arXiv subjects

M. Nagao

Publications and source records attributed to M. Nagao.

24 records · Page 2Linked to original sources

arXiv2003

Upper Critical Field of a Novel 18-K Superconductive Phase in Metastable Yttrium Sesquicarbide Prepared Using High Pressure Technique

The metastable phase of an yttrium sesquicarbide compound, which was vary recently reported as a new superconductive phase with a Tc value of 18 K, was prepared under high pressure from the nominal composition of Y2C3 and Y2C2.9B0.1 in order to investigate this phase. We have succeeded in reproduction, and in the transport measurement for this 18-K phase. It is considered that the reason for the higher Tc value than the 11.5 K reported previously is not the small amount of B as the impurity element from the BN crucible. The Bc2 value at 0 K estimated from the resistivity data for the 18-K phase seems to be over 30 T. It means that the Tc and Bc2 values of the 18-K phase are as high as those of the general A15 compounds.

cond-mat.supr-con↗

arXiv2001

Spontaneous vortex phase in ErNi2B2C

Below T_{WFM} ~ 2.75K, a weak ferromagnetism and superconductivity coexist in ErNi2B2C. In the present paper, a possibility of a spontaneous vortex phase was examined directly by small angle neutron scattering technique. An external magnetic field was applied to align ferromagnetic domains so that the internal magnetic field induced by the weak ferromagnetism becomes uniform and uniaxial over the bulk sample. When the field is removed, the flux line lattice subsisted below T_{WFM} but disappeared above it. A pinning effect is also discussed. We conclude that the spontaneous vortex state is realized in ErNi2B2C.

cond-mat.supr-con↗

arXiv1999

Resolution of Indirect Anaphora in Japanese Sentences Using Examples 'X no Y (Y of X)'

A noun phrase can indirectly refer to an entity that has already been mentioned. For example, ``I went into an old house last night. The roof was leaking badly and ...'' indicates that ``the roof'' is associated with `` an old house}'', which was mentioned in the previous sentence. This kind of reference (indirect anaphora) has not been studied well in natural language processing, but is important for coherence resolution, language understanding, and machine translation. In order to analyze indirect anaphora, we need a case frame dictionary for nouns that contains knowledge of the relationships between two nouns but no such dictionary presently exists. Therefore, we are forced to use examples of ``X no Y'' (Y of X) and a verb case frame dictionary instead. We tried estimating indirect anaphora using this information and obtained a recall rate of 63% and a precision rate of 68% on test sentences. This indicates that the information of ``X no Y'' is useful to a certain extent when we cannot make use of a noun case frame dictionary. We estimated the results that would be given by a noun case frame dictionary, and obtained recall and precision rates of 71% and 82% respectively. Finally, we proposed a way to construct a noun case frame dictionary by using examples of ``X no Y.''

cs.CL↗

arXiv1999

Pronoun Resolution in Japanese Sentences Using Surface Expressions and Examples

In this paper, we present a method of estimating referents of demonstrative pronouns, personal pronouns, and zero pronouns in Japanese sentences using examples, surface expressions, topics and foci. Unlike conventional work which was semantic markers for semantic constraints, we used examples for semantic constraints and showed in our experiments that examples are as useful as semantic markers. We also propose many new methods for estimating referents of pronouns. For example, we use the form ``X of Y'' for estimating referents of demonstrative adjectives. In addition to our new methods, we used many conventional methods. As a result, experiments using these methods obtained a precision rate of 87% in estimating referents of demonstrative pronouns, personal pronouns, and zero pronouns for training sentences, and obtained a precision rate of 78% for test sentences.

cs.CL↗

arXiv1999

An Estimate of Referent of Noun Phrases in Japanese Sentences

In machine translation and man-machine dialogue, it is important to clarify referents of noun phrases. We present a method for determining the referents of noun phrases in Japanese sentences by using the referential properties, modifiers, and possessors of noun phrases. Since the Japanese language has no articles, it is difficult to decide whether a noun phrase has an antecedent or not. We had previously estimated the referential properties of noun phrases that correspond to articles by using clue words in the sentences. By using these referential properties, our system determined the referents of noun phrases in Japanese sentences. Furthermore we used the modifiers and possessors of noun phrases in determining the referents of noun phrases. As a result, on training sentences we obtained a precision rate of 82% and a recall rate of 85% in the determination of the referents of noun phrases that have antecedents. On test sentences, we obtained a precision rate of 79% and a recall rate of 77%.

cs.CL↗

arXiv1999

Resolution of Verb Ellipsis in Japanese Sentence using Surface Expressions and Examples

Verbs are sometimes omitted in Japanese sentences. It is necessary to recover omitted verbs for purposes of language understanding, machine translation, and conversational processing. This paper describes a practical way to recover omitted verbs by using surface expressions and examples. We experimented the resolution of verb ellipses by using this information, and obtained a recall rate of 73% and a precision rate of 66% on test sentences.

cs.CL↗