Abstract: A foam production method includes mixing liquid nitrogen with a foaming material to produce foam. A gas is produced in situ from liquid nitrogen. As the ratio of the volume of the gas produced by gasification of liquid nitrogen to the volume of the liquid nitrogen is relatively high, when a large gas supply flow is needed to generate a large foam flow, a liquid nitrogen storage device of a small volume can be used instead of bulky air supply devices such as high-pressure gas cylinders, air compressors, air compressor sets and the like, reducing the volume of the air supply device. In addition, the liquid nitrogen used in foaming will release nitrogen gas after the foam blast, such that the nitrogen is also able to inhibit combustion on the surface of burning materials, accelerating the extinguishing of the fire.

Abstract: The present invention discloses an opposite belt-type precise seeding device. The opposite belt-type precise seeding device comprises a seed metering tube consisting of a U-shaped shell and a cover plate, two conveying devices provided inside the seed metering tube in parallel, and a conveying plate provided at the lower end of the seed metering tube. The opposite belt-type precise seeding device belongs to the field of agricultural machinery. In a seeder, a tubular seed conveying tube is usually used for guiding movement of seeds, but the movement of the seeds in the seed conveying tube has certain randomness, so that the seed distance consistency of the seeds in a seed bed is reduced. Through control of the seeds by the conveying devices, the stable movement of the seeds is achieved and the seed distance consistency of the seeds in the seed bed is guaranteed.

Abstract: The present invention discloses an opposite belt-type precise seeding device. The opposite belt-type precise seeding device comprises a seed metering tube consisting of a U-shaped shell and a cover plate, two conveying devices provided inside the seed metering tube in parallel, and a conveying plate provided at the lower end of the seed metering tube. The opposite belt-type precise seeding device belongs to the field of agricultural machinery. In a seeder, a tubular seed conveying tube is usually used for guiding movement of seeds, but the movement of the seeds in the seed conveying tube has certain randomness, so that the seed distance consistency of the seeds in a seed bed is reduced. Through control of the seeds by the conveying devices, the stable movement of the seeds is achieved and the seed distance consistency of the seeds in the seed bed is guaranteed.

Abstract: Method and related apparatus for generating an output signal with audio reverberation effect according to an input signal. In the invention, a constant echo interval is chosen, then a plurality of delay signals, which are delayed signals of the input signal, are generated such that a delay signal and its adjacent delay signal has a delay time equal to the echo interval; and a quantity of the delay signals is adaptively determined according to how many echo intervals are covered in an early reflection portion of the reverberation effect. These delay signals are low-pass filtered for forming the early reflection portion of the output signal, and comb filtering is performed on these delay signals for forming a late reverberation portion of the output signal.