ABSTRACT
Microfluidic chips are important tools to study the microscopic flow of fluid. To better understand the research clues and development trends related to microfluidic chips, a bibliometric analysis of microfluidic chips was conducted based on 1115 paper records retrieved from the Web of Science Core Collection database. CiteSpace and VOSviewer software were used to analyze the distribution of annual paper quantity, country/region distribution, subject distribution, institution distribution, major source journals distribution, highly cited papers, coauthor cooperation relationship, research knowledge domain, research focuses, and research frontiers, and a knowledge domain map was drawn. The results show that the number of papers published on microfluidic chips increased from 2010 to 2023, among which China, the United States, Iran, Canada, and Japan were the most active countries in this field. The United States was the most influential country. Nanoscience, energy, and chemical industry and multidisciplinary materials science were the main fields of microfluidic chip research. Lab on a Chip, Microfluidics and Nanofluidics, and Journal of Petroleum Science and Engineering were the main sources of papers published. The fabrication of chips, as well as their applications in porous media flow and multiphase flow, is the main knowledge domain of microfluidic chips. Micromodeling, fluid displacement, wettability, and multiphase flow are the research focuses in this field currently. The research frontiers in this field are enhanced oil recovery, interfacial tension, and stability.
ABSTRACT
During the underground mining process, various coal seams with different bedding structures are often encountered. The presence of bedding structures is one of the primary factors that influence the strength and deformation characteristics of the coal seam and then affect gas extraction and gas disaster prevention. However, there is still a lack of mechanical properties of coal rock with structural anisotropy influenced by bedding structures. In this study, numerical models were established by using the particle flow code method to simulate coal specimens containing bedding with varying inclination angles. The results demonstrate the impact of the bedding inclination angle on the mechanical properties, crack propagation patterns, and the temporal and spatial evolution of the stress field in coal specimens with bedding during the loading process. Furthermore, three crack initiation patterns were investigated for coal specimens with different bedding angles. Additionally, the quantitative relationship between the mechanical properties and the fractal dimension was analyzed. The numerical simulation results were effectively validated through laboratory tests.
ABSTRACT
Gas explosions or coal and gas outbursts can cause transient destruction of combined coal-rock, and the dynamic mechanical response of combined coal-rock masses plays a key role in accident failure, but we now know little about the dynamic mechanical responses of combined coal-rock. In this article, we selected three rocks (limestone, shale, sandstone) and two coals (bituminous coal and anthracite coal) to form combined coal-rock, and analyze their dynamic mechanical properties by using the SHPB system. We find that the dynamic compressive strength and elastic modulus of combined rock-coal are lower than the average value of single rock and coal, while the ultimate strain and strain rate of combined coal-rock are higher than the average values of single rock and coal. Compressive strength and elastic modulus of the combined body increase gradually with increasing confining pressure, and the strain decreases accordingly. The dynamic stress-strain curve demonstrates an obvious double-peak at high strain rate (85.55 s-1 and above in the present work), while there is no obvious double-peak of the curve at low strain rate. Dynamic compressive strength of combined coal-rock body increases significantly with increasing confining pressure at low strain rate, but it increases more smoothly at higher strain rate. The elastic modulus also increases with increasing confining pressure, and it seems to be stable as confining pressure increases at low strain rate. The ultimate strain decreases gradually with increasing confining pressure but more gently compared with that at low strain rate. Besides, longitudinal fractures of combined coal-rock bodies include penetrating fractures, partially penetrating fractures, and interrupted fractures stopped at the coal-rock interface. The dynamic mechanical response of combined coal-rock is of guiding significance for maintaining the stability of the roadway and formulating the support measures for the roadway.
