ABSTRACT:When a shock wave interacts with a group of solid spheres, non-linear aerodynamic behaviors come into effect. The complicated wave reflections such as the Mach reflection occur in the wave propagation process. The wave interactions with vortices behind each sphere's wake cause fluctuation in the pressure profiles of shock waves. This paper reports an experimental study for the aerodynamic processes involved in the interaction between shock waves and solid spheres. A schlieren photography was applied to visualize the various shock waves passing through solid spheres. Pressure measurements were performed along different downstream positions. The experiments were conducted in both rectangular and circular shock tubes. The data with respect to the effect of the sphere array, size, interval distance, incident Mach number, etc., on the shock wave attenuation were obtained.

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The implementation of an optical transport network, especially between datacenters, has been progressing. Similar to the Internet, communications on the optical transport network are protected by public-key cryptography and symmetric-key cryptography, but there are concerns that advances in the research and development of quantum computers will pose a risk to current cryptographic systems, public-key cryptography and key exchange in particular. In response to this problem, researchers at NTT Social Informatics Laboratories and NTT Network Innovation Laboratories are engaged in the research and development of safe key-exchange schemes to counter the cryptographic risks posed by quantum computers. They are also engaged in architecture design and tests with actual equipment with the aim of applying such key-exchange schemes to the optical transport network.

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