Transferable microfiber laser arrays for high-sensitivity thermal sensing.

Functional microfibers have attracted extensive attention due to their potential in health monitoring, radiation cooling, power management and luminescence. Among these, polymer fiber-based microlasers have plentiful applications due to their merits of full color, high quality factor and simple fabrication. However, developing a facile approach to fabricate stable microfiber lasing devices for high-sensitivity thermal sensing is still challenging. In this research, we propose a design of a stable and transferable membrane inlaid with whispering-gallery-mode plasmon hybrid microlaser arrays for thermal sensing. By integrating plasmonic gold nanorods with polymer lasing microfiber arrays that are embedded in the polydimethylsiloxane matrix, whispering-gallery-mode lasing arrays with high quality are achieved. Based on the thermo-optical effect of the membrane, a tuning range of 1.462 nm for the lasing peak shift under temperature variation from 30.6 °C to 38.7 °C is obtained. The ultimate thermal sensing sensitivity can reach up to 0.181 nm °C-1 and the limit of detection is 0.131 °C, with a high figure of merit of 2.961 °C-1. Moreover, a stable laser linewidth can be maintained within the tuning range due to plasmon-improved photon confinement and PDMS-reduced scattering loss. This work is expected to provide a facile approach for the fabrication of high-sensitivity on-chip thermometry devices.

Fault Diagnosis for Abnormal Wear of Rolling Element Bearing Fusing Oil Debris Monitoring.

The abnormal wear of a rolling element bearing caused by early failures, such as pitting and spalling, will deteriorate the running state and reduce the life. This paper demonstrates the importance of oil debris monitoring and its effective feature extraction for bearing health assessment. In this paper, a rolling bearing-rotor test rig with forced lubrication is set up and the nonferrous contaminants with higher hardness were introduced artificially to accelerate the occurrence of pitting and spalling. The early failure and abnormal wear of rolling bearings cannot be effectively detected only through the vibration signal; the temperature and oil debris monitoring data are also collected synchronously. Two features regarding the ferrous particle size distribution are extracted and fused with vibration based-features to form a feature set. The sensitive features are extracted from the features set using the Neighborhood Component Analysis method to avoid feature redundancy. Finally, the importance of the oil debris based-features for the diagnosis of abnormal bearing wear is analyzed with different machine learning algorithms. Taking SVM classifier as an example, the experiment results show that the introduction of oil debris based-features increases the diagnostic accuracy by 15.7%.

Parameter Sensitivity Analysis of Mounting Pedestals and Multi-Objective Optimization for a Multi-Support Rigid Body System.

In this paper, a parameter sensitivity analysis of mounting pedestals and a multi-objective optimization design for vibration reduction in a multi-support rigid body system, taking an aeroengine-lubricating oil tank supported by multiple mounting pedestals as an example, are conducted based on the third version of non-dominated sorting genetic algorithm (NSGA-Ⅲ) combined with Sobol's sensitivity analysis method (SSAM). An aeroengine-lubricating oil tank with three mounting pedestals is simplified as a three-support dynamic system, and its dynamics model is established. Several structural parameters of mounting pedestals are taken as the design variables, and the system vibration response and the reaction force of the front and rear mounting pedestals are considered as the objective functions. The first-order results and total sensitivity index of different design parameters for each objective function are obtained via SSAM, and the five most sensitive parameters are selected. Based on the above five design parameters, multi-objective optimization designing for vibration reduction in a simplified lubricating oil tank system is conducted based on NSGA-Ⅲ, and the results of the above triple-objective optimization are obtained as a Pareto-front surface with an obvious frontier. It can be observed from the simulation results that the oil tank vibration of the optimized system is effectively suppressed under the unbalanced excitation of two typical engine speeds. The established method and the main results can provide guidance for designers of aeroengine external structural systems, which can help to achieve superior system dynamic performances in engineering applications.