in my research for creativity, I've come across researches that analyses how the brains of the great scientists and inventors work. They are excellent resources for problem solving, and I have discovered that the great minds surrender a lot more to their subconscious mind then I ever thought. A lot of them talked about releasing their problems to the void, go take a walk, have a sleep, do something they enjoy, and the next thing you know, the answer will strike them when they least expected it. As far as studying is concern, my opinion is no matter what time of day you study, take regular breaks to flex your brain muscle. Go outside for some fresh air, have a brisk walk, grab a snack. Oxygen is very important booster for brain power. Also, our brain learns by repetition, it wires neurons together by repetitive connection. I hope this helps. All the best for your study.