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991.
Quantitative measurements are important for imaging fluid content in porous media. Conventional MRI methods suffer from contrast because of relaxation times in porous media, resulting in measurements of apparent fluid content, not the true fluid content. We compare four magnetic resonance imaging methods for fluid content imaging in several water‐saturated reservoir core plugs: frequency‐encoded spin echo, single point ramped imaging with T1 enhancement, hybrid spin echo single point imaging (SE‐SPI), and T2 mapping SE‐SPI. 1‐D profiles obtained with each method were compared in terms of image quality, image sensitivity, and quantification of water content. The image quality of short T2 lifetime samples suffered from blurring in hybrid SE‐SPI images. Image sensitivity was the highest in the profiles obtained with frequency‐encoded spin echo. The quantification of frequency‐encoded spin echo, T2 mapping SE‐SPI, and hybrid SE‐SPI suffered in core plugs with a significant population of short T2 components because of T2 attenuation. Overall, single point ramped imaging with T1 enhancement was found to be the most general method for fluid content imaging. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
992.
The successive approximation method was applied for the first time by N.I. Ioakimidis to solve practical cases of a Cauchy singular integral equation: the airfoil one. In this paper we study a more general case. We prove the convergence of the method in this general case. The proposed method has been tested for two kernels which are particularly important in practice. Finally, some numerical examples illustrate the accuracy of the method. 相似文献
993.
The existence theorems of common fixed points for two weakly increasing mappings satisfying an almost generalized contractive condition in ordered metric spaces are proved. Some comparative example are constructed which illustrate the values of the obtained results in comparison to some of the existing ones in literature. 相似文献
994.
In this paper we will prove the pointwise convergence of L(f; x, y, λ) to f(x0, y0), as (x, y, λ) tends to (x0, y0, λ0) in the space L2π, by the three parameter family of singular operators. In contrast to previous works, the kernel function is radial. 相似文献
995.
Lech Maligranda Volodymyr V. Mykhaylyuk 《Journal of Mathematical Analysis and Applications》2011,375(2):401-411
A negative solution of Problem 188 posed by Max Eidelheit in the Scottish Book concerning superpositions of separately absolutely continuous functions is presented. We discuss here this and some related problems which have also negative solutions. Finally, we give an explanation of such negative answers from the “embeddings of Banach spaces” point of view. 相似文献
996.
We study a non-homogeneous boundary value problem in a smooth bounded domain in RN. We prove the existence of at least two non-negative and non-trivial weak solutions. Our approach relies on Orlicz-Sobolev spaces theory combined with adequate variational methods and a variant of Mountain Pass Lemma. 相似文献
997.
998.
999.
The existence of coincidence points and common fixed points for four mappings satisfying generalized contractive conditions without exploiting the notion of continuity of any map involved therein, in a cone metric space is proved. These results extend, unify and generalize several well known comparable results in the existing literature. 相似文献
1000.
The cloud point temperature, the temperature at which the first wax crystals appear in solution, is one of the most important specifications associated with the low temperature behaviour of a fuel. A database of about 80 fuels and fuel blends was collected and used to assess the performance of the three predictive local composition models (Wilson, NRTL and UNIQUAC) for cloud point prediction. The results indicates that Predictive UNIQUAC can predict the cloud points of the fuels within the experimental uncertainty of the measurements. It could thus be a useful tool in the production of fuels both in the design of refining process and the blend of fuels to meet the low temperature specifications. 相似文献