| http://www.w3.org/ns/prov#value | - tic film material using an ultrasonically resonating resonator and a layer of gas, such as air, for coupling the ultrasonic energy tothe film material.Still another important object of this invention is the provision of a method for welding thin thermoplastic film material using a support surface having a cavity and coupling ultrasonic energy to the film material at the area of the cavity bymeans
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