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Your search keyword '"Tsukamoto, Yasuyuki"' showing total 24 results
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24 results on '"Tsukamoto, Yasuyuki"'

1. Existence of strongly proper dyadic subbases

Author

Tsukamoto, Yasuyuki

Subjects
Mathematics - General Topology, I.1.1, F.3.2, F.4.1
Abstract

We consider a topological space with its subbase which induces a coding for each point. Every second-countable Hausdorff space has a subbase that is the union of countably many pairs of disjoint open subsets. A dyadic subbase is such a subbase with a fixed enumeration. If a dyadic subbase is given, then we obtain a domain representation of the given space. The properness and the strong properness of dyadic subbases have been studied, and it is known that every strongly proper dyadic subbase induces an admissible domain representation regardless of its enumeration. We show that every locally compact separable metric space has a strongly proper dyadic subbase., Comment: 11 pages

Published
2017
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2. On the consistency problem for modular lattices and related structures

Author

Herrmann, Christian, Tsukamoto, Yasuyuki, and Ziegler, Martin

Subjects
Mathematics - Logic
Abstract

The consistency problem for a class of algebraic structures asks for an algorithm to decide for any given conjunction of equations whether it admits a non-trivial satisfying assignment within some member of the class. By Adyan (1955) and Rabin (1958) it is known unsolvable for (the class of) groups and, recently, by Bridson and Wilton (2015) for finite groups. We derive unsolvability for (finite) modular lattices and various subclasses; in particular, the class of all subspace lattices of finite dimensional vector spaces over a fixed or arbitrary field of characteristic $0$. The lattice results are used to prove unsolvability of the consistency problem for (finite) rings and (finite) representable relation algebras. These results in turn apply to equations between simple expressions in Grassmann-Cayley algebra and to functional and embedded multivalued dependencies in databases.

Published
2016

3. New examples of oriented matroids with disconnected realization spaces

Author

Tsukamoto, Yasuyuki

Subjects
Mathematics - Combinatorics, Mathematics - Algebraic Geometry, 52C40
Abstract

We construct oriented matroids of rank 3 on 13 points whose realization spaces are disconnected. They are defined on smaller points than the known examples with this property. Moreover, we construct the one on 13 points whose realization space is a connected and non-irreducible semialgebraic variety., Comment: 8 pages, 3 figures

Published
2012

4. Sudoku Colorings of a 16-Cell Pre-fractal

Author

Tsuiki, Hideki, Tsukamoto, Yasuyuki, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Akiyama, Jin, editor, Ito, Hiro, editor, Sakai, Toshinori, editor, and Uno, Yushi, editor

Published
2016
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5. Imaginary Hypercubes

Author

Tsuiki, Hideki, Tsukamoto, Yasuyuki, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Akiyama, Jin, editor, Ito, Hiro, editor, and Sakai, Toshinori, editor

Published
2014
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23. Reactivity of Peroxomonophosphoric Acid in the Oxidation of Benzaldehydes and Dimethyl Sulfoxide in Aqueous Ethanol

Author

Ogata, Yoshiro, Sawaki, Yasuhiko, and Tsukamoto, Yasuyuki

Abstract

Oxidation of benzaldehydes and dimethyl sulfoxide with peroxomonophosphoric acid (PMPA) has been studied in 40% aqueous EtOH in order to examine the reactivity of undissociated and dissociated PMPA in comparison with that of peroxycarboxylic acid. The reactivity for DMSO was in the order RCO3−>H3PO5>H2PO5−>RCO3H>HPO52−. As in the peroxycarboxylic acid oxidation, PMPA oxidation of substituted benzaldehydes afforded phenols by aryl migration and benzoic acids by hydride migration. The product ratio changed with substituents and pH; salicylaldehyde (o-HO) gave only catechol by aryl migration, while p-chloro and unsubstituted benzaldehydes afforded benzoic acids predominantly. The oxidation of aldehydes bearing p-MeO and p-Me was a borderline case and the migratory ratio of Ar∼/H∼ was higher at lower pH, i.e., the order being H3PO5>H2PO5−>HPO52−. The substituent effect in the apparent kobsdvalues was very small (i.e., ρ≈0), but the effect for aryl migration (kAr∼) estimated from product selectivity gave ρ=−2.88(σ). The rate for hydride migration (kH∼) resulted in ρ=1.7 and 2.0 (σ). Reactivity of PMPA in each dissociated form was compared with that of RCO3H.

Published
1981
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