Frequency Quantized Nondiffracting X Waves in a Confined Space
  This paper presents theoretical results indicating that newly discovered nondiffracting beams we call X waves, can propagate in a confined space (wave guide) with specific quantized temporal frequencies. These results could have applications in nondispersive transmission of acoustic, electromagnetic (microwaves) and optical energy through wave guides as well as provide new localized wave functions of de Broglie waves in quantum mechanics. 
Jian-yu Lu