1. I have developed a mathematical model of a mechanism taking into account the effect of the linkages mass. After I have developed the model, I have read in another paper saying that, since the mass of the linkages are actually very small, the model can just be approximated using motor model (no need to take the mass of the linkages into consideration). How to respond to examiner's question if he points out that it is useless to use my method since the effect of the linkages mass is actually insignificant? And I am actually quite agree with this.

2. How to respond if they ask, 'Since the mass of the linkages are small, your experiment actually does not verify your proposed model' ? How to answer this, because I think this is quite true.

3. In the model, I have assumed that the potential energy is negligible (to simplify the modeling process),and I have tested the model that I have developed by experiment. But then, when I use the model to simulate of my controller, I have included the potential energy (the model with potential energy has not been tested by experiment). How can I answer if the examiner point this out? I think I did a lot and huge mistakes in my research.

4. How to answer to theoretical questions that I don't know how to answer?

5. How to answer to the things that you heard for the 1st time in the viva?

6. How can we know when to defend and when to accept the examiners' comments?

7. I feel like I don't have enough time to review all my work and I am feeling so tired right now. Any tips on how to prepare at the very last minutes?

8. Is it ok to say 'I don't know' in the viva?

I had a hellish viva during my master, and 2 (I will have 5) of my PhD examiners will be the same ones from my master viva . It's really traumatic and my mind goes blank everytime I look at them- and of course I will be facing them during my PhD viva. They are also really expert in my field. I am really scared. Feeling like jumping on to the rail tracks at the moment. T_T

Please... any advice will be appreciated. Please, please, please help me. I'm panicking already.
Thanks.

is there any benefit of using your model as compared to the motor model?

perhaps motor model can only *approximate* the computation but not provide an exact calculation. can accuracy be the selling point of ur research?

what does ur experiment do? what is the goal of ur model?
does the experiment prove the validity of the model? if no, why do u think so?

4. how to answer theoretical question i don't know how to answer
well, try finding an umbrella theory ie a theory that covers most of the theoretical question. in emergency cases, use the all encapsulating umbrella theory to reason out the answer.

5. How to answer to the things that you heard for the 1st time in the viva?
that's why it's important to bounce ur ideas prior to the viva with friends etc. to prepare urself for the unexpected.
another way, is to think aloud. try to find something known to hinge the unknown upon.

examiner : what do u think would happen to ur model in situation X?
you : (gulp, i've never heard of X before).. well, the model responds quite well to situation Y. although i have not come across X per se, it can be reasoned that X shares a significant similarity with Y from the aspect of such and such. in effect, i would anticipate that the model would respond well to X as well.
(hinge X (unknown) to Y(known))

6. How can we know when to defend and when to accept the examiners' comments?
u could read the body language. if the examiner is frowning, or his facial structure does not portray cordiality, then maybe u should try defense.

7. I feel like I don't have enough time to review all my work and I am feeling so tired right now. Any tips on how to prepare at the very last minutes?
create a simple visual model ie cartoon like model of all ur research. have fun with it. humour can ease tension, strengthen memory and spark creativity.

hope it helps.

Definitely do get someone to give you a mock viva. If your supervisor won't do one then get someone else to, and even make up some questions for them to ask you if necessary. It will be practice answering the questions out loud and help you see weaknesses in your answers by presenting them to someone else. Get the Rowena Murray book 'how to survive your viva'. When is your viva?

You should be able to identify potential weaknesses and questions partly by thinking about where various people have critiqued your work in the past - e.g. have supervisors raised concerns about particular issues or passages, or have questions been raised about certain parts of your work or your arguments in conference papers? Any questions remaining that were asked at the first year/Masters viva panel? The better you know your thesis the better you will be able to handle any questions they throw at you. I'm sure if you think carefully you will be able to come up with answers to likely concerns and questions that the panel will have if you are familiar with some of them from previous panels. You will know what their prejudices/concerns/interests are likely to be and you can cater to them. If you know that one of them is likely to ask for a particular correction given your knowledge of their interests well you can craft a response in advance.

As a general rule, you should be able to answer at these questions:

1) What?
2) Why?
3) How?
4) So what?

I also suggest a mock presentation with a critical friend, this would be highly effective in preparing yourself for the 'real thing'. Good luck!

Hi,

Thanks pikircool, nearlyfinished and vadro.

I had my 1st viva (we have 2 in my university) last week and none of these questions were asked in the viva... but posting them here and your replies made me calm down a bit and be more prepared for the viva.
And I had a mock viva with my supervisor before the real one and it really helped a lot.

Thank you, thank you, thank you so much.