A blowing agent blend for making thermoplastic polymer foams includes methyl formate. A semiconductor chip includes a semiconductor substrate and a transistor on the semiconductor substrate. The first metal layer and the transparent conductive layer are patterned to form a gate pattern and a pixel electrode pattern. The ultrasonic sensor as a transmitter transmits ultrasonic waves to a sheet being fed and conveyed. It is one key feature of the present invention that the combination of the down-mix channels is achieved by simple, computationally inexpensive arithmetic operations. The method may further include placing refined nodes at parametric grid locations wherein the refined nodes have subindices linked to the existing indices.