Sumiyasu Yamamoto

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Let G be an abelian group. A collection of (G, k, λ) disjoint difference families, {F0,F1, · · · ,Fs−1}, is a complete set of disjoint difference families if ∪0≤i≤s−1∪B∈FiB form a partition of G− {0}. In this paper, several construction methods are provided for complete sets of disjoint difference families. Applications to one-factorizations of complete(More)
A new balanced file organization scheme of order two for binary-valued records is given which we call HUBFS2 (Hiroshima University balanced file organization scheme). It can be constructed for a wide range of parameters as is in NBFS2. Moreover, it has the least redundancy among the file organization schemes of order two under a general class of probability(More)
We introduce here two types of balanced nested designs (BND), which are called symmetric and pair-sum BNDs. In this paper, we give a construction for pair-sum BNDs of BIBDs from nested BIBDs and perpendicular arrays. We also give some direct constructions for pair-sum BNDs of BIBDs, based on the result obtained by Wilson (1972). By use of these(More)
A file organization scheme in an information storage and retrieval system which will be called a generalized Hiroshima University balanced multiple-valued file organization scheme of order two (GHUBMFS<inf>2</inf>) is presented, where the information about the records is indexed by m attributes having n values. The number of buckets to be organized and the(More)
A new balanced file-organization scheme of order two for multiple-valued records is presented. This scheme is called HUBMFS<subscrpt>2</subscrpt> (Hiroshima University Balanced Multiple-valued File-organization Scheme of order two). It is assumed that records are characterized by <italic>m</italic> attributes having <italic>n</italic> possible values each,(More)
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