Experimental diffusion of hydrogen into synthetic fluid inclusions in quartz

Abstract Quartz-hosted, synthetic CO₂-H₂O fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory-simulated metamorphic re-equilibration at 650, 750 and 825°C and 1.5 kbar total pressure with f_O2 defined by the C-CH₄ buffer. Microthermometry and Raman spectroscopy show that the initial CO₂-H₂O inclusions become CO₂-CH₄-H₂-H_2O
inclusions after diffusive influx of hydrogen from the reducing confining medium. Measurable changes are observed in inclusion compositions after only 15 days of re-equilibration, implying significant hydrogen mobility at still lower temperatures over geological time spans. Results of synthetic inclusion re-equilibrium experiments have profound implications for the interpretation of natural fluid-inclusion data; failure to account for potential hydrogen migration in inclusions from high-temperature geological environments may lead to erroneous estimates of P-T, and/or the compositions of metamorphic fluids.     

Accuracy of kinematic wave and diffusion wave approximations for space-independent flows on infiltrating surfaces with lateral inflow neglected in the momentum equation

Error equations for the kinematic wave and diffusion wave approximations with lateral inflow neglected in the momentum equation are derived under simplified conditions for space-independent flows. These equations specify error as a function of time in the flow hydrograph. The kinematic wave, diffusion wave and dynamic wave solutions are parameterized through a dimensionless parameter γ which is dependent on the initial conditions. This parameter reflects the effect of initial flow depth, channel-bed slope, lateral inflow, infiltration and channel roughness when the initial condition is non-vanishing; it reflects the effect of bed slope, channel roughness and acceleration due to gravity when the initial condition is vanishing. The error equations are found to be the Riccati equation. The structure of the error equations in the case when the momentum equation neglects lateral inflow is different from that when the lateral inflow is included.     

随机扩散水质模型研究

考虑湖泊中影响总磷沉积过程的众多生态因子的变化过程,假定湖泊中总磷沉积过程由标准布朗运动驱动,建立了一个总磷浓度的随机扩散方程,推广确定性富营养化Vollenweider水质模型为随机扩散模型,获得了总磷浓度过程的解析解,进而求出了总磷浓度过程的均值和方差,指出了一种依据沉积系数调控湖泊中总磷浓度的方法。模型被应用于巢湖总磷浓度过程的模拟。     

Importance of advective zone in longitudinal mixing experiments

One-dimensional Fickian dispersion models such as the advection diffusion equation (ADE) are commonly used to analyse and predict concentration distributions downstream of contamination events in watercourses. Such models are only valid once the tracer had entered the equilibrium zone. This paper compares previous theoretical, experimental and numerical estimates of the distance to reach the equilibrium zone with new experimental values, obtained by examining the change of skewness in a tracer profile, downstream of a cross-sectionally well mixed source. Closer agreement was found with Fischers’ theoretical estimate than prior experimental and numerical studies.     

A filtering approach for estimating lake water quality from remote sensing data

In this paper we consider the estimation of lake water quality constituent distributions from hyperspectral remote sensing data. We present a computational approach that can be used to assimilate information from mathematical evolution models into data processing. The method is based on a reduced order iterated extended Kalman filter, and a convection–diffusion model is used to describe the movement of the water quality constituents. The performance of the technique is evaluated in a simulation study. The results show that the filter approach with an appropriate evolution model yields estimates that have better spatial and temporal resolutions than those obtained with conventional methods. Furthermore, the use of a feasible evolution model may make it possible to obtain information also on the concentrations in the lower parts of the lake.     

利用非线性扩散的半自动纹理图像分割

介绍了一种非线性扩散过滤器法从包含纹理的图像中获取灰度、尺度和方向信息，并形成经过耦合保边平滑的5通道向量值图像，对纹理图像的分割变为对此向量值图像的分割。针对半自动操作的特点，在合理的假设前提下，采用了多通道统计区域分割法。试验结果表明，本文的纹理分割方法能有效地利用重要纹理特征与灰度的混合信息，是一种半自动的无监督纹理图像分割方法。     

Disc structure around strongly magnetic accretors: a full disc solution with buoyancy diffusivity

A full numerical solution is found for the effect of a strongly magnetic star on its accretion disc, for the case of magnetic buoyancy diffusion. As in the previously considered case of turbulent diffusion, the disc becomes disrupted when magnetic and viscous stresses become comparable. A magnetically induced temperature elevation leads to electron scattering opacity and radiation pressure becoming significant far from the stellar surface, with consequent viscous instability and vertical disruption of the disc. This, together with the previous turbulent case, suggests that such a disruption mechanism owing to strongly magnetic accretors is generally operable.     

The Locations of Wal-Mart and Kmart Supercenters: Contrasting Corporate Strategies

Wal-Mart and Kmart, the two largest American discount retailers, have begun to utilize a supercenter retailing format that combines a full-service grocery store with a discount department store. Supercenters are expected to be the major format for future expansion of each of these firms. The purpose of this paper is to analyze the spatial expansion strategies of each firm for the locations of its supercenters. Wal-Mart is quickly expanding its number of supercenters in modest-sized communities clustered around its grocery distribution centers, especially in Southern states. Conversely, most Super Kmart Centers are located inthe suburbs of widely scattered major metropolitan markets, and Kmart has yet to develop a grocery distribution network. Kmart currently has major financial problems that severely restrict the expansion of the Super Kmart Center format.     

辽东湾东海岸地区热内边界层特性研究

利用辽东湾东海岸三个低空探测点的实测资料计算了各低空探测点的热内边界层平均高度,并将观测值与用经验公式得到的估算值进行了比较,给出了可用于这一地区的计算公式。     

Three‐parameter discontinuous distributions for hydrological samples with zero values

A consistent approach to the frequency analysis of hydrologic data in arid and semiarid regions, i.e. the data series containing several zero values (e.g. monthly precipitation in dry seasons, annual peak flow discharges, etc.), requires using discontinuous probability distribution functions. Such an approach has received relatively limited attention. Along the lines of physically based models, the extensions of the Muskingum‐based models to three parameter forms are considered. Using 44 peak flow series from the USGS data bank, the fitting ability of four three‐parameter models was investigated: (1) the Dirac delta combined with Gamma distribution; (2) the Dirac delta combined with two‐parameter generalized Pareto distribution; (3) the Dirac delta combined with two‐parameter Weibull (DWe) distribution; (4) the kinematic diffusion with one additional parameter that controls the probability of the zero event (KD3). The goodness of fit of the models was assessed and compared both by evaluation of discrepancies between the results of both estimation methods (i.e. the method of moments (MOM) and the maximum likelihood method (MLM)) and using the log of likelihood function as a criterion. In most cases, the DWe distribution with MLM‐estimated parameters showed the best fit of all the three‐parameter models. Copyright © 2005 John Wiley & Sons, Ltd.