On display there were many inventions of actual value in production and construction.

The Kim Chaek University of Technology presented the process of copper production by wet method, which helps raise the extraction rate of copper up to 15 percent and the sulfuric acid output four times by dry method, cutting power consumption by half and preventing environmental pollution.

This invention has been already introduced to several economic units, bringing a big profit.

The Pyongyang University of Architecture elaborated a theory on designing structure and gearing of a tower crane with horizontal jib as well as the technique for manufacturing it.

And it worked out designs for urban and rural dwelling houses based on a heating and cooling system by geotherm and solar heat, which have been applied in practice, saving a huge quantity of coal.

The inventions also include a method of building arch dam and a 300-watt wind-driven generator.