Tetrahydrofuran (THF) hydrate was formed in bulk as well as in glass beads pack with a mean diameter of 3.0 mm by controlling the temperature under ambient pressure. Images of THF hydrate formation procedure were obtained using the magnetic resonance imaging (MRI) technique. The experiment results showed that MRI is an effective method for the detection of hydrate formation. Saturation of hydrate formed both in bulk and glass beads can be confirmed by intensity integration of MRI images. 相似文献
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke... 相似文献
Experimental phase equilibrium conditions data for carbon dioxide (CO2) hydrate in porous medium with the presence of sodium chloride (NaCl) solution were investigated in this study. The experimental data were generated using graphic-method in presence of solutions contained (0, 0.2, 0.4, 0.6, and 0.8) mol/L NaCl. The results indicated the increase of NaCl concentration caused the enhancement in the equilibrium pressure of CO2 hydrate as the pore size and the temperature were kept the same. Effects of NaCl solutions on CO2 hydrate equilibrium conditions could be neglected when the temperature is lower than ice point. An improved model was used to predict CO2 hydrate equilibrium conditions, and the predictions showed good agreement with experimental measurements. 相似文献
To investigate the effects of sequestration condition on hydrogen bonds between mineral and water, molecular dynamics simulations have been performed. The simulations were conducted at conditions related with geologic sequestration sites: pressure (3.1–32.6 MPa), temperature (318 and 383 K), salinity (0–3 M), salt (NaCl and CaCl2) and silica surface models Q2 (geminal), Q3 (isolated) and amorphous Q3. The hydrogen bonds were classified into four types: silica–silica, silica–dissolved CO2, silica–water as donors and silica–water as acceptors. The mean numbers of hydrogen bonds for each type were analysed. The results show that: (1) silica surface silanol groups do not form H-bonds with dissolved CO2 molecules in water (brine); (2) The mean number of hydrogen bonds between silanol groups follows the order: Q2 > amorphous Q3 > Q3; (3) The mean number of hydrogen bonds between silanol and water molecules follows the order: Q3 > amorphous Q3 > Q2. 相似文献
The relationship between the age-related reorganization of brain networks and individual behavior has attracted much attention. However, how age induces changes in neural activity at different frequencies in the brain to balance the demands of network integration and segregation, and how age-induced changes in network integration and segregation relate to behavior remain enigmatic. Here, a nested-spectral partition method was used to analyze behavioral-related dynamic functional balance in the aging brain with electroencephalogram signals collected from 56 healthy participants (age: 20–80 years) at rest. The nested-spectral partition approach measures hierarchical segregation and integration across multiple levels by detecting hierarchical modules in brain functional networks. Declines in general personality and general cognitive ability in older adults were captured by exploratory factor analysis. We showed that the brain network of elderly individuals contains more hierarchical modules to generate higher segregation, and it is closer to the functional balance state in the theta and alpha bands but away from this state in the gamma band. Meanwhile, the abnormal variability of functional balance in the elderly brain supports more flexible transitions between segregated and integrated states in the alpha band but reduces the transitions in the beta and gamma bands. Crucially, the degeneration of general personality and general cognitive ability is significantly associated with higher segregation and abnormal flexibility of the brain, especially in the theta, beta, and gamma bands. Our results provide deep insights from a spectral partitioning perspective into the brain dynamic mechanisms that are associated with age-related personality and cognitive degeneration.
The regeneration conditions of the deactivated catalyst 18wt%NiO/a-A12O3 used in methane reforming with carbon dioxide were studied by using a fix-bed flow reactor and TPR technique. When the deactivated catalyst was reduced at 1 123 K in a conventional regeneration process, the activity increased a little, but was still much lower than that of the fresh catalyst. When the deactivated catalyst was reduced, then treated in site With an activity-rejuvenating agent of 5-10 vo1% C (aqueous hydrogen peroxide solution) and reduced again at 1123K, the activity was renewed to approach that of the fresh one. 相似文献
Based on the models of hydrate phase equilibrium in bulk water and porous media, an improved model was proposed to predict the methane hydrate equilibrium in marine sediment environment. In the suggested model, mechanical equilibrium of force between the interfaces in hydrate-liquid-vapor system was considered. When electrolyte was present in pore water, interfacial energy between hydrate and liquid was corrected by an equation that is expressed as the function of temperature and electrolyte concentration. The activity of water is calculated based on the Pitzer model and the interfacial energy between liquid and gas is solved using the Li method. The prediction results show good agreement with the experimental data. By comparison with other models, it is proved that this model can improve the accuracy for predicting hydrate phase equilibrium in marine sediment environment. 相似文献