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1.
The study of the chemical stability of vitreous material in aqueous media is well‐established. There has to date been little consideration of the implications of variations in the chemical durability of tephra in Quaternary tephrochronology. Chemical alteration can take the form of cationic leaching from the matrix, or complete destruction of the silica network, either of which could constrain the ability to chemically identify distal tephra. Here we apply established models of vitreous durability to the published chemical analyses of a large number of Icelandic tephras in order to predict their relative durabilities under equivalent conditions. This suggests that some important tephras have relatively poor chemical stability, and that rhyolitic tephras are, in general, more stable than basaltic. We conclude that tephras should be expected to show predictable differential chemical stability in the post‐depositional environment. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Abstract. For the purpose of development of methane hydrate, occurring in the deep marine subsurface, as a resource, the most important issue is to understand the methane hydrate system (generation, migration and accumulation) as well as to delineate the methane hydrate reservoir properties. We have applied the Amplitude Versus Offset (AVO) analysis to the seismic data acquired in the Nankai Trough, offshore Japan, in order to confirm the occurrence of gas just below the methane hydrate-bearing zone, assuming that gas will show a so-called Class-3 AVO response. Knowledge of the amount and occurrence of gas in the sediment below methane hydrate-bearing zone is one of the keys to understand the methane hydrate system.
We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate-bearing zone and the underlying gas-bearing zone. In the region of MITI Nankai Trough Well PSW-3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset-amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate-bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate-bearing zone in the Nankai Trough well drilling. 相似文献
We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate-bearing zone and the underlying gas-bearing zone. In the region of MITI Nankai Trough Well PSW-3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset-amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate-bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate-bearing zone in the Nankai Trough well drilling. 相似文献
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在狭窄场地上进行大吨位单桩竖向静载试验时,需要解决的问题是在试验设备受场地限制无法增加的情况下如何提供足够大的反力荷载。根据此次试验场地地层中基岩埋藏丰富且深度较浅的情况,通过采用预应力锚索,进行加载反力装置设计,最终采用十字形加载反力装置,有效地解决了反力荷载不足的问题,从而为类似的试验提供了一种思路和选择。同时,通过对试验中出现的一些问题诸如锚固力、自由段变形等进行深入地分析和研究,提出了有关改进和完善反力装置现方案的建议。 相似文献
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Technique for Controlling Spread of Limnotic Oncomelania 总被引:1,自引:0,他引:1
Schistosomiasis is a parasitic disease mostly found in areas along the Changjiang River of China. The disease is spread solely through an intermediary named oncomelania, so its spread of schistosomiasis can be controlled by properly designing water intakes which prevent oncomelania from entering farming land or residential areas. This paper reports a successful design process and a new oncomelania-free intake device. The design of the new intake is based on a sound research program in which extensive experimental studies were carried out to gain knowledge of oncomelania eco-hydraulic behavior and detailed flow field information through CFD simulation. 相似文献
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SUN Xiaoming 《《地质学报》英文版》2011,85(3):656-660
In the present study, the modified Sverjensky–Molling equation, derived from a linear-free energy relationship, is used to predict the Gibbs free energies of formation of crystalline phases of α-MOOH (with a goethite structure) and α-M2O3 (with a hematite structure) from the known thermodynamic properties of the corresponding aqueous trivalent cations (M3+). The modified equation is expressed as ΔG0f,MVX=aMVXΔG0n,M3++bMVX+βMVXγM3+, where the coefficients aMVX, bMVX, and βMVX characterize a particular structural family of MvX (M is a trivalent cation [M3+] and X represents the remainder of the composition of solid); γ3+ is the ionic radius of trivalent cations (M3+); ΔG0f,MVX is the standard Gibbs free energy of formation of MvX; and ΔG0n,M3+ is the non-solvation energy of trivalent cations (M3+). By fitting the equation to the known experimental thermodynamic data, the coefficients for the goethite family (α-MOOH) are aMVX=0.8838, bMVX=?424.4431 (kcal/mol), and βMVX=115 (kcal/mol.?), while the coefficients for the hematite family (α-M2O3) are aMVX=1.7468, bMVX=?814.9573 (kcal/mol), and βMVX=278 (kcal/mol.?). The constrained relationship can be used to predict the standard Gibbs free energies of formation of crystalline phases and fictive phases (i.e. phases that are thermodynamically unstable and do not occur at standard conditions) within the isostructural families of goethite (α-MOOH) and hematite (α-M2O3) if the standard Gibbs free energies of formation of the trivalent cations are known. 相似文献