Effects of finite-width pulses in the pulsed-field gradient measurement of the diffusion coefficient in connected porous media
Effects of finite-width pulses in the pulsed-field gradient measurement of the diffusion coefficient in connected porous media
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DOI：
10.1016/s1090-7807(03)00248-9
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发表时间：
2003-11-01
影响因子：
2.2
通讯作者：
Sen, PN
中科院分区：
文献类型：
--
作者：
Zielinski, LJ;Sen, PN
本文以有限宽脉冲脉冲场梯度（PFG）实验为例，分析计算了开放受限几何结构（如扩展多孔介质）的表观扩散系数D-app。在短期和长期的限制，我们给出明确的。与模型无关的表达式，该表达式适用于脉冲的有限持续时间，可用于提取孔隙表面与体积（S/V）比以及弯曲度。对于所有时间，我们使用可以从理想窄脉冲PFG获得的实际时间相关扩散系数D(t)的成熟模型形式来计算Dapp。我们比较了Dapp和D(t)，发现无论脉冲宽度和几何相关参数如何，这两个量的偏差都小于20%。这些结果与封闭几何的研究结果形成鲜明对比[J]。粉剂。的原因。[A] 117(1995) 209]，其中有限梯度脉冲宽度的影响很大。本文给出的分析结果可以很容易地适用于不同的脉冲协议和时间序列。(C) 2003 Elsevier Inc.版权所有。
We analytically compute the apparent diffusion coefficient D-app for an open restricted geometry, such as an extended porous medium, for the case of a pulsed-field gradient (PFG) experiment with finite-width pulses. In the short- and long-time limits, we give explicit. model-independent expressions that correct for the finite duration of the pulses and can be used to extract the pore surface-to-volume (S/V) ratio as well as the tortuosity. For all times, we compute Dapp using a well-established model form of the actual time-dependent diffusion coefficient D(t) that can be obtained from an ideal narrow-pulse PFG. We compare Dapp and D(t) and find that, regardless of pulse widths and geometry-dependent parameters, the two quantities deviate by less than 20%. These results are in sharp contrast with the studies on closed geometries [J. Magn. Reson. A 117 (1995) 209], where the effects of finite gradient-pulse widths are large. The analytical results presented here can be easily adapted for different pulse protocols and time sequences. (C) 2003 Elsevier Inc. All rights reserved.