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1.
Babadagli T 《Journal of colloid and interface science》2002,246(1):203-213
Capillary imbibition is an oil recovery mechanism in naturally fractured reservoirs if rock matrix is water wet and there is enough water in fractures in contact with matrix. It, however, may not yield an effective recovery under certain circumstances even if these conditions are maintained. Heavy matrix oil, high interfacial tension (IFT), oil-wet matrix sample, and limited contact area of matrix with water in fractures require additional effort to enhance the oil recovery by capillary imbibition. Chemicals and heat can be injected into naturally fractured reservoirs to improve the capillary imbibition recovery performance. With the involvement of low IFT fluid, heat, and polymer solution in the process, capillary imbibition dynamics may change and this entails an identification of the dynamics of the process through laboratory experiments before injection of these expensive fluids into oil reservoirs. In this study, the dynamics of capillary imbibition was studied experimentally. Static imbibition experiments were conducted on oil- and water-wet rock samples under different boundary conditions and saturated with different types of oil. The analyses were conducted using three indicators, namely the capillary imbibition rate, ultimate oil recovery, and shape of the recovery profile. Based on these indicators, the dynamics of capillary imbibition of different aqueous phases were evaluated for different oil types and matrix properties. The conditions that cause weak or strong capillary imbibition were identified. 相似文献
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Alkan A Kutlu R Hallac T Sigirci A Emul M Pala N Altinok T Aslan M Sarac K Ozcan C 《Magnetic resonance imaging》2004,22(5):707-713
Our purpose was to investigate, by magnetic resonance (MR) spectroscopy, the metabolite changes in the brains of subjects in the shoemaking industry who had been chronically exposed to organic solvents. A total of 49 male subjects and 30 age-matched healthy volunteers underwent detailed neurological and psychiatric examinations. All subjects had long-echo [repetition time (TR) 2000 ms, echo time (TE) 136 ms] single-voxel MR spectroscopy. Voxels (15 x 15 x 15 mm(3)) were placed in the parietal white matter, thalamus, and basal ganglia. N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from thalamus, basal ganglia, and parietal white matter. Cho/Cr ratios in thalamus, basal ganglia, and parietal white matter were found to be significantly increased compared to controls. There was a positive correlation between basal ganglia Cho/Cr ratio and duration of exposure (r = 0.63). MR spectroscopy should be performed to reveal metabolite changes and determine the degree of brain involvement in solvent-related industry workers. 相似文献
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O. Yilmaz F. Y. Lambrecht N. Gokmen S. Erbayraktar K. Durkan 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):311-313
The aim of the present study was to demonstrate the possible transplacental transmission of 131I labeled recombinant human erythropoietin (131I-rh-EPO) in pregnant rats and its distribution through maternal and fetal organs. Six Wistar Albino Rats in their pregnancy
of 18 days were used 131I labeled recombinant human erythropoietin (specific activity = 2.4 μCi/IU) was injected into the tail vein of rats. After
30 minutes labeled erythropoietin infusion maternal stomach, kidney, lung, liver, brain and heart as well as fetus were removed.
Then, the same organs were removed from each fetus. Measuring weight of maternal and fetal organs as well as placenta were
followed by radioactivity count via Cd(Te) detector. 131I labeled recombinant human erythropoietin was found to be able to pass rat placenta and its distribution order in fetal organs
was similar to those of maternal organs. Besides, as measurements were performed closer to cornu uteri, uptakes were decreasing
in every fetus and its corresponding placenta. 相似文献
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Most of the techniques developed for infrared (IR) image enhancement (IE) depend heavily on the scene, environmental conditions, and the properties of the imaging system. So, with a set of predefined scenario properties, a content-based IR-IE technique can be developed for better situational awareness. This study proposes an adaptive IR-IE technique based on clustering of wavelet coefficients of an image for sea surveillance systems. Discrete wavelet transform (DWT) of an image is computed and feature vectors are constructed from subband images. Clustering operation is applied to group similar feature vectors that belong to different scene components such as target or background. Depending on the feature vectors, a weight is assigned to each cluster and these weights are used to compute gain matrices which are used to multiply wavelet coefficients for the enhancement of the original image. Enhancement results are presented and a comparison of the performance of the proposed algorithm is given through subjective tests with other well known frequency and histogram based enhancement techniques. The proposed algorithm outperforms previous ones in the truthfulness, detail visibility of the target, artificiality, and total quality criteria, while providing an acceptable computational load. 相似文献
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Firat AK Karakaş HM Yakinci C Altinok T Alkan A Biçak U 《Magnetic resonance imaging》2004,22(9):1329-1332
Acute disseminated encephalomyelitis (ADEM) is an immune-mediated demyelinating disorder usually encountered in children or adolescents and characterized by multifocal neurological deficits of rapid onset. Typical target areas of demyelination include the corona radiata, centrum semiovale, periventricular white matter, cerebellar peduncles and brainstem. Involvement of deep gray matter nuclei is also frequent. We report a 6-year-old boy with ADEM who had only brainstem involvement. Serial magnetic resonance images representing the stage of disease and response to steroid treatment are presented. 相似文献
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Tayfun E. Tezduyar 《国际流体数值方法杂志》2009,60(11):1289-1290
Some comments are provided on the citations offered in a recent paper (M. Behr, Int. J. Numer. Meth. Fluids 2008; 57 :1421–1434) that describes space–time finite element computations of advection of ‘Gaussian hills’, including computations with mesh refinement in the time direction. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Although, the effects of ultrasonic irradiation on multiphase flow through porous media have been studied in the past few
decades, the physics of the acoustic interaction between fluid and rock is not yet well understood. Various mechanisms may
be responsible for enhancing the flow of oil through porous media in the presence of an acoustic field. Capillary related
mechanisms are peristaltic transport due to mechanical deformation of the pore walls, reduction of capillary forces due to
the destruction of surface films generated across pore boundaries, coalescence of oil drops due to Bjerknes forces, oscillation
and excitation of capillary trapped oil drops, forces generated by cavitating bubbles, and sonocapillary effects. Insight
into the physical principles governing the mobilization of oil by ultrasonic waves is vital for developing and implementing
novel techniques of oil extraction. This paper aims at identifying and analyzing the influence of high-frequency, high-intensity
ultrasonic radiation on capillary imbibition. Laboratory experiments were performed using cylindrical Berea sandstone and
Indiana limestone samples with all sides (quasi-co-current imbibition), and only one side (counter-current imbibition) contacting
with the aqueous phase. The oil saturated cores were placed in an ultrasonic bath, and brought into contact with the aqueous
phase. The recovery rate due to capillary imbibition was monitored against time. Air–water, mineral oil–brine, mineral oil–surfactant
solution and mineral oil-polymer solution experiments were run each exploring a separate physical process governing acoustic
stimulation. Water–air imbibition tests isolate the effect of ultrasound on wettability, capillarity and density, while oil–brine
imbibition experiments help outline the ultrasonic effect on viscosity and interfacial interaction between oil, rock and aqueous
phase. We find that ultrasonic irradiation enhances capillary imbibition recovery of oil for various fluid pairs, and that
such process is dependent on the interfacial tension and density of the fluids. Although more evidence is needed, some runs
hint that wettability was not altered substantially under ultrasound. Preliminary analysis of the imbibition recoveries also
suggests that ultrasound enhances surfactant solubility and reduce surfactant adsorption onto the rock matrix. Additionally,
counter-current experiments involving kerosene and brine in epoxy coated Berea sandstone showed a dramatic decline in recovery.
Therefore, the effectiveness of any ultrasonic application may strongly depend on the nature of interaction type, i.e., co-
or counter-current flow. A modified form of an exponential model was employed to fit the recovery curves in an attempt to
quantify the factors causing the incremental recovery by ultrasonic waves for different fluid pairs and rock types. 相似文献
10.
Herbert Danninger Tayfun Kara Michael Ruhnow Hans -Jürgen Ullrich 《Mikrochimica acta》1990,101(1-6):219-229
Homogenization of Mo, W and Cr in alloyed P/M carbon steels during sintering with a transient liquid phase has been investigated by microscopic and microanalytical means. The reaction was found to start with carburization of the VIa metal, continues with the formation of different carbides, and generation of a liquid phase between the carbide and -Fe. The steady state equilibrium remains stable until all VIa metal has been consumed. Microprobe analysis was found to yield optimum results if selected model samples, in which homogenization should not proceed too fast, are investigated.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday 相似文献