In situ neutron diffraction study on the effect of aluminium fluoride on phase transformation of mullite from alumina/clay

The effect of aluminium fluoride (AIF3) on the phase transformation sequence of mullite (3AI2032Si02) from two different types of kaolin (kaolinite and halloysite) (AI2Si20s(OH)4-2H20) within an alumina (A1203) matrix for a temperature range of 20 - 1500 C was investigated using in situ neutron diffraction. Samples containing a mixture of A1F3 (0 - 5 wt%), AI203 and kaolin were heated up to 1500 C and then furnace cooled. During the heating procedure, one hour neutron diffraction scans were conducted at 600, 900, 1100, 1200, 1300 and 1400 C, followed by six consecutive one hour scans at 1500 C and finally a one hour scan at room temperature upon cooling. The diffraction patterns collected between 1100 and 1500 C were analyzed by Rietveld analysis. The observed phase transformations exhibited a typical sequence found inclay/alumina ceramics. Corundum, mullite and cristobalite were observed. A common feature among the specimens containing different amounts of AIF3 and kaolin was that the content of corundum decreased as the amount of mullite increased, whilst the cristobalite content tended to peak near the temperature where the amounts of corundum and mullite were approximately equal. The mullitization temperature was reduced as the AIF3 content increased for both kaolinite and halloysite. The presence of AIF3 appeared to reduce the onset temperature for mullite nucleation, which is at a much lower temperature compared to that of grain growth. However, AIF3 also seemed to lower densification. Likewise mechanical properties of the resulting specimens were determined

地震発生帯における深部掘削孔を用いた長期計測

Large earthquakes occur frequently in subduction zones. Most earthquakes are generated in the seismogenic zone, a fairly limited area confined to the shallower regions of the subduction plate boundary. To understand the processes of earthquake generation, it is essential to monitor the physical and mechanical properties of the seismogenic zone over long periods. At present, there are no deep borehole observations of the seismogenic zone more than 3km below seafloor, because it has, until now, been impossible to penetrate to such depths below the sea floor. The Integrated Ocean Drilling Program (IODP), scheduled to begin in 2003, plans to drill boreholes beneath the ocean floor using a multiple-drilling platform operation. The IODP riser-quipped drilling ship (Chikyu) enables the emplacement of boreholes up to 0km beneath the ocean floor, and will provide opportunities to conduct long-term deep borehole observations in the seismogenic zone. Long-term borehole observations in the seismogenic zone are expected to require the development of advanced sampling, monitoring, and recording technology. Here, we discuss the scientific objectives, engineering and technical challenges, and experimental design for a deep borehole, long-term deepborehole monitoring system aimed at understanding the processes of earthquake generation in the seismogenic zone of subduction plate boundaries. We focus specifically on the relationships between environmental conditions in the deep subsurface, details of monitoring and recording, and design and implementation of scientific tools and programs

La dynamique spatiale de la zone côtière autour de la baie de Tokyo

Spatial dynamics of the coastal areas around Tokyo-bay. This article explores the past, the present ans the futur of the coastal areas around Tokyo-bay. The reclaimed lands of this zone have always been the stage of big projects for city planning of the world greatest metropolis, Tokyo.Cet article s'interroge sue le passé, le présent et le futur de la zone côtière autour de la baie de Tokyo. Les remblais littoraux de cette zone ont toujours été le théâtre des grands aménagements de la plus grande métropole du monde, Tokyo.Tezuka Akira, Takahashi Nobuo. La dynamique spatiale de la zone côtière autour de la baie de Tokyo. In: Hommes et Terres du Nord, 1998/4. Hommage à Pierre Bruyelle Aménagement du territoire et régions urbanisées. pp. 225-228

Structure et dynamisme d'un quartier dans le centre-ville de Tokyo

This article explores by example of one neighbourhood district of Tokyo's urban center, Kanda-Izumi, the horizontal and vertical differentiation of urban functions, the character of day-night population and the persistence of community life. With the extension of the C.B.D. of Tokyo, the district of Kanda-Izumi has been transformed into a business district. But this phenomenon of tertiarization has been developed in different ways in the center and the surrounding belt of this district. The pattern of land parcels remains almost intact in the inner part of this district, where small buildings of four or five stories are mixed with traditional wooden houses. In spite of the decrease of residential population, community life has stayed very active and various events are organized, particularly by a local association of inhabitants «cho-kai», all the year round.Cet article montre par l'exemple d'un quartier du centre-ville de Tokyo, celui de Kanda-Izumi, la différenciation horizontale et verticale des fonctions, le caractère de la population diurne et nocturne et la persistance de la vie communautaire. Avec l'extension du C.B.D. de Tokyo, ce quartier était transformé en quartier d'affaires. Mais ce phénomène de tertiarisation s'est déroulé de manière différente entre le centre et la lisière du quartier. La maille parcellaire reste à peu près intacte à l'intérieur du quartier, où se mêlent les petites maisons de bois et les petits bâtiments à trois ou quatre étages. En dépit de la diminution des habitants, la vie communautaire reste très active et les diverses activités (culturelle, sociale, amicale, etc.) se déroulent tout le long de l'année, rythmées et organisées surtout par les activités de « cho-kai », une association des habitants de quartier.Tezuka Akira, Takahashi Nobuo, Tabayashi Akira, Ugawa Kana. Structure et dynamisme d'un quartier dans le centre-ville de Tokyo . In: Annales de Géographie, t. 107, n°602, 1998. pp. 410-430