Abstract: Disclosed is a method of manufacturing a polyurethane filter foam having excellent air permeability, elasticity, and restoring force. In the method of manufacturing the polyurethane filter foam, the cell size of the filter foam is made regular by controlling the pressure by adjusting the diameter of the foaming head of a foaming machine, rather than adding a cell opener, cell irregularity caused by poor dispersion of the cell opener is alleviated, and air permeability, porosity, and compression set are excellent.

Abstract: A raster graphic system is provided having a scan converter for producing pixel data, a pixel cache for storing data sequentially supplied from the scan converter, and a frame buffer. The system includes a mask control logic circuit arranged between the pixel cache and the frame buffer. The mask control logic circuit allows the pixel data stored in the frame buffer to be maintained as is, without reading the pixel data out from the frame buffer when new data is to be written into the frame buffer. The mask control logic circuit includes NOR gates for NORing data of the tile pixels from the pixel cache, in which data is unwritten by the scan converter. The mask control logic circuit further includes OR gates for ORing the outputs of the NOR gates with write enable signal WE#, and for supplying the ORed results as write enable signals WE#0 to WE#1 to the frame buffer.