 4AS, UK.
2. Postdoctoral Research Associate, School of the Built Environment, Heriot-Watt Univ., Edinburgh EH14 4AS, UK (corresponding author).
3. Professor, School of Mathematical and Computer Sciences, Maxwell Institute for Mathematical Sciences, Heriot-Watt Univ., Edinburgh EH14 4AS, UK.
4. Lecturer, School of the Built Environment, Heriot-Watt Univ., Edinburgh EH14 4AS, UK.