Department of Engineering Science

Lei (Oddo) Zhang

PhD in Engineering Science, completed, to graduate in May of 2013 BE in Engineering Science, 2008

Photograph of Lei (Oddo) Zhang


Software Developer (2012)
The Optima Corporation

After receiving a Bachelor of Engineering (majoring in Engineering Science), I simply had two options: (1) Find a job, or (2) Do postgrad study. The first option was ruled out very quickly, as I really wanted to do some challenging and interesting research. The next question was what kind of research area I wanted to jump into. My fourth year project was a combination of Fluid Dynamics and Operations Research (OR), which gave me an opportunity to explore both subjects. I decided to further pursue my interest in OR.

My PhD research, supervised by Andrew Mason and Andy Philpott, was focused on optimising ambulance redeployment. Ambulance redeployment is the practice of relocating ambulances in real-time in an attempt to achieve quick response times for emergency calls.

I was highly motivated by the mathematical complexity and the potential social impact of this research topic. Furthermore, my dad happens to be an ambulance driver, so if I made good progress I could be able to `dispatch’ him instead of getting `dispatched’ by him.

After four and a half years of hard work, I did it! I finished my oral exam on my birthday, which was such a big bonus! Almost the whole department sang happy birthday for me at my celebration drinks. This will definitely be a very memorable birthday in my life.

It was my pleasure to study in the Department and I enjoyed the last few years immensely. If I have to pick a favourite day of a week, it would be Wednesday because of the weekly staff/postgrad social soccer game! No offence, I think I am the best!

Now it is time for me to leave and start my professional career. I have started working with The Optima Corporation, which is an ambulance-logistics software company located in Auckland. Optima kindly supported my PhD research by providing their world-class ambulance simulation software. Now I am very happy to be part of the team and bring my knowledge of optimising ambulance resources to the company.


Oddo's PhD thesis

Title: "Simulation Optimisation and Markov Models for Dynamic Ambulance Redeployment

The study of dynamic ambulance redeployment, also known as move-up or sys- tem status management, is the main concern of this investigation. Move-up is a practice of dynamically deciding stand-by locations for free ambulances in attempt to achieve quick response times.

In the first part of the investigation, we study optimal move-up policies based on three small-scale Markov models to gain insights. The first Markov model considers one ambulance and aims to maximise the benefit of move-up for just the next call. The second Markov model still considers one ambulance, but aims to the maximise the average benefit per unit time over an infinite horizon.

The third Markov model extends the second Markov model by considering two ambulances. Numerical experiments are used to gain insights into optimal move-up policies based on the three models.

In the second part of the investigation, we present three move-up models for realistic-sized problems. The first two of these models extend existing work by proposing a new simulation-based optimisation algorithm. The third move- up model is a new integer programming model which incorporates some of the insights obtained from the small-scale Markov models. Simulation-based numerical optimisation is employed to tune the model parameters and consequently, the model can also be viewed as an approximate dynamic programming model.

Artificial call data generated for the city of Auckland, New Zealand, are used for computational experiments. We find that when move-up is performed appropriately, it can significantly improve the system performance.
Moreover, the integer program proposed in this work gives the best performance.



  • 2010 Second Prize Winner of Young Practitioner Competition at Operations Research Society of New Zealand (ORSNZ) conference, Auckland
  • 2009 New Zealand Postgraduate Study Abroad Awards (NZPSAA)
  • 2007 First Prize Winner of Young Practitioner Competition at Operations Research Society of New Zealand (ORSNZ) conference, Auckland