• East Asian mathematical journal
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• v.16 no.1
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• pp.49-55
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• 2000

In this paper we find some classes of operators implying normaity. The main result is as follows. If T is restriction-convexoid and is reduced by each of its eigenspaces corresponding to isolated eigenvalues, which is a class including hyponormal operators, and if $\sigma$(T) is countable then T is diagonal and normal.

• Bulletin of the Korean Mathematical Society
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• v.38 no.1
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• pp.163-174
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• 2001

In this paper we introduce a notion of the $\chi-CLASS$ operators, which is a class including hyponormal operators and consider their spectral properties related to Weyl spectra.

• East Asian mathematical journal
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• v.16 no.1
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• pp.147-159
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• 2000

In this paper, we investigate the properties of non-normal(convexoid, hyponormal) adjacency operators for a graph under two operations, tensor product and Cartesian one.