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91.
Enhanced Viscosity of Poly(acrylamide) Solution in the Presence of Chromium Citrate Triggered by Release of CO2
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Ai-guo Mo Yu-pu Wang Yi-kun Liu Wan-fu Zhou Quan Zhou Akram Yasin Hai-yang Yang 《化学物理学报(中文版)》2018,31(1):117-122
Partially hydrolyzed polyacrylamide (HPAM) has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3+ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3+ so that the crosslinking between HPAM and Cr3+ can be prevented completely. Due to the decomposition of the bicarbonate (HCO3-) embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3+ increased accordingly. When the complexation of Cr3+ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased significantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate (KH2PO4), the release of CO2 was very slow and the condition was highly controlled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3+ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery. 相似文献
92.
Dinc Ali Caliskan Hakan Ekici Selcuk Sohret Yasin 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12693-12707
Journal of Thermal Analysis and Calorimetry - In this study, the kerosene fueled turboprop engine of a freight aircraft is investigated along with exergy dynamic, sustainability,... 相似文献
93.
Sahib M. A. A. B. Zulkipli Nur Farhanah Rosol Ahmad Haziq Aiman Yasin Moh Harun Sulaiman Wadi 《Journal of Russian Laser Research》2022,43(3):328-333
Journal of Russian Laser Research - We propose a MXene Ti3C2Tx thin-film and demonstrate as saturable absorber (SA) to generate mode-locked laser pulses. In constructing the SA, titanium carbide... 相似文献
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The general aim of this study is to provide a guide to the future marketing decisions of a firm, using a model to predict customer lifetime values. The proposed framework aims to eliminate the limitations and drawbacks of the majority of models encountered in the literature through a simple and industry-specific model with easily measurable and objective indicators. In addition, this model predicts the potential value of the current customers rather than measuring the current value, which has generally been used in the majority of previous studies. This study contributes to the literature by helping to make future marketing decisions via Markov decision processes for a company that offers several types of products. Another contribution is that the states for Markov decision processes are also generated using the predicted customer lifetime values where the prediction is realized by a regression-based model. Finally, a real world application of the proposed model is provided in the banking sector to show the empirical validity of the model. Therefore, we believe that the proposed framework and the developed model can guide both practitioners and researchers. 相似文献
97.
It is well known that the selectivity of a receptor for an anion depends on the compatibility of the cavity size of the receptor and the size of the anion. In this work the macrobicyclic [H6L(X)]5+ (X−=F, Cl, Br); are studied theoretically and compared with [H6L′(F)]5+ having a smaller cavity size. It was shown that the ideal match between the sizes of the protonated azacryptand and the fluoride ion exists in the [H6L′(F)]5+ complex but the [H6L]6+ is a better receptor than [H6L′]6+ in solution. Thus the results clearly indicate that in some special cases a better receptor is not one whose cavity size has better compatibility with the anion size. 相似文献
98.
Zuleyha Kudas Ufuk Atmaca Tuba Saruhan Murat Celik Duygu Ekinci 《Electroanalysis》2020,32(6):1379-1390
In this study, the influence of the film structure was investigated on the electrocatalytic oxygen reduction at GC electrodes covered with porphyrin and metalloporphyrin rings via the diazonium modification method. For that purpose, primarily, tetraphenylporphyrin (TPP) films on GC electrode surfaces were prepared by electroreduction of in situ generated diazonium salts of 5‐(4‐aminophenyl)‐10,15,20‐triphenylporphyrin (APP) and 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin (TAPP) molecules. Next, the formation of metalloporphyrin films on the modified surfaces was accomplished through the complexation reactions of surface porphyrin rings with metal ions in the salt solutions containing Mn(II), Fe(III) and Co(II) ions. The resulting porphyrin and metalloporphyrin layers were identified with XPS and ICP‐MS. The electrochemical barrier properties of the films on GC surfaces were examined by cyclic voltammetry in K3Fe(CN)6 aqueous solution. The electrocatalytic abilities of the resulting films were also investigated for the oxygen electrochemical reduction by employing cyclic voltammetry in PBS solutions saturated with oxygen. The results showed that the oxygen reduction potentials on modified GC electrodes were shifted to less negative potentials compared to that of bare GC electrode. Also, it was obtained that the oxygen reduction reaction was more effective on the GC electrodes modified with TPP rings by using TAPP molecules than those prepared by using APP molecules. 相似文献
99.
A new unbridged metallocene catalyst bis(2,4-dimethyl-7-methoxyindenyl) zirconium dichloride was synthesized and polymerization of propylene was carried out with this catalyst and the results are compared with bis(2,4,7-trimethylindenyl) zirconium dichloride. The presence of π-donor substitutent on the indenyl ring led to a decrease in catalytic activity of the catalyst as well as the resulting molecular weight of the polymer as compared to its tri-alkyl substituted congener. The methoxy group deactivates the catalyst and also suppresses the favorable effect of other methyl substituents present in the indenyl ligand. 相似文献
100.
Sensitivity enhancement of indium determination by flame atomic absorption spectrometry (FAAS) was achieved; using a slotted quartz tube (SQT-FAAS) and slotted quartz tube atom trap (SQT-AT-FAAS). SQT was used as an atom trap (AT) where the analyte is accumulated in its inner wall prior to re-atomization. The signal is formed after re-atomization of analyte on the trap surface by introduction of 10 μL of isobutyl methyl ketone (IBMK). Sensitivity was improved 400 times using SQT-AT-FAAS system with respect to conventional FAAS and 279 times with respect to SQT-FAAS without any collection. Characteristic concentration (C0) and limit of detection values were found to be 3.63 ng mL−1 and 2.60 ng mL−1, respectively, using a sample flow rate of 7.0 mL min−1 and a collection period of 5.0 min. In addition, interference effects of some elements on indium signal were studied. In order to characterize indium species trapped, X-ray Photoelectron Spectrometry (XPS) was utilized and it was found that indium was collected on the inner surface of SQT as In2O3. The accuracy of the procedure was checked to determine indium in the standard reference material (Montana Soil, SRM 2710). 相似文献