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排序方式: 共有557条查询结果,搜索用时 31 毫秒
211.
Akira Tsuchiyama Masayuki Uesugi Kentaro Uesugi Tsukasa Nakano Ryo Noguchi Toru Matsumoto Junya Matsuno Takashi Nagano Yuta Imai Akira Shimada Akihisa Takeuchi Yoshio Suzuki Tomoki Nakamura Takaaki Noguchi Masanao Abe Toru Yada Akio Fujimura 《Meteoritics & planetary science》2014,49(2):172-187
In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B. 相似文献
212.
213.
Mineralogy and Petrology - In the Gotsu area of the c. 200 Ma high-P/T Suo metamorphic belt in the Inner Zone of southwest Japan, blueschists occur as lenses or layers within pelitic... 相似文献
214.
Babloo Chaudhary Hemanta Hazarika Akira Murakami Kazunori Fujisawa 《Acta Geotechnica》2018,13(4):997-1017
Many breakwaters have collapsed in the past due to earthquakes and subsequent tsunamis, resulting in considerable devastation as the breakwaters failed to prevent the tsunami from entering the coastal plain areas. Breakwater failures are mainly caused by damage to its foundation ground. However, the damage mechanism of breakwater foundation during earthquakes and tsunamis remains unclear. This study focuses on the breakwater failure mechanism due to collapse of its foundation under the action of an earthquake and subsequent tsunami. In addition, reinforcing countermeasures for breakwater foundation to mitigate damage due to compound geodisasters triggered by earthquakes and tsunamis are proposed. Sheet piles and gabions were used in the breakwater foundation as reinforcing countermeasures. To evaluate the effectiveness of the reinforced foundation, a series of shaking table tests and hydraulic model tests were performed. The tsunami overflow tests were conducted on the same model after the earthquake loadings, and comparisons were made between the conventional and reinforced foundations. It was observed during the tests that the reinforced foundation could effectively reduce the damage to the breakwater caused by earthquake and tsunami-induced forces. Numerical analyses were performed to clarify the mechanism of the soil–breakwater–reinforcement–fluid system. Overall, this study is useful in practical engineering, and the reinforcing foundation model could be adopted for offshore structures to reduce damage from earthquakes and tsunamis in the future. 相似文献
215.
A new isolation interface is proposed in this study to retrofit existing buildings with inadequate soft stories as well as new structures to be constructed with soft first story intended for architectural or functional purposes. The seismic interface is an assembly of bearings set in parallel on the top of the first story columns: the multiple‐slider bearings and rubber bearings. The multiple‐slider bearing is a simple sliding device consisting of one horizontal and two inclined plane sliding surfaces based on polytetrafluoroethylene and highly polished stainless steel interface at both ends set in series. A numerical example of a five‐story reinforced concrete shear frame with soft first story is considered and analyzed to demonstrate the efficiency of the proposed isolation system in reducing the ductility demand and damage in the structure while maintaining the superstructure above the bearings to behave nearly in the elastic range with controlled bearing displacement. Comparative study with the conventional system as well as various isolation systems such as rubber bearing interface and resilient sliding isolation is carried out. Moreover, an optimum design procedure for the multiple‐slider bearing is proposed through the trade‐off between the maximum bearing displacement and the first story ductility demand ratio. The results of extensive numerical analysis verify the effectiveness of the multiple‐slider bearing in minimizing the damage from earthquake and protecting the soft first story from excessively large ductility demand. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
216.
The Inference of Geo-Mechanical Properties of Soft Rocks and their Degradation from Needle Penetration Tests 总被引:2,自引:1,他引:1
Needle penetration tests (NPTs) are used for inferring the uniaxial compressive strength of soft rocks, particularly in tunneling through squeezing rocks and foundations on weathered rocks in Japan. The device measures the applied load and the penetration depth of its needle. The ratio of applied load to penetration depth was originally called the needle penetration index (NPI). In this study, this device has been used to infer the geo-mechanical properties of soft rocks from Japan, Turkey, Indonesia, and Egypt. Various equations are presented to infer the geo-mechanical properties in terms of the NPI and compared with the experimental results. The possibility of evaluating the anisotropy of geo-mechanical properties is shown. Furthermore, the characterization of geo-mechanical properties of fault/fracture and slip (shear) surfaces is explained. Some additional equations are given to consider the degradation of geo-mechanical properties as a function of water content, weathering state, and number of cycles of freezing–thawing. Furthermore, the possibility of evaluating the time-dependency characteristics of soft rocks by needle penetration testing is discussed through experiments. It is shown that the effects of water content, weathering state, and number of cycles of freezing–thawing and time-dependency can be evaluated using the NPT technique. 相似文献
217.
Ryohei Takahashi Hiroharu Matsueda Victor M. Okrugin Naotatsu Shikazono Shuji Ono Akira Imai Elena D. Andreeva Koichiro Watanabe 《Resource Geology》2013,63(2):210-223
In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ34SCDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ34SCDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of 32S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition. 相似文献
218.
219.
Yoshihito KAMATA Miyako KATO Katsumi UENO Akira MIYAHIGASHI Thasinee CHAROENTITIRAT Apsorn SARDSUD 《地球学报》2012,33(S1):33-35
Tectonic subdivision of mainland Thailand has been discussed by means of Paleozoic and Mesozoic stratigraphy, micropaleontology represented by fo-raminiferal and radiolarian biostratigraphy and paleo-biogeography, tectonic settings of granitoids, and ul-tramafic rocks that are distinctive of suture lines. Re-cently, Ueno (2002) and Ueno and Charoentitilat (2011) proposed a new tectonic scheme of mainland Thailand and divided it into three geotectonic units: the Sibu-masu Block, Sukhothai Zone, and Indochina Block from west to east, which are separated by the Mae Yuan Fault, the Chiang Rai Tectonic Line, and the Nan–Uttaradit Suture, respectively. In Northern Thai-land, moreover, the peculiar Inthanon Zone is recog-nized in the eastern part of the Sibumasu Block, where Paleo-Tethyan oceanic rocks are widely distributed as tectonic slices. These geotectonic subdivisions in Northern Thailand are relatively clear. However, the tectonic subdivisions of Central and Southeast Thai-land have not been well documented and are still con-troversial because there is short of information about basement rocks in those areas. In this circumstance, we have examined Paleozoic to Mesozoic stratigraphy, lithology, and radiolarian ages of siliceous rocks dis-tributed in Southeast Thailand to clarify the geotec-tonic belongings of this area and the southern exten-sions of geotectonic units consisting of Northern Thailand. In the course of this research, we could ob-tain Middle to Late Devonian radiolarians from well-bedded siliceous rocks distributed in southwest of Klaeng, Rayong Province. In this study, we report lithology and age of the radiolaria-bearing rocks and discuss their stratigraphy and geological correlation nearby the Klaeng region. 相似文献
220.
ICT-based remediation with knowledge information management is presented for the pump-and-treat method of contaminated groundwater. The usefulness of ICT is discussed for monitoring contaminants and groundwater level, transferring data between the remediation well and the remote remediation center, and decision support analysis for controlling the remediation well. A prototype system was developed and applied to field measurement. The prototype system performed reliably for ~600 days. As a decision support analysis, a fuzzy inference model is discussed. The membership functions were determined based on simple reliability theory. The effectiveness of the proposed method was assessed by numerical simulations. The simulation results suggest that the proposed method is likely to reduce the pumped quantity compared to PID control or an engineer’s empirical knowledge. Analysis results are also shown for cancer risks from contaminants and ground settlement risks due to excess pumping up of groundwater. 相似文献