Hisashi NAKAI (中井 日佐司)

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Grant-in-Aid for Scientific Research (C), Fund Type: -, Overall Grant Amount: - (direct: 3500000, indirect: 270000)
The purpose of this study is the development of on-line educational materials of fundamental subjects of engineering for students who are non-native speakers of Japanese. This was pursued through the following investigations.
1. Investigation of vocabulary and expressions found in mathematics textbooks used in Japanese high schools.
(1) Listing mathematical vocabulary and expressions found in the textbooks Differential, in Mathematics II, and Mathematics III. The complete list contains a total of 3367 vocabulary items, collocations, sentence patterns, and discourse patterns.
(2) Translating the Japanese expressions in this list into Chinese and Korean.
(3) Contrasting these translations in order to analyze differences among the three languages and difficulties for non-native speakers of Japanese.
2. Investigation of mathematic problem solving by Chinese students.
Two studies were conducted : 1) a study of Japanese expressions found in the solutions of differential problems calculated by Chinese students and 2) a study of the relations among Japanese language ability, mathematical ability, and the understanding and solving of mathematic problems by Chinese students. In study 1), it was found that low Japanese proficiency students use only a "noun WA noun" structure and some basic conjunctions. It was also found that it is difficult for both low and high Japanese proficiency students to use Japanese expressions for naming and replacement in the absence of a model. In study 2), it was found that students with low Japanese proficiency but an adequate background in mathematics can solve mathematical problems written in Japanese. It was also found that Japanese proficiency equivalent to grade 2 of the Japanese proficiency test is necessary for solving such mathematical.problems.

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Grant-in-Aid for Scientific Research (C), Fund Type: -, Overall Grant Amount: - (direct: 2500000, indirect: -)
In this work, the preparation and characterization of Co-Ti-N films have been conducted. First, we have disclosed the relation between the preparation condition and the structure of the Co-Ti-N films. Co-Ti-N films have been prepared by dc sputtering of Co-Ti complex target in Ar +N_2 gas mixture. For the films deposited at appropriate N_2 partial pressure, the reaction between Ti and N occurs to form TiN during post-deposition thermal anneal. As a result Co and Ti separate with each other, to form Co-TiN nano-composite. The sizes of Co and TiN grains in the longitude direction are about 10 nm in diameter. And fiber-like structure is developed along the normal direction of the film surface. Next the magnetic properties of the Co-TiN nanocomposite films have been investigated. It has been found Co-TiN nanocomposite films with their thickness less than 100 nm show similar magnetization behavior in both longitude and perpendicular directions. However, those films with their thickness above 100 nm show perpendicular magnetic anisotropy, I.e. perpendicular direction becomes the easy axis of magnetization. Furthermore, the dependence of magnetic properties on the thermal anneal condition and film structure have been investigated. The as-deposited films almost do not show ferromagnetic performance. When the films were annealed at 400 - 700℃, they show clearly ferromagnetic performance and the saturation magnetization increased with increasing anneal temperature. This is because that in the as-deposited state, Co atoms are bonded to Ti and N, upon thermal anneal at elevated temperature, N atoms preferentially react with Ti atoms, therefore, Co is separated. The magnetic properties of the Co-TiN films also depend strongly on the amount of N incorporated into the films. When N amount is too small, the phase separation can not fully proceed. On the other hand, when the N amount is too large, Co is also nitrided except Ti. Both cases will impair the saturation magnetization. Therefore it is important to control the N amount in the film.
Beside the magnetic properties, we have found that the resistivity and hardness of Co-TiN nanocomposite films are very high compared with metal and alloy films.
According to the result of this research work, we consider the Co-TiN-based nanocomposite films very promising as ultra-high density perpendicular magnetic recording media.