Facile synthesis of porous C-doped C3N4: fast charge separation and enhanced photocatalytic hydrogen evolution

A facile gaseous-bubbles templating approach to synthesize porous C-doped g-C3N4 with enhanced photocatalytic activity for hydrogen evolution reaction.

Ultrasound Measurement Technique for Validation of Cryogenic Flows

An ultrasound sensor system based on the transmission-mode approach is developed to enable the monitoring and sensing of cryogenic liquids and gases—especially gaseous bubbles and gas-liquid interfaces in liquid nitrogen (LN2). Common sensors do not meet requirements of cryogenic and microgravity-environments. Therefore, a special encapsulation design for the optimization of the electrical connection and the mechanical coupling of the ultrasound sensors is needed. The ultrasound system is qualified in LN2 and is able to measure bubbles (size and location) and fill levels with a high spatial resolution in a submillimetre range and a sampling rate of more than 500 Hz.

Operation Parameters' Effect on Gaseous Bubbles in Lubricant of Groove Textured Journal Bearing

Operation parameter influences on the behavior of the gaseous bubble in the lubricant for a groove textured journal bearing are studied under the consideration of the thermal effect of the bearing–shaft system. The influence is analyzed by simultaneously solving Rayleigh–Plesset (RP), energy, and Reynolds equations. The computer code for the analyzing the bubble behavior is validated. Numerical results show that appropriately increasing the width–diameter ratio of the bearing and rotational speed of the shaft, or decreasing the applied load and inlet temperature of the lubricant, can decrease the maximum radius, collapse pressure, and temperature of the bubble.

Effect of Groove Textures on the Performances of Gaseous Bubble in the Lubricant of Journal Bearing

Effects of groove textures on the performances for gaseous bubbles in the lubricant used for a textured journal bearing is studied under the consideration of thermal effect of lubricant. The Reynolds, energy, and Rayleigh–Plesset (RP) equations are solved simultaneously for simulating the behavior of the bubble. Numerical results show that the gaseous bubble radius shows a nonlinearly oscillation in a full cycle period, and high bubble pressure and temperature appear when the bubble collapses. Moreover, appropriately choosing groove length, width, or interval can reduce the maximum radius, collapse pressure, and collapse temperature of the bubble. There exists a critical groove depth minimizing the bubble pressure and temperature.

The Improvement of Machining Accuracy on Quartz and Glasses by Electrochemical Discharge Machining

In the present study, a tungsten rod with diameter of 100μm is used as the tool to drill a quartz plate by Electrochemical Discharge Machining (ECDM). KOH solution mixed with different concentration of Ethanol is used as the electrolyte. The influences of different working parameters, such as electrolyte concentration, applied voltage, pulse frequency, and electrolyte level, on the gas film stability, gas film thickness, and machining accuracy are investigated. The experimental results show that the overcut and surface roughness is improved by the use of electrolyte with addition of 6.5wt% ethanol. The effect of gaseous bubbles is reduced during the machining, and the circulation of electrolyte is better. Compared with machining with pure KOH electrolyte, the overcut is reduced around 57% by the use of electrolyte with addition of 6.5wt% ethanol. The heat-effected zone on the machining is also largely reduced.