In [N. Alon, M. Feldman, A. D. Procaccia, and M. Tennenholtz, A note on competitive diffusion through social networks, Inform. Process. Lett. 110 (2010) 221-225], the authors introduced a game-theoretic model of diffusion process through a network. They showed a relation between the diameter of a given network and existence of pure Nash equilibria in the game. Theorem 1 of their paper says that a pure Nash equilibrium exists if the diameter is at most two. However, we have an example which does not admit a pure Nash equilibrium even if the diameter is two. Hence we correct the statement of Theorem 1 of their paper.

This paper deals with broadcasting in a network with t-locally bounded Byzantine faults. One of the simplest broadcasting algorithms under Byzantine failures is referred to as a certified propagation algorithm (CPA), which is the only algorithm we know that does not use any global knowledge of the network topology. Hence, it is worth focusing on a graph-theoretic parameter such that CPA will work correctly. Using the theory of maximum adjacency (MA) ordering, a new graph-theoretic parameter for CPA is proposed.

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This paper presents two new scaling algorithms for the minimum cost network flow problem, one a primal cycle canceling algorithm, the other a dual cut canceling algorithm. Both algorithms scale a relaxed optimality parameter, and create a second, inner relaxation. The primal algorithm uses the inner relaxation to cancel a most negative node-disjoint family of cycles w.r.t. the scaled parameter, the dual algorithm uses it to cancel most positive cuts w.r.t. the scaled parameter. We show that in a network with n nodes and m arcs, both algorithms need to cancel only O(mn) objects per scaling phase. Furthermore, we show how to efficiently implement both algorithms to yield weakly polynomial running times that are as fast as any other cycle or cut canceling algorithms. Our algorithms have potential practical advantages compared to some other canceling algorithms as well. Along the way, we give a comprehensive survey of cycle and cut canceling algorithms for min-cost flow. We also clarify the formal duality between cycles and cuts.

A joint team of hospital staff and OR/MS researchers launched a healthcare service innovation project at the University of Tsukuba, Japan, in April 2011. We plan to develop a web-based software system for bed allocation to patients by mathematical optimization in the Tsukuba University Hospital. For attaining this goal successfully, we analyze the unique medical network system of Japan and study the expectation of potential patients as well as hospital staff. This is done in parallel with the operational analysis and simulation of patient flows inside the university hospital. In this paper, we describe the scope of our project and share the first-year progress with expert participants in the conference.