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Differences in the maturation level among life histories of the Japanese eel Anguilla japonica in the Nagata River, Japan

Chino N., Imai C., Sakai H., Arai T.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 4

472--477

EN

In order to understand the silver eel migration behavior of the Japanese eel Anguilla japonica, the life history of both the yellow stage (immature stage) and the silver stage (early maturing stage) was examined during the silver eel migration period, using otolith microchemical analysis of strontium (Sr) and calcium (Ca) concentrations. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicate eels of several general categories of migratory histories, including sea eels (average Sr:Ca ratios, ≥ 6.0 × 10-3), estuarine eels (average Sr:Ca ratios, 2.0 × 10-3 ≤ Sr:Ca < 6.0 × 10-3) and river eels (average Sr:Ca ratios, < 2.0 × 10-3), based on the criteria reported previously in A. japonica. A significant negative correlation was observed between the gonadosomatic index (GSI) and the mean Sr:Ca ratios during the growth phase after recruitment. Gonads of river eels were more developed compared to eels with other migratory histories. It thus appears that the maturation level for the silver eel migration to the open ocean varies depending on the life history.

2

Apriori-Based Rule Generation in Incomplete Information Databases and Non-Deterministic Information Systems

Sakai H., Wu M., Nakata M.

Fundamenta Informaticae

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2014

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Vol. 130, nr 3

343--376

EN

This paper discusses issues related to incomplete information databases and considers a logical framework for rule generation. In our approach, a rule is an implication satisfying specified constraints. The term incomplete information databases covers many types of inexact data, such as non-deterministic information, data with missing values, incomplete information or interval valued data. In the paper, we start by defining certain and possible rules based on non-deterministic information. We use their mathematical properties to solve computational problems related to rule generation. Then, we reconsider the NIS-Apriori algorithm which generates a given implication if and only if it is either a certain rule or a possible rule satisfying the constraints. In this sense, NIS-Apriori is logically sound and complete. In this paper, we pay a special attention to soundness and completeness of the considered algorithmic framework, which is not necessarily obvious when switching from exact to inexact data sets. Moreover, we analyze different types of non-deterministic information corresponding to different types of the underlying attributes, i.e., value sets for qualitative attributes and intervals for quantitative attributes, and we discuss various approaches to construction of descriptors related to particular attributes within the rules' premises. An improved implementation of NIS-Apriori and some demonstrations of an experimental application of our approach to data sets taken from the UCI machine learning repository are also presented. Last but not least, we show simplified proofs of some of our theoretical results.

3

Effective Procedures for Handling Possible Equivalence Relations in Non-deterministic Information Systems

Sakai H.

Fundamenta Informaticae

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2001

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Vol. 48, nr 4

343-362

EN

This paper presents a tool for handling equivalence relations in non-deterministic information systems. Some applications of equivalence relations are also shown. In a deterministic information system, it is possible to define an equivalence relation for any set of attributes. However, in a non-deterministic information system, some kinds of equivalence relations which we call possible equivalence relations are definable. This paper proposes two effective procedures producing all possible equivalence relations for any non-deterministic information system and any set of attributes. The details of algorithms, the implementation of algorithms and applications to the rule extraction, etc. are presented.