Effects of channel wall wettability on gas-liquid dynamics mass transfer under Taylor flow in a serpentine microchannel

The wall wettability of microchannels plays an important role in the gas-liquid mass transfer dynamics under Taylor flow.In this study,we regulated the contact angle of the wall surface through surface chemical grafting polymerization under controlled experimental conditions.The dynamic changes of CO_(2)bubbles flowing along the microchannel were captured by a high-speed video camera mounted on a stereo microscope,whilst a unit cell model was employed to theoretically investigate the gas-liquid mass transfer dynamics.We quantitatively characterized the effects of wall wettability,specifically the contact angle,on the formation mechanism of gas bubbles and mass transfer process experimentally.The results revealed that the gas bubble velocity,the overall volumetric liquid phase mass transfer coefficients(kLa),and the specific interfacial area(a)all increased with the increase of the contact angle.Conversely,gas bubble length and leakage flow decreased.Furthermore,we proposed a new modified model to predict the gas-liquid two-phase mass transfer performance,based on van Baten’s and Yao’s models.Our proposed model was observed to agree reasonably well with experimental observations.

Prompt: Discuss social problem related to the discussions we had in class. Explain the means in which this specific problem impacts the society as a whole or segments of society

The progression of society tends to be linked with higher moral standards.Evolution has changed humanity from barbaric creatures to intelligent beings capable of making ethical decisions.In recent years,the gradual disappearance of Jim Crowism was noticeable as shown by the reduction in explicit racist behaviors—the most convincing sign being Barack Obama’s successful election to become the first African American president.

Design of Defect-Rich MgCo-Layered Double Hydroxide Microspheres as Highly Effective Sulfur Reduction Reaction Electrocatalyst for High-Performance Li-S Batteries

Designing advanced sulfur electrocatalysts has long been heralded as an efficient approach to settle the issues of the dreadful shuttle effect and sluggish reaction kinetics of the lithium polysulfides(LiPSs)in lithium-sulfur(Li-S)batteries.Therefore,we designed a hierarchical bimetal defective MgCo LDH@rGO nanosphere as a sulfur electrocatalyst to regulate the LiPSs catalytic conversion behavior,which demonstrated efficient catalytic activity and robust structural stability.The introduction of etching Mg^(2+)formed a hollow structure and Lewis acid points in MgCo LDH@rGO,serving as active sites for effective LiPS immobilization.The excellent conductivity and larger specific surface area of reduced graphene oxide(rGO)levered the utilization of sulfur and alleviated volume expansion during lithiation,rendering enhanced stability.Meanwhile,the vibrant regulation of active sites in the MgCo LDH@rGO resulted in more effective LiPS catalytic conversion and completed Li_(2)S transformation,as revealed by ex-situ X-ray adsorption spectroscopy analysis.Attributed to these inimitable structural features,the Li-S batteries delivered excellent performance under a high areal capacity of over 7 mAh cm^(−2)and remarkable cyclic stability over 500 cycles.This structural design strategy endowed the sulfur cathode with superior LiPS catalytic activity,opening a new insight into high-performance Li-S batteries.