A graph is s-regular if its automorphism group acts regularly on the set of its s-arcs. In this paper, the s-regular elementary abelian coverings of the complete bipartite graph K 3,3 and the s-regular cyclic or elementary abelian coverings of the complete graph K 4 for each s 1 are classified when the fibrepreserving automorphism groups act arc-transitively. A new infinite family of cubic 1-regular graphs with girth 12 is found, in which the smallest one has order 2058. As an interesting application, a complete list of pairwise non-isomorphic s-regular cubic graphs of order 4p, 6p, 4p 2 or 6p 2 is given for each s 1 and each prime p.

An automorphism group of a graph is said to be s-regular if it acts regularly on the set of .s-arcs in the graph. A graph is s-regular if its full automorphism group is .s-regular. For a connected cubic symmetric graph X of order 2p" for an odd prime p, we show that if p ^ 5,7 then every Sylow p-subgroup of the full automorphism group Aut(X) of X is normal, and if p ^ 3 then every .s-regular subgroup of Aut(X) having a normal Sylow p-subgroup contains an (s -l)-regular subgroup for each 1 < . $ < 5. As an application, we show that every connected cubic symmetric graph of order 2p" is a Cayley graph if p > 5 and we classify the .s-regular cubic graphs of order 2p 2 for each 1 < s < 5 and each prime p, as a continuation of the authors' classification of 1-regular cubic graphs of order 2p 2 . The same classification of those of order 2p is also done.2000 Mathematics subject classification: primary 05C25, 20B25.

Although the Ulleung Basin is an important biological ''hot spot'' in East/Japan Sea (hereafter the East Sea), very limited knowledge for seasonal and annual variations in the primary productivity exists. In this study, a recent decadal trend of primary production in the Ulleung Basin was analyzed based on MODIS-derived monthly primary production for a better annual production budget. Based on the MODISderived primary production, the mean daily primary productivity was 766. the Ulleung Basin during the study period. The monthly contributions of primary production were not largely variable among different months, and a relatively small interannual production variability was also observed in the Ulleung Basin, which indicates that the Ulleung Basin is a sustaining biologically productive region called as ''hot spot'' in the East Sea. However, a significant recent decline in the annual primary production was observed in the Ulleung Basin after 2006. Although no strong possibilities were found in this study, the current warming sea surface temperature and a negative phase PDO index were suggested for the recent declining primary production. For a better understanding of subsequent effects on marine ecosystems, more intensive interdisciplinary field studies will be required in the Ulleung Basin.

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A graph is called s-regular if its automorphism group acts regularly on the set of its s-arcs. In this paper, the s-regular cyclic or elementary abelian coverings of the Petersen graph for each s 1 are classified when the fibre-preserving automorphism groups act arc-transitively. As an application of these results, all s-regular cubic graphs of order 10p or 10p 2 are also classified for each s 1 and each prime p, of which the proof depends on the classification of finite simple groups.