Pressure is one basic parameter involved in microfluidic systems. In this study, we developed an easy capillary-based method for measuring fluid pressure at one or multiple locations in a microchannel. The principal component is a commonly used capillary (inner diameter of 400 μm and 95 mm in length), with one end sealed and calibrated scales on it. By reading the height (h) of an air-liquid interface, the pressure can be measured directly from a table, which is calculated using the ideal gas law. Many factors that affect the relationship between the trapped air volume and applied pressure (p_applied) have been investigated in detail, including the surface tension, liquid gravity, air solubility in water, temperature variation, and capillary diameters. Based on the evaluation of the experimental and simulation results of the pressure, combined with theoretical analysis, a resolution of about 1 kPa within a full-scale range of 101.6–178 kPa was obtained. A pressure drop (Δp) as low as 0.25 kPa was obtained in an operating range from 0.5 kPa to 12 kPa. Compared with other novel, microstructure-based methods, this method does not require microfabrication and additional equipment. Finally, we use this method to reasonably analyze the nonlinearity of the flow-pressure drop relationship caused by channel deformation. In the future, this one-end-sealed capillary could be used for pressure measurement as easily as a clinical thermometer in various microfluidic applications.

The gear is one of the important parts of a rotary gearbox. Once catastrophic gear failure occurs, it will cause a great threat to production and life safety. The crack is an important failure factor causing changes in time-varying stiffness and vibration response. It is difficult to effectively identify the vibration response and meshing stiffness changes when there is a fine crack in the gear. Therefore, it is of great importance to improve the accuracy of meshing stiffness calculation and dynamic simulations under micro-cracks. Investigations of meshing stiffness and the vibration response of a gearbox is almost all about fixed gear shape parameters. However, the actual production process of gear system needs to change gear shape parameters. In this paper, the meshing stiffness and vibration response of the dynamic simulation signals of gear teeth with different crack depths at different tooth shape parameters (the pressure angle, the modulus, and the tooth number) were calculated, respectively. The influence of cracks on the vibration response was investigated by the fault detection indicators, the Root Mean Square (RMS), the kurtosis, and the crest factor. The result shows that when the pressure angle and modulus change, the vibration response changes erratically. However, when the tooth numbers change, the vibration response changes regularly. The results could be a guide for choosing gears in different shape parameters when system stability is the aim.

The efficient conversion of biomass into biofuels is closely associated with the topochemistry of the cell wall. In this study, the topochemical correlation between carbohydrates and lignin in the Eucommia ulmoides cell wall was investigated in situ by confocal Raman microscopy. The carbohydrates and lignin were mainly collocated in the secondary wall of the fiber, ray parenchyma, and vessel in E. ulmoides. High carbohydrates were associated with low lignin or vice versa, indicating that a high concentration of carbohydrates leads to a drop in the degree of lignification. Furthermore, the band intensity ratio of S- and G-lignin to carbohydrates (I1333/I2889 and I1274/I2889) in morphologically distinct regions of fiber was calculated. In accordance with the wet chemical analysis, a higher ratio of lignin to carbohydrates was observed within the middle layer of the 3-year-old E. ulmoides fiber secondary wall. The results potentially extend the current understanding of the carbohydrate and lignin topochemistry in woody biomass and may facilitate an efficient wood bioconversion process in future biorefineries.

In this paper, the commercial FEM software package Abaqus is used to investigate the effects of microgrooved cutting tools in high speed orthogonal cutting of AISI 1045 steel. Microgrooves are designed and fabricated on the rake face of cemented carbide (WC/Co) cutting inserts. A coupled Eulerian-Lagrangian (CEL) finite element model is developed based on Abaqus to solve the evolution of the cutting temperature, chip morphology, cutting force, and phase constitutes simultaneously. This model is validated by comparing the numerical results with the experimental data for orthogonal high speed cutting of AISI 1045 steel with various cutting conditions. In addition, this model is also validated by comparing with the experimental data of regular tool and microgrooved cutting tool under the cutting speed of 120m/min. This validated CEL FEM model is then utilized to investigate the effects of microgrooved cutting tools on the phase transformation, cutting force, cutting temperature, and chip morphology in high speed orthogonal cutting of AISI 1045. The effects of microgroove width, edge distance (the distance from cutting edge to the first microgroove), and microgroove depth are examined and assessed in terms of cutting force, cutting temperature, chip morphology, and phase transformation. It is found that this CEL FEM model can capture the essential features of orthogonal high speed cutting of AISI 1045 using microgrooved cutting tools. It is also concluded that microgrooved cutting tools can not effectively reduce the cutting force in high speed machining, which is contrary to the conclusion obtained for low speed machining in previous research. However, microgrooves on the rake face have influence on the austenite percentage in the chip near the rake face. This research provides insightful guidance for optimizing the cutting performance in terms of cutting temperature, cutting force, chip morphology, and phase transformation in high speed machining of AISI 1045 steel.