Nomenclatures and symbols expansion in text In my thesis there are 7 chapters. Each chapter contains many nomenclatures and symbols. 

Nomenclature: 

Chapter 1

Monte Carlo (MC) simulation is wonderful. MC is a stochastic process. 

Chapter 2/3/../7

Do I need to re-expand the nomenclatures at the beginning of each chapter or expanding at the chapter 1 (or first occurrence) is enough?

Symbol:
Same question applies for Symbols also. For example, Temperature (T)

(Note: Apart from the above, the list of abbreviations and symbols is a must in the thesis as per institute guideline.)
Unlike papers, theses are longer and typically not read in full (someone is going to say “typically not read at all”, but if you are writing yours, please don't listen to these people!). So expanding acronyms for the first time in each chapter makes sense. On the other hand, people who will read chapter 4 of your thesis are probably experts, and so they already know the common acronyms in your field.

For example, Monte Carlo (MC) is trivially used by anyone who knows molecular simulations and wouldn't need to be expanded more than once. On the other hand, acronyms of less common methods might warrant expansion once per chapter: Transition Matrix Monte Carlo (TMMC), Self-Learning Adaptive Umbrella Sampling (SLAUS), etc.

Another solution is to include a list of abbreviations and symbols at the end of your thesis!