For decades, vibration and oil analysis have usually been used to detect early bearing faults and track their progression over time. Progress has been seen in condition monitoring through vibration analysis of rolling element bearings using improved sensors and advanced signal processing techniques. In this paper, the authors investigate the use of air-coupled ultrasound and eddy current sensors as diagnostic tools for the detection of bearing faults. A series of experiments was carried out in a laboratory environment: localized defects with different sizes were created intentionally on the test bearing components simulating evolving cracks or other related faults. The resulting data for a constant bearing speed and load have shown that both sensors are capable of detecting different types of defects located on the bearing components. The data from the air-coupled ultrasound and eddy current sensors were also compared with those obtained from an accelerometer. The test method and the processing technique are described and the spectra of the different signals are analyzed and discussed.
Integrating strategic and tactical decisions to location-allocation and green inventory planning by considering e-commerce features will pave the way for supply chain managers. Therefore, this study provides an effective framework for making decisions related to different levels of the dual-channel supply chain. We provide a bi-objective location-allocation-inventory optimization model to design a dual-channel, multi-level supply chain network. The main objectives of this study are to minimize total cost and environmental impacts while tactical and strategic decisions are integrated. Demand uncertainty is also addressed using stochastic modeling, and inventory procedure is the periodic review . We consider many features in inventory modeling that play a very important role, such as lead time, shortage, inflation, and quality of raw materials, to adapt the model to the real conditions. Since a dual-channel supply chain is becoming more important for sustainable economic development and resource recovery, we combine online and traditional sales channels to design a network. We generate five test problems and solve them by using the augmented ε-constraint method. Also, the Grasshopper optimization algorithm was applied to solve the model in a reasonable time for a large size problem. In order to provide managerial insights and investigate the sensitivity of variables and problem objectives with respect to parameters, sensitivity analysis was performed.
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