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41.
Gen SHIMODA Noboru NAKAMURA Makoto KIMURA Tomomi KANI Susumu NOHDA Koshi YAMAMOTO 《Meteoritics & planetary science》2005,40(7):1059-1072
Abstract— The timing and processes of alteration in the CV parent body are investigated by the analysis of Sr isotopes, major and trace elements, and petrographic type and distribution of the secondary minerals (nepheline and sodalite) in 22 chondrules from the Allende (CV3) chondrite. The Sr isotopic compositions of the chondrules are scattered around the 4.0 Ga reference line on the 87Sr/86Sr evolution diagram, indicating that the chondrules have been affected by late thermal alteration event(s) in the parent body. The degree of alteration, determined for individual chondrules based on the distribution of nepheline and sodalite, is unrelated to the disturbance of the Rb‐Sr system, suggesting that the alteration process that produced nepheline and sodalite is different from the thermal process that disturbed the Rb‐Sr system of the chondrules. Considering the geochemical behavior of Rb and Sr, the main host phase of Sr in chondrules is likely to be mesostasis, which could be most susceptible to late thermal alteration. As there is a poor connection between the alteration degree determined from abundances of nepheline and sodalite and the disturbance of Rb‐Sr isotopic system, we consider the mesostasis to provide a constraint on the late parent body alteration process. From this point of view, 23 mesostasis‐rich chondrules, including those from literature data, were selected. The selected chondrules are closely correlated on the 87Sr/86Sr evolution diagram, with an inferred age of 4.36 ± 0.08 Ga. This correlation would represent an age of the final major Sr isotopic redistribution of the chondrules in the parent body. 相似文献
42.
43.
Song Hong (Red River) delta evolution related to millennium-scale Holocene sea-level changes 总被引:2,自引:0,他引:2
Susumu Tanabe Kazuaki Hori Yoshiki Saito Shigeko Haruyama Van Phai Vu Akihisa Kitamura 《Quaternary Science Reviews》2003,22(21-22):2345-2361
The Song Hong (Red River) delta occurs on the northwest coast of the South China Sea. Its evolution in response to Holocene sea-level changes was clarified on the basis of sedimentary facies and 14 radiocarbon dates from the 40 m long Duy Tien core from the delta plain, and using previously reported geological, geomorphological, and archaeological data. The delta prograded into the drowned valley as a result of early Holocene inundation from 9 to 6 cal. kyr BP, as sea-level rise decelerated. The sea-level highstand at +2–3 m from 6 to 4 cal. kyr BP allowed widespread mangrove development on the delta plain and the formation of marine notches in the Ha Long Bay and Ninh Binh areas. During sea-level lowering after 4 cal. kyr BP, the former delta plain emerged as a marine terrace, and the delta changed into the present tide- and wave-influenced delta with accompanying beach ridges. Delta morphology, depositional pattern, and sedimentary facies are closely related to Holocene sea-level changes. In particular, falling sea level at 4 cal. kyr BP had a major impact on the evolution of the Song Hong delta, and is considered to be linked to climate changes. 相似文献
44.
Consideration of fabric anisotropy is crucial to gaining an improved understanding of the behavior of granular materials. This paper presents a constitutive model to describe the sand behavior associated with fabric anisotropy within a framework of a strain space multiple mechanism model. In the proposed model, a second-order fabric tensor is extended by incorporating a new function that represents the effect of inherent (or initial fabric) anisotropy, along with three additional parameters: two of them, a1 and a2 , control the degree of anisotropy, and the second mode of inherent anisotropy can be expressed by introducing the parameter a2 as well as the first mode by the parameter a1 . The third parameter, θ0 , expresses the principal direction of inherent anisotropy (eg, the normal vector direction of bedding planes relative to horizontal axis). The formulation of the dilative component of dilatancy (ie, positive dilatancy) is also extended to consider the effect of inherent anisotropy based on the interlocking mechanism. Experimental data on the complex anisotropic responses of Fraser River sand and Toyoura sand under monotonic loading is used to validate this model. The proposed model is shown to successfully capture anisotropic responses, which become contractive or dilative depending on different principal-stress directions, with a single set of anisotropy parameters; thus, the model is considered to possess the capability to simulate the anisotropic behaviors of granular materials. In addition to different loadings on the same fabric, the effects of different fabric anisotropies upon the sand behavior under the same loadings are also investigated. 相似文献
45.
Hiroko Okawachi Susumu Ohtsuka Norshida Binti Ismail B. A. Venmathi Maran Kazuo Ogawa 《Ocean Science Journal》2012,47(3):181-187
The seasonal occurrence and microhabitat of the monogenean Udonella fugu that hyperparasitizes exclusively on adults of the caligid copepod Pseudocaligus fugu that infects the skin of the grass puffer Takifugu niphobles were investigated in the Seto Inland Sea, western Japan from November 2004 to December 2006. The udonellids occurred and bred mostly during the occurrence of P. fugu on the fish host. The average prevalence and intensity of U. fugu on P. fugu during the whole investigation were 29% and 3.6, respectively. The main attachment sites of U. fugu were the posterior side of leg 3 and the dorsal marginal side of the cephalothorax for feeding and copulation, while eggs were predominantly located on the ventral side of the urosome to avoid detachment. More attention should be paid to the ecology of U. fugu, due to recent high prevalence of P. fugu on cultured tiger puffer in western Japan. 相似文献
46.
黄土液化机理和判别标准的再研究 总被引:2,自引:0,他引:2
本文结合作者的试验研究和国外最新研究进展对黄土液化问题作了一些深入讨论。在一定的条件下,黄土可能发生液化,而且相当一部分黄土符合“修正的中国标准”。从液化机理上讲,黄土液化属于流滑。试验研究发现,黄土液化过程与应变发展有内在的联系,因而在动三轴试验中用轴向应变作为黄土初始液化的判别条件更符合实际。最后,通过对俄罗斯、美国和中国黄土的对比研究,作者认为黄土的粒度组成对黄土的液化特性有明显的影响。 相似文献
47.
Li Wei LDaren Shoichiro Fukao Mamoru Yamamoto Toshitaka Tsu Susumu Kato 《Acta Meteorologica Sinica》1991,5(3):293-298
Preliminary results of the wind velocity estimation using the Maximum Entropy Method (MEM) to MUradar observation data sets are presented. The comparison of the results from the periodogram method and theMEM shows that the MEM estimation is reliable, and has higher accuracy, resolution and detectability than theestimation from periodogram method. The high accuracy power spectrum obtained by the MEM is veryuseful to studying the atmospheric turbulence structure. However. the MEM needs the longer computingtime for obtaining the high accuracy spectrum. Particularly, the estimation of MEM will bring serious devia-tion at lower signal-to-noise ratio. 相似文献
48.
Hiroshi Tateyama Susumu Shimoda Toshio Sudo 《Contributions to Mineralogy and Petrology》1978,66(2):149-156
In the system Na2CO3-MgO-SiO2-H2O a new sodium magnesium silicate was synthesized under hydrothermal conditions; 450–600 ° C and 300–1000 Kg/cm2. The structure of the specimen was determined by X-ray powder methods, and its properties were studied by chemical, infrared and TG analyses. The specimen has a triple chain structure (space group, C2/c) with the ideal chemical composition, 4 (Na2Mg4Si6O16(OH)2) and lattice parameters, a= 10.152(2), b=27.137(4), c=5.276(1) Å, and = 106.97(3) °.The essential feature of the structure is shown by the presence of SiO4 tetrahedra linked to form chains which have three times the width of those in pyroxene. These triple chains have a periodicity, 5.27 Å, along their lengths, and are bonded to each other laterally by the brucite layer made up by eight Mg cations and sandwiched between two inward pointing bands of tetrahedra. These units are linked back to back by cations (Mg or Na) in the Na(2) site and by a large cation (Na) at the Na(1) site. 相似文献
49.
Interchannel hydraulic geometry and hydraulic efficiency of the anastomosing Columbia River,southeastern British Columbia,Canada 总被引:2,自引:0,他引:2
The morphodynamics of the anastomosing channel system of upper Columbia River in southeastern British Columbia, Canada, is examined using an adaptation of conventional hydraulic geometry termed ‘interchannel hydraulic geometry’. Interchannel hydraulic geometry has some of the characteristics of downstream hydraulic geometry but differs in that it describes the general bankfull channel form and hydraulics of primary and secondary channels in the anastomosing channel system. Interchannel hydraulic geometry generalizes these relationships and as such becomes a model of the geomorphology of channel division and combination. Interchannel hydraulic geometry of upper Columbia River, based on ?eld measurements of ?ow velocity and channel form at 16 test sections, is described well by simple power functions: wbf = 3·24Qbf0·64; dbf = 1·04Qbf0·19; vbf = 0·30Qbf0·17. These results, with other related measurements of ?ow resistance, imply that channel splitting leads to hydraulic inef?ciency (higher ?ow resistance) on the anastomosing Columbia River. Because these ?ndings differ from those reported in studies elsewhere, we conclude that hydraulic ef?ciency does not provide a general explanation for anabranching in river channels. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
50.