Plane Formation by Synchronous Mobile Robots without Chirality

We consider a distributed system consisting of autonomous mobile computing entities called robots moving in the three-dimensional space (3D-space). The robots are anonymous, oblivious, fully-synchronous and have neither any access to the global coordinate system nor any explicit communication medium. Each robot cooperates with other robots by observing the positions of other robots in its local coordinate system. One of the most fundamental agreement problems in 3D-space is the plane formation problem that requires the robots to land on a common plane, that is not predefined. This problem is not always solvable because of the impossibility of symmetry breaking. While existing results assume that the robots agree on the handedness of their local coordinate systems, we remove the assumption and consider the robots without chirality. The robots without chirality can never break the symmetry consisting of rotation symmetry and reflection symmetry. Such symmetry in 3D-space is fully described by 17 symmetry types each of which forms a group. We extend the notion of symmetricity [Suzuki and Yamashita, SIAM J. Compt. 1999] [Yamauchi et al., PODC 2016] to cover these 17 symmetry groups. Then we give a characterization of initial configurations from which the fully-synchronous robots without chirality can form a plane in terms of symmetricity

Catch performance of coastal squid jigging boats using LED panels in combination with metal halide lamps

Squid attracting light systems consisting of low power light emitting diode panels (LEDs) and conventional metal halide lamps (MHs) were tested to describe the influence of combinations of LEDs and MHs on squid catch. Fishing trials using LEDs (9. kW) and different numbers of MHs were carried out in August and September 2009 targeting two squid species: (1) Japanese common squid Todarodes pacificus in northern waters of the Sea of Japan (off Hokkaido) by 4 coastal squid jigging boats (19 gross tonnage) and (2) swordtip squid Photololigo edulis in western waters (off Iki) by 5 boats of the same class. Catches of both species tended to increase with the number of MHs. Generalized Linear Model analysis revealed that in addition to the number of MHs, the catch amount was influenced by fishing power (ability) of boat and by the monthly variation of squid abundance (only for P. edulis off Iki). The expected catch (number of boxes) was not proportional to the number of MHs. The largest catch was expected for P. edulis off Iki by using LEDs with 24 MHs. The optimal combination of LEDs and MHs for T. pacificus off Hokkaido was less clear because the combination with 36 MHs had the largest positive effect on the catch; this was the maximum number MHs used