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81.
82.
Two new hydrothermal acid-base buffers have been developed and calibrated. The Ag+AgBr and the Ag+AgI buffers in conjunction with an external hydrogen buffer control the fugacities of HBr and HI respectively at the pressure and temperature of the experiment. Both buffers are much less acid than the Ag+AgCl buffer of Frantz and Eugster (1973). For corresponding conditions, the molalities of HBr and HI are one and three orders of magnitudes smaller respectively than the molality of HC1.Both buffers have been calibrated using quench bromide, iodide and pH measurements. At higher temperatures HBr and HI are apparently not dissociated and the measured molalities agree closely with those calculated from thermochemical data. At lower temperatures the degree of dissociation increases greatly, and dissociation constants for HBr and HI at P and T have been calculated from the data.The Ag+AgBr and Ag+AgI buffers have been tested by measuring constants for the quartz-talc reaction in H-O-Br and H-O-I solutions respectively. These constants in conjunction with available thermochemical data can be used to calculate the free energies of formation for MgBr2 and MgI2.The Ag+AgBr and Ag+AgI buffers extend the pH range towards neutral solutions over which acid-base reactions in supercritical fluids can now be measured. This allows the use of less concentrated solutions and of minerals which are not stable in acid solutions. 相似文献
83.
I-Ming Chou Hans P. Eugster Peter Berens John H. Weare 《Geochimica et cosmochimica acta》1978,42(3):281-288
The diffusion of hydrogen through platinum membranes has been measured at 450, 500, 550 and 600°C at 2000 bar pressure, using the hydrogen sensor technique. Ag + AgCl + 3 M HC1 was the starting solution inside the platinum tube. Hydrogen diffuses out of the platinum tube into a system containing Fe2O3 + Fe3O4 + H2O; that is, a solution with a fixed hydrogen fugacity. After quench, the drop in fH2 inside the platinum tube was calculated from measurements of pH and chloride molality. fH2 is initially roughly proportional to . Diffusion constants were calculated from these data by numerical integration, and the results can be expressed by logD (cm2/sec) = ? 5489.6/T, K - 4.648. 相似文献
84.
初始场作用的衰减与算子的特性 总被引:12,自引:2,他引:12
本文根据描述大气运动的原始方程的算子的性质论证了初始场影响的衰减。对研究某些实际问题来说原始方程必须简化,作者建议,在进行这样那样的简化或离散化时应注意保持算子的性质不变。 相似文献
85.
Thermal analysis of the halite liquidus in the system NaCl-H2O has been conducted for NaCl mole fractions (XNaCl) greater than 0.25 (i.e., > 50 wt. % NaCl) at pressures between 0.3 and 4.1 kb and temperatures greater than 450°C. The position of the liquidus was located by differential thermal analysis (DTA) of cooling scans only, as heating scans did not produce definitive DTA peaks. The dP/dT slope of the liquidus is positive and steep at high pressures, but at high XNaCl, and pressures below 0.5 kb it appears to reverse slope and intersects the three-phase curve (liquid-halite-vapour) at a shallow angle. However, due to the complex nature of the DTA signal when P <- 0.5 kb, there is considerable doubt about exactly what event has been recorded in the experiments conducted at these low pressures.The solubility of halite can be expressed as a function of the mole-fractional-based activity of NaCl in the liquid phase (L) in temperature (T, °K) and pressure (P, bars) In Our liquidus data (based on 10 compositions) above 500 bars for these brines were combined with this equation to generate activity coefficients of NaCl which were fit within their experimental uncertainties to the following one parameter Margules equation In . Concentrated solutions of NaCl show negative deviations from ideality which rapidly increase in magnitude with decreasing XNaCl. 相似文献
86.
This study was undertaken to develop an approach for modelling changes of sediment chemistry related to the accumulation of aquaculture waste. Metal composition of sediment Al, Cu, Fe, Li, Mn, and Zn; organic carbon and < 63 microm particles were used to determine the extent of detectable effects around the cage. This study showed marked differences in the sediment chemistry between aquaculture sites and the natural background: (1) negative correlations between sediment Cu and Zn with Al, (2) poor correlations between metals and Li, and (3) concentrations of Fe and Mn decreased with increased accumulation of organic carbon. There is a trend among normalised metals, organic carbon and particles related to normal, hypoxic and anoxic sediment conditions. The trends are useful for detecting and assessing the cumulative effects from aquaculture wastes to the marine environment. Lithium is less interactive with other metals in aquaculture sediments compared with the natural background sediments. Principal components analysis (PCA) was carried out on the metals, organic carbon, and particles to cluster the similarities of the variables so as to establish the predicted or adjusted environmental monitoring program (EMP) ratings. This approach, using the adjusted EMP rating based on sediment chemistry, yields a regression model with R2 = 0.945 compared to R2= 0.653 for the regression model using unadjusted EMP for assessing the environmental conditions. 相似文献
87.
Two ungrouted post‐tensioned, precast concrete‐filled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal‐height circular CFT segments, and a footing. Strands were placed through the column and post‐tensioned to provide a precompression of the column against the footing. One specimen also contained energy‐dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy‐dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the segmental column. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
88.
Summary The Runoff of the Changjiang River and the Huanghe River were investigated with the method of wavelet transform. Several significant periods were found. Comparison between wavelet analysis and Fourier analysis was made, which shows the advantages of the former. Finally, the application of the wavelet analysis to operational prediction is discussed.This study is supported by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Chinese Academy of Sciences.With 6 Figures 相似文献
89.
90.