Why do most of the radioactive materials follow first order kinetics?
This is because the fact that radioactive material have weak nuclear bonding. Hence, they try to a stabler nucleus by fusion or fission. This, essentially, mean that the radioactive phenomena does not depend on any other molecule/atom to attack. It is self-sufficient to react. So, this of course means that reaction will depend only on itself, and hence reaction rate will also depend only on itself.
What is the advantage of machine learning in control systems of mechanical devices?
In control systems, we need to have the governing equations/models. So, we simulate and tune the models for achieving a control over the device by certain control rules. But often getting the governing model is very very difficult. Say, we see an extremely non-linear behaviour in a system, and we are not able to find the accurate model. Then, does this mean, we can't control that system? Machine learning helps us here. It take the response behaviour for large number of times and prepares a data set. This data set is used to train the system, how to respond to certain stimuli. It is pretty much like training a dog/any animal. So, these data goes through algorithms which could do the regression to give result similar to that from an accurate model, inspite of not knowing the theory behind the system.
Is conduction heat transfer greater than convection heat transfer?
Heat transfer depends on two things, energy transfer-ability and interaction. Firstly, the energetic molecules need to interact with surrounding molecules. Only then, energy can be transferred to the neighbours, or energy can flow. Then comes transfer-ability. If the molecule has better transfer-ability then it will easily transfer the heat. So, there is a trade off between these two factors. This, essentially, means that the statement in the question is not generalised. If the molecule has more transferability as well as more interaction, which is the case in metal, then we see conduction. But if the metal is gasified, the interaction reduces and hence the heat transfer rate falls. If the material in the case was not a metal but non-metal then the transferability would decrease. So, here is a much worse case.