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Otaru, Japan

Otaru University of Commerce is a national university in Japan. The main campus of the university is in Otaru, Hokkaido, with a satellite campus in Chūō-ku, Sapporo. Wikipedia.


Haraguchi K.,Otaru University of Commerce | Ono H.,Kyushu University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Among many variations of pencil puzzles, Latin square Completion-Type puzzles (LSCP), such as Sudoku, Futoshiki and BlockSum, are quite popular for puzzle fans. Concerning these puzzles, the solvability has been investigated from the viewpoint of time complexity in the last decade; it has been shown that, in most of these puzzles, it is NP-complete to determine whether a given puzzle instance has a proper solution. In this paper, we investigate the approximability of LSCP. We formulate LSCP as the maximization problem that asks to fill as many cells as possible, under the Latin square condition and the inherent condition. We then propose simple generic approximation algorithms for LSCP and analyze their approximation ratios. © 2014 Springer International Publishing.


Harada M.,Otaru University of Commerce
Physics Essays | Year: 2011

Contrary to the prevailing lore, the twin paradox is shown to lose its raison d'tre when a proper account is taken of the intrinsic role of time in relativity theory. © 2011 Physics Essays Publication.


Ishii T.,Otaru University of Commerce | Akiyama Y.,Allied Telesis K.K. | Nagamochi H.,Kyoto University
Algorithmica (New York) | Year: 2010

Given an undirected multigraph G = (V,E), a family W of areas W⊆V, and a target connectivity k≥1, we consider the problem of augmenting G by the smallest number of new edges so that the resulting graph has at least k edge-disjoint paths between v and W for every pair of a vertex v ∈ V and an area W ∈ W. So far this problem was shown to be NP-complete in the case of k = 1 and polynomially solvable in the case of k = 2. In this paper, we show that the problem for k≥3 can be solved in O(m + n(k 3 + n 2)(p + kn + nlog n)logk + pkn 3log(n/k)) time, where n = |V|, m = |{{u,v}|(u,v)∈E}|, and p = |W|. © 2008 Springer Science+Business Media, LLC.


Hasunuma T.,Tokushima University | Ishii T.,Otaru University of Commerce | Ono H.,Kyushu University | Uno Y.,Osaka Prefecture University
Journal of Discrete Algorithms | Year: 2012

A (2,1)-total labeling of a graph G is an assignment f from the vertex set V(G) and the edge set E(G) to the set {0,1,...,k} of nonnegative integers such that |f(x)-f(y)|≥2 if x is a vertex and y is an edge incident to x, and |f(x)-f(y)|≥1 if x and y are a pair of adjacent vertices or a pair of adjacent edges, for all x and y in V(G) ∪ E(G). The (2,1)-total labeling number λ T 2 (G) of G is defined as the minimum k among all possible (2,1)-total labelings of G. In 2007, Chen and Wang conjectured that all outerplanar graphs G satisfy λ T 2 (G)≤Δ(G)+2, where Δ(G) is the maximum degree of G. They also showed that it is true for G with Δ(G)≥5. In this paper, we solve their conjecture, by proving that λ T 2 (G)≤Δ(G)+2, even when Δ(G)≤4. © 2011 Elsevier B.V.


Hirasawa N.,Otaru University of Commerce
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

Challenges for incorporating "quality in use" in embedded system development were discussed. In the Japanese embedded system industries the foundation of the quality in use management is not necessarily established because of their various backgrounds and histories. In the paper three key points to introduce the quality in use into the design process in the industries were proposed. These were implementation of user requirement process, understanding of "service" as final outcome and synchronization to functional safety. © 2013 Springer-Verlag Berlin Heidelberg.

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