Earlier I have already used optics to understand the experiment, used C language to learn to use matlab, used linear algebra to do data analysis. Today I used another tool, ordinary differential equations, to solve some kinetics problem after we assumed a model. (I helped in working out the equation

**dy/dx+p(x)y=f(x)**).

Before, Many many many students claimed that physics, programming, and even some math were useless. Now, I'm using my example to argue it's not that case. If I had never learnt that, how could achieve this in these day's work?

It's really a feeling of achievement. Keep studying, treating everything with full devotion. One day we may use the seemingly useless thing!

I'm really happy here doing research work.