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61.
62.
Projectile impact on soft,porous rock 总被引:1,自引:0,他引:1
SummaryProjectile Impact on Soft, Porous Rock An experimental investigation was conducted to study the penetration phenomena associated with the normal impact of 60° conical and hemispherically-tipped cylindrical projectiles with a 6.35 mm diameter on green shale in the velocity range from 18 to 40 m/s. In addition to initial velocity, a special device measured the velocity history of the striker during penetration, and the deformation pattern of the target was obtained from grid lines inscribed on a vertical diametral section of the specimen which was reassembled by emplacement in a steel ring before testing. The results showed that the tip geometry controlled the penetration depth which was quadratically related to the initial kinetic energy. Comparison with other data using spherical strikers indicated that only the contact geometry, and not the configuration nor mass of the rest of the striker determined the indentation depth for the same initial bullet energy within the present range of impact parameters.The tests also indicated that target deformation was comprised of material compaction varying in degree from a maximum at the initial contact point towards the target interior and equivolumnial material distortion. A computational model was constructed incorporating both of these features based on an experimentalempirical relation between hydrostatic pressure and volumetric strain and two representations for the effective stress-strain relation of an elastic-perfectly plastic comportment of the material. It was found that good agreement was obtained between the observed deformation pattern and the predictions of this model when flow stress was considered to be independent of volumetric strain, but less so when this quantity was taken as a function of this strain. The model also adequately predicted the velocity history of the projectile both for the present tests and those involving spherical strikers conducted previously.With 15 Figures 相似文献
63.
An evaporation experiment on matrix material of the Murchison (C2) meteorite up to 1900°C in vacuo has revealed the evaporation sequence of primitive dust material and the associated evolution of residual solid phases from hydrous silicates through magnesium silicates and iron-metal to calcium-aluminum oxides. The comparison with primitive meteorites suggests that the evaporation metamorphism coupled with the re-condensation may have played an important role in the generation of diverse primitive meteorites in the early solar nebula. 相似文献
64.
Ground cracks in Ethiopian Rift Valley: facts and uncertainties 总被引:2,自引:0,他引:2
No accurate relationship has been obtained in this study between ground cracks in Ethiopian Rift Valley and the most common causes of earth fissures such as aquifer-system compaction and increased horizontal seepage stresses. This is due to the fact that the level of groundwater withdrawal responsible for these processes is still negligible in Ethiopia. If aquifer-system compaction and increased horizontal seepage stresses have a certain role, then it should be through the long-term effect of groundwater flow from basins to neighboring lakes. The ground cracks appeared also not to have a direct link with active faulting or distant earthquakes. Structurally, the Ethiopian Rift Valley is dominated by NE–SW-trending tensional faults, but no evidence is obtained in this study to associate the process of surface cracking with major tectonics. However, an aseismic elastic strain, which originates at depth and propagates upward through sediments without the formation of bedrock faults, could result in conditions conducive to the development of cracks. Then, fissures might ultimately be created after heavy rainfalls by near-surface processes such as piping and hydrocompaction along water-line sources. 相似文献
65.
Hidemi M. Ito Akihiko Wakayama Mitsuyuki Hoshiba De-Yi Feng Ming-Zhou Lin 《地震学报(英文版)》1993,6(4):813-821
We have developed a workstation-assisted information processing system. The system has three major functions: information
retrieval from seismic data, detection of earthquake precursors, and graphical display of relevant results. Fuzziness is inevitably
involved in these functions, an adequate treatment of which is vital. The system accepts instructions given by a successive
choice of words in hierarchal structure, which is followed by a tune-up of the corresponding membership function. The degrees
of fuzziness in the outputs are recognized visually, for example, by coloring. This contrivance together with dynamic data
exchange among the above functions facilitates the operation of the system.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 399–406, 1993.
This study is partly supported by a project “Fuzzy systems and their applications to human and natural sciences” of Science
and Technology Agency. 相似文献
66.
C. Uyeda T. Takeuchi A. Yamagishi A. Tsuchiyama T. Yamanaka M. Date 《Physics and Chemistry of Minerals》1993,20(6):369-374
The diamagnetic properties of sheetsilicates are studied by measuring the magnetic orientation of micron-sized crystals. In the case of synthetic phlogopite with the average diameter of 0.65 μm and the thickness of 0.2 μm, the alignment of the grains is achieved in the magnetic field below 35 kOe. The planes of the platy single-crystal grains were alignned parallel to the field when the alignment was achieved. The alignment of the grains is realized because the field-induced anisotropic energy, caused by the diamagnetic anisotropy in the mineral's crystal structure, exceeds thermal agitation energy in the applied field. By analyzing the field dependence of grain alignment, the diamagnetic anisotropy per formula unit, Δχ, of sheetsilicate mineral is estimated even if a large single crystal is not provided. The field-induced anisotropic energy is proportional to NΔχ where N is the number of molecules in the grain. A linear correlation has been found between the Δχ value and the F/OH mole ratio among the measured sheetsilicates. This correlation supports the assumption that the hexagonally packed oxygen-layer in the crystal lattice induces the anisotropies of the sheetsilicates. 相似文献
67.
68.
Sayaka Yasunaka Yukihiro Nojiri Taketo Hashioka Chisato Yoshikawa Taketoshi Kodama Shin-ichiro Nakaoka Sanae Chiba Fuminori Hashihama Masahide Wakita Ken Furuya Daisuke Sasano Akihiko Murata Hiroshi Uchida Michio Aoyama 《Journal of Oceanography》2018,74(1):1-11
We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH4 +) and nitrite (NO2 ?) concentrations in the Pacific Ocean. The highest NH4 +, NO2 ?, and nitrate (NO3 ?) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH4 + concentrations were elevated during May–October in the western subarctic North Pacific, May–December in the eastern subarctic North Pacific, and June–September in the subtropical South Pacific. NO2 ? concentrations were highest in winter in both hemispheres. The seasonal cycle of NH4 + was synchronous with NO2 ?, NO3 ?, and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll-a but out of phase with NO2 ? and NO3 ? in the subarctic regions. 相似文献
69.
Characteristics of Sea Surface Circulation and Eddy Field in the South China Sea Revealed by Satellite Altimetric Data 总被引:4,自引:0,他引:4
Temporal and spatial variations of sea surface circulation in the South China Sea were revealed with use of altimetric data provided by TOPEX/POSEIDON from December 1992 to October 1997. The estimated distribution of sea surface dynamic heights from altimetric data coincide well with the results of observation by Soong et al. (1995) and Chu et al. (1998). The RMS variability of sea surface dynamic height, which is obtained after tidal correction based on Yanagi et al. (1997), is high in the central part of the South China Sea, the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand. The high RMS variability in the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand is due to set up and set down of sea water by the East Asian monsoon, which is northeasterly during winter and southwesterly during summer. Also, the high RMS variability in the central part of the South China Sea is due to the variations of basin-wide circulation. The circulations are dominant in the central part of the South China Sea during summer and winter, an anticyclonic circulation during summer and a cyclonic circulation during winter. It is suggested that these circulations are controlled by the East Asian monsoon. Hence, there is an interannual variability of the basin-wide circulation associated with the variation of the East Asian monsoon. 相似文献
70.
Akihiko Morimoto Shoichiro Kojima Sen Jan Daisuke Takahashi 《Estuarine, Coastal and Shelf Science》2009
We investigated the movement of the Kuroshio axis on the northeast shelf of Taiwan associated with the passage of typhoons, using sea surface current data observed by the ocean radar system on Yonaguni and Ishigaki islands. First, we examined daily Kuroshio axis variation on the northeast shelf of Taiwan during typhoon events. The ocean radar data showed that the Kuroshio axis moved onto the shelf after passages of typhoons. The Kuroshio moved onto the shelf and stayed there after the passage of Typhoon Hai-Tang; while the Kuroshio maintained this pattern, southerly wind blew continuously for 4 days. The mean current speed northeast of Taiwan after the typhoon's passage increased by 18 cm s−1. In addition, the sea level difference between two satellite altimetry tracks east of Taiwan increased by 14.4 cm. These results suggest that coastal upwelling east of Taiwan caused by the southerly wind generated an east–west sea level difference that, in turn, generated a northward geostrophic current. This current could have enhanced the Kuroshio east of Taiwan, and pushed it onto the shelf. 相似文献