A system for communication flow estimation and method therefore are described. Additionally, the layer is essentially free from voids and essentially free from residual stresses. A pull down cable is connected to the rotary head for pulling the rotary head downward for pushing the drill string into the ground. A viewer provides access to the contents of the database. The maximum diameter of the infant accommodation region is in the range 20 to 50cm, and the inner enclosure wall includes, when viewed from above, three curved apex regions separated by curved side regions. in a manner known per se in a multistage fluidized bed and wherein a nitrogen compound is added into the furnace andor at least one stage of the multistage fluidized bed.