Search

This study used the Massachusetts Institute of Technology general circulation model (MITgcm) to simulate the seabed liquefaction process in the Chengdao area. The liquefied soil and the overlying water are considered as a two-layer fluid system in the model. By constructing various topographies using Gaussian functions, it is possible to achieve an agreement between simulation and measurement. The simulation results reveal the characteristics of pore pressure in different topographies. The main findings include the following: (1) The expansion of liquefaction zone leads to an accelerated attenuation of pore pressure amplitude. (2) A decrease in topographic slope diminishes the wave group characteristics of pore pressure due to the sensitivity of certain wave components with specific frequencies to topographic slope. [ABSTRACT FROM AUTHOR]

Polyacrylamide-based gel plugging agents are extensively utilized in oilfields for water shutoff. However, their thermal stability, salt tolerance, and shear resistance are limited, making it difficult to achieve high-strength plugging and maintain stability under high-temperature and high-salinity reservoir conditions. This study proposes the use of chitosan (CTSs), a polysaccharide with a rigid cyclic structure, as the polymer. The organic cross-linker N,N′-methylenebisacrylamide (MBA) is incorporated via the Michael addition reaction mechanism to develop an ultra-stable, organically cross-linked chitosan gel system. The CTS/MBA gel system was evaluated under various environmental conditions using rheological testing and thermal aging to assess gel strength and stability. The results demonstrate significant improvements in gel strength and stability at high temperatures (up to 120 °C) and under high-shear conditions, as the increased cross-linking density enhanced resistance to thermal and mechanical degradation. Rapid gelation was observed with increasing MBA concentration, while pH and salinity further modulated gel properties. Scanning electron microscopy revealed the formation of a three-dimensional microstructure after gelation, which contributed to the enhanced properties. This study provides novel insights into optimizing polymer gel performance for the petroleum industry, particularly in high-temperature and high-shear environments. [ABSTRACT FROM AUTHOR]

Human fetal scleral fibroblasts (HFSFs) are components of the sclera and play important roles in its structure and function. In myopia, scleral remodeling reduces collagen fibers and the sclera begins to thin. NANOG is a key transcription factor essential for pluripotent and self-renewing phenotypes of undifferentiated embryonic stem cells. To determine whether NANOG improves human fetal scleral fibroblast quality and the underlying mechanisms in these cells, we established stable NANOG-overexpressing HFSFs. We studied type I collagen (COL1A 1) and Rho-associated coiled-coil protein kinase 1 (ROCK1) expression in transfected cells. We also investigated POU5F1, SOX2, KLF4, MYC and SALL4 expression in NANOG stably-overexpressed fibroblasts. Our data show that NANOG expression increased proliferation rates in fibroblasts. When compared to controls, expression of COL1A 1 in transfected fibroblasts was increased and the expression of ROCK1 was decreased. Similarly, the expression of POU5F1, SOX2 and KLF4 was downregulated, the expression of MYC was upregulated and there was no significant change in the expression of SALL4 in transfected fibroblasts. Our results suggest that in fibroblasts, NANOG regulates ROCK1 expression and improves COL1A 1 expression to delay scleral remodeling.

Soil organic carbon (SOC) is widely recognized as an essential indicator of the quality of arable soils and the health of ecosystems. In addition, an accurate understanding of the spatial distribution of soil organic carbon content for precision digital agriculture is important. In this study, the spatial distribution of organic carbon in topsoil was determined using four common machine learning methods, namely the back-propagation neural network model (BPNN), random forest algorithm model (RF), geographically weighted regression model (GWR), and ordinary Kriging interpolation method (OK), with Helan County as the study area. The prediction accuracies of the four different models were compared in conjunction with multiple sources of auxiliary variables. The prediction accuracies for the four models were BPNN (MRE = 0.066, RMSE = 0.257) > RF (MRE = 0.186, RMSE = 3.320) > GWR (MRE = 0.193, RMSE = 3.595) > OK (MRE = 0.198, RMSE = 4.248). Moreover, the spatial distribution trends for the SOC content predicted with the four different models were similar: high in the western area and low in the eastern area of the study region. The BPNN model better handled the nonlinear relationship between the SOC content and multisource auxiliary variables and presented finer information for spatial differentiation. These results provide an important theoretical basis and data support to explore the spatial distribution trend for SOC content. [ABSTRACT FROM AUTHOR]

The filtration characteristics of low oil saturation reservoirs are obviously different from that of conventional reservoirs. The development performance and the influence factors for low oil saturation reservoirs were studied using laboratory large model physical modeling and reservoir numerical simulation, to match and establish the empirical formula of water cut variation. In the numerical stimulation process, the effect of threshold pressure on filtration for low permeability reservoirs was considered, which made the results more realistic. There wasn't a period of oil recovery without water for low oil saturation reservoirs; the water cut increased rapidly at the beginning, and dropped slightly before the period of oil production with stable water cut. The higher the initial water saturation, the shorter the production time with stable water cut. Recovery changed greatly with the injection/production pressure gradient when the injection/production pressure gradient was close to the pseudo threshold pressure gradient. Recovery changed little, even no change, with the injection/production pressure gradient when the injection/production pressure gradient was far larger than the pseudo threshold pressure gradient. There was a positive correlation between recovery degree and water injection rate when the injection/production pressure gradient was less than the pseudo threshold pressure gradient. Key words: low oil saturation reservoir, low permeability reservoir, pseudo threshold pressure gradient, filtration

Nanosheet molybdenum disulfide (MoS2) electrode materials for supercapacitor were prepared by high-temperature solid-phase method combined with ball milling using sodium molybdate and thiourea in a Mo to S molar ratio of 1:15 as raw materials. The thermal stability, phase structure and microstructure were characterized by thermogravimetric-differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. The eletrochemical properties of the samples were tested by cyclic voltammetry (CV), galvanostatic charge/discharge cycling (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the number of MoS2 layers prepared by sintering at 750 °C and ball milling at 700 r·min-1 for 10 h is 88. The specific capacitances of the samples are 82. 4 and 60. 9 F·g-1 at the current density of 0. 5 and 1 A·g-1, respectively (better than 54. 6 and 24. 0 F·g-1 before ball milling). After 2 000 cycles, the specific capacitance retention rate is 92%. [ABSTRACT FROM AUTHOR]

A modified digital element approach (DEA) is applied to simulate fabric perforation process under ballistic impact. The previous version of the DEA is capable of simulating ballistic impact of textile fabric using rigid body spherical and cylindrical projectiles only. Fragment simulating projectile (FSP) and real bullets are not modeled. The subject of this research is to perform ballistic penetration process against projectile of arbitrary shape and validate the modified DEA. A fabric to solid body projectile contact search and contact force calculation algorithm is established. Ballistic impact of textile fabrics against spherical and cylindrical projectiles is performed using the previous DEA and the modified DEA separately. Numerical results are compared to the well published DEA results to investigate the fabric bullet resistant performance.

A study was done on the chemisorption and thermal decomposition of methylamine on Ru(001) surface. Results show that molecular adsorption of methylamine occurs via lone pair donation of the nitrogen atom and its desorption occurs reversibly from a saturated first layer in the temperature range of 200 to 340 K. Thermal decomposition of irreversibly adsorbed methylamine produces H2,N2 and NH3.