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In view of the concentration of measurement points in the traditional sensor optimization method with a large number of configurations,the relationship between optimization results and prediction errors was analyzed based on the information entropy theory,and an improved optimization method considering prediction errors was proposed. The reciprocal of the sum of normalized modal strain energy was used as the principal diagonal element of the prediction error covariance matrix,and the non-diagonal element was expressed by an exponential correlation equation combining the distance of measurement points and the response level. Aiming at maximizing the determinant of Fisher information matrix,the forward sequential sensor placement method was used to obtain the optimal location of measurement points. The finite element analysis results of the urban rail vehicle frames showed that the improved sensor optimization method is superior to the classical method in the performance of three evaluation criteria,and significantly reduces the concentrating effect of measurement points,which proves the effectiveness of the improved method in the configuration of bogie frame strain sensors. [ABSTRACT FROM AUTHOR]

To explore the regulation of tool wear on milling surface of DD5 under the conditions of dry cutting and water-based minimum quantity lubrication(WMQL)， carbide tool with four blades and PVD-TiAlN coating， super depth of field microscope and scanning electron microscopy(SEM)were employed. Taking the wear width of minor flank surface of cutting tool as the evaluation indicator， tool wear forms and wear mechanism were analyzed and studied. Three-dimensional measuring system profiler was used to measure the machined surface roughness. The result shows that， compared to dry cutting， water-based MQL technology can prolong tool life and improve the milling performance. The wear of carbide tool is caused by adhesion wear， oxidative wear， abrasive wear and diffusion wear. [ABSTRACT FROM AUTHOR]

Numerical simulation on heat transfer and permeability of Fuyu oil shale reservoir after hydraulic fracturing was carried out by using thermal-fluid coupling analysis model. It is found that the fluid mainly flows out of the fracture along the oil shale bedding direction. However, as the temperature increases, the porosity increases and a little fluid flows out of the primary pores of the oil shale. The seepage field pressure shows a downward trend in the same section from the fracture perpendicular to the oil shale bedding. The heat conduction of fluid to oil shale formation was mainly in the direction of fracture. As the heating time increases, the oil shale cracks on both sides of the fissure, and with the porosity increase, the diffusion rate of nitrogen to the oil shale reservoir is also improved. After 40 days of heating, the oil shale around the fracture first reaches the cracking temperature. Between 60 and 100 days of heating, the average temperature of oil shale rises from 500 K to 650 K, and the whole oil shale can be effectively cracked. [ABSTRACT FROM AUTHOR]

Using the high voltage industrial frequency current to heat oil shale， the plasma channels can be formed in oil shale. The in-situ cracking of oil shale is realized by heating the oil shale with the generated plasma and the carbonized inner surface of the conductive channel. In this paper， a three-dimensional coupled model of oil shale was established by finite element analysis software， and the distribution of temperature field during the high frequency oil shale pyrolysis was obtained by numerical calculation. When the voltage is 1000V and the current is 5A， the temperature at the center of electrode， after 6 minutes heating， reached 597℃， and the temperature at the areas around the electrode 30mm away reached 347℃， meeting the pyrolysis demand of oil shale. With the increase of current， the increased temperature of oil shale during the same heating time showed a steady rise， and the range of effective pyrolysis also went up. According to the results of numerical simulation， using the high voltage industrial frequency to heat oil shale can gain a fast heating rate and high energy efficiency. [ABSTRACT FROM AUTHOR]