One of the more relatively new concepts to me is the idea of a dip in bar velocity DURING the pull from the floor to the hips. I first saw and learned about this idea during the USAW Level 2 seminar. The article below is a research paper from John Garhammer of the 1984 Olympic Games. He took 5 gold medal winners and measured their bar velocity, bar track, as well as some other factors of the lifts and reported some interesting data. A word of warning. This article is more scholastics and data-driven than the other two I have posted BUT it gives some great information both about the lifts as a whole and about the specific of the change in bar velocity.
Note Garhammer shows that ALL 5 LIFTERS studied show a decrease in bar speed after the bar crosses the knees before it reaches the hips. As they rebend their knees and move the bar into position at the hips the bar actually slows down. This fact alone should show how important lifters make the power position and getting the bar to the hips properly.
Take a look at this and don’t gloss over even the basic information about the bar tracking off the floor and at the hips.
Biomechanical Profiles of Olympic Weightlifters