A projection type screen comprises a reflection surface array and a lenticular sheet. The method includes detecting an operating condition of an upwind wind generator, the upwind wind generator located upstream of a downwind wind generator relative to a wind flow direction. The flat 32-bit format allows the ROM device and ROM image to exceed one megabyte in size, which permits many modules to be included to allow the ROM image to provide support for a full spectrum of hardware of the computer system. Furthermore, shifting between the forward speed ratios is dynamic. The network device also includes an output port through which the mixed audio stream can be transmitted to the user.